Patent Application
20240392064
This patent application is based on and claims priority pursuant to 35 U.S.C. § 119 to Japanese Patent Application No. 2023-084943, filed on May 23, 2023, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
The present invention is related to a toner polyester resin emulsion, a resin particle, ant a toner.
There is a demand for toners used in electrophotographic image forming devices to have excellent low-temperature fixability due to market requirements for energy efficiency. Additionally, toners with excellent blocking resistance to prevent fusion of toner particles even under harsh conditions such as high temperature and high humidity are also required, as well as toners with superior mechanical durability to withstand the stress associated with the high-speed performance of image forming apparatuses.
In recent years, development of toners with a so-called core-shell structure, wherein a shell layer is provided on the surface of the toner particles has been progressing to impart heat resistance and mechanical durability. Various techniques for core-shell formation of toners have been proposed and implemented, and chemical toners utilizing polyester resin with excellent low-temperature fixability for both core and shell particles have become mainstream.
According to embodiments of the present disclosure, a polyester resin emulsion is provided that contains resin particles(S), each containing a polyester resin (A) obtained by polycondensation of an alcohol component and a carboxylic acid component, and an aqueous medium in which the resin particles(S) are dispersed, wherein the alcohol component contains tri- or tetra-alcohol having a backbone of a linear or branched saturated fatty acid with a carbon number of 4 to 6, and the ratio (OHV/AV) of a hydroxyl value (OHV) of the polyester resin (A) to an acid value (AV) of the polyester resin (A) is from 0.20 to 0.60.
As another aspect of embodiments of the present disclosure, a resin particle is provided that contains a resin particle (T) with a core-shell structure, including a core particle containing a binder resin and a shell particle covering the core particle, wherein the shell particle is formed of the polyester resin emulsion mentioned above.
As another aspect of embodiments of the present disclosure, a toner is provided that contains a core-shell structure including a core particle containing a binder resin and a shell particle covering the core particle, wherein the shell particle is formed of the polyester resin emulsion mentioned above.
Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the detailed description when considered in connection with the accompanying drawing in which like reference characters designate like corresponding parts throughout and wherein:
FIGURE is a schematic diagram illustrating an example of the image forming apparatus according to an embodiment of the present disclosure.
The accompanying drawing is intended to depict example embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawing is not to be considered as drawn to scale unless explicitly noted.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Embodiments of the present invention are described in detail below with reference to accompanying drawings. In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.
For the sake of simplicity, the same reference number will be given to identical constituent elements such as parts and materials having the same functions and redundant descriptions thereof omitted unless otherwise stated.
According to the present disclosure, a polyester resin emulsion is provided that has a core-shell structure with excellent mechanical durability, along with aggregation and uniformity of the shell particles to the core particles.
Toners with a core-shell structure are known that, from the perspective of low-temperature fixability, heat resistance stability, and mechanical durability of the toner, it is highly necessary for the shell layer formed on the surface of the core particle to be uniformly distributed, covering the entire of the core particle. More specifically, unless the shell particles (shell layer) are uniformly distributed and cover the entire of the core particle, the mechanical durability of the toner decreases, leading to concerns that the shell layer may peel off from the core particle due to development stress inside the image forming apparatus, resulting in significant deterioration of various toner properties.
For example, a toner for electrostatic charge development, which mixes polyethylene terephthalate (PET) with the resin in both the core and shell portions, has been proposed in Japanese Unexamined Patent Application Publication No. 2017-111416 (Japanese Patent No. 6632066).
In the art described in Japanese Unexamined Patent Application Publication No. 2017-111416 mentioned above, the introduction of polyethylene terephthalate (PET) into the shell portion of toners with a core-shell structure is used to improve the durability of the toner and reduces wax exposure on the toner surface. However, introducing polyethylene terephthalate (PET) into the shell particles forming the shell portion is concerning because it reduces the hydrophobicity of the shell particles, leading to decreased aggregation of the core and shell particles, making it difficult to create a uniform shell layer on the surface of the core particle.
Through thorough investigation, the present inventors of the present invention have discovered that the use of an emulsion, in which a polyester resin with a specific ratio (hydroxyl value (OHV)/acid value (AV)) is dispersed in an aqueous medium, to form a core-shell structure—i.e., to aggregate shell particles on the surface of core particles-enhances the propensity and uniformity of shell particle aggregation on the core particles, resulting in the production of toners with excellent mechanical durability. Specifically, it is as follows.
In the production of toner with a core-shell structure, achieved by aggregating shell particles on the surface of core particles, resin emulsion containing shell particles is dispersed into a liquid dispersion containing dispersed core particles to induce aggregation, utilizing the collision energy of particles through stirring, heat energy from heating, and an aggregating agent such as an inorganic metal salt or surfactant. The properties of the resin constituting the shell particles not only affect the stability of the emulsion and the aggregation with core particles but also influence adhesion with core particles during the heating fusion to form the shell layer.
Representative characteristics of the resin constituting the shell particles include acid value (AV), hydroxyl value (OHV), hydrophilicity/hydrophobicity, compatibility with solvents, and melt viscosity. Among these, it has been found that the ratio of hydroxyl value (OHV) to acid value (AV) in the resin constituting the shell particles being 0.20 to 0.60 enhances the aggregation of shell particles towards core particles, leading to uniform aggregation and distribution on the surface of core particles (uniform aggregation), and enables the formation of the shell layer without detachment of the shell particles during heating fusion. This ratio (OHV/AV) can be controlled by using a trivalent or tetravalent alcohol having a backbone of a linear or branched saturated fatty acid with a carbon number of 4 to 6 as the alcohol component in the resin.
The present disclosure is described in detail below.
The polyester resin emulsion of the present disclosure for toner is resin particles(S) containing polyester resin (A) that are dispersed in an aqueous medium. The polyester resin emulsion may optionally contain other resins and other components.
The resin particles(S) contain polyester resin (A) and other optional components.
The polyester Resin (A) is obtained by polycondensating an alcohol component with a carboxylic acid and may optionally contain other alcohol components, repeating units derived from polyethylene terephthalate (PET), and other components.
The alcohol component mentioned above includes tri- or tetra-functional alcohols with a backbone of linear or branched saturated fatty acids containing 4 to 6 carbon atoms.
In this specification, the term “alcohol” may be used simply to refer to the “tri- or tetra-functional alcohols with a backbone of linear or branched saturated fatty acids containing 4 to 6 carbon atoms. Any alcohol not falling under the category of “tri- or tetra-functional alcohols with a backbone of linear or branched saturated fatty acids containing 4 to 6 carbon atoms” may be termed as “other alcohols.
In this specification, “straight-chain” refers to a structure indicating a carbon chain (also referred to as main chain) connected by the minimum number of bonds between two oxygen atoms derived from hydroxyl groups in the monomer units of the alcohol component, which are randomly selected. This structure excludes carbon-carbon bonds other than the main chain.
In this specification, “branched-chain” refers to a structure indicating carbon-carbon bonds other than the main chain.
The polyester resin (A), which contains, as the alcohol component, a tri- or tetra-functional alcohol with a backbone of a linear or branched saturated fatty acid containing 4 to 6 carbon atoms can control the hydroxyl value (OHV) of the polyester resin (A) and enhance the aggregation and adhesiveness to core particles.
As for the alcohol, there are no particular restrictions as long as it is a tri- or tetra-functional alcohol with a backbone of a linear or branched saturated fatty acid containing 4 to 6 carbon atoms. It can be appropriately selected depending on the purpose. For example, tri-functional aliphatic alcohols with 4 to 6 carbon atoms or tetra-functional aliphatic alcohols with 4 to 6 carbon atoms can be listed.
Specific examples of tri-functional aliphatic alcohols with 4 to 6 carbon atoms include, but are not limited to, 1,2,3-butanetriol, 1,2,4-butanetriol, trimethylolethane, 1,2,3-pentanetriol, 1,2,4-pentanetriol, 1,2,5-pentanetriol, 1,3,5-pentanetriol, 2,3,4-pentanetriol, trimethylolpropane, 1,2,3-hexanetriol, 1,2,6-hexanetriol, 1,3,5-hexanetriol, and 2-isopropylpropane-1,2,3-triol.
Specific examples of tetra-functional aliphatic alcohols with 4 to 6 carbon atoms include, but are not limited to, pentaerythritol, 1,2,3,4-butanetetraol, 1,2,3,4-pentanetetraol, 1,2,3,5-pentanetetraol, 1,2,4,5-pentanetetraol, 1,2,4,5-hexanetetraol, and 1,2,5,6-hexanetetraol. These diols can be used alone or in combination.
The proportion of the alcohol is not particularly limited and can be suitably selected to suit to a particular application. It is preferable that the alcohol content in the polyester resin (A) be from 0.5 mol percent to 10 mol percent, with a more preferable range being from 2 mol percent to 5 mol percent, relative to the total amount of alcohol component in the polyester resin (A).
When the proportion of the alcohol is 0.5 mol percent or more to the total amount of alcohol component in the polyester resin (A), it can adequately resolve issues such as insufficient aggregation of shell particles to core particles, resulting in an increase in the number of shell particles unincorporated into the shell layer.
To the contrary, when the proportion of the alcohol is 10 or less mol percent relative to the total amount of alcohol component in the polyester resin (A), it can effectively resolve issues such as an increased branched chain of the polyester resin (A). This increase raises a concern about reduced melt viscosity of the shell layer in toners, which in turn leads to inadequate heat resistance and hot offset resistance.
Carboxylic acid is not particularly limited and can be suitably selected depending on the purpose.
Specific examples include, but are not limited to, aliphatic di carboxylic acids or their anhydrides such as oxalic acid, adipic acid, succinic acid, azelaic acid, dodecanedioic acid, maleic acid, citraconic acid, itaconic acid, alkene succinic acid, and fumaric acid; polyfunctional aliphatic carboxylic acids or their anhydrides with three or more carboxyl groups such as 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxy-2-methyl-2-methylenepropane, tetra(methylenecarboxy)methane, 1,2,7,8-octanetetracarboxylic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid; polyfunctional aromatic carboxylic acids with three or more carboxyl groups such as trimellitic acid, pyromellitic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, and their anhydrides and partial lower alkyl esters.
These dicarboxylic acids can be used alone or in combination.
The method of polycondensation between the alcohol component and the carboxylic acid component is not particularly limited and can be suitably selected depending on the purpose. One such polycondensation method can be conducted at a temperature ranging from 180 to 250 degrees C. under an inert gas atmosphere and in the presence of an esterification catalyst.
The esterification catalyst is not particularly limited and can be suitably selected to suit to a particular application. It includes, for example, titanium compounds and tin (II) compounds not having Sn—C bonds.
These esterification catalysts can be used alone or in combination.
The titanium compounds are not particularly limited and can be suitably selected depending on the purpose.
Specific examples include, but are not limited to, titanium isopropylate bis-triethanolamine, titanium isopropylate bis-diethanolamine, titanium pentylate bis-triethanolamine, titanium dietholate bis-triethanolamine, titanium hydroxyoctylate bis-triethanolamine, titanium stearate bis-triethanolamine, titanium triisopropylate triethanolamine, titanium monopropylate tris(triethanolamine), tetra-n-butyl titanate, tetrapropyl titanate, tetra-stearyl titanate, tetra-milistyl titanate, tetra-octyl titanate, dioctyl dihydroxyoctyl titanate, and dimilistyl dioctyl titanate.
Among these, titanium compounds with Ti—O bonds are preferable due to their high activity and ability to reduce the proportion of low molecular weight components of polyester resins. Compounds with alkoxyl, alkenyl oxy, or acyl oxy groups, totaling 1 to 28 carbon atoms, are even more preferable.
The content of the titanium compounds is not particularly limited and can be suitably selected depending on the purpose. The content preferably ranges from 0.01 to 1.0 part by mass, with a preference for 0.1 to 0.5 parts by mass, relative to the total amount of 100 parts by mass of the alcohol component and the carboxylic acid component. This range helps to control the reaction speed of polymerization and ensures the quality of polyester resins.
As for tin (II) compounds not having Sn—C bonds, there are no specific restrictions, and they can be suitably selected depending on the purpose. Tin (II) compounds with Sn—O bonds or Sn—X bonds (where X represents a halogen atom) are preferable, with tin (II) compounds having Sn—O bonds being even more preferable.
Specific examples of tin (II) compounds having Sn—O bonds include, but are not limited to, carboxylic acid tin (II) compounds with carbon numbers ranging from 2 to 28, such as stannous oxalate, stannous acetate, stannous octanoate, stannous 2-ethylhexanoate, stannous laurate, stannous stearate, and stannous oleate; alkoxyl tin (II) compounds with carbon numbers ranging from 2 to 28, such as octyloxyl tin (II), lauryloxyl tin (II), stearyloxyl tin (II), and oleyloxyl tin (II); tin oxide (II); and tin sulfate (II).
Specific examples of tin (II) compounds having Sn—X bonds include halogenated tin (II) compounds such as tin (II) chloride and tin (II) bromide.
The content of the tin (II) compounds is not particularly limited and can be suitably selected depending on the purpose. The content preferably ranges from 0.01 to 1.0 part by mass, with a preference for 0.1 to 0.5 parts by mass, relative to the total amount of 100 percent by mass of the alcohol component and the carboxylic acid component. This range helps to control the reaction speed of polymerization and ensures the quality of polyester resins.
In the case of using both the titanium compounds and the tin (II) compounds in combination, the total content of the titanium compounds and the tin (II) compounds is not particularly limited and can be suitably selected depending on the purpose. The content of the titanium compounds and tin (II) compounds is not particularly limited and can be suitably selected depending on the purpose. The content preferably ranges from 0.01 to 1.0 part by mass, with a preference for 0.1 to 0.5 parts by mass, relative to the total amount of 100 parts by mass of the alcohol component and the carboxylic acid component. This range helps to control the reaction speed of polymerization and ensures the quality of polyester resins.
