KR100509492B1 - Toner for electrophotography - Google Patents

Abstract

The present invention provides a toner containing a binder resin, a colorant, and an external additive used in an output device including a printer, a fax machine, or a copier, wherein the external additive is 0.1 to 3.0 wt% of large particle silica, and 0.1 to 3.0 small particle silica. Wt%, from 0.1 to 2.0 wt% of positively charged aluminum oxide having a charge per unit mass of +50 to +500 μC / g, from 0.1 to 2.0 wt% of particulate titanium dioxide, and from 80 to 95 wt% of the binder resin, A toner comprising 0.5 to 10% by weight of a colorant.

When two kinds of silicas having different particle diameters of the present invention, positively charged aluminum oxide, and inorganic fine particle titanium dioxide are used as external additives, the toner of 0.3 to 1.0 mg / cm 2 or less while maintaining the toner amount (M / A) on the toner carrier uniformly By forming a thin layer to maintain stable charge distribution and toner fluidity over a long life, it is possible to suppress contamination, scattering generation, development efficiency and toner durability.

Description

Toner for electrophotography {Toner for electrophotography}

The present invention relates to an electrophotographic toner, and more particularly, two different silicas, titanium dioxide (TiO ₂ ) and positively charged aluminum oxide (Al ₂ O ₃ ) are added as an external additive for electrophotographic with improved development efficiency. It relates to toner.

As a developing method used for electrophotographic methods, there are a two-component developing method and a one-component developing method. The one-component development method can be further divided into a magnetic one-component development method and a nonmagnetic one-component development method. The magnetic one-component developing method is a method of developing with a magnetic one-component developing toner, and the nonmagnetic one-component developing method is a non-magnetic one-component developing toner that forms a toner layer on a developing roller to contact or non-contact with a photosensitive member. That's the way it is.

Among the various development methods using the one-component developer, the contact nonmagnetic one-component development method is very competitive in price, but it is difficult to obtain high quality images due to the weak dot reproducibility, line reproducibility, and high resolution. On the other hand, in the non-contact nonmagnetic one-component development method, the developing device structure is simple, which makes it possible to miniaturize and obtain high quality images such as color reproducibility, edge reproducibility, excellent tone gradation and high resolution. .

The nonmagnetic non-contact developing method is composed of a mechanism including a charging step, an exposure step, a developing step, a transfer step, and a cleaning step. Toner used in the conventional non-magnetic non-contact developing method has a colorant, a charge control agent, a mold release agent, and the like uniformly embedded in the binder resin to improve color, charge characteristics, and fixability, and have fluidity, charge stability, and cleaning properties. In order to give), several kinds of external additives are added.

Japanese Laid-open Patent Application Hei 11-0095486 discloses a toner in which conductive silica particles are included as an external additive. Japanese Laid-Open Patent Application Hei 11-295921 discloses a technique for attaching three kinds of silicas having different particle sizes to the toner.

In the non-contact nonmagnetic one-component developing method, it is important to form a thin toner layer on the developing roller in the developing area in order to improve the prevention of contamination or background of the non-image portion and to prevent scattering of the toner. However, when the toner layer is formed on the developing roller, an increase in the amount of toner charging causes a rapid decrease in developing efficiency and thus a decrease in image density. In addition, when the toner charging amount is adjusted downward to improve such deterioration of developing efficiency, an increase in non-image contamination and contamination by scattering may occur.

Accordingly, there has been a demand for the development of a technique for stably maintaining the charge amount and charge distribution while forming a thin toner layer on the developing roller in the developing area, which is closely related to the type and composition of the additive to be added to the toner.

The technical problem to be achieved by the present invention is to control the type and content of the toner external additive, to suppress the generation of fog and scattering, and to provide a toner having improved development efficiency and durability.

