JP2006227311A - Electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic toner which is unaffected by change in the temperature and humidity, even if development by continuous use is repeated and is superior in electrostatic charge stability for reproduction of images stably for a long time, and to provide an electrophotographic toner which is superior in at least transparency and is satisfactory in color reproducibility, when it is used as a color toner. <P>SOLUTION: The electrophotographic toner comprises at least a binder resin, a colorant and an electrostatic charging control agent. The binder resin is a polyester resin comprising an alcohol component of an aromatic system. The electrostatic charging control agent has a salt structure, consisting of alkaline bentonite and organic cations. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic toner. More specifically, the present invention relates to an electrophotographic toner used as a developer in a so-called electrophotographic image forming apparatus such as an electrostatic copying machine or a laser beam printer.

  Image formation in an electrophotographic image forming apparatus is performed according to each process of charging, exposure, development, transfer, and fixing. First, in the charging step, the surface of the photoreceptor, which is an image carrier for forming an electrostatic latent image, is uniformly charged. In the exposure step, an electrostatic latent image is formed on the surface of the photoconductor by irradiating the charged photoconductor surface with light according to image information. In the development process, for example, black toner is selectively attached to the formed electrostatic latent image, and a visible image (toner image) is formed on the surface of the photoreceptor. In the transfer step, the toner image is transferred onto transfer paper by an electric force. In the final fixing step, the toner image transferred onto the transfer paper is melted by heat to fix the toner image onto the transfer paper.

  In recent years, colorization technology in electrophotography has been rapidly developed, and full-color image forming apparatuses have been developed and provided to the market. The market for full-color image forming apparatuses is expanding with the spread of black-and-white image forming apparatuses. Generally, for color reproduction in a full-color image forming apparatus, three subtractive primary colors, yellow (Y), magenta (M), cyan (C), or black (K) are added to these three colors. Four color toners are used. As a color reproduction procedure, for each of C, M, Y, and K colors, the steps from charging, exposure, development, and transfer in the image forming process are repeated, and toner composed of a plurality of color toners on the transfer paper. A full color image is formed by overlapping the images. In the final fixing step, the superimposed toner images are melted and fixed on the transfer paper. In this procedure, the superimposed toner images are mixed by being melted, so that the color is reproduced according to the principle of subtractive color mixing.

  In such a full-color electrophotographic method, development is performed a plurality of times, and it is necessary to superimpose several types of toner images having different colors on the same support as a fixing process. Fixing characteristics become a very important factor.

  That is, in order to maintain a stable and good color reproducibility of a full-color image, it is necessary to first transfer a predetermined amount of toner onto the transfer paper during the transfer from the development process. The toner adhesion amount in the development and transfer processes is greatly influenced by the charging characteristics of the toner, such as the rising characteristics of the toner charge quantity, the environmental stability of the charge quantity, and the stability and durability over time. For this reason, the toner contains a charge control agent so that good chargeability is maintained. Further, as a binder resin for a full color toner, a resin excellent in sharp melt property, color developability and fixability is required, and a polyester resin is usually used. Toners using polyester resins are usually negatively charged, and negative charge control agents include oil-soluble dyes such as oil black and spiron black, metal-containing azo dyes, metal naphthenates, alkyls. Salicylic acid metal salts, fatty acid soaps, resin acid soaps, and the like are used.

  It is known that it is important for the charge control agent to be finely dispersed uniformly in the toner particles or on the surface of the toner particles in order to improve the charging characteristics of the toner. Even if the charge control agent is agglomerated in a part of the toner or evenly dispersed, if it is not finely divided and exists as coarse particles, the initial charge amount cannot be obtained. In addition, if the charge control agent is not dispersed, the charge rise characteristic becomes poor, or the toner has a remarkable charge attenuation. For this reason, various ideas have been made to uniformly and finely disperse the charge control agent in the toner, and the selection of the type and chemical composition of the binder resin is an important factor. Therefore, in order to improve the charge characteristics of the toner, not only a charge control agent having excellent charge characteristics is used, but also the charge control agent can be uniformly finely dispersed according to the charge control agent used. It is important to select and use a resin.

