JPH08220809A - Electrophotographic positively charged toner - Google Patents

Abstract

PURPOSE: To provide an electrophotographic positively charged toner which has excellent stability of a rising characteristic of electrostatic charge and particularly the toner characteristics under high-temp. and high-humidity condition, is capable of forming good images free from toner splashing, fogging, etc., and is capable of forming color images of bright and clear color tones even when the toner is made into color toners. CONSTITUTION: This electrophotographic toner consists of at least a binder resin, coloring agents and charge control agent. The charge control agent consists of a copolymer of 1 to 30wt.% methacryloyl oxytrimethyl ammonium sulfate expressed by the formula and 99 to 70wt.% other vinyl based monomer copolymerizable therewith. In addition, the charge control agent is incorporated into the toner in a range of 0.1 to 10 pts.wt. per 100 pts.wt. binder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positively charged toner for electrophotography which is used when a latent electrostatic image is made into a visible image in dry electrophotography.

[0002]

2. Description of the Related Art In dry electrophotography, toner particles used to form an electrostatic latent image into a visible image are generally binders, colorants, charge control agents, magnetic powders and other additives. After the agents are premixed, they are melt-kneaded, pulverized, and then classified so as to have a desired particle size.

When these toner particles are used as a two-component developer, they are mixed and stirred together with magnetic powder to cause friction between the toner particles, and when used as a one-component developer, the toner particles and the sleeve are mixed. Electric charges are accumulated on the surface of toner particles due to friction with a space, and are used for visualizing (developing) an electrostatic latent image, but the electric charges accumulated on the surface of toner particles by frictional charging are electrostatic latent images. Depending on the type of photoconductive photoconductor used to form the image, either a positive or negative charge is required, and a sufficient amount of charge is required to more accurately visualize the electrostatic latent image. Therefore, it is common to mix and disperse the charge control agent or the conductive material in the binder.

Conventionally, charge control agents for imparting a positive charge to toner particles include (1) azine-based nigrosine, nigrosine bases, nigrosine derivatives, (2) naphthenic acid or higher fatty acid metal salts, (3) Alkoxylated amines, (4) Organic quaternary ammonium salts such as benzylmethyl-hexyldecylammonium chloride or decyl-trimethylammonium chloride, (5) Alkylamides and the like are generally used. Has a structure that is complicated and its properties are unstable. Therefore, it has a drawback that it is easily decomposed or deteriorated due to thermal and mechanical influences in the melt-kneading and pulverizing steps during toner production, and the charge controllability is deteriorated. However, there is a problem that the toner characteristics of the obtained toner are significantly deteriorated.

Further, these positive charge control agents are not well compatible with the thermoplastic resin which is the binder, and are present only in the binder in the state of particle dispersion similar to the colorant. In the crushing step of the toner particles, or during fluid friction in the copying machine when electric charges are accumulated on the surface of the toner particles, the charge control agent present in the surface layer of the toner particles falls off and changes the charge amount. However, there is a problem that the charge amount of the toner varies, and it is difficult to maintain the charged state of the toner stably for a long period of time. Further, since these positive charge control agents are generally colored and poor in transparency, there is also a problem that a color copy having a clear color tone cannot be obtained when an arbitrary coloring is attempted in correspondence with color copying. .

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention is intended to solve the above-mentioned problems in the above-mentioned conventional positively charged toner for electrophotography, and is excellent in charge rising characteristics and its stability. At the same time, toner scattering, a good image without fog, etc. can be formed, and as a result of further study to provide a positively charged toner for electrophotography, which does not cause a problem such as deterioration of toner characteristics even when used at high temperature and high humidity, as a result, The present invention has been completed by finding that the above object can be achieved by using a copolymer of methacryloyloxytrimethylammonium sulfate represented by a specific chemical formula and a vinyl monomer copolymerizable therewith. Is.

