JPH0580662B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to an electrostatographic liquid developer. PRIOR TECHNOLOGY The main components of general liquid developers for electrostatic photography are colorants such as carbon black, organic pigments, or dyes, and binders made of synthetic or natural resins such as acrylic resins, phenol-modified alkyd resins, rosins, and synthetic rubbers. A toner containing a polarity control agent such as lecithin, metal soap, linseed oil, or higher fatty acid is placed in a carrier liquid whose main component is a highly insulating, low dielectric constant solvent such as a petroleum-based aliphatic hydrocarbon. It is dispersed in In the development process, such toner causes electrophoresis in accordance with the charge of the electrostatic latent image formed on the surface layer of the electrophotographic photosensitive material or electrostatic recording material.
It adheres to that area and forms an image, but in conventional liquid developers, resins and polarity control agents diffuse into the carrier liquid over time, causing aggregation and making the polarity unclear, resulting in poor image quality. In addition to the problem that the image density deteriorates significantly,
The adhesion of the toner, and therefore the fixing power of the image, is weak, so it is easily erased with an eraser, and when used in color electrophotography, the transparency of the toner is insufficient.
The overlapping of the four colors yellow, red, blue, and black becomes uneven, making faithful color reproduction impossible.Also, an image was formed on zinc oxide photosensitive paper and used as an offset master for offset printing. In this case, there is a problem that the number of printed sheets does not increase and printing defects also occur. Objective The first objective of the present invention is to provide an electrostatographic liquid developer that can form high-quality images by improving the storage stability of toner. The second object of the present invention is to improve the adhesion of toner, which is difficult to erase with an eraser, and which can solve the problem of color reproduction in color electrophotography and the problems of printing durability and printing defects in offset printing. An object of the present invention is to provide a liquid developer for electrophotography. Structure The present invention relates to an electrostatographic liquid developer comprising a toner containing a colorant and a binder as main components dispersed in a carrier liquid containing an aliphatic hydrocarbon as the main component, wherein the binder is an aliphatic carbon General formula () in the presence of a polymerization initiator in a hydrogen solvent

[Chemical formula] (However, R is -H or -CH ₃ , X is -
COOCnH ₂ n+ ₁ or −OCOCnH ₂ n+ ₁ , n is 6 to
is an integer of 20. ) Monomer A represented by the general formula ()

[Chemical formula] (However, Z ¹ and Z ² are -H, an alkyl group, a halogen, or an allyl group, and at least one of Z ¹ and Z ² is an allyl group.) It is characterized by using a resin obtained by polymerization. Incidentally, as a result of various studies conducted by the present inventors regarding the properties of the binder (resin) that should be used in order to achieve the above-mentioned objective,
The following conclusions were reached. That is, the properties of this polymer are: 1. A solvate component is present in the polymer, and this polymer has a uniform crosslinked structure. 2 Contains a crosslinking monomer component that does not cause a rapid crosslinking reaction. 3 Contains monomer components that cause copolymerization and crosslinking reactions to occur separately. 4. It has an affinity for pigments, and 5. It does not dissolve in non-aqueous solvents and therefore can simply be dispersed in non-aqueous solvents. Subsequently, the present inventor conducted research on various polymers from these viewpoints, and as a result, the unsaturated compound (monomer A) represented by the above general formula () was found to be a monomer that can be solvated both before and after polymerization.
It has been found that a copolymer obtained by copolymerizing and crosslinking the monomer B and monomer B represented by the general formula () as a monomer that can serve as a crosslinking component after polymerization is optimal. The present invention was completed based on such knowledge. To produce the binder (polymer) of the present invention,
Monomer A and monomer B may be thermally polymerized in one or two steps in the presence of a polymerization initiator such as benzoyl peroxide or azobisisobutyronitrile in an aliphatic hydrocarbon solvent. Here, "one step" means monomer A and monomer B.
and in the presence of a polymerization initiator such as benzoyl peroxide that causes polymerization at a relatively high temperature.
This means that the polymerization reaction is carried out in one go by heating to a relatively high temperature of about 150°C. Also, "two-step" means that monomer A and monomer B are first heated to a relatively low temperature of about 60 to 90°C in the presence of a polymerization initiator such as azobisisobutyronitrile that causes polymerization at a relatively low temperature. After the polymerization reaction is carried out, a high-temperature polymerization initiator as described above is added to the reaction solution, and the polymerization reaction is carried out again by heating to a relatively high temperature of about 80 to 150℃ in the presence of this high-temperature polymerization initiator. , or after first polymerizing only monomer B under similar low-temperature conditions, monomer A and a high-temperature polymerization initiator are added to the reaction solution, and polymerization is performed again under similar high-temperature conditions in the presence of this high-temperature polymerization initiator. It means to carry out a reaction. Monomer A/monomer B ratio is 50~99.5/0.5~
50 (by weight), and the amount of the polymerization initiator is suitably about 0.1 to 5% (by weight) of the amount of monomers (total monomers in the case of one stage) used in each polymerization step. In the present invention, in the manufacturing process of the resin, other polymerizable monomers, silica fine particles, and
It is possible to add wax or polyolefin at a temperature of about °C. When fine silica particles are used, it is thought that the copolymer is obtained with fine silica particles incorporated into its crosslinked structure. In this case, it is thought that the silica itself will not undergo physical changes such as dissolution during the reaction. In any case, in the case of silica, dispersion stability can be further improved by having a specific gravity similar to that of an aliphatic hydrocarbon as a dispersion medium and by preventing gelation of the copolymer. When wax or polyolefin is used,
These are dissolved in the reaction system by heating during the polymerization reaction, but as a result of cooling after the reaction, they precipitate in the form of particles.
It is thought that the copolymer is obtained in a state where it is adsorbed on these fine particles. Here, wax or polyethylene has a specific gravity similar to that of the dispersion medium, prevents gelation of the copolymer, and has a molecular structure similar to that of the dispersion medium, so it not only helps improve dispersion stability, but also has a softening point. Since it is low, it also helps improve adhesion. The appropriate amount of silica, wax or polyolefin added is about 5 to 50 parts by weight per 100 parts by weight of the copolymer. Next, the materials used in the present invention will be explained. Specific examples of monomer A represented by the general formula () include lauryl methacrylate, lauryl acrylate, stearyl methacrylate, stearyl acrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, dodecyl methacrylate, dodecyl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, hexyl Examples include methacrylate, hexyl acrylate, octyl methacrylate, octyl acrylate, cetyl methacrylate, cetyl acrylate, vinyl laurate, and vinyl stearate. Specific examples of the monomer B represented by the general formula () include the following.

