JP7708626B2 - Toner and two-component developer containing the same - Google Patents

Description

The present invention relates to a toner that can achieve both low-temperature fixability and heat-resistant storage stability, and a two-component developer that contains the toner.

2. Description of the Related Art In recent years, with the remarkable development of office automation equipment, image forming apparatuses using electrophotography, such as copying machines, printers, and facsimile machines, have come into widespread use, and various image forming methods have been proposed and put to practical use.
For example, in a heat fixing method in which a toner image is fixed onto a recording paper by heating and melting the toner, it is necessary to fix the toner image at as low a temperature as possible in order to achieve energy saving, and therefore a toner with good low-temperature fixing properties is required.
In order to improve the low-temperature fixing property of the toner, for example, a technique of adding a small amount of crystalline polyester to an amorphous polyester as a binder resin has been proposed. By adding crystalline polyester, the viscosity of the toner can be sharply reduced, and the melting temperature can be reduced. However, as the amount of crystalline polyester added increases, the crystallinity in the toner increases, and the sharp melt domain diameter of the crystalline polyester increases, which deteriorates the heat-resistant storage stability and fixing properties at high temperatures of the toner. Therefore, there is a limit to the amount of crystalline polyester added, making it difficult to expand the low-temperature fixing range.

Various techniques have been proposed to improve the above-mentioned problems with toner.
For example, Japanese Patent Publication No. 6-56503 (Patent Document 1) proposes a toner composition comprising resin particles selected from the group consisting of thermotropic liquid crystal polycarbonates, copolycarbonates, polyurethanes, polyesters and copolyesters, and a pigment resin.

Special Publication No. 6-56503

The toner resin composition described in Patent Document 1 contains, as its main component, a thermotropic liquid crystal polymer in which liquid crystal-exhibiting moieties are arranged in the main chain, and has a high softening point, making it difficult to use as a binder resin for toner.

Therefore, the objective of the present invention is to provide a toner that can achieve both low-temperature fixability and heat-resistant storage stability, and a two-component developer that contains the toner.

The inventors conducted extensive research to solve the above problems and discovered that by using a liquid crystalline polyester having liquid crystallinity-exhibiting moieties in the side chains as a binder resin, it is possible to suppress an increase in the sharp melt domain diameter of the toner and maintain heat-resistant storage stability, and the low temperature side of the fixable region can be expanded due to the rapid drop in viscosity around the phase transition temperature, and the softening point can be controlled by the number of liquid crystallinity-exhibiting moieties in the side chains, i.e., it is easy to lower the melting point of the resin and design a resin for low temperature fixation, which led to the completion of the present invention.

Thus, according to the present invention, a toner is provided that contains at least a binder resin and a release agent, and the binder resin contains a side-chain type liquid crystalline polyester resin having a liquid crystal exhibiting portion in the side chain.

The present invention also provides a two-component developer that contains the above toner and a carrier.

The present invention provides a toner that can achieve both low-temperature fixability and heat-resistant storage stability, and a two-component developer that contains the toner.

(1) Toner The toner of the present invention contains at least a binder resin and a release agent, and is characterized in that the binder resin contains a side chain type liquid crystalline polyester resin having a liquid crystallinity-producing moiety in the side chain.
The crystallinity of side-chain liquid crystalline polyester resins changes with temperature. At low temperatures, the liquid crystal-exhibiting sites are oriented, exhibiting properties similar to those of crystalline polyester resins. When the temperature exceeds a threshold temperature, i.e., the liquid crystal isotropic phase transition temperature Tni, the molecular orientation collapses, the viscosity drops sharply, and the same effect as that of crystalline polyester resins is obtained.
On the other hand, since the crystalline domains of the side-chain type liquid crystalline polyester resin are dispersed at the molecular level, the domain diameter does not increase with an increase in the amount added, and the heat-resistant storage stability and fixing properties at high temperatures do not deteriorate. Therefore, it is possible to replace all the binder resins with liquid crystalline polyester resins without using a combination of high and low molecular weight polyester resins as in the past.
The binder resin, which is a characteristic part of the toner of the present invention, will be described below, followed by the toner (also called "toner base particles") which is the basis of the toner, a method for producing the toner, and a two-component developer containing the toner.

