JP7142542B2 - electrophotographic toner - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic toner used for developing latent images formed in, for example, electrophotography, electrostatic recording, electrostatic printing, and the like.

Patent Document 1 discloses a positively chargeable toner containing at least a binder resin, a colorant, and a charge control agent, which is used in a non-magnetic one-component development system, and in which the binder resin has an acid value of 10 mgKOH/g or less. and polytetrafluoroethylene fine particles having an average primary particle diameter of 0.05 μm or more and less than 0.5 μm are added to the surface of the toner particles. ing.

Patent Document 2 discloses an invention relating to a developer in which positively chargeable resin fine particles (A), weakly chargeable resin fine particles (B) and inorganic fine powder (C) are added to the surface of toner particles.

In Patent Document 3, the surfaces of toner particles are coated with inorganic fine powder and organic fine powder, and the inorganic fine powder species [N _I ] are 2 to 5 kinds, and the organic fine powder species [N _O ] are 1 to 3 kinds. and an invention relating to an image forming method using a toner that satisfies a predetermined relationship between the external additive amount and the average particle size of both.

JP-A-9-127727 JP-A-4-274250 Japanese Patent Application Laid-Open No. 2003-307875

The inventors of the present invention have investigated external additives and found that polymer beads with a large particle size tend to disperse uniformly on the toner surface and tend to improve the initial image density, while tending to reduce the image density in the final stage of printing. I found out that there is a problem.

The present invention relates to an electrophotographic toner capable of maintaining excellent image density from the initial stage of printing to the final stage of printing.

The present invention provides an electrophotographic toner containing toner particles and an external additive, wherein the external additive contains polymer beads L and polymer beads S having a charge polarity different from that of the toner particles. , the number average particle diameter of the polymer beads L is larger than the number average particle diameter of the polymer beads S, the shape index of the polymer beads L is 1.3 or more, and the shape index of the polymer beads S is less than 1.3. .

The electrophotographic toner of the present invention can maintain excellent image density from the initial stage of printing to the final stage of printing.

The electrophotographic toner of the present invention is characterized by the use of two types of polymer beads having different charging polarities from the toner particles and having different particle sizes and shapes as external additives. have.

By externally adding polymer beads that are oppositely charged to the toner particles, they act as microcarriers, improve the chargeability of the toner, and improve the image quality. Among them, irregular-shaped large-diameter polymer beads are easy to disperse uniformly on the toner surface and improve the image density at the beginning of printing. Concentration tends to decrease. On the other hand, spherical small-diameter polymer beads tend to self-aggregate and have too good fluidity, so they cannot be uniformly dispersed on the surface of the toner particles, making it difficult to improve the image density at the initial stage of printing. As a result, the surface of the toner particles is made uniform, and the image density can be improved. Therefore, by using both of them together, the image density in the early stage of printing can be improved by the large-diameter polymer beads, and the image density in the final stage of printing can be improved by the small-diameter polymer beads. Further, in the present invention, the deformed large-diameter polymer beads disaggregate the spherical small-diameter polymer beads and disperse them on the toner particle surfaces, thereby increasing the contact surface with the toner particles and increasing the charging ability. Since the fluidity of the large particle size polymer beads is also improved, it is possible to suppress the decrease in the image density at the end of printing due to the large particle size polymer beads, and the image density after the endurance printing can be further improved. .

The electrophotographic toner of the present invention contains toner particles and an external additive.

In the present invention, the toner particles preferably contain a binder resin and a colorant.

The binder resin is not particularly limited, and includes polyester resins, vinyl resins such as styrene-acrylic resins, epoxy resins, polycarbonates, polyurethanes, and composite resins containing two or more of these resins. , from the viewpoint of low-temperature fixability, it is preferable to contain a polyester resin.

The polyester resin in the present invention may be amorphous or crystalline, and the binder resin may contain the polyester resin as part of the composite resin.
Accordingly, binder resins containing a polyester resin that are suitable in the present invention include amorphous polyester resins, amorphous polyester resins and crystalline polyester resins, amorphous polyester resins and crystalline composite resins, and amorphous composite resins. Examples include a resin and a crystalline polyester resin, an amorphous composite resin and a crystalline composite resin, etc. Among these, a combination of an amorphous polyester resin and a crystalline composite resin is preferred.

The crystallinity of the resin is represented by the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter, that is, the crystallinity index defined by the value of [softening point/maximum endothermic peak temperature]. The crystalline resin is a resin having a crystallinity index of 0.6 or more, preferably 0.7 or more, more preferably 0.9 or more, and 1.4 or less, preferably 1.2 or less, more preferably 1.1 or less. is a resin with a crystallinity index greater than 1.4, preferably greater than 1.5, more preferably 1.6 or higher, or less than 0.6, preferably 0.5 or lower. The crystallinity of the resin can be adjusted by the type and ratio of raw material monomers, production conditions (eg, reaction temperature, reaction time, cooling rate), and the like. The maximum endothermic peak temperature refers to the temperature of the highest endothermic peak among the observed endothermic peaks. In a crystalline resin, the maximum endothermic peak temperature is taken as the melting point.

The amorphous polyester resin is preferably a polycondensate of an alcohol component and a carboxylic acid component.

