JP2838498B2 - Electrophotographic toner - Google Patents

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 used in a copying machine or a printer employing a hot roll fixing system.

[0002]

2. Description of the Related Art In recent years, as copiers and printers using an electrophotographic system have spread, the energy consumption (power consumption) has been reduced mainly for the purpose of dissemination to homes and multifunctional copiers or printers. Reduction), speeding up for the purpose of spreading to a so-called gray area located at the border between the printing machine and the copying machine is desired, or simplifying the heat fixing roll to reduce the machine cost, for example, low roll Pressure is desired. Also, with the upsizing of copiers, copiers equipped with a two-sided copy function and an automatic document feeder have become widespread, so the toner for electrophotography used in copiers and printers has a low fixing temperature, In order to prevent the occurrence of stains during double-sided copying and the occurrence of stains in an automatic document feeder, an electrophotographic toner having an excellent fixing strength to transfer paper is required.

Heretofore, attempts have been made to satisfy the above requirements by improving the molecular weight and molecular weight distribution of the binder resin as described below. Specifically, attempts have been made to lower the fixing temperature by using a resin having a low molecular weight as the binder resin. However, although the purpose of lowering the melting point of the toner can be achieved by using a binder resin having a low molecular weight, the melt viscosity also decreases at the same time, whereby the phenomenon that the toner adheres to the heat fixing roll, a so-called phenomenon. A new problem that an offset phenomenon occurs occurs. In order to prevent the occurrence of the 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 a high molecular portion has been performed. However, in order for the toner to have sufficient low-temperature fixability by these methods, the glass transition temperature of the binder resin has to be lowered in expectation of an anchor effect on transfer paper. However, simply lowering the glass transition temperature of the binder resin lowers the melting start temperature of the toner, causing the toner to start melting at around room temperature, resulting in a new problem that storage stability is impaired.
Also, if a large amount of low molecular weight resin in the binder resin is blended,
The toner itself becomes brittle and easily crushed due to mechanical friction or the like, and the transfer paper becomes dirty during double-sided copying and the inconvenience of contaminating the automatic document feeder occurs. There is also a method of including a release agent such as low molecular weight polypropylene to prevent the offset phenomenon. However, the melting point of conventionally commercially available low molecular weight polypropylene is 135 to 145 ° C., and when the low molecular weight polypropylene is contained in the toner and fixed at a low fixing temperature, the effect of preventing the offset phenomenon is sufficiently obtained. As a result, offset occurs and the melting point of the toner increases, so that there is a problem that sufficient fixing strength to transfer paper cannot be obtained. Japanese Patent Application Laid-Open No. 61-2 / 1986 discloses that a toner is blended with a Fischer-Tropsch wax made of coal.
No. 73554. However, such a toner is effective in preventing offset, but has a problem in storage stability of the toner in a high-temperature atmosphere.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to be able to fix at a low fixing temperature, to have no practical problem in non-offset property and storage stability, and to have excellent fixing strength to transfer paper. To provide a toner for electrophotography.

[0005]

SUMMARY OF THE INVENTION The present invention provides a differential scanning calorimeter.
An electrophotographic toner comprising a natural gas-based Fischer-Tropsch wax having a melting point of 85 to 100 ° C as measured by an analyzer .

Hereinafter, the present invention will be described in detail. The natural gas-based Fischer-Tropsch wax applied to the electrophotographic toner of the present invention is produced by the Fischer-Tropsch method using natural gas as a raw material, and is a waxy carbon synthesized by catalytic hydrogenation of carbon monoxide. Hydrogen. Structurally, such a natural gas-based Fischer-Tropsch wax, which is a linear paraffin-based wax having few methyl branches, includes Shell-MD.
S-brand product name: FT-100 etc. is on the market. Natural gas-based Fischer-Tropsch wax has a melting point of 85 to 85 according to a differential scanning calorimeter (hereinafter abbreviated as DSC).
It needs to be 100 ° C. When the melting point is lower than 85 ° C., a problem is likely to occur in the storage stability of the toner, and the fluidity is liable to deteriorate. On the other hand, if the temperature is higher than 100 ° C., the effect of lowering the melting start temperature of the toner is small, so that it is difficult to obtain low-temperature fixing characteristics of the toner. Also, natural gas-based Fischer-Tropsch wax is JIS K-22.
The penetration at 25 ° C. measured at 35 is preferably 2 or less, and if it is more than 2, the fluidity tends to be poor when the toner is formed, which causes problems in storage stability and triboelectricity with carrier particles. Easy to occur. Further, the content of the natural gas-based Fischer-Tropsch wax in the toner for electrophotography is preferably 1 to 20% by weight of the total toner. If the amount is less than 1% by weight, the releasability of the electrophotographic toner is insufficient, and the high-temperature offset resistance tends to be insufficient. Further, since the effect of lowering the melting start temperature of the toner is small, when fixing is performed at a low fixing temperature, it is difficult to obtain sufficient fixing strength on transfer paper. On the other hand, if the content is more than 20% by weight, the compatibility with the binder resin is poor, so that the dispersion of the wax tends to be poor, and the high-temperature offset resistance is liable to be deteriorated due to detachment of the wax alone during the pulverization, which is not preferable.

