JPH05204192A - Electrophotographic liquid developer and its production - Google Patents

Abstract

PURPOSE:To obtain a clear toner image having enough density by using a developer containing a high-insulating carrier liquid having low dielectric constant and a toner dispersed in the carrier, the toner essentially comprising ethylene copolymers and a pigment coated with rosin or its deriv. CONSTITUTION:Toner particles essentially comprising a colorant and a resin to fix and impart charges to the toner particles are dispersed in a high-insulating carrier liquid having low dielectric constant. The colorant of the toner particle is a pigment coated with rosin or its deriv. The resin in the toner is ethylene copolymers. Both of the rosin or its deriv. which covers pigment particles and the ethylene copolymer form such a structure that the ethylene copolymer is adsorbed or deposited on the rosin or its deriv. The ethylene copolymer is preferably ethylene-vinyl acetate copolymers and/or ethylene acrylate copolymers having >=10 melt index and >=10wt.% polar group content.

Description

Detailed Description of the Invention

[Background of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer used in a recording apparatus such as a copying machine and a printer which uses an electrophotographic wet developing method, and particularly, in an intermediate transfer recording apparatus, a small pressure is applied to a recording paper. To a developer that provides a toner image with sufficient density and a clear contour.

[0002]

2. Description of the Related Art Conventionally, as a liquid developer for electrophotography,
It is known that a toner mainly composed of a thermoplastic resin such as styrene resin or acrylic resin and a colorant composed of a pigment or dye such as carbon black is dispersed in a carrier liquid composed of a petroleum-based aliphatic hydrocarbon solvent. (For example, JP-A-55-35321). Furthermore, in order to obtain higher resolution, an ethylene copolymer resin compatible with a nonpolar solvent when heated is used (US Pat. No. 4,794,651, 4).
No. 842974 and JP-A-61-189248) have been proposed.

However, in the liquid developer as described above, there are variations in the adsorption of the resin and the charge control agent to the pigment, and it may be difficult to stabilize the developing characteristics. In addition, carbon black, in particular, has conductivity unlike many other organic pigments. Therefore, in the case of full-color recording, there is a difference in development characteristics between black and other colors, which makes adjustment difficult.

Further, when recording is performed by an intermediate transfer type recording apparatus using such a liquid developer, the transfer efficiency is poor and an image having a sufficient density cannot be obtained on the recording paper, and an image with a clear outline is obtained. It had a problem that it could not be done. Here, the intermediate transfer method forms an electrostatic latent image on a photoconductor,
This is developed with a liquid developer, this image is transferred to an intermediate transfer belt or drum, and this toner image is further transferred to a recording paper (for example, US Pat. No. 4,708,460).
(See the official gazette). In this intermediate transfer system, the toner image is transferred from the intermediate transfer belt to the recording paper while applying a pressure between them, and this pressure is increased in order to sufficiently adhere the toner image to the recording paper. There is a need to.
However, there is a limit to the pressure that can be applied in an actual device, a sufficient adhesive force cannot be obtained, and thus the transfer efficiency is reduced.

[Outline of the Invention]

SUMMARY OF THE INVENTION Therefore, the present invention provides a developer having excellent characteristics used in a recording apparatus such as a copying machine or a printer, which uses an electrophotographic wet developing method, and a method for producing the same. Has a purpose.

A further object of the present invention is to provide a developer which gives a toner image having sufficient density and a clear contour on a recording paper by a small pressure in an intermediate transfer type recording apparatus, and a method for producing the same.

[0007]

The liquid developer for electrophotography according to the present invention comprises (a) a highly insulating low dielectric constant carrier liquid and (b) a rosin or a derivative thereof dispersed in the carrier liquid. And a toner containing a coated pigment and an ethylene copolymer as a main component.

Further, in the method for producing a liquid developer for electrophotography of the present invention, an ethylene copolymer is added to a highly insulating low dielectric constant carrier liquid and dissolved by heating, and a pigment coated with rosin or its derivative is further added. In addition, it is characterized by being dispersed thereafter.

DETAILED DESCRIPTION OF THE INVENTION The liquid developer according to the present invention comprises toner particles containing (i) a colorant and (ii) a resin for fixing and for imparting an electric charge to the toner particles as main components. , High insulating low dielectric constant carrier liquid (hereinafter referred to simply as "carrier liquid"
It may be said that it is dispersed. The toner particles of the liquid developer according to the present invention use a pigment coated with rosin or its derivative as a colorant and an ethylene copolymer as a resin.

