JP2982108B2 - Electrophotographic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, with the spread of copying machines and printers using an electrophotographic system including general households and the like, the use of low energy (mainly for the purpose of multifunctional copying machines and printers) has been promoted. Reduction of power consumption), speeding up for the purpose of spreading to the so-called gray area located at the border between the printing machine and copying machine, or lowering the roll pressure to simplify the fixing roll to reduce machine cost. Is desired. In addition, as copiers have become more sophisticated, since copiers equipped with a two-sided copy function and an automatic document feeder have become widespread, the fixing temperature of electrophotographic toner used in copiers and printers is low, and the There is a demand for a sheet having an excellent offset property and an excellent fixing strength to transfer paper in order to prevent stains during double-sided copying and the occurrence of stains in an automatic document feeder.

[0003] In response to the above demands, in the prior art, there have been proposed ones in which the molecular weight and molecular weight distribution of the binder resin are improved. Specifically, attempts have been made to lower the fixing temperature by lowering the molecular weight of the binder resin. However, the lowering of the molecular weight lowers the melting point but also lowers the viscosity at the same time, so that there has been a problem that an offset phenomenon to the fixing roll occurs. In order to prevent this offset phenomenon, a method of adjusting the low molecular weight region and the high molecular region of the binder resin to broaden the molecular weight distribution, or cross-linking the high molecular portion has been performed. However, in this method, the glass transition temperature (Tg) of the binder resin must be lowered in order to sufficiently enhance the fixing property, and it is inevitable 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 during duplex copying and stains in the automatic document feeder have been generated. Furthermore, there is a method of including a polyolefin-based release agent in order to prevent the offset phenomenon. However, when the release agent is contained, the melting point of the toner increases, and therefore, when fixing is performed at a low temperature, there is a problem that sufficient fixing strength to transfer paper cannot be obtained. There is also a method in which a low melting point wax such as carnauba wax, rice wax, candelilla wax, and caster wax is contained. However, the melting point is 80 to 100 ° C., and a large amount of the toner is required to sufficiently lower the melting point of the toner. If the addition is required, and if the addition amount is sufficient to effectively contribute to the fixability of the toner, a high-temperature offset phenomenon occurs, and problems occur in the chargeability and the storage stability.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to be able to fix at a low fixing temperature, to cause no practical problem in non-offset property, and to provide excellent fixing strength to transfer paper and excellent image characteristics. An object of the present invention is to provide an electrophotographic toner.

[0005]

SUMMARY OF THE INVENTION The present invention comprises a hardening oil having a melting point of 60 to 80 ° C. obtained from at least a binder resin, a colorant and a fatty acid containing erucic acid , and melt kneading.
And then pulverized and classified .

Hereinafter, the present invention will be described in detail. The hardened oil used in the present invention is obtained by adding about 0.2% of a reduced nickel catalyst to a triglyceryl ester of a fatty acid composed of a saturated fatty acid and an unsaturated fatty acid and glycerin, that is, glyceride as a main component, at a reaction temperature of 150 to 150. It is obtained by blowing hydrogen at 160 ° C. and a reaction pressure of 15 kg / cm ³ or less and stirring for about 3 hours. Various hardened oils can be obtained from the hardened oil according to the type of unsaturated fatty acid contained in the fatty acid.
As a hardened oil used for toner, a hardened oil obtained from castor oil, that is, caster wax has been conventionally known. The main component of the fatty acid constituting the triglyceride is ricinoleic acid, and the caster wax contains about 80 to 90% by weight of the whole fatty acid. But,
Castor wax generally has a melting point of 80 to 90 ° C., and since it has a high melting point, sufficient improvement in fixability at a low temperature cannot be obtained even when added to toner. In the present invention, since the melting point of the hardened oil is 60 to 80 ° C. by adding erucic acid, which is an unsaturated fatty acid, to the fatty acid, when this is added to the toner, the melting start temperature of the toner is greatly reduced. The effect which makes it do is obtained. The content of erucic acid is preferably at least 40% by weight of the total fatty acids. When the content of erucic acid is less than 40% by weight and the content of unsaturated fatty acids other than erucic acid is large, the melting point becomes too high and the fixability deteriorates. On the other hand, when the content of erucic acid is less than 40% by weight and the content of saturated fatty acids is large, the melting point of the hardened oil becomes too low, and the storage stability of the toner deteriorates. Specific examples of such a hardened oil include hardened rapeseed oil having a content of hydrogenated glyceride obtained from rapeseed oil of about 50.0% and erucic acid obtained by hydrogenating glyceride obtained from poppy oil. About 41.5
% Hardened poppy oil and the like. Table 1 shows the compositions and properties of the hardened rapeseed oil and hardened rapeseed oil used in the examples described below and the hardened oil not containing erucic acid used in the comparative examples.

[Table 1]

When hydrogenated triglyceride is added to a fatty acid to form a hardened oil, it is preferable to reduce the degree of unsaturation as much as possible. If the degree of unsaturation is high, the melting point is lowered and the storage stability of the toner is deteriorated. Therefore, it is preferable that the iodine value which is an index of the degree of unsaturation is 5 or less. In the present invention, the iodine value is measured using a Wies method. The melting point of the hardened oil is preferably from 60 to 80C. If the temperature is lower than 60 ° C., there is a problem in the storability of the toner. The melting point as used herein indicates the peak temperature of the amount of heat absorbed by DSC. The method of measuring the peak temperature of the absorbed heat by DSC is performed as follows. For example, using a differential scanning calorimeter SSC-5200 manufactured by Seiko Denshi Kogyo KK, about 10 mg of hardened oil is weighed and placed on a DSC, and 50 ml of N ₂ gas is blown in for 1 minute. Then, between 20 and 150 ° C, 10 ° C per minute
And the amount of heat absorbed at that time is measured. When a plurality of peaks are obtained, the peak temperature showing the maximum heat of absorption is defined as the melting point. The content of the hardened oil is preferably 2 to 30 parts by weight based on 100 parts by weight of the binder resin. If the amount is less than 2 parts by weight, the effect on the low-temperature fixability is small, and if it is more than 30 parts by weight, the melt viscosity becomes too low and a high-temperature offset occurs, which is not preferable.

As the binder resin used in the present invention, any resin commonly used for toners can be used, but in particular, the melting start temperature is preferably as low as possible for the purpose of improving low-temperature fixing performance. The melting start temperature of the toner is preferably from 60 to 100C. 100 ℃
If it is higher, the fixability is not sufficient, and if it is lower than 60 ° C., the blocking property is deteriorated, causing a problem in storage stability. The melting start temperature referred to here means the temperature at which the plunger starts lowering when measured under the following measuring instrument and measuring conditions. Measuring machine; Koka type flow tester CF-500 manufactured by Shimadzu Corporation Measurement conditions: Plunger: 1 cm ² Die diameter: 1 mm Die length: 1 mm Load: 20 kgF Preheating temperature: 50 to 80 ° C Preheating time: 300 sec Heating rate : 6 ° C / min

The electrophotographic toner of the present invention comprises a binder resin,
The coloring agent, the hardened oil, and other additives such as a charge control agent and a magnetic substance, if necessary, are mixed in a desired composition, melt-kneaded, cooled, solidified, and then pulverized and classified . Examples of the binder resin described above include styrene resin, polyacrylate resin, styrene- (meth) acrylate copolymer resin, polyvinyl chloride, polyvinyl acetate,
Polyvinylidene chloride, phenolic resin, epoxy resin,
A polyester resin is exemplified.

As the colorant, carbon black,
Nigrosine dye, aniline blue, chaco 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. These colorants need to be contained in a sufficient ratio to form a visible image having a sufficient concentration, and usually a ratio of about 1 to 20 parts by weight based on 100 parts by weight of the binder resin. Is done.

