EP0712049B1

EP0712049B1 - Calixarenes as charge control agents and toner

Info

Publication number: EP0712049B1
Application number: EP19950117332
Authority: EP
Inventors: Shun-ichiro c/o ORIENT CHEM. IND. LTD. Yamanaka; Kazuaki c/o ORIENT CHEM. IND. LTD. Sukata
Original assignee: Orient Chemical Industries Ltd
Current assignee: Orient Chemical Industries Ltd
Priority date: 1994-11-11
Filing date: 1995-11-03
Publication date: 2001-07-11
Anticipated expiration: 2015-11-03
Also published as: DE69521662T2; EP0712049A1; DE69521662D1; JP3325730B2; JPH08137138A

Description

The present invention relates to a toner for developing electrostatic images used to develop electrostatic latent images in electrophotography, electrostatic printing and other purposes, more specifically to a toner for developing electrostatic images that has good fixability and offset resistance, and a charge control agent for controlling the amount of charges of the toner.
In copying machines, printers and other instruments based on electrophotography, various toners containing a coloring agent, a fixing resin and other substances are used to visualize the electrostatic latent image formed on the photoreceptor having a light - sensitive layer containing an inorganic or organic photoconductive substance. These toners must show satisfactory performance as to chargeability, fixability, offset resistance, etc.
Chargeability is a key factor in electrostatic latent image - developing systems. Thus, to appropriately control toner chargeability, a charge control agent providing a positive or negative charge is often added to the toner. Of the conventional charge control agents in actual application, those providing a positive charge for a toner include nigrosine dyes and quaternary ammonium salt compounds. Charge control agents providing a negative charge include chromium complexes of azo dyes and metal complexes (metal salts) of alkylsalicylic acid and hydroxynaphthoic acid. However, dye type charge control agents lack versatility for use in color toners, although providing good chargeability. Quaternary ammonium salt type charge control agents generally lack environmental resistance under high - temperature high - humidity conditions. Metal complexes or salts with an aromatic hydroxycarboxylic acid or the like as a ligand are inferior to dye type charge control agents in dispersibility in resin.
In recent years, to improve image quality while increasing copying and printing speeds, there has been increasing demand regarding toner charge properties, such as increased rise speed, and toner fixing properties on recording paper, such as good low - temperature fixability and offset resistance.
However, not a few such conventional charge control agents affect the thermal melting property of the binder resin in the toner, resulting in decreased fixing performance.
There are a number of known toners supplemented with various phenol compounds for the purpose of improving toner fixability and long - run property or preventing surface - treated carrier deterioration. For example, Unexamined Japanese Patent Publication No. 138357/1988 discloses a toner containing an oligomer of a phenol compound having an alkyl - substituted amino group. Unexamined Japanese Patent Publication No. 291569/1990 discloses a toner incorporating a compound having a phenolic OH group and a xanthene dye. Unexamined Japanese Patent Publication No. 266462/1988 discloses toners containing a compound such as 2,6 - di - tertiary - butyl - 4 - ethylphenol or 2,2' - methylene - bis - (4 - methyl - 6 - tertiary - butylphenol). However, the developing agents incorporating these toners are unsatisfactory in charging properties.
CHEMICAL ABSTRACTS, vol. 121, no. 16, 17 October 1994, Columbus, Ohio, US; abstracts no. 191222y, p. 878; column 1; & JP-A-05 341 577 (RICOH), US-A-5 350 657 (M ANNO ET AL) and EP-A-0 385 580 (ORIENT CHEMICAL INDUSTRIES) disclose specific calix(n)arene compounds.
The object of the present invention, developed in view of the above problems in the prior art, is to provide a charge control agent which is excellent in charge control property, stability to changes in temperature and humidity, i.e., environmental resistance, and storage stability, versatile for use in color toners, including the three subtractive primaries yellow, magenta and cyan colors, good in heat resistance and binder resin affinity, and which ensures the excellent fixability and offset resistance of the toner used, and a toner for developing electrostatic images which is excellent in charge property, environmental resistance and storage stability, which can be used as a toner with various chromatic or achromatic colors and which is excellent in fixability and offset resistance.
Some of the present inventors have developed a charge control agent and toner which are based on a calix(n)arene compound and which are excellent in charge property, environmental resistance, storage stability, etc.; they are disclosed in Unexamined Japanese Patent Publication Nos. 201378/1990 and 346360/1992, respectively.
The present inventors found that calix(n)arene compounds, as negative charge control agents, wherein some of the n phenolic ―OH groups have been replaced with -OR groups, are excellent in negative charge control performance and that when used in a toner containing a binder resin, they markedly improve the fixability and offset resistance of the toner. Accordingly, the negative charge - providing property and charge stability are attributable to the phenolic- OH groups present in the structure of calix(n)arene compounds. However, such hydroxyl groups have been found to be faulty in that they interact with the binder resin and other components (e.g., releasing agent) of the toner, resulting in a narrowed fixing zone of the binder resin. The present inventors found that a toner having a wide fixing zone while maintaining the thermal melting and other properties of the binder resin and the charge property of a calix(n)arene compound by modifying some of the phenolic - OH groups in the original calix(n)arene compound with alkyl groups, benzyl groups, or the like. Based on this finding, the present inventors developed the present invention.