In the present invention, both the rosin or its derivative coating the surface of the pigment and the ethylene copolymer are
It has a structure in which an ethylene copolymer is adsorbed and / or attached to the surface of rosin or its derivative. Here, the adsorption and / or adhesion means a state in which the rosin or its derivative and the ethylene copolymer are physically bound via a hydrogen bond or the like when viewed microscopically, and macroscopically. When viewed, it means that the surface of rosin or its derivative is covered with an ethylene copolymer resin. Furthermore, the interface between the rosin or its derivative and the ethylene copolymer when viewed macroscopically does not need to be uniform, and may have compatible parts mixed with each other, and Having a portion is advantageous in the present invention.

In order to realize the toner particle structure as described above, it is necessary to have a property that it is hardly soluble or slightly soluble in rosin or its derivative and is compatible with the ethylene copolymer upon heating and dissolution. First, it is necessary to select a carrier liquid having the same, and it is necessary to select a combination in which the rosin or its derivative and the ethylene copolymer are completely compatible at room temperature.

In the present invention, the rosin means a resin containing abietic acid as a main component, and the derivative thereof means a resin obtained by hydrogenating, esterifying or polymerizing rosin. Specific examples of the derivative include gum rosin, wood rosin, rosin glycerin ester, rosin pentaerythritol ester, partially hydrogenated rosin, fully hydrogenated rosin, partially hydrogenated rosin methyl ester, partially hydrogenated rosin triethylene glycol ester, partially hydrogenated rosin glycerin. Ester, partially hydrogenated rosin pentaerythritol ester, fully hydrogenated rosin glycerin ester, fully hydrogenated rosin pentaerythritol ester, rosin alcohol, maleic acid modified rosin, maleic acid modified rosin ester, rosin modified phenol, polymerized rosin, polymerized rosin ester, etc. Is mentioned.

The pigment coated with rosin or its derivative is dissolved in a solvent such as ketone, ester or toluene which dissolves rosin or its derivative well, and the desired pigment is added to the pigment with a disperser such as an attritor or a ball mill. After the dispersion, it can be produced by distilling off the solvent. Further, it can be manufactured by the flushing dispersion method. The weight ratio of pigment to rosin or its derivative is preferably 1: 0.1 to 1: 1. It is more preferably 1: 0.2 to 1: 0.5.

It is also possible to use a commercially available processed pigment coated with rosin ester, and specific examples thereof include Microlith Yellow 2G-T, Microlith Yellow 3R-T, Microlith Brown 5R-T and Microlith Brown. Squirrel Scarlet R-T, Micro Res red BR-
T, Microlith Blue GS-T, Microlith Blue 4G-T, Microlith Green GT, Microlith Black CT (above, manufactured by Ciba Geigy) and the like.

According to a preferred embodiment of the present invention, examples of the ethylene copolymer include ethylene vinyl acetate copolymer resin and ethylene ethyl acrylate copolymer resin. Particularly, those having a melt index (MI) of 10 or more and a polar group content of 10% by weight or more are preferable. When the MI is less than 10, the dispersion stability of the toner particles may be insufficient, which is not preferable. If the polar group content is less than 10% by weight, the charge amount of the toner particles may become insufficient, which is not preferable. MI is 10
Specific examples of the ethylene vinyl acetate copolymer having a polar group content of 10% by weight or more include NUC-3.
140, NUC-3140BK, NUC-3145, N
UC-3460, DQDJ-3868, NUC-315
0, NUC-3160, NUC-3190, DQDJ-
3269, NUC-3165, NUC-3170, DQ
DJ-7179, NUC-3185, MB-010, M
B-030, MB-600, MB-850, MB-99
0, MB-080 (above, made by Nippon Unicar), EV4
5X, EV40, EV40X, V577-2, EV-1
50, V523, EV-210, V541, EV22
0, V542, EV220NC, EV250, EV25
0SS, EV250C, EV310, V577, EV4
10, EV420, EV450, EV550, P140
7C, P1207, P1207C, EV640 (above,
Mitsui DuPont Polychemical Co., Ltd.) and the like.