As the magnetic material, ferromagnetic metals or alloys such as ferrite and magnetite, cobalt, nickel and the like, or compounds containing these elements or ferromagnetic elements are not contained, or a suitable heat treatment is performed. Alloys that become ferromagnetic when applied, such as manganese-copper-aluminum, manganese-copper-tin, and other alloys of the type called Heusler alloys containing manganese and copper, or chromium dioxide, and the like. .
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 mixed with a carrier made of ferrite powder, iron powder or the like to form a two-component developer. When a magnetic material is contained, it may be used as it is as a one-component developer without mixing with a carrier for developing an electrostatic image, or may be mixed with a carrier and used as a two-component developer. Further, the present invention can be applied to a non-magnetic one-component developing method.

[0013]

The present invention will be described below with reference to examples. In the examples, parts are parts by weight. <Example 1> The above materials were mixed by a super mixer, melt-kneaded, and pulverized and classified to obtain negatively-chargeable toner base particles having an average particle size of 11 μm. Thereafter, 0.3 parts of hydrophobic silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) was adhered to the surface with a Henschel mixer to obtain an electrophotographic toner of the present invention. The melting start temperature of this electrophotographic toner was 99 ° C. <Example 2> Based on the above composition, an electrophotographic toner of the present invention was obtained in the same manner as in Example 1. The melting start temperature of this electrophotographic toner was 95 ° C.

<Embodiment 3> Based on the above composition, an electrophotographic toner of the present invention was obtained in the same manner as in Example 1. The melting start temperature of this electrophotographic toner was 92 ° C. <Example 4> Based on the above composition, an electrophotographic toner of the present invention was obtained in the same manner as in Example 1. The melting start temperature of this electrophotographic toner was 97 ° C.

Comparative Example 1 A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that no rapeseed oil was blended. The melting start temperature of this electrophotographic toner is 1
09 ° C. <Comparative Example 2> A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that 5 parts of castor wax was used instead of the hardened rapeseed oil. The melting start temperature of this electrophotographic toner was 104 ° C. <Comparative Example 3> Example 1 was repeated except that 5 parts of polyethylene wax (melting point 81.1 ° C) was blended in place of the rapeseed hardened oil.
In the same manner as in Example 1, a comparative electrophotographic toner was obtained. In addition,
The melting start temperature of this electrophotographic toner was 105 ° C. <Comparative Example 4> A comparative electrophotographic toner was obtained in the same manner as in Example 2, except that 10 parts of hardened coconut oil was used instead of hardened rapeseed oil. The melting start temperature of this electrophotographic toner was 90 ° C. <Comparative Example 5> 1 hardened palm kernel oil was used instead of hardened rapeseed oil.
An electrophotographic toner for comparison was obtained in the same manner as in Example 2 except that 0 part was blended. The melting start temperature of this electrophotographic toner was 91 ° C. Comparative Example 6 Hardened palm oil was replaced with 10 hardened rapeseed oils.
An electrophotographic toner for comparison was obtained in the same manner as in Example 2 except that the components were blended. The melting start temperature of this electrophotographic toner was 93 ° C.

Next, the following items were tested for the above Examples and Comparative Examples. (1) Non-Offset Temperature Region First, 4 parts of each of the electrophotographic toners obtained in the above Examples and Comparative Examples and 96 parts of a ferrite carrier (product name: FL-1020, manufactured by Powdertech Co.) without resin coating were used. By mixing, a two-component developer was prepared. Next, a commercially available copying machine (trade name: SF-9, manufactured by Sharp Corporation) is used by using the developer.
800), a plurality of belt-shaped unfixed images having a length of 2 cm and a width of 5 cm were prepared on A4 transfer paper. Next, a heat fixing roll having a surface layer formed of Teflon and a pressure fixing roll having a surface layer formed of silicone rubber are paired and rotated by a fixing machine having a roll pressure of 1 kg / cm ² and a roll speed of 50 kg / cm ^2.
mm / sec, and the surface temperature of the heat fixing roll was changed stepwise to fix the toner image of the transfer paper having the unfixed image at each surface temperature. At this time, observation was made as to whether or not the toner was contaminated in the blank portion, and a temperature region in which no contaminant was generated was defined as a non-offset temperature region. The difference between the maximum value and the minimum value in the non-offset temperature region was defined as the non-offset temperature width.