The charge control agent of the present invention contains a calix(n)arene compound represented by the following general formula [I]:
wherein the sum of x and y is n, x and y each representing an integer of 1 or more, n representing an integer from 4 to 8; the repeat units in a number of x and those in a number of y can be arranged in any order;
R¹ and R² independently represent hydrogen atom, alkyl group having 1 to 12 carbon atoms that is branched or not branched, aralkyl group having 7 to 12 carbon atoms that has or does not have substituent, phenyl group that has or does not have substituent, cycloalkyl group having 4 to 8 ring carbon atoms, halogen, nitro group, amino group, alkyl - or phenyl - substituted amino group, ― Si(CH₃)₃ or ― SO₃H. In the ― OR groups in a number of n, 1 to (n ― 1) are hydrogen atoms, the remaining (n ― 1) to 1 being Z. Z represents saturated or unsaturated alkyl group that is branched or not branched, phenyl or aralkyl group that has or does not have substituent, cycloalkyl group, ― COR³, R³ represents hydrogen atom, saturated or unsaturated alkyl group that is branched or not branched, phenyl or aralkyl group that has or does not have substituent, or cycloalkyl group, ― Si(CH₃)₃, ― (CH₂)_m COOR⁴, R⁴ represents hydrogen atom or lower alkyl group; m represents an integer from 1 to 3, ― (CH₂CH₂O)_rH, r represents an integer from 1 to 10, or the following:
wherein q represents an integer from 1 to 10.
The toner of the present invention for developing electrostatic images comprises the above - described charge control agent, a coloring agent and a binder resin.
According to one aspect of the invention, the toner comprises a calix(n)arene compound of formula [I] wherein R¹ is identical with R², R in a number of x being hydrogen atoms, R in a number of y being Z.
According to another aspect of the invention, the toner comprises a calix(n)arene compound of formula [I] wherein R¹ is not identical with R², R in a number of x being hydrogen atoms, R in a number of y being Z. In formula [I], the substituent ― OR of the benzene nucleus having R¹ is ― OH, and the substituent ― OR of the benzene nucleus having R² is ― OZ.
According to still another aspect of the invention, the toner comprises a calix(n)arene compound of formula [I] wherein R¹ is not identical with R², R in a number of x being hydrogen atoms, R in a number of (y - b) being hydrogen atoms, R in a number of b being Z, b representing an integer of 1 to 6. In formula [I], the substituent ―OR of the benzene nucleus having R¹ is - OH, and the substituent - OR of the benzene nucleus having R² is ― OH or ― OZ .
According to a further aspect of the invention, the toner comprises a calix(n)arene compound of formula [I] wherein R¹ is not identical with R², R in a number of x being Z, R in a number of ( y ― b) being hydrogen atoms, R in a number of b being Z, b representing an integer of 1 to 6. In formula [I], the substituent ― OR of the benzene nucleus having R¹ is ― OZ, and the substituent - OR of the benzene nucleus having R² is ― OH or ― OZ.
According to a still further aspect of the invention, the toner comprises a calix(n)arene compound of formula [I] wherein R¹ is not identical with R², R in a number of (x - a) being hydrogen atoms, R in a number of a being Z, R in a number of (y ― b) being hydrogen atoms, R in a number of b being Z, a and b each representing an integer of 1 to 5. In formula [I], the substituent - OR of the benzene nucleus having R¹ is ― OH or ― OZ, and the substituent ― OR of the benzene nucleus having R² is- OH or ― oz.
According to another aspect of the invention, the toner comprises a mixture of two or more varieties of calix(n)arene compounds of formula [I] wherein each x represents 1 to (n-1).
According to another aspect of the invention, the toner comprises a mixture of two or more varieties of calix(n)arene compounds of formula [I] wherein numbers of ― OH as ― OR are 1 to (n-1).
According to further aspect of the invention, the toner comprises a mixture of two or more varieties of calix(n)arene compounds wherein each x represents 1 to (n-1), numbers of ― OH as ― OR being 1 to (n-1).
The charge control agent of the present invention is good in dispersibility in binder resin, excellent in charge control performance, environmental resistance, storage stability and durability, and causes almost no color deterioration in toner images even when added to various chromatic or achromatic toners, and does not affect the fixability and offset resistance conferred by the binder resin, releasing agent, etc. used in the toner; therefore, it ensures the fixability and offset resistance, especially excellent high - temperature offset resistance, of the toner used.
In addition, containing this negative charge control agent, the toner of the present invention for developing electrostatic images is excellent in chargeability, environmental resistance and storage stability, causes almost no color deterioration in toner images even when used to obtain various chromatic or achromatic colors, and does not affect the fixability and offset resistance conferred by the binder resin, releasing agent, etc. used in the toner; therefore, it is excellent in fixability and offset resistance, especially high-temperature offset resistance.
