JPH0844228A - Fixing method of electrophotographic toner - Google Patents

Abstract

PURPOSE:To enable to fix even at a low temp. and to attain excellent fixing strength without causing the problem in non-offset property by fixing an unfixed image of a thermosetting toner, which is formed on a transferred paper, by the use of a fixing device having a pair of a rotated roller and belt. CONSTITUTION:The thermosetting toner is a particle dispersedly containing a binding resin, a hardener, a curing catalyst and a coloring agent and another toner component such as a charge controlling agent, a releasing agent and a magnetic material and having 5-20mum average particle diameter. As the binding resin, a polyester resin or the like is applied. And the fixing device is provided with the heat roller 1 and the belt 6, the heat roller 1 is provided with a heater 2 at the center part and the fluororesin layer 4 is provided on the outer circumference of an aluminum core metal 3. And the belt 6 and the heat roller 1 are rotated in the direction of the arrow as a pair and nip width produced by the heat roller 1 and the belt 6 is enlarged. The transferred paper carrying the unfixed image 7 is passed through the nip and a fixed image 7 is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner fixing method, and more particularly to an electrophotographic toner fixing method for a copying machine or a printer which employs heat fixing.

[0002]

2. Description of the Related Art In recent years, electrophotographic copying machines and printers have been widely used in general households and the like. (Reduction of power consumption), high speed for the purpose of spreading to so-called gray area located at the boundary between printing machine and copying machine, or low roll pressure for simplification of fixing roll to reduce machine cost. Is desired. 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 a sheet having excellent offset properties and excellent fixing strength on a transfer sheet in order to prevent stains during double-sided copying and stains in the automatic document feeder.

In the prior art, a fixing device using a heat roll and a thermoplastic toner have been used to meet the above demands. In order to lower the fixing temperature by this heat roll fixing, proposals have been made of those in which the binder resin of the toner has improved the molecular weight and the molecular weight distribution. Specifically, attempts have been made to lower the fixing temperature by lowering the molecular weight of the binder resin. However, the melting point was lowered by lowering the molecular weight, but at the same time, the hot melt viscosity was also lowered, so that there was a problem that an offset phenomenon to the fixing roll occurred. 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 (Tg) of the resin has to be lowered in order to provide sufficient fixability, and it is unavoidable that the storage stability of the toner is impaired. Conventionally, a method of adhering inorganic fine particles such as silica, titanium, and alumina or resin fine particles to the toner surface has been used as a means for ensuring the preservability. However, it is difficult to completely uniformly coat the surface of the toner with these fine particles, and the toner having a low Tg cannot maintain sufficient storage stability. Further, in order to completely cover the surface of the toner, a large amount of fine particles must be added, resulting in deterioration of fixing property and offset property. Furthermore, a large amount of fine particles adversely affect the charging characteristics, causing a problem in the life of the developer. Further, in the heat roll fixing device, measures such as increasing the nip pressure of the roller or increasing the nip width by lowering the rubber hardness of the pressure roller have been taken in order to improve the fixing strength. In these methods, it is necessary to increase the strength of the supporting member of the fixing device for maintaining the pressure, which raises the cost and causes problems such as paper wrinkles when the transfer paper passes through. Further, in order to increase the nip width, it is necessary to increase the diameter of the roller, and it has not been possible to meet the recent demand for miniaturization. Further, when the rubber hardness of the pressure roller is lowered, deformation with time occurs, which is a problem.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is for electrophotography, which can fix at a low fixing temperature, does not cause any practical problems even in non-offset properties, and has excellent fixing strength on transfer paper. It is to provide a fixing method of toner.

[0005]

SUMMARY OF THE INVENTION The present invention is characterized in that an unfixed image of thermosetting toner formed on a transfer paper is fixed by using a fixing device in which a roller and a belt rotate in pairs. This is a method of fixing photographic toner. In the present invention, a thermosetting toner is used to form a toner image on a photoconductor, this toner image is transferred onto a transfer paper, and then the unfixed toner image on the transfer paper is paired with a roller and a belt. Fix using a rotating fixing machine.

The present invention will be described in detail below. As the toner applied to the fixing method of the electrophotographic toner of the present invention, a thermosetting toner is used. The thermosetting toner undergoes a curing reaction by heating, the melt viscosity increases when the fixing device is heated and pressed, and the offset phenomenon of the toner to the fixing device can be prevented. Further, the fixing strength on the transfer paper is remarkably stronger than that of the thermoplastic toner because it is cured while melting on the transfer paper. The thermosetting toner used in the present invention contains at least a binder resin and a crosslinking agent that crosslinks the binder resin. The binder resin may be any material as long as it contains a functional group such as an epoxy resin, a polyester resin, a phenol resin, etc., and causes crosslinking by a crosslinking agent or self-crosslinking by heat. If the binder resin is an epoxy resin, polyamine, polyamide, amino resin, polybasic acid, high acid value polyester or the like can be used as a crosslinking agent. When the binder resin is a resin containing a hydroxyl group such as a phenol resin, a polyester resin, and a hydroxyl group-containing acrylic resin, polyisocyanate,
Amino resins, melamine resins, urea resins, metal chelating agents, etc. can be used.

