JPH08220812A - Electrophotographic liquid developer - Google Patents

Abstract

PURPOSE: To obtain a liquid developer with which a developing speed is improved and high vividness and high image density (I.D.) are obtainable by simultaneously dispersing toner particles, base dispersion resin and acidic dispersion resin which are respectively specific into a carrier liquid. CONSTITUTION: This electrophotographic liquid developer is composed by dispersing the toner particles consisting of a binder resin and coloring agents, the acid dispersion resin and basic dispersion resin soluble in the electrically insulatable carrier liquid into the carrier liquid. The basic dispersion resin acts to improve the chargeability of the toner particles by well adsorbing on the toner particle surfaces in the carrier liquid, and the acid dispersion resin is used to associate together with the basic dispersion resin by which the number of contact times of the toner particles and the basic dispersion resin is decreased and the degradation in the migration rate of the toner particles by neutralization is averted. The developing speed is thereby improved. The sufficient toner image density ID on the photoreceptor drum is assured and the images having the decreased floggings, etc., are obtd. at a high developing speed as well if the solid images are formed by changing the speed of the photoreceptor drum 1 and the ID is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developer for electrophotography 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, in the wet development method in which the toner is handled in a liquid, the toner particle size can be practically used even in the submicron range, and a high-definition image which cannot be obtained by the dry development method can be obtained. Further, there are advantages such as excellent gradation and easy fixing.

Usually, a liquid developer contains charged colored fine particles (in a carrier liquid having a high volume resistance value of about 10 ¹⁰ Ω · cm or more, for example, a solution of paraffin hydrocarbon, halogen hydrocarbon or polysiloxane). Toner particles) are suspended and dispersed. Then, the colored fine particles in the liquid are electrophoresed according to the electrostatic latent image formed on the latent image carrier such as the photoconductor or the electrostatic paper, and the development is performed by the electric force.

For the purpose of controlling the charge polarity or charge level of the toner particles, a metal salt of an organic acid, a polar group-soluble polymer, a nitrogen-containing compound or a surfactant such as lecithin is dissolved in a carrier liquid. Or it is considered to disperse. For example, JP-B-51-40465 discloses a liquid developer in which a basic polymer having N-vinyl-2-pyrrolidone as a constituent monomer is dissolved as a charge control agent in a carrier liquid. Further, Japanese Patent Publication No. 59-37826 discloses a liquid developer in which a polymer having an ethylenically unsaturated compound having a morpholino group as a monomer is added to a carrier liquid as a pigment dispersant having charge controllability.

[0005]

However, even when the charge control agent is contained as described above, the charge control effect or the dispersion stabilizing effect based on the charge control agent is low and a sufficient image density (hereinafter referred to as ID) is obtained. Is difficult to obtain. It is considered that this is because the colored fine particles are not properly charged because the basic polymer or the pigment dispersant that acts as a charge control agent in the carrier liquid does not undergo ion dissociation and exists as a simple substance.

Ricoh Technical Report, NO.9,22 (198
3) discloses a liquid developer in which adietic acid, acidic colored fine particles containing lauryl methacrylate and glycidyl methacrylate and a pyridine monomer alone are added to a developer, and the acidic colored fine particles in the developer have a negative polarity. It has been reported to be charged. However, in the above-mentioned constitution, although the chargeability of the colored fine particles is improved and the image density is obtained to the extent that there is no practical problem, the electrophoretic speed of the colored fine particles is very slow and the system speed is high. Was not applicable to.

Therefore, the object of the present invention is not limited to a copying machine or a printer, but is to secure a developing speed sufficient to be used as a substitute for a high-speed printing machine, etc. D is to provide a liquid developer.

[0008]

As various substances to be added to the carrier liquid, they serve to sufficiently contribute to the chargeability of the toner particles, and the toner particles in the carrier liquid can secure a high electrophoretic velocity. It needs to be operative to obtain. The present inventors have made various studies on this point, and as a result, a liquid that achieves the above object by simultaneously dispersing three components of toner particles, a basic dispersion resin and an acidic dispersion resin soluble in the carrier liquid in the carrier liquid. It has been found that a developer can be obtained.

That is, according to the present invention, toner particles composed of a binder resin and a colorant, an acidic dispersion resin and a basic dispersion resin soluble in the carrier liquid are dispersed in an electrically insulating carrier liquid. The present invention relates to a liquid developer characterized by the above.

