JPH0251180B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to improvements in binders used in electrostatographic liquid developer toners. General liquid developers for electrostatic photography have as main components a colorant made of carbon black, organic pigment or dye, and a binder made of synthetic or natural resin such as acrylic resin, phenol-modified alkyd resin, rosin, or synthetic rubber. A toner containing a polarity control agent such as lecithin, metal soap, linseed oil, or higher fatty acid is dispersed in a carrier liquid whose main component is a highly insulating, low dielectric constant solvent such as a petroleum-based aliphatic hydrocarbon. This is what I did. During the development process, such toner undergoes 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, and adheres to that area to form an image. However, in conventional liquid developers, the resin and polarity control agent diffuse into the carrier liquid over time.
This causes problems such as agglomeration and unclear polarity, resulting in significant deterioration of image quality, especially image density.In addition, toner adhesion and therefore image fixation are weak, making it easy to erase with an eraser. When used in color electrophotography, the toner lacks transparency, resulting in uneven layering of the four colors yellow, red, blue, and black, making faithful color reproduction impossible. If this is formed and used as an offset master for offset printing, there is a problem that the number of sheets to be printed does not increase and printing defects also occur. A first object of the present invention is to provide an electrostatographic liquid developer capable of forming high quality images by improving the storage stability of the 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. That is, the developer of the present invention is an electrostatographic liquid developer comprising a toner containing a colorant and a binder resin as main components dispersed in a carrier liquid containing petroleum-based aliphatic hydrocarbons and/or halides thereof as main components. In the resin, petroleum-based aliphatic hydrocarbon and/or
or its halide in the presence of a polymerization initiator, the general formula [However, R ₁ is hydrogen or methyl group, A is -COOC _o
H _2o+1 or -OCOC _o H _2o+1 (n is an integer from 6 to 20)] and cyclohexyl (meth)
Monomer A selected from the group consisting of acrylates
and the general formula (However, R ₂ and R ₃ are hydrogen or methyl groups, m is 1 to 20
(an integer of ) and monomer B consisting of a compound represented by
It is characterized by containing a nonaqueous copolymer resin obtained by polymerization reaction and crosslinking in a ratio of (0.5 to 50). The inventors of the present invention have conducted various studies on what kind of properties the resin (polymer) should have in order to achieve all of the above objects, and have reached the following conclusion. In other words, the properties of this polymer are (1) that a solvate component is present in the polymer and that this polymer has a uniform crosslinked structure, and (2) that it contains a crosslinking monomer component that does not cause a rapid crosslinking reaction. ,
(3) Contains a monomer component that causes copolymerization and crosslinking reactions to occur separately, (4) Has affinity for pigments, and (5) Does not dissolve in non-aqueous solvents and is therefore simply It can be dispersed in non-aqueous solvents. Therefore, the present inventors investigated various polymers from these viewpoints, and found that monomer A, such as an unsaturated compound of the above general formula, is a monomer that can be solvated both before and after polymerization, and a monomer that can become a crosslinking component after polymerization. It has been found that a copolymer obtained by copolymerizing and crosslinking the allyl group-containing unsaturated compound of the general formula with monomer B is optimal. The present invention is based on such knowledge. To produce the copolymer resin used in the present invention, monomer A and monomer B as described above are generally mixed in a solvent consisting of petroleum-based aliphatic hydrocarbon and/or its halide with benzoyl peroxide, azobisisobutylene, The polymerization may be carried out by heating in one or two stages in the presence of a polymerization initiator such as lonitrile.
Here, "one step" means that monomer A and monomer B are polymerized in the presence of a polymerization initiator such as benzoyl peroxide at a relatively high temperature.
