JP2000147830A - Production of toner for developing electrostatic charge image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily attain uniform dispersion of the constituent materials of a toner, to impart necessary characteristics to separate toner particles and to simplify production by working the constituent materials in the form of a film whose thickness is almost equal to the average particle diameter of the toner and comminuting the resultant filmlike formed body. SOLUTION: The constituent materials of a toner such as a binder resin, a magnetic powder and an electric charge controlling agent are diluted and dispersed in a solvent in an appropriate ratio. The surface of a substrate such as a polyethylene terephthalate substrate is coated with the prepared dispersion by dip coating or other method in the form of a film whose thickness A is almost equal to the average particle diameter of the toner. After coating and drying, resultant filmlike formed body 1 is converted into particles by comminution and classification. An additive is then added and post-treatment such as rounding is carried out to obtain the objective toner. The toner is easily made uniform in particle diameter and powdering is very easy because the filmlike formed body 1 is a thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a toner for developing an electrostatic image used in a copying machine, a printer, a facsimile or the like to which an electrophotographic system is applied.

[0002]

2. Description of the Related Art Conventionally, a developing means, to which a conductive magnetic toner is supplied, is arranged in contact with a photosensitive drum having a transparent electrode layer and a photoconductive layer formed on a transparent support in this order via the toner layer. There is a recording method called a back-exposure electrophotographic recording process in which exposure is performed from the back while applying a developing bias (see JP-A-5-6060). The developing means includes a magnetic roller and a non-magnetic conductive sleeve, and conveys toner by rotation of the sleeve. In addition, a developing bias is applied between the conductive sleeve and the photoconductor. An exposure LED array is arranged inside the photoconductor so as to face the conductive sleeve, and image exposure is performed from the back of the photoconductor. The transfer section performs transfer by a roller to which a voltage having a polarity opposite to that of the toner is applied.

In the recording process, when the photoconductor and the toner layer come into contact with each other, electric charges are injected into the surface of the photoconductor via the conductive magnetic toner. When image exposure is performed immediately before the photoconductor is separated from the toner layer, the photocarrier moves to the photoconductor surface, neutralizes the surface charge of the photoconductor, and becomes almost zero potential.
The toner injected into the portion where the charge has been removed adheres to the surface of the photoreceptor by electrostatic force. Since the attached toner immediately separates from the conductive sleeve, there is no time to contact and charge the surface of the photoreceptor via the toner layer, and the electrostatic force of the attached toner remains on the surface of the photoreceptor while being strong. However, since the conductive magnetic toner is used, there is a disadvantage that the charge of the toner leaks during the electrostatic transfer, the transfer efficiency is deteriorated, and the image is easily blurred. Therefore, Japanese Patent Application Laid-Open No. 4-349471 discloses a method of using a conductive magnetic toner in which conductive particles have insulating portions in the form of islands,
It has been proposed to use a conductive magnetic toner having a conductive portion.

[0004]

Incidentally, this type of toner for developing an electrostatic image has conventionally been disclosed in Japanese Patent Application Laid-Open No. 5-34668.
5, as described in JP-A-7-104510, etc., it has generally been produced by a pulverization method. The pulverization method comprises a melt kneading step of melting and kneading necessary materials constituting the toner, a pulverizing step of pulverizing the kneaded material obtained in the melt kneading step, and a classification step of classifying the pulverized material obtained in the pulverizing step. is there. However, according to the pulverization method, it is extremely difficult to uniformly disperse the necessary materials constituting the toner, and there is a problem that it is very difficult to give each toner particle the required constant characteristics. Incidentally, it is particularly difficult to manufacture a functional toner having a certain amount of the above-described high resistance (insulating) portion and low resistance (conductive) portion. From the viewpoint of imparting certain characteristics, a suspension polymerization method has been proposed (JP-A-7-72659, JP-A-8-264853).
Is not advantageous in terms of manufacturing costs.

[0005] The present invention has been made in view of such a background, and it is easy to uniformly disperse the toner constituent materials, and individual toner particles can be easily provided with necessary characteristics. It is an object of the present invention to obtain a toner production method that is advantageous in terms of production cost.

[0006]

According to the present invention, first, the material constituting the toner is processed into a film having a thickness approximately equal to the average particle diameter of the toner, and the resulting film is formed. And a method for producing a toner for developing an electrostatic image, characterized by pulverizing an object.

Secondly, in the method for producing a toner for developing an electrostatic image according to the first aspect, the film-like product is composed of a plurality of layers having different characteristics. A manufacturing method is provided.

Thirdly, in the method for producing a toner for developing an electrostatic charge image according to the second aspect, the plurality of layers having different characteristics are formed of a laminate of two or more layers. A method for manufacturing a toner is provided.

Fourth, in the method for producing a toner for developing an electrostatic image described in the second aspect, the plurality of layers having different characteristics are layers formed by one coating step. A method for manufacturing a toner for developing a charge image is provided.

Fifth, in the method for producing a toner for developing an electrostatic image described in the second, third or fourth aspect, at least one of the plurality of layers having different characteristics has a low electric resistance. A method for producing a toner for developing an electrostatic image, characterized by comprising:

Sixth, in the method for producing an electrostatic image developing toner according to the second, third or fourth aspect, at least one of the plurality of layers having different characteristics has magnetic characteristics. The present invention provides a method for producing an electrostatic image developing toner.

Hereinafter, the present invention will be described in detail. As described above, the method for producing a toner for developing an electrostatic image according to the present invention is characterized in that the material constituting the toner is processed into a film having a thickness approximately equal to the average particle diameter of the toner, and the resulting film-like product is obtained. Is to be crushed. According to this, the film is formed into a film having a thickness approximately equal to the average particle size of the toner, so that the particle size of the toner is easily made uniform. Powdering is very easy to obtain as a powder.

Further, by forming the above-mentioned film-shaped product into a plurality of layers having different properties, for example, the conductivity, insulation,
It is easy to impart properties such as magnetic and non-magnetic properties to the toner in a localized manner, and it is easy to manufacture each layer with a uniform thickness, so that the properties of individual toners can be made constant. As the plurality of layers, a film-like product may be used as a laminate, or a plurality of layers having different characteristics may be formed in one application step. In the case of one time, the production is naturally simple.

Further, by forming at least one of the plurality of layers as a layer having an electrically low resistance, a toner having a low resistance portion and a high resistance portion partially can be easily obtained. According to such a toner, it is possible to secure the developing characteristics with little edge effect by utilizing the low resistance in the developing portion, and to provide the charging and developing functions in the recording process by the above-described back exposure method. Furthermore, in the transfer section of the recording process, it is possible to easily manufacture a toner that can exhibit characteristics such as enhancing transfer efficiency by utilizing high resistance.

Further, by making at least one of the plurality of layers a layer having magnetism, individual magnetic characteristics of the magnetic toner can be easily made constant.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a method for producing a toner of the present invention in which a toner composition is formed into a film and pulverized will be described by taking a monochrome (black) magnetic toner as an example for convenience of explanation. FIG. 1 shows a process of forming a toner. As a material constituting the toner, a binder resin, magnetic powder, a charge controlling agent, and the like are diluted and dispersed in a solvent at an appropriate ratio, and dip coating, spray coating, doctor blade coating, etc. And the like, is applied to a film having a thickness approximately the same as the average particle size of the toner, dried, and then granulated by a known pulverization method / classification method. Thereafter, if necessary, post-processing such as addition of an additive and rounding is performed to obtain a toner. FIG. 2 is a conceptual diagram of a line cut by pulverization. Generally, the average particle size of the toner is selected to be about 5 to 20 μm. Therefore, the thickness of the film is also set in this range.

The binder resin is appropriately selected according to the fixing method. For example, in the case of the heat roll fixing method, a polyester resin, an epoxy resin, a polyol resin, a styrene / acrylic copolymer, and a styrene / butadiene copolymer are used. A combined resin and a mixed resin thereof are used.

As the magnetic powder, alloys or compounds containing ferromagnetic elements such as iron, cobalt and nickel, such as ferrite and magnetite, can be used, but the average particle size is 2 μm to be contained in the toner. Less than,
Preferably about 0.03 to 1 μm, more preferably about 0.05 to 0.6 μm, and more preferably 0.1 to 1 μm.
Those having a thickness of about 0.4 μm are preferable. The amount contained in the toner is about 10 to 200% by weight, preferably about 20 to 170% by weight, more preferably 30 to 15% by weight of the total weight of the resin.
It is about 0% by weight.