Next, a fixing device for fixing the electrophotographic toner of the present invention will be described. FIG. 1 is a partial cross-sectional view showing an example of the fixing device of the present invention, which includes a heat roller 1 and a belt 6.
Is provided. It is preferable that the heat roller 1 has a heater 2 at the center and a fluororesin layer 4 provided on the outer periphery of an aluminum core metal 3. The pair of the belt 6 and the heat roller 1 is rotated in the direction of the arrow to increase the nip width N between the heat roller 1 and the belt 6. The transfer paper 8 carrying the unfixed image 7 obtains a fixed image 7'after passing through the nip. According to such a method, the heating time at the time of fixing becomes longer than that of a fixing device having only a roller. Since the thermosetting toner has a slow curing speed, complete curing cannot be expected by heating for a short time. Therefore, it is preferable that the nip width is as wide as possible in order to obtain the offset phenomenon to the fixing device and the sufficient fixing strength to the transfer paper. The nip width is preferably 10 mm or more when used in currently marketed electrophotographic equipment. Further, as illustrated in FIG. 2, in order to further accelerate the curing reaction of the thermosetting toner, it is effective to preheat the belt in advance and heat the toner before entering the nip. It is desirable to design various parameters so that the nip width and fixing speed of the fixing device and the curing time of the thermosetting toner are matched.

The thermosetting toner of the present invention is a particle in which a binder resin, a curing agent, a curing catalyst and a colorant are appropriately dispersed and containing other toner components such as a charge control agent, a releasing agent and a magnetic material. And the average particle size is in the range of 5 to 20 μm. A polyester resin, an epoxy resin, a phenol resin, an acrylic resin containing a carboxyl group, a hydroxyl group or a glycidyl group, or the like is applied as the binder resin constituting the thermosetting toner in the present invention. Further, as the curing agent, polyamine, polyamide, polyisocyanate, amino resin, metal chelating agent and the like are applied, and as the catalyst, inorganic acid and redox type initiator are applied. Usually, the amount of the functional groups in the binder resin and the amount of the functional groups in the curing agent are equimolar. A toner for electrophotography may be formed by adding and mixing a fluidity improver made of fine silica powder or the like to the particles thus obtained.

Regarding the melting characteristics of the thermosetting toner used in the present invention, the melting start temperature of the toner is preferably 60 ° C. or higher and 100 ° C. or lower in order to improve the fixing property at a lower temperature. If the temperature is higher than 100 ° C, the fixability will be insufficient, and 60 ° C
If it is lower than the above range, the blocking property may be deteriorated and the storage property may be deteriorated. The melting start temperature refers to 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 rate : 6 ° C / min

The thermosetting toner used in the present invention preferably contains a release agent. By including the release agent, the releasability from the fixing device is improved, the occurrence of the offset phenomenon can be prevented, and the toner can be used at a wider fixing temperature.
As the release agent used in the present invention, natural waxes such as olefin synthetic waxes such as polypropylene and polyethylene, rice wax, carnauba wax, and castor-hardened oil are preferable.

In the fixing device equipped with the belt used in the present invention, it is possible to apply silicone oil to the roller surface in order to improve the releasability. The silicone oil is preferably a method in which a nonwoven fabric such as felt is impregnated with silicone oil and pressed against a roller or belt. In addition, a device for supplying silicone oil to these silicone oil-impregnated felts may be provided in order to replenish the consumed oil if necessary.

The fixing belt used in the present invention is made of silicone rubber, fluorine resin such as perfluoroalkoxy resin, silicon rubber, polyamide resin, polyimide resin, or metal. Further, the surface of these materials may be coated with a fluororesin.

The heat roller constituting the fixing device of the present invention can be any roller as long as it is currently used in heat roll fixing, but among them, the surface of a metal roll made of aluminum, iron or the like is coated with fluororesin or silicone rubber. It is most preferable that the heat-resistant release layer is provided by coating with the above.

The toner for electrophotography of the present invention may be used as a two-component developer by mixing a carrier composed of iron powder, ferrite, granulated magnetite, etc. You may use it as a component developer.

