JP4076997B2 - Toner for electrophotography - Google Patents

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. Flow characteristics and fixing characteristics are extremely important factors.

  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, the flow characteristics, such as the rising characteristics of the charge quantity of the toner, the environmental stability of the charge quantity, and the stability and durability over time.

  For this reason, an external additive is added to the toner in order to improve and adjust the charge amount, fluidity, etc., to the base particles containing a binder resin, a colorant, a charge control agent and the like.

  As the binder resin for full-color toner, a resin excellent in sharp melt property, color developability and fixing property is required, and a polyester resin is usually used. Polyester resins usually have strong negative band characteristics. Toners using this resin are designed for negative chargeability, and negative charge control agents used for the toner include oil black, spiron black and other oils. Soluble dyes, metal-containing azo dyes, naphthenic acid metal salts, metal salts of alkylsalicylic acid, fatty acid soaps, resin acid soaps, and the like are used.

Examples of the external additive include inorganic fine powders such as silicon dioxide, titanium oxide, aluminum oxide, cerium oxide, zinc oxide, tin oxide, and zirconium oxide, and hydrophobic treatment agents such as silicon oil and silane coupling agents. Examples thereof include surface-treated ones, polystyrene, acrylic, styrene acrylic, polyester, polyolefin, cellulose, polyurethane, benzoguanamine, melamine, nylon, silicon, phenol, vinylidene fluoride, and the like.

  In order to achieve excellent toner chargeability, it is known that it is important that the charge control agent is uniformly finely dispersed in the toner particles or on the toner particle surfaces. 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.

  As an external additive for improving chargeability, fluidity, adhesion, etc., generally, an inorganic oxide fine powder is added, and silica fine particles are generally added to the toner base particles, and the toner Have gained. However, in the case of normally used silica fine particles, the effect of improving the toner fluidity is particularly excellent, but the negative polarity is strong and the charge of the negatively chargeable toner is excessively increased particularly under low temperature and low humidity.

  Further, since moisture is taken in under high temperature and high humidity to reduce the chargeability, a large difference in chargeability occurs between low temperature and low humidity and high temperature and high humidity. As a result, it is not possible to optimize toner transportability and chargeability on the developer carrying member at both high temperature and high humidity and low temperature and low humidity, resulting in poor image density reproduction, fogging, toner dropping, Furthermore, there has been a problem of causing in-flight contamination and the like.

  For the purpose of improving these, silica fine particles whose surface is treated with an amino compound to reduce the negative charging effect are used. However, the use of these silica fine particles alone does not provide a satisfactory effect of reducing the environmental difference in charge amount. In the case where a polyester resin is used as the binder resin in the toner base particles, a sufficient effect is obtained. There is no. In a case where sufficient chargeability can be imparted at high temperature and high humidity, the amount of charge becomes too high at low temperature and low humidity, and the charge distribution becomes broad, and developability deteriorates and the degree of fogging becomes particularly serious.

  Therefore, as a method for eliminating the environmental fluctuation of the toner particle characteristics, a method of surface treatment with a hydrophobizing agent such as silicon oil or a silane coupling agent is used.

  As described above, even if the silica fine particles are subjected to a hydrophobizing treatment, a treatment for reducing negative chargeability, etc., they have not yet improved the environmental dependency of the charge, the charging speed, and the poor charge distribution of silica. Is the current situation.

Therefore, external addition of inorganic compounds other than silica fine particles has been studied, and titanium oxide or the like has been used. This titanium oxide has a low charge level, and has an advantage that it is easy to control the charge level and the environment dependency using a treatment agent. However, in general, titanium oxide is obtained by a method of extracting titanium oxide crystals by a sulfuric acid method using ilmenite ore, and these titanium oxides are obtained by heating and firing after purification by a wet method. Since titanium oxide naturally has chemical bonds that are generated by the dehydration condensation reaction, strong aggregates are present therein. With existing technology, it is not easy to redisperse such aggregated particles. That is, the crystalline titanium oxide taken out as a fine powder contains secondary aggregates and tertiary aggregates, and the effect of improving the fluidity of the toner was extremely low compared to silica.

  Furthermore, in recent years, there has been an increasing demand for higher image quality, particularly in color, and attempts have been made to achieve higher image quality by reducing the particle size of the toner. The adhesion force is increased and the fluidity of the toner is further reduced. This phenomenon is particularly likely to appear in titanium oxide.

