JP2002311647A - Electrophotographic full color toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic full color toner ensuring a small toner consumption, free of scattering, excellent in transferability and capable of forming a good image. SOLUTION: When a kneaded material containing a binder resin and colorants is pulverized and the resulting raw material particles are heat-treated and ensphered to obtain an electrophotographic full color toner, the average circularity of the toner particles is <=1.30 and 0.2-3 pts.wt. fine silica powder having 30-80 m<2> /g specific surface area and 0.3-3 pts.wt. inorganic oxide having 0.5-18m<2> /g specific surface area, based on 100 pts.wt. toner particles, are added after the heat treatment to obtain the objective electrophotographic full color toner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a full-color toner for electrophotography. More specifically, the present invention relates to a full-color toner for electrophotography, which consumes a small amount of toner, has no toner scattering, has excellent transferability, and can form a good image.

[0002]

2. Description of the Related Art In recent years, demand for full-color image forming apparatuses for use in printers has been increasing. As a full-color image developing method, a non-magnetic developing method of forming a thin layer of toner on a developing roller with a regulating blade, uniformly charging the toner, and developing the toner is adopted in order to reduce the size and simplify maintenance. Further, as a full-color image forming method, a method of sequentially transferring toner images of respective colors formed on a photoreceptor to an intermediate transfer member, temporarily holding the same, and then collectively retransferring them onto paper is well known. Conventional toner particles obtained by pulverizing a kneaded material containing a binder resin, a colorant, etc. with a jet mill or the like have an irregular and angular shape, strong cohesion between toner particles, and Since the toner layer on the roller is thick and non-uniform, and the charge amount is also non-uniform, there are problems such as an increase in toner consumption and toner scattering. Further, such a toner having a strong cohesive force and non-uniform charge is inferior in transferability, and in particular, in an image forming apparatus having an intermediate transfer member, a sufficient image density cannot be obtained because of two transfer steps. . As one of the techniques for solving this problem, spherical toner particles have been studied, and polymerized toner has been commercialized. However, for the toner produced by the polymerization method, equipment used for kneading, pulverizing, classifying, etc., which is currently used in the production of toner, cannot be used, and a huge amount of new capital investment is required. Further, the range of resins that can be selected as a binder resin is narrow, and it is difficult to uniformly disperse an internal additive such as a colorant and an electrification control agent in resin particles. As a result, the charging characteristics of the obtained toner particles become uneven, and various obstacles such as toner scattering and uneven development occur. Attempts have also been made to make toner particles spherical by instantaneously heating particles obtained by pulverizing a kneaded material containing a binder resin, a colorant and the like. For example, Japanese Patent Publication No. 3-179363 discloses that when toner particles produced by a pulverization method are sphericalized by hot air treatment,
As a method for producing a toner capable of preventing aggregation of toner particles, a method has been proposed in which an inorganic substance is attached to the surface of toner particles prior to hot air treatment. Also, Japanese Patent Application Laid-Open No. Hei 5-281783 discloses that a toner particle containing a thermoplastic resin is prepared as an electrophotographic toner having improved fluidity, reduced fog, and excellent charging characteristics and image characteristics. There has been proposed an electrophotographic toner in which toner particles are made spherical. Further, JP-A-11-2959
No. 29 discloses a method for producing a toner for developing an electrostatic latent image capable of improving the classification accuracy and improving the yield of a toner having a desired particle diameter. A method of performing a surface modification treatment and classifying has been proposed. However, even if the raw material particles obtained by pulverizing the kneaded material are spheroidized by hot air treatment, the toner particles are still easily scattered and the transfer efficiency is insufficient, so that further improvement has been desired.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a full-color toner for electrophotography which consumes a small amount of toner, has no toner scattering, has excellent transferability, and can form a good image. It was made for the purpose.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, heated raw material particles obtained by pulverizing a kneaded material containing a binder resin and a colorant have been heated. The toner particles having a roundness of 1.30 or less are processed, and the specific surface area is 30 per 100 parts by weight of the toner particles.
