JPH08123077A - Electrophotographic toner - Google Patents

Abstract

PURPOSE: To obtain an electrophotographic toner fixable at a low fixing temp., causing no problem on offsetting property in practical use and excellent in fixing strength to transfer paper by specifying the components of a toner. CONSTITUTION: This electrophotographic toner contains 12-hydroxystearic acid and polyester resin. The 12-hydroxystearic acid content is preferably 1-30wt.% of the amt. of the polyester resin. In order to maintain satisfactory anti- offsetting property, the mol.wt. distribution of the polyester resin is preferably extended by polymerizing multifunctional monomers other than bifunctional monomers, that is, polyhydric alcohol other than dihydric adcohol and/or polycarboxylic acid other than dicarboxylic acid. When this toner is produced, it is preferable that crosslinking is further accelerated using a crosslinking agent at the time of kneading with a solvent. The melting start temp. of the polyester resin is desirably regulated to 60-100 deg.C so as to improve fixability especially at low temp. and to attain superior fixing strength.

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, a reduction in energy consumption (power consumption) has been made mainly for the purpose of widespread use in homes and multifunctionalization 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. 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.

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. There is also a method of lowering the fixing temperature by using a low melting point wax such as carnauba wax, rice wax and candelilla wax, but it is a mixture of several kinds of esters and free fatty acid and alcohol remain. Therefore, there is a problem in the storability of the toner. When a low-melting wax is melt-kneaded with a binder resin, the melting viscosities of the two are extremely different, so that the low-melting wax is poorly dispersed. There is a problem that the toner characteristics are deteriorated due to the non-uniform content of the melting point wax.

[0004]

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.

[0005]

SUMMARY OF THE INVENTION The present invention is an electrophotographic toner containing 12-hydroxystearic acid and a polyester resin.

The present invention will be described in detail below. The 12-hydroxystearic acid in the present invention is obtained, for example, by saponifying and decomposing hardened castor oil. That is, the same amount of warm water is added to hydrogenated castor oil, caustic soda solution is added, and the mixture is heated (maximum temperature 96 ° C.) and stirred for saponification and decomposition. Then, it is obtained by adding a sulfuric acid solution for neutralization and aging for several tens of minutes at 95 to 100 ° C. The structural formula is as follows. _{CH 3 - (CH 2) 5} -CH (OH) - (CH 2) 10 -CO
OH

According to the present invention, the above-mentioned 12-hydroxystearic acid has a lower melting point than the conventionally used polyolefin-based waxes and has releasability from a fixing roller, and is contained in a toner for electrophotography together with a polyester resin. In that case, the softening point of the toner is lowered and the toner is sufficiently melted even with a low-temperature heat fixing roll, so that there is an effect that excellent non-offset properties and fixing strength are obtained.

The content of 12-hydroxystearic acid in the electrophotographic toner of the present invention is preferably 1 to 30% by weight based on the binder resin. 1% by weight
If the amount is less than the above, the effect of lowering the softening point of the electrophotographic toner, that is, the melting start temperature is small, so that when fixing at a low fixing temperature, it is difficult to obtain sufficient fixing strength on the transfer paper. Because of the poor compatibility of
The dispersion of 12-hydroxystearic acid may be deteriorated, and the blocking property of the toner and the charging stability may be deteriorated. Further, the melt viscosity may be too low, which may deteriorate the non-offset property with respect to the fixing roll, which is not preferable. Considering the dispersibility in the polyester resin, the addition amount is preferably 4% by weight to 25% by weight with respect to the entire binder resin.

