JPS6046565A - Toner for developing electrostatically charged image - Google Patents

Abstract

PURPOSE:To lower fixation temperature and improve offset resistance and blocking resistance by crosslinking the binding resin of toner which has specific mean grain size and practical spheroidicity by using a crosslinking agent which has specific solubility in water. CONSTITUTION:The quantity mean grain size of the toner is set to 5-25mum, and the Wadell practical spheroidicity is set to 0.95-1.00; and the binding resin in use is crosslinked by using the crosslinking agent which has 0.05-10wt% solubility in water. The toner is manufactured by a suspension polymerizing method. Then, a polymerizing monomer, coloring agent, polymerization initiator, and other additives are suspended in water and polymerized in the presence of a dispersion stabilizer to obtain particles having uniform particle size. In this case, the polymerization is performed by using the crosslinking agent which is solved in water slightly to gather the crosslinking agent which is affinitive to water to the surface layer of the toner in the polymerizing process, and the crosslinking is carried out, thereby improving the blocking resistance. Consequently, the toner which has excellent fluidity and superior developing performance is obtained, and an excellent shart image having no fog is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner for developing an electrostatic image and a method for producing the toner.

Conventionally, toner has generally been produced by melt-mixing colorants and other additives in a thermoplastic resin, uniformly dispersing the mixture, cooling it, and using a pulverizer or classifier to produce toner with the desired particle size. .

Although this manufacturing method can produce fairly good toners, there are certain limitations in the selection of materials for the toner.

That is, in order to easily crush the toner obtained using the crushing method, the warping material 1 must have some degree of brittleness. However, if the toner is too brittle, it will be pulverized too much, and in order to obtain a toner with an appropriate particle size distribution, the fine powder must be removed.・This results in increased costs. Further, in some cases, the toner is further pulverized in the developing device of the copying machine. Also,
When a low melting point material or a pressure fixable material is used to improve heat fixability, a fusion phenomenon occurs in a crushing device or a classification device, and continuous production may not be possible.

Other requirements for the toner are that it has triboelectric properties suitable for development, that it forms an excellent image, that there is no change in performance when left unused, that it does not solidify (blocking, etc.), and that it has suitable heat or pressure fixation. Examples include having certain characteristics and not contaminating the surface of the photoreceptor.

Particularly in fixing, an offset phenomenon occurs in which toner adheres to a fixing roller during fixing and is retransferred onto the primary copy paper.

The roller that comes into contact with the toner image usually has at least its surface layer made of silicone rubber or fluorine resin, which has good releasability. There is also a method of applying a mold release oil such as oil. However, the method of applying oil has problems such as the provision of an oil application system which complicates the fixing device and the evaporation of the oil causing discomfort to the user. Therefore, it is not preferable to try to prevent offset by applying a single oil; rather, it is currently desired to develop a toner with good offset resistance over a wide fixing temperature range.

In order to solve the problem of fixing offset as described above, it is conceivable to use a resin with a high molecular weight or a crosslinked resin. However, in the conventional method, not only is a very large amount of energy required to heat-knead colorants and other additives into the resin, but even if heat-kneaded, it takes a very large amount of energy. A phenomenon occurs in which the resin molecules are cut and the molecular weight is reduced or the crosslinks are broken, and as a result, the resulting toner cannot exhibit sufficient offset resistance during fixing. In addition, since these hot kneaded products are very hard,
High energy is also required to pulverize toner particles.

Furthermore, in the toner produced by the conventional pulverization method, each grain of I.Q. has a different shape and is irregular, so it is thought that the triboelectric properties of each grain will differ, and the fluidity will also be different. It is said to be bad and cause variations in developability.

Spherical toners have been proposed to overcome these various drawbacks of toners produced by the pulverization method. for example,
Spray methods have been known for a long time. However, in this method, the resin is thermally melted or dissolved in a solvent, sprayed out in a mist form from a nozzle, and then cooled or dried to obtain toner. However, since the crosslinked resin does not melt under heat or dissolve in a solvent, it is impossible to obtain a toner that satisfies the aforementioned drawback of offset resistance during fixing.