In the polyester resin (A) of the present disclosure, in addition to the alcohol mentioned above, other alcohols may also be included.
These other alcohols are not particularly limited and can be suitably selected depending on the purpose.
Specific examples include, but are not limited to, aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol; diols with oxyalkylene groups such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; alicyclic diols such as 1,4-cyclohexanedimethanol, 1,4-sorbitan, hydrogenated bisphenol A; adducts of alkylene oxides such as ethylene oxide, propylene oxide, or butylene oxide with the alicyclic diols; bisphenols such as bisphenol A, bisphenol F, bisphenol S; adducts of alkylene oxides such as alkylene oxides such as ethylene oxide, propylene oxide, or butylene oxide with the bisphenols; tri- or higher alicyclic alcohols such as heptanetriol, octanetriol, decanetriol, sorbitol, dipentaerythritol; polyphenols such as trisphenol, phenol novolak, cresol novolak; adducts of alkylene oxide such as ethylene oxide, propylene oxide, and butylene oxide with the polyphenols.
Among these, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 2,3-butanediol are preferable.
By using these diols as other alcohol components in the polyester resin (A), it is possible to form a shell layer with excellent balance between low-temperature fixability and mechanical durability, resulting in good aggregation and uniformity of shell particles on core particles, making it preferable.
Additionally, from the perspective of reducing carbon dioxide emissions when the resultant toner is ultimately incinerated, it is more preferable for these diols to be derived from biomass.
Furthermore, in this specification, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 2,3-butanediol may be referred to as diols (D).
These dicarboxylic acids can be used alone or in combination.
In the case of 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 2,3-butanediol as the other alcohols, it is preferable that at least one of these diols selected from among them be present in the total alcohol component in an amount of 30 mol percent or more, more preferably 50 mol percent or more, and even more preferably 80 mol percent or more. In other words, it is preferable that the total content of these diols be 30 or more mol percent relative to the total amount of the alcohol component in the polyester resin (A), more preferably 50 or more mol percent, and even more preferably 80 or more mol percent.
When the total content of 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 2,3-butanediol is 30 mol or more percent by mol relative to the total amount of the alcohol component in the polyester resin (A), it is suitable to achieve good low-temperature fixability, mechanical durability, and environmental impact reduction.
Repeating Unit Derived from Polyethylene Terephthalate (PET)
The polyester resin (A) of the present disclosure may also contain repeating units derived from the condensate of terephthalic acid and ethylene glycol, known as polyethylene terephthalate (PET), in addition to the above components. In this specification, the “repeating units derived from polyethylene terephthalate (PET)” may be referred to as “PET repeating units.”
The polyester resin (A) containing these PET repeating units exhibits excellent mechanical durability, making it suitable for application in the shell layer of toners with a core-shell structure. Furthermore, from the perspective of reducing environmental impact such as reducing the use of petroleum resources, it is preferable to use retrieved PET, also known as recycled PET, as the PET material.
The polyester resin (A) containing the aforementioned PET repeating unit can be obtained by subjecting the polyester resin (A) materials to condensation polymerization during ester exchange reactions.
As mentioned above, in the conventional method of introducing PET into shell particles to form a shell layer, the hydrophobicity of the shell particles decreases, leading to reduced aggregation of core and shell particles, thus making it challenging to achieve a uniform shell layer on the surface of the core particles. On the other hand, the polyester resin emulsion for toner according to the present disclosure maintains moderate hydrophobicity because the ratio (OHV/AV) of the polyester resin (A) is 0.20 to 0.60. Thus, a condition is created where heteroaggregation with core particles occurs preferentially, and even when PET is introduced into the shell particles, it does not impair the aggregation or adhesion with the core particles, making it preferable.
There is no specific limitation on the content of the PET repeating unit, and it can be appropriately selected according to the purpose. It is preferable that the content of the PET repeating unit be 10 to 70 percent by mass of the total amount of the polyester resin (A), with a more preferable range being 30 to 60 percent by mass.
The inclusion of the PET repeating unit at 10 or more percent by mass of the total amount of the polyester resin (A) is preferable to achieve excellent mechanical durability.
On the other hand, the inclusion of the PET repeating unit at 70 or less percent by mass of the total amount of the polyester resin (A) is preferable for improved solubility in organic solvents and low-temperature fixing properties.
In the present disclosure, it is preferable that the ratio of hydroxyl value (OHV) of the polyester resin (A) to its acid value (AV) (OHV/AV) be 0.20 to 0.60, with a more preferable range being 0.35 to 0.50. Furthermore, in this specification, the ratio of hydroxyl value (OHV) of the polyester resin (A) to its acid value (AV) is also referred to as OHV/AV ratio.
An OHV/AV ratio between 0.20 and 0.60 is preferable for addressing issues such as poor aggregation of shell particles on core particles, inability to uniformly distribute shell particles on the surface of core particles, occurrence of defects in the formed shell layer, increase in the proportion of shell particles that do not aggregate with core particles, and resulting deposition of such non-aggregating shell particles as fines in the toner, which can lead to degradation of toner quality. Additionally, it is preferable for shell particles to adhere more firmly to core particles during the formation of the shell layer by heating and melting the shell particles, making the shell layer less prone to peeling.
There is no specific limit on the acid value (AV) of the polyester resin (A), and it can be appropriately selected according to the purpose. It is preferable that the AV be 15 to 30 mg KOH/g, with a more preferable range being 18 to 25 mg KOH/g.
An acid value (AV) of 15 or higher mg KOH/g is preferable to stabilize the emulsion, resolving the problem such as difficulty in emulsification, and improve the aggregation of shell particles on core particles.
When the acid value (AV) is 30 or less mg KOH/g, the charging stability of the toner against environmental changes is improved, and the aggregation of shell particles on core particles becomes better, making it preferable.
The method of measuring the acid value (AV) of the aforementioned polyester resin
(A) is not particularly restricted and can be selected as appropriate depending on the purpose. For example, it can be measured using the method outlined in JIS K0070 format (Test methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products).
The hydroxyl value (OHV) of the aforementioned polyester resin (A) is not particularly restricted and can be selected as appropriate depending on the purpose. When the acid value (AV) is between 15 mg KOH/g and 30 mg KOH/g, the hydroxyl value (OHV) is preferably between 3 mg KOH/g and 18 mg KOH/g.
The method for measuring the hydroxyl value (OHV) of the aforementioned polyester resin (A) is not particularly restricted and can be selected as appropriate depending on the purpose. For example, it can be measured using the method outlined in JIS K0070 format mentioned above.
The glass transition temperature (Tg) of the aforementioned polyester resin (A), determined by the second temperature rising (heating) of differential scanning calorimetry (DSC), is not particularly restricted and can be selected as appropriate depending on the purpose. The glass transition temperature (Tg) is preferably between 50 degrees C. and 80 degrees C., with a more preferred range being between 60 degrees C. and 75 degrees C. Additionally, in this specification, the “glass transition temperature determined by the second heating in differential scanning calorimetry (DSC)” may be referred to as “Tg2nd”.
A Tg2nd of the polyester resin (A) is at or above 60 degrees C. is preferable to improve the heat resistance of toner during storage.
When the Tg2nd of the polyester resin (A) is at or below 75 degrees C., it is preferable to improve the low-temperature fixability of toner.
There is no specific limitation on the method for measuring the glass transition temperature (Tg) of the aforementioned polyester resin (A). For example, it can be measured using a differential scanning calorimeter (DSC) (e.g., Q-200 by TA Instruments). One such measurement method for the glass transition temperature (Tg) is as follows.
A total of 5.0 mg of the polyester resin (A) is placed in an aluminum sample pan and placed on the holder unit in an electric furnace. A total of 10 mg of alumina is placed in an aluminum sample pan as a reference. Under a nitrogen atmosphere, the reference is heated from 0 to 150 degrees C. at a heating rate of 10 degrees/minute (first heating), then cooled from 150 to 0 degrees C. at a cooling rate of 10 degrees/minute (cooling process), and heated again from 0 to 150 degrees C. at a heating rate of 10 degrees/minute (second heating). The endothermic and exothermic change during these processes is measured and the graph of temperature against the amount of heat flow is plotted to create a DSC curve, followed by analysis using the analysis program in the Q-200 system. The DSC curve for the second heating cycle is selected. The glass transition temperature of the polyester resin (A) is determined from the intersection of the baseline extension of the DSC curve at temperatures lower than the enthalpy relaxation and the tangent indicating the maximum slope during enthalpy relaxation.
For the weight average molecular weight (Mw) of the aforementioned polyester resin (A) measured by gel permeation chromatography (GPC), there are no specific limitations, and it can be chosen as appropriate depending on the purpose. It is preferable for Mw to be at or above 0.8×104 and at or below 1×105, with a more preferred range being at or above 1×104 and at or below 5×104. In this specification, “weight average molecular weight (Mw) measured by gel permeation chromatography (GPC)” may simply be referred to as “weight average molecular weight (Mw).”
A weight average molecular weight (Mw) of the polyester resin (A) of 0.8×104 or above is preferable to improve the mechanical durability of toner.
When the weight average molecular weight (Mw) of the polyester resin (A) is 5×104, it is preferable to improve the low-temperature fixing properties of toner.
There are no specific limitations on the method for measuring the weight average molecular weight (Mw), but it can be measured using a gel permeation chromatography (GPC) measuring device (for example, HLC-8220GPC by Tosoh Corporation). One such measuring method for the weight average molecular weight (Mw) is as follows.
The column used is a TSKgel SuperHZM-H 15 cm 3-column (available from Tosoh Corporation). The polyester resin (A) to be measured is dissolved in tetrahydrofuran (THF) (containing stabilizers, available from Fujifilm Wako Pure Chemical Corporation) to prepare a 0.15 percent by mass solution. After filtration through a 0.2 μm filter, the filtrate is used as the sample. A total of 100 μl of the THF sample solution is injected into the measuring device, and measurements are conducted at a flow rate of 0.35 ml/min at a temperature of 40 degrees C. The molecular weight is calculated using a calibration curve created by monodisperse polystyrene standard samples. For the polystyrene standard samples, THE solutions (solutions A to C) of three types of monodisperse polystyrene standard samples from the Showdex STANDARD series available from Showa Denko Co., Ltd. are prepared. Measurements are conducted under the above conditions, and the retention time of the peak top is used to create the calibration curve for the light scattering molecular weight of the monodisperse polystyrene standard samples. A refractive index (RI) detector is used as a detector.
The volume-average particle size of the resin particles(S) in the polyester resin emulsion for toner is not specifically restricted and can be chosen appropriately depending on the purpose. It is preferable that the median diameter (D50) be between 0.05 μm and 0.8 μm, with a more preferred range being between 0.1 μm and 0.5 μm, and even more preferably between 0.15 μm and 0.3 μm.
A volume-average particle size of the resin particles(S) at or above 0.05 μm in median diameter (D50) is preferable to achieve efficient aggregation of shell particles on core particles, enabling the formation of a shell layer with sufficient thickness on the toner surface.
A volume-average particle size of the resin particles(S) is at or below 0.8 μm in median diameter (D50) is preferable to achieve uniform aggregation of shell particles on core particles, enabling the formation of a sufficiently uniform shell layer.
The method of measuring the median diameter (D50) is not particularly limited and can be suitably selected to suit to a particular application. One way of measuring is to use a laser diffraction particle size analyzer LA-920 (available from HORIBA, Ltd.).
The polyester resin emulsion for toner may optionally furthermore include other resins in addition to the polyester resin (A) as long as it does not have an adverse impact on the effects of the present disclosure.
There is no specific limitation to the other resins and it can be suitably selected to suit to a particular application.
Specific examples include, but are not limited to, styrene polymers and substituted styrene polymers such as polystyrene, poly-p-styrene, and polyvinyltoluene; styrene copolymers such as styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-methyl acrylate copolymers, styrene-ethyl acrylate copolymers, styrene-methacrylate copolymers, styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-butyl methacrylate copolymers, styrene-α-methyl chloromethacrylate copolymers, styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isopropyl copolymers, and styrene-maleic acid ester copolymers; and other resins such as polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyesters, epoxy resins, polyurethane resins, polyvinyl butyral resins, polyacrylic resins, rosin, modified rosins, terpene resins, phenol resins, aliphatic or aromatic hydrocarbon resins, aromatic petroleum resins, and the resins specified above which are modified to have a functional group reactive with an active hydrogen group such as an isocyanate group.
These can be used alone or in combination.
The proportion of the solid portion in the polyester resin emulsion for toner is not particularly limited and can be suitably selected to suit to a particular application. For example, it is preferably from 5 to 50 percent by mass and more preferably from 30 to 45 percent by mass. When the solid content concentration in the polyester resin emulsion for toner is 5 percent by mass or more, the aggregation efficiency of shell particles to core particles is improved, thereby enhancing the productivity of the toner, making it suitable.
A solid content concentration in the polyester resin emulsion for toner of 50 or less percent by mass enhances the emulsion stability, making it suitable.
The method of measuring the solid content concentration in the polyester resin emulsion for toner is not particularly restricted and can be selected appropriately according to the purpose. For example, it can be determined by drying the emulsion sample weighed on an aluminum cup in a constant temperature bath set at 150 degrees C. for 3 hours and weighing the emulsion sample before and after drying.
As will be described in detail later, it is preferable that the polyester resin emulsion for toner include a shell resin emulsion used in the production of toners having a core-shell structure including core particles containing a binder resin and shell particles covering the core particles.
The method of manufacturing the polyester resin emulsion for toner is not particularly restricted and can be chosen as appropriate according to the purpose. For example, methods such as shear emulsification, phase inversion emulsification, and other known dispersion methods can be employed.
As an example of the shear emulsification method, the polyester resin (A) dissolved in an organic solvent is added to an aqueous medium, followed by dispersing with such mechanical shear forces as low-speed shear, high-speed shear, frictional shear, high-pressure jet, ultrasonic homomixer, homogenizer, ball mill with media, sand mill, and Dyno mill.
An example of the phase inversion emulsification method involves dissolving the polyester resin (A) in an organic solvent and then adding an aqueous medium to induce phase inversion.
Of these methods, the phase inversion emulsification method is preferred for producing emulsions that are homogeneous with sharp particle size distribution.
The phase inversion emulsification method involves adding an aqueous medium to the resin solution obtained by dissolving the polyester resin (A) in an organic solvent to induce phase inversion.
The organic solvent used in the phase inversion emulsification method is not particularly restricted and can be chosen appropriately according to the purpose. For example, ethanol, isopropanol, isobutanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, dibutyl ether, tetrahydrofuran, dioxane, methyl acetate, ethyl acetate, isopropyl acetate, toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, and dichloroethylene, can be listed.
Among these, methyl ethyl ketone, ethyl acetate, and isopropyl acetate are preferable from the perspectives of solvent removal efficiency and solubility of polyester resin.
These can be used alone or in combination.
It is preferable that the emulsion consisting of the aforementioned resin solution and the aqueous medium preferably be rapidly purged of the organic solvents from the perspective of dispersion stability. There are no particular restrictions on the methods of removing the organic solvent, and a known solvent removal method can be selected depending on the purpose. It includes, for example, a method of gradually heating the emulsion with stirring to evaporate the organic solvents within the system, a method of spraying the emulsion while stirring into a dry atmosphere such as air or nitrogen to remove the organic solvents within the system, and a method of reducing the pressure while stirring the emulsion to evaporate the organic solvents within the system.
These can be used alone or in combination.
The aqueous medium used in the phase inversion emulsification method is not particularly restricted and can be appropriately selected depending on the purpose. For example, water or mixtures of water with organic solvents miscible with water can be used.
There are no specific restrictions on the content of the aqueous medium, and it can be selected appropriately depending on the purpose. The amount of the aqueous medium is preferably 80 to 150 parts by mass per 100 parts by mass of the resin solution.
In the phase inversion emulsification method, there are no specific restrictions on the rate of addition of the aqueous medium from the beginning of phase inversion of the resin solution until its completion. It can be selected appropriately depending on the purpose. Preferably, the rate of addition is 0.1 to 60 parts by mass per minute per 100 parts by mass of the resin solution, and more preferably 1 to 3 parts by mass per minute.
A rate of addition of the aqueous medium of 0.1 or more parts by mass per minute to 100 parts by mass of the resin solution is preferable to improve the productivity of toner.
When the rate of addition of the aqueous medium is 60 parts by mass per minute to 100 parts by mass of the resin solution, it is preferable to achieve a sharp particle size distribution and good aggregation of shell particles with core particles, thus allowing for the formation of a uniform shell layer.
In the phase inversion emulsification method, additives such as neutralizing agents, surfactants, and polymeric protection colloids can be added to the resin solution or aqueous medium without an adverse impact on the effects of the present disclosure.
The neutralizing agent is not particularly limited and can be suitably selected to suit to a particular application. One such example is a basic substance.
Specific examples of such basic substances include, but are not limited to, ammonia, trimethylamine, ethylamine, diethylamine, triethylamine, diethanolamine, triethanolamine, tributylamine, lithium hydroxide, sodium hydroxide, and potassium hydroxide.
Among these, ammonia and sodium hydroxide are preferably used to ensure the quality of the emulsion.
The degree of neutralization (r), which is the molar ratio of the neutralizing agent to the acid value (AV) of the polyester resin (A), can be selected appropriately depending on the purpose without specific restrictions. It is preferable for the degree of neutralization to be 30 to 150 percent, with more preferable values ranging from 60 to 100 percent.
When the degree of neutralization (r) is 30 percent or more, it is suitable to promote phase inversion emulsification, resulting in the formation of uniform particle size emulsions.
When the degree of neutralization (r) is 150 percent or less, it is suitable to facilitate phase inversion emulsification.
The amount of neutralizing agent used is not particularly restricted and can be appropriately selected depending on the purpose. For example, it can be determined by the following equation (1). In the equation below, AV represents the acid value of the resin (mg KOH/g), M represents the amount of resin used (g), and r represents the degree of neutralization (percent).
The choice of surfactant is not particularly restricted and can be appropriately selected depending on the purpose.
Specific examples include, but are not limited to, anionic surfactants such as alkylbenzene sulfonates, alpha-olefin sulfonates, and phosphate esters; amine salt types such as alkylamine salts, aminoalcohol fatty acid derivatives, polyamine fatty acid derivatives, and imidazolines; cationic surfactants such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkylbenzyldimethylammonium salts, pyridinium salts, alkylisoquinolinium salts, and benzethonium chloride; nonionic surfactants such as fatty acid amide derivatives and polyhydric alcohol derivatives; and zwitterionic surfactants such as alanine, dodecyl dimethyl glycine, di(octylaminoethyl) glycine, and N-alkyl-N,N-dimethylammonium betaines.
The polymeric protection colloids are not particularly limited and can be suitably selected to suit to a particular application.
Specific examples include, but are not limited to, polymers and copolymers prepared using monomers, for example, acids (e.g., acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, and maleic anhydride), (meth)acrylic monomers having a hydroxyl group (e.g., β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, γ-hydroxypropyl acrylate, γ-hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl acrylate, 3-chloro-2-hydroxypropyl methacrylate, diethylene glycolmonoacrylic acid esters, diethylene glycolmonomethacrylic acid esters, glycerinmonoacrylic acid esters, N-methylolacrylamide and N-methylolmethacrylamide); vinyl alcohol and its ethers (e.g., vinyl methyl ether, vinyl ethyl ether and vinyl propyl ether), esters of vinyl alcohol with a compound having a carboxyl group (i.e., vinyl acetate, vinyl propionate and vinyl butyrate); acrylic amides (e.g., acrylamide, methacrylamide, and diacetoneacrylamide) and their methylol compounds, acid chlorides (e.g., acrylic acid chloride and methacrylic acid chloride); monomers having a nitrogen atom or a heterocyclic ring having a nitrogen atom (e.g., vinyl pyridine, vinyl pyrrolidone, vinyl imidazole, and ethylene imine); polyoxyethylene compounds (e.g., polyoxyethylene, polyoxypropylene, polyoxy ethylene alkyl amines, polyoxypropylene alkyl amines, polyoxy ethylenealkyl amides, polyoxypropylene alkyl amides, polyoxyethylene nonylphenyl ethers, polyoxyethylene lauryl phenyl ethers, polyoxyethylene stearylphenyl esters, and polyoxyethylene nonylphenyl esters), and cellulose compounds, for example, methyl cellulose, hydroxyethyl cellulose, and hydroxy propyl cellulose.
The resin particles (T) of the present disclosure are resin particles (T) having a core-shell structure including a core particle containing a binder resin and a shell particle covering the core particle, the shell particle being formed from a polyester resin emulsion for toner. The resin particles (T) may optionally contain additives and other components.
The toner of the present disclosure is a toner having a core-shell structure including a core particle containing a binder resin and a shell particle covering the core particle, the shell particle being formed from a toner polyester resin emulsion. The toner may optionally contain additives and other components.
It should be noted that the “polyester resin emulsion for toner” is the same as described in the item “Polyester Resin Emulsion for Toner” above, so further explanation is omitted.
Furthermore, the resin particles(S) contained in the polyester resin emulsion for toner and the resin particles (T) containing the polyester resin emulsion for toner are different.
The core-shell structure, for example, may denote a structure (1) where resin particles forming the shell are distributed on the outermost surface of core particles containing a binder resin, thereby covering the surface of the core particles, or a structure (2) where a resin-based shell layer is formed on the outermost surface of core particles containing a binder resin, also covering the surface of the core particles.
Of the two, the structure (2) is preferable, which offers superior homogeneity, heat resistance, and mechanical durability of the toner, with the added advantage of the shell layer being less prone to detachment due to stress.
In the resin particles (T) and toner with a core-shell structure, it may not be necessary for the surface of the core particles to be completely covered by the shell particles or shell layer, the coverage area is preferably 90 or more percent of the total surface area of the core particles to achieve toner homogeneity, heat resistance, and mechanical durability.
The core particles contain a binder resin and may optionally include crystalline resins as fixing aids, colorants, release agents, and charge control agents.
There is no specific limit to the binder resin and it can be suitably selected to suit to a particular application.
Specific examples include, but are not limited to, styrene polymers and substituted styrene polymers such as polystyrene, poly-p-styrene, and polyvinyltoluene; styrene copolymers such as styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-methyl acrylate copolymers, styrene-ethyl acrylate copolymers, styrene-methacrylate copolymers, styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-butyl methacrylate copolymers, styrene-α-methyl chloromethacrylate copolymers, styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isopropyl copolymers, and styrene-maleic acid ester copolymers; and other resins such as polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyesters, epoxy resins, polyurethane resins, polyvinyl butyral resins, polyacrylic resins, rosin, modified rosins, terpene resins, phenol resins, aliphatic or aromatic hydrocarbon resins, aromatic petroleum resins, and the resins specified above which are modified to have a functional group reactive with an active hydrogen group.
These can be used alone or in combination.
The binder resin is preferably supplemented with at least one type of amorphous polyester resin (B) to enhance adhesion between core and shell particles and improve the toner's mechanical durability. There are no specific restrictions regarding the polyester resin in the amorphous polyester resin (B), and it can be appropriately selected depending on the purpose. For instance, the same types of polyester resin as those described in the Polyester Resin (A) section above can be utilized.
The crystalline resin is not particularly limited and can be suitably selected to suit to a particular application as long as it has crystallinity. Examples include, but are not limited to, polyester resin, polyurethane resin, polyurea resin, polyamide resin, polyether resin, vinyl resin, and modified crystalline resin. Among these, polyester resin is preferred for its excellent combination of low-temperature fixing capability and heat resistance.
These can be used alone or in combination.
The crystalline resin is preferably melted near the fixing temperature of the toner. Including this crystalline resin in the toner ensures that it melts at the fixing temperature, becoming compatible with the binder resin. This enhances the toner's sharp melting properties and provides excellent low-temperature fixing capability, which is preferable.
There are no specific restrictions on the melting point of the crystalline resin. It is preferably between 60 degrees C. and 100 degrees C.
A melting point of the crystalline resin of 60 degrees C. or above facilitates its melting at low temperatures, ensuring good heat resistance of the toner.
When the melting point of the crystalline resin is at or below 100 degrees C., it is suitable to improve the toner's low-temperature fixability.
The colorant has no particular limitation and can be suitably selected to suit to a particular application.
Specific examples include, but are not limited to, carbon black, Nigrosine dyes, black iron oxide, Naphthol Yellow S, Hansa Yellow (10G, 5G and G), Cadmium Yellow, yellow iron oxide, loess, chrome yellow, Titan Yellow, polyazo yellow, Oil Yellow, Hansa Yellow (GR, A, RN and R), Pigment Yellow L, Benzidine Yellow (G and GR), Permanent Yellow (NCG), Vulcan Fast Yellow (5G and R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazane Yellow BGL, isoindolinone yellow, red iron oxide, red lead, orange lead, cadmium red, cadmium mercury red, antimony orange, Permanent Red 4R, Para Red, Fire Red, p-chloro-o-nitroaniline red, Lithol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine BS, Permanent Red (F2R, F4R, FRL, FRLL and F4RH), Fast Scarlet VD, Vulcan Fast Rubine B, Brilliant Scarlet G, Lithol Rubine GX, Permanent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, BON Maroon Light, BON Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarine Lake, Thioindigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, polyazo red, Chrome Vermilion, Benzidine Orange, perynone orange, Oil Orange, cobalt blue, cerulean blue, Alkali Blue Lake, Peacock Blue Lake, Victoria Blue Lake, metal-free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS and BC), Indigo, ultramarine, Prussian blue, Anthraquinone Blue, Fast Violet B, Methyl Violet Lake, cobalt violet, manganese violet, dioxane violet, Anthraquinone Violet, Chrome Green, zinc green, chromium oxide, viridian, emerald green, Pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalocyanine Green, Anthraquinone Green, titanium oxide, zinc oxide, and lithopone.
These can be used alone or in combination.
The content of the colorant is not particularly restricted and can be appropriately selected depending on the purpose. It is preferable that the content of the colorant is from 1 to 15 percent by mass of the total amount of the resin particles (T) or the total amount of the toner, and more preferably from 3 to 10 percent by mass.
When the content of the colorant is at least 1 percent by mass of the total amount of the resin particles (T) or the total amount of the toner, the coloring power of the toner is improved, making it suitable.
A content of the colorant of 15 or less percent by mass of the total amount of the resin particles (T) or the total amount of the toner exhibits good dispersion state of the pigment in the toner, leading to good coloring power and charging properties of the toner, making it suitable. The colorant and the resin for master batch can be used in combination as a master batch.
There is no specific limitation to the resin for master batch and it can be suitably selected to suit to a particular application.
Specific examples thereof include, but are not limited to, styrene or substituted polymers thereof, styrene-based copolymers, polymethyl methacrylate resins, polybutyl methacrylate resins, polyvinyl chloride resins, polyvinyl acetate resins, polyethylene resins, polypropylene resins, polyesters resins, epoxy resins, epoxy polyol resins, polyurethane resins, polyamide resins, polyvinyl butyral resins, polyacrylic resins, rosin, modified rosins, terpene resins, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffin, and paraffin.
These can be used alone or in combination.
The release agent is not particularly limited and can be suitably selected to suit to a particular application.
