JPH0792741A - Liquid developer - Google Patents

Abstract

PURPOSE:To enhance developing speed and transfer properties and to keep the characteristics of a developer from varying even after a long period of use by specifying the volume-average particle diameter and the particle diameter distribution of polymer particulates dispersed in a medium liquid. CONSTITUTION:In the liquid developer comprising polymer particulates dispersed in a medium liquid, the polymer particulates have a volume-average particle diameter d50 of 0.5 to 5.0mum, preferably 0.5 to 3.0mum, with such a sharp distribution of particle diameters that 80 vol% of the total quantity of polymer particulates have particle diameters in the range of d50+ or -1mum, preferably d50+ or -0.5mum. An example of a resin composing the polymer particulates is a polyester resin soluble in nonaqueous organic solvents, which is obtained by emulsion dispersion granulation method, etc., with a variety of additives, e.g. pigment and charge controlling agent, blended therein at need. An isoparaffin solvent and the like is used as the dispersion medium, with the concentration of the polymer particulates in the dispersion medium being 0.5 to 50wt.%, preferably 2 to 10wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developer used for developing a latent image formed on a latent image carrier.

[0002]

2. Description of the Related Art Electrophotographic systems are roughly classified into a dry development method and a wet development method. Among them, the wet development method in which the toner is used in the liquid has the advantages that the toner particle size can be used even in the submicron range and that it has high resolution, excellent gradation, and easy fixing. .

However, in the conventional wet development method in which particles of sub-micron size are used as toner, a high electric field is required when electrostatic transfer is performed because the charge of the toner becomes too high, which makes transfer difficult. Further, as the toner particle size decreases, the toner mobility in the liquid decreases,
It has a drawback that the developing speed is slow and it is not suitable for high speed.

In order to solve these drawbacks, for example, in US Pat. Nos. 4,794,651 and 4,842,974, resin particles having fibrous protrusions on the surface thereof are used as toner particles (average particle size 1 to 1).
The liquid developer used as 3 μm) is disclosed. The resin particles are produced by an in-liquid pulverization method in which shear stress is applied in the liquid to tear the resin. In particular,
A method of cooling a resin solution in which a resin and a pigment are dispersed in a dispersion medium to form a sea surface product, and pulverizing the resin solution to a desired particle size in the liquid, slowly cooling the resin solution while stirring to precipitate the resin particles. As a method, a method of kneading a resin and a pigment at a melting point or higher and then crushing the kneaded product in a liquid is mentioned.

[0005]

However, the above toner also has the following drawbacks.

The resin fine particles produced by the submerged pulverization method have a broad particle size distribution. Considering that the development speed depends on the particle size, if the development is continued with a developer having irregular particle sizes, the toner with a large particle size develops, so the characteristics of the developer change after long-term use. The so-called particle size selection development occurs.

Therefore, an object of the present invention is to solve the above-mentioned problems, improve the developing speed and transferability, and have a sharp particle size distribution to prevent particle size selective development from occurring even after long-term use. It is to provide a liquid developer whose characteristics are hard to change.

[0008]

The present invention is a liquid developer in which polymer particles are dispersed in a medium liquid, wherein the polymer particles have a volume average particle diameter d ₅₀ of 0.5 to 5.0 μm and the polymer particles are fine. Is present in the range of d ₅₀ ± 1 μm.

The volume average particle diameter d _{50 of the} polymer fine particles is 5.
If it is larger than 0 μm, a high-definition image cannot be obtained, while
If it is less than 0.5 μm, the transferability is adversely affected. When the particle size distribution of the polymer particles is broad, the particles having a large particle size are developed, and the characteristics of the developer change after long-term use.

Therefore, the volume average particle diameter d _{50 of the} polymer fine particles dispersed in the dispersion medium is 0.5 to 5.0 μm, preferably 0.5 to 3.0 μm, and 8 times the total amount of the polymer fine particles.
0 vol% is d ₅₀ ± 1 μm, preferably d ₅₀ ± _0.5 μ
The liquid developer of the present invention that achieves the above-described desired effects can be provided by using a material having a sharp particle size distribution that exists in the range of m.