Further, MI is 10 or more and the polar group content is 1
The ethylene ethyl acrylate copolymer resin of 0% by weight or more includes DPDJ-9169 and NUC-607.
0, MB-730, MB-870, MB-900, MB
-910 (above, manufactured by Nippon Unicar Co., Ltd.), A-704, A
-706, A-707, A-709 (above, Mitsui DuPont Polychemical Co., Ltd. make) etc. are mentioned.

As the high insulating low dielectric constant carrier liquid, as long as the pigment and the ethylene copolymer coated with the rosin or its derivative as described above are used, those used in conventional liquid developers for electrophotography are used. It can be used as it is. For example, a carrier liquid having a high insulating property of 10 ¹³ Ω · cm or more and a low dielectric constant of 3 or less is preferably used. Specifically, aliphatic hydrocarbon solvents such as Exsol, Isopar (hereinafter Exxon Chemical Co., Ltd.), IP Solvent (Idemitsu Petrochemical Co., Ltd.), Shell Sol (Shell Chemical Co., Ltd.)
Etc. are preferably used.

If necessary, additives such as a charge control agent can be used as a third component in order to improve various properties of the developer.

The liquid developer according to the present invention can be manufactured as follows. First, an ethylene copolymer is added to the above-described high-insulating low-dielectric-constant carrier liquid and heated and melted. The pigment coated with the rosin or its derivative is further added to this solution and mixed. The pigment coated with the rosin or its derivative may be added either while the heated solution of the carrier liquid and the ethylene copolymer is heated or after cooling, but the addition after cooling is preferable. The addition ratio of the pigment coated with the ethylene copolymer and the rosin or its derivative is preferably 0.01 to 1 part by weight of the pigment.
The amount is 10 parts by weight, more preferably about 0.1 to 4 parts by weight. The heating dissolution temperature may be a temperature at which the ethylene copolymer resin can be uniformly dissolved in the carrier liquid, but specifically, it is preferably about 80 to 200 ° C, more preferably 100.
It is about 170 ° C. The added mixture of pigments coated with rosin or its derivatives can be stirred by a suitable method to obtain a homogeneous gelled concentrate. This concentrated liquid is dispersed by a conventional method such as a ball mill,
Toner particles having a desired particle size are obtained by dispersing with an attritor, a bead mill, or the like. The size of the toner particles can be appropriately determined depending on the use conditions, but is preferably about 0.1 to 5 μm. After dispersion, it can be used as a developer by further diluting it with a carrier liquid to give an appropriate concentration. If the dispersion method used has an appropriate viscosity range, it may be diluted with a carrier liquid before the dispersion step.

The developer according to the present invention can be directly applied to an electrophotographic developing device using a conventional wet developing method. The developer according to the present invention can realize excellent transfer efficiency as compared with the conventional developers. Specifically, it is possible to increase the transfer efficiency, which was conventionally about 70% at the maximum, to about 90%. In particular, when the developer according to the present invention is used in the above-mentioned intermediate transfer type recording apparatus, since the transfer efficiency of the developer is high, it is possible to form a toner image having a clear contour with sufficient density on the recording paper even with a small pressure. Is.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 MB-870 (Ethylene ethyl acrylate copolymer resin manufactured by Nippon Unicar Co., Ltd., MI: 20, polar group content: 41)
%) 10 g was added to 100 g Isopar G (aliphatic hydrocarbon solvent manufactured by Exxon Chemical Co., Ltd.) and heated and dissolved at 150 ° C. in a vessel equipped with a reflux stirrer. After cooling, 10 g of Microlith Black CT (a rosin ester-processed pigment manufactured by Ciba Geigy) and lecithin (charge control agent) 0.2 were added to the solution.
g and 79.8 g of Isopar G were added, and this mixture was dispersed in an attritor for 5 hours to obtain 200 g of a concentrated liquid. Further, it was diluted with 800 g of Isopar G to obtain a liquid developer for electrophotography. Comparative Example 1 Example 1 except that carbon black # 44 (manufactured by Mitsubishi Kasei Co., Ltd.) was used instead of Microlith Black CT.
A liquid developer for electrophotography was obtained in the same manner as in.

