JPH09258474A - Electrostatic charge image developing toner and multicolor image forming method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form full-color images having high image quality and to obtain developers having high reliability by constituting the toner developers of specific color toners and black toners. SOLUTION: This developer is the plural toner developers used for a color copying machine. The toner developers are composed of the color toners having Wadells operational sphericity ψ of >=0.8, volumetric average rain size Dv of 4 to 8μm and a fluctuation coefft. (standard deviation/Dv) σ of <=35% and the black toners having the Wadells operational sphericity smaller than the Wadells operational sphericity of all of these color toners and the large volumetric average grain size. In such a case, the sphericity ψis expressed by ψ = (the diameter of the circle of an area equal to the projection area of particles)/(the diameter of the min. circle circumscribing the projected image of the particles) and may be easily calculated by taking a suitable amt. of the toners on sliding glass, magnifying the images thereof with a microscope and making measurement with arbitrary 100 pieces of the toners.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic charge image developing toner and a multicolor image forming method using the same, and more particularly to a toner and a full color image forming method useful for forming a high quality full color image. .

[0002]

2. Description of the Related Art In recent years, the improvement of image quality in the field of electrophotography has been studied from various angles. Above all, it has been recognized that it is extremely effective to reduce the diameter and sphere of toner. However, as the diameter and sphere of the toner progresses, the adhesion of the toner particles to the photoconductor increases, and the blade cleaning properties used in electrophotographic copying machines tend to deteriorate, making cleaning the photoconductor difficult. Is becoming. Further, there is a tendency that as the diameter of the toner is reduced, the developing ability and the transferability are deteriorated, resulting in a poor image. On the other hand, however, it has been found that the transferability is improved by making the toner spherical.

However, in order to improve the cleaning property, for example, Japanese Unexamined Patent Publication No. 1-100562 proposes that the toner is made into an irregular shape. However, this method inevitably sacrifices transferability as described above. Further, in JP-A-60-103355, a spherical toner containing silicone oil by suspension polymerization is tried, but in such a method, silicone exudes and adversely affects various places. Next, it is a problem unique to full-color copiers, but even with full-color copiers, the ratio of black and white copying is surprisingly large, so that black toner developer deteriorates faster than color developer,
The spread of full-color copying machines in recent years has begun to cause problems.

[0004]

SUMMARY OF THE INVENTION The first object of the present invention is to solve the above-mentioned problems, to form a high-quality full-color image, and to provide a highly reliable developer.
A second object of the present invention is to provide an image forming method having excellent cleaning properties. A third object of the present invention is to provide an image forming method without toner scattering. A fourth object of the present invention is to provide a toner capable of obtaining a high image density even with a small particle size toner.

[0005]

According to the present invention, (1)
A plurality of toner developers used in a color copying machine, wherein the toner developers have a Wader practical sphericity ψ of 0.8 or more, a volume average particle diameter Dv of 4 to 8 μm, and a coefficient of variation (standard deviation / Dv). An electrostatic charge image developing toner comprising: a color toner having a σ of 35% or less; and a black toner having a smaller Wader practical sphericity and a larger volume average particle size than any of the color toners. (2) In (1) above, at least the color toner among the toners has a Wader practical sphericity ψ of 0.8 or more, a volume average particle diameter Dv of 4 to 8 μm, and a variation coefficient σ of 35% or less, and these toners The image density ID of each color is 0.5
Yellow / 0.9, Magenta / 1.3, and Cyan / 1.2 at mg / cm ² , toner for developing an electrostatic image, characterized in that (3) the toner in (1) or (2) above. At least a color toner among them is a toner produced by a dispersion polymerization method, and a toner for developing an electrostatic charge image is provided.

According to the present invention, there is also provided (4) a method for forming a multicolor image using an electrophotographic copying machine, comprising a plurality of toner developers, wherein the toner developers are color toner developers. At least a color toner of the black toner developer has a Wader practical sphericity ψ of 0.8 or more, a volume average particle diameter Dv of 4 to 8 μm, and a coefficient of variation σ of 35.
% Or less, and a carbon black-containing carrier is used only for the black toner developer. (5) In (4), at least the color toner is a wadel practical spherical toner. Degree ψ is 0.8
As described above, the volume average particle diameter Dv is 4 to 8 μm, and the variation coefficient σ is 3
When the image density ID of each color of these toners is 5% or less and the toner adhesion amount is 0.5 mg / cm ² , the yellow is less than 0.5.
9 or more, magenta 1.3 or more, and cyan 1.2 or more, (6) above (4)
Alternatively, in (5), there is provided a multicolor image forming method, wherein at least a color toner among the toners is a toner manufactured by a dispersion polymerization method.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the toner according to the present invention, at least the color toner needs to have a value of the Wadell practical sphericity ψ0.8 or more. The sphericity ψ here is represented by ψ = (diameter of a circle having an area equal to the projected area of the particle) / (diameter of the smallest circle circumscribing the projected image of the particle). It can be easily calculated by enlarging (500 times) with an appropriate amount of a microscope and measuring for arbitrary 100 toner particles.