(1-1) Binder Resin The side-chain type liquid crystalline polyester resin contained as a binder resin in the toner of the present invention is different from ordinary polyester resins in that it takes a glass state, a liquid crystal phase state, or an isotropic phase state as the temperature rises. Below the glass transition temperature Tg, it becomes a glass state and does not show fluidity, like ordinary polyester resins. On the other hand, at the glass transition temperature Tg or higher, it undergoes a phase transition from the glass state to a liquid crystal phase state, and the flexible part of the liquid crystalline polyester resin starts molecular motion, showing slight fluidity, but the molecules are oriented like crystalline polyester resins, and it has blocking resistance and offset resistance. In addition, at the liquid crystal isotropic phase transition temperature Tni or higher, it undergoes a phase transition to an isotropic phase state, and like ordinary polyester resins, it becomes a molten state and can be fixed. In the present invention, by using a liquid crystalline polyester in such a specific temperature range, it is possible to achieve low-temperature fixing while maintaining sufficient thermal properties.

(Glass transition temperature Tg)
According to an embodiment of the present invention, the side chain type liquid crystalline polyester resin preferably has a glass transition temperature Tg of 50° C. or more and 70° C. or less.
If the glass transition temperature Tg is less than 50° C., the heat-resistant storage stability and the high-temperature region side of fixing may deteriorate, whereas if the glass transition temperature Tg is more than 70° C., the low-temperature fixing property may deteriorate.
The glass transition temperature Tg is more preferably 60° C. or higher and 70° C. or lower.
The method for measuring the glass transition temperature Tg will be described in the Examples.

(Liquid crystal isotropic phase transition temperature Tni)
According to an embodiment of the present invention, the side chain type liquid crystalline polyester resin preferably has a liquid crystal isotropic phase transition temperature Tni of 100° C. or more and 140° C. or less.
The liquid crystal isotropic phase transition temperature Tni means a temperature at which a phase transition occurs from a liquid crystal phase in which the molecules are aligned to an isotropic phase in which the molecules are not aligned.
If the liquid crystal isotropic phase transition temperature Tni is less than 100° C., the heat-resistant storage stability and the high-temperature region side of fixing may deteriorate. On the other hand, if the liquid crystal isotropic phase transition temperature Tni exceeds 140° C., the low-temperature fixing property may deteriorate.
The liquid crystal isotropic phase transition temperature Tni is more preferably 120° C. or higher and 130° C. or lower.
A method for measuring the liquid crystal isotropic phase transition temperature Tni will be described in the examples.

(Peak top molecular weight Mp)
According to an embodiment of the present invention, the side chain type liquid crystalline polyester resin preferably has a peak top molecular weight Mp of 4,000 or more and 15,000 or less as measured by GPC.
If the peak top molecular weight Mp is less than 4,000, the heat resistant storage stability and the high temperature region side of the fixing may deteriorate, whereas if the peak top molecular weight Mp exceeds 15,000, the low temperature fixing property may deteriorate.
The peak top molecular weight Mp is more preferably 8,000 or more and 15,000 or less.
The method for measuring the peak top molecular weight Mp will be described in the Examples.

(resin structure)
The side-chain type liquid crystalline polyester resin is a side-chain type liquid crystalline polymer, which has a polymer skeleton in the main chain and a liquid crystal exhibiting site in the side chain.
Side-chain liquid crystalline polyester resins are preferred because, compared with main-chain liquid crystalline polyester resins, they have lower glass transition temperatures Tg and liquid crystal isotropic phase transition temperatures Tni, and their thermal properties can be controlled by the main chain structure and the type and introduction rate of the side chains introduced.

According to an embodiment of the present invention, the side chain type liquid crystalline polyester resin preferably has any one selected from siloxane, acrylic, and methacrylic in the main chain skeleton.
These main chain skeletons are generally used in liquid crystalline polyesters, and are preferable because side chains can be easily introduced therein and the glass transition temperature Tg can be adjusted by selecting the main chain skeleton.

According to an embodiment of the present invention, the side chain type liquid crystalline polyester resin has a structure represented by the following formula:
It is preferable that the side chain has a basic skeleton selected from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and biphenyl, represented by the following formula:
These skeletal structures are not only commonly used, but also have low melting points and low viscosities at high temperatures, making them suitable for low-temperature fixing.

(Liquid Crystal Phase)
The liquid crystal phase is called differently depending on the order of the oriented molecular orientation, and includes a nematic phase, a smectic phase, a cholesteric phase, etc., and the toner of the present invention may be in any phase form.
Among these phase forms, the nematic phase is the least ordered, the molecular orientation is quickly destroyed and formed, and the viscosity drop with increasing temperature is sharper than other phases, so that the same effect as that of the crystalline polyester resin can be obtained. In addition, the viscosity of the nematic phase is lower than that of other phases. For these reasons, the low-temperature fixability of the toner can be improved by using a liquid crystal polyester resin that forms a nematic phase.
Therefore, according to an embodiment of the present invention, the side chain type liquid crystalline polyester resin preferably has a nematic phase as the liquid crystal phase.