Example 2 5 g of EV-410 (ethylene vinyl acetate copolymer resin manufactured by Mitsui DuPont Polychemical Co., MI: 400, polar group content: 19%) was added to IP Solvent 1620 (aliphatic hydrocarbon manufactured by Idemitsu Petrochemical Co., Ltd.). System solvent) 100 g, and heated and dissolved at 150 ° C. in a vessel equipped with a reflux stirrer, and after cooling, 15 g of Microlith Yellow 2G-T (rosin ester processed pigment manufactured by Ciba Geigy) and lecithin (charge control agent) ) 0.3 g and IP Solvent 1620
79.7 g was added, and this mixture was mixed with an attritor 4
After time-dispersion, 200 g of concentrated liquid was obtained. In addition, 800
It was diluted with 1 g of IP solvent 1620 to obtain a liquid developer for electrophotography. Comparative Example 2 A liquid developer for electrophotography was obtained in the same manner as in Example 2 except that Benzidine Yellow was used instead of Microlith Yellow 2G-T.

Example 3 5 g of EV-450 (ethylene vinyl acetate copolymer resin manufactured by Mitsui DuPont Polychemical, MI: 15, polar group content: 19%) and MB-900 (ethylene ethyl acrylate copolymer manufactured by Nippon Unicar Co., Ltd.) Resin, MI: 150
0, polar group content; 23%) 15g shell sol 70L
(Aliphatic hydrocarbon solvent manufactured by Shell Chemical Co.) was added to 100 g, and the mixture was heated and dissolved at 150 ° C. in a vessel equipped with a reflux stirrer.
After cooling, 7 g of Microresid BR-T (a rosin ester-processed pigment manufactured by Ciba Geigy), 0.14 g of lecithin (charge control agent), and Shell Sol 70L 7 were added to this solution.
2.86 g was added and the mixture was dispersed with an attritor for 4 hours to obtain 200 g of a concentrated liquid. In addition, 800g
Was diluted with 70 L of shell sol to prepare a liquid developer for electrophotography. Comparative Example 3 A liquid developer for electrophotography was obtained in the same manner as in Example 3 except that Brilliant Carmine 6B was used in place of Microresid BR-T.

Example 4 10 g of A-709 (ethylene ethyl acrylate copolymer resin manufactured by Mitsui DuPont Polychemical Co., MI: 25, polar group content: 35%) was replaced with Isopar H (aliphatic hydrocarbon solvent manufactured by Exxon Chemical Co.). ) 100 g, and heated and dissolved at 150 ° C. in a vessel equipped with a reflux stirrer. After cooling, 10 g of Microlith Blue 4G-T (a rosin ester-processed pigment manufactured by Ciba Geigy) and 0.2 g of lecithin were added to this solution.
79.8 g of Isopar H was added, and this mixture was dispersed for 4 hours with an attritor to obtain 200 g of a concentrated liquid. Further, it was diluted with 800 g of Isopar H to obtain a liquid developer for electrophotography. Comparative Example 4 Instead of A-709, A-701 (Mitsui DuPont Polychemical Co., Ltd. ethylene ethyl acrylate copolymer resin, M
Example 4 except that I: 5 and polar group content: 9%) were used.
A liquid developer for electrophotography was obtained in the same manner as in.

Example 5 NUC-3185 (Ethylene vinyl acetate copolymer resin manufactured by Nippon Unicar Co., MI: 400, polar group content: 2)
8%) (3 g) was added to 100 g of Isopar G (aliphatic hydrocarbon solvent manufactured by Exxon Chemical Co., Ltd.) and heated and dissolved at 150 ° C. in a vessel equipped with a reflux stirrer. After cooling, add KE to this solution.
T YELLOW 402 (CI PIGMENT YELLOW 154 manufactured by Dainippon Ink and Chemicals, Inc.) was coated with steberite ester 7 (partially hydrogenated rosin glycerin ester manufactured by Rika Hercules Co., Ltd. (weight ratio 1 :).
0.3) and Sansepara 100 (manufactured by Sanyo Chemical Industries, Ltd. sodium dioctyl sulfosuccinate).
2g and Isopar G86.8g were added, and this mixture was mixed with Eiger ENGINE.
It was dispersed for 20 minutes with an ERING LIMITED bead mill) to obtain 200 g of a concentrated liquid. Further, it was diluted with 800 g of Isopar G to obtain a liquid developer for electrophotography. Comparative Example 5 KETYELLOW 402 (CI PIGMENT YELLOW manufactured by Dainippon Ink and Chemicals, Inc.) was used without coating treatment in place of the pigment coated with steberite ester 7.
A liquid developer for electrophotography was obtained in the same manner as in Example 5 except that 154) was used.