In order to achieve the object of the present invention, in the toner comprising a binder resin, a colorant and an external additive used in an output device including a printer, a fax or a copier, 0.1 to 3.0% by weight of the large-diameter silica, Small particle silica comprises 0.1 to 3.0% by weight, positively charged aluminum oxide having a charge per unit mass of +50 to + 500μC / g 0.1 to 2.0% by weight, fine particles titanium dioxide 0.1 to 2.0% by weight, the binder resin 80 To 95% by weight, toner including 0.5 to 10% by weight of the colorant is provided.

The positively charged aluminum oxide may have a charge amount per unit mass of +100 to +300 μC / g.

The average particle diameter of the positively charged aluminum oxide is 0.1 to 3.0㎛, the average particle diameter of the fine titanium dioxide may be 10 to 100nm, more preferably the average particle diameter of the positively charged aluminum oxide is 0.1 to 2.0㎛, The average particle diameter of the particulate titanium dioxide may be 15 to 80 nm.

The average particle diameter of the large particle size silica may be 20 to 200 nm, and the average particle size of the small particle size silica may be 5 to 20 nm.

The weight ratio of the large particle silica and the small particle silica may be 1: 1 to 3: 1, and more preferably, the weight ratio of the large particle silica to the small particle silica may be 1.5: 1 to 2.5: 1. .

It is preferable that the acid value of the said binder resin is 3-12 (mgKOH / g).

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

The present invention relates to a toner additive comprising silica, positively charged aluminum oxide and titanium dioxide having different particle diameters as a constituent of the toner.

The major role of the large-sized silica is spacer particles, which prevents toner deterioration due to durability and improves transferability. The main role of the small-sized silica of the present invention is to impart fluidity to the toner. In addition, M / A (mg / ㎠) decreases as the amount of large-size silica increases, but fluidity decreases, and M / A increases and increases as the amount of small-size silica with a small average particle diameter increases. There are characteristics such as deterioration of the properties. In the above description, M / A refers to the toner weight per unit area measured on the developing roller after passing through the toner layer regulating apparatus. Since the M / A should be kept at a low level to achieve the effect of improving the fogging characteristics and preventing scattering, it is important to form a thin toner layer having an M / A value of 0.3 to 1.0 mg / cm 2. Therefore, it is important to improve the toner performance by optimally adjusting the particle size, content, blending ratio and the like of the large and small particle silica.

The large particle size silica of the present invention preferably has an average particle diameter of 20 to 200 nm, more preferably 30 to 150 nm.

When the particle size of the large-size silica is less than 20 nm, the large-size silica is easily buried in the toner, and it is difficult to play a role as a spacer particle. When it exceeds 200 nm, it is easy to be released without adhering to the toner, and the function as the spacer particle is also inferior.

The small particle size silica of the present invention preferably has an average particle diameter of 5 to 20 nm, more preferably 7 to 16 nm.

When the particle size of the small particle silica is less than 5 nm, it is easy to be buried in minute unevenness on the surface of the toner particles, and there is a problem in adjusting the chargeability and fluidity, and when it exceeds 20 nm, there is a problem that the toner fluidity is not sufficiently high.

The toner of the present invention is characterized in that it comprises 0.1 to 3.0% by weight of the large particle silica. If the weight of the large-size silica is less than 0.1% by weight, it does not function as a spacer particle, and if it exceeds 3.0% by weight, it may be liberated from the toner or may cause photoreceptor surface damage, and image resolution may be lowered.

The toner of the present invention is characterized in that it comprises 0.1 to 3.0% by weight of the small particle silica. If the weight of the small particle silica is less than 0.1% by weight, there is a high possibility that the toner fluidity decreases, and if it exceeds 3.0% by weight, problems such as toner fixability and excessive charge may occur.

The blending ratio of the large particle silica and the small particle silica may vary depending on the developing system, but the present invention is characterized in that the amount of the large particle silica added is controlled to be less than the amount of the small particle silica for thinning the toner layer.

Therefore, the weight ratio of the large-size silica and the small-size silica is preferably 1: 1 to 3: 1, more preferably 1.5: 1 to 2.5: 1.