Calixarene compounds have a cyclic structure similar to that of cyclodextrin, and can, for example, be obtained at high yields when prepared from the starting materials phenol and formaldehyde, especially in the presence of concentrated alkali.
Zinke et al. found that reacting phenol and formaldehyde in the presence of sodium hydroxide yields a high melting point substance (calixarene). Later, Gutsche et al. presented a detailed report on the production, structure and physical properties of various calix(n)arene derivatives [J. Am. Chem. Soc., 103, 3782 (1981)].
With respect to the above formula[I] as active ingredient of the charge control agent of the present invention, R¹ and R² are exemplified by hydrogen atoms;
saturated alkyl groups having 1 to 12 carbon atoms that are branched or not branched, such as methyl, ethyl, propyl, isopropyl, n ― butyl, tert ― butyl, isoamyl, octyl, tert ― octyl, 2 - ethylhexyl and dodecyl, unsaturated alkyl groups such as allyl, isobutenyl;
aralkyl groups having 7 to 12 carbon atoms that have or do not have substituents (e.g., alkyl or alkoxyl group having 1 to 4 carbon atoms), such as benzyl, ― CH(CH₃) ― C₆H₅, ― C(CH₃)₂ ― C₆H₅, ― CH₂CH₂ ― C₆H₅, ― CH₂ ― C₆H₄CH₃, ― CH₂ ― C₆H₄OCH₃ and naphthylmethyl;
phenyl groups that have or do not have substituents (e.g., alkyl, haloalkyl or alkoxyl group having 1 to 4 carbon atoms, or halogen atom), such as phenyl, tolyl, xylyl, p - chlorophenyl, trifluoromethylphenyl and methoxyphenyl;
alicyclic groups (alicyclic saturated hydrocarbon groups) including cycloalkyl groups such as cyclohexyl and cycloheptyl;
halogens such as chlorine, bromine, iodine and fluorine;
nitro groups; amino groups; alkyl - (e.g., alkyl or alkoxyl group having 1 to 4 carbon atoms) or phenyl - substituted amino groups; ― Si(CH₃)₃; and ― SO₃H.
R are exemplified by hydrogen atoms;
saturated alkyl groups having 1 to 12 carbon atoms that are branched or not branched, such as methyl, ethyl, propyl, isopropyl, n ― butyl, tert ― butyl, isoamyl, octyl, tert ― octyl, 2 ― ethylhexyl and dodecyl;
unsaturated alkyl groups such as allyl, isobutenyl;
phenyl groups that have or do not have substituents (e.g., alkyl, haloalkyl or alkoxyl group having 1 to 4 carbon atoms, or halogen), such as phenyl, tolyl, xylyl, p ― chlorophenyl, trifluoromethylphenyl and methoxyphenyl; aralkyl groups having 7 to 12 carbon atoms that have or do not have substituents (e.g., alkyl or alkoxyl group having 1 to 4 carbon atoms), such as benzyl, ― CH(CH₃) ― C₆H₅, ― C(CH₃)₂-C₆H₅, ― CH₂CH₂ ― C₆H₅, ― CH₂ ― C₆H₄CH₃, ― CH₂ ― C₆H₄OCH₃ and naphthylmethyl;
alicyclic groups including cycloalkyl groups such as cyclohexyl and cycloheptyl;
carbonyl groups substituted by alkyl groups, phenyl groups having or not having substituents (e.g., alkyl or alkoxyl group having 1 to 4 carbon atoms), aralkyl groups having or not having substituents (e.g., alkyl or alkoxyl group having 1 to 4 carbon atoms), allyl groups or alicyclic groups including cycloalkyl groups, such as ― COCH₃, ― COC₂H₅, ― COC₆H₅, ― COCH₂C₆H₅, ― COC₆H₄CH₃, ― COC₆H₄OCH₃, ― COCH₂ CH=CH₂ or ― COC₆H₁₁ (cyclohexyl);
― Si(CH₃)₃; ― CH₂COOR⁴, ― (CH₂)₂COOR⁴, ― (CH₂)₃COOR⁴ (R⁴ represents a hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms such as methyl, ethyl, propyl, isopropyl or n - butyl); ethylene oxide groups represented by ― (CH₂CH₂O)_rH (r represents an integer from 1 to 10);
and epoxyalkyl groups represented by the formula:
wherein q represents an integer from 1 to 10.
Calix(n)arene compounds and derivatives thereof can be synthesized in accordance with the methods described in a large number of references, including the report presented in Gendai Kagaku, 182, 14 ― 23 (1986). Synthesis of a calix(n)arene compound (general formula [I] above) relating to the present invention by modifying the hydroxyl group (phenolic ― OH group) can be achieved by the methods described in references such as J. Am. Chem. Soc., 115, 6572 ― 6579 (1993) and Org. Chem. 1994, 59, 1542 - 1547.
A calix(n)arene compound of general formula [I] above, an active ingredient of the charge control agent of the present invention, can, for example, be synthesized as follows:
First, a cyclic n - mer (may be a mixture of n ― mers of different n numbers) represented by the following structural formula is synthesized by an ordinary method of synthesis (x, y, R¹ and R² have the same definitions as those given for general formula [I]).
The calix(n)arene compound thus obtained and an alkali [e.g., K₂(CO₃), NaH, NaF, CsF, BaO/Ba(OH)₂] are refluxed in an organic solvent [e.g., methyl isobutyl ketone (MIBK), methyl ethyl ketone, acetone, xylene, toluene, dimethylformamide] for not less than 5 hours, preferably 6 to 10 hours, after which a desired halide (e.g., methyl bromide, methyl iodide, ethyl iodide, n ― butyl bromide, amyl bromide, benzyl bromide, allyl bromide, isobutenyl chloride, benzoyl chloride, toluoyl chloride, anisoyl chloride, acetyl chloride, octyl bromide, dodecyl chloride, epichlorohydrin), diethylene oxide tosyl, trimethylsilyl chloride, methyl chloroacetate, etc., are added, followed by reaction under refluxing conditions for not less than 10 hours, preferably 15 to 30 hours. After being allowed to cool at room temperature, the reaction mixture is subjected to suction filtration; the resulting filtrate is evaporated to dryness under reduced pressure. The resulting residue is recrystallized, reprecipitated, or otherwise treated using chloroform/n ― hexane or an alcohol such as methanol, to yield a calix(n)arene compound of general formula [I] of the present invention.
Examples of the calix(n)arene compound of the present invention and example syntheses thereof are given below, but are not to be construed as limitative on the calix(n)arene compound of the present invention.

