JPH10268566A - Manufacture of color toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent color developing property and transparency even in the case of forming an image on a recording paper and an OHP sheet by mixing specific binder resin and chromatic coloring agent, and then, mixing specific binder resin with the mixture. SOLUTION: In the case of manufacturing color toner containing at least the binder resin and the chromatic coloring agent through a material mixing process, a melting/kneading process, a size reduction process and a classifying process, the material mixing process is provided with a 1st mixing process for mixing the binder resin having an average grain size of 1 to 3 mm and the chromatic coloring agent and a 2nd mixing process for mixing the binder resin having an average grain size of 0.1 to 0.5 mm with the mixture obtained at the 1st mixing process. The size of the coloring agent is more reduced at the 2nd mixing process, and it is allowed to put material other than the material mixed at the 1st mixing process, such as charge control agent and wax, etc., together with resin particles of a small grain size into the mixture and mix them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a color toner used in a full-color image forming apparatus such as a full-color electrostatic copying machine and a full-color laser beam printer.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image formed on an electrostatic latent image carrier such as a photoreceptor is developed using toner, and this toner image is transferred onto a recording member such as recording paper. Image forming methods for forming images are widely used in copiers, printers, facsimiles, and the like. In recent years, full-color image forming apparatuses that reproduce a multicolor image by superimposing a plurality of color toners have been put to practical use. I have.

In such a full-color image forming apparatus, for example, an electrostatic latent image is formed for each dot on a negatively charged organic photosensitive member by digital writing such as irradiation of a light beam, and this latent image is formed. Is developed in reverse using magenta toner, cyan toner, yellow toner and black toner as required, and a multicolor image is reproduced by superimposing toner images of each color.

The above-described full-color image formation mainly includes a picture,
It is used to reproduce photographs, graphic images, and the like. As described above, a multicolor image is reproduced by superimposing a plurality of color toners. Such multicolor images are widely used not only for forming images on recording paper but also for transparent sheets (OHP sheets) for overhead projectors. Even when a color toner image has a vivid color reproducibility when formed on a recording paper, the color becomes blackish when the image is formed on an OHP sheet and actually projected on a screen, and the color reproducibility is increased. Is reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a color toner which has solved the above-mentioned problems.

That is, an object of the present invention is to provide a method for producing a color toner having excellent color developability and transparency regardless of whether an image is formed on a recording paper or an OHP sheet.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method for producing a color toner, which comprises producing a color toner containing at least a binder resin and a chromatic colorant through a raw material mixing step, a melt kneading step, a pulverizing step and a classification step. In the method, the raw material mixing step is a first mixing step of mixing a chromatic colorant with a binder resin having an average particle size of 1 to 3 mm,
The average particle size of the mixture obtained in the first mixing step is 0.1 to 0.1.
And a second mixing step of mixing a 5 mm binder resin.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a toner of the present invention is a kneading and pulverizing method for producing toner particles through a raw material mixing step, a melt kneading step, a pulverizing step, and a classification step. In this case, the dispersibility of the chromatic colorant is improved, and the coloring and the transparency are improved. The chromatic colorant is usually a very small one at the time of synthesis.
Although it is obtained as secondary particles, when it is dried, secondary agglomeration occurs, resulting in a secondary aggregate having a volume average particle size of about 2 to 10 μm. When this secondary aggregate colorant is used,
The chromatic colorant cannot be sufficiently finely dispersed in the toner by simply producing the chromatic colorant in the toner simply by the usual kneading and pulverizing method. For this reason, the raw material mixing step is divided into multiple stages, and specific raw materials are sequentially mixed to sufficiently disintegrate the secondary agglomerated colorant to improve dispersibility.

First, as a first mixing step, the average particle size is 1 to 3
mm binder resin and chromatic colorant only. As the mixing device, a device such as a Henschel mixer that applies a shearing force to the object to be processed is used. When the binder resin particles having a large particle diameter and the colorant are mixed in such a manner, the colorant which has undergone secondary aggregation is quickly crushed because the large particle diameter resin particles have a large collision energy acting on the colorant. Once it has been crushed to some extent, it will no longer be finer.
On the other hand, when the small resin particles and the colorant are mixed,
Since the collision energy acting on the colorant is small, it takes time to disintegrate the secondary aggregated colorant. However, the colorant is disintegrated more finely than when large-diameter resin particles are used. be able to. From such a viewpoint, small-sized resin particles having an average particle size of 0.1 to 0.5 mm are added to the mixture obtained in the first mixing step using the large-sized resin particles, and secondly mixed. The colorant is finely crushed by the second mixing step. In the second mixing step, raw materials other than those mixed in the first mixing step, for example, a raw material such as a charge control agent or a wax may be charged and mixed together with the small-diameter resin particles. Furthermore, in the second mixing step, only the small-diameter resin particles are charged and mixed, and the other mixture is added to the obtained mixture, and the third mixing is performed, whereby the dispersibility of the colorant is further improved. Color reproducibility is improved.

[0010] When the toner fine powder generated in the pulverizing step or the classifying step is collected and reused as a raw material for toner production, the collected toner fine powder is put into the mixture obtained through the above-mentioned mixing step and mixed. I just need.

According to this method, fine dispersion of the chromatic colorant can be achieved without performing a pretreatment such as a flashing process or a master batch process on the chromatic colorant, thereby reducing the production cost. be able to.

In the present invention, the volume average particle diameter is obtained through a step of melt-kneading the mixture obtained by the above-described multi-stage mixing step, a step of pulverizing the cooled kneaded substance, and a step of classifying the obtained pulverized particles into fine powder. A toner having a chromatic colorant of 4 to 9 μm finely dispersed is obtained. The toner thus obtained has improved dispersibility of the chromatic colorant, and has excellent transparency and color reproducibility.

As the chromatic colorant usable in the present invention, known dyes and pigments can be used and are not particularly limited. I. Pigment Red 1-19, 21-23,
30-32, 37-41, 48-55, 57, 60, 6
3, 64, 68, 81, 83, 87 to 90, 112, 1
14, 122, 123, 163, 184, 202, 20
Magenta colorants such as C.6, 207 and 209; I.
Pigment Yellow 1-7, 10-17, 23, 65,
73, 83 and 180, C.I. I. Bat Yellow 1,
Yellow colorants such as 3 and 20; I. Pigment Blue 2, 3, 15 to 17 and the like. The content of the chromatic colorant is 100
It is 1 to 15 parts by weight, preferably 1 to 10 parts by weight based on parts by weight.

As the binder resin that can be used in the present invention, it is preferable to use a resin having specific melting characteristics in order to obtain excellent translucency and color reproducibility as a full-color toner. Is 5
× 10 ⁴ to 1 × 10 ⁶ poise, and the ratio V ₁ between the melt viscosity V _{1 at} 90 ° C. and the melt viscosity V _{2 at} 100 ° C.
/ V ₂ is 8 or more, and preferably V ₁ / V ₂ is 8 to 40. If the ratio V ₁ / V ₂ is smaller than 8, the surface smoothness of the image is impaired, and irregular reflection is likely to occur. Further, it is preferable to use a binder resin having a softening point of 90 to 115 ° C. from the viewpoint of fixability. The type of resin is not limited as long as it is such a binder resin, and for example, a styrene-acrylic copolymer resin, a polyester resin, an epoxy resin, or the like can be used, and these may be used alone or in combination. be able to. Among these resins, a polyester resin is particularly preferable.

In the present invention, a preferred polyester resin comprises a bisphenol A alkylene oxide adduct as an alcohol component as a main component, and a phthalic dicarboxylic acid or a phthalic dicarboxylic acid and an aliphatic dicarboxylic acid as an acid component. It is synthesized by a polycondensation reaction.

[0016] In the present invention, BET specific surface area of 20 to 300 m ² / g, preferably 30～250M ²
/ G of metal oxide fine particles may be dispersedly contained in the binder resin together with the coloring agent. As such metal oxide fine particles, it is necessary to use colorless or white particles which do not affect the color reproducibility of the color toner. For example, silicon oxide (silica), titanium dioxide (titania), aluminum oxide (alumina) ), Tin oxide, zinc oxide, calcium oxide and the like. From the viewpoint of environmental stability of the toner, it is preferable to use a hydrophobic metal oxide fine particle surface-treated with a hydrophobizing agent.

It is necessary to use a colorless, white or light-colored charge control agent. For example, chromium salicylate complex salts E-81 and 82 (manufactured by Orient Chemical Industries),
Zinc salicylate complex E-84 (manufactured by Orient Chemical Industries), aluminum salicylate complex E-86 (manufactured by Orient Chemical Industries), calixarene-based compound E-89
(Manufactured by Orient Chemical Industry Co., Ltd.), boron benzylate complex salts and the like.

If necessary, a wax such as a low molecular weight polypropylene wax, a low molecular weight polyethylene wax, a carnauba wax, a sasol wax or the like may be used to improve offset resistance. It may be added to prevent the toner from sticking to the regulating blade or the developing roller.

Further, in the present invention, in order to adjust the fluidity and chargeability of the toner particles obtained through the above-described steps, 0.2 to 3% by weight of inorganic fine particles with respect to the toner particles is used. External addition may be mixed. As such inorganic fine particles, silica, titania, alumina, strontium titanate, tin oxide and the like can be used alone or in combination of two or more. It is preferable to use inorganic fine particles that have been surface-treated with a hydrophobizing agent from the viewpoint of improving environmental stability. In addition, other than such an inorganic oxide, 1 μm
The following resin fine particles may be externally added to improve the cleaning property.

The color toner of the present invention can be used as a non-magnetic toner for a two-component developer used by mixing with a carrier, or as a non-magnetic one-component toner without using a carrier.

[0021]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited thereto. The binder resin used in the following Examples and Comparative Examples is a polyester resin obtained from bisphenol A propylene oxide adduct / bisphenol A ethylene oxide adduct / terephthalic acid, having a softening point of 98 ° C. and a glass transition point of 62 ° C. , Melt viscosity at 100 ° C. 1 × 10 ⁵ poise, melt viscosity at 90 ° C./melt viscosity at 100 ° C. = 9.

The above-mentioned softening point and melt viscosity were measured using a flow tester (CFT-500; manufactured by Shimadzu Corporation).
Using a die of 0 mm, heating rate 3.0 ° C./min, preheating time 180 seconds, load 30 kg, measurement temperature range 60-1
The measurement was performed under the condition of 40 ° C. The softening point of the sample was 1
The temperature at the time of outflow was taken as the softening point. The glass transition point was measured for a 10 mg sample weighed using a differential scanning calorimeter (DSC-200; manufactured by Seiko Denshi), and alumina was used as a reference at 30 to 80 ° C.
The shoulder value of the main endothermic peak in the range was defined as the glass transition point.

(Adjustment of Binder Resin Particles A1 and A2) The above-mentioned polyester resin was pulverized by a feather mill (screen: 3 mm), sieved with a 28-mesh sieve, and the material on the sieve was treated with binder resin particles A1 (average). (Particle size 1.8 mm). What passed through the sieve was obtained as binder resin particles A2 (average particle size 0.3 mm).

(Adjustment of Binder Resin Particles A3) The above-mentioned polyester resin was subjected to feather mill (screen: 5 mm).
And then sieved with an 8-mesh sieve, and the material on the sieve is binder resin particles A3 (average particle size 3.7 mm).
As obtained.

(Preparation of Binder Resin Particles A4) The above binder resin particles A2 are further sieved with a 120-mesh sieve, and those that have passed through the sieve are separated into binder resin particles A4.
(Average particle size 0.06 mm).

(Example 1) 3 parts of binder resin particles A1
00g and C.I. I. Pigment Red 184 (secondary aggregate volume average particle size: about 3 μm) 30 g
Was put into a 9-liter Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), and mixed at a peripheral speed of 40 m / sec for 5 minutes to perform first mixing. 700 g of the binder resin particles A2 and 10 g of a negative charge control agent (E-84; manufactured by Orient Chemical Industry Co., Ltd.) were added to the obtained mixture, and the peripheral speed was 40 m / sec.
Second mixing was performed by mixing for 4 minutes at c.

The obtained mixture is subjected to a twin screw extruder (PCM).
-30; manufactured by Ikegai Iron Works Co., Ltd.), and the cooled kneaded material was coarsely pulverized by a feather mill, finely pulverized by a jet mill, and further classified by a pneumatic classifier to obtain a magenta having a volume average particle size of 8.6 μm. Thus, toner particles A were obtained. The volume average particle size was measured using a coulter counter (manufactured by Coulter Electronics Co., Ltd.).

1000 g of the obtained toner particles were mixed with hydrophobic silica (TS5
00; manufactured by Cabosil Co., Ltd.) into a Henschel mixer and mixed at a peripheral speed of 20 m / sec for 2 minutes to obtain magenta toner A.

As chromatic colorants, C.I. I. Pigment Yellow 180 (secondary aggregate volume average particle size of about 2.
5 μm), except that the yellow toner A having a volume average particle size of 8.8 μm is the same as the magenta toner A.
I got Similarly, C.I. I. Pigment Blue 15-3 (secondary aggregate volume average particle size of about 3
A magenta toner A having a volume average particle size of 8.3 μm was obtained in the same manner as for the magenta toner A except that m.

Example 2 In the same manner as in Example 1, except that the amount of the binder resin particles A1 was changed to 600 g and the amount of the binder resin particles A2 was changed to 400 g, the magenta toner B and the yellow toner B were changed. And cyan toner B.

Example 3 In Example 1, the raw material to be charged in the second mixing step was limited to the binder resin particles A2 only, and a negative charge control agent was added to the mixture obtained in the second mixing, and the peripheral speed was changed. Magenta toner C, yellow toner C and cyan toner C were obtained in the same manner except that the third mixing was performed by mixing at 40 m / sec for 3 minutes.

(Example 4) In Example 1, the raw material to be added in the second mixing step was 70
Magenta toner D in the same manner except that 0 g, negative charge control agent 10 g, carnauba wax (manufactured by Kato Yoko Co., Ltd.) 20 g and hydrophobic silica (H2000; manufactured by Hoechst Co., Ltd .; BET specific surface area 140 m ² / g) were used. Yellow toner D and cyan toner D were obtained.

(Example 5) In Example 4, only the binder resin particles A2 were used as the raw materials to be charged in the second mixing step, and the mixture obtained in the second mixing was mixed with a negative charge control agent, carnauba wax and hydrophobic resin. Magenta toner E and yellow toner E in the same manner as above except that the third mixing is performed by charging the silica and mixing at a peripheral speed of 40 m / sec for 3 minutes.
And cyan toner E.

Comparative Example 1 In Example 1, 1 kg of the binder resin particles A1 and 30 g of the chromatic colorant were mixed at a peripheral speed of 40 m / sec for 9 minutes in the first mixing step, which was obtained in the first mixing step. A magenta toner F, a yellow toner F, and a cyan toner F were obtained in the same manner except that 10 g of a negative charge control agent was added to the mixture and mixed at a peripheral speed of 40 m / sec for 3 minutes.

Comparative Example 2 A magenta toner G, a yellow toner G and a cyan toner G were obtained in the same manner as in Comparative Example 1, except that the binder resin particles A1 were changed to the binder resin particles A2.

Comparative Example 3 In Comparative Example 1, the binder resin particles A1 (1 kg) were replaced with the binder resin particles A1.
(600 g) and binder resin particles A2 (400
g) A magenta toner H, a yellow toner H, and a cyan toner H were obtained in the same manner except for changing to g).

Comparative Example 4 A magenta toner I, a yellow toner I and a cyan toner I were obtained in the same manner as in Example 1, except that the binder resin particles A1 were changed to the binder resin particles A3.

Comparative Example 5 A magenta toner J, a yellow toner J and a cyan toner J were obtained in the same manner as in Example 1, except that the binder resin particles A2 were changed to the binder resin particles A4.

Comparative Example 6 In Comparative Example 1, except that 10 g of negative charge control agent, 20 g of carnauba wax (manufactured by Kato Yoko) and 10 g of hydrophobic silica (H2000; manufactured by Hoechst) were added in the second mixing step. In the same manner, magenta toner K, yellow toner K and cyan toner K were obtained.

The color toner A obtained as described above
Regarding each of Nos. To K, a full-color image was formed on an OHP sheet using a non-magnetic one-component developing type full-color printer described below. This image was projected on a screen by an OHP, and a color image on the screen was visually evaluated. Regarding the color reproducibility, ◎ indicates that the color reproducibility was excellent, る も の indicates that the color reproducibility was slightly poor, の indicates that the color reproducibility was low but the color could be identified, and △ indicates that the color was difficult to distinguish. Was evaluated as x. The transparency was evaluated as ◎ for bright ones, を for slightly bright ones, Δ for slightly dark ones, and x for dark ones. Table 1 shows the results.

[0041]

[Table 1]

The full-color printer used for this evaluation has the structure shown in FIG. 1, and is a photosensitive drum 10 (hereinafter, photosensitive body 10) that is driven to rotate in the direction of the arrow in the figure.
, Laser scanning optical system 20, full-color developing device 3
0, an endless intermediate transfer belt 40 that is driven to rotate in the direction of the arrow in the drawing, and a paper feed unit 60. Around the photoconductor 10, a charging brush 11 for charging the surface of the photoconductor 10 to a predetermined potential and a cleaner 12 for removing toner remaining on the photoconductor 10 are provided.

The laser scanning optical system 20 is a well-known type including a laser diode, a polygon mirror, and an fθ optical element, and its control unit includes cyan (C), magenta (M), yellow (Y), and black (BK). Each print data is transferred from the host computer. The laser scanning optical system 20 sequentially outputs print data for each color as a laser beam, and scans and exposes the photoreceptor 10. As a result, an electrostatic latent image for each color is sequentially formed on the photoconductor 10.

The full-color developing device 30 includes C, M, Y, B
The four color developing units 31C, 31M, 31Y, and 31BK containing a one-component developer composed of K non-magnetic toner are integrated, and can be rotated clockwise about a support shaft 33 as a fulcrum. Each developing device includes a developing sleeve 32 and toner regulating blades 34a and 34b. The toner conveyed by the rotation of the developing sleeve 32 is
It is charged by passing through a pressure contact portion (restriction portion) between 4a and 34b and the developing sleeve 32.

The intermediate transfer belt 40 is driven to rotate in the direction of the arrow in FIG. Intermediate transfer belt 40
Is pressed by the rotatable primary transfer roller 41 and the photosensitive member 1
0 is in contact. The intermediate transfer belt 40 is in contact with a rotatable secondary transfer roller 43 at a portion supported by a support roller 42.

Further, a cleaner 50 is provided in a space between the developing device 30 and the intermediate transfer belt 40. The cleaner 50 has a blade for removing residual toner on the intermediate transfer belt 40. The blade and the secondary transfer roller 43 can contact and separate from the intermediate transfer belt 40.

The paper supply unit 60 includes a paper supply tray 61 that can be opened to the front side of the image forming apparatus main body 1, a paper supply roller 62,
And a timing roller 63. The recording sheets S are stacked on a paper feed tray 61, fed one by one in the drawing by the rotation of a paper feed roller 62, and synchronized with an image formed on the intermediate transfer belt 40 by a timing roller 63. To the secondary transfer section. The horizontal transport path of the recording sheet is constituted by an air suction belt 66 and the like including the paper feed section, and a vertical transport path 80 provided with a transport roller is provided from the fixing device 70. Recording sheet S
Is discharged from the vertical conveyance path 80 to the upper surface of the image forming apparatus main body 1.

Here, the printing operation of the full-color printer will be described. When the printing operation is started, the photoconductor 10 and the intermediate transfer belt 40 are driven to rotate at the same peripheral speed, and the photoconductor 10 is charged to a predetermined potential by the charging brush 11.

Subsequently, exposure of the cyan image is performed by the laser scanning optical system 20, and an electrostatic latent image of the cyan image is formed on the photosensitive member 10. This electrostatic latent image is immediately developed by the developing device 31C, and the toner image is transferred onto the intermediate transfer belt 40 in the primary transfer section. Immediately after the end of the primary transfer, the developing device 31M is switched to the developing unit D, and then exposure, development, and primary transfer of the magenta image are performed. Further, switching to the developing device 31Y, exposure and development of a yellow image,
Primary transfer is performed. Further, switching to the developing device 31BK, exposure and development of a black image, primary transfer are performed, and
The toner image is superimposed on the intermediate transfer belt 40 every time the next transfer is performed.

When the final primary transfer is completed, the recording sheet S is sent to the secondary transfer section, and the full-color toner image formed on the intermediate transfer belt 40 is transferred onto the recording sheet S. When the secondary transfer is completed, the recording sheet S is conveyed to the belt-type contact heating and fixing device 70, where the full-color toner image is fixed on the recording sheet S and discharged to the upper surface of the printer body 1.

[0051]

According to the present invention, it is possible to provide a method for producing a color toner excellent in transparency and color development.

Further, according to the present invention, a color toner having the above-mentioned excellent characteristics can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a full-color printer.

[Explanation of symbols]

10: photosensitive drum, 11: charging brush, 12: cleaner, 20: optical system, 30: full color developing device, 4
0: intermediate transfer belt, 60: paper feed unit, 70: fixing unit.

Claims (3)

[Claims] 1. A method for producing a color toner, comprising producing a color toner containing at least a binder resin and a chromatic colorant through a raw material mixing step, a melt kneading step, a pulverizing step and a classification step, wherein the raw material mixing step is ,
A first mixing step of mixing a binder resin having an average particle diameter of 1 to 3 mm and a chromatic colorant, and mixing a binder resin having an average particle diameter of 0.1 to 0.5 mm into the mixture obtained in the first mixing step. A method for producing a color toner, comprising a second mixing step. 2. In the second mixing step, only the mixture obtained in the first mixing step and a binder resin having an average particle diameter of 0.1 to 0.5 mm are mixed, and the mixture obtained in the second mixing step is mixed. The method according to claim 1, further comprising a third mixing step of mixing raw materials other than the raw materials used in the first and second mixing steps. 3. The raw material other than the raw material used in the first mixing step is mixed with the binder resin having an average particle diameter of 0.1 to 0.5 mm in the second mixing step. Production method of color toner.