JP2015158532A - electrophotographic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner that has high offset resistance and excellent blocking resistance in consideration of global environmental protection, and a manufacturing method of the toner.SOLUTION: There is provided an electrophotographic toner including pigment, and a benzylated polyester resin obtained by benzylating a polyester resin, which is a polycondensation product of a polyalcohol and rosin as a binder resin, with a benzylating agent.

Description

The present invention relates to an electrophotographic toner.
More specifically, the present invention relates to an electrophotographic toner excellent in low-temperature fixability and blocking resistance, comprising at least a benzylated polyester resin and a pigment.

  Toner that visualizes a latent image is used in various image forming processes, and as an example, it is known to be used in an electrophotographic image forming process.

  In an image forming apparatus using an electrophotographic image forming process, generally, a charging process for uniformly charging a photosensitive layer on a surface of a photosensitive drum as a latent image carrier, and a surface of a charged photosensitive drum. An exposure process for projecting signal light of a document image to form an electrostatic latent image, a developing process for supplying an electrophotographic toner to the electrostatic latent image on the surface of the photosensitive drum to visualize it, and a toner on the surface of the photosensitive drum Use a cleaning blade to transfer the image onto a medium such as paper or an OHP sheet, a fixing process to fix the toner image on the medium by heating or pressing, and the toner remaining on the surface of the photosensitive drum after transferring the toner image. A desired image is formed on the media by performing a cleaning process of removing and cleaning. Transfer of the toner image to the medium may be performed via an intermediate transfer medium.

  As the developer used in such an image forming apparatus, there are a one-component developer mainly composed of toner and a two-component developer using a mixture of toner and carrier. The toner used in these developers is produced by a polymerization method represented by, for example, a kneading and pulverizing method, a suspension polymerization method, and an emulsion polymerization aggregation method.

  In the kneading and pulverization method, the toner material, which is mainly composed of a binder resin and a colorant, and added with a release agent and a charge control agent as necessary, is melt-kneaded, cooled and solidified, and then pulverized. The toner is manufactured by classification.

  In recent years, many efforts have been made in various technical fields from the viewpoint of global environmental conservation. Currently, many raw materials for products are manufactured from petroleum, but efforts to reduce the carbon dioxide generated during the production and incineration of these raw materials and the required energy are from the perspective of preventing global warming. Very important.

  In addition, energy conservation is being studied from various angles as another initiative that helps prevent global warming. In the field of electrophotography, by reducing the fixing temperature of toner transferred onto media such as paper and OHP sheets. There is a growing recognition that reducing fixing energy is effective. Further, further speeding up of copying machines and facsimile machines is also desired. From these trends, it is indispensable to lower the melting point of the toner.

The lowering of the melting point of the toner described above means lowering the lower limit fixing temperature, whereby low temperature fixing can be achieved.
As a method for fixing a toner image transferred on a medium such as paper or an OHP sheet, a contact heating type fixing method in which a toner image is heated and melted by a heat roll or the like and is pressed and fixed is often used. The fixability of the toner in the system can be evaluated by the fixable temperature range from the lower limit fixing temperature to the hot offset start temperature.

  As the binder resin for toner, a resin having a crosslinked structure or a resin containing a high molecular weight substance and a low molecular weight substance is used. In such a binder resin, a crosslinking component is used to improve hot offset resistance. If the content of the high molecular weight component is increased, the melt viscosity of the resin becomes too high, and the low-temperature fixability of the toner may be insufficient. On the other hand, if the content of the low molecular weight substance is increased in order to improve the low-temperature fixability, the melt viscosity of the resin is reduced, but the elasticity of the toner is lowered and the hot offset resistance may be lowered.

  Therefore, in order to achieve a low melting point of the toner while maintaining the offset resistance at high temperature, it is particularly important to design a new binder resin for toner.

  In addition, the use of plant-derived resources called biomass has attracted a great deal of attention as a new initiative that helps prevent global warming. Carbon dioxide generated when burning biomass is originally atmospheric carbon dioxide taken up by plants by photosynthesis, so overall, the balance of atmospheric carbon dioxide is zero, and the total amount is considered to be unchanged. It has been. In this way, the property that does not affect the increase or decrease of carbon dioxide in the atmosphere is called carbon neutral, and it is possible to fix the amount of carbon dioxide in the atmosphere by using plant-derived resources that are carbon neutral. it can. Plastics produced from such biomass are called by names such as biomass polymer, biomass plastic, and non-petroleum polymer material, and the monomers used as these raw materials are also called biomass monomers.

