JPH0527482A - Electrophotgraphic toner - Google Patents

Abstract

PURPOSE:To avoid reduction of electrification characteristics of a developer even for repeated use for a long time by specifying the proportion of a charge controlling dye existing on the surface of the toner particles to the total amt. of the charge controlling dye. CONSTITUTION:A fixing resin contains a colorant and charge controlling dye. The proportion of charge controlling dye existing on the surface of the toner particles (rate of dye existing on the surface) is specified to 10-27wt.% to the total amt. of the charge controlling dye. By controlling the surface present rate of the dye to this range, the time for premixing of the dye is controlled in the production process of the toner by mixing, kneading and pulverizing. If the amt. of the dye on the surface exceeds 27wt.%, 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 proportion is <10wt.%, the concn. of the surface dye relatively decreases, which decreases the electrification characteristics of the toner itself.

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 conventional electrophotographic toner, the ratio of the charge control dye present on the surface of the toner particles in the total amount of the charge control dye (hereinafter referred to as “dye surface abundance ratio”) is 30 to 90% by weight. %, A large amount of charge control dye is exposed on the surface of the toner particles.

In a high-speed type image forming apparatus, the developer is agitated under more severe conditions than in a normal image forming apparatus. The dye exposed on the surface of the toner drops off from the toner particles, contaminates the carrier, and deteriorates the charging characteristics of the developer as a whole, which causes the above-mentioned problems.

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 characteristics of a developer even when it is repeatedly used for a long period of time. Has a purpose.

[0009]

In order to solve the above problems, the electrophotographic toner of the present invention comprises a fixing resin containing a colorant and a charge control dye, and the toner particles are provided on the surface thereof. The ratio of the existing charge control dye in the total amount of the charge control dye (dye surface presence rate) is 1
It is characterized in that it is in the range of 0 to 27% by weight.

In the electrophotographic toner of the present invention having the above-mentioned constitution, the amount of the dye existing on the surface of the toner particle and falling off from the surface of the toner particle by stirring or the like is small, and as a result, the carrier due to the falling dye is used. The pollution of can be reduced. The reason why the surface abundance of the dye is limited within the above range is as follows. That is, when the surface abundance of the dye exceeds 27% by weight, as described above, the amount of the charge control dye which is detached from the toner particles and contaminates the carrier when used repeatedly for a long period of time increases, Problems such as pre-drawing, toner scattering, and instability of image density occur with the deterioration of the charging property of the developer.

On the other hand, when the surface abundance ratio of the dye is less than 10% by weight, the surface dye concentration is relatively lowered and the charging property of the toner itself is deteriorated, so that the charging property of the developer is deteriorated at the initial stage of image formation. As a result, the above problem occurs. 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 are used. , 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.

[0014]

[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 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 and cadmium selenide. 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 controlling 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.

[0026]

[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 release 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.

In order to adjust the surface abundance ratio of the dye in the toner within the above range, the time of the pre-mixing step (pre-mixing time) in manufacturing the electrophotographic toner by the above-mentioned toner manufacturing method by mixing, kneading and pulverizing. ) Should be adjusted. That is, when the pre-mixing time is short, the charge control dye is not subjected to a shearing force due to mixing so much that it is mixed and kneaded in the fixing resin in a relatively large lump. For this reason, the charge controlling dye will then be present in a relatively large lump state on the surface of the toner produced by pulverization and classification, and the surface abundance of the dye 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 abundance of the dye tends to be low. Since the length of the premixing time and the surface abundance rate of the dye described above are substantially proportional to each other, the surface abundance rate of the dye can be adjusted by adjusting the premixing time.

For finer adjustment of the surface abundance of the dye, it is sufficient to combine the adjustment of the charge control dye and the adjustment of the premixing time. The surface dye concentration of the toner particles is not particularly limited in the present invention and may be the same level as in the prior art, but in consideration of reducing the detachment of the charge control dye from the toner particles, it is, for example, 1.0. × 1
It is preferably in the range of 0 ^{−3 to} 4.0 × 10 ⁻³ g / g, which is lower than the conventional range.

The particle size of the electrophotographic toner of the present invention is 3 to.
The thickness is preferably 35 μm, more preferably 5 to 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 to be used as a two-component developer in an image forming apparatus.

[0035]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. Examples 1-5, Comparative Examples 1, 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 with a twin-screw kneader, cooled, pulverized, and classified by a conventional method, and then treated with silica fine powder as a fluidizing agent to obtain surface dyes shown in Table 1. Median particle size 12 having density and surface abundance of dye
A μm electrophotographic toner was prepared. The surface dye concentration of the electrophotographic toner and the surface abundance of the dye are
It was determined as follows.

100 mg of the electrophotographic toner was put in 50 ml of methanol, and sufficiently mixed by stirring to extract the charge control dye on the surface of the toner particles, and the supernatant obtained by precipitating the toner particles was measured by a spectrophotometer. From the measurement results, the surface dye concentration was calculated using a predetermined calibration formula. Next, from the concentration of the charge control dye in all components (total dye concentration g / g) and the surface dye concentration (g / g),
The surface abundance (% by weight) of the dye was determined based on the following formula.

[0038]

[Equation 1]

Among the electrophotographic toners obtained in each of the above-mentioned Examples and Comparative Examples, Example 1 having a low surface dye concentration was used.
2. In Comparative Example 2, 100 parts by weight of the toner was added to a ferrite carrier having a high triboelectrification series chargeability and whose surface was coated with an acrylic / melamine resin (average particle size: 10).
0 μm) was mixed and uniformly mixed with stirring to prepare a two-component developer having a toner concentration of 4.5%.

Further, Examples 3 to 5 having a high surface dye concentration,
In Comparative Example 1, 100 parts by weight of the toner was mixed with a ferrite carrier (average particle size 100 μm) whose surface was coated with an acrylic resin having a low triboelectrification chargeability, and the mixture was uniformly stirred and mixed to obtain a toner. A two-component developer having a concentration of 4.5% was prepared. The following tests were conducted using the obtained developer.

Initial Image Density Measurement 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.

[0043]

[Table 1]

From the above Table 1, it is considered that in the developer containing the electrophotographic toner of Comparative Example 1 in which the surface abundance of the dye exceeds 27% by weight, the charging property of the developer is deteriorated due to the contamination of the carrier. However, it was found that pre-drawing and toner scattering occurred in the copying process for 1,000 sheets, and the life of the developer was short.
On the other hand, in the developer containing the electrophotographic toner of Comparative Example 2 in which the surface abundance of the dye is less than 10% by weight, it is considered that the decrease in the charging property of the developer due to the lack of the surface dye causes the pre-coating and toner Scattering occurs in the copying process of 4,000 sheets,
Although somewhat longer than Comparative Example 2, it was found that the life of the developer was still short.

On the other hand, all the developers containing the electrophotographic toners of Examples 1 to 5 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 5 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.

[0046]

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.

Front Page Continuation (72) Inventor Kaoru Tanaka 1-2-2 Tamatsukuri, Chuo-ku, Osaka-shi, Osaka Mita Industry Co., Ltd.

Claims (1)

Claims: 1. A fixing resin containing a colorant and a charge control dye, and the charge control dye present on the surface of toner particles accounts for the total amount of the charge control dye. Ratio is 1
A toner for electrophotography, characterized in that it is in the range of 0 to 27% by weight.