Examples of alcohol components include aliphatic diols, preferably aliphatic diols having 2 to 20 carbon atoms, more preferably 2 to 15 carbon atoms, and formula (I):

(Wherein, OR and RO are oxyalkylene groups, R is an ethylene group and/or propylene group, x and y represent the average number of added moles of alkylene oxide, each being a positive number, and x and y is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, and still more preferably 4 or less)
bisphenol A, bisphenol A, hydrogenated bisphenol A, glycerin and the like. Specific examples of aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol.

As the alcohol component, an alkylene oxide adduct of bisphenol A represented by formula (I) is preferred. The content of the alkylene oxide adduct of bisphenol A represented by formula (I) is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more, still more preferably It is 95 mol % or more, more preferably 100 mol %.

In the carboxylic acid component, the divalent carboxylic acid compound includes, for example, dicarboxylic acids having 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, more preferably 3 to 10 carbon atoms, and their anhydrides. , or derivatives such as alkyl esters in which the number of carbon atoms in the alkyl group is 1 or more and 3 or less. Specific examples of dicarboxylic acids include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, sebacic acid; and aliphatic dicarboxylic acids such as succinic acid substituted with a group hydrocarbon group.

The carboxylic acid component preferably contains an aromatic dicarboxylic acid-based compound. The content of the aromatic dicarboxylic acid compound in the carboxylic acid component is preferably 20 mol% or more, more preferably 35 mol% or more, still more preferably 50 mol% or more, and 100 mol% or less, preferably It is 90 mol % or less, more preferably 80 mol % or less.

The trivalent or higher carboxylic acid compound has, for example, 4 to 20 carbon atoms, preferably 6 to 20 carbon atoms, more preferably 7 to 15 carbon atoms, still more preferably 8 to 12 carbon atoms, and Preferred examples include trivalent or higher carboxylic acids having 9 to 10 carbon atoms, their anhydrides, or derivatives such as alkyl esters having 1 to 3 carbon atoms in the alkyl group. Specific examples include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), and acid anhydrides thereof.

The content of the trivalent or higher carboxylic acid compound in the carboxylic acid component is preferably 3 mol% or more, more preferably 5 mol% or more, still more preferably 10 mol% or more, from the viewpoint of durability, and , from the viewpoint of low-temperature fixability, it is preferably 50 mol % or less, more preferably 40 mol % or less, still more preferably 30 mol % or less.

From the viewpoint of adjusting the molecular weight and softening point of the polyester resin, the alcohol component may contain a monohydric alcohol, and the carboxylic acid component may contain a monovalent carboxylic acid-based compound.

The equivalent ratio (COOH group/OH group) between the carboxylic acid component and the alcohol component in the amorphous polyester resin is preferably 0.6 or more, more preferably 0.7 or more, from the viewpoint of adjusting the softening point of the amorphous polyester resin. It is more preferably 0.75 or more, preferably 1.1 or less, and more preferably 1.05 or less.

Amorphous polyester resin, for example, an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, further optionally in the presence of an esterification co-catalyst, a polymerization inhibitor, etc. , preferably 130°C or higher, more preferably 170°C or higher, and preferably 250°C or lower, more preferably 240°C or lower.

In addition, in the present invention, the polyester resin may be a polyester resin that has been modified to such an extent that its properties are not substantially impaired. Modified polyester resins include, for example, grafting or blocking with phenol, urethane, epoxy, etc. by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, etc. Among the modified polyester resins, urethane-modified polyester resins obtained by urethane-extending a polyester resin with a polyisocyanate compound are preferred.

The softening point of the amorphous polyester resin is preferably 90° C. or higher, more preferably 100° C. or higher, and still more preferably 110° C. or higher from the viewpoint of hot offset resistance. is 160° C. or lower, more preferably 150° C. or lower, and even more preferably 140° C. or lower.

The glass transition temperature of the amorphous polyester resin is preferably 40° C. or higher, more preferably 45° C. or higher, and still more preferably 50° C. or higher from the viewpoint of heat-resistant storage stability. is 75°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower.

The acid value of the amorphous polyester resin is preferably 1 mgKOH/g or more, more preferably 3 mgKOH/g or more, still more preferably 5 mgKOH/g or more, and preferably 40 mgKOH/g or less, more preferably 30 mgKOH/g. 25 mgKOH/g or less, more preferably 25 mgKOH/g or less.

As the crystalline composite resin, a composite resin containing a crystalline polyester resin and a styrenic resin is preferable.

As the crystalline polyester resin, a polycondensate of an alcohol component containing an aliphatic diol and a carboxylic acid component is preferred.

The number of carbon atoms in the aliphatic diol is preferably 2 or more, more preferably 4 or more, still more preferably 5 or more from the viewpoint of low-temperature fixability, and preferably 9 or less, more preferably from the viewpoint of development stability. is 8 or less, more preferably 7 or less.

Aliphatic diols having 2 to 9 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. , 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,9-nonanediol, and the like.

In addition, the aliphatic diol having 2 to 9 carbon atoms is preferably an α,ω-aliphatic diol having a hydroxyl group at the end of the carbon chain from the viewpoint of improving the low-temperature fixability of the toner. Alkanediols are more preferred.

The alcohol component may contain alcohols other than aliphatic diols, but the content of aliphatic diols, preferably aliphatic diols having 2 to 9 carbon atoms, is preferably 80 mol% or more, more preferably is 90 mol % or more, more preferably 95 mol % or more, more preferably 100 mol %.