The liquid developer of the present invention will be described below. As described above, the liquid developer of the present invention is made by dispersing at least polymer fine particles having a specific volume average particle size and a specific particle size distribution in a dispersion medium.

The fine polymer particles used in the present invention are
Resin fine particles in which various additives such as pigments, charge control agents, waxes, etc. are added to the resin as necessary, and appropriately selected from conventionally known methods in accordance with the resin component and the desired particle size or shape. Then it can be manufactured. For example, a suspension polymerization method, an emulsion polymerization method, a non-aqueous dispersion polymerization method, an emulsion dispersion granulation method, a wet production method such as a seed polymerization method, a spray drying method, a dry production method such as a pulverization method, etc. From the viewpoint of obtaining spherical resin particles in high yield, a wet manufacturing method or a spray drying method is preferable. Further, among the wet production methods, polymer fine particles obtained by the emulsification dispersion granulation method are used in view of the large number of types of usable resins, the ease of adjusting the molecular weight, the resin blending property, the sharpness of the particle size distribution, and the like. Is desirable.

In the emulsification dispersion granulation method, a polymer solution obtained by dissolving a polymer in a non-water-soluble organic solvent is emulsified and dispersed in an aqueous dispersion to form an O / W type emulsion, and the O / W type emulsion is stirred while stirring. It is carried out by applying heat to the emulsion to evaporate the organic solvent to precipitate polymer particles. According to this, the process is simplified and polymer fine particles can be obtained by a relatively simple operation. Therefore, the production efficiency can be improved and the cost can be reduced.
Further, it has advantages such as a sharper particle size distribution and a wider variety of usable resins as compared with the pulverization method. The emulsification dispersion method will be specifically described below.

Resin for constituting polymer fine particles (100 parts by weight)
And a coloring pigment (5 to 20 parts by weight) in a water-insoluble organic solvent (3
(100 to 1000 parts by weight) to thoroughly disperse the resin solution.
At this time, various color pigments such as carbon black and phthalocyanine can be used as the colorant, but the colorant is not limited to this, and can be used even if the dye or the resin itself is colored.

The resin for forming the polymer fine particles may be any polymer as long as it is a polymer soluble in a water-insoluble organic solvent, and is not limited thereto. For example, polyester resin, styrene-acrylic copolymer, polystyrene, polyvinyl chloride. Resins such as polyvinyl acetate, polymethacrylic acid ester, polyacrylic acid ester, epoxy resin, polyethylene, polyurethane, polyamide and paraffin wax are used alone or in combination of two or more.

Unlike the dry development method, the liquid development method does not perform charging by rubbing toner particles (polymer fine particles) with a charging member such as carrier particles, so that the toner spent or fusion is taken into consideration. No need to select resin properties. Therefore, in the liquid developer of the present invention, a low melting point resin can be used, which can reduce the heat of fixing.

The non-water-soluble organic solvent is one which dissolves the polymer and is insoluble or hardly soluble in water. Particularly, those having a boiling point of 0 ° C. or higher and 50 ° C. or lower are preferable. Specific examples thereof include, but are not limited to, methylene chloride, diethyl ether, acetone, toluene, methyl acetate and the like.

Subsequently, the obtained resin solution is dispersed in the aqueous dispersion using a high shearing force agitator. The aqueous dispersion may be appropriately selected, but water or a mixture thereof in which an appropriate amount of methyl alcohol or ethyl alcohol is added can be used, and water is particularly preferable. When water is used, the resin solution (30 to 100 parts by weight) is used as a dispersion stabilizer and a dispersion stabilization aid (1 to 5 parts).
It is preferable to disperse it in water (100 parts by weight) together with (parts by weight). Specifically, an O / W emulsion is obtained by using a stirrer such as a homomixer at a stirring speed according to the desired particle size. At this time, the volume average particle diameter d ₅₀ of the polymer fine particles is set to 0 by appropriately adjusting the stirring speed, stirring time and the like.
5 to 5.0 μm and the total amount of polymer particles is 80 vol.
% Is in the range of d ₅₀ ± 1 μm, more preferably d ₅₀ ± 0.5 μm. In general, the larger the stirring speed, the smaller the particle size, and the longer the stirring time, the sharper the particle size distribution tends to be. Therefore, if the stirring time is too short, a sharp particle size distribution cannot be obtained, and the stirring time is preferably 10 minutes or longer.
It is preferable to carry out stirring for 30 minutes or more.

