KR20060070163A - Electrophotographic developing agent - Google Patents

Abstract

Toner particles comprising a binder resin, a colorant, and a charge control agent; And an external additive added to the surface of the toner particles, wherein the external additive comprises 0.1 to 3.0 parts by weight of large particle size silica having a primary average particle diameter of 20 to 200 nm; 0.1 to 3.0 parts by weight of small particle silica having a primary average particle diameter of 5 to 20 nm; 0.1 to 2.0 parts by weight of hydrophobic titanium oxide having a primary average particle diameter of less than 500 nm; And it relates to an electrophotographic developer comprising polyaniline (polyaniline). The developer according to the present invention uses polyaniline as an external additive in the manufacture of toner to uniformly distribute the charge, improve the image density and Blur problems in the initial and long life, and reduce the contamination of the charging roller. In addition, such an electrophotographic developer may be usefully used in various electrophotographic image forming apparatuses.

Description

Electrophotographic developing agent

1 is a schematic view showing an embodiment of an electrophotographic apparatus of a non-contact developing method.

<Short description of drawing symbols>

1: photosensitive member 2: charging means

3: exposure signal 4: developing device

5: developing roller 6: feeding roller

7: developer regulation blade 8: developer

8 ': Waste Toner 9: Transfer Means

10: cleaning blade 12: power

13: print media

The present invention relates to an electrophotographic developer, and more particularly, to an electrophotographic developer comprising polyaniline (PANI), which is a conductive polymer, as an external additive in a developing apparatus of an electrophotographic image processing apparatus.

The electrophotographic image processing apparatus that is widely used at present is a laser printer, a facsimile machine, a copier, etc., which use a laser to create a latent image on the photosensitive member, and then use a potential difference to transfer the toner to the latent image on the photosensitive member, and print it on paper It is transferred to a medium to form a desired image.

1 illustrates an example of an image forming apparatus of a non-contact developing method, and an operation principle thereof will be described below.

The nonmagnetic one-component developer is supplied onto the developing roller 5 by the supply roller 6 made of elastic members such as polyurethane foam and sponge. The developer 8 supplied onto the developing roller 5 reaches the contact portion between the developer regulating blade 7 and the developing roller 5 as the developing roller 5 rotates. The developer regulating blade 7 is made of an elastic member such as metal or rubber. When the developer passes between the developer regulating blades 7 and the contact portions of the developing roller 5, the layer of the developer 8 is regulated to a constant layer so that a thin layer is formed and the developer is sufficiently charged. The thinned developer 8 is transferred to the developing region in which the developer 8 is developed by the developing roller 5 on the electrostatic latent image of the photosensitive member 1, which is a latent image bearing member.

The developing rollers 5 face each other without contact with the photosensitive member 1 at regular intervals. The developing roller 5 rotates in the counterclockwise direction and the photosensitive member 1 rotates in the clockwise direction. The developer 8 transferred to the developing region is an electrostatic latent image of the photosensitive member 1 according to the electric force generated by the potential difference between the DC superimposed AC voltage applied to the developing roller 5 and the latent image potential of the photosensitive member 1. Develop.

The developer 8 developed on the photosensitive member 1 reaches the position of the transfer means 9 in accordance with the rotational direction of the photosensitive member 1. The developer developed on the photosensitive member 1 transfers the printing paper 13 to the printing paper while the printing paper 13 passes by the transfer means 9 to which the reverse high voltage to the developer 8 is applied in the form of corona discharge or roller. An image is formed.

The image transferred to the printing paper passes through a high temperature and high pressure fixing unit (not shown), and the developer is fused to the printing paper to fix the image. On the other hand, the undeveloped residual developer on the developing roller 5 is recovered by the supply roller 6 in contact with the developing roller 5. The above process is repeated.

Recently, as image forming apparatuses such as an electrophotographic LBP, a multifunction printer, and a color copying machine are widely used, high quality image quality is required. To this end, as the developer used in the developing apparatus, the developer is designed to have characteristics such as stable charge amount, developing efficiency, and no fog, even with changes in environment as well as changes over time due to long-term image printing.

