JP2000056504A - Electrophotographic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic toner being excellent in fixing property and color mixing property, having sufficient offset resistance, and having stable frictional chargeability and blocking resistance that are unaffected by the environment. SOLUTION: A binding resin is a polyester resin with an acid value of 6 to 15 mgKOH/g, a weight average molecular weight Mw of 15,000 to 60,000, a number average molecular weight Mn of 2,000 to 4,000, with the ratio of the weight average molecular weight Mw to the number average molecular weight Mn being 6 to 18, a glass transition point of 50 to 60 deg.C, and a softening point of 100 to 120 deg.C, obtained by condensing 1.0 to 1.2 moles of propoxylated and/or ethoxylated etherified diphenol constituents and 0.01 to 0.15 moles of aliphatic diol constituents for 1 mole of carboxylic acid constituents comprising 70 to 85 mole % aromatic dicarboxylic acid constituents and 15 to 30 mole % polyvalent carboxylic acid constituents with a value of three or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner used for developing an electrostatic image in electrophotography, electrostatic printing and the like.

[0002]

2. Description of the Related Art Conventionally, charged toner particles are adhered to an electrostatic latent image formed on a photoreceptor and developed, and the toner image is transferred to a support such as transfer paper, and then heated and heated. 2. Description of the Related Art Image forming apparatuses such as copiers and printers using an electrophotographic method for forming an image by fixing by pressure or the like have been widely used, and in recent years, a full-color image using a plurality of color toners has been used. Has come to be used. In recent years, demand for full-color images has been increasing. A full-color image is obtained by decomposing information of a color original document into three or four colors of magenta, cyan, yellow, and, if necessary, black, and forming an electrostatic latent image corresponding to image information of each color on a photoconductor for each color. To form an electrostatic latent image of each color,
A predetermined toner selected from a magenta toner, a cyan toner, a yellow toner, and, if necessary, a black toner is applied thereto, transferred to the same support, that is, paper, etc., and then each color superimposed on the same support. Is formed by fixing the above toner. For this reason, in a full-color toner, in each step of a development process, a transfer process, and a fixing process, each color must have a required function in a well-balanced manner.
There are still points to be improved such as color mixing, fixability and color reproducibility.

[0003] A binder resin for a full-color toner is required to have a good mixing property and a good coloring property in a fixing step and a sharp melt property, and usually a polyester resin is used. However, when using a binder resin with good sharp melt properties,
There is a problem that an offset phenomenon occurs in the fixing process. In order to prevent this offset phenomenon, it is conceivable to crosslink the binder resin. However, in general, the crosslinked resin is not suitable as a binder resin for a full-color toner because the sharp melt property is reduced. Separately, a method has been proposed in which wax such as polyolefin is added to the toner itself to prevent the offset phenomenon, but the wax added to the toner has insufficient compatibility with the binder resin. Therefore, the transparency of the image after fixing is deteriorated. Therefore, the offset phenomenon is usually prevented by applying silicone oil or the like to the surface of the fixing roller.
However, if silicone oil or the like is applied to the surface of the fixing roller, the oil adheres to the copy, so that the amount of use is limited.

[0004] Since polyester resin is easily charged negatively, it is an excellent binder resin for negatively charged toner. The chargeability varies depending on the concentration of the carboxyl group, which is a hydrophilic group at the polymer end, and the hydroxyl group, that is, the acid value or hydroxyl value of the polyester resin.In particular, the acid value is high due to the negative charging property of the carboxyl group. It is known that the negative chargeability of the resin increases as much as possible. However, if the acid value and the hydroxyl value are too high, the charge amount becomes insufficient due to the hydrophilicity due to moisture absorption at high temperature and high humidity, and as a result, the image may be deteriorated. To solve these problems, a method for stabilizing the charging property by controlling the acid value and the hydroxyl value within a specific range has been proposed, but a sufficient effect has not been obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned drawbacks, and it is an object of the present invention to provide excellent fixing property and color mixing property and sufficient offset resistance. Another object of the present invention is to provide an excellent electrophotographic toner having stable triboelectric charging properties and blocking resistance which are not affected by the environment.