In order to solve the problem related to the charging characteristics of the toner, the following Patent Document 1 discloses that an alcohol component, which is a binder resin, contains an aliphatic benton resin as an aliphatic polyester resin and contains organic bentonite as a charge control agent. Techniques have been proposed for improving the charge characteristics of a toner by improving the uniform fine dispersion of the charge control agent. Furthermore, Patent Document 1 discloses that an aliphatic polyester resin having an alcohol component has good compatibility with waxes and can improve fixing characteristics.
Japanese Patent Laid-Open No. 2004-4207

  The polyester resin in which the alcohol component used as the binder resin described in Patent Document 1 is an aliphatic resin is inferior to the humidity resistance environment characteristics than the polyester resin in which the alcohol component is an aromatic resin, so that sufficient charging stability is achieved. It is predicted that sex will not be obtained. For this reason, as the image is repeatedly formed, there is a problem that the image is liable to be stained or the inside of the machine due to toner scattering.

Accordingly, the present invention provides an electrophotographic toner that is excellent in charging stability in order to reproduce a stable image for a long time without being affected by changes in temperature and humidity even when repeated development is performed by continuous use. With the goal.
Another object of the present invention is to provide a toner that is excellent in at least transparency and has good color reproducibility when used as a color toner.

  An electrophotographic toner of the present invention that solves the above problems is a toner containing at least a binder resin, a colorant and a charge control agent, wherein the binder resin is a polyester resin comprising an aromatic alcohol component. The charge control agent is characterized by comprising a salt structure composed of alkaline bentonite and an organic cation.

  According to the toner having the above-described configuration, the charge control can be performed in the toner without impairing the characteristics of the polyester resin by including a specific charge control agent in the polyester resin composed of an aromatic alcohol component as the binder resin. An electrophotographic toner can be obtained in which the agent can be uniformly and finely dispersed, and there is little variation in environmental charge and less variation in charge due to repeated development due to continuous use (excellent life charge stability).

Hereinafter, the present invention will be described in detail.
As the binder resin constituting the electrophotographic toner of the present invention, a conventionally known polyester resin in which an alcohol component is aromatic can be used, and one or a combination of two or more can be used.

  The binder resin constituting the electrophotographic toner of the present invention will be described. Examples of the aromatic alcohol component of the polyester resin that is the binder resin according to the present invention include bisphenol A, polyoxyethylene- (2.2) -2,2-bis (4-hydroxyphenyl) propane, and polyoxy. Ethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (2 .2) -Polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (6) -2,2-bis (4-hydroxyphenyl) propane, polyoxy Propylene- (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (2.4) -2,2-bis 4-hydroxyphenyl) propane, polyoxypropylene - (3.3) -2,2-bis (4-hydroxyphenyl) propane and derivatives thereof.

  The polybasic acid component of the polyester resin includes succinic acid, adipic acid, sebacic acid, azelaic acid, dodecenyl succinic acid, n-dodecyl succinic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid. , Dibasic acids such as cyclohexanedicarboxylic acid, orthophthalic acid, isophthalic acid and terephthalic acid, acids having tribasic acids or more such as trimellitic acid, trimetic acid and pyromellitic acid, and anhydrides and lower alkyl esters thereof. . Of these, terephthalic acid or its lower alkyl ester is particularly preferred from the viewpoint of heat-resistant aggregation.

The acid value of the polyester resin constituting the electrophotographic toner of the present invention is in the range of 4 mgKOH / g to 31 mgKOH / g, more preferably in the range of 5 mgKOH / g to 30 mgKOH / g. preferable.
When the acid value is less than 5 mg KOH / g, the charging characteristics of the resin are lowered, and the salt structure composed of alkaline bentonite and an organic cation as a charge control agent is difficult to disperse in the polyester resin. As a result, the charge amount stability (life charge amount stability) tends to be adversely affected by rising of the charge amount or repeated development by continuous use.
Further, when the acid value is 2 mg KOH / g or less, the dispersion of the salt structure composed of alkaline bentonite and organic cation is deteriorated, the charging property of the resin is deteriorated, the pigment dispersion is also deteriorated, and the color reproducibility is narrowed. . On the other hand, when the acid value exceeds 35 mg KOH / g, moisture adsorption in a high-temperature and high-humidity environment increases and the moisture content increases. As a result, the resistance of the toner is lowered, and even if a charge control agent is added, it is difficult to control the environment dependence, and the charge fluctuation in repeated development due to continuous use increases.
The acid value was measured according to the method described in JIS K 0070-1992.

