JPH0315858A - Negatively chargeable polymerized toner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

[Prior Art] Toners that make electrical or magnetic latent images noticeable are used in various processes for forming and recording images.

As an electrophotographic method, which is one of such image forming processes, many methods are known, as described in, for example, US Pat. No. 2,297,691. In this electrophotographic method, a photoconductive substance is generally used to form an electrical latent image on a photoreceptor by various means, and then the latent image is developed using toner to form a toner image. If necessary, the toner image is transferred to a transfer material such as paper, and then the toner image is fixed to the transfer material using heat, pressure, solvent vapor, etc. to obtain a copy. Various methods have been proposed in the past as a method of developing using toner or a method of fixing a toner image, and methods that involve passing through each image forming process have been adopted.

Conventionally, toners used for these purposes are generally produced by melting and mixing a colorant consisting of a dye or pigment in a thermoplastic resin, uniformly dispersing the colorant, and then finely pulverizing and classifying it into the desired particles. It has been manufactured as a toner with a diameter.

Although this production method (pulverization method) can produce a fairly good toner, there are certain limitations, namely the range of selection of materials for the toner. For example, the resin colorant dispersion must be sufficiently brittle that it can be comminuted in economically available manufacturing equipment. Due to this requirement, it is necessary to make the resin colorant dispersion sufficiently brittle. Therefore, when this dispersion is actually pulverized at high speed, particles with a wide range of particle sizes are likely to be formed, especially relatively large particles. A problem arises in that a proportion of particles that are too finely ground are included in this particle population. Furthermore, such highly brittle materials are susceptible to further pulverization or powdering when used for actual development in copying machines and the like. In addition, with this pulverization method, it is difficult to uniformly disperse solid particles such as magnetic powder or colorant into the resin, and depending on the degree of dispersion of the solid particles, fog may increase. Since this causes a decrease in image density, sufficient attention must be paid to the degree of this dispersion. Furthermore, exposure of the colorant to the fractured surface of the colored resin fine powder may cause variations in toner development characteristics.

On the other hand, in order to overcome the problems of toner produced by these pulverization methods, a method for producing toner by a suspension polymerization method has been proposed (Japanese Patent Publication No. 36-10231, etc.).

In this suspension polymerization method, polymerizable monomers and colorants (
Furthermore, a polymerization initiator, a crosslinking agent, and a charge control agent are added as necessary.
After homogeneously dissolving or dispersing other additives to form a monomer composition, the monomer composition is added to a continuous phase (e.g. aqueous phase) containing a dispersion stabilizer using an appropriate stirrer. toner particles having a desired particle size are obtained by simultaneously performing a polymerization reaction.

Since this suspension polymerization method does not include a mechanical pulverization step, there are no inconveniences caused during pulverization that occur in pulverization methods.

In polymerized toners, polymers and copolymers having polar groups are added as additives during suspension polymerization in water. This polar group-containing polymer is electrostatically attracted to the dispersant of opposite polarity dispersed in water on the particle surface, and the dispersant covers the particle surface, thereby preventing the particles from coalescing and stabilizing them. In addition to contributing to granulation stability, polymers and copolymers having polar groups also act as charge control substances, which are important for toner performance. For this reason, the selection of the charge control agent is deeply related to the granulation properties of the toner, and the selection is even more difficult than for toners produced by pulverization. The charge control substances that have been used so far do not fully satisfy both granulation and charge control properties. [Problems to be Solved by the Invention] An object of the present invention is to provide a toner having excellent granulation properties and a sharp particle size distribution, excellent charge controllability, and stable charging characteristics. A further object of the present invention is to provide a toner with excellent fixing properties.

[Means and effects for solving the problems] An object of the present invention is to provide a polymerized toner obtained by suspension polymerizing in water a polymerizable monomer system containing at least a substance having a polar group and a release agent. The polar group-containing substance has a copolymerization ratio of styrene and/or α-methylstyrene and 2-acrylamido-2-methylpropanesulfonic acid of 98:
2-80:20 with a weight average molecular weight of 2000-15.0
This is achieved using a polymerized toner characterized by being a polymer of 0.00 (hereinafter referred to as an octapolymer).

