KR100571924B1 - Non-magnetic one component toner for non-contact electrophotographic imaging apparatus - Google Patents

Abstract

The present invention relates to a nonmagnetic one-component toner for a noncontact electrophotographic image forming apparatus, and more particularly, to a noncontact electrophotographic image forming apparatus including colored particles and an external additive including a binder resin, a colorant, a mold release agent and a charge control agent. In the nonmagnetic one-component toner, the external additive includes hydrophobic silica fine particles having the same polarity as the colored particles, hydrophobic silica fine particles having the reverse polarity with the colored particles, and resin fine particles having the reverse polarity with the colored particles. A nonmagnetic one-component toner for a non-contact electrophotographic image forming apparatus. According to the present invention, even if the number of prints as well as the initial printing is increased, a uniform image density can be obtained, and in particular, defective images such as fog can be prevented.

Nonmagnetic one-component toner, silica fine particles, resin fine particles

Description

Non-magnetic one component toner for non-contact electrophotographic imaging apparatus

1 is a view schematically showing 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)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonmagnetic one-component toner for a noncontact electrophotographic image forming apparatus, and more particularly to a noncontact electrophotographic image capable of obtaining a uniform image density over a long period of time, and in particular, preventing a bad image such as fog. A nonmagnetic one-component toner for a forming apparatus.

FIG. 1 schematically shows an example of a conventional non-contact developing electrophotographic image forming apparatus, the operation manner of which is described below. That is, after the photosensitive member 1 is charged by the charging device 6, a latent image is formed on the photosensitive member by image exposure through a laser scanning unit (LSU) 9. The nonmagnetic toner 4 is supplied to the developing roller 2 by the 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 on an electrostatic latent image formed on the photosensitive member 1, and the developed toner is transferred to the paper by a transfer roller (not shown) and fixed by a fixing unit (not shown). The residual toner 8 after transfer on the photoconductor is also cleaned by the cleaning blade 7.

The developing process is divided into a contact method and a non-contact method. The contact method refers to a method in which toner is developed on the latent image by contact between the developing roller and the surface of the photoconductor, and the contactless method has a distance between the surface of the developing roller and the photoconductor. The toner is spaced apart and refers to a method in which the toner is moved and developed by an electric force generated according to the potential difference between the voltage applied to the developing roller and the latent potential of the photosensitive member. Among these developing methods, the contact method has a problem of abrasion of the photosensitive member and the developing roller, while the non-contact method has excellent durability because the device is excellent in durability and developed by electric force.

Also, in general, a one-component toner refers to a toner which causes charging through friction between toner particles or friction with a sleeve, and a two-component toner generates charging through friction with a carrier by mixing nonmagnetic toner and magnetic carrier particles. Means. While the two-component toner is relatively stable and can obtain a good recording image and is advantageous for high speed development, the deterioration of carriers and the fluctuation of the mixing ratio of the toner and the carrier are liable to occur, and the apparatus is enlarged. Many one-component toners are used for reasons such as saving and high reliability.

In addition, a nonmagnetic toner refers to a toner that is moved by the fluidity of the toner particles themselves without using a magnetic force. A magnetic toner refers to a toner that is moved by using a magnetic force by mixing a magnetic material such as ferrite in the toner. Since it does not use a magnetic material, it is inexpensive and has advantages of color printing.

Non-magnetic, one-component toners for non-contact electrophotographic image forming apparatuses should have no fluidity and electrical properties sensitive to changes in time and environmental conditions (eg, temperature, humidity). The conventional nonmagnetic one-component toner for a non-contact electrophotographic image forming apparatus obtains a predetermined charging characteristic through frictional charging with a toner carrier, a toner layer regulating device, and a toner supply member. However, when the printing process is repeated, the external additives of the toner are stressed and buried in the toner resin or fall off. When the external additive of the toner is buried or dropped into the toner resin, the fluidity of the toner decreases, and the physical adsorption force between the toner carrier, the toner layer regulating device, and the toner increases. As a result, uniform triboelectric charging of the toner is not performed, so that the predetermined triboelectric charge characteristics are deteriorated and an uncharged or reverse polarity toner is generated. Such uncharged toner or reverse polarity toner is developed in a non-image area, resulting in a fog-like image. It will cause contamination.

