JPH0315741B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to improvements in resins used in electrostatographic liquid developers. Liquid developers used in electrostatic photography are generally prepared by kneading and pulverizing a coloring agent such as carbon black and a resin, if necessary, together with a polarity control agent such as a higher fatty acid metal salt in the presence of a small amount of an aliphatic hydrocarbon solvent. This is diluted with a carrier liquid consisting of a similar solvent, and the resin is an acrylic resin (a homopolymer of acrylic or methacrylic ester, a combination of acrylic or methacrylic ester and a vinyl monomer such as vinyl chloride, vinyl acetate, or styrene). Resins that are soluble in the carrier liquid are used, such as copolymers, etc.), alkyd resins, styrene resins, and synthetic rubbers. In such a developer, the resin envelops the colorant, adsorbs it, and disperses it as positively or negatively charged toner particles having a particle size of about 0.1 to 0.5 μm. In this case, the dispersion stability and polarity controllability of the toner mainly depend on the adsorption power of the resin, and this adsorption power is thought to be due to ionic bonds, hydrogen bonds, etc. between resin molecules and colored dispersed molecules. In particular, functional groups in the molecule (e.g. -COOH,
-OH, -C=O, -N, -N=N- groups, etc.).
However, since conventional liquid developers use resins that do not have functional groups and therefore have weak adsorption power, they have had the disadvantage that the toner becomes coarse and causes sedimentation and aggregation during storage. Furthermore, when making many copies, the developer is forcibly circulated within the developing section of the copying machine so that it can be applied at a uniform density. However, if approximately 10,000 copies are made, the toner particles are removed from the colorant by this forced circulation. By mechanical adsorption force cutting between resins
They are micronized to about 0.05 μm or less, elute into the carrier liquid, and become non-polar. These non-polar fine particles may adhere to and contaminate the electrodes of the developing device or the non-image areas of copies, or reduce the electrical resistance of the toner and reduce the image density. It also had the disadvantage of reducing the clarity of the image. The object of the present invention is to improve the dispersion stability and polarity controllability of toner by using a resin that has a functional group and therefore has strong adsorption power, thereby improving the storage stability and durability of the toner. Another object of the present invention is to provide a liquid developer. That is, the liquid developer of the present invention is an electrostatographic liquid developer in which a toner mainly composed of a colorant and a resin is dispersed in a carrier liquid made of an aliphatic hydrocarbon solvent. , the general formula () in the presence of a polymerization initiator (R ₁ represents hydrogen or a methyl group, and n represents an integer of 8 to 20.) After polymerizing the monomer represented by the formula (R 1 represents hydrogen or a methyl group, and n represents an integer of 8 to 20), the general formula () [R ₁ is hydrogen or methyl group, R ₂ is -COOH, -
CmH ₂ mOH (m is an integer from 2 to 4),