[0007]

The positively charged toner for electrophotography provided by the present invention is an electrophotographic toner comprising at least a binder, a colorant and a charge control agent,
The charge control agent is represented by the following general formula (1)

[0008]

Embedded image 1 to 30% by weight of methacryloyloxytrimethylammonium sulfate represented by and 99 to 70% by weight of another vinyl monomer copolymerizable therewith, and the charge control agent is a binder. It is characterized in that 0.1 to 10 parts by weight is contained with respect to 100 parts by weight of the binder.

The positively charged toner for electrophotography of the present invention (hereinafter referred to as the toner of the present invention) having the above-mentioned structure is capable of being copolymerized with methacryloyloxytrimethylammonium sulfate represented by the above general formula (1). A major feature of the copolymer is a positive charge control agent obtained by copolymerizing the above copolymer with a vinyl monomer at a specific copolymerization ratio described above. When the copolymerization ratio of trimethylammonium sulfate is less than 1% by weight, it becomes difficult to accumulate a sufficient amount of charge in the toner obtained, and the toner scatters a lot and cannot be used. On the contrary, when the copolymerization ratio of methacryloyloxytrimethylammonium sulfate exceeds 30% by weight, the electric resistance value of the obtained toner becomes low, the stability of the change of the charge amount with time deteriorates, and the binder The compatibility with and becomes poor and the transparency is impaired. Therefore, it is preferable that the copolymer has a copolymerization ratio of 5 to 25% by weight of methacryloyloxytrimethylammonium sulfate and 95 to 75% by weight of another vinyl monomer copolymerizable therewith.

The other vinyl-based monomer that can be used as a copolymerization component with the above methacryloyloxytrimethylammonium sulfate is not particularly limited, and any vinyl-based monomer having a polymerizable unsaturated bond can be used. It is possible. As a specific example, styrene,
o, m, p-chlorostyrene, α-methylstyrene, vinyltoluene, (meth) acrylic acid, maleic acid, itaconic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, amyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate, (meth)
Stearyl acrylate, behenyl (meth) acrylate,
Acrylamide, vinyl chloride, vinyl acetate and the like can be mentioned. Among these vinyl-based monomers, it is preferable to use at least one selected from styrene and (meth) acrylic acid alkyl ester. As the (meth) acrylic acid alkyl ester, Is preferably a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms.

The method for producing the copolymer of methacryloyloxytrimethylammonium sulfate for obtaining the charge control agent in the toner of the present invention and another vinyl monomer copolymerizable therewith is not particularly limited. A known radical polymerization method can be adopted. Specifically, it is a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, or the like, and in particular, a solution polymerization method of advancing the polymerization reaction in an organic solvent in the presence of an appropriate polymerization initiator is suitable. There is. There is no particular limitation as the polymerization initiator at that time, and known initiators usually used in radical polymerization reactions (for example, benzoyl peroxide, ter-butyl perbenzoate, dicyclohexyl peroxide, dicumyl peroxide, azobis) are used. Isobutyronitrile, azobismethylbutyronitrile, azobisdimethylvaleronitrile, etc.) can be used.

There are no particular restrictions on the molecular weight, glass transition temperature, etc. of the above-mentioned copolymer when used in the toner of the present invention, but it can be mixed in the binder in a transparent state,
In addition, the weight-average molecular weight (hereinafter referred to as Mw) of 5,000 to 5,000 is preferable because the finally obtained toner can maintain good storage stability and charging characteristics for a long period of time.
500,000, glass transition temperature (hereinafter referred to as Tg)
It is preferably in the range of 30 to 100 ° C.

As the binder that can be used in the toner of the present invention, any of various synthetic resins conventionally used as a binder for electrophotography can be used. As a specific example, at least one diol component selected from the group consisting of polystyrene and homopolymers of (meth) acrylic acid ester or a copolymer resin thereof, bisphenol diol, rosin diol and glycol, and phthalic acid , A polyester resin synthesized from at least one dicarboxylic acid selected from the group consisting of aromatic dicarboxylic acids such as isophthalic acid and terephthalic acid, or trimellitic acid.