Therefore, if the amount of the external additive is increased in order to prevent the above problems, the amount of frictional charge of the toner increases and the ordinary power of the toner carrier increases, so that the amount of movement of the toner to the photosensitive member decreases, thus developing efficiency and image density. A problem arises that is lowered. In addition, as the amount of the external additive is increased, the cleaning property of the cleaning blade that removes the residual toner may be deteriorated, whereby the charging roller is contaminated and residual toner or foreign matter always remains on the latent image carrier so that the image may be uneven. There is a problem in that image quality deteriorates, such as vertical white lines / black lines.

Therefore, the technical problem to be achieved by the present invention is to solve the problems of the prior art to obtain a uniform image density over a long period of time, nonmagnetic 1 for non-contact electrophotographic image forming apparatus that can prevent defective images such as fog It is to provide a component toner.

The present invention to achieve the above technical problem,

A nonmagnetic one-component toner for a non-contact electrophotographic image forming apparatus comprising a binder resin, a colorant, a mold release agent, and a charge control agent, and an external additive, wherein the external additive includes hydrophobic silica fine particles having the same polarity as the colored particles, A nonmagnetic one-component toner for a noncontact electrophotographic image forming apparatus comprising the colored particles and hydrophobic silica fine particles of reverse polarity and the colored particles and resin fine particles of reverse polarity.

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

The toner particles according to the present invention include colored particles including a binder resin, a colorant, a mold release agent, and a charge control agent.

Binder resins that may be used in the present invention include, but are not limited to, polystyrene-co-butadiene, polystyrene-co-acrylonitrile, modified acrylic polymers, polyvinyl acetate, styrene-alkyd resins, soya-alkyl water Paper, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polycarbonate, polyacrylic acid, polyacrylate, polymethacrylate, styrene polymer, polyvinyl butyral, alkyd resin, polyamide , Polyurethanes, polyesters, polysulfones, polyethers, polyketones, phenoxy resins, epoxy resins, silicone resins, polysiloxanes, poly (hydroxyether) resins, polyhydroxystyrene Copolymers of the monomers used in the feeders, novolaks, poly (phenylglycidylether) -co-dicyclopentadiene, and the aforementioned polymers , And which is a combination, particularly a polyester-based resin is suitable for a color developer is excellent in fixing performance and transparency.

As the colorant, carbon black or aniline black may be used in the case of black and white toner, and the nonmagnetic toner according to the present invention is easy to produce color toner. In the case of the color toner, black 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 anthrakin 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, naphthol compound, benzo imidazole compound, thioindigo compound, or 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.

The cyan colorant is a copper phthalocyanine compound and derivatives thereof, an anthrakin compound and the like. 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, but is preferably 2 to 20 parts by weight based on 100 parts by weight of the binder resin. If it is less than 2 parts by weight, the coloring effect is insufficient, and if it exceeds 20 parts by weight, the electrical resistance of the toner is lowered, so that a sufficient amount of frictional charge cannot be obtained, resulting in problems such as contamination.

Charge control agents that can be used in the present invention include, but are not limited to, ancillary charge control agents such as organometallic complexes or chelating compounds such as chromium-containing azo dyes or monoazo metal complexes; Metal containing salicylic acid compounds such as chromium, iron, aluminum and zinc; And organometallic complexes of aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids may be used. Examples of positively charged charge control agents include products modified with nigrosine and fatty acid metal salts thereof; Triphenylmethane derivatives; And tributylbenzylammonium 1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, stearyldimethylbenzylammonium paratoluenesulfonate, stearyldimethylbenzylammonium methylsulfate, stearyldimethylphenethylammonium methyl Onium salts including quaternary ammonium salts such as sulfate, distearyldimethylammonium chloride, decyltrimethylammonium hydroxide, and the like can be used alone or in combination of two or more thereof.

Release agents that can be used in the present invention include, but are not limited to, low molecular weight polypropylene, polyalkylene waxes such as low molecular polyethylene, ester waxes, carnauba waxes, paraffin waxes, higher fatty acids, fatty acid amides, and the like. Specific examples thereof include fluorinated polymers, siloxane polymers, fluorosilicone polymers, polysilanes, polyethylene, polypropylene, polyacrylates, poly (methyl methacrylate-co-methacrylic acid), urethane resins, Urethane-epoxy resins, acrylated-urethane resins, urethane-acrylic resins, or a combination thereof can be used as the release agent.

The toner according to the present invention also includes hydrophobic silica fine particles having the same polarity as the colored particles, hydrophobic silica fine particles having the reverse polarity with the colored particles, and external additives containing the resin fine particles having the reverse polarity with the colored particles.