(Content)
According to an embodiment of the present invention, the side chain type liquid crystalline polyester resin is preferably contained in the toner in an amount of 50% by mass or more and 85% by mass or less.
If the content of the side chain liquid crystalline polyester resin in the toner is less than 50% by mass, the liquid crystallinity of the side chain liquid crystalline polyester resin in the toner may not be expressed, whereas if the content in the toner is more than 85% by mass, the resin ratio in the toner increases and the additive ratio decreases, which may significantly deteriorate the properties of the toner.
The content of the side chain type liquid crystalline polyester resin in the toner is more preferably from 70% by mass to 85% by mass.

(Other binder resins)
The toner of the present invention may contain, as a binder resin, in addition to the above-mentioned side chain type liquid crystalline polyester resin, crystalline and amorphous polyester resins commonly used in the technical field, as long as the effects of the present invention are not impaired. In combination with the side chain type liquid crystalline polyester resin, an amorphous polyester resin is preferred.
The content of the amorphous polyester resin in the toner is preferably 0% by mass or more and 30% by mass or less, and more preferably 0% by mass or more and 15% by mass or less.

(1-2) Releasing Agent The releasing agent contained in the toner of the present invention has a function of imparting releasability to the toner when the toner is fixed to a recording medium, and any releasing agent commonly used in the art can be used.
Examples of the release agent include petroleum waxes such as paraffin wax and microcrystalline wax and derivatives thereof; hydrocarbon synthetic waxes such as Fischer-Tropsch wax, polyolefin wax (polyethylene wax, polypropylene wax, etc.), low molecular weight polypropylene wax and polyolefin polymer wax (low molecular weight polyethylene wax, etc.) and derivatives thereof; vegetable waxes such as carnauba wax, rice wax, candelilla wax and derivatives thereof, and Japan wax; animal waxes such as beeswax and spermaceti; oil-based synthetic waxes such as fatty acid amides and phenol fatty acid esters; long-chain carboxylic acids and derivatives thereof; long-chain alcohols and derivatives thereof; silicone polymers; higher fatty acids, and among these, hydrocarbon waxes are preferred.
The above derivatives include oxides, block copolymers of vinyl monomers and wax, and graft modified products of vinyl monomers and wax.
In the present invention, the above-mentioned release agents can be used alone or in combination of two or more.

The content of the release agent in the toner of the present invention is not particularly limited, but is preferably from 0.5 to 5% by mass, and more preferably from 2 to 4% by mass.
If the content of the releasing agent is within the above range, it is possible to obtain a toner that is capable of achieving both low-temperature fixability and heat-resistant storage stability without impairing various physical properties of the toner.
In order to improve the dispersibility of the release agent in the toner, a release agent dispersant such as a styrene-acrylic copolymer resin may be used in combination.

(1-3) Colorant The toner of the present invention may contain a colorant, if necessary, within a range that does not impair the effects of the present invention. Organic and inorganic pigments and dyes of various types and colors commonly used in the technical field can be used. Examples of the colorant include black, white, yellow, orange, red, purple, blue and green colorants.

Examples of black colorants include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, non-magnetic ferrite, magnetic ferrite, and magnetite.
Examples of white colorants include zinc oxide, titanium oxide, antimony white, and zinc sulfide.

Examples of yellow colorants include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 15, C.I. Pigment Yellow 17, C.I. Pigment Yellow 93, C.I. Pigment Yellow 94, and C.I. Pigment Yellow 138.

Examples of orange colorants include red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Balkan orange, industren brilliant orange RK, benzidine orange G, industren brilliant orange GK, C.I. Pigment Orange 31, and C.I. Pigment Orange 43.

Examples of red colorants include red iron oxide, cadmium red, red lead, mercuric sulfide, cadmium, permanent red 4R, lithol red, pyrazolone red, watching red, calcium salt, lake red C, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139, C.I. Pigment Red 144, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 222, etc.

Purple colorants include, for example, manganese violet, fast violet B, and methyl violet lake.
Examples of blue colorants include Prussian blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated product, fast sky blue, indanthrene blue BC, C.I. Pigment Blue 15, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16, C.I. Pigment Blue 60, and the like.
Examples of green colorants include chrome green, chromium oxide, pigment green B, mica light green lake, final yellow green G, C.I. pigment green 7, and the like.

