JPH0534996A - Electrophotographic liquid developer and method for producing the same - Google Patents

Abstract

(57) [Summary] [Structure] 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 hydrogenated jojoba. It is an oil coated pigment and the resin is an ethylene copolymer. With the liquid developer for electrophotography of the present invention, a toner image having a sufficient density and a clear contour can be obtained on a recording paper with a small pressure in an electrophotographic recording apparatus of an intermediate transfer system.

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 or a printer which uses an electrophotographic wet developing method, and in particular, 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 colorant composed of a pigment or 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 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 has conductivity unlike many other organic pigments, 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 the two in order to sufficiently adhere 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 an aim.

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, characterized in that the colorant is a pigment coated with hydrogenated jojoba oil and the resin is an ethylene copolymer.

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 hydrogenated jojoba oil is added. In addition, it is characterized by being dispersed thereafter.

Further, the present invention will be described in detail.

In the liquid developer according to the present invention, the toner particles containing a colorant and a resin for fixing and for imparting an electric charge to the toner particles as a main component are highly insulating and low dielectric constant carrier liquid (hereinafter referred to simply as "carrier"). It may be referred to as a "liquid"). The toner particles of the liquid developer according to the present invention use a pigment coated with hydrogenated jojoba oil as a colorant and an ethylene copolymer as a resin. In the present invention, the hydrogenated jojoba oil is a jojoba solid wax having a melting point of 68 to 78 ° C. obtained by hydrogenating jojoba oil, and the hydrogenated jojoba oil and the ethylene copolymer are on the hydrogenated jojoba oil surface of the pigment. It has a structure in which an ethylene copolymer is adsorbed and / or attached. Here, adsorption and / or adhesion means a state in which the hydrogenated jojoba oil and the ethylene copolymer are physically bound to each other through a hydrogen bond or the like when viewed microscopically, and macroscopically. When viewed, it means a state in which the surface of the hydrogenated jojoba oil is covered with an ethylene copolymer resin. Further, when viewed macroscopically, the interface between the hydrogenated jojoba oil and the ethylene copolymer does not need to be uniform, and may have compatible parts mixed with each other, and such a compatible Having a portion is advantageous in the present invention.

In order to realize the toner particle structure as described above, the carrier liquid has a solubility of hydrogenated jojoba oil which is hardly soluble or slightly soluble and is compatible with the ethylene copolymer when dissolved. First, it is necessary to select, and it is necessary to select a combination in which the hydrogenated jojoba oil 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 as 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, made 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, the 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 pigment coated with the hydrogenated jojoba oil is dissolved in a solvent such as toluene which dissolves the hydrogenated jojoba oil well, and the desired pigment is added to the attritor or ball mill. It can be produced by dispersing with a disperser such as the above and then distilling off the solvent. It can also be produced by dispersing the desired pigment in the hydrogenated jojoba oil with a triple roll heated to a temperature above the melting point of the hydrogenated jojoba oil. Further, it can be manufactured by the flushing dispersion method. Also,
The weight ratio of pigment to hydrogenated jojoba oil is 1: 0.1 to 1: 1.
Is preferred. It is more preferably 1: 0.2 to 1: 0.5.

As for the highly insulating low dielectric constant carrier liquid, as long as the pigment and the ethylene copolymer coated with the above-mentioned hydrogenated jojoba oil are used, those used in the conventional liquid developer for electrophotography are used. Used as is. For example,
Aliphatic hydrocarbons, specifically, Exol, Isopar (above, manufactured by Exxon Chemical Co., Ltd.), IP solvent (made by Idemitsu Petrochemical Co., Ltd.), shell sol (made by Shell Chemical Co., Ltd.) and the like can be mentioned.

If necessary, an additive such as a charge control agent may be used as a third component for improving various characteristics 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-mentioned high-insulating low-dielectric-constant carrier liquid and heated and melted. The pigment coated with the above-mentioned hydrogenated jojoba oil is further added to this solution and mixed. The pigment coated with the hydrogenated jojoba oil 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 ethylene copolymer and the pigment is preferably 0.01 with respect to 1 part by weight of the pigment.
-10 parts by weight, more preferably 0.1 to 0.1 to 4 parts by weight. The heating dissolution temperature may be a temperature at which the resin can be uniformly dissolved in the carrier liquid, and specifically, it is 80 to
It is preferably about 200 ° C, more preferably 100 to 17
It is about 0 ° 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 about 70% at the maximum in the past, 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 manufactured by Nippon Unicar Co., Ltd. MI: 2)
0 polar group content: 41%) 10 g was added to 100 g Isopar G (aliphatic hydrocarbon solvent manufactured by Exxon Chemical Co., Ltd.) and dissolved by heating 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.
10 g of low 17) coated with hydrogenated jojoba oil in a weight ratio of 1: 0.3 and 0.2 g of lecithin (charge control agent)
And a mixture of 79.8 g of Isopar G were dispersed in an attritor for 2 hours to obtain a concentrated liquid of 200 g. Furthermore, 80
It was diluted with 0 g of Isopar G to obtain a liquid developer for electrophotography.

