KR20050054780A - Toner for electrophotographic imaging apparatus having improved charging properties - Google Patents

Abstract

The present invention relates to a toner for an electrophotographic image forming apparatus having improved charging characteristics. Specifically, the present invention relates to maintaining a stable amount of toner charging and charging distribution, improving cleaning performance of a charging apparatus, preventing contamination of a charging apparatus, and improving dispersibility and incident chargeability. The present invention relates to a toner for an electrophotographic image forming apparatus capable of achieving effects such as black streaking improvement and developing defect reduction.

Description

Toner for electrophotographic imaging apparatus having improved charging properties

The present invention relates to a toner for an electrophotographic image forming apparatus, and more particularly, to maintain a stable amount of toner charge and charge distribution, to improve the cleaning property of the charging device, to prevent contamination of the charging device, to improve the dispersibility and incident charge, and to black streaks. A toner for an electrophotographic image forming apparatus having characteristics such as improvement and development defect reduction.

Fig. 1 schematically shows an example of a conventional non-contact developing electrophotographic image forming apparatus, and the operation thereof is as described below. That is, after the photosensitive member 1 is charged by the charging device 6, an electrostatic latent image is formed on the photosensitive member by image exposure through a laser scanning unit (LSU) 9. The toner 4 is supplied to the developing roller 2 by the toner supply roller 3. The toner supplied to the developing roller 2 is thinned to a uniform thickness by the toner layer regulating device 5, and charged with high friction. The toner that has passed through the toner layer restricting device 5 is developed by electrostatic force on the electrostatic latent image formed on the photoconductor 1, and the developed toner is transferred to the paper by a transfer roller (not shown), and then fixed by a fuser (not shown). Settles down. The residual toner 8 after transfer on the photoconductor is also cleaned by the cleaning blade 7.

In the image forming method in which charging → exposure → development → transfer → cleaning → charging (repeating afterward) as described above, the image formation is performed using the toner layer regulating device (M / A) of the toner conveyed to the developing area (mg / cm). ² : Toner weight per unit weight measured on the developing roller after passing through the toner layer regulating device, and Q / M (μc / g: toner charging per unit weight measured on the developing roller after passing through the toner layer controlling device) Amount), and is made by an electric field acting between the developing roller and the photosensitive member. The developing process of the process is divided into a contact type and a non-contact type, wherein the contact type refers to a method in which the developer is transferred to the latent image by contacting the surface of the developing roller and the photoconductor. The developer refers to a method in which the latent image is transferred and developed by an electric force generated according to a potential difference between the voltage applied to the developing roller and the latent potential of the photosensitive member. Among these developing methods, the contact type has a problem of wear of the photosensitive member and the developing roller, while the non-contact type has the advantage of excellent resolution because the durability of the device is excellent and developed by electric force.

In general, in the electrophotographic image processing apparatus as described above, the developer means a state in which a carrier is mixed with the toner, and when the carrier is not used, the toner itself may be referred to as a developer. A nonmagnetic developer is a developer that moves by the fluidity of the developer particle itself without using a magnetic force. A magnetic developer is a phenomenon in which a magnetic material is moved by mixing magnetic materials such as ferrite in the developer. The non-magnetic developer does not use a magnetic material, so it is inexpensive and has advantages in color printing.

Recently, low temperature fixing properties of toner are required for lowering energy and reducing printing waiting time. For this purpose, binder resins, release agents, and charge control agents having excellent fixing properties in a long range are used. In order to improve transfer efficiency and prevent fogging of non-image parts, toner particles are spheroidized and silica, TiO _2, etc., to improve the fluidity and charging characteristics of toner particles. However, depending on the type, the charge control agent may cause problems such as low triboelectric chargeability, poor dispersion, low storage stability, and the release agent added as an offset inhibitor makes it difficult to disperse as the amount of the additive is increased and adheres to the photosensitive member. As a result, the toner adhesion of the external additive is lowered, which causes problems such as contamination in the photoconductor and the charging device.