Alcohol components other than aliphatic diols include aromatic diols such as alkylene oxide adducts of bisphenol A, trihydric or higher alcohols such as glycerin, and the like.

The carboxylic acid component of the crystalline polyester preferably contains an aromatic dicarboxylic acid compound.

Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid, and the like. Among these, terephthalic acid is preferred. In the present invention, the carboxylic acid compounds include not only free acids but also anhydrides that decompose during the reaction to produce acids, and alkyl esters having 1 to 3 carbon atoms.

The content of the aromatic dicarboxylic acid compound is preferably 80 mol% or more, more preferably 90 mol% or more, still more preferably 95 mol% or more, and still more preferably 100 mol%.

Other carboxylic acid components include aliphatic dicarboxylic acids, trivalent or higher carboxylic acids, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

The equivalent ratio (COOH group/OH group) between the carboxylic acid component and the alcohol component in the crystalline polyester resin is preferably 0.70 or more, and preferably 1.10 or less, from the viewpoint of adjusting the softening point of the composite resin. It is preferably 1.05 or less.

The polycondensation reaction of the raw material monomers for the crystalline polyester resin should be carried out in an inert gas atmosphere, if necessary, in the presence of an esterification catalyst, a polymerization inhibitor, etc., at a temperature of about 130°C or higher and 230°C or lower. can be done.

Styrenic resins are addition polymers of raw material monomers containing at least styrene or styrene derivatives such as α-methylstyrene and vinyltoluene (hereinafter, styrene and styrene derivatives are collectively referred to as "styrene compounds").

The content of the styrene compound in the crystalline composite resin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass, from the viewpoint of transferability and durability in the raw material monomer of the styrene resin. Above, more preferably substantially 100% by mass, more preferably 100% by mass.

Raw material monomers for styrene resins include raw material monomers other than styrene compounds, such as (meth)acrylic acid alkyl esters, ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; Halovinyls; vinyl esters such as vinyl acetate and vinyl propionate; ethylenic monocarboxylic acid esters such as dimethylaminoethyl (meth)acrylate; vinyl ethers such as methyl vinyl ether; vinylidene halides such as vinylidene chloride; N-vinyl compounds such as pyrrolidone may also be included.

The addition polymerization reaction of raw material monomers for styrene-based resins can be carried out, for example, in the presence of a polymerization initiator such as dicumyl peroxide, a polymerization inhibitor, a cross-linking agent, or the like, or in the presence or absence of an organic solvent. The temperature conditions are preferably 110° C. or higher, more preferably 140° C. or higher, and preferably 200° C. or lower, more preferably 170° C. or lower.

When using an organic solvent for the addition polymerization reaction, xylene, toluene, methyl ethyl ketone, acetone, etc. can be used. The amount of the organic solvent used is preferably 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the raw material monomer for the styrene resin.

In the present invention, from the viewpoint of pulverization, the composite resin is chemically bonded to the polyester resin and the styrene resin through a bi-reactive monomer that can react with both the raw material monomer of the polyester resin and the raw material monomer of the styrene resin. Resins are preferred.

Both reactive monomers have, in the molecule, at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an epoxy group, a primary amino group and a secondary amino group, preferably a hydroxyl group and/or a carboxyl group. A compound having a group, more preferably a carboxy group, and an ethylenically unsaturated bond is preferred, and at least one selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid and maleic anhydride is more preferred, At least one selected from the group consisting of acrylic acid, methacrylic acid and fumaric acid is more preferable from the viewpoint of reactivity in polycondensation reaction and addition polymerization reaction. However, when used together with a polymerization inhibitor, polyvalent carboxylic acid compounds having an ethylenically unsaturated bond such as fumaric acid function as raw material monomers for polyester resins. In this case, fumaric acid or the like is not a bireactive monomer but a starting monomer for the polyester resin.

Also, the dual-reactive monomer may be one or more (meth)acrylic esters selected from acrylic esters and methacrylic esters in which the alkyl group has 6 or less carbon atoms.

The (meth)acrylic acid ester is preferably an alkyl (meth)acrylic acid ester from the viewpoint of reactivity to transesterification, and the number of carbon atoms in the alkyl group is preferably 2 or more, more preferably 3 or more, and is preferably is 6 or less, more preferably 4 or less. The alkyl group may have a substituent such as a hydroxyl group.

Specific examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, (iso)propyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, ( (iso- or tertiary) butyl meth)acrylate, hexyl (meth)acrylate, and the like. In addition, "(iso or tertiary)" means including both cases where these groups are present and cases where they are not present, and when these groups are not present, normal indicates

In the present invention, the acrylic ester is preferably an alkyl acrylate having an alkyl group having 2 to 6 carbon atoms, more preferably butyl acrylate, and the methacrylic ester preferably has an alkyl group having a carbon number of A methacrylic acid alkyl ester of 2 or more and 6 or less, more preferably butyl methacrylate.