As the charge control agent, known dyes or pigments can be used. For example, a nigrosine dye having a positive triboelectric charge or a nigrosine dye modified with a higher fatty acid, a metal-containing (Cr) azo dye having a negative triboelectric charge, or the like can be used. Although the content of the charge control agent varies depending on the charge amount of the toner, the type of the binder resin, the presence or absence of other additives, the toner production method, and the like, it cannot be uniquely determined, but is preferably from 0.1 to the total weight of the resin. The content is preferably about 10% by weight, more preferably about 0.1 to 5% by weight.

Next, a description will be given of a production method in the case where the above-mentioned film-shaped product is composed of a plurality of layers having different characteristics. FIG.
Shows a case where two layers of film-like products having different properties are laminated as a plurality of layers. As an example of different characteristics, in the case of presence or absence of magnetism, a diluted solution of a binder resin in which magnetic powder is dispersed is applied as a first layer to the substrate surface, dried, and then dried.
As a layer, a diluted solution of a binder resin in which a charge control agent is dispersed is applied on the first layer. Also, as an example of different characteristics, in the case of the presence or absence of conductivity, a diluted solution of a binder resin in which ITO is dispersed is applied to the first layer, and then a diluted solution of the binder resin in which a charge control agent is dispersed is applied to the second layer. Apply.

Next, a method of forming a plurality of layers having different characteristics by a single coating step will be described, as an example, in the presence or absence of magnetism. FIG. 4 shows a film-like product produced by this method. When a diluted solution of a binder resin in which a magnetic powder and a charge control agent are dispersed is applied on a substrate and the solvent is dried over time, the magnetic powder moves in the direction of gravity until the solvent is dried. Magnetic powder will accumulate in the lower layer of the layer. By utilizing this phenomenon, a multilayer structure can be substantially formed in one coating step.

At least one of the plurality of layers having different characteristics described above
When the layer is a layer having low resistance, the above-mentioned ITO is used.
One that applies a diluted solution of a dispersed binder resin or S
iO _TwoLaminate single or multiple conductive layers of film, etc.
May be used. In addition, multiple layers with different characteristics
If at least one of the layers has magnetic properties,
Applying a diluting solvent for binder resin in which solid magnetic powder is dispersed
Can be implemented.

Although the method for producing the toner of the present invention has been mainly described using magnetic toner as an example, it is needless to say that the production method may be a non-magnetic toner and a colorant is added.
As the colorant contained in the toner, magnetic powder or any appropriate pigment or dye is used. Magnetite, ferrite, or the like is used as the magnetic powder. Generally, the content of the colorant is preferably about 2 to 10% by weight of the total weight of the binder resin as an amount necessary for maintaining the image density after fixing. Examples of pigments include carbon black, aniline black, acetylene black, naphthol yellow, hansa yellow, rhodamine lake, alizarin lake, bengala, phthalocyanine blue, indanthrene blue, and the like. .1-20
%, Preferably about 0.2 to 10% by weight. Further, there are azo dyes, anthraquinone type, xanthene type, methine type and the like in the dye, and the content of the dye is preferably about 0.1 to 20% by weight, more preferably 0.3 to 10% by weight of the total weight of the binder resin. Content is good.

In the above embodiment, the method of manufacturing by solution coating is described, but a method of manufacturing by melt molding such as a T-die method may be used. From the viewpoint of cost, the T-die method is more preferable.

[0025]

The present invention will be described more specifically with reference to the following examples. Example 1 (Melting the high resistance part layer and the low resistance part layer) 100 parts by weight of styrene / acrylic copolymer resin, 6 parts by weight of copper phthalocyanine, 1 part by weight of salicylic acid complex (charge control agent), polypropylene powder (mold release) Agent) A mixture consisting of 1 part by weight was mixed with a Henschel mixer and extruded by a T-die method into a sheet having a thickness of 5 μm (this is referred to as sheet A). Next, 100 parts by weight of a styrene / acrylic copolymer resin and an average particle size of 0.
10 parts by weight of 02 μm ultrafine ITO powder, 6 parts by weight of copper phthalocyanine, and 1 part by weight of polypropylene powder were mixed with a Henschel mixer, and were laminated on the sheet A prepared above while extruding the sheet by the T-die method in the same manner. The laminated laminated sheet having a thickness of 10 μm obtained in this manner was pulverized by a jet mill. Next, hydrophobic silica was added as an external additive to obtain an electrostatic image developing toner having an average particle diameter of 10 μm. The resulting toner has a volume ^{resistivity: 10 5 ~10 6 Ω · cm} , average particle diameter: 10 [mu] m, particle size distribution: a 8 to 12 .mu.m, a low-resistance toner (volume resistivity according to the conventional grinding method: 10 ³ ~10 ⁶ Ω · cm, average particle diameter: 11 [mu] m, particle size distribution: 5 to 20 [mu] m) compared to been able to sharpen the electrical resistance and particle size distribution. The toner was loaded into a back-exposure type experimental machine described in JP-A-5-6060, and an organic photoreceptor (layer thickness: 20 μm), a developing bias voltage: -300 V, and a transfer bias were applied. When an image was formed at a voltage of 200 V, the image density was 1.4 and the transfer efficiency was 10
An image with 0% increase and resolution: 20% increase was obtained.