  In the field of electrophotography, in consideration of global environmental conservation, efforts are being made to use biodegradable resins including biomass, which is excellent in environmental safety and effective in reducing carbon dioxide.

  For example, in general, a polyester resin is produced by polycondensation of a carboxylic acid and an alcohol. However, in Patent Document 1, at least an alcohol component and a rosin compound are combined with the total mass of the alcohol component and the carboxylic acid component. A technique has been proposed in which a polyester resin obtained by polycondensation with a carboxylic acid component containing 5% by mass or more is used as a binder resin for toner.

JP 2010-152291 A

  However, although the toner produced by the method shown in Patent Document 1 is excellent in low-temperature fixability and offset resistance, it has a low steric hindrance of abietic acid and a hydroxyl group at each adjacent position, which is poor in reactivity 1 Since 2-polypropanediol is polycondensed, the unreacted hydroxyl group and carboxy group remain, which deteriorates the crystallinity and heat resistance of the resin. Therefore, the toner produced using the resin has a problem that it is easily blocked and offset under a high temperature environment.

  The present invention has been made in view of the above-described problems, and mainly provides a toner having high offset resistance and excellent blocking resistance in consideration of global environmental conservation, and a method for producing the toner. Let it be an issue.

  The inventor of the present invention, as a result of diligent research, has reacted at least the unreacted hydroxyl group and carboxy group present in the polyester resin obtained by polycondensation of rosin and polyhydric alcohol with a benzylating agent. The electrophotographic toner containing the obtained polyester resin and pigment was found to have high offset resistance and excellent blocking resistance, and the present invention was completed.

  Thus, according to the present invention, at least a polyester resin that is a polycondensate of rosin and a polyhydric alcohol as a binder resin, and a benzylated polyester resin benzylated with a benzylating agent, and a pigment are included. An electrophotographic toner (hereinafter referred to as “electrophotographic toner” or simply “toner”) is provided.

  Further, according to the present invention, the toner in which the rosin is one or more compounds selected from the group consisting of abietic acid, neoabietic acid, dihydroabietic acid, pimaric acid, isopimaric acid, and sandaracopimaric acid. Provided.

  The present invention also provides the toner, wherein the benzylating agent is a benzyl halide.

  Further, according to the present invention, there is provided the toner, wherein the benzylating agent is one or more benzylating agents selected from the group consisting of benzyl fluoride, benzyl chloride, benzyl bromide and benzyl iodide. .

  Further, according to the present invention, there is provided the toner in which the benzylation is performed in the presence of a basic compound.

  According to the invention, there is provided the toner in which the benzylation is performed in the presence of one or more basic compounds selected from imidazole, triethylamine, diisopropylethylamine, pyridine and 4-N, N-dimethylaminopyridine. Provided.

  Further, according to the present invention, there is provided the toner in which the benzylated polyester resin has a weight average molecular weight (Mw) of 3000 to 40000.

  Further, according to the present invention, there is provided the toner in which the benzylated polyester resin has a softening temperature of 110 to 160 ° C.

  Furthermore, according to the present invention, there is provided the toner in which the benzylated polyester resin has a glass transition temperature of 50 to 80 ° C.

  The electrophotographic toner according to the present invention has excellent storage stability, excellent charging stability under high humidity conditions, offset resistance and blocking resistance, suppresses low temperature offset, satisfies high temperature offset, and provides stable high image quality. Can provide.

  The toner according to the present invention includes at least a polyester resin that is a polycondensate of rosin and a polyhydric alcohol as a binder resin, further benzylated with a benzylating agent, and a pigment. .

  More specifically, the toner according to the present invention includes a polyester resin in which an unreacted hydroxyl group and / or carboxyl group present in a polyester resin obtained by polycondensation of rosin and a polyhydric alcohol is further protected with a protecting group. It is characterized by that.

  The protecting group used for protecting the unreacted hydroxyl group and / or carboxy group can usually be selected from protecting groups known to those skilled in the art as protecting groups for the hydroxyl group and carboxy group.