The present invention has been made on the basis of experimental facts. By simultaneously dispersing the above-mentioned three components in an electrically insulating carrier liquid, a sufficient developing speed can be secured and a high definition can be obtained. And high I.D. It is based on the fact that D can provide a liquid developer. The reason for this is presumed as follows.

It is considered that the decrease in the developing speed when the liquid developer is used is due to the number of collisions between the toner particles and the counter ion particles.

That is, two toner particles and a basic dispersion resin are used.
In the case of the component constitution, charges are exchanged between the toner particles and the basic resin in the carrier liquid, and the toner particles are generally negatively charged and the basic resin (counter ion particles) are generally positively charged. Then, by applying a potential difference between the photoconductor and the developing electrode so that the photoconductor becomes positive, the toner particles are electrophoresed on the photoconductor side, and the basic dispersion resin is electrophoresed on the developing electrode side to perform development. In the carrier liquid, the toner particles and the basic dispersion resin, which are oppositely charged, move in opposite directions, so that the two particles collide with each other. The collision neutralizes the charge held by the particles, which causes the particles to stop migrating and the migration speed to become extremely slow. The migration of particles is temporarily suspended until the particles are charged again, which appears as a decrease in the developing speed. Therefore, by decreasing the number of collisions between the toner particles and the basic dispersion resin (counter ion particles) and performing the development without interrupting the migration of the toner particles, it is possible to improve the decrease in the developing speed. As described above, the liquid developer of the present invention is composed of the toner particles, the basic dispersion resin and the acidic dispersion resin. In this configuration, for example, when the toner is negatively charged, the acidic dispersion resin is negatively charged in the carrier liquid as in the toner particles, and migrates in the opposite direction to the positively charged basic dispersion resin. Therefore, since the basic dispersion resin collides with the acid dispersion resin in addition to the toner particles, the number of collisions between the toner particles and the basic dispersion resin is apparently reduced. Then, it is considered that the toner particles have a higher probability of migrating to the photoconductor while holding the charge, and the developing speed is improved. Also, the toner particles are
Although it may collide with the acidic dispersion resin, since both are charged to the same polarity, even if they collide with each other, charge neutralization does not occur, which affects the migration speed of toner particles, that is, the development speed of the liquid developer. There are few things.

Therefore, in the present invention, in the carrier liquid, the basic dispersion resin works well to adsorb on the surface of the toner particles to improve the chargeability of the toner particles, and the acidic dispersion resin is used in combination. By reducing the number of contact between the toner particles and the basic dispersion resin to improve the migration rate of the toner particles due to neutralization, the developing rate can be significantly improved.

Although the case where the toner is negatively charged has been described above, the present invention can be used even when the toner is positively charged.
In the case of positive charging, the acidic dispersion resin acts on the surface of the toner particles to improve the positive chargeability of the toner particles, and the basic dispersion resin acts to improve the migration speed of the toner particles. It is considered to be a thing. further,
The viscosity of the carrier liquid can be adjusted by the total amount of the acidic dispersion resin and the basic dispersion resin, and the dispersion stability of the toner particles in the carrier liquid can be controlled.

First, the toner particles dispersed in the carrier liquid in the liquid developer of the present invention will be described.

