JP2835961B2 - One-component magnetic toner for electrostatic image development - Google Patents

Description

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

[Prior Art] Conventionally, as electrophotography, U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 (U.S. Pat.No. 3,666,363), and Japanese Patent Publication No. 43-24748 (U.S. Pat. Three
Numerous methods are known, for example, Japanese Patent Application Laid-Open No. 61 (1994). Generally, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means, and then the latent image is developed using a toner or a developer, and if necessary, a transfer material such as paper. After the transfer of the toner image to the toner image, the toner image is fixed by a heat, pressure, pressure and heat roller or a solvent vapor to obtain a copy.
In the case where a step of transferring a toner image is provided, a step for removing residual toner on the photoconductor is usually provided.

A developing method for visualizing an electric latent image using toner is as follows.
For example, the magnetic brush method described in U.S. Pat.No. 2,874,063, the cascade developing method described in U.S. Pat. A method using a conductive magnetic toner described in the specification is known.

Conventionally, fine powders in which a dye or a pigment is dispersed in a natural or synthetic resin have been used as a toner 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 a one-component developer, a magnetic toner containing magnetic particles such as magnetite is used. In the case of a system using a two-component developer, the toner is used by being mixed with carrier particles composed of glass beads, iron powder, ferrite, or resin-coated particles thereof.

In general, these toners need to have uniform chargeability, and in order to achieve this, a positive or negative charge control agent is contained depending on the type of application. Further, if necessary, silica is added for the purpose of imparting fluidity to the toner.

However, in the conventional toner, as the copying is continued, the developing characteristics of the toner are reduced, or the carrier is contaminated by the charge control agent, and the image density is reduced.
There were problems such as fogging. Further, when the toner is left for a long period of time, fogging becomes remarkable.

[Problems to be Solved by the Invention] An object of the present invention is to provide a one-component magnetic toner for developing an electrostatic image, which solves the above-mentioned problems.

That is, an object of the present invention is to provide a one-component magnetic toner for developing an electrostatic image having stable charging properties.

Another object of the present invention is to provide a one-component magnetic toner for developing an electrostatic image, which does not cause a change in image characteristics even when left for a long period of time.

It is another object of the present invention to provide a one-component magnetic toner for developing an electrostatic image, which does not cause a decrease in image density.

Another object of the present invention is to provide a one-component magnetic toner for developing an electrostatic image, which can provide a clear image without fogging.

[Means for Solving the Problem (and Action)] The inventors of the present invention have studied the above-mentioned problems,
It has been found that the charge control agent contained in the toner is closely related to the state of dispersion in the toner. That is, if the dispersion state is poor, the charge control agent is unevenly distributed as the durability increases,
Causes a decrease in concentration. In addition, when silica is added, it is apparently adhered immediately after the addition, but if left for a long period of time, the charge control agent occupies the majority of the toner surface, and the silica adheres where it is not. Since the state is different and the adhesive force to the charge control agent is weak, the silica drops off and the silica is unevenly distributed, which causes fogging. There are various possible causes of these dispersion defects, but the source is that the particle size of the charge control agent is large.
Due to the fact that they are mixed up to 10 microns. When particles larger than the particle size of the toner are present, uniform dispersion cannot be expected in a general pulverization method as a toner production method, and most of the toner particles are occupied by the charge control agent or are released alone. It will be in the state of having done.

In the present invention, in a one-component magnetic toner containing magnetic particles containing at least 10 to 70% by weight of magnetic fine particles based on a binder resin, a charge control agent and magnetic toner particles, and a silica fine particle, the magnetic toner is The following conditions: 5 ≦ B ≦ 20 and A ≦ 0.3 × B [where A represents the volume average particle size (μm) of the charge control agent, and B represents the volume average particle size (μm) of the toner. Wherein the charge controlling agent is a quaternary ammonium compound, a metal complex salt of an organic dye or a monoazo dye, a metal complex salt of salicylic acid,
A compound selected from the group consisting of a metal complex salt of an alkylsalicylic acid, a metal complex salt of a dialkylsalicylic acid and a metal complex salt of a naphthoic acid, wherein the content of particles having a volume diameter of 12.7 μm or more in the particle size distribution of the charge control agent is 1.0 wt%. The present invention provides a one-component magnetic toner for developing an electrostatic image, characterized by the following.

 Hereinafter, the present invention will be described in detail.

