JPH06230600A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To provide an electrophotographic toner fixable at a low fixing temp., causing no problem with respect to offsetting property in practical use and excellent in fixing strength to transfer paper. CONSTITUTION:This electrophotographic toner contains at least one kind of vegetable wax selected from among candelilla wax, carnauba wax and rice wax each having <=3mgKOH/g acid value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner, and more particularly to an electrophotographic toner for a copying machine or printer which employs heat roll fixing.

[0002]

2. Description of the Related Art In recent years, with the spread of electrophotographic copying machines and printers in general households and the like, energy saving (power consumption) has been mainly aimed at making multifunctional copying machines or printers. It is desired that the speed be increased for the purpose of spreading to a so-called gray area located at the boundary between the printing machine and the copying machine, or that the roll pressure be reduced to simplify the fixing roll to reduce the machine cost. ing. In addition, copiers equipped with a double-sided copy function and an automatic document feeder have become widespread with the sophistication of copiers, and therefore the fixing temperature of electrophotographic toner used in copiers and printers is low and There is a demand for a sheet having excellent offset properties and excellent fixing strength on a transfer sheet in order to prevent stains during double-sided copying and stains in the automatic document feeder.

In response to the above demands, in the prior art, the following proposals have been made to improve the molecular weight and molecular weight distribution of the binder resin.

Specifically, attempts have been made to lower the fixing temperature by lowering the molecular weight of the binder resin. However, when the molecular weight is lowered, the melting point is lowered, but at the same time, the viscosity is also lowered, which causes a problem that an offset phenomenon occurs on the fixing roll. In order to prevent this offset phenomenon, a method of widening the low molecular weight region and the high molecular weight region of the molecular weight distribution of the binder resin, or cross-linking of the polymer portion has been performed. However, in this method, the glass transition temperature of the resin must be lowered in order to have sufficient fixing property, and it is unavoidable that the preservability of the toner is impaired. Further, if the low molecular weight portion of the binder resin is increased, the toner itself becomes brittle, and stains are generated during double-sided copying and stains on the automatic document feeder. Furthermore, there is also a method of incorporating a polyolefin-based release agent in order to prevent the offset phenomenon. However, when the release agent is contained, the melting point of the toner becomes high,
Therefore, when fixing is performed at a low fixing temperature, there is a problem that sufficient fixing strength on the transfer paper cannot be obtained.

[0005]

The object of the present invention is to fix an electrophotographic toner which can be fixed at a low fixing temperature, does not cause any practical problem in offset property, and has excellent fixing strength on a transfer paper. To provide.

[0006]

According to the present invention, at least one selected from candelilla wax, carnauba wax and rice wax having an acid value of 3 mgKOH /
An electrophotographic toner containing a vegetable wax of g or less.

The present invention will be described in detail below. The candelilla wax applied to the electrophotographic toner of the present invention is
Carnauba wax is a plant wax that is refined from carnauba wax, carnauba palm from rice wax, and rice wax from rice bran oil. These waxes have a lower softening point than those of animal waxes, mineral waxes, petroleum waxes or synthetic waxes and dissolve sharply with heat. The softening point of the toner is lowered, and even the low temperature heat fixing roll is sufficiently melted to enable low energy fixing. Since the waxes according to the present invention have an acid value of 3 mgKOH / g or less, the content of free fatty acids in the wax is small, which has the effect of suppressing an increase in the triboelectric charge amount when copying a large number of sheets. You can get quality. The acid value of the waxes is 3 mgKO
If it is larger than H / g, the triboelectric charge amount increases when a large number of sheets are copied, and a practically sufficient image density cannot be obtained.

The method for obtaining candelilla wax, carnauba wax and rice wax having an acid value of 3 mgKOH / g or less is a method of accelerating the esterification at the time of refining the wax to reduce the acid value, and a commercially available wax described above and a polyhydric alcohol. To reduce the acid value by esterification, to melt the commercially available wax under heating and reduced pressure to reduce the acid value, or to add a solvent such as an aqueous alkali solution to the commercially available wax, and to remove the alcohol content. And the like to reduce the acid value. The method for measuring the acid value of candelilla wax, carnauba wax and rice wax is in accordance with JIS K5902. Acid value 3 mgK in the electrophotographic toner of the present invention
The content of candelilla wax, carnauba wax, and rice wax of OH / g or less is 3 to 30% by weight in the resin component composed of the binder resin and the plant wax constituting the electrophotographic toner. preferable. Three
If it is less than wt%, the effect of including the above wax is not so great, and sufficient fixing strength for transfer paper in low temperature fixing cannot be obtained. On the other hand, if it is more than 30% by weight, high temperature offset is likely to occur, which is not preferable.

