JPH0645232B2 - Correction fluid for printing plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an offset printing plate that eliminates ink acceptability by converting unnecessary portions of an image formed on a printing plate into hydrophilicity. Image correction fluid for
More specifically, by printing the surface of the unnecessary portion of the image on the offset printing plate formed by a photographic or physical method with a specific treatment agent at any stage in the printing process, particularly printing characteristics, The present invention relates to completely hydrophilizing a base material or the like without causing any trouble, thereby eliminating ink acceptability. Usually, in the printing field, such a process is called “correction”, and the present inventors will follow it.

Further, the processing material used for the correction operation will be referred to as "correction agent".

(B) Prior Art and Problems Thereof In general, the parts that need to be corrected in the printing original plate produced by the photoengraving method are those that already exist in the copy original, those that occur during exposure, and other non-uniformities. There are things that are generated by various development processing processes.

That is, for example, when an unnecessary image is present in the copy original, dust and dirt particles, fingerprints or other stains are present, or when an original made by laminating various originals is used, Shadows may be projected during exposure. In order to obtain a good printed matter, all of these points must be corrected at the stage of plate making and printing. Generally speaking, the correction operation is indispensable, and it is desirable that the necessary correction can be performed at any stage of the plate making and printing process.

Many attempts have been made to correct unwanted images in offset printing plates that utilize the image as ink acceptability.

For example, JP-A-48-92101 and JP-A-51-2190
1, the compounds having a mercapto or thione group and a hydrophilic group described in JP-A-54-53002, JP-A-59-9661 and the like can make a silver image hydrophilic by a reliable and almost instantaneous reaction. is there.

Further, JP-A-48-41808 discloses red blood salt and EDTA.
A modifier consisting of a silver oxidizer such as a metal salt and a thiocyanate is described.

Further, the present inventors have separately proposed a corrector composed of a ferric organic acid complex salt and a halide (eg, potassium bromide, ammonium bromide, potassium iodide, etc.).

Further, as a correcting agent for a zinc oxide master, for example, a metal salt described in JP-B-48-5681 is known.

However, when using the conventional corrective agents, such as the method commonly referred to as matchstick correction or the method using a correction pen, when making a slight rubbing on the image area, the corrected edge often becomes gradually ink-accepting and causes smearing. There is a drawback that causes.

Further, in the case of the correction pen method, there is a drawback that the correction liquid at the pen tip is easily evaporated and dried and cannot be corrected.

(C) Object of the Invention An object of the present invention is to provide a correction liquid for an offset printing plate which can be surely corrected and is excellent in storage stability of a correction agent solution.

Another object of the present invention is that the drying property with a pen tip is extremely slow,
It is an object of the present invention to provide a correction liquid for offset printing plates which is suitable for a correction pen system in which the drying property after correction is fast and the correction can be surely performed.

(D) Structure of the Invention The above object of the present invention is to provide an offset printing plate correction liquid,
Achieved by the above correction fluid characterized by containing low molecular weight gelatin.

As is well known, gelatin is used for applications such as photographic materials and foods.

Known gelatins include alkali-treated gelatin, acid-treated gelatin, and gelatin derivatives treated and modified by various methods, and generally have an average molecular weight of tens or hundreds of thousands.

For the measurement of molecular weight, analysis of terminal groups, analysis of amino acid composition,
Known methods include light scattering, gel filtration, ultracentrifugation, and surface pressure.

As is well known, a gelatin-containing photographic layer is applied by utilizing the phenomenon that gelatin is gelled (called a set) after applying a gelatin coating solution.

Gelatinization of gelatin is said to be recognized from an average molecular weight of about 30,000. Normally, gelatin commonly used as photographic gelatin has an average molecular weight of about 100,000.
It generally has an average molecular weight of about 70,000 to about 150,000. Gelatin having an average molecular weight of about 30,000 or less does not have a set phenomenon or is extremely weak even if it exists, and it is difficult to form a good photographic layer with a coating solution containing gelatin alone, and it is usually used for photography. Absent.

The term low molecular weight gelatin as used herein means gelatin having the above-mentioned properties.

The typical average molecular weight of low molecular weight gelatin is about 3,000.
0 to about 30,000, preferably about 5,000
To 20,000.

