JPH08179547A - Electrophotographic toner - Google Patents

Abstract

PURPOSE: To provide a toner fixable at a low fixing temp., causing no problem on anti-offsetting property and excellent in fixing strength and image characteristics by incorporating a binder resin, a colorant and hardened oil obtd. from fatty acids including erucic acid. CONSTITUTION: This toner contains at least a binder resin, a colorant and hardened oil obtd. from fatty acids including erucic acid. The hardened oil is obtd. by adding a reducing nickel catalyst to fats and oils based on triglyceryl esters of fatty acids with glycerol, that is, glyceride. Since erucic acid as an unsatd. fatty acid is included in the fatty acids, the m.p. of the hardened oil is regulated to 60-80 deg.C, and when the oil is added to a toner, the melting start temp. of the toner is considerably reduced. The content of erucic acid is preferably >=40wt.% of the total amt. of the fatty acids. This toner maintains a satisfactory anti-offsetting temp. region, can be fixed at a low temp., is excellent in fixing strength and can ensure satisfactory image density.

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, 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 order to meet the above requirements, the prior art has proposed proposals for improving 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 adjusting the low molecular weight region and the high molecular region of the binder resin to widen the molecular weight distribution, or cross-linking the high molecular portion has been performed. However, with this method, the glass transition temperature (Tg) of the binder resin must be lowered in order to provide sufficient fixability, and 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, there is also a method of incorporating a polyolefin-based release agent in order to prevent the above-mentioned offset phenomenon. However, when the release agent is contained, the melting point of the toner becomes high, so that when fixing at a low temperature, there is a problem that sufficient fixing strength on the transfer paper cannot be obtained. There is also a method of adding a low melting point wax such as carnauba wax, rice wax, candelilla wax, and castor wax, but the melting point is 80 to 100 ° C. Addition is required, and when an addition amount that effectively contributes to the fixing property of the toner is added, a high temperature offset phenomenon occurs, and there are problems in chargeability and storage stability.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to fix at a low fixing temperature, practically no problem occurs even in non-offset property, and excellent in fixing strength to transfer paper and image characteristics. It is to provide a toner for electrophotography.

[0005]

SUMMARY OF THE INVENTION The present invention is an electrophotographic toner containing at least a binder resin, a colorant, and a hardened oil obtained from a fatty acid containing erucic acid.

The present invention will be described in detail below. The hydrogenated oil used in the present invention comprises a triglyceryl ester of a fatty acid composed of a saturated fatty acid and an unsaturated fatty acid and glycerin; It can be obtained by blowing hydrogen at 160 ° C. at a reaction pressure of 15 kg / cm ³ or less and stirring for about 3 hours. As the hardened oil, various hardened oils can be obtained depending on the type of unsaturated fatty acid contained in the fatty acid.
As a hardened oil used for a toner, a hardened oil obtained from castor oil, that is, a caster wax has been conventionally known. Castor wax contains ricinoleic acid as a main component of fatty acids constituting triglyceride, and contains about 80 to 90% by weight of all fatty acids. But,
The melting point of castor wax is generally 80 to 90 ° C., and even if it is added to the toner, it is not possible to sufficiently improve the fixing property at a low temperature because the melting point is high. In the present invention, since the fatty acid contains erucic acid which is an unsaturated fatty acid, the melting point of the hardened oil becomes 60 to 80 ° C. Therefore, when this is added to the toner, the melting start temperature of the toner is significantly lowered. The effect is obtained. The content of erucic acid is preferably 40% by weight or more of the total fatty acids. When the content of erucic acid is less than 40% by weight and the amount of unsaturated fatty acid other than erucic acid is large, the melting point becomes too high and the fixability deteriorates, which is not preferable. Further, when the content of erucic acid is less than 40% by weight and the saturated fatty acid is large, the melting point of the hardened oil becomes too low and the storage stability of the toner deteriorates, which is not preferable. Specific examples of such hydrogenated oils include hydrogenated rapeseed oil obtained from rapeseed oil and having a content of erucic acid of about 50.0%, and erucic acid obtained from hydrogenated glyceride obtained from mustard oil. The amount is about 41.5
%, Such as hardened mustard oil. In addition, Table 1 shows the composition and characteristics of the rapeseed hydrogenated oil and the mustard hardened oil used in Examples described later and the hardened oil containing no erucic acid used in Comparative Examples.

[Table 1]

When hydrogenated triglyceride is added to 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, the iodine value, which is an index of the degree of unsaturation, is preferably 5 or less. The iodine value in the present invention is measured using the Wis method. The melting point of the hardened oil is preferably 60 to 80 ° C. If it is lower than 60 ° C., there is a problem in the storage stability of the toner, and if it is higher than 80 ° C., the low temperature fixability is deteriorated, which is not preferable. The melting point referred to here is the peak temperature of the amount of heat absorbed by DSC. The method of measuring the peak temperature of the absorbed heat quantity by DSC is carried out as follows. For example, using a differential scanning calorimeter SSC-5200 manufactured by Seiko Denshi Kogyo Co., Ltd., as a measurement condition, about 10 mg of hardened oil is weighed and placed on the DSC, and 50 ml of N ₂ gas is blown for 1 minute. And 10 ℃ per minute between 20 and 150 ℃
The temperature is raised at a rate of, and the amount of absorbed heat at that time is measured. When a plurality of peaks are obtained, the peak temperature showing the maximum amount of absorbed heat is taken as the melting point. The content of the hardened oil is preferably 2 to 30 parts by weight with respect to 100 parts by weight of the binder resin. If it is less than 2 parts by weight, the effect on the low-temperature fixing property is small, and if it is more than 30 parts by weight, the melt viscosity is excessively lowered and a high temperature offset occurs, which is not preferable.

As the binder resin used in the present invention, all the resins usually used for toners can be used, but it is preferable that the melting start temperature is as low as possible particularly for the purpose of improving low temperature fixing performance. A toner having a melting start temperature of 60 to 100 ° C. is preferably used. 100 ° C
If it is higher, the fixing property is not sufficient, and if it is lower than 60 ° C., the blocking property is deteriorated and the storage property becomes a problem. The melting start temperature as used herein refers to the temperature at which the plunger starts falling when measured with the following measuring machine and measuring conditions. 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 electrophotographic toner of the present invention comprises a binder resin,
A colorant, the above-mentioned hardened oil, and other additives such as a charge control agent and a magnetic material, if necessary, are mixed in a desired composition, melt-kneaded, cooled, solidified, and pulverized and classified. Further, a so-called polymerization method toner prepared by mixing the above materials at the time of resin polymerization may be used. Examples of the binder resin include styrene resin, polyacrylic acid ester resin, styrene- (meth) acrylic acid ester copolymer resin, polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride, phenol resin, epoxy resin, Examples include polyester resins.

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 so that a visible image having a sufficient density is formed. Usually, the ratio is about 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin. To be done.

As the above-mentioned magnetic material, a metal or alloy exhibiting ferromagnetism such as ferrite, magnetite, and other iron, cobalt, nickel, etc., or a compound containing these elements, or an appropriate heat treatment without containing ferromagnetic elements. 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 mixed with a carrier composed of ferrite powder, iron powder or the like to form a two-component developer. When a magnetic substance is contained, it may be used as it is as a one-component developer for developing an electrostatic image without mixing with a carrier, or may be mixed with a carrier and used as a two-component developer. Further, it can be applied to a non-magnetic one-component developing method.