[0006]

SUMMARY OF THE INVENTION The present invention provides an electrophotographic color toner comprising a binder resin and a colorant.
The binder resin is composed of 70 to 85 mol% of an aromatic dicarboxylic acid component (a) and 15 to 30 mol% of a carboxylic acid component (b) having a valence of 3 or more, and 1 mol of the carboxylic acid component.
1.0 to 1.2 mol of propoxylated and / or ethoxylated etherified diphenol component (c) and 0.01
An acid value of 6 to 15 mgKOH / g, a weight average molecular weight Mw of 15,000 to 60,000, and a number average molecular weight Mn of 2,000 to 15 mgKOH / g obtained by condensing 0.15 mol of the aliphatic diol component (d). 4,000, the ratio (Mw / Mn) of the weight average molecular weight Mw to the number average molecular weight Mn is 6 to 18,
Glass transition point is 50-60 ° C and softening point is 100-1
An electrophotographic toner, which is a polyester resin at 20 ° C.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polyester resin used in the present invention has the characteristics of a non-linear cross-linked polyester resin added to a linear polyester resin. , Good coloring,
In addition, a toner having offset resistance and blocking resistance can be obtained. Further, as a component constituting the polyester resin, having an aromatic component having excellent chargeability,
Further, by controlling the acid value to a specific range, a toner having excellent moisture resistance can be obtained without impairing negative chargeability.

The aromatic dicarboxylic acid component (a), which is one of the raw material components of the polyester resin used in the present invention, comprises an aromatic dicarboxylic acid such as isophthalic acid or terephthalic acid, an acid anhydride thereof, or an ester thereof. These may be selected, and these may be used alone or in combination of two or more. The aromatic dicarboxylic acid component (a) increases the glass transition temperature of the polyester resin and contributes to the improvement of the blocking resistance of the toner.
The hydrophobic nature of the benzene ring is also effective in improving the moisture resistance of the toner. In the present invention, in order to obtain sufficient blocking resistance of the toner, the aromatic dicarboxylic acid component (a) needs to be 70 mol% or more of all the carboxylic acid components. On the other hand, when the content of the aromatic dicarboxylic acid component (a) is more than 85 mol% in all the carboxylic acid components, it will be relatively described later that 3
The polyvalent carboxylic acid component (b) having a valency or higher is less than 15 mol%, and the crosslinking of the polyester resin is insufficient, and the offset resistance as a toner is impaired. Therefore, the aromatic dicarboxylic acid component (a) accounts for 70 to 8 of all carboxylic acid components.
It needs to be 5 mol%.

The polyvalent carboxylic acid component (b) having three or more valences, which is one of the raw material components of the polyester resin used in the present invention, is a polycarboxylic acid such as trimellitic acid and pyromellitic acid; An anhydride or an ester thereof, which can be used alone or in combination of two or more. The trivalent or higher polyvalent carboxylic acid component (b) is a cross-linking monomer component, and is used together with the aromatic dicarboxylic acid component (a) to adjust the molecular weight of the polyester resin, the molecular weight distribution and the balance of melt viscosity, This is to increase the resin strength of the polyester resin and improve the offset resistance of the toner.
In the present invention, the content of the trivalent or higher polycarboxylic acid component (b) needs to be 15 to 30 mol% of the total acid component. 15 or more trivalent or more polyvalent carboxylic acid components (b)
If it is less than mol%, crosslinking of the polyester resin becomes insufficient, and the offset resistance of the toner is impaired. On the other hand, 30
If it exceeds mol%, the melt viscosity of the polyester resin increases, and the fixability and color development of the toner decrease.

The propoxylated and / or ethoxylated etherified diphenol component (c), which is one of the raw material components of the polyester resin used in the present invention, is, for example, polyoxypropylene-2,2-bis (4 '-Oxyphenyl) propane, polyoxyethylene-2,2-bis (4'-oxyphenyl) propane and the like can be used, and propylene oxide and ethylene oxide are 2,2-bis (4'-oxyphenyl) propane 1 It is preferable to add about 4 to 6 moles per mole, that is, about 2 to 3 moles per one benzene ring. The propoxylated and / or ethoxylated etherified diphenol component (c) is a component having a function of increasing the glass transition temperature of the polyester resin and improving the blocking resistance of the toner, and may be used alone or in combination of two or more. Can be used. Further, since the polyoxypropylene chains or polyoxyethylene chains located on both sides of the benzene ring function as soft segments, the low-temperature fixability of a toner using a polyester resin obtained by condensing the component (c) is improved. In addition, since it contains a hydrophobic benzene ring and has a large molecular weight as a diol component, the density of ester bonds per unit weight of the polyester resin condensed with the benzene ring decreases, and the amount of the hydrophilic unit relative to the hydrophobic unit is reduced. Can be reduced. Therefore, the moisture resistance is improved, and the charge stability of the toner can be improved together with the excellent charge retention performance of the benzene ring. Sufficient blocking resistance, low-temperature fixability,
In order to ensure moisture resistance, it is important to condense 100 mol% or more of the propoxylated and / or ethoxylated etherified diphenol component (c) with respect to 1 mol of the carboxylic acid component. The polyester resin used in the present invention is obtained by condensing the aromatic dicarboxylic acid (a) as one of the carboxylic acid components as described above, and the dicarboxylic acid generally needs to be reacted at a high temperature. The propoxylated and / or ethoxylated etherified diphenol component (c) is easily thermally decomposed at a high temperature, and the propoxylated and / or ethoxylated etherified diphenol component (c) is used per mole of the carboxylic acid component. ) Is more than 120 mol%, it is not preferable because a large amount of decomposition products are generated by thermal decomposition.

