JPH06110256A - Liquid developer for electrohotographic plate making - Google Patents

Abstract

PURPOSE:To provide the developer which less affects a development mechanism, has a high maintenance characteristic, forms the images stable to repetitive development and does not disturb the images even after long-term preservation by incorporating a prescribed ratio of dibasic fatty acid ester as a dispersant into the developer. CONSTITUTION:The fatty acid ester (ester of dibasic fatty acids, such as adipic acid, azelaic acid, sebacic acid and ricinolic acid) is incorporated at 0.5 to 1.2wt.% as the dispersant into the liquid developer prepd. by dispersing coloring agent, binder and charge control agent as main constituting components into a nonpolar carrier solvent. The fatty acid ester to be used has excellent affinity to the coloring agents and the binder. The liquid developer exhibits extremely stable dispersibility in the nonpolar carrier solvent. The developer is capable of stably forming the good images free from collapse and tailing of the images, the disorption of the coloring agents, etc., in spite of repetitive development.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition of a liquid developer used for developing an electrostatic latent image formed by electrophotography. More specifically, the present invention is used when offset printing is performed by forming an image by a normal electrophotographic method using an electrophotographic photoreceptor having a conductive substrate coated with zinc oxide, an organic photo-semiconductor and the like. In particular, it relates to a liquid developer for electrophotographic platemaking which is excellent in maintainability, fixability, storability and stability and has high image contrast.

[0002]

2. Description of the Related Art In general, a liquid developer for electrophotographic copying and plate making has a polymerizable active double bond which becomes insoluble by being dissolved or polymerized in a non-polar highly insulating carrier solvent, for example, acetic acid, A vinyl ester such as vinyl propionate and a monomer having an aliphatic group having 8 or more carbon atoms which is dissolved or has an affinity for this solvent at the time of polymerization, for example, 2-
Monomers having ethylhexylmethacrylate, laurylmethacrylate, stearylmethacrylate, etc., and a polar group for further controlling the charge and having a polymerization active double bond, such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, acrylamide, etc. Are copolymerized in a non-polar highly insulating carrier solvent to prepare copolymerized polymer particles, which are then colored with carbon, an organic dye, a pigment or the like (JP-A-60-249160).
Issue).

Such a liquid developer for plate making for electronic copying, which has excellent fixability on the surface of a zinc oxide photoconductor or an organic photoconductor, adheres to and cures on a copy development mechanism or the like.
It deteriorates maintenance such as clogging of liquid transfer pump.
In addition, by repeatedly making a large number of copies and making development, the colorant is released from the polymer particles, the image is distorted, the image is trailed, the amount of toner adhered to the image area is reduced, and the toner to the non-image area is removed. Adhesion occurs, and further, the particles in the developer are agglomerated, and the particles become coarse, causing precipitation.

On the other hand, a colorant composed of an organic pigment or dye, a fixing agent such as an alkyd resin, an acrylic resin, a synthetic rubber or a rosin derivative, and a charge control agent composed of a metallic soap, an aliphatic or aromatic carboxylic acid or the like. Is obtained by kneading with a three-roll, ball mill or the like and dispersing in a non-polar / highly insulating solvent (Japanese Patent Publication No. 51-1301). Such liquid developer for electrostatic copying and platemaking is less affected by toner adhesion to the developing mechanism, but has poor fixability and uneven toner particle size, and finally tends to aggregate during long-term storage. There are drawbacks.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks of the liquid developers for electrophotographic copying and plate making proposed so far. That is,
An object of the present invention is to provide a highly maintainable liquid developer which does not cause failure of the developing device due to toner sticking to the developing device and clogging of a liquid feed pump even after repeated use for a long period of time. Another object of the present invention is to provide a liquid developer whose fixing property and long-term storage property and whose performance does not deteriorate even after repeated development. Still another object of the present invention is to provide an excellent liquid developer having high contrast and high image quality.

[0006]

As a result of intensive studies, the present inventor has conducted a liquid development in which a colorant, a binder and a charge control agent are dispersed as main constituents in a non-polar carrier solvent. The purpose of the present invention is to contain 0.5 to 1.2% by weight of a fatty acid ester (ester of dibasic fatty acid such as adipic acid, azelaic acid, sebacic acid, ricinoleic acid) as a dispersant in the agent. Was achieved. The fatty acid ester used in the present invention has excellent affinity with a colorant and a binder, and a liquid developer using the fatty acid ester exhibits very stable dispersibility in a non-polar carrier solvent. The agent is capable of stably forming a good image without image collapse, tailing, detachment of colorant, and the like even after repeated development. Further, it has excellent long-term storage stability, does not cause precipitation, and has excellent imageability and stability over time. It is considered that this is because the dibasic fatty acid ester has a strong affinity for the colorant and the binder and is uniformly dispersed in the nonpolar solvent. Further, this fatty acid ester is particularly compatible with the binder, and when it adheres to the developing mechanism, it can be easily washed by simple circulation washing with a non-polar solvent, and an image was formed on zinc oxide or an organic photoreceptor. In this case, since only this fatty acid ester penetrates into the photoreceptor and the binder is firmly fixed, it exhibits good printing durability when used as an offset printing plate.

Next, the present invention will be described in detail. The non-polar solvent used in the present invention preferably has an electric resistance of 10 ⁹ Ωcm or more and a dielectric constant of 3 or less. For example,
Aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons and halogenated hydrocarbons can be used, but isoparaffins are preferred from the viewpoint of odor and toxicity. Specific examples include Shell Sol 71 (manufactured by Shell Chemical), Isopar G,
Isopar H, Isopar L (all manufactured by Esso Standard Co., Ltd.) and the like are used.

The binder used in the present invention is a resin or polymer which plays a role of fixing, and is a polymerizable / active polymer which becomes insoluble by being dissolved or polymerized in a nonpolar / highly insulating carrier solvent. A monomer having a polymerizing bond, for example, a vinyl ester such as acetic acid or vinyl propionate, and an aliphatic group having a carbon number of 8 or more which is dissolved or has an affinity for this solvent during polymerization, for example, 2-ethylhexyl methacrylate, lauryl methacrylate, When stearyl methacrylate or the like is used, a monomer having a polar group and having a polymerization active double bond is further added to play a role of charge control.For example, acrylic acid methacrylic acid, maleic acid, maleic anhydride, acrylamide, etc. are non-polar high Copolymerized in an insulating carrier solvent is generally used.

The colorant plays a role of visualization.
There are many inorganic and organic pigments, and dyes,
Examples thereof include carbon black, deep blue, ultramarine blue, phthalocyanine pigments, azine diameter pigments, triphenylmethane pigments, azo pigments and condensation pigments.

The fatty acid ester, which is the most important constituent component used in the present invention, is selected from non-toxic and odorless dibasic fatty acid esters having particularly low volatility. Examples thereof include dioctyl adipate, diisobutyl adipate, dibutyl adipate, diisodecyl adipate, dibutyl diglycol adipate, dioctyl azelate, dibutyl sebacate, dioctyl sebacate, and methylacetyl ricinolate.

The content of the dibasic fatty acid ester in the developer of the present invention is 0.5 to 1.2% by weight. If it is less than 0.5%, the toner may stick to the developing mechanism and precipitate during long-term storage. On the other hand, if it is more than 1.2%, tailing, transfer, etc. occur, and the image density decreases due to repeated development of a large number of sheets.

[0012]

EXAMPLES The present invention will now be described in detail by way of examples, but the examples are not limited to these examples and can be used in combination. Example 1 Lauryl methacrylate monomer 15 parts Vinyl acetate monomer 60 parts Maleic anhydride 2 parts Benzoyl peroxide 1 part Isopar E (manufactured by Exxon Co.) 170 parts were put into a four-necked flask, and a stirrer, a condenser, a nitrogen inlet tube, and a temperature were introduced. Wearing a meter and introducing nitrogen, 80
Polymerization is carried out at 0 ° C for 3 hours, then the temperature is raised to 100 ° C and the polymerization is continued for 10 hours. Then, 1 part of 1,1-azobiscyclohexane-1-carbonitrile was added, and the mixture was further added at 100 ° C. for 5 minutes.
Polymerization was performed for a time to obtain a cloudy polymer dispersion.

To 100 parts of this polymer dispersion, 50 parts of dioctyl adipate (manufactured by Daihachi Chemical Co., Ltd.) and 2 parts of carbon black NO1000 (manufactured by Mitsubishi Kasei) were dispersed in a sand grinder for 3 hours to obtain a concentrated toner. This concentrated toner 3
When 0 part was dispersed in 2000 mL of Isopar G (manufactured by Exxon) and introduced into AP-10EX (manufactured by Iwasaki Tsushinki Co., Ltd.) and developed by an electronic copying master EL-3 (manufactured by Iwasaki Tsushinkisha Co., Ltd.), A clear master plate for offset printing was obtained. Further, even after the development of the 5,000th plate, the toner sticking to the developing device was less likely to be contaminated by circulation cleaning with the non-polar solvent Isopar G (manufactured by Exxon Chemical Co.). Further, as a result of offset printing of 10000 sheets of this master plate, thinning and chipping of the image were hardly seen.

Example 2 A concentrated toner was obtained in the same manner by using 65 parts of dibutyl sebacate (manufactured by Daihachi Chemical Co., Ltd.) in place of the dioctyl adipate of Example 1. When the image was developed by the same device as in Example 1, the fixing of the developing device was small even after the development of the 5000th plate.