In the toner of the present invention, the charge control agent is used in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder. If the amount is more than 10 parts by weight, the hygroscopicity of the toner becomes strong and the change of the charge amount with time becomes large.

In the toner of the present invention, various known colorants such as organic pigments, inorganic pigments, extender pigments and dyes are used in order to obtain toner particles having a desired color tone. Specific examples of colorants that can be used include black pigments (carbon black, acetylene black, run black, etc.), yellow pigments (yellow lead, yellow iron oxide, mineral fast yellow, navel yellow, hunter yellow, benzidine yellow, permanent). Yellow, etc.), red pigment (red iron oxide, cadmium red, permanent red, lake red, brilliant carmine, etc.), blue pigment (dark blue,
Cobalt blue, phthalocyanine blue, fast sky blue, induslen blue, etc., green pigments (chrome green, malachite green lake, etc.), white pigments (zinc white, titanium oxide, etc.), extender pigments (barium carbonate,
Examples thereof include pigments such as clay, silica, talc, and alumina white), and dyes such as benzidine yellow, Hansa yellow, and chromophthalie. These colorants can be used alone or in combination of two or more kinds.

The toner of the present invention can be manufactured by various known methods. As an example thereof, a predetermined amount of the above-mentioned binder, charge control agent, colorant, and if necessary, conventional amounts of various other additives for toner are mixed through the steps of mixing, melt-kneading, and pulverizing, and A method of manufacturing by absorbing and distributing so as to have an average particle size of 20 μm, or a raw material other than the main resin (charge control agent, colorant, etc.) is dispersed in a monomer constituting the main resin, and formed during polymerization of the main resin. Polymerized toner method in which these raw materials are incorporated into the toner particles to be produced, and a method in which the toner constituent materials are dissolved or dispersed in an appropriate organic solvent and granulated using an apparatus such as spray drying. .

The toner of the present invention can be used as a two-component developer by blending it with a suitable carrier. As the carrier, resin-coated glass beads, steel balls, or the like is used when the cascade development method is performed, and ferrite or fine iron powder, or a so-called binder type carrier or the like is used when the magnetic brush development method is performed. Further, the toner of the present invention itself may be manufactured as an insulating magnetic toner and used as a one-component developer to carry out the magnetic brush development method. Further, it may be used as a toner when implementing the impression development system.

The present invention has been described above with respect to a positively charged toner for electrophotography. However, since the charge control agent used in the present invention is a copolymer having electric characteristics which it is good at, it has this characteristic. It may be used in various other applications that can be applied, for example, as a surface coating agent for an electrophotographic carrier or a resin binder for powder coating. The copolymer in this case may be used alone, or may be used by blending it with other appropriate resin.

[0019]

EXAMPLES The present invention will be specifically described below based on examples. The copolymerization ratios and mixing ratios of the respective components in the examples are shown by weight ratio unless otherwise specified.

Example 1 Production of charge control agent 2 equipped with a stirrer, a condenser, a thermometer, and a nitrogen introducing tube
A flask was charged with 400 g of methyl ethyl ketone, 510 g of styrene, 60 g of butyl acrylate, 30 g of a monomer mixture of 30 g of methacryloyloxytrimethylammonium sulfate, and 12 g of azobisisobutyronitrile were stirred, and solution polymerization was carried out at 80 ° C. for 10 hours under nitrogen introduction. After completion of the polymerization reaction, the reaction mixture was transferred to a reduced pressure heating furnace and the methyl ethyl ketone was desolvated to obtain a copolymer (weight average molecular weight = 20,000, Tg = 75 ° C.), and this copolymer was used as a positive charge control agent. .

Manufacture of Toner 100 parts of styrene / acrylic copolymer resin, 5 parts of the charge control agent obtained above, carbon black (manufactured by Mitsubishi Kasei Co., Ltd.,
MA # 40) 5 parts and Viscole 550P (manufactured by Sanyo Kasei Kogyo Co., Ltd.) are mixed and melt-kneaded by a Labo Plastomill (manufactured by Toyo Seiki Seisakusho Co., Ltd.), finely pulverized by a jet mill and classified to obtain an average particle size. A toner having a diameter of 10 μm was manufactured.

Evaluation of Toner The toner obtained above was evaluated by the following method,
The results are shown in Table 2 below. (1) Chargeability Toner and carrier (reduced iron powder) are mixed at a ratio of 3: 100, and the mixture is kept under a condition of 20 ° C. and 65% RH for a predetermined time (10
Min, 60 min, 3 hours) After triboelectrification, charge quantity (μ
c / g) was measured. (2) High-temperature and high-humidity characteristics In the same manner as in the charging property evaluation method of (1) above, toner and carrier (reduced iron powder) were mixed at a ratio of 3: 100, and the mixture was heated at 35 ° C / 8
Triboelectrically charge for 60 minutes in a high temperature and high humidity atmosphere of 5% RH,
The amount of charge (μc / g) was similarly measured (the amount of charge at this time was C1). On the other hand, the charging amount C0 after 60 minutes frictional charging in the above (1) is defined as
The high-temperature and high-humidity characteristics were determined to be good when the residual amount of charge was 90% or more. Charging amount residual rate (%) = (C1 / C0) × 100 (3) Electrophotographic characteristics The toner obtained above was subjected to a copy test using a commercially available copying machine for positively charged toner, and fogging and stains on the photoreceptor were observed. Etc. were visually observed and evaluated according to the following evaluation criteria. Fog: ○: No abnormalities, ×: Soil on the ground Photosensitive material stains: ○: No abnormality, ×: Toner adhered

Examples 2-5 and Comparative Examples 1-5 Methacryloyloxytrimethylammonium sulphate (MTAS) and styrene as the other vinyl monomer copolymerizable with the MTAS, 2-ethylhexyl acrylate (2EHA), Butyl acrylate (BA)
In accordance with the formulation shown in Table 1 below, each charge control agent was produced in the same manner as in Example 1 above.

Then, the charge control agent obtained above was added to 100 parts by weight of the binder according to the formulation shown in Table 1 below to prepare a toner in the same manner as in Example 1, and each obtained toner was evaluated in the same manner. The results are shown in Table 2. Also,
Table 1 shows the measurement results of Mw and Tg of the charge control agents of Examples and Comparative Examples.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

The positively charged toner for electrophotography provided by the present invention is a copolymer of methacryloyloxytrimethylammonium sulfate represented by a specific chemical formula as a charge control agent and a vinyl monomer copolymerizable therewith. Since it is composed by including the coalesced in a specific ratio,
As a result, stable positive charging characteristics can be obtained, the change in charge amount is small even with environmental changes, and excellent electrophotographic characteristics are provided. Further, even when the binder and the positive charge control agent are mixed, a colorless or light-colored transparent state can be obtained. Therefore, when a color toner is formed, a colored toner capable of forming a color image having a clear color tone can be obtained. It has an excellent effect.

Claims (3)

[Claims] 1. An electrophotographic toner comprising at least a binder resin, a colorant and a charge control agent, wherein the charge control agent is represented by the following general formula (1): And 1 to 30% by weight of methacryloyloxytrimethylammonium sulfate represented by the above formula, and 99 to 70% by weight of another vinyl-based monomer copolymerizable therewith, and the charge control agent is a binder. A positively charged toner for electrophotography, characterized by containing 0.1 to 10 parts by weight with respect to 100 parts by weight of the agent. 2. The other copolymerizable vinyl-based monomer is
The positively charged toner for electrophotography according to claim 1, which is at least one selected from styrene, alkyl acrylate, and alkyl methacrylate. 3. The positively charged toner for electrophotography according to claim 2, wherein the acrylic acid alkyl ester and methacrylic acid alkyl ester are alkyl esters having an alkyl group having 1 to 18 carbon atoms.