Examples of the diol component which is a monomer constituting the polyester resin used in the present invention include polyoxypropylene 2,2-2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene ( 3, 3)
-2,2-bis (4-hydroxyphenyl) propane,
Polyoxyethylene (2,0) 2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2,0) -polyoxyethylene (2,0) -2,2-
Bis (4-hydroxyphenyl) propane, polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,
4-butanediol, neopentyl glycol, 1,4
-Butenediol, 1,5-pentanediol, 1,6
Examples of hexanediol or polyhydric alcohol having 3 or more valences include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1, 2,4-butanetriol, 1,2,5-
Pentanetriol, glycerol, diglycerol,
2-methylpropanetriol, 2-methyl-1,2,2
4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxybenzene and the like can be mentioned. As the acid component, divalent acids such as fumaric acid, maleic acid, phthalic acid, isophthalic acid, itaconic acid, glutaconic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid and alkenylsuccinic acid can be used. Examples of organic acids or polycarboxylic acids having 3 or more valences are 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4.
4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2
-Methylene carboxy propane, tetra (methylene carboxylic) methane, 1,2,7,8-octane tetracarboxylic acid, etc. are mentioned. The monomer constituting the polyester resin used in the present invention is a polyfunctional monomer having a valence of 3 or more, that is, a polyhydric alcohol having a valence of 3 or more and / or a polyvalent having a valence of 3 or more in order to maintain good non-offset properties. It is preferable to widen the molecular weight distribution by polymerizing using a carboxylic acid.

Further, in the present invention, it is preferable that a crosslinking agent is used in the production of the toner to further promote the crosslinking in the melt-kneading. Examples of the crosslinking agent include epoxy resins, glycidyl group-containing resins, metal oxides, metal alkoxides, metal chelate compounds, cyanates, and isocyanate compounds.
When the polyester resin is crosslinked during melt-kneading, the molecular weight can be easily increased, the molecular weight distribution can be expanded, the melt viscosity of the toner can be increased, and offset to the fixing roller can be prevented.
Since the hydroxystearic acid reacts with each other to improve the compatibility, the toner can be prevented from being excessively pulverized, and the charging characteristics can be improved. The content of the cross-linking agent in the electrophotographic toner depends on the content of the functional group of the binder resin constituting the electrophotographic toner and the content of 12-hydroxysteric acid, but is approximately 0.1 in the toner. It is preferable that the content is up to 20% by weight. If the amount is less than 0.1% by weight, the effect of adding the crosslinking agent is small, and thus it is difficult to obtain the fixing offset width and the fixing strength. If the amount is more than 20% by weight, the crosslinking density with the binder resin is too high and the fixing becomes difficult, and the fixing is performed. It is not preferable because it deteriorates the property.

In the present invention, a catalyst can be used for the crosslinking reaction to appropriately control the crosslinking density. Examples of the catalyst include triethylamine, triethyldiamine, tin octoate, dibutyltin di (2-ethylhexoate), dibutyltin dilaurate, lead 2-ethylhexoate, ο-phenyl soda, potassium oleate,
Bismuth nitrate, 2-ethylhexyl titanate, tin chloride, iron chloride, iron 2-ethylhexoate, cobalt 2-ethylhexoate, zinc naphthenate, antimony trichloride and the like can be used.

The toner for electrophotography of the present invention contains a colorant in addition to the above components, and if necessary, a binder resin other than polyester, a magnetic material, a charge control agent, an anti-offset agent, a fluidizing agent. Characteristic improvers such as can be used.
In the present invention, as a resin that can be used in addition to the polyester resin, a resin such as a styrene acrylic resin, a polyethylene resin, an epoxy resin, a silicone resin, a polyamide resin, or a polyurethane resin may be blended.

As the colorant, carbon black,
Nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, mixtures thereof, and the like. it can. It is necessary that these colorants be contained in a sufficient ratio to form a visible image having a sufficient density, and the ratio is usually about 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin. It is said that

As the magnetic substance, a metal or alloy exhibiting ferromagnetism such as ferrite, magnetite, and other iron, cobalt, nickel, etc., or a compound containing these elements, or no ferromagnetic element, but an appropriate heat treatment. 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.