  In addition, the above-mentioned protecting group can be selected from known protecting groups described in Protective Groups in Organic Synthesis, 1981, John Wiley & Sons by Theodora W. Green.

  However, in the present invention, a benzylating agent is used as the protecting group from the viewpoints of ease, cost, safety and the like when the protecting group is used on an industrial scale. It is not meant to limit only the benzylating agent as the above protecting group.

  That is, the toner for electrophotography according to the present invention includes a benzylated polyester resin and a pigment obtained by benzylating an unreacted hydroxyl group and carboxy group present in a polyester resin which is a polycondensate of rosin and a polyhydric alcohol with a benzylating agent. It is characterized by including.

  The rosin used in the production of the benzylated polyester resin according to the present invention includes a tall rosin obtained by steam distillation of crude tall oil produced as a by-product in a manufacturing process in which pine wood is pulped by the kraft method; There is a gum rosin obtained by steam-distilling the raw pine crab collected and collected; and a wood rosin obtained by distilling the harvested pine root stock into chips and extracting it with an organic solvent, followed by distillation. These rosins are obtained by a conventionally known production method.

  About 90% of the rosin is a resin acid, and the main component is a mixture of resin acids such as abietic acid, neoabietic acid, dihydroabietic acid, dehydroabietic acid, parastrinic acid, pimaric acid, isopimaric acid, and sandaracopimaric acid. It is said.

  Therefore, the rosin, which is a monocarboxylic acid monomer raw material used for the production of the benzylated polyester resin according to the present invention, is selected from the group consisting of abietic acid, neoabietic acid, dihydroabietic acid, pimaric acid, isopimaric acid and sandaracopimaric acid One or more compounds may be used.

Moreover, you may use a dicarboxylic acid monomer further for manufacture of the benzylation polyester resin by this invention. Specifically, what is known as a monomer for polyester can be used, for example, aromatic carboxylic acids such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalenedicarboxylic acid; maleic anhydride, fumaric acid Aliphatic carboxylic acids such as acid, succinic acid, alkenyl succinic anhydride, and adipic acid; and lower alkyl esters of these polybasic acids such as ester compounds of methyl, ethyl, n-propyl, i-propyl, or t-butyl, etc. Is mentioned.
A polybasic acid can be used individually by 1 type, or can use 2 or more types together.

As the polyhydric alcohol, those known as monomers for polyesters can be used. For example, aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentylglycol, glycerin; And alicyclic polyhydric alcohols such as methanol and hydrogenated bisphenol A; aromatic diols such as an ethylene oxide adduct of bisphenol A and a propylene oxide adduct of bisphenol A;
A polyhydric alcohol can be used individually by 1 type, or can use 2 or more types together.

  The polycondensation reaction of a monocarboxylic acid or polybasic acid and a polyhydric alcohol can be carried out according to a conventional method. For example, the monocarboxylic acid or polybasic acid and polyhydric alcohol are polymerized in the presence of an organic solvent and a polycondensation catalyst. Is done by letting

The polymerization reaction may be terminated when the acid value, softening temperature, etc. of the polyester resin to be produced reach a predetermined value.
In this way, a polyester resin is obtained.

In some cases, an organic solvent may not be used. When a methyl esterified product of a polybasic acid is used as a part of the polybasic acid, a demethanol polycondensation reaction is performed. In this polycondensation reaction, for example, the carboxyl group content at the end of the polyester can be adjusted by appropriately changing the mixing ratio of polybasic acid and polyhydric alcohol, the reaction rate, etc., and thus the properties of the resulting polyester are changed. be able to.
When trimellitic anhydride is used as the polybasic acid, a carboxyl group can be easily introduced into the main chain of the polyester, and a modified polyester can be obtained.

The polycondensation of the alcohol component and the carboxylic acid component is preferably performed in the presence of an esterification catalyst. Preferable examples of the esterification catalyst in the present invention include a titanium compound and an inorganic tin (II) compound, and these are used alone or in combination. As a titanium compound, the titanium compound which has a Ti-O bond is preferable, and the compound which has a C1-28 total carbon number alkoxy group, an alkenyloxy group, or an acyloxy group is more preferable.
In addition, as said C1-C28 alkoxy group, a methoxy group, an ethoxy group, isopropyl alkoxy group, t-butyl alkoxy group, a pentoxy group etc. can be used, for example.

