JPH06175396A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To provide an electrophotographic toner fixable at a low fixing temp., not causing any problem in practical use with respect to offsetting property and excellent in fixing strength to transfer paper. CONSTITUTION:This electrophotographic toner contains a styrenic copolymer having at least one peak of mol.wt. in each of the regions of 10<3>-10<4> and 10<5>-10<7> in a chromatogram obtd. by gel permeation chromatography and styrenic grafted polyethylene wax contg. 20-60 pts.wt. styrenic grafted and having <=80 deg.C melting start temp. The polyethylene wax has been dispersed in the form of particles having <=3mum diameter.

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, low energy consumption (power consumption) has been mainly aimed at spreading to households and multifunctional functions of copying machines or printers. (Reduction), high speed for the purpose of spreading to so-called gray area located at the boundary between the printing machine and the copying machine, or low roll pressure for simplification of the fixing roll to reduce machine cost is desired. Cage,
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 an electrophotographic toner that has excellent offset properties and that has excellent fixing strength on a transfer paper 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 storage stability 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, conventionally, as a means for preventing the offset phenomenon, low molecular weight waxes such as polypropylene and polyethylene, or waxes such as natural wax have been used as an offset phenomenon preventing agent. However, these waxes have poor compatibility with the binder resin,
When mixed by a method such as melt-kneading, wax was scattered in the toner to form an island structure. In this case, if the lumps of wax scattered in the toner are too large, the toner will have a non-uniform proportion of each material after pulverization, resulting in poor charging and wax filming on the photosensitive member. on the other hand,
It is desirable to add a large amount of wax in order to prevent the offset phenomenon and improve the fixing strength, but due to these problems, the conventional wax has a limited amount of addition.

[0005]

Accordingly, the object of the present invention is to fix an electrophotographic image which can be fixed at a low fixing temperature, has no practical problem in offset property, and has excellent fixing strength on a transfer paper. To provide toner for use.

[0006]

The present invention has a molecular weight peak position of 10 ³ to 10 ⁴ in a GPC chromatogram.
And a styrene-based copolymer having at least one in each region of 10 ⁵ to 10 ⁷ and a graft amount of styrene of 20 to 60 parts by weight, and a melting start temperature of 80 ° C. or less. A toner for electrophotography, comprising a wax, and wherein the styrene-based graft polyethylene wax is dispersed in a state of having a diameter of 3 μm or less.

The present invention will be described in detail below. The styrene-based copolymer of the present invention has a molecular weight peak position of 10 ³ to 1 in a chromatogram measured by gel permeation chromatography (hereinafter referred to as GPC).
There is at least one in each region of 0 ⁴ and 10 ⁵ to 10 ⁷ , and there is no peak position outside the range of the region. In this case, the peak position of the molecular weight is 10 ³
If it is less than 1, it becomes difficult to maintain good offset resistance, and the glass transition temperature is lowered, so that the storage stability is deteriorated. On the other hand, if the peak position of the molecular weight exceeds 10 ⁷ , the toner is not sufficiently melted by the fixing roll, and the toner is in a low temperature offset state.

In the present invention, the molecular weight at the peak position of the molecular weight distribution of the styrene-based copolymer is a value measured by GPC under the following conditions. That is, a solvent (tetrahydrofuran) is caused to flow at a flow rate of 1 ml per minute at a temperature of 25 ° C., and 8 mg of a tetrahydrofuran sample solution having a concentration of 0.4 gr / dl is injected as a sample weight for measurement. Further, in measuring the molecular weight of a sample, the measurement conditions in which the molecular weight distribution of the sample is included within the range in which the logarithm of the molecular weight and the count number of the calibration curve prepared by several kinds of monodisperse polystyrene standard samples are linear Select. In addition, in this measurement, the reliability of the measurement is based on the NBS70 measured under the above-mentioned measurement conditions.
6 polystyrene standard sample (Mw = 28.8 × 10 ⁴ , M
Mw of n = 13.7 × 10 ⁴ , Mw / Mn = 2.11)
It can be confirmed that / Mn is 2.11 ± 0.10.

