JPH0743928A - Electrophotographic toner - Google Patents

Abstract

(57) [Abstract] [Purpose] It can be fixed at a low fixing temperature, does not cause any practical problems even if it is fed by double-sided copying or automatic document feeder, and has excellent fixing strength on transfer paper. An object is to provide an electrophotographic toner. [Structure] An electrophotographic toner containing glycerin = tri-12-hydroxystearate and a resole.

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, various improvements have been desired mainly for the purpose of multifunctionalization. For example, high speed is desired for the purpose of low energy (reduction of power consumption) and popularization in so-called gray area located at the boundary between the printing machine and the copying machine, and the fixing roll is simplified to reduce the machine cost. Therefore, lower roll pressure is desired. In addition, copiers equipped with a double-sided copy function and an automatic document feeder have become widespread along with the sophistication of copiers, so 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 transfer paper in order to prevent stains during double-sided copying and stains in the automatic document feeder.

Conventionally, in order to meet the above requirements, a substance having a low melting start temperature, for example, glycerin = tri-12-hydroxystearate is added to the binder resin which is the main component of the electrophotographic toner to form a binder resin as a whole. Attempts have been made to lower the melting start temperature and improve low temperature fixability.

[0004]

By adding the above glycerin = tri-12-hydroxystearate to the binder resin, excellent low temperature fixability can be imparted to the toner. The compatibility with the binder resin such as styrene-acrylic acid ester was poor, and the resin was not uniformly dispersed in the binder resin and was mixed in a poorly dispersed state. As a result, the interface between the binder resin and glycerin = tri-12-hydroxystearate easily breaks, and glycerin = tri-12-hydroxystearate is released from the binder resin during pulverization and classification of the toner, and after fixing. At the same time, it had a defect that the mechanical strength of the toner layer was lowered. As described above, the toner having low mechanical strength has not only low fluidity, but when development and cleaning are repeated in a copying machine, fusion to the photoreceptor may occur, which may cause deterioration in image quality. It was

[0005]

SUMMARY OF THE INVENTION Accordingly, the object of the present invention is to provide 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 transfer paper. To do.

[0006]

The above object was achieved by incorporating glycerin = tri-12-hydroxystearate and resole into an electrophotographic toner.

The toner for electrophotography of the present invention is a toner 12-
It is composed of hydroxystearate, a resole, a binder resin, and a property improving agent which is added as necessary.

The above glycerin = tri-12-hydroxystearate is a compound having the structural formula shown below.

In order to obtain glycerin = tri-12-hydroxystearate, a reduced nickel catalyst is added to refined castor oil in an amount of 0.2% by weight based on 100% by weight of refined castor oil, and a reaction temperature of 150 ° C. to 160 ° C. 15 kg /
Hydrogen may be added under a reaction pressure of cm ² to reduce both of them. Usually, this reduction reaction is completed in about 3 hours.

This glycerin = tri-12-hydroxystearate has a content of 0.1% when the total toner is 100% by weight.
It is preferably added in the range of 5% by weight to 50% by weight. When the amount is less than 0.5% by weight, the effect of lowering the melting point of the electrophotographic toner is small, so that when fixing at a low fixing temperature, it is difficult to obtain sufficient fixing strength on the transfer paper, which is not preferable. On the other hand, when the content is more than 50% by weight, even if the resol is contained, it is not sufficiently dispersed in the binder resin, and the blocking property of the toner and the stability of charging are deteriorated, which is not preferable.

The resol is a phenolic resin,
In the present invention, it is used as a crosslinking agent. It is usually obtained by reacting phenols with formaldehyde in the presence of an alkaline catalyst (alkali hydroxide, ammonia, amine, etc.). The general formula is shown below.

[0012]

[Chemical 1]

The amount of resol added is glycerin = tri-1.
10 to 100 parts by weight of 2-hydroxystearate
It is preferably from 100 to 100 weight, and it is necessary to control within this range according to the formulation of the toner material other than the resol, the fixing speed of the fixing device, and the fixing temperature.

As the resin used as the binder resin,
A resin containing a hydroxyl group is preferable because the dispersibility of glycerin = tri-12-hydroxystearate is further improved. Specifically, a resin obtained by copolymerizing parahydroxystyrene, hydroxyethylhexyl acrylate, hydroxyethyl methacrylate and the like with another hydroxyl group-containing monomer such as styrene and acryl, or a polyester resin having a terminal hydroxyl group is preferable. As the polyester resin, a resin obtained by adding ethylene oxide to bisphenol A as an alcohol component or a resin obtained by adding propylene oxide to bisphenol A is particularly preferable. Further, a resin having fumaric acid, phthalic acid or the like as an acid component is preferable.