By adding ~80m ² / silica fine powder 0.2 to 3 parts by weight of g and an inorganic oxide having a specific surface area 0.5~18m ² / g 0.2~3 parts by weight, scattering of toner particles prevented As a result, it was found that the transferability was improved, and the present invention was completed based on this finding. That is, the present invention
(1) A full-color toner for electrophotography obtained by subjecting raw material particles obtained by pulverizing a kneaded material containing a binder resin and a coloring agent to a heat treatment, wherein the toner particles have an average roundness of 1. 30 or less, 0.2 to 3 parts by weight of silica fine powder having a specific surface area of 30 to 80 m ² / g, and 0.5 to 18 of specific surface area per 100 parts by weight of toner particles after heat treatment.
(2) a full-color toner for electrophotography, wherein 0.2 to 3 parts by weight of m ² / g of inorganic oxide is added.
3. The electrophotographic full-color toner according to claim 1, which is used in a full-color image forming apparatus having an intermediate transfer member in a non-magnetic developing system, and (3) the electrophotography according to claim 1, wherein the binder resin is a polyester resin. (4) a specific surface area of 3 parts by weight based on 100 parts by weight of raw material particles obtained by pulverizing the kneaded material before heat treatment for spheroidization.
4. The full-color toner for electrophotography according to any one of items 1 to 3, wherein 0.2 to 3 parts by weight of a silica fine powder of 0 to 400 m ² / g is added, and (5) strontium titanate is used as the inorganic oxide. Or the first to fourth items are barium titanate.
The present invention provides a full-color toner for electrophotography according to the above item.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The full-color toner for electrophotography according to the present invention is a full-color toner for electrophotography obtained by subjecting raw material particles obtained by pulverizing a kneaded product containing a binder resin and a colorant to a heat treatment to form spherical particles. Wherein the circularity of the toner particles is 1.30 or less, and 0.2 to 3 parts by weight of a silica fine powder having a specific surface area of 30 to 80 m ² / g with respect to 100 parts by weight of the toner particles after the heat treatment. Surface area 0.5-18m
^This is a full-color electrophotographic toner to which 0.2 to 3 parts by weight of a ² / g inorganic oxide is added. There is no particular limitation on the binder resin used in the present invention, for example, polystyrene,
Examples include styrene-based copolymers such as styrene-methyl acrylate copolymer and styrene-acrylonitrile copolymer, polyester resins, epoxy resins and the like. One of these binder resins can be used alone, or two or more can be used in combination. Among them, a polyester resin can be particularly preferably used. Polyester resin has a large degree of decrease in viscosity with temperature rise, has a wide control range of roundness by heat treatment, and can easily obtain a uniform and nearly spherical shape. Further, the polyester resin has a good coloring property of the colorant, and can obtain a toner of a clear color. There is no particular limitation on the colorant used in the present invention.As a black colorant, for example, carbon black, magnetic powder, etc., as a cyan colorant, for example, copper phthalocyanine, methylene blue, Victoria blue, etc., a magenta colorant Examples thereof include rhodamine dyes, dimethylquinacridone, dichloroquinacridone, and carmine red, and examples of yellow colorants include benzidine yellow, chrome yellow, naphthol yellow, and disazo yellow.

[0006] The toner of the present invention may contain a wax. There is no particular limitation on the wax used,
For example, polyethylene, polyolefin wax such as polypropylene, carnauba wax, rice wax,
Sasol wax, montan-based ester wax and the like can be mentioned. By including wax in the toner, the offset resistance can be improved.
The toner of the present invention can contain a charge control agent. There is no particular limitation on the charge control agent used, for example,
Metal complexes such as nigrosine, basic dyes and monoazo dyes; chromium such as salicylic acid and dicarboxylic acid; metal complexes such as iron; and organic dyes. By including a charge control agent in the toner, the toner can be charged efficiently. In the present invention, a binder resin, a colorant, a wax, a charge control agent, and the like are mixed using a Henschel mixer or the like, and kneaded using a twin-screw extruder or the like, and then the kneaded material is pulverized into raw material particles. . The pulverizer used for pulverizing the kneaded material is not particularly limited, and examples thereof include a jet mill and a turbo mill. The raw material particles can be classified as needed. Since the raw material particles become spherical by heat treatment and become toner particles,
The size of the toner particles is determined by the size of the raw material particles. The toner particles of the toner of the present invention preferably have a volume average particle diameter of 4 to 15 μm, more preferably 6 to 10 μm.

In the present invention, the raw material particles obtained by pulverizing a kneaded material containing a binder resin, a colorant and the like are subjected to a heat treatment to form a sphere. Before heat treatment for spheroidization, 0.2 to 3 parts by weight of a silica fine powder having a specific surface area of 30 to 400 m ² / g is added to 100 parts by weight of raw material particles obtained by pulverizing the kneaded material. Is preferred. By adding the silica fine powder to the raw material particles, it is possible to improve the fluidity of the raw material particles during the heat treatment and prevent the raw material particles from being coarsened by fusion. When the specific surface area of the silica fine powder is less than 30 m ² / g, the effect of improving the fluidity may not be sufficiently exhibited. If the specific surface area of the silica fine powder exceeds 400 m ² / g, the silica fine powder may be too fine and the workability may be reduced. If the added amount of the silica fine powder is less than 0.2 parts by weight per 100 parts by weight of the raw material particles, the effect of improving the fluidity may not be sufficiently exhibited. If the amount of the silica fine powder exceeds 3 parts by weight per 100 parts by weight of the raw material particles, toner filming of the photoconductor may occur. In the present invention, the heat treatment of the raw material particles is preferably performed using an apparatus capable of heating the raw material particles in a short time within several seconds. Examples of such an apparatus include a surfing system of Nippon Pneumatic Co., Ltd. By heating the raw material particles in a short time, fusion of the raw material particles can be prevented, and the raw material particles can be made spherical. By subjecting the raw material particles to a heat treatment to make the toner particles spherical, the fluidity of the toner is improved, the cohesive force is reduced, the thickness of the toner layer on the developing roller becomes uniform, and the uniformity of charging is improved. And scattering of toner can be prevented. Further, the adhesion between the toner particles and the photoreceptor and the adhesion between the toner particles and the intermediate transfer body are reduced, the mobility of the toner to the subject is improved, the transferability is significantly improved, and a good image density is obtained. Can be.

The toner particles of the present invention have an average roundness of 1.30 or less, and more preferably 1.25 or less. When the average roundness of the toner particles exceeds 1.30,
There is a possibility that the fluidity of the toner is reduced, the toner is scattered due to non-uniform charging, and the density is reduced due to the deterioration of transferability, thereby deteriorating the image quality. The roundness is a value calculated by the following equation. Roundness = circumferential length of the projected image of the particle / circumference of a circle having an area equal to the projected area of the particle When the toner particle is a true sphere, the circularity is 1 and the shape of the toner particle deviates from the true sphere The value of the roundness increases as the value increases. The roundness can be determined by analyzing a projected image of a toner particle by a scanning electron micrograph using an image processing analyzer. Examples of the image processing analyzer include, for example, a general-purpose high-speed image processing system IIA-
550note and the like.