The styrene type copolymer in the present invention is prepared by synthesizing the following monomers by suspension polymerization method, emulsion polymerization method, solution polymerization method, bulk polymerization method and the like. As the monomer, styrene, α-methylstyrene, styrene such as chlorostyrene, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, acrylic ester such as alkyl acrylate, Examples thereof include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, octyl methacrylate, stearyl methacrylate, glycidyl methacrylate, and alkyl methacrylate. Other copolymerization components include acrylonitrile, maleic acid,
Polymerization of vinyl monomers such as maleic acid ester, methyl methacrylate, methyl acrylate, vinyl chloride, vinyl acetate, vinyl benzoate, vinyl methyl ketone, vinyl hexyl ketone, vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether. To 30% by weight
You may contain below.

Such a styrene-based copolymer is the above-mentioned GP
In the C chromatogram, the molecular weight of 10 ³ to 10 ⁴ and 1
It may be prepared at the stage of synthesis so as to have at least one peak position in each of the regions of 0 ⁵ to 10 ⁷ , or as another method, a low molecular weight polymer having a peak position of 10 ³ to 10 ⁴ You may mix and prepare the high molecular weight polymer which molecular weight has a peak position in 10 < ⁵ > -10 < ⁷ >. In that case, the mixing ratio of the low molecular weight polymer and the high molecular weight polymer is preferably from 70:30 to 95: 5 because the fixability and the non-offset property are good. If the proportion of the low molecular weight polymer is more than 95%, it causes a problem of high temperature offset, which is not preferable. On the other hand, the proportion of high molecular weight polymer is 3
When it is more than 0%, a large amount of heat energy is required for fixing on the heat fixing roll, which is not preferable. When the peak position of the high molecular weight polymer is close to 10 ⁵ , the mixing ratio of the high molecular weight polymer is set to a value close to 30%,
When the peak position of the high molecular weight polymer is close to 10 ⁷ ,
It is preferable to set the mixing ratio of the high molecular weight polymer to a value close to 5% to control the mixing ratio of the low molecular weight polymer and the high molecular weight polymer because high temperature offset can be prevented. Furthermore, in order to improve the storage stability of the electrophotographic toner,
It is preferable to use a styrene-based copolymer having a glass transition temperature of 60 ° C. or higher.

Next, the styrene-based graft polyethylene wax that constitutes the present invention is a resin obtained by grafting a styrene-based monomer onto polyethylene wax. What is polyethylene wax grafted with styrene monomer?
High-pressure polyethylene by thermal decomposition, high-pressure polymerized polyethylene wax obtained by radical polymerization of ethylene at high pressure, and further ethylene or ethylene and propylene, 1
-Putene, 1-hexene, 4-methyl-1-pentene,
It is obtained by medium- and low-pressure polymerization of an α-olefin such as 1-decene with a transition metal compound catalyst. The styrenic monomer is styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4.
-Dimethylstyrene, pn-butylstyrene, pt
ert-butyl styrene, pn-hexyl styrene,
pn-octyl styrene, pn-nonyl styrene,
pn-decylstyrene, pn-dodecylstyrene,
Examples thereof include p-methoxystyrene, p-phenylstyrene, p-chlorostyrene and 8,4-dichlorostyrene. As a method of grafting the styrene-based monomer onto the polyethylene wax, a usual method can be adopted. For example, a method in which polyethylene wax is directly contacted or dissolved in a solvent and a styrene-based monomer is added with or without a radical initiator to perform grafting, a method in which ozonized polyethylene is reacted with a styrene-based monomer, or It is possible to use a method of performing grafting using radiation.