Further, as the binder resin, a resin such as polyethylene resin, epoxy resin, silicone resin, polyamide resin, polyurethane resin or the like may be used in addition to the above-mentioned copolymer or polyester resin.

As the above-mentioned characteristic improving agent, a coloring agent, a magnetic substance,
Examples thereof include a charge control agent and a fluidizing agent. As the colorant, carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinone yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, these And the like. It is necessary that these colorants be contained in a sufficient ratio so that a visible image having a sufficient density is formed, and usually about 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin. It is added in proportion.

As the magnetic substance, metals exhibiting ferromagnetism such as ferrite, magnetite and other iron, cobalt, nickel, alloys or compounds containing these elements, or no ferromagnetic elements, but suitable heat treatment is applied. An alloy that becomes ferromagnetic by this, such as manganese-
Mention may be made of alloys of the type called Heusler alloys containing manganese and cylinders such as cylinder-aluminum, manganese-body-tin, or chromium dioxide. 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 of toner 100
It is 20 to 70 parts by weight, preferably 40 to 70 parts by weight, per part by weight.

Examples of the charge control agent include complex metal complex dyes, alkoxylated amines, quaternary ammonium salts, alkylamides and the like. Examples of the fluidizing agent include silicon varnish, metal soap, nonionic surfactant, colloidal silica and the like.

The method for producing the electrophotographic toner of the present invention will be described below. First, tri-12-hydroxystearate, a resole, a binder resin, and a property-improving agent that is added as necessary are mixed in a predetermined mixing ratio with a spar mixer, and melt-kneaded. At this time, the hydroxyl group contained in the resol and the hydroxyl group contained in the binder resin are crosslinked, and the crosslinking reaction rate can be appropriately controlled by using an acidic catalyst such as salicylic acid as a catalyst. When salicylic acid is used as the crosslinking catalyst, it is 0.01 to 0.05 with respect to 100 parts by weight of the resole.
It is preferable to add about 1 part by weight. Then, by pulverizing and classifying, an electrophotographic toner having a desired average particle diameter can be obtained.

The electrophotographic toner of the present invention is mixed with a carrier composed of ferrite powder, iron powder or the like to form a two-component developer. If the toner itself contains a magnetic material, it can be used as it is as a one-component developer for developing an electrostatic image without being mixed with a carrier. Further, it can be applied to a non-magnetic one-component developing method.

Among the electrophotographic toners having the above constitution, the electrophotographic toner having a melting start temperature of 60 ° C. to 100 ° C. is particularly preferable in order to improve the fixability at low temperature. If it is higher than 100 ° C., the fixability is not sufficient, and if it is lower than 60 ° C., the blocking property is deteriorated, which may cause a problem in storage stability. To obtain a toner having a melting start temperature in such a range, the molecular weight of the binder resin is lowered, the glass transition point (Tg) is lowered, or the binder resin and glycerin = tri-12-hydroxystearate are reduced. The blending ratio with and may be adjusted.

In the present specification, the "melting start temperature" means the lowering start temperature of the plunger under the following conditions. Measuring instrument; Shimadzu's advanced flow tester CF-500 Measuring conditions: Plunger: 1 cm2 Die diameter: 1 mm Die length: 1 mm Load: 20 KgF Preheating temperature: 50-80 ° C Preheating time: 300 sec Temperature rising rate: 6 ° C / min

[0023]

The toner for electrophotography according to the present invention is characterized by containing glycerin = tri-12-hydroxystearate and resole. By adding the resol which is a cross-linking agent to the binder resin, the hydroxyl group in the binder resin and the hydroxyl group of glycerin = tri-12-hydroxystearate are cross-linked. As a result, the low compatibility between the two is improved, and it is possible to prevent the release of glycerin = tri-12-hydroxystearate from the binder resin, which often occurs during pulverization and classification.

[0024]

EXAMPLES The present invention will be described below based on examples. In the examples, “parts” means “parts by weight”.

(Example 1) Styrene 58 parts, butyl acrylate 22 parts, hydroxyethyl methacrylate 20
Parts are copolymerized, and the weight average molecular weight is 14 × 10 ⁴ ,
A styrene-acrylic acid ester copolymer resin having a hydroxyl group having a number average molecular weight of 0.4 × 10 ⁴ was obtained. Next, the above styrene-based copolymer and other raw materials are mixed with a supermixer in the following compounding ratio, and after melt kneading,
The particles were pulverized and classified to obtain particles having an average particle diameter of 11 μm. After that, hydrophobic silica (product name by Nippon Aerosil Co., Ltd .; R-
972) 0.3 part was adhered to the surface of the particles using a Henschel mixer to obtain a negatively chargeable electrophotographic toner of this example. -90 parts of the styrene-based copolymer-Resol 5 parts (Arakawa Chemical Co., Ltd. trade name; Tamanol 521) -Glycerin = tri 12-hydroxystearate 10 parts (Kawaken Fine Chemicals trade name; K-3 Wax-200) -Carbon black 6.5 parts (Mitsubishi Chemical Co., Ltd. trade name: MA-100) -Chromium metal dye 2 parts (Orient Chemical Co., Ltd. trade name: S-34) -Polypropylene 3 parts (Sanyo Chemical Co., Ltd.) Product name: Viscor 330P)

Example 2 The styrene-based copolymer obtained in Example 1 and other raw materials were mixed with a supermixer in the following blending ratio, melt-kneaded, and then ground and classified. Particles having an average particle diameter of 11 μm were obtained. After that, hydrophobic silica (product name by Nippon Aerosil Co., Ltd .; R-972)
0.3 part was attached to the surface of the particles using a Henschel mixer to obtain a negatively chargeable electrophotographic toner of this example. -Styrene-based copolymer obtained in Example 1 80 parts-Resol 10 parts (Arakawa Chemical Industry Co., Ltd. product name; Tamanol 521) -Glycerin = tri 12-hydroxystearate 20 parts (Kawaken Fine Chemical product name; K -3 Wax-200) -Carbon black 6.5 parts (Mitsubishi Chemical Co., Ltd. trade name; MA-100) -Chromium metal dye 2 parts (Orient Chemical Industry trade name; S-34) -Polypropylene 3 parts (Product name of Sanyo Kasei Co., Ltd .; Viscole 330P)

Example 3 The styrene-based copolymer obtained in Example 1 and other raw materials were mixed with a supermixer in the following blending ratio, melt-kneaded, and then ground and classified. Particles having an average particle diameter of 11 μm were obtained. After that, hydrophobic silica (product name by Nippon Aerosil Co., Ltd .; R-972)
0.3 part was attached to the surface of the particles using a Henschel mixer to obtain a negatively chargeable electrophotographic toner of this example. -Styrene-based copolymer obtained in Example 1 70 parts-Resol 15 parts (Arakawa Chemical Co., Ltd. trade name; Tamanor 521) -Glycerin = tri 12-hydroxystearate 30 parts (Kawaken Fine Chemical trade name; K -3 Wax-200) -Carbon black 6.5 parts (Mitsubishi Chemical Co., Ltd. trade name; MA-100) -Chromium metal dye 2 parts (Orient Chemical Industry trade name; S-34) -Polypropylene 3 parts (Product name of Sanyo Kasei Co., Ltd .; Viscole 330P)

(Example 4) The styrene-based copolymer obtained in Example 1 and other raw materials were mixed with a supermixer in the following mixing ratio, melt-kneaded, and then ground and classified. Particles having an average particle diameter of 11 μm were obtained. After that, hydrophobic silica (product name by Nippon Aerosil Co., Ltd .; R-972)
0.3 part was attached to the surface of the particles using a Henschel mixer to obtain a negatively chargeable electrophotographic toner of this example. -Styrene-based copolymer obtained in Example 1 60 parts-Resol 20 parts (Arakawa Chemical Industry Co., Ltd. product name: Tamanor 521) -Glycerin = tri 12-hydroxystearate 40 parts (Kawaken Fine Chemical product name; K -3 Wax-200) -Carbon black 6.5 parts (Mitsubishi Chemical Co., Ltd. trade name; MA-100) -Chromium metal dye 2 parts (Orient Chemical Industry trade name; S-34) -Polypropylene 3 parts (Product name of Sanyo Kasei Co., Ltd .; Viscole 330P)

(Example 5) The styrene-based copolymer obtained in Example 1 and other raw materials were mixed with a supermixer in the following mixing ratio, melt-kneaded, and then ground and classified. Particles having an average particle diameter of 11 μm were obtained. After that, hydrophobic silica (product name by Nippon Aerosil Co., Ltd .; R-972)
0.3 part was attached to the surface of the particles using a Henschel mixer to obtain a negatively chargeable electrophotographic toner of this example. -Styrene-based copolymer of Example 1 50 parts-Resol 25 parts (Arakawa Chemical Industry Co., Ltd. trade name; Tamanol 521) -Glycerin = tri 12-hydroxystearate 50 parts (Kawaken Fine Chemical trade name; K-3 wax) -200) -Carbon black 6.5 parts (trade name; MA-100, manufactured by Mitsubishi Kasei Kogyo Co., Ltd.)-Metallic dye containing chromium 2 parts (trade name: S-34, manufactured by Orient Chemical Co., Ltd.)-Polypropylene 3 parts (Sanyo Kasei Co., Ltd.) Kogyo Co., Ltd. product name: Viscole 330P)

(Comparative Example 1) In Example 1, 90 parts of the styrene copolymer was contained, whereas in this Comparative Example, 100 parts were included.
Parts, and further resole and glycerin = tri 12-
A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that hydroxystearate was not used.

(Comparative Example 2) In Example 5, 50 parts of the styrene-based copolymer was contained, while in this Comparative Example 100
And a comparative electrophotographic toner was obtained in the same manner as in Example 5 except that no resol was used.

Next, the following characteristics of the toners obtained in the above Examples and Comparative Examples were evaluated. (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 develop a two-component system. An agent was prepared. Then, a commercially available copying machine (trade name: SF-980, manufactured by Sharp Corporation) using the developer is used.
In 0), a plurality of belt-shaped unfixed images having a length of 2 cm and a width of 5 cm were prepared on A4 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 / cm2 and roll speed 100mm / se
c so that the set temperature of the heat fixing roll is 1
The temperature was set to 30 ° C., and the toner image on the transfer paper having the unfixed image was fixed. Then, the formed fixed image was rubbed with a cotton pad, the fixing temperature was calculated by the following formula, and the fixing strength, which is an index of low energy fixing property, was measured. Image density of fixed image after rubbing / image density of fixed image before rubbing × 100 (%)

(2) Image Density and Background Fogging Further, a continuous copying test of up to 10,000 sheets was conducted using a commercially available copying machine (trade name: BD-3801 manufactured by Toshiba Corp.) using each of the above-mentioned developers. Then, using a Macbeth reflection densitometer (RD-914), the image densities of the transfer paper at the initial stage of copying and the 10,000th copy paper were measured. Furthermore, a color difference meter (manufactured by Nippon Denshoku Co., Ltd., product name: MODE
LZ-1001DP) was used to measure the degree of background fog. However, the background fog is the difference in whiteness between the transfer paper before copying and the non-image after copying.

(3) Non-offset temperature range The temperature of the heat fixing roll used in the above (1) is 100 ° C.
The temperature at which fixing offset occurs was investigated by changing the temperature to 200 ° C.

(4) Melting start temperature Evaluation was made under the above-mentioned measurement conditions.

Table 1 shows the results of the respective examples and comparative examples obtained by the above test.

[0037]

[Table 1]

[0038]

[Table 2]

Since the electrophotographic toner of this embodiment is a toner characterized by sharing glycerin = tri-12-hydroxystearate and resole, the fixing strength can be obtained even when the temperature of the heat fixing roll is as low as 130 ° C. Is 90%
It was confirmed from the results in Table 1 above that the fixing strength was excellent. On the other hand, it was confirmed that the electrophotographic toner obtained in Comparative Example 1 could not maintain a good fixing strength and had a practical problem. Further, it was confirmed that the toner obtained in Comparative Example 2 had a problem in practical use because the image density was lowered and the background fog was increased in a copy test of 10,000 sheets.

[0040]

The toner for electrophotography of the present invention is characterized by containing glycerin = tri-12-hydroxystearate and resole. Since the resol which is a cross-linking agent is added, the hydroxyl group in the binder resin and the hydroxyl group of glycerin = tri-12-hydroxystearate cross-link. As a result, the low compatibility of the two was improved, and glycerin from the binder resin during pulverization and classification =
The elimination of tri-12-hydroxystearate can be prevented. Therefore, the electrophotographic toner of the present invention has not only excellent mechanical strength but also excellent fixing strength on transfer paper.

Further, the electrophotographic toner of the present invention contains glycerin = tri-12-hydroxystearate, and this glycerin = tri-12-hydroxystearate is compared with the waxes widely used in the past. It also has a low melting point and has releasability from the fixing roller. Therefore, since the melting start temperature of the electrophotographic toner of the present invention is low, the toner can be fixed with sufficient fixing strength even if the temperature of the heat fixing roll is low. Further, when applied to a copying machine or a printer, the power consumption can be reduced and the copying speed can be increased.

Claims (4)

[Claims] 1. A toner for electrophotography comprising glycerin = tri-12-hydroxystearate and resole. 2. The content of the glycerin = tri-12-hydroxystearate is 0.5 to 50% by weight of the total toner.
The electrophotographic toner according to claim 1, wherein 3. The toner for electrophotography according to claim 1, further comprising a binder resin containing a hydroxyl group. 4. The melting start temperature of the toner is from 60 ° C. to 100.
The toner for electrophotography according to claim 1, which is at a temperature of ℃.