Synthesis Example 1 (synthesis of Example Compound 1)

After 12.96 g (0.01 mol) of p ― tert ― butyl calix(8)arene and 4.14 g (0.03 mol) of potassium carbonate were refluxed in 100 ml of methyl isobutyl ketone (MIBK) for 8 hours, 5.1 g (0.03 mol) of benzyl bromide was added, followed by reaction under refluxing conditions for 30 hours. After being allowed to cool at room temperature, the reaction mixture was subjected to suction filtration; the resulting filtrate was evaporated to dryness under reduced pressure. This residue was recrystallized from chloroform/n - hexane to yield 8.1 g of a white powder (Example Compound 1) (recovery 58.5%) having a melting point of 205 to 210°C.

Synthesis Example 2 (synthesis of Example Compound 6)

After 12.96 g (0.01 mol) of p ― tert ― butyl calix(8)arene and 4.14 g (0.03 mol) of potassium carbonate were refluxed in 100 ml of methyl isobutyl ketone (MIBK) for 6 hours, 4.8 g (0.03 mol) of allyl bromide was added, followed by reaction under refluxing conditions for 17 hours. After being allowed to cool at room temperature, the reaction mixture was subjected to suction filtration; the resulting filtrate was evaporated to dryness under reduced pressure. This residue was recrystallized from methanol to yield 9.8 g of a yellowish white powder (Example Compound 6) (yield 71.2%) having a melting point of 145 to 153°C.

Synthesis Example 3 (synthesis of Example Compound 5)

0.5 mol of p - tert - butylphenol, 0.5 mol of tert - octylphenol, 1.2 mol of p - formaldehyde and 1.0 g of potassium hydroxide were reacted under refluxing conditions in 500 ml of xylene for 7 hours while water was removed, to yield 15.2 g (0.01 mol) of a calix(8)arene mixture. After 4.14 g (0.03 mol) of potassium carbonate was refluxed in 100 ml of methyl isobutyl ketone (MIBK) for 8 hours, 5.1 g (0.03 mol) of benzyl bromide was added, followed by reaction under refluxing conditions for 10 hours. After being allowed to cool at room temperature, the reaction mixture was subjected to suction filtration; the resulting filtrate was evaporated to dryness under reduced pressure. This residue was recrystallized from methanol to yield 9.0 g of a light yellowish white powder (Example Compound 5) (yield 55.9%) having a melting point of 169 to 172°C.

Synthesis Example 4 (synthesis of Example Compound 7)

After 12.96 g (0.01 mol) of p - tert - butylcalix(8)arene and 6.9 g (0.05 mol) of potassium carbonate were refluxed in 100 ml of methyl isobutyl ketone (MIBK) for 1 hour, 5.6 g (0.06 mol) of epichlorohydrin was added, followed by reaction under refluxing conditions for 12 hours. After being allowed to cool at room temperature, the reaction mixture was subjected to suction filtration; the resulting filtrate was evaporated to dryness under reduced pressure. This residue was reprecipitated with chloroform/n ― hexane; the resulting precipitate was collected by filtration, washed and dried to yield 8.3 g of a white powder (Example Compound 7) (yield 56.7%) having a melting point of 315 to 320°C.