Ordinary polyethylene wax has poor compatibility with styrene copolymers and is very difficult to disperse.
In the present invention, in order to improve the dispersibility of the polyethylene wax, the polyethylene wax is grafted with a styrene monomer. When the amount of ordinary polyethylene wax added is 10 parts by weight or more with respect to the styrene-based copolymer, fine dispersion becomes impossible and it becomes difficult to form an island structure, and a continuous phase is easily formed, which causes a problem. However, in the case of the styrene-based graft polyethylene wax used in the present invention, the affinity for the styrene-based copolymer is good,
Fine dispersion is possible. If the amount of the styrene-based monomer grafted to the polyethylene is too small, the compatibility with the styrene-based copolymer will be poor and the dispersibility of the styrene-based graft polyethylene wax will be poor. On the other hand, if the graft amount of the styrene-based monomer is too large, the crystallinity of polyethylene is lowered and the blocking temperature is lowered, so that the storage stability of the toner is deteriorated. Therefore, the amount of the styrene-based monomer grafted to polyethylene should be 20 to 60 parts by weight based on 100 parts by weight of polyethylene. Further, the higher the molecular weight of polyethylene, the higher the softening point and the lower the fixability and offset resistance. Therefore, the molecular weight of the styrene-based graft polyethylene is preferably about 1000 to 3000, and it is necessary to set the melting start temperature to 80 ° C. or lower in order to satisfy the fixability and the offset resistance.

The amount of the styrene-based monomer grafted on the styrene-based graft polyethylene wax can be measured by the NMR method. The melting start temperature referred to in the present invention is a value measured by the following measuring machine and measuring conditions. The melting start temperature means the temperature at which the plunger starts to fall. Measuring instrument; Shimadzu's advanced flow tester CF-500 Measuring condition: Plunger: 1 cm ² Die diameter: 1 mm Die length: 1 mm Load: 20 KgF Preheating temperature: 50-80 ° C Preheating time: 300 sec Temperature rising Speed: 6 ° C / min

The styrene-based graft polyethylene wax constituting the electrophotographic toner of the present invention must be dispersed in a state of having a diameter of 3 μm or less. When the particles are dispersed in a state of having a diameter larger than 3 μm, the wax fine particles are detached from the electrophotographic toner particles during the pulverization step during the production of the electrophotographic toner. Further, the wax is detached from the electrophotographic toner particles by the impact of the carrier or the stirring blade of the developing device. The released wax adheres to the photosensitive member to cause filming and deteriorate charging characteristics. The styrene-based graft polyethylene wax in the electrophotographic toner of the present invention has a diameter of 3 μm.
Examples of dispersion methods include melt-kneading at low temperature, coexistence polymerization at the time of producing a styrene-based copolymer, and a master batch method in which the polyethylene wax is previously dispersed in the styrene-based copolymer. The method for confirming the dispersion state of the styrene-based graft polyethylene wax in the electrophotographic toner particles is as follows. That is, a kneaded product obtained by melt-kneading a styrene-based copolymer, a styrene-based graft polyethylene wax and other additives such as a colorant and a charge control agent with a melt-kneader such as a single-screw extruder or a twin-screw kneading extruder. Alternatively, after melt-kneading the above materials, electrophotographic toner particles crushed and classified and hardened with an epoxy resin adhesive are cut into a width of about 1 μm with a microtome, and the cut pieces are taken with an optical microscope at a magnification of 100 to 20.
It is possible to confirm whether or not the styrene-based graft polyethylene wax is dispersed in a state of having a diameter of 3 μm or less by visually observing at 0 times.

As the binder resin for the electrophotographic toner of the present invention, a polyethylene resin in addition to the styrene-based copolymer,
Resins such as epoxy resin, silicone resin, polystyrene, polyamide resin and polyurethane resin may be blended.

The toner for electrophotography of the present invention is a powder obtained by appropriately dispersing and containing other toner components such as a colorant, a magnetic material and a property improving agent in the styrene copolymer and the styrene graft polyethylene wax as described above. It is a body, and its average particle size is in the range of 5 to 30 μm. A toner may be formed by adding and mixing a flow improver made of fine silica powder or the like to the powder thus obtained. 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, lamp black, rose bengal, a mixture thereof, and the like. It is necessary that these colorants be contained in a sufficient ratio to form a visible image with a sufficient concentration, and usually 1 to 100 parts by weight of the binder resin.
The ratio is about 20 parts by weight.

As the magnetic substance, a metal or alloy exhibiting ferromagnetism such as ferrite, magnetite, and other iron, cobalt, nickel, or the like, a compound containing these elements, or a material containing no ferromagnetic element, but an appropriate heat treatment is used. An alloy which exhibits ferromagnetism when applied, for example, a type of alloy called a Heusler alloy containing manganese and copper, such as manganese-copper-aluminum, manganese-copper-tin, or chromium dioxide, or the like can be given. .
These magnetic materials are uniformly dispersed in the binder resin in the form of fine powder having an average particle size of 0.1 to 1 micron. The content is 20 to 70 parts by weight, preferably 40 to 70 parts by weight, per 100 parts by weight of the toner.