According to the studies made by the present inventors, the sphericity ψ is related to the toner cleaning property. Cleaning of the photoconductor is usually performed by using a rubber blade to block the residual toner after transfer. However, when the particle size of the toner becomes small, the toner easily passes between the cleaning blade and the photoconductor. Further, the blade cleaning property deteriorates as the spherical shape of the toner approaches the spherical shape. On the contrary, it was found that the toner having a large particle size and an irregular shape is easily cleaned.
Therefore, in terms of image quality, the black toner, which has the least need to be made smaller in diameter and spherical, is treated as it was in the past, and the black toner is used to familiarize the cleaning blade (the black toner with good cleaning property is accumulated at the tip of the cleaning blade). It was confirmed that the blades of other color toners can be prevented from breaking through.

When the particle diameter of the toner is gradually reduced, the points of contact between the toner particles also increase, and the fluidity of the toner itself disappears. As a result, both the amount of development on the drum and the amount of transfer to paper are reduced, and the overall image density is reduced. Therefore, in order to solve this problem, it is effective to raise the coloring degree of the toner itself in advance. That is, it is possible to increase the amount of the colorant used in the toner so that a sufficient image density can be obtained even if the amount of toner adhered is low. More specifically, the image density of each color of the toner is 0.5 mg / toner adhesion amount.
The amount of the colorant in the toner was set so as to be the following value or more in cm ² . Yellow: 0.9 or more, preferably 1.1 or more Magenta: 1.3 or more, preferably 1.6 or more Cyan: 1.2 or more, preferably 1.5 or more

On the other hand, as the spherical shape of the toner approaches the sphere, the fluidity of the toner tends to increase and the transferability tends to improve. In particular, the dispersion-polymerized toner is almost spherical, and the transfer rate is very good. Therefore, it is possible to form an image having excellent fine line reproducibility and giving a sharp impression.

The color toner of the present invention has a volume average particle diameter Dv.
Is 4 to 8 μm, preferably 6 to 8 μm. Dv value is 4
If it is smaller than μm, toner scattering may occur during development, and conversely, if it is larger than 8 μm, the sharpness of a color image is deteriorated.

The color toner of the present invention has a coefficient of variation σ
Is 35% or less. The “variation coefficient σ” as used herein means the breadth of the particle size distribution. Therefore, if the σ value is 35% or more, a large amount of toner with a large particle size is contained, and a sufficient image sharpness is obtained. I can't get it.

By the way, one of the problems peculiar to full-color copying is that the degree of copying of each color varies depending on the use environment, so that the degree of deterioration of the developer varies depending on the color. Generally, even in a full-color copying machine, the black-and-white copy is most often made, so that the black developer is liable to be deteriorated and the toner may be scattered. The carrier used for the full-color developer is usually coated only with a thin film in order to keep the resistance low, but this is also one of the factors that shorten the life of the developer. Therefore, the present inventors have found that it is effective to disperse carbon black in the carrier coat in order to improve the life of the black developer for full color. Since the resistance is low even if the coat thickness is made relatively thick by adding carbon black, it becomes easy to design the carrier coat considering the agent life. However, carrier formulations using this carbon black cannot be used for color toner developers because of the possibility of color contamination.

[0014]

The present invention will be described in more detail by the following examples, which should not be construed as limiting the invention. Parts are parts by weight.

(Production Example of Yellow Toner 1) Styrene-n-butyl methacrylate (55/45) copolymer 92 parts (Mn = about 3200, Mw = 18000) Chromium-containing azo dye 2 parts Disazo yellow (yellow) 5 parts The resulting mixture was melt-kneaded, finely pulverized, and then rounded by a hybridizer. Next, the rounded fine particles were classified to obtain fine powder having a volume average particle diameter of 6 μm. To 100 parts of this fine powder, 0.5 part of hydrophobic silica R976 (manufactured by Nippon Aerosil Co., Ltd.) was added and mixed by a high speed mixer to obtain a yellow toner.

(Production Example of Magenta Toner 1) Dimethylquinacridone (magenta) instead of 2 parts of Disazo Yellow
Magenta Toner 1 was obtained in exactly the same manner as Yellow Toner 1 except that 5 parts were used.