The toner particles are colored particles in which resin particles are mixed with a pigment or dye, and various additives such as wax, if necessary, and are conventionally known in accordance with the resin component and the desired particle size or shape. The manufacturing method may be appropriately selected from the available methods. For example, a method of fixing a pigment on the surface of resin fine particles obtained by a known method such as a wet pulverization method, an emulsion dispersion method, a spray drying method, an emulsion polymerization method, or the resin fine particles are not substantially dissolved, but the dye is For example, a method of dyeing resin fine particles with a dye in a solvent that dissolves. Specific devices for fixing the pigment to the surface of the resin fine particles include a hybridization system (manufactured by Nara Machinery Co., Ltd.), Ongmill (manufactured by Hosokawa Micron Co., Ltd.), and Dispercoat (manufactured by Nisshin Engineering Co., Ltd.). Incidentally, the spray drying method is most preferable for producing the resin fine particles. The spray drying method has advantages such as easy control of particle size of resin fine particles obtained by adjusting conditions such as resin solution concentration and spray pressure, and the fact that resin fine particles having a narrow particle size distribution can be obtained. Further, according to this method, since no surfactant is used and resin fine particles free of impurities are obtained, in the present invention, the effects of various dispersion resins added for imparting chargeability are not impaired. Further, the colored resin obtained by melt-kneading the colorant and the binder resin is roughly pulverized to a particle size of about 1 mm and further finely pulverized by using a dry fine pulverization device such as a jet mill.
Alternatively, a method of atomizing a coarsely pulverized product in a solvent using an apparatus such as a wet media mill can be used. Typical dry pulverization methods include a jet mill (manufactured by Nippon Pneumatic Mfg. Co., Ltd.) and a kryptron crusher (manufactured by Kawasaki Heavy Industries, Ltd.). Examples of wet media mills include Mitsubishi UF mill (manufactured by Mitsubishi Heavy Industries), Aigamoter mill (manufactured by Eiger Japan), Ultra Visco mill (manufactured by AIMEX), spike mill (manufactured by Inoue Seisakusho) and the like.

The most preferable method for the toner particles used in the liquid developer of the present invention is the above-mentioned melt-kneading method in which the variation of the charge amount due to the colorant is less likely to occur. More preferably, it is a method of wet pulverization using a media mill in an isoparaffin-based solvent. This method is particularly effective for a developer used for full-color development in which toners of different colors are simultaneously used. That is, since the chargeability of each toner is different depending on the type of colorant, the development amount of each color is not stable in full color, and a problem in terms of color reproducibility easily occurs. By using the dispersed toner, the colorant is covered with the resin, and the exposure amount of the colorant is suppressed, so that these problems can be solved.

The method for producing toner particles is not particularly limited to the above method as long as it is a method capable of producing particles in which a colorant (pigment, dye, etc.) and other additives are contained in the resin. Not something. It can be used regardless of whether the charging polarity is positive or negative.

If the average particle diameter of the toner particles is too small, it becomes 1
Since the surface area per particle is small, the amount of acidic dispersion resin or basic dispersion resin adsorbed in the carrier liquid is small, and a sufficient amount of charge cannot be obtained. Further, since the mobility of the toner particles is too low, the developing speed is slow, and there is a possibility that the image density cannot be sufficiently obtained in a region where the system speed is above a certain level. Further, if the average particle size becomes too large, it becomes impossible to obtain a high resolution and high definition image. Therefore, the volume average particle size of the colored fine particles is 0.5 to 5.0 μm,
It is desirable that the thickness be in the range of 1.0 to 3.0 μm. The values of the volume average particle size in the present invention are all SA
It was measured using LD-1100 (manufactured by Shimadzu Corporation).

As the binder resin constituting the toner particles in the liquid developer of the present invention, a binder resin generally used for ordinary toner can be used. For example, polyester resin, styrene-acrylic copolymer, polystyrene, polyvinyl chloride, polyvinyl acetate, polymethacrylic acid ester, polyacrylic acid ester, epoxy resin,
Resins such as polyethylene, polyurethane, polyamide, and paraffin wax are used alone or in combination of two or more. Further, in order to adjust the amount of functional groups existing on the resin surface, for example, polyacrylic acid, polymethacrylic acid or a copolymer thereof may be added. The liquid developing method does not perform charging by rubbing the toner particles (colored fine particles) with a charging member such as carrier particles, unlike the dry developing method, so that the toner particles may be spent or fused. 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 also reduce the heat of fixing.

Next, the acidic and basic dispersion resins will be described.

Examples of the basic dispersion resin or the acidic dispersion resin used in the liquid developer of the present invention include an acidic monomer containing a functional group exhibiting acidity or basicity, or a polymer formed from a basic monomer. Alternatively, any copolymer can be used as long as it is soluble in a carrier liquid having an electrically insulating property described later.

