JP2782216B2 - Toner for developing electrostatic images - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel toner for developing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing, and the like.

[Related Art] Conventionally, development methods applied to electrophotography and the like are roughly classified into dry development methods and wet development methods. The former is further divided into a method using a two-component developer and a method using a one-component developer. Among the two-component developing methods, there are a magnet brush method using an iron powder carrier, a cascade method using a bead carrier, a fur brush method using a fur, and the like, depending on the type of the carrier for transporting the toner.

In addition, those belonging to the one-component developing method include a powder cloud method in which toner particles are used in a spray state, and a contact developing method in which toner particles are brought into direct contact with an electrostatic latent image surface for development (contact development or toner development). Jumping development method in which the toner particles are charged and fly toward the latent image surface by an electric field of the electrostatic latent image without bringing the toner particles into direct contact with the electrostatic latent image surface, magnetic conductivity There is a magnedry method or the like in which a toner is brought into contact with an electrostatic latent image surface and developed.

Conventionally, fine powders obtained by dispersing dyes and pigments in natural or synthetic resins have been used as toners applied to these developing methods. For example, particles obtained by finely pulverizing a dispersion of a colorant in a binder resin such as polystyrene to about 1 to 30 μm are used as toner. As the magnetic toner, a toner containing magnetic particles such as magnetite instead of or in addition to the dye or pigment described above is used. In the case of a system using a so-called two-component developer, the above-mentioned toner is usually used by being mixed with carrier particles such as glass beads and iron powder.

Further, the toner is given a positive or negative charge in advance according to the polarity of the electrostatic latent image to be developed.

In order to impart electric charge to the toner, it is possible to use only the frictional charging property of the resin which is a component of the toner,
In this method, the chargeability of the toner is small, so that the image obtained by development is easily fogged and unclear. Therefore, in order to impart a desired frictional charging property to the toner, a charge control agent such as a dye or a pigment for enhancing the charging property is added.

Today, charge control agents known in the art include nigrosine dyes, azine dyes (JP-B-42-1627), metal complex salts of monoazo dyes, metal complex salts of salicylic acid, naphthoic acid, and dicarboxylic acid. And copper phthalocyanine pigments. Many of these charge control agents are derived from dyes and pigments, generally have a complicated structure, and many of them have strong coloring properties. Therefore, when these charge control agents are used in a color toner, the color clarity of the toner is impaired.

Also, recently proposed colorless or light-colored charge control agents include quaternary ammonium salts such as tributylbenzylammonium hydroxynaphthylsulfonic acid, organic tin oxides such as dibutyltin oxide, and the like.
Alternatively, there are polyamines such as a vinyl polymer containing an amino group and a condensation polymer containing an amino group. However, many of these charge control agents are hydrophilic, and the amount of triboelectric charge is reduced particularly under high humidity conditions. On the other hand, when the amount of triboelectric charge does not decrease under high humidity conditions, the amount of triboelectric charge abnormally increases under low humidity conditions. When a toner containing a charge control agent whose frictional charge is remarkably fluctuated by humidity is used, the image quality changes due to changes in temperature and humidity, and it is extremely difficult to always provide good quality images. .

By the way, in addition to conventional cadmium sulfide etc. as a photoreceptor for copying machines and printers using an electrophotographic method, an amorphous silicon photoreceptor having high durability and capable of obtaining a clear image for a medium speed copying machine. Is used. Due to the nature of these photoconductors, a toner having a negative chargeability is required for development. In addition, even if organic photoconductors are increasing due to reasons such as ease of production, low cost, and harmlessness, high performance negative toners will be produced due to the increase in laser beam type copiers and printers using reversal development. is necessary. In addition, along with the colorization of copying, a color toner which has good color reproducibility and gives a clear color image is required.

Recently, the number of copies has increased with the increase in the amount of information in offices, and the copying speed of copying machines has inevitably tended to increase. Accordingly, the charging characteristics of the toner are required to be different from those of the conventional toner for a medium-speed copying machine.

At present, negative chargeable charge control agents are listed in JP-B-63-1994.
And metal complexes of monoazo dyes as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2000-209, and the like. This metal complex has excellent characteristics among conventionally proposed charge control agents in terms of imparting charge to toner particles. However, one of its essential defects is that it is a colored substance and cannot be used for color toners that require vivid colors.