The toner according to the present invention simultaneously contains colored particles and hydrophobic silica particles having the same polarity and reverse polarity, so that the toner is less affected by environmental changes and changes over time, and it is possible to maintain a constant charge amount continuously and stably. It is possible to effectively suppress the generation of the polar toner, thereby obtaining a uniform toner charging amount distribution.

Preferably, the colored particles and the hydrophobic silica fine particles of reverse polarity have an average particle diameter of 30 to 50 nm. If the average particle diameter of the colored particles and the hydrophobic silica fine particles of reverse polarity is less than 30 nm, there is no improvement effect of fog fixed to the non-image portion, and there is a problem that the fixing characteristics are lowered. It is not preferable because there is a problem that the characteristics supplied from the feed roller to the developing roller are lowered.

The content of the hydrophobic silica fine particles of the same polarity and reverse polarity as the colored particles is preferably 0.01 to 2% by weight based on the total weight of the toner. When the content of the silica fine particles having the same polarity is less than the above range, there is a problem of deterioration of the toner fluidity and charging characteristics, and when it exceeds the above range, there are problems such as poor fixation characteristics and image contamination. In addition, when the content of the reverse polarized silica fine particles is less than the above range, there is no effect of improving non-image contamination, and when it exceeds the above range, there is a problem such as deterioration of the toner supply characteristic to the developing roller and deterioration of fixing characteristics. .

The toner according to the present invention contains, as an external additive, in addition to the silica fine particles, fine resin particles of a reverse polarity to the colored particles. In the non-contact developing method using a nonmagnetic one-component toner, the stress of the toner increases as the number of prints increases, so that the smaller average particle diameter of the additive is buried into the toner resin, and the larger particle average diameter is separated from the toner base. Since the resin fine particles used in the present invention have a relatively large particle size among the additives, the resin fine particles are stressed as the number of printed sheets increases, and they are separated from the toner base. Since the separated resin fine particles are more positive in polarity than the hydrophobic silica fine particles in terms of the triboelectric charge sequence, the resin fine particles tend to adhere to the supply rollers applied relatively negatively than the developing roller. Therefore, as the number of prints increases, the amount of resin fine particles remaining undeveloped increases in the developing chamber, which acts as a kind of carrier having reverse polarity with respect to the toner, thereby making it uniform in the triboelectric charge characteristics of the toner. That is, the resin fine particles serve as a carrier having a kind of reverse polarity, thereby suppressing generation of reverse polarity toner or uncharged toner, thereby reducing the fog concentration in the non-image area.

As a result, the toner according to the present invention can obtain excellent image quality at both the beginning and the second half of printing. That is, the colored particles and the hydrophobic silica fine particles of reverse polarity effectively serve to triboelectrically charge the toner particles at the beginning of printing, for example, about 6,000 sheets or less. For example, the toner particles are effectively triboelectrically charged at about 6,000 print sheets or more. Therefore, according to the toner according to the present invention, by the complementary action of the colored particles and the reverse polarity hydrophobic silica fine particles and the colored particles and the reverse polarity resin particles, it is possible to obtain excellent image quality evenly in both the beginning and the second half of the printing.

The resin fine particles have an average particle diameter of 0.1 to 15 mu m, and the content thereof is preferably 0.01 to 2 wt% based on the total weight of the toner. If the average particle diameter of the resin fine particles is less than 0.1 μm, the cleaning property is poor. If the average particle size of the resin fine particles is more than 15 μm, the frictional chargeability is weakened, so that the supplyability of the toner is lowered and the fog concentration is high. .

On the other hand, the content of the resin fine particles is preferably 0.01 to 2% by weight based on the total weight of the toner, if the content is less than 0.01% by weight, the addition effect is insignificant, and when the content of the resin fine particles exceeds 2.0% by weight, there is a concern that the supply of toner may be reduced. It is not desirable because there is.

The resin fine particles may be styrene-based, fluorine-based, or acrylic polymers, but are not limited thereto. Examples of the styrene-based polymers include polystyrene, poly-P-chlorostyrene, and poly-α-methylstyrene. Examples of the polymer include polytetrafluoroethylene, polytrifluorochloroethylene, and polyvinylidene fluoride. Examples of the acrylic polymer include polymethyl (meth) acrylate, polyethyl (meth) acrylate, and polybutyl. (Meth) acrylate etc. are mentioned.

In addition, it is preferable that the charged fine particles of the resin fine particles have a positive value than that of the binder resin, and the fine resin particles serve as a carrier for making the toner itself negatively charged by friction with the binder resin. That is, when using polyester as a binder resin, the resin fine particle which has a more positive charge sequence should be used, for example, polystyrene can be used.

In addition, the glass transition temperature of the polymer used as the resin fine particles is preferably 50 ~ 70 ℃, when the glass transition temperature is less than 50 ℃ of the cake phenomenon or blocking phenomenon that the toner is hardened at high temperature There is a concern, and when it exceeds 70 ° C, there is a problem that the fixability is lowered, which is not preferable.

On the other hand, the weight average molecular weight of the polymer used as the resin fine particles is not particularly limited, but is preferably 10,000 to 100,000. When the weight average molecular weight is less than 10,000, there is a risk of causing a phase change when left for a long time. It is not preferable because it may adversely affect the fixability.

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 agitated to attach the external additive to 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 part of the external additive particles to the surface of the toner particles. You may bury it and fix it.

Hereinafter, a preferred embodiment of the present invention will be described in more detail, but the present invention is not limited thereto.

Example. Preparation of Toner According to the Present Invention (Unchargeable Toner Standard)

A toner having the following composition was prepared.

90 wt% polyester

5% by weight carbon black

Secondary antistatic agent (Hodogaya, T-77, Fe complex) 2.5% by weight

2% by weight of low molecular weight polypropylene wax

The composition was premixed uniformly using a Henschel type mixer, then fed into a twin screw extruder to extrude the melt mixture at 130 ° C., cooled and solidified. Thereafter, untreated toner particles having an average particle diameter of about 8 μm were obtained using a pulverizer, and then the external additives were subjected to external treatment to prepare toners according to the present invention.

1.0 weight% of silica fine particle (primary particle diameter 7-16 nm, Nippon Aerosil) with respect to colored particle

0.3 wt% of the reverse polarized silica fine particles (primary particle size: 30-50 nm, Waker)

0.3 weight% of resin fine particle (primary particle size 0.1-15 micrometers, polystyrene type) of reverse polarity with respect to a colored particle

Comparative Example 1. Preparation of Toner According to the Prior Art (Uncharged Toner Standard)

A toner according to the prior art was prepared under the same composition and conditions as in Example 1, except that only silica fine particles having the same polarity were added to the colored particles as the external additive.

1.0 weight% of silica fine particle (primary particle diameter 7-16 nm, Nippon Aerosil) with respect to colored particle

0.3 weight% of silica fine particle (primary particle diameter 30-50 nm, Nippon Aerosil) with respect to colored particle

Comparative Example 2. Preparation of Toner According to the Prior Art (Uncharged Toner Standard)

A toner according to the prior art was prepared under the same composition and conditions as in Example 1, except that only the silica particles having the same polarity and the silica particles having the reverse polarity were added to the colored particles as the external additives as follows.

1.0 weight% of silica fine particle (primary particle diameter 7-16 nm, Nippon Aerosil) with respect to colored particle

0.3 wt% of the reverse polarized silica fine particles (primary particle size: 30-50 nm, Waker)

Comparative Example 3. Preparation of Toner According to the Prior Art (Uncharged Toner Standard)

A toner according to the prior art was prepared under the same composition and conditions as in Example 1, except that only the silica particles having the same polarity and the resin particles having the reverse polarity were added to the colored particles as an external additive as described below.

1.0 weight% of silica fine particle (primary particle diameter 7-16 nm, Nippon Aerosil) with respect to colored particle

0.3 weight% of resin fine particle (primary particle size 0.1-15 micrometers, polystyrene type) of reverse polarity with respect to a colored particle

Experimental Example Image evaluation experiment

Image evaluation experiments were performed on the toners prepared in Examples and Comparative Examples 1 to 3 under the following conditions and methods.

<Image evaluation condition>

Image evaluation was performed on a 20 ppm laser printer of a nonmagnetic one-component developing method, and the developing conditions were as follows.

Latent image carrier surface potential: -600 V

Latent Image Carrier Solid Exposure Potential: -100 V

Developing voltage: V _pp = 1.8 kV, frequency = 2 kHz, V _avg = -30 V, duty ratio = 35% (square wave)

Development gap (GAP): 300 μm

<Image evaluation method>

The toners of Examples and Comparative Examples 1 to 3 were subjected to 8,000 print tests in a 5% character pattern at room temperature and humidity under the image evaluation experiment conditions described above, and the image density of solids and fog ( fog) concentration was measured and compared.

The image density of the solid was measured using a SpectroEye densitometer manufactured by Gretag Macbeth, and the fog density was measured by tapping the fog of the latent image carrier when printing on white paper with 3M acetate adhesive tape. It was measured using a Spectroeye densitometer from Gretack Macbed.

Table 1 and Table 2 below show the solid image density and fog concentration for the toners of Examples and Comparative Examples 1 to 3 according to the number of prints.

Solid image density The number of prints 0 2,000 4,000 6,000 8,000 Example O O O O O Comparative Example 1 O O O O O Comparative Example 2 O O O O O Comparative Example 3 O O O O O

Burn Density: Less than 1.2 (not practical) = X

          1.2 ~ 1.3 (Available Level) = △

          1.3 or higher (good level) = O

Fog concentration The number of prints 0 2,000 4,000 6,000 8,000 Example △ O O O O Comparative Example 1 X X X X X Comparative Example 2 △ O O △ X Comparative Example 3 X △ △ O O

Fog Concentration: 0.13 or more (Unusable Level) = X

                 0.11 ~ 0.13 (Available Level) = △

                 0.11 or less (good level) = O

As can be seen from the results of Table 1 and Table 2, in the case of the toner according to Comparative Example 1, the image density was good up to 8,000 sheets, but the fog density was not practical from the beginning. In the case of the toner according to Comparative Example 1, the image density was good up to 8,000 sheets, but the fog density began to deteriorate after 4,000 sheets. In the case of the toner according to Comparative Example 3, the image density was good up to 8,000 sheets, Unlike Examples 1 and 2, the initial fog concentration was not good at an impractical level, and after 6,000 sheets, the image density was somewhat good.

However, in the case of the toner according to the present invention, both the image density and the fog density showed good levels from the beginning of printing. From this, in the toner according to the present invention, the colored particles and the reverse polarity hydrophobic silica fine particles and the reversed polarity of the colored particles and the reverse polarized particles are complementary at time intervals, so that consistently good quality is maintained throughout the initial printing and the late printing. It can be seen that an image can be obtained.

As described above, when the non-magnetic one-component toner for a non-contact electrophotographic image forming apparatus according to the present invention is used, a uniform image density can be obtained not only at the beginning of printing but also when the number of prints increases, in particular, a bad image such as fog. Can be prevented.

Claims (8)

A nonmagnetic one-component toner for a non-contact electrophotographic image forming apparatus comprising colored particles and an external additive including a binder resin, a colorant, a mold release agent and a charge control agent, The external additive is hydrophobic silica fine particles of the same polarity with respect to the colored particles, hydrophobic silica fine particles with a reverse polarity with respect to the colored particles, and styrene or fluorine resin fine particles with a reverse polarity with respect to the colored particles, with an average particle diameter of 0.1 to 15. A nonmagnetic one-component toner for a non-contact electrophotographic image forming apparatus, characterized in that it contains fine resin particles. The nonmagnetic one-component toner for a non-contact electrophotographic image forming apparatus according to claim 1, wherein the content of hydrophobic silica fine particles having the same polarity with respect to the colored particles is 0.01 to 2% by weight based on the total weight of the toner. The non-contact electrophotographic image according to claim 1, wherein the hydrophobic silica fine particles of reverse polarity with respect to the colored particles have an average particle diameter of 30 to 50 nm and a content of 0.01 to 2% by weight based on the total weight of the toner. Nonmagnetic one-component toner for forming apparatus. The nonmagnetic one-component toner for a non-contact electrophotographic image forming apparatus according to claim 1, wherein the content of the resin fine particles is 0.01 to 2% by weight based on the total weight of the toner. delete The nonmagnetic one-component toner for a non-contact electrophotographic image forming apparatus according to claim 1, wherein the charging sequence of the resin fine particles has a positive value than that of the binder resin. 2. The nonmagnetic one-component toner for a non-contact electrophotographic image forming apparatus according to claim 1, wherein the glass transition temperature of the polymer used as the resin fine particles is 50 to 70 deg. The nonmagnetic one-component toner for a non-contact electrophotographic image forming apparatus according to claim 1, wherein the weight average molecular weight of the polymer used as the resin fine particles is 10,000 to 100,000.

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