[0013]

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

<Example 3> An electrophotographic toner of the present invention was obtained in the same manner as in Example 1 based on the above composition. The melting start temperature of this electrophotographic toner was 92 ° C. <Example 4> An electrophotographic toner of the present invention was obtained in the same manner as in Example 1 based on the above composition. 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 hydrogenated rapeseed oil was not added. The melting start temperature of this electrophotographic toner is 1
It was 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 blended in place of the hydrogenated rapeseed oil. The melting start temperature of this electrophotographic toner was 104 ° C. Comparative Example 3 Example 1 except that 5 parts of polyethylene wax (melting point 81.1 ° C.) was blended in place of the rapeseed hydrogenated oil.
A comparative electrophotographic toner was obtained in the same manner as in. 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 coconut hardened oil was blended in place of the rapeseed hardened oil. The melting start temperature of this electrophotographic toner was 90 ° C. <Comparative Example 5> 1 part of hardened palm kernel oil was used instead of hardened oil of rapeseed.
A comparative electrophotographic toner was obtained in the same manner as in Example 2 except that 0 part was compounded. The melting start temperature of this electrophotographic toner was 91 ° C. <Comparative Example 6> Hardened palm oil was replaced by 10 instead of hardened rapeseed oil.
A comparative electrophotographic toner was obtained in the same manner as in Example 2 except that the parts were mixed. 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 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. Next, 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 to rotate a fixing machine, and the roll pressure is 1 Kg / cm ² and the roll speed is 50.
The surface temperature of the heat fixing roll was changed stepwise so as to fix the toner image on the transfer paper having the unfixed image 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. Further, 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 device 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 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

(3) Storability The storability of the electrophotographic toners obtained in the above Examples and Comparative Examples was evaluated. The storability was evaluated by filling 20 g of various electrophotographic toners obtained in a 150 CC bottle with 5
After standing for 8 hours in a high temperature bath of 0 ° C., the caking state (blocking) of the electrophotographic toner was visually confirmed. The judgment conditions are shown below. ◯: No blocking occurred X: Toner blocked and did not collapse even when shaken. The test results of the above items are shown in Table 2.

[0019]

[Table 2]

From the results shown in Table 2 above, the electrophotographic toner according to this embodiment has a fixing strength of 90% or more and a non-offset width of 65 to 75 ° C., and shows good fixing characteristics. In addition, the storability was at a level where there was no practical problem. However, in Comparative Examples 1 to 3, the fixing strength was 77% or less, and it was confirmed to be inferior to the Examples. Comparative Example 4
It was confirmed that in Nos. 6 to 6, the non-offset temperature width was as narrow as 35 to 55 ° C, and there was a problem in practical use with respect to storability. In addition, using each of the developers described in (1) above, a commercially available copying machine (trade name: BD-3801 manufactured by Toshiba Corp.) was used.
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 from the initial stage.
It is a practical problem because the value changes from -20 μc / g to -25 μc / g between 00 sheets and the image density changes from 1.45 to 1.40 between the initial and 10000 sheets. It was confirmed that there is no. The copied original was A4 with a black portion of 6%, the triboelectric charge amount was measured using a blow-off triboelectric charge amount measuring device manufactured by Toshiba Chemical Co., and the image density was measured by a Macbeth reflection densitometer RD-914.
It was used.

[0021]

The electrophotographic toner of the present invention is capable of fixing at a low temperature while maintaining a sufficient non-offset temperature region, is excellent in fixing strength, and is capable of obtaining a sufficient number of image densities. It has the effect of being able to. Therefore, the heat fixing device can be maintained at a considerably lower temperature than in the past, and the power consumption of the copying machine or the like can be reduced.

Claims (6)

[Claims] 1. An electrophotographic toner comprising at least a binder resin, a colorant, and a hardened oil obtained from a fatty acid containing erucic acid. 2. The toner for electrophotography according to claim 1, wherein the content of erucic acid is 40% by weight or more based on the whole fatty acid. 3. The toner for electrophotography according to claim 1, wherein the hydrogenated oil has an iodine value of 5 or less. 4. The electrophotographic toner according to claim 1, wherein the cured oil has a melting point of 60 to 80 ° C. 5. The toner for electrophotography according to claim 1, wherein the content of the hardened oil is 2 to 30 parts by weight with respect to 100 parts by weight of the binder resin. 6. The melting start temperature of the toner is 60 to 100 ° C.
The electrophotographic toner according to claim 1, wherein