Furthermore, in the case of conventionally used toners, overcharge occurs in a low temperature and low humidity environment, and a problem such as fog, toner scattering, etc., in which a non-image part is contaminated due to a decrease in charge amount in a high temperature and high humidity environment, etc. Variation in toner charging characteristics with respect to environmental changes is very large. In addition, although it has a uniform charge amount and charge distribution at the beginning of printing, the charge amount decreases greatly when it is left, and the image density decreases due to a decrease in charge amount and uneven charge amount distribution during image printing over a long period of time. Fog and toner scattering occur.

In order to solve the above problems and to provide uniform chargeability to the toner, a method of forming a thin toner layer on the developing roller is also possible, but if the toner layer is made too thin, The rapid rise in developing efficiency drastically lowers the image density, and the decrease in image density tends to occur. When the toner charging amount is adjusted downward to improve the reduction in developing efficiency, fog increases and contamination by toner scattering occurs. Done. In addition, toner charge may be controlled by adding an external additive such as silica or TiO ₂ to maintain the charge stability and uniform charge distribution of the toner during long term operation. There is a limit to gender improvement.

The technical problem to be achieved by the present invention is to maintain the stable toner charge amount and charge distribution, to improve the cleaning property of the charging device, to prevent contamination of the charging device, to improve the dispersibility and incidentality, to improve the black streak, to reduce the development defect It is to provide a toner for an electrophotographic image forming apparatus capable of obtaining.

Another object of the present invention is to provide an electrophotographic image forming apparatus employing the toner.

In order to achieve the above technical problem, the present invention,

A toner for an electrophotographic image forming apparatus comprising a binder resin, a colorant, a mold releasing agent, and a charge control agent, the toner for an electrophotographic image forming apparatus comprising as an additive a negatively charged titanium dioxide (TiO ₂ ) particle. to provide.

In order to achieve the above another technical problem, the present invention,

An electrophotographic image forming apparatus employing the toner is provided.

The toner according to the present invention can provide stable charge quantity distribution, excellent fluidity and cleaning property, thereby achieving black streaking improvement, developing efficiency improvement, and preventing external additive contamination in the charging device, resulting in high quality images. Makes it possible to form

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

The present invention relates to a toner used in an electrophotographic image forming apparatus such as a laser printer, a facsimile machine, a copier, etc., comprising a binder resin, a colorant, a mold releasing agent, and a charge control agent, wherein the negatively charged titanium dioxide (TiO ₂ ) particles are used as an additive. It provides a toner for an electrophotographic image forming apparatus comprising a.

Preferably, the particle diameter of the titanium dioxide particles is 10 nm to 300 nm. If the particle diameter of the titanium dioxide particles is less than 10 nm, there is a problem such as poor dispersion, if the particle size exceeds 300 nm, there is a problem such as drum contamination.

In addition, the BET surface area of the titanium dioxide particles is 30 m ² / g to 70 m ² / g, the pH is 3 to 6, the apparent density is preferably 100 to 300 g / L.

The reason for limiting the BET surface area to the above range is because of problems such as dispersion, the reason why the pH should be within the above range is due to the chargeability, and the reason why the above range is preferable as the apparent density is due to the mixing property as the internal additive.

The content of the titanium dioxide particles is preferably included 0.1 to 3.0 parts by weight based on 100 parts by weight of the toner. When the content is less than 0.1 part by weight, there is a problem such as poor dispersion, and when the content exceeds 3.0 parts by weight, there is a problem such as drum contamination.

Titanium dioxide particles may serve as a release agent to make the mixing state of the internal additives more smoothly to achieve a uniform mixing. However, unlike conventional waxes, titanium dioxide particles do not melt, and have an advantage of achieving uniform mixing between raw materials as a sieving pigment.

Binder resins that can be used in the toner for an electrophotographic image forming apparatus according to the present invention include, but are not limited to, polystyrene-co-butadiene, polystyrene-co-acrylonitrile, modified acrylic polymer, polyvinyl acetate, styrene -Alkyd resins, soya-alkyl resins, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polycarbonates, polyacrylic acid, polyacrylates, polymethacrylates, styrene polymers, polyvinyl buty Ral, alkyd resins, polyamides, polyurethanes, polyesters, polysulfones, polyethers, polyketones, phenoxy resins, epoxy resins, silicone resins, polysiloxanes, poly (hydroxyethers ) Resins, polyhydroxystyrene resins, novolac, poly (phenylglycidyl ether) -co-dicyclopentadiene, mentioned above And the copolymer, and combinations of the monomers used in the reamer, particularly polyester resin is suitable for a color developer is excellent in fixing performance and transparency.