The charge control agent used in the toner of the present invention includes, for example, a quaternary ammonium compound and an organic dye, particularly a basic dye and a salt thereof, as a positive charge control agent. Nigrosine base or nigrosine is used. As the negative charge control agent, a metal complex salt of a monoazo dye, a metal complex salt of salicylic acid, alkyl salicylic acid, dialkyl salicylic acid or naphthoic acid is used.

Most of these charge control agents are subjected to a loosening step such as crushing after synthesis to remove giant particles such as aggregates. However, when examining the particle size distribution of these product groups, the distribution is very broad, ranging from several microns to one hundred and several tens of microns. When a toner is manufactured using these charge control agents, the toner is loosened to some extent in the melt-kneading process, but most of the toner is kneaded as it is. When used as an agent, problems such as a decrease in charging ability and fog occur. On the other hand, after crushing, uneven distribution can be prevented by further crushing using a general crusher (for example, a jet mill or the like) or further using a charge control agent obtained by cutting coarse particles with an air classifier or the like. The particle size distribution of the charge control agent is a value measured with a commercially available Coulter Counter TA-II, and the volume average diameter of the charge control agent must be 30% or less of the average toner diameter for development. If it exceeds 30%, the dispersion of the charge control agent becomes worse and uneven distribution occurs. Further, the content of 12.7 μm or more in volume diameter is 1.0 wt% or less, preferably 0.5 wt% or less.
If it exceeds 1.0 wt%, uneven distribution occurs due to poor dispersion.

The volume average particle size of the developing toner is preferably 5 μm or more and 20 μm or less. An interface (manufactured by Nikkaki) and a CX-1 personal computer (manufactured by Canon) that output a number average distribution and a volume average distribution using a Coulter Counter TA-II type (manufactured by Coulter) as a particle size measuring device.
And 1% NaCl using 1st grade sodium chloride
Prepare an aqueous solution. As a measuring method, the above-mentioned electrolytic aqueous solution 100
To 150 ml, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant, and 0.5 to 50 mg of a measurement sample is further added. The electrolytic solution in which the sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the Coulter Counter TA II was used to measure the particle size distribution of 2 to 40 μ particles using a 100 μ aperture as an aperture. Find the volume average distribution and number average distribution.

The measurement of the charge amount was performed by measuring 10 g of toner particles and 90 g of carrier iron powder (eg, EFV200 / 300 manufactured by Nippon Iron Powder Co., Ltd.) having a main particle size of 200 to 300 mesh and not being coated with a resin under the above-described environment. Enough in an aluminum pot with a volume of c (hold in hand and shake up and down approximately 50 times)
Mix and by the usual blow-off method using an aluminum cell with a 400 mesh screen.

Examples of the binder resin of the toner according to the present invention include homopolymers of styrene such as polystyrene and polyvinyltoluene and substituted products thereof; styrene-propylene copolymer, styrene-vinyltoluene copolymer, and styrene-vinylnaphthalene copolymer. Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate-methyl methacrylate Polymer, styrene-ethyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketin copolymer Coalescence, styrene-butadiene copolymer Copolymers, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer, and other styrene-based copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl Butyral, polyacrylic acid resin, rosin, modified rosin, temper resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, paraffin wax, carnauba wax, etc. can be used alone or in combination.

In the toner of the present invention, magnetic fine particles are used as a colorant, a substance which is magnetized by being placed in a magnetic field is used as the magnetic fine particles, and powder of a ferromagnetic metal such as iron, cobalt, nickel or magnetite γ is used. -Fe ₂ O _3, alloys and compounds such as ferrite can be used.

These magnetic fine particles preferably have a BET specific surface area of ^{2 to 20} m ² / g, particularly 2.5 to 12 m ² / g, and a Mohs hardness of 5 to 7 by nitrogen adsorption. The content of the magnetic powder is preferably from 10 to 70% by weight based on the weight of the toner.

Further, the toner according to the present invention has a volume resistivity of 10 ¹⁰ Ω
cm or more is preferable in terms of triboelectric charge and electrostatic transferability. The volume resistivity referred to here is 100 kg / cm ^{2 of} toner.
And applied with an electric field of 100 V / cm, and is defined as a value converted from a current value one minute after the application.

Further, a fluidity-imparting agent, a lubricant, a conductivity-imparting agent, and the like may be added to the toner of the present invention as needed. For example, fine silica powder, polytetrafluoroethylene powder, polyvinylidene fluoride powder, higher fatty acid metal salt, carbon black, conductive tin oxide and the like are used.

In the production of the toner of the present invention, the constituent materials are kneaded well by a heat kneader such as a hot roll, a kneader, an extruder and the like, followed by mechanical pulverization and classification, or by dispersing the materials in a binder resin solution. After that, a method obtained by spray-drying, or a polymerization method in which a predetermined material is mixed with a monomer to constitute the binder resin to form an emulsified turbid liquid and then polymerized to obtain a toner. Method can be applied.

Although the toner of the present invention can be applied to various developing methods, the following developing methods are preferable.

 Here, an example of a developing process to which the present invention can be applied will be described.

 FIG. 1 is a sectional view showing one embodiment of the developing step.

In the figure, the electrostatic image carrier (photosensitive drum) is a photosensitive layer 5
And a conductive substrate 11 and moves in the direction of the arrow. The non-magnetic cylinder as the developer carrier 6 rotates in the developing section so as to advance in the same direction as the surface of the electrostatic image carrier. Inside the non-magnetic cylinder 6, a multi-pole permanent magnet is arranged so as not to rotate. The developer 10 in the developing device 8 is applied on the non-magnetic cylindrical surface,
In addition, triboelectric charges are given to the toner particles by friction between the cylindrical surface and the toner particles. Further, a magnetic doctor blade 9 made of iron is brought close to the cylindrical surface (at an interval of 50 μm to 500 μm).
m), the thickness of the toner layer is reduced (interval of 30 μm to 30 μm) by disposing the multi-pole permanent magnet so as to face one magnetic pole position.
0 μm) and uniformly regulated to form a developer layer thinner than the distance between the electrostatic image holding member and the developing carrier in the developer. By adjusting the rotation speed of the cylinder 6, the surface layer speed and preferably the internal speed of the developer layer are substantially equal to or close to the speed of the electrostatic image holding surface. The opposed magnetic poles may be formed using permanent magnets instead of iron as the magnetic doctor blade 9. Also,
In the developing section, an AC bias or a pulse bias may be applied between the developer carrier 6 and the electrostatic image holding surface by the bias unit 14. This AC bias is f 200 ~ 4,0
00Hz and Vpp should be 500-3,000V.

In this development step, a non-magnetic cylinder 6 containing a multi-pole permanent magnet was used in order to stably hold the one-component magnetic toner on the developer carrier. In order to form the developer layer thinly and uniformly, a doctor blade 9 made of a magnetic thin plate or a permanent magnet is arranged close to the surface of the cylinder 6. When using a magnetic doctor blade like this,
An opposing magnetic pole is formed between the magnetic pole of the permanent magnet included in the developer carrier, and the toner particle chains are forcibly raised between the doctor blade and the developer carrier, and the This is advantageous for restricting the thickness of the developer layer in other portions, for example, the developing portion facing the electrostatic image surface. Further, by applying such a forced movement to the developer, the developer layer becomes more uniform, and a thin and uniform toner layer can be formed. In addition, since the distance between the doctor blade and the sleeve can be set wider, there is also an effect of preventing destruction and aggregation of toner particles. When the toner particles are transferred in the developing portion, the toner particles are transferred to the electrostatic image side due to the electrostatic force of the electrostatic image holding surface and the action of the AC bias or the pulse bias.

Further, instead of the doctor blade 9, an elastic blade formed of an elastic material such as silicone rubber may be used to regulate the layer thickness of the developer layer by pressing and apply the developer on the developer carrier. .

In the image forming apparatus shown in FIG. 1, the photosensitive layer 5 charged by the primary charger 13 is exposed by a predetermined light source to form an electrostatic image. Since the developer according to the present invention has a higher degree of agglomeration than an ordinary negatively chargeable developer, the developer 10 in the developing device 8 is stirred by the stirring rod 9 and supplied to the sleeve one by one. The electrostatic image is developed by a one-component developer on a developer carrier of a developing device 8, and the toner image on the photosensitive layer 5 is corona-transferred to a transferred transfer material 20 by a transfer charger 15. The transfer material 20 having the toner image is
The toner image is separated from the electrostatic image holding member by the fixing roller 12, and is fixed via a separation roller 21 and a conveying roller 18 by a heat and pressure fixing device including a heating roller 16 and a pressure roller 17. After the transfer of the toner image, the remaining toner on the electrostatic image holding member is removed by the cleaning blade 16, and the image forming process is sequentially repeated.

[Examples] Hereinafter, the present invention will be specifically described based on examples. Parts in the examples are parts by weight.

Example 1 As a charge control agent, a chromium complex of a monoazo dye was obtained by a general synthesis method, crushed, and then crushed by a jet mill crusher. Classification was further performed using an air classifier to obtain a fine powder of a charge control agent. The particle size distribution of each of the charge control agents at the time of synthesis, at the time of pulverization, and after classification was measured by a Coulter counter as described above, and the results are as shown in the table below.

A toner was obtained by the following procedure using the charge control agent obtained after the pulverization and classification.

The above components were mixed and melt-kneaded at 160 ° C. in a roll mill. After cooling, the mixture was roughly pulverized with a hammer mill, finely pulverized with a jet mill pulverizer, and then classified using an air classifier to obtain a black fine powder having a volume average diameter of 12.3 μm. To 100 parts of the black fine powder (magnetic toner particles), 0.4 parts of silica fine particles (average diameter: 15 μm) subjected to hydrophobic treatment were added and sufficiently mixed to obtain a magnetic toner. The magnetic toner was evaluated using a page printer.

In the page printer used, the negative charging
Use an OPC photosensitive drum and set the distance between the sleeve and the blade to 2
40 μm and the closest distance between the sleeve and the photosensitive drum is 270
μm, the thickness of the developer layer on the sleeve was 80 μm, and a toner image was formed by a reversal development method while applying an AC bias of 1,500 Vpp, 1,400 Hz and a DC bias of -450 V to the sleeve.

Example 2 A 10.3 μm toner was prepared in the same manner as in Example 1 except that two parts of the chromium di-tert-butylsalicylate was used instead of the chromium complex of the monoazo dye used in Example 1. After classification, the particle size distribution of the used charge control agent was 2.3 μm in number average diameter, 2.9 μm in volume average diameter, and 12.7 μm in volume diameter.
0.2% above, 0% above 16.0μm in volume diameter
Met. The particle size distribution after synthesis was 5.6 μm in number average diameter.
m, volume average diameter 14.3μm, content rate of volume diameter 12.7μm or more
The content was 51.2% with a volume diameter of 16.0 μm or more, 41.2%.

The toner thus obtained was evaluated using the same page printer as in Example-1.

Comparative Example 1 The charge control agent used in Example 1 was used without pulverization and classification after pulverization, and a toner was obtained and evaluated in the same manner as in Example 1.

Comparative Example-2 The charge control agent used in Example 2 was not pulverized and classified,
The toner was used as it was after the synthesis, and a toner was obtained and evaluated in the same manner as in Example-2.

Example 3 Nigrosine pulverized and classified as a positive charge control agent was used to obtain a 15.2 μm toner of the following components in the same procedure as in Example 1.

The toner was evaluated using a Canon copier NP-150Z.

Comparative Example 3 A 10.8 μm toner was obtained in the same manner as in Example 3. This toner does not satisfy the relationship of A ≦ 0.3 × B.

The results of image evaluation of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in the following table.

[Effects of the Invention] As described above, by using a charge control agent from which fine and coarse particles have been removed by pulverization and classification, stable chargeability can be obtained, clear images without fog can be obtained, and durability can be obtained. There are advantages such as improvement in

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment of an image forming apparatus to which the present invention can be applied. 5 photosensitive layer 6 sleeve 10 developer 12 separation belt 14 bias applying means 16 heating roller 17 pressure roller

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Claims (3)

(57) [Claims] 1. A one-component magnetic toner comprising: magnetic toner particles containing at least 10 to 70% by weight of magnetic fine particles based on a binder resin, a charge control agent and magnetic toner particles; and silica fine particles. Is the following condition: 5 ≦ B ≦ 20 and A ≦ 0.3 × B [wherein, A represents the volume average particle size (μm) of the charge control agent, and B represents the volume average particle size (μm) of the toner. Wherein the charge controlling agent is a quaternary ammonium compound, a metal complex salt of an organic dye or a monoazo dye, a metal complex salt of salicylic acid,
A compound selected from the group consisting of a metal complex salt of an alkylsalicylic acid, a metal complex salt of a dialkylsalicylic acid and a metal complex salt of a naphthoic acid, wherein the content of particles having a volume diameter of 12.7 μm or more in the particle size distribution of the charge control agent is 1.0 wt%. A one-component magnetic toner for developing an electrostatic charge image, comprising: 2. The one-component magnetic toner for developing an electrostatic image according to claim 1, wherein the organic dye is nigrosine base or nigrosine. 3. The one-component magnetic toner for developing an electrostatic image according to claim 1, wherein the organic dye is a basic dye or a salt thereof.