  The melting temperature of the polyester resin constituting the electrophotographic toner of the present invention described above can be an important factor for achieving transparency. For example, when used as a color toner, it is necessary to sufficiently melt the toner so that there is no boundary between the toners when the toners of the respective colors are overlapped. Therefore, the melting temperature of the polyester resin is preferably 90 ° C to 135 ° C. If the melting temperature of the binder resin is less than 90 ° C., the toner cohesive force is too low and high temperature offset tends to occur. On the other hand, if it is higher than 135 ° C., it becomes difficult to eliminate the boundary toner particles between the particles and to obtain sufficient transparency. In the case of a black toner, it can be used at 90 ° C. to 160 ° C.

Here, the melting temperature of the above-described resin is a flow tester CFT-500 type (manufactured by Shimadzu Corporation), a sample amount of 1.0 g, a die size of 1.0 × 1.0, and an extrusion load of 20 kgf / cm ^2. Under the measurement conditions of a temperature rising rate of 6 ° C., a starting temperature of 60 ° C., and a preheating time of 300 seconds, the temperature at the 1/2 stroke when measured was defined as the melting temperature.

Next, the charge control agent constituting the electrophotographic toner of the present invention will be described. As the charge control agent, a charge control agent having a salt structure composed of alkaline bentonite and an organic cation is used. Bentonite is a natural clay mineral mainly composed of SiO ₂ and Al ₂ O ₃ and having a layered structure mainly composed of montmorillonite, and an inorganic metal cation such as sodium or potassium exists between the layers. By ion exchange of this, an organic cation such as an alkylammonium ion is taken in between layers to form a composite (interlayer compound) in which organic and inorganic materials are alternately laminated. The organic bentonite having a salt structure composed of alkaline bentonite and an organic cation used as a charge control agent in the present invention is obtained by exchanging inorganic cations in bentonite with organic cations generated from an organic cation-forming compound.

  A known compound can be used as the organic cation-forming compound for producing the organic bentonite. For example, dodecyltrimethylammonium chloride, lauryltrimethylammonium chloride, hexadecyltrimethylammonium chloride, dodecylammonium chloride, dodecylammonium bromide, dimethyldistearylammonium chloride, stearyldimethylbenzylammonium chloride, tetrabutylammonium chloride, tetrapentylammonium fluorophosphate, There are quaternary ammonium salts such as tetraethylammonium benzoate, tetraethylammonium acetate, tetrabutylammonium iodide, triethylmethylammonium iodide, and the like.

  Further, there are pyrididium salts such as isopropylpyridinium chloride, butylpyridinium chloride, heptylpyridinium chloride, decylpyridinium chloride, dodecylpyridinium bromide, cetylpyridinium chloride, and the like.

  Furthermore, polyalkyleneimines such as polyethyleneimine, poly- (4-vinylpyridine), polyallylamine, aminoacetylated polyvinyl alcohol, poly- (L) -lysine, chitosan, polypyrrole, or amino groups such as diethylaminoethyl methacrylate There is a polymeric ammonium salt obtained from a copolymer with a vinyl monomer containing a containing acrylate.

  The anion component of the organic cation-forming compound for producing the organic bentonite is not particularly limited, but from the viewpoint of safety or environmental protection, chromium, cobalt, copper, nickel, molybdenum, lead, mercury It is preferable that the anion does not contain a heavy metal such as.

  It does not specifically limit as a method for preparing the organic bentonite used by this invention, It can manufacture by the ion exchange operation used conventionally. For example, it is obtained by immersing bentonite in water, a mixture of water and an organic solvent, or adding an organic cation-forming compound thereto, leaving it for a certain period of time, filtering and washing it, and drying. Can do.

  And as for the organic bentonite used by this invention, what has the salt structure which consists of alkaline bentonite and an organic cation as mentioned above is preferable. As a result, the charge imparting function to the toner can be sufficiently exhibited even in a small amount.

