JPS6026358A - Offset master toner image retouching solution - Google Patents

Abstract

PURPOSE:To enable beautiful retouching of a copy without causing oozing out of the part to be retouched and peeling of a hydrophilic coating by using a solvent composed essentially of ethylene glycol diacetate. CONSTITUTION:The retouching soln. of an offset master toner image is composed essentially of ethylene glycol diacetate (EG2AC). Such EG2AC has a dissolving power not so strong as dissolving many kinds of resins, and when it is used for actual retouching, it dissolves or swells only a part of the resin components of the toner. It can dissolve styrene and acrylic resins, etc., and it cannot dissolve epoxy and phenol resins, etc., and the toner image of the retouched part is not converted into fine particles or liquid, but it becomes a beautiful face and does not cause peeling or the like of a hydrophilic coating, etc. The EG2AC does not change with the lapse of time. Other solvents may be added to the EG2AC retouching soln. when needed. As a result, beautiful retouching can be executed.

Description

TECHNICAL FIELD The present invention relates to a correction fluid for toner images, and more particularly to a correction fluid suitable for retouching toner images of offset printing masters produced by electrophotography.

Prior Art Currently, planographic printing original plates include (1) electrophotographic printing original plates having a photosensitive layer in which inorganic photoconductive particles such as zinc oxide particles are dispersed in a binder resin, and (11) water-resistant treatment. A one-mound receiving Jc/j in which an inorganic pigment such as titanium oxide is dispersed in a binder resin is provided on a coated paper, etc.
This layer is directly inscribed with oil-based ink or typed to form an image.It is provided on a direct plate original plate, and its exposure to light jV, j
Presensitizing plates (PS plates), which form lipophilic images by utilizing the difference in solubility between exposed and unexposed areas, are known and are in practical use.

Furthermore, recently, it has become possible to form an oil-based toner image on the direct plate original plate (11) using an electrophotographic method using a plain paper copying machine (PPCm), and use this as a lithographic printing plate (offset master). , from the ease of plate making, etc.
It is becoming widely practiced. The original plate (plate material) suitable for such plate making is also commercially available as, for example, the ppc type MA master made by (t@IJ Co.).
It is then processed with an etching solution (etching solution) before being used for printing.

By the way, toner images formed using a PPC machine are
The reality is that it is often revised.

Correcting toner images is also commonly performed in the correction of second originals for diazo reproduction. Examples of toner image correction fluids that have traditionally been considered superior include diethylene glycol diethyl ether and diethylene glycol monoether ether acetate.If toxicity and flammability are not considered, toluene, acetate ether,
Carbon tetrachloride can also be used as a correction fluid.

However, these generally commercially available toner image correction liquids (solvents) cannot be used for correction of offset masters. The first reason is that the solubility of these solvents is so strong that they also dissolve the hydrophilic resin that makes up the non-image area. The second reason is that these solvents dissolve all the resins that form the toner image, that is, the resin components that make up the toner, and become fine particles or liquid that spread to non-image areas as stains. .

Incidentally, examples of the hydrophilic resin (binder resin) include casein, oxidized starch, polyvinyl alcohol, carboxymethyl cellulose metal salt, alginate metal salt, etc., and examples of the resin component of the toner include, for example. , styrene resin, acrylic resin, polyester resin,
Examples include epoxy resin, phenol resin, and fluorine IMJ resin.

OBJECTS The present invention provides a toner image correction liquid suitable for obtaining a high-quality offset master, which eliminates the above-mentioned disadvantages.

Configuration: Offset master toner 1 of the present invention [ili&'
l$ Positive hydraulic pressure liquid ethylene glycol diacetic acid is the main component 4! It is a sign.

Ethylene glycol diacetic acid has a high nodal point of 191°C and a flash point of 96°C, has almost no odor due to evaporation, and is highly safe for the human body, so it is not regulated by laws and regulations other than dangerous goods class III petroleum. do not have.

Ethylene glycol diacetic acid does not have enough dissolving performance to dissolve many types of resins, so even during correction, it only dissolves or swells a portion of the resin components of the toner. Examples of soluble resins include styrene, acrylic, and polyester resins, and those that do not dissolve include epoxy, phenol, and Teflon resins.

Therefore, in the repaired area, the toner image does not turn into fine particles or liquid, but peels off in the form of scales, which easily sticks to a cotton swab or the like and is removed, and the repaired area easily becomes an attractive surface. , and there is no peeling of the hydrophilic coating (hydrophilic resin layer in the non-image area).

One of the features of the present invention is that ethylene glycol diacetic acid alone can be used as an excellent correction fluid, that is, there is no change in correction ability over time; however, if necessary, other solvents may be used. may be added.

Solvents that can be washed include solvents with low toxicity and flammability,
For example, polyhydric alcohol spinners (ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol-e/methyl ether, dipropylene glycol monomethyl ether, diethylene f li:=I-rumonomethyl ether Acetate, diethylene glycol monoether ether acetate, etc.) and esters (methyl acetoacetate, aceto[[ethyl, etc.)].

The amount of these other solvents (addable bath additives) to be added is determined in consideration of odor, correction ability, etc., but the preferred amount is less than 30 volume i%.

Example Commercially available electrophotographic camera (manufactured by Ricoh, FT-4060)
Offset printing master plate material (manufactured by Ricoh, PPC)
A copy toner image is formed on the inventive product (ethylene glycol 2
This was done with ``acetic acid''. The correction method involved holding a cotton swab in a solvent (ethylene glycol diacetic acid) and rubbing the toner image on the print master several times.

For comparison, toluene, butyl acetate,
The toner image was modified in the same manner as above except that carbon tetrachloride was used.

The results were as shown in -fi-1.

Table 1 Note) As for the correction fluid conditions, ◎ means it is corroded, (○ means good, △ has some problems), and X means it cannot be used because of a gap.

As is clear from the above deception, the correction fluid according to the present invention does not bleed into areas other than the correction area or cause the hydrophilic coating to peel off (and has excellent properties that contribute to the beauty of printed matter, etc.). It has characteristics.

Claims (1)

[Claims] 1. Offset master toner image correction liquid containing ethylene glycol/l/2 acetic acid as a main component.