In order to control the toner charge stabilization, fog prevention, and development efficiency improvement, various additives such as silica, TiO ₂ , and Al ₂ O ₃ have been tried to toner, but there is a limit to improvement of image quality. There is a situation. That is, variations in toner charging characteristics due to environmental changes such as low temperature, low humidity, and high temperature and high humidity are largely generated, and in the initial stage of printing, a uniform charge amount and a charge distribution are generated, but the charge amount decreases greatly when left to stand. In addition, a decrease in image density, fog and toner scattering occur due to a decrease in charge amount and uneven charge amount distribution during image printing over a long service life.

Therefore, the type of external additives added for improving various image quality is increasing, and the amount of external additives is gradually increasing. Such external additives preferably maintain a stable adhesion state on the surface of the toner for a long time. However, in reality, the external additives are buried in the toner particles or some external additives are separated / detached from the toner, causing contamination of the developing member and resulting burns. It is causing pollution. In addition, the charge distribution on the toner particles was not uniform, resulting in poor image density and poor Blur characteristics.

In order to solve the above problems, the present invention,

An object of the present invention is to provide a developer for electrophotographic which maintains a stable amount of toner charging and a uniform charge distribution even in a change due to environmental changes and long-term image printing, and prevents image contamination caused by contamination of the developing member.

Moreover, an object of this invention is to provide the electrophotographic image forming apparatus which employ | adopted the said developer.

In order to achieve the above object, the present invention,

Toner particles comprising a binder resin, a colorant, and a charge control agent; And

In the electrophotographic developer comprising an external additive added to the surface of the toner particles, the external additive

0.1 to 3.0 parts by weight of large particle silica having a primary average particle diameter of 20 to 200 nm;

0.1 to 3.0 parts by weight of small particle silica having a primary average particle diameter of 5 to 20 nm;

0.1 to 2.0 parts by weight of hydrophobic titanium oxide having a primary average particle diameter of less than 500 nm; And

Provided is an electrophotographic developer comprising polyaniline.

In order to achieve the above another object, the present invention provides an electrophotographic image forming apparatus employing the above electrophotographic developer.

The electron developer according to the present invention attaches polyaniline, which is a conductive polymer, as an external additive to the surface of the toner particles. As a result, it is possible to maintain the stable charge amount and maintain the charge amount distribution to suppress the contamination of the charging roller in the initial and long life, and to improve the Blur problem.

Hereinafter, the present invention will be described in more detail.

The present invention provides an electrophotographic developer comprising a toner particle comprising a binder resin, a colorant, and a charge control agent and an external additive added to the surface of the toner particle, wherein the external additive has a primary average particle diameter of 20 to 200. 0.1-3.0 parts by weight of large particle silica having a nm; 0.1 to 3.0 parts by weight of small particle silica having a primary average particle diameter of 5 to 20 nm; 0.1 to 2.0 parts by weight of hydrophobic titanium oxide having a primary average particle diameter of less than 500 nm; And it provides a developer for electrophotography comprising polyaniline.

The present invention can use a conductive polymer to prevent occurrence of image contamination due to developing member contamination and to impart uniform chargeability to toner particles.

In general, conductive polymers have excellent processability, flexibility, strength, and chemical inertness compared to metals. In addition, there is an advantage that the size of the electrical conductivity can be adjusted according to the doping has increased the use of electronic components as a material.

The types of conductive polymers include, but are not limited to, polyaniline, polyacetylene, polypyrrole, polythiophene, poly (3-alkyl-thiophene), polyphenylene sulfide, polyphenylenevinylene, polythienylene vinylene, poly Isothianaphthalene, polyphenylene, polyfuran, and the like, and polyaniline can be preferably used. The conductive polymers may be widely used in fuel cells, organic electroluminescent devices, solar cells, and electromagnetic shielding.

Among the conductive polymers, polyacetylene has a high direct current conductivity (˜105 S / cm) but is not stable to air and heat, and is not easy to synthesize and process. However, the polyaniline is stable in air and has excellent processability. Because of this, it can be suitably used in the present invention. The shape of the polyaniline in the above may be prepared in various shapes in order to excellent chargeability, but preferably may be spherical or rod-shaped.

The polyaniline conductive polymer has a conjugated polymer structure in which a single bond and a double bond are alternately around a carbon having an sp ² hybrid orbit. Various chemical synthesis methods can control physical properties such as electrical conductivity, dielectric constant and crystallinity.

The structure of polyaniline which can be used in the present invention is shown in the formula:

Formula 1 represents polyaniline (PANI-EB) in the form of Emeraldine base, and Formula 2 represents polyaniline in the form of Emeraldine salt (PANI-ES) in a conductive state. Polyaniline (PANI-EB) in the form of emeraldine base is insulated with electrical conductivity of ~ 10-10S / cm.However, protonic acid doping such as hydrochloric acid (hyd-rochloric acid, HCl) gives an electrical conductivity of 10 Transitions to polyaniline (PANI-ES) in the form of Emeraldine salt, which has a conductivity of more than S / cm. Electrical conductivity varies depending on the doping level, the organic solvent used, the type of dopant, the molecular weight, etc., and as the doping level increases, an insu-lator-metal transition occurs. . PANI-ES forms a mobile defect, polaron, in a one-dimensional chain structure, and serves as a charge carrier.

In order for the polyaniline to be used as the conductive polymer, the specific resistance must be 1 × 10 ³ Ωcm to 1 × 10 ⁵ Ωcm. 1 × 10 ³ because Ωcm is less than in the case of not preferable because the flow in charging performance is excessive can not stay around the toner particle exceeds 1 × 10 ⁵ Ω is not passing through the substantially current preferred for the role of the conductive polymer I can't.

The conductive polymer polyaniline may uniformly distribute the charge on the toner particles to improve the developing amount and developing efficiency from the developing roller to the photoconductor, and improve the transfer efficiency to improve the Blur characteristics. In addition, the cleaning property on the photoconductor is improved as compared with the use of an external additive in the form of polymer beads, which may contribute to the production of toner with less contamination of the charging roller.

In general polymerization and pulverized toners, colorants, charge control agents, mold release agents and the like are uniformly embedded in the binder resin in order to improve chromaticity, charge characteristics, fixability, and the like, and impart fluidity, charge stability, and cleaning properties. In order to achieve this, various kinds of external additives are added. In the addition of the external additives, the removal and burial of the external additives on the surface of the toner, which causes image deterioration, may occur, so that two or more types of external additives having different average particle diameters may be used together to prevent them.

As the inorganic fine particles used in the present invention, silica having two different particle diameters can be preferably added. In this case, the two kinds of silica added may include a large particle size silica having an average particle size of 20 to 200 nm and a small particle size silica having an average particle size of 5 to 20 nm. In using silica particles having different particle diameters, large-size silica is a spacer particle to prevent toner deterioration due to durability and to improve transferability, and small-size silica mainly plays a role of imparting fluidity to the toner. .

The content of the large-size silica and the small-size silica particles is independently 0.1 to 3.0 parts by weight based on the toner base particles, and when the content is less than 0.1 part by weight, it is difficult to obtain an effect due to the addition of silica. When it exceeds 3.0 parts by weight, deterioration in fixability, overcharge and poor cleaning occur, which is not preferable.

Using only silica with a relatively large specific surface area yields quite good results in terms of transfer efficiency, but drum contamination can occur when a large amount of power is produced for a long period of time. Therefore, inorganic fine particles other than silica can be used for remarkable improvement effect. The material which can be used as the inorganic fine particles can be selected from the group consisting of hydrophobic strontium titanate, aluminum oxide, zinc oxide, magnesium oxide, celium oxide, iron oxide, copper oxide or tin oxide. Preferably hydrophobic strontium titanate can be used.