Example 6 MB-910 (Ethylene ethyl acrylate copolymer resin manufactured by Nippon Unicar Co., Ltd., MI: 1100, polar group content: 2)
8%) (5 g) was added to 100 g of Isopar G (aliphatic hydrocarbon solvent manufactured by Exxon Chemical Co., Ltd.) and heated and dissolved at 120 ° C. in a vessel equipped with a reflux stirrer. After cooling, add KE to this solution.
T RED 308 (C. manufactured by Dainippon Ink and Chemicals, Inc.
I. PIGMENT RED 31) with pentaline A-
10 (weight ratio 1: 0.3) coated with JA (rosin pentaerythritol ester manufactured by Rika Hercules) 10
g, Sansepara 100 (Sanyo Chemical Co., Ltd. sodium dioctyl sulfosuccinate) 0.2 g, and Isopar G
84.8g and added to this mixture EIGER ENGINEERING LIMI
It was dispersed in a TED bead mill) for 20 minutes to obtain 200 g of a concentrated liquid. Further, it was diluted with 800 g of Isopar G to obtain a liquid developer for electrophotography. Comparative Example 6 Electrophotographic was performed in the same manner as in Example 6 except that KET RED 308 (CI PIGMENT RED 31 manufactured by Dainippon Ink and Chemicals, Inc.) was used instead of the pigment coated with pentaline A-JA. A liquid developer for use was obtained.

Example 7 MB-850 (ethylene vinyl acetate copolymer resin manufactured by Nippon Unicar Co., Ltd., MI: 800, polar group content: 22)
%) 2 g was added to 100 g of Isopar G (aliphatic hydrocarbon solvent manufactured by Exxon Chemical Co., Ltd.) and heated and dissolved at 130 ° C. in a vessel equipped with a reflux stirrer. After cooling, KET is added to this solution.
BLUE 118 (C. manufactured by Dainippon Ink and Chemicals, Inc.
I. PIGMENT BLUE 15) with pentaline 4
10 g coated with 820 (maleic acid modified rosin ester manufactured by Rika Hercules Co., Ltd.) (weight ratio 1: 0.3)
, Sansepara 100 (Sanyo Chemical Co., Ltd. sodium dioctyl sulfosuccinate) 0.2 g, and lecithin 0.1
g and Isopar G87.7 g were added, and the mixture was mixed with Eiger ENGINEE.
It was dispersed for 20 minutes with a RING LIMITED bead mill) to obtain 200 g of a concentrated liquid. Further, it was diluted with 800 g of Isopar G to obtain a liquid developer for electrophotography. Comparative Example 7 An electrophotographic liquid was prepared in the same manner as in Example 7, except that KET BLUE 118 (CI PIGMENT BLUE 15 manufactured by Dainippon Ink and Chemicals, Inc.) was used instead of the pigment coated with pentaline 4820. A developer is obtained.

Example 8 Evaflex V577-2 (ethylene vinyl acetate copolymer resin manufactured by Mitsui DuPont Polychemical Co., MI: 4)
00, polar group content 33%) 7 g was added to 100 g Isopar G (aliphatic hydrocarbon solvent manufactured by Exxon Chemical Co.),
It melt | dissolved by heating at 120 degreeC in the container with a reflux mixer. After cooling, this solution was coated with carbon black # 10B (manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) with Tamanol 135 (rosin modified phenol manufactured by Arakawa Chemical Industry Co., Ltd.) (weight ratio 1: 0.3) 1.
0 g, Sansepara 100 (Sanyo Chemical Co., Ltd. sodium dioctyl sulfosuccinate) 0.2 g, and Isopar G 82.8 g were added, and this mixture was mixed with an Eiger Motor Mill (EIGER ENGINEERING LIM).
It was dispersed in an ITED bead mill) for 20 minutes to obtain 200 g of a concentrated liquid. Further, it was diluted with 800 g of Isopar G to obtain a liquid developer for electrophotography. Comparative Example 8 A liquid developer for electrophotography was obtained in the same manner as in Example 8 except that uncoated carbon black # 10B (manufactured by Mitsubishi Kasei Co., Ltd.) was used in place of the pigment coated with Tamanor 135.