[ka]

[ka]

[ka]

[ka]

[ka]

[ka]

[ka]

[ka]

[Chemical] In addition to the above-mentioned polymerization initiators, benzoyldimethylaniline peroxide, diethylzinc, hydrogen peroxide, etc. are used for low-temperature polymerization, and lauryl peroxide, t-butyl peroxide are used for high-temperature polymerization. , di-t-butyl peroxide, cumene hydroperoxide, dicumyl peroxide and the like. Further, specific examples of commercially available waxes or polyolefins having a softening point of 60 to 130°C are as follows.

【table】

[Table] Examples of the above-mentioned "other polymerizable monomers" include styrene, vinyltoluene, nitrostyrene, vinyl acetate, vinylpyrrolidone, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, etc. . Next, as specific examples of the non-aqueous solvent (aliphatic hydrocarbon), kerosene, ligroin, cyclohexane, n-hexane, n-pentane, n-heptane, n-octane, isooctane, isododecane, isononane (the above commercially available products Examples include Isopar H, G, L, and K manufactured by Exxon; Naphtha No. 6; and Ciel Sol manufactured by Shell Sekiyu Co., Ltd.). These aliphatic hydrocarbons have high insulating properties (electrical resistance
10 ¹⁰ Ω・cm) and low dielectric constant (dielectric constant 3 or less). Furthermore, when used as a carrier liquid, aromatic solvents such as benzene and toluene can be added to these aliphatic solvents in small amounts. Here, an example of manufacturing the binder (a non-aqueous dispersion of the resin) is as follows. Production Example 1 500g of kerosene was placed in a flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping funnel.
While heating to 85° C. and stirring, 100 g of lauryl acrylate, 50 g of the monomer (1) above, and 5 g of azobisisobutyronitrile were added dropwise to the mixture via a dropping funnel over 2 hours. Thereafter, the polymerization reaction was carried out at this temperature for 4 hours with stirring, and then 3 g of di-t-butyl peroxide was added and the polymerization reaction was further carried out at 110°C for 6 hours to obtain a resin dispersion with a polymerization rate of 96.0% and a viscosity of 350 cp. Obtained. Production Example 2 Add 400% n-hexane to the flask used in Production Example 1.
g was taken, heated to 60°C, and while stirring, 95 g of 2-ethylhexyl methacrylate, 25 g of the monomer (4) above, and 2 g of azobisisobutyronitrile were added dropwise through a dropping funnel over 1 hour, and then,
The polymerization reaction was carried out at this temperature for 6 hours. Next, 4 g of benzoyl peroxide was added and the polymerization reaction was carried out at 90°C for an additional 4 hours with stirring, resulting in a polymerization rate of 95.0.
A resin dispersion with a viscosity of 200 cp was obtained. Production Example 3 Add Isopar G to the flask used in Production Example 1.
400 g was taken, heated to 90°C, and 200 g of hexyl acrylate, 10 g of the monomer (6) above, and 3 g of benzoyl peroxide were added dropwise through a dropping funnel over 4 hours while stirring. Next, styrene 30
g and 3 g of benzoyl peroxide were added thereto, and a polymerization reaction was carried out at the above temperature for 4 hours with stirring to obtain a non-aqueous resin dispersion with a polymerization rate of 94.8% and a viscosity of 180 cp. Production example 4 Isopar L200 was added to the flask used in production example 1.
g and polyethylene (AC made by Allied Chemical Co., Ltd.
50g of polyethylene (1106) was taken and heated to 90°C to dissolve the polyethylene. In this, 200 g of the monomer (9) above and azobisisobutyronitrile
10g was dropped over 2 hours using a dropping funnel.
The polymerization reaction was carried out at the above temperature for 6 hours while stirring.
Next, 100 g of cetyl methacrylate and 5 g of t-butyl peroxide were added, and the polymerization reaction was further carried out at 130°C for 6 hours with stirring.
A polyethylene-containing resin dispersion of 98.0% and a viscosity of 160 cp was obtained. Production Example 5 18g of AC polyethylene 615 was added to the resin dispersion obtained in Production Example 2, and after heating and dissolving at 90°C for 2 hours,
The mixture was allowed to cool to produce a polyethylene-containing resin dispersion having a viscosity of 260 cp. Production Example 6 40g of Sunwax 131-P was added to the polyethylene-containing resin dispersion obtained in Production Example 4, and the mixture was heated at 90℃ for 2 hours.