JP-A-62-262055 and the like disclose a metal complex having salicylic acid as a ligand. This salicylic acid metal complex is an excellent charge control agent which exhibits high negative chargeability and is colorless or pale enough to be regarded as substantially colorless and can be used in color toners.

However, in a high-speed machine, the charging ability by a machine is increased as compared with a conventional medium-speed machine. When a conventional salicylic acid metal complex-containing toner is used, the charge amount is too high under a low temperature and a low humidity, and a phenomenon of causing a decrease in the density may occur. Therefore, by lowering the charge amount of the entire toner to make the charge amount under low temperature and low humidity an appropriate amount,
The charge amount under high humidity is reduced, the image density is reduced, and fogging may occur.

As described above, the speed of copying increases the temperature of the toner charge amount.
More strict conditions are required for the humidity dependency than before, and the temperature / humidity dependency of the chargeability of the charge control agent is also strict.

For these reasons, there is a strong demand in the art for the development of a light-colored negatively chargeable charge control agent that has a low humidity dependence of the triboelectric charge amount and can be considered colorless or substantially colorless.

[Problem to be Solved by the Invention] An object of the present invention is to provide a new technique for controlling the charge of a toner, which has solved the above-mentioned problems.

It is an object of the present invention to stabilize the amount of triboelectric charge between toner particles, between a toner and a carrier, between a toner and a toner carrier such as a sleeve in the case of one-component development, without being affected by changes in temperature and humidity. Another object of the present invention is to provide a developer capable of reproducing a stable image which is hardly affected by changes in environmental conditions.

An object of the present invention is to provide a vivid chromatic developer.

Means and Action for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have at least an alkyl group as a substituent that is light enough to be considered colorless or substantially colorless. The present inventors have found that salicylic acid having a molecular weight of 251 or more has a sufficient negative chargeability and has a sufficient triboelectric charge amount even under high humidity conditions, and has reached the present invention.

That is, the present invention relates to a toner for developing an electrostatic image, comprising salicylic acid having a molecular weight of at least 251 and having at least an alkyl group as a substituent.

The negative charging performance of salicylic acid differs depending on the type of the substituent, and in order to improve the negative charging performance, salicylic acid having at least an alkyl group introduced as a substituent is preferable.

Examples of the substituent that can be used together with the alkyl group of salicylic acid include an aryl group, an alkoxy group, an aryloxy group, an amino group, an acyloxy group, an acylamide group, a vinyl group, a carbonyl group, a hydroxy group, an alkylthioxy group, an arylthioxy group, Sulfinyl group, sulfonyl group, halogeno group, nitro group, cyano group, sulfoxy group,
And carboxy groups, which may have a substituent.

The position of the substituent in the benzene skeleton of salicylic acid is not uniquely limited, but it is more preferable to arrange an electron donating group at the 3- and 5-positions and an electron-withdrawing group at the 4-position.

Considering the high charge-imparting ability and the ease of production, an alkyl group, or an alkyl group, an aryl group,
Salicylic acid having at least one substituent selected from an alkoxy group, an alkoxy group, an amino group, an acyloxy group and an acylamide group is preferred.

Furthermore, considering the thermal stability of the salicylic acid compound, the molecular weight of salicylic acid having at least an alkyl group as a substituent is preferably 251 or more.

The alkyl group preferably has 1 to 24 carbon atoms, and more preferably has 1 to 18 carbon atoms in view of ease of production. In consideration of the charge-imparting ability, it is more preferable that the carbon bonded to the salicylic acid skeleton on the substituent is a quaternary carbon.

Examples of the aryl group include groups having 4 to 18 carbon atoms,
In addition to hydrocarbon rings such as phenyl and naphthyl, substituents having a heterocyclic structure such as pyridyl, thienyl and pyrrolyl are also included. Considering ease of production, carbon number is 6-12.
Groups are preferable, and in consideration of the improvement of the charge-imparting ability, it is more preferable that the substituent has an electron-donating group.

Alkoxy groups and aryloxy groups have 1 to 24 carbon atoms
And may have an electron donating functional group. The aryloxy group also includes a substituent having a heterocyclic structure such as a pyridyl group, a thienyl group, and a pyrrolyl group. A group having 1 to 12 carbon atoms is more preferable in consideration of ease of production.

As the amino group, the substituent is hydrogen, having 1 to 1 carbon atoms.
Those having 22 alkyl groups and aryl groups are mentioned. Considering the improvement of charging ability and easiness in manufacturing, carbon number 1
Up to 6 alkyl groups are preferred.

The acyloxy group and the acylamide group have 1 to 16 carbon atoms.
Groups are preferred. Taking into consideration the ease of production, a carbon number of 1 to 12 is more preferable.

Although the triboelectric charging mechanism of the salicylic acid compound is not always clear, it is considered that the arrangement of the hydroxy group adjacent to the carboxy group on the aromatic ring plays an important role in negative triboelectric charging.

From the demand for charge control agents with good environmental properties, we have investigated the use of salicylic acid compounds, salicylic acid metal complexes, and salicylic acid esters with substituents in terms of water absorption and negative triboelectric chargeability when converted to toner, and images using high-speed machines. The environmental characteristics of the characteristics were studied.

As a result, the salicylic acid esters have low water absorption, but low negative frictional charging ability, and it is difficult to control the toner charge amount.

Further, the salicylic acid metal complex is characterized by having a high negative triboelectric charge, and has been widely used by utilizing this characteristic. However, the water absorption of the metal complex is stronger than that of the corresponding salicylic acid derivative, and therefore, the amount of triboelectricity tends to change due to the increase or decrease in the amount of adsorbed water. Therefore, when a metal complex of salicylic acid is used as a charge controlling agent, the selection or combination of other toner raw materials, for example, a binder resin, a magnetic substance, a dye and a pigment is limited.

On the other hand, with an increase in the speed of a copying machine, a corresponding toner is desired. In this case, the negative triboelectric charge does not need to be as large as the salicylic acid metal complex. Rather, those having low water absorption and low triboelectric charge dependency on the environment are preferable when other toner raw materials are selected. From this point of view, although the triboelectric charge is lower than that of the salicylic acid metal complex, a salicylic acid derivative having less environmental dependency is more preferable. As will be described later in the examples, when a toner containing a salicylic acid derivative was used to obtain an image with a medium / high speed machine (25 sheets A4 / min or more), a clear image with high density was obtained in any environment.

As described above, as a result of examining the dependence of the negative triboelectric chargeability and the charge amount on each environment, the salicylic acid compound having a substituent has a smaller absolute value of the charge amount than the salicylic acid complex, but has a smaller dependence on the environment. As a result, they have found that they are more preferable as a charge control agent used for a toner for a high-speed machine, and have reached the present invention.

Next, specific examples of the salicylic acid compound of the present invention are shown below.

The salicylic acid compound can be produced by a known method. For example, for compound (1), 2-methyl-2-heptanol is first allowed to act on phenol in the presence of sulfuric acid to synthesize 2,4-bis (α, α-dimethylhexyl) phenol.
Next, the target compound (1) is obtained by reacting the 2,4-bis (α, α-dimethylhexyl) phenol with potassium hydroxide in methanol and further reacting carbon dioxide under high temperature and high pressure conditions.

By blending the salicylic acid compound as described above in a toner (colored fine powder) containing a binder resin and a colorant as essential components, the toner of the present invention can be obtained. As a form of compounding, any of a so-called internal addition form in which the toner is included in a uniform or capsule form and a so-called external addition form in which the toner is mixed and adhered to the toner can be adopted.

In the case of internal addition, the amount of the salicylic acid compound used is determined by the type of the binder resin, the presence or absence of additives used as necessary, the toner production method including the dispersion method, and is generally limited. However, it is preferably used in the range of 0.1 to 20 parts by weight (more preferably 0.5 to 10 parts by weight) based on 100 parts by weight of the binder resin.

When externally added, 0.01 parts by weight to 100 parts by weight of resin
~ 10 parts by weight is desirable. As the external addition method, it is particularly preferable to fix by a mechanochemical method.

In addition, if necessary, a conventionally known charge control agent can be used in combination with the charge control agent of the present invention.

As the binder resin for the toner, polystyrene, poly-p
-Homopolymer of styrene such as chlorostyrene and polyvinyltoluene and a substituted product thereof; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer , Styrene-methyl acrylate copolymer,
Styrene-acrylic copolymers such as styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-acrylic acid 2-ethylhexyl copolymer, and styrene-methacrylic acid Methyl copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-
Vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene- Styrene copolymers such as maleic acid copolymer and styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin , Polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin,
Phenol resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes, etc., can be used alone or in combination.

In particular, the following binder resins can be used alone or in combination as a binder resin suitable for providing a toner suitable for pressure fixing.

Polyolefin (low molecular weight polyethylene, low molecular weight polypropylene, polyethylene oxide, polytetrafluoroethylene, etc.), epoxy resin, polyester resin, styrene-butadiene copolymer (monomer ratio: 5-30: 95-70),
Olefin copolymer (ethylene-acrylic acid copolymer,
Ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-vinyl acetate copolymer, ionomer resin), polyvinyl pyrrolidone, methyl vinyl ether-maleic anhydride copolymer, Maleic acid-modified phenolic resin, phenol-modified terpene resin.

Coloring agents include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine 6G, lake, calco oil blue, chrome yellow, quinacridone, benzidine yellow, and rose. Conventionally known dyes and pigments, such as bengal, triarylmethane dyes, monoazo and disazo dyes, can be used alone or in combination. The colorant is preferably used in an amount of 1 to 10 parts by weight based on 100 parts by weight of the binder resin. Further, the toner of the present invention can be used as a magnetic toner by further containing a magnetic material. Examples of the magnetic material contained in the magnetic toner of the present invention include iron oxides such as magnetite, maghemite, and ferrite; metals such as iron, cobalt, and nickel; and metals such as aluminum, cobalt, and copper;
Examples include alloys with metals such as lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, and vanadium, and mixtures thereof.

These ferromagnetic materials have an average particle size of about 0.1 to 2 μm, particularly
It is preferably from 0.1 to 1.0 μm, and the amount contained in the toner is about 20 to 200 parts by weight, particularly preferably 40 to 150 parts by weight, based on 100 parts by weight of the resin component.

Further, additives other than those described above may be added to the toner of the present invention as needed. Examples of the additive include a lubricant such as Teflon and zinc stearate; an abrasive such as cerium oxide and silicon carbide; a fluidity imparting agent such as colloidal silica, titanium oxide and aluminum oxide; a caking inhibitor; Conductivity imparting agents such as tin; fixing aids such as low molecular weight polyethylene;
In particular, alkylchlorosilane, alkylaminosilane,
It is preferable that hydrophobic silica treated with alkylalkoxysilane or silicone oil is externally added to the toner.

In order to produce the electrostatic image developing toner according to the present invention,
The salicylic acid compound charge control agent according to the present invention, the binder resin as described above, and a pigment or dye as a colorant, a magnetic material as needed, additives and the like are sufficiently mixed by a ball mill or other mixer. Melting and kneading using a hot kneader such as a heating roll, kneader, extruder, etc. to disperse or disperse the pigments or dyes while the resins are mutually compatible, solidify by cooling, pulverize and classify, A toner having a diameter of 5 to 20 μ can be obtained.
Alternatively, a method in which a material is dispersed in a binder resin solution and then obtained by spray drying, or a method in which a predetermined material is mixed with a monomer to constitute the binder resin to form an emulsion suspension and then polymerized. A polymerization method for obtaining a toner, a method for producing a toner, a method for incorporating a core material and / or a shell material in a so-called microcapsule toner comprising a core material and a shell material, and the like can be applied.

Further, the toner of the present invention can be used as a two-component developer, in which case it is used by mixing with a carrier powder. As the carrier that can be used in the present invention, known carriers can be used, and examples thereof include magnetic powders such as iron powder, ferrite powder, and nickel powder, glass beads, and the like. And the like.

Polystyrene, styrene-
Acrylic ester copolymers, styrene-methacrylic ester copolymers, acrylic resins, silicone resins, fluororesins and the like can be mentioned.

The toner or developer produced by the above method can be used for development for visualizing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing, or the like by a conventionally known means.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples. All parts in the following formulations are parts by weight. The image density is the density after 1000 sheets of the durability test.

Example 1 Salicylic acid compound (1) used in the present invention left for 2 days in each environment, the following salicylic acid compounds (4) and (4)
Was measured for the amount of water absorption of the zinc salicylate complex (A) having the ligand as a ligand. The measurement was performed using a Karl Fischer trace moisture content measuring device.

Example 2 After the above materials were mixed well in a blender, they were kneaded with two rolls heated to 110 ° C. After cooling the kneaded material, the mixture was coarsely pulverized by a cutter mill, pulverized using a fine pulverizer using a jet stream, and further classified using an air classifier to obtain a fine powder having a particle size of 5 to 20 μm. To 100 parts of this fine powder, 0.5 part of dry silica treated with hexamethyldisilazane was externally added by a hesin shell mixer to obtain a toner.

The toner was allowed to stand for 2 days under environmental conditions of 35 ° C./85%, 23 ° C./60%, and 15 ° C./10%, and mixed with an iron powder carrier having a particle size of 50 to 75 μm at a weight ratio of 1/10. After shaking for a minute, the amount of triboelectric charge was measured using a blow-off charge amount measuring device manufactured by Toshiba Chemical Corporation. Table 2 summarizes the measurement results. The charge amount was a sufficient value under each environmental condition.

Next, 100 parts of an acrylic-coated ferrite carrier having an average particle diameter of 70 μm was mixed at a ratio of 5 parts of the toner to prepare a developer. Next, a commercially available Canon copier (trade name)
(NP6650; 50 sheets A4 / min), and the image test was performed. The image obtained under the environmental conditions of 23 ° C./60% exhibited a bright blue color, a high density of 1.30, and a good image without fog was obtained. Environmental conditions are 35 ℃ / 85%, 15 ℃
A good image was obtained even when it was changed to / 10%. These results are summarized in Table 3.

Comparative Example 1 A toner fine powder was prepared in the same manner as in Example 2, except that 4 parts of the compound (1) was changed to 7 parts of the compound (4). Next, the amount of triboelectric charge was measured in the same manner, and an image test was performed. As shown in Table 3, the image density under a high humidity environment was slightly lower than that of the toner of Example 2.

Comparative Example 2 A toner fine powder was prepared in the same manner as in Example 1, except that 4 parts of the compound (1) in Example 1 was replaced with 4 parts of the zinc salicylate complex (A). Next, the amount of triboelectric charge was measured and an image test was performed in the same manner. Good images were obtained under the conditions of 23 ° C / 60% and 35 ° C / 85%, but the charge amount was too high under the condition of 15 ° C / 10%, and the initial density was 1.38. The density dropped to 1.01 on the 1000th sheet.

Example 3 After the above materials were mixed well in a blender, they were kneaded with two rolls heated to 110 ° C. After cooling the kneaded product, the mixture was coarsely pulverized by a cutter mill, pulverized using a fine pulverizer using a jet stream, and further classified using an air classifier to obtain a fine powder having an average particle diameter of 11 μm.

Next, 0.8 parts of hydrophobic silica treated with low molecular weight silicone oil was externally mixed and added to 100 parts of the fine powder with a hesin shell mixer to prepare a toner.

This toner was purchased from a commercially available Canon copier (product name NP665).
When an image test was performed by applying the method to 0), the image density was 1.32 under an environmental condition of 23 ° C./60%, and a clear image without fog was obtained. Even under the conditions of 15 ° C./10% and 35 ° C./85%, the density was as high as 1.35 and 1.30, and good images without fog and scattering were obtained.

Comparative Example 3 A toner was produced in the same manner as in Example 3, except that 10 parts of the compound (6) was replaced with 5 parts of the zinc salicylate complex (A).
When this was subjected to an image test in the same manner, 23 ° C / 60%, 35
Under an environmental condition of ° C./85%, a satisfactory image was obtained at a sufficient image density of 1.40 and 1.32. However, under the condition of 15 ° C and 10%, the initial concentration was 1.25, but the concentration gradually decreased.
After 1000 sheets, it decreased to 1.09.

[Effects of the Invention] As described above, the toner containing the salicylic acid compound of the present invention as a charge control agent has a uniform triboelectric charge between toner particles, and is easy to control the charge amount. Does not cause fog. Further, salicylic acid has a small change in water absorption with respect to a change in humidity, and a toner containing a salicylic acid compound is a toner having an extremely stable triboelectric charge. For this reason, obstacles such as scattering at the time of transfer under high and low humidity and omission of transfer are eliminated.

Further, since the charge control agent causes less color hindrance, a color image having excellent color can be formed by using the color toner.

Claims (2)

(57) [Claims] 1. A toner for developing an electrostatic image, comprising salicylic acid having a molecular weight of at least 251 and having at least an alkyl group as a substituent. 2. The toner according to claim 1, wherein the alkyl group has 24 or less carbon atoms.