The volume average particle diameter d ₅₀ and the particle diameter distribution in the present invention were all measured using SALD-1100 manufactured by Shimadzu Corporation.

As the above-mentioned dispersion stabilizer, those which become hydrophilic colloid in the aqueous dispersion are preferable, and especially gelatin,
Examples thereof include gum arabic, agar, cellulose derivatives (eg, hydroxymethyl cellulose, hydroxypropyl cellulose, etc.), synthetic polymers (eg, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylate, polymethacrylate, etc.).

As the dispersion stabilizing aid, a surface active agent is usually used, and a natural surface active agent such as saponin, a nonionic surface active agent such as alkylene oxide type, glycerin type or glycidol type, carboxylic acid, sulfonic acid,
Examples thereof include anionic surfactants containing an acidic group such as phosphoric acid, a sulfuric acid ester group and a phosphoric acid ester group.

The combination of the dispersion stabilizer and the dispersion stabilizing auxiliary is particularly preferable as a cellulose derivative (methyl cellulose derivative) and an anionic surfactant (sodium dodecylbenzene sulfonate) or polyvinyl alcohol and an anionic surfactant. It is an agent.

Next, in order to remove the organic solvent in the droplets dispersed in the aqueous dispersion, the temperature of the entire system is slowly raised, and the organic solvent in the droplets is evaporated while stirring. Then, the fine particles are taken out from the emulsion through a separation step such as filtration or centrifugation, and if necessary, a step such as washing is added and then dried to obtain desired polymer fine particles.

The polymer fine particles obtained by the above-mentioned emulsion dispersion granulation method have a spherical shape and a smooth surface, but in the wet development method of the present invention, they are spherical fine particles. However, it can be used as a developer.

On the other hand, it is also possible to obtain fine polymer particles having a relatively narrow particle size distribution by the spray drying method. The spray drying method will be described below.

Similar to the emulsion dispersion granulation method, the polymer is first dissolved in an organic solvent to prepare a resin solution. A desired polymer fine particle is obtained by jetting from the nozzle a sufficiently dispersed colorant such as a pigment in the obtained resin solution and then heating to evaporate the organic solvent.

The solvent, polymer and colorant used may be the same as those used in the emulsion dispersion granulation method. If the concentration of the resin to be dissolved in the solvent is high, the particle size of the produced resin particles is large and the effect of the present invention cannot be obtained, while if it is too low, the yield is deteriorated. %, More preferably 1.5 to 15% by weight. Similar to the emulsion dispersion granulation method, the spray drying method has a wide selection range of the solvent and the polymer, and as the solvent, tetrahydrofuran (THF) which is a water-soluble solvent or the like can be used in addition to the above-mentioned ones. Further, two or more kinds of solvents may be mixed to adjust the viscosity, boiling point and the like.

This spray drying method can be carried out by a spray drying apparatus such as Dispercoat (manufactured by Nisshin Engineering Co., Ltd.). First, the above-mentioned resin solution is jetted into the drying chamber by a high-speed air stream, and dried by hot air blown from the lower part of the chamber to produce resin fine particles.
Desired polymer particles can be obtained by collecting the resin particles rising in the peripheral portion of the chamber in a collecting bottle or the like.

In the spray drying method, the particle size of the obtained fine particles can be easily controlled by adjusting the conditions such as the resin solution concentration and the spray pressure. Further, according to this method, since no surfactant or the like is used, resin particles free from impurities can be obtained, and it is not necessary to wash the resin particles with water, so that the process can be shortened.

Subsequently, the polymer fine particles obtained by the above method are added with known additives such as a charge control agent, a dispersion aid, a dispersion stabilizer and a resin, if necessary, to obtain a medium liquid (dispersion medium). An ultrasonic disperser or the like is used to disperse the liquid developer, and the liquid developer is prepared.

An electrically insulating organic material is generally used as the dispersion medium. For example, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes and the like can be used, but isoparaffinic solvents are preferable from the viewpoints of harmlessness, odor and cost. . Specifically, Isopar G, Isopar H, Isopar L,
Isopar K (above, manufactured by Esso), Shersol 71
(Manufactured by Shell Petrochemical Co., Ltd.), IP Solvent 1620, I
P solvent 2028 (above, Idemitsu Petrochemical Co., Ltd. make) is mentioned. Further, Japanese Patent Publication No. 51-19988 discloses a developing method using a water-based developer. When such a method is used, it is not necessary to use an electrically insulating substance as a dispersion medium and a low resistance such as water is obtained. A solvent can also be used.

The concentration of the polymer particles in the dispersion medium is
From the viewpoints of development speed, image fog and the like, it is desirable that the amount is 0.5 to 50% by weight, preferably 2 to 10% by weight. Incidentally, this concentration is a concentration at the time of development, and the concentration at the time of storage, replenishment, transportation, etc. may be higher than the above. Further, the substance used as the dispersion medium only needs to be liquid at the time of development, and need not be liquid at room temperature. Therefore, in the present invention, waxes or paraffins which are solid at room temperature can be used as the dispersion medium.

A charge control agent that imparts a charge of each polarity may be added to the dispersion medium. Known charge control agents can be used. For example, in order to charge the developer to a positive polarity, a metal salt of a fatty acid such as stearic acid, a metal salt of a sulfosuccinate ester, a metal salt of an organic acid such as a metal salt of abietic acid, or an alkyd resin adsorbed on particles, etc. Examples of the soluble polymer include a surfactant such as lecithin, a nitrogen-containing compound, or a soluble polymer such as a polyamide resin that is adsorbed on the particles in order to be charged negatively.

The charge control agent is added in an amount of 0.0001 to 10% by weight, preferably 0.001 to 3% by weight, based on the dispersion medium.

Furthermore SiO ₂ of the same amount about the charge control agent as a charge auxiliary _{agent, Al 2 O 3, TiO 2} , a metal oxide or the like may be added, such as ZnO.

Further, in order to stabilize the dispersion of the particles in the liquid developer, various surfactants or soluble polymers may be added as a dispersion aid or a dispersion stabilizer. Specific examples include polyolefin petroleum resin, linseed oil, polyalkylmethacrylate, and the like. Further, in order to enhance the affinity between the dispersion medium and the polymer particles, a small amount of a monomer having a polar group such as methacrylic acid, acrylic acid, and alkylaminoethyl methacrylate may be copolymerized and added.

Any amount of these may be added as long as the particles are dispersed so as not to agglomerate and cause no problem in use.
Also, since it depends on the type, it cannot be specified in a general way,
If the addition amount is too small, the dispersion effect is small and the particles agglomerate. If the addition amount is too large, the viscosity of the solution becomes too large and the particles do not easily move, and the developing speed is extremely reduced. Therefore,
Most preferably 0.01 to 20% by weight with respect to the dispersion medium,
More preferably, about 0.1 to 10% by weight is desirable.

Since the polymer fine particles of the present invention have a larger particle size than the conventional liquid developer, if they are left for a long time, the particles may settle, but an operation such as stirring at the time of use. There is no practical problem as long as it returns to the original dispersion state.

According to the above method, the particle size distribution of the fine polymer particles is sharp, the development speed and transferability are improved, and the particle size selective development hardly occurs even after long-term use and the characteristics of the developer are improved. A liquid developer that does not change easily is obtained.

[0040]

EXAMPLES The present invention will be specifically described below with reference to examples. In the following examples in "parts" shall be read refers to "parts by weight" unless otherwise indicated, the term "d _50" represents "average particle diameter".

Example 1 Low molecular weight polyester resin (M _W : 15000, M _n : 6000) 100
Parts were completely dissolved in methylene chloride so as to be 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of phthalocyanine as a colorant was dispersed in the resin solution. The resin solution obtained as described above was used as Metroose 65SH-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) 1
% And an aqueous dispersion of sodium lauryl sulphate 1% using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) 800
The emulsion was emulsified and dispersed at room temperature for 0 minutes for 30 minutes to obtain an O / W type emulsion. Next, replace with 4 blades for 40
Distill off the methylene chloride while stirring at ~ 45 ° C for 3 hours,
An aqueous suspension (suspension) of polymer fine particles for toner having a d ₅₀ of 2 μm was obtained. The solid content was taken out from the obtained aqueous suspension of polymer fine particles for toner by a centrifuge, washed well with water, filtered and dried to obtain polymer fine particles for toner having ad ₅₀ of 2 μm.

Example 2 100 low molecular weight polyester resin (M _W : 15000, M _n : 6000)
Parts were completely dissolved in methylene chloride so as to be 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of phthalocyanine as a colorant was dispersed in the resin solution. The resin solution obtained as described above was used as Metroose 65SH-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) 1
% And an aqueous dispersion of sodium lauryl sulphate 1% using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) 800
The emulsion was emulsified and dispersed at room temperature for 0 minutes for 10 minutes to obtain an O / W type emulsion. Next, replace with 4 blades for 40
Distill off the methylene chloride while stirring at ~ 45 ° C for 3 hours,
An aqueous suspension (suspension) of polymer fine particles for toner having a d ₅₀ of 2 μm was obtained. The solid content was taken out from the obtained aqueous suspension of polymer fine particles for toner by a centrifuge, washed well with water, filtered and dried to obtain polymer fine particles for toner having ad ₅₀ of 2 μm.

Example 3 Low molecular weight polyester resin (M _W : 15000, M _n : 6000) 100
Parts were completely dissolved in methylene chloride so as to be 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of phthalocyanine as a colorant was dispersed in the resin solution.

The resin solution obtained as described above was added to a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) in an aqueous dispersion of 1% Metroze 65SH-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) and 1% sodium lauryl sulfate. Using, 12000 rpm 3
The mixture was emulsified and dispersed for 0 minutes at room temperature to obtain an O / W type emulsion. Next, replace with 4 blades of stirring blade, 40 ~ 45 ℃
Methylene chloride was distilled off with stirring for 3 hours to obtain an aqueous suspension (suspension) of polymer fine particles for toner having ad ₅₀ of 0.5 μm. From the obtained aqueous suspension of polymer fine particles for toner, the solid content was taken out by a centrifuge, washed well with water, filtered and dried to obtain d _50.
To give 0.5 μm of fine polymer particles for toner.

Example 4 100 low molecular weight polyester resin (M _W : 15000, M _n : 6000)
Parts were completely dissolved in methylene chloride so as to be 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of phthalocyanine as a colorant was dispersed in the resin solution. The resin solution obtained as described above was used as Metroose 65SH-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) 1
% And an aqueous dispersion of 1% sodium lauryl sulfate using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) at a rate of 500 per minute.
The emulsion was emulsified and dispersed at room temperature for 0 minutes for 30 minutes to obtain an O / W type emulsion. Next, replace with 4 blades for 40
Distill off the methylene chloride while stirring at ~ 45 ° C for 3 hours,
An aqueous suspension (suspension) of polymer particles for toner having a d ₅₀ of 5 μm was obtained. The solid content was taken out from the obtained aqueous suspension of fine polymer particles for toner by a centrifuge, washed well with water, filtered and dried to obtain fine polymer particles for toner having d ₅₀ of 5 μm.

Example 5 100 low molecular weight polyester resin (M _W : 15000, M _n : 6000)
Toluene was completely dissolved such that 1.5 parts by weight of the mixture was obtained. Eiger motor mill (made by Eiger Japan)
Was used to disperse 20 parts of phthalocyanine as a colorant in the resin solution. Using the resin solution obtained as described above, the liquid supply rate was 1 L / hr and the drying temperature was 8 by Dispercoat (manufactured by Nisshin Engineering Co., Ltd.).
Spray granulation was carried out under conditions of 0 ° C. and a spray pressure of 5.5 kgf / cm ² to obtain polymer particles for toner having a d ₅₀ of 2.5 μm.

Comparative Example 1 Low molecular weight polyester resin (M _W : 15000, M _n : 6000) 100
Parts were completely dissolved in methylene chloride so as to be 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of phthalocyanine as a colorant was dispersed in the resin solution. The resin solution obtained as described above was used as Metroose 65SH-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) 1
% And an aqueous dispersion of sodium lauryl sulphate 1% using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) 800
It was emulsified and dispersed at room temperature for 5 minutes with 0 rotation to obtain an O / W type emulsion. Next, replace with 4 blades of stirring blades
Methylene chloride was distilled off while stirring at 45 ° C. for 3 hours, and d
An aqueous suspension (suspension) of polymer particles for toner having a ₅₀ of 2 μm was obtained. From the obtained aqueous suspension of polymer fine particles for toner, the solid content was taken out by a centrifuge, washed well with water, filtered and dried to obtain d _50.
To give 2 μm of polymer particles for toner.

Comparative Example 2 Low molecular weight polyester resin (M _W : 15000, M _n : 6000) 100
Parts were completely dissolved in methylene chloride so as to be 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of phthalocyanine as a colorant was dispersed in the resin solution. The resin solution obtained as described above was used as Metroose 65SH-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) 1
% And sodium lauryl sulfate 1% in an aqueous dispersion, using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), the emulsion was dispersed at 3000 rpm for 30 minutes at room temperature to obtain an O / W type emulsion. Then replace with 4 blades of stirring blades
Methylene chloride was distilled off while stirring at 3 ° C. for 3 hours to obtain an aqueous suspension (suspension) of polymer fine particles for toner having ad ₅₀ of 8 μm. The solid content was taken out from the obtained aqueous suspension of polymer particles for toner by a centrifuge, washed well with water, filtered, and dried to obtain polymer particles for toner having d ₅₀ of 8 μm.

Comparative Example 3 Low molecular weight polyester resin (M _W : 15000, M _n : 6000) 100
Parts were completely dissolved in methylene chloride so as to be 20% by weight. Using an Eiger motor mill (manufactured by Eiger Japan), 6 parts of phthalocyanine as a colorant was dispersed in the resin solution. The resin solution obtained as described above was used as Metroose 65SH-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) 1
% And an aqueous dispersion of 1% sodium lauryl sulfate using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) at a rate of 150 min.
The emulsion was emulsified and dispersed at room temperature for 30 minutes at 00 revolutions to obtain an O / W type emulsion. Next, replace with 4 stirring blades and 4
Methylene chloride was distilled off with stirring at 0 to 45 ° C. for 3 hours to obtain an aqueous suspension (suspension) of polymer fine particles for toner having ad ₅₀ of 0.4 μm. The solid content was taken out from the obtained aqueous suspension of polymer particles for toner by a centrifuge, washed well with water, filtered, and dried to obtain polymer particles for toner having d ₅₀ of 0.4 μm. .

80% by weight of the d _{50 of the} polymer fine particles for toner and the total amount of the particles obtained in the above Examples and Comparative Examples.
The range in which% is present is shown in Table 1 below.

[0051]

[Table 1]

3 parts of the polymer fine particles for each of the above-mentioned Examples 1 to 4 and Comparative Examples 1 to 3 were used as an electrically insulating isoparaffin solvent IP solvent 1620 (manufactured by Idemitsu Petrochemical Co., Ltd.).
It is added to 00 parts, 3 parts of lauryl methacrylate-methacrylic acid copolymer (lauryl methacrylate / methacrylic acid = 95/5) and 0.5 part of aluminum dihydroabietate are added thereto, and mixed with an ultrasonic disperser for 20 minutes. Seven kinds of liquid developers were obtained by dispersing.

Using each of the obtained liquid developers, copying was performed using the image forming apparatus shown in FIG. In Figure 1, (1)
Is a photosensitive drum that rotates in the direction of the arrow. Around the photoconductor drum (1) using a corotron charger (3),
After charging to 1000 V, an electrostatic latent image is written by the laser beam scanner (4). Reference numeral (20) is a developer bath, which is filled with each developer described above. (2)
Is a developing roller for drawing up the developer from the developer bath (20). In the developing area (8) facing the developing roller (2), the electrostatic latent image is visualized by each developing solution. At this time, the rotation speed of the photosensitive drum (1) is variable, and the rotation speed of the developing roller (2) is the ratio of the peripheral speed with respect to the photosensitive drum (1) (θ: rotation speed of developing roller / photosensitive drum The rotation speed was adjusted to be constant at θ = 10.

After that, the developer excessively adhered to the photoconductor is squeezed by a squeeze roller (5) to form a toner image containing a slight amount of solvent on the surface of the photoconductor drum (1). When the toner image is rotated as it is to the transfer position (9) facing the transfer roller (6), it is electrostatically transferred to the paper conveyed from another direction. At this time,
A voltage of -1000V is applied to the transfer roller (6). After the transfer paper is separated from the photoconductor drum (1), it is conveyed to a heat fixing roller pair (7), where it is fixed by heat and pressure, thereby completing a series of copying operations.

In addition, with respect to the above Examples 1 to 4 and Comparative Examples 1 to 3, the development rate, transferability, long-term printing durability and sedimentation of particles were evaluated as described below, and the results are shown in Table 2.

(Development Speed) A solid image was output by changing the speed of the photoconductor drum (1) using the above image forming apparatus, and the image density ID on the photoconductor drum (1) was measured.
At this time, the lower limit of ID is defined as ID = 1.5, and the rotation speed of the maximum photosensitive drum (1) that can obtain this ID is ranked as the maximum developing speed as follows, and Δ or more is passed. . The image density ID is measured using the Sakura Densitometer PDA-6.
5 (manufactured by Konica) was used. ◎: Maximum development speed of 500 mm / s or more ○: Maximum development speed of 200 mm / s or more and 500 mm / s or less △: Maximum development speed of 50 mm / s or more and 200 mm / s or less ×: Maximum development speed of 50 mm / s or less (transferability) Above image After a solid image was output using a forming apparatus and transferred to paper, the amount of developer attached on the transfer paper and the amount of residual developer left on the photosensitive drum (1) were measured. The transfer efficiency was calculated based on the following formula and ranked as follows, and Δ or higher was regarded as acceptable. Transfer efficiency = (Amount of developer on paper) / (Amount of developer on paper + residual developer) ◎: Transfer efficiency 95% or more ○: Transfer efficiency 80% or more 95% or less △: Transfer efficiency 60% or more 80% Below x: Transfer efficiency 60% or less (printing durability) A solid image was output after 1000 sample images with a B / W ratio of 5% were output using the above image forming apparatus, and comparison with the initial image was performed. . The image density IDs before and after the printing of 1,000 sheets were measured and ranked according to the degree of change as follows. A level of Δ or above, which is a level that causes no problem in practical use, was passed. The “B / W ratio” is Whit.
Indicates the ratio of Black (image area) to e (paper surface). ◎: Image density change of 5% or less ○: Image density change of 5% or more and 10% or less △: Image density change of 10% or more and 20% or less ×: Image density change of 20% or more (particle sedimentation property) When polymer fine particles settle The density changes, the characteristics of the developer change, and the output image changes. Therefore, the finer the polymer particles, the more stable the image reproducibility is when the particles are less likely to settle, and generally the smaller the particle size is, the slower the settling speed is. In order to evaluate the particle settling property, a settling acceleration test was performed using a centrifuge, and the results were ranked as follows, and a value of Δ or higher was passed. The conditions for centrifugation were 5000 rpm and 5 min. ◎: Sedimentation particle amount 20wt% or less ○: Sedimentation particle amount 20wt% or more 40wt% or less △: Sedimentation particle amount 40wt% or more 60wt% or less ×: Sedimentation particle amount 60wt% or more

[0057]

[Table 2]

[0058]

As described in detail above, the high-definition property, which is a characteristic of liquid development, is not impaired, the developing speed and transferability are improved as compared with the conventional ones, and the characteristics of the developer change even after repeated use. It was possible to provide a liquid developer that is hard to do and does not affect the image change.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming apparatus that forms an image using the liquid developer of the present invention.

[Explanation of symbols]

 1 photoconductor drum 2 developing roller 20 developer bath

Claims (1)

[Claims] 1. A liquid developer in which particulate polymer particles are dispersed in a medium liquid, wherein the volume average particle diameter d ₅₀ of the polymer particles is 0.5 to 5.0 μm and the total amount of the polymer particles is 80 vol. % In the range of d ₅₀ ± 1 μm.