Next, materials other than the vegetable wax constituting the toner for electrophotography of the present invention, that is, the binder resin, the colorant and the like will be described. As the binder resin used in the present invention, polystyrene resin, polyacrylic acid ester resin, styrene-acrylic acid ester copolymer resin, styrene-methacrylic acid ester copolymer resin, polyvinyl chloride, polyvinyl acetate, polyvinyl Examples thereof include vinylidene chloride, phenol resin, epoxy resin, polyester resin and the like. As the colorant, carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red,
Examples thereof include quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate and a mixture thereof, and the like. It is necessary that these colorants are contained in a sufficient amount so that a visible image having a sufficient density can be formed.
The ratio is about 1 to 20 parts by weight with respect to 00 parts by weight.

The electrophotographic toner of the present invention is a particle obtained by appropriately dispersing and containing other toner components such as a charge control agent, a release agent and a magnetic material in the above-mentioned plant wax, binder resin and colorant. And the average particle size is 5 to 2
It is in the range of 0 μm. A toner for electrophotography may be formed by adding and mixing a fluidity improver made of fine silica powder or the like to the particles thus obtained.

The electrophotographic toner of the present invention may be used as a two-component developer by being mixed with a carrier composed of iron powder, ferrite, granulated magnetite or the like, or may be used as a carrier when a magnetic substance is contained. It may be used as it is in the development of an electrostatic image as a one-component developer without being mixed.

[0012]

EXAMPLES The present invention will be described below based on examples. In the examples, “part” means “part by weight”. Example 1 The raw materials having the above blending ratios are mixed with a super mixer, hot melt kneaded with a twin-screw kneader, pulverized with a jet mill, and then classified with a dry air stream classifier to obtain an average particle diameter of 10
Particles of μm were obtained. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-53 manufactured by Cabot Corporation)
0.4 parts of 0) was stirred for 1 minute in a Henschel mixer, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Embodiment 2 The raw materials having the above blending ratios are mixed with a super mixer, hot melt kneaded with a twin-screw kneader, pulverized with a jet mill, and then classified with a dry air stream classifier to obtain an average particle diameter of 10
Particles of μm were obtained. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-53 manufactured by Cabot Corporation)
0.4 parts of 0) was stirred for 1 minute in a Henschel mixer, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Example 3 The raw materials having the above blending ratios are mixed with a super mixer, hot melt kneaded with a twin-screw kneader, pulverized with a jet mill, and then classified with a dry air stream classifier to obtain an average particle diameter of 10
Particles of μm were obtained. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-53 manufactured by Cabot Corporation)
0.4 parts of 0) was stirred for 1 minute in a Henschel mixer, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Example 4 The raw materials having the above blending ratios are mixed with a super mixer, hot melt kneaded with a twin-screw kneader, pulverized with a jet mill, and then classified with a dry air stream classifier to obtain an average particle diameter of 10
Particles of μm were obtained. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-53 manufactured by Cabot Corporation)
0.4 parts of 0) was stirred for 1 minute in a Henschel mixer, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Example 5 The raw materials having the above blending ratios are mixed with a super mixer, hot melt kneaded with a twin-screw kneader, pulverized with a jet mill, and then classified with a dry air stream classifier to obtain an average particle diameter of 10
Particles of μm were obtained. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-53 manufactured by Cabot Corporation)
0.4 parts of 0) was stirred for 1 minute in a Henschel mixer, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Embodiment 6 The raw materials having the above blending ratios are mixed with a super mixer, hot melt kneaded with a twin-screw kneader, pulverized with a jet mill, and then classified with a dry air stream classifier to obtain an average particle diameter of 10
Particles of μm were obtained. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-53 manufactured by Cabot Corporation)
0.4 parts of 0) was stirred for 1 minute in a Henschel mixer, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Comparative Example 1 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the candelilla wax having an acid value of 2.8 mgKOH / g was not mixed.

Comparative Example 2 The same procedure as in Example 1 was repeated except that 10 parts of polypropylene wax (trade name: Viscole 550P manufactured by Sanyo Chemical Industry Co., Ltd.) was mixed in place of the candelilla wax having an acid value of 2.8 mgKOH / g. A comparative electrophotographic toner was obtained.

Comparative Example 3 A comparative example was prepared in the same manner as in Example 1 except that 10 parts of a candelilla wax having an acid value of 3.8 mgKOH / g was mixed in place of the candelilla wax having an acid value of 2.8 mgKOH / g. An electrophotographic toner was obtained.

Comparative Example 4 Comparative Example 4 was carried out in the same manner as in Example 1 except that 10 parts of a candelilla wax having an acid value of 9.6 mgKOH / g was mixed in place of the candelilla wax having an acid value of 2.8 mgKOH / g. An electrophotographic toner was obtained.