Next, materials other than the natural gas-based Fischer-Tropsch wax constituting the electrophotographic toner of the present invention, that is, a binder resin, a colorant and the like will be described. As the binder resin used in the present invention, polystyrene resin, polyacrylate resin, styrene-acrylate copolymer resin, styrene-methacrylate copolymer resin, polyvinyl chloride, polyvinyl acetate,
Polyvinylidene chloride, phenolic resin, epoxy resin,
A polyester resin is exemplified. Colorants include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate and mixtures thereof, and others. Can be mentioned. These colorants need to be contained in a sufficient ratio to form a visible image having a sufficient concentration, and usually a ratio of about 1 to 20 parts by weight based on 100 parts by weight of the binder resin. Is done.

The toner for electrophotography of the present invention comprises a natural gas-based Fischer-Tropsch wax, a binder resin and a colorant as described above, and other toner components such as a charge control agent.
The particles are particles containing a release agent, a magnetic material and the like in an appropriate dispersion, and have an average particle diameter of 5 to 20 μm. Further, a fluidity improver composed of silica fine powder or the like may be added to and mixed with the particles thus obtained to form an electrophotographic toner. The electrophotographic toner of the present invention is used for one component without mixing with a carrier composed of iron powder, ferrite, granulated magnetite, a fine resin powder containing a magnetic powder, etc. It may be used as a developer.

[0009]

A polypropylene wax conventionally used for electrophotographic toner (melting point: 135 to 145 ° C.)
Was excellent in high-temperature offset resistance, but had a high molecular weight and melting point and was not suitable for fixing at low temperatures. Therefore, it has been proposed to add a low melting point wax having a low melting point and a sharp melting behavior in order to lower the melting start temperature of the toner. However, petroleum paraffin wax conventionally known as low melting point wax and low melting point microcrystalline wax containing isoparaffin, naphthene, aromatic or the like have a problem in storage stability as a toner due to low molecular weight. Further, since the petroleum-based paraffin wax and microcrystalline wax have a penetration of as large as 5 or more, when they become fine powder such as toner, the powder fluidity is lowered and it is easy to adversely affect image characteristics. The natural gas-based Fischer-Tropsch wax applied to the present invention has a lower melting point than polypropylene wax, so that it has excellent low-temperature fixability, and is compatible with existing petroleum-based paraffins.
Very low melting point component compared to fin wax, so it has excellent storage stability and at the same time, its penetration is as small as 2 or less. Does not occur. In addition, the conventional method of extracting water gas from coal and synthesizing it by the Fischer-Tropsch method
Compared to coal-based Fischer-Tropsch wax, natural-gas-based Fischer-Tropsch wax not only satisfies the prevention of offset to the heat fixing roll and the storage stability of the toner at the same time, but also has the advantage of being able to supply toner at low cost because it is made from natural gas. Having.

[0010]

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

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

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

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

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

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

Comparative Example 1 Commercially available polypropylene wax (trade name: Viscol 550P, melting point 140 ° C., manufactured by Sanyo Chemical Industries, Ltd.) in place of the natural gas-based Fischer-Tropsch wax of Example 2.
Was obtained in the same manner as in Example 2 except that 6 parts of was mixed.

Comparative Example 2 In place of the natural gas-based Fischer-Tropsch wax of Example 2, a petroleum-based paraffin wax (manufactured by Nippon Seirowa Co., Ltd.)
Product name: No. An electrophotographic toner for comparison was obtained in the same manner as in Example 2 except that 155 melting point 70 ° C., penetration 15) 6 parts were used.

Comparative Example 3 Instead of the natural gas-based Fischer-Tropsch wax of Example 2, a petroleum-based paraffin wax (manufactured by Nippon Seirowa Co., Ltd.)
Product name: HNP-0190 Melting point 87 ° C, penetration 6) 6
An electrophotographic toner for comparison was obtained in the same manner as in Example 2 except that parts were used.

Comparative Example 4 Coal-based Fischer-Tropsch wax in place of the natural gas-based Fischer-Tropsch wax of Example 2 (trade name: H1 manufactured by Sasol Co., Ltd .; melting point is 80 ° C. and 107 ° C., penetration 1) 6 parts Example 2 except that
In the same manner as in Example 1, a comparative electrophotographic toner was obtained.