The low molecular weight gelatin is produced by, for example, a method of subjecting ordinary photographic gelatin to an enzymatic decomposition treatment.

Low molecular weight gelatin is about 1 to about 100 per correction fluid.
It can be used in an amount range of g, preferably about 5 to about 50 g.

The correction fluid of the present invention containing low molecular weight gelatin is particularly effective for use in a so-called correction pen system such as a felt pen. That is, as described above, it not only improves the temporal stability of the modified edge portion, but also has a function as a drying inhibitor for preventing overdrying of the correction pen.

The correction fluid of the present invention containing low molecular weight gelatin contains the above-mentioned correction agent, but is not limited to the type of the correction agent.

The correction fluid of the present invention preferably uses water, various alcohols, or a mixed solution thereof as a solvent.

Further, it can be contained as an element for making the liquid such as carboxymethyl cellulose, polyvinyl alcohol, glycerin viscous, or an element for coloring the liquid such as a dye, an organic or inorganic pigment, but these are essential elements. is not.

Further, a fine particle powder as described in JP-A-51-21901 may be included.

The correction fluid of the present invention is stable. In addition, it can be corrected quickly and completely, and even if it is rubbed strongly after the correction, the ink does not get on the correction part. Therefore, it is possible to print a larger number of sheets.

Examples of the offset printing plate used in the present invention include JP-B-48-30562, JP-A-53-21602, US Pat. Nos. 3,721,559 and 3,490,905, and US Pat. 3,454,398, JP-A-5
Included are offset printing plates which have silver halide images as ink receptive such as No. 3-9603.

Further, it may be a zinc oxide master, a PS plate or the like.

(E) Example Example 1 Hydroquinone 1.0 g / m ^{2 was} contained in the physical development nucleus layer of the offset printing plate (plate No. 3) described in Example 1 of JP-A-53-21602. A lithographic printing material was prepared in the same manner.

After exposing the lithographic printing material image-wise, it is immersed in a transfer developer at 30 ° C. for 30 seconds to perform transfer development, and subsequently, immersed in a stop solution for 30 seconds (25 ° C.) and squeezed to remove excess. The liquid was removed and the material dried under atmospheric conditions.

A correction fluid was prepared using the compounds and amounts shown in Table 1 below and filled into felt correction pens. The portions to be corrected of the planographic printing plate were corrected by rubbing with these correction pens.

The printing plate thus obtained was mounted on an offset printing machine ABB Dick 350CD (trade name of AB Dick350CD), and an exclusive etchant and dampening liquid for Silver Master (trade name of Mitsubishi Paper Mills) were used. 10,000
I printed one sheet.

In the portion corrected with the correction liquid A, ink was deposited on the edge to cause background stain, and the background stain increased as the number of printed sheets increased. On the other hand, the portion corrected with the correction fluid B is 10,000
Even when printing one sheet, other stains did not occur at all.

Furthermore, the cap of the correction pen containing the correction liquids A and B was removed, and after leaving it in the atmosphere at room temperature of 25 ° C. and humidity of 40% RH, the correction was performed to examine the drying property. The pen containing the correction fluid A could not be stably corrected because the pen tip dried in only one hour, whereas the pen containing the correction fluid B was
It was possible to correct without any problem even after leaving it for 3 days.

Example 2 N-methylethanolamine was added to the correction fluid B of Example 1
The same results were obtained with the correction solution containing ml.

Example 3 The same results were obtained with the correction liquid prepared by using the low-molecular weight gelatin having an average molecular weight of about 10,000 as the correction liquid B of Example 1.

Example 4 A test was performed according to Example 1 using a correction pen filled with the following correction liquid. Similar results were obtained.

<Correction fluid> (F) Effects of the Invention The correction fluid of the present invention does not cause scumming of the correction portion and can maintain the correction effect in a stable manner. Efficiency can also be improved.

Claims (1)

[Claims] 1. A silver complex salt diffusion transfer utilizing a silver image as an ink accepting property, which comprises a modifier capable of rendering a lipophilic silver image hydrophilic and a low molecular weight gelatin having an average molecular weight of about 30,000 or less. Correction liquid for offset printing plates.