  Therefore, it is known that hydrophobic titanium oxide and hydrophobic silica are added to the toner particles in order to improve both the fluidity of the toner and the environmental dependency of charging.

  On the other hand, in order to solve the problem relating 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. There has been proposed a technique for improving the charge characteristics of a toner by improving the uniform fine dispersion of the charge control agent therein. Further, Patent Document 1 discloses that hydrophobized silica and titanium oxide are used as external additives. As a result, the charging characteristics and the like are improved, an image free of background stains can be obtained even at high speed development, toner scattering in the developing device can be reduced, and a stable image can be obtained from the beginning to the end of development. Is disclosed.

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, problems such as image contamination and internal contamination due to toner scattering are assumed.

  Further, Patent Document 1 discloses nothing about the optimization of the external additive for charge control, and does not suggest the problem of stability of image quality due to environmental changes or the like, and suppressing changes in image density. It is not touched at all.

  Therefore, the present invention provides an electrophotographic toner that can reproduce a stable and uniform image for a long time without being affected by changes in temperature and humidity even when repeated development is performed by continuous use. Objective.

  For this reason, the present invention aims to achieve the above-mentioned object by optimizing external additives for charge control and providing an electrophotographic toner having excellent charge stability and fluidity.

  Another object of the present invention is to provide an electrophotographic toner that is excellent in at least transparency and has good color reproducibility when used as a color toner.

The present invention for solving the above-mentioned problems is an electrophotographic toner comprising toner base particles containing at least a binder resin, a colorant, a charge control agent, and a wax, and an external additive.
The binder resin is a polyester resin obtained by reacting an aromatic alcohol component, and has an acid value of 4 to 31 mgKOH / g,
The charge control agent has a salt structure composed of alkaline bentonite and an organic cation, the volume average particle diameter D ₅₀ is 2 to 9 μm, and the addition amount is 0.4 to 6% by weight,
The external additive includes metatitanic acid hydrophobized, the hydrophobizing agent is alkoxysilane, the volume average particle diameter of metatitanic acid is 25 to 55 nm, and the addition amount of metatitanic acid is 0.2 to 2 The toner for electrophotography is characterized by being 2% by weight.
The present invention also relates to an electrophotographic toner comprising toner base particles containing at least a binder resin, a colorant, a charge control agent, and a wax, and an external additive.
The binder resin is a polyester resin obtained by reacting an aromatic alcohol component, and has an acid value of 5 to 28 mgKOH / g,
The charge control agent has a salt structure composed of alkaline bentonite and an organic cation, the volume average particle diameter D ₅₀ is 2 to 7 μm, and the addition amount is 0.6 to 4% by weight,
The external additive includes metatitanic acid hydrophobized, the hydrophobizing agent is alkoxysilane, the volume average particle size of metatitanic acid is 30 to 50 nm, and the amount of metatitanic acid added is 0.3 to 2 The toner for electrophotography is characterized by having a weight percentage.
In the invention, it is preferable that the external additive further includes silica subjected to hydrophobic treatment.
In the invention, it is preferable that the colorant is added in an amount of 2 to 20% by weight .

  According to the toner having the above-described configuration, a specific charge control agent is contained in a polyester resin obtained by reacting an aromatic alcohol component as a binder resin, so that the characteristics of the polyester resin are not impaired. The charge control agent can be evenly and finely dispersed, and the charge amount distribution and fluidity can be stabilized by using an external additive containing metatitanic acid that has been hydrophobized. An electrophotographic toner that reproduces a stable and uniform image with little charge fluctuation during development (excellent in life charge stability) can be obtained.

  For example, compared to a polyester resin composed of an aliphatic alcohol component, a polyester resin composed of an aromatic alcohol component can control the charge amount easily with little change in the resistance of the toner due to a change in the external environment. The charging characteristics (life characteristics) are stable even after repeated development by continuous use. This difference is largely attributed to the chemical structure of the resin, and the alcohol component of the aromatic polyester resin is more hydrophobic than the aliphatic group, and therefore has high moisture resistance.

  In addition, the resin contains organic bentonite as a charge control agent, and includes a hydrophobized metatitanic acid that can uniformly adhere to the surface of the toner base particles in a state close to primary particles as an external additive optimized for the charge control agent. By using it as an external additive, it is possible to provide a toner having good flowability and sharp charge distribution even in repeated development by continuous use.

