JPH03290672A - Toner - Google Patents

Abstract

PURPOSE:To enable the stable formation of images having a high resolution and high image quality many times without entailing cleaning defects by specifying the BET specific surface area and volume average grain size of colored particles obtd. by granulation and polymn. to specific ranges. CONSTITUTION:At least polymerizable monomers, such as styrene and n-butyl methacrylate, and coloring agents, such as carbon black, and if necessary, polypropylene wax, etc., are made to exist in an aq. medium and the mixture is granulated and polymerized to form the colored particles. The BET specific surface area of the particles is specified to 2 to 4m<2>/g and the volume average grain size thereof to 2 to 8mum, by which the cleanability of the toner is improved and the images having the high resolution and the high image quality are formed. The image density is liable to be low if the grain size is smaller than the above-mentioned range. The resolution is low if the grain size is too large. The cleanability is additionally improved if an inog. oxide is added and mixed at 0.5 to 5wt.% ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a toner used for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like.

[Conventional technology]

In an example of electrophotography, an electrostatic charge image is formed on an image carrier by charging and exposure, this electrostatic charge image is developed with a developer containing toner to form a toner image, and then this toner image is The image is transferred to a transfer material and fixed to form a visible image.

On the other hand, toner remaining on the image carrier without being transferred to the transfer material is preferably cleaned by a cleaning member such as a blade that is placed in pressure contact with the surface of the image carrier.

A so-called pulverization method is known as a method for producing toner constituting a developer. This pulverization method is a method in which a colorant and other additives used as necessary are added to a thermoplastic resin as a binder, the mixture is melted and kneaded, and then pulverized and classified to produce a toner.

However, the toner obtained by the pulverization method generally has a wide particle size distribution, and therefore has the disadvantage that the triboelectric charging properties of the toner are uneven and fogging is likely to occur. Furthermore, due to production efficiency issues, it is difficult to obtain toner with a small volume average particle size of 2 to 8 μm, and therefore, there is a problem that the demand for high image quality cannot be met.

Under these circumstances, in recent years, the application of granulation polymerization has been considered. 20 Granulation polymerization method is a method of manufacturing toner by granulation polymerization of a composition containing a polymerizable monomer for forming a resin as a binder and additives such as a colorant. (Unexamined Japanese Patent Publication No. 110945-1
Publication No. 10951, JP-A-61-255353-25
Publication No. 5357, JP-A-58-50544-5054
Publication No. 5, etc.).

According to this granulation polymerization method, it is possible to produce a toner having a small volume average particle diameter of 2 to 8 μm, and there is an advantage that the toner has a narrow particle size distribution. Moreover, since expensive equipment such as a jet crusher is not required, it is also possible to reduce production costs.

[Problems to be Solved by the Invention] However, in the toner obtained by the granulation polymerization method, surface tension acts during the polymerization process, so the sphericity of the particles becomes high. There is a problem in that it is difficult to clean the remaining toner with a blade, which is preferable as a cleaning means.

An object of the present invention is to provide a toner that can stably form high-resolution, high-quality images many times without causing cleaning failures.

[Means to solve the problem]

In order to achieve the above object, the present inventor has conducted extensive research and found that the BET specific surface area of the toner is a factor that greatly influences the cleaning performance, and by defining this BET specific surface area within a specific range, The present invention was completed by discovering that the cleaning properties of toner obtained by particle polymerization are also significantly improved.

That is, the toner of the present invention is a toner made of colored particles obtained by granulation polymerization in the presence of at least a polymerizable monomer and a colorant in an aqueous medium,
Specific surface area is 2~4m''/g, volume average particle size is 2~8μ
A configuration in which m is adopted.

In the above toner, it is preferable that wax is further present in the aqueous medium.

It is preferable that an inorganic oxide is further added to the above toner in a proportion of 0.5 to 5% by weight.

[Effect]

With a toner having a volume average particle diameter of 2 to 8 μm, a high-quality image with high resolution can be obtained.

However, since the toner obtained by the granulation polymerization method has high sphericity, poor cleaning may occur, but in the present invention, the toner has a BET specific surface area of 2 to 4 m'7 g.
Therefore, cleaning performance is greatly improved.

Further, when wax is further present in the aqueous medium, the fixing properties of the toner are improved.

Furthermore, when a predetermined proportion of an inorganic oxide is added and mixed into the toner from the outside, the cleaning performance is further improved.

[Specific explanation of configuration]

Hereinafter, the configuration of the present invention will be specifically explained.