The salt structure composed of alkaline bentonite and an organic cation as the charge control agent used in the present invention has good dispersibility (uniform dispersion) in the polyester resin as the binder resin, so that the charging characteristics of the toner are good. it can. To that end, the volume average particle diameter D ₅₀ of the salt structure consisting of alkaline bentonite and organic cation is preferably adjusted to 8μm or less. The particle size is measured by optical microscope inspection or laser light diffraction, and can be controlled by various dispersion techniques such as an air jet mill, a cutting mill, a hammer mill, a bead mill, and an impact mill. As a result, the charge control agent is present on the toner surface almost uniformly with a fine diameter, and the charge control agent is difficult to separate from the toner particles, and the toner has excellent charge amount rise characteristics and charge life stability. can do. When the volume average particle diameter D ₅₀ of the salt structure as the charge control agent exceeds 8 μm, the charge control agent is uniformly dispersed in the toner, but the charge control agent has a non-uniform size and a little charging efficiency. drop down. Therefore, it is preferable that the said volume average particle size D ₅₀ in 8μm or less. Here, when you try pulverizing said volume average particle size D ₅₀ in 1μm or less, it takes a considerable time and energy, the productivity is deteriorated, resulting in cost and the like. However, if the object of the present invention is achieved in consideration of dispersibility, a charge control agent having a volume average particle diameter D ₅₀ of 1 μm or less can be used. Incidentally, if an object to inexpensively produce a toner, the volume average particle diameter D ₅₀ may be used 1μm or more charge control agents.

  The salt structure composed of alkaline bentonite and an organic cation as the charge control agent according to the present invention has a great influence on the charge characteristics depending on the amount of addition and the color reproducibility in a color toner or the like. Therefore, the addition amount of the charge control agent of the present invention is preferably 0.5% by mass to 5% by mass with respect to the total amount of toner. For example, when the addition amount is less than 0.5% by mass, the image quality deteriorates and the toner scatters easily in the apparatus due to a decrease in the rising property of the charge amount of the toner and a deterioration in the charge life stability. On the other hand, if it exceeds 5% by mass, the color reproducibility of the toner starts to deteriorate, which is not desirable. Therefore, a more preferable range of the addition amount of the charge control agent is 0.8% by mass to 3% by mass. By making it within such a range, the color reproducibility is improved and the charging performance is not easily lowered.

  In the present invention, a conventionally known charge control agent can be used in combination. However, the charge control agent mainly used in the present invention is a negative charge control agent, and thus differs from the charge control agent disclosed below. When a charge control agent is used in combination, the charge control agent is preferably a negative charge control agent.

  In the electrophotographic toner of the present invention, conventionally known colorants can be used for each color of yellow, magenta, cyan, and black, and each color can be used alone or in combination of two or more.

  The colorant of the yellow toner is not intended to be interpreted as being limited to the following. I. Pigment Yellow 1, 3, 4, 5, 6, 12, 13, 14, 15, 16, 17, 18, 24, 55, 65, 73, 74, 81, 83, 87, 93, 94, 95, 97, 98, 100, 101, 104, 108, 109, 110, 113, 116, 117, 120, 123, 128, 129, 133, 138, 139, 147, 151, 153, 154, 155, 156, 168, 169, 170, 171, 172, 173, 180, 185 and the like. I. Pigment Yellow 17 (bisazo), 74 (monoazo), 155 (condensed azo), and 180 (benzimidazolone) are preferable.

  The colorant for magenta toner is not intended to be interpreted as being limited to the following. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 17, 18, 22, 23, 31, 37, 38, 41, 42, 48: 1, 48: 2, 48: 3, 48: 4, 49: 1, 49: 2, 50: 1, 52: 1, 52: 2, 53: 1, 53: 3, 54, 57: 1, 58: 4, 60: 1, 63: 1, 63: 2, 64: 1, 65, 66, 67, 68, 81, 83, 88, 90, 90: 1, 112, 114, 115, 122, 123, 133, 144, 146, 147, 149, 150, 151, 166, 168, 170, 171, 172, 174, 175, 176, 177, 178, 179, 185, 187, 188, 189, 190, 193, 194, 202, 208, 209, 214, 216, 220, 221, 224, 242, 243, 243: 1, 245, 246, 247 and the like. I. Pigment Red 48: 1 (barium red), 48: 2 (calcium red), 48: 3 (strontium red), 48: 4 (manganese red), 53: 1 (lake red), 57: 1 (brilliant carmine), 122 (quinacridone magenta) and 209 (dichloroquinacridone red) are preferred.