(Production Example of Cyan Yellow 1) Copper phthalocyanine (cyan) 1.5 instead of 2 parts of disazo yellow
Cyan Toner 1 was obtained in the same manner as in the production method of Yellow Toner 1 except that parts were used.

(Production Example of Black Toner 1) Black Toner 1 was obtained in the same manner as Yellow Toner 1 except that 3 parts of carbon black (black) was used instead of 2 parts of Disazo Yellow.

(Production Example of Yellow Toner 2) Yellow Toner 1 except that the amount of disazo yellow is increased from 2 to 10 parts.
Yellow toner 2 was obtained in exactly the same manner as in the manufacturing method of.

(Production Example of Magenta Toner 2) Magenta Toner 2 was obtained in the same manner as Yellow Toner 1 except that 8 parts of dimethylquinacridone was used instead of 2 parts of Disazo Yellow.

(Production Example of Cyan Toner 2) A cyan toner 2 was obtained in the same manner as in the production of the yellow toner 1, except that 3 parts of copper phthalocyanine was used instead of 2 parts of disazo yellow.

(Production Example of Black Toner 2) Styrene-n-butyl methacrylate (55/45) copolymer 92 parts (Mn = about 3200, Mw = 18000) Chromium-containing azo dye 2 parts Carbon black 3 parts Was melt-kneaded, finely pulverized, and then classified to obtain fine powder having a volume average particle diameter of 8 μm. This fine powder 100
0.5 part of hydrophobic silica R976 (manufactured by Nippon Aerosil Co., Ltd.) was added to each part and mixed by a high speed mixer to obtain a black toner 2.

(Production Example of Yellow Toner 3) A sealable reaction container equipped with a stirring blade, a cooling condenser, and a nitrogen gas introduction pipe was installed in a thermostatic chamber, and the reaction container was charged with the following composition. Methanol 90 parts Methyl vinyl ether / maleic anhydride (1/1) copolymer 2 parts A mixture of 2 parts is mixed to completely dissolve the methyl vinyl ether / maleic anhydride copolymer, and then the following composition is obtained. Was charged into the container. Styrene 30 parts Methyl acrylate 15 parts tert-Dodecyl mercaptan 1 part tert-Butyl acrylamide sulfonic acid 1 part When the air in the container is completely replaced with nitrogen gas, the temperature in the water tank is raised to 65 ° C. 0.4 parts of bisisobutyronitrile and 1 part of methanol were added. Then, the reaction was continued for 24 hours and then cooled to room temperature. next,
After adding 6 parts of Disperse Yellow-5G (yellow),
The temperature was raised to 70 ° C. and the reaction was carried out for 5 hours. The average particle size of the dye particles in this dye solution was 6 μm (standard deviation σ10%). Excess components in the dyeing solution were removed by centrifugation three times to obtain a dispersion A. In this dispersion A, the solid content of 10
To 0 part, 1 part of a fluorine-containing quaternary ammonium salt shown below was added as a surface treatment agent, stirred for 1 hour at room temperature, and then charged into a spray dryer GS31 (made by Yamato Scientific Co., Ltd.) to obtain dry particles B. . The dried particles B were mixed at high speed in the same manner as in Production Example 1 of Yellow Toner 1 to obtain Yellow Toner 3.

Embedded image

(Production Example of Magenta Toner 3) Disperse Yellow 5G Disperse Red FB instead of 6 parts
Magenta toner 3 was obtained in exactly the same manner as in the production example of yellow toner 3 except that 4 parts of (magenta) was used.

(Production Example of Cyan Toner 3) Cyan Toner 3 was prepared in the same manner as Production Example of Yellow Toner 3 except that 4 parts of Disperse Blue Green B (cyan) was used instead of 6 parts of Disperse Yellow 5G. Obtained.

(Production of Carrier Used) Carrier α: Ferrite carrier coated with silicon resin (volume average particle diameter of about 50 μm, σs 65 emu / g)
(Aminosilane 4 parts in 100 parts of silicon resin, coat thickness 0.2 μm) Carrier β: Ferrite carrier coated with silicon resin (volume average particle size of about 50 μm, σs 65 emu / g)
(Aminosilane 4 parts and carbon black 2 parts in 100 parts of silicon resin, coat thickness 0.4 μm)

Example 1 Yellow toner 2, magenta toner 2, cyan toner 2
95 parts of carrier α was mixed with 5 parts of each color toner of 3 to obtain a color developer of three colors. Further, 95 parts of the carrier β was mixed with 5 parts of the black toner to obtain a black toner developer. These developers can be used with Ricoh Copier (PRETE
When a copy test was performed with R550) at room temperature and normal humidity (20 ° C., 50% RH), the initial image density (Macbeth densitometer) was high for each color and the image had a strong impact. When continuous copying ¹⁾ of 40,000 sheets was carried out, an excellent image having no unevenness in the solid image and no background stain was obtained. Next, in order to confirm the cleaning allowance of the photoconductor, replacement with a deteriorated cleaning blade ²⁾ and a copy test did not cause cleaning failure. The detailed results are summarized in Tables 1 and 2. 1) A full color 20% chart, A4 100 sheets, then a black character 6% chart, A4 100 sheets, a full color 20% chart, A4 100 sheets, and so on. 2) Used for continuous copying of 120,000 sheets.

Example 2 Yellow toner 3, magenta toner 3, cyan toner 3
95 parts of carrier α was mixed with 5 parts of each color toner of 3 to obtain a color developer of three colors. In addition, the same black toner developer as in Example 1 was prepared. When these developers were evaluated in the same manner as in Example 1, excellent images were obtained in which the initial image density was uniform in each color and the solid image was not uneven, and the background was free from stains. The image was particularly excellent in fine line reproducibility and felt sharp. Next, there was no problem with the cleaning allowance of the photoconductor as in Example 1. The detailed results are summarized in Tables 1 and 2.

Comparative Example 1 95 parts of carrier α was mixed with 5 parts of each color toner of yellow toner 1, magenta toner 1, cyan toner 1 and black toner 1 to obtain a developer of four colors. When these developers were evaluated in the same manner as in Example 1, the image density was insufficient and the image was felt light. Next, after the continuous copying was completed, the periphery of the developing section in the actual machine was observed, and intense toner scattering was confirmed in the black developing section. There was almost no cleaning margin for the photoconductor, and streaky stains frequently occurred on the image. The detailed results are summarized in Tables 1 and 2.

[0030]

[Table 1] φ: The color toner has the smallest sphericity of the three colors. Dv: The color toner has the maximum volume average particle diameter of the three colors. σ: For the color toner, the average coefficient of variation of the three colors is shown. ID (Y / M / C): image density of each color (toner adhesion amount 0.5 mg / cm ² ).

[0031]

[Table 2] ID (Y / M / C): Maximum image density of yellow, magenta, and cyan on the image

[0032]

According to the present invention, when a black toner having a larger particle size and a smaller sphericity is used as compared with the color toner, the cleaning property is improved. Further, normally, a black toner developer which is frequently used is easily deteriorated, but when a carrier containing carbon black is used, the toner is hardly scattered.
Further, the saturation image density can be easily obtained by increasing the coloring degree of the toner itself.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akemi Sugiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (6)

[Claims] 1. A plurality of toner developers used in a color copying machine, wherein the toner developers have a Wader practical sphericity ψ of 0.8 or more, a volume average particle diameter Dv of 4 to 8 μm, and a coefficient of variation ( An electrostatic charge comprising a color toner having a standard deviation / Dv) σ of 35% or less and a black toner having a smaller Wader practical sphericity and a larger volume average particle diameter than any of the color toners. Toner for image development. 2. At least a color toner among the toners has a Wader practical sphericity ψ of 0.8 or more, a volume average particle diameter Dv of 4 to 8 μm, a variation coefficient σ of 35% or less, and each color of these toners. The image density ID is 0.
^{2. The} toner for developing an electrostatic charge image according to claim 1, which has a yellow content of 5 or more, a magenta content of 1.3 or more, and a cyan content of 1.2 or more at 5 mg / cm ² . 3. The electrostatic image developing toner according to claim 1, wherein at least a color toner among the toners is a toner manufactured by a dispersion polymerization method. 4. A method for forming a multicolor image using an electrophotographic copying machine, comprising a plurality of toner developers, the toner developers comprising a color toner developer and a black toner developer. At least color toner among these toners is
Practical sphericity ψ of Wader is 0.8 and volume average particle diameter Dv
Is 4 to 8 μm, the coefficient of variation σ is 35% or less, and a carbon black-containing carrier is used only for the black toner developer, and a multicolor image forming method. 5. At least a color toner among the toners has a Wader practical sphericity of 0.8 or more, a volume average particle diameter Dv of 4 to 8 μm, a variation coefficient σ of 35% or less, and an image of each color of these toners. Density ID is 0.5 toner adhesion amount
The multicolor image forming method according to claim 4, wherein the content is 0.9 or more for yellow, 1.3 or more for magenta, and 1.2 or more for cyan at mg / cm ² . 6. The multicolor image forming method according to claim 4, wherein at least a color toner among the toners is a toner manufactured by a dispersion polymerization method.