As described above, the toner of the present invention is colored particles obtained by granulation polymerization in which at least a polymerizable monomer, a colorant, and optionally a wax are present in an aqueous medium. The BET specific surface area is 2 to 4 m27 g
, preferably 2.5 to 3 m2/g, with a volume average particle size of 2
~8 μm.

In addition, 0.5 to 5% by weight of an inorganic oxide is added to the colored particles.
The toner may be constituted by adding and mixing them at a ratio of .

Here, the volume average particle diameter is determined using a laser diffraction particle size distribution analyzer rHELO3 (distributor: JEOL ■).
This is a value measured by a method using laser light scattering.

BET specific surface area is determined by “Flowsorb I” manufactured by Shimadzu Corporation.
This is a value measured without heating using a "Model I 2300".

If the BET specific surface area of the toner is between 2 and b, the cleaning properties of the toner will be significantly improved even though it is a small-diameter toner obtained by granulation polymerization. On the other hand, when the BET specific surface area is less than 2 m2/g, poor cleaning is likely to occur, while when it exceeds 4 m2/g, it is difficult to manufacture and the environment dependence increases.

If the volume average particle diameter of the toner is in the range of 2 to 8 μm, it is possible to form an image with high resolution and high quality. On the other hand, when the volume average particle diameter is less than 2 μm, image density tends to decrease and toner scattering tends to occur. On the other hand, when the volume fraction average particle size exceeds 8 μm, resolution tends to decrease.

In the present invention, in order to make the BET specific surface area of the toner within the range of 2 to 4 m''7 g as described above, the following method can be adopted.

(1) A method of forming irregularly shaped secondary polymer particles by associating primary polymer particles during granulation polymerization.

(2) A method in which, during granulation polymerization, a monomer that reacts preferentially with functional groups exposed on the surface of particles that serve as the core of polymerization is dropped to form irregularly shaped polymer particles.

(3) Producing polymerized particles made of the two types of polymers by performing granulation polymerization using polymerizable monomers that will yield two or more types of polymers that are incompatible with each other,
A method in which a post-treatment is then performed to dissolve one of the polymers to form irregularly shaped polymer particles.

The polymerizable monomer used in the toner of the present invention is used to form a resin as a binder of the toner. As such resin, styrene/acrylic resin is preferable.

Polymerizable monomers for obtaining styrene/acrylic resin include styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methylstyrene,
-ethylstyrene, 2,4 dimethylstyrene, pn-
Butylstyrene, p-tert-butylstyrene, p-
n-hexylstyrene, p-n-octylstyrene, p
-n-nonylstyrene, p-n-decylstyrene, p-
Styrenic monomers such as n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, methyl acrylate,
Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodenyl acrylate, urinoheacrylate 2-ethylhexynopea acrylate, stearyl acrylate, 2-chloroethyl acrylate , phenyl acrylate, α-methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, propinope methacrylate n-
α of butinope methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, pheninope methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc. Examples include acrylic monomers such as methylene aliphatic monocarboxylic acid esters, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide.

These monomers may be used in combination as appropriate.

When producing styrene/acrylic resin by granulation polymerization in an aqueous medium using the above polymerizable monomers, the polymerization initiator is 0.5 to 10% by weight based on the polymerizable monomers. It may be used within the range of As such a polymerization initiator, a peroxide initiator, an azo initiator, etc. can be used.

Coloring agents to be present in the aqueous medium together with the above polymerizable monomers include carbon black, nigrosine dye, aniline blue, calco oil blue chrome yellow, ultramarine blue, DuPont oil red, Orient oil red #330, quinoline yellow. , methylene blue chloride, phthalocyanine blue, malachite green offsalate, lamp black, rose bengal, oil black, azo oil black and the like. The surface of these colorants may be treated with a silane coupling agent or the like, or may be grafted.

Other toner components, such as wax, may be present in the aqueous medium, if necessary.

Examples of the wax include low molecular weight polyolefin waxes such as polyethylene and polypropylene, paraffin waxes, fatty acid ester waxes, fatty acid amide waxes, and the like.

As the granulation polymerization method, a suspension polymerization method can be preferably used. In this suspension polymerization method, the polymerization composition is dispersed and suspended in an aqueous medium as dispersed particles of a predetermined particle size by mechanical stirring, and polymerization is performed, but as the polymerization progresses, the stickiness of the dispersed particles increases. Therefore, the dispersed particles tend to coalesce excessively and become large in diameter. Therefore, it is preferable to use a suspension stabilizer to prevent excessive coalescence of dispersed particles.

