JPH0527483A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To avoid reduction of electrification characteristics of a developer even for repeated use for a log time by specifying the surface concn. of a charge controlling dye. CONSTITUTION:A fixing resin contains a colorant and charge controlling dye. The surface concn. of the charge controlling dye is specified to 1.0X10<-3>-1.7X10<-3>g/g. To control the surface dye concn. of the toner to this range, the compounding amt. of the dye is controlled and the time for premixing of the dye is controlled in the production process of the toner by mixing, kneading and pulverizing. If the concn. on the surface exceeds 1.7X10<-3>g/g, the dye drops out from the toner particles for long term use and contaminates the carrier, which reduces the electrification characteristics of the developer. If the concn. is <1.0X10<-3>, the electrification characteristics of the toner itself decreases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner, and more particularly to an electrophotographic toner used in an image forming apparatus such as an electrostatic copying machine or a laser beam printer.

[0002]

2. Description of the Related Art In the image forming apparatus described above, first, the surface of a photoconductor is exposed to form an electrostatic latent image on the surface of the photoconductor. Next, a developer containing an electrophotographic toner and a carrier is brought into contact with the surface of the photoreceptor. Then, the electrophotographic toner electrostatically adheres to the electrostatic latent image, and the electrostatic latent image is visualized as a toner image. This toner image
When the image is transferred from the surface of the photoconductor onto the paper and fixed, an image corresponding to the electrostatic latent image is formed on the surface of the paper.

As the above-mentioned electrophotographic toner, a fixing resin in which a colorant such as carbon black or a charge control dye is mixed and granulated to a predetermined particle size is used. In such an electrophotographic toner, the amount of the charge control dye, which is exposed on the surface of the toner particles and contributes to the generation of electric charges, per 1 g of the toner particles, that is, the surface dye concentration greatly influences the charging characteristics of the toner. It is known.

In order to improve the charging property, the surface dye concentration, which was conventionally about 2.0 × 10 ^{−3 to} 4.0 × 10 ⁻³ g / g, was changed to 4.0 × 10 ^{−3 to} 9 × 9. 0.0 × 10 ^-3 g / g
There has been proposed an electrophotographic toner having a heightened level (see JP-A-61-36757). The surface dye concentration is the amount of the extracted dye obtained by selectively extracting the dye on the surface of the toner particles with a solvent such as methanol that dissolves only the charge control dye, and measuring the extract by absorbance measurement or the like. Is converted to the amount of dye per 1 g of toner particles.

[0005]

However, conventional electrophotographic toners, including those having a high surface dye concentration, have the following problems.
In particular, when repeatedly used for a long period of time in a high-speed image forming apparatus having a high image forming speed, problems such as pre-drawing due to deterioration of charging characteristics of the developer, toner scattering, and unstable image density may occur. I understood. It should be noted that the term "pre-drawing" used herein refers to a phenomenon in which a large amount of toner electrostatically adhered to an electrostatic latent image flows toward the front in the image forming direction when the toner is rubbed by a magnetic brush of a developing device because the charging property is low. Point to.

When the cause of the above problems was examined, the following was revealed. That is, in the high-speed image forming apparatus, the developer is agitated under more severe conditions than in the normal image forming apparatus. Therefore, when the developer is repeatedly used for a long period of time, the dye exposed on the surface of the toner particles falls off from the toner particles, contaminates the carrier, and deteriorates the charging property of the developer as a whole. As a result, the above-mentioned problems occur.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an electrophotographic toner which does not deteriorate the charging property of a developer even when it is repeatedly used for a long period of time. Has a purpose.

[0008]

To solve the above problems, the electrophotographic toner of the present invention contains a colorant and a charge control dye in a fixing resin, and comprises a charge control dye. Surface dye concentration is 1.0 × 10 ^{-3 to} 1.7 ×
It is characterized in that it is in the range of 10 ⁻³ g / g. In the electrophotographic toner of the present invention having the above structure, since the surface dye concentration is low, the amount of the dye falling off from the surface of the toner particles is small, and as a result, the contamination of the carrier by the falling dye can be reduced. ..

The surface dye concentration of the electrophotographic toner is limited within the above range for the following reasons. That is,
When the surface dye concentration exceeds 1.7 × 10 ⁻³ g / g, as described above, the amount of the dye for charge control, which is detached from the toner particles and contaminates the carrier when repeatedly used for a long time, becomes large. Increase, and with the deterioration of the charging property of the developer, forward pulling,
Problems such as toner scattering and unstable image density occur.