When the addition amount of large-diameter silica was 1.0 times or more than the addition amount of the small-diameter silica, M / A of 0.3-1.0 mg / cm 2 was stably obtained, and the results were found to be able to suppress fog and scattering. If the large-size silica exceeds the range above the sintered silica (more than 3: 1), the problem of deterioration of the toner fluidity occurs. When too much (less than 1: 1), the toner layer becomes thick and there are problems such as a decrease in charge amount and poor fixability.

When the small particle size silica is too large in excess of the above range, the toner layer becomes thicker, and the charge amount decreases, and poor fixability occurs. On the contrary, the small sized silica becomes less than the above range and the large sized silica becomes the small size silica. When too much, the toner fluidity deteriorates.

The toner of the present invention contains aluminum oxide and titanium dioxide as external additives. The main purpose of adding aluminum oxide and titanium dioxide is to improve charging stability and flowability.

In the case of using inorganic fine particle titanium dioxide alone, the toner charging performance decreases during the long-term use of the toner and contaminants such as scattering are generated, and in order to improve the charging of the toner generated in the long-term use by adding external electrostatic aluminum oxide It is possible to improve the deterioration and nonuniformity of the charge distribution.

Therefore, the present invention seeks to improve the performance of toner by further using positively charged aluminum oxide. In the case of inorganic fine particle titanium dioxide, it contributes to the uniformity of fluidity and charge distribution, and in the case of positively charged aluminum oxide, it contributes to the charging stability in the long-term use of the toner, so control of its content may be important. As in the silica described above, properties as external additives such as the average particle diameter size of the positively charged aluminum oxide and the inorganic fine particle titanium dioxide and the amount of charge per unit mass of each particle are important criteria for selection.

The positively charged aluminum oxide may have a charge amount per unit mass of +50 to +500 μC / g, and preferably have a charge amount per unit mass of +100 to +300 μC / g. When the degree of chargeability of the positively charged aluminum oxide exceeds +500 µC / g, problems such as toner charging unevenness and non-image part contamination are likely to occur, and when less than +50 µC / g, the effect of addition does not occur.

The average particle diameter of the positively charged aluminum oxide particles is preferably 0.1 to 3 µm, more preferably 0.1 to 2.0 µm. If the average particle diameter of the positively charged aluminum oxide is less than 0.1 mu m, there is a problem such as deterioration of charging performance. If it exceeds 3.0 mu m, it is easy to be released from the toner, and developing members such as the photoconductor are easily damaged.

The average particle diameter of the inorganic fine particle titanium dioxide particles is preferably 10 to 100 nm, more preferably 15 to 80 nm.

 If the average particle diameter of the inorganic fine particles of titanium dioxide is less than 10 nm, there is a problem in charging performance, and if it exceeds 100 nm, there is a problem of poor fluidity.

As with the silicas above, such external additives are important for proper combination of large and small particles. Inorganic particulate titanium dioxide contributes to fluidity, and positively charged aluminum oxide contributes to charging stability at the end of life. Therefore, in the present invention, the properties of the toner are improved by mixing the positively charged aluminum oxide and the inorganic fine particle titanium dioxide at an appropriate ratio.

In the toner of the present invention, the positively charged aluminum oxide may include 0.1 to 2.0 wt%, and the inorganic fine particle titanium dioxide may include 0.1 to 2.0 wt%.

If the content of the positively charged aluminum oxide is less than 0.1% by weight, the effect of addition cannot be obtained. If the content of the positively charged aluminum oxide is higher than 2.0% by weight, toner charging unevenness occurs, poor fixability, image contamination by glass from toner, and damage to developing members such as photoreceptor. It may cause problems such as. When the content of the inorganic fine particle titanium dioxide is less than 0.1% by weight, there is a problem in fluidity, and when it exceeds 2.0% by weight, there is a problem in charging stability and fixability.

The toner of the present invention contains a binder resin.