[0009] The toner of the present invention, the silica fine powder 0.2 to 3 parts by weight of the specific surface area 30~80m ² / g with respect to 100 parts by weight of the toner particles after the heat treatment, more preferably 0.25
To 2 parts by weight, and 0.2 to 3 parts by weight, more preferably 0.25 to ² parts by weight, of an inorganic oxide having a specific surface area of 0.5 to 18 m ² / g. As silica fine powder,
For example, hydrophobic silicon oxide fine powder treated with silicone oil, alkylsilane, or the like can be used. Examples of the inorganic oxide include strontium titanate and barium titanate. By adding the silica fine powder to the toner particles after the heat treatment, the silica fine powder serves as a roller between the toner particles and the regulating blade, so that the stress on the toner of the regulating blade is relieved, and the blade can be used even in a long-term continuous operation. The occurrence of fusion can be prevented. In addition, since the embedding of the silica fine particles in the surface of the toner particles is also reduced, the change in the charge amount is small even in a long-term continuous operation, so that the transfer rate and the image density can be prevented from lowering. further,
By adding the silica fine powder, it acts as a spacer between toner particles and prevents aggregation of the toner particles, so that the toner layer on the developing roller can be thinned to obtain a uniform charge amount. As a result, toner scattering is reduced and transferability is improved. When the toner particles are made spherical by heat treatment, a change in the composition such as oozing out of the wax occurs on the toner surface. In addition, the so-called blade fusion in which toner particles are melted and fixed to the regulating blade occurs, and furthermore, the photoreceptor filming tends to occur due to the improvement in roundness, but by adding silica fine powder to the toner particles. , These obstacles can be prevented.

When the specific surface area of the silica fine powder is less than 30 m ² / g, adhesion to the surface of toner particles becomes insufficient,
There is a possibility that the effects of preventing scattering of toner particles and improving transferability may not be sufficiently exhibited. Specific surface area of silica fine powder is 80m
If it exceeds ² / g, the size of the silica particles becomes too fine, and the role of the spacer between the toner and the regulating blade or between the toner particles may be reduced. The addition amount of the silica fine powder is 0.2 per 100 parts by weight of the toner particles.
If the amount is less than the weight part, blade fusion and toner scattering may occur, and transferability may be deteriorated. If the addition amount of the silica fine powder exceeds 3 parts by weight per 100 parts by weight of the toner particles, the released silica fine powder may damage the photoconductor, and toner filming may occur on the photoconductor. By adding the inorganic oxide to the toner particles after the heat treatment, the inorganic oxide is a ferroelectric substance, has low chargeability, and is easily released from the toner. By cleaning the silica fine powder and toner particles, the toner filming of the photoconductor can be prevented. The specific surface area of the inorganic oxide is 0.5
If it is less than m ² / g, the photoreceptor may be damaged. When the specific surface area of the inorganic oxide exceeds 18 m ² / g,
There is a possibility that toner filming may occur on the photoconductor. When the amount of the inorganic oxide added is 0.1 to 100 parts by weight of the toner particles.
When the amount is less than 2 parts by weight, toner filming of the photoconductor may occur. When the addition amount of the inorganic oxide exceeds 3 parts by weight per 100 parts by weight of the toner particles, the fluidity of the toner is reduced, and there is a possibility that unevenness in image density may occur due to a decrease in transportability to the developing roller. The shape of the inorganic oxide added to the toner particles after the heat treatment is not particularly limited, and an inorganic oxide having an arbitrary shape such as a spherical shape and an amorphous shape can be used.

In the present invention, the heat-treated toner particles have a specific surface area of 8 with respect to 100 parts by weight of the toner particles.
It is preferable to add 0.1 to 3 parts by weight of inorganic fine particles exceeding 0 m ² / g, and it is more preferable to add 0.3 to 1.5 parts by weight. Examples of the inorganic fine particles include hydrophobic silica, titanium oxide, and alumina treated with a silane coupling agent, silicone oil, or the like. By adding inorganic fine particles to the toner particles after the heat treatment, the fluidity of the toner can be improved. If the amount of the inorganic fine particles is less than 0.1 part by weight per 100 parts by weight of the toner particles, the effect of improving the fluidity may not be sufficiently exhibited. If the amount of the inorganic fine particles exceeds 3 parts by weight per 100 parts by weight of the toner particles, toner filming of the photoconductor may occur. In the present invention, the specific surface area of silica fine powder, inorganic oxide, inorganic fine particles, and the like can be determined by measuring a gas adsorption isotherm near its boiling point and applying a BET isothermal adsorption method. The full-color toner for electrophotography of the present invention,
It can be particularly suitably used in a full-color image forming apparatus having a non-magnetic developing system and an intermediate transfer member. The full-color toner for electrophotography of the present invention can form a good image without scattering of toner, can have high transfer efficiency, and can reduce toner consumption.

[0012]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In the examples and comparative examples, evaluation of the toner was performed by the following method. (1) Average roundness A projection image obtained by scanning electron microscopy is converted into an image processing / analyzing device [Inotech Co., Ltd., general-purpose high-speed image processing system IIA-
550note]. (2) Full-color printer [Hewlett-Packard]
Co., Ltd., HP-LJ4500], and a single color of 1,000
After printing 0 sheets, the state of toner scattering was observed, and evaluated according to the following criteria. ：: No contamination due to toner scattering occurs. Δ: Slight contamination occurs due to toner scattering, but there is no practical problem. X: Severe contamination due to toner scattering is present, and there is a practical problem. (3) Transfer Efficiency In the printing of 1,000 sheets of the above single color, the amount of toner A (g) consumed in the full-color printer and the amount of toner B (g) collected in the collection box are calculated by the following formula. Calculated. Transfer efficiency = {(AB) / A} × 100 (%)

EXAMPLE 1 Polyester resin [Mitsubishi Rayon Co., Ltd., FC433] 1
Using a Henschel mixer, 100 parts by weight, 12.0 parts by weight of a master batch composed of 40% by weight of dimethylquinacridone pigment and 60% by weight of the above polyester resin, 4.8 parts by weight of a zinc salicylate complex, and 2.4 parts by weight of polypropylene were used. After mixing, the mixture was melted and kneaded using a twin screw extruder. The obtained kneaded material is cooled to 2 using a cooling press roller.
It was rolled to a thickness of mm and coarsely pulverized with a feather mill. Next, the mixture was pulverized using a fine pulverizer using an air jet method, and classified using an airflow classifier to obtain a volume average particle size of 7.
5 μm raw material particles were obtained. The average roundness of the raw material particles was 1.59. To 100 parts by weight of the obtained raw material particles, 2.0 parts by weight of a silica fine powder having a specific surface area of 50 m ² / g was added, and a peripheral speed of 30 was added using a Henschel mixer.
The mixture was mixed at m / s for 4 minutes to obtain magenta toner particles. The toner particles are referred to as toner A. Toner A
Surfusing system [Nippon Pneumatic Co., Ltd.
[SFS-3 type] at a processing temperature of 460 ° C. to obtain magenta toner particles. The toner particles are referred to as toner B. 0.25 parts by weight of silica fine powder having a specific surface area of 50 m ² / g, 0.5 parts by weight of silica fine powder having a specific surface area of 100 m ² / g, and strontium titanate having a specific surface area of 1.5 m ² / g were added to 100 parts by weight of toner B. Fine particles (2.0 parts by weight) were added, and a peripheral speed of 30 was added using a Henschel mixer.
After mixing at m / s for 4 minutes, the mixture was sieved with a sieve having an opening of 74 μm to obtain magenta toner particles of the present invention. The toner particles are referred to as toner C. The average roundness of the toner C was 1.25. In a test using a full-color printer, no contamination due to toner scattering occurred. The transfer efficiency of the toner was 73%. Example 2 Example 2 was repeated except that 2.0 parts by weight of barium titanate having a specific surface area of 4 m ² / g was added instead of 2.0 parts by weight of strontium titanate fine particles having a specific surface area of 1.5 m ² / g. Similarly, magenta toner particles of the present invention were obtained. The toner particles are referred to as toner D. The average roundness of the toner D was 1.25. In a test using a full-color printer, no contamination due to toner scattering occurred. The transfer efficiency of the toner was 74%.

Comparative Example 1 Toner A, which was obtained by simply adding fine silica powder to raw material particles obtained by pulverizing a kneaded product and not subjected to heat treatment, was evaluated. The average roundness of Toner A was 1.59. In a test using a full-color printer, contamination due to toner scattering was severe. 23% toner transfer efficiency
Met. Comparative Example 2 Heat treatment temperature of 350 ° C. by surfaging system
A toner E was obtained in the same manner as in Example 1, except for the following. The average roundness of the toner E was 1.32. In a test using a full-color printer, some contamination due to toner scattering occurred, but there was no practical problem.
The transfer efficiency of the toner was 42%. Comparative Example 3 Toner F was obtained in the same manner as in Example 1 except that strontium titanate fine particles were not added to toner B after the heat treatment, and only silica fine powder was added. The average roundness of the toner F was 1.25. In a test using a full-color printer, some contamination due to toner scattering occurred, but there was no practical problem. However, toner filming occurred on the photoconductor. The transfer efficiency of toner is 6
8%. Comparative Example 4 Example 1 was repeated except that the silica fine powder having a specific surface area of 50 m ² / g and the silica fine powder having a specific surface area of 100 m ² / g and strontium titanate fine particles were added to the toner B after the heat treatment. In the same manner as in the above, a toner G was obtained. Toner G
Has an average roundness of 1.25. In a test using a full-color printer, contamination due to toner scattering slightly occurred, but there was no practical problem. The transfer efficiency of the toner was 51%. Examples 1-2 and Comparative Examples 1
Table 1 shows the results of No. 4.

[0015]

[Table 1]

As can be seen from Table 1, the toner C of Example 1 and the toner D of Example 2 each have a small average roundness and a nearly spherical shape, and in a test using a full-color printer, There is no contamination due to toner scattering, and the transfer efficiency is high. On the other hand, the toner A of Comparative Example 1, which was not subjected to the heat treatment, had a large average roundness, an irregular and angular shape, and in a test using a full-color printer, contamination due to toner scattering was severe, The transfer efficiency is also very low. Further, the toner E of Comparative Example 2 in which the heat treatment temperature was low, the average roundness was slightly large, and the shape was out of a spherical shape, and the toner G of Comparative Example 4 in which silica fine powder was not added, were used for a full-color printer. In some tests, although not practically a problem, some contamination due to toner scattering occurred and the transfer efficiency was rather low. Specific surface area 0.5
In a test using a full-color printer, the toner F of Comparative Example 3 in which no inorganic oxide fine particles of ~ 18 m ² / g was added did not cause a practical problem, but some contamination due to toner scattering occurred, and Toner filming has occurred on the body.

[0017]

The full-color toner for electrophotography of the present invention can form a good image without scattering of toner in a full-color image forming apparatus, has high transfer efficiency, and saves toner consumption. Can be.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Narutoshi Asano 1630-8 Takatsu, Mitsu-cho, Mitsu-gun, Okayama Prefecture F-term in IMEX Co., Ltd. (Reference) 2H005 AA01 AA08 AA15 AA21 AB04 AB09 CA08 CA21 CB08 CB13 EA07 EA10 FA07

Claims (5)

[Claims] An electrophotographic full-color toner obtained by subjecting raw material particles obtained by pulverizing a kneaded product containing a binder resin and a colorant to a heat treatment, wherein the toner particles have an average roundness. 1.30 or less and a specific surface area of 30 to 80 m ^{2 with} respect to 100 parts by weight of toner particles after heat treatment.
/ G silica fine powder 0.2 to 3 parts by weight and specific surface area 0.5
A full-color toner for electrophotography, wherein 0.2 to 3 parts by weight of an inorganic oxide of from 18 to 18 m ² / g is added. 2. A full-color toner for electrophotography according to claim 1, which is used in a full-color image forming apparatus having a non-magnetic developing system and an intermediate transfer member. 3. The full-color toner for electrophotography according to claim 1, wherein the binder resin is a polyester resin. 4. A silica fine powder having a specific surface area of 30 to 400 m ² / g with respect to 100 parts by weight of raw material particles obtained by pulverizing a kneaded material before heat treatment for spheroidization. 4. The full-color toner for electrophotography according to claim 1, further comprising: 5. The full-color electrophotographic toner according to claim 1, wherein the inorganic oxide is strontium titanate or barium titanate.