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 for obtaining the polyester resin which is the binder resin according to the present invention include bisphenol A, polyoxyethylene- (2.2) -2,2-bis (4-hydroxyphenyl) propane. , Polyoxyethylene- (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 , Polyoxypropylene- (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, particularly bisphenol A are preferred.

  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, terephthalic acid, acids having three or more bases such as trimellitic acid, trimetic acid, pyromellitic acid, and anhydrides thereof, and lower alkyl esters. From the viewpoint of heat-resistant aggregation, terephthalic acid or its lower alkyl ester is preferred.

  Accordingly, the acid value of the polyester resin constituting the electrophotographic toner of the present invention is more preferably within the following range. For example, the acid value of the polyester resin is preferably 5 to 30 mgKOH / g. When the acid value is less than 5 mgKOH / g, the charging characteristics of the resin are lowered, and the organic bentonite as the charge control agent is difficult to disperse in the polyester resin. This adversely affects the charge amount stability of repeated development due to rising of the charge amount or continuous use.

  On the other hand, when the acid value is 2 mgKOH / g or less, the dispersion of the organic bentonite is deteriorated, and the charging characteristics of the resin are further deteriorated. Further, the pigment dispersion is deteriorated and the color reproducibility is narrowed.

On the other hand, when the acid value exceeds 35 mgKOH / 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 when a charge control agent is added, it is difficult to stably control the charge amount against environmental changes, and the charging characteristics of repeated development by continuous use are not stabilized.
Here, 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 is an important factor for achieving transparency. For example, when used as a color toner, it is necessary to melt sufficiently so that the boundaries between the toners disappear when the toners of the respective colors are stacked. 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 the temperature is higher than 135 ° C., it becomes difficult to eliminate the boundary between the toner particles and provide sufficient transparency. In the case of black toner, it can be used at 90 ° C. to 160 ° C.

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

Next, the charge control agent constituting the electrophotographic toner of the present invention will be described. As this charge control agent, organic bentonite is used. The organic bentonite is a substance produced mainly from an organic cation-forming compound and bentonite, and bentonite is a viscosity having a layered structure mainly composed of SiO ₂ and Al ₂ O ₃ and mainly composed of montmorillonite. It is a mineral. Bentonite, which is such a natural layered compound, can take in organic molecules between layers by ion exchange or the like. Between the bentonite layers, inorganic metal cations such as sodium and potassium originally exist, but by exchanging these ions, organic cations such as alkylammonium ions are intercalated (inclusion), and organic and inorganic substances are separated. Alternating composites (interlayer compounds) are produced. The organic bentonite 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 it is an anion which does not contain heavy metals, 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.

  Furthermore, the organic bentonite used in the present invention preferably has a salt structure composed of alkaline bentonite and an organic cation. Thereby, even in a small amount, the charge imparting function to the toner can be sufficiently exhibited.

The organic bentonite, which is a charge control agent used in the present invention, can improve the charging characteristics of the toner by improving the dispersibility (uniformly dispersing) in the polyester resin as the binder resin described above. To that end, the volume mean diameter D ₅₀ of the organic bentonite, it is preferably adjusted to 8μm or less. As a result, the charge control agent is present on the toner surface almost uniformly with a fine diameter, and is difficult to separate from the toner particles, so that the toner can be excellent in charge amount rise characteristics, charge life stability, and the like. When the volume average diameter D ₅₀ exceeds 8 μm, the charge control agent is uniformly dispersed in the toner, but the size becomes non-uniform and the charging efficiency slightly decreases. Therefore, the volume average diameter D ₅₀ is preferably about 8 μm or less. Here, if the volume average diameter D ₅₀ is to be finely pulverized to 1 μm or less, considerable time and energy are required, resulting in poor productivity and an increase in cost. However, a material having a volume average diameter D ₅₀ of 1 μm or less can be used as long as the object of the present invention is achieved in consideration of dispersibility. Also, if an object to inexpensively produce a toner, it may be used more than 1μm in volume average diameter D _50.