[0015]

EXAMPLES The present invention will be described below based on examples. In the examples, “part” means “part by weight”. Example 1 Condensation polymerization was carried out using 85 mol% of bisphenol A ethylene oxide adduct as an alcohol component, 15 mol% of trimethylolpropane, 10 mol% of trimellitic acid as an acid component, and 85 mol% of dodecenylsuccinic acid, and a number average molecular weight of 7,500 was obtained. A polyester resin A having a weight average molecular weight of 52,000, a hydroxyl group of 30, Tg of 47 ° C. and a melting start temperature of 88.5 ° C. was obtained. Polyester resin A 90 parts Chromium-containing metal dye 1.5 parts (Orient Chemical Co., Ltd. product name: Bontron S-34) Carbon black 6.5 parts (Mitsubishi Kasei product name: MA-100) Blocked isophorone diisocyanate 10 Part (manufactured by HULS company: IPDI-B 1530) polypropylene 3 parts (manufactured by Sanyo Chemical Co., Ltd .: product name: Viscole 330P) The raw materials having the above mixing ratios are mixed with a super mixer, and hot-melt kneaded with a twin-screw kneader. After that, it was crushed with a jet mill and then classified with a dry airflow classifier to obtain an average particle size of 10
To obtain thermosetting toner particles having a size of μm. The melting start temperature of the toner particles was 88.1 ° C. Then, 100 parts by weight of the toner particles and 0.1 parts of dibutyltin dilaurate are used.
Parts by weight and were put into a Henschel mixer and stirred for 5 minutes. Further, 100 parts of the toner particles and hydrophobic silica (trade name: Cabosil TS-530 manufactured by Cabot Corporation).
0.4 part was stirred in a Henschel mixer for 1 minute, and hydrophobic silica was attached to the surface of the particles to obtain an electrophotographic toner of the present invention.

A two-component developer was prepared by mixing 4 parts of the electrophotographic toner and 96 parts of a ferrite carrier (trade name: FL-1020 manufactured by Powder Tech Co., Ltd.) which is not coated with a resin. Next, using the developer, a plurality of unfixed images of a belt-shaped thermosetting toner of 2 cm in length and 5 cm in width are formed on an A4 transfer paper with a commercially available copying machine (trade name: SF-9800 manufactured by Sharp Corporation). did. Next, the heat roller (60φ) 1 whose surface layer shown in FIG. 1 is formed of the fluororesin layer 4
And a fixing device in which a fixing belt 6 formed of silicone rubber rotates in a pair at a roll speed of 50 mm / se.
c, the nip width was adjusted to 30 mm, the surface temperature of the heat roller was set to 100 ° C., and the unfixed image 7 of the transfer paper 8 on which the unfixed image was formed 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. As the image density, a reflection densitometer RD-914 manufactured by Macbeth was used. Fixing strength (%) = Image density of fixed image after rubbing / Image density of fixed image before rubbing × 100

Example 2 Polyester resin 100 parts (manufactured by Nippon Carbide Co., Ltd .: trade name: NCP-33B Tg: 60 ° C., hydroxyl value: 50 mgKOH / g) 50 parts novolak type phenolic resin (trade name: Tamanor manufactured by Arakawa Chemical Industry Co., Ltd.) 751 Softening point 70 ° C.) Hexamethylenetetramine 5 parts Carbon black 6.5 parts (Mitsubishi Chemical Co., Ltd. product name: MA-100) Chromium metal dye 2 parts (Orient Chemical Industry product name: Bontron S-34) Polypropylene 3 parts (manufactured by Sanyo Kasei Kogyo Co., Ltd .: Viscole 330P) The raw materials having the above blending ratios are mixed in a super mixer, melt-kneaded by a twin-screw kneader, pulverized by a jet mill, and then dried by a dry air stream classifier. After classification, the average particle size is 10
To obtain thermosetting toner particles having a size of μm. The melting start temperature of the toner particles was 89.4 ° C. Then, 100 parts by weight of the toner particles and 0.2 parts by weight of salicylic acid were put into a Henschel mixer and stirred for 5 minutes. Further, 100 parts of the toner particles and 0.4 part of hydrophobic silica (trade name: Cabosil TS-530 manufactured by Cabot Corporation) are stirred in a Henschel mixer for 1 minute to attach the hydrophobic silica to the surface of the particles, and thus the present invention To obtain a toner for electrophotography. A fixing test was carried out on the electrophotographic toner by the same fixing method as in Example 1.

Example 3 Epoxy resin 50 parts (Okaka Shell Co., Ltd. trade name: Epicoat 1004) Epoxy resin 50 parts (Okaka Shell Co., Ltd. trade name: Epicoat 1007) Epomate 50 parts (Okaka Shell Co., Ltd. trade name: Epomate B-001) Carbon black 6.5 parts (Mitsubishi Chemical Co., Ltd. product name: MA-100) Charge control agent 2 parts (Orient Chemical Co., Ltd. product name: P-51) Polypropylene 5 parts (Sanyo Chemical Co., Ltd. product) Product name: Viscole 330P) The 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
To obtain thermosetting toner particles having a size of μm. The melting start temperature of the toner particles was 89.1 ° C. Further, 100 parts of the toner particles and 0.4 part of hydrophobic silica (trade name: Cabosil TS-530 manufactured by Cabot Corporation) are stirred in a Henschel mixer for 1 minute to attach the hydrophobic silica to the surface of the particles, and thus the present invention To obtain a toner for electrophotography. A fixing test was carried out on the electrophotographic toner by the same fixing method as in Example 1.

