JPS6039227B2 - Toner for plate making - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner for developing electrostatically charged images in electrophotography, and more specifically, toner that can be used as a toner original image for making a printing original plate such as a dry offset printing original plate. The present invention relates to a toner for plate making.

In the method of using electrophotography as a plate-making means for a dry offset printing original plate, a toner image is transferred onto the surface of an ink-repellent layer provided on a support by an indirect method, and then transferred as is by a method such as heating or pressure. A toner image is fixed or a surface layer mainly composed of a photoconductive photosensitive material such as zinc oxide and a binder resin is provided on a conductive support, and a toner image is formed thereon by a direct method. There is a way to establish them in a similar way and make them permanent visible troops.

As is well known, the conventional plate-making toner used in this case is a thermoplastic resin such as pisphenol A general-purpose epoxy resin, phenol resin, polyester resin, polystyrene resin, polyacrylate ester, polyethylene, and ketone resin, and a colorant. The main component is by the way,
In order to obtain good printing characteristics, the toner for plate making must not only obtain a high-quality original image on the printing plate, but also have a surface that is sufficient to maintain the desired printing durability as a printing plate. This means that adhesion strength is required.

However, among offset printing original plates, for example, dry offset plates, which are used for printing without using etchant or dampening water, are coated with silicone or fluorine compounds to prevent ink stains in non-line areas. Conventional plate making toners have insufficient adhesion to the surface of the original plate, resulting in a lack of printing durability. It did not have the performance to be used as an original image for a printing plate.

In addition, conventional toner is not limited to dry offset plates, but also for offset plates that use regular etch liquid and overflow water.
The adhesion properties tend to be greatly affected by the surface composition and surface physical properties of the plate, and therefore, it was not necessarily satisfactory as a toner for plate making.

The present invention has been made in view of the above circumstances, and provides a toner for plate making whose main components are a resin and a colorant, characterized in that the resin is a nitrile rubber-modified epoxy resin. The purpose of this method is to obtain a toner that firmly adheres to surfaces having releasable properties such as dry offset printing plates.

The nitrile rubber-modified epoxy resin referred to in the present invention is a reaction product of an epoxy resin having an average of one or more reactive 1,2-epoxy groups per molecule and nitrile rubber.

Examples of epoxy resins having an average of one or more 1,2-epoxy groups per molecule include diglycidyl phenols of polyhydric phenols, glycidyl ethers of novolak resins, and glycidyl ethers of aliphatic polyols. and thermosetting polyethers such as nitrogen-containing glycidyl ethers.

A suitable diglycidyl ether of polyhydric phenol is a condensation product of epichlorohydrin and bisphenol A (bisphenol A type general-purpose epoxy resin), and an example of a commercially available product is Epiquat 1004 (Shell Chemical Co., Ltd.). ), Eport YD-014 (manufactured by Toto Kasei Co., Ltd.), etc. On the other hand, nitrile rubber is a copolymer of butadiene and acrylonitrile, and particularly suitable for the present invention are carboxylated acrylonitrile-butadiene copolymers in which carboxyl groups are distributed at the ends of the nitrile rubber or throughout the polymer chain, such as Acrylonitrile 15-43%
, a nitrile rubber derived from 57-85% butadiene and less than 15% carboxylic acid.

Commercially available nitrile rubbers include Nipol 1072 (manufactured by Nippon Zeon), Chemi Gum 550 (manufactured by Goodyear), and Tyrac 211A (manufactured by DuPont). Above 1.
To synthesize a nitrile rubber-modified epoxy resin from an epoxy resin having a 2-epoxy group and nitrile rubber, for example, in a reaction vessel equipped with a fly trap device and a temperature control device,
First, add 10 parts by weight of the epoxy resin and heat to 150 to 200 CO while stirring, then 5 to 5 parts by weight of nitrile rubber.
5% by weight is added to the reaction vessel, the mixture is maintained at a temperature of 150 to 20,000° C. for several hours, and then the reaction contents are removed and cooled to room temperature.

To prepare the toner for plate making of the present invention, for example, in the case of a two-component dry toner, a coloring agent or additives such as a polarity control agent and a solvent are mixed as necessary with a nitrile rubber-modified epoxy resin, and the mixture is rolled milled. The toner is melted and kneaded in a mixer such as an extruder, coarsely pulverized with a hammer mill, etc., finely divided with a vibrating ball mill, etc., and classified into particles of about 5 to 25 particles using a method such as centrifugation. And it is sufficient.

The colorant used here can be all the dyes and pigments conventionally used in electrophotographic toners, such as pigments such as carbon black, aniline black, acetylene black, nigrosine base, Victoria blue, and final blue. For example, dyes such as

The toner for plate making created in this way is mixed with carrier substances such as iron powder and glass beads, and electrophotographic plate making using a dry developing mechanism such as the cascade method, bristle brush method, magnetic brush method, powder cloud method, etc. Served on the machine. Furthermore, if a magnetic substance such as ultrafine iron powder is contained in the toner, a one-component plate-making toner that does not require a carrier substance can be obtained.

Furthermore, suitable polarity control agents such as lecithin, metallic soap, linseed oil, and higher fatty acids are added to the nitrile rubber-modified epoxy resin and colorant system to form a toner, which is dispersed in a non-aqueous solvent with high edge supply and low dielectric constant. If so, the present invention can also be practiced as a liquid developer.

The toner for plate making of the present invention having the above-mentioned structure was applied to a dry type electronic copying machine having a two-component developing mechanism, and transferred to a dry offset plate having a silicone rubber made of addition-curable organopolysiloxane as a surface layer. However,
It was possible to obtain an original image with extremely clear contrast and no fog.

In addition, due to the low softening point of 70 to 8yo, it can be easily fixed in a short time and at a relatively low temperature, and there is no toner aggregation phenomenon that tends to occur in the image area after fixing due to the releasability of silicone.
It was confirmed that it was formed uniformly. When the printing plate thus obtained was set in an offset printing machine and offset printing was performed without etching or using dampening water, there was no difference in the image area even after printing more than 300 forks. There was no plate dropping and sufficient printing durability was achieved. The toner for plate making of the present invention is not limited to dry offset systems, and can of course be applied to plate making for offset printing using ordinary dampening water, as well as for use in electrophotography. It can be applied to a wide range of applications such as developing office copy paper, electrostatic recording, and electrostatic printing.

Examples of the present invention and examples of comparisons according to the prior art are shown below.

Example 1 A mixture of 10 parts by weight of a nitrile rubber-modified epoxy resin having a molecular weight of 10.00 and a wind softening point of 75 to 830 C (as measured by a field-of-view type melting point measuring device), 5 parts by weight of carbon black, and 3 parts by weight of a nigrosine dye was prepared. 1 in a roll mill
The mixture was kneaded for 10q×4 minutes.

After cooling, the kneaded product was coarsely powdered using a hammer mill, further pulverized using a vibrating pole mill, and then classified to produce a toner having a particle size distribution of 5 to 25 degrees and a softening point of 783°. Next, 5 parts by weight of this toner was mixed with 100 parts by weight of carrier iron powder to prepare a dry developer.

Set this in an indirect method electronic copying machine (Sharpfax 72 diamond type), phenyl group 10 mol%, vinyl group 2 mol%
An original image was formed on a dry offset printing plate having a surface layer of silicone rubber made of an addition-curing organopolysiloxane containing . This original image was further heat-fixed by passing it once through an infrared fixing machine for offset printing plates (manufactured by Iwasaki Tsushinki Co., Ltd.).

The resulting image showed a reading of 1.6 on a Macbeth reflection densitometer, and was clear with no fog in non-image areas. Using this printing plate, a small offset printing machine (A/B Dick3
When printing was carried out up to 300 mm without etching or applying dampening water using the 2-layer type, the image area did not fall off and sufficient printing durability was confirmed.

Example 2 The plate-making toner used in Example 1 was transferred to a direct method electronic copying machine (
It was set in the developer of Elefuax PC301W (manufactured by Iwasaki Tsushinki Co., Ltd.).

On the other hand, a surface photosensitive layer containing zinc oxide, methyl methacrylate resin, and rose bengal as a sensitizer was provided on a support that had been previously subjected to low-resistance treatment to prepare an electrophotographic printing original plate, and this was applied to the above-mentioned electronic copying machine. A printing plate was prepared by applying heat fixing and making a plate. The resulting image has a reflection density of 1.
It was a clear image with a contrast of 5. This printing plate is etched and a small offset printing machine (
AP131 top type (manufactured by Ricoh) with dampening water.
When printing was performed up to the end of 0, sufficient printing durability was observed with no image areas falling off. Comparative example Bisphenol A type general-purpose epoxy resin (Epicote 10
A mixture of 10 parts by weight of 04 (manufactured by Shell Oil Company), 5 parts by weight of carbon black and 3 parts by weight of nigrosine dye was kneaded for 100 minutes in a roll mill.

After cooling, the mixture was coarsely milled using a hammer mill, and then powdered using a vibrating ball mill and then classified to produce a toner having a particle size distribution of 5 to 25 particles.

Next, 5 parts by weight of this toner was mixed with 100 parts by weight of iron powder carrier to form a dry developer, which was then used in an indirect method electronic copying machine (
An original image was formed on a dry offset plate having a silicone rubber made of addition-curable organopolysiloxane containing 10 mol% of phenyl groups and 2 mol% of vinyl groups as a surface layer. .

This original image was further passed once through a fixing device for offset printing to be thermally fixed. The resulting image was clear with contrast and no fog in the non-image areas, but when printed on a small offset printer,
The image area fell off after 30 sheets, and the plate did not function as a printing plate. Polystyrene resin (Picolastic D-
125 (manufactured by Esso Standard Co., Ltd.) or a natural resin-modified maleic acid resin (Betsukasite 1111 (manufactured by Dainippon Ink Co., Ltd.)), similar results were obtained.

Claims (1)

[Claims] 1. A toner for plate making whose main components are a resin and a colorant, characterized in that the resin is a nitrile rubber-modified epoxy resin.