In the toner of the present invention, the above colorants may be used alone or in combination of two kinds, and the combination may be of different colors or the same color.
Two or more kinds of colorants may be used in the form of composite particles. The composite particles can be produced, for example, by adding an appropriate amount of water, a lower alcohol, etc. to two or more kinds of colorants, granulating the mixture with a general granulator such as a high-speed mill, and drying the mixture. Furthermore, in order to uniformly disperse the colorant in the binder resin, the colorant may be used in the form of a master batch. The composite particles and the master batch are mixed into the toner composition during dry mixing.

The content of the colorant in the toner of the present invention is not particularly limited, but is preferably from 2 to 10% by mass, and more preferably from 3 to 10% by mass.
If the content of the colorant is within the above range, it is possible to obtain a toner that is capable of achieving both low-temperature fixability and heat-resistant storage stability without impairing various physical properties of the toner.

(1-4) Charge control agent (charge control agent)
The toner of the present invention may contain a charge control agent, if necessary, within the scope of not impairing the effects of the present invention, and charge control agents commonly used in the art for positive charge control and negative charge control can be used.
Examples of charge control agents for controlling positive charges include nigrosine dyes, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrine, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, nigrosine dyes and derivatives thereof, triphenylmethane derivatives, guanidine salts, and amidine salts.
Examples of charge control agents for negative charge control include oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal naphthenates, metal complexes and metal salts of salicylic acid and its derivatives (metals include chromium, zinc, zirconium, etc.), boron compounds, fatty acid soaps, long-chain alkyl carboxylates, and resin acid soaps.
In the toner of the present invention, the above charge control agents may be used alone or in combination of two or more.
In the toner of the present invention, the above charge control agents may be used alone or in combination of two or more.

The content of the charge control agent in the toner of the present invention is not particularly limited, but is preferably from 0.5 to 5% by mass, and more preferably from 1 to 4% by mass.
If the content of the charge control agent is within the above range, it is possible to obtain a toner that is capable of achieving both low-temperature fixability and heat-resistant storage stability without impairing various physical properties of the toner.

(1-5) External Additives The toner may contain external additives in order to improve its transportability, chargeability, and stirring ability with the carrier in a two-component developer.
As the external additive, an external additive commonly used in the technical field can be used, and examples thereof include inorganic fine particles such as silica and titanium oxide. Those that have been surface-treated (hydrophobized) with a silicone resin, a silane coupling agent, or the like are preferred, and silica particles are particularly preferred in terms of imparting electrostatic charge to the toner.
The external additive is preferably inorganic fine particles having an average primary particle size of 6 to 200 nm.
The amount of the external additive added is not particularly limited, but is preferably 0.2 to 5.0 parts by mass, and more preferably 0.5 to 2.5 parts by mass, based on 100 parts by mass of the toner.

(1-6) Toner Manufacturing Method The toner used in the present invention can be manufactured by a known method using a known device commonly used in the technical field, such as a mixing/kneading step of mixing/kneading materials including at least a binder resin and a release agent, a coarse grinding step of coarsely grinding the obtained molten/kneaded product to obtain a coarsely ground product, a fine grinding step of finely grinding the obtained coarsely ground product to obtain a finely ground product, a classification step of classifying the obtained finely ground product to obtain toner base particles, and an external addition step of adding an external additive to the toner base particles and mixing them to obtain an externally added toner.
Dry methods are preferred in that they require fewer steps and less equipment cost than wet methods, and among them, the pulverization method is particularly preferred.
The conditions for each of the following steps may be appropriately set depending on the target material and the desired physical properties.

(2) Two-Component Developer The two-component developer of the present invention is characterized by containing the toner of the present invention and a carrier.
(Career)
The toner of the present invention can be used in the form of either a one-component developer or a two-component developer. When used as a two-component developer, the toner further contains a carrier in addition to the external additive.
As the carrier, any carrier commonly used in the art can be used, such as a single or composite ferrite made of iron, copper, zinc, nickel, cobalt, manganese, chromium, etc., and a carrier core particle surface-coated with a known coating material.
The average particle size of the carrier is preferably from 10 to 100 μm, and more preferably from 20 to 50 μm.
The content of the carrier is not particularly limited, but is preferably from 85 to 97% by mass, and more preferably from 90 to 95% by mass, based on the total amount of the developer.

The present invention will be specifically described below with reference to Synthesis Examples, Examples, and Comparative Examples. However, the present invention is not limited to the following Examples as long as it does not depart from the gist of the present invention.
In the examples and comparative examples, the physical properties were measured by the methods described below.