Next, the aliphatic diol component (d) constituting the polyester resin used in the present invention will be described. Examples of the aliphatic diol component (d) include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and the like.
They can be used alone or in combination of two or more. The aliphatic diol component (d) improves the polycondensation reaction rate of the polyester resin and has an effect on the fixability as a toner. The content of the aliphatic diol component (d) is 1 mol% or more based on 1 mol of the total carboxylic acid component. used. Condensation of the aliphatic diol component (d) in excess of 15 mol% with respect to 1 mol of all carboxylic acid components increases the amount of hydrophilic units in the polyester resin, and reduces the moisture resistance and chargeability of the toner. In addition, the softening point of the toner tends to be lower than that of the component (c).
This will reduce the offset resistance of the toner. Therefore, the aliphatic diol component (d) is composed of the total carboxylic acid component 1
It is important to use it in the range of 1 to 15 mol% based on the mol.

It is important that the polyester resin obtained by condensation of the above (a) to (d) has an acid value of 6 to 15 mgKOH / g. A toner using a polyester resin having an acid value higher than 15 mgKOH / g has an unstable environmental stability, particularly a charge amount with respect to humidity, and has an acid value of 6 mgKOH / g.
If the amount is lower than OH / g, it becomes difficult to obtain a charge amount. Incidentally, the acid value of the polyester resin in the present invention,
It was determined by a titration method using a KOH solution.

The polyester resin obtained by condensing the above (a) to (d) has a weight average molecular weight Mw of 15,000.
0 to 60,000, number average molecular weight Mn is 2,000 to
It is important that the ratio (Mw / Mn) of the weight average molecular weight Mw to the number average molecular weight Mn is 6 to 18. When each value is less than the lower limit, sufficient offset resistance cannot be obtained when the toner is used, and when the value exceeds the upper limit, the fixability decreases. In addition, the weight average molecular weight (Mw) and the number average molecular weight (M
n) is a gel permeation chromatography (HCL-8 manufactured by Tosoh Corporation) using tetrahydrofuran as a solvent.
200).

Further, it is important that the polyester resin obtained by condensation of the above (a) to (d) has a glass transition point of 50 to 60 ° C. and a softening point of 100 to 120 ° C. A toner using a polyester resin having a glass transition point lower than 50 ° C. has poor heat resistance, and the toner tends to aggregate during storage. On the other hand, if a toner having a glass transition point higher than 60 ° C. is used, the fixing strength of the toner And the color mixing property also decreases, resulting in poor color reproducibility. Further, in the case of a toner using a polyester resin having a softening point lower than 100 ° C., high-temperature offset tends to occur during image formation. On the other hand, when a toner having a softening point higher than 120 ° C. is used, the obtained toner , The heat-fusibility decreases, the fixing strength decreases, and the light transmittance and color mixing properties decrease, and the color reproducibility deteriorates. The glass transition temperature (° C.) of the polyester resin in the present invention is measured by a differential scanning calorimeter (DSC20).
(Seiko Electronics Co., Ltd.) and the contact point between the tangent line of the endothermic curve near the glass transition temperature measured at a heating rate of 10 ° C./min and the base line was defined as the glass transition temperature. The softening temperature (° C) was measured using a flow tester (CFT-5 manufactured by Shimadzu Corporation).
00), using a nozzle of 0.5 mmφ × 10 mm, a sample amount of 1.0 g, a load of 20 kgf, and a heating rate of 6
The temperature was measured at a constant temperature increase of ° C./min, and the temperature at the time of 4 mm penetration was defined as the softening temperature.

The polyester resin used in the present invention can be produced by a conventional method. For example, the above-mentioned condensation components (a) to (d) are charged into a reaction vessel, and an esterification reaction or a transesterification reaction is performed by heating and raising the temperature. At this time, if necessary, a commonly known esterification catalyst or transesterification catalyst such as sulfuric acid, titanium butoxide, dibutyltin oxide, magnesium acetate, manganese acetate, tin acetate, zinc acetate, tin disulfide, antimony trioxide, and dioxide Germanium or the like can be used.
Next, water or alcohol generated by the reaction is removed according to a conventional method. Thereafter, unreacted diol components may be distilled off under reduced pressure of 150 mmHg or less. The polymerization temperature, polymerization time, and amount of catalyst are not particularly limited, and may be arbitrarily selected as needed.

The colorants used in the magenta, cyan, and yellow toners of the present invention include:
Various organic pigments, inorganic pigments, and dyes can be used. For example, phthalocyanine blue, induslen blue, permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow, benzidine yellow and the like can be mentioned as typical ones. The colorant used in the black toner among the toners of the present invention includes a three-color mixture of yellow, cyan, and red pigments,
Alternatively, carbon black or the like can be used. As the carbon black, any known carbon black, furnace black, lamp black and the like can be used.
When an organic pigment is used as a colorant, it is preferable to use a flushing pigment in order to uniformly disperse the organic pigment particles as fine particles in the binder resin.

When an organic pigment is used as a colorant,
The content is preferably 1 to 10% by weight based on 100% by weight of the toner. If it is less than 1% by weight, the coloring power is weakened,
If the content is more than 10% by weight, transparency and color reproducibility decrease. Also,
When carbon black is used as the colorant for the black toner, it is preferably contained in an amount of 2 to 10% by weight based on 100% by weight of the toner. If it is less than 2% by weight, it is difficult to obtain a desired image density, and if it exceeds 10% by weight, the conductivity becomes large, and it becomes difficult to obtain a desired charge amount.

The toner of the present invention contains a binder resin and a colorant as described above. In addition, the toner of the present invention contains a charge control agent for adjusting the chargeability of the toner. Is also good. As the charge control agent, a colorless or light-colored negative charge control agent that does not affect the color tone or light transmittance of the toner is preferable. Examples of the negative charge control agent include an organic metal complex such as a metal complex of an alkyl-substituted salicylic acid (for example, a chromium complex, an aluminum complex or a zinc complex of ditertiary butyl salicylic acid). Usually, the charge control agent is preferably contained in the toner in a range of 10 parts by weight or less based on 100 parts by weight of the binder resin.

The toner of the present invention can be obtained according to various methods. For example, the polyester resin, the colorant, and, if necessary, the charge control agent are mixed in a desired ratio, melted and kneaded by a kneader, an extruder or the like, cooled, and then pulverized by means such as a jet mill. Can be obtained by classifying the obtained pulverized product with an air classifier.

The toner of the present invention contains a binder resin and a colorant as described above.
Various external additives may be further added to improve the fluidity of the toner. As the external additive, known ones such as silica, alumina and titanium oxide can be used, and from the viewpoints of the fluidity of the toner and the environmental stability against charging, etc., those subjected to a hydrophobic treatment are preferable. Usually, the external additive is preferably used in the range of 0.2 to 3.0 parts by weight based on 100 parts by weight of the toner.

[0021]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples. However, this does not limit the embodiment of the present invention at all.

Polyester resin production example 1 75 mol of terephthalic acid 25 mol of trimellitic acid Polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane (number of moles of polyoxypropylene added: 2.3) 118 2 moles of ethylene glycol 2 moles of the above raw material compound and 0.08 parts by weight of dibutyltin oxide with respect to 100 parts by weight of the carboxylic acid component are stirred at 260 ° C. under normal pressure in a reaction vessel having a distillation column, and water is removed. After distilling and performing the esterification reaction, 220 ° C. under reduced pressure
Then, while distilling off the diol component, a condensation reaction is performed,
Resin A was obtained.

Polyester Resin Production Examples 2 to 5 Resins B to G were obtained in the same manner as in the polyester resin production example 1 under the recipe shown in Table 1.

Table 1 shows the acid value, weight average molecular weight Mw, number average molecular weight Mn, Mw / Mn, glass transition temperature Tg and softening temperature Tm of each of the polyester resins A to G obtained in the polyester resin production examples 1 to 5. Indicated.

Toner Production Example 1 96 parts by weight of polyester resin A I. Pigment Blue 15:34 parts by weight Each of the above formulation amounts was premixed with a Hensiel mixer, melt-kneaded with a twin-screw extruder, cooled, coarsely ground with a hammer mill, and then finely ground with a jet mill. Thereafter, the particles were classified with an air classifier to obtain colorant-containing fine particles having an average particle size of 9.5 μm, that is, toner base particles. To 100 parts by weight of the obtained toner base particles, 0.7 parts by weight of a hydrophobic titanium oxide fine powder having an average particle diameter of 0.05 μm was added as a fluidity improver, and mixed with a Hensiel mixer to obtain cyan toner C.
1 was obtained. 150 cc of 40 grams of cyan toner C1
And left standing at 50 ° C./90% RH for 24 hours, then slowly cooled and opened, observing the aggregation state of the toner, and evaluating the blocking property of the toner as follows. It is shown in Table 1. ：: No aggregation at all. Δ: There is some aggregation. ×: Remarkably aggregated.