Among various spheronization methods, a suspension polymerization method is used to obtain particles containing a gel component and having a particle size suitable for a toner. According to this method, it is possible to produce a toner (11) which is practically spherical, contains a gel component, and satisfies both developability and fixing properties. However, simply increasing the degree of crosslinking of the toner , r# offset property is good], but the fixing temperature tends to be high and fixing becomes difficult, so it is necessary to set the degree of crosslinking to an appropriate value and balance the offset property and fixing temperature. , and also has a lower glass transition temperature Tg.
It is also possible to use v+I toner with a lower fixing temperature by copolymerizing it, but in this case.

Bronching may occur. However, more energy-saving constant fixation 1, for example, lower temperature fixing, and Off-Sera I over a wide usage temperature range from low to high temperatures.
・It is becoming necessary to not cause this phenomenon and to have excellent anti-blocking properties.

In order to solve these problems, adjustments to the degree of crosslinking, selection of monomers, copolymerization ratio, or combination with polyolefins have been considered. However, with these methods, for example, even if the fixing temperature is very low and a toner with sufficient offset resistance is obtained, the anti-blocking performance often becomes a practical problem and cannot be used. This is because the toner has a somewhat uniform composition from the inside to the surface layer, so it tries to improve fixation.
When the toner is melted at a low temperature, the surface area also becomes soft at a low temperature, resulting in blocking, a phenomenon in which toner particles stick together.

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner for developing electrostatic images that overcomes these drawbacks.

That is, an object of the present invention is to provide superior fixing characteristics, that is, to maintain low fixing temperature and to maintain off-cera I over a wide temperature range.
- To provide a toner for developing an electrostatic image that does not cause any phenomenon and has special anti-blocking properties.

Furthermore, the object of the present invention is an I for developing electrostatic images with excellent developability, that is, with no fine line reproducibility, gradation, or fog.
・Providing support for

A further object of the present invention is to provide a toner for developing electrostatic images with excellent fluidity.

A further object of the present invention is to provide a toner for developing electrostatic images that is easy to manufacture, that is, the process is known, and the cost is low.

Its characteristics include a toner with a number average particle size of 5 to 25 gm, and a Wardell practical sphericity of 0.
85 to 1.00, and the toner for electrostatic image development is crosslinked using a crosslinking agent whose solubility in water is 0.05 to 10% by weight.

In a preferred embodiment, the toner is produced by a suspension polymerization method.

If the number average particle diameter is less than 5 pm, fluidity becomes poor and fogging is likely to occur, resulting in poor developability, which is not preferable. If the number average particle diameter exceeds 25 pm, the image performance during development will be poor, such as poor fine line reproducibility of one image, which is undesirable.

The number average diameter was determined by calibration using a styrene standard sample using a Coulter counter Typell and an aperture diameter toop.

The suspension polymerization method is, for example, suspending a polymerizable monomer, a colorant, a polymerization initiator, and other additives in water and polymerizing them in the presence of a dispersion stabilizer to obtain particles with uniform diameters. It is something. In this case, one polymerizable monomer may contain a polymer or a crosslinked polymer.

Spherical toner is produced by suspension polymerization, emulsion polymerization, microcapsules,
Although it can be obtained by spray drying etc., for the purpose of the present invention, W
Practical sphericity of Adell (Wardell) is 0.85 to 1
．． 00 substantially spherical toner was developed and used with good results.

The practical sphericity of Wade I is expressed by the following formula.

Wadell's Practical Sphericity In the present invention, if the Wadell's practical sphericity is less than 0.85, it is essentially the same as a two-amorphous shape, triboelectric charging becomes non-uniform, fluidity also decreases, This is not preferable because the developability becomes poor.

Without being bound by any theory, the present invention is intended to change the physical properties of the interior and surface layers of the toner. In other words, toners with excellent fixing properties and anti-offset properties often have poor blocking resistance, which is a practical problem. The idea was to eliminate the adhesion of particles, that is, the blocking phenomenon. If a completely water-soluble crosslinking agent is used, the surface of the toner is only slightly crosslinked, and no practical effect can be obtained. Therefore, we tried using a crosslinking agent that is slightly soluble in water, and it was very effective. That is, sufficient effects were obtained when the solubility in water was 0.05 to 10 wt%. In other words, this is considered to be because when suspension polymerization is performed in an aqueous dispersion medium, a crosslinking agent having an affinity for water gathers in the surface layer of the toner during the polymerization process, and the surface layer is directly crosslinked.