  The colorant of the cyan toner is not intended to be interpreted as being limited to the following, but phthalocyanine C.I. I. Pigment Blue 1, 2, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 15, 16, 17: 1, 27, 28, 29, 56, 60, 63, etc. In particular, C.I. I. Pigment Blue 15: 3 (phthalocyanine blue G), 15 (phthalocyanine blue R), 16 (metal-free phthalocyanine blue), and 60 (indanthrone blue) are preferable.

  Carbon black is suitable as a colorant for the black toner. The carbon black may be appropriately selected from various conventionally known carbon blacks such as channel black, loin black, disc black, gas furnace black, oil furnace black, and acetylene black.

  The content of these colorants is preferably 2% by mass to 20% by mass. Within this range, it is possible to obtain a high-density image that is excellent in transparency, coloring power, color reproducibility, and fixability and is uniform throughout the image. Although the transparency is good at a pigment concentration of less than 2% by mass, since the coloring power is not sufficient, a uniform high density image cannot be obtained. On the other hand, if it exceeds 20% by mass, it is difficult to ensure a sufficient color gamut due to lack of lightness and saturation, and the fixing strength deteriorates due to a decrease in the resin component, so that it cannot withstand actual use. More preferably, it is 2 mass%-15 mass%. By setting the amount within this range, sufficient color reproducibility can be ensured and deterioration of fixability can be suppressed.

  For the electrophotographic toner of the present invention, conventionally known waxes can be used, and one or a combination of two or more can be used. Specifically, petroleum wax such as paraffin wax, oxidized paraffin wax, microcrystalline wax, mineral wax such as montan wax, animal and plant wax such as beeswax, carnauba wax, polyolefin wax (polyethylene, polypropylene, etc.) Synthetic waxes such as oxidized polyolefin wax, Fischer-Tropsch wax and the like, but are not necessarily intended to be limited thereto.

  The wax can be contained in an amount of 0.1 to 15 parts by mass, preferably 1 to 10 parts by mass with respect to the binder resin, whereby a good fixing offset performance can be obtained. When the content is less than 0.1 parts by mass, the offset resistance is liable to be impaired, and when the content is more than 15 parts by mass, the fluidity of the toner tends to be deteriorated.

  In the electrophotographic toner of the present invention, various external additives such as a fluidizing agent and a surface resistance adjusting agent can be used as necessary. The external additives that can be used in the present invention are not necessarily intended to be limited to the following, but examples thereof include silicon dioxide, titanium oxide, aluminum oxide, cerium oxide, zinc oxide, tin oxide, and zirconium oxide. Inorganic fine powder and those surface-treated with silicone oil, hydrophobizing agent such as silane coupling agent, polystyrene, acrylic resin, styrene acrylic resin, polyester, polyolefin, cellulose, polyurethane, benzoguanamine, melamine, nylon, silicone, Examples thereof include resin fine powders such as phenol and vinylidene fluoride. These can be used alone or in combination of two or more.

  Further, the electrophotographic toner of the present invention can be used as a one-component developer that itself is used alone, or can be used as a two-component developer in which the electrophotographic toner of the present invention and a carrier are mixed. it can.

  In general, a carrier in which magnetic material particles are coated with a resin is used, and this can also be used in the present invention. Examples of the resin covering the carrier surface include styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, acrylic acid ester copolymer, methacrylic acid ester copolymer, silicone resin, fluorine-containing resin, and polyamide resin. , Ionomer resins, polyphenylene sulfide resins, and mixtures thereof can be used.

  As the magnetic material used for the carrier core, oxides such as ferrite, iron-rich ferrite, magnetite, and γ-iron oxide, metals such as iron, cobalt, and nickel, or alloys thereof can be used. The elements contained in these magnetic materials are iron, cobalt, nickel, aluminum, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium. Etc.

  In general, a carrier in which magnetic material particles are coated with a resin is used. However, other types of carriers such as particles made only of a magnetic material, or those in which magnetic particles are dispersed in resin particles are used. It may be used in the invention.

