JPH0713766B2 - Liquid developer for electrostatic photography - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid developer for electrostatic photography, and more specifically, a liquid developer in which a novel copolymer is applied as a resin (binder) used in a toner. Regarding

[Prior art]

A general liquid developer for electrostatic photography contains carbon black, a colorant composed of an organic pigment or a dye, and a binder composed of a synthetic or natural resin such as an acrylic resin, a phenol-modified alkyd resin, rosin and a synthetic rubber as main components. Lecithin,
Toner added with a polarity control agent such as metal soap, linseed oil, higher fatty acid, etc. dispersed in a carrier liquid mainly composed of a solvent with high insulation and low dielectric constant such as petroleum aliphatic hydrocarbon. is there.

However, such a conventional toner causes electrophoresis in the developing process according to the charge of the electrostatic latent image formed on the surface layer of the electrophotographic photosensitive material or the electrostatic recording material, and adheres to that portion to form an image. However, in such a liquid developer, the resin or the polarity control agent diffuses into the carrier liquid over time, causing agglomeration or making the polarity unclear, and therefore the image quality, particularly the image density is significantly deteriorated. In addition to the above problem, the toner has a weak adhesive force (that is, the fixing power of an image), so that it is easily erased by an eraser, and when used in color electrophotography, the transparency of the toner is insufficient, so that yellow, red, blue and black are used. In this case, the four-color overlay becomes uneven, and faithful color reproduction is impossible. Also, when an image is formed on a zinc oxide photosensitive paper and this is used as an offset master for offset printing, the number of printable sheets increases. There is a problem that cause no or printing failure.

〔Purpose〕

A first object of the present invention is to provide a liquid developer for electrostatic photography which is capable of forming a high quality image with good gradation by improving the storage stability of the toner.

A second object of the present invention is to improve the adhesive strength of the toner so that it is difficult to erase with an eraser, and the problems of color reproduction in color electrophotography, printing durability in offset printing and printing defects can be solved. A liquid developer for electrophotography is provided.

〔Constitution〕

The present invention provides a liquid developer for electrostatic photography, comprising a colorant and a toner containing a resin as a main component dispersed in an aliphatic hydrocarbon solvent carrier liquid, wherein the resin is represented by the general formula (I). [However, R ¹ is —H, —CH ₃ , and X is —COOC _n H _{2n + 1} or —OCOC _n H _{2n + 1} (n is an integer of 6 to 20). ] The monomer A represented by the following general formula (II) [However, R ² and R ³ is an integer of -H or -CH _3, m is from 1 to 20. ] A non-aqueous resin obtained by polymerizing a system containing at least a monomer B represented by the following and a monomer C having a carboxyl group or a glycidyl group.

By the way, the inventors of the present invention have conducted various studies on what kind of properties (resin) should be used in order to achieve the above purpose, and have reached the following conclusions. That is, the properties of this polymer are: 1) a solvating component is present in the polymer, and the polymer has a uniform grafting point, 2) a crosslinking monomer component in which the crosslinking reaction does not occur too rapidly is included, 3 ) It contains a monomer component such that the copolymerization reaction and the crosslinking reaction occur separately, 4) it has an affinity for the pigment, 5) it does not dissolve in a non-aqueous solvent, and therefore it is simply dispersed in a non-aqueous solvent. To obtain, 6) to make a polymer structure in which a polar group is introduced to disperse the pigment, and 7) to introduce a polar group to increase the adhesive strength.

Therefore, as a result of further studies and investigations on various polymers from these viewpoints, the present inventors have found that the monomer A represented by the general formula (I) is a monomer that is solvable before and after polymerization. A polymer obtained by copolymerizing a monomer B represented by the general formula (II), which is a monomer capable of becoming a grafting point or a crosslinking component after polymerization, and a monomer C having a carboxyl group or a glycidyl group, Also,
It has been found that a polymer obtained by further polymerizing a monomer insoluble in a nonaqueous solvent (for convenience, hereinafter referred to as "monomer D") after the polymerization of this polymer is optimal. The present invention has been completed based on such findings.

To produce the resin dispersion of the present invention, a system containing at least Monomer A, Monomer B and Monomer C in an aliphatic hydrocarbon (for example, a petroleum aliphatic hydrocarbon and / or a solvent thereof) is used. In the presence of a polymerization initiator such as azobisisobutyronitrile (AIBN) or benzoyl peroxide (BPO) which initiates the polymerization at a relatively low temperature, the polymerization reaction may be carried out at a temperature of about 60 to 120 ° C.
The polymerization reaction in this case is an ordinary copolymerization reaction.

For example, the copolymerization reaction using lauryl methacrylate as the monomer A and methacrylic acid or glycidyl methacrylate as the monomer C is as follows.

In addition, subsequently, when methyl methacrylate (MMA) is used as the monomer D and is polymerized in a solvent containing the copolymer (E), the reaction is as follows. Here, it is ideal that methyl methacrylate is graft-polymerized to the allyl group, but a homopolymer may be polymerized.

As described above, the monomer A represented by the general formula (I) is a monomer that can be a solvated component even after polymerization, and specific examples thereof include lauryl methacrylate, lauryl acrylate, stearyl methacrylate, stearyl acrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, dodecyl methacrylate, dodecyl acrylate, hexyl methacrylate, hexyl acrylate, octyl acrylate, octyl methacrylate, cetyl methacrylate, cetyl acrylate, vinyl laurate, vinyl stearate, nonyl methacrylate, nonyl acrylate, decyl methacrylate decyl acrylate, cyclohexyl methacrylate , Cyclohexyl acrylate, etc.

The monomer B represented by the general formula (II) is a monomer that can be a grafting point or a cross-linking component after polymerization. and so on.

Monomer C is a polar group (carboxyl group, glycidyl group)
It is a component that imparts a charge to a polymer in a non-aqueous solvent with a polymerizable monomer having, and is well adsorbed on the surface of a pigment to contribute to dispersibility, adhesiveness, and fixability.

Examples of the polymerizable monomer having a carboxyl group include acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid, and examples of the glycidyl group-containing monomer include glycidyl acrylate, glycidyl methacrylate, glycidyl propyl methacrylate and glycidyl propyl acrylate. , Glycidyl butyl acrylate, glycidyl butyl methacrylate and the like.

Further, the monomer D is a component that forms fine particles in the non-aqueous dispersion liquid, and enhances the film forming property. Specific examples of the monomer D include methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, propyl methacrylate, propyl acrylate, n-butyl methacrylate, iso-butyl methacrylate, vinyl acetate, vinyltoluene, styrene, p-chloro. Styrene, divinylbenzene, diethylene glycol, dimethacrylate, trimethylolpropane trimethacrylate, dimethylaminoethyl methacrylate,
Acrylonitrile, vinylpyrrolidone, vinylpyridine, dimethylaminomethylmethacrylate, etc. may be mentioned.

The weight ratio of monomer A / monomer B / monomer C is 50 to 95/1.
.About.25 / 1 to 25 are suitable, and the weight ratio of the copolymer of the monomer A, the monomer B and the monomer C / the monomer D is about 50 to 95/5 to 50.

In the present invention, if necessary, another polymerizable monomer may be added to the monomer A, the monomer B, the monomer C or the monomer D in an appropriate amount for copolymerization. Further, in the production process of the non-aqueous resin dispersion liquid of the present invention, silica fine particles and wax or polyolefin having a softening point of about 60 to 130 ° C. can be added.

When the silica fine particles are used, it is considered that the resin is obtained in a state in which the silica fine particles are incorporated in the crosslinked structure (in the network structure). In this case, the silica itself, of course, is not subjected to physical changes such as dissolution during the reaction. In any case, in the case of silica, the dispersion stability can be further improved by making the specific gravity approximate to that of the aliphatic hydrocarbon which is the dispersion medium and by preventing the resin from gelling.

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 in the form of fine particles by cooling, and the resin is obtained in the state of being adsorbed by these fine particles. Conceivable. Here, the wax or polyethylene has a specific gravity similar to that of the dispersion medium and prevents gelation of the resin, and since the molecular structure is similar to that of the dispersion medium, it not only helps to improve dispersion stability, but also has a low softening point. It also helps improve adhesion.

An appropriate amount of silica, wax or polyolefin added is about 5 to 50 parts by weight per 100 parts by weight of the resin obtained.

Specific examples of commercially available wax or polyolefin having a softening point of 60 to 130 ° C. are as follows.

Polyethylene example Example of wax (paraffin wax) Manufacturer Product name Softening point
(° C) Pure chemistry Paraffin wax 60 to 98 Kobayashi Kako bleached beeswax 65 Cetanol 80 Nagai Kako bleached beeswax 65 Iron Chemistry Frozen 110 The above-mentioned "other polymerizable monomers" include styrene, vinyltoluene, nitrostyrene, vinyl acetate. , Vinylpyrrolidone, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate and the like.

The polymerization catalyst used in the present invention includes AIBN and BPO.
Besides, phenylazotriphenylmethane, lauryl peroxide, di-t-butyl peroxide, t-butyl peroxide, cumene hydroperoxide and the like can be mentioned.

As the solvent, petroleum-based aliphatic hydrocarbons or halogenated aliphatic hydrocarbons such as kerosene, ligroin, n-hexane, n-heptane, n-octane, i-octane, i-dodecane (these commercial products manufactured by Exxon Corporation Isopar H, G, L, K;
Naphtha No. 6; Solvesso 100, etc.), carbon tetrachloride, perfluoroethylene and the like. A small amount of an aromatic solvent such as toluene or xylene can be added to these aliphatic hydrocarbon solvents.

The polymer particles of the present invention having a separation stability of about 0.1 to 5 μm have good separation stability and intermolecular adhesion, and are effective as a resin for toner.

Here, some of the production examples of the above resin are as follows.

Production Example 1 500 g of kerosene was charged into a 3.0 l flask equipped with a stirrer, a thermometer, a condenser and a dropping funnel, heated to 80 ° C., and lauryl acrylate (monomer A) was added thereto while stirring.
A monomer solution consisting of 100 g, 50 g of the monomer B (No. 1), 10 g of methacrylic acid (monomer C) and 5 g of azobisisobutyronitrile was added dropwise over 2 hours. Then, it was polymerized at this temperature for 4 hours. As a result, the polymerization rate is 95% and the viscosity is 18
A resin dispersion having 0 cp and a particle size of 0.05 to 0.15 μm was obtained.

Production Example 2 400 g of n-hexane was placed in the flask used in Production Example 1 at 90 ° C.
While heating to and stirring, 2-ethylhexyl methacrylate (monomer A) 95 g, monomer B (No. 4) 25
g, glycidyl propyl acrylate (monomer C) 10
g, 5 g of acrylic acid (monomer C) and 2 g of azopis isobutyronitrile were added dropwise over 1 hour,
Then, a polymerization reaction was carried out at this temperature for 6 hours.

As a result, the polymerization rate was 98.3%, the viscosity was 260 cp, and the particle size was 0.08 to 0.24.
A resin dispersion of μm was obtained.

Production Example 3 400 g of Isopar G was placed in the same flask as in Production Example 1 at 90 ° C.
While heating and stirring, 200 g of cyclohexyl acrylate (monomer A), 10 g of monomer B (No. 6),
Methacrylic acid (monomer C) 5g, glycidyl methacrylate (monomer C) 10g and benzoyl peroxide 3
After adding a monomer solution consisting of g and conducting a polymerization reaction at the above temperature for 4 hours, 0.1 g of vinyl pyridine is added thereto.
Esterified at 0 ° C for 10 hours. As a result, the polymerization rate 96.6
%, A viscosity of 280 cp and a particle size of 0.10 to 0.32 μm were obtained.

Production Example 4 200 g of Isopar H and polyethylene (AC Polyethylene 1106 manufactured by Bride Chemical Co.) were added to the flask used in Production Example 1.
50 g was taken and heated to 90 ° C. to dissolve polyethylene. Stearyl methacrylate (monomer A)
A monomer solution consisting of 100 g, monomer B (No. 9) 200 g, acrylic acid (monomer C) 1 g, glycidyl acrylate (monomer C) 8 g and azobisisobutyronitrile 10 g was added dropwise with a dropping funnel over 2 hours, A polymerization reaction was carried out at the above temperature for 6 hours while stirring. Next, 100 g of methyl methacrylate (monomer D) and 5 g of t-butyl peroxide were added, and a polymerization reaction was further carried out at 130 ° C. for 6 hours with stirring to give a polymerization rate of 98.0%, a viscosity of 290 cp, and a particle size of 0.06 to
A 0.23 μm resin dispersion was obtained.

Production Examples 5 to 10 A resin dispersion liquid was obtained in the same manner as in Production Example 1 or 4 using Monomer A, Monomer B, Monomer C and Monomer D shown in Table 1.

To prepare a liquid developer using the copolymer (resin) thus obtained, generally 0.3 to 3 parts of resin are used per 1 part by weight of colorant.
Parts by weight, and this is sufficiently dispersed with a disperser such as an attritor, ball mill or kedi mill in the presence of 10 to 20 parts by weight of a petroleum-based aliphatic hydrocarbon or halogenated aliphatic hydrocarbon carrier liquid to form a concentrated toner. Then, if necessary, it may be diluted 5 to 10 times with a similar solvent.

In this case, the copolymer dispersion liquid (resin dispersion liquid) obtained as described above can be used as it is as the resin and the solvent. If necessary, a resin other than the resin according to the present invention or a polarity control agent such as metal soap, lecithin, linseed oil, or higher fatty acid can be added to the mixture when the concentrated toner is prepared. Since the resin of the present invention has strong polarity and good dispersion stability, it is not necessary to add a polarity control system.

As the colorant, it is possible to use a general inorganic or organic pigment, but in particular pigment particles are dispersed to primary particles,
A colorant produced by the francing method is useful in order to further improve gradation, resolution, image density and the like.

In the flanging method, a pigment or a water-containing paste of a pigment is put together with a resin solution in a kneader called a flasher and mixed well (in this process, water existing in the surrounding of the pigment is replaced by the resin solution), and the kneader is used. The taken-out aqueous phase is discarded, the pigment-dispersed resin solution is dried to remove the solvent, and the obtained lump is pulverized. This is referred to as "flushing colorant" in the present invention. It should be noted that it is possible to take measures such as removing water and the solvent by reducing the pressure while kneading with a kneader. In the flushing process, since not only the pigment but also the dye is kneaded and used in a mud form with water to obtain almost the same result as the pigment, in the present invention, the dye to be flushed is also adopted as the toner component. Is possible. The ratio of the dye / pigment to the resin at the time of flushing is appropriately 10 to 60 parts by weight with respect to 100 parts by weight of the resin. Also, the flushing process is humic acid,
It is particularly advantageous to carry out in the presence of a humic acid salt (Na salt, NH ₄ salt, etc.) or a humic acid derivative. An appropriate amount of these humic acids added is about 0.1 to 30% by weight of the dye-pigment water-containing liquid.

The resin used for flushing has a softening point of 50-
140 ° C. polyolefin, polyolefin-vinyl acetate and copolymer resin or modified resins thereof, wax (polyethylene wax) and the like are preferable, and the following can be exemplified.

Examples of other resins that can be added to the developer include acrylic resins, ester gums, natural resins such as cured rosin, maleic acid resins modified with these natural resins, phenol resins, polyesters, pentaerythritol resins, and the like.

Further, in the liquid developer of the present invention, it is desirable to contain and disperse solid particles of 1 to 20 μm in order to improve image quality, particularly sharpness and resolution. Specific examples of the solid particles include resin particles (for example, homopolymer of methyl methacrylate, BR89, BR85, Mitsubishi Dianal resin), inorganic substances (for example, glass, silica, titanium oxide,
ZnO) and the like. The addition amount of such solid particles having a particle size of 1 to 20 μm is suitably 0.05 to 5 parts by weight based on 100 parts by weight of the entire liquid developer excluding the solid particles.

The liquid developer of the present invention thus obtained has excellent transferability and excellent fixability on transfer paper when the toner image obtained by developing the electrostatic latent image is transferred to a transfer machine. It was confirmed to have the property. Further, this developer has high image density, high fixing property, and excellent durability and storability.

Such a developer is suitable not only for general electrophotography but also for offset printing, chard transfer, pressure transfer, magnetic transfer and the like.

Next, examples will be shown. Parts here are parts by weight.

Example 1 10 g of carbon black (# 44 manufactured by Mitsubishi Carbon Co., Ltd.) 50 g of the resin obtained in Production Example 1 100 g of kerosene were dispersed in a pole mill for 20 hours to obtain a concentrated toner having a viscosity of 42.0 cp, and 10 g of the toner was dispersed in kerosene 1. To produce a liquid developer for electrostatic photography.

Next, when this developer was put in a commercially available electrophotographic copying machine and copied onto commercially available zinc oxide photosensitive paper, many good copies were obtained with an image density of 1.40, gradation of 10 steps and image fixing rate of 86.0%. I got one. The fixing rate (%) is (X is the initial image density of the copy, Y is the image density after 5 reciprocating erases with an eraser tester).

Example 2 Carbon black (Raven 14 manufactured by Columbia Carbon Co., Ltd.) 15 g Resin 100 g obtained in Production Example 2 100 g Isopar G was treated in the same manner as in Example 1 to prepare a concentrated toner.
100 g of the dispersion was dispersed in Isopar H1 to prepare a liquid developer for electrostatic photography. When this was placed in an electrophotographic copying machine (Ricoh Co., Ltd., Recopy 5700) and ordinary copying was carried out, a number of good copies with an image density of 1.38, an image fixing rate of 88.3% and a gradation of 11 steps were obtained. . Moreover, when it was copied to a print master and used for printing, it was possible to print 10,000 sheets.

Example 3 Phthalocyanine blue-3 parts / ethylene-vinyl acetate copolymer (Evaflex 210) 7 parts Flushing colorant 100 g Resin 70 g obtained in Preparation Example 4 70 g Kerosene 100 g was treated in the same manner as in Example 1 to give a color. A liquid developer for electrostatic photography was prepared. The particle size of the concentrated toner was 120 cp. Next, put this developer in a commercially available color electrophotographic copying machine,
When a color copy was made on a commercially available zinc oxide photosensitive paper, a clear color image was formed.

Also, an electrophotographic copying machine (Ricoh's Ricopy DF1800R)
Even when copied with, a 12-step blue copy with gradation was obtained.

Example 4 20 g of carbon black (MA-11 manufactured by Mitsubishi Carbon Co., Ltd.) The resin obtained in Production Example 5 (130 g) and Isopar H (100 g) 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 120 cp. Thereafter, copying was carried out in the same manner as in Example 1 to obtain a copy having an image fixing rate of 84.1% at an image density of 1.3 g. When this concentrated toner was stored at room temperature for 3 months and the viscosity was measured, it was 124 cp, and the toner did not settle, and when a similar copy was performed using this, a copy with an image density of 1.30 and an image fixing rate of 83% was obtained. Was obtained.

Example 5 Flashing of 4.5 parts of benzine yellow / 5.5 parts of epollen E-15 (polyethylene) Colorant 100 g 300 g of the resin obtained in Production Example 6 300 g of Isopar H was dispersed for 10 hours in a kedeimir to prepare a concentrated toner.
100 g was dispersed in Isopar H1 to prepare a color liquid developer for electrophotography. An electrophotographic copying machine (Ricoh Co., Ltd., Recopy DT1800R was used to make a gradation of 12
A large number of good copies were obtained with a step, an image fixing rate of 88.0% and a resolution of 10 lines / mm.

Example 6 Carbon black (Mitsubishi # 44) 4 parts / Polyethylene (Sun wax 171-P) 6 parts / Humic acid 0.5 part Flushing colorant 100 g Polymer 100 g obtained in Preparation Example 7 Myisoper G 300 g 4 It was dispersed for a time to obtain a concentrated toner. To this, 1.09 of Dianal BR-85 (having an average particle size of 13 μm) was added and stirred. 100 g of this dispersion was dispersed in Isopar G1 to prepare a liquid developer for electrophotography.

An electrostatic copying machine (Sepier Copier
When copied with 5040), the image density was 1.44, the image fixing rate was 86.4%, and the gradation was 10 levels, and the image quality was more sharp.

〔result〕

As described above, the liquid developer for electrostatic photography according to the present invention has excellent dispersibility and adhesiveness, and is useful for obtaining a good quality copy.

Claims (2)

[Claims] 1. A liquid developer obtained by dispersing a colorant and a toner containing a resin as a main component in an aliphatic hydrocarbon carrier liquid, wherein the resin is represented by the general formula (I). [However, R ¹ is -H or -CH _3, X is -COOC _n H _{2n + 1} or -OCOC _n H _{2n +} 1 _(n is 6 to 20 integer). ] The monomer A represented by the following general formula (II) [However, R ² and R ³ is an integer of -H or -CH _3, m is from 1 to 20. ] A system containing at least a monomer B represented by the following formula and a monomer C having a carboxyl group or a chrysidyl group is polymerized, or polymerization is carried out in the presence of this copolymer by adding a monomer insoluble in a non-aqueous solvent after polymerization. A liquid developer for electrostatic photography, which is a non-aqueous resin obtained by the above. 2. The liquid developer according to claim 1, which contains solid particles having a particle size of 1 to 20 μm.