Toner for the development of electrostatic images

Abstract: Described are toners for development of electrostatic images containing one or more compounds of the general formulae (I) where A and R each represent an aromatic moiety, and the hydroxyl group and the amido group in the formula are bonded to the aromatic ring A at adjacent positions, and/or (II) where A¹, A², R¹ and R² each represent an aromatic moiety, and the hydroxyl group and the amido group in the formula are bonded to the aromatic moiety A¹ or A² at adjacent positions, and n represents an integer. The toners are non toxic and have sufficient charging property and charging stability.

Description: The present invention relates to toners for the development of electrostatic images, which are used in electronic duplicators and the like, such as xerographic copiers. A developer (toner) for electronic duplicators such as xerographic copiers is selectively attracted to the charge pattern formed on a photoreceptor there by developing the charge pattern. The toner image is then transferred from the photoreceptor to a paper and fixed by softening and fusing the toner to the paper. As the developers to be used in the process for developing an electrostatic image (latent image) formed on the photoreceptor two-component developers comprising a carrier and a toner and one-component developers (magnetic toner) without a carrier are known. One important characteristic of a toner is its charging property. That is, a toner is specifically needed to be charged either positively or negatively at a suitable level, the charged level being essentially stable even in continuous use or under severe conditions. The charging property of a toner depends on the type of the binder resin and of the colorant. Incorporation of an agent to a toner for giving it a charging property (a charge controlling agent) has been known. Examples of such charge controlling agents are positive charging nigrosine dyes and quaternary ammonium salts, and negative charging metal-containing monoazo dyes, salicylic acid-metal complexes and copper phthalocyanine pigments. The closest state of the art is JP-A-61 26 7059, US-A-4 147 645 and US-A-4 099 968 which disclose toners comprising as charge controlling agents compounds having an aromatic moiety, carrying a hydroxyl and/or an amide substituent. However, such conventional charge controlling agents are not completely satisfactory with respect to giving an appropriate charging property and other various characteristics of a toner. One problem is that the charge controlling agents interfere with the safety of a toner containing them. Almost all conventional charge controlling agents, especially negative charge controlling agents are metal-containing dyes containing, for example, a chromium or the like, as the generating charge level of them is high. However, since a toner is used in close proximity to humans, it is preferred that a metal, such as chromium, which would be toxic to humans is not incorporated into a toner. Recently, in particular, the safety of substances to humans has become more stringent. Therefore, the development of charge controlling agents for toners is desired, which do not contain toxic metals such as chromium, which have better charging properties than conventional charge controlling agents and which have other various excellent characteristics suitable for toners for xerography. Another problem is that the charging stability of the conventional charge controlling agents is poor. In fact, many of the conventional charge controlling agents do not have a sufficient charging stability, although they have a high charging level. Therefore, if they are used in the continuous duplication or continuous printing, the charging level of these agents often varies with the lapse of time and the duplicated or printed copies are stained. This is not desired. Recently, the problem is exacerbated with increase for the demand for rapid-processing duplicators capable of continuously and rapidly duplicating a large amount of copies. In view of this situation, the development of charge controlling agents having an improved charging stability is desired. Thus, the technical problem underlying the present invention is to provide metal-free toners of high quality for the development of electrostatic images, which have a sufficient charging level and an excellent charging stability so that staining of copies is essentially avoided. Specifically, one problem of the present invention is to provide metal-free toners having a sufficient charging level and excellent charging stability and additionally having other necessary properties, such as moisture resistance, light fastness and heat resistance, and to also provide metal-free toners of high quality which are stable even in continuous use under severe conditions to stably yield a suitable printing density without causing staining of copies. Another problem of the present invention is to provide safe (non toxic) toners. These problems are solved by toners for the development of electrostatic images, which contain one or more compounds of the general formulae (I) where A and R each represent an aromatic moiety, and the hydroxyl group and the amido group in the formula are bonded to the aromatic ring A at adjacent positions (o-positions), and/or (II) where A¹, A², R¹ and R² each represent an aromatic moiety, and the hydroxyl group and the amido group in the formulae are bonded to the aromatic moiety A¹ or A² at adjacent positions, and n represents an integer from 1 to 5. The toner for development of electrostatic images of the present invention is characterized by containing one or more compounds of the general formulae (I) and/or (II). In the general formulae (I) and (II), A, A¹, A², R, R¹ and R² each represent an aromatic moiety, which may have one or more substituents. These moieties may have a heterocyclic structure or may have a condensed aromatic-heterocyclic structure. Specific examples of aromatic moieties are derived from benzene, naphthalene, anthracene, phenantrene, carbazole, fluorene, fluorenone, dibenzofuran, dibenzothiophene and benzocarbazole. Specific examples of substituents, if any, on the aromatic moiety include alkyl groups such as a methyl group, an ethyl group, a propyl group, a n-butyl group and a tert-butyl group; amino groups; alkoxy groups such as a methoxy group and an ethoxy group; halogen atoms such as a chlorine atom and a bromine atom; nitro groups; and phenyl groups. The number of the substituents on the moiety may be from 1 to 5. If several substituents are on the moiety, they may be same as or different from each other. A and R in the general formula (I) as well as A¹, A², R¹ and R² in the general formula (II) may be same as or different from one another. In the general formula (I) the moieties A and R preferably each are a moiety selected from the group consisting of an optionally substituted benzene, naphthalene, anthracene, phenanthrene, carbazole, fluorene, fluorenone, dibenzofuran, dibenzothiophene and benzocarbazole. The preferred substituents of A and R in the general formula (I) are selected from the group consisting of alkyl, amino, alkoxy, halogen, nitro and phenyl groups. The preferred moiety A in the general formula (I) is a moiety selected from the group consisting of naphthalene, anthracene, carbazole and benzocarbazole. The preferred moiety R in the general formula (I) is a moiety selected from the group consisting of benzene, naphthalene and anthracene. The most preferred moiety A in the general formula (I) is a naphthalene moiety and R is a benzene or naphthalene moiety. In another embodiment of the invention the compound is one represented by the general formula (II), in which A¹, A², R¹ and R² each are a moiety selected from the group consisting of an optionally substituted benzene, naphthalene, anthracene, phenanthrene, carbazole, fluorene, fluorenone, dibenzofuran, dibenzothiophene and benzocarbazole. The preferred substituents of A¹, A², R¹ and R² in the general formula (II) are selected from the group consisting of alkyl, amino, alkoxy, halogen, nitro and phenyl. The preferred moieties A¹ and/or A² in the general formula (II) each are a moiety selected from the group consisting of naphthalene, anthracene, carbazole and benzocarbazole. The preferred moieties R¹ and/or R² in the general formula (II) are a moiety selected from the group consisting of benzene, napnthalene and anthracene. The most preferred moieties A¹ and/or A² in the general formula (II) are a naphthalene moiety and R¹ and/or R² is a benzene or naphthalene moiety, and preferably A¹ and A², or R¹ and R² are the same moieties. In the general formula (II), the number (n) of carbon atoms constituting the alkylene chain of bonding A¹ and A² to each other is from 1 to 5, preferably from 1 to 3. Compounds of the general formula (I) may be produced by the following method. For instance, compounds of general formulae (III) and (IV): H₂N - R where A and R have the same meaning as in the general formula (I), are reacted in a solvent such as toluene or chlorobenzene at elevated temperatures in the presence of phosphorus trichloride, to obtain a compound of the general formula (I). Compounds of the general formula (II) may be produced by a method as described in Brass, Sommer, Berichte der Deutsch. chem. Ges., Bd. 61 (1928), 998. For instance, compounds of the general formulae (V) and (VI): where A¹, A², R¹ and R² have the same meaning as those in the general formula (II), are reacted in the presence of formaldehyde in an alkaline