JP2838509B2 - 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 could be achieved by using a binder resin having a low molecular weight, the melt viscosity also decreased at the same time, whereby the phenomenon that the toner adhered to the heat fixing roll, There is a new problem that a so-called offset phenomenon 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, and the toner starts melting at around room temperature,
There has been a new problem that storage stability is impaired. Also, if a large amount of low molecular weight resin is mixed in the binder resin, the toner itself becomes brittle and easily crushed due to mechanical friction, etc., and the transfer paper becomes dirty during double-sided copying, and the automatic document feeder is contaminated. The inconvenience of doing so occurred.
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. Although such a toner is effective in preventing offset, it has a problem in the storage stability of the toner in a high-temperature atmosphere.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic apparatus which can fix at a low fixing temperature, does not cause any practical problem in non-offset properties, and has excellent fixing strength to transfer paper. To provide a toner.

[0005]

The present invention comprises a natural gas-based Fischer-Tropsch wax and a toner having a melt viscosity at 110 ° C. of 1 × 10 ⁵ to 1 × 10 ⁶ po.
a toner for electrophotography, which is an electrophotographic toner.

Hereinafter, the present invention will be described in detail. The Fischer-Tropsch wax applied to the electrophotographic toner of the present invention is produced by a Fischer-Tropsch method using natural gas as a raw material, and is a waxy hydrocarbon synthesized by catalytic hydrogenation of carbon monoxide. And structurally, it is a linear paraffin wax having few methyl branches. Such natural gas-based Fischer-Tropsch wax is a product name of Shell MDS:
FT-100, FT-0030, FT-0050, FT
-0070, FT-0165, FT-1155, FT-
60S etc. are on the market. Natural gas-based Fischer-Tropsch wax is a differential scanning calorimeter (hereinafter referred to as DS).
And a melting point of 85 to 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, when the temperature is higher than 100 ° C., the effect of lowering the melt viscosity of the toner is small, so that it is difficult to obtain low-temperature fixability of the toner. The natural gas-based Fischer-Tropsch wax preferably has a penetration at 25 ° C. of 2 or less as measured by JIS K-2235. A problem is likely to occur in the properties and the triboelectricity with the carrier particles. The natural gas-based Fischer-Tropsch wax is not very compatible with the binder resin, so if used in a large amount, the dispersion of the wax deteriorates, and the high-temperature offset resistance due to detachment of the wax alone during pulverization, the fluidity deteriorates. It is not preferable because it is easy. Therefore, 1 to 1
Preferably it is 20% by weight.

Further, the electrophotographic toner of the present invention comprises 11
The melt viscosity at 0 ° C. is 1 × 10 ⁵ to 1 × 10 ⁶ pois
It is necessary to be e for the following reason. That is, since the natural gas-based Fischer-Tropsch wax used in the present invention has a low melting point as described above, the dispersibility of the natural gas-based Fischer-Tropsch wax when directly used in a binder resin conventionally used for a polypropylene wax is used. May be inferior. This is because the conventional binder resin has a melt viscosity characteristic suitable for the melting point of the polypropylene wax, and the dispersibility of the wax is improved by kneading at a kneading temperature suitable for the polypropylene wax. However, when using the natural gas-based Fischer-Tropsch wax used in the present invention, the difference in melt viscosity between the natural resin-based Fischer-Tropsch wax and the natural gas-based Fischer-Tropsch wax is large. , The non-offset temperature on the low temperature side increases, and the fixing strength at low temperature fixing is low. On the other hand, if the kneading temperature is too low, the high molecular weight body of the binder resin is cut, and the high-temperature offset resistance deteriorates. Therefore, the inventor tried to lower the molecular weight ratio of the binder resin by lowering the molecular weight ratio by further lowering the molecular weight of the binder resin and increasing the molecular weight of the polymer to lower the melting start temperature of the binder resin to 110 ° C. or lower.
A binder resin having a melt viscosity at 0 ° C. of 1 × 10 ⁶ poise or less was prepared. The resin is used to reduce the difference in melt viscosity from natural gas-based Fischer-Tropsch wax, and is kneaded at a lower temperature than in the prior art, so that the melt viscosity at 110 ° C. of the electrophotographic toner is 1 × 10 ⁵ to 1x
It was 10 ⁶ poise. The melt viscosity of such an electrophotographic toner at 110 ° C. is 1 × 10 ⁵ to
By setting it to 1 × 10 ⁶ poise, the dispersibility of the natural gas-based Fischer-Tropsch wax is improved, the non-offset temperature region can be set to a lower temperature side, the fixing strength of low-temperature fixing increases, and the high-temperature resistance increases. The offset property is improved. 11 of electrophotographic toner
If the melt viscosity at 0 ° C. is lower than 1 × 10 ⁵ poise, problems such as deterioration of storage stability and occurrence of high-temperature offset occur. If the melt viscosity is higher than 1 × 10 ⁶ poise, low-temperature kneading cannot be performed. Dispersion becomes poor, resulting in poor fluidity and high-temperature offset. The melting start temperature and the melt viscosity in the present invention were measured using a flow tester CFT-500 manufactured by Shimadzu Corporation, using a die 1.0 × 1.0 (mm) and a load of 20 kgF.
It was measured at a preheating of 60 to 80 ° C and a heating rate of 6 ° C / min. Further, the melting point by DSC in the present invention is the peak temperature of the absorbed heat, and is the
The process of raising the temperature between 20 and 150 ° C. at a rate of 10 ° C./min using C-5200 and then rapidly cooling from 150 ° C. to 20 ° C. was repeated twice, and the second heat absorption was measured.

Next, materials other than Fischer-Tropsch wax made from natural gas, which constitute the electrophotographic toner of the present invention, that is, binder resins, colorants and the like will be described. Examples of the binder resin used in the present invention include polystyrene resin, polyacrylate resin, styrene-acrylate copolymer resin, styrene-methacrylate copolymer resin, polyvinyl chloride, polyvinyl acetate, and poly (vinyl acetate). Examples include vinylidene chloride, a phenol resin, an epoxy resin, and a polyester resin. 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.

[0010]

The polypropylene wax (melting point: 135 to 145 ° C.) conventionally used for electrophotographic toner 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. Petroleum paraffin wax and low-melting microcrystalline wax containing isoparaffin, naphthene, aromatic, etc., which have been conventionally known as low-melting wax, 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 and thus has excellent low-temperature fixability, and has a very low melting point component compared to existing petroleum-based paraffin wax and thus has excellent storage stability. At the same time, since the penetration is as small as 2 or less, the fluidity is not impaired when the toner is formed, and there is no problem in triboelectric charging. Also, compared to conventional coal-based Fischer-Tropsch wax, which extracts water gas from coal and synthesizes it by the Fischer-Tropsch method, natural-gas-based Fischer-Tropsch wax only simultaneously satisfies the prevention of offset to the heat fixing roll and the storage stability of the toner. In addition, since natural gas is used as a raw material, there is an advantage that toner can be supplied at low cost.

[0011]

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 with a super mixer, and after hot-melt kneading with a twin-screw kneader (set temperature 105 ° C.),
The particles were pulverized by a jet mill and then classified by a dry air classifier to obtain particles having an average particle diameter of 10 μm. Then, 100 parts of the particles and 0.3 parts of hydrophobic silica (trade name: Cabosil TS-530, manufactured by Cabot Corp.) are stirred for 1 minute in a Henschel mixer to adhere the hydrophobic silica to the surface of the particles, and the present invention is applied. Was obtained. The melt viscosity of this toner at 110 ° C. was 9 × 10 ⁵ poise.

Embodiment 2 The raw materials having the above mixing ratios are mixed with a super mixer, and after hot-melt kneading with a twin-screw kneader (set temperature 100 ° C.),
The particles were pulverized by a jet mill and then classified by a dry air classifier to obtain particles having an average particle diameter of 10 μm. Then, 100 parts of the particles and 0.3 parts of hydrophobic silica (trade name: Cabosil TS-530, manufactured by Cabot Corp.) are stirred for 1 minute in a Henschel mixer to adhere the hydrophobic silica to the surface of the particles, and the present invention is applied. Was obtained. The melt viscosity of this toner at 110 ° C. was 7 × 10 ⁵ poise.

Embodiment 3 The raw materials having the above mixing ratios are mixed with a super mixer, and after hot-melt kneading with a twin-screw kneader (set temperature 100 ° C.),
The particles were pulverized by a jet mill and then classified by a dry air classifier to obtain particles having an average particle diameter of 10 μm. Then, 100 parts of the particles and 0.3 parts of hydrophobic silica (trade name: Cabosil TS-530, manufactured by Cabot Corp.) are stirred for 1 minute in a Henschel mixer to adhere the hydrophobic silica to the surface of the particles, and the present invention is applied. Was obtained. The melt viscosity of this toner at 110 ° C. was 6 × 10 ⁵ poise.

Embodiment 4 The raw materials having the above mixing ratios are mixed with a super mixer, and after hot-melt kneading with a twin-screw kneader (set temperature 100 ° C.),
The particles were pulverized by a jet mill and then classified by a dry air classifier to obtain particles having an average particle diameter of 10 μm. Then, 100 parts of the particles and 0.3 parts of hydrophobic silica (trade name: Cabosil TS-530, manufactured by Cabot Corp.) are stirred for 1 minute in a Henschel mixer to adhere the hydrophobic silica to the surface of the particles, and the present invention is applied. Was obtained. The melt viscosity of this toner at 110 ° C. was 6 × 10 ⁵ poise.

Comparative Example 1 In Example 1, the melting start temperature was changed to 117 ° C. and 120 ° C. instead of the styrene-acrylate copolymer resin.
Styrene-acrylate copolymer resin having a melt viscosity of 7 × 10 ⁵ poise (melt viscosity cannot be measured at 110 ° C.) (trade name: CPR-, manufactured by Mitsui Toatsu Chemicals, Inc.)
100) A comparative electrophotographic toner was obtained in the same manner except that 92 parts were used. The melt viscosity at 120 ° C. of this toner was 6 × 10 ⁵ poise.

Comparative Example 2 In Example 4, the melting start temperature was changed to 117 ° C. and 120 ° C. instead of the styrene-acrylate copolymer resin.
Styrene-acrylate copolymer resin having a melt viscosity of 7 × 10 ⁵ poise (melt viscosity cannot be measured at 110 ° C.) (trade name: CPR-, manufactured by Mitsui Toatsu Chemicals, Inc.)
100) A comparative electrophotographic toner was obtained in the same manner except that 85 parts were used. The melt viscosity at 120 ° C. of this toner was 6 × 10 ⁵ poise.

Comparative Example 3 In Example 1, the melting start temperature was changed to 117 ° C. and 120 ° C. instead of the styrene-acrylate copolymer resin.
Styrene-acrylate copolymer resin having a melt viscosity of 7 × 10 ⁵ poise (melt viscosity cannot be measured at 110 ° C.) (trade name: CPR-, manufactured by Mitsui Toatsu Chemicals, Inc.)
100) 92 parts, and 8 parts of polypropylene wax (trade name: Viscol 550P, melting point 145 ° C., manufactured by Sanyo Chemical Industries, Ltd.) in place of the natural gas-based Fischer-Tropsch wax, and set the hot melt kneading temperature to 13
An electrophotographic toner for comparison was obtained in the same manner except that the temperature was changed to 0 ° C. The melt viscosity at 110 ° C. of this toner is 7 ×
It was 10 ⁵ poise.