From the viewpoint of enhancing the dispersibility of the styrene-based resin and the polyester resin and improving the durability of the toner, the amount of the bi-reactive monomer used is preferably 1 per 100 mol of the total alcohol component of the crystalline polyester resin. It is mol or more, more preferably 2 mol or more, and from the viewpoint of low-temperature fixability, it is preferably 30 mol or less, more preferably 20 mol or less, and still more preferably 10 mol or less.
In addition, the amount of the bi-reactive monomer used is determined from the viewpoint of improving the dispersibility of the styrene resin and the crystalline polyester resin and improving the durability of the toner for a total of 100 parts by mass of the raw material monomers for the styrene resin. , preferably 1 part by mass or more, more preferably 2 parts by mass or more, and from the viewpoint of low temperature fixability, preferably 30 parts by mass or less, more preferably 20 parts by mass or less, further preferably 10 parts by mass or less be. Here, the polymerization initiator is included in the sum of the raw material monomers for the styrene resin.

Specifically, the composite resin obtained using the bireactive monomer is preferably produced by the following method. From the viewpoint of improving the durability of the toner and improving the low-temperature fixability and heat-resistant storage stability of the toner, the dual-reactive monomer is preferably used in addition polymerization reaction together with the raw material monomer of the styrene-based resin.

(i) A method in which the addition polymerization reaction step (B) is performed with the raw material monomers of the styrene resin and the bi-reactive monomer after the step (A) of the polycondensation reaction with the raw material monomers of the crystalline polyester resin. Step (A) is carried out under reaction temperature conditions suitable for condensation reaction, the reaction temperature is lowered, and step (B) is carried out under temperature conditions suitable for addition polymerization reaction. It is preferable to add the raw material monomer of the styrene resin and the bi-reactive monomer into the reaction system at a temperature suitable for the addition polymerization reaction. Both reactive monomers undergo an addition polymerization reaction and also react with the crystalline polyester resin.
After the step (B), the reaction temperature is raised again, and if necessary, a raw material monomer for a crystalline polyester resin having a valence of 3 or more, which serves as a cross-linking agent, is added to the reaction system, and the polycondensation reaction of the step (A) or Further reactions with bi-reactive monomers can be carried out.

(ii) A method in which the step (A) of the polycondensation reaction with the raw material monomer of the crystalline polyester resin is performed after the step (B) of the addition polymerization reaction with the raw material monomer of the styrene resin and the bi-reactive monomer. The step (B) is carried out under reaction temperature conditions suitable for the polymerization reaction, the reaction temperature is raised, and the polycondensation reaction of the step (A) is carried out under the temperature conditions suitable for the polycondensation reaction. Both reactive monomers participate in addition polymerization reactions as well as polycondensation reactions.
The raw material monomer for the crystalline polyester resin may be present in the reaction system during the addition polymerization reaction, or may be added to the reaction system under temperature conditions suitable for the polycondensation reaction. In the former case, the progress of the polycondensation reaction can be controlled by adding the esterification catalyst at a temperature suitable for the polycondensation reaction.

(iii) The step (A) of the polycondensation reaction with the raw material monomers of the crystalline polyester resin and the step (B) of the addition polymerization reaction with the raw material monomers of the styrene resin and the bi-reactive monomer are carried out in parallel. Method of carrying out the reaction In this method, the step (A) and the step (B) are performed in parallel under reaction temperature conditions suitable for the addition polymerization reaction, the reaction temperature is raised, and the temperature conditions suitable for the polycondensation reaction are carried out. Then, it is preferable to add a raw material monomer for the crystalline polyester resin having a valence of 3 or more, which is a cross-linking agent, to the polymerization system as necessary, and to further carry out the polycondensation reaction of the step (A). At that time, under temperature conditions suitable for the polycondensation reaction, a radical polymerization inhibitor may be added to allow only the polycondensation reaction to proceed. Both reactive monomers participate in addition polymerization reactions as well as polycondensation reactions.

In the method (i) above, a pre-polymerized crystalline polyester resin may be used instead of the step (A) of conducting the polycondensation reaction. In the above method (iii), when the step (A) and the step (B) are performed in parallel, a mixture containing raw material monomers for the styrene resin is added to the mixture containing the raw material monomers for the polyester resin. It can also be added dropwise for reaction.

The above methods (i) to (iii) are preferably carried out in the same container.

The mass ratio of the styrene resin to the crystalline polyester resin (styrene resin/crystalline polyester resin) in the composite resin is preferably 3/97 or more, more preferably 7/93 or more, and still more preferably 7/93 or more, from the viewpoint of durability. It is 10/90 or more, and from the viewpoint of heat resistance and storage stability, it is preferably 45/55 or less, more preferably 40/60 or less, still more preferably 35/65 or less, and still more preferably 30/70 or less. In the above calculation, the mass of the crystalline polyester resin is the amount obtained by subtracting the amount of reaction water dehydrated by the polycondensation reaction (calculated value) from the mass of the raw material monomer of the crystalline polyester resin used. The amount of both reactive monomers is included in the amount of raw material monomers for the crystalline polyester resin. Further, the amount of styrene resin is the total amount of the raw material monomers of the styrene resin, and does not include the amount of the polymerization initiator.

The melting point of the crystalline composite resin is preferably 50°C or higher, more preferably 60°C or higher, still more preferably 70°C or higher from the viewpoint of heat-resistant storage stability, and preferably 130°C from the viewpoint of low-temperature fixability. Below, it is more preferably 120° C. or lower, still more preferably 110° C. or lower.

The mass ratio of the amorphous polyester resin to the crystalline composite resin (amorphous polyester resin/crystalline composite resin) is preferably 70/30 or more, more preferably 80/20 or more, and still more preferably 80/20 or more, from the viewpoint of durability. is 90/10 or more, and is preferably 99/1 or less, more preferably 98/2 or less from the viewpoint of low-temperature fixability.