Comparative Example 1 KET without the coating treatment in place of the pigment coated with the hydrogenated jojoba oil in Example 1
A liquid developer for electrophotography was obtained in the same manner except that Yellow 403 (CI Pigment Yellow 17, manufactured by Dainippon Ink and Chemicals, Inc.) was used.

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) 100 g, 150 in a container equipped with a reflux stirrer
Dissolve by heating at ℃, cool, and then KET Red with the solution
308 (CI Pigme manufactured by Dainippon Ink and Chemicals, Inc.
nt Red 31) coated with hydrogenated jojoba oil in a weight ratio of 1: 0.2 and 15 g of Sansepara 100 (sodium dioctyl sulfosuccinate manufactured by Sanyo Kasei Co., Ltd.).
39.7 g and 79.7 g of IP Solvent 1620 were added, and dispersed by an attritor for 3 hours to obtain a concentrated liquid of 200 g. Further, it was diluted with 800 g of IP Solvent 1620 to obtain a liquid developer for electrophotography.

Comparative Example 2 KET without coating treatment in place of the pigment coated with hydrogenated jojoba oil in Example 2
Red 308 (C.I. manufactured by Dainippon Ink and Chemicals, Inc.
Pigment Red 31) was used in the same manner as above to obtain a liquid developer for electrophotography.

(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) coated with hydrogenated jojoba oil in a weight ratio of 1: 0.5, a mixture of lecithin (charge control agent) 0.14 g and shell sol 70L 72.86 g was dispersed in an attritor for 4 hours. , 200 g of concentrated solution was obtained. Furthermore, it was diluted with 800 g of shell sol 70 L to obtain a liquid developer for electrophotography.

COMPARATIVE EXAMPLE 3 Instead of the pigment coated with hydrogenated jojoba oil in Example 3, uncoated KET
Blue 106 (C. manufactured by Dainippon Ink and Chemicals, Inc.
I. Pigment Blue 15-4) was used, and an electrophotographic liquid developer was obtained in the same manner.

(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 hydrogenated jojoba oil in a weight ratio of 1: 0.3. A mixture of 10 g of the resulting mixture, 0.2 g of lecithin and 79.8 g of Isopar H was dispersed for 4 hours with an attritor to obtain a concentrated liquid of 200 g. 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.

Various liquid developers for electrophotography of Examples 1 to 4 and Comparative Examples 1 to 4 were prepared according to the methods described in Japanese Patent Application No. 1-294606 and Japanese Patent Application Laid-Open No. 2-264280. It was recorded on the recording paper.

FIG. 1 is a sectional view of an intermediate transfer type recording apparatus using the liquid developer for electrophotography of the present invention. Around the photosensitive drum 1, 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.
The intermediate transfer drum 5 includes a metal hollow drum 11 and an elastic layer 12 that covers the metal hollow drum 11. It is desirable that the elastic layer 12 has a carrier liquid absorbing property, and such an elastic layer can be obtained by using silicon rubber. The intermediate transfer drum 5 is provided with a cleaning device 9 that removes 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 exposing process. The electrostatic latent image is developed by the developing device 4 using a liquid developer. The development is carried out by selectively attaching the charged toner to the electrostatic latent image by electrophoresis, and
A toner image is formed on top. Next, the intermediate transfer drum 5 and the photosensitive drum 1 are brought into contact with each other and an electric field is applied to transfer the toner image to the intermediate transfer drum 5. 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 transfer 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 kind 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.

[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 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 photoconductor drum 2 Charging device 3 exposure equipment 4 Developing device 5 Intermediate transfer drum 6 pressure roller 7 peeling nail 8 cleaning device 9 Cleaning device 10 Static eliminator 11 Metal hollow drum 12 Elastic layer 20 Paper feeder 21 Recording paper 22 Transfer 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 coated with hydrogenated jojoba oil. A liquid developer for electrophotography, which is a pigment and 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 described electrophotographic liquid developer. 3. A liquid for electrophotography, which comprises adding an ethylene copolymer to a highly insulating low dielectric constant carrier liquid, heating and dissolving it, further adding a pigment coated with hydrogenated jojoba oil, and then dispersing the pigment. Developer manufacturing method. 4. A liquid developer for electrophotography 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, a pigment coated with hydrogenated jojoba oil is added. 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, the method for producing a liquid developer for electrophotography according to claim 3 or 4, which uses an ethrene ethyl acrylate copolymer. 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.