JP2003149872A - Positive electrification liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrification liquid developer which realizes excellent image quality and stable formation of high-quality images. SOLUTION: The positive electrification liquid developer comprises at least an insulating carrier liquid, toner particles and an organic metal compound containing aluminum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positively chargeable liquid developer, and more particularly to a copying machine such as an electrophotographic system or an electrostatic recording system, a facsimile, a printer, a printing machine, a printed circuit board manufacturing apparatus and a photo. The present invention relates to a positively chargeable liquid developer characterized by a structure for giving stable charges to toner particles in a liquid developer used in an image forming apparatus such as a mask manufacturing apparatus.

[0002]

BACKGROUND OF THE INVENTION Electrophotography is described in US Pat. No. 2,297,391.
As described in the specification, etc., a method using a photoconductive insulator is generally used. In this method, a photoconductive insulator charged by a corona or roller is irradiated with light or the like. An electrostatic latent image is formed, and resin particles colored with a pigment or dye called toner are electrostatically adhered to this latent image to develop the image.After transferring this image onto paper or film, heat, pressure, A visible image is obtained by fusing with light or the like.

An example of a conventional process unit by electrophotography will be described with reference to FIG. See FIG. 3. FIG. 3 is a cross-sectional view showing a conceptual configuration of a process unit according to a conventional electrophotographic method. The photosensitive drum 11, which is an electrostatic latent image carrier, a charging device 12, an exposure device 13, a developer supply roller. 14 and a developing roller 15 as a developer carrying member and a collecting blade 16, a transfer device having a pressure roller 19 for transferring a toner image onto a recording sheet 20, a cleaning blade 17, a charge eliminating lamp and the like. Recording sheet 20 including a static eliminator 18 and the like.
A fixing device (not shown) is provided on the discharge side of.

The photoconductor drum 11 is formed of a photoconductive insulator such as an organic photoconductor, a selenium photoconductor, or an amorphous silicon photoconductor, and the surface of the photoconductor drum 11 is removed by a charging device 12. After being charged in this manner, an electrostatic latent image is formed on the surface of the photosensitive drum 11 by irradiation with laser light or the like in accordance with image information or print information by the exposure device 13, and The electrostatic latent image is conveyed to the developing unit as it rotates, and the electrostatic latent image is conveyed to the position of the pressure roller 19 where the toner image formed by the toner adhering to the electrostatic latent image is transferred to the recording paper 20. After the visible image transferred by the roller 19 is fixed by a fixing device (not shown), the recording paper 20 on which the visible image is fixed is discharged to a stacker (not shown). The surface of the photosensitive drum 11 that has completed the transfer is cleaned by the cleaning blade 17,
The charge is removed by the charge removing device 18 to return to the initial state.

The electrophotographic method is roughly classified into a dry developing method and a wet developing method (liquid developing method). In the dry developing method, toner particles are used alone or as toner as a developer. Used as a mixture with magnetic particles called a carrier, both are methods using a powdery developer, while the wet development method uses a liquid developer in which toner is dispersed in a liquid serving as a carrier. It is a method.

In these developing systems, the toner particle size is smaller in order to more faithfully reproduce the electrostatic latent image formed on the photoconductive insulator and to output a higher definition image. Is preferred.

However, in the dry development method, it has been pointed out that when the particle size becomes small, the inside of the apparatus is contaminated, the handling property is poor, and it is easily inhaled into the human body and the harmfulness becomes large, and the particle size is about 5 μm. It is not very practical to use the following toners in dry development.

On the other hand, in the wet development, since the toner particles are present in the liquid, a high-definition image can be obtained without causing the above problems even when the toner particles having a particle size of about 5 μm or less are used. There is an advantage to be.

Generally, a liquid developer for electrophotography contains toner particles mainly composed of a coloring agent such as carbon black, organic pigments and dyes and a binder resin, such as petroleum-based aliphatic hydrocarbon and silicone oil. It has a structure in which a substance having a high insulating property and a low dielectric constant is dispersed in a carrier liquid.