As the coloring agent, dyes, pigments, magnetic substances, etc., which are used as coloring agents for toners, can be used. For example, Carbon Black, Phthalocyanine Blue, Permanent Brown FG, Brilliant First Scarlet, Pigment Red 122, Pigment Green B, Rhodamine-B Base, Solvent Red 49, Solvent Red 146, Solvent Blue 35, Quinacridone, Carmine 6B, Isoindoline, Disazo Yellow. etc. In the present invention, the toner particles may be either black toner or color toner.

The content of the colorant is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of the binder resin, from the viewpoint of improving the image density and low-temperature fixability of the toner, and It is preferably 40 parts by mass or less, more preferably 10 parts by mass or less.

In addition to the binder resin and the colorant, the toner particles of the present invention contain release agents, charge control agents, magnetic powders, fluidity improvers, conductivity modifiers, reinforcing fillers such as fibrous substances, and antioxidants. , an additive such as a cleaning property improver.

Release agents include hydrocarbon waxes such as polypropylene wax, polyethylene wax, polypropylene polyethylene copolymer wax, microcrystalline wax, paraffin wax, Fischer-Tropsch wax, Sasol wax, and oxides thereof; carnauba wax, montan Waxes and their deacidified waxes, ester waxes such as fatty acid ester waxes; fatty acid amides, fatty acids, higher alcohols, fatty acid metal salts and the like;

The melting point of the release agent is preferably 60° C. or higher, more preferably 70° C. or higher, from the viewpoint of toner transferability, and preferably 160° C. or lower, more preferably 140° C., from the viewpoint of low-temperature fixability. 120° C. or lower, more preferably 110° C. or lower.

The content of the release agent is preferably 0.5 parts by mass or more, or more, with respect to 100 parts by mass of the binder resin, from the viewpoints of low-temperature fixability and anti-offset properties of the toner and dispersibility in the binder resin. It is preferably 1 part by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less.

The charge control agent is not particularly limited, and may contain either a positive charge control agent or a negative charge control agent.

Examples of positive charge control agents include nigrosine dyes such as "Nigrosine Base EX", "Oil Black BS", "Oil Black SO", "Bontron N-01", "Bontron N-04", and "Bontron N-07". , "Bontron N-09", "Bontron N-11" (manufactured by Orient Chemical Industry Co., Ltd.), etc.; triphenylmethane dyes containing tertiary amines as side chains, quaternary ammonium salt compounds, "Bontron P-51" (manufactured by Orient Chemical Industry Co., Ltd.), cetyltrimethylammonium bromide, "COPY CHARGE PX VP435" (manufactured by Clariant Co., Ltd.), etc.; polyamine resins such as "AFP-B" (Orient Chemical Industry Co., Ltd.) ), etc.; imidazole derivatives, such as “PLZ-2001” and “PLZ-8001” (manufactured by Shikoku Kasei Co., Ltd.), etc.; styrene-acrylic resins, such as “FCA-701PT” and “FCA-201- PS" (manufactured by Fujikura Kasei Co., Ltd.) and the like.

In addition, as a negative charge control agent, a metal-containing azo dye such as "Barifast Black 3804", "Bontron S-31", "Bontron S-32", "Bontron S-34", "Bontron S-36" ” (manufactured by Orient Chemical Industry Co., Ltd.), “Eizenspiron Black TRH”, “T-77” (manufactured by Hodogaya Chemical Industry Co., Ltd.), etc.; metal compounds of benzilic acid compounds, such as “LR- 147", "LR-297" (manufactured by Nippon Carlit Co., Ltd.), etc.; metal compounds of salicylic acid compounds, such as "Bontron E-81", "Bontron E-84", "Bontron E-88", " Bontron E-304" (manufactured by Orient Chemical Industry Co., Ltd.), "TN-105" (manufactured by Hodogaya Chemical Industry Co., Ltd.), etc.; copper phthalocyanine dye; quaternary ammonium salt, such as "COPY CHARGE NX VP434" (manufactured by Clariant), nitroimidazole derivatives and the like; organometallic compounds and the like.

From the viewpoint of the charging stability of the toner, the content of the charge control agent is preferably 0.01 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 10 parts by mass with respect to 100 parts by mass of the binder resin. parts or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less. When the charge control agent is a polymer such as a resin, it is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more with respect to 100 parts by mass of the binder resin, and It is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

The toner particles may be a toner obtained by any conventionally known method such as a melt-kneading method, an emulsification phase inversion method, a polymerization method, etc. However, from the viewpoint of productivity and dispersibility of a colorant, melt-kneading may be used. A ground toner according to the method is preferred. In the case of the pulverized toner by the melt-kneading method, for example, raw materials such as a binder resin and a colorant are uniformly mixed with a mixer such as a Henschel mixer, and then a closed kneader, a single-screw or twin-screw extruder, or an open-roll type It can be produced by melt-kneading with a kneader or the like, cooling, pulverizing, and classifying.

The volume median particle size ( _D50 ) of the toner particles is preferably 3 μm or more, more preferably 4 μm or more, and preferably 15 μm or less, more preferably 10 μm or less. In the present specification, the volume-median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated as a volume fraction is 50% from the smaller particle size.

In the present invention, the external additive contains polymer beads L and polymer beads S having a charge polarity different from that of the toner particles. That is, when the toner particles are positively charged, the negatively charged polymer beads L and S are used, and when the toner particles are negatively charged, the positively charged polymer beads L and S are used.

Positively charged polymer beads include melamine-formaldehyde resin, styrene (St)/methyl methacrylate (MMA) copolymer, St/butyl acrylate (BA) copolymer, MMA/BA copolymer, and the like.

Examples of negatively charged polymer beads include fluorine-based resins such as polytetrafluoroethylene, trifluoroethylene, vinylidene fluoride, and fluoroethylene.

The materials of the polymer beads L and S may be the same or different, but are preferably the same resin.

The number average particle diameter of the polymer beads L is larger than the number average particle diameter of the polymer beads S.
The ratio of the number average particle diameters of the polymer beads L and the polymer beads S (polymer beads L/polymer beads S) is preferably 1.5 or more, more preferably 1.7 or more, and still more preferably 2.0 or more, from the viewpoint of stabilizing the image density. and is preferably 5.0 or less, more preferably 4.0 or less, still more preferably 3.0 or less.

From the viewpoint of the initial image density, the number average particle diameter of the polymer beads L is preferably 300 nm or more, more preferably 350 nm or more, still more preferably 400 nm or more, and is preferably 1000 nm or less, more preferably 800 nm or less. It is preferably 700 nm or less.

The number average particle diameter of the polymer beads S is preferably 100 nm or more, more preferably 130 nm or more, still more preferably 150 nm or more, and preferably 400 nm or less, more preferably 350 nm or less, from the viewpoint of image density at the end of printing. , and more preferably 300 nm or less.

Moreover, the polymer beads L and the polymer beads S have different shapes. In the present invention, a shape index is used as a shape index. Here, the shape index is a value calculated from the ratio of the particle size calculated from the number average particle size and the BET specific surface area (the number average particle size/the particle size calculated from the BET specific surface area).

The shape index of the polymer beads L is 1.3 or more, preferably 1.4 or more, more preferably 1.5 or more from the viewpoint of initial image density, and preferably 3.0 or less, more preferably 2.5 from the viewpoint of fluidity. 2.0 or less, more preferably 2.0 or less.

The shape index of the polymer beads S is less than 1.3, preferably 1.2 or less, more preferably 1.1 or less, from the viewpoint of image density at the end of printing, and preferably 0.5 or more, more preferably 0.5 or more, from the viewpoint of chargeability. is 0.6 or more, more preferably 0.7 or more.

The charge ratio of polymer beads L to polymer beads S (polymer beads L/polymer beads S) is preferably 2 or more, more preferably 4 or more, from the viewpoint of initial image density, and from the viewpoint of fluidity. , preferably 20 or less, more preferably 15 or less, still more preferably 10 or less.

The content of the polymer beads L is preferably 0.04 parts by mass or more, more preferably 0.08 parts by mass or more, relative to 100 parts by mass of the toner particles. parts or less, more preferably 0.7 parts by mass or less.

The content of the polymer beads S is preferably 0.03 parts by mass or more, more preferably 0.07 parts by mass or more, relative to 100 parts by mass of the toner particles. parts or less, more preferably 0.4 parts by mass or less.

Further, the mass ratio of polymer beads L and polymer beads S (polymer beads L/polymer beads S) is preferably 20/80 or more, more preferably 30/70 or more, and still more preferably 40/80 from the viewpoint of initial image density. It is 60 or more, and from the viewpoint of the image density at the final stage of printing, it is preferably 90/10 or less, more preferably 85/15 or less, and still more preferably 80/20 or less.

The toner of the present invention may contain an external additive other than the polymer beads L and S, and preferably contains inorganic particles from the viewpoint of fluidity and transferability.

Inorganic particles include silica, alumina, titania, zirconia, tin oxide, zinc oxide and the like. Among these, silica is preferable, and from the viewpoint of toner transferability, hydrophobic silica subjected to hydrophobic treatment is more preferable.

Hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), silicone oil, octyltriethoxysilane (OTES), methyltriethoxysilane and the like are examples of hydrophobizing agents for hydrophobizing the surface of silica particles. be done.

The number average particle diameter of the inorganic particles is preferably 5 nm or more, more preferably 15 nm or more, and is preferably 250 nm or less, more preferably 200 nm or less, and still more preferably 100 nm, from the viewpoint of toner fluidity and transferability. Below, more preferably 50 nm or less, more preferably 30 nm or less.

The content of the inorganic particles is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass, with respect to 100 parts by mass of the toner before being treated with an external additive, from the viewpoints of chargeability, fluidity, and transferability of the toner. Above, more preferably 0.3 parts by mass or more, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less.

A mixer such as a Henschel mixer can be used to mix the toner particles and the external additive.

The toner of the present invention can be used as a toner for one-component development, or mixed with a carrier to be used as a two-component developer.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. Physical properties such as resins were measured by the following methods.

[Resin softening point]
Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), while heating a 1 g sample at a temperature increase rate of 6 ° C / min, a load of 1.96 MPa was applied with a plunger, and the diameter was 1 mm and the length was 1 mm. extruded from the nozzle of Plot the amount of plunger descent of the flow tester against the temperature, and let the softening point be the temperature at which half of the sample flows out.