Comparative Example 5 A comparative example was prepared in the same manner as in Example 3 except that 10 parts of carnauba wax having an acid value of 3.5 mgKOH / g was mixed in place of carnauba wax having an acid value of 2.2 mgKOH / g. An electrophotographic toner was obtained.

Comparative Example 6 Comparative Example 6 was carried out in the same manner as in Example 3 except that 10 parts of carnauba wax having an acid value of 8.5 mgKOH / g was mixed in place of carnauba wax having an acid value of 2.2 mgKOH / g. An electrophotographic toner was obtained.

Comparative Example 7 An electrophotographic photograph for comparison was made in the same manner as in Example 5 except that 10 parts of a rice wax having an acid value of 3.6 mgKOH / g was mixed in place of the rice wax having an acid value of 2.5 mgKOH / g. To obtain toner for use.

Comparative Example 8 An electrophotographic photograph for comparison was made in the same manner as in Example 5 except that 10 parts of a rice wax having an acid value of 9.8 mgKOH / g was mixed in place of the rice wax having an acid value of 2.5 mgKOH / g. To obtain toner for use.

Next, the following items were tested for the above Examples and Comparative Examples. (1) Non-Offset Temperature Region First, 4 parts of each electrophotographic toner obtained in the above-mentioned Examples and Comparative Examples and 96 parts of a ferrite carrier (Powder Tech Co., Ltd. product name: FL-1020) not coated with a resin were prepared. A two-component developer was prepared by mixing. Next, a commercially available copying machine (trade name: SF-9, manufactured by Sharp Corporation) is used using the developer.
800), a plurality of belt-shaped unfixed images having a length of 2 cm and a width of 5 cm were formed on an A4 transfer paper. Next, a heat-fixing roll having a surface layer made of Teflon and a pressure-fixing roll having a surface layer made of silicone rubber are paired and rotated in a fixing machine at a roll pressure of 1 Kg / cm ² and a roll speed of 10.
The surface temperature of the heat fixing roll was changed stepwise so that the toner image on the transfer paper having the unfixed image was fixed at each surface temperature. At this time, it was observed whether or not the toner was smeared in the blank area, and the temperature region in which the toner was not smeared was set as the non-offset temperature region.

(2) Fixing strength The surface temperature of the heat fixing roll of the fixing machine is 150 ° C. and 1
The temperature was set to 70 ° C., and the toner image on the transfer paper on which the unfixed image was formed was fixed. Then, the formed fixed image was rubbed with a cotton pad, and the fixing strength was calculated by the following formula to be used as an index of low energy fixing property.
As the image density, a reflection densitometer RD-914 manufactured by Macbeth was used. Fixing strength (%) = image density of fixed image after rubbing / image density of fixed image before rubbing × 100

(3) Multiple copy test 1000 using a commercially available copying machine (trade name: SF-9800 manufactured by Sharp Co.) using each developer described in (1) above.
A continuous copy test up to 0 sheets was performed, and the initial and 100
The triboelectric charge amount and the image density after the 00th sheet were measured. In addition,
The copied original is A4 with 10% black,
For the triboelectric charge amount, a blow-off triboelectric charge amount measuring device manufactured by Toshiba Chemical Co. was used, and as the image density, a reflection densitometer RD-914 manufactured by Macbeth Co. was used. Table 1 shows the test results of the above items
And shown in Table 2.

[0029]

[Table 1]

[0030]

[Table 2]

As is clear from the test results of Tables 1 and 2, the non-offset temperature range of the electrophotographic toner of the present invention does not cause an offset from a low temperature to a high temperature, and its temperature range is 65 to 75 ° C. It was confirmed that the practically sufficient range was maintained. Further, the fixing strength at a fixing temperature of 150 ° C. is 60% or more, which has a practically sufficient fixing strength, is stable without increasing the triboelectric charge amount even after copying 10,000 sheets, and has an image density after copying 10,000 sheets. It was confirmed that the initial high concentration was maintained. On the other hand, in Comparative Examples 1 and 2, the fixing temperature was 150.
It was confirmed that the fixing strength at ° C was as low as 45%. Further, in Comparative Examples 3 to 8, it was confirmed that the triboelectric charge amount increased at the time of copying a large number of sheets and the image density after copying 10,000 sheets was remarkably lowered.

[0032]

The electrophotographic toner of the present invention is capable of fixing at a low temperature while maintaining a sufficient non-offset temperature region, is excellent in fixing strength, and is capable of obtaining a sufficient number of image densities. It has the effect of being able to.

Claims (1)

[Claims] 1. At least one selected from candelilla wax, carnauba wax and rice wax.
An electrophotographic toner containing a seed type plant wax having an acid value of 3 mgKOH / g or less.