Specific examples include, but are not limited to, carnauba wax, rice wax, montan wax, trimethylolpropane tribehenate, pentaerythrityl tetrabehenate, pentaerythrityl diacetate dibehenates, glyceryl tribehenate, stearyl icosenoate, behenyl eicosylate, behenyl behenate, stearyl behenate, phenyl behenate, and stearyl stearate, among alkanic acid esters; polyalcohol esters such as trimellitic acid tristearate, and distearyl maleate; polyalkanoic acid amides such as dibehenylamide; polyalkyl amides such as trimellitic acid and tristearlyl amide; dialkyl ketones such as distearyl ketone; polyolefin waxes such as polyethylene wax, and polypropylene wax; and wax types such as paraffin wax, microcrystalline wax, and Sazol wax, which are long-chain hydrocarbons. Among these, wax types of alkanic acid esters are preferable.
These can be used alone or in combination.
The melting point of the release agent is not particularly restricted and can be appropriately selected depending on the purpose. It is from 40 to 160 degrees C., more preferably from 50 to 120 degrees C., and even more preferably from 60 to 90 degrees C.
When the melting point of the release agent is at least 40 degrees C., it is suitable for good heat resistance.
When the melting point of the release agent is at 160 degrees C. or below, the occurrence of cold offset during low-temperature fixing occurs less frequently, which is preferable.
The content of the release agent is not particularly limited and can be suitably selected to suit to a particular application. It is preferably 1 to 20 parts by mass to the entire mass of the resin particles (T) or the toner as a whole, more preferably 3 to 15 percent by mass, and even more preferably 3 to 7 parts by mass.
When the content of the release agent is 20 or less parts by mass to the entire mass of the entire of the resin particles (T) or the toner, it is suitable for improving the fluidity of the toner.
There is no specific limitation to the selection of the charge control agent and it can be suitably selected to suit to a particular application.
Specific examples include, but are not limited to, nigrosine dyes, triphenylmethane dyes, chrome containing metal complexes, chelate compounds of molybdic acid, Rhodamine dyes, alkoxyamines, quaternary ammonium salts, alkylamides, phosphor and compounds including phosphor, tungsten and compounds including tungsten, fluorine-containing activators, metal salts of salicylic acid and metal salts of salicylic acid derivatives.
The proportion of the charge control agent is not particularly limited and can be suitably selected to suit to a particular application. The number of parts of the release agent is preferably from 0.1 to 10 parts by mass and more preferably from 0.2 to 5 parts by mass to 100 parts of the resin particles (T) or the toner.
A content of the charge controlling agent of 10 or less parts by mass per 100 parts by mass of the resin particles (T) or the toner is preferable to improve the charging properties of the toner, thereby minimizing the decrease in developer fluidity and image density.
The volume average particle diameter (Dv) of the core particles is not particularly restricted and can be appropriately selected depending on the purpose. It is preferable for the median diameter (D50) to be from 4 to 7 μm to enhance particle size distribution, sharpness, and fine line reproducibility.
The method of measuring the median diameter (D50) is not particularly limited and can be suitably selected to suit to a particular application. One way of measuring is to use a laser diffraction particle size analyzer LA-920 (available from HORIBA, Ltd.).
The average circularity of the core particles is not particularly restricted and can be appropriately selected depending on the purpose. It is preferable for the circularity to be from 0.940 to 0.990 to enhance transfer efficiency, fine line reproducibility, and cleaning properties of toner residues on image bearers or transfer belts.
There are no specific restrictions on the method for measuring the average circularity of the core particles, and it can be appropriately selected depending on the purpose. The average circularity can be measured using equipment such as a flow-type particle image analyzer FPIA-3000 (available from Sysmex Corporation).
The method of manufacturing the core particles is not particularly restricted and can be appropriately selected depending on the purpose. For example, methods such as kneading pulverization and granulating particles in an aqueous medium, known as the so-called chemical method, can be used.
Specific examples of the chemical method of granulating toner particles in an aqueous medium include, but are not limited to, a suspension polymerization method, emulsification polymerization method, a seed polymerization method, and a dispersion polymerization method that manufacture a toner using a monomer as the initial material, a dissolution suspension method of dissolving a resin precursor and a resin followed by dispersion and/or emulsification in an aqueous medium, a phase change emulsification method of adding water to a solution containing a resin, a resin precursor, and a suitable emulsifier, and an agglomeration method of granulating particles having desired size by agglomerating the resin particles obtained by these methods which are dispersed in the aqueous medium followed by processes such as heating and melting.
Among these, the dissolution suspension method, phase inversion emulsification method, and aggregation method are preferable for easily handling polyester resins with excellent low-temperature fixability.
The core particles are preferably aqueous dispersions for aggregating with the toner polyester resin emulsion, and more preferably, these aqueous dispersions are obtained through chemical methods.
In the case of core particles obtained through the kneading pulverization method mentioned earlier, it is preferable to use core particles that have undergone sphericalization treatment and surface smoothing treatment by, for example, heating to form a uniform shell layer.
Core particles without any substances added such as additives and flowability improvers are preferable to aggregate shell particles on their surface.
The shell layer can be obtained by subjecting a polyester resin emulsion containing resin particles(S) to a process of aggregating onto the outermost surface of the core particles and subsequently heating and fusing.
The core particles and the shell particles (or shell layer) are preferably in a state where they adhere to each other, or in a state where they are not completely miscible with each other, with regions consisting only of core particles or shell particles (or shell layer).
The average thickness of the shell layer has no particular limit and can be suitably selected to suit to a particular application. For example, it is preferably from 50 to 500 nm and more preferably from 100 to 200 nm.
An average thickness of the shell layer at or above 50 nm enhances the protective function on the core particles, leading to improved heat resistance and mechanical durability, making it preferable.
On the other hand, with an average thickness of the shell layer at or below 500 nm, it becomes preferable for good low-temperature fixability.
There are no specific restrictions on the method of measuring the average thickness of the shell layer, and it can be chosen appropriately according to the purpose. One such method involves measuring using a transmission electron microscope (TEM) an ultrathinly sectioned material obtained by sectioning a sample of toner particles embedded in such a substance as epoxy resin with a microtome or ultramicrotome. In some cases, staining ultrathin sections with staining agents such as ruthenium tetroxide or osmium tetroxide makes the core-shell structure more visible, which is advantageous.
A specific method is as follows.
A sample of toner particles embedded in such a substance as epoxy resin is sectioned into ultrathin slices using an ultramicrotome. Its cross-section image is captured at a factor of 20,000 magnification using a transmission electron microscope (TEM) (JEM-2100F, available from JEOL Ltd.). The captured image is then imported into an image analysis device (LuzeX AP/available from Nileco), where the thickness of the shell layer is measured at five points for each of the 30 toner particles. The average thickness is then calculated from these measurements.
The volume average particle diameters (Dv) of the resin particles (T) and the toner are not particularly limited and they can be suitably selected to suit to a particular application. They are preferably from 3 to 10 μm, with 4 to 7 μm being more preferable, to produce high-quality images with excellent particle size distribution, sharpness, and fine line reproduction.
A volume average particle size (Dv) of the resin particles (T) and the toner at or above 3 μm is suitable to achieve good toner fluidity and transferability.
The ratio (Dv/Dn) of the volume average particle diameter (Dv) of the resin particles (T) and the toner to the number average molecular weight (Dn) of the resin particles (T) and the toner represents the particle size distribution of the resin particles (T) and the toner, with values closer to 1 indicating a sharp particle size distribution.
This ratio (Dv/Dn) is preferably 1.20 or less, with values of 1.15 or less being more preferable to enhance sharpness and fine line reproduction.
There are no particular restrictions on the method of measuring the volume average particle diameter (Dv) and number average molecular weight (Dn) of the resin particles (T) and the toner. It can be measured using, for example, a Coulter Multisizer III (aperture diameter 100 μm) (available from Beckman Coulter).
The average circularities of the resin particles (T) and the toner are not particularly limited and can be suitably selected according to the purpose. It is preferable to be from 0.940 to 0.990. Additionally, it is more preferable that the proportion of the resin particles (T) and the toner with an average circularity of from 0.960 to 0.985 and an average circularity below 0.940 is 15 or less percent by mass of the total amount of the resin particles (T) and the toner.
Toner with circularity within the above range, i.e., substantially spherical toner, is effective in achieving excellent transfer efficiency, forming high-resolution images with moderate density and reproducibility. Moreover, fine line images with less transfer voids can be obtained. This is because the smooth surface of the toner reduces contact points with the image bearer, decreasing toner voids and transfer defects to transfer materials.
When the average circularity of the resin particles (T) and the toner is 0.940 or above, it is preferable to achieve good transferability.
When the average circularity of the resin particles (T) and the toner is 0.990 or below, it is preferable for systems employing blade cleaning to solve an issue of poor cleaning that may occur on the photoconductor and transfer belt, resulting in image dirt. For example, minimal residual toner resulting from development or transfer with a low image area ratio causes no significant cleaning issues. However, in the case of high image area ratio color photographic images, toner of formed images untransferred due to defects such as paper feeding defects may accumulate on the photoconductor as residual toner, causing image fouling. Furthermore, problems may arise with contamination of the charging roller and other charging devices, leading to a decrease in their original charging capacity. The present disclosure can resolve these issues effectively.
There are no specific restrictions on the method for measuring the average circularity of the resin particles (T) and toner, and it can be appropriately selected depending on the purpose. The average circularity can be measured using equipment such as a flow-type particle image analyzer FPIA-3000 (available from Sysmex Corporation). Specifically, the circularity of each particle is calculated from the two-dimensional image area of each particle captured by a charge coupled diode (CCD) camera. The circularity of each particle is then summed, and the sum is divided by the total number of particles to obtain the average circularity. The circularity of each particle can be calculated by dividing the perimeter of a circle with the same projected area as the particle image by the perimeter of the particle's projected image.
There are no specific restrictions on the external additives, and they can be suitably chosen according to the purpose. Examples include, but are not limited to, inorganic particles, polymer-based particles, flow improver, and cleaning improvers.
Specific examples of such inorganic particulates include, but are not limited to, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, sand-lime, diatom earth, chromium oxide, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride.
The primary particle diameter of the inorganic fine particle is not particularly limited and can be suitably selected to suit to a particular application. For example, it is preferably from 5 nm to 2 μm and more preferably from 5 to 500 nm.
When the primary particle diameter of the inorganic particles is at or above 5 nm, it is preferable to minimize its embedding into the surface of toner particles caused by mechanical stress. When the primary particle diameter of the inorganic particles is at or below 2 μm, it is preferable to minimize detachment from toner particles.
In addition, the specific surface area of such inorganic particulates measured by a BET method is preferably from 20 to 500 m2/g.
The content of the inorganic particles is preferably from 0.01 to 5 percent by mass to the total amount of resin particles (T) and toner.
The fine polymer particles include, but are not limited to, polystyrene, methacrylates, and acrylates obtained by soap-free emulsion polymerization, suspension polymerization, or dispersion polymerization, and polycondensed particles such as silicone, benzoguanamine, and nylon, and polymer particles of thermocuring resin.
There is no particular limitation to the flow improver mentioned above and it can be suitably selected to suit to a particular application as long as it is surface-treated for enhancing hydrophobicity and can keep the fluidity and chargeability even in a highly humid environment.
Specific examples include, but are not limited to, silane coupling agents, silylating agents, silane coupling agents including an alkyl fluoride group, organic titanate coupling agents, aluminum-containing coupling agents, silicone oil, and modified silicone oil.
The silica and titanium dioxide, which are inorganic particles mentioned above, are preferably hydrophobized by the flowability improver to be used as hydrophobic silica and hydrophobic titanium dioxide.
The cleaning improver is not particular limited as long as it can be added to the toner to remove the developing agent remaining on the image bearer (photoconductor) or a primary intermediate transfer element after image transfer.
Specific examples include, but are not limited to, metal salts of fatty acid including stearic acid, zinc stearate, and calcium stearate, polymer particulates such as polymethyl methacrylate particulates and polystyrene particulates, which are prepared by a soap-free emulsion polymerization method.
The fine polymer particles preferably have a relatively sharp particle size distribution and its volume average particle diameter is preferably from 0.01 to 1 μm.
The external additive is attached to the particle surface by mixing with the resin particles (T) and the toner.
There are no particular restrictions on the methods of mixing mentioned above. For example, methods include applying impact force to the mixture by blades rotating at high speed, and introducing the mixture into a high-speed airflow to collide particles or composite particles with a suitable collision plate in an accelerated manner.
Specific examples of such mixing devices include, but are not limited to, ONG MILL (available from Hosokawa Micron Co., Ltd.), modified I TYPE MILL (available from Nippon Pneumatic Mfg. Co., Ltd.) in which the pressure of pulverization air is reduced, HYBRIDIZATION SYSTEM (manufactured by Nara Machine Co., Ltd.), KRYPTRON SYSTEM (available from Kawasaki Heavy Industries, Ltd.), and automatic mortars.
The volume average particle diameter (Dv) of the toner is not particularly restricted and can be appropriately selected depending on the purpose. It is preferable for the median diameter (D50) to be from 4 to 7 μm to enhance particle size distribution, sharpness, and fine line reproducibility.
The method of measuring the median diameter (D50) is not particularly limited and can be suitably selected to suit to a particular application. One way of measuring is to use a laser diffraction particle size analyzer LA-920 (available from HORIBA, Ltd.).
The average circularity of the toner is not particularly restricted and can be appropriately selected depending on the purpose. It is preferable for the circularity to be from 0.940 to 0.990 to enhance transfer efficiency, fine line reproducibility, and cleaning properties of toner residues on image bearers or transfer belts.