Synthesis Example 5 (synthesis of Example Compound 15)

After 12.96 g (0.01 mol) of p ― tert ― butylcalix(8)arene and 1.57 g (0.01 mol) of potassium carbonate were refluxed in 100 ml of acetone for 3 hours, 4.42 g (0.03 mol) of methyl iodide was added, followed by reaction under refluxing conditions for 30 hours. After being allowed to cool at room temperature, the reaction mixture was dispersed in 3500 ml of water and stirred for 1 hour, after which it was filtered. The residue collected by the filtration was washed with water and evaporated to dryness under reduced pressure; this residue was reprecipitated with chloroform/n - hexane. The resulting precipitate was collected by filtration and dried to yield 11.5 g of a light yellowish white powder (yield 74.2%) having a melting point of 235 to 243°C.
The example compounds obtained by the above - described example syntheses and other example compounds synthesized by methods similar to the above - described methods are given below. With respect to the following example compounds, units in parentheses are arranged circularly in any optional order.

Example Compound 1

Example Compound 2

Example Compound 3

Example Compound 4

Example Compound 5

(Example Compound 5 is a mixture of compounds wherein u and v each represent an integer from 0 to 6, and the sum of u and v is 6.)

Example Compound 6

Example Compound 7

Example Compound 8

Example Compound 9

Example Compound 10

Example Compound 11

Example Compound 12

Example Compound 13

Example Compound 14

Example Compound 15

(Example Compound 15 is a mixture of compounds wherein u represents an integer from 1 to 3, v represents an integer from 5 to 7, and the sum of u and v is 8.)

Example Compound 16

Example Compound 17

Example Compound 18

Example Compound 19

Example Compound 20

Example Compound 21

(Example Compound 21 is a mixture of compounds wherein u represents an integer from 0 to 3, v represents an integer from 5 to 8, and the sum of u and v is 8.)

Example Compound 22

(Example Compound 22 is a mixture of compounds wherein u represents an integer from 0 to 3, v represents an integer from 5 to 8, and the sum of u and v is 8.)

The toner of the present invention for developing electrostatic images may contain one or more kinds of the above - described charge control agent of the present invention. The toner of the present invention may also contain the original calix(n)arene compound [calix(n)arene wherein all - OR groups in general formula [I] are -OH groups], as long as the object of the present invention is accomplished. Specifically, the object of the present invention can be accomplished, even when the original calix(n)arene compound is contained at content ratios of not more than about 30% by weight of the total calix(n)arene compound content, in addition to the calix(n)arene compound of the present invention.
It is desirable that the toner of the present invention for developing electrostatic images contain the calix(n)arene compound, as a charge control agent, of the present invention, in a ratio of 0.1 to 10 parts by weight per 100 parts by weight of binder resin. More preferably, the content ratio is 0.5 to 5 parts by weight per 100 parts by weight of binder resin.
To improve toner quality, additives such as electroconductive grains, fluidity - improving agents, releasing agents and image peeling - preventing agents may be added internally or externally.
Examples of resins used in the toner of the present invention include the following known binder resins for use in toners. Specifically, styrene resin, styrene - acrylic resin, styrene - butadiene resin, styrene ― maleic acid resin, styrene - vinyl methyl ether resin, styrene - methacrylic acid ester copolymer, phenol resin, epoxy resin, polyester resin, polypropylene resin, paraffin wax, etc. may be used singly or in blends.
For preferable use of a binder resin for toners in a toner for full - color imaging by subtractive mixing or for OHP (overhead projectors) etc., the binder resin is required to be transparent, substantially colorless (no tone damage occurs in the toner image) and compatible with the charge control agent of the present invention.
Also, the binder resin is required to have desired thermal melting property, elasticity, fluidity, and other properties, so as to meet the requirements regarding toner fixability to paper upon melting, toner offset resistance for heat roller, and toner blocking resistance during storage. Examples of such resins for preferable use include acrylic resin, styrene - acrylic resin, styrene - methacrylic acid ester copolymer and polyester resin.
The toner of the present invention may incorporate various known dyes or pigments as coloring agents, which may be used singly or in combination.
Examples of pigments include organic pigments such as Quinophthalone Yellow, Hansa Yellow, Isoindolinone Yellow, Perinone Orange, Perillene Maroon, Rhodamine 6G Lake, Quinacridone Red, Anthanthrone Red, Rose Bengale, copper Phthalocyanine Blue, copper Phthalocyanine Green and diketopyrrolopyrrole pigments; and inorganic pigments such as Carbon Black, Titanium White, Titanium Yellow, Ultramarine, Cobalt Blue and Red Iron Oxide.
Examples of coloring agents for preferable use in color toners include various oil - soluble or dispersc dyes such as azo dyes, quinophthalone dyes, anthraquinone dyes, phthalocyanine dyes, indophenol dyes and indoaniline dyes; and xanthene and triarylmethane dyes modified with resins such as rosin, rosin-modified phenol and maleic acid.
Dyes and pigments having a good spectral property can be preferably used to prepare a toner of the three primaries for full - color imaging. Chromatic monocolor toners may incorporate an appropriate combination of a pigment and dye of the same color tone (e.g., quinophthalone pigment and dye, xanthene or Rhodamine pigment and dye, phthalocyanine pigment and dye).
The toner of the present invention for developing electrostatic images is, for example, produced as follows:
A dry negatively chargeable toner having an average grain size of 5 to 20 µ m can be obtained by thoroughly mixing a binder resin and coloring agent as described above, the charge control agent of the present invention, and, if necessary, a magnetic material, a fluidizing agent and other additives, using a ball mill or another mechanical mixer, subsequently kneading the mixture in a molten state using a hot kneader such as a heat roll, kneader or extruder, cooling and solidifying the mixture, and then pulverizing the solid and classifying the resulting particles.
Other usable methods include the method in which starting materials, such as a coloring agent and the charge control agent of the present invention, are dispersed in a binder resin solution and then spray dried, and the polymerizing toner production method in which a given set of starting materials are mixed in a monomer for binder resin to yield an emulsified suspension, which is then polymerized to yield the desired toner.
When the toner of the present invention is used as a two - component developer, development can be achieved by the two-component magnetic brush developing process or the like using the toner in mixture with carrier powder.
Any known carrier can be used. Examples of the carrier include iron powder, nickel powder, ferrite powder and glass beads about 50 to 200 µ m in particle size, and such materials as coated with acrylic acid ester copolymer, styrene - acrylic acid ester copolymer, styrene - methacrylic acid ester copolymer, silicone resin, polyamide resin, ethylene fluoride resin or the like.
When the toner of the present invention is used as a one - component developer, fine powder of a ferromagnetic material such as iron powder, nickel powder or ferrite powder may be added and dispersed in preparing the toner as described above. Examples of developing processes which can be used in this case include contact development and jumping development.