Example 4 The electrophotographic toner of Example 1 was applied to the fixing device shown in FIG. That is, FIG. 2 shows a pair of a nip width N of a belt 6 made of silicon rubber interposed between rollers (30φ) 5 made of aluminum rotating in the direction of the arrow and a pressure roller 9 having a surface layer covered with silicone rubber. It has a mechanism that rotates with. A roll speed was set to 50 mm / sec, a heat roller temperature was set to 100 ° C., and a nip width was set to 20 mm, and a fixing test was carried out in the same manner as in Example 1. The unfixed image 7 of the thermosetting toner on the transfer paper 8 passes through the support plate 10 and is supplied to the nip width N.

Comparative Example 1 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that the isophorone diisocyanate was not used. A fixing test was conducted on this comparative electrophotographic toner in the same manner as in Example 1.

Comparative Example 2 The fixing device of Example 1 was replaced by the fixing device shown in FIG. That is, FIG. 3 rotates in the direction of the arrow and includes a heater 2 and an aluminum core metal 3, a heat roller 1 having a surface layer made of a fluororesin layer 4, and a pressure roller 9 having a surface layer made of silicone rubber in a pair. The rotating fixing unit has a nip width N of 10 mm and a roll speed of 50 mm / se.
The fixing test was carried out in the same manner as in Example 1 by using a fixing device in which the surface temperature of the heat roller was set to 100 ° C. The unfixed image 7 on the transfer paper 8
Becomes a fixed image 7'after passing through the nip width N.

The test results of the above items are shown in Tables 1 and 2.

[Table 1]

[Table 2]

As is clear from the test results of Tables 1 and 2, the fixing method of the electrophotographic toner of the present invention has a fixing strength of 90% or more at a fixing temperature of 100 ° C. and has a practically sufficient fixing strength. confirmed. On the contrary,
In the comparative example, it was confirmed that the offset phenomenon occurred on the heat roller and the fixing strength was low, which was a problem in practical use. In addition, a commercially available copying machine (trade name: BD-3801, manufactured by Toshiba Corp.) is used by using each of the developers described in (1) above.
As a result of conducting a continuous copy test up to 0000 sheets, in all of Examples 1 to 4, the triboelectric charge amount was from -20 μc / g to -25 μ from the initial stage to 10000 sheets.
It was confirmed that there was no problem in practical use because the image density changes from c / g and the image density changes from 1.45 to 1.40 from the initial stage to 10000 sheets. The copied original was A4 with a black portion of 6%. The triboelectric charge amount was measured by a blow-off triboelectric charge amount measuring device manufactured by Toshiba Chemical Corporation. The image density was measured by a reflection densitometer RD-914 manufactured by Macbeth.

[0024]

The electrophotographic toner of the present invention has the effects of being able to be fixed at a low temperature, having excellent offset properties, and being capable of obtaining a sufficient number of image densities.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a fixing device used in Example 1.

FIG. 2 is a partial cross-sectional view of a fixing device used in Example 4.

FIG. 3 is a partial cross-sectional view of a fixing device used in Comparative Example 2.

[Explanation of symbols] 1 heat roller 2 heater 3 aluminum cored bar 4 fluororesin layer 5 belt roller 6 belt 7 unfixed image 7'fixed image 8 transfer paper 9 pressure roller 10 support plate N nip width

Claims (7)

[Claims] 1. A method of fixing an electrophotographic toner, wherein an unfixed image of a thermosetting toner formed on a transfer paper is fixed using a fixing device in which a roller and a belt rotate in pairs. 2. The melting start temperature of the thermosetting toner is 60 ° C.
The method for fixing an electrophotographic toner according to claim 1, wherein the temperature is 100 ° C. or lower. 3. The method of fixing an electrophotographic toner according to claim 1, wherein the thermosetting toner contains a release agent. 4. A method for fixing electrophotographic toner according to claim 1, further comprising means for preheating the belt. 5. The nip width between the roller and the belt is 10 mm.
The method for fixing an electrophotographic toner according to claim 4, wherein the above is the case. 6. The method of fixing a toner for electrophotography according to claim 1, further comprising means for applying a release agent to the roller or the belt. 7. The method for fixing an electrophotographic toner according to claim 6, wherein the release agent is silicone oil.