In addition, the toner according to the present invention may further include a colorant, and as such a colorant, carbon black or aniline black may be used in the case of black and white toner, and in the case of color toner, black is used in the colorant of carbon black. The color further comprises 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, a condensed nitrogen compound, anthrakin, quinacridone compound, a base dye late compound, a naphthol compound, a benzo imidazole compound, a thioindigo compound, or a perylene compound is 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.

Release agents for enhancing release properties may also be known release agents, polyalkylene waxes such as low molecular weight polypropylene, low molecular polyethylene, ester wax, carnauba wax, paraffin wax, higher fatty acids, fatty acid amide, etc. In addition, higher fatty acids and metal salts thereof may be appropriately added in order to protect the photoconductor, prevent deterioration of development characteristics, and obtain a high quality image. Specifically, fluorinated polymer, siloxane polymer, fluorosilicone polymer, polysilane, polyethylene, polypropylene, polyacrylate, poly (methyl methacrylate-co-methacrylic acid), urethane resins, urethane-epoxy water Feeders, acrylate-urethane resins, urethane-acrylic resins, or combinations thereof may be used.

Examples of the negatively charged charge control agent include organometallic complexes or chelate compounds such as chromium-containing azo dyes or monoazo metal complexes; 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. In addition, the antistatic charge control agent includes a product modified with nigrosine and fatty acid metal salts thereof, quaternary ammonium salts such as tributylbenzyl ammonium 1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate. It may be used alone or in combination of two or more.

In addition, the toner according to the present invention may further include other particles in addition to the binder resin, colorant, mold release agent, and charge control agent as an external additive, and include, for example, silicas, silicon carbides, aluminas, and other polymer beads. It may include.

Among these, especially when silica is included as an external additive, effects such as fluidity, transferability and durability improvement can be obtained. One or more kinds of the silica may be added, and preferably two kinds of silica having different particle diameters may be added. In this case, one of the two kinds of silica added may be referred to as the first silica, the other one having a small particle diameter, the second silica. The first silica has a relatively large primary particle size in the range of 30 to 200 nm, and the second silica has a small primary particle size in the range of 5 to 20 nm. As such, the primary role of the first silica in the use of silica particles having different particle diameters is spacer particles, which prevents toner deterioration due to durability and improves transferability, and the second silica mainly provides fluidity to the toner. Play a role.

The toner 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 are blended in a predetermined ratio, and stirred in a Henschel mixer or the like. It is loaded into the apparatus and stirred to attach the external additive on the surface of the toner particles, or both particles are loaded and stirred 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 it and fix it.

The present invention also provides an electrophotographic image forming apparatus employing the toner. The electrophotographic image forming apparatus in which the toner according to the present invention may be employed includes a conventional electrophotographic image forming apparatus such as a laser printer, a facsimile, a copier, and the like, and specifically, a laser beam or an LED print head type printer, a facsimile, Examples thereof include copiers and multifunction machines.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

Example 1

Preparation of the toner according to the present invention

89 weight% of polyester resin with weight average molecular weight 100,000, average primary particle diameter of 50 nm, average BET surface area of 50 m ² / g, pH 5, 1.0 weight% of titanium dioxide with an apparent density of 150 g / L, carbon black as a coloring agent ( 5% by weight of Mitsubishi Chemical Co., Ltd., 2% by weight of a charge control agent (manufactured by S34 Orient Chemical Co., Ltd.), and 3% by weight of low molecular weight polypropylene wax (manufactured by Sanyo Chemical Industry Co., Ltd.) were premixed using a Henschel type mixer. Next, the mixture was introduced into a twin screw extruder to extrude the melt mixture at 130 ° C. and cooled to solidify, and then to obtain untreated toner particles having an average particle diameter of about 8 μm using a pulverizer, and then as an external additive. 1.0 wt% of the first silica having a primary particle size of 30 to 50 nm (-300 to -600 μC / g) and 1.0 wt% of the second silica having a primary particle size of 7 to 16 nm (-400 to -800 μC / g). Was added to prepare a toner according to the present invention.

