JPH0594040A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic toner excellent in low temp. fixing property, offset resistance, blocking resistance, and color tone. CONSTITUTION:This electrophotographic toner contains a coloring agent and a binder resin essentially comprising a nonlinear polyester resin. This nonlinear polyester resin is obtd. by polymn. condensation of following components. (A) As for a diol component, etherified diphenols by 60-85mol% of the whole diol component and polyoxyalkylene glycols expressed by formula I or II by 15-40mol% of the whole diol component, (B) at least one aromatic dicarboxylic acid as an acid component selected from aromatic dicarboxylic acids, acid anhydrides or lower alkyl esters of these by 70-97mol% of the whole acid component, and (C) tervalent or higher valent aromatic polycarboxylic acids as a crosslinking component by 3-30mol% of the total acid component. (In formulae I and II, (n) is an integer 3 or 4.)

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, and more specifically, it has excellent low-temperature fixing property, anti-offset property, anti-blocking property and color tone. The present invention relates to a toner for electrophotography.

[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.

Further, since alkenyl succinic acid is a mixture of isomers and is colored yellow, the polyester resin obtained by using it also has a poor color tone. In black printing, which is the mainstream of electrophotography, the color of the binder resin is not restricted, but the binder resin for color printing is
It is required to be colorless and have good transparency.

[0010]

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. Another object of the present invention is to provide a colorless binder resin that can be used for color printing.

The inventors of the present invention have conducted extensive studies in order to overcome the above-mentioned problems of the prior art. As a result, as a binder resin for an electrophotographic toner, an aromatic dicarboxylic acid compound and an etherified diphenol compound have been identified. It has been found that the use of a non-linear polyester resin obtained by polycondensation using polyoxyalkylene glycols as the main component achieves the above object, and based on this finding, the present invention has been completed.

[0012]

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). As a diol component,
The etherified diphenols are contained in the total diol components of 60 to 8
5 mol% and the following formula [1] or [2]

[0013]

[Chemical 3]

[0014]

[Chemical 4] [In each formula, n is an integer of 3 or 4. ] The polyoxyalkylene glycol represented by the above is used in a proportion of 15 to 40 mol% of the total diol component, and as the (B) acid component,
At least one aromatic dicarboxylic acid selected from the group consisting of aromatic dicarboxylic acids, their acid anhydrides and their lower alkyl esters is used in a proportion of 70 to 97 mol% of the total acid components, and (C) a crosslinking component. As a non-linear polyester resin obtained by polycondensation using trivalent or higher aromatic polycarboxylic acids in a proportion of 3 to 30 mol% of all acid components. Toner is provided.

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.

(A) Diol Component In the present invention, the diol component used as a raw material for the polyester resin contains both etherified diphenols and polyoxyalkylene glycols.

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 polyoxyalkylene glycols are compounds represented by the above formulas [1] and [2], and examples thereof include triethylene glycol, tetraethylene glycol, tripropylene glycol and tetrapropylene glycol. These compounds can be used alone or in combination of two or more.

When n is 2 or less in the above formulas [1] and [2], the polyoxyalkylene glycols do not sufficiently lower the softening point of the binder resin and the fixing temperature of the toner becomes high. On the other hand, if it is 5 or more, the glass transition temperature of the binder resin is lowered and the blocking resistance of the toner is deteriorated, so that both are not preferable.

The polyoxyalkylene glycols are used in a proportion of 15 to 40 mol% based on the total diol components. If this ratio is less than 15 mol%, the softening point of the binder resin will not be sufficiently lowered, and the fixing temperature of the toner will be high, while if it is more than 40 mol%, the glass transition temperature of the binder resin will be too low, All of them are not preferable because the blocking resistance of the toner is deteriorated.

It is not preferable to use aliphatic glycols other than etherified diphenols and polyoxyalkylene glycols, for example, ethylene glycol as the main component of the diol component, because the blocking resistance of the toner is deteriorated.

(B) Acid Component In the present invention, the acid component used as a raw material for the polyester resin is at least one aromatic dicarboxylic acid selected from the group consisting of aromatic dicarboxylic acids, their acid anhydrides and their lower alkyl esters. Is.

Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-
2,7-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid and the like can be used.

These acid components may be used alone or in combination of two or more. Aromatic dicarboxylic acids are used in a proportion of 70 to 97 mol% of all acid components. However, the total acid component means the total of the (B) acid component and the (C) crosslinking component.

(C) Crosslinking Component In the present invention, the crosslinking component used as a raw material for the polyester resin is a component that introduces a crosslinking structure into the polyester resin to make it non-linear, and is a trivalent or higher polyvalent aromatic polycarboxylic acid. used.