The organic bentonite according to the present invention has a great influence on the charging characteristics depending on the amount of the organic bentonite and the color reproducibility in a color toner or the like. Therefore, the amount of organic bentonite added is preferably 0.5% by weight to 5% by weight with respect to the total amount of toner. For example, when the addition amount is less than 0.5% by weight, image quality deterioration and toner scattering in the apparatus are likely to occur due to a decrease in charge amount rise characteristic of the toner and deterioration in charge amount life stability. On the other hand, if it exceeds 5% by weight, the color reproducibility of the toner starts to deteriorate, which is not desirable. A more preferable range is 0.8 to 3% by weight. By making it within such a range, the color reproducibility is improved and the charging performance is not easily lowered. In the present invention, other charge control agents can be used in combination.

  The toner base particles constituting the electrophotographic toner of the present invention may contain a conventionally known wax. As this wax, 1 type (s) or 2 or more types can be used in combination. 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% by weight, preferably 1 to 10% by weight, based on the binder resin, whereby good fixing offset performance can be obtained. When the content is less than 0.1 parts by weight, the offset resistance is liable to be impaired, and when the content is more than 15% by weight, the fluidity of the toner tends to be deteriorated.

In the above description, various additives included in the toner base particles have been described. Hereinafter, external additives added to the toner base particles for achieving the object of the present invention will be described. . The external additive used in the present invention is metatitanic acid that has been hydrophobized. This external additive is manufactured by the sulfuric acid method using the following ilmenite ore as a raw material.
FeTiO ₂ + 2H ₂ SO ₄ → FeSO ₄ + TiOSO ₄ + 2H ₂ O
TiOSO ₄ + 2H ₂ O → TiO (OH) ₂ + H ₂ SO ₄

By adding a silane compound into the aqueous dispersion state of TiO (OH) ₂ (metatisanic acid) obtained by the above method, and treating at least a part (part or all) of the hydroxyl groups in TiO (OH) ₂ As described above, by reacting in solution, the silane compound is hydrolyzed, and the hydroxyl group of TiO (OH) ₂ particles uniformly dispersed in the solution reacts with the hydrolyzed silane compound. . As a result, metatitanic acid hydrophobized with a silane compound from TiO (OH) ₂ is generated in the form of primary particles. Thereby, it becomes possible to obtain titanium in a primary particle state without aggregation. Further, in the above reaction, fine adjustment of the specific gravity and negative chargeability of titanium can be controlled by the type of silane compound and its treatment amount.

  As the silane compound, alkoxysilane or chlorosilane type compounds can be used. Specific examples include i-butyltrimethoxysilane, n-propyltrimethoxysilane, n-hexyltrimethoxysilane, ethyltrimethoxysilane, methyltrichlorosilane, trimethylchlorosilane and the like. Particularly preferred as the treating agent is i-butyltrimethoxysilane. The external additive is preferably 0.3% by weight to 2% by weight with respect to the total amount of toner. If it is less than 0.3% by weight, the chargeability is deteriorated, so that the image quality is lowered and the toner in the apparatus is likely to be scattered. When the amount exceeds 2% by weight, the color reproduction range starts to narrow. The volume average diameter is preferably in the range of 30 to 50 nm from the viewpoint of fluidity. If it is less than 30 nm, the transfer efficiency starts to deteriorate. At 50 nm or more, it becomes easy to release.

  The binder resin, charge control agent, and external additive used in the present invention constituting the electrophotographic toner have been described above. Together with these constituent materials, a colorant is further added to determine the color of the toner. As this colorant, that is, the colorant constituting each color toner, for example, each color toner of yellow, magenta, cyan and black, conventionally known ones can be used. Each color can be used alone or in combination of two or more.

Examples of the colorant for obtaining the yellow toner include C.I. 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 (disazo), 74 (monoazo), 155 (condensed azo), and 180 (benzimidazolone) are preferable.

  Examples of the colorant for obtaining magenta toner include C.I. 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.

  As a colorant for obtaining a cyan toner, 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.

  Further, carbon black is suitable as a colorant for obtaining a 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 weight to 20% by weight. 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. When the pigment concentration is less than 2% by weight, the transparency is good, but the coloring power is not sufficient, and a uniform high-density image cannot be obtained. On the other hand, if it exceeds 20% by weight, a sufficient color reproduction range cannot be ensured due to lack of lightness and saturation, and fixing strength deteriorates due to a decrease in the resin component. More preferably, it is 2 to 15% by weight. By setting it within this range, sufficient color reproducibility can be secured and there is little deterioration in fixing properties.