(2) Fixing Strength The surface temperature of the heat fixing roll of the fixing machine was set to 140 ° C., and the toner image on the transfer paper 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 according to the following equation, which was used as an index of low energy fixing property. The image density was measured using a reflection densitometer RD-914 manufactured by Macbeth. Fixing strength (%) = Image density of fixed image after rubbing / Image density of fixed image before rubbing × 100

(3) Storage Property The storage properties of the electrophotographic toners obtained in the above Examples and Comparative Examples were evaluated. The storage stability was evaluated by filling a 150 cc bottle with 20 g of each of the obtained electrophotographic toners.
After standing in a high-temperature bath at 0 ° C. for 8 hours, the caking state (blocking) of the electrophotographic toner was visually checked. The conditions for the determination are shown below. ：: no blocking occurred x: toner blocked and did not collapse even after shaking Table 2 shows the test results of the above items.

[0019]

[Table 2]

From the results shown in Table 2, the toner for electrophotography according to the present embodiment exhibited good fixing characteristics with a fixing strength of 90% or more and a non-offset width of 65 to 75 ° C. Also, the storage stability was at a practically acceptable level. However, in Comparative Examples 1 to 3, the fixing strength was 77% or less, which was inferior to that of Example. Comparative Example 4
In Nos. To 6, it was confirmed that the non-offset temperature width was as narrow as 35 to 55 ° C., and that there was a practical problem in storage stability. Further, a 10-minute commercial copying machine (trade name: BD-3801 manufactured by Toshiba Corp.) was used using the respective developers described in (1) above.
As a result of conducting a continuous copy test up to 000 sheets, in all of Examples 1 to 4, the triboelectric charge amount was 100
The value varies from -20 .mu.c / g to -25 .mu.c / g up to 00 sheets, and the image density also varies from 1.45 to 1.40 from the initial to 10,000 sheets. It was confirmed that there was no. The copied original
R> is A4 having a black portion of 6%, the triboelectric charge is measured by a blow-off triboelectric charge measuring device manufactured by Toshiba Chemical Co., and the image density is measured by a reflection densitometer RD-914 manufactured by Macbeth.
It was used.

[0021]

The toner for electrophotography according to the present invention can maintain a sufficient non-offset temperature region and can be fixed at a low temperature, and is excellent in fixing strength and can obtain a large number of sheets of sufficient image density. It has the effect of being able to. Accordingly, the temperature of the heat fixing device can be maintained at a considerably lower temperature than in the past, and the power consumption of a copying machine or the like can be reduced.

Claims (5)

(57) [Claims] 1. A melting point obtained from at least a binder resin, a colorant and a fatty acid containing erucic acid is 60 to 80 ° C.
A toner for electrophotography, comprising: a hardened oil , melt-kneaded, and pulverized and classified . 2. The electrophotographic toner according to claim 1, wherein the content of erucic acid is at least 40% by weight of the whole fatty acid. 3. The electrophotographic toner according to claim 1, wherein the iodine value of the hardened oil is 5 or less. 4. The electrophotographic toner according to claim 1, wherein the content of the hardening oil is 2 to 30 parts by weight based on 100 parts by weight of the binder resin. 5. A melting start temperature of the toner is 60 to 100 ° C.
The electrophotographic toner according to claim 1, wherein: