JP2000221732A - Negatively chargeable toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the negatively chargeable toner not attaching with melting to a layer-regulating member and a toner carrier even in the case of being used for a long time at a comparatively high speed and preventing occurrence of uneven striations of images and fog on a background by incorporating a polyester resin having an urethane cross-linking component and a specified compound. SOLUTION: The polyester resin to be used for the negatively chargeable toner having the urethane cross-linking component is obtained by cross-linking the polyester base resin with a diisocyanate to expand the resin and mixing the other polyester, when needed. The negatively chargeable toner contains this resin having cross-linking components and further, the boron compound represented by the formula in which each of R1 and R4 is an H atom or an alkyl or optionally substituted aromatic ring or condensed ring; each of R2 and R3 is an optionally substituted aromatic ring or condensed ting; Xn+ is a cation; and (n) is 1 or 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negatively charged toner used in an electrophotographic image forming apparatus employing a non-magnetic one-component reversal developing system.

[0002]

2. Description of the Related Art Currently, an electrophotographic image forming apparatus such as a printer uses a negatively charged electrophotographic photosensitive member, particularly an organic photosensitive member (hereinafter referred to as an OPC), and is uniformly charged by a semiconductor laser or a light emitting diode (LED). A process of forming a negative latent image on an OPC and reversal developing the latent image with a negatively charged toner is generally used. In addition, as a development method, because a developing device can be provided at a low cost,
A so-called non-magnetic one-component developing method has been used in which a thin layer of toner is formed on a toner carrier by a layer regulating member, and the thin layer is brought into contact with a photoreceptor to develop the toner. In the non-magnetic one-component reversal developing method, the developing potential is the difference between the bias voltage applied to the developing device and the residual potential of the photoreceptor after exposure, and is compared with a general developing method for developing a non-exposed portion. And development contrast is difficult to obtain. Further, in the non-magnetic one-component reversal developing method, toner is charged by friction with a toner supply roller or a layer regulating member, but it is generally difficult to charge all toner particles to a sufficient level by this charging mechanism. . because of these reasons,
In the non-magnetic one-component reversal developing method, background fogging always becomes a problem. As a remedy from the device side for these background fogs, as a material for the layer regulating member and the toner carrier, a metal-based material having a low resistance or a polymer whose resistance is adjusted so that sufficient triboelectricity can be imparted to the toner. Attempts have been made to use materials and the like, but not enough. Further, in the non-magnetic one-component reversal developing method, the toner is subjected to a mechanical stress between the supply roller and the layer regulating member and the toner carrier, so that the toner is fused to the layer regulating member and the toner carrier after a long use. This may cause problems such as streak-like image unevenness and ground fogging.
In order to solve these problems, as a toner used in the non-magnetic one-component reversal developing method, a polyester resin having the same molecular weight and a higher resin strength than a vinyl-based resin or a specific external additive is used. Thus, the durability of the toner has been improved, and the chargeability of the toner has been improved by selecting the composition of the polyester resin, the charge control agent and the external additive. However, it has not been possible to achieve both sufficient durability and good chargeability in the studies so far.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a negatively charged toner used in a non-magnetic one-component reversal developing system using a negatively charged photoreceptor. An object of the present invention is to provide a negatively charged toner in which toner does not fuse to a member or a toner carrier, and does not cause problems such as streak-like image unevenness and background fog.

[0004]

The present invention is a negatively charged toner comprising a polyester resin having a urethane crosslinking component and a compound represented by the following general formula (I).

Embedded image (In the formula, R ₁ and R ₄ represent a hydrogen atom, an alkyl group, a substituted or unsubstituted aromatic ring (including a condensed ring), and R ₂ and R ₃ represent a substituted or unsubstituted aromatic ring (including a condensed ring. ), X ^{n +} represents a cation, and n is 1 or 2.)

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A polyester resin having a urethane crosslinking component used in the negatively charged toner of the present invention is obtained by crosslinking a polyester resin as a basic resin (hereinafter referred to as a base polyester resin) with a diisocyanate and urethane crosslinking.
It is obtained by urethane elongation to obtain a urethane crosslinked polyester resin, and then mixing another polyester resin as necessary. Compared with a general polyester resin for toner synthesized from carboxylic acids and alcohols, the urethane crosslinked polyester resin has a tougher urethane bond than an ester bond in its molecular chain, so that the durability of the toner is improved. (The ability to fuse the toner to the layer regulating member and the toner carrying member) can be improved. The base polyester resin is obtained by polycondensation of a polycarboxylic acid and a polyhydric alcohol. As polyvalent carboxylic acids,
For example, malonic acid, succinic acid, glutaric acid, adipic acid,
Aliphatic dibasic acids such as azelaic acid, sebacic acid, hexahydrophthalic anhydride, maleic acid, maleic anhydride,
Use is made of aliphatic unsaturated dibasic acids such as fumaric acid, itaconic acid and citraconic acid, aromatic dibasic acids such as phthalic anhydride, terephthalic acid and isophthalic acid, and lower alkyl esters thereof. Examples of the polyhydric alcohol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, and neopentyl glycol. , Diethylene glycol, dipropylene glycol, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct,
A diol such as bisphenol A propylene oxide adduct and a triol such as glycerin, trimethylolpropane, and trimethylolethane are used.

As the polycondensation method, there are known high-temperature polycondensation,
Solution polycondensation and the like are used. The usage ratio of the polyhydric carboxylic acid and the polyhydric alcohol is generally 0.8 to 1.4, which is the ratio of the former carboxyl group to the latter hydroxyl group.
The number average molecular weight of the base polyester resin is 100
It is from 0 to 30,000, preferably from 2000 to 15,000. If the number average molecular weight is less than 1,000, the offset resistance of the toner may decrease, which is not preferable. Also, 30
If it exceeds 000, the viscosity increases significantly during the reaction between the base polyester and the diisocyanate, which is not preferable from the viewpoint of production. In this case, the fixing strength of the toner may decrease. Examples of the diisocyanate include methylene diisocyanate, hexamethylene diisocyanate, isophone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and tetramethyl xylylene diisocyanate. The use range of the diisocyanate is 0.3 to 0.1 per mol of the base polyester resin.
95 mol, especially 0.5 to 0.8 mol, is preferred. If the amount of diisocyanate is less than 0.3 mol, the offset resistance of the toner may decrease, which is not preferable. Also, 0.95
If the molar ratio is exceeded, the viscosity increases significantly during the reaction, and in some cases, stirring becomes impossible due to an increase in viscosity, which is not preferable in production.

The urethane crosslinked polyester resin is
For example, it is obtained by charging a base polyester resin with diisocyanate and reacting at a temperature of 50 to 150 ° C. for several hours in the presence or absence of a solvent. In addition, the polyester resin having a urethane cross-linking component may be obtained by heating a solution containing the urethane cross-linking polyester resin alone or a solution containing the urethane cross-linking polyester resin, and a solution containing another polyester resin alone or containing another polyester resin as necessary in a container. Then, after stirring and mixing, it is obtained by treating at high temperature and vacuum in order to remove unnecessary solvents, residues and odor. The other polyester resin is obtained by the same method as the base polyester resin, and has a number average molecular weight of 1,000 to 10,000, preferably 2,000 to 600.
0. If the number average molecular weight is less than 1,000, the offset resistance of the toner may be reduced, and if it exceeds 10,000, the fixing strength may be reduced. Polyhydric carboxylic acids and polyhydric alcohols used in other polyester resins may be the same as or different from the base polyester. In the polyester resin having a urethane cross-linking component, the compounding ratio of the urethane cross-linking polyester resin and the other polyester resin is 20:80 to 95: 5 by weight ratio,
Preferably it is 30: 70-80: 20. If the compounding ratio of the urethane crosslinked polyester resin is less than 20% by weight of the total of the two, the offset resistance of the toner decreases, and if the compounding ratio of the other polyester resin is less than 5% by weight of the total, the pulverization in the toner manufacturing process. It is not preferable because the fixing property is deteriorated and the fixing strength is also lowered. The glass transition point (Tg) of the polyester resin having a urethane crosslinking component is 40.
-80 ° C, preferably 55-70 ° C. Tg is 40
If the temperature is lower than 80 ° C., the blocking resistance of the toner may be deteriorated. If the temperature is higher than 80 ° C., the fixing strength may be deteriorated.