Comparative Example 4 In Example 3, polypropylene wax (trade name: Viscol 550P, melting point 145, manufactured by Sanyo Chemical Industries, Ltd.) was used instead of the natural gas-based Fischer-Tropsch wax.
C) except that 8 parts were used to obtain a comparative electrophotographic toner. The melt viscosity of this toner at 110 ° C. was 6 × 10 ⁵ poise.

Comparative Example 5 In Example 3, polyethylene wax (trade name: PE-190, manufactured by Hoechst, melting point 132 ° C., penetration 1) was used in place of the natural gas-based Fischer-Tropsch wax.
An electrophotographic toner for comparison was obtained in the same manner except that 8 parts were used. The melt viscosity of this toner at 110 ° C. was 6 × 10 ⁵ poise.

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 Apparent density according to JIS K5101 as an index indicating fluidity of toner Was measured. Table 1 shows the test results of the above items.
Shown in

[0022]

[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 electrophotographic toner of the present invention, and the temperature range is 8
It was confirmed that a practically sufficient range of 0 to 85 ° C. was maintained. In addition, since the fixing strength at a fixing temperature of 130 ° C. is 80% or more, which is a practically sufficient fixing strength, it has been confirmed that there is no practical problem when used in an automatic document feeder or the like. In contrast, Comparative Examples 1, 2, and 3 have a high non-offset temperature on the low temperature side and a fixing temperature of 130 ° C.
Was as low as 50% or less. Further, in Comparative Examples 1 and 2, the non-offset temperature upper limit is as low as 180 ° C. or less, and the non-offset temperature width is also 50 ° C.
The narrow range was as follows. In Comparative Examples 4 and 5, both the non-offset temperature width and the fixing strength were inferior to those of the Examples. In addition, it was confirmed that Comparative Examples 2, 4, and 5 had low apparent densities and poor fluidity due to poor wax dispersion in the electrophotographic toner.

Further, a continuous copy test of up to 10,000 sheets was performed with a commercially available copying machine (manufactured by Toshiba Corporation ) using each developer of the embodiment in the above item (1). In all cases, the triboelectric charge amount was 1000
It changes from -25 μc / g to -28 μc / g up to 0 sheets, and the image density also changes from 1.38 to 1.41 from the initial to 10,000 sheets, with less fog and practical It was confirmed that there was no problem. On the other hand, in Comparative Examples 2, 4, and 5, since the image defects of the stripes and the rear end chipped were confirmed from the beginning, the continuous copy test was omitted. The continuously copied original was A4 with a black portion of 6%. The triboelectric charge was measured using a blow-off triboelectric charge measuring device manufactured by Toshiba Chemical Co., Ltd., and the image density was measured using a reflection densitometer RD- manufactured by Macbeth. 914 was used to. The first embodiment
Table 2 shows the results of the continuous copy test in Nos. 1 to 4. Further, 20 g of the electrophotographic toner of Examples 1 to 4
Put in a 0 cc polyethylene bottle, store in a 50 ° C constant temperature bath for 24 hours, and then cool to room temperature, remove the toner from the bottle, and observe the condition. No abnormalities were observed, and the storage stability was also confirmed. It was confirmed that there was no problem.

[0025]

[Table 2]

[0026]

The toner for electrophotography according to the present invention can maintain a sufficient non-offset temperature region and can be fixed at a low temperature, and is excellent in fixing strength and can obtain a large number of sheets of sufficient image density. It has the effect of being able to. 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 (4)

(57) [Claims] 1. An electrophotographic toner containing natural gas-based Fischer-Tropsch wax and having a melt viscosity at 110 ° C. of 1 × 10 ⁵ to 1 × 10 ⁶ poise. 2. The electrophotographic toner according to claim 1, wherein the melting point of the natural gas-based Fischer-Tropsch wax measured by DSC is 85 to 100 ° C. 3. 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. 4. The electrophotographic toner according to claim 1, wherein the content of the natural gas-based Fischer-Tropsch wax is 1 to 20% by weight of the total toner.