[Measurement of Tg and Tni of Liquid Crystalline Polyester]
Using a differential scanning calorimeter (Model: DSC220, manufactured by Seiko Electronics Industries Co., Ltd. (currently Hitachi High-Tech Science Corporation)), 1 g of a toner sample is heated to a temperature of 200° C. at a heating rate of 10° C./min, then held at 200° C. for 2 minutes, and cooled to 30° C. at a heating rate of 10° C./min, to measure a DSC curve. The endothermic peak temperature (glass transition temperature) Tg (° C.) on the low-temperature side during heating of the obtained DSC curve and the endothermic peak temperature (liquid crystal isotropic phase transition temperature) Tni (° C.) on the high-temperature side are determined.

[Measurement of Tg and Tm of amorphous polyester]
The DSC curve of the amorphous polyester is measured in the same manner as in the above DSC measurement. The endothermic peak temperature (glass transition temperature) Tg (°C) on the low-temperature side during heating of the obtained DSC curve and the endothermic peak temperature (melting temperature) Tm (°C) on the high-temperature side are determined.

[Measurement of toner flow start temperature and softening temperature]
Using a flow property evaluation device (Shimadzu Corporation, Flow Tester, Model: CFT-100C), 1 g of sample was heated from an initial temperature of 40°C at a heating rate of 6°C/min while applying a load of 20 kgf/ ^cm2 (9.8 x 105 Pa) to cause the sample to flow out of a die (nozzle diameter 1 mm, length 1 mm). The temperature at which the sample began to flow out was recorded as the flow initiation temperature "Ti", and the temperature at which half the sample had flowed out was recorded as the softening temperature "Tm".

[GPC measurement (peak top molecular weight: Mp)]
The peak top molecular weight (Mp) of the binder resin and the toner is measured by gel permeation chromatography (GPC) under the following conditions.
The peak top molecular weight refers to the molecular weight showing the maximum peak height in a chromatogram obtained by GPC measurement.
In measuring the molecular weight, the polyester resin is dissolved in tetrahydrofuran (THF), and the insoluble matter is filtered off using a glass filter, and the resulting solution is used as a sample solution.
(Apparatus and Conditions)
Equipment: Tosoh Corporation, model: HLC-8120
Column: 2 TSK GEL GMH6 columns manufactured by Tosoh Corporation Measurement temperature: 40°C
Sample solution: 0.25% by mass THF solution Solution injection amount: 100 μl
Detector: Refractive index detector Reference material: 12 types of standard polystyrene (TSKstandard POLYSTYRENE) manufactured by Tosoh Corporation (molecular weights: 500, 1050, 2800, 5970, 9100, 18100, 37900, 96400, 190000, 355000, 1090000, and 2890000)

(Synthesis Example 1: Synthesis of Liquid Crystalline Polyester A)
90 mL of methanol was added to a 300 mL glass flask equipped with a stirrer, a reflux condenser, and a dropping funnel, and 27.7 g of p-hydroxybenzoic acid was dissolved therein. 34.2 g of potassium hydroxide was dissolved in 220 mL of methanol, which was then added dropwise to the p-hydroxybenzoic acid solution and stirred at room temperature (25°C) for 2 hours. 26 mL of allyl chloride was added to the resulting solution, and the mixture was stirred at a temperature of 70°C for 6 hours. The solvent was then distilled off under reduced pressure, and the resulting reaction product was washed with 160 mL of water and 160 mL of diethyl ether. The resulting aqueous solution was then neutralized with hydrochloric acid, and the precipitate was recrystallized with isopropanol to obtain compound A.

In a 300 mL glass flask equipped with a stirrer, 4.93 g of compound A and 70 mL of thionyl chloride were added and stirred for 2 hours. Thereafter, the solvent was distilled off under reduced pressure, and 30 mL of dichloromethane was added to prepare a compound A solution.
5.21 g of p-methoxyphenol and 8.66 mL of triethylamine were added to 17 mL of dichloromethane, and the mixture was added dropwise to the compound A solution in an ice bath, followed by stirring for 6 hours. The solvent was then distilled off under reduced pressure, and the resulting reaction product was washed with ethyl acetate and an aqueous sodium hydroxide solution and recrystallized from ethanol to obtain a mesogen that is a liquid crystal generating site.