The negatively charged toner of the present invention contains the above-mentioned polyester resin having a urethane crosslinking component and a boron compound represented by the following general formula (I).

Embedded image (In the formula, R ₁ and R ₄ represent a hydrogen atom, an alkyl group, a substituted or unsubstituted aromatic ring (including a condensed ring), and R ₂ and R ₃ represent a substituted or unsubstituted aromatic ring (including a condensed ring. ) And X ^{n +} represents a cation, and n is 1 or 2.) The above compound is, for example, a product name: L from Nippon Carlit Co., Ltd.
It is commercially available as R-147. The content of the compound represented by the general formula (I) is 0.5 to 3.0% by weight in the toner.
It is desirable that When the amount is less than 0.5% by weight, the amount of triboelectricity of the toner becomes insufficient, so that it is difficult to obtain a sufficient image density, and the degree of background fog tends to be poor. On the other hand, when the content exceeds 3.0% by weight, the charge amount of the toner becomes too high, so that the thickness of the toner layer on the toner carrier becomes too thick, and the background fog sometimes rises.

The negatively charged toner of the present invention may contain, as other components, a colorant and a charge controlling agent other than the compound represented by formula (I). Examples of the coloring agent include carbon black generally used in toners and color pigments such as quinacridone pigments, azo pigments, naphthol pigments, phthalocyanine blue, benzidine yellow, and benzimidazolone. The colorant is used in an amount of 0.1 to 20 in the toner in an amount capable of satisfying the image density after fixing.
%, Preferably 1 to 10% by weight. In the negatively charged toner of the present invention, a release agent of a natural wax such as a low molecular weight polypropylene wax, a low molecular weight polyethylene wax, a paraffin wax, a carnauba wax and a candelilla wax may be used in combination. Further, an external additive may be attached to the surface of the particles of the negatively charged toner of the present invention. Examples of the external additive include fluidity improvers such as silica and alumina, and abrasives such as magnetite, strontium titanate and cerium oxide. In order to attach these external additives to the toner particles, a mixer having a stirring blade such as a super mixer or a Henschel mixer can be used.

The negatively charged toner of the present invention is obtained by mixing and stirring a polyester resin having a urethane cross-linking component, a colorant, a charge control agent, and other components, melt-kneading, cooling, and pulverizing and classifying to obtain toner particles. Thereafter, if necessary, it can be produced by attaching an external additive using a mixer. The negatively charged toner of the present invention forms an electrostatic latent image by exposing an image portion of a photoconductor negatively charged by a charging member, and is formed on the toner carrier by the layer regulating member on the electrostatic latent image. It is suitably used in a non-magnetic one-component reversal development system in which a thin layer of negatively charged toner is brought into contact and a bias voltage is applied between a toner carrier and a photoreceptor to develop a latent image. In particular, the layer regulating member and the toner carrier are suitably used in a non-magnetic one-component developing device composed of a metal / polymer material or a polymer material / metal, respectively.

[0011]

EXAMPLES Example 1 Production of Polyester Resin Having Urethane Crosslinking Component
In a polymerization vessel, 1700 parts by weight of a bisphenol A propylene oxide adduct, 150 parts by weight of diethylene glycol, and 860 parts by weight of isophthalic acid were charged, and polycondensation was performed at 240 ° C. while introducing nitrogen into the polymerization vessel to obtain a base polyester resin. . Next, when the acid value of the base polyester resin becomes 5 mgKOH / g or less, the base polyester resin is cooled to 130 ° C, 2500 parts by weight of xylene and 100 parts by weight of methylene diisocyanate are added, and the mixture is reacted at 120 ° C for 4 hours. I got on the other hand,
In another polymerization vessel, 1400 parts by weight of a bisphenol A propylene oxide adduct, 100 parts by weight of diethylene glycol, 800 parts by weight of isophthalic acid, and 50 parts by weight of phthalic anhydride were charged, and polycondensation was performed at 230 ° C. while introducing nitrogen into the polymerization vessel. Then, another polyester resin was obtained. The urethane crosslinked polyester resin and another polyester resin were mixed in a xylene solvent at a weight ratio of 40:60, and the solvent was removed in a vacuum system to obtain a polyester resin (A) having a urethane crosslinked component. The molecular weight of the polyester resin (A) soluble in tetrahydrofuran (hereinafter referred to as THF) as determined by GPC was weight average molecular weight (Mw) = 168,000, number average molecular weight (Mn) = 3900, and the acid value was 12 mgKOH / g.
And the THF insoluble content was 5%. [Production of Toner] 91.0% by weight of polyester resin (A) above 2.0% by weight of polypropylene wax (trade name: Viscol 550P manufactured by Sanyo Chemical Industries, Ltd.) 5.0% by weight of carbon black (manufactured by Cabot Corporation) Name: REGAL330R)-2.0% by weight of the compound represented by the general formula (I) (trade name: LR-147, manufactured by Nippon Carlit Co.) After stirring and mixing the above materials with a super mixer for 5 minutes,
The mixture was melt-kneaded with a twin-screw extruder, pulverized with a jet mill, and classified with an air classifier to have a volume average particle size of 9.
A classified product of 0 μm was obtained. To 100 parts by weight of the classified product, add hydrophobic silica particles (trade name: TS, manufactured by Cabot Corporation).
-530) 0.4 part by weight was added and mixed with a Henschel mixer manufactured by Mitsui Mining Co., Ltd. to obtain a negatively charged toner of the present invention.

Example 2 [Production of polyester resin having urethane crosslinking component]
In a polymerization vessel, 1700 parts by weight of a bisphenol A propylene oxide adduct, 150 parts by weight of diethylene glycol, and 860 parts by weight of isophthalic acid were charged, and polycondensation was performed at 240 ° C. while introducing nitrogen into the polymerization vessel to obtain a base polyester resin. . Next, when the acid value of the base polyester resin becomes 5 mgKOH / g or less, the base polyester resin is cooled to 130 ° C, 2500 parts by weight of xylene and 100 parts by weight of methylene diisocyanate are added, and the mixture is reacted at 120 ° C for 4 hours. I got on the other hand,
In another polymerization vessel, 1400 parts by weight of a bisphenol A propylene oxide adduct, 100 parts by weight of diethylene glycol, 600 parts by weight of isophthalic acid, and 30 parts by weight of phthalic anhydride were charged, and polycondensation was performed at 230 ° C. while introducing nitrogen into the polymerization vessel. Then, another polyester resin was obtained. The urethane crosslinked polyester resin and another polyester resin were mixed in a xylene solvent at a weight ratio of 40:60, and the solvent was removed in a vacuum system to obtain a polyester resin (B) having a urethane crosslinked component. The molecular weight of the polyester resin (B) soluble in tetrahydrofuran (hereinafter referred to as THF) by GPC method is weight average molecular weight (Mw) = 152000, number average molecular weight (Mn) = 3400, and acid value is 10 mgKOH / g.
And the THF-insoluble content was 3%. [Production of Toner] 91.0% by weight of polyester resin (B) above 2.0% by weight of polypropylene wax (trade name: Viscol 550P manufactured by Sanyo Chemical Industries, Ltd.) 5.0% by weight of carbon black (manufactured by Cabot Corporation) Name: REGAL330R)-2.0% by weight of the compound represented by the general formula (I) (trade name: LR-147, manufactured by Nippon Carlit Co.) After stirring and mixing the above materials with a super mixer for 5 minutes,
The mixture was melt-kneaded with a twin-screw extruder, pulverized with a jet mill, and classified with an air classifier to have a volume average particle size of 9.
A 3 μm classified product was obtained. To 100 parts by weight of the classified product, add hydrophobic silica particles (trade name: TS, manufactured by Cabot Corporation).
-530) 0.4 part by weight was added and mixed with a Henschel mixer manufactured by Mitsui Mining Co., Ltd. to obtain a negatively charged toner of the present invention.

Example 3 [Production of Toner] 92.5% by weight of polyester resin (A) 2.0% by weight of polypropylene wax (trade name: Viscol 550P manufactured by Sanyo Chemical Industries, Ltd.) 5.0% by weight of carbon black % (Trade name: REGAL330R, manufactured by Cabot) 0.5% by weight of the compound represented by the general formula (I) (trade name: LR-147, manufactured by Nippon Carlit Co.) After stirring and mixing the above materials for 5 minutes with a super mixer. ,
The mixture was melt-kneaded with a twin-screw extruder, pulverized with a jet mill, and classified with an air classifier to have a volume average particle size of 9.
A 1 μm classified product was obtained. To 100 parts by weight of the classified product, add hydrophobic silica particles (trade name: TS, manufactured by Cabot Corporation).
-530) 0.4 part by weight was added and mixed with a Henschel mixer manufactured by Mitsui Mining Co., Ltd. to obtain a negatively charged toner of the present invention.

Example 4 [Production of Toner] 90.0% by weight of polyester resin (A) 2.0% by weight of polypropylene wax (trade name: Viscol 550P manufactured by Sanyo Chemical Industries, Ltd.) 5.0% by weight of carbon black % (Manufactured by Cabot Corporation: REGAL330R) 3.0% by weight of the compound represented by the general formula (I) (manufactured by Nippon Carrit Company: LR-147) After stirring and mixing the above materials with a super mixer for 5 minutes ,
The mixture was melt-kneaded with a twin-screw extruder, pulverized with a jet mill, and classified with an air classifier to have a volume average particle size of 9.
A classified product of 0 μm was obtained. To 100 parts by weight of the classified product, add hydrophobic silica particles (trade name: TS, manufactured by Cabot Corporation).
-530) 0.4 part by weight was added and mixed with a Henschel mixer manufactured by Mitsui Mining Co., Ltd. to obtain a negatively charged toner of the present invention.

Comparative Example 1 [Production of Toner] 91.0% by weight of polyester resin having no urethane cross-linking component (THF insoluble content: 8%, THF soluble content: Mw = 9,7000, Mn = 3600 by GPC method) And an acid value of 15 mg KOH / g)-2.0% by weight of polypropylene wax (trade name: Viscol 550P, manufactured by Sanyo Chemical Industry Co., Ltd.)-5.0% by weight of carbon black (trade name: REGAL330R, manufactured by Cabot Corporation)-The above general 2.0% by weight of a compound represented by the formula (I) (trade name: LR-147, manufactured by Nippon Carlit Co.) After stirring and mixing the above materials with a super mixer for 5 minutes,
The mixture was melt-kneaded with a twin-screw extruder, pulverized with a jet mill, and classified with an air classifier to have a volume average particle size of 9.
A 1 μm classified product was obtained. To 100 parts by weight of the classified product, add hydrophobic silica particles (trade name: TS, manufactured by Cabot Corporation).
-530) was added and mixed with a Henschel mixer manufactured by Mitsui Mining Co., Ltd. to obtain a negatively charged toner for comparison.

Comparative Example 2 [Production of Toner] 91.0% by weight of polyester resin (A) above 2.0% by weight of polypropylene wax (trade name: Viscol 550P manufactured by Sanyo Chemical Industries, Ltd.) 5.0% by weight of carbon black % (Manufactured by Cabot Corp .: REGAL330R) ・ Chromium complex compound 2.0% by weight (manufactured by Orient Chemical Co., Ltd .: Bontron S-34) After stirring and mixing the above materials with a super mixer for 5 minutes,
The mixture was melt-kneaded with a twin-screw extruder, pulverized with a jet mill, and classified with an air classifier to have a volume average particle size of 9.
A 2 μm classified product was obtained. To 100 parts by weight of the classified product, add hydrophobic silica particles (trade name: TS, manufactured by Cabot Corporation).
-530) was added and mixed with a Henschel mixer manufactured by Mitsui Mining Co., Ltd. to obtain a negatively charged toner for comparison.

Next, the toners of Examples 1 to 4 and Comparative Examples 1 and 2 were commercialized using a non-magnetic one-component reversal developing system having negatively charged OPC (trade name: IPSI manufactured by Ricoh Company).
OColor2000) and a printing test was performed. The developing device of the printer uses a metal toner carrier and a urethane layer regulating member. Table 1 shows the results of the initial image of printing and the image after 30 minutes of the developing device stirring test. Here, the developing device stirring test means that the developing device is taken out of the printer main body, and the developing device is operated for 200 minutes.
This is a test in which the toner carrier is rotated at a peripheral speed of mm / sec. The ID in the table is the reflection density obtained by measuring the solid image with a Macbeth reflection densitometer (RD-914). The PC fog is obtained by transferring the ground fog on the OPC photoreceptor to Scotch's mending tape. Is a value obtained by subtracting a value measured for white paper from an average value obtained by measuring nine reflection densities with a Macbeth reflection densitometer (RD-914) after pasting on white paper. The occurrence of image unevenness was evaluated by visually checking streak-like image unevenness caused by toner fusion. The mark x indicates that image unevenness occurred within 1 hour after stirring, the mark も の indicates image unevenness occurred within 1 hour to 2 hours, and the mark 、 indicates image unevenness even after 2 hours. Does not occur. In this case, those marked with ○ and ◎ are within the practical range.

[0018]

[Table 1]

As shown in Table 1, the negatively charged toners of Examples 1 to 4 exhibited a sufficient ID value from the beginning, had a low PC fog value, and had good image characteristics even after 30 minutes of stirring in the developing device.
It was confirmed that image non-uniformity caused by fusion of the toner to the layer regulating member and the toner carrying member was small and the durability was excellent. On the other hand, the negatively-charged toner of Comparative Example 1 had the same initial image characteristics as the negatively-charged toner of Example, but a decrease in ID was confirmed after 30 minutes of stirring of the developing device. Further, the toner fusing property to the layer regulating member and the toner carrier was inferior to the negatively charged toner of Example. Comparative Example 2
Negatively-charged toner, compared with the negatively-charged toner of Example,
The result was that the PC fog value was high both in the initial stage and after 30 minutes of stirring in the developing device.

[0020]

The negatively charged toner of the present invention does not fuse to the layer regulating member or the toner carrier even when used for a long period of time, and does not cause problems such as generation of streak-like image unevenness and increase of background fog. .

Claims (4)

[Claims] 1. A negatively charged toner comprising a polyester resin having a urethane crosslinking component and a compound represented by the following general formula (I). Embedded image (In the formula, R ₁ and R ₄ represent a hydrogen atom, an alkyl group, a substituted or unsubstituted aromatic ring (including a condensed ring), and R ₂ and R ₃ represent a substituted or unsubstituted aromatic ring (including a condensed ring. ), X ^{n +} represents a cation, and n is 1 or 2.) 2. The negatively charged toner according to claim 1, wherein the content of the compound represented by the general formula (I) is 0.5 to 3% by weight in the toner. 3. An image portion of a photoconductor charged by a charging member is exposed to form an electrostatic latent image, and a thin layer of toner formed on a toner carrier by a layer regulating member is formed on the electrostatic latent image. A negatively charged toner used in a non-magnetic one-component reversal developing system in which a bias voltage is applied between a toner carrier and a photoconductor while being in contact with the toner carrier, and the toner is a polyester having a urethane cross-linking component. A negatively charged toner comprising a resin and a compound represented by the following general formula (I). Embedded image (In the formula, R ₁ and R ₄ represent a hydrogen atom, an alkyl group, a substituted or unsubstituted aromatic ring (including a condensed ring), and R ₂ and R ₃ represent a substituted or unsubstituted aromatic ring (including a condensed ring. ), X ^{n +} represents a cation, and n is 1 or 2.) 4. The negatively charged toner according to claim 3, wherein the content of the compound represented by the general formula (I) is 0.5 to 3% by weight in the toner.