solution under heating to 50 to 120°C to obtain a compound of the general formula (II). Preferred, non limiting examples of compounds of the general formulae (I) and (II) to be incorporated into the toner of the present invention are those of the following structural formulae. Examples of Compounds of the general Formula (I): Examples of Compounds of the general Formula (II): The toners of the present invention contain a resin (a resinous binder), which may be selected from a broad range of known resins. For instance, the resin may be selected from styrene resins (homopolymers or copolymers containing styrene or substituted styrenes), such as polystyrene, polychlorostyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylate copolymers (e.g., styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer and styrene-phenyl acrylate copolymer), styrene-methacrylate copolymers (e.g., styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer and styrene-phenyl methacrylate copolymer), styrene-methyl α-chloroacrylate copolymer, and styrene-acrylonitrile-acrylate copolymers; as well as vinyl chloride resins, maleinized rosin resins, phenolic resins, epoxy resins, polyester resins, low molecular polyethylene, low molecular polypropylene, ionomer resins, polyurethane resins, silicone resins, ketone resins, ethylene-ethyl acrylate copolymers, xylene resins and polyvinyl butyral resins. Especially preferred resins (binders) for use in the present invention are styrene-acrylate copolymers, styrene-methacrylate copolymers, saturated or unsaturated polyester resins and epoxy resins. The resins may be incorporated into the toners of the present invention alone or in combination of two or more resins. The toners of the present invention contain a colorant, which may be selected from known colorants of a broad range. For instance, the colorant may be selected from carbon black, lamp black, iron black, ultramarine, nigrosine dyes, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow, Rose Bengal, triarylmethane dyes, monoazo dyes, and disazo dyes. Compounds of the general formulae (I) and (II) are of pale yellow color and they may be incorporated into blue, red or yellow color toners. In this case, colorants (dyes and pigments) each having the necessary color tone are incorporated into the color toners. The content of the colorant component in the toner is preferably from 3 to 20 parts by weight per 100 parts by weight of the resin. For the incorporation of one or more compounds of the general formulae (I) and/or (II) and any other additional charge controlling agent(s) into the toner of the present invention, a simultaneous addition method may be used. In this method the compound(s) is (are) added to and blended with a toner along with a resin. Furthermore, a separate addition method may be used in which the compound(s) is (are) added to and blended with toner grains. The simultaneous addition method is more general and preferable. The content of compound(s) of the general formulae (I) and/or (II) in the toner of the present invention is preferably from 0.1 to 20 parts by weight, more preferably from 0.5 to 5 parts by weight, most preferably from 0.5 to 5 parts by weight, per 100 parts by weight of the resin. If the content is too small, the effect of elevating the charging property of the toner cannot be attained. If it is too large, the quality of the toner is impaired. The toners of the present invention may further contain, in addition to compound(s) of the general formulae (I) and/or (II), any other charge controlling agent, including known ones, such as nigrosine dyes, quaternary ammonium salts and metal-containing complex compounds. The toners of the present invention may also contain any other known additives, for example, conductors such as solid electrolytes, polyelectrolytes, charge transfer complexes and metal oxides (e.g. tin oxide), as well as semiconductors, ferroelectric substances and magnetic substances so as to control the electric properties of the toners. The toners may further contain other auxiliary additives such as various kinds of plasticizers and surface lubricants, for example, low molecular weight olefin polymers, for the purpose of controlling the thermal characteristics and physical characteristics of the toners. The addition of finely powdered TiO₂, Al₂O₃ or SiO₂ to the toner grains is also possible so as to coat the surface of the grains, whereby the fluidity and anticoagulating property of the toner may be improved. For preparing the toners of the present invention, the components may be mixed and kneaded in a kneader or the like, cooled, ground and classified. The toners of the present invention may be used for two-component developers and also for one-component developers (magnetic toner) such as capsule toners, polymer toners or magnetite-containing toners. The mean grain size of the toner grains of the present invention is desirably from 5 to 20 µm. As a carrier to be blended with the toner of the present invention to form a developer, any known magnetic substance e.g. iron powder, ferrite or magnetite carrier, as well as a resin-coated carrier to be prepared by coating a resin on the surface of the magnetic substance and a magnetic resin carrier may be used. As a resin for such resin-coated carriers any known resin is usable such as styrene resins, acrylic resins, styrene-acrylic copolymer resins, silicone resins, modified silicone resins and fluorine polymers. However, these are not limitative. The mean grain size of the carrier grains is not critical. Preferably, it is from 10 to 200 µm. The proportion of the carrier grains is preferably from 5 to 100 parts by weight per one part by weight of the toner. The present invention will be explained in more detail by way of the following examples. These examples are not intended to restrict the scope of the present invention. All "parts" in the following examples are by weight, unless otherwise specifically defined. EXAMPLE 1: Styrene Resin (SBM-600, product by Sanyo Chemical Co.) 100 parts Carbon Black (#44, product by Mitsubishi Kasei Corp.) 10 parts Compound (3) (the charge controlling agent) 2 parts The above-mentioned components were mixed, kneaded, ground and classified to obtain a black toner having a mean grain size of 11 µm. 5 parts of the toner and 100 parts of an acrylic resin-coated carrier having a mean grain size of about 100 µm were blended and stirred to prepare a developer. Using the developer, duplication was effected with a duplicator having a selenium photoreceptor to give clear copies. EXAMPLE 2: The same process as in Example 1 was repeated, except that one part of compound (4) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 3: The same process as in Example 1 was repeated, except that one part of compound (5) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 4: The same process as in Example 1 was repeated, except that one part of compound (6) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 5: The same process as in Example 1 was repeated, except that one part of compound (7) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 6: The same process as in Example 1 was repeated, except that 3 parts of compound (10) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 7: The same process as in Example 1 was repeated, except that 3 parts of compound (14) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 8: The same process as in Example 1 was repeated, except that 3 parts of compound (19) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 9: The same process as in Example 1 was repeated, except that 2 parts of compound (21) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 10: The same process as in Example 1 was repeated, except that 3 parts of compound (25) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 11: The same process as in Example 1 was repeated, except that one part of compound (28) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 12: The same process as in Example 1 was repeated, except that one part of compound (31) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 13: The same process as in Example 1 was repeated, except that one part of compound (32) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 14: The same process as in Example 1 was repeated, except that 3 parts of compound (37) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 15: The same process as in Example 1 was repeated, except that 3 parts of compound (39) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 16: The same process as in Example 1 was repeated, except that 4 parts of compound (40) was used as the charge controlling agent. Good copies were obtained like Example 1. EXAMPLE 17: Styrene-acrylic Resin 100 parts Carbon Black 7 parts Polypropylene Wax 1 part Charge Controlling Agent; see Table 1 0,9 part The above-mentioned components were mixed, kneaded, ground and classified to obtain a black toner. 0.1 g of the toner and 9.9 g of iron powder carrier were put in a glass bottle and shaken for 10 minutes. The amount of charge of the blend was measured by the blow-off method. The results are summarized in Table I. From the experiment, it is evident that the compounds of the general formulae (I) and/or (II) have a charging property comparable to the conventional metal-containing charge controlling agent. As has been explained in detail in the above, the toners of the present invention are safe (non toxic) and have a sufficient charging level and a satisfactory charging stability. They are of high-quality not causing the staining of copies.

Claims: A toner for the development of electrostatic images, comprising a resin as binder and a colorant and containing one or more compounds of the general formulae (I) where A and R each represent an aromatic moiety, and the hydroxyl group and the amido group in the formula are bonded to the aromatic moiety A at adjacent positions, and/or (II): where A¹, A², R¹ and R² each represent an aromatic moiety, and the hydroxyl group and the amido group in the formula are bonded to A¹ or A² at adjacent positions, and n represents an integer from 1 to 5. The toner as claimed in claim 1, in which the compound is one represented by a general formula (I): where A and R each represent an aromatic moiety, and the hydroxyl group and the amido group in the formula are bonded to the aromatic moiety A at adjacent positions. The toner as claimed in claim 2, in which A and R in formula (I) each are a moiety selected from the group consisting of an optionally substituted benzene, naphthalene, anthracene, phenanthrene, carbazole, fluorene, fluorenone, dibenzofuran, dibenzothiophene and benzocarbazole. The toner as claimed in claim 2 or 3 in which R in the general formula (I) is an aromatic moiety having one or more substituents selected from the group consisting of alkyl, amino, alkoxy, halogen, nitro and phenyl groups. The toner as claimed in anyone of claims 2 to 4, in which A and R in the general formula (I) each are an aromatic moiety having one or more substituents selected from the group consisting of alkyl, amino, alkoxy, halogen, nitro and phenyl groups. The toner as claimed in anyone of claims 2 to 5, in which A in the general formula (I) is a moiety selected from the group consisting of naphthalene, anthracene, carbazole and benzocarbazole. The toner as claimed in anyone of claims 2 to 6, in which R in the general formula (I) is a moiety selected from the group consisting of benzene, naphthalene and anthracene. The toner as claimed in anyone of claims 2 to 7, in which A in the general formula (I) is a naphthalene moiety and R is a benzene or naphthalene moiety. The toner as claimed in claim 1, in which the compound is one represented by the general formula (II): where A¹, A², R¹ and R² each represent an aromatic moiety, and the hydroxyl group and the amido group in the formula are bonded to A¹ or A² at adjacent positions, and n represents an integer from 1 to 5. The toner as claimed in claim 9, in which A¹, A², R¹ and R² in the general formula (II) each are a moiety selected from the group consisting of an optionally substituted benzene, naphthalene, anthracene, phenanthrene, carbazole, fluorene, fluorenone, dibenzofuran, dibenzothiophene and benzocarbazole. The toner as claimed in claim 9 or 10, in which R¹ and/or R² in the general formula (II) each are an aromatic moiety having one or more substituents selected from the group consisting of alkyl, amino, alkoxy, halogen, nitro and phenyl. The toner as claimed in anyone of claims 9 to 11, in which A¹, A², R¹ and R² in the general formula (II) each are an aromatic moiety having one or more substituents selected from the group consisting of alkyl, amino, alkoxy, halogen, nitro and phenyl. The toner as claimed in anyone of claims 9 to 12, in which A¹ and/or A² in the general formula (II) each are a moiety selected from the group consisting of naphthalene, anthracene, carbazole and benzocarbazole. The toner as claimed in anyone of claims 9 to 13, in which R¹ and/or R² in the general formula (II) is a moiety selected from the group consisting of benzene, naphthalene and anthracene. The toner as claimed in anyone of claims 9 to 14 in which A¹ and/or A² in the general formula (II) is a naphthalene moiety and R¹ and/or R² is a benzene or naphthalene moiety. The toner as claimed in anyone of claims 9 to 15, in which A¹ and A², or R¹ and R² are the same moieties. The toner as claimed in anyone of claims 1 to 16, which contains one or more compounds of the general formulae (I) and (II) in an amount of from 0.1 to 20 parts by weight per 100 parts by weight of the resin.

Inventors: ANDO OSAMU, ONO HITOSHI, TAKEUCHI MASAKO, ANDO, OSAMU, ONO, HITOSHI, TAKEUCHI, MASAKO
Applicants: MITSUBISHI CHEM CORP, MITSUBISHI CHEMICAL CORPORATION
Application year: 1992
Main classification: G03G9
IPC codes: G03G9