Examples of aromatic polycarboxylic acids 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 crosslinking components are also acid components,
It is necessary to use it in a ratio 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. The non-linear polyester resin used as the binder resin in the present invention has a good color tone close to colorless.

(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, 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 releasing 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.

[0033]

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 305 g (0.8 mol), polyoxyethylene (2) -2 , 2-bis (4-hydroxyphenyl) propane 262 g (0.8 mol), triethylene glycol 60 g (0.4 mol), terephthalic acid 244.6 g (1.54 mol), trimellitic anhydride 4
6.1 g (0.24 mol) and 1.1 g of di-n-butyltin oxide were placed in a 2-liter glass four-necked flask, equipped with a thermometer, a stir bar, a downflow condenser and a nitrogen inlet tube, 22 in a nitrogen stream in an electric heating mantle
The polycondensation reaction was carried out while stirring at 0 ° C.

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 H) were synthesized in the same manner as described above using the components shown in Table 1. Table 1 collectively shows the raw material components (molar ratio), the acid value and the softening point of these polyester resins (A to H).

[0037]

[Table 1]

BP2P: polyoxypropylene (2)-
2,2-bis (4-hydroxyphenyl) propane BP2E: polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) propane TEG: triethylene glycol TPG: tripropylene glycol DEG: diethylene glycol PEG: polyethylene glycol 300 (average molecular weight 3
00) EG: ethylene glycol DSA: dodecenyl succinic anhydride TPA: terephthalic acid IPA: isophthalic acid TMA: trimellitic anhydride (crosslinking component) crosslinking component (%): ratio of crosslinking component to total acid component (mol%) Color number: Number of colors (Helige) 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 iron powder carrier (manufactured by Nippon Iron & Powder Co., 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 the case of fixing at 140 ° C.,
It was confirmed by the peeling test of the pressure-sensitive adhesive tape that the toner was sufficiently fixed. Further, no offset phenomenon was observed even at 240 ° C.

[Example 2, Comparative Example 1-2] Using each of the polyester resins (B) to (H) 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.

<Preservability (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.

[0048]

[Table 2]

As is clear from Table 1, the polyester resin obtained by using the specific polyoxyalkylene glycols has a color number of 3 and is almost colorless. As is clear from Table 2, the toner of the present invention (Examples 1 and 2) has a low minimum fixing temperature and a high offset generation temperature. Also,
The image quality is also good. Furthermore, it has good blocking resistance and excellent storage stability.

On the other hand, when the polyester resin containing no specific polyoxyalkylene glycol as the diol component is used as the binder resin (Comparative Example 4), the fixing temperature is high and the offset generation temperature is low. Further, when a resin containing alkenylsuccinic acid is used (Comparative Example 5), the blocking resistance is poor.

When diethylene glycol (n = 2 in the formula [1]) was used as the polyoxyalkylene glycol (Comparative Example 2), the fixing temperature of the toner was increased, and the polyethylene glycol 300 (the formula [1] was used). Medium, n =
When 6) is used (Comparative Example 3), the blocking resistance of the toner becomes poor. When the polyoxyalkylene glycol is 10 mol% of all diol components (Comparative Example 1), the fixing temperature of the toner becomes high. When ethylene glycol is used as the main component of the diol component (Comparative Example 6),
The offset generation temperature becomes low and the blocking resistance becomes poor.

[0052]

According to the present invention, there is provided an electrophotographic toner excellent in low-temperature fixing property, anti-offset property and anti-blocking property. Further, according to the present invention, a nearly colorless binder resin can be obtained, so that a toner suitable for color printing is also provided.

 ─────────────────────────────────────────────────── ─── 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. An electrophotographic toner comprising a binder resin containing a non-linear polyester resin as a main component and a colorant, wherein the non-linear polyester resin comprises (A) a diol component and an etherified diphenol as a total diol. 60 to 85 mol% of the component and the following formula [1] or [2] [Chemical 2] [In each formula, n is an integer of 3 or 4. ] The polyoxyalkylene glycol represented by the following is used in a proportion of 15 to 40 mol% of the total diol component, and (B) as an acid component, aromatic dicarboxylic acid, its acid anhydride and its lower alkyl ester At least one aromatic dicarboxylic acid selected is used in a proportion of 70 to 97 mol% of the total acid component, and further, (C) a trivalent or more aromatic polycarboxylic acid as a crosslinking component of 3 to 3 of the total acid component. A toner for electrophotography, which is a non-linear polyester resin obtained by polycondensation at a ratio of 30 mol%.