EXAMPLES

The present invention is hereinafter described in more detail by means of the following examples, which are not to be construed as limitative on the present invention. In the description below, "part(s) by weight" are referred to as "part(s)" for short.

Example 1

Styrene - acrylic copolymer resin [HIMER SMB600 (trade name), produced by Sanyo Kasei Co., Ltd.]... 100 parts
Low polymer polypropylene [Biscal 550P (trade name), produced by Sanyo Kasei Co., Ltd.]... 10 parts
Carbon black [MA - 100 (trade name), produced by Mitsubishi Chemical Industries, Ltd.]... 7 parts
Charge control agent (Example Compound 1)... 2 parts
The above ingredients were uniformly pre - mixed using a high ― speed mixer, and then kneaded in a molten state using an extruder, cooled, and roughly milled in a vibration mill. The obtained coarse product was finely pulverized using an air jet mill equipped with a classifier to yield a negatively chargeable black toner 10 to 20 µ m in particle size.
Five parts of this toner was admixed with 95 parts of an iron powder carrier [TEFV 200/300 (trade name), produced by Powdertech Co., Ltd.) to yield a developer; initial chargeability and fixability were determined. The results are shown in Table 1.
When this developer was used for repeated cycles of actual imaging, high - quality black images free of density reduction and fogging were obtained, with good charge stability (narrow variation in amount of charges) and sustainability.
Initial chargeability: The amount of initial blowoff charges of the developer was determined under normal conditions, (25°C air temperature, 50% relative humidity), low - temperature low - humidity conditions (5 °C air temperature, 30% relative humidity), and high - temperature high - humidity conditions (35°C air temperature, 90% relative humidity). The same applies to the working examples and comparative examples shown below.
Fixability: The developer was set on a commercial electrophotographic copying machine of which the fixing device had been modified. With the copying machine, an actual imaging experiment was conducted at various heat roller fixing temperatures to identify the temperature range within which good fixing performance was achieved without the offset phenomenon to the fixing heat roller (offset-free zone).

Example 2

A toner and developer according to the present invention were prepared in the same manner as in Example 1, except that the charge control agent used in Example 1 was replaced with Example Compound 6 obtained in Synthesis Example 2; initial chargeability and fixability were determined. The results are shown in Table 1.

Example 3

A toner and developer according to the present invention were prepared in the same manner as in Example 1, except that the charge control agent used in Example 1 was replaced with Example Compound 5 obtained in Synthesis Example 3; initial chargeability and fixability were determined. The results are shown in Table 1.

Example 4

Polyester resin [HP ― 301 (trade name), produced by The Nippon Synthetic Chemical Industry, Co., Ltd.]... 100 parts
Low polymer polypropylene [Biscal 550P (trade name), produced by Sanyo Kasei Co., Ltd.]... 10 parts
Rhodamine dye [Oil Pink #312 (trade name), produced by Orient Chemical Industries Ltd.]... 3 parts
Quinacridone Red... 3 parts
Charge control agent (Example Compound 6)... 2 parts
The above ingredients were treated in the same manner as in Example 1 to yield a negatively chargeable toner, which was then used to prepare a developer. The initial chargeability and fixability of this developer were determined. The results are shown in Table 1.
When this developer was used for repeated cycles of actual imaging, high - quality magenta images free of density reduction and fogging were obtained, with good charge stability and sustainability.