  Further, the electrophotographic toner comprising the toner base particles and the external additive of the present invention can be used alone, but the electrophotographic toner of the present invention and a carrier are mixed to form a two-component developer. It can also be used.

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, silicon resin, fluorine-containing resin, and polyamide resin. , Ionomer resins, polyphenylene sulfide resins, and mixtures thereof can be used.

  As the magnetic material 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.

  The carrier is generally made of a magnetic material particle coated with a resin. In addition, other types of carriers such as particles made only of a magnetic material, or magnetic particles 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 diameter is less than 4 μm, the individual particles cannot have sufficient chargeability, and toner scattering, image fogging, and the like become remarkable and cannot be used in actual use. On the other hand, if the thickness exceeds 8 μm, the layer thickness of the formed image is increased, and an image having a remarkably graininess is undesirable.

  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.

(1) Production Example of Charge Control Agent A bentonite suspension is prepared by dispersing 10 g of bentonite having a pH of 7 to 12 in 300 ml of deionized water at 80 ° C. and stirring for 1 hour. Next, 5.3 g of 77% aqueous distearyldimethylammonium chloride (DSDMAC) solution was adjusted to pH 9 with dilute NaOH solution, added to the bentonite suspension, stirred at 80 ° C. for 1 hour, filtered Separately, after washing several times with deionized water, it was dried at 60 ° C. under vacuum and subjected to a particle size reduction treatment to produce charge control agents (organic bentonites) having different average volume particle sizes D ₅₀ . The average volume particle diameter D ₅₀ of the charge control agent prepared is as respective Examples and Comparative Examples described in Table 1.

Example 1
・ Polyester resin (acid value: 21mgKOH / g)
Aromatic alcohol components: PO-BPA and EP-BPA
Acid components: fumaric acid and merit anhydride
87.5% by weight
C. I. Pigment Blue 15: 1 5% by weight
Nonpolar paraffin wax (DSC peak 78 ° C., weight average molecular weight Mw 8.32
× 10 ² ) 6% by weight
Charge control agent (volume average diameter 2 μm created in the above production example) 1.5% by weight
The nonpolar paraffin wax Mw exhibits a weight average molecular weight as is well known.

Each of the above constituent materials was premixed with a Henschel mixer and then melt-kneaded with a twin-screw extrusion kneader. The kneaded product was coarsely pulverized with a cutting mill, then finely pulverized with a jet mill, and then classified with an air classifier to produce toner base particles having an average particle size of 6.5 μm. Next, 97.8% by weight of the classified toner base particles, 1.2% by weight of metatitanic acid hydrophobized with i-butyltrimethoxysilane having a volume average diameter of 40 nm, and silica hydrophobized with HMDS having a volume particle diameter of 12 nm 1.0% by weight of fine particles were added and mixed with a hensil mixer, followed by external addition treatment to prepare a cyan 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 diameter of the organic bentonite as 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 diameter of the organic bentonite as 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 weight of the organic bentonite as the charge control agent was changed to 0.4% by weight as shown in Table 1.

Example 9
A toner was prepared in the same manner as in Example 1 except that the weight part of the organic bentonite as the charge control agent was changed to 0.6% by weight as shown in Table 1.

(Example 10)
A toner was prepared in the same manner as in Example 1 except that the weight part of the organic bentonite as the charge control agent was changed to 4% by weight 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 weight of the organic bentonite as the charge control agent was changed to 6% by weight as shown in Table 1.

(Example 12)
A toner was prepared in the same manner as in Example 1 except that the volume average diameter of metathisanoic acid as an external additive was changed to 30 nm.

(Example 13)
A toner was prepared in the same manner as in Example 1 except that the volume average diameter of metathisanoic acid as an external additive was changed to 25 nm.

(Example 14)
A toner was prepared in the same manner as in Example 1 except that the volume average diameter of metathisanoic acid as an external additive was changed to 50 nm.

(Example 15)
A toner was prepared in the same manner as in Example 1 except that the volume average diameter of metathisanoic acid as an external additive was changed to 25 nm.

(Example 16)
A toner was prepared in the same manner as in Example 1 except that the addition weight% of the metathesanoic acid external additive was changed to 0.3.

(Example 17)
A toner was prepared in the same manner as in Example 1 except that the addition weight% of the metathesanoic acid external additive was changed to 0.2.