The hydrophobic titanium oxide improves the fluidity of the toner, and can maintain high high efficiency even when outputting a large amount for a long time. In addition, it is possible to improve the environmental stability by preventing drum contamination. In particular, the problem of toner charge up at low temperature and low humidity can be prevented, and the problem of charge down of toner at high temperature and high humidity can be solved. The primary average particle diameter of the hydrophobic titanium oxide is preferably 10 to 500 nm, more preferably in the range of 10 to 100 nm. If the primary average particle size exceeds 500 nm, it is not preferable because charge down at high temperature and high humidity is a problem, and if it is less than 10 nm, fixation failure and charging nonuniformity tend to occur, which is not preferable.

The content of the hydrophobic titanium oxide may be changed by controlling with the two kinds of silica particles, preferably 0.1 to 2.0 parts by weight, more preferably 0.1 to 1.5 parts by weight based on the toner base particles. If the content of hydrophobic titanium oxide is less than 0.1 part by weight, the effect of removing drum contamination is reduced, which may cause burn contamination. Not desirable

The toner base particles of the present invention include a binder resin, a colorant, a charge control agent, and a release agent.

As the binder resin used in the developer according to the present invention, various known resins can be used, for example, polystyrene, poly-P-chlorostyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer. , Styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-propyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, Styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-methacrylate propyl copolymer, styrene-butyl methacrylate copolymer, styrene- alpha -chloro methacrylate copolymer, styrene- Acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl ethyl ketone Styrene-based copolymers such as copolymers, styrene-butadiene copolymers, styrene-acrylonitrile-indene copolymers, styrene-maleic acid copolymers and styrene-maleic acid esters, polymethyl methacrylates, polyethyl methacrylates, and polybutyl methacrylates Acrylates, copolymers thereof, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral resin, rosin, modified rosin, terpene resin, phenolic resin, Aliphatic or cycloaliphatic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like may be used alone or in combination. Of these, polyester resins are excellent in fixability and transparency and are suitable for color developers.

The developer according to the present invention may include a colorant, and as such a colorant, carbon black or aniline black may be used in the case of a black and white toner, and the nonmagnetic toner according to the present invention is easy to prepare a color toner. In the case of the color toner, the black color of the colorant uses carbon black and the color further includes yellow, magenta, and cyan colorants.

As said yellow colorant, a condensed nitrogen compound, an isoindolinone compound, an atlakin compound, an azo metal complex, or an allyl imide compound is used. Specifically C.I. Pigment Yellow 12, 13, 14, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168 or the like can be used.

As the magenta colorant, condensed nitrogen compounds, anthraquines, quinacridone compounds, base dye late compounds, naphthol compounds, benzo imidazole compounds, thioindigo compounds, or perylene compounds are used. Specifically C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, or 254 may be used.

As the cyan colorant, a copper phthalocyanine compound and a derivative thereof, an anthrakin compound, a basic dye rate compound and the like are used. Specifically C.I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66 or the like can be used.

Such colorants may be used alone or in admixture of two or more thereof, and are selected in consideration of color, saturation, lightness, weather resistance, dispersibility in toner, and the like.

The content of the colorant may be any amount sufficient to color the toner capable of forming a visible image by development. For example, 2 to 20 parts by weight is preferable based on 100 parts by weight of the binder resin. If the content is less than 2 parts by weight, the coloring effect is insufficient. If the content is more than 20 parts by weight, the electric resistance of the toner is lowered, so that a sufficient amount of triboelectric charge cannot be obtained, which is undesirable.

The charge control agent used in the present invention may use both an antistatic charge control agent and a positive charge control agent, and the antistatic charge control agent may be an organic metal such as chromium-containing azo dyes or a monoazo metal complex. Complex or chelate compounds; Metal containing salicylic acid compounds such as chromium, iron and zinc; And organometallic complexes of aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids may be used, and any known ones are not particularly limited. The antistatic charge control agent also includes a quaternary ammonium salt such as a product modified with nigrosine and a fatty acid metal salt thereof, tributylbenzyl ammonium 1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate. It may be used alone or in combination of two or more. Since the charge control agent stably supports the toner on the developing roller by the electrostatic force, the use of the charge control agent as described above enables stable and fast charging speed.

The content of the charge control agent included in the toner composition is generally within the range of 0.1 parts by weight to 10 parts by weight with respect to 100 parts by weight of the toner base particles.

On the other hand, the toner particles according to the present invention may further include a release agent, higher fatty acids or metal salts thereof. As the release agent, polyalkylene waxes such as low molecular weight polypropylene and low molecular polyethylene, ester wax, carnauba wax, paraffin wax, higher fatty acids, fatty acid amides, and the like can be used, and the higher fatty acids and the metal salts thereof are photosensitive members. It can be suitably used to obtain high quality images by protecting and preventing deterioration of developing characteristics.

The colorant may use a pre-flushing process or a master batch melt-kneaded with the resin at a high concentration so as to be uniformly dispersed in the resin. For example, it can be mixed by kneading means, such as a 2-roll, 3-roll, a pressurized kneader, or a twin screw extruder, using a binder resin and a coloring agent as an essential component. At this time, the colorant is uniformly dispersed and melt kneaded at a temperature of 80 to 180 ° C. for 10 minutes to 2 hours. Then, the fine powder is pulverized using, for example, a mill such as a jet mill, a friction mill, or a rotary mill, and powders are prepared by preparing toner particles having an average particle size of 3 to 15 µm and attaching an external additive. It improves fluidity and charging stability.

The developer according to the present invention may be prepared by a melt kneading pulverization method as well as a polymerization method. In order to attach the external additives to the toner particles, the toner particles and the external additives may be blended in a predetermined ratio, such as a Henschel mixer or the like. It is loaded in an agitator and stirred to attach the external additive to the surface of the toner particles in a state where it is applied, or both particles are loaded and agitated by a surface reformer such as a `` nara hybridizer '' and at least a portion of the external additive particles on the surface of the toner particles. You may bury a part and fix.

The developer according to the present invention can be equally applied to a toner of a contact nonmagnetic one-component developing method in addition to the electrophotographic apparatus using the noncontact nonmagnetic one-component toner as described above. It can also be applied to both ancillary or antistatic toner.

The present invention also provides a toner particle comprising a binder resin, a colorant, and a charge control agent; And

An electrophotographic developer comprising an external additive added to a surface of the toner particles, wherein the external additive comprises 0.1 to 3.0 parts by weight of large particle size silica having a primary average particle diameter of 20 to 200 nm; 0.1 to 3.0 parts by weight of small particle silica having a primary average particle diameter of 5 to 20 nm; 0.1 to 2.0 parts by weight of hydrophobic titanium oxide having a primary average particle diameter of less than 500 nm; And an electrophotographic image forming apparatus including a polyaniline.

Although an Example is given to the following and this invention is demonstrated to it in more detail, this invention is not limited to these.

Example

The content unit of the material used below is used as "part by weight", which is based on 100 parts by weight of the toner base particles.

Preparation of Toner Particles

90.5 parts by weight of polyester with a weight average molecular weight of 100,000, 5 parts by weight of carbon black (manufactured by Mitsubishi Chemical Corporation), 2.5 parts by weight of incidental charge control agent (manufactured by Hodogaya, Fe complex), low molecular weight polypropylene wax (manufactured by Sanyo Chemical Industry Co., Ltd.) 2 The parts by weight were premixed using a Henschel type mixer. Next, the mixture was introduced into a twin screw extruder, and the melt mixture was extruded and cooled to solidify at 130 ° C., followed by obtaining a toner particle (untreated toner) having an average particle diameter of about 8 μm using a grinding classifier.

Example 1

The toner of Example 1 of the present invention was prepared by subjecting the following external additives to the non-added toner particles prepared by the grinding method.