The present invention will be described in detail below.

As a result of intensive research, the present inventors have found that in a polymerized toner obtained by suspension polymerizing a polymerizable monomer system containing at least a substance having a polar group and a release agent in water, the substance having the polar group The inventors have discovered that a polymerized toner having a sharp particle size distribution and stable charging characteristics can be obtained by using Polymer A as a polymer, and has thus arrived at the present invention.

This A polymer is polymerizable! # It is compatible with the weight system and is oriented uniformly near the particle surface during granulation, so it interacts with the dispersant in water and stabilizes the granulated particles. The octapolymer has particularly excellent granulation stability compared to conventional polar substances, and can produce a toner with a sufficient effect and a narrow particle size distribution even when added in a small amount. The amount of octapolymer added is 0.05~
It is preferably 5 parts by weight, more preferably 0.05 to 2 parts by weight. As described above, a small amount is sufficient; on the other hand, if the amount added is excessive, the balance at the particle interface is disrupted and granulation becomes impossible.

Even more preferable is this A! Since the coalescence is uniformly oriented near the surface of the particles, it is possible to impart excellent charging properties and to produce toners with excellent durability and environmental stability. Furthermore, since the octapolymer is dispersed in the binder resin in a colorless or pale transparent state, problems such as color turbidity do not occur even when used in color toners.

Since the polymerized toner of the present invention is produced by suspension polymerization in water, it can contain a wax with a low melting point that cannot be used by the pulverization method. That is, a non-polar component such as wax does not exist near the surface of the particle, contrary to the polar component, but forms a pseudo-capsule-like structure covered with the polar component on the surface. This low melting point wax melts at a temperature lower than the fixing temperature during fixing and acts as a good heat transfer material. This bird is able to settle at low temperatures. Furthermore, this wax acts as a mold release agent and is effective in preventing offset.

The wax used in the present invention is preferably paraffin wax with a melting point of 55°C to 70°C. Since the wax is encapsulated in a pseudo-capsule, blocking does not occur, but when the toner environment exceeds the melting point of the wax, the wax melts in the toner and oozes out onto the toner surface, causing blocking.

Considering the temperature environment inside a copying machine, the melting point of wax is 55℃.
The above is preferable, and since the wax must be uniformly dissolved in the polymerizable monomer system during suspension polymerization of the toner, the melting point of the wax is preferably 70° C. or lower. Also,
The amount used is preferably 1 to 301 parts. Polymerizable monomers that can be applied to the toner of the present invention include:
Styrene, O-methylstyrene, m-methylstyrene,
Styrene and its derivatives such as p-methylstyrene, p-methoxystyrene, p-ethylstyrene; methyl methacrylate, ethyl methacrylate, probyl methacrylate, n-butyl methacrylate, isobutyl methacrylate,
Methacrylic acid esters such as n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylayonoethyl methacrylate, diethylamine ethyl methacrylate; methyl acrylate, ethyl acrylate, Acrylic acid esters such as n-butyl acrylate, isobutyl acrylate, probyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; There are vinyl-based polymers such as acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide. These monomers can be used alone or in combination. Among the above-mentioned monomers, it is preferable to use styrene or a styrene derivative alone or in combination with other monomers as a polymerizable monomer in terms of the development characteristics and durability of the toner.

The polymerized toner of the present invention uses an octapolymer as a polar substance, and uses a dispersant having an opposite charge as a suspension stabilizer. As a result, the polymer and the dispersant attract each other electrostatically near the surface of the granulated droplets, and the dispersant covers the particle surface, thereby preventing the particles from coalescing and stabilizing the particles.

Dispersants include positively charged silica fine powder such as aminoalkyl-modified colloidal silica. Such a dispersant is preferably used in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the polymerizable polymer. More preferably, it is 0.3 to 15 parts by weight.

As the coloring agent used in the present invention, conventionally known dyes, pigments, carbon black, etc. that do not inhibit polymerization radical reactions can be used. For example, C. I. Solvent Red 52, C. I. P
igment Blue 15:3, C. I. Pig
ment Yellow 17,C. I. Pigme
nt Yellow 14, C. I. Pigment
Red 122, C. I. Pigment Red
5. There are carbon blacks treated with aluminate-based cutting agents.

As the polymerization initiator, any suitable polymerization initiator may be used, such as 2,2'-azobis-(2,4-dimethylvaleronitrile). 2.2'-azobisisobutyronitrile,
l,1'-Azobis(cyclohexane-1-carponitrile). 2.2'-azobis-4-methoxy-2.
4-Dimethylvaleronitrile, other azo or diazo polymerization initiators such as azobisisobutyronitrile (AIBN); benzoyl peroxide, methyl ethyl ketone peroxide, isoprobil baroxy carbonate, cumene hydroperoxide, 2.4 - Peroxide-based polymerization initiators such as dichloryl benzoyl peroxide and lauroyl peroxide can be mentioned. Generally, about 0.5 to 10% of the polymerization initiator based on the weight of the polymerizable monomer is sufficient.

Additionally, a fluidity modifier may be mixed (externally added) with toner particles and used. Fluidity modifiers include colloidal silica, fatty acid metal salts, and Teflon fine powder. In addition, fillers such as calcium carbonate and finely powdered silica are added for the purpose of increasing the volume.
It may be blended into the toner in a range of 5 to 20% by weight.

The polymerized toner used in the present invention can be obtained by the following method. In other words, a monomer system containing a suspension stabilizer is obtained by adding wax, colorant, polymerization initiator, and other additives to a polymerizable polymer and uniformly dissolving or dispersing it using an ultrasonic dispersion machine, homogenizer, etc. into the aqueous phase (ie, continuous phase) using a conventional stirrer, homomixer, homogenizer, etc. Preferably, the stirring speed and time are adjusted so that the monomer droplets have the desired toner particle size, generally 30 μm or less, and after that, this state is maintained approximately by the action of the separation stabilizer. Stirring should be carried out to the extent that sedimentation of particles is prevented. The polymerization temperature is set at 40°C or higher, generally between 50 and 90°C. After the reaction is complete, the generated toner particles are washed, collected by filtration, and dried. In the suspension polymerization method, 1,000 nomers are usually used! 300 to 30 parts of water
It is preferable to use 0.00 parts by weight as a dispersion medium. [Example] The contents will be explained in detail below based on an example. The following numbers of parts are by weight. East direct group Yu AI! Method of manufacturing a combination 2 equipped with a stirrer, condenser, thermometer, and nitrogen inlet tube
300 g of methanol, 100 g of toluene in 1 flask
g, 570 g of styrene, 30 g of 2-acrylamido-2-methylbrovanesulfonic acid, and 12 g of lauroyl peroxide were charged, stirred, and subjected to solution polymerization at 65° C. for 10 hours under nitrogen introduction. The contents were taken out from the flask, dried under reduced pressure, and then heated in a jet mill. to produce an octapolymer (Mw
-3000), Toner formulation The above formulation was heated to 70°C and uniformly dissolved or dispersed to obtain a monomer composition.

Separately, add 0.3 silane cobbling agent [KBE903 (manufactured by Shin-Etsu Silicone) to 1200 mf of ion exchange water.
g Uniformly disperse colloidal silica [Aerosil #2
00 (manufactured by Nippon Aerosil)] and further uniformly dispersed. This dispersion was adjusted to pl{=6 with HC1 to prepare a separation medium system.

The above-mentioned monomer composition was immersed in this dissolving medium system and stirred at 6500 rpm for 60 minutes at 70°C in a nitrogen atmosphere using a TK type homomixer to granulate a monomer composition. After that, the temperature was heated to 70°C while stirring with a paddle stirring blade. Polymerization took place in 10 hours.

After the polymerization reaction is completed, the reaction product is cooled and 20 wt% NaO
Add 42g of H aqueous solution, perform alkaline treatment for 11 nights to dissolve the dispersant, filter through oven, and wash with water. A polymerized toner was obtained by drying.

When the particle size of the obtained toner was measured with a Coulter counter (aperture diameter: 100 μffl), it had a volume average diameter of 11.0 gm and a very sharp particle size distribution with 3% of particles of 4 μm or less in the number distribution. This toner's iron powder (
200/300 mesh) by the blow-off method was -18 μc/g.

9 parts of resin coated ferrite carrier for 6 parts of this toner.
A durability test was conducted by mixing 4 parts of the developer as a developer, and it showed stable charging characteristics and good image density was maintained even after running 20,000 sheets. Furthermore, the image had excellent color tone with no offset at a fixing temperature of 160° C., and had good transparency. Toner formulation: 170 parts of styrene The above formulation was heated to 70°C, uniformly dissolved or decomposed to obtain a monomer composition, and immersed in a dispersion medium system prepared in the same manner as in Example 1 for granulation. When the particle size of the obtained toner was measured using a Coulter counter (aperture diameter 100μ), the volume average diameter was 10.5μ, and the number distribution was 4μ.
It had a very sharp particle size distribution with less than 1% being 6%. The amount of triboelectric charge (triboelectric value) of this toner using the blow-off method against iron powder (2007300 mesh) is -20
It was μc/g.

An durability test was conducted using 6 parts of this toner mixed with 94 parts of resin-coated ferrite and rear as a developer, and it showed stable charging characteristics and maintained good image density even after running 20,000 sheets. Furthermore, the image had excellent color tone with no offset at a fixing temperature of 150° C., and had good transparency.

The above formulation was dispersed for 15 minutes using an ultrasonic dispersion device (Nippon Seiki Co., Ltd., RUS-300, frequency 20 KHz, output 30 W) heated to 70° C. to hydrophobize the carbon black.

Next, the above formulation was heated to 70°C, dissolved or dispersed to prepare a monomer system, and the monomer system was introduced into a dispersion medium system prepared in the same manner as in Example 1, and the mixture was granulated and polymerized to obtain a toner. When the particle size of the obtained toner was measured using a Coulter counter (aperture diameter 100 pm), the volume average particle size was 11.2 pm, and the number distribution was 4.
It had an extremely sharp particle size distribution of 5% below μm. Frictional charge amount (tribo value) of this toner by blow-off method with iron powder (200/300 mesh)
was -21.5←c/g.

A durability test was conducted by mixing 6 parts of this toner with 94 parts of a resin-coated ferrite carrier as a developer, and it showed stable charging characteristics and good image density was obtained even after running 20,000 sheets. Further, the image had excellent color tone without offset at a fixing temperature of 150°C.

In the formulation of Example 1, the amount of octapolymer was changed to 10 parts,
Although granulation was attempted in the same manner as in Example 1, the granulation system was unstable and the droplets coalesced, making granulation impossible.

A toner was obtained by granulating the formulation of Example 2 in the same manner as in Example 2 without adding paraffin wax and allowing the polymerization reaction to proceed. The obtained toner had particle size distribution and tribovalue comparable to those of Example 2, but offset occurred during fixing and was not suitable for practical use.

[Advantageous Effects of the Invention 1] According to the present invention, a toner having excellent charging characteristics and being stable against the environment and durability can be obtained. In addition, the action of the encapsulated wax enables low-temperature fixing while preventing offset.

Claims (2)

[Claims] (1) In a polymerized toner obtained by suspension polymerizing a polymerizable monomer system containing at least a polar substance and a release agent in water, the polar substance is styrene and/or α.
- Copolymerization ratio of methylstyrene and 2-acrylamido-2-methylpropanesulfonic acid is 98:2 to 80:20
A polymerized toner characterized in that it is a polymer having a polymerization average molecular weight of 2,000 to 15,000. (2) The polar substance may be contained in an amount of 0.0% per 100 parts by weight of the toner.
Claim (1) characterized in that the content is 05 to 5 parts by weight.
) The polymerized toner described in ).