Such suspension stabilizers include water-soluble polymer substances such as gelatin, starch, and polyvinyl alcohol, poorly water-soluble salts such as barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, and calcium phosphate, and these poorly water-soluble salts. Combinations with surfactants such as sodium dodecylbenzenesulfonate and sodium dodenyl sulfate, inorganic polymeric substances such as talc, clay, silicic acid, and diatomaceous materials, and poorly water-soluble inorganic compounds such as metal oxides can be used.

In addition, an ionic substance such as a nitrogen-containing polymerizable monomer, a cationic substance or anionic substance such as poorly water-soluble amines is present in the aqueous medium, and when dispersed in the aqueous medium, the dispersed particles In the case of being charged to either positive or negative polarity, an ionic dispersant that is charged to the opposite polarity when dispersed in an aqueous medium, such as negatively charged colloidal silica, positively charged colloidal silica, etc. aluminum oxide, etc. can be effectively used as a suspension stabilizer.

Next, an example of manufacturing the toner of the present invention by applying the suspension polymerization method will be described.

First, a polymerizable monomer, wax, polymerization initiator, etc. are thoroughly mixed using a Santo Starr or the like to prepare a polymerization composition. This polymerization composition is added to an aqueous medium containing a suspension stabilizer, suspended and dispersed using a high-speed stirrer such as a homojetter, and maintained at a predetermined temperature condition to form the first suspension dispersion. Prepare.

On the other hand, a second suspension dispersion liquid is prepared by suspending and dispersing a coloring agent such as carbon black into a polymerization composition similar to that described above dispersed in an aqueous medium.

This second suspension and dispersion is gradually dropped into the first suspension and dispersion, and a certain amount of a coloring agent such as carbon black is used as a core, and a polymerizable monomer is added to the functional group on the surface. The polymerization reaction is carried out while preferentially precipitating and growing the body.

The polymer particles thus obtained are colored particles containing a coloring agent therein, and their surfaces are appropriately shaped. The degree of irregularity can be controlled by adjusting the polymerization time, etc., so BET
The specific surface area can be easily defined in the range of 2 to 4 m2/g.

In addition, the particle size of the polymer particles can be determined depending on the suspension and dispersion state of the polymerization composition, so by adjusting the dispersion conditions, polymer particles with a body average particle size of 2 to 8 μm can be easily obtained. be able to.

In the present invention, the toner may be composed only of the colored particles obtained as described above, but the toner may be formed by further adding and mixing an inorganic oxide to the colored particles at a ratio of 0.5 to 5% by weight. It is preferable to configure. By adding this a-free oxide, the cleaning properties of the toner can be further improved. As such inorganic oxides, fine particles of silica, aluminum oxide, titanium oxide, etc. can be used.

Further, the toner may be constituted by further adding and mixing other external additives to the colored particles. Other external additives include carbide particles, nitride particles, silicone resin particles, acrylic resin particles, fatty acids such as stearic acid, fatty acid metal salts, and the like.

〔Example〕

Examples of the present invention will be described below along with comparative examples, but the embodiments of the present invention are not limited to these Examples. In addition, in the following, "1 part" represents "part by weight".

<Example 1> Styrene 80 parts n-butyl methacrylate 20 parts Polypropylene wax 10 parts 2.2°-Azobis(2
,4-dimethylvaleronitrile)
A composition for polymerization was prepared by thoroughly mixing two or more parts of the materials using a Santo Starrer. This polymerization composition is added to an aqueous medium containing a suspension stabilizer, suspended and dispersed using a homojetter, and maintained at a temperature of 40 to 50°C to form a first suspension dispersion fl). ill! did.

On the other hand, a second suspension dispersion was prepared by suspending and dispersing 112 parts of the same polymerization composition as above and 10 parts of carbon black in an aqueous medium containing a suspension stabilizer using a homojetter. . This second suspension and dispersion is gradually dropped into the first suspension and dispersion to preferentially precipitate the polymerizable monomer on the functional groups on the surface of a certain amount of carbon black. The polymerization reaction was carried out for 30 hours while growing.

Thereafter, the reaction solution was filtered to collect solid matter, which was washed and dried to produce a toner made of colored particles. The BET specific surface area of this toner is 3.03 m"
/g, and the volume average particle size was 5.5 μm.

Comparative Example 1 Styrene 80 parts n-butyl methacrylate 20 parts Carbon black 10 parts Polypropylene wax 10 parts 2.2°-Azobis(2,4-
dimethylvaleronitrile)
A composition for polymerization was prepared by thoroughly mixing two or more parts of the materials using a Santo Starrer. This polymerization composition is
It is added to an aqueous medium containing a suspension stabilizer, suspended and dispersed using a homojetter, and maintained at a temperature of 40 to 50°C.
The polymerization reaction was carried out for 0 hours.

Thereafter, the reaction solution was filtered to collect solid matter, which was washed and dried to produce a comparative toner consisting of perfectly spherical colored particles. The BET specific surface area of this comparative toner is 1.50 m'/g, and the volume average particle diameter is 6.0 μm.
Met.

<Example 2> Styrene 80 parts Lauryl methacrylate 20 parts Polyethylene wax 10 parts 2.2'-azobis(
2,4-dimethylvaleronitrile)
A composition for polymerization was prepared by thoroughly mixing two or more parts of the materials using a Santo Starrer. A toner consisting of colored particles was produced in the same manner as in Example 1 using this polymerization composition. The BET specific surface area of this toner is 2.
At 80 m'/g, the volume average particle size was 7.0 p m.

<Comparative Example 2> Styrene 80 parts Lauryl methacrylate 20 parts Carbon black 10 parts Polyethylene wax
10 parts 2.2°-azobis(2,4-dimethylvaleronitrile)
A composition for polymerization was prepared by thoroughly mixing two or more parts of the materials using a Santo Starrer. A comparative toner comprising colored particles was produced in the same manner as in Comparative Example 1 using this polymerization composition. The BET specific surface area of this comparative toner is 1
．． The volume average particle size was 7.0 μm at 39 m2/g.

<Comparative Example 3> In the same manner as Comparative Example 2, the BET specific surface area was 4.85 m2.
/g, and a comparative toner with a volume average particle size of 1.5 μm was produced.

<Example 3> Colored particles were produced in the same manner as in Example 1, and an inorganic oxide consisting of silicon oxide was externally added and mixed to the colored particles at a ratio of 0.8% by weight to produce a toner.

<Example 4> Colored particles were produced in the same manner as in Example 2, and an inorganic oxide consisting of titanium oxide was externally added and mixed to the colored particles at a ratio of 1.0% by weight to produce a toner.

Evaluation> A two-component developer was prepared by mixing each toner obtained in the above examples and comparative examples with a carrier, and using each two-component developer, an electrophotographic copying machine manufactured by Konica ■ was used. machine rU-B
A real-photography test was conducted to form a copy image using ix 1550J, and the following items were evaluated. The results are shown in Table 1 below.

(Resolution) Judgment was made based on the number of fine lines per mm that can be clearly identified by visual inspection.

(Cleanability) Judgment was made based on the presence or absence of image defects due to poor cleaning.

(Durability of developer) Judgment was made based on the number of copies that resulted in a clear copy image.

(Image density) Relative density was measured and determined using a Sakura densitometer on the side of Konica.

(Toner scattering) Judgment was made by visually observing the copied image and the inside of the electrophotographic copying machine.

As is clear from Table 1, according to the toner of the example of the present invention, image defects due to poor cleaning do not occur, toner scattering does not occur, and clear copies with high resolution and high image density are produced. It is clear that images can be stably formed many times.

On the other hand, in the toner of Comparative Example 1, the BET specific surface area is too small and the volume average particle diameter is too large, so the resolution and
It is clear that these toners are inferior to the toners of Examples of the present invention in terms of cleaning properties and durability.

Furthermore, since the BET specific surface area of the toner of Comparative Example 2 is too small, it is clear that the toner of Comparative Example 2 is inferior to the toner of Examples of the present invention in terms of cleaning performance and durability.

Furthermore, in the toner of Comparative Example 3, the BET specific surface area was too large and the volume average particle diameter was too small.
It is clear that the toners are inferior to the toners of Examples of the present invention in terms of image density, toner scattering, and durability.

〔Effect of the invention〕

According to the toner of the present invention, the BET specific surface area is 2 to 4 m''
/g and the volume average particle diameter is 2 to 8 μm, so high-resolution, high-quality images can be stably formed many times without cleaning defects.

Further, when wax is further present in the aqueous medium, the effect of improving the fixing properties of the toner is synergized.

Further, when an inorganic oxide is further added to the toner at a ratio of 0.5 to 5% by weight, the cleaning properties of the toner are further improved.

Claims (3)

[Claims] (1) A toner consisting of colored particles obtained by granulation polymerization in the presence of at least a polymerizable monomer and a colorant in an aqueous medium, with a BET specific surface area of 2 to 4 m^2/g, A toner having a volume average particle diameter of 2 to 8 μm. (2) The toner according to claim 1, further comprising wax in the aqueous medium. (3) A toner comprising the toner according to claim 1 or 2 further mixed with an inorganic oxide in a proportion of 0.5 to 5% by weight.