Next, the following items were tested for the electrophotographic toners obtained in the above Examples and Comparative Examples. (1) Non-offset temperature region and non-offset temperature range First, 4 parts of each electrophotographic toner and a non-coated ferrite carrier (trade name: FL-102, manufactured by Powder Tech)
0) 96 parts to prepare a two-component developer. Next, using the developer, a commercially available copying machine (trade name: SF-9800, manufactured by Sharp Corp.) was used to transfer 2c portraits onto A4 transfer paper.
A plurality of belt-shaped unfixed images having a width of 5 cm and a width of 5 cm were prepared. Then, a heat fixing roll having a surface layer formed of Teflon and a pressure fixing roll having a surface layer formed of silicone rubber are rotated in pairs, and the fixing device is rotated at a roll pressure of 1 kg / cm ² and a roll speed of 50 mm / sec. So as to gradually change the surface temperature of the heat fixing roll,
At each surface temperature, the toner image on the transfer paper having the unfixed image was fixed. At this time, observation was made as to whether or not the toner was contaminated in the blank portion, and a temperature region in which no contaminant was generated was defined as a non-offset temperature region. The difference between the maximum value and the minimum value in the non-offset temperature region was defined as the non-offset temperature width.

(2) Fixing Strength The surface temperature of the heat fixing roll of the fixing machine was set to 130 ° C., and the toner image on the transfer paper on which the unfixed image was formed was fixed. Then, the image density of the formed fixed image is measured with a reflection densitometer (trade name: RD-91, manufactured by Macbeth Co., Ltd.).
After measurement using 4), the fixed image was rubbed with a cotton pad, and then the image density was measured in the same manner. From the obtained measured values, the fixing strength was calculated according to the following formula, and used as an index of low energy fixing property. Fixing strength (%) = (image density of fixed image after rubbing / image density of fixed image before rubbing) × 100

(3) Fluidity The apparent density was measured according to JIS K5101 as an index indicating the fluidity of the toner. (4) Storage stability 20 g of the toner was put into a 150 cc polyethylene bottle and stored in a 50 ° C. constant temperature bath for 24 hours. After cooling to room temperature, the toner is taken out of the bottle and the fusion state (blocking) between the toner particles is observed. If no fusion occurs, a mark "O" indicates that fusion occurs and a practical problem of the toner occurs. Is marked with x. Table 1 shows the test results of the above items.

[0023]

[Table 1]

As is clear from the test results in Table 1, no offset occurs from the low temperature to the high temperature in the non-offset temperature region of the toner for electrophotography of the present invention, and the temperature range is 7 times.
It was confirmed that a practically sufficient range of 0 to 85 ° C. was maintained. Further, the fixing strength at a fixing temperature of 130 ° C. was 80% or more, and it was confirmed that there was no practical problem. It was also confirmed that there was no problem in fluidity and storage stability. In contrast, Comparative Example 1 had a high non-offset temperature on the low temperature side and a low fixing strength of 66%. In Comparative Example 2, the non-offset temperature width was as narrow as 55 ° C., the apparent density due to the fluidity was small, and there was a problem in storage stability. In Comparative Examples 3 and 4, it was confirmed that in the storage stability test, there was a problem that toner fusion occurred.

Further, using the developer in each embodiment of the above item (1), a commercially available copying machine (manufactured by Toshiba Corporation )
A continuous copy test was performed up to 000 sheets, and the results are shown in Table 2. As a result, it was confirmed that there was no problem in the image density, fog in the non-image area, and the triboelectric charge amount in all of the electrophotographic toners of Examples 1 to 6 of the present invention. In the case of a continuously copied original, the black part is 6
% A4, the image density is a reflection densitometer RD-914 manufactured by Macbeth, and the fog is a color difference meter manufactured by Nippon Denshoku .
Friction charge amount was used for the blow-off triboelectric charge measurement equipment manufactured by Toshiba Chemical Corporation.

[0026]

[Table 2]

[0027]

The toner for electrophotography of the present invention can maintain a sufficient non-offset temperature region and can be fixed at a low temperature, has excellent fixing strength and storage stability, and has a sufficient image density. This has the effect that one can obtain one sheet. Therefore, when the electrophotographic toner of the present invention is applied to a copying machine, a printer, or the like, power consumption can be reduced, and effects such as reduction in machine cost due to lower roll pressure and higher copying speed can be obtained.

Claims (3)

(57) [Claims] (1) a melting point of 85 to 85 measured by a differential scanning calorimeter;
An electrophotographic toner containing a natural gas-based Fischer-Tropsch wax at 100 ° C. 2. The electrophotographic toner according to claim 1, wherein the penetration of the natural gas-based Fischer-Tropsch wax at 25 ° C. is 2 or less. 3. The electrophotographic toner according to claim 1, wherein the content of the natural gas-based Fischer-Tropsch wax is 1 to 20% by weight in the total toner.