This means that the polymerization reaction is carried out in one step by heating to a relatively high temperature of about 150°C, and "two-step" means that monomer A and monomer B are first heated at a relatively low temperature such as azobisisobutyronitrile. After the polymerization reaction is carried out by heating to a relatively low temperature of about 60 to 90°C in the presence of a polymerization initiator that causes polymerization, the high-temperature polymerization initiator as described above is added to the reaction solution, and the high-temperature initiator is Either the polymerization reaction is carried out again by heating to a relatively high temperature of about 80 to 150°C in the presence of monomer B, or after the monomer B is first subjected to the polymerization reaction under similar low temperature conditions,
Add monomer A and high temperature polymerization initiator to the reaction solution,
This means that the polymerization reaction is carried out again under the same high temperature conditions in the presence of this high temperature polymerization initiator. In any case, in both the one-stage polymerization reaction and the two-stage polymerization reaction, it is thought that the following copolymerization reaction and crosslinking reaction occur. For example, when lauryl methacrylate is used as monomer A and allyl methacrylate is used as monomer B, the following is the case. In the above polymerization reaction, a binary copolymer of monomer A and monomer B is obtained, but in the present invention, by further adding other polymerizable monomers to the reaction system and carrying out the polymerization reaction, a ternary or more copolymer is obtained. Can be combined. In any case, the monomer A/monomer B ratio is 50
~99.5/0.5~50 (by weight) is appropriate, and the amount of polymerization initiator is 0.1~5% of the amount of monomers (total monomers in the case of one stage) used in each polymerization step.
(weight) is appropriate. Further, in the present invention, fine silica particles, wax or polyolefin having a softening point of about 60 to 130°C can be added to the copolymer manufacturing process. When fine silica particles are used, the copolymer is considered to be obtained by incorporating fine silica particles into its crosslinked structure. In this case, not only the silica itself but also the silica itself during the reaction,
It is thought that it will not undergo physical changes such as dissolution. In any case, in the case of silica, dispersion stability can be further improved by making the specific gravity similar to that of aliphatic hydrocarbons or their halides, which are dispersion media, and by preventing gelation of the copolymer. . On the other hand, when wax or polyolefin is used, these are dissolved in the reaction system by heating during the polymerization reaction, but after the reaction, they are precipitated into particles by cooling, and the copolymer is obtained in a state in which these fine particles are adsorbed. It is considered that the 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 low softening point. Therefore, it also helps improve adhesion. The amount of silica, wax or polyolefin added is 5 parts by weight per 100 parts by weight of the copolymer.
~50 parts by weight is appropriate. To make a liquid developer using the copolymer obtained in this way, it is generally necessary to add 1 part by weight of the copolymer to 1 part by weight of the colorant.
Mix 0.3 to 3 parts by weight of the petroleum-based aliphatic hydrocarbon or halogenated aliphatic hydrocarbon carrier liquid and thoroughly disperse the mixture using a dispersion machine such as an attritor, ball mill, or Kedai mill. The concentrated toner may then be diluted 5 to 10 times with a similar solvent. In this case, the copolymer dispersion obtained as described above can be used as is as the copolymer and solvent. Further, when preparing a concentrated toner, other resins other than the copolymer of the present invention and a polarity control agent such as metal soap may be added to the mixture as necessary. Since the developer thus obtained has a low viscosity, it is easy to handle and can be suctioned sufficiently when toner is supplied to a copying machine, and has the advantage that it is hard to harden even when stored for a long period of time. Next, the materials used in the present invention will be explained. First, specific examples of monomer A include lauryl methacrylate, lauryl acrylate, stearyl methacrylate, stearyl acrylate, 2
-ethylhexyl methacrylate, 2-ethylhexyl acrylate, dodecyl methacrylate,
Examples include dodecyl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, hexyl methacrylate, hexyl acrylate, octyl methacrylate, octyl methacrylate, cetyl methacrylate, cetyl acrylate, vinyl laurate, and vinyl stearate. Specific examples of the monomer B of the general formula include the following. Examples of polymerization initiators for low-temperature polymerization include azobisisobutyronitrile, benzoyldimethylaniline peroxide, diethylzinc, and hydrogen peroxide, while those for high-temperature polymerization include benzoyl peroxide, lauryl peroxide, and t. -butyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, dicumyl peroxide and the like. Petroleum-based aliphatic hydrocarbons or halogenated aliphatic hydrocarbons used as reaction solvents or carrier liquids include keroshishi, ligroin, cyclohexane, n
-hexane, n-pentane, n-heptane, n-
Octane, isooctane, isododecane, isononane (commercially available products include Exxon's Isopar H, G, L, K; Naphtha No. 6, Shell Oil Co., Ltd.'s Cielzol, etc.), carbon tetrachloride, perchlorethylene, perchlorethylene, etc. Examples include fluoroethylene. These aliphatic hydrocarbons or halogenated aliphatic hydrocarbons are solvents with high insulation properties (electrical resistance of 10 ¹⁰ Ω·cm or more) and low dielectric constants (dielectric constant of 3 or less).