After heating and dissolving for a period of time, the mixture was allowed to cool to produce a wax and polyethylene-containing resin dispersion having a viscosity of 560 cp. Next, examples will be shown. Example 1 Carbon black (Mitsubishi Carbon Co., Ltd. #44)
10 g of the resin dispersion obtained in Production Example 1, 150 g of kerosene, and 100 g of kerosene were dispersed for 10 hours in a Kedimill to obtain a concentrated toner with a viscosity of 78.0 cp, and 10 g of the resin dispersion obtained in Production Example 1 was dispersed in kerosene 1 to prepare a liquid developer for electrostatic photography. . Subsequently, this developer was placed in a commercially available electrophotographic copying machine and copies were made on commercially available zinc oxide photosensitive paper, resulting in copies with an image density of 1.32 and an image fixation rate of 86.4%. The fixing rate (%) was determined from the formula: Y/X x 100 (X is the initial image density of the copy, Y is the image density after 5 reciprocating erasing with an eraser tester). Example 2 15 g of carbon black (Label 14 manufactured by Columbia Carbon), 100 g of the resin dispersion obtained in Production Example 2, 100 g of Isopar G, and 1 g of manganese naphthenate were treated in the same manner as in Example 1 to produce an electrostatic photographic liquid developer. It was created. Furthermore, the viscosity of concentrated toner is
It was 39.0 cp. Next, using this developer, copying was performed in the same manner as in Example 1, and the image density was
1.36, and a copy with an image fixation rate of 78.9% was obtained. Example 3 15 g of carbon black (Raben 5250 manufactured by Columbia Carbon), 100 g of the resin dispersion obtained in Production Example 3, and 100 g of kerosene were treated in the same manner as in Example 1 to prepare a liquid developer. The viscosity of the concentrated toner was 88 cp. After copying in the same manner as in Example 1, it was subjected to a desensitizing treatment and used as an offset master for offset printing, resulting in a print life of 20,000 sheets. The image fixation rate of the copy (therefore, the offset master) was 88.4%. Example 4 50 g of benzidine yellow (manufactured by Dainichiseika Kaisha, Ltd.), 120 g of the polyethylene-containing resin dispersion obtained in Production Example 4, and 100 g of kerosene were treated in the same manner as in Example 1 to prepare a liquid developer for color electrophotography. Concentrated toner viscosity is 85cp
It was hot. Next, this developer was placed in a commercially available color electrophotographic copying machine and color copies were made on commercially available zinc oxide photosensitive paper, and a clear color image was formed. Example 5 Carbon black (MA- manufactured by Mitsubishi Carbon Co., Ltd.)
11) 20 g of the polyethylene-containing resin dispersion obtained in Production Example 5 (130 g) and 100 g of kerosene were treated in the same manner as in Example 1 to prepare a liquid developer for electrostatic photography. The viscosity of the concentrated toner was 38 cp. Hereinafter, in the same manner as in Example 1, Recopy DT-
1220 (manufactured by Ricoh), and the image density
1.28, a copy with an image fixation rate of 83.2% was obtained. After storing this concentrated toner at room temperature for 3 months, the viscosity was measured and found to be 20 cp, with no sedimentation or gelation of the toner.
When copies were made in the same manner, copies with an image density of 1.25 and a fixation rate of 80.5% were obtained. Effects As described above, by using the liquid developer according to the present invention, a large number of high-quality copies can be obtained. Also,
Since this developer has extremely good toner dispersibility, it also has excellent storage stability.

Claims (1)

[Scope of Claims] 1. A liquid developer for electrostatography comprising a toner containing a colorant and a binder resin as main components dispersed in a carrier liquid containing an aliphatic hydrocarbon as the main component, wherein the resin is an aliphatic hydrocarbon. In the presence of a polymerization initiator in a hydrocarbon solvent, the general formula () [C] (where R is -H or -CH ₃ and X is -
COOCnH ₂ n+ ₁ or −OCOCnH ₂ n+ ₁ , n is 6 to
is an integer of 20. ) and the general formula () (where Z ¹ and Z ² are -H, an alkyl group, a halogen, or an allyl group. At least one of ^{Z 1} and Z ² is an allyl group. 1. A liquid developer for electrostatic photography, characterized in that the main component thereof is a resin obtained by polymerizing a system containing at least monomer B represented by: