JPH0594051A - Electrophotographic liquid developer and method for producing the same - Google Patents

Abstract

PURPOSE:To allow the formation of a toner image having a sufficient density and distinct contour on recording paper with a small pressure by dispersing a toner essentially consisting of coloring agents and a resin into a carrier liquid having a high insulating characteristic and a low dielectric constant to form the developer and forming the coloring agents of pigments coated with beeswax and the resin of an ethylene copolymer. CONSTITUTION:This developer is prepd. by dispersing the toner particles essentially consisting of the coloring agents and the resin for binding and for imparting electric charges to the toner particles into the carrier liquid having the high insulating characteristic and the low dielectric constant. The toner particles of such liquid developer are formed by using the pigments coated with the beeswax as the coloring agents and the ethylene copolymer as the resin. The beeswax refers to the waxy beeswax essentially consisting of higher fatty acid and the ester of higher alcohol and having 60 to 70 deg.C m.p. Such beeswax and the ethylene copolymer are made into the structure adsorbed and/or stuck with the ethylene copolymer on the beeswax surface of the pigments. The toner image of the sufficient density and the distinct contour is obtd. on the recording paper by the small pressure in this way.

Description

Detailed Description of the Invention

[0001]

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, a toner mainly composed of a thermoplastic resin such as styrene resin or acrylic resin and a coloring agent composed of a pigment or a dye such as carbon black is used as a petroleum-based fat. Those dispersed in a carrier liquid composed of a group hydrocarbon solvent are known (for example, JP-A-55-35321). Further, in order to obtain higher resolution, a resin using an ethylene copolymer resin compatible with a non-polar solvent when heated (JP-A-61-189248) has 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. Further, in particular, carbon black, unlike many other organic pigments, has electrical conductivity, so that 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 carried out by an intermediate transfer type recording apparatus using such a liquid developer, the transfer efficiency is poor and an image of sufficient density cannot be obtained on the recording paper, and a clear image of the contour is obtained. It had the problem of not having it. Here, the intermediate transfer method forms an electrostatic latent image on a photoconductor,
This is a method in which 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 recording paper. (For example, US Pat. No. 4,708,
In this intermediate transfer method, the toner image is transferred from the intermediate transfer belt to the recording paper while applying a pressure between them, in order to sufficiently attach the toner image to the recording paper. Needs to increase this pressure. 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.

[0005]

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 is a liquid developer for electrophotography which is obtained by dispersing a toner containing a colorant and a resin as main components in a highly insulating low dielectric constant carrier liquid. A liquid developer, wherein the colorant is a beeswax-coated pigment, and the resin is an ethylene copolymer.

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 then a pigment coated with beeswax is added. It is characterized by dispersion.

Further, the present invention will be described in detail.

In the liquid developer according to the present invention, the toner particles mainly composed of a colorant and a resin for fixing and for imparting an electric charge to the toner particles are used as a highly insulating low dielectric constant carrier liquid (hereinafter simply referred to as "carrier. It is sometimes referred to as "liquid"). The toner particles of the liquid developer according to the present invention use a beeswax-coated pigment as a colorant and an ethylene copolymer as a resin. In the present invention, beeswax is a wax-like substance having an ester of a higher fatty acid and a higher alcohol as a main component and having a melting point of 60 ° C. to 70 ° C.
The beeswax and the ethylene copolymer have a structure in which the ethylene copolymer is adsorbed and / or attached to the surface of the pigment beeswax. Here, adsorption and / or adhesion means a state in which beeswax and an ethylene copolymer are physically bound to each other via a hydrogen bond when viewed microscopically, and when viewed macroscopically. A state in which the beeswax surface is covered with an ethylene copolymer resin. Furthermore, the interface between the beeswax and the ethylene copolymer does not have to be uniform only when viewed macroscopically, and may have compatible parts mixed with each other, or have such compatible parts. That is advantageous in the present invention.

In order to realize the toner particle structure as described above, the carrier liquid is selected such that beeswax has poor solubility or slight solubility and is compatible with the ethylene copolymer when dissolved. First, it is necessary to select a combination such that beeswax and the ethylene copolymer are completely compatible when dissolved.

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 resin having a polar group content of 10% by weight or more include NUC-
3140, NUC-3140BK, NUC-3145,
NUC-3460, DQDJ-3868, NUC-31
50, NUC-3160, NUC-3190, DQDJ
-3269, NUC-3165, NUC-3170, D
QDJ-7179, NUC-3185, MB-010,
MB-030, MB-600, MB-850, MB-9
90, MB-080 (above, manufactured by Nippon Unicar), EV
45X, EV40, EV40X, V577-2, EV-
150, 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.

According to a preferred embodiment of the present invention, the beeswax-coated pigment is dissolved in a solvent such as toluene that dissolves beeswax well, and the desired pigment is added and dispersed by a disperser such as an attritor or a ball mill. After that, it can be produced by distilling off the solvent. It can also be produced by dispersing a desired pigment in beeswax with a three-roll roller heated to a temperature higher than the melting point of beeswax.
Further, it can be manufactured by the flushing dispersion method. The weight ratio of pigment to beeswax is 1: 0.1.
~ 1: 1 is preferred. More preferably 1: 0.2 to 1:
It is 0.5.

As the high-insulating, low-dielectric-constant carrier liquid, as long as the pigment and the ethylene copolymer coated with beeswax as described above are used, those used in conventional liquid developers for electrophotography can be used as they are. .. For example, aliphatic hydrocarbons, specifically exol, isoper (above,
Exxon Chemical Co., Ltd.), IP Solvent (made by Idemitsu Petrochemical Co., Ltd.), Shell Sol (made by Shell Chemical Co., Ltd.) and the like.

If desired, additives such as a charge control agent can be used as a third component for improving 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 beeswax-coated pigment is further added to this solution,
Mix. The beeswax-coated pigment may be added either while the heated solution of the carrier liquid and the ethylene copolymer is being heated or after being cooled, but the addition after cooling is preferable. The addition ratio of ethylene copolymer and pigment is 1
It is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 0.1 to 4 parts by weight, based on parts by weight. The heating dissolution temperature may be a temperature at which the resin can be uniformly dissolved in the carrier liquid, but specifically, it is preferably about 80 to 200 ° C, more preferably about 100 to 170 ° C. The pigmented mixture can be stirred by a suitable method to obtain a uniform gelled concentrate. The concentrated liquid is dispersed by a conventional dispersing means such as a ball mill, an attritor, or a bead mill to obtain toner particles having a desired particle size. 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.

[0019]

The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

Example 1 MB-870 (Ethylene ethyl acrylate copolymer resin MI: 2 manufactured by Nippon Unicar Co., Ltd.)
0 polar group content: 41%) 10 g was added to 100 g Isopar G (aliphatic hydrocarbon solvent manufactured by Exxon Chemical Co.), heated and dissolved at 150 ° C. in a vessel equipped with a reflux stirrer, and after cooling, the solution and KET Yellow 403 (CI Pigment Yel manufactured by Dainippon Ink and Chemicals, Inc.
A mixture of 10 g of low17) coated with beeswax at a weight ratio of 1: 0.3, 0.2 g of lecithin (charge control agent) and 79.8 g of Isoper G was dispersed for 2 hours in an attritor to obtain a concentrated liquid of 200 g. .. Further, it was diluted with 800 g of Isopar G to obtain a liquid developer for electrophotography.

Comparative Example 1 KET Yel without the coating treatment in place of the beeswax-coated pigment in Example 1
low 403 (CIP from Dainippon Ink and Chemicals, Inc.
IGMENT Yellow 17) was used, and a liquid developer for electrophotography was obtained in the same manner.

(Example 2) 5 g of EV-410 (ethylene vinyl acetate copolymer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. MI: 400 polar group content: 19%) was added to IP Solvent 1620 (aliphatic hydrocarbon manufactured by Idemitsu Petrochemical Co., Ltd.). System solvent) 100g, 150 in a container equipped with a reflux stirrer
Dissolve by heating at ℃, and after cooling, the solution and KET Red
308 (CI Pigme manufactured by Dainippon Ink and Chemicals, Inc.
nt Red 31) in a weight ratio of 1: 0.2 and coated with beeswax (15 g), Sansepara 100 (Sanyo Chemical Co., Ltd. sodium dioctylsulfosuccinate) 0.3 g, and IP solvent 1620 (79.7 g) were added, followed by dispersing with an attritor for 3 hours. Then, 200 g of a concentrated solution was obtained. In addition, 8
It was diluted with 00 g of IP Solvent 1620 to obtain a liquid developer for electrophotography.