In addition, a small amount of an aromatic solvent such as benzene or toluene may be added to these aliphatic solvents when used as a carrier liquid. In the present invention, other polymerizable monomers, wax-like substances, etc. can be used in the copolymer manufacturing process, but other polymerizable monomers include styrene, vinyltoluene, nitrostyrene, vinyl acetate, vinylpyrrolidone, dimethylaminoethyl methacrylate. , dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, etc. Further, specific examples of commercially available waxes or polyolefins having a softening point of 60 to 130°C are as follows. Polyethylene example

【table】

【table】 Example of wax (paraffin wax)

[Table] Coloring agents include dyes such as carbon black, oil blue, alkali blue, phthalocyanine blue, phthalocyanine green, spirit black, aniline black, oil violet, benzidine yellow, methyl orange, brilliant carmine, fast red, and crystal violet. Or pigments may be mentioned. Other resins that can be added to the developer include acrylic resins, ester gums, natural resins such as hardened rosins, and maleic acid resins, phenolic resins, polyesters, and pentaerythritol resins modified with these natural resins. Examples of the polarity control agent include common ones such as metal soap, lecithin, linseed oil, and higher fatty acids. Production examples of copolymer resins and examples of the present invention are shown below. Production Example 1 500g of kerosene was placed in a flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping funnel.
Heat to 85°C and add 100g of lauryl acrylate and compound No. 1 monomer B50 into the mixture while stirring.
g and 5 g of azobisisobutyronitrile were added dropwise over 2 hours using a dropping funnel. Thereafter, the polymerization reaction was carried out at this temperature for 4 hours with stirring, and then
- By adding 3 g of butyl peroxide and carrying out a polymerization reaction at 110°C for an additional 6 hours, the polymerization rate was 94.2.
% and a viscosity of 250 cp was obtained. Production Example 2 Add 400% n-hexane to the flask used in Production Example 1.
2-ethylhexyl methacrylate, 25 g of monomer B of compound No. 4, and 22 g of azobisisobutyronitrile.
g was added dropwise over 1 hour using a dropping funnel, and then a polymerization reaction was carried out at this temperature for 6 hours. Next, 4 g of benzoyl peroxide was added and a polymerization reaction was carried out at 90°C for an additional 4 hours with stirring to obtain a resin dispersion with a polymerization rate of 96.2% and a viscosity of 180 cp. 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 cyclohexyl acrylate, 10 g of monomer B of compound No. 6, and 3 g of benzoyl peroxide were added dropwise through a dropping funnel over 4 hours while stirring. Next, 360g of styrene and 33g of benzoyl peroxide.
g was 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 95.8% and a viscosity of 230 cp. Production Example 4 Carbon tetrachloride was added to the flask used in Production Example 1.
200g and polyethylene (manufactured by Allied Chemical Co., Ltd.)
50g of AC polyethylene (1106) was taken and heated to 90°C to dissolve the polyethylene. 200 g of monomer B of Compound No. 9 and 10 g of azobisisobutyronitrile were added dropwise to this mixture over a period of 2 hours using a dropping funnel, and a polymerization reaction was carried out at the above temperature for 6 hours with stirring. Next, add 100 g of cetyl methacrylate and 5 g of t-butyl peroxide, and add 130 g of t-butyl peroxide.
By carrying out a polymerization reaction under stirring at °C for 6 hours,
A polyethylene-containing resin dispersion with a polymerization rate of 98.0% and a viscosity of 290 cp was obtained. Production Example 5 18g of AC polyethylene 615 was added to the resin dispersion prepared in Production Example 2, and after heating and dissolving at 90℃ for 2 hours,
A polyethylene-containing resin dispersion having a viscosity of 320 cp was produced by cooling. 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 230 cp. Example 1 10 g of carbon black (#44 manufactured by Mitsubishi Carbon Co., Ltd.), 50 g of the resin dispersion obtained in Production Example 1, and 100 g of kerosene were dispersed for 10 hours in a kedimir to make a concentrated toner with a viscosity of 50.2 cp, and the 10 g was added to kerosene 1. A liquid developer for electrostatic photography was prepared by dispersing the mixture. Next, 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 1.33 and an image fixation rate of 87.3%. The retention rate (%) is Y/X x 100
(X is the initial image density after copying, Y is the image density after erasing 5 times using an eraser tester). Example 2 15 g of carbon black (Raben 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. The viscosity of concentrated toner is
It was 22.6cp. Next, using this developer, copying was carried out in the same manner as in Example 1, and the image density was 1.32.
A copy with an image fixation rate of 85.4% 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, 100 g of kerosene, and 3 g of lecithin were treated in the same manner as in Example 1 to prepare a liquid developer. The concentrated toner viscosity was 16.0. After copying in the same manner as in Example 1, desensitization treatment was performed,
When this was used as an offset master for offset printing, a print life of 20,000 sheets was obtained. The image fixation rate of the copy (therefore, the offset master) was 87.0%. Example 4 Benzidine Yellow (manufactured by Dainichiseika Kaisha) 30g Polyethylene-containing resin dispersion obtained in Production Example 4
70 g of kerosene, 100 g of nickel naphthenate, and 5 g of nickel naphthenate were treated in the same manner as in Example 1 to prepare a yellow liquid developer for color electrostatic photography. Further, a cyan liquid developer and a magenta liquid developer were prepared using the same formulation except that benzidine yellow was replaced with phthalocyanine blue and thioindigolet, respectively. Next, when these three kinds of developers were put into a commercially available color electrophotographic copying machine and color copying was performed on commercially available zinc oxide photosensitive paper, a clear color copy image was obtained. Example 5 Carbon black (Mitsubishi Carbon MA-11)
20g Polyethylene-containing resin dispersion obtained in Production Example 5
130 g of kerosene 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 15 cp. Thereafter, copies were made in the same manner as in Example 1, and copies with an image density of 1.35 and an image fixation rate of 86.3% were obtained. After storing this concentrated toner at room temperature for 3 months, the viscosity was measured and found to be 20 cp, with little toner sedimentation.When copies were made in the same manner, the image density was 1.31 and copies with a fixation rate of 83% were obtained. Ta. Comparative Production Example When polymerization was carried out in the same manner as in Production Example 1 except that divinylbenzene was used instead of monomer B, gelation occurred in the first polymerization step and the second polymerization step could not be carried out. .

Claims (1)

[Scope of Claims] 1. An electrostatic photographic liquid developer comprising a toner containing a colorant and a binder resin as main components dispersed in a carrier liquid containing petroleum-based aliphatic hydrocarbons and/or their halides as main components. In the resin, in the presence of a polymerization initiator, the general formula [However, R ₁ is hydrogen or methyl group, A is -COOC _o
H _2o+1 or -OCOC _o H _2o+1 (n is an integer from 6 to 20)] and cyclohexyl (meth)
A monomer A selected from the group consisting of acrylates and a general formula (However, R ₂ and R ₃ are hydrogen or methyl groups, m is 1 to 20
(an integer of ) and monomer B consisting of a compound represented by
A liquid developer for electrostatic photography, characterized in that it contains a non-aqueous copolymer resin obtained by polymerization and crosslinking reaction in a ratio of (0.5 to 50).