There are no specific restrictions on the method for measuring the average circularity of the toner, and it can be appropriately selected depending on the purpose. The average circularity can be measured using equipment such as a flow-type particle image analyzer FPIA-3000 (available from Sysmex Corporation).
Method of Manufacturing Resin Particle (T) with Core-shell Structure and Toner
Methods of manufacturing the resin particles (T) and toner are not particularly limited. It may include aggregation processes and fusion processes, along with other optional processes such as rinsing, drying, and annealing.
The agglomeration process involves adding shell particles to a liquid dispersion of core particles in an aqueous medium and agitating to aggregate shell resin onto the surface of the core particles.
As the liquid dispersion of core particles in an aqueous medium, a polyester resin emulsion containing the resin particles(S) of the present disclosure can be used.
The aggregation process may be conducted during heating.
The temperature of the aqueous medium in the aggregation process is not particularly limited, and it can be selected appropriately depending on the purpose. For efficient aggregation, the temperature is preferably at or above 20 degrees C., and not higher than the glass transition temperature (Tg) of the polyester resin (A).
To facilitate the aggregation process, it is permissible to add an aggregating agent or adjust pH.
The aggregating agent is not particularly limited and can be appropriately selected depending on the purpose.
Specific examples include, but are not limited to, aluminum chloride, zinc sulfate, magnesium sulfate, aluminum sulfate, potassium aluminum sulfate, sodium chloride, sodium bromide, sodium iodide, sodium fluoride, sodium acetate, sodium acetate, lithium chloride, lithium bromide, lithium iodide, lithium fluoride, lithium acetate, lithium acetate, potassium chloride, potassium bromide, potassium iodide, potassium fluoride, potassium acetate, magnesium bromide, magnesium chloride, magnesium iodide, magnesium fluoride, magnesium acetate, magnesium acetate, calcium chloride, calcium bromide, barium bromide, barium chloride, barium iodide, barium fluoride, barium acetate, barium acetate, strontium bromide, strontium chloride, strontium iodide, strontium fluoride, strontium acetate, strontium acetate, zinc bromide, zinc chloride, zinc iodide, zinc fluoride, zinc acetate, zinc acetate, copper bromide, copper chloride, copper iodide, copper fluoride, copper acetate, copper acetate, iron bromide, iron chloride, iron iodide, iron fluoride, iron acetate, and iron acetate.
These can be used alone or in combination.
The proportion of the aggregating agent is not particularly limited and can be suitably selected to suit to a particular application. The number of parts of the aggregating agent is preferably from 0.1 to 20 parts by mass and more preferably from 0.5 to 10 parts by mass to 100 parts by mass of the total of the core particles and toner.
Using the aggregating agent as an aqueous solution is preferable to achieve uniform aggregation within the reaction system. When using the aggregating agent as an aqueous solution, it is preferable that the content of the aggregating agent be 1 to 50 percent by mass of the total amount of the aqueous solution, more preferably 5 to 20 percent by mass.
The rate of adding the aggregate to the aqueous medium is not particularly limited and can be appropriately selected depending on the purpose. For the aqueous medium containing 100 parts by mass of the core particles and shell particles, the rate is preferably 0.1 to 5 parts by mass per minute, more preferably 0.5 to 2 parts by mass per minute.
The agglomeration reaction in the aggregation process can be halted as necessary. Methods of ceasing aggregation are not particularly limited. They include a method of adding salts with low valency, chelating agents, or surfactants, a method of adjusting pH, a method of lowering the temperature of a liquid dispersion, or a method of diluting the concentration by adding a large amount of aqueous medium.
Specific examples of the chelating agents include, but are not limited to, metal salts such as ethylenediaminetetraacetic acid sodium salt, sodium gluconate, sodium tartrate, sodium citrate, potassium citrate, and nitrotriacetate salts, as well as polymeric electrolytes.
In the fusion process, the aggregated particles, containing core particles and shell particles obtained in the aggregation process, are heated and fused to form a shell layer.
It is preferable to heat the liquid dispersion of the aggregated particles during stirring in the fusion process.
There is no particular restriction on the temperature in the fusion process. Preferably, the temperature is the glass transition temperature (Tg) or higher of the polyester resin (A).
In the aforementioned rinsing process, the resin particles (T) or toner obtained by the fusion process are rinsed.
There are no particular restrictions on the method of cleaning in this rinsing process, and it can be selected appropriately depending on the purpose.
Examples include centrifugation, vacuum filtration, and filter press methods. If the resin particles (T) or toner is not sufficiently rinsed in one operation, the cake obtained from this rinsing process can be dispersed again into an aqueous solvent to form a slurry, and the process of extracting resin particles (T) or toner using any of the above methods may be repeated. Furthermore, in the case of vacuum filtration or filter press methods, it is also acceptable to conduct washing by allowing the aqueous solvent to penetrate the cake.
As for the aqueous solvent used for this rinsing, there are no particular restrictions. Examples include water or mixed solvents such as water mixed with methanol, ethanol, or other alcohols. Among these, water is preferable considering the cost and environmental burden caused by wastewater treatment.
The aforementioned drying process is a step to dry the cake obtained from the rinsing process.
There are no particular restrictions on the drying method in this drying process, and it can be appropriately selected depending on the purpose. Examples include spray dryers, vacuum freeze dryers, vacuum dryers, static shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers, agitated dryers, and other drying machines.
It is preferable for the drying to continue until the moisture content in the cake is less than one percent. Furthermore, the resin particles (T) and toner obtained after drying may be pulverized using devices such as jet mills, Henschel mixers, super mixers, coffee mills, Oster blenders, or food processors to break up aggregates.
Annealing is preferably conducted for the core particles containing crystalline polyester resin.
Annealing is preferably conducted at a temperature at or above the glass transition temperature and at or below the melting point of the crystalline polyester resin. Additionally, the annealing time is preferably conducted for a period of at least 3 hours and up to 24 hours, with more preference of from 6 to 15 hours.
The toner of the present disclosure can be used as a developing agent containing appropriately selected optional components such as carrier.
The developing agent such as a one-component developing agent and a two-component developing agent can be used and the two-component developing agent is preferable in terms of life length thereof particularly when used in a high speed printer that meets the demand of high speed information processing speed of late.
When a one-component developing agent using the toner described above is used and replenished, i.e., the supply of toner to the developer and the consumption of toner due to development, the variation in the particle diameter of the toner is small, no filming of the toner on the developing roller occurs, and no fusion bonding of the toner onto members such as a blade for regulating the thickness of the toner layer occurs. Consequently, good and stable development performance and image quality can be achieved even during long-term use (stirring) of the developing device.
In a case of a two-component developing agent using the toner described above, extended toner replenishment over time does not significantly alter the particle size of the toner in the developing agent, which leads to excellent and stable development performance during long-term agitation in the developing device.
There is no specific limitation to the carrier and it can be suitably selected to suit to a particular application. It is preferable to use a carrier particle that has a core material and a resin layer covering the core material.
There is no specific limitation to the material for the core material and it can be suitably selected to suit to a particular application. For example, manganese-strontium (Mn—Sr) based material and manganese-magnesium (Mn—Mg) based material having 50 to 90 emu/g are preferable. To ensure the image density, highly magnetized materials such as iron powder having 100 emu/g or more and magnetite having 75 to 120 emu/g are preferable. In addition, weakly magnetized copper-zinc (Cu—Zn) based materials having 30 emu/g to 80 emu/g are preferable to reduce the impact of the contact between the toner filaments formed on the development roller and the image bearer, which is advantageous in improvement on the image quality.
These can be used alone or in combination.
The core material preferably has an average particle diameter (weight average particle diameter D50) of from 10 to 200 μm and more preferably from 40 to 100 μm.
An average particle size (weight average particle size (D50)) of 10 or more μm is preferable to effectively resolve issues such as an increase in fine powder in the carrier particle distribution, resulting in reduced magnetization per particle and causing carrier scatter.
An average particle size (weight average particle size D50) is 200 or less μm is preferable to effectively address issues such as toner scatter due to decreased specific surface area, particularly affecting the reproduction of full-color prints with many solid areas, resulting in poor reproduction of solid areas.
There is no specific limitation to the selection of the material for the resin layer mentioned above and any known resin can be suitably selected to suit to a particular application.
Specific examples include, but are not limited to, amino-based resins, polyvinyl-based resins, polystyrene-based resins, polycarbonate-based resins, polyethylene resins, polyvinyl fluoride resins, polyvinylidene fluoride resins, polytrifluoroethylene resins, polyhexafluoropropylene resins, copolymers of vinylidene fluoride and acrylate monomer, copolymers of vinylidene fluoride and vinyl fluoride, fluoroterpolymers such as terpolymers of tetrafluoroethylene, fluorovinylidene, and monomer including no fluorine atom, and silicone resins. Of these, silicone resins are preferable.
These can be used alone or in combination.
There is no specific limitation to the silicone resins and any known silicone resins are suitably selected to suit to a particular application.
Specific examples include, but are not limited to, straight silicone resins formed of only organosiloxane bond; and silicone resins modified by alkyd resins, polyester resins, epoxy resins, acrylic resins, and urethane resins.
The silicone resin can be synthesized or procured. Specific examples of procurable silicone resins include, but are not limited to, KR271, KR255, and KR152, available from Shin-Etsu Chemical Co., Ltd. and SR2400, SR2406, and SR2410, available from DOW CORNING TORAY CO., LTD.
Synthetic or procured polyether-modified siloxane compound are usable.
Specific examples of the procurable modified silicone resins include, but are not limited to, KR206 (alkyd-modified), KR5208 (acrylic-modified), ES1001N (epoxy-modified), and KR305 (urethane-modified), all available from Shin-Etsu Chemical Co., Ltd. and SR2115 (epoxy-modified) and SR2110 (alkyd-modified), both available from DOW CORNING TORAY CO., LTD.
It is possible to use a silicone resin alone. Moreover, it is possible to use it with components such as a cross-linkable component and a charge size control component, simultaneously.
Optionally, electroconductive powder can be added to the resin layer.
Specific examples of such electroconductive powder include, but are not limited to, metal powder, carbon blacks, titanium oxide, tin oxide, and zinc oxide.
The average particle diameter of the electroconductive powder is preferably 1 or less μm to facilitate controlling the electric resistance.
The resin layer described above can be formed by, for example, dissolving the silicone resin described above, etc. in a solvent to prepare a liquid application and applying the liquid application to the surface of the core material described above by a known application method followed by drying and baking.
Specific examples of the known application methods include, but are not limited to, a dip coating method, a spray coating method, and a brushing method.
There is no specific limitation to the solvent and it can be suitably selected to suit to a particular application.
Specific examples include, but are not limited to, toluene, xylene, methylethylketone, methylisobutyll ketone, cellosolve, and butylacetate.
There is no specific limitation to the baking. An external heating system or an internal heating system can be used. For example, a fixed electric furnace, a fluid electric furnace, a rotary electric furnace, a method of using a burner furnace, and a method of using a microwave can be suitably used.
There is no specific limit to the proportion of the polymer and it can be suitably selected to suit to a particular application. It is preferably 0.01 to 5.0 percent by mass to the total content of the resin layer.
When the content of the carrier is 0.01 or more percent by mass relative to the entire mass of the resin layer, it is preferable to enable the formation of a uniform resin layer on the surface of the core material.
When the content of the carrier is 5.0 or less percent by mass to the entire mass of the resin layer, it is preferable to effectively address issues such as an increase in the thickness of the resin layer, agglomeration of carriers, and inability to obtain uniform carrier particles.
When the developing agent described above is a two component developing agent, there is no specific limit to the content of the carrier in the two component developing agent. The content is preferably from 90 to 98 percent by mass and more preferably from 93 to 97 percent by mass to the entire mass of the two-component developing agent.
The ratio of mixing the toner with the carrier in the two component developing agent is preferably from 1 to 10.0 parts by mass based on 100 parts by mass of the carrier.
The image forming apparatus of the present disclosure is not particularly limited, and it can be suitably selected to suit to a particular application as long as the toner of the present disclosure is used. For example, it may include a latent electrostatic image bearer, a latent electrostatic image forming device, and a developing device, with other optional devices.
The image forming method of the present disclosure is not particularly limited, and it can be suitably selected to suit to a particular application as long as the toner of the present disclosure is used. For example, it may include forming latent electrostatic images, developing the latent electrostatic images, and conducting other optional processes.
There is no specific limitation to the image bearer with regard to the material, shape, structure, and size thereof, and it can be suitably selected from any known image bearers to suit to a particular application. The image bearer suitably employs a drum-like or belt-like shape. Also, an inorganic image bearer made of amorphous silicon or selenium, or an organic image bearer made of polysilane, or phthalopolymethine is suitably used.
An example of the organic photoconductor is a layered photoconductor, including layers a charge-generating layer formed of non-metallic materials like phthalocyanines or titanyl phthalocyanines dispersed in a binder resin and a charge-transport layer formed of charge transport materials dispersed in a binder resin-stacked on a substrate such as an aluminum drum.
Another type is a single-layer photoconductor with a single-layer structure on a substrate, featuring a photosensitive layer formed of both charge-generating and charge-transport materials dispersed in a binder resin. In the single-layer type photoconductor, it is also possible to add hole transport agents and electron transport agents as charge transport materials to the photosensitive layer.
Additionally, the option exists to include an undercoat layer between the substrate and either the charge-generating layer in the laminate photoconductor or the photosensitive layer in the single-layer photoconductor.
The linear speed of a latent electrostatic image bearer is preferably at least 300 mm/s.
The latent electrostatic image forming device has no particular limitation as long as it can form a latent electrostatic image on a latent electrostatic image bearer and can be suitably selected to suit to a particular application. For example, a device including a charging member for charging the surface of a latent electrostatic image bearer and an irradiating device for irradiating the surface of the latent electrostatic image bearer imagewise is suitable.