Examples of the property improving agent include a charge control agent, an offset preventing agent, a fluidity improving lubricant and the like.

The electrophotographic toner of the present invention is mixed with a carrier made of ferrite powder, iron powder or the like to be a two-component developer, but when a magnetic substance is contained, it is not mixed with the carrier and is used as it is. It may be used as a component type developer for developing an electrostatic image, or may be mixed with a carrier and used as a two component type developer.

[0020]

The reason why the above styrene copolymer and styrene graft polyethylene wax are contained in the electrophotographic toner of the present invention is as follows. That is, a low molecular weight wax such as polyethylene which has been conventionally used as a means for preventing an offset phenomenon has a poor compatibility with a styrene resin and is very difficult to disperse. In particular,
When the addition amount of the low molecular weight wax was 10 parts by weight or more with respect to the styrene-based resin, fine dispersion was impossible in the resin and the wax was contained in a large lump. However, the styrene-based graft polyethylene wax used in the present invention has a very good affinity for a styrene-based resin and is dispersed as fine particles in the resin. Therefore, the effect of the present invention can be obtained by combining the good fixing property of the styrene-based copolymer composed of the low molecular weight polymer part and the high molecular weight polymer part with the good non-offset property of the styrene-based graft polyethylene wax. You can

[0021]

EXAMPLES The present invention will be described below based on examples. In the examples, “part” means “part by weight”. Example 1 Weight average molecular weight 9 × 10 ⁵ and number average molecular weight 3.9 × 1
0 ⁵ of styrene - butyl acrylate copolymer (A) 30
Parts, weight average molecular weight 8 × 10 ³ and number average molecular weight 2.
70 parts of 7 × 10 ³ styrene-butyl acrylate copolymer (B) was mixed, and a styrene copolymer having a molecular weight of 7.5 × 10 ⁵ and a peak position of 4.5 × 10 ³ in the GPC chromatogram. Got united. Next, the styrene-based copolymer and other raw materials were mixed in a supermixer in the following mixing ratio, melt-kneaded, pulverized and classified to obtain particles having an average particle size of 11 μm, and then hydrophobic 0.3 part of silica (trade name; R-972 manufactured by Nippon Aerosil Co., Ltd.) was adhered to the surface of the particles by a Henschel mixer to obtain a negatively chargeable electrophotographic toner of the present invention.

Example 2 Weight average molecular weight 9 × 10 ⁵ and number average molecular weight 3.9 × 1
0 ⁵ of styrene - butyl acrylate copolymer (A) 20
Parts, weight average molecular weight 8 × 10 ³ and number average molecular weight 2.
80 parts of 7 × 10 ³ styrene-butyl acrylate copolymer (B) was mixed to give a styrene copolymer having a molecular weight of 7.5 × 10 ⁵ and a peak position of 4.5 × 10 ³ in the GPC chromatogram. Got united. Next, the above-mentioned polymer mixture and other raw materials are mixed in a supermixer in the following blending ratio, melt-kneaded, pulverized and classified to obtain particles having an average particle diameter of 11 μm, and then the hydrophobic silica ( 0.3 parts of R-972 manufactured by Nippon Aerosil Co., Ltd. was attached to the surface of the particles by a Henschel mixer to obtain a negatively chargeable electrophotographic toner of the present invention.

Example 3 Weight average molecular weight 1 × 10 ⁶ and number average molecular weight 5 × 10 ⁵
10 parts by weight of styrene-butyl acrylate copolymer (C), a weight average molecular weight of 8 × 10 ³ and a number average molecular weight of 2.7.
× 10 ³ styrene-butyl acrylate copolymer (B)
90 parts were mixed to obtain a styrene copolymer having peak positions at molecular weights of 8.0 × 10 ⁵ and 5.2 × 10 ³ in the GPC chromatogram. Next, the styrene-based copolymer and other raw materials were mixed in a supermixer in the following mixing ratio, melt-kneaded, pulverized and classified to obtain particles having an average particle size of 11 μm, and then hydrophobic 0.3 part of silica (trade name; R-972 manufactured by Nippon Aerosil Co., Ltd.) was adhered to the surface of the particles by a Henschel mixer to obtain a negatively chargeable electrophotographic toner of the present invention.

Example 4 Weight average molecular weight 1 × 10 ⁶ and number average molecular weight 5 × 10 ⁵
10 parts by weight of styrene-butyl acrylate copolymer (C), a weight average molecular weight of 8 × 10 ³ and a number average molecular weight of 2.7.
× 10 ³ styrene-butyl acrylate copolymer (B)
90 parts were mixed to obtain a styrene copolymer having peak positions at molecular weights of 8.0 × 10 ⁵ and 5.2 × 10 ³ in the GPC chromatogram. Next, the styrene-based copolymer and other raw materials were mixed in a supermixer in the following mixing ratio, melt-kneaded, pulverized and classified to obtain particles having an average particle size of 11 μm, and then hydrophobic 0.3 part of silica (trade name; R-972 manufactured by Nippon Aerosil Co., Ltd.) was adhered to the surface of the particles by a Henschel mixer to obtain a negatively chargeable electrophotographic toner of the present invention.

Example 5 Weight average molecular weight 1 × 10 ⁶ and number average molecular weight 5 × 10 ⁵
10 parts by weight of styrene-butyl acrylate copolymer (C), a weight average molecular weight of 8 × 10 ³ and a number average molecular weight of 2.7.
× 10 ³ styrene-butyl acrylate copolymer (B)
90 parts were mixed to obtain a styrene copolymer having peak positions at molecular weights of 8.0 × 10 ⁵ and 5.2 × 10 ³ in the GPC chromatogram. Next, the styrene-based copolymer and other raw materials were mixed in a supermixer in the following mixing ratio, melt-kneaded, pulverized and classified to obtain particles having an average particle size of 11 μm, and then hydrophobic 0.3 part of silica (trade name; R-972 manufactured by Nippon Aerosil Co., Ltd.) was adhered to the surface of the particles by a Henschel mixer to obtain a negatively chargeable electrophotographic toner of the present invention.

Comparative Example 1 Comparative Example 1 was repeated except that the styrene-butyl acrylate copolymer (A) was not used in Example 1 but the styrene-butyl acrylate copolymer (B) was 100 parts. An electrophotographic toner was obtained.

Comparative Example 2 Comparative Example 2 was carried out in the same manner as in Example 1 except that the styrene-butyl acrylate copolymer (B) was not used and the styrene-butyl acrylate copolymer (A) was 100 parts. An electrophotographic toner was obtained.

Comparative Example 3 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the styrene-based graft polyethylene wax was not used.

Comparative Example 4 A comparative electrophotographic toner was obtained in the same manner as in Example 5 except that 10 parts of polyethylene wax (molecular weight 1000, melting start temperature 98.0 ° C.) was used instead of the styrene-based graft polyethylene wax. It was

Comparative Example 5 Example 3 was repeated except that the styrene-based graft polyethylene wax used in Example 1 was replaced with 10 parts of a styrene-based graft polyethylene wax (styrene 10 parts by weight graft, molecular weight 1100, melting start temperature 75.6 ° C.). In the same manner as in Example 1, a comparative electrophotographic toner was obtained.

Comparative Example 6 Example 6 was repeated except that the styrene-based graft polyethylene wax used in Example 1 was replaced with 10 parts of a styrene-based graft polyethylene wax (70 parts by weight of styrene graft, molecular weight 1700, melting start temperature 48.7 ° C.). In the same manner as in Example 1, a comparative electrophotographic toner was obtained.