  As the inorganic tin (II) compound, a tin (II) compound having a Sn-halogen bond is preferable, and tin (II) fluoride, chloride, bromide, iodide and the like can be used.

The polyester resin in the present invention uses a self-dispersing polyester that exhibits self-dispersibility in water by bonding a hydrophilic group such as a carboxyl group or a sulfonic acid group to the main chain and / or side chain of the polyester. You can also.
A resin obtained by grafting polyester and acrylic resin can also be used.

  As the benzyl halide as the benzylating agent, one kind can be used alone from the group consisting of benzyl fluoride, benzyl chloride, benzyl bromide and benzyl iodide, and two or more kinds may be used.

The reaction of the polyester resin and benzyl halide in the present invention is carried out, for example, by reacting an unreacted hydroxyl group and carboxy group present in the polyester resin with benzyl halide in the presence of an organic solvent and a basic compound. The process is terminated when the hydroxyl value, acid value, softening temperature, and the like of the resulting benzylated polyester reach predetermined values.
The weight average molecular weight (Mw) of the benzylated polyester resin according to the present invention is in the range of 2000 to 50000, preferably 3000 to 40000, from the viewpoint of the production of the photoreceptor.

The hydroxyl value of the benzylated polyester resin according to the present invention is preferably 12 or less, more preferably 9 or less.
The acid value of the benzylated polyester resin according to the present invention is preferably 20 or less, more preferably 18 or less.
Moreover, the softening temperature of the benzylated polyester resin according to the present invention is preferably 100 to 180, more preferably 110 to 160.
Furthermore, the glass transition temperature of the benzylated polyester resin according to the present invention is preferably 40 to 90, more preferably 50 to 80.

  Preferable examples of the amine as the basic compound used in the present invention include imidazole, triethylamine, diisopropylethylamine, pyridine and 4-N, N-dimethylaminopyridine. Any of the above amines may be used alone or in combination.

As the colorant used in the toner of the present invention, various kinds and colors of various colors can be used regardless of whether they are organic or inorganic.
Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite.

  Yellow pigments 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, and quinoline. Coloring agents such as yellow lake, permanent yellow NCG, and tartrazine lake are listed.

  Examples of the orange pigment include colorants such as red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.

  Examples of red pigments include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red C, lake red D, brilliant carmine 6B, eosin lake, Coloring agents such as rhodamine lake B, alizarin lake, and brilliant carmine 3B may be mentioned.

Examples of purple pigments include colorants such as manganese purple, fast violet B, and methyl violet lake.
Examples of the blue pigment include colorants such as bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated product, first sky blue, and indanthrene blue BC.

  Examples of the green pigment include colorants such as chromium green, chromium oxide, pigment green B, micalite green lake, and final yellow green G.

The colorant concentration in the toner of the present invention is preferably 5 to 12% by weight, more preferably 6 to 8% by weight in the case of a black colorant such as carbon black.
The colorant concentration in the case of a color image is preferably in the range of 3 to 8% by weight, and more preferably in the range of 4 to 6% by weight.

In the toner of the present invention, in addition to the above-described amorphous resin, crystalline resin, and colorant, agents such as magnetic powder, a release agent, and a charge control agent can be blended as necessary.
Examples of the magnetic powder include magnetic materials such as magnetite, γ-hematite, and various ferrites.

  Examples of the release agent include various release agents, in particular, low molecular weight polypropylene, polyethylene, oxidized polypropylene, and polyolefin waxes such as polyethylene. By using these release agents, the fixability of the toner of the present invention can be mentioned. Can be improved.

In addition, it is preferable that the addition amount of a mold release agent shall be 1-10 weight part with respect to 100 weight part of binder resin.
There are two types of charge control agents for negatively charged toner and positively charged toner.