0.501g of mesogen, 0.139g of polymethylsiloxane, and 5mL of toluene were added to a 50mL glass flask equipped with a stirrer and a reflux condenser, and the flask was filled with nitrogen. Then, a catalytic amount of hexachloroplatinic (IV) acid hexahydrate was added, and the mixture was reacted at a temperature of 110°C for 24 hours. The solvent was distilled off under reduced pressure, and the resulting reaction product was purified by a reprecipitation method using methanol as a poor solvent and toluene as a good solvent, to obtain 0.309g of liquid crystalline polyester A (resin A) as a side chain type liquid crystalline polyester resin.
It was confirmed by NMR analysis that the obtained resin was Resin A having siloxane in the main chain skeleton and p-hydroxybenzoic acid in the side chain skeleton, and by observation with a polarizing microscope that the obtained resin was in a liquid crystal state having a nematic phase as the liquid crystal phase.
Furthermore, the glass transition temperature Tg, liquid crystal isotropic phase transition temperature Tni and peak top molecular weight Mp of resin A were measured by the above-mentioned measuring methods.

(Synthesis Examples 2 to 10: Synthesis of Liquid Crystalline Polyesters B to J)
Liquid crystalline polyesters B to J (resins B to J) were obtained as side chain type liquid crystalline polyester resins in the same manner as in Synthesis Example 1, except that acrylic or methacrylic, 6-hydroxy-2-naphthoic acid or biphenyl shown in Table 1 were used instead of the siloxane main chain skeleton and the p-hydroxybenzoic acid side chain skeleton.

(Synthesis Example 11: Synthesis of amorphous polyester K)
In a 5 L reaction tank, 440 g (2.7 mol) of terephthalic acid, 235 g (1.4 mol) of isophthalic acid, 7 g (0.05 mol) of adipic acid, 554 g (8.9 mol) of ethylene glycol, and 0.5 g of tetrabutoxy titanate as a polymerization catalyst were placed and reacted for 5 hours at 210° C. under a nitrogen stream while distilling off the water and ethylene glycol produced. Thereafter, the reaction was continued for 1 hour under a reduced pressure of 5 to 20 mmHg.
Next, 103 g (0.54 mol) of trimellitic anhydride was added, and the mixture was reacted under normal pressure for 1 hour, and then reacted under reduced pressure of 20 to 40 mmHg, and a resin was taken out at a predetermined softening point. The amount of ethylene glycol recovered was 219 g (3.5 mol). The obtained resin was cooled to room temperature and then pulverized to form particles, which were used as amorphous polyester resin K.
The amorphous polyester resin K had a Tm of 145° C. and a peak top molecular weight Mp of 12,000.

(Synthesis Example 12: Synthesis of amorphous polyester L)
In the same manner as in Synthesis Example 11, an amorphous polyester L having a predetermined softening point was obtained.

Example 1
<Material mixing, kneading, crushing, and classification processes>
Binder resin: Resin A (glass transition temperature Tg 50° C., liquid crystal isotropic phase transition temperature Tni 140° C., peak top molecular weight Mp 15,000, see Synthesis Example 1) 84% by mass
Colorant: Carbon black (manufactured by Cabot Corporation, product name: Regal 1330)
6% by mass
Release agent: ester wax (manufactured by NOF Corporation, product name: WEP8) 3% by mass
Release agent dispersant: styrene-acrylic copolymer resin (manufactured by Mitsui Chemicals, Inc., product name: SA800) 5% by weight
Charge control agent: Salicylic acid compound (Orient Chemical Industry Co., Ltd., product name: Bontron E-84) 2% by mass

The above materials were premixed for 5 minutes using an air flow mixer (Henschel mixer, manufactured by Mitsui Mining Co., Ltd. (currently Nippon Coke and Engineering Co., Ltd.), model: FM20C), and then melt-kneaded using a twin-screw extruder (manufactured by Ikegai Co., Ltd., model: PCM30) under conditions of a cylinder setting temperature of 110° C., a barrel rotation speed of 300 rpm, and a raw material supply rate of 20 kg/hour to obtain a molten kneaded product [Mixing and kneading process].
The resulting molten kneaded product was cooled with a cooling belt and then coarsely pulverized using a cutting mill (manufactured by Orient Co., Ltd., Model: VM-16) to obtain a coarsely pulverized product [coarse pulverization step].
Next, the obtained coarsely pulverized product was finely pulverized using a jet pulverizer (manufactured by Nippon Pneumatic Mfg. Co., Ltd., model: IDS-2) to obtain a finely pulverized product [fine pulverization step].
The resulting finely pulverized product was classified using an air classifier (manufactured by Nittetsu Mining Co., Ltd., model: EJ-LABO) to obtain toner base particles having an average primary particle size of 6.5 μm [classification step].

<External addition process>
To 100 parts by mass of the obtained toner base particles, 1.0 part by mass of commercially available silica fine particles (average primary particle diameter 7 nm, manufactured by Aerosil Corporation, product name: R976S) was added, and the obtained mixture was mixed for 2 minutes using an air flow mixer (Henschel mixer, manufactured by Mitsui Mining Co., Ltd. (now Nippon Coke and Engineering Co., Ltd.), model: FM20C) with the tip speed of the stirring blade set to 40 m/sec, to obtain an externally added toner [external addition process].