The latent electrostatic image forming process has no particular limit as long as it can form a latent electrostatic image on the latent electrostatic image bearer and can be suitably selected to suit to a particular application. For example, the process is conducted by charging the surface of a latent electrostatic image bearer and irradiating the surface imagewise with the latent electrostatic image forming device.
The charging device (charger) is not particularly limited and can be suitably selected to suit to a particular application.
Specific examples include, but are not limited to, a known contact type charger that includes an electroconductive or semiconductive roller, brush, film, or a rubber blade, and a non-contact type charger using corona discharging such as corotron and scorotron. Of these, using a contact type charger is preferable for obtaining an image forming apparatus with reduced ozone production.
The charger may employ a roller form and any other form such as a magnetic brush and a fur brush, and can be selected according to the specification or form of an image forming apparatus.
Charging is accomplished, for instance, by applying a bias to the surface of the image bearer using the charger.
The irradiating device (irradiator) is not particularly limited and can be suitably selected to suit to a particular application as long as it can irradiate the surface of a latent electrostatic image bearer charged with the charger imagewise.
Specific examples include, but are not limited to, a photocopying optical system, a rod lens array system, a laser optical system, and a liquid crystal shutter optical system.
The light source for the irradiator has no particular limitation and can be suitably selected to suit to a particular application.
Specific examples include, but are not limited to, typical luminous materials such as a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), and electroluminescence (EL).
Variety of optical filters can be used as the light source for used in the irradiator to irradiate a latent electrostatic image bearer with beams of light having only a desired wavelength.
It includes, but is not limited to, a sharp cut filter, a band-pass filter, a near infrared filter, a dichroic filter, a coherent filter, and a color conversion filter.
The irradiation is conducted by, for example, irradiating the surface of the latent electrostatic image bearer with the irradiator.
Embodiments of the present disclosure can employ a dorsal irradiation system, where the latent electrostatic image bearer is irradiated from the rear side in an imagewise manner.
The developing device is not particular limited and can be suitably selected to suit to a particular application as long as it can contain a toner for developing a latent electrostatic image formed on a latent electrostatic image bearer to form a visible image.
The developing process has no particular limitation as long as the process develops a latent electrostatic image formed on the latent electrostatic image bearer with toner to render the image visible and can be suitably selected to suit to a particular application. For example, the developing process can be conducted by a developing device.
Preferably, the developing device includes a stirrer for triboelectrically charging toner, a magnetic field generator fixed inside, and a rotatable developing agent bearer that bears a developing agent containing the toner on its surface.
Examples of the aforementioned other devices include, but are not limited to, transfer device, a fixing device, a cleaning device, a discharging (quenching) device, and a recycling device.
The other processes include, for example, a transfer process, a fixing process, a cleaning process, a discharging process, and a recycling process.
The transfer device has no particular limit as long as it can transfer the toner image to a recording medium and can be suitably selected to suit to a particular application. For example, a transfer device is preferable which includes a primary transfer device to transfer visible images onto an intermediate transfer body to form a complex transfer image and a secondary transfer device to transfer the complex transfer image to a recording medium.
The transfer process has no particular limit as long as it can transfer a visible image onto a recording medium and can be suitably selected to suit to a particular application.
It is preferable to employ a configuration in which a visible image is primarily transferred to an intermediate transfer body and thereafter secondarily transferred to a recording medium.
The transfer process can be performed by, for example, charging the latent electrostatic image bearer (photoconductor) with a transfer charging device and by the transfer device.
If an image secondarily transferred to a recording medium is a color image formed of multiple color toners, it is possible to have a configuration in which each color toner image is sequentially overlapped on the intermediate transfer body by the transfer device to form an image thereon, which is then secondarily transferred once to a recording medium by the intermediate transfer device.
The intermediate transfer body is not particularly limited and can be suitably selected from the known transfer members including an intermediate transfer belt.
The transfer device (the primary transfer device, the secondary transfer device) preferably has a transfer unit for peeling-charging the visible image formed on the image bearer to the side of the recording medium.
Specific examples of the transfer unit include, but are not limited to, a corona transfer unit using corona discharging, a transfer belt, a transfer belt, a transfer roller, a pressure transfer roller and an adhesive transfer unit.
A typical example of the recording medium is plain paper but any paper to which a non-fixed image after development is transferred can be suitably used. PET base for an overhead projector can be also used.
The fixing device has no particular limit provided that it can fix a transfer image transferred onto a recording medium and can be suitably selected to suit to a particular application. Known heating and pressure devices are preferable.
A combination of a heating roller and a pressure roller and a combination of a heating roller, a pressure roller, and an endless belt can be used as the heating and pressure device.
The fixing process has no particular limit provided that it includes a process of fixing a visible image transferred onto a recording medium and can be suitably selected to suit to a particular application. For example, fixing can be conducted each time an image is transferred for each color toner, or subsequent to transferring a stacked image of all color toners at once. The fixing process can be conducted by the fixing device.
The heating temperature at the heating and pressing device is preferably from 80 to 200 degrees C.
In the present disclosure, for example, any known optical fixing device can be used in combination with or in place of the fixing device depending on a particular application.
There is no specific limitation to the surface pressure in the fixing process and it can be suitably selected to suit to a particular application. Preferably, the surface pressure is from 10 to 80 N/cm2.
There is no specific limitation to the selection of the cleaning device and any known cleaner that can remove the toner remaining on the image bearer is suitably used.
Specific examples of such cleaners include, but are not limited to, a magnetic brush cleaner, an electrostatic brush cleaner, a magnetic roller cleaner, a blade cleaner, a brush cleaner, and a web cleaner.
Any cleaning process that can remove the toner remaining on the image bearer is suitably used. For example, the cleaning process can be conducted by the cleaning device mentioned above.
The quenching (discharging) device has no particular limit as long as it can apply a discharging bias to a photoconductor for discharging and can be suitably selected to suit to a particular application. For example, a discharging lamp is suitable.
The discharging process has no specific limit as long as it includes applying a discharging bias to a photoconductor for discharging and can be suitably selected to suit to a particular application. For example, the charging process can be conducted by the charging device.
The recycling device has no particular limit as long as it recycles toner removed by the cleaning device to the development device and can be suitably selected to suit to a particular application. For example, known conveying devices are suitable.
The recycling process has no particular limit as long as it includes recycling toner removed in the cleaning process to the developing device and can be suitably selected to suit to a particular application. For example, the recycling process can be conducted by the recycling device.
Hereinafter, the image forming method relating to the present disclosure is described with reference to the accompanying drawings. It is to be noted that the following embodiments are not limiting the present disclosure and any deletion, addition, modification, change, etc. can be made within a scope in which man in the art can conceive including other embodiments, and any of which is included within the scope of the present disclosure as long as the effect and feature of the present disclosure are demonstrated.
Next, an embodiment of image forming with the image forming apparatus of the present disclosure is described with reference to FIGURE. One of the image forming apparatuses in the present embodiment is a printer. However, the image forming apparatus is not particularly limited to an apparatus such as a printer, a photocopier, a facsimile machine, or a multifunction peripheral as long as it can form images with toner.
An image forming apparatus 200 includes a sheet feeding unit 210, a conveyance unit 220, an image forming unit (latent electrostatic image forming device) 230, a transfer unit (transfer device) 240, and a fixing unit (fixing device) 250.
The sheet feeding unit 210 includes a sheet feeding cassette 211 on which sheets to be fed are piled and a feeding roller 212 that feeds a sheet (recording medium) P piled on the sheet feeding cassette 211 one by one.
The conveyance unit 220 includes a roller 221 for conveying the sheet P fed by the feeding roller 212 toward the transfer unit 240, a pair of timing rollers 222 for pinching the front end of the sheet P conveyed by the roller 221 on standby and sending out the sheet P to the transfer unit 240 at a particular timing, and ejection rollers 223 for ejecting the sheet P on which a color toner image is fixed by the fixing unit 250 to an ejection tray 224.
The image forming unit 230 includes an image forming unit (latent electrostatic image bearer) 180Y that forms an image using a developing agent containing yellow toner, an image forming unit 180C that forms an image using a developing agent containing cyan toner, an image forming unit 180M that forms an image using a developing agent containing magenta toner, and an image forming unit 180K that forms an image using a developing agent containing black toner, sequentially standing from left to right in the drawing with a particular interval, and an irradiator 233.
The image forming unit 180 (180Y, 180C, 180M, 180K) is provided to be rotatable clockwise in the drawing and includes a drum photoconductor 231 (231Y, 231C, 231M, 231K) where latent electrostatic images and toner images are formed, a charger 232 (232Y, 232C, 232M, 232K) for uniformly charging the surface of the drum photoconductor 231 (231Y, 231C, 231M, 231K), and a cleaner 236 (236Y, 236C, 236M, 236K) for removing residual toner from the surface of the drum photoconductor 231 (231Y, 231C, 231M, 231K).
The image forming unit 180 (180Y, 180C, 180M, 180K) includes toner bottles 234 (234Y, 234C, 234M, 234K) for containing toner for each color, and sub-hoppers 160 (160Y, 160C, 160M, 160K) for replenishing toner supplied from the toner bottles 234 (234Y, 234C, 234M, 234K).
Any of the image forming units 180 (180Y, 180C, 180M, 180K) can be referred to as an image forming unit when it indicates an arbitrary unit.
The irradiator 233 irradiates the drum photoconductor (231Y, 231C, 231M, and 231K) with a laser beam L emitted from a light source 233a in response to image data, and the laser beam L is reflected by a polygon mirror (233bY, 233bC, 233bM, and 233bK) rotatably driven by a motor.
In addition, the developing agent contains toner and carrier. The four image forming units 180 (180Y, 180C, 180M, 180K) have substantially the same structure except for the individual developing agents used for respective image forming units.
The transfer unit 240 includes a driving roller 241, a driven roller 242, an intermediate transfer belt 243 disposed rotatable counterclockwise in the drawing in accordance with the drive of the driving roller 241, a primary transfer roller 244 (244Y, 244C, 244M, and 244K) disposed facing the drum photoconductor 231 (231Y, 231C, 231M, and 231K) with the intermediate transfer belt 243 therebetween, and a secondary facing roller 245 and a secondary transfer roller 246 disposed facing each other at the point of the toner image transferred to the sheet P with the intermediate transfer belt 243 therebetween.
A fixing unit 250 with a heater inside includes a fixing belt 251 for heating the sheet P and a pressing roller 252 for forming a nip with the fixing belt 251 by rotatably pressing it. Heat is applied with pressure to the color toner image on the sheet P at the nipping portion, thereby fixing the color toner image.
The sheet P on which the color toner image is fixed is ejected to the ejection tray 224 by the ejection rollers 223, which completes a series of image forming process.
The terms of image forming, recording, and printing in the present disclosure represent the same meaning.
Also, recording media, media, and print substrates in the present disclosure have the same meaning unless otherwise specified.
Having generally described preferred embodiments of this disclosure, further understanding can be obtained by reference to certain specific examples which are provided herein for the purpose of illustration only and are not intended to be limiting. In the descriptions in the following examples, the numbers represent weight ratios in parts, unless otherwise specified.
The present invention is described next in detail with reference to Examples and Comparative Examples but is not limited to these Examples.
The measuring methods are as follows:
The glass transition temperature Tg of the resin was measured with a differential scanning calorimetry (DSC) system, Q-200, available from TA Instruments. A total of 5.0 mg of the resin sample was put into an aluminum sample pan, which was then held on the holder unit and placed in an electric furnace. A reference sample of alumina (aluminum oxide, available from FUJIFILM Wako Pure Chemical Corporation) weighing 10 mg was used, and like the sample, it was placed in an aluminum sample pan. Under a nitrogen atmosphere, the sample was heated from 0 to 150 degrees C. at a heating rate of 10 degrees C./min (first heating), then cooled from 150 to 0 degrees C. at a cooling rate of 10 degrees C./min (cooling process), and heated again from 0 to 150 degrees C. at a heating rate of 10 degrees C./min (second heating). The heat flux changes during these processes were measured, and a graph of temperature versus heat flux was plotted to obtain a DSC curve. The DSC curve obtained was analyzed using the analysis program in the Q-200 system. The DSC curve for the second heating was selected, and the glass transition temperature of the resin sample was determined from the intersection of the baseline extension line of the DSC curve at temperatures lower than the enthalpy relaxation and the tangent indicating the maximum slope during enthalpy relaxation. Similarly, the DSC curve for the second heating was selected, and the peak temperature of heat absorption was considered as the melting point of the crystalline resin or wax sample.
The weight average molecular weight (Mw) of the resin can be measured by using a gel permeation chromatography (GPC) measuring device, GPC-8220 GPC, available from TOSOH CORPORATION. The column used was TSK gel Super HZM-M 15 cm triplet (available from TOSOH CORPORATION). The resin to be measured was dissolved in tetrahydrofuran (THF) (containing stabilizers, available from Fujifilm Wako Pure Chemical Corporation) to prepare a 0.15 percent by mass solution. After filtration through a 0.2 μm filter, the filtrate was used as the sample. The aforementioned THE sample solution was injected into the measuring instrument at 100 μL, and measurements were conducted at a temperature of 40 degrees C. with a flow rate of 0.35 mL/min. Molecular weight calculations were performed using a calibration curve prepared using monodisperse polystyrene standard samples. The polystyrene standard samples used were the THF solutions (solutions A to C) of the following three types of monodisperse polystyrene standard samples from the Showdex STANDARD series, available from Showa Denko Co., Ltd. Measurements were conducted under the aforementioned conditions to create a calibration curve using the retention time of the peak top as the light-scattering molecular weight of the monodisperse polystyrene standard samples. A refractive index (RI) detector was used as the detector.