  The charge control agents for negatively charged toners include chromium / azo complex dyes, iron azo complex dyes, cobalt / azo complex dyes, salicylic acid, salicylic acid derivative chromium complexes, zinc complexes, aluminum complexes, and boron complexes. A salicylate compound, a naphtholic acid, a chromium, zinc, aluminum and boron complex of a naphtholic acid derivative, a naphtholic acid compound, a benzylic acid and a chromium, zinc, aluminum and boron complex of a benzylic acid derivative, Surfactants such as benzylate compounds, long-chain alkyl carboxylates, and long-chain alkyl sulfonates can be mentioned.

  Examples of charge control agents for positively charged toners include derivatives such as nigrosine dyes, nigrosine dye derivatives, triphenylmethane derivatives, quaternary ammonium salts, quaternary phosphonium salts, quaternary pyridinium salts, guanidine salts, and amidine salts.

The charge control agent is preferably added in an amount of 0.01 to 5 parts by weight with respect to 100 parts by weight of the binder resin.
For example, additives added for the purpose of adjusting fluidity, preventing toner filming on the photoreceptor, and improving the cleaning properties of residual toner on the photoreceptor drum include silica, alumina, titania, zirconia, Inorganic oxides such as tin oxide and zinc oxide, and compounds such as acrylic acid esters, methacrylic acid esters, and styrene, and copolymer resin fine particles, fluororesin fine particles, silicone resin fine particles, and stearic acid And higher fatty acids, metal salts of the higher fatty acids, and agents such as carbon black, fluorinated graphite, silicon carbide, and boron nitride.

  The addition amount of these various additives is preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the binder resin.

  The toner of the present invention produced by the method described above is used to form an image on a sheet such as a copy sheet in an image forming apparatus such as a copying apparatus and a printer apparatus.

  In the image forming apparatus using the toner of the present invention, when an image is formed on a sheet, the photosensitive drum is uniformly charged, and an optical image based on the image to be formed on the charged photosensitive drum is scanned. An electrostatic latent image is formed, and the formed electrostatic latent image is developed to make a visible image by attaching the toner of the present invention, the obtained visible image is transferred onto a sheet, and the transferred toner Is fixed on a sheet to form an image.

Next, the present invention will be specifically described using examples and comparative examples. However, the present invention is not particularly limited to these examples as long as the gist thereof is not exceeded.
Each physical property value in Examples and Comparative Examples was measured as follows.

Glass transition temperature (Tg) of binder resin
Using a differential scanning calorimeter (trade name: Diamond DSC, manufactured by PerkinElmer Japan Co., Ltd.), 0.01 g of a sample was heated at a heating rate of 10 ° C./minute (10 ° C./min) according to Japanese Industrial Standard (JIS) K7121-1987. ) And the DSC curve was measured. The intersection of the straight line obtained by extending the low-temperature base line of the endothermic peak corresponding to the glass transition of the obtained DSC curve to the high-temperature side and the tangent line drawn at the point where the slope is maximum with respect to the low-temperature curve of the peak. The temperature was determined as the glass transition temperature (Tg).

Softening temperature (T _1/2 )
Using a flow characteristic evaluation apparatus (trade name: Flow Tester CFT-500C, manufactured by Shimadzu Corporation), 1 g of a sample is inserted into a cylinder, and a load of 10 kgf / cm ² (0.9980665 MPa) is applied so as to be extruded from a die. While heating at a heating rate of 6 ° C./min (6 ° C./min), the temperature at which half of the sample flowed out of the die was determined as the softening temperature. A die having a diameter of 1 mm and a length of 1 mm was used.

Measurement of peak top molecular weight, weight average molecular weight (Mw) and molecular weight distribution index (Mw / Mn) Using a GPC apparatus (trade name: HLC-8220 GPC, manufactured by Tosoh Corporation), 0.25 weight of the sample at a temperature of 40 ° C. A molecular weight distribution curve was obtained by setting a% tetrahydrofuran (hereinafter referred to as “THF”) solution as a sample solution and an injection amount of the sample solution as 200 μL. The molecular weight at the peak of the obtained molecular weight distribution curve was determined as the peak top molecular weight. Further, from the obtained molecular weight distribution curve, a weight average molecular weight Mw and a number average molecular weight Mn are obtained, and a molecular weight distribution index (Mw / Mn; hereinafter, simply “Mw / Mn”) which is a ratio of the weight average molecular weight Mw to the number average molecular weight Mn. ). The molecular weight calibration curve was prepared using standard polystyrene.