(Example 18)
A toner was prepared in the same manner as in Example 1 except that the addition weight% of the external additive methisanic acid was changed to 2.0.

(Example 19)
A toner was prepared in the same manner as in Example 1 except that the addition weight% of the metathesanoic acid external additive was changed to 2.2.

(Example 20)
A toner was prepared in the same manner as in Example 1 except that the external additive was changed to chlorosilane-based methyltrichlorosilane as shown in Table 1.

  A comparative example for comparison and comparison with the toner of the present invention according to each embodiment prepared as described above will be described below.

(Comparative Example 1)
As shown in Table 1, the polyester resin is composed of an aliphatic alcohol component. Alcohol component: ethylene glycol, dierylene glycol, and neopentyl glycol Acid component: except that the polyester resin is composed of naphthylene dicarboxylic acid and terephthalic acid A toner was prepared in the same manner as in Example 1.

(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 zirconium compound of salicylic acid 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 external additive was changed to a titanium oxide having a volume average diameter of 40 as shown in Table 1 and hydrophobized with i-butyltrimethoxysilane.

  The toners of Examples 1 to 20 and Comparative Examples 1 to 4 prepared above and a silicon-coated ferrite core carrier having an average particle diameter of 60 μm were prepared so that the toner concentration was 5% by weight, and a two-component developer was prepared. .

In Table 1 below, the particle diameter is the volume average diameter D ₅₀ , and the number of parts is by weight%. The organic bentonite has a salt structure composed of alkaline bentonite and an organic cation, and is obtained in the above production example.

（注）比較例４の外添剤は、従来の酸化チタンにｉ−ブチルトリメトキシシラン処理したものである。

(Note) The external additive of Comparative Example 4 is obtained by treating conventional titanium oxide with i-butyltrimethoxysilane.

(2) The evaluation method of an Example and a comparative example is demonstrated.
i. The initial charge amount developer is set in a copier (Sharp Co., Ltd. AR-C160) having a commercially available two-component developing device, and after idling for 3 minutes at room temperature and normal humidity, the developer is collected and suction charging is performed. The charge amount was measured with a quantity measuring device (TREK: 210H-2A Q / M Meter). When the charge amount is -20 μC / g or more, it can be used, and when the charge amount is -25 μC / g or more, it is judged good.

ii. Charging start-up characteristic A 5 ml glass bottle containing 0.95 g carrier (silicon coated ferrite core carrier) and 0.05 g toner is stirred for 1 minute in a rotary incubator at 32 rpm. The charge amount was measured with an apparatus. Further, after stirring for 3 minutes, 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.

iii. Attenuation characteristics of charging A 100 ml polyethylene container 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 the charge amount of the developer was measured and exposed to high temperature and high 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. .

iv. Life characteristics of charging After setting the developer in a copying machine (Sharp Co., Ltd. AR-C160) having a commercially available two-component developing device, and taking 50,000 solid images under normal temperature and humidity, the image density and 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. Whiteness, tristimulus values X, Y, and Z determined using a Nippon Denshoku Industries Co., Ltd. SZ90 type spectroscopic color difference meter, accessible when the value of ΔX is 0.7 or less, 0.5 or less It was judged as good. 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.

v. Fixing characteristics A fixing device (oilless system) of a commercially available full color copier (Sharp Co., Ltd. ARC-260) was modified, and an external fixing machine that can freely set the roller temperature was used, and the paper feed was fixed at 120 mm / sec. The temperature was changed in increments of 5 ° C. from 100 ° C. to 230 ° C. At this time, an offset phenomenon in which the image was retransferred to the non-image portion was observed, and a temperature at which the image was not retransferred was defined as a non-offset temperature.
In the non-offset region, a product having a width of 40 ° C. or more can be used, and a value of 50 ° C. or more was judged good.

The evaluation results from i to v are shown in Table 2. Evaluation was made in three stages: comprehensive evaluation, ◎, ○, and ×. 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 developers in the prior art

  From the results shown in Table 2 above, the cyan toner produced in each of Examples 1 to 20 according to the present invention has both charging characteristics and fixing characteristics as follows as compared with the cyan toners shown in Comparative Examples 1 to 4. It is excellent in this aspect and can maintain stable development.