Example 2 (Solution coating of high resistance layer and low resistance layer) 100 parts by weight of polyester resin, 8 parts by weight of quinacridone, 1 part by weight of tetraphenyl boron compound (charge control agent), polyethylene powder (release agent) 1) A mixture of 1 part by weight and 400 parts by weight of tetrahydrofuran was dispersed in a sand mill for 4 hours.
It was coated on a polyethylene terephthalate film substrate with a wire bar and dried to obtain a coating film having a thickness of 4 μm. A mixture of 100 parts by weight of polyester resin, 8 parts by weight of quinacridone, 10 parts by weight of ultrafine ITO powder having an average particle size of 0.03 μm, 1 part by weight of polyethylene powder and 400 parts by weight of tetrahydrofuran was dispersed by a sand mill for 5 hours. The coating solution was applied with a doctor blade and dried to obtain a sheet-like laminated film having a thickness of 8 μm in a laminated portion. The laminated film thus obtained was peeled from the polyethylene terephthalate substrate, pulverized by a jet mill, and then added with hydrophobic silica to obtain a toner for developing an electrostatic image having an average particle diameter of 8 μm. The resulting toner has a volume resistivity: 1
0 ⁴ to 10 ⁵ Ω · cm, average particle size: 8 μm, particle size distribution: 6
10 μm to 10 μm, and a low-resistance toner by a conventional pulverization method (volume resistivity: 10 ³ to 10 ⁶ Ω · cm, average particle size: 1)
(1 μm, particle size distribution: 5 to 20 μm), the electric resistance and the particle size distribution could be sharpened. Also,
When this toner was loaded into the back exposure type experimental machine used in Example 1 and an image was formed under the same conditions as in Example 1, the image density was 1.4, the transfer efficiency was increased by 80%, and the resolution was increased. A 40% up image was obtained.

Example 3 (Melting part of magnetic part layer and non-magnetic high resistance part layer)
Acrylic copolymer resin 100 parts by weight, average particle size 0.1μ
m of magnetite and 1 part by weight of polypropylene powder were mixed with a Henschel mixer.
A sheet having a thickness of 5 μm was obtained by a die method. 100 parts by weight of styrene / acrylic copolymer resin, 5 parts by weight of carbon black, chromium complex of monoazo dye (charge control agent)
A mixture comprising 1 part by weight of polypropylene powder and 1 part by weight of polypropylene powder was mixed with a Henschel mixer and laminated while being extruded by a T-die method to obtain a sheet having a thickness of 10 μm. The laminated sheet thus obtained was pulverized by a jet mill, and hydrophobic silica was added to obtain an electrostatic image developing toner having an average particle diameter of 10 μm.
The obtained toner had a saturation magnetization of 60 emu / g, an average particle diameter of 10 μm, and a particle size distribution of 8 to 12 μm, and was a low-resistance toner (saturation magnetization: 85 emu / g) by a conventional pulverization method.
g, average particle size: 11 μm, particle size distribution: 5 to 20 μm). Further, when this toner was loaded into the back exposure type experimental machine used in Example 1 and an image was formed under the same conditions as in Example 1, the image density was 1.4 and the transfer efficiency was increased by 80%. Resolution: An image with a 20% increase was obtained.

Example 4 (Solution coating of magnetic part layer and non-magnetic high resistance part layer)
Acrylic copolymer resin 100 parts by weight, average particle size 0.1μ
m, 50 parts by weight of magnetite, 1 part by weight of polypropylene powder, and 400 parts by weight of tetrahydrofuran were dispersed in a sand mill for 10 hours.
It was applied on a 00 μm thick polyethylene terephthalate film substrate and dried to form a 3 μm thick thin film. A mixture of 100 parts by weight of styrene / acrylic copolymer resin, 5 parts by weight of carbon black, 1 part by weight of chlorinated polyester (charge control agent), 1 part by weight of polypropylene powder, and 400 parts by weight of tetrahydrofuran was further mixed with a sand mill. The coating solution dispersed for a time was similarly coated and dried with a wire bar to obtain a 6 μm-thick laminate. After the laminate was separated from the substrate, hydrophobic silica was added and pulverized with a jet mill to obtain a toner for developing an electrostatic image having an average particle diameter of 6 μm. The obtained toner has a saturation magnetization of 70 emu / g,
Average particle size: 6 μm, particle size distribution: 5 to 8 μm, low-resistance toner by a conventional pulverization method (saturation magnetization: 85 emu /
g, average particle size: 11 μm, particle size distribution: 5 to 20 μm). Further, when this toner was loaded into the back exposure type experimental machine used in Example 1 and an image was formed under the same conditions as in Example 1, the image density was 1.3 and the transfer efficiency was increased by 80%. Resolution: An image with a 40% increase was obtained.

[0029]

As described above, in the method for producing a toner according to the first aspect, the material constituting the toner is processed into a film having a thickness approximately equal to the average particle diameter of the toner, and the resulting film is formed. According to this method, the toner is processed into a film having a thickness approximately the same as the average particle diameter of the toner and then crushed. It is easy to manufacture because the product is broken into pieces.

According to a second aspect of the present invention, in the manufacturing method of the first aspect, the film-like product is formed in a plurality of layers having different characteristics. In addition, it is easy to impart characteristics such as magnetic and non-magnetic properties to the toner by being unevenly distributed, and by forming a layer, the thickness can be easily manufactured to be uniform, and individual characteristics of the toner can be kept constant.

In the manufacturing method according to the third aspect, a plurality of layers having different characteristics are formed as a laminate, and the thickness of each layer can be easily manufactured uniformly, and a toner having individual characteristics can be easily obtained. Further, the manufacturing method according to claim 4 is for manufacturing a plurality of layers having different characteristics by a single coating process, and is easy to manufacture.

According to a fifth aspect of the present invention, at least one of the plurality of layers having different characteristics is a layer having a low resistance, and a toner having a low resistance part and a high resistance part partially can be easily prepared. For example, it is possible to secure development characteristics with little edge effect by making use of low resistance in a development part, and to easily obtain a toner having a charging / developing function in a recording process using a backside exposure method.

According to a sixth aspect of the present invention, at least one of the plurality of layers having different characteristics is a layer having magnetic characteristics, and it is easy to obtain a magnetic toner in which each magnetic characteristic is constant.

[Brief description of the drawings]

FIG. 1 is an example of a process chart of a method for producing a toner of the present invention.

FIG. 2 is a conceptual diagram of a cutting line when a film-shaped product is cut by pulverization according to the method for producing a toner of the present invention.

FIG. 3 is a conceptual diagram showing a case where the film-shaped product is a laminate.

FIG. 4 is a conceptual diagram showing a case where the film-shaped product is manufactured by one process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Film-shaped product A Thickness about the same as the average particle diameter of toner 2 Line cut by pulverization 3 For one toner 4 Magnetic powder or conductive particles

Claims (6)

[Claims] 1. A material for developing an electrostatic image, comprising: processing a material constituting a toner into a film having a thickness substantially equal to the average particle diameter of the toner; and pulverizing the obtained film-like product. Manufacturing method of toner. 2. The method for producing a toner for developing an electrostatic image according to claim 1, wherein the film-like product is composed of a plurality of layers having different characteristics. 3. The method for producing a toner for developing an electrostatic charge image according to claim 2, wherein the plurality of layers having different characteristics comprise a laminate of two or more layers. Method. 4. The method for producing a toner for developing an electrostatic image according to claim 2, wherein the plurality of layers having different characteristics are formed by a single coating step. Of manufacturing toner for toner. 5. The method for producing a toner for developing an electrostatic charge image according to claim 2, wherein at least one of the plurality of layers having different characteristics has a low electric resistance. A method for producing a toner for developing a charge image. 6. A method for producing a toner for developing an electrostatic image according to claim 2, wherein at least one of the plurality of layers having different characteristics has magnetic characteristics. Of manufacturing toner for toner.