<Manufacturing process of resin-coated carrier>
Coating resin (1) (silicone-based, trade name: KR240, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.375 parts by weight, and coating resin (2) (trade name: KR251, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.375 parts by weight were dissolved in 12 parts by weight of toluene, and conductive particles (trade name: VULCAN XC-72, manufactured by Cabot Corporation) 0.0375 parts by weight, and coupling agent (trade name: AY43-059, manufactured by Dow Corning Toray Co., Ltd.) 0.0225 parts by weight were added thereto and dispersed to prepare a coating resin liquid. The surface of 100 parts by weight of ferrite carrier core material having a volume average diameter of 40 μm was coated with 12.8 parts by weight of the coating resin liquid by the immersion method. Thereafter, the carrier was produced by passing through a curing process at a curing temperature of 200 ° C. and a curing time of 1 hour, and then sieving with an opening of 150 μm.

<Developer manufacturing process>
The obtained toner with external additives and the resin-coated carrier were put into a V-type mixer (manufactured by Tokuju Machine Works, Ltd., product name: V-5) so that the concentration of the toner with external additives relative to the total amount of the two-component developer was 7% by mass, and mixed for 30 minutes to obtain a two-component developer with a toner concentration of 7%.

(Examples 2 to 12)
Toners and developers containing external additives were obtained in the same manner as in Example 1, except that the binder resins shown in Table 1 were used.
The binder resin in Example 5 was made of 50% by mass of resin B, which was a liquid crystalline polyester resin, and 34% by mass of resin K, which was an amorphous polyester resin.
Resin K was an amorphous polyester resin synthesized using PO-BPA (propoxylated bisphenol A) and EO-BPA (ethoxylated bisphenol A) as aromatic alcohol components and fumaric acid and mellitic anhydride as acid components, and having an outflow start temperature Ti of 105°C, a melting temperature Tm of 145°C, and a peak top molecular weight Mp of 12,000 in flow tester measurement.

In addition, as the binder resin in Example 6, 45% by mass of resin B, which is a liquid crystalline polyester resin, and 39% by mass of resin L, which is a non-crystalline polyester resin, were used.
Resin L was an amorphous polyester resin synthesized using PO-BPA and EO- BPA as aromatic alcohol components and fumaric acid and mellitic anhydride as acid components, and having an outflow start temperature Ti of 104°C, a melting temperature Tm of 112°C, and a peak top molecular weight Mp of 5,500 as measured with a flow tester.

(Comparative Examples 1 to 2)
Toners and developers containing external additives were obtained in the same manner as in Example 1, except that the binder resins shown in Table 1 were used.
As the binder resin in Comparative Example 1, 84% by mass of resin L, which is an amorphous polyester resin, was used instead of the liquid crystalline polyester resin.

As the binder resin in Comparative Example 2, 84% by mass of Resin M, a main chain type liquid crystalline polyester resin, was used instead of the liquid crystalline polyester resin.
Resin M was a commercially available main-chain liquid crystalline polyester resin having a main chain with p-hydroxybenzoic acid as the basic skeleton, a glass transition temperature Tg of 45° C., a liquid crystal isotropic phase transition temperature Tni of 210° C., and a peak top molecular weight Mp of 10,000.

[evaluation]
The toners and two-component developers prepared in Examples 1 to 12 and Comparative Examples 1 and 2 were evaluated for the following items, and a comprehensive evaluation was made based on the results. The results are shown in Table 2.

[Evaluation 1: Fixability (low temperature fixability and high temperature fixability)]
The fixing property of the two-component developer was evaluated using a commercially available copying machine (manufactured by Sharp Corporation, model: MX-M5100FN) modified for the evaluation.
First, a sample image including a solid image (a rectangle measuring 20 mm in length and 50 mm in width) was formed as an unfixed image on a recording paper (manufactured by Sharp Corporation, PPC paper, model: SF-4AM3). At this time, the amount of toner adhering to the recording paper in the solid image was adjusted to be 0.5 mg/ ^cm2 .
Next, a fixed image was produced using a hard roller fixing device. The fixing process speed was set to 120 mm/sec, and the temperature of the fixing roller was increased in increments of 5° C. from 110° C. to determine the minimum and maximum temperatures at which low-temperature offset and high-temperature offset did not occur, respectively.
The terms "low temperature offset" and "high temperature offset" are defined as a state in which toner is not fixed to the recording paper during fixing, but remains attached to the fixing belt and adheres to the recording paper after the fixing belt has made one revolution.