As the basic monomer constituting the basic dispersion resin, a nitrogen-containing basic monomer can be mentioned. For example,
N, N-dimethylaminoethyl (meth) acrylate, N,
N-diethylaminoethyl (meth) acrylate, N, N
-Dibutylaminoethyl (meth) acrylate, N, N-
Hydroxyethylaminoethyl (meth) acrylate, N
-Ethylaminoethyl (meth) acrylate, N-octyl, N-ethylaminoethyl (meth) acrylate, N,
(Meth) acrylates having an aliphatic amino group such as N-dihexylaminoethyl (meth) acrylate, N-methylacrylamide, N-octylacrylamide, N
-Phenylmethyl acrylamide, N-cyclohexyl acrylamide, N-phenyl acrylamide, Np
-Methoxy-phenylacrylamide, N, N-dimethylacrylamide, N, N-dibutylacrylamide,
(Meth) acrylamides such as N-methyl and N-phenylacrylamide, aromatic substituted ethylene-based monomers having a nitrogen-containing group such as dimethylaminostyrene, diethylaminostyrene, dimethylaminomethylstyrene and dioctylaminostyrene, vinyl- Such as N-ethyl-N-phenylaminoethyl ether, vinyl-N-butyl-N-phenylaminoethyl ether, triethanolamine divinyl ether, vinyldiphenylaminoethyl ether, N-vinylhydroxyethylbenzamide, m-aminophenylvinylether. Examples thereof include nitrogen-containing vinyl ether monomers. Further suitable nitrogen-containing basic monomers include nitrogen-containing heterocyclic compounds, of which pyrroles such as N-vinylpyrrole and N-
Pyrrolines such as vinyl-2pyrroline and N-vinyl-3-pyrroline, N-vinylpyrrolidine, vinylpyrrolidine amino ether, pyrrolidines such as N-vinyl-2-pyrrolidone, and imidazole such as N-vinyl-2-methylimidazole , Imidazolines such as N-vinylimidazoline, indoles such as N-vinylindole, indolines such as N-vinylindoline, carbazoles such as N-vinylcarbazole and 3,6-dibromo-N-vinylcarbazole, 2 -Pyridines such as vinyl pyridine, 4-vinyl pyridine, and 2-methyl-5-vinyl pyrazine,
(Meth) acrylic piperidine, N-vinyl piperidone, N
-Piperidines such as vinylpiperazine, quinolines such as 2-vinylquinoline and 4-vinylquinoline, pyrazoles such as N-vinylpyrazole and N-vinylpyrazoline,
Particularly preferred are oxazoles such as 2-vinyl oxazole and 2-vinyl oxazole, and oxazines such as 4-vinyl oxazine and morpholinoethyl (meth) acrylate. Basically, at least the basic skeleton has a structure of each of the above types, and various functional groups may be added or substituted as long as they show basicity. Examples of the basic dispersion resin used in the liquid developer of the present invention include polymers or copolymers of the above monomers. Among these, it is preferable to use a basic dispersion resin using a monomer having a basic skeleton of pyrrolidines and oxazines. For example, a random copolymer or a graft copolymer of N-vinylpyrrolidone or dimethylaminoethyl methacrylate and a methacrylic acid ester having an alkyl group having 10 to 20 carbon atoms is more preferable.

The nitrogen atom-containing monomer component in the basic nitrogen atom-containing basic dispersion resin is preferably contained in an amount of about 0.1 to 20% by weight based on the dispersion resin.

On the other hand, as the acidic monomer constituting the acidic dispersion resin, for example, a monomer having a carboxyl group such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, vinylacetic acid, vinylglycogenic acid, vinylacrylic acid or vinylbenzoic acid. And its metal salts (Li, Na,
K, Ca, Mg, Al, etc.), vinyl sulfonic acid, vinyl benzene sulfonic acid, vinyl benzyl sulfonic acid, vinyl benzene sulfinic acid, and other sulfone groups, monomers having a sulfin group and metal salts thereof, and other phosphoric acid, etc. Monomers having a functional group exhibiting acidity can be used alone or in combination of two or more kinds.

The amount of the dispersion resin added varies depending on the type and molecular weight of the dispersion resin, the polar group, etc. and cannot be specified unconditionally. It is desirable to add about 10% by weight.
If the addition amount of the dispersion resin is too large, the viscosity of the solution becomes high, and it becomes difficult for the toner particles to move inside the solution. If the amount of the dispersion resin added is too small, the toner particles cannot be sufficiently charged, and the image quality such as fogging is adversely affected. Furthermore, it is desirable that the addition ratio of the basic dispersion resin and the acidic dispersion resin is 1: 5 to 5: 1, preferably 1: 2 to 2: 1, and more preferably the same amount.