[Formula] (m is an integer of 2 to 4, h is an integer of 1 to 4)
5 parts of monomer of general formula () per 100 parts by weight
It is characterized by being a colloidal polymer obtained by polymerizing ~50 parts by weight. The polymer of the monomer represented by the general formula () used in the colloidal polymer of the present invention is soluble in an aliphatic hydrocarbon solvent, whereas the polymer of the monomer represented by the general formula () is insoluble in the solvent. It is. Therefore, the colloidal polymer of the present invention exists in a colloidal state (suspension state) in an aliphatic hydrocarbon solvent. Furthermore, since such colloidal polymers have polar groups such as -COOH, -C=O, and -N groups, they have strong adsorption power and are therefore excellent in dispersion stability and polarity controllability. Furthermore, even if this adsorption force is mechanically cut off and the particles become fine particles, which increases their solubility in the carrier liquid, the fine particles will not elute into the carrier liquid and lose their charge because they have an insoluble portion. Therefore, the developer of the present invention has excellent storage stability and durability. Although the colloidal polymer of the present invention is obtained as described above, both the first polymerization reaction and the second polymerization reaction are usually carried out at a temperature of 70 to 110°C. The appropriate amount of the monomer of the general formula () used in the second polymerization reaction is 5 to 50 parts by weight based on 100 parts by weight of the monomer of the general formula () obtained in the first polymerization reaction. be. Specific examples of the monomer of the general formula () include 2-ethylhexyl acrylate (or methacrylate), lauryl acrylate (or methacrylate), stearyl acrylate (or methacrylate), and the like. Specific examples of monomers of general formula () include acrylic acid (or methacrylic acid), hydroxyethyl acrylate (or methacrylate), hydroxypropyl acrylate) or methacrylate),
Examples include dimethylaminoethyl acrylate (or methacrylate). As the polymerization initiator, common ones such as azobisisobutyronitrile and benzoyl peroxide are used. Other materials used in the developer of the present invention may be the same as conventional ones. That is, examples of aliphatic hydrocarbon solvents include n-hexane, ligroin, n-heptane, n-pentane, indodecane, and isooctane. The commercially available petroleum aliphatic hydrocarbons include Isopar E, Isopar G, Isopar L, Isopar H, Isopar K, Naphtha No. 6, Solbetsuso 100, manufactured by Exxon.
Examples include Ciel Sol 71 manufactured by Ciel Sekiyu. These can be used alone or in combination. As the colorant, conventionally known ones such as alkali blue, phthalocyanine green, oil blue, spirit black, carbon black, oil violet, phthalocyanine blue, benzicine yellow, methyl orange, brilliant carmine, fast red, and methyl violet can be used. Examples include pigments or dyes such as. To make the liquid developer of the present invention, the colloidal polymer obtained as described above is mixed with 0.1 to 10 parts by weight of a colorant and an appropriate amount of carrier liquid per 1 part by weight of this polymer using a three-roll mill or an attrition mill. The concentrated toner may be kneaded using a kneader such as a lighter or a ball mill, and then diluted with a certain amount of carrier liquid. In this case, a small amount of a polarity control agent may be added if necessary. Note that higher fatty acid metal salts such as lecithin and calcium naphthenate can be used as the polarity control agent. Next, production examples of colloidal polymers used in the present invention and examples of the present invention will be shown. Production example 1 Isopar H 300g, 2-ethylhexyl methacrylate 100g and benzoyl peroxide
Put 1.5g into a flask and incubate at 90℃ in a nitrogen stream for 5 minutes.
A time polymerization reaction was carried out to obtain a colorless and transparent polymer solution with a viscosity of 80 cp (20°C). Next, add 5 g of methacrylic acid and 0.2 g of benzoyl peroxide to this solution.
A solution consisting of 10 g was added dropwise and a polymerization reaction was carried out at the above temperature for 3 hours to obtain a colorless colloidal polymer liquid with a solid content of 25.0%. Production example 2 Isopar E 300g, 2-ethylhexyl methacrylate 100g and benzoyl peroxide
Put 1.5g into a flask and incubate at 90℃ in a nitrogen stream for 5 minutes.
A time polymerization reaction was carried out to obtain a colorless and transparent polymer solution with a viscosity of 75 cp (20°C). Next, add 2-
A solution consisting of 5 g of hydroxyethyl methacrylate and 0.2 g of benzoyl peroxide was added dropwise,
The polymerization reaction was carried out at the above temperature for 3 hours, and the solid content was 25.1
% white colloidal polymer liquid was obtained. Production example 3 Isopar H 300g, lauryl methacrylate
100 g and 1.5 g of benzoyl peroxide were placed in a flask, and a polymerization reaction was carried out at 90° C. for 5 hours in a nitrogen stream to obtain a colorless and transparent polymer solution with a viscosity of 83 cp (20° C.). Next, after lowering the temperature of this solution to 80°C, 7 g of dimethylaminoethyl methacrylate was added.
A solution consisting of 0.3 g of azobisisobutyronitrile was added dropwise, and a polymerization reaction was carried out for 3 hours to reduce the solid content.
A 25.0% yellow to brown colloidal polymer liquid was obtained. Production Example 4 300 g of Isopar G, 100 g of stearyl methacrylate, and 1.5 g of benzoyl peroxide were placed in a flask, and a polymerization reaction was carried out at 90°C for 5 hours in a nitrogen stream to obtain a colorless and transparent polymer solution with a viscosity of 93 cp (20°C). . Next, add 5 acrylic acid to this solution.
A solution consisting of g, 5 g of 2-hydroxyethyl methacrylate and 0.3 g of benzoyl peroxide was added dropwise, and a polymerization reaction was carried out at the above temperature for 3 hours to obtain a colorless colloidal polymer liquid with a solid content of 25.5%. Example 1 Colloidal polymer liquid of Production Example 1 (solid content 25
%) 40g Carbon Black (manufactured by Columbia Carbon) NEO SPECTRA MARK 5g Alkali Blue (manufactured by Orient Kasei)
A mixture of 0.5 g of Isopar H and 120 g of Isopar H was kneaded for 48 hours in a ball mill to obtain a concentrated toner, and 200 g of the concentrated toner was dispersed in Isopar H2 to obtain a liquid developer. Note that the average particle size of the toner was 0.15μ. Next, put this developer into a 10ml capacity electrode cell.
When a voltage of -500V was applied, it showed strong negative polarity. When this developer was placed in a commercially available wet transfer type electrophotographic copying machine and copies were made, an image was formed with an image density of 1.3 and a toner fixation rate of 85%.
Furthermore, this developer was stored at 50° C. for 30 days, but the particle size hardly changed and no aggregation or sedimentation was observed. Furthermore, when images were formed using the developer after storage, there was almost no deterioration in image quality. The toner fixation rate was calculated from the formula D ₁ /D ₀ ×100, where D ₁ is the image density when the copy image immediately after development is rubbed with cotton, and D ₀ is the image density when it is not rubbed. Example 2 Carbon black (MA- manufactured by Mitsubishi Carbon Co., Ltd.)
100) A mixture consisting of 50g of the colloidal polymer liquid (solid content 25.1%) obtained in Production Example 2 (solid content 25.1%), 2g of calcium naphthenate, and 200g of isododecane was kneaded in an attritor for 4 hours to make a concentrated toner, and 40g of the mixture was mixed with Schierzol 71.
A liquid developer was obtained by dispersing it in 1000ml. Note that the average particle size of the toner was 0.22μ. Further, as in Example 1, strong negative polarity was exhibited by applying a voltage of -500V. Next, copying was carried out in the same manner as in Example 1 using this developer to obtain an image with an image density of 1.26 and a toner fixation rate of 72%. Furthermore, when this developer was stored at 50° C. for 30 days, the particle size hardly changed, no aggregation or precipitation occurred, and the image quality hardly changed. Example 3 A mixture consisting of 28 g of phthalocyanine blue (manufactured by Dainichiseika Chemical Co., Ltd.), 160 g of the colloidal polymer liquid obtained in Production Example 3 (solid content 25.0%), 8 g of lecithin, and 200 g of isododecane was kneaded for 2 hours in a Kedai mill to obtain a concentrated toner, That 46g is 1000 of Cielsol 71
ml to obtain a liquid developer. The average particle size of the toner was 0.24μ. Also, as in Example 1-
It showed strong negative polarity when a voltage of 500V was applied. Next, when this developer was put into a commercially available color electrophotographic copying machine and copies were made, the image density was 0.88.
An image with a fixation rate of 78% was formed. When stored at 50°C for 30 days, there was almost no change in particle size, no aggregation or precipitation, and no change in image quality. Examples 4 to 9 Liquid developers were prepared in the same manner as in Example 2, except that the colorants and colloidal polymers listed in Table 1 were used, and the same tests as in Example 2 were conducted. The results are shown in Table-2. Note that some durability tests have been added to Table 2. This durability was expressed by the number of copies made until the initial image density decreased to 0.8 after continuous copying. Although not listed in Table 2, each developer exhibited strong negative polarity when a voltage of -500V was applied, as in Example 2.

【table】

[Table] Those that did not cause ◎, some agglomeration
Or those in which precipitation occurred were rated as ○.
Comparative production example 1 Place 300 g of Isopar H, 5 g of methacrylic acid, and 0.2 g of benzoyl peroxide in a flask.
The polymerization reaction was started at 90°C under a nitrogen stream. After about 10 minutes, a white fibrous substance was precipitated, and after 1 hour, it had grown into a lump and adhered to the flask wall. Thereafter, 100 g of 2-ethylhexyl methacrylate and 1.5 g of benzoyl peroxide were added dropwise over 1 hour, followed by a polymerization reaction for 5 hours. The white lumps remained as they were, and no colloidal dispersion was obtained. Comparative Production Example 2 300 g of Isopar H, 100 g of 2-ethylhexyl methacrylate, 5 g of methacrylic acid, and 1.5 g of benzoyl peroxide were placed in a flask, and a polymerization reaction was carried out at 90°C under a nitrogen stream for 5 hours. ) was obtained. Comparative Example A mixture consisting of 40 parts by weight of the polymer obtained in Comparative Production Example 2, Carbon Black 5, Alkali Blue 0.5, Isopar H 120, was kneaded for 48 hours in a ball mill to obtain a concentrated toner, and 200 g of the mixture was mixed with Isopar H2.
A liquid developer was prepared by dispersing the liquid in the liquid developer. The average particle size of this toner was 0.18 μm. Next, a copying test was conducted in the same manner as in Example 1, and the image density was 1.2, which showed sufficient characteristics.
The retention rate was low at 62%. Furthermore, when this developer was stored at 50° C. for 30 days, the toner agglomerated and precipitated. When this was stirred, the toner particle size was as large as 0.37 μm.
It was also found that the redispersibility was poor.

Claims (1)

[Scope of Claims] 1. A liquid developer for electrostatic photography comprising a toner containing a colorant and a resin as main components dispersed in a carrier liquid comprising an aliphatic hydrocarbon solvent, wherein the resin is in the solvent, General formula () in the presence of a polymerization initiator (However, R ₁ represents hydrogen or a methyl group, and n represents an integer of 8 to 20.) After polymerizing the monomer represented by the formula (R 1 represents a hydrogen or methyl group, and n represents an integer of 8 to 20), the general formula () [However, R ₁ is hydrogen or methyl group, R ₂ is -COOH,
-CmH ₂ mOH (m is an integer from 2 to 4),
[Formula] (m is an integer of 2 to 4, h is an integer of 1 to 4)
5 parts of monomer of general formula () per 100 parts by weight
A liquid developer for electrostatic photography, characterized in that it is a colloidal polymer obtained by polymerizing ~50 parts by weight.