The electrophotographic toner of the present invention is as described above.
It has a composition and is particularly suitable for fixing at lower temperatures.
In order to achieve excellent fixing strength,
It is desirable that the temperature is 60 ° C. or higher and 100 ° C. or lower. Melting
If the melting start temperature is higher than 100 ° C, the fixing property is not sufficient,
If the temperature is lower than 60 ° C, the blocking property deteriorates and there is a problem in storage stability.
May occur. The melting start temperature as used in the present invention
The degree is the plunger under the following measuring machine and measuring conditions.
-The temperature at which the temperature begins to fall. Measuring instrument; Shimadzu's advanced flow tester CF-500 Measuring condition: 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

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. When the toner contains a magnetic material, it is used as a one-component developer as it is for developing an electrostatic image without being mixed with a carrier, or it is mixed with a carrier and used as a two-component developer. Good. Further, it can be applied to a non-magnetic one-component developing method.

[0017]

EXAMPLES The present invention will be described below based on examples. In the examples, “part” means “part by weight”. Example 1 Polyester resin 95 parts (Nippon Carbide Industry Co., Ltd. trade name; NCP-33B) Blocked isophorone diisocyanate 3 parts (HULS Co. Ltd. trade name; IPDI-BF 1540) 12-Hydroxystearic acid 5 parts Dibutyltin dilaurate 0.3 Part 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. trade name; Viscole 330P) The raw materials having the above blending ratios are mixed in a super mixer, melt-kneaded by a twin-screw kneader, ground by a jet mill, and then classified by a dry air stream classifier to obtain an average particle size of 10
Particles of μm were obtained. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-53 manufactured by Cabot Corporation)
0) 0.4 part was stirred in a Henschel mixer for 1 minute, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Example 2 Polyester resin 90 parts (manufactured by Nippon Carbide Industry Co., Ltd .; trade name: NCP-33B) Blocked isophorone diisocyanate 5 parts (manufactured by HULS, trade name: IPDI-BF 1540) 12-hydroxystearic acid 10 parts dibutyltin dilaurate 0.3 parts 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: Viscole 330P) Raw materials having the above blending ratios are mixed in a super mixer, hot melt kneaded in a twin-screw kneader, pulverized in a jet mill, and then classified in a dry airflow classifier to obtain an average particle size of 10
Particles of μm were obtained. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-53 manufactured by Cabot Corporation)
0) 0.4 part was stirred in a Henschel mixer for 1 minute, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Example 3 Polyester resin 80 parts (trade name: NCP-33B manufactured by Nippon Carbide Industry Co., Ltd.) Blocked isophorone diisocyanate 10 parts (trade name: IPDI-BF 1540 manufactured by HULS) 12 parts Hydroxystearic acid 20 parts Dibutyltin dilaurate 0.3 parts 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: Viscole 330P) Raw materials having the above blending ratios are mixed in a super mixer, hot melt kneaded in a twin-screw kneader, pulverized in a jet mill, and then classified in a dry airflow classifier to obtain an average particle size of 10
Particles of μm were obtained. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-53 manufactured by Cabot Corporation)
0) 0.4 part was stirred in a Henschel mixer for 1 minute, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Example 4 Polyester resin 70 parts (trade name: NCP-33B, manufactured by Nippon Carbide Industry Co., Ltd.) 20 parts blocked isophorone diisocyanate (trade name: IPDI-BF 1540, manufactured by HULS) 30 parts of dihydroxytin dilaurate 12-hydroxystearic acid 0.3 parts 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: Viscole 330P) Raw materials having the above blending ratios are mixed in a super mixer, hot melt kneaded in a twin-screw kneader, pulverized in a jet mill, and then classified in a dry airflow classifier to obtain an average particle size of 10
Particles of μm were obtained. Then, 100 parts of the particles and hydrophobic silica (trade name: Cabosil TS-53 manufactured by Cabot Corporation)
0) 0.4 part was stirred in a Henschel mixer for 1 minute, and hydrophobic silica was adhered to the surface of the particles to obtain the electrophotographic toner of the present invention.

Comparative Example 1 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that 12-hydroxystearic acid was not used. Comparative Example 2 A comparative electrophotographic toner was obtained in the same manner as in Example 2 except that styrene acrylic resin Heimer TB-1000 (manufactured by Sanyo Kasei Co., Ltd.) was used instead of the polyester resin. Comparative Example 3 A comparative electrophotographic toner was obtained in the same manner as in Example 2 except that carnauba wax was used instead of 12-hydroxystearic acid.

Next, the following items were evaluated for the above Examples and Comparative Examples. (1) Non-Offset Temperature Region First, 4 parts of each electrophotographic toner obtained in the above-mentioned Examples and Comparative Examples and 96 parts of a ferrite carrier (Powder Tech Co., Ltd. product name: FL-1020) not coated with a resin were prepared. A two-component developer was prepared by mixing. Next, a commercially available copying machine (trade name: SF-9, manufactured by Sharp Corporation) is used using the developer.
800), a plurality of belt-shaped unfixed images having a length of 2 cm and a width of 5 cm were formed on an A4 transfer paper. Then, a heat fixing roll having a surface layer made of Teflon and a pressure fixing roll having a surface layer made of silicone rubber are paired and rotated, and a fixing device is rotated at a roll pressure of 1 Kg / cm ² and a roll speed of 50.
The surface temperature of the heat-fixing roll was changed stepwise at intervals of 5 ° C., and the toner image on the transfer paper having the unfixed image was fixed at each surface temperature. . At this time, it was observed whether or not the toner was smeared in the blank area, and the temperature region in which the toner was not smeared was set as the non-offset temperature region. (2) Non-offset temperature width The difference between the maximum value and the minimum value in the above non-offset temperature region was defined as the non-offset temperature width.

(3) Fixing Strength The toner image of the transfer paper having the unfixed image was fixed by setting the temperature of the heat fixing roll to 130 ° C. 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. For the image density, a reflection densitometer RD-914 manufactured by Macbeth was used. Image density of fixed image after rubbing / image density of fixed image before rubbing × 100 (%) (4) Melting start temperature According to the above-described measuring device and method.

(5) Image characteristics Using the developer prepared in the above item (1), a commercially available copying machine (manufactured by Toshiba Corporation, trade name: BD-3801) 10,000.
A continuous copy test up to a sheet was performed, and the image density and the background fog were measured as follows. Image density: Macbeth reflection densitometer RD-914 Ground fog: Nippon Denshoku color difference meter MODEL Z-100
1DP numerical value shows the difference in whiteness between the transfer paper before copying and the non-image area after copying. Table 1 shows the evaluation results of the above items.

[0025]

[Table 1]

As is clear from the results shown in Table 1, the electrophotographic toner of the present invention was excellent in fixing strength of 90% or more even at a low temperature of the heat fixing roll of 130 ° C. On the other hand, it was confirmed that the electrophotographic toners of Comparative Examples 1 and 2 could not maintain good fixing strength and had practical problems. Further, it was confirmed that the toner of Comparative Example 3 has a narrow non-offset temperature range and the image density is lowered and fog is increased in a copy test of 10,000 sheets, which is a practical problem.

[0027]

The electrophotographic toner of the present invention has a sufficient fixing strength even when the temperature of the heat fixing roll is low, and when applied to a copying machine or a printer, the power consumption can be reduced. The effects of lowering the roll cost and reducing the machine cost and increasing the copying speed are achieved.

Claims (5)

[Claims] 1. An electrophotographic toner containing at least 12-hydroxystearic acid and a polyester resin. 2. The toner for electrophotography according to claim 1, wherein the content of 12-hydroxystearic acid in the toner is 1 to 30% by weight. 3. The toner for electrophotography according to claim 1, wherein the polyester resin is synthesized by using a polyfunctional monomer having a valence of 3 or more. 4. The toner for electrophotography according to claim 1, wherein a cross-linking agent is used. 5. The melting start temperature of the toner is 60 ° C. or higher and 10
The toner for electrophotography according to claim 1, which has a temperature of 0 ° C. or lower.