Example 5

Styrene - acrylic copolymer resin [HIMER SMB600 (trade name), produced by Sanyo Kasei Co., Ltd.]... 100 parts
Low polymer polypropylene [Biscal 550P (trade name), produced by Sanyo Kasei Co., Ltd.]... 10 parts
Copper phthalocyanine dye [VALIFAST Blue 2606 (trade name), produced by Orient Chemical Industries Ltd.]... 2 parts
Copper phthalocyanine pigment... 3 parts
Charge control agent (Example Compound 15)... 2 parts
The above ingredients were treated in the same manner as in Example 1 to yield a negatively chargeable toner, which was then used to prepare a developer. The initial chargeability and fixability of this developer were determined. The results are shown in Table 1.
When this developer was used for repeated cycles of actual imaging, high - quality cyan images free of density reduction and fogging were obtained, with good charge stability and sustainability.

Example 6

A toner and developer according to the present invention were prepared in the same manner as in Example 5, except that the charge control agent used in Example 5 was replaced with Example Compound 8. The initial chargeability and fixability of this developer were determined. The results are shown in Table 1.

Example 7

Styrene - acrylic copolymer resin [HIMER SMB600 (trade name), produced by Sanyo Kasei Co., Ltd.]... 100 parts
Low polymer polypropylene [Biscal 550P (trade name), produced by Sanyo Kasei Co., Ltd.]... 10 parts
Hydroxyquinophthalone dye [C.I. Disperse Yellow 64]... 3 parts
Charge control agent (Example Compound 22)... 2 parts
The above ingredients were treated in the same manner as in Example 1 to yield a negatively chargeable toner, which was then used to prepare a developer. The initial chargeability and fixability of this developer were determined. The results are shown in Table 1.
When this developer was used for repeated cycles of actual imaging, high - quality yellow images free of density reduction and fogging were obtained, with good charge stability and sustainability.

Example 8

Styrene - 2 - ethylhexyl methacrylate copolymer resin (80/20)... 100 parts
Tri - iron tetroxide [EPT - 500 (trade name), produced by Toda Kogyo Corporation]... 50 parts
Low polymer polypropylene [Biscal 550P (trade name), produced by Sanyo Kasei Co., Ltd.]... 10 parts
Carbon black [MA - 100, produced by Mitsubishi Chemical Industries, Ltd.]... 6 parts
Charge control agent (Example Compound 7)... 2 parts
The above ingredients were uniformly pre - mixed using a ball mill to yield a premix, which was then kneaded in a molten state at 180°C using a twin - screw extruder, cooled and thereafter roughly crushed, finely pulverized and classified to yield a one - component toner having a particle size range from 5 to 15 µ m.
When this toner was used for a commercial copying machine to form toner images, fog - free high - quality images with good thin-line reproducibility were obtained.

Comparative Example 1

To compare chargeability and fixability, a black toner was prepared in the same manner as in Example 1, except that the charge control agent of the present invention used in Example 1 (Example Compound 1) was replaced with the p - tert - butylcalix(8)arene compound (phenolic ―OH groups not modified) used in Synthesis Example 1 as a starting material for Example Compound 1; initial chargeability and fixability were determined.
Although no marked difference was noted in terms of initial chargeability, the developer was found to be likely to undergo the offset phenomenon at high temperatures, with a narrow offset-free zone. The results are shown in Table 1.

Comparative Example 2

A comparative toner was prepared in the same manner as in Example 1, except that the charge control agent of the present invention used in Example 1 (Example Compound 1) was replaced with a p - cyclohexylcalix(8)arene compound (phenolic - OH groups not modified); initial chargeability and fixability were determined. The results are shown in Table 1.

Comparative Example 3

A comparative toner was prepared in the same manner as in Example 1, except that the charge control agent of the present invention used in Example 1 (Example Compound 1) was replaced with a p - methylcalix(8)arene compound; initial chargeability and fixability were determined. The results are shown in Table 1.

Comparative Example 4

A comparative toner was prepared in the same manner as in Example 1, except that the charge control agent of the present invention used in Example 1 (Example Compound 1) was replaced with a p - phenylcalix(8)arene compound; initial chargeability and fixability were determined. The results are shown in Table 1.

Comparative Example 5

A comparative toner was prepared in the same manner as in Example 4, except that the charge control agent of the present invention used in Example 4 (Example Compound 6) was replaced with a p - tert - butylcalix(8)arene compound; initial chargeability and fixability were determined. The results are shown in Table 1.

Comparative Example 6

A comparative toner was prepared in the same manner as in Example 8, except that the charge control agent of the present invention used in Example 8 (Example Compound 7) was not used. This comparative toner was evaluated as unacceptable because of image sputtering, blurs and fogging.

