JPH0594038A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic toner being excellent in fixing ability at low temp., offset resistance and blocking resistance. CONSTITUTION:In a electrophotographic toner containing a binder resin composed essentially of a nonlinear polyester resin and a colorant, the nonlinear polyester resin is obtained by polycondensating using (A) at least a kind of compound selected from a group of bivalent carboxylic acid, its acid anhydride and lower alkyl ester as an acid compound, (B) a glycidyl ester of tert. synthetic fatty acid having 6-20 carbon number and etherified diphenoles as diol component and (c) an aromatic polycarboxylic acids as a crosslinking agent to manufacture the electrophotographic toner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner for developing an electrostatic latent image in an electrophotographic method. More specifically, it is an electrophotographic toner excellent in low-temperature fixing property, offset resistance and blocking resistance. For toner.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic method, in general, an electrostatic latent image is formed on the surface of a photoconductor, the electrostatic latent image is developed by a dry developer (toner) made of colored fine powder, A typical method is to transfer a colored fine powder onto a transfer sheet such as paper and then melt the thermoplastic resin (binder resin) in the toner by heating or pressing to fix it on the transfer sheet to form a copy image. It is a target.

In recent years, in order to improve the efficiency of copying work, high-speed fixing is required, and a heating roll fixing system having a compact mechanism and high thermal efficiency has been adopted as a fixing process. However, in the heating roll fixing method, since the roll and the toner on the transfer sheet are pressure-bonded to each other, a part of the toner adheres to the roll surface and stains the subsequent transfer sheet, so-called offset phenomenon easily occurs.

On the other hand, in order to further improve the fixing speed, it is necessary to adopt a heating roll system and also lower the fixing temperature by lowering the softening point by lowering the molecular weight of the binder resin. Therefore, the offset phenomenon is more likely to occur. Moreover, since the glass transition temperature of the binder resin is lowered with the decrease in the molecular weight, the phenomenon of blocking of the toner during storage occurs and the storage stability is deteriorated.

Therefore, there is a demand for a toner which can be fixed at a low temperature and in which an offset phenomenon and a blocking phenomenon are prevented or suppressed, that is, a toner which is excellent in low-temperature fixing property, offset resistance and blocking resistance. .. However, many styrene-acrylic acid ester-based copolymers that have been widely used as binder resins in the past generally have poor low-temperature fixability.

On the other hand, various polyester resins have been proposed as binder resins having excellent low-temperature fixability. These polyester resins are polycondensation resins containing aromatic dicarboxylic acids and etherified diphenols as main monomer components, but all have poor balance between low-temperature fixability and offset resistance or blocking resistance. Met.

For example, in a toner containing a polyester resin as a binder resin, in order to improve offset resistance, a polyester resin made non-linear by using a polyol or polycarboxylic acid having a valence of 3 or more as a crosslinking component is used. There is a method to use. However, if the polyester resin is made non-linear until it has sufficient offset resistance, there is a problem that the softening point rises and the low temperature fixability is impaired.

Further, in order to lower the softening point of the non-linear polyester resin, dicarboxylic acids having a long chain aliphatic hydrocarbon as a side chain such as alkenylsuccinic acid are used,
Attempts have been made to introduce a soft segment into a resin, but when such a long-chain aliphatic dicarboxylic acid is used, the glass transition temperature of the obtained polyester resin becomes low and the blocking resistance of the toner is lowered.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic toner having improved offset resistance without impairing low-temperature fixability. Another object of the present invention is to provide an electrophotographic toner having excellent blocking resistance and good storage stability.

The inventors of the present invention have conducted extensive studies to overcome the above-mentioned problems of the prior art, and as a result, formed a soft segment with a dicarboxylic acid and an etherified diphenol as a binder resin for an electrophotographic toner. When a non-linear polyester resin obtained by polycondensation using a specific diol component as described above is used as a main component, it has been found that the above object can be achieved, and the present invention has been completed based on this finding.

[0011]

Thus, according to the present invention, in a toner for electrophotography containing a binder resin containing a non-linear polyester resin as a main component and a colorant, the non-linear polyester resin is (A). At least one compound selected from the group consisting of a divalent carboxylic acid, an acid anhydride thereof and a lower alkyl ester thereof is used as the acid component, and a (B) diol component having 3 to 6 carbon atoms is used.
Using glycidyl ester of high-grade synthetic fatty acid and etherified diphenols, and further as (C) cross-linking component,
Provided is a toner for electrophotography, which is a non-linear polyester resin obtained by polycondensation using trivalent or higher aromatic polycarboxylic acids.

The present invention will be described in detail below. (Non-Linear Polyester Resin) The binder resin contained in the electrophotographic toner of the present invention is a non-linear polyester resin obtained by polycondensing the following components.

Acid Component In the present invention, the acid component used as a raw material for the polyester resin is at least one compound (dicarboxylic acid) selected from a divalent carboxylic acid (dicarboxylic acid), its acid anhydride, and its lower alkyl ester. ).

As the dicarboxylic acid, there are usually aromatic dicarboxylic acids and other dicarboxylic acids. As the aromatic dicarboxylic acid, for example, terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,7-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid and the like can be used. Examples of other acids include maleic acid, fumaric acid,
Succinic acid and adipic acid can be used. These acid components may be used alone or in combination of two or more.

Diol Component In the present invention, the diol component used as a raw material for the polyester resin contains both a glycidyl ester of a tertiary synthetic fatty acid having 6 to 20 carbon atoms and an etherified diphenol.

The glycidyl ester of tertiary synthetic fatty acid is
It constitutes the soft segment of the non-linear polyester resin and functions to lower the softening point of the resin. Specifically, a glycidyl ester mainly containing a tertiary acid having 10 carbon atoms is sold by Yuka Shell Epoxy Co., Ltd. under the trade name "CARDURA E 10".

The etherified diphenols include, for example, etherified bisphenols obtained by adding 2 to 10 mol of ethylene oxide or propylene oxide to bisphenol A.

The glycidyl ester of tertiary synthetic fatty acid is preferably used in a proportion of 3 to 45 mol% in all diol components. If the usage ratio is less than 3 mol%, the softening point of the binder resin will not be sufficiently lowered, and the fixing temperature of the toner will be high. On the contrary, if it is more than 45 mol%, the glass transition temperature of the binder resin will be too low. However, the blocking resistance of the toner is deteriorated, which is not preferable.

Crosslinking Component In the present invention, the crosslinking component used as a raw material for the polyester resin is a component which introduces a crosslinking structure into the polyester resin to make it non-linear, and aromatic polycarboxylic acids having a valence of 3 or more are used. ..

Examples of the aromatic polycarboxylic acid having a valence of 3 or more include trimellitic acid, pyromellitic acid, 2,5,7.
-Naphthalene tricarboxylic acid, 1,2,4-naphthalene tricarboxylic acid, and their anhydrides can be used.
You may use these in combination of 2 or more types.

These cross-linking components are also acid components,
It is preferably used in a proportion of 3 to 30 mol% in all acid components. If this usage ratio is less than 3 mol%, the non-linearity of the binder resin will be insufficient and the offset resistance will decrease, whereas if it is more than 30 mol%, the softening point of the binder resin will increase and the fixing temperature will increase. However, both of them are not preferable.

Production Method and Non-Linear Polyester Resin The non-linear polyester resin used in the present invention is polycondensed with the above-mentioned acid component, diol component and crosslinking component at a temperature of 150 to 300 ° C. in an inert gas atmosphere. It can be manufactured by At this time, in order to accelerate the reaction, for example, dibutyltin oxide, zinc oxide, dibutyltin dilaurate or the like can be used as a catalyst. Also,
For the same purpose, the reaction may be carried out under reduced pressure, or the reaction may be carried out under solvent reflux.

The number of moles of carboxyl groups in the total acid component,
The ratio with the number of moles of hydroxyl groups in all diol components is 0.8 to
It is preferably set to 1.2. If this ratio deviates significantly from this range, the molecular weight of the polyester resin becomes small, and the offset resistance of the toner deteriorates.

The non-linear polyester resin used in the present invention has an acid value of 1 to 30 and a ring and ball softening point of 100 to 180 ° C.
Is preferred. When the acid value is too high, the hygroscopicity of the toner becomes high, and the toner cannot withstand use under high humidity. On the other hand, if the softening point is too low, the offset resistance is not sufficient, and conversely, if it is too high, the fixing temperature becomes high.

(Colorant) Examples of the colorant used in the present invention include pigments such as carbon black, silicon dioxide, zinc oxide and titanium oxide; nigrosine base, aniline blue, chrome yellow, chalco oil blue and ultramarine. Dyes such as Blue, Orient Oil Red, Phthalocyanine Blue, Malachite Green Oxalate, etc .; Magnetic particles such as iron, cobalt, nickel, iron sesquioxide, ferrosoferric oxide, iron oxide manganese, iron oxide zinc, iron oxide nickel; Can be mentioned.

(Arbitrary Component) In the present invention, a release agent, a fluidity modifier, etc. may be added to the toner, if necessary. Examples of the release agent include low molecular weight olefin polymers or copolymers such as low molecular weight polyethylene and low molecular weight polypropylene. Examples of the fluidity modifier include hydrophobic silica, titanium oxide, zinc oxide, cerium oxide, calcium carbonate and the like.

[0027]

EXAMPLES The present invention will be specifically described below with reference to Reference Examples, Examples and Comparative Examples, but the present invention is not limited to these Examples. The parts and% in the following examples are based on weight unless otherwise specified.

[Reference Example 1] (Production Example of Polyester Resin) Polyoxypropylene (2) -2,2-bis (4-hydroxyphenyl) propane 351 g (1.0 mol), polyoxyethylene (2) -2 , 2-bis (4-hydroxyphenyl) propane 196.2 g (0.6 mol), a glycidyl ester of a tertiary fatty acid having 10 carbon atoms (Okaka Shell Epoxy Co., trade name Kajura E10) 100.8
g (0.4 mol), terephthalic acid 244.6 g (1.5
4 mol), 46.1 g (0.24 mol) of trimellitic anhydride, and 1.1 g of di-n-butyltin oxide were placed in a 2-liter glass four-necked flask, and a thermometer, a stirring bar,
Attaching a flow-down condenser and a nitrogen introducing tube, stirring in an electric heating mantle under a nitrogen stream at 220 ° C,
A polycondensation reaction was performed.

The degree of polymerization was investigated from the ring and ball softening point (SP), and the polycondensation reaction was terminated when the softening point reached 130 ° C. The obtained non-linear polyester resin (A) was a pale yellow transparent solid.

Polyester resins (B to D) were synthesized by using each component shown in Table 1 in the same manner as above. The raw material components (molar ratio), acid value and softening point of these polyester resins (A to D) are collectively shown in Table 1.

[0031]

[Table 1] BP2P: polyoxypropylene (2) -2,2-bis (4-hydroxyphenyl) propane BP2E: polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) propane C ₁₀ E: having 10 carbon atoms Tertiary synthetic fatty acid glycidyl ester DSA: dodecenyl succinic anhydride TPA: terephthalic acid IPA: isophthalic acid TMA: trimellitic anhydride (crosslinking component) Ratio of crosslinking component: ratio of crosslinking component to all acid components (mol%) SP: softening point (Ring and ball type) (℃)

Example 1 100 parts of non-linear polyester resin (A) and carbon black (manufactured by Cabot Co.,
2 rolls of 8 parts of product name Cabot BPL), 1 part of metal-containing dye (made by Hodogaya Chemical Co., Ltd., trade name Spiron Black TRH), and 4 parts of low molecular weight polypropylene (made by Sanyo Chemical Co., Ltd., trade name Viscole 660P) After being melt-kneaded in, the mixture is pulverized by a jet mill, and further classified by wind power to have a number average particle diameter of 12 μm and a fine powder amount of 5 μm or less is 10
A toner material of less than number% was obtained.