In any case, in the present invention, the addition amounts of the acidic dispersion resin and the basic dispersion resin are adjusted so that the chargeability, migration speed and dispersion stability of the toner particles are controlled to desired values. .

The above dispersion resin can be obtained by any conventionally known method such as a solution polymerization method, an emulsion polymerization method and a bulk polymerization method. In the polymerization, as a polymerization initiator that accelerates the generation of radicals, known compounds such as peroxides such as benzoyl peroxide and azobis compounds such as azobisisobutyronitrile may be appropriately used.

The electrophotographic liquid developer of the present invention is prepared by dispersing the toner particles in a carrier liquid prepared by previously dissolving such a basic dispersion resin and an acidic dispersion resin.

As the carrier liquid, a resistance value of about 10 ¹¹ to 10 ¹⁶ Ω · cm, which does not disturb the electrostatic latent image on the photoconductor,
It is preferable to use one having a resistance of about 10 ¹² to 10 ¹⁶ Ω · cm. Furthermore, it is particularly preferable to use a solvent having a relatively high flash point without odor and toxicity. The carrier liquid may be in any form at room temperature as long as it is liquid when used as a 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.

The concentration of the toner particles in the carrier liquid is
From the standpoints of development speed, image fog, etc., it is desirable that the amount is 0.5 to 50% by weight, preferably 2 to 10% by weight.
It should be noted that this density is the density at the time of development, and the density at the time of storage, replenishment, and transportation may be higher than this.

In the present invention, the solubility and basicity or acidity of the above dispersion resin in a carrier liquid are
It can be easily controlled by adjusting the substituents of the monomer components constituting the dispersion resin and changing the ratio of the copolymer components.

[0033]

EXAMPLES The present invention will be specifically described below with reference to examples. In the following examples, "parts" means "parts by weight" unless otherwise specified.

Manufacture of Basic Dispersion Resin a 100 parts of IP Solvent 1620 (manufactured by Idemitsu Petrochemical Co., Ltd., volume resistance value: 1.5 × 10 14 Ω · cm), 47 parts of lauryl methacrylate represented by the following chemical formula [I], basic As a monomer, 3 parts of N-vinyl-2-pyrrolidone represented by the following chemical formula [II] and 0.2 part of azobisisobutyronitrile, which is a polymerization initiator, are reacted under a nitrogen atmosphere at a reaction temperature of 60 to 7
The reaction was carried out at 0 ° C. for about 12 hours to obtain a basic dispersion resin a composed of a basic nitrogen-containing heterocyclic compound.

[0035]

Embedded image

Production of Basic Dispersion Resin b In the production of the above dispersion resin a, the basicity is the same as that for the dispersion resin a except that 47 parts of stearyl methacrylate represented by the following chemical formula [III] is used instead of lauryl methacrylate. Dispersion resin b was obtained.

[0037]

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Production of Basic Dispersion Resin c In the production of the above dispersion resin a, instead of N-vinyl-2-pyrrolidone as the basic monomer, the following chemical formula [IV] is used.
A basic dispersion resin c was prepared in the same manner as the dispersion resin a except that 3 parts of morpholinoethyl methacrylate shown in was used.

[0039]

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Production of Basic Dispersion Resin d In the production of the above dispersion resin a, instead of N-vinyl-2-pyrrolidone as the basic monomer, the following chemical formula [V] is used.
A basic dispersion resin d was obtained in the same manner as the dispersion resin a except that 3 parts of 2-vinylpyridine represented by was used.

[0041]

[Chemical 4]

Production of Basic Dispersion Resin e In the production of the above dispersion resin a, instead of N-vinyl-2-pyrrolidone as the basic monomer, the following chemical formula [VI] is used.
A basic dispersion resin e was obtained in the same manner as the dispersion resin a except that 3 parts of N-vinylcarbazole represented by was used.

[0043]

Embedded image

Production of Basic Dispersion Resin f In the production of the above dispersion resin a, instead of N-vinyl-2-pyrrolidone as the basic monomer, the following chemical formula [VI
A basic dispersion resin f was obtained in the same manner as the dispersion resin a except that 3 parts of dimethylaminoethyl methacrylate represented by the formula [I] was used.

[0045]

[Chemical 6]

Production of acidic dispersion resin g 100 parts of IP Solvent 1620 (made by Idemitsu Petrochemical Co., Ltd.),
49 parts of lauryl methacrylate, 1 part of methacrylic acid represented by the following chemical formula [VIII] as an acidic monomer, and 0.2 part of azobisisobutyronitrile, which is a polymerization initiator, under a nitrogen atmosphere at a reaction temperature of 80 to 90 ° C. The reaction was carried out for about 12 hours to obtain an acidic dispersion resin g.

[0047]

[Chemical 7]

Production of Acid Dispersion Resin h In the production of Dispersion Resin g, the same procedure as for Dispersion Resin g was carried out except that 1 part of acrylic acid represented by the following chemical formula [IX] was used as the acidic monomer instead of methacrylic acid. An acid dispersed resin body h was obtained.

[0049]

Embedded image

Production of resin fine particles A Low molecular weight polyester resin (MW: 15000, Mn: 6000) 100
Parts were completely dissolved in toluene to a concentration of 1.5% by weight. Eiger motor mill (made by Eiger Japan)
Was used to disperse 6 parts of a phthalocyanine pigment as a colorant in the resin solution.

The resin solution obtained as described above was treated with Dispercoat (manufactured by Nisshin Engineering Co., Ltd.) under the conditions of a liquid supply rate of 1 liter / hour, a drying temperature of 80 ° C. and a spraying pressure of 5.5 kgf / cm 2. Spray granulation was performed to obtain resin particles A having a spherical shape and an average particle diameter of 2.5 μm.

Example 1 In 100 parts of an electrically insulating solvent IP solvent 1620 (made by Idemitsu Petrochemical Co., Ltd.), 1.5 parts of a basic dispersion resin a,
Add 1.5 parts of acidic dispersion resin g and stir well for about 30 minutes. After confirming that all of the dispersed resin was dissolved, 3 parts of the resin fine particles obtained by the spray drying method were added and mixed and dispersed by an ultrasonic disperser for about 20 minutes to obtain a developer 1.

Example 2 In the same manner as in Example 1 except that the basic dispersion resin b was used in place of the basic dispersion resin a in Example 1,
Developer 2 is obtained.

Example 3 In the same manner as in Example 1 except that the basic dispersion resin c was used in place of the basic dispersion resin a in Example 1,
Developer 3 is obtained.

Example 4 In the same manner as in Example 1 except that the basic dispersion resin d was used in place of the basic dispersion resin a in Example 1,
Developer 4 is obtained.

Example 5 The procedure of Example 1 was repeated except that the basic dispersion resin a was replaced with the basic dispersion resin e.
Developer 5 is obtained.

Example 6 A developer 6 was obtained in the same manner as in Example 1 except that the acidic dispersion resin h was used instead of the acidic dispersion resin g.

Example 7 In Example 1, the amount of the basic dispersion resin added was 0.75.
Parts, and a developer 7 was obtained in the same manner as in Example 1 except that the addition amount of the acidic dispersion resin g was 2.25 parts.

Example 8 A developer 8 was obtained in the same manner as in Example 1 except that the addition amount of the basic dispersion resin was 2 parts and the addition amount of the acidic dispersion resin g was 1 part. .

Example 9 Developer 9 was obtained in the same manner as in Example 1 except that 1.5 parts of basic dispersion resin f was added in place of basic dispersion resin a.

COMPARATIVE EXAMPLE 1 No basic dispersion resin or acidic dispersion resin was added, and IP
Comparative developer 1 was obtained by adding 3 parts of the resin fine particles to 100 parts of Solvent 1620 (manufactured by Idemitsu Petrochemical Co., Ltd.) and mixing and dispersing with an ultrasonic disperser for about 20 minutes.

Comparative Example 2 Comparative developer 2 was obtained in the same manner as in Example 1 except that the basic dispersion resin was not added at all and 3 parts of acidic dispersion resin g was added.

Comparative Example 3 Comparative developer 3 was obtained in the same manner as in Example 1 except that the acidic dispersion resin was not added at all and the basic dispersion resin a was added in 3 parts.

Comparative Example 4 Comparative developer 4 was obtained in the same manner as in Example 1 except that 1.5 parts of pyridine was added as a basic compound instead of basic dispersion resin a.

Comparative Example 5 A resin fine particle B having an acidic functional group introduced on the surface thereof was prepared by blending polyacrylic acid in a polyester resin at the time of producing resin fine particles and carrying out a spray drying method as in Example.
A comparative developer 5 was obtained in the same manner as in Comparative Example 3 except that the resin fine particles B were replaced with the basic dispersed resin a instead of the resin fine particles A, and the basic dispersed resin f was added.

(Evaluation) With respect to each of the obtained liquid developers of the above-mentioned Examples and Comparative Examples, the developing rate, the toner charge amount, and the electrophoretic rate were evaluated, and the results are shown in Table 1.

Development Speed The development speed was evaluated by using the image forming apparatus for liquid development shown in FIG.

In FIG. 1, (1) is a photosensitive drum which rotates in the direction of the arrow. After charging the photosensitive drum (1) to about -1000v using the corotron charger (3), an electrostatic latent image is written by the laser beam scanner (4).
(20) is a developer bath in which each of the liquid developers is filled. (2) is a developing roller for drawing up the developing solution from the developer bath (20). In the developing area (8) facing the developing roller (2), the electrostatic latent image is developed with each developing solution. At this time, the peripheral speed ratio (θ developing roller rotation speed / photosensitive drum rotation speed) with the photosensitive drum (1) is θ =
It was adjusted to be constant at 10.

After that, the developer excessively adhered to the photoconductor is squeezed by the squeeze roller (5) to form a toner image on the surface of the photoconductor drum (1) containing a slight amount of solvent. When the toner image is rotated as it is to the transfer position (9) facing the transfer roller (6), it is electrostatically transferred onto the transfer 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.

Photosensitive drum using the above image forming apparatus
A solid image was formed by changing the speed in (1), and the toner image density (ID) on the photosensitive drum was measured. At this time, the lower limit value of ID is defined as 1.5, and the rotation speed of the maximum photosensitive drum (1) at which this ID can be obtained is ranked as the maximum development speed as follows, and there is no problem in practical use. I passed. The image density ID is measured by the Macbeth densitometer PDA-65.
(Manufactured by Konica).

◎: Maximum developing speed of 500 mm / s or more ○: Maximum developing speed of 200 mm / s or more and less than 500 mm / s △: Maximum developing speed of 50 mm / s or more and less than 200 mm / s ×: Maximum developing speed of less than 50 mm / s Charge amount and Electrophoretic speed Each liquid developer obtained in the above Examples and Comparative Examples was placed in an electric conductivity measuring cell (LE22, manufactured by Ando Electric Co., Ltd.), and 350
The voltage of v was applied for 10 seconds, and electrophoresis was performed. The toner particles migrated to the positive application side. Distance between electrodes is about 1.5 mm,
The electrode area was about 28.7 cm 2, and the sample injection volume was about 6.1 cm 3. The integrated value of the current flowing during the migration of the particles was recorded by an XY recorder, and this was taken as the charge amount Q. In addition, 1
The weight M of the toner particles that have electrophoresed for 0 seconds and adhered to the electrode (the positive application side in this example) is measured by thoroughly drying the solvent, and the toner charge amount Q / M (μ
c / g) was calculated. The results are shown in Table 1. Also,
The amount M / T of the electrophoretic particles attached to the electrode per unit time was calculated as the electrophoretic velocity (mg / s). The results are shown in Table 1.

[0072]

[Table 1]

As is clear from Table 1, the liquid developer of the present invention showed good chargeability, secured a sufficient ID even at a high developing speed, and obtained an image with less noise such as fog.

Further, in Comparative Example 5, the charge amount showed the same level as that of the examples of the present invention, but the electrophoresis speed and the developing speed were low, and sufficient performance for practical use could not be obtained.

In the above examples, the obtained polymers were these random copolymers, but any form such as alternating copolymers, block copolymers and graft copolymers can be used. There is no problem in use.

[0076]

As described in detail above, there is provided a liquid developer which secures a high charge level and improves the developing speed by increasing the electrophoretic speed of toner particles in the carrier liquid of the chargeable liquid developer. Could be provided.

[Brief description of drawings]

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

[Explanation of symbols]

 1 photoconductor drum 2 developing roller 20 developer bath

Claims (1)

[Claims] 1. An electrically insulating carrier liquid in which toner particles composed of a binder resin and a colorant, an acidic dispersion resin and a basic dispersion resin soluble in the carrier liquid are dispersed. Liquid developer for electrophotography.