Measurement of THF-insoluble matter 1 g of a sample was put into a cylindrical filter paper and applied to a Soxhlet extractor. Using 100 mL of tetrahydrofuran (THF) as an extraction solvent, the mixture was heated to reflux for 6 hours to extract a THF soluble fraction from the sample. After removing the solvent from the extract containing the THF soluble fraction, the THF soluble fraction was dried at 100 ° C. for 24 hours, and the obtained THF soluble fraction was weighed to determine the weight X (g). . From the THF-soluble fraction weight X (g) and the weight of the sample used for the measurement (1 g), the following formula (1):
P (% by weight) = {1 (g) −X (g)} / 1 (g) × 100 (1)
Based on the above, the ratio P (% by weight) of the THF-insoluble fraction in the sample was calculated. Hereinafter, this ratio P is referred to as THF insoluble matter.

Measurement of Acid Value and Hydroxyl Value The potentiometric titration method described in JIS K 0070 (Test method for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponified product of chemical products) was performed. A potentiometric titrator (trade name: AT-510, manufactured by Kyoto Electronics Industry Co., Ltd.) was used.

Example 1
Preparation process of benzylated polyester resin 7 kg of abietic acid melted at 170 ° C., 1 kg of terephthalic acid (manufactured by Kishida Chemical Co., Ltd.), 1.1 kg of 1,3-propanediol (manufactured by Kishida Chemical Co., Ltd.), glycerin (Kishida Chemical Co., Ltd.) 500 g, bisphenol A (manufactured by Kishida Chemical Co., Ltd.) 3.2 kg, and titanium diisopropoxybistriethanolamate (1.02 kg (100 parts by weight based on the total amount of acid component and alcohol component) as an esterification catalyst 0.080 parts by weight equivalent)), and a reflux condenser that was flushed with 25 ° C. water, and a 98 ° C. warm water flushed fractionator, nitrogen inlet, dehydrator, stirrer, and temperature In a 20 liter four-necked flask equipped with a meter under a nitrogen atmosphere at 165 ° C. for 2 hours and then 2 hours over 4 hours. And the temperature was raised to 0 ℃. Thereafter, the pressure was reduced to 50 kPa. The reaction was carried out until the desired softening point (110 ° C.) was reached to obtain a polyester. Furthermore, 5 L of dimethylformamide (manufactured by Kishida Chemical Co., Ltd.), 3 kg of imidazole (manufactured by Aldrich), 7.64 kg of benzyl bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) are added, and the desired softening point (125 ° C.) is reached at 40 ° C. Until 13.0 kg of benzylated polyester was obtained.

Pre-mixing step 85 parts by weight of benzylated polyester resin, 10 parts by weight of a copper phthalocyanine pigment kneaded (pigment concentration 4%) preliminarily kneaded and dispersed in an amorphous polyester resin at a concentration of 40% by weight as a colorant, Polyethylene wax as a mold (trade name: PW-600, manufactured by Baker Petrolite, melting point (Tm): 87 ° C.) 3 parts by weight, charge control agent (trade name: Copy Charge N4P VP 2481, manufactured by Clariant Japan Co., Ltd.) Toner raw material (10 kg) containing 2 parts by weight was mixed with a Henschel mixer (trade name: FM20C, manufactured by Mitsui Mining Co., Ltd.) for 10 minutes to obtain a raw material mixture (9.9 kg). The THF insoluble content of this mixture was 15.8%.

Melt-kneading process The obtained raw material was melt-kneaded with a 2-axis kneader PCM-37 manufactured by Ikegai Co., Ltd. at a set temperature of 140 ° C. and a supply amount of 5 kg / H to prepare a melt-kneaded product (9.5 kg). The kneaded product had a THF-insoluble content of 21.8%.

Crushing and classifying step The melt-kneaded product (9.5 kg) obtained in the melt-kneading step was cooled to room temperature and solidified, and then coarsely pulverized with a cutter mill (trade name: VM-16, manufactured by Orient Corporation). Next, the coarsely pulverized product obtained by coarse pulverization was finely pulverized by a counter jet mill (trade name: AFG, manufactured by Hosokawa Micron Corporation), and the obtained pulverized product was then subjected to a rotary classifier (trade name: TSP separator, Hosokawa Micron). The toner was classified according to an unextracted toner (8.1 kg).