	Initial chargeability (µC/g)	Fixability (°C) [offset-free zone]
	Standard conditions	High-temperature high-humidity	Low-temperature low-humidity
Example 1	- 21.5	- 21.0	- 21.7	120 - 240
Example 2	- 23.3	- 22.5	- 23.8	120 - 240
Example 3	- 25.1	- 24.9	- 25.6	120 - 240
Example 4	- 35.6	- 33.9	- 35.9	120 - 240
Example 5	- 20.3	- 20.1	- 20.9	120 - 240
Example 6	- 26.2	- 25.5	- 26.4	120 - 240
Example 7	- 25.7	- 25.2	- 25.8	120 - 240
Example 8	-	-	-	120 - 240
Comparative Example 1	- 22.2	- 21.3	- 22.6	120 - 160
Comparative Example 2	- 20.3	- 19.8	- 20.4	120 - 135
Comparative Example 3	- 19.4	- 19.1	- 19.6	120 - 140
Comparative Example 4	- 23.1	- 23.0	- 23.5	140 - 160
Comparative Example 5	- 38.1	- 37.5	- 38.4	130 - 150
Comparative Example 6	-	-	-	140 - 160

Claims

Charge control agent which comprises a calix(n)arene compound, characterized in that the calix(n)arene compound is represented by the following formula [I]:

wherein the sum of x and y is n, x and y each representing an integer of 1 or more, n representing an integer from 4 to 8; the repeat units in a number of x and those in a number of y can be arranged in any order;

R¹ and R² independently represent hydrogen atom, alkyl group having 1 to 12 carbon atoms that is branched or not branched, aralkyl group having 7 to 12 carbon atoms that has or does not have substituent, phenyl group that has or does not have substituent, cycloalkyl group having 4 to 8 ring carbon atoms, halogen atom, nitro group, amino group, alkyl- or phenyl-subsituted amino group, -Si(CH₃)₃ or -SO₃H;

in the -OR groups in a number of n, 1 to (n - 1) R are hydrogen atoms, the remaining (n - 1) to 1 being Z, Z representing saturated or unsaturated alkyl group that is branched or not branched, phenyl or aralkyl group that has or does not have substituent, cycloalkyl group, -COR³, R³ represents hydrogen atom, saturated or unsaturated alkyl group that is branched or not branched, phenyl or aralkyl group that has or does not have substituent, or cycloalkyl group], -Si(CH₃)₃, -(CH₂)_mCOOR⁴,

R⁴ represents hydrogen atom or lower alkyl group; m represents an integer from 1 to 3, - (CH₂CH₂O)_rH, r represents an integer from 1 to 10, or the following:

wherein q represents an integer from 1 to 10.
Toner for developing electrostatic images that comprises a coloring agent, a binder resin and a charge control agent which comprises a calix(n)arene compound, characterized in that the calix(n)arene compound is represented by the following formula [I]:

wherein the sum of x and y is n, x and y each representing an integer of 1 or more, n representing an integer from 4 to 8;

the repeat units in a number of x and those in a number of y can be arranged in any order;

R¹ and R² independently represent hydrogen atom, alkyl group having 1 to 12 carbon atoms that is branched or not branched, aralkyl group having 7 to 12 carbon atoms that has or does not have substituent, phenyl group that has or does not have substituent, cycloalkyl group having 4 to 8 ring carbon atoms, halogen atom, nitro group, amino group, alkyl- or phenyl-substituted amino group, - Si(CH₃)₃ or - -SO₃H;

in the - OR groups in a number of n, 1 to (n - 1) R are hydrogen atoms, the remaining (n - 1) to 1 being Z, Z representing saturated or unsaturated alkyl group that is branched or not branched, phenyl or aralkyl group that has or does not have substituent, cycloalkyl group, - COR³, R³ represents hydrogen atom, saturated or unsaturated alkyl group that is branched or not branched, phenyl or aralkyl group that has or does not have substituent, or cycloalkyl group, Si(CH₃)₃, -(CH₂)_mCOOR⁴, R⁴ represents hydrogen atom or lower alkyl group; m represents an integer from 1 to 3, - (CH₂CH₂O)_rH, r represents an integer from 1 to 10, or the following:
wherein q represents an integer from 1 to 10.
Toner according to claim 2, wherein R¹ is identical with R², R in a number of x being hydrogen atoms, R in a number of y being Z.
Toner according to claim 2, wherein R¹ is not identical with R², R in a number of x being hydrogen atoms, R in a number of y being Z.
Toner according to claim 2, wherein R¹ is not identical with R², R in a number of x being hydrogen atoms, R in a number of (y - b) being hydrogen atoms, R in a number of b being Z, b representing an integer of 1 to 6.
Toner according to claim 2, wherein R¹ is not identical with R², R in a number of x being Z, R in a number of (y - b) being hydrogen atoms, R in a number of b being Z, b representing an integer of 1 to 6.
Toner according to claim 2, wherein R¹ is not identical with R², R in a number of (x - a) being hydrogen atoms, R in a number of a being Z, R in a number of (y - b) being hydrogen atoms, R in a number of b being Z, a and b each representing an integer of 1 to 5.
Toner according to claim 2, wherein the charge control agent comprises a mixture of two or more varieties of calix(n)arene compounds wherein each x represents 1 to (n - 1).
Toner according to claim 2, wherein the charge control agent comprises a mixture of two or more varieties of calix(n)arene compounds wherein numbers of -OH as -OR are 1 to (n - 1).
Toner according to claim 2, wherein the charge control agent comprises a mixture of two or more varieties of calix(n)arene compounds wherein each x represents 1 to (n - -1), numbers of -OH as -OR being 1 to (n - 1).