As the binder resin, 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 methacrylate methyl copolymer, Styrene-acrylonitrile copolymer, Styrene- Vinylmethyl ether copolymer, styrene-vinylethyl ether copolymer, styrene-vinylethyl ketone copolymer, styrene-butadiene air Sieve, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-based copolymers such as styrene-maleic acid ester, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, 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 alicyclic hydrocarbon resin, aromatic Type petroleum resins, chlorinated paraffin, paraffin wax and the like are used alone or in combination. Among these, polyester resin is excellent in fixability and is suitable for a color developer.

The content of the binder resin is preferably 80 to 95% by weight.

The performance of the toner of the present invention is also affected by the acid value of the binder resin. The higher the acid value, the lower the acid value is preferable because of the greater toner adhesion to the blade. Specifically, the acid value of the binder resin is preferably 3 to 12 mgKOH / g. If the acid value is less than 3 mgKOH / g, the charging performance may be lowered. If the acid value is more than 12 mgKOH / g, the stability of the toner charging amount against humidity fluctuations may be impaired, which may cause problems such as increased adhesion to the developing member. There is this.

The present invention includes a colorant.

Colorants include carbon black, aniline black, aniline blue, chaco oil blue, chrome yellow, ultramarine blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, roda And dyes such as minor dyes or pigments, anthraquinone dyes, monoazo and bisazo dyes, and quinacridone magenta dyes. These colorants need to be contained in a ratio sufficient to form a sufficient concentration of visible image.

When the coloring agent is carbon black, it is preferable that the primary particle diameter is 15-70 nm, especially 20-55 nm, and the specific surface area is 200 m <2> / g or less. When such carbon black is used, dispersibility and disintegration property with other materials are favorable in a melting and kneading method.

The content of the colorant may be any amount sufficient to color the toner capable of forming a visible image by development, for example, 0.5 to 10 wt% is preferable, 0.5 to 8 wt% is more preferable, and 1 to 5 wt% is most preferred. desirable.

 If the amount is less than 0.5% by weight, the coloring effect is insufficient. If the amount is more than 10% by weight, the image density becomes saturated while the developing performance of the toner is lowered. For example, the electric resistance of the toner is lowered to obtain a sufficient amount of frictional charge, resulting in contamination and the like.

The toner of the present invention may be included in such a manner that a charge control agent (CCA), a release agent (Wax), and the like are uniformly embedded in the binder resin in order to improve charging characteristics, fixability, and the like.

The toner is required to be stably supported on the developing roller by the electrostatic force, and since the electrostatic force of such toner is generated by the charging blade, a fast charging speed is required. Therefore, a charge control agent is necessary to stabilize the charge of the toner.

Examples of charge control agents include metal azo dyes, salicylic acid metal complexes, nigrosine dyes, quaternary ammonium salts, triphenylmethane control agents, oil-soluble dyes such as oil black, naphthenic acid, salicylic acid, octylic acid and their manganese and cobalt. And metal salts such as iron, zinc, aluminum, and lead, and alkyl salicylate metal chelates.

The content of the charge control agent is preferably 0.1 to 10% by weight. When the content of the charge control agent is less than 0.1% by weight, the effect of the addition is not exerted, and when it exceeds 10% by weight, the problem of charge instability may occur.

Recently, low temperature fixing properties of toner are required to achieve the purpose of lowering energy and reducing warm-up time. Therefore, use of a release agent having excellent fixing properties in a wide temperature range is required for this purpose. It is becoming.

Examples of the release agent (lubricant) include polyalkylene waxes such as low molecular weight polypropylene and low molecular polyethylene, paraffin wax, higher fatty acids, fatty acid amides, and the like. The content of the release agent is preferably 0.1 to 10% by weight. When the content of the release agent is less than 0.1% by weight, the effect of the addition is not exerted, and when it exceeds 10% by weight, problems of offset, fluidity, and cake formation may occur.

As a method of incorporating a charge control agent, a releasing agent, or the like into the toner, there are an internal addition method to be added to the inside of the toner, and a method of adhering to the surface of the toner particles. In addition, in order to protect the photosensitive member, to prevent deterioration of development characteristics, and to obtain a high quality image, higher fatty acids and metal salts thereof may be appropriately added.

Example

Composition of toner

Binder Resin

Polyester: 92 wt%

Acid Value: 7 mgKOH / g

Colorant (Carbon black)

MA100 (manufactured by Mitsubishi Chemical Corporation): 5% by weight

Charge control agent (Fe complex)

Bontron S-34 (Orient Chemical Industries, Ltd.) product: 1 wt%

Release Agent (Low Molecular Weight Polypropylene Wax)

660P (Sanyo Chemical Co., Ltd.): 2% by weight

According to a method of preparing a conventional toner by mixing the above components, an untreated toner having a particle size of 8 μm was obtained, followed by external treatment of the following external additive to prepare an toner of an embodiment of the present invention.

Large Particle Silica (H05TM, Wacker from Wacker-Chemie GmbH)

Average particle diameter 30 nm

1% by weight relative to 100% by weight untreated toner

Small particle silica (H3005, Wacker from Wacker-Chemie GmbH)

Average particle diameter 15 nm

0.6% by weight relative to 100% by weight untreated toner

Electrostatic aluminum oxide (ET-500W, product of Ishihara Sangyo Kaisha)

500 nm

1% by weight relative to 100% by weight untreated toner

Charge amount per unit mass + 300μC / g

Inorganic fine particle titanium dioxide (NKT90, Nippon Aerosol Co., Ltd. product)

Average particle diameter 20 nm

1% by weight relative to 100% by weight untreated toner

Comparative example

Except for the external addition of the inorganic fine particles titanium dioxide alone, the same composition and conditions as in the above-described Examples were carried out as follows.

Composition of toner

Binder Resin

Polyester: 92 wt%

Acid value 7 mgKOH / g

Colorant (Carbon black)

MA100 (manufactured by Mitsubishi Chemical Corporation): 5% by weight

Charge control agent (Fe complex)

Bontron S-34 (Orient Chemical Industries, Ltd.) product: 1 wt%

Release Agent (Low Molecular Weight Polypropylene Wax)

660P (Sanyo Chemical Co., Ltd.): 2% by weight

According to a method of preparing a conventional toner by mixing the above components, an untreated toner having a particle size of 8 μm was obtained, followed by external treatment of the following external additive to prepare a toner of a comparative example of the present invention.

Large Particle Silica (H05TM, Wacker from Wacker-Chemie GmbH)

Average particle diameter 30 nm

1% by weight relative to 100% by weight untreated toner

Small Particle Silica Large Particle Silica (H05TM, Wacker from Wacker-Chemie GmbH)

Average particle size 16 nm

0.6% by weight relative to 100% by weight untreated toner

Inorganic fine particle titanium dioxide (NKT90, Nippon Aerosol Co., Ltd. product)

Average particle diameter 20 nm

1% by weight relative to 100% by weight untreated toner

Test Example

The images were evaluated using a 20 ppm LBP printer for the toners of the Examples and Comparative Examples. Toner by measuring I / D: (Image Density), B / G: (Background or fog), Streaks The performance of was evaluated. At this time, the I / D measured the density of the solid pattern on the paper, and the B / G measured the concentration in the non-image area on the photoreceptor using a densitometer (SpectroEye, manufactured by GretagMacbeth). Dot reproducibility and streaks were visually evaluated.

The implementation conditions of the developing apparatus were as follows.

Surface potential (Vo):-700 V

Latent potential (VL):-100 V

Developing roller applied voltage

Vp-p = 1.8 KV, Frequency = 2.0 kHz,

Vdc =-250 V, Duty Ratio = 40% (square wave)

Development gap (GAP): 250 μ

Developing Roller

(1) in the case of aluminum

Roughness: Rz = 1 ~ 2.5 (After Nickel Plating)

(2) In case of rubber roller

Resistance: 5 x 10 ⁵ Ω

Hardness: 50

toner

Charge amount (q / m) = -14 to -20μC / g ((on developing roller after passing through regulator)

Toner amount per area = 0.4 to 0.8 mg / cm 2

The results of the test are in Tables 1 and 2 below.

Measurement result of Example    Purchase Items Early 2,000 4,000 6,000 8,000 10,000 I / D ○ ○ ○ ○ ○ ○ B / G ○ ○ ○ ○ ○ △ Dot reproducibility ○ ○ ○ ○ △ △ Streak ○ ○ ○ ○ ○ ○

The evaluation index I / D was evaluated as "O" in the case of 1.3 or more, "Δ" in the case of 1.1 to 1.3, and "X" in the case of less than 1.1.

The evaluation index B / G was evaluated as "O" in the case of 0.14 or less, "Δ" in the case of 0.15 to 0.16, and "X" in the case of 1.7 or more.

The evaluation index dot reproducibility and the streak were evaluated as "O" when the above-mentioned occurrence of the problem was not recognized by visual inspection, and "X" in case of severe occurrence.

Measurement result of comparative example    Purchase Items Early 2,000 4,000 6,000 8,000 10,000 I / D ○ ○ ○ ○ △ X B / G ○ ○ ○ △ X X Dot reproducibility ○ ○ ○ △ △ X Streak ○ ○ ○ △ △ X

As can be seen from the above test results, when the inorganic fine particle titanium dioxide and the positively charged aluminum oxide were externally added, I / D, B / G, dot reproducibility, and streak were all improved. In particular, as the number of prints increased, B / G and Streak improved significantly.

When two kinds of silica having different particle diameters and positively charged aluminum oxide and titanium dioxide having different particle diameters were used as external additives, I / D, B / G, dot reproducibility, and streak were all improved. Increasingly, B / G and streak are much better.

 In addition, the present invention by controlling the type and content of the toner external additive to form a toner thin layer of 0.3 to 1.0mg / ㎠ or less while maintaining the toner amount (M / A) on the toner carrier uniformly stable charge distribution and toner fluidity By maintaining the composition over a long life, it is possible to suppress contamination, scattering generation, development efficiency and toner durability.

Claims (8)

A toner comprising a binder resin, a colorant, and an external additive used in an output device including a printer, a fax, or a copy machine, As the external additive, 0.1 to 3.0% by weight of large particle silica, 0.1 to 3.0% by weight of small particle silica, 0.1 to 2.0% by weight of positively charged aluminum oxide having a charge per unit mass of +50 to +500 μC / g, fine titanium dioxide 0.1 to 2.0 wt%, 80 to 95 wt% of the binder resin, 0.5 to 10 wt% of the colorant.  The toner according to claim 1, wherein the positively charged aluminum oxide has a charge amount per unit mass of +100 to +300 µC / g.   The toner according to claim 1, wherein the average particle diameter of the positively charged aluminum oxide is 0.1 to 3 mu m, and the average particle diameter of the fine particle titanium dioxide is 10 to 100 nm. The toner according to claim 1, wherein the average particle diameter of the positively charged aluminum oxide is 0.1 to 2.0 mu m, and the average particle diameter of the fine titanium dioxide is 15 to 80 nm. The toner according to claim 1, wherein the average particle diameter of the large particle size silica is 20 to 200 nm, and the average particle size of the small particle size silica is 5 to 20 nm. The toner according to claim 1, wherein the weight ratio of the large size silica to the small size silica is 1: 1 to 3: 1. The toner according to any one of claims 1 to 4, wherein a weight ratio of the large particle silica to the small particle silica is 1.5: 1 to 2.5: 1. The toner of claim 1, wherein an acid value of the binder resin is 3 to 12 (mgKOH / g).