The acid value (AV) and hydroxyl value (OHV) of the resin were measured according to JIS K0070 (Test methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products). The measuring solvent of acid value used was a mixed solvent of acetone (available from Fujifilm Wako Pure Chemical Corporation), methanol (available from Fujifilm Wako Pure Chemical Corporation), and toluene (available from Fujifilm Wako Pure Chemical Corporation) at a ratio of acetone:methanol:toluene=12.5:12.5:75.
The measuring solvent of hydroxyl value used was tetrahydrofuran (THF) (available from Fujifilm Wako Pure Chemical Corporation).
The volume average particle diameter (Dv) of resin particles and toner was measured using a Coulter Multisizer III (aperture diameter 100 μm, available from Beckman Coulter) and analysis software, Beckman Coulter Multisizer 3 (version 3.51, available from Beckman Coulter). A measuring sample of 10 mg was added to 5 mL of a 10 percent surfactant solution (alkylbenzenesulfonic acid salt, NeoGen SC-A, available from DKS Co., Ltd.) and dispersed for 1 minute using an ultrasonic disperser. Then 25 mL of electrolyte solution, Isoton III (available from Beckman Coulter), was added as desired, and dispersed for 1 minute to prepare a sample dispersion solution using an ultrasonic disperser. Subsequently, an appropriate amount of the electrolyte solution and the sample dispersion solution of 100 mL were added to a beaker, and 30,000 particles were measured at a concentration where the particle diameter of 30,000 particles was able to be measured in 20 seconds. The volume average particle diameter (Dv) was then determined from its particle size distribution.
The average circularity and the amount of microfines (2 or less μm) of the resin particles and toner were measured using a Flow Particle Imaging Analyzer FPIA-3000 (available from Sysmex Corporation). One percent NaCl aqueous solution was prepared using sodium chloride (first grade, available from Fujifilm Wako Pure Chemical Corporation), and then dispersant, alkylbenzenesulfonic acid salt (NeoGen, available from DKS Co., Ltd.), was added in the range of 0.1 to 5 mL to a liquid of 50 to 100 mL filtered through a 0.45 μm filter. Subsequently, 1 to 10 mg of the sample was added. The mixture was dispersed for 1 minute using an ultrasonic disperser to adjust the particle concentration to 5,000 to 15,000 particles/μL.
This dispersion solution with adjusted particle concentration was then measured.
To a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen introduction pipe, materials shown in Tables 1 to 4 were added, at a molar ratio (OH/COOH) of hydroxyl groups to carboxylic acids adjusted to 1.2.
Additionally, a condensation catalyst, tetra-n-butoxy titanate (titanium dihydroxy bis(triethanolaminate), available from Tokyo Chemical Industry Co. Ltd.), was added at 1,000 ppm to the entire of the monomer. The temperature was raised to 200 degrees C. over 2 hours under a nitrogen stream, then further raised to 230 degrees C. over 8 hours, during which water produced was removed, and the reaction was allowed to proceed for 5 hours. Subsequently, the reaction was carried out for 1 hour under a reduced pressure of 5 to 15 mmHg, then cooled to 20 degrees C. Anhydrous trimellitic acid (available from Tokyo Chemical Industry Co., Ltd.) was added, and the reaction was carried out for 1 hour at 200 degrees C. under atmospheric pressure. The reaction was continued under reduced pressure of 5 to 20 mmHg until the desired molecular weight was reached, obtaining Polyester Resins A-1 to A-20 as Polyester Resins A.
Polyester Resins A-1 to A-20 obtained were subjected to measurements of glass transition temperature (Tg), weight average molecular weight, acid value (AV), hydroxyl value (OHV), and the ratio (OHV/AV). The results are shown in Tables 1 to 4.
A total of 150 parts by mass of Polyester resin (A-1) and 150 parts by mass of methyl ethyl ketone (available from Fujifilm Wako Pure Chemical Corporation) were placed in a 500 mL separable flask equipped with a stirrer. Additionally, sodium hydroxide (0.3N) (available from Fujifilm Wako Pure Chemical Corporation) was added at 80 percent equivalent to the acid value of Polyester Resin A-1 to neutralize it, preparing a resin liquid mixture. Subsequently, while stirring the resin liquid mixture, deionized water was gradually added up to 400 parts to conduct phase inversion emulsification. Then the resulting substance was subjected to solvent removal under reduced pressure using an evaporator. Deionized water was added to achieve a solid content concentration of 25 percent by mass, obtaining Polyester Resin Emulsion EM-1.
The same procedure was followed for Polyester Resins A-2 to A-20, obtaining Polyester Resin Emulsions EM-2 to EM-20.
The Polyester Resin Emulsions EM-1 to EM-20 obtained were subjected to measurement of median diameter D50. The results are shown in Tables 1 to 4.
To a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen introduction pipe, acid monomers and alcohol monomers shown in Table 4 were added, at a molar ratio (OH/COOH) of hydroxyl groups to carboxylic acids adjusted to 1.2.
Additionally, a condensation catalyst, tetra-n-butoxy titanium, was added at 1,000 ppm to the entire of the monomer.
The temperature was raised to 200 degrees C. over 2 hours under a nitrogen stream, then further raised to 230 degrees C. over 8 hours, during which water produced was removed. The reaction was allowed to proceed for 5 hours. Subsequently, the reaction was carried out for 1 hour under a reduced pressure of 5 to 15 mmHg, then cooled to 200 degrees C. Anhydrous trimellitic acid was added in the amounts shown in Table 4, and the reaction was carried out for 1 hour at 200 degrees C. under atmospheric pressure. Finally, the reaction was continued under reduced pressure of 5 to 20 mmHg until the desired molecular weight was reached, obtaining Amorphous Polyester Resins B-1 to B-2 as Amorphous Polyester Resins B.
Amorphous Polyester Resins B-1 to B-2 obtained were subjected to measurements of glass transition temperature (Tg), weight average molecular weight, acid value (AV), and hydroxyl value (OHV). The results are shown in Table 4.
To a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen introduction pipe, 1,6-hexanediol (available from Tokyo Chemical Industry Co., Ltd.) and sebacic acid (available from Tokyo Chemical Industry Co., Ltd.) as the dicarboxylic acid component were introduced to achieve a molar ratio (OH/COOH) of hydroxyl groups to carboxylic acids of 1.1. Additionally, as a condensation catalyst, titanium dihydroxy bis(triethanolaminate) (available from Tokyo Chemical Industry Co., Ltd.) was added at 500 ppm relative to the entire of the monomer. The temperature was raised to 180 degrees C. over 2 hours under a nitrogen stream, and the generated water was removed while the reaction proceeded for 8 hours. Subsequently, the temperature was gradually raised to 220 degrees C. while removing the generated water under a nitrogen stream, and the reaction was allowed to proceed for 5 hours. Under a reduced pressure of 5 to 20 mmHg, Crystalline Polyester Resin C with a melting point of 68 degrees C., an acid value of 10.5 mg KOH/g, and a weight average molecular weight of 11,000 was obtained.
In a reaction vessel equipped with a cooling pipe, a thermometer, and a stirrer, 10 parts by mass of Crystalline Polyester Resin (C) and 90 parts by mass of ethyl acetate (available from FujiFilm Wako Pure Chemical Corporation) were placed and heated to 77 degrees C. until fully dissolved. The mixture was then cooled to 30 degrees C. over 1 hour with stirring.
Subsequently, wet grinding was conducted using an Ultra Bead Mill (available from Aimex Corporation) under the following conditions: liquid feed rate of 1.0 kg/hr, disc peripheral speed of 10 m/second, 80 percent volume of 0.5 mm zirconia beads, and 6 passes. Ethyl acetate was added to adjust the solid content to 10 percent by mass, resulting in Liquid Dispersion C-1 of Crystalline Polyester Resin with a median particle diameter D50 of 0.3 μm, as measured by a laser particle size distribution analyzer LA-920 (available from HORIBA, Ltd.).
In a 500 ml separable flask equipped with a stirrer, 150 parts by mass of Crystalline Polyester Resin (C), 75 parts by mass of methyl ethyl ketone (available from FujiFilm Wako Pure Chemical Corporation), and 75 parts by mass of isopropyl alcohol (available from FujiFilm Wako Pure Chemical Corporation) were placed and heated to 65 degrees C. to dissolve it. Subsequently, to the resulting liquid, ammonia solution (available from FujiFilm Wako Pure Chemical Corporation) equivalent to 60 percent of the acid value of Crystalline Polyester Resin C was added to prepare a liquid mixture of the resin. Next, the liquid mixture of the resin was stirred at 65 degrees C. while 400 parts of deioniezd water was gradually added to conduct phase inversion emulsification. Afterward, the obtained material was subjected to solvent removal under reduced pressure using an evaporator, and deionized water was added to adjust the solid content to 25 percent by mass. This process resulted in Liquid Dispersion C-2 of Crystalline Polyester Resin, which contained a crystalline polyester resin emulsion with a median diameter D50 of 0.3 μm.
A total of 100 parts of Amorphous Polyester Resin B-1, 100 percent by mass of cyan pigment (Pigment Blue 15:3), and 50 parts by mass of deionized water were thoroughly mixed, and the mixture was kneaded using an open roll type kneading machine (Kneadex, available from NIPPON COKE & ENGINEERING CO., LTD.). The kneading temperature was maintained at 80 degrees C., then raised to 120 degrees C. to remove water, obtaining Colorant Master Batch MB-1 with a resin-to-pigment ratio (mass ratio) of 1:1.
Similarly, the treatment was conducted for Amorphous Polyester Resin B-2, obtaining Colorant Master Batch MB-2.
A total of 30 parts by mass of cyan pigment (Pigment Blue 15:3), 3 parts by mass of anionic surfactant (sodium linear alkylbenzenesulfonate (Neogen, available from Daiichi Kogyo Seiyaku Co., Ltd.), and 67 parts by mass of deionized water were placed in a container. The mixture was then dispersed for 30 minutes at 6,000 rpm using a TK homomixer (available from Tokushu Kikai Co., Ltd.), followed by dispersion process using a high-pressure disperser, Ultimiser (Starburst, available from Sugino Machine Limited), at a pressure of 245 MPa for 20 passes. Subsequently, deionized water was added to adjust the solid content concentration to 25 percent by mass, obtaining Liquid Dispersion of Colorant.
In a reaction vessel equipped with a cooling pipe, a thermometer, and a stirrer, 20 parts by mass of ester wax (WE-11, melting point of 70 degrees C., available from NOF CORPORATION) and 80 parts by mass of ethyl acetate (available from FujiFilm Wako Pure Chemical Corporation) were placed and heated to 77 degrees C. until fully dissolved. The mixture was then cooled to 30 degrees C. over 1 hour with stirring. Subsequently, wet grinding was conducted using an Ultra Bead Mill (available from Aimex Corporation) under the following conditions: liquid feed rate of 1.0 kg/hr, disc peripheral speed of 10 m/second, 80 percent volume of 0.5 mm zirconia beads, and 6 passes. Ethyl acetate was added to adjust the solid content to 20 percent by mass, resulting in Liquid Dispersion W-1 of Wax with a median particle diameter D50 of 0.6 μm, as measured by a laser particle size distribution analyzer LA-920 (available from HORIBA, Ltd.).
A total of 30 parts by mass of ester wax with a melting point of 70 degrees C. (WE-11, available from NOF CORPORATION), 2 parts by mass of anionic surfactant (sodium linear alkylbenzenesulfonate (Neogen, available from DKS Co., Ltd.), and 68 parts by mass of deionized water were placed in a container. The mixture was dispersed in the container cooled with ice water for 2 hours at 8,000 rpm using a TK homomixer (available from Tokushu Kikai Co., Ltd.). Subsequently, deionized water was added to adjust the solid content concentration to 25 percent by mass, obtaining Liquid Dispersion W-2 of Wax with a median diameter D50 measured by a laser particle size distribution analyzer LA-920 (manufactured by Horiba, Ltd.) of 0.6 μm.
In a container equipped with a stirrer and a thermometer, 68 parts by mass of deionized water, 1 part by mass of sodium carboxymethyl cellulose (available from DKS Co., Ltd.), 16 parts by mass of a 48 percent aqueous solution of sodium dodecyl diphenyl ether disulfonate (Eleminol MON-7, available from Sanyo Chemical Industries, Ltd.), and 5 parts by mass of ethyl acetate were mixed and stirred. Subsequently, 10 parts by mass of an emulsion for particle size control containing a copolymer of styrene-methacrylic acid-butyl acrylate-ethylene oxide adduct sulfonic ester sodium salt (solid content concentration: 20 percent, median diameter: 50 nm, available from Sanyo Chemical Industries, Ltd.) were added to prepare Aqueous Phase Liquid.
Next, in another container equipped with a stirrer and a thermometer, 76 parts by mass of Amorphous Polyester Resin B-1, 60 parts by mass of Liquid Dispersion C-1 of Crystalline Polyester Resin, 30 parts by mass of Liquid Dispersion W-1 of Wax, and 12 parts by mass of Colorant Master Batch MB-1 were added. Ethyl acetate was then added to adjust the solid content concentration to 50 percent, and the mixture was stirred until completely dissolved. Using a TK homomixer (available from Tokushu Kikai Co., Ltd.), the mixture was then dispersed at a rotation speed of 8,000 rpm for 2 hours to achieve uniform dissolution and suspension, thereby preparing the Oil Phase.
A total of 50 parts by mass of Oil Phase was added to a container containing 75 parts by mass of Aqueous Phase to obtain emulsification slurry by mixing for 1 minute at a rotation speed of 12,000 rpm using a TK homomixer (available from Tokushu Kikai Co., Ltd.) at a liquid temperature of 30 to 40 degrees C.