Next, the following items were tested for the above Examples and Comparative Examples. (1) Fixing Strength First, 3 parts of each of the electrophotographic toners obtained in the above-mentioned Examples and Comparative Examples and 100 parts of a non-coated ferrite carrier (trade name: FL-1020 manufactured by Powder Tech Co., Ltd.) were mixed to prepare a developer. did. Then, using the developer, a commercially available copying machine (trade name: SF-9800 manufactured by Sharp Co.) was used to A4.
A plurality of belt-shaped unfixed images each having a length of 2 cm and a width of 5 cm were prepared on the copy paper. Next, a fixing device comprising a heat fixing roll having a surface layer made of Teflon and a pressure fixing roll having a surface layer made of silicone rubber was used at a roll pressure of 5 kg / cm ^2.
Then, the roll speed was adjusted to 450 mm / sec, the set temperature of the heat fixing roll was set to 160 ° C., and the toner image of the transfer paper having the unfixed image 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. Image density of fixed image after rubbing / image density of fixed image before rubbing × 100 (%)

(2) High-temperature offset property The set temperature of the heat fixing roll of the fixing device is adjusted to 220 ° C. to fix the toner image on the transfer paper having the unfixed image, and the margin of the transfer paper is fixed. It was observed whether or not the toner stains on the area. (3) Filming property and charging property 3 parts of each electrophotographic toner obtained in the above-mentioned Examples and Comparative Examples and a non-coated ferrite carrier (manufactured by Powder Tech Co., Ltd.)
A developer was prepared by mixing 100 parts of trade name; FL-1020). Next, 10,000 A4 originals (black ratio 10%) were copied using a commercially available copying machine (trade name: SF-9800 manufactured by Sharp Corporation) using the developer. Then, after copying, the surface of the photoconductor set in the copying machine was visually observed to confirm whether the toner filming occurred. Also, the triboelectric charge amount of the electrophotographic toner before copying and the electrophotographic toner amount of the electrophotographic toner after copying 10,000 sheets were measured by a blow-off triboelectric charge measuring device,
The change in the triboelectric charge amount before and after copying was confirmed and used as an index of charging characteristics. (4) Storage stability 50% of each of the electrophotographic toners obtained in the above Examples and Comparative Examples was used.
After being placed in a cc polyethylene container and stored under environmental conditions of a temperature of 50 ° C. and a humidity of 90%, it was observed whether or not the electrophotographic toner blocked.

The results of each of the examples and comparative examples obtained by the above test are shown in Table 1. In Table 1, each electrophotographic toner was fixed with an epoxy resin adhesive and cut into a width of about 1 μm with a microtome, and the cut portion was observed with an optical microscope to find a state in which the styrene-based graft polyethylene wax was dispersed. The results of confirmation of are also described. In Table 1, regarding the high temperature offset property, the filming property and the storage stability, “O” indicates that high temperature offset, filming or blocking occurred, and “X” indicates that high temperature offset, filming or blocking did not occur. The charging characteristics are indicated by O when the difference between the triboelectric charge amounts before and after copying is within 5 μc / g, and by X otherwise.

[0035]

[Table 1]

As is clear from the results of Table 1, the electrophotographic toner of the present invention has a fixing strength of 90% or more even when the temperature of the heat fixing roll is as low as 160 ° C. No charging or blocking occurred, and the charging characteristics were good. On the other hand, it has been confirmed that the electrophotographic toner for comparison cannot maintain good fixing strength, high-temperature offset property, filming property, charging property and storage stability, and has a problem in practical use.

[0037]

The electrophotographic toner of the present invention has sufficient fixing strength even when the temperature of the heat fixing roll is low and does not cause high temperature offset or filming on the photoconductor, so that it can be used in copying machines, printers, etc. When it is applied to, the power consumption can be reduced, and the effect of reducing the machine cost by lowering the roll pressure and increasing the copying speed can be obtained.

Front Page Continuation (72) Inventor Yoshiaki Harada 3-1, Somyo-cho, Shizuoka-shi, Shizuoka Prefecture Inside the Tomagawa Paper Mill Chemicals Mill (72) Inventor Koji Nakayama 3-1, Somae-cho, Shizuoka-shi Issued by Tomoegawa Paper Co., Ltd.

Claims (1)

[Claims] 1. A styrene-based copolymer having at least one peak position of molecular weight in the GPC chromatogram in the respective regions of 10 ³ to 10 ⁴ and 10 ⁵ to 10 ⁷ and a graft amount of styrene of 20 to 60. And a styrene-based graft polyethylene wax having a melting start temperature of 80 ° C. or lower, and the styrene-based graft polyethylene wax is dispersed in a diameter of 3 μm or less. Photographic toner.