  For example, as shown in Table 2, the electrophotographic toner according to Example 1 of the present invention had an initial charge amount of −30 μC / g and a value of −25 μC / g or more. In addition, the charge rising characteristics were −30 μC / g after 1 minute of stirring and −32 μC / g after 3 minutes of stirring, and the absolute amount difference in charge amount was 5 μC / g or less. Further, the attenuation characteristics were −28 μC / g on the first day, −26 μC / g after 10 days, and the absolute 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 1.53, 1.4 or more, and the whiteness is 0.00. 2 and 0.5 or less. Thus, it can be said that the toner has very excellent charging characteristics.

  In addition, when the toner is melted and fixed, the low temperature offset and the range in which the high temperature offset does not occur (fixing characteristics) are 145 to 210 ° C. and 50 ° C. or more. For this reason, the toner is sufficiently melted, the boundary between the toner particles is eliminated, the transparency is improved, and good fixing can be performed. Thus, good results were obtained in all the items.

  Also, in Examples 2, 3, 6, 9, 10, 12, 14, 16, and 18, 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 mg KOH / g, the charging characteristics are somewhat lower than in Example 1. However, the initial charging characteristics and the charge rising characteristics can be used without being sufficiently implemented. It was an area.

  In Example 5, since the acid value of the resin was as high as 31 mg KOH / g, the charge amount attenuation at a higher temperature and higher humidity was larger than that in Example 1, but it was a usable area that could be fully used. .

Further, in Example 7, since the volume average diameter of organic bentonite is as large as 9 μm, the charging characteristics are worse than those in Example 1, but the charge rising characteristics are sufficient, and the whiteness is also in the usable range. It can be said that there is.

  In Example 8, although the amount of addition of organic bentonite was reduced to 0.4% by weight, the charging characteristics were somewhat 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 a great area.

  In Example 11, although the amount of addition of organic bentonite increased to 6% by weight, the fixing characteristics were slightly lowered in Example 1, but there was no problem with other charging characteristics and the like, and it was a sufficiently usable region. .

  In Example 13, since the volume average diameter of metatitanic acid was as small as 25 nm, the transfer efficiency was reduced to 1.38.

  In Example 15, although the volume average diameter of metatitanic acid was as large as 55 nm, the charging characteristics were lowered and the whiteness was 0.6, but the area was sufficiently usable in performance judgment.

  In Example 17, although the addition amount of metatitanic acid was reduced to 0.2% by weight, the charging characteristics deteriorated, and the charge amount rising characteristic and whiteness deteriorated to 0.7. It was an available area.

  In Example 19, since the addition amount of metatitanic acid was increased to 2.2% by weight, the influence charging characteristics of the free substance decreased, and the charge amount rising characteristic and the whiteness were reduced to 0.7. It was a fully usable area.

  In Example 20, since the surface treatment of metatitanic acid was performed using chlorosilane-based methyltrichlorosilane, the charging characteristics deteriorated, and the charge amount rising characteristics and whiteness deteriorated to 0.7. It was an available area.

  As described above, the use of an aromatic polyester resin with an alcohol component provides excellent humidity environment characteristics and a low charge decay rate at high temperature and high humidity. In addition, since the present resin contains organic bentonite and nonpolar paraffin wax, the organic bentonite finely dispersed in the toner exhibits proper characteristics of the initial charge amount and charge rise of the toner, and also improves life stability. Furthermore, the metatitanic acid that has been hydrophobically treated in this configuration can improve the charging characteristics of the toner.

  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 20 of the present invention described above, good results were not obtained.

  In Comparative Examples 2 and 3, since an object other than organic bentonite was used as the charge control agent, the initial charge amount was reduced, and an image with a background fogging with high whiteness was obtained, and the fixing characteristics were also deteriorated, and good results could not be obtained. It was.

  In Comparative Example 4, the initial charge amount was reduced by using ordinary titanium oxide as the external additive instead of metatitanic acid, and an image having a background fogging with high whiteness was obtained, and a good result was not obtained.

  As mentioned above, in order to satisfy both the charging property and the fixing property, the overall result of the comparison between Examples 1 to 20 and Comparative Examples 1 to 4 according to the present invention is the aromatic resin as described above. The basic constitution is to include a polyester resin obtained by reacting an alcohol component, an organic bentonite as a charge control agent, and metatitanic acid hydrophobized as an external additive.

