JP2002278169A - Liquid developer and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developer capable of giving an image having high image density and high resolution and to provide an image forming method. SOLUTION: The liquid developer is obtained by dispersing toner particles containing a colorant and a dispersive resin in a carrier fluid. The carrier fluid is an aliphatic hydrocarbon, silicone oil, a higher fatty acid ester or vegetable oil. The colorant is a pigment or dye coated with a polyhydroxypolyolefin- containing coating resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid developer used for electrophotography, electrostatic recording, electrostatic printing, and the like, and an image forming method.

[0002]

2. Description of the Related Art Conventionally, for example, an electrophotographic method has been widely used as an image forming method capable of easily forming a high-quality image. In the electrophotographic method, a latent image formed on a photoconductor is generally developed using toner, transferred to a transfer material such as paper as necessary, and then fixed to obtain a recorded image.

[0003] As a system for developing a latent image, there are a dry development system using a powder developer and a liquid development system using a liquid developer. The dry developing method is easy to handle, but has a limit in obtaining a clear image because the particle diameter of the powder developer is considerably coarse, for example, about 7 μm. In the liquid developing method, since the particle diameter of the toner particles is extremely fine, for example, 0.1 to 2.0 μm, a clear image can be obtained. The liquid developer used in the liquid developing system is generally manufactured by dispersing toner particles comprising a binder resin, a colorant, and charge control in a high-resistance carrier liquid.

By the way, as a method of fixing a developed toner image to a transfer material such as paper, fixing by a heat roll,
Various fixing methods such as fixing with hot air and fixing from the back of the paper with a hot plate are used, and fixing with a hot roll has attracted attention as a fixing method with high thermal efficiency and high-speed fixing.
As a liquid developer used for fixing by a hot roll,
For example, JP-A-63-301966-30196
No. 9, JP-A-64-50062 to 50067
JP, JP-A-64-52167, JP-A-64-52167
JP-A-142560 and JP-A-64-142561 disclose those using a carrier liquid containing an aliphatic hydrocarbon as a main component.

[0005]

However, in a hot roll fixing roll system using an aliphatic hydrocarbon as a carrier liquid, the releasability of the toner layer from the fixing roll is poor, and oil must be applied to the fixing roll. The offset phenomenon may occur. For this reason, an oil applying device for supplying oil to the fixing roll must be separately provided, which complicates the copying machine. Also, the number of consumables increases.

The present invention has been made in view of the above problems, and has as its object to provide a liquid developer and an image forming method capable of preventing occurrence of an offset phenomenon without supplying oil to a fixing roll. I do. Another object of the present invention is to provide a liquid developer and an image forming method capable of obtaining a high-resolution image with a high image density.

[0007]

In order to achieve the above object, a liquid developer according to a first aspect of the present invention is a liquid developer in which toner particles containing a colorant and a dispersion resin are dispersed in a carrier liquid. Wherein the carrier liquid is an aliphatic hydrocarbon,
It is a silicone oil, a higher fatty acid ester, or a vegetable oil, and the colorant is characterized in that a pigment or a dye is coated with a coating resin containing polyhydroxypolyolefin.

According to this structure, since the pigment or the dye is coated with the coating resin containing the polyhydroxypolyolefin, the cohesive force of the toner is increased. Therefore, when an image is formed using such a liquid developer, high image density,
A high-resolution image is obtained. Also, no offset occurs.

An image forming method according to a second aspect of the present invention is an image forming method for developing a latent image formed on a photoconductor using a liquid developer and transferring the latent image to a transfer product to obtain a recorded image. Wherein the liquid developer according to the first aspect is used as the liquid developer, and the liquid developer is formed into a thin layer on a roller or a belt for development.

According to this configuration, the liquid developer according to the first aspect is used as the liquid developer. For this reason, by developing this liquid developer in a thin layer on a roller or a belt, an image with high image density and high resolution can be obtained. Also, no offset occurs.

Preferably, the latent image is developed after the thin layer is subjected to corona discharge. When the latent image is developed after corona discharge, the resolution and sharpness are improved.

It is preferable that the latent image is developed after a pre-wet liquid is attached to a latent image portion where the latent image is formed. When the latent image is developed after the pre-wet liquid is applied to the latent image portion, the transfer rate and the image density are improved.

After developing the latent image, it is preferable to form an image on a transfer product via an intermediate transfer member. When an image is formed on a transfer product via the intermediate transfer member, a transfer pressure can be applied, and the transfer rate and the image density are improved.

It is preferable to use a photoconductor having a water-repellent and oil-repellent surface. The surface of the photoconductor has water and oil repellency (θ = 3
(0 ° or more), the transfer rate and the cleaning property are improved, and the image quality can be improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid developer and an image forming method of the present invention will be described. In the liquid developer, toner particles containing a colorant and a dispersion resin as main components are dispersed in a carrier liquid.

The colorant has a pigment and a coating resin for coating the pigment as main components. As the pigment, a pigment generally used for a liquid developer can be used. Specifically, various pigments such as PRINTEX V (manufactured by Degussa), Mitsubishi # 44 (manufactured by Mitsubishi Carbon), and Mogal A (manufactured by Columbia Carbon) can be applied.

As the coating resin, a resin containing polyhydroxypolyolefin is used. By using a resin containing polyhydroxypolyolefin as the coating resin, the cohesive force of the toner can be increased. Such a resin, in addition to polyhydroxy polyolefin, polyhydroxy polyolefin, polyolefin, acrylic resin,
It may be a mixture of resins such as rosin-modified resin and styrene-butadiene resin. Specifically, the melting point is 50
~ 130 ° C, specific gravity 0.8 ~ 1.10, hydroxyl value 2-1
Those having a value of 00 (KOH mg / g) are suitable for the coating resin of the present invention. Products include Mitsubishi Chemical's Polyether H,
HA, HE, KH, HC, HU and the like.

As a method for producing a coloring agent, there is a flushing method. A pigment or a water-containing paste of a pigment is put into a kneader called a flasher together with a resin solution or a resin and mixed well (in this process, water existing around the pigment is removed from the resin). This is removed by a kneader, the aqueous phase is discarded, the pigment in the resin solution or resin is heated or kneaded and dispersed at room temperature, and the solvent is removed. Is crushed.
In addition, care may be taken to remove water and solvent under reduced pressure while kneading with a kneader.

In the flushing method, not only the pigment but also the dye is kneaded with water in a mud-like state, so that almost the same result as the pigment can be obtained. Is possible. The ratio between the dye and pigment and the resin when flushing is
It is preferable that the dye / pigment is 10 to 60 parts by weight based on 100 parts by weight of the resin. It is particularly advantageous to carry out the flushing treatment in the presence of humic acid, humates (Na salt, NH ₄ salt, etc.) or humic acid derivatives. The amount of humic acids added is preferably about 0.1 to 30% by weight of the aqueous solution of the dye and pigment.

The dispersing resin used in the present invention includes:

Embedded image (R ₁ is H or CH ₃ , n is an integer of 6 to 20)
And a vinyl monomer A represented by

Embedded image And each of monomers B selected from vinyl monomers and vinyl pyridine, vinyl pyrrolidone, ethylene glycol dimethacrylate, styrene, divinyl benzene, and vinyl toluene, or several types of copolymers and graft copolymers. Can be

The carrier liquid used in the present invention includes silicone oil, aliphatic hydrocarbon, aliphatic ester, vegetable oil and the like. As silicone oil, KF9
6 (viscosity 1 to 10000 cst manufactured by Shin-Etsu Silicon Co., Ltd.),
SH200, SH344 (Toray Silicon), TSF45
1 (Toshiba Silicon), etc. In addition, decamethyltetrasiloxane and octamethyltrisiloxane may be used.

Further, in order to improve dispersibility in silicon, a silicon material having an acroyl group, such as LS4080 manufactured by Shin-Etsu Silicon Co., may be copolymerized. Similarly, AK-5 manufactured by Toa Gosei Chemical Co., Ltd. Company's TM070
1, FM0711, FM0721, and FM0725 may be used.

Further, by developing this liquid developer in a thin layer on a roller or belt and developing, a high-density, high-resolution image can be obtained. This layer thickness is preferably about 1 to 15 μm, and more preferably 3 to 10 μm. When the layer thickness is 1 μm or less, the concentration is not sufficient, and when the layer thickness is 15 μm or more, the resolution is reduced.

After a corona discharge is applied to a liquid developer thin film (toner layer) formed on a roller or a belt, the latent image is developed, whereby the toner cofusion can be increased, and the resolution can be further improved. Can be. Corona discharge is highly effective when it has the same polarity as the toner, and the voltage is preferably about 500 to 8000 V.

After the pre-wetting liquid is applied to the latent image portion where the latent image is formed, the latent image is developed to improve the transfer efficiency and obtain high image quality. The prewet liquid film has a thickness of about 0.1 to 5 μm, preferably about 0.3 to 1 μm. If the thickness is 0.1 μm or less, the effect is low, and if it is 5 μm or more, the resolution decreases.

After developing the latent image, a toner image is transferred to an intermediate transfer member, and an image is formed on the transferred material, whereby a transfer pressure can be applied, and high image quality can be obtained even with plain paper. The material of the intermediate transfer member is preferably a solvent-resistant and elastic material such as urethane rubber, nitrile rubber, and hydrin rubber, and is more preferably coated with a fluorine resin or the like.

By making the surface of the photoconductor forming the latent image water-repellent and oil-repellent (θ = 30 ° or more), the transfer rate and the cleaning property can be improved, and the image quality can be improved. The water repellency and oil repellency can be enhanced by, for example, coating a fluororesin-containing block polymer such as Nippon Oil and Fatty Modiper F200, 210 or the like.

Next, an image forming process of the image forming method using the liquid developer as described above will be described. Figure 1
FIG. 3 is an explanatory diagram of an image forming process to which the image forming method of the present invention is applied.

FIG. 1 shows a photoconductor L rotating in the direction of the arrow.
(For example, an organic optical semiconductor, selenium, or amorphous silicone), and the photoconductor is charged by corona charging E while being rotated. F is a roller for prewetting the carrier liquid. G is a writing exposure unit. K is supplied with toner from a toner container I by a developing roller, and is uniformly applied by a toner roller J. The toner layer on the developing roller is provided with a corona discharge portion H if necessary.
And a latent image on the photoconductor L is developed by the developing roller K and visualized. As each roller, a roller having a groove such as a metal bar, a rubber, a plastic, a sponge, a wire bar, and a gravure roller can be used.

The transfer material B transfers the toner image formed on the photoconductor L by the transfer roller A onto the transfer material B. The transfer method can form an image on a transfer material by a combination of pressure, corona discharge, heating, heating and pressure, corona and pressure, corona and heating, and the like.

The residual toner remaining on the photoconductor L is removed by a cleaning roller C and a cleaning blade D for cleaning the photoconductor.
Prepare for the next image.

FIG. 2 is another explanatory view of an image forming process to which the image forming method of the present invention is applied. The difference from FIG. 1 is that it includes a step of coating the pre-wet liquid with a felt F from a roller. The pre-wet liquid is applied with felt as needed. The toner is applied to the developing roller K from the toner container I through the rollers J1 and J2, and a DC voltage is applied to the applied toner layer from the corona discharge unit H. The developing roller K of FIG. 2 has a longer contact width with the photoconductor L than that of FIG. 1, and is designed to sufficiently develop a latent image. The toner image developed on the photoconductor L is transferred to the transfer member B by the corona discharge unit A to form an image.

FIG. 3 shows an example of a developing process for outputting a color copy. Yellow, magenta, cyan, and black toner containers I on photoconductor L,
J, the latent image of the photoconductor L is developed for each color, transferred to the intermediate transfer member M, and further transferred to the transfer member B by the transfer roller A by pressure, corona, heat, or the like.

FIG. 4 shows another image forming process for color copying. As in FIG. 3, yellow, magenta, cyan,
The latent image on the photoconductor L is developed by a belt N for applying a toner layer to the toner containers J and I containing black toner, and the toner image is transferred to the transfer member B. The belt N for applying the toner layer is cleaned by a cleaning roller O and a cleaning blade P.

Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples. Further, all parts in the following examples represent parts by weight.

<Manufacture of Coloring Agent> (Coloring Agent 1) Ammonium humate (20 g) was dissolved in water (200 g) in a gallon kneader, and 250 g of carbon (Mitsubishi # 44, manufactured by Mitsubishi Carbon Co.) was added to this solution. And mixed well. Next, 75
0 g was added, and the mixture was heated and mixed at about 100 ° C. to separate water. Subsequently, after kneading at about 120 ° C. for 4 hours, vacuum drying, cooling,
It was pulverized to obtain Colorant 1.

(Colorant 2) 200 g of water in gallon kneader
10 g of humic acid sodium salt was dissolved in the solution, and carbon (Mogal A, manufactured by Columbia Carbon Co., Ltd.) was added to the solution.
0 g was added and mixed and dispersed in a kneader. Next, 300 g of polytail HA was added and heated and kneaded at about 150 ° C.
Subsequently, after kneading at 120 ° C. for 2 hours, vacuum drying, cooling,
It was pulverized to produce Colorant 2.

(Colorant 3) Printex V 300 parts Polytail HE 500 parts Ammonium humate 25 parts Water 150 parts Using the above composition, Colorant 3 was produced according to the procedure of Colorant 1.

(Example 1) Coloring agent 1 60 parts KF96 of lauryl methacrylate / methyl methacrylate / methacrylic acid / glycidyl methacrylate (80/10/5/5) copolymer (manufactured by Shin-Etsu Silicone, viscosity 10 cst) 20% solution 100 parts KF96 (manufactured by Shin-Etsu Silicon, viscosity 100 cst) 200 parts After the mixture of the above composition is dispersed in a ball mill for 24 hours, KF96 (manufactured by Shin-Etsu Silicon, viscosity 100 cst)
Was added and dispersed for 1 hour to obtain a concentrated toner. Take 200g of concentrated toner, KF96 (Shin-Etsu Silicon,
It was diluted in a viscosity of 100 cst) to obtain a developer.

Example 2 Colorant 2 50 parts Stearyl methacrylate / methyl methacrylate / methacrylic acid / hydroxymethyl methacrylate (85/7/4/4) copolymer KF96 (manufactured by Shin-Etsu Silicone, viscosity 10 cst) 10% Solution 200 parts Safflower white squeezed oil 100 parts Using the mixture having the above composition, a developer was obtained according to the procedure of Example 1.

Example 3 A developer was obtained in the same manner as in Example 1 except that the colorant was changed to Colorant 3 and the dispersion medium was changed to higher fatty acid ester (IPM).

Comparative Example 1 A developer was obtained in the same manner as in Example 1 except that the polytail H of the coloring agent 1 was changed to a rosin-modified maleic resin.

Comparative Example 2 A developer was obtained in the same manner as in Example 2 except that the safflower white squeezed oil of Example 2 was changed to kerosene.

Comparative Example 3 A developer was obtained in the same manner as in Example 3 except that the dispersion medium in Example 3 was changed to Isopar H.

The developer prepared as described above was used in a tester attached to a hot roll fixing machine of the image forming apparatus shown in FIG. 1 to perform an oilless fixing test. The image density is X-
Measured by Rite. Sharpness and offset were determined based on a 5-stage sample in which the best one was 5 and the worst one was 1. Table 1 shows the results.

[Table 1]

As shown in Table 1, it was confirmed that even when the developer of the present invention was fixed without oil, no offset phenomenon was exhibited. Therefore, the developer of the present invention provides a temperature range within a range in which the heat roller can be fixed without showing the offset phenomenon, and it can be seen that the heat roller can be fixed.

Example 4 Using the developer of Example 1 and applying a corona discharge of 5000 V to the toner layer using the apparatus of FIG. 2, development was performed. Table 2 shows the results.

[Table 2] As shown in Table 2, the image density, the resolving power, and the sharpness were improved by applying corona discharge to the toner layer.

Example 5 Using the developer of Example 2 and the pre-wet roller F, the latent image on the photoconductor was converted to silicone oil KF-96 (viscosity 30) using the apparatus of FIG.
0 cst) and developed by prewetting (layer thickness 0.5 μm). Table 3 shows the results.

[Table 3] As shown in Table 3, image density, resolution, sharpness,
Transfer rate and offset improved.

Example 6 Using the developer of Example 3, an intermediate transfer member (intermediate transfer drum) M (urethane rubber,
The surface was subjected to development using a device. Table 4 shows the results.

[Table 4] As shown in Table 4, the image density, sharpness, and transfer rate were improved.

Example 7 Using the developer of Example 3, the photoconductor of the apparatus shown in FIG. 4 was subjected to an oil-repellent treatment with a fluorine-acrylic block copolymer resin (MODIPA F210 manufactured by NOF Corporation) (film thickness 2 μm). And developed. Table 5 shows the results.

[Table 5] As shown in Table 5, the image density, sharpness, and transfer rate were improved. The contact angle of KF-96 (viscosity 100 cst) was 45 °.

[0051]

As described above, according to the present invention,
The occurrence of the offset phenomenon can be prevented without supplying oil to the fixing roll. Further, a high-resolution image having a high image density can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an image forming process to which an image forming method according to an embodiment of the present invention is applied.

FIG. 2 is another explanatory diagram of an image forming process to which the image forming method according to the embodiment of the present invention is applied.

FIG. 3 is an explanatory diagram of a developing process when outputting a color copy according to the embodiment of the present invention.

FIG. 4 is another explanatory diagram of a developing process when outputting a color copy according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List A transfer roller B transfer material C cleaning roller D cleaning blade E corona discharge F roller G exposure unit H corona discharge unit I toner container J toner roller K developing roller L photoconductor M intermediate transfer member N belt O cleaning roller P cleaning blade

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiko Umemura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Aiko Ishikawa 1-3-6 Nakamagome, Ota-ku, Tokyo Share Company Ricoh F-term (reference) 2H068 AA28 FC08 2H069 BA00 BA01 CA07 CA27 2H074 AA03 AA04 BB02 EE07

Claims (6)

[Claims] 1. A liquid developer in which toner particles containing a colorant and a dispersion resin are dispersed in a carrier liquid, wherein the carrier liquid is an aliphatic hydrocarbon, silicone oil, higher fatty acid ester, or vegetable oil. The liquid developer, wherein the colorant is coated with a coating resin containing a polyhydroxypolyolefin in a pigment or a dye. 2. An image forming method for developing a latent image formed on a photoconductor using a liquid developer and transferring the latent image to a transfer product to obtain a recorded image, wherein the liquid developer is provided with a liquid developer. Using the liquid developer described in the above,
An image forming method, comprising developing the liquid developer in a thin layer on a roller or a belt. 3. The image forming method according to claim 2, wherein the latent image is developed after performing a corona discharge on the thin layer. 4. The image forming method according to claim 2, wherein a pre-wet liquid is applied to a latent image portion where the latent image is formed, and then the latent image is developed. 5. The image forming method according to claim 2, wherein after the latent image is developed, an image is formed on a transfer product via an intermediate transfer member. 6. A water-repellent and oil-repellent photoconductor having a surface.
The image forming method according to any one of claims 2 to 5, wherein: