JPH08272150A - Liquid toner - Google Patents

Abstract

PURPOSE: To provide a liquid toner which can make effective transfer of an apparent image onto an intermediate transfer body and which is free from deterioration of the produced image such as dot tailing and roughing of the image. CONSTITUTION: An electrostatic latent image on an electrostatic latent image carrier is developed by a liquid toner, and the apparent image turned apparent by the development is contacted with an intermediate transfer body and transferred electrostatically, and this apparent image on the intermediate transfer body is re-transferred on a material to be transferred. This image forming method uses a liquid toner, wherein the condition 5<A/B<200 should be met where A represents the zeta potential in mv of toner particles while B represents the mean particle diameter (μm) of the toner particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention develops an electrostatic latent image on an electrostatic latent image carrier with a liquid toner and electrostatically develops the developed image by contacting it with an intermediate transfer member. After transferring to
The present invention relates to a liquid toner used in an image forming method for re-transferring a visible image on the intermediate transfer member onto a transfer material, for example, a liquid toner used in an image forming method used in a copying machine or a laser beam printer. It is a thing.

[0002]

2. Description of the Related Art As a liquid toner, Japanese Patent Publication No. 7-360
6, the average particle size of the toner particles is from 0.2 μm to
Liquid toner of 0.4 μm is known. However, after developing the electrostatic latent image on the electrostatic latent image carrier as described above with a liquid toner and electrostatically transferring the developed image visualized by this development to the intermediate transfer body, When such a toner is used in an image forming method of re-transferring a visible image on the intermediate transfer member to a transfer material, an image such as dot tailing (a phenomenon in which an image is tailed in the printing direction) Deterioration occurs. For this reason, there has been a demand for a toner that does not cause problems such as dot tailing in the image forming method described above.

[0003]

The requirements necessary for the toner used in the image forming method as described above include the following items. (1) When the visible image is electrostatically transferred while being in contact with the intermediate transfer member, the visible image is efficiently transferred to the intermediate transfer member, and there is no image deterioration such as dot tailing. (2) Sufficient print density.

The present invention was devised in view of the above-mentioned drawbacks, and an object of the present invention is to efficiently transfer a visible image to an intermediate transfer member, thereby causing image deterioration such as dot tailing and image roughening. It is to provide a liquid toner that does not bring about.

[0005]

As a result of earnest research, the inventors of the present invention set the ratio of the zeta potential of the toner particles in the liquid toner to the average particle diameter within a certain range, thereby achieving the above object of the present invention. The present invention has been completed by finding that the above can be achieved.

That is, according to the present invention, the electrostatic latent image on the electrostatic latent image carrier is developed by a liquid toner, and the developed image visualized by this development is electrostatically contacted with the intermediate transfer body. In the liquid toner used in the image forming method of re-transferring the developed image on the intermediate transfer member to the transfer material after the transfer, the zeta potential (mv) of the toner particles is A, and the average particle size of the toner particles ( The liquid toner is characterized in that A / B is 5 or more and 200 or less, where μm) is B.

The present invention will be described in detail below.

The liquid toner of the present invention comprises toner particles, which are colored particles containing a pigment or dye and a resin as main components, dispersed in a dispersion medium, and has a zeta potential (mv) of the toner particles of A And the average particle size (μm) of the toner particles is B
In that case, A / B is 5 or more and 200 or less, and preferably 20 or more and 150 or less.

In this image forming method, when the toner particles are transferred from the electrostatic latent image carrier to the intermediate transfer body, the latent image on the electrostatic latent image carrier is brought into contact with the electrostatic latent image carrier. Therefore, pressure is generated in the latent image. Here, it has been found that when the zeta potential of the toner is large, the structure tends to become unstable due to the repulsive force between the toner particles. However, a detailed study of this relationship has revealed that not only the zeta potential but also the average particle size of the toner particles is related. As a result of further earnest studies, it was found that when the zeta potential (mv) of the toner particles is A and the average particle diameter of the toner is B, dot tailing occurs when A / B exceeds 200. It was also found that the print density was low when A / B was less than 5.

The zeta potential is 10 mv or more 9
It is preferably 0 mv or less. Further, the average particle size of the toner particles is preferably in the range of 0.4 to 2.5 μm.

The dispersion medium used in the liquid toner of the present invention is preferably a petroleum hydrocarbon type insulating solvent such as n-hexane, n-heptane, n-nonane, n-octane, isooctane and indodecane. Petroleum-based aliphatic hydrocarbons such as ligroin and mixtures thereof (commercially available as "Isopar" E, G, manufactured by Esso Standard Oil Co., Ltd.
H, L, M "Cristol" 52,352, Shell Sole 71 manufactured by Shell Oil Co., Solvesso 150, etc.)
Is used.

The toner particles are mainly composed of a pigment or dye and a resin, but colored particles in which the pigment is dispersed in the resin are preferable. The proportion of the pigment in the particles is preferably 5% by weight or more and 30% by weight or less.

Examples of the resin include alkyd resin, styrene resin, phenol resin, acrylic resin, styrene-acrylic resin, polyester resin, rosin-modified phenol resin, rosin-modified maleic acid resin and rosin-modified fumaric acid resin. It is preferable to use a modified maleic acid resin or a rosin-modified fumaric acid resin.

Commonly used pigments and dyes are used. If they are black, carbon black (commercially available products are, for example, # 30, # 40, # 50, MA-1 manufactured by Mitsubishi Kasei Co., Ltd.).
1. Cabot MONARCH 700,900, R
In addition to EGAL300, 400, 600R, etc.), it is also possible to mix alkali blue with carbon black. Benzidine yellow is used for yellow, brilliant carmine, fast red, quinacridone red for red, phthalocyanine blue for indigo, and phthalocyanine green, oil violet, methyl orange, and methyl violet.

The toner particles are mainly composed of pigment and resin, but polyethylene glycol, polypropylene glycol or the like may be added for adjusting the softening point.

Further, in the particles, a charge control agent on the surface of the particles,
Wax or the like may be added to control charge and improve dispersibility.

The content of toner particles in the liquid toner of the present invention is not particularly limited, but is usually about 0.1 to 20% by weight.

The liquid toner of the present invention comprises a resin and a coloring agent.
Axial extruder, melt kneading by applying heat with a kneader, etc., after coarsely crushing it, together with additives such as a charge control agent and wax, if necessary, in the above dispersion medium,
It can be obtained by dispersing using a ball mill, a vibration mill, an attritor or the like. The longer the dispersion treatment is performed with a ball mill, a vibration mill, an attritor or the like, the smaller the particle size of the obtained particles. Therefore, it is possible to obtain the toner particles having a desired average particle diameter by appropriately selecting the dispersion treatment time.

The zeta potential of the toner particles can generally be increased by increasing the amount of charge control agent added and increasing the acid value of the resin. However, the combination of the resin and the type of charge control agent is also an important factor. Therefore, by selecting the appropriate type and acid value of the resin and the type and amount of the appropriate charge control agent corresponding to the resin, the desired zeta It is possible to obtain toner particles that have an electric potential.

Next, an image forming method using the liquid toner of the present invention will be described.

The liquid toner of the present invention develops the electrostatic latent image on the electrostatic latent image carrier with a liquid toner, and electrostatically develops the developed image by contacting the intermediate transfer body with the developed image. It is used in an image forming method in which a visible image on an intermediate transfer member is retransferred onto a transfer target material after being transferred onto the transfer material. This image forming method is
For example, it is used in a copying machine or a laser beam printer.

Here, the contact with the intermediate transfer member means that the intermediate transfer member and the electrostatic latent image bearing member are in contact with each other at two or more points without developing the toner. In the process of actually developing and transferring the toner, it is considered that the intermediate transfer body and the electrostatic latent image carrier are in contact with each other via the toner image.

As the intermediate transfer member of the present invention, one having a silicone rubber layer on the surface of rubber having high heat resistance such as fluororubber via an adhesive layer is used.

Further, the image forming method is a color image forming method, in which multiple colors are superposed on the intermediate transfer member.
It is preferable that the image forming method is one in which an image is formed, and a visible image on the intermediate transfer member is retransferred onto a transfer material by one transfer.

The material to be transferred referred to in the present invention is as follows.
Any type of paper, such as paper, plastic film, metal, cloth, and board, which can be printed normally, may be used.

[0026]

EXAMPLES The present invention will be described more specifically below based on Examples and Comparative Examples. However, the present invention is not limited to the following examples.

Method of Measuring Average Particle Size The average particle size was measured using a Shimadzu centrifugal sedimentation type particle size distribution analyzer SA-CP3. Dilute the liquid toner with the dispersion medium so that it matches the absorbance measurement range of the measuring machine. Furthermore, the particle size distribution of this sample was measured from the change in absorbance in the accelerated rotation mode of 240 rpm / min, and the median diameter was calculated as the average particle size.

Measuring method of zeta potential The zeta potential was measured using a light scattering photometer (ELS-800 manufactured by Otsuka Electronics Co., Ltd.). Dilute the liquid toner with the dispersion medium so that it matches the light scattering intensity range of the measuring machine. Furthermore, this sample was measured at a measurement angle of 20 ^° , a voltage of 40 V, and a measurement temperature of 25 ° C. using a narrow gap cell.

Example 1 Rosin-modified maleic acid resin (Uniletz 709, acid value 1
10, softening point 120 ° C, Union Camp Co., Ltd.) 154
0 g, carbon black (MOGUL-L) 400 g,
60 g of polyethylene glycol (PEG6000, manufactured by Sanyo Kasei Co., Ltd.) was premixed with a mixer, and then melt-kneaded using a twin-screw extruder (feed amount 2 kg / hr, temperature 100 ° C.). After cooling the obtained melt-kneaded product, a sample mill was used to obtain a coarse powder having a particle size of about 50 μm. 200 g of this coarse powder and acrylic polymer type charge control agent solution 1
10 g (produced by the method described in Example XI of US Pat. No. 3,900,412, solid content: 14%), carnauba wax 15 g, and Isopar M (isoparaffin solvent, manufactured by Exxon) 1250 g are mixed, It was pulverized for 7 hours in a vibration mill to obtain a liquid toner having an average particle diameter of 1 μm. This stock solution was diluted with Isopar M to a solid content concentration of 2% to obtain a developer. Further, when this developer was diluted and the zeta potential was measured using a light scattering photometer, it was 50 mv. A liquid toner having an A / B of 50 was obtained.

Using a Se drum as a photoconductor, development with the liquid developer thus obtained, an image is formed on an intermediate transfer member having a silicone rubber stuck on the drum as the outermost layer, and the image is formed. When a linear pressure of 20 kg was applied to the art paper under the condition that the temperature of the pressure roller was 200 ° C., good printed matter without dot tailing could be obtained. Further, when the solid portion was measured with a Macbeth densitometer, the print density was 1.5, and it was found that there was no problem.

Comparative Example 1 Rosin-modified maleic acid resin (Uniletz 709, acid value 1
10, softening point 120 ℃, manufactured by Union Camp) 140
0 g, carbon black (MOGUL-L) 400 g,
200 g of polyethylene glycol (PEG6000, manufactured by Sanyo Kasei Co., Ltd.) was premixed with a mixer and then melt-kneaded using a twin-screw extruder (feed amount 2 kg / hr, temperature 100 ° C.). After cooling the obtained melt-kneaded product, a sample mill was used to obtain a coarse powder having a particle size of about 50 μm. 200 g of this coarse powder and acrylic polymer type charge control agent solution 10
g (prepared by the method described in Example XI of US Pat. No. 3,900,412, solid content 14%), carnauba wax 15 g, Isopar M (isoparaffinic solvent,
1250 g (manufactured by Exxon) and pulverized for 6 hours with an attritor to obtain a liquid toner stock solution having an average particle size of about 2 μm. This stock solution was diluted with Isopar M to a solid content concentration of 2% to obtain a developer. Further, when this developer was diluted and the zeta potential was measured using a light scattering photometer, it was 5 mv. A liquid toner having an A / B of 2.5 was obtained.

When the same evaluation as in Example 1 was carried out using this developer, it was found that the print density was 0.8, which was an insufficient print density.

Comparative Example 2 A toner was produced under the same conditions as in Example 1 except that the dispersion time was 11 hours. The average particle size was 0.3 μm.
A liquid toner having m and zeta potential of 80 mv was obtained. A /
B was 267.

When printing was performed using this toner in the same manner as in the example, dot tailing occurred in which dots flowed in the printing direction, and a good image could not be obtained.

[0035]

As described above, the liquid toner of the present invention is used.
By using, it is possible to obtain a good image without dot tailing.

Claims (1)

[Claims] 1. An electrostatic latent image on an electrostatic latent image carrier is developed with a liquid toner, and the developed image visualized by this development is electrostatically transferred while contacting an intermediate transfer body, In the liquid toner used in the image forming method in which the visible image on the intermediate transfer member is retransferred onto the transfer material, the zeta potential (m
v) is A and the average particle diameter (μm) of the toner particles is B, A / B is 5 or more and 200 or less.