Development Tests The electrophotographic liquid developers of Examples 1 to 8 and Comparative Examples 1 to 8 were prepared according to the methods described in JP-A-3-154085 and JP-A-2-26428.
Recording was carried out on various recording papers basically according to the method described in JP-A-0.

FIG. 1 is a cross-sectional view of an intermediate transfer type recording apparatus using the electrophotographic liquid developer of the present invention. A charging device 2, an exposure device 3, a developing device 4, an intermediate transfer drum 5, a pressure roller 6, a peeling claw 7, a cleaning device 8, and a charge eliminating device 10 are sequentially arranged around the photosensitive drum 1. The intermediate transfer drum 5 is composed of a hollow metal drum 11 and an elastic layer 12 covering the hollow metal drum 11. Elastic layer 12
It is preferable that the elastic layer has an absorbability of the carrier liquid, and such an elastic layer can be obtained by using silicon rubber. The intermediate transfer drum 5 is provided with a cleaning device 9 for removing transfer residual toner.

The recording operation is performed as follows. An electrostatic latent image is formed on the photosensitive drum 1 through the charging process and the exposure process. The electrostatic latent image is developed by the developing device 4 using a liquid developer. The development is performed by electrifying the charged toner selectively on the electrostatic latent image, and
A toner image is formed on top. Next, the toner image is transferred to the intermediate transfer drum 5 by bringing the intermediate transfer drum 5 and the photosensitive drum 1 into contact with each other and applying an electric field. On the other hand, the recording paper 21, which is a recording medium, carried out from the paper feeding device 20 is conveyed to a contact position with the intermediate transfer drum 5. Pressure is applied by the pressure roller 6. Here, the toner image on the intermediate transfer drum 5 adheres to the recording paper 21 and is transferred. The recording paper 21 on which the toner image has been transferred is further conveyed to the fixing device 22, fixed under heat and pressure, and stored in the paper discharge tray 23.

By the above recording method, bit image recording and character recording were performed on general high-quality paper, bond paper, and PPC paper, and it was found that better recording could be achieved compared to the comparative example regardless of the type of recording paper. confirmed. Further, Table 1 shows the results of measuring the reflection density of the image with a Macbeth densitometer TR-927 type.

[0033]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a recording apparatus used for recording an electrophotographic liquid developer of the present invention.

[Explanation of symbols]

 1 Photoreceptor Drum 2 Charging Device 3 Exposure Device 4 Developing Device 5 Intermediate Transfer Drum 6 Pressure Roller 7 Peeling Claw 8 Cleaning Device 9 Cleaning Device 10 Electrifying Device 11 Metal Hollow Drum 12 Elastic Layer 20 Paper Feeding Device 21 Recording Paper 22 Fixing Device 23 Output tray

Claims (6)

[Claims] 1. A composition comprising (a) a highly insulating low dielectric constant carrier liquid, (b) a pigment coated with rosin or a derivative thereof and an ethylene copolymer dispersed in the carrier liquid. A liquid developer for electrophotography, comprising a toner. 2. The ethylene copolymer is an ethylene vinyl acetate copolymer and / or an ethylene ethyl acrylate copolymer having a melt index of 10 or more and a polar group content of 10% by weight or more. 1
The described electrophotographic liquid developer. 3. An electrophotographic apparatus, which comprises adding an ethylene copolymer to a highly insulating low dielectric constant carrier liquid, heating and dissolving the solution, further adding a pigment coated with rosin or a derivative thereof, and then dispersing the pigment. Liquid developer manufacturing method. 4. The electrophotographic liquid developer according to claim 3, wherein an ethylene copolymer is added to a highly insulating low dielectric constant carrier liquid, the mixture is heated and dissolved, and after cooling, a pigment coated with rosin or a derivative thereof is added. Agent manufacturing method. 5. An ethylene vinyl acetate copolymer and / or an ethylene ethyl acrylate copolymer having a melt index of 10 or more and a polar group content of 10% by weight or more is used as the ethylene copolymer. The method for producing a liquid developer for electrophotography according to 3 or 4. 6. The method for producing a liquid developer for electrophotography according to claim 3, wherein 0.1 to 10 parts by weight of an ethylene copolymer is used with respect to 1 part by weight of the pigment.