Comparative Example 1

Toner was prepared in the same manner as in Example 1 except that no titanium dioxide was added.

<Image evaluation test>

The images were evaluated using a 20 ppm LBP printer for the toners of the Examples and Comparative Examples. Toner performance was evaluated by measuring image density, black streak, dot reproducibility (degree of partial image density difference), and charging device contamination. At this time, the image density was measured by using a densitometer (SpectroEye, GretagMacbeth Co., Ltd.) of the density of the solid pattern on the paper, and black streaks, dot reproducibility and charging device contamination was visually evaluated. The implementation conditions of the developing apparatus were as follows.

Surface potential (V _o ):-700 V

Latent potential (V _L ):-100 V

Developer roller applied voltage: V _pp = 1.8 KV, frequency = 2.0 kHz,

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

Developing gap: 150 ~ 400 developing 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 (hardness measured with Type E durometer according to JIS K6253)

Toner: Charge amount (q / m) = -5 to -30 μC / g (on developing roller after passing through the layer regulator)

Toner amount per area = 0.3 to 1.0 mg / ㎠

Image evaluation results according to the increase in the number of prints for the toner according to the present invention and the toner according to the comparative example are shown in Tables 1 and 2, respectively.

The number of prints 0 1,000 2,000 3,000 4,000 5,000 Burn density ○ ○ ○ ○ ○ ○ Black streak ○ ○ ○ ○ ○ ○ Dot reproducibility ○ ○ ○ ○ △ △ Charging device contamination ○ ○ ○ ○ ○ ○

The number of prints 0 1,000 2,000 3,000 4,000 5,000 Burn density ○ ○ ○ ○ ○ ○ Black streak ○ ○ ○ △ △ X Dot reproducibility ○ ○ ○ ○ △ X Charging device contamination ○ ○ ○ △ X X

Image concentration evaluation

Image density was evaluated as follows.

○: 1.3 or more

△: 1.1 to 1.3

X: less than 1.1

Evaluation of Black Streaks, Dot Reproducibility, and Charge Device Contamination

Black streaks, dot reproducibility, and contamination of the charging device were determined as follows by visual observation.

○: When the problem is not recognized by visual inspection

(Triangle | delta): When a trouble occurrence is recognized by visual observation, but it is not severe

X: When serious problem is recognized by visual judgment

According to the present invention, stable toner charge amount and charge distribution can be maintained, improving the cleaning property of the charging device, preventing contamination of the charging device, improving dispersibility and incidentality, improving black streaks, reducing developing defects, and the like. A toner for an electrophotographic image forming apparatus can be provided.

1 illustrates an example of a conventional non-contact developing electrophotographic image forming apparatus.

<Description of Drawing>

1: photosensitive member

2: developing roller

3: toner feed roller

4: toner

5: toner layer regulating device

6: charging device

7: cleaning blade

8: residual toner

9: Laser Scanning Unit (LSU)

Claims (5)

A toner for an electrophotographic image forming apparatus comprising a binder resin, a colorant, a releasing agent, and a charge control agent, the toner for an electrophotographic image forming apparatus comprising as an additive a negatively charged titanium dioxide (TiO ₂ ) particle. The toner for electrophotographic imaging apparatus according to claim 1, wherein a particle diameter of the titanium dioxide particles is 10 nm to 300 nm. The toner for electrophotographic imaging apparatus according to claim 1, wherein the BET surface area of the titanium dioxide particles is 30 m ² / g to 70 m ² / g, and the apparent density is 100 to 300 g / L. The toner for electrophotographic imaging apparatus according to claim 1, wherein the content of the titanium dioxide particles is 0.1 to 3.0 parts by weight based on 100 parts by weight of the toner. The toner for electrophotographic image forming apparatus according to claim 1, wherein the titanium dioxide particles have a pH of 3 to 6.