             1.0 parts by weight of auxiliary silica (primary particle size 30-50 nm)

             1.0 parts by weight of secondary silica (primary particle size 7-16 nm)

             0.5 parts by weight of hydrophobic titanium oxide (primary particle size 10-50 nm)

             0.5 parts by weight of polyaniline (primary particle size 300 to 700 nm: spherical shape)

Example 2

The toner of Example 2 of the present invention was prepared by subjecting the following external additives to the non-added toner particles prepared by the grinding method.

               1.0 parts by weight of auxiliary silica (primary particle size 30-50 nm)

               1.0 parts by weight of secondary silica (primary particle size 7-16 nm)

               0.5 parts by weight of hydrophobic titanium oxide (primary particle size 10-50 nm)

               0.5 parts by weight of polyaniline (primary particle size 300 to 700 nm: rod type)

Comparative Example 1

Toner of Comparative Example 1 of the present invention was prepared by externally treating the following external additive to the non-added toner particles prepared by the grinding method.

               1.0 parts by weight of auxiliary silica (primary particle size 30-50 nm)

               1.0 parts by weight of secondary silica (primary particle size 7-16 nm)

               0.5 parts by weight of hydrophobic titanium oxide (primary particle size 10-50 nm)

Melanin beads (primary particle size 300-500 nm) 0.5 part by weight

Comparative Example 2

The toner of Comparative Example 2 of the present invention was prepared by subjecting the non-added toner particles to the following external additives.

               1.0 parts by weight of auxiliary silica (primary particle size 30-50 nm)

               1.0 parts by weight of secondary silica (primary particle size 7-16 nm)

               0.5 parts by weight of hydrophobic titanium oxide (primary particle size 10-50 nm)

<Image Evaluation Test (Unchargeable Toner Standard)>

Surface potential (Vo):-700 V

Latent potential (VL):-100 V

Developer roller applied voltage: Vp-p = 1.8 KV, frequency = 2.0 kHz,

                        Vdc =-500 V, efficiency ratio = 35% (square wave)

Development gap: 150 to 400 μm

Develop roller:

   (1) in the case of aluminum

      Roughness: Rz = 1 ~ 2.5 (after nickel plating)

   (2) For rubber rollers (NBR-based elastic rubber rollers)

Resistance: 1 X 10 ⁵ ~ 5 x 10 ⁶ Ω

      Hardness: 50

      Toner: Charge Amount (q / m) = -5 to -30 μC / g

                   (On the developing roller after passing the layer regulator)

            Toner amount per area = 0.3 to 1.0 mg / cm 2

<Image evaluation result (based on negatively charged toner)>

High temperature and humidity (H / H: 35 ° C, 85 Rh%), room temperature (N / N: 25 ° C, 60 Rh%) using a 20 ppm LBP printer for the toners of Examples 1 and 2 and Comparative Examples 1 and 2 And low temperature and low humidity (L / L: 10 ° C, 20 Rh%) images were evaluated. Image density, Blur characteristics, and contamination of the charging roller were measured for this image to evaluate the performance of each toner. At this time, the image density was measured the density of the solid pattern on the paper, and the Blur characteristics and the contamination of the charging roller were visually evaluated.

<Image density: L / L environment>      The number of items Early 1k 3k 5k Example 1 ○ ○ ○ ○ Example 2 ○ ○ ○ ○ Comparative Example 1 ○ ○ △ △ Comparative Example 2 ○ △ △ ×

<Image density: N / N environment>       The number of items Early 1k 3k 5k Example 1 ○ ○ ○ ○ Example 2 ○ ○ ○ ○ Comparative Example 1 ○ ○ ○ △ Comparative Example 2 ○ ○ ○ △

<Image density: H / H environment>       The number of items Early 1k 3k 5k Example 1 ○ ○ ○ ○ Example 2 ○ ○ ○ ○ Comparative Example 1 ○ ○ ○ ○ Comparative Example 2 ○ ○ ○ △