The obtained emulsified slurry was transferred to another container equipped with a stirrer, a nitrogen introduction tube, and a thermometer, and during stirring, it was heated to 50 degrees C. to remove ethyl acetate under a nitrogen atmosphere. A ten percent aqueous solution of sodium hydroxide (available from Fuji Film Wako Pure Chemical Corporation) was added to adjust the pH of the emulsified slurry to 12. Thereafter, it was heated at 45 degrees C. for 10 hours, dissolving and removing the emulsion for particle size control adhering to the particle surface in the emulsified slurry, followed by suction filtration to obtain solid content.
The solid content obtained was subjected to a washing process of reslurrying with deionized water equivalent to 40 times the mass of the solid content, followed by filtering after through stirring. This washing process was repeated once more, and deionized water was added again to adjust the solid content concentration to 25 percent by mass, thereby obtaining Liquid Dispersion CR-1 of Core Particle.
Liquid Dispersion CR-2 of Core Particle was obtained in the same manner except that Colorant Master Batch MB-1 was changed to Colorant Master Batch MB-2 for Amorphous Polyester Resin B-2.
Liquid Dispersions CR-1 and CR-2 of Core Particle were subjected to measurements of volume average particle diameter and average circularity. The results are shown in Table 5.
To a container equipped with a stirrer, 150 parts by mass of Amorphous Polyester Resin B-1 and 150 parts of methyl ethyl ketone were added. Furthermore, sodium hydroxide (0.3N) was added at a neutralization rate of 70 percent equivalent to the acid value of Amorphous Polyester Resin B-1 to prepare a resin liquid mixture. Next, while the resin liquid mixture was stirred, 400 parts of deionized water was gradually added to conduct phase inversion emulsification. Subsequently, solvent removal was carried out under reduced pressure using an evaporator, and deionized water was added to adjust the solid content concentration to 25 percent. This process yielded Polyester Resin Emulsion (B) with a median diameter (D50) measured by laser-type particle size distribution measurement device LA-920 (available from Horiba, Ltd.) of 0.2 μm.
Then 328 parts by mass of Polyester Resin Emulsion B, 24 parts by mass of Liquid Dispersion C-2 of Crystalline Polyester Resin, 24 parts by mass of Liquid Dispersion W-2 of Wax, and 24 parts by mass of Colorant Liquid Dispersion were placed in another container equipped with a stirrer and a thermometer. While the mixture was stirred, a 20 percent aqueous solution of magnesium sulfate (available from Fuji Film Wako Pure Chemical Corporation) at 20 parts by mass per 2 parts by mass per minute was added dropwise, followed by heating to 55 degrees C. After the emulsion volume average particle size Dv reached 5 μm, a 10 percent aqueous solution of sodium chloride (available from Fuji Film Wako Pure Chemical Corporation) at 120 parts by mass was added. The mixture was then heated to 60 degrees C. and stirred for 1 hour, followed by cooling to room temperature. Deionized water was then added to adjust the solid content concentration to 25 percent, obtaining Liquid Dispersion CR-3 of Core Particle.
Liquid Dispersion CR-3 of Core Particle was subjected to measurements of volume average particle size and average circularity. The results are shown in Table 5.
A total of 76 parts by mass of Amorphous Polyester Resin B-1, 6 parts by mass of Crystalline Polyester Resin C, 6 parts by mass of ester wax (WE-11, available from NOF CORPORATION) with a melting point of 70 degrees C., and 12 parts by mass of Colorant Master Batch (MB-1) were preliminarily mixed using a Henschel mixer (FM10B, available from Mitsui Miike Chemical Engineering Machinery), then melted and kneaded at 85 degrees C. using a twin-screw kneader (PCM-30, available from Ikegai Corporation). The melt-kneaded material obtained was cooled to room temperature and coarse-ground to 200 to 300 μm using a hammer mill. Next, using a counter jet mill (200AFG, available from Hosokawa Micron Corporation), the material was finely ground under the powder air pressure adjusted to achieve a weight average particle diameter of 5.6±0.3 μm. Subsequently, classification was performed using an air classifier (MDS-I, available from Nippon Pneumatic Mfg. Co., Ltd.) to achieve a weight average particle diameter of 6.0±0.2 μm and a proportion of fine particles at or below 4 μm of 10 or less percent by number, under the louver opening adjusted as necessary, to obtain Classified Particles. Then 25 parts by mass of Classified Particles, 73 parts by mass of deionized water, and 2 parts by mass of anionic surfactant (linear sodium alkylbenzenesulfonate, Neogen, available from DKS Co., Ltd.) were placed in another container equipped with a stirrer. Through sufficient stirring, Liquid Dispersion of Core Particle CR-4 adjusted to a solid content concentration of 25 percent was obtained.
Liquid Dispersion CR-4 of Core Particle obtained was subjected to measurements of volume average particle size and average circularity. The results are shown in Table 5.
A total of 5,000 parts by mass of Mn ferrite particles with a weight average particle diameter of 35 μm was used as the core material.
For the coating material, a coating solution was prepared by dispersing the following ingredients for 10 minutes using a stirrer: 300 parts by mass of toluene (available from Fuji Film Wako Pure Chemical Corporation), 300 parts by mass of butyl cellosolve (available from Fuji Film Wako Pure Chemical Corporation), 60 parts by mass of an acrylic resin solution (containing methyl methacrylate: methacrylic acid: 2-hydroxyethyl acrylate=5:9:3, solid content 50 percent in toluene solution, Tg 38 degrees C.), 15 parts by mass of N-tetramethoxymethylbenzoguanamine resin solution (degree of polymerization 1.5, solid content 77 percent by mass in toluene solution), and 15 parts by mass of alumina particles (average primary particle diameter 0.30 μm).
The coating solution prepared was then applied onto the core material using a coating device that applied coating while forming a swirling flow with a rotating bottom plate disk and stirring blades in a fluidized bed. The resulting coated material was baked in an electric furnace at 220 degrees C. for 2 hours to obtain Carrier.
A total of 320 parts by mass of Liquid Dispersion CR-1 of Core Particle (solid content concentration 25 percent by mass) and 80 parts by mass of polyester resin emulsion EM-1 (solid content concentration 25 percent by mass) were added to a container equipped with a stirrer and a thermometer. A 20 percent by mass magnesium sulfate aqueous solution was added dropwise at a rate of 2 parts by mass per minute during stirring, until the magnesium sulfate reached 1 percent by mass of the entire solid content. The temperature was then raised to 55 degrees C., and stirring was continued for 30 minutes. Subsequently, 100 parts by mass of a 10 percent by mass sodium chloride aqueous solution was added, the temperature was raised to 70 degrees C., and stirring was continued for 1 hour. Samples were taken, and the volume average particle diameter Dv, average circularity, and the amount of fine particles with a Dv of 2 or less μm were measured after the shell particles agglomerated. The samples were evaluated based on the evaluation criteria below.
Similarly, the amount of the 20 percent by mass magnesium sulfate aqueous solution was changed to levels where magnesium sulfate accounted for 2, 3, and 4 percent by mass of the entire solid content, followed by the same process and evaluation.
A smaller amount of fine particles with a Dv of 2 or less μm indicates better aggregation of shell particles to core particles. Moreover, when the volume average particle diameter of the particles after aggregation of the shell particles is 1 or more μm larger than the volume average particle diameter of the core particles, the aggregation stability can be said to be poor even if the amount of fine particles with a Dv of 2 or less μm is small.
The value obtained by subtracting the volume average particle diameter of the core particles from the volume average particle diameter of the particles after aggregation of the shell particles is denoted as ΔDv. Additionally, among the levels of the amount of magnesium sulfate added as an aggregated salt, the result with the highest rank evaluation is taken as the comprehensive evaluation result of the aggregation of the shell particles. The results are shown in Tables 6 to 10. Tables 6 to 10 also include the amount of fine particles with a Dv of 2 or less μm (percent by number).
Following the evaluation of aggregation properties for the aggregation salt of the shell particles, the samples under the conditions of the most optimal aggregation salt for aggregation properties were measured for their average circularity. The samples with an average circularity below 0.970 was further stirred at 70 degrees C. until the average circularity reached 0.970. Subsequently, the container was moved to an ice bath for cooling to room temperature, followed by suction filtration to obtain solids.
To the obtained solids, 800 parts by mass of deionized water were added, stirred to re-slurry, and then subjected to suction filtration to obtain solids. This process was repeated five times, followed by drying at 45 degrees C. for 48 hours in a fluidized bed dryer. The resulting dried matter was sieved with a 75 μm mesh to obtain Resin Particles (T), referred to as Resin Particles (T-1).
A total of 1.0 part by mass of hydrophobic silica (HDK-2000, available from Wacker Chemie AG) and 0.3 parts by mass of titanium oxide (MT-150AI, available from TAYCA CORPORATION) were added to 100 parts by mass of Resin Particles (T-1) obtained, and mixed using a Henschel mixer. The mixture was then sieved with a 25 μm mesh to obtain Toner (TN-1). The toner obtained was measured about volume average particle diameter (Dv) and average circularity. The results are shown in Tables 6 to 10.
Resin Particles T-1 were embedded in procured epoxy resin (S-31, available from DEVCON) and hardened. Subsequently, ultra-thin sections were prepared using a diamond knife with an ultramicrotome (Leica EM UC7, available from Leica). Its thickness of the sections was adjusted to around 100 nm, utilizing the interference color of the epoxy resin. Furthermore, the sections were placed on copper grid meshes and subjected to vapor staining using a 5 percent aqueous solution of ruthenium tetroxide (available from FujiFilm Wako Pure Chemical Corporation). Images of the resin particle cross-sections were recorded utilizing a transmission electron microscope (JEM-2100F, available from JEOL Ltd.). The formation state of the shell layer was determined based on whether crystalline polyester resin, wax, and colorant were exposed on the surface of the resin particles based on the fact that those components are not exposed on the surface of the cross section of toner particles with a shell layer. Specifically, the cross-sections of 30 randomly selected resin particles were observed to determine the proportion (P) of particles with no exposure of crystalline polyester resin, wax, and colorant on the surface. The proportion (P) indicates the degree of homogeneity in the aggregation state of the shell particles. The evaluation was conducted based on the following criteria, and the results are shown in Tables 6 to 10.
Developing Agent D-1, which was a two-component developing agent, was obtained by uniformly mixing 7 parts by mass of Toner TN-1 with 100 parts by mass of Carrier using a type of tumbler mixer (available from Willy A. Bachofen (WAB) GmbH) that rotated the container at 48 rpm for 5 minutes.
Developing Agent D-1 was loaded into the developing unit of the digital color multifunction printer RICOH IM C5500 (available from Ricoh Co., Ltd.), and after printing 30,000 sheets in monochrome mode, the developing agent was extracted. An appropriate amount of the developing agent extracted was then placed in a gauge with a mesh opening of 32 μm, followed by air blowing to separate the toner from the carrier. Subsequently, the obtained carrier (10 g) was placed in a 50 ml glass bottle, and 10 ml of methyl ethyl ketone was added. The mixture was hand-shaken 50 times and left to rest for 10 minutes. Afterward, the supernatant methyl ethyl ketone solution was loaded in a glass cell, and the transmittance of the methyl ethyl ketone solution was measured using a turbidity meter. The evaluation was conducted based on the following criteria, and the results are shown in Tables 6 to 10.
Resin Particles (T-2) to (T-25), Toners (TN-2) to (TN-25), and Developing Agents (D-2) to (D-25) were obtained in the same manner as in Example 1 except that the combinations of Liquid Dispersions (CR-1) to (CR-4) of Core Particle and Polyester Resin Emulsions (EM-1) to (EM-20) were changed as shown in Tables 6 to 10. Each was evaluated in the same manner as in Example 1. The results are shown in Tables 6 to 10.
Aspects of the present disclosure are, for example, as follows.
A polyester resin emulsion contains resin particles(S), each containing a polyester resin (A) obtained by polycondensation of an alcohol component and a carboxylic acid component, and an aqueous medium in which the resin particles(S) are dispersed, wherein the alcohol component contains tri- or tetra-alcohol having a backbone of a linear or branched saturated fatty acid with a carbon number of 4 to 6, and the ratio (OHV/AV) of a hydroxyl value (OHV) of the polyester resin (A) to an acid value (AV) of the polyester resin (A) is from 0.20 to 0.60.
The polyester resin emulsion according to Aspect 1 mentioned above, wherein the acid value of the polyester resin (A) is from 15 to 30 mgKOH/g.
The polyester resin emulsion according to Aspect 1 or 2 for use in manufacturing a toner with a core shell structure of shell particles and core particles containing a binder resin.
The polyester resin emulsion according to Aspect 3 mentioned above, wherein the binder resin contains an amorphous polyester resin (B).
The polyester resin emulsion according to any one of Aspects 1 to 4 mentioned above, wherein the alcohol component comprises at least one member selected from the group consisting of 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 2,3-butanediol, at least one member accounting for 30 mol percent of the entire of the alcohol component.
The polyester resin emulsion according to any one of Aspects 1 to 5 mentioned above, wherein the polyester resin (A) contains a repeating unit derived from polyethylene terephthalate (PET) containing a condensate of terephthalic acid and ethylene glycol.
The polyester resin emulsion according to any one of Aspects 1 to 6 mentioned above, wherein the resin particles(S) have a glass transition temperature (Tg) of from 60 to 75 degrees C. at a second temperature rising in a differential scanning calorimetry (DSC).
A resin particle contains a resin particle (T) with a core-shell structure containing a core particle containing a binder resin and a shell particle covering the core particle, wherein the shell particle is formed of the polyester resin emulsion of any one of Aspects 1 to 7 mentioned above.
A toner contains a core-shell structure containing a core particle containing a binder resin and a shell particle covering the core particle, wherein the shell particle is formed of the polyester resin emulsion of any one of Aspects 1 to 7 mentioned above.
The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-084943 | May 2023 | JP | national |