On the other hand, the surface dye concentration is 1.0 × 10 ^-3 g /
If it is less than g, the charging property of the toner itself is deteriorated, so that the above-mentioned problems occur at the initial stage of image formation due to deterioration of the charging property of the developer. In the electrophotographic toner of the present invention, a fixing resin is mixed with various additives such as a colorant, a charge control dye, and a release agent (anti-offset agent), and the mixture is subjected to steps such as pulverization and classification. It is manufactured by granulating to a predetermined particle size.

As the fixing resin, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer. , Styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer,
Styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylic acid ester copolymer (styrene-methacrylic acid) Methyl acid copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile -Styrene resins such as acrylate copolymers (homopolymers or copolymers containing styrene or styrene substitute), polyvinyl chloride, low molecular weight polyethylene, low molecular weight polypropylene, ethylene-ethyl acrylate copolymer, Polyvinyl butyral, ethylene-acetic acid Examples include nyl copolymers, rosin-modified maleic acid resins, phenol resins, epoxy resins, polyester resins, ionomer resins, polyurethane resins, silicone resins, ketone resins, xylene resins, polyamide resins, etc., which may be used alone or in combination. The above is mixed and used.

Among them, styrene resins, especially styrene-
Styrene-acrylic copolymers such as acrylic acid ester copolymers and styrene-methacrylic acid ester copolymers are preferably used. As the styrene-based monomer constituting the styrene-acrylic copolymer, vinyltoluene, α-methylstyrene, etc. can be used in addition to styrene. As the acrylic monomer, those represented by the following general formula (I) can be used.

[0013]

[Chemical 1]

In the formula, R ¹ is a hydrogen atom or a lower alkyl group, R ² is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group, a vinyl ester group or an aminoalkyl group. Examples of the acrylic monomer represented by the above general formula (I) include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate. , Methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate,
β-Hydroxyacrylate, γ-Hydroxyacrylate, δ-Hydroxyacrylate, β
-Ethyl hydroxymethacrylate, γ-aminopropyl acrylate, γ-N, N-diethylaminopropyl acrylate, ethylene glycol dimethacrylate,
Examples thereof include tetraethylene glycol dimethacrylate.

The above copolymer can be produced from each monomer according to a conventionally known polymerization method such as a solution polymerization method. Examples of the colorant include various color pigments, extender pigments, conductive pigments, magnetic pigments and photoconductive pigments. These are used alone or in combination of two or more depending on the application.

The following pigments are preferably used as the color pigment. Black furnace black, channel black, thermal,
Carbon black such as gas black, oil black and acetylene black, lamp black, aniline black.

White zinc white, titanium oxide, antimony white, zinc sulfide. Red red iron oxide, cadmium red, red lead, mercury sulfide, permanent red 4R, resole red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B.

Orange reddish yellow lead, molybdenum orange, permanent orange GTR, pyrazolo orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK. Yellow Yellow Lead, Zinc Yellow, Cadmium Yellow, Yellow Iron Oxide, Mineral Fast Yellow, Nikketsu Titanium Yellow, Naples Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow rake, permanent yellow NCG, tartrazine rake.

Green chrome green, chrome oxide, pigment green B,
Malachite Green Rake, Fanal Yellow Green G. Blue Navy Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue Lake, Phthalocyanine Blue Partial Chloride, Fast Sky Blue, Indanthrene Blue B
C.

Purple manganese purple, first violet B, methyl violet lake. As extender pigments, barite powder, barium carbonate, clay, silica, white carbon, talc,
Alumina white and the like can be mentioned. Examples of the conductive pigment include conductive carbon black and aluminum powder.

As the magnetic pigment, various ferrites, for example,
For example, ferric oxide (Fe₃O_Four), Ferric oxide (γ-Fe₂O
₃), Zinc oxide (ZnFe₂O_Four), Yttrium iron oxide
(Y ₃Fe_FiveO₁₂), Iron cadmium oxide (CdFe₂O_Four),acid
Gatrinium Iodide (Gd₃Fe_FiveO _Four), Iron oxide copper (CuFe₂O
_Four), Iron oxide lead (PbFe₁₂O₁₉), Iron oxide neodymium (NdFe
O₃), Iron oxide barium (BaFe₁₂O₁₉), Iron oxide magne
Cium (MgFe₂O_Four), Iron manganese oxide (MnFe
₂O_Four), Lanthanum iron oxide (LaFeO₃), Iron powder, kobaru
Examples of the powder include nickel powder and nickel powder.