<Blur Characteristics: L / L Environment>      The number of items Early 1k 3k 5k Example 1 ○ ○ ○ ○ Example 2 ○ ○ ○ △ Comparative Example 1 ○ △ △ × Comparative Example 2 ○ △ × ×

<Blur Characteristics: N / N Environment>       The number of items Early 1k 3k 5k Example 1 ○ ○ ○ ○ Example 2 ○ ○ ○ ○ Comparative Example 1 ○ ○ △ △ Comparative Example 2 ○ △ × ×

<Blur Characteristics: H / H Environment>       The number of items Early 1k 3k 5k Example 1 ○ ○ ○ ○ Example 2 ○ ○ ○ ○ Comparative Example 1 ○ ○ ○ △ Comparative Example 2 ○ ○ △ ×

<Pollution degree of charging roller: L / L environment>      The number of items Early 1k 3k 5k Example 1 ○ ○ ○ ○ Example 2 ○ ○ ○ △ Comparative Example 1 ○ ○ △ × Comparative Example 2 ○ △ △ ×

<Pollution degree of charging roller: N / N environment>       The number of items Early 1k 3k 5k Example 1 ○ ○ ○ ○ Example 2 ○ ○ ○ ○ Comparative Example 1 ○ ○ △ △ Comparative Example 2 ○ ○ △ ×

<Pollution degree of charging roller: H / H environment>       The number of items Early 1k 3k 5k Example 1 ○ ○ ○ ○ Example 2 ○ ○ ○ ○ Comparative Example 1 ○ ○ ○ △ Comparative Example 2 ○ ○ △ △

Evaluation standard

In the above Tables 1a to 1c, the evaluation index image concentration was evaluated as " (circle) " when more than 1.3, " Δ " for 1.1 to 1.3, and " X "

In the above Tables 2A to 2C, the Blur characteristic on the evaluation index initialization was evaluated as "○" when the occurrence of the problem was not recognized by visual inspection, and as "X" in case of severe occurrence.

In Tables 3a to 3c, the contamination of the charging roller was also evaluated as ○, △, × depending on the severity of the occurrence of the problem.

As can be seen from the above experimental results, in Examples 1 and 2 including polyaniline as an external additive, all of the image density, the Blur characteristics, and the contamination of the charging roller showed an effect. In the case of Comparative Example 1 and Comparative Example 2, which does not contain polyaniline, Blur was serious as well as the contamination problem of the charging roller as the number of sheets increased. Rather, image concentration, Blur characteristics, and charge roller contamination were more problematic under low temperature and low humidity conditions.

 The electrophotographic developer according to the present invention improves image density and Blur problems in the initial and long life by using polyaniline as an external additive in toner production, and can reduce the contamination of the charging roller. In addition, such an electrophotographic developer may be usefully used in various electrophotographic image forming apparatuses.

Claims (5)

Toner particles comprising a binder resin, a colorant, and a charge control agent; And In the electrophotographic developer comprising an external additive added to the surface of the toner particles, the external additive 0.1 to 3.0 parts by weight of large particle silica having a primary average particle diameter of 20 to 200 nm; 0.1 to 3.0 parts by weight of small particle silica having a primary average particle diameter of 5 to 20 nm; 0.1 to 2.0 parts by weight of hydrophobic titanium oxide having a primary average particle diameter of less than 500 nm; And An electrophotographic developer comprising polyaniline. The electrophotographic developer according to claim 1, wherein the polyaniline has a primary average particle diameter of 0.1 to 3 µm and a content of 0.1 to 3.0 parts by weight. The electrophotographic developer according to claim 1, wherein the polyaniline has a specific resistance of 1 × 10 ³ Ω to 1 × 10 ⁵ Ω. The electrophotographic developer according to claim 1, wherein the polyaniline has a spherical or rod-like particle shape. An electrophotographic image forming apparatus comprising the electrophotographic developer according to any one of claims 1 to 4.

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