[Maximum peak temperature of resin endotherm]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), weigh 0.01 to 0.02 g of the sample in an aluminum pan and cool it from room temperature (25 ° C) to a cooling rate of 10 ° C. /min to 0°C and hold at 0°C for 1 minute. After that, measure at a heating rate of 10°C/min. Among the observed endothermic peaks, the temperature of the highest endothermic peak is defined as the maximum endothermic peak temperature.

[Glass transition temperature of resin]
Using a differential scanning calorimeter "DSC Q20" (manufactured by TA Instruments Japan), weigh 0.01 to 0.02 g of the sample in an aluminum pan, heat it up to 200 ° C, and then cool it down at a rate of 10 from that temperature. Cool to 0°C at °C/min. Next, the sample is heated at a heating rate of 10°C/min, and the endothermic peak is measured. The glass transition temperature is defined as the temperature at the intersection of the extended line of the baseline below the maximum endothermic peak temperature and the tangential line showing the maximum slope from the rising portion of the peak to the apex of the peak.

[Acid value of resin]
Measured based on the method of JIS K 0070:1992. However, only the measurement solvent is changed from the mixed solvent of ethanol and ether specified in JIS K 0070 to a mixed solvent of acetone and toluene (acetone:toluene = 1:1 (volume ratio)).

[Melting point of release agent]
Using a differential scanning calorimeter "DSC Q20" (manufactured by TA Instruments Japan Co., Ltd.), weigh 0.01 to 0.02 g of the sample in an aluminum pan and heat it up to 200 ° C at a heating rate of 10 ° C / min. The temperature is raised and then cooled to -10°C at a cooling rate of 5°C/min. Next, the sample is heated up to 180°C at a heating rate of 10°C/min and measured. The maximum endothermic peak temperature observed from the melting endothermic curve thus obtained is taken as the melting point of the release agent.

[Volume Median Particle Diameter of Toner Particles]
Measuring machine: Coulter Multisizer II (manufactured by Beckman Coulter, Inc.)
Aperture diameter: 100 μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (manufactured by Beckman Coulter, Inc.)
Electrolyte: Isoton II (manufactured by Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB (griffin): 13.6) was dissolved in the electrolytic solution to adjust it to 5% by mass Dispersion conditions: 10 mg of measurement sample in 5 mL of the dispersion and dispersed for 1 minute with an ultrasonic dispersion machine (machine name: US-1 manufactured by SND Co., Ltd., output: 80 W), then 25 mL of the electrolytic solution is added, and furthermore, the ultrasonic dispersion machine Disperse for 1 minute to prepare a sample dispersion.
Measurement conditions: Add the sample dispersion to 100 mL of the electrolytic solution so that the particle size of 30,000 particles can be measured in 20 seconds, measure 30,000 particles, and determine the volume from the particle size distribution. Determine the median particle size ( _D50 ).

[Number Average Particle Diameter of External Additive]
The particle size (average value of major and minor diameters) of 500 particles is measured from a scanning electron microscope (SEM) photograph, and the number average value is obtained.

[Particle size of polymer beads calculated from BET specific surface area]
(1) Measure the BET specific surface area of the particles by the nitrogen adsorption method under the following conditions.
・Measurement device: Specific surface area measurement device “Micromeritics FlowSorb III” (manufactured by Shimadzu Corporation)
・Sample amount: 0.04 to 0.08g
・Degassing conditions: 40℃, 10 minutes ・Adsorption gas: Nitrogen gas
(2) Apply the BET specific surface area to the following formula to calculate the particle size of the polymer beads.
d = 6000/(BET specific surface area ( ^m2 /g) x density (g/ ^cm3 ))

[Shape index of polymer beads]
The ratio of the particle size A (number average particle size) to the particle size B (particle size calculated from the BET specific surface area) calculated from the following formula is defined as the shape index.
Shape index = particle size A/particle size B

[Charge amount of polymer beads]
Blow-off type charge amount measurement of the amount of charge when polymer beads are triboelectrically charged with a standard carrier for positive charge polarity toner (P-01) and a standard carrier for negative charge polarity toner (N-01) (provided by the Imaging Society of Japan). Measured using a device, the charge amount is the sum of the measurement result of P-01 and the measurement result of N-01.

Resin production example 1
Raw material monomers other than trimellitic anhydride and the esterification catalyst shown in Table 1 were placed in a 10 L four-necked flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, and heated to 200°C under a nitrogen atmosphere. The mixture was heated and reacted for 6 hours. After further raising the temperature to 210°C, trimellitic anhydride was added, reacted at normal pressure (101.3 kPa) for 1 hour, and further reacted at 40 kPa until the desired softening point was reached to obtain an amorphous polyester resin. (Resin A1). Table 1 shows the physical properties of the obtained resin.

Resin production example 2
The raw material monomers for the crystalline polyester resin and the esterification catalyst shown in Table 2 were placed in a 10 L four-necked flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, heated to 160°C, and reacted for 6 hours. let me
After that, the raw material monomer for the styrenic resin shown in Table 2, the bi-reactive monomer, and the polymerization initiator were added dropwise with a dropping funnel over 1 hour. After aging the addition polymerization reaction for 1 hour while maintaining the temperature at 160° C., the temperature was maintained at 8.3 kPa for 1 hour. Further, the temperature was raised to 200° C. over 8 hours, and the mixture was reacted at 8.3 kPa for 2 hours to obtain a crystalline composite resin (resin C1). Table 2 shows the physical properties of the obtained resin.