From the obtained results, the "low temperature fixability" was judged according to the following criteria.
A: Minimum temperature less than 110°C B: Minimum temperature 110°C or more and less than 120°C C: Minimum temperature 120°C or more and less than 125°C D: Minimum temperature 125°C or more and less than 130°C E: Minimum temperature 130°C or more Furthermore, from the obtained results, "high temperature fixability" was judged according to the following criteria.
A: Maximum temperature is 195°C or higher)
B: Maximum temperature is 185°C or higher but less than 195°C)
C: Maximum temperature is 180°C or higher but less than 185°C)
D: Maximum temperature is 175°C or higher but less than 180°C)
E: Maximum temperature is less than 175°C)

[Evaluation 2: Heat-resistant storage stability]
The heat resistance storage stability was evaluated based on the presence or absence of aggregates after high-temperature storage.
5 g of the prepared toner with external additives was weighed (total weight of toner: g), placed in a 50 mL plastic container, sealed, and left for 48 hours at a temperature of 50° C. Thereafter, the toner was taken out and classified using a 200 mesh sieve, and the toner remaining on the sieve was weighed (weight of toner remaining on the sieve: g).
The ratio of the weight of the sieved toner to the total weight of the toner, which was weighed in advance, was calculated as the remaining amount (%), and the heat-resistant storage stability was evaluated according to the following evaluation criteria.
A: Less than 0.5% remaining B: Between 0.5% and 7% remaining C: Between 7% and 10% remaining D: Between 10% and 12% remaining E: Between 12% and 12% remaining
The lower the residual amount value, the less blocking occurs in the toner, and the more sufficiently the toner base particles are covered with the coating layer.

[Overall Judgment]
Based on the above evaluation results, an overall judgment was made according to the following criteria.
A: All evaluation items are A (usable)
B: At least one evaluation item has a B (usable)
C: At least one evaluation item has a C (usable)
D: At least one evaluation item has a D (usable)
E: At least one evaluation item has an E (cannot be used)

From Tables 1 and 2, the following can be seen:
(1) Two-component developers (Examples 1 to 12) containing toners satisfying the requirements of the present invention can achieve both low-temperature fixability and heat-resistant storage stability. (2) On the other hand, two-component developers (Comparative Examples 1 and 2) containing toners not satisfying the requirements of the present invention cannot achieve both low-temperature fixability and heat-resistant storage stability. (3) A two-component developer (Example 9) containing toners using resins with low glass transition temperatures Tg is excellent in low-temperature fixability but poor in high-temperature fixability, and a two-component developer (Example 10) containing toners using resins with high glass transition temperatures Tg is excellent in high-temperature fixability but poor in low-temperature fixability. From this, it can be seen that high-temperature and low-temperature fixability can be maintained at a certain level or higher within the preferred range of glass transition temperatures Tg, but high-temperature and low-temperature fixability can be increased to a level that is more than necessary by adjusting the glass transition temperature Tg to a more optimal range. (4) Both two-component developers (Examples 5 and 6) containing toners containing a mixture of side-chain liquid crystalline polyesters and amorphous polyesters are poor in high-temperature and low-temperature fixability. For this reason, it is preferable to use the side chain type liquid crystalline polyester alone, and the addition of an amorphous polyester may inhibit the expression of the properties of the side chain type liquid crystalline polyester.

Claims (6)

The composition includes at least a binder resin and a release agent, the binder resin includes a side-chain liquid crystalline polyester resin having a liquid crystallinity-exhibiting portion in the side chain,
the side chain type liquid crystalline polyester resin has a peak top molecular weight Mp of 8,000 or more and 15,000 or less as measured by GPC;
The side chain type liquid crystalline polyester resin has the following structural formula:
and biphenyl. The toner according to claim 1, wherein the side-chain liquid crystalline polyester resin has a glass transition temperature Tg of 50°C or higher and 70°C or lower. 3. The toner according to claim 1 , wherein the side chain type liquid crystalline polyester resin has any one selected from the group consisting of siloxane, acrylic and methacrylic in the main chain skeleton. 4. The toner according to claim 1, wherein the side chain type liquid crystalline polyester resin has a nematic phase as a liquid crystal phase. 5. The toner according to claim 1 , wherein the side chain type liquid crystalline polyester resin is contained in the toner in an amount of 50% by mass or more and 85% by mass or less. A two-component developer comprising the toner according to any one of claims 1 to 5 and a carrier.