Such crosslinking agents include polyethylene glycol #
400 dimethacrylate-1 (Shin Nakamura Chemical), polyethylene glycol #600 dimethacrylate (Shin Nakamura Chemical)
, polyethylene glycol #400 diacrylate (Shin Nakamura Chemical), polyethylene glycol #600 diacrylate-1 (Shin Nakamura Chemical), triethylene glycol dimethacrylate-1, polyethylene glycol #200 dimethacrylate (Shin Nakamura Chemical), polyethylene Glycol #200 diacrylate (Shin Nakamura Chemical).

212'bis-(4-methacryloxyjethoxyphenyl)propane, trimethylolpropane triacrylate, tetramethylolmethane triacrylate-1-, l
, 4Ptylene gellicol dimethacrylate), 2
, 2'-bis=(4-7cryloxydiethoxyphenyl)propane, and the like.

Examples of the resin monomer used in the present invention include styrene, 0-methylstyrene, P-methylstyrene, 2φ
4-dimethylstyrene, P-n-butylstyrene, P-
tert-butylstyrene.

P-n dodecylstyrene, P-chlorostyrene, P-
Styrenes such as phenylstyrene; methyl acrylate,
Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-nitylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, acrylic Strict phenyl.

Methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, methacrylate α-methylene aliphatic monocarboxylic acid esters such as stearyl acid, saponphenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate; acrylic acid or methacrylic acid derivatives such as acrylonitrile, lyl methacrylate, and acrylamide; Generally known materials such as these may be used, and these may also be used as copolymers.

As the polymerization initiator, compounds that are generally decomposed by heat or light to generate radicals can be applied to the present invention, and Azobisni! - As a lyle type, 2,2'-azobisisobutyronitrile, 2,2'-arabispropionitrile, 2.
2'-azobisba has lonitrile, 2,2'-7zobis(2,4-dimethylvaleronitrile) g. As an organic peroxide type.

Examples include benzoyl peroxide, nuclear substituted benzoyl peroxide, lauroyl peroxide, acetyl peroxide, and cumene hydroperoxide. Diazoaminobenze as an azo and diazo compound system? , azothioether, etc. Other examples include sulfins and aromatic sulfinic acids.

As suspension stabilizers, sparingly soluble fine powder inorganic compounds (e.g., Ba5O4, CaSO4, HgCO3+ BaC
O3.

Slightly soluble salts such as CaCO3, Ca3('PO4)2+; inorganic polymers such as diatomaceous earth, talc, silicic acid, clay, and talc; powders of metal oxides), water-soluble polymers (e.g. polyvinyl alcohol, Gelatin, 12 powder, methylcellulose, ethylcellulose, carboxymethylcellulose, polyacrylic acid and their salts, alginate), etc. can be applied to the present invention.

These suspension stabilizers are generally used in a range of 0.1-10% by weight.

For fine dispersion of the hardly soluble, finely powdered inorganic compound, a surfactant may be used within the range of 0.001 to θ, 1% by weight, and is used for such purposes. Examples of surfactants include anionic surfactants such as sodium dodecylbenzene sulfonate, sodium allyl-alkylpolyether sulfonate, and sodium oleate; and nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene alkyl allyl ether. Usually used.

Generally known dyes and pigments can be used in the present invention. Furthermore, carbon black and magnetic materials can also be used.

As the crosslinked polymer used in the present invention, generally known ones can be used, for example.

Crosslinked vinyl polymers, polyesters, styrene-butadiene crosslinked polymers, ionomers, etc. can be used as appropriate. In this case, it is particularly preferable to use it after pulverizing it. Further, the polymerizable monomer used in the present invention may contain a non-crosslinked polymer or copolymer.

In addition, monomers that are easily soluble in water cause emulsion polymerization in water at the same time, and the resulting suspended polymer is contaminated with small emulsion polymer particles, so it is necessary to add a water-soluble polymerization inhibitor, such as a metal salt, to emulsify it in the aqueous phase. It is also good to add glycerin, glycol, etc. to the water to prevent polymerization and to prevent coalescence of particles, especially clay as a medium. Me, NaCQ, KCjL, N to reduce the solubility of easily soluble monomers in water.
It is also possible to use salts such as a2SO4.

In the suspension method, a monomer system in which a polymerization initiator, magnetic material, monomer, and additives are uniformly dissolved or dispersed is added to a conventional aqueous phase, that is, a continuous phase containing a suspension stabilizer. Disperse using a stirrer, homomixer, homogenizer, etc.

Preferably, the monomer droplets have the desired toner particle size,
In general, adjust the stirring speed and time so that the particles have a size of 30 #L or less, and then stir to an extent that prevents sedimentation of the particles so that this state is maintained by the action of the dispersion stabilizer. The polymerization temperature is set at 50°C or higher, generally 70 to 90°C. After the reaction is completed, the generated toner particles are washed, filtered, decanted, centrifuged, etc. Collect and dry by appropriate method.

This toner can be applied to all known development methods. For example, two-component development methods such as cascade method, magnetic brush method, microtoning method; conductive-component development method, insulating-component development method, and jumping development method. A one-component development method containing a magnetic material such as; a powder cloud method and a fur brush method; a non-magnetic component development method in which the toner is held on a toner carrier by electrostatic force and transported to a developing section for development, etc. can be mentioned.

[Example 1] Styrene 185g n-butyl acrylate 15g Polyethylene glycol ÷ 200 dimethacrylate 0
．． 5g Asobis Imptiwanitrile 7g Heliogen Blue L-7080 (BASF fi) 1
0g First Gunpuru NK (manufactured by Dainippon Ink Co., Ltd.)
The mixture was uniformly mixed for about 5 minutes in a container equipped with a high shear mixing device such as Homo Mixer (manufactured by Tokushu Kogyo Co., Ltd.). During this time, the temperature was maintained at 70°C. 2 g of polyvinyl alcohol was dispersed in 800 g of water using the homomixer, and the mixture was maintained at 70°C. The above slurry was added to this system under stirring using a homomixer, and the slurry was stirred at about 400 rpm for about 40 minutes. Thereafter, this reaction mixture system was stirred with paddle blade stirring to complete the polymerization. After washing with water, filtering and drying, the particle size was measured using a Coulter Co., Ltd. type with an aperture diameter of 100 .mu.m, and a toner having a number average diameter of 10.0 .mu.m was obtained. The toner was substantially spherical with a Waaelx practical sphericity of between 0.95 and 1.0.

This toner and iron powder carrier 250/400 (Japanese iron powder)
were mixed at a weight ratio of 10:100, and NP-
8500, a good image was obtained which was sharp and had no capri. Also, in terms of retention,
There was no offset phenomenon at all, and even when the set temperature was lowered by 17 degrees Celsius than before, it remained firmly fixed. Furthermore, a blocking test was carried out at 50° C. for about one week, and no blocking occurred at all, indicating good fluidity.

[Example 2] Styrene 160g 2-ethylhexyl methacrylate 40g trimethylolpropane triacrylate) 0.1g 2.2'-Azohis 2-4 dimethacrylate (leronitrile 5g triethyl glycol dimethacrylate 1g acetylsalicylic acid pm) 5 g of CaGOB and 10 g of phthalocyanine green were mixed in the same manner as in Example 1 to obtain a slurry. 10 g of CaGOB was added to 800 g of water in the same manner as in Example 1, and stirred at about 4000 rpm for about 50 minutes. At this time,
The system was kept at 60°C. After this, stir with a paddle blade for about 6 minutes.
The polymerization was completed by stirring while maintaining the temperature at 0°C. CaCO2 was removed using dilute acid in a conventional manner, followed by washing with water, filtering through P5, and drying to obtain a toner. This was measured in the same manner as in Example 1, and the number average diameter was 9.0 μm, and the practical sphericity of Wadθ11 was between 0.95 and 1.0.

This toner and iron powder carrier 250/400 (Japan Iron Powder) were mixed at a volume ratio of 107100 to form a developer.
5500 was used for image display. The image was sharp and good. Furthermore, during fixing, there was no offset phenomenon at all, and even when the set temperature was lowered by 18 degrees Celsius than before, sufficient fixing was achieved. Further, a blocking test was conducted at 50° C. for about one week, and no problems were found, indicating good fluidity.

Publisher: Canon Co., Ltd.

Claims (1)

[Scope of Claims] (1) In a toner having a number of 'lLi'-J particle diameters of 5 to 257 zm, the Wardell's practical spherical shape of I.na is 0.9
5 to 1.00, and the binder resin of the toner is crosslinked using a crosslinking agent whose solubility in water is 0.05 to 10 wt%. (2) The toner for developing electrostatic images according to claim 1, wherein the toner is produced by a suspension polymerization method.