Toner Production Example 2 I. Pigment Blue 15: 3 as C.I. I. Magenta toner M1 was obtained in the same manner as in Toner Production Example 1 except that Pigment Red 122 was used, and the blocking property was evaluated in the same manner. The results are shown in Table 1.

Toner Production Example 3 C.I. I. Pigment Blue 15: 3 as C.I. I. Pigment Yellow 17 except that Pigment Yellow 17 was used, and a yellow toner Y1 was obtained in the same manner as in the case of Toner Production Example 1 described above.

Toner Production Examples 4 to 9 Cyan toners C2 to C7 were obtained in the same manner as in Toner Production Example 1 except that polyester resins B to G were used instead of polyester resin A, and the blocking properties were similarly evaluated. The results are shown in Table 1. Was.

Example 1 5 parts by weight of each of the cyan toner C1, magenta toner M1, and yellow toner Y1, and ferrite 1 having a particle size of 50 μm
95 parts by weight of a silicone resin-coated ferrite carrier in which 00 parts by weight was coated with 0.3 parts by weight of an organopolysiloxane were mixed to obtain cyan, magenta, and yellow two-component developers.

Examples 2 to 3 and Comparative Examples 1 to 4 Cyan two-component developers were obtained in the same manner as in Example 1 except that cyan toners C2 to C7 were used instead of cyan toner C1.

Using the two-component developer of each color obtained in the above Examples and Comparative Examples, a commercially available full-color copying machine (using an organic photoreceptor, an oil-supply type heat roller fixing mechanism, a fixing temperature of 150 ° C., and a development contrast potential) 23 ° C / 50% RH, 30 ° C / 85% RH, 15 ° C /
An image was formed under each environment of 10% RH, and the environmental stability of each toner and the fixing property and offset property of a copy copied under an environment of 23 ° C./50% RH were evaluated. Shown in

[Environmental stability] [Evaluation of chargeability of developer] The frictional charge of the developer on the developing device sleeve was measured by a blow-off charge meter (Toshiba Chemical Corporation).

[Evaluation of Image Density] The image density of the obtained copy was measured with an RD917 reflection densitometer (manufactured by Macbeth). ：: 1.2 or more Δ: 1.0 or more, less than 1.2 ×: less than 1.0

[Evaluation of fog] The fog of the obtained copy was measured with a 577 type reflection meter (made by Photobolt).
Was measured. ：: less than 0.7 △: 0.7 or more, less than 1.0 ×: 1.0 or more

Evaluation of Fixing Property The image fixed on the paper was rubbed with a finger, and the degree of toner peeling was confirmed. ：: Does not peel at all. Δ: Slight peeling. X: It peels off remarkably.

Evaluation of Offset Property After 10,000 sheets were copied, the silicone oil impregnated web attached to the fixing roller was observed, and contamination by offset toner was confirmed. ：: no dirt Δ: Some stains are observed. ×: Extremely dirty.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

By using a specific polyester resin as a binder resin for a toner, it has excellent fixing properties and color mixing properties, has sufficient offset resistance, and has stable friction without being affected by the environment. A toner having chargeability and blocking resistance can be obtained, and a stable image can be provided.

Claims (1)

[Claims] 1. An electrophotographic toner comprising a binder resin and a colorant, wherein the binder resin comprises 70 to 85 mol%.
0.1 to 1.2 mol of propoxylation per 1 mol of a carboxylic acid component comprising an aromatic dicarboxylic acid component (a) and 15 to 30 mol% of a trivalent or higher polycarboxylic acid component (b). And / or an ethoxylated etherified diphenol component (c) and 0.01 to 0.15 mol of an aliphatic diol component (d) condensed with an acid value of 6 to 15
mgKOH / g, weight average molecular weight Mw of 15,000-
60,000, number average molecular weight Mn is 2,000-4.0.
00, the ratio (Mw / Mn) of the weight average molecular weight Mw to the number average molecular weight Mn is 6 to 18, and the glass transition point is 50 to 6
A toner for electrophotography, which is a polyester resin having 0 ° C. and a softening point of 100 to 120 ° C.