  The toner for electrophotography of the present invention can be produced by a conventionally known method (kneading and pulverizing method, chemical method, etc.). Here, when it is intended to obtain a high-quality and high-density image, the volume average particle diameter of the obtained toner is preferably in the range of 4 μm to 8 μm. By reducing the particle size to this range, a high image density can be obtained even with a small amount of adhesion, and the toner consumption can be reduced. When the particle size is less than 4 μm, the individual particles cannot have sufficient chargeability, and toner scattering, image fogging, and the like become significant and cannot be used in actual use. On the other hand, if the thickness exceeds 8 μm, the layer thickness of the formed image becomes high, and the image feels remarkably grainy.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example and a comparative example, this invention is not specifically limited unless the summary is exceeded.

(Production Example 1 of Charge Control Agent)
10 g of alkaline bentonite is stirred at 80 ° C. for 1 hour to be dispersed in 300 ml of deionized water to prepare a bentonite suspension. Next, 5.3 g of 77% by weight aqueous solution of distearyldimethylammonium chloride (DSDMAC) was adjusted to a pH of about 9 using dilute NaOH solution, added to the bentonite suspension, and stirred at 80 ° C. for 1 hour. Filtered, washed several times with deionized water, dried at 60 ° C. under vacuum, subjected to particle size reduction treatment, alkaline bentonite and organic cation of charge control agent shown in each example having different volume particle size A salt structure consisting of

(Production Example 2 of Charge Control Agent)
Acidic bentonite is operated in the same manner as in Production Example 1 using acidic bentonite instead of alkaline bentonite and diallylmethylbenzyl / distearyldimethylammonium chloride (DSAMB / DSDMAC) mixed solution instead of distearyldimethylammonium chloride (DSDMAC). And a salt structure composed of organic cations.

Example 1
・ Polyester resin (acid value: 21mgKOH / g)
Aromatic alcohol components: PO-BPA and EP-BPA
Acid component: fumaric acid and merit anhydride 88.5% by mass
C. I. Pigment Blue 15: 1 5% by mass
・ Polyethylene wax (Clariant Japan Co., Ltd. PE130) 5% by mass
-Salt structure consisting of alkaline bentonite and organic cation (according to Production Example 1)
(Volume average particle diameter 2 μm) Each constituent material of 1.5% by mass or more was premixed with a Henschel mixer and then melt-kneaded with a twin-screw extrusion kneader. The kneaded material was coarsely pulverized with a cutting mill, then finely pulverized with a jet mill, and then classified with an air classifier to produce an average toner of 6.5 μm. To 100 parts by mass of the classified toner, 1 part by mass of silica fine particles (Nippon Aerosil Co., Ltd. R972) as a fluidizing agent was externally added to obtain an evaluation toner.

(Example 2)
A toner was prepared in the same manner as in Example 1 except that the acid value of the polyester resin was changed to 5 mg KOH / g as shown in Table 1 below.
(Example 3)
A toner was prepared in the same manner as in Example 1 except that the acid value of the polyester resin was changed to 28 mg KOH / g as shown in Table 1.
Example 4
A toner was prepared in the same manner as in Example 1 except that the acid value of the polyester resin was changed to 4 mg KOH / g as shown in Table 1.
(Example 5)
A toner was prepared in the same manner as in Example 1 except that the acid value of the polyester resin was changed to 31 mg KOH / g as shown in Table 1.
(Example 6)
A toner was prepared in the same manner as in Example 1 except that the volume average particle size of the charge control agent was changed to 7 μm as shown in Table 1.
(Example 7)
A toner was prepared in the same manner as in Example 1 except that the volume average particle size of the charge control agent was changed to 9 μm as shown in Table 1.
(Example 8)
A toner was prepared in the same manner as in Example 1 except that the number of parts by mass of the charge control agent was changed to 0.4% by mass as shown in Table 1.
Example 9
A toner was prepared in the same manner as in Example 1 except that the number of parts by mass of the charge control agent was changed to 0.6% by mass as shown in Table 1.
(Example 10)
A toner was prepared in the same manner as in Example 1 except that the number of parts by mass of the charge control agent was changed to 4% by mass as shown in Table 1.
(Example 11)
A toner was prepared in the same manner as in Example 1 except that the number of parts by mass of the charge control agent was changed to 6% by mass as shown in Table 1.

(Comparative Example 1)
As shown in Table 1, the polyester resin is composed of an aliphatic alcohol component.
・ Alcohol component: Ethylene glycol
And diethylene glycol and neopentyl glycol Acid component: A toner was prepared in the same manner as in Example 1 except that the polyester resin was changed to naphthalenedicarboxylic acid and terephthalic acid.

(Comparative Example 2)
A toner was prepared in the same manner as in Example 1 except that the charge control agent was changed to a salt structure composed of acidic bentonite and organic cation prepared in Production Example 2 as shown in Table 1.
(Comparative Example 3)
A toner was prepared in the same manner as in Example 1 except that the charge control agent was changed to a zirconium compound of salicylic acid as shown in Table 1.
(Comparative Example 4)
A toner was prepared in the same manner as in Example 1 except that the charge control agent was changed to a zirconium compound of salicylic acid as shown in Table 1.

  The toners of Examples 1 to 11 and Comparative Examples 1 to 4 prepared above and a silicon-coated ferrite core carrier (Powder Tech Co., Ltd.) having an average particle size of 60 μm were adjusted so that the toner concentration was 5% by mass, A developer was prepared.

(Evaluation of Examples and Comparative Examples)
(1) Initial charge amount The developer is set in a copying machine (Sharp Corporation AR-C160) having a commercially available two-component developing device, and after idling for 3 minutes at room temperature and humidity, the developer is collected, The charge amount was measured with a suction-type charge amount measuring device (TREK: 210H-2A Q / M Meter). When the charge amount was −20 μC / g or more, it was usable, and when it was −25 μC / g or more, it was judged good.

(2) Rise characteristics of charge amount A 5 ml glass bottle containing 0.95 g of carrier (silicon coated ferrite core carrier) and 0.05 g of toner is stirred for 1 minute in a rotary incubator at 32 rpm, and the developer is collected and sucked. The charge amount was measured with a type charge amount measuring device. The mixture was further stirred for 2 minutes (3 minutes in total), and the charge amount was measured in the same manner. It can be used when the difference between the charge amounts after 1 minute and 3 minutes is 7 μC / g or less in absolute value, and it is judged good if it is 5 μC / g or less.

(3) Attenuation characteristics of charge amount A polyethylene container having a capacity of 100 ml containing 76 g of a carrier (silicon-coated ferrite core carrier) and 4 g of toner was stirred for 60 minutes with a ball mill at 150 rpm, and then the charge amount of the developer was measured. Exposed under humidity. After 1 day, 3 days, and 10 days, the charge amount of the developer was measured. If the difference from the charge amount on the first day was 7 μC / g or less in absolute value, it was usable, and if it was 5 μC / g or less, it was judged good. .

(4) Life characteristics of charge amount Developer Set in a copier (Sharp Co., Ltd. AR-C160) having a commercially available two-component developing device, and after taking 50000 solid images under normal temperature and humidity, The image density, the whiteness of the non-image area, and the charge amount of the developer were measured. The image density was measured with an X-Rite 938 spectrocolorimetric densitometer and judged to be good if the image density was 1.4 or higher. As for whiteness, color differences X, Y, and Z were obtained using an SZ90 type spectroscopic color difference meter manufactured by Nippon Denshoku Industries Co., Ltd., and judged to be good if the value of Z was 0.5 or less. The charge amount of the developer was measured with a suction-type charge amount measuring device, and it was determined that the developer was usable if the difference from the initial charge amount was 7 μC / g or less in absolute value, and good if it was 5 μC / g or less.

Tests were performed on the above four characteristics (1) to (4), and the results of the test were comprehensively evaluated to evaluate in three stages, ◎, ○, and ×. The obtained evaluation results are shown in Table 2 below.
In addition, each evaluation standard of (double-circle), (circle), and x is as follows.
◎: Very good developer within the scope of the present invention ○: Developer within the scope of the present invention ×: Inferior to the developer in the prior art

  From the results shown in Table 2 above, the cyan toner produced in each of Examples 1 to 10 according to the present invention has excellent charging characteristics as described below and stable development as compared with the cyan toners shown in Comparative Examples 1 to 5. Can be maintained.

  For example, as shown in Table 2, the electrophotographic toner according to Example 1 of the present invention had an initial charge amount of −28 μC / g and a value of −25 μC / g or more. The charge amount rising characteristic was −26 μC / g after 1 minute of stirring, −29 μC / g after 3 minutes of stirring, and the absolute amount difference between the charged amounts was 5 μC / g or less. Further, the attenuation characteristic was −27 μC / g on the first day, −24 μC / g after 10 days, and the absolute amount difference in charge amount was 5 μC / g or less. The charge amount after the 5000 sheets are actually photographed is −25 μC / g, the difference from the initial charge amount is 5 μC / g or less, the image density is 1.45, 1.4 or more, and the whiteness is 0.00. 4 and 0.5 or less. Thus, it can be said that the toner has very excellent charging characteristics. Thus, good results were obtained in all the items.

  Also, in Examples 2, 3, 6, and 9, good results were obtained in all items as in Example 1.

  In Example 4, although the acid value of the resin is as low as 4 mgKOH / g, the charging characteristics are lower than in Example 1, but the initial charging characteristics and the charge rising characteristics can be sufficiently used in the implementation. Met.

  In Example 5, since the acid value of the resin was as high as 31 mgKOH / g, the charge amount attenuation at a higher temperature and higher humidity was larger than that in Example 1, but it was an available area that could withstand the implementation sufficiently. .

  Further, in Example 7, the volume average particle size of organic bentonite is as large as 9 μm, so that the charging characteristics are worse than those in Example 1, but it can be said that the charging rise characteristics and whiteness are also in the usable range. .

  In Example 8, the amount of addition of organic bentonite was reduced to 0.4 parts by mass, so that the charging characteristics were lower than in Example 1. However, it can be used sufficiently for performance evaluation of initial charge amount, charge rising characteristics, and whiteness. It was an area.

  On the other hand, Comparative Example 1 uses a polyester resin whose alcohol component is aliphatic, so that the image has a background fogging with a large attenuation of the charge amount under high temperature and high humidity and further whiteness. Even when compared with the toners of Examples 1 to 10 of the present invention described above, good results were not obtained.

  In Comparative Example 2, since the salt structure of acidic bentonite was used as the charge control agent, the initial charge amount was lowered, the image density was reduced, and an image with a background fogging with high whiteness was obtained, and good results were not obtained.

  In Comparative Examples 3 and 4, since a substance other than bentonite was used as the charge control agent, the initial charge amount was reduced, and an image having a background fogging with high whiteness was obtained, and good results were not obtained.

  As mentioned above, in order to satisfy the chargeability as a general review of the results of comparing Examples 1 to 10 and Comparative Examples 1 to 4 according to the present invention, the polyester resin comprising the aromatic alcohol component as described above. It is necessary that the charge control agent has a basic structure having a salt structure composed of alkaline bentonite and an organic cation.

  Further, from the results shown in Table 2, the acid value of the polyester resin of the present invention is in the range of 4 mg KOH / g to 31 mg KOH / g in order to improve the charge amount rising property, As specified above, the range of 5 mgKOH / g to 30 mgKOH / g is a preferable range, and the more preferable range is the range of 5 mgKOH / g to 28 mgKOH / g.

  In addition, as a charge control agent of the present invention, a basic structure of a salt structure composed of alkaline bentonite and an organic cation makes it possible to improve the chargeability, and the addition amount is 0.4 from the results shown in Table 2. The range of mass% to 6 mass% is a feasible range, and as specified above, the range of 0.5 mass% to 5 mass% is the preferred range, and the more preferred range is 0.6 mass% to It can be said that the range of 4% by mass is preferable.

In addition, when using a salt structure composed of alkaline bentonite which is the charge control agent of the present invention and an organic cation, as a further requirement, the particle size (volume average particle size D ₅₀ ) is sufficiently charged up to 9 μm. It is a stable feasible range, and as specified above, 8 μm or less is good, and more preferably 7 μm or less, it is preferable. This is somewhat affected by the acid value range of the binder resin, which is another component.

Claims (4)

A toner comprising at least a binder resin, a colorant, and a charge control agent, wherein the binder resin is a polyester resin comprising an aromatic alcohol component, and the charge control agent is a salt structure comprising an alkaline bentonite and an organic cation. An electrophotographic toner comprising: 2. The electrophotographic toner according to claim 1, wherein the charge control agent has a volume average particle diameter D ₅₀ of 9 μm or less. 3. The electrophotographic toner according to claim 1, wherein an addition amount of the charge control agent is in a range of 0.4 mass% to 6 mass%. The toner for electrophotography according to any one of claims 1 to 3, wherein the acid value of the binder resin is in a range of 4 mgKOH / g to 31 mgKOH / g.