Example 3 A concentrated toner was obtained in the same manner by using 80 parts of dioctyl sebagate instead of the dioctyl adipate of Example 1.
When developed with the same apparatus as in Example 1, 5000
Even after the plate was developed, the fixing of the developing device was small. Also, a slight precipitate was generated after long-term storage, but it was easily dispersed and the image was not disturbed.

Example 4 2-Ethylhexyl Methacrylate Monomer 20 parts Vinyl Acetate Monomer 60 parts Acrylic Acid 1 part Benzoyl Peroxide 1 part Isopar G (manufactured by Exxon) 170 parts were charged into a four-necked flask, and a stirrer, a condenser, and nitrogen were added. With an introduction tube and a thermometer attached, while introducing nitrogen,
Polymerization was carried out at 0 ° C for 3 hours, then the temperature was raised to 100 ° C and the polymerization was continued for 10 hours. Then, 1 part of 1,1-azobiscyclohexane-1-carbonitrile was added, and the mixture was further added at 100 ° C. for 5 minutes.
Polymerization was performed for a time to obtain a cloudy polymer dispersion.

To 100 parts of this polymer dispersion, 60 parts of dibutyl adipate (manufactured by Daihachi Chemical Co., Ltd.) and 2 parts of Reflex Blue R-51 (manufactured by Hoechst) were dispersed with a sand grinder for 3 hours to obtain a concentrated toner. Twenty-five parts of this concentrated toner was dispersed in 2000 mL of Isopar H (manufactured by Exxon) and developed in the same apparatus as in Example 1. As a result, a very clear master plate for offset printing was obtained.
Even after the development of the 5000th plate, there was little toner sticking to the developing device, and most of the toner could be removed by circulating cleaning with the non-polar solvent Isopar E (manufactured by Exxon Chemical). Further, as a result of performing offset printing on 10000 sheets of this master plate, thinning and chipping of the image were hardly seen.

Example 5 A concentrated toner was obtained in the same manner by using 100 parts of dibutyl glycol adipate (manufactured by Daihachi Chemical Co., Ltd.) in place of the dibutyl adipate of Example 4. When the image was developed by the same device as in Example 4, the fixing of the developing device was small even after the development of the 5000th plate.

Example 6 A concentrated toner was obtained in the same manner by using 90 parts of methylacetylricinolate (manufactured by Daihachi Chemical Co., Ltd.) in place of the dibutyl adipate of Example 4. When the image was developed by the same apparatus as in Example 4, the development apparatus did not stick much after the development of the 5000th plate, and the image quality was good even after the repeated development of the 5000th plate.

Example 7 A concentrated toner was obtained in the same manner by using 55 parts of dioctyl sebagate (manufactured by Daihachi Chemical Co., Ltd.) in place of the dibutyl adipate of Example 4. When the image was developed by the same device as in Example 4, the fixing of the developing device was small even after the development of 5000 plate,
Also, there was almost no image distortion after long-term storage.

Comparative Example 1 A liquid developer was prepared in the same manner as in Example 1 except that dioctyl adipate of the concentrated toner in Example 1 was omitted, and when the liquid developer was developed in the same manner, the toner adhered to the developing device and a non-polar solvent was used. It was impossible to wash.

Comparative Example 2 A liquid developer was prepared in the same manner as in Example 4 except that the content of methyl acetyl ricinoleate in the concentrated toner in Example 4 was increased to 180 parts. And the transfer was observed, and the image density was remarkably reduced in the repeated development of the 5000th plate.

Next, these performances are summarized in Table 1.

[Table 1]

[0024]

As described above, according to the present invention, it is possible to obtain a developing solution which has little influence on the developing mechanism and has high maintainability. Further, a stable image can be obtained even with repeated development, and an excellent developer can be obtained without image distortion even after long-term storage.

Claims (5)

[Claims] 1. A liquid developer comprising a colorant, a binder and a charge control agent as constituents dispersed in a non-polar carrier solvent, wherein the dibasic fatty acid ester is 0.5 to 0.5 as a dispersant. A liquid developer for electrophotographic plate making, which contains 1.2% by weight. 2. The liquid developer for electrophotographic plate making according to claim 1, wherein the fatty acid ester is an adipic acid ester. 3. The liquid developer for electrophotographic plate making according to claim 1, wherein the fatty acid ester is an azelaic acid ester. 4. The liquid developer for electrophotographic plate making according to claim 1, wherein the fatty acid ester is sebacic acid ester. 5. The liquid developer for electrophotographic plate making according to claim 1, wherein the fatty acid ester is a ricinoleic acid ester.