(Comparative Example 2) In Example 2, only KET Red was coated without the wax-coated pigment.
308 (CI Pigm manufactured by Dainippon Ink and Chemicals, Inc.
A liquid developer for electrophotography was obtained in the same manner except that entRed31) was used.

Example 3 5 g of EV-450 (ethylene vinyl acetate copolymer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. MI: 15 polar group content: 19%) and MB-
900 (Ethylene ethyl acrylate copolymer resin manufactured by Nippon Unicar MI: 1500 Polar group content: 23%)
15 g was added to 100 g of shell sol 70 L (aliphatic hydrocarbon solvent manufactured by Shell Chemical Co., Ltd.), heated and dissolved at 150 ° C. in a vessel equipped with a reflux stirrer, and after cooling, the solution and KET B
lue 106 (CI Pig, manufactured by Dainippon Ink and Chemicals, Inc.)
ment Blue 15-4) in a weight ratio of 1: 0.5 coated with beeswax 7 g and lecithin (charge control agent)
A mixture of 0.14 g and 72.86 g of shell sol 70L was dispersed for 4 hours with an attritor to obtain 200 g of a concentrated liquid. Furthermore, it was diluted with 800 g of shell sol 70 L to obtain a liquid developer for electrophotography.

(Comparative Example 3) In Example 3, only the pigment coated with beeswax was replaced by KET Blu which was not coated.
e 106 (CI Pig, manufactured by Dainippon Ink and Chemicals, Inc.
A liquid developer for electrophotography was obtained in the same manner except that the ment Blue 15-4) was used.

Example 4 10 g of A-709 (ethylene ethyl acrylate copolymer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. MI: 25 polar group content: 35%) was added to Isopar H (aliphatic hydrocarbon solvent manufactured by Exxon Chemical Co., Ltd.). ) 10
In addition to 0 g, it was heated and dissolved in a vessel equipped with a reflux stirrer at 150 ° C., and after cooling, the solution and carbon black # 44 (manufactured by Mitsubishi Kasei Co., Ltd.) were coated with beeswax at a weight ratio of 1: 0.3, 10 g And lecithin 0.2g and Isopar H7
Disperse the mixture with 9.8g in an attritor for 4 hours and
00 g of concentrated liquid was obtained. Further, it was diluted with 800 g of Isopar H to obtain a liquid developer for electrophotography.

Comparative Example 4 Instead of A-709 in Example 4, A-701 (ethylene ethyl acrylate copolymer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. MI: 5 polar group content: 9%) was used. Others were obtained in the same manner as above to obtain a liquid developer for electrophotography.

The electrophotographic liquid developers of Examples 1 to 4 and Comparative Examples 1 to 4 were prepared according to the methods described in JP-A-3-154085 and JP-A-2-154085.
Recording was performed on various recording papers basically according to the method described in Japanese Patent No. 264280.

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. The elastic layer 12 preferably has a carrier liquid absorbing property, and such an elastic layer can be obtained by using silicone 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 photosensitive drum 1 is
It 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 was possible 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 an image with a Macbeth densitometer TR-927 type.

[0032]

[Table 1]

[0033]

As described above, the liquid developer for electrophotography of the present invention is a toner image of sufficient density and clear contour on a recording paper with a small pressure in an intermediate transfer type recording apparatus. Has the effect of being obtained.

[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 liquid developer for electrophotography, comprising a toner mainly composed of a colorant and a resin dispersed in a highly insulating low dielectric constant carrier liquid, wherein the colorant is a beeswax-coated pigment. A liquid developer for electrophotography, characterized in that the resin is an ethylene copolymer. 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. The liquid developer for electrophotography according to claim 1. 3. A liquid developer for electrophotography, characterized in that an ethylene copolymer is added to a highly insulating low dielectric constant carrier liquid, heated and dissolved, and a pigment coated with beeswax is further added and then dispersed. Manufacturing method. 4. The electrophotographic liquid according to claim 3, wherein an ethylene copolymer is added to a highly insulating low dielectric constant carrier liquid, and the mixture is heated and dissolved, and after cooling, the beeswax-coated pigment is added. Developer manufacturing method. 5. The ethylene copolymer having a melt index of 10 or more and a polar group content of 10% by weight.
Ethylene vinyl acetate copolymer and /
Alternatively, an ethylene ethyl acrylate copolymer is used, and the method for producing a liquid developer for electrophotography according to claim 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.