Further, with respect to 100 parts of this toner material,
Hydrophobic silica (Aerosil, trade name R972) 0.
3 parts was added and mixed with a Henschel mixer to obtain a toner. When this toner was allowed to stand at a temperature of 50 ° C. for 24 hours and examined for the presence of aggregates, no formation of aggregates was observed and the blocking resistance was excellent.

Next, 5 parts of this toner and an iron powder carrier (manufactured by Nippon Iron Powder Co., Ltd., trade name TEFV150 / 250) 95
Parts were mixed with a ball mill to prepare a developer. Charge this developer into a commercial copying machine with the fixing unit removed,
An image was printed on the copy paper, and a fixing test was conducted by using a heating roll fixing device made of polytetrafluoroethylene and variously changing the roll temperature.

The results are shown in Table 2. In addition, it was confirmed in the peeling test of the adhesive tape that the fixing was performed at 140 ° C. was sufficiently fixed. Further, no offset phenomenon was observed even at 240 ° C.

[Example 2, Comparative Example 1-2] Using the polyester resins (B) to (D) shown in Table 1, a toner and a developer were prepared in the same manner as in Example 1, and their physical properties were evaluated. evaluated. The results are collectively shown in Table 2.

The methods for evaluating the physical properties are as follows. <Minimum fixing temperature> A copying paper on which an electrostatic image has been transferred is subjected to a fixing test by changing the roll temperature with a heating roll fixing device made of polytetrafluoroethylene. Examined.

<Offset Occurrence Temperature> The temperature of the heating roll was raised and the temperature at which the toner did not adhere to the roll was examined.

<Image Quality> The image quality of the image fixed between the minimum fixing temperature and the offset generation temperature was visually judged.

<Preservation (blocking resistance)> The toner was left at a temperature of 50 ° C. for 24 hours and examined for the presence of aggregates.
The case where the formation of aggregates was not observed was defined as good, and the case where the formation of aggregates was observed was defined as unacceptable.

[0041]

[Table 2]

As is clear from Table 2, the toners of the present invention (Examples 1 and 2) have a low minimum fixing temperature and a high offset generation temperature. The image quality is also good. Furthermore, it has good blocking resistance and excellent storage stability.

On the other hand, when a polyester resin containing no glycidyl ester of tertiary synthetic fatty acid as the diol component was used as the binder resin, the fixing temperature was high and the offset generation temperature was low (Comparative Example 1). Alternatively, the offset generation temperature is low and the blocking resistance is poor (Comparative Example 2).

[0044]

According to the present invention, there is provided an electrophotographic toner excellent in low-temperature fixing property, offset resistance and blocking resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Ishihara, Inventor Koichi Ishiguchi, Kakogawa City, Hyogo Prefecture, 4 67-1, Mizukashi, Central Research Laboratory, Harima Kasei Co., Ltd. (72) Inventor, Yoshiaki Ishibashi 671, Noguchi Town, Kakogawa City, Hyogo Prefecture No. 4 Harima Kasei Co., Ltd. Central Research Laboratory

Claims (1)

[Claims] 1. In an electrophotographic toner containing a binder resin containing a non-linear polyester resin as a main component and a colorant, the non-linear polyester resin comprises a divalent carboxylic acid or an acid thereof as the (A) acid component. At least one compound selected from the group consisting of anhydrides and lower alkyl esters thereof is used, and the (B) diol component has 6 carbon atoms.
To 20 obtained by polycondensation using glycidyl esters of tertiary synthetic fatty acids and etherified diphenols of 20 to 30 and (C) a trivalent or higher aromatic polycarboxylic acid as a crosslinking component. A toner for electrophotography, which is a linear polyester resin.