  In addition, 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. From the results of the examples, it is proved that the range of 5 mg KOH / g to 30 mg KOH / g is a preferable range as specified. Moreover, it can be said that the range of 5 mgKOH / g-28 mgKOH / g is suitable as a more preferable range from an Example.

  Further, by using the organic bentonite which is the charge control agent of the present invention, the chargeability can be improved, and the addition amount can be in the range of 0.4 wt% to 6 wt% from the results of Table 2. From the results of the examples, it was proved that the range is 0.5% by weight to 5% by weight as specified above. Furthermore, according to the examples, it can be said that a more preferable range is 0.6% by weight to 4% by weight.

In addition, when using organic bentonite in the charge control agent of the present invention, the particle size (volume average diameter D ₅₀ ) as another requirement is a feasible range in which the chargeability is sufficiently stable up to 9 μm. From the results of the examples, it was proved that 8 μm or less is good as specified in the above. Moreover, it can be said that the particle size is preferably 7 μm or less according to the examples. This is somewhat affected by the acid value range of the binder resin, which is another component.

  In addition, by using metatitanic acid hydrophobized as an external additive of the present invention, the charging characteristics can be improved, but the addition amount for the addition is 0.2% by weight to 2% from the results of Table 2. A range of .2% by weight is a workable range, which, as specified above, has proved to be a preferred range of 0.3% to 2.0% by weight.

  Further, from the result of Comparative Example 4, even when the toner base particles contain organic bentonite, the charging characteristics are maintained well by using titanium oxide instead of hydrophobized metatitanic acid which is an external additive to be used. Can not. In this respect, according to the present invention, by using metatitanic acid hydrophobized as the external additive, this state can be maintained in a state in which organic bentonite is contained and charging characteristics are improved. Therefore, it can be said that the use of hydrophobized metatitanic acid as an external additive for toner base particles containing organic bentonite is very useful as described above.

  As described above, in this embodiment, cyan toner is exemplified as the electrophotographic toner. This is because C.I. I. Pigment Blue 15: 3 is included, but it can be similarly carried out by including the various colorants exemplified above instead of the colorant.

  Therefore, when yellow, magenta, cyan toner described in the examples, and black toner are prepared and a color image is formed, the toner particles of the superimposed colors are melted to eliminate the boundary between the toner particles, and sufficient transparency is achieved. The faithful color reproduction can be made possible by obtaining In addition, regarding the charging characteristics, the above-described color reproducibility can be expected since the stable development can be achieved by obtaining a sufficiently stable charge amount that is rich in moisture resistance from the results shown in Table 2.

In addition, not only color images but also monochrome images with black toner, that is, black-and-white images are formed, toners with excellent charging characteristics and fixing characteristics are always stable and faithful regardless of environmental changes. Reproducible images.

Claims (4)

In an electrophotographic toner comprising toner base particles containing at least a binder resin, a colorant, a charge control agent, and a wax, and an external additive,
The binder resin is a polyester resin obtained by reacting an aromatic alcohol component, and has an acid value of 4 to 31 mgKOH / g,
The charge control agent has a salt structure composed of alkaline bentonite and an organic cation, the volume average particle diameter D ₅₀ is 2 to 9 μm, and the addition amount is 0.4 to 6% by weight,
The external additive includes metatitanic acid hydrophobized, the hydrophobizing agent is alkoxysilane, the volume average particle size of metatitanic acid is 25 to 55 nm, and the amount of metatitanic acid added is 0.2 to 2 An electrophotographic toner characterized by being 2% by weight. In an electrophotographic toner comprising toner base particles containing at least a binder resin, a colorant, a charge control agent, and a wax, and an external additive,
The binder resin is a polyester resin obtained by reacting an aromatic alcohol component, and has an acid value of 5 to 28 mgKOH / g,
The charge control agent has a salt structure composed of alkaline bentonite and an organic cation, the volume average particle diameter D ₅₀ is 2 to 7 μm, and the addition amount is 0.6 to 4% by weight,
The external additive includes metatitanic acid hydrophobized, the hydrophobizing agent is alkoxysilane, the volume average particle size of metatitanic acid is 30 to 50 nm, and the amount of metatitanic acid added is 0.3 to 2 An electrophotographic toner, characterized in that it is in weight percent.   The electrophotographic toner according to claim 1, wherein the external additive further contains hydrophobized silica.   The electrophotographic toner according to claim 1, wherein the colorant is added in an amount of 2 to 20% by weight.