Examples 1 to 4 and Comparative Examples 1 and 2
97 parts by mass of resin A1 and 3 parts by mass of resin C1 as binder resins, 3.0 parts by mass of positive charge control agent "Bontron N-04" (manufactured by Orient Chemical Industry Co., Ltd.), positive charge control resin "FCA -201-PS" (manufactured by Fujikura Kasei Co., Ltd.) 6.0 parts by mass, coloring agent "REGAL 330R" (manufactured by Cabot Specialty Chemicals, Inc.) 6.0 parts by mass, and release agent "SP-105" (( Kato Yoko Co., Ltd., Fischer-Tropsch wax, melting point: 105° C.) was mixed for 1 minute using a Henschel mixer, and then melt-kneaded under the following conditions.

A co-rotating twin-screw extruder “PCM-30” (manufactured by Ikegai Co., Ltd., shaft diameter: 2.9 cm, shaft cross-sectional area: 7.06 cm ² ) was used. The operating conditions were as follows: barrel set temperature 110°C, shaft rotation speed 200 r/min (shaft rotation peripheral speed 0.30 m/sec), mixture supply speed 10 kg/h (mixture supply amount per unit cross-sectional area of shaft 1.42 kg/h・cm ² ).

The obtained resin kneaded product is cooled, coarsely pulverized with a pulverizer “Rotoplex” (manufactured by Hosokawa Micron Corporation), and a coarsely pulverized product having a volume median particle size of 2 mm or less is obtained using a sieve with an opening of 2 mm. Obtained. The obtained coarsely pulverized material was finely pulverized by adjusting the pulverization pressure so that the volume median particle diameter was 7.0 μm using a DS2 type air classifier (collision plate type, manufactured by Nippon Pneumatic Co., Ltd.). The obtained finely pulverized material is classified by adjusting the static pressure (internal pressure) so that the volume median particle size is 7.5 μm using a DSX2 type air classifier (manufactured by Nippon Pneumatic Co., Ltd.). , to obtain positively charged toner particles.

100 parts by mass of the obtained toner particles, polymer beads shown in Table 4 as an external additive, 0.5 parts by mass of hydrophobic silica "R972" (manufactured by Nippon Aerosil Co., Ltd., average particle size: 16 nm) and hydrophobic silica " TG-820F" (manufactured by Cabot Specialty Chemicals, Inc., number average particle diameter: 8 nm) 1.0 part by mass, using a Henschel mixer (manufactured by Nippon Coke Industry Co., Ltd.) at 2100 r / min (peripheral speed 29 m / sec) for 3 minutes to obtain a toner.

Details of the polymer beads used are shown in Table 3.

Test Example 1 [initial image density]
The toner was mounted in a toner cartridge for HL-2040 manufactured by Brother Industries, Ltd. and left for 24 hours under the conditions of a temperature of 20° C. and a humidity of 50%. After that, after printing 200 sheets of images with a print rate of 5% using the printer "HL-2040" (manufactured by Brother Industries, Ltd.), a black solid image is printed, and the image density of the part 3 cm from the top of the paper is measured. It was measured using a measuring instrument "GRETAG SPM50" (manufactured by Gretag). Table 4 shows the results.

Test Example 2 [Image density at the end of printing]
After measuring the initial image density, after printing 1300 sheets of 5% coverage with a printer "HL-2040" (manufactured by Brother Industries, Ltd.), a solid black image is printed, and the image of the part 3 cm from the top of the paper is printed. Density was measured using an image densitometer "GRETAG SPM50" (manufactured by Gretag). Table 4 shows the results.

From the above results, it can be seen that the toners of Examples 1 to 4 are excellent in both the initial image density and the image density at the final stage of printing.
On the other hand, in Comparative Example 1 using only polymer beads with a large particle size, the image density at the final stage of printing is low, and in Comparative Example 2 using only polymer beads with a small particle size, the image density is low at the initial stage. In Comparative Example 2, the image density at the final stage of printing was good due to the small particle size polymer beads. It can be seen that the effect is superior to that of Comparative Example 2.

The electrophotographic toner of the present invention is suitable for developing latent images formed in electrophotography, electrostatic recording, electrostatic printing, and the like.

Claims (4)

An electrophotographic toner containing toner particles and an external additive, wherein the external additive contains polymer beads L and polymer beads S having a charge polarity different from that of the toner particles, and the polymer beads L and the polymer beads S are polytetrafluoroethylene particles, the number average particle size of the polymer beads L is larger than the number average particle size of the polymer beads S, the shape index of the polymer beads L is 1.3 or more, and the shape of the polymer beads S An electrophotographic toner having an index of less than 1.3. 2. The electrophotographic toner according to claim 1, wherein the ratio of the number average particle diameters of the polymer beads L and the polymer beads S (polymer beads L/polymer beads S) is 1.5 or more and 5.0 or less. 3. The electrophotographic toner according to claim 1, wherein the mass ratio of polymer beads L to polymer beads S (polymer beads L/polymer beads S) is 20/80 or more and 90/10 or less. 4. The electrophotographic toner according to claim 1, wherein the external additive further contains inorganic particles.