External Addition Step Next, a hydrophobic silica fine powder (BET specific surface area 140 m ² / g) which has been surface-treated with a silane coupling agent and dimethyl silicone oil with respect to 100 parts by weight of the obtained non-externally added toner particles. 2 parts by weight, 0.8 part by weight of hydrophobic silica fine powder (BET specific surface area 30 m ² / g) surface-treated with a silane coupling agent, 0.5 part by weight of titanium oxide (BET specific surface area 130 m ² / g) Was added and mixed with a Henschel mixer (trade name: FM mixer, manufactured by Mitsui Mining Co., Ltd.) to produce the toner (7.8 kg) of Example 1.

Examples 2 to 20
Toners of Examples 2 to 20 were obtained in exactly the same manner as in Example 1 except that the composition of the polyester resin preparation step was changed as shown in Table 1.

Comparative Example 1
A toner of Comparative Example 1 was obtained in exactly the same manner as in Example 1 except that the benzylation reaction using a benzylating agent and an amine compound was not performed.

  Various evaluations were performed on the produced toners of Examples 1 to 20 and Comparative Example 1 as follows.

Particle size distribution (volume average particle size (D ₅₀ ) and coefficient of variation (CV value) of toner)
20 ml of a sample and 1 ml of sodium alkyl ether sulfate (dispersant, manufactured by Kishida Chemical Co., Ltd.) are added to 50 ml of an electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter), and an ultrasonic dispersion device (trade name: UH-50, manufactured by SMT Co., Ltd.) was subjected to ultrasonic dispersion treatment at an ultrasonic frequency of 20 kHz for 3 minutes as a measurement sample. For this measurement sample, a particle size distribution measuring device (trade name: Multisizer 3, manufactured by Beckman Coulter, Inc.) was used to measure the particle diameter of the sample particles under the conditions of an aperture diameter of 20 μm and a measurement particle number of 50000 counts. From the obtained measurement results, the volume particle size distribution of the sample particles was obtained, and the volume average particle size D ₅₀ (μm) was calculated from the obtained volume particle size distribution. Moreover, the standard deviation in volume particle size distribution was calculated | required, and the variation coefficient (CV value,%) was computed based on following formula (3). The volume average particle diameter D ₅₀ (μm) indicates a particle diameter at which the cumulative volume from the large particle diameter side in the cumulative volume distribution becomes 50%.
CV value (%) = {standard deviation in volume particle size distribution / volume average particle size (μm)} × 100 (3)

Fixing area evaluation A ferrite core carrier having a volume average particle diameter of 45 μm was used as a carrier, and a V-type mixer / mixer (trade name: Trade name: V-5, manufactured by Tokuju Kogyo Co., Ltd.) for 20 minutes to prepare a two-component developer.

Using the two-component developer obtained by modifying a color composite machine (trade name: MX-2700, manufactured by Sharp Corporation), a recording paper (trade name: PPC paper SF-4AM3, Sharp) that is a recording medium is used. Co., Ltd.), a sample image including a rectangular solid image portion having a length of 20 mm and a width of 50 mm has a toner adhesion amount of 0.5 mg / cm ² in a solid image portion in an unfixed state. Thus, an unfixed image was prepared. The non-offset area of the obtained unfixed image was fixed at a predetermined temperature using an external fixing device prepared using a fixing unit of a color multifunction peripheral, and the presence or absence of offset on the paper surface was visually evaluated. The fixing machine has a process speed of 124 mm / sec, 52 g / m ² paper is used for A4 size test paper, and a temperature range in which neither low-temperature offset nor hot offset occurs is defined as a non-offset range, which is used as an index of fixability. .

Evaluation criteria for fixing evaluation In this evaluation method:
G (good): non-offset region is 60 ° C. or higher;
NB (not bad): non-offset region is 45 to 55 ° C;
B (bad): non-offset region is 45 ° C. or lower;
NB and above were set at a level where there was no problem in actual use.

Storage toner 100 g was put in a polyethylene container and sealed, and then left in a constant temperature and humidity chamber at 50 ° C. for 48 hours. This toner was oscillated at 60 hz for 1 minute using a vibration sieve equipped with a 200 mesh screen, the weight of the toner on the mesh was measured, and the storage stability was evaluated in three stages according to the following criteria. The level was not problematic for use.

Evaluation criteria in storage stability evaluation G (good): The mesh-up rate is less than 1.0%.
NB (not bad) (no problem in practical use): The mesh-up rate is 1.0% or more and less than 3.0%.
B (bad): The mesh-up rate is 3.0% or more.

Durability Evaluation Printing processing was continuously performed on 10,000 sheets of paper, and developer aggregation was evaluated. The paper is A4 size. Further, the printing rate of the image printed on each sheet is 5%. For developer aggregation, the flowability of the developer after the printing process was measured to determine the presence or absence of aggregation. The fluidity was measured using a fluidity measuring device (vibration transfer type fluidity measuring device manufactured by Etowas Co., Ltd.) by measuring the developer transfer time under the test conditions of a voltage of 60 V and a vibration frequency of 137 Hz. Here, the transfer time of the unused developer was less than 5 minutes.

Evaluation criteria in durability evaluation G (good): transfer time less than 5 minutes NB (not bad) (no problem in practical use): transfer time of 5 minutes or more and less than 10 minutes B (bad): transfer time 10 minutes or more

Evaluation of Charging Stability Under an environment of room temperature of 30 ° C. and humidity of 85%, printing processing was continuously performed on 10,000 sheets of paper, and charging stability was evaluated. The paper is A4 size. Further, the printing rate of the image printed on each sheet is 5%. For the charge stability, the charge amount before and after the printing test was measured. The charge stability was measured using a charge amount measuring device (manufactured by Trek).

Evaluation criteria for charging stability G (good): The amount of decrease in charge before and after printing is less than 5 μC / g. NB (not bad): No problem in practical use: The amount of decrease in charge before and after printing is 5 μC / g or more. Less than 10 μC / g B (bad): The amount of decrease in charge amount before and after printing is 10 μC / g or more.

Comprehensive evaluation In the above non-offset area, storage stability and durability evaluation:
VG (very good): all evaluations are G;
G (good): There is one NB in all evaluations;
NB (not bad): There are two NBs in all evaluations;
B (bad): B is 1 or more in all evaluations.

  From the table above, the benzylated polyester resin of Examples 1 to 20 according to the present invention and the polyester resin of Comparative Example 1 that was not benzylated were produced using these resins. It has been found that significant differences occur in the storage stability, durability and charge stability of photographic toners.

  The electrophotographic toner according to the present invention has excellent storage stability, excellent charging stability under high humidity conditions, offset resistance and blocking resistance, suppresses low temperature offset, satisfies high temperature offset, and provides stable high image quality. Can provide.

Claims (9)

  An electrophotographic toner, comprising at least a benzylated polyester resin obtained by benzylating a polyester resin, which is a polycondensate of rosin and a polyhydric alcohol as a binder resin, with a benzylating agent, and a pigment.   2. The electrophotographic toner according to claim 1, wherein the rosin is one or more compounds selected from the group consisting of abietic acid, neoabietic acid, dihydroabietic acid, pimaric acid, isopimaric acid, and sandaracopimaric acid.   The toner for electrophotography according to claim 1, wherein the benzylating agent is benzyl halide.   The electron according to any one of claims 1 to 3, wherein the benzylating agent is one or more benzylating agents selected from the group consisting of benzyl fluoride, benzyl chloride, benzyl bromide and benzyl iodide. Toner for photography.   The electrophotographic toner according to claim 1, wherein the benzylation is performed in the presence of a basic compound.   The benzylation is carried out in the presence of one or more basic compounds selected from imidazole, triethylamine, diisopropylethylamine, pyridine and 4-N, N-dimethylaminopyridine. The toner for electrophotography as described.   The electrophotographic toner according to claim 1, wherein the benzylated polyester resin has a weight average molecular weight (Mw) of 3000 to 40000.   The electrophotographic toner according to claim 1, wherein the benzylated polyester resin has a softening temperature of 110 to 160 ° C.   The toner for electrophotography according to any one of claims 1 to 8, wherein the benzylated polyester resin has a glass transition temperature of 50 to 80 ° C.