Examples of the photoconductive pigment include zinc oxide, selenium, cadmium sulfide, cadmium selenide and the like. The colorant is 1 to 3 parts by weight with respect to 100 parts by weight of the fixing resin.
It is used in a proportion of 0 parts by weight, preferably 2 to 20 parts by weight. As the charge control dye, depending on the polarity of the toner,
Either one of the two types of charge control dyes for positive charge control and negative charge control is used.

The charge control dye for positive charge control includes
For example, basic dyes, aminopyrine, pyrimidine compounds,
Examples thereof include polynuclear polyamino compounds, aminosilanes and the like, and fillers surface-treated with the above compounds. More specifically, color index classification C.I. I. Solve
Black (1, 2, 3, 5, 7) of t (oil-soluble dye) is preferable.

As the charge control dye for controlling the negative charge,
Examples include compounds containing a carboxy group (for example, metal chelate of alkylsalicylic acid, etc.), metal complex salt dyes, fatty acid soaps, metal salts of naphthenic acid, and the like. Among the complex salt azo dyes containing chromium, iron or cobalt, those which are alcohol-soluble Is preferably used. More preferably, a sulfonylamine derivative of copper phthalocyanine, or the following formula
A 2: 1 type metal-containing monoazo dye represented by (II) can be given.

[0025]

[Chemical 2]

(In the above formula, A represents a residue of a diazo component having a phenolic hydroxyl group at the ortho position, B represents a residue of a coupling component, M represents a chromium, iron, aluminum, zinc or cobalt atom. And [Y] ⁺ represents an inorganic or organic cation.) The charge control dye is 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the fixing resin. Is compounded in.

Examples of the releasing agent (anti-offset agent) include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, and various waxes. Of these, aliphatic hydrocarbons having a weight average molecular weight of about 1,000 to 10,000 are preferable. Specifically, one or a combination of two or more of low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, a low molecular weight olefin polymer composed of olefin units having 4 or more carbon atoms is suitable.

The release agent is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the fixing resin. The toner for electrophotography of the present invention, a mixture obtained by homogeneously premixing the above respective components by a dry blender, a Henschel mixer, a ball mill, etc., a Banbury mixer, a roll, a uniaxial or biaxial extrusion kneader, etc. After uniformly melt-kneading using a kneading device, the obtained kneaded product is cooled and pulverized, and if necessary, classified, or may be produced by a suspension polymerization method or the like.

As a method of adjusting the surface dye concentration of the toner within the above range, a method of adjusting the compounding amount of the charge controlling dye is generally used. The time of pre-mixing step (pre-mixing time) when manufacturing the electrophotographic toner by the manufacturing method
The surface dye concentration can also be adjusted by adjusting.

That is, when the pre-mixing time is short, the charge controlling dye is not subjected to a shearing force due to the mixing so much that it is mixed and kneaded in the fixing resin as a relatively large lump. Therefore, after that, the charge control dye is present in a relatively large lump state on the surface of the toner produced by pulverization and classification, and the surface dye concentration tends to increase.

On the other hand, when the pre-mixing time is taken long, the charge control dye is uniformly dispersed in the fixing resin in the state of being finely crushed by the shearing force due to the mixing. For this reason,
The amount of the charge control dye exposed on the surface of the manufactured toner particles, that is, the surface dye concentration tends to be low. Since the length of the pre-mixing time and the surface dye concentration of the toner described above are substantially proportional to each other, the surface dye concentration can be adjusted by adjusting the pre-mixing time.

For finer adjustment of the surface dye concentration, the adjustment of the blending amount of the charge control dye and the adjustment of the premixing time may be combined. The particle diameter of the electrophotographic toner of the present invention is preferably 3 to 35 μm, and 5
More preferably, it is about 25 μm. The surface of the electrophotographic toner of the present invention may be sprinkled with a surface treatment agent (fluidizing agent) to improve the fluidity and the chargeability. As the surface treatment agent, various conventionally known materials such as inorganic fine particles and fluorine resin particles can be used. In particular, a silica-based surface treatment agent containing hydrophobic or hydrophilic silica fine particles, for example, ultrafine particulate anhydrous silica or Colloidal silica and the like are preferably used.

The electrophotographic toner of the present invention can be mixed with a magnetic carrier such as ferrite or iron powder and used as a two-component developer in an image forming apparatus.

[0034]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. Examples 1 to 4, Comparative Examples 1 and 2 Styrene-acrylic copolymer 10 as fixing resin
0 parts by weight, 10 parts by weight of carbon black as a colorant, and 2.5 parts by weight of low-molecular-weight polypropylene as an anti-offset agent were further compounded with chromium-containing monoazo dyes in the amounts shown in Table 1 as charge control dyes. Using a Henschel mixer, pre-mixing treatment was performed for the time shown in the table.

Next, the above mixture was melt-kneaded by a twin-screw kneader, cooled, pulverized and classified by a conventional method, and then treated with silica fine particles as a fluidizing agent to obtain surface dye concentrations shown in Table 1. A toner for electrophotography having a central particle diameter of 12 μm was produced. The surface dye concentration of the electrophotographic toner was determined as follows. Electrophotographic toner 100
After adding 50 mg of methanol to 50 ml of methanol and sufficiently stirring and mixing to extract the charge control dye on the surface of the toner particles, the supernatant obtained by precipitating the toner particles is measured by a spectrophotometer, and the predetermined result is determined. The surface dye concentration was calculated using a calibration formula.

100 parts by weight of the electrophotographic toners obtained in each of the above Examples and Comparative Examples were mixed with a ferrite carrier having an average particle size of 100 μm, the surface of which was coated with an acrylic melamine resin, and uniformly mixed by stirring. Then, a two-component developer having a toner concentration of 4.5% was prepared. The following tests were conducted using the obtained developer. The electrophotographic toner of Comparative Example 2 having a surface dye concentration of more than 1.7 × 10 ⁻³ g / g had an excessively high chargeability in the system using the above carrier and had an initial image density of 1.212. It has dropped significantly. Therefore, a two-component developer having a toner concentration of 4.5% was prepared using a ferrite carrier (average particle size 100 μm) whose surface is coated with an acrylic resin and which has a low triboelectric charging property. The test was conducted.

Measurement of Initial Image Density The above developer was used in an electrophotographic copying machine (model DC-2055 manufactured by Mita Kogyo Co., Ltd.) to copy a black solid original. Then, a reflection densitometer (Model TC-6 manufactured by Tokyo Denshoku Co., Ltd.
D) was used to measure the initial image density (ID). Measurement of Life of Developer The above developer was used in an electrophotographic copying machine (model DC-2055 manufactured by Mita Kogyo Co., Ltd.) to continuously copy 20,000 black solid originals. Then, while observing whether or not the copied image is pre-loaded and observing whether or not toner is scattered around the developing device of the electrophotographic copying machine during continuous copying, 2
Even if the copying of ten thousand sheets was repeated, the copy image was not pre-cured, and the toner scattering around the developing device was small, evaluated as ◯. It was recorded whether it occurred on the first sheet.

The above results are shown in Table 1.

[0039]

[Table 1]

From Table 1 above, the surface dye concentration is 1.7 × 1.
In the developer containing the electrophotographic toner of Comparative Example 2 in an amount of more than 0 ⁻³ g / g, there is 1 in the amount of pre-advancement or toner scattering, which is considered to be caused by the deterioration of the charging property of the developer due to contamination of the carrier.
It occurred in the process of copying 1,000 sheets, and it was found that the life of the developer was short. On the other hand, in the developer containing the electrophotographic toner of Comparative Example 1 having a surface dye concentration of less than 1.0 × 10 ⁻³ g / g, it is considered that the charging property of the developer is deteriorated due to insufficient surface dye concentration. It was found that the pre-drawing and the toner scattering occurred in the copying process of 4,000 sheets and were a little longer than Comparative Example 2, but the life of the developer was still short.

On the other hand, all the developers containing the electrophotographic toners of Examples 1 to 4 were excellent in the initial image density,
The life of the developer is as long as 20,000 sheets or more, and no pre-drawing or toner scattering occurs. Therefore, the electrophotographic toners of Examples 1 to 4 have excellent initial charging characteristics and a long term. It has been found that there is no possibility of deteriorating the charging characteristics of the developer even if it is repeatedly used.

[0042]

EFFECT OF THE INVENTION Since the electrophotographic toner of the present invention is as described above, there is no fear of deteriorating the charging property of the developer even if it is repeatedly used for a long period of time.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaoru Tanaka 1-2-2 Tamatsukuri Chuo-ku, Osaka City, Osaka Prefecture Mita Industry Co., Ltd.

Claims (1)

Claims: 1. A fixing resin contains a colorant and a charge control dye, and the surface dye concentration of the charge control dye is 1.
A toner for electrophotography, characterized in that it is in the range of 0 × 10 ^{−3 to} 1.7 × 10 ⁻³ g / g.