At this time, the chargeability of the toner particles and the colorant particles in the carrier liquid is important, and by controlling the charge amount of the toner particles to an appropriate level, good developing characteristics can be obtained and high quality can be obtained. Images can be formed. In general,
In many cases, a charge control agent is added in the toner particles or in the carrier liquid for the purpose of such charge adjustment.

As such a charge control agent, for example,
Titanium-based organic compounds (see Japanese Patent Application No. 04-311106), metal soaps such as naphthenic acid metal salts and octylic acid metal salts, and surfactants such as lecithin and higher fatty acids (Japanese Patent Application No. 06-170506). , Japanese Patent Application No. 09-50
0997, Japanese Patent Application No. 09-071851, Japanese Patent Application No. 08-072806, etc.) are used.

[0012]

However, even if such a titanium-based organometallic compound or surfactant is used, it is difficult to say that a sufficient effect can be obtained.

Therefore, the present invention provides excellent image quality,
An object is to provide a liquid developer for stably forming a high quality image.

[0014]

Means for solving the problems of the present invention will now be described. In order to achieve the above object, the present invention provides a positively chargeable liquid developer,
It is characterized by being composed of at least an insulating carrier liquid, toner particles, and an organometallic compound containing aluminum.

As shown in FIG. 1, by adding the organometallic compound containing aluminum to the insulating carrier liquid, the toner particles can be stably charged with a large electric charge in the insulating carrier liquid, and the toner particles are excellent. Development characteristics and dispersion stability can be obtained, and as the charge amount increases, the fogging decreases as shown in FIG. 1, so that a good image without fogging can be formed.

As the organometallic compound exhibiting such an effect, an organometallic compound in which at least one bond of aluminum is bound to oxygen, typically an alkoxide compound represented by the chemical formula [1] and a chemical formula A chelate compound represented by [2] is mentioned.

[Chemical 1]

[Chemical 2]

In this case, the chelate compound is
In addition to being less likely to change quality by reacting with moisture in the air, it is less likely to change quality in an insulating carrier liquid by reacting with other components. These compounds have different dispersibility in the insulating carrier liquid depending on their chemical structures, but those that cannot be dispersed in the insulating carrier liquid are not preferable, and can be dissolved or micelle (colloidal) and dispersed in the insulating carrier liquid. Those are preferable.

Examples of such compounds include ethyl acetate aluminum diisobutoxide as the alkoxide compound, and ethyl acetate aluminum diisopropoxide and alkylacetoacetate aluminum diisopropoxide as the chelate compound.

These organometallic compounds containing aluminum may be used alone or in combination of two or more, and the organometallic compound may be used in a carrier liquid in an amount of 0.0
It is preferable to add 1 to 10% by weight, and more preferably 0.01 to 5% by weight. If it exceeds 10% by weight, floating charges increase in the insulating carrier liquid, and it becomes difficult to move the particles due to the electric field.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Now, a procedure suitable for carrying out the present invention will be described. First, as a method for producing a liquid developer in the present invention, a known method is used, for example, a binder resin, a colorant, a material such as an insulating carrier liquid is mixed by a method such as a ball mill, Method for obtaining a toner in which a binder resin and a colorant are adsorbed (JP-A-55-36847)
(See Japanese Patent Publication) may be used.

As another manufacturing method, a material such as a colorant, a binder resin, an isoparaffin organic liquid is heated to solvate the binder resin and the organic liquid, and then the temperature of the solution is lowered. Alternatively, a method of depositing a binder resin containing a colorant as particles (see JP-A-61-180248) may be used.

Further, a toner composition prepared by kneading a colorant and other necessary additives in a binder resin is pulverized in a carrier liquid by using various pulverization and mixing devices such as a bead mill and an attritor to form fine particles. It is also possible to use the method described above or a method in which particles composed of a binder resin and a colorant are separately prepared and then the particles are dispersed in an insulating carrier liquid using a mixer or a bead mill.

The average particle diameter of the toner particles thus dispersed is preferably 0.1 to 10 μm, and the content of the toner particles is 1 to 50% by weight based on the total amount of the liquid developer.
Is preferred.

In any case, in the present invention, an organometallic compound containing 0.01 to 10% by weight of aluminum in the insulating carrier liquid, in particular, an organometallic compound in which at least one of the aluminum bonds is bound to oxygen. A compound, typically an alkoxide compound or a chelate compound, is added.

Examples of the insulating carrier liquid of the liquid developer used in such a manufacturing process include petroleum saturated hydrocarbon compounds such as isoparaffin, silicone oils such as dimethyl silicone and fluorosilicone, soybean oil and linseed oil. Vegetable oil etc. are mentioned.

Further, these contain a polymer type dispersion stabilizer which is soluble in the insulating carrier liquid and a dispersion stabilizer which is insoluble in the insulating carrier liquid such as silica particles, alumina particles and titania particles. Is also good.

Further, it is preferable that the toner particles are practically insoluble in the insulating carrier liquid used, and if the binder resin and the like of the toner particles are dissolved and present in the insulating carrier liquid in a large amount, the toner particles are It is not uncommon to reduce charging characteristics and developing characteristics, and even when an organometallic compound containing aluminum is added, the charge control effect is obtained by the interaction with the components dissolved in the insulating carrier liquid. May not be obtained sufficiently.

The toner particles used in the present invention are
It is composed of a binder resin and a colorant, but if the binder resin is a thermoplastic resin that can be fixed on a recording medium such as recording paper, it can be used regardless of the resin composition, glass transition temperature, softening temperature, or molecular weight. can do. However, in order to obtain preferable melt fixing characteristics, it is preferable to use a binder resin having a low flow tester softening temperature or a glass transition point, and a toner flow tester softening temperature of 140 ° C. or lower is particularly preferable.

Further, a toner having a glass transition point of 75 ° C. or lower is particularly preferable. For example, vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, epoxy resin, styrene resin, acrylic resin, polyethylene resin, polypropylene resin, Fluorine-based resin, polyamide-based resin, polyacetal-based resin, polyester-based resin, phenol-based resin, polyurethane-based resin, rosin and rosin-modified resin, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer and the like can be mentioned.

It is also possible to use known waxes such as paraffin wax, polyethylene wax, polypropylene wax, polyester wax, alcohol wax and urethane wax. Furthermore, it is also possible to use a mixture of a plurality of these resins and wax.

The colorant used in the present invention is not particularly limited, and many inorganic pigments, organic pigments and dyes can be used. For example, the inorganic pigments include carbon black, red iron oxide, ferrite, magnetite, etc., and the organic pigments include monoazo red pigments, disazo red pigments, quinacridone magenta pigments, phthalocyanine cyan pigments, and anthraquinone blue pigments. And so on. Further, two or more kinds may be mixed and used, and in any case, the above pigment content is preferably 1 to 90% by weight based on the total amount of the toner particles. In addition to this, the toner particles may contain a charge control agent such as a quaternary amine compound.

Next, the liquid developer prepared as described above is subjected to charge amount measurement and printing test in order to evaluate the characteristics. First, in the charge measurement test, the toner particle size is measured using a particle size distribution measuring device CIS-1 (trade name, manufactured by GALAI). Next, the liquid developer was filled between the facing electrode plates, electrolysis was applied, and the charge amount per unit weight of the toner was calculated from the amount of current flowing between the electrodes and the weight of the toner particles adhering to the electrodes for evaluation. To do.

Next, a printing test is performed on this liquid developer using a laser printer (a prototype by the applicant of the present invention) using the liquid developer. In this case, the liquid developer is supplied from the developer supply roller to the developing roller and stretched to form a thin toner layer having a thickness of several μm. The toner layer is brought into contact and the toner is developed on the photosensitive drum. The developed toner layer is transferred onto a recording paper via an intermediate transfer body to obtain a printed matter. The characteristics of the liquid developer are evaluated by measuring the image densities of the image portion and the non-image portion of the print image thus formed.

Based on the above matters,
The present invention will be specifically described with reference to examples, but of course,
The present invention is not limited to the following, and comparative examples will also be described in order to clarify the effects of the present invention.

Example 1 First, 30 parts by weight of a polyester resin (NCP-001J; trade name of Nippon Carbide) 70 parts by weight of cyan pigment (B2G; trade name of Clariant Co., Ltd.) were put into a Henschel mixer and premixed. After going
Melt-kneading with an extruder (TCS30; trade name of Buss), and coarse pulverization with a rotoplex pulverizer to obtain a toner composition coarse powder.

Then, 20.0 g of this toner composition coarse powder, 1.0 g of alkylacetate aluminum diisopropylate (Plenact AL-M; trade name manufactured by Ajinomoto Fine-Techno Co., Inc.) which is a chelate compound, and Isopar H (isoparaffin carrier liquid) 179.0 g (trade name, manufactured by ExxonMobil) were mixed, put together with zirconia beads in a ceramic pot, stirred for 120 hours, and pulverized to obtain a liquid developer.

When the above-mentioned particle size measurement and charge amount measurement were performed on this liquid developer, the average particle size of the toner particles contained in the liquid developer was 2.5 μm, and the charge amount was 248 μm.
C / g, indicating good positive charging property. In addition, when the above-mentioned printing test was conducted using this liquid developer,
The fog was 0.001 and a clear image having substantially no fog in the non-image area was obtained.

Example 2 Example 2 was repeated except that the alkyl acetate aluminum diisopropylate of Example 1 was replaced by ethyl acetoacetate aluminum diisopropylate (ALCH; trade name of Kawaken Fine Chemicals), which is also a chelate compound. A liquid developer was prepared in the same manner as in Example 1.

When the above-mentioned particle size measurement and charge amount measurement were performed on this liquid developer, the average particle size of the toner particles contained in the liquid developer was 2.3 μm, and the charge amount was 209 μm.
C / g, indicating good positive charging property. In addition, when the above-mentioned printing test was conducted using this liquid developer,
The fog was 0.005, and a clear image having substantially no fog in the non-image area was obtained.

(Example 3) The alkylacetate aluminum diisopropylate of Example 1 described above was converted into a chelate compound of aluminum = monoisopropoxymonooleoxyethylacetoacetate (OL-100).
A liquid developer was prepared in the same manner as in Example 1 except that the product name was 0; Kawaken Fine Chemical Co., Ltd.).

When the above-mentioned particle size measurement and charge amount measurement were performed on this liquid developer, the average particle size of the toner particles contained in the liquid developer was 2.2 μm, and the charge amount was 216 μm.
C / g, indicating good positive charging property. In addition, when the above-mentioned printing test was conducted using this liquid developer,
The fog was 0.002, and a clear image having substantially no fog in the non-image area was obtained.

Example 4 Example 4 was repeated except that the alkylacetate aluminum diisopropylate of Example 1 was replaced with ethyl acetoacetate aluminum dibutyrate (EB-2; Hope Pharmaceutical Co., Ltd.) which is an alkoxide compound. A liquid developer was prepared in the same manner as in 1.

When the above-described particle size measurement and charge amount measurement were performed on this liquid developer, the average particle size of the toner particles contained in the liquid developer was 2.4 μm, and the charge amount was 207 μm.
C / g, indicating good positive charging property. In addition, when the above-mentioned printing test was conducted using this liquid developer,
The fog was 0.002, and a clear image having substantially no fog in the non-image area was obtained.

Comparative Example 1 A liquid developer was prepared in the same manner as in Example 1 except that the alkyl acetate aluminum diisopropylate of Example 1 was not added.

When the above-mentioned particle size measurement and charge amount measurement were performed on this liquid developer, the average particle size of the toner particles contained in the liquid developer was as large as 4.6 μm, and the charge amount was 39 μC. It was as small as / g, and the chargeability was significantly reduced. Further, when the above-mentioned printing test was conducted using this liquid developer, the fog was 0.121, and a clear fog was visually observed in the non-image area.

(Comparative Example 2) The same procedure as in Example 1 was carried out except that the alkyl acetate aluminum diisopropylate of Example 1 was replaced by a titanium-based organometallic compound (KR-TTS; trade name of Ajinomoto Fine Chemicals). A liquid developer was prepared.

When the above-mentioned particle size measurement and charge amount measurement were performed on this liquid developer, the average particle size of the toner particles contained in the liquid developer was as large as 3.8 μm, and the charge amount was It was as small as 25 μC / g, and a large decrease in chargeability was observed. Further, when the above-mentioned printing test was conducted using this liquid developer, the fog was 0.1
In No. 03, a clear fog was visually observed in the non-image area.

(Comparative Example 3) The same procedure as in Example 1 was carried out except that the alkylacetate aluminum diisopropylate of Example 1 was replaced by a titanium-based organometallic compound (KR-38S; trade name of Ajinomoto Fine Chemicals). A liquid developer was prepared.

When the above-described particle size measurement and charge amount measurement were performed on this liquid developer, the average particle size of the toner particles contained in the liquid developer was 2.5 μm, which was equivalent to that in Example 1. However, the amount of charge is still small at 44 μC / g,
A great decrease in the charging property was observed. Further, when the above-mentioned printing test was conducted using this liquid developer, the fog was 0.075, and a clear fog was visually observed in the non-image area.

(Comparative Example 4) The same procedure as in Example 1 was carried out except that the alkyl acetate aluminum diisopropylate of Example 1 was replaced by a titanium-based organometallic compound (KR-9SA; trade name, manufactured by Ajinomoto Fine Chemicals, Inc.). A liquid developer was prepared.

When the above-mentioned particle size measurement and charge amount measurement were performed on this liquid developer, the average particle size of the toner particles contained in the liquid developer was 3.1 μm, which was rather large, and the charge amount was It was still as small as 35 μC / g, and a large decrease in chargeability was observed. Further, when the above-mentioned printing test was conducted using this liquid developer, the fog was 0.07.
In No. 6, a clear fog was visually observed in the non-image area.

(Comparative Example 5) The above-mentioned alkyl acetate aluminum diisopropylate of Example 1 was converted into a titanium-based organometallic compound (TA-30; trade name of Matsumoto Pharmaceutical Co., Ltd.).
A liquid developer was prepared in the same manner as in Example 1 except for the above.

When the above-mentioned particle size measurement and charge amount measurement were performed on this liquid developing solution, the average particle size of the toner particles contained in the liquid developing solution was a little large at 2.9 μm, and the charge amount was It was still as small as 89 μC / g, and a large decrease in chargeability was observed. Further, when the above-mentioned printing test was conducted using this liquid developer, the fog was 0.03.
In No. 8, a clear fog was visually observed in the non-image area.

(Comparative Example 6) The same procedure as in Example 1 was carried out except that the alkyl acetate aluminum diisopropylate of Example 1 was replaced by a titanium-based organometallic compound (TC-750; trade name of Matsumoto Pharmaceutical Co., Ltd.). To prepare a liquid developer.

When the above-described particle size measurement and charge amount measurement were performed on this liquid developer, the average particle size of the toner particles contained in the liquid developer was 3.1 μm, which was rather large, and the charge amount was It was still as small as 98 μC / g, and a large decrease in chargeability was observed. Further, when the above printing test was conducted using this liquid developer, the fog was 0.02.
In No. 6, light fogging was visually observed in the non-image area.

(Comparative Example 7) Example 1 was repeated except that the alkyl acetate aluminum diisopropylate of Example 1 was replaced by zirconium octylate (Nikka Octix Zr (T); trade name of Nippon Kagaku Sangyo Co., Ltd.). A liquid developer was prepared in the same manner.

When the above-mentioned particle size measurement and charge amount measurement were performed on this liquid developer, the average particle size of the toner particles contained in the liquid developer was 2.8 μm, which was rather large, and the charge amount was It increased to 152 μC / g. Also,
When the above-mentioned printing test was conducted using this liquid developer, the fog was 0.018, and light fog was visually observed in the non-image area.

(Comparative Example 8) The same procedure as in Example 1 was carried out except that the alkyl acetate aluminum diisopropylate of Example 1 was changed to zinc octylate (Nikka Octix Zn; trade name manufactured by Nippon Kagaku Sangyo Co., Ltd.). Liquid developer was prepared.

When the above-mentioned particle size measurement and charge amount measurement were performed on this liquid developing solution, the average particle size of the toner particles contained in the liquid developing solution was slightly large at 3.0 μm, and the charge amount was 166 μC / g, which was slightly higher. Also,
When the above-mentioned printing test was conducted using this liquid developer, the fog was 0.021, and light fog was visually observed in the non-image area.

FIG. 2 FIG. 2 shows the above-mentioned Examples 1 to 4 and Comparative Example 1.
To a summary of the test results for Comparative Example 8,
The charge control agents added, the amount of charge, the average particle size of the toner particles, and the fog are shown. As is clear from FIG. 1, when the charge amount exceeds 200 μC / g, the fog becomes 0.005 or less, and it is understood that good printing characteristics can be obtained.

Referring again to FIG. 1, FIG. 1 is a graph of the results summarized in FIG.
There is an inversely proportional correlation between the charge amount and the fog. It is considered that this is because the toner particles are more likely to be dispersed in the insulating carrier liquid due to the electric repulsive force due to the increase in the amount of charge, and good dispersion stability can be obtained.

Further, as the average particle size of the toner particles increases, the fog tends to increase, which is considered to be because the dispersion stability decreases when the toner particles are large.

Here, the detailed features of the present invention will be described again. (Supplementary Note 1) At least an insulating carrier liquid, toner particles,
A positively chargeable liquid developer comprising an organometallic compound containing aluminum. (Supplementary Note 2) The positively chargeable liquid developer according to Supplementary Note 1, wherein the organometallic compound is an organometallic compound in which at least one bond of aluminum is bound to oxygen. (Supplementary Note 3) Supplementary note 2 characterized in that the organometallic compound is a partially chelated organometallic compound.
The positively chargeable liquid developer described. (Supplementary Note 4) The positively chargeable liquid developer according to Supplementary Note 2, wherein the organometallic compound is an alkoxide compound. (Supplementary Note 5) The positively chargeable liquid developer according to any one of Supplementary Notes 1 to 4, wherein the organometallic compound is added to the insulating carrier liquid in an amount of 0.01 to 10% by weight. . (Supplementary Note 6) The positive charging according to any one of claims 1 to 5, wherein the toner particles are composed of at least a colorant and a binder resin and are insoluble in the insulating carrier liquid. Liquid developer.

[0064]

According to the present invention, since an organic metal compound containing aluminum such as an alkoxide compound or a chelate compound is added to the insulating carrier liquid, the charge amount of the toner particles in the positively chargeable liquid developer is increased. It is possible to increase the dispersion stability and increase the dispersion stability, which enables image formation with excellent image quality, and greatly contributes to the spread of high-performance wet development type image forming apparatuses.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of charge amount dependency of fogging of a liquid developer.

FIG. 2 is an explanatory diagram of an additive charge adjusting agent for fog of a liquid developer, a charge amount of toner particles, and an average particle size dependency.

FIG. 3 is a conceptual configuration diagram of a process unit by electrophotography.

[Explanation of symbols]

11 Photosensitive drum 12 Charging device 13 Exposure equipment 14 Developer supply roller 15 Developing roller 16 Recovery blade 17 Cleaning blade 18 Static eliminator 19 Pressure roller 20 recording paper

Claims (3)

[Claims] 1. A positively chargeable liquid developer comprising at least an insulating carrier liquid, toner particles, and an organometallic compound containing aluminum. 2. The positively chargeable liquid developer according to claim 1, wherein the organometallic compound is a partially chelated organometallic compound. 3. The positively chargeable liquid developing device according to claim 1, wherein the toner particles are composed of at least a colorant and a binder resin and are insoluble in the insulating carrier liquid. Agent.