JPS63273674A - Ink composition for water-free planographic printing - Google Patents

Abstract

PURPOSE:To provide the titled ink composition outstanding in substrate stain resistance and light resistance, containing specified amount of particulate titanium dioxide. CONSTITUTION:The objective ink composition containing 1-20 (pref. 1-10) wt.% of titanium dioxide with an average particle size <=0.1mu (pref. <=0.05mu). The vehicle resin component is pref. rosin-modified phenolic resin or petroleum resin; and such a resin with a softening point >=140 deg.C is pref. contained in such amount as to be >=15wt.% in the final ink composition.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ink composition for waterless lithographic printing that has good background stain resistance and excellent light resistance in waterless lithographic printing. .

[Prior Art] In contrast to the lithographic printing method that utilizes the ink repellency of dampening water, which is the mainstream of current printing, a waterless lithographic printing method that uses a lithographic printing plate that does not require dampening water has been proposed. ,
In particular, a method of printing using a lithographic printing plate provided with silicone or rubber in the non-image area has been put into practical use.

In such waterless planographic printing, it is known that printing using conventional oil-based inks causes background smearing, which is undesirable.

The phenomenon of background smudge in waterless planographic printing is caused by the friction of the drive unit and rollers of the printing press during printing, which causes the plate surface temperature to rise and the cohesive force of the ink itself to decrease, which is due to its inherent ink repellency. Ink adheres to the non-image areas.

Such a phenomenon does not need to be considered at all in conventional planographic plates that use dampening water, but is a problem unique to waterless planographic printing plates. This is because in the case of conventional lithographic printing that uses dampening water, the ink repulsion mechanism is different, and the increase in plate surface temperature is considerably suppressed by the evaporation of dampening water, so there is no need to take this scumming phenomenon into account. It is said that it is preferable for the ink to have a small cohesive force.

From this point of view, when designing an ink for waterless planographic printing, a different approach from the conventional technical idea is required.

Further, printed matter obtained using ordinary process inks may change in hue when exposed to outdoor light for a long time. For this purpose, it is necessary to use ink that uses pigments with excellent light resistance, but this causes problems such as insufficient color clarity and the inability to obtain ink with excellent printability due to the characteristics of the pigment. . For this reason, those skilled in the art would like a means to improve the light fastness without significantly impairing the properties of ordinary process inks.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve the above-mentioned drawbacks of conventional inks,
An object of the present invention is to provide an ink composition for waterless planographic printing which has excellent background stain resistance and light resistance.

[Means for Solving the Problems] The object of the present invention is to provide an ink composition for waterless lithographic printing characterized by containing 1 to 20 parts by weight of titanium oxide having an average particle diameter of 0.1 μ or less. achieved.

The titanium oxide used in the present invention has an average particle size of 0.
It is 1μ or less, more preferably 0.05μ or less. Here, the average particle diameter of titanium oxide is 0.1μ
If it exceeds 100%, the titanium oxide particles scatter light, making the ink opaque and causing the hue to become cloudy.

Further, the content of titanium oxide in the ink composition is 1 to 20
Although it is expressed as % by weight, it is more preferably 1 to 10% by weight. Here, if the content of titanium oxide is 1% by weight, the effect of absorbing ultraviolet light of 4QQnm or less, which affects light resistance, will be small, and if the content of titanium oxide is 2% by weight,
If it exceeds 0% by weight, the light transmittance in the visible region becomes low and the ink becomes opaque, resulting in cloudy hue, which is not preferable.

Vehicle resin components that can be used in the ink compositions of the present invention include those known in the art, such as rosin,
Rosin esters, phenolic resins, rosin-modified phenolic resins, petroleum resins, acrylic resins, etc. can be used.
Particularly preferred are rosin-modified phenolic resins and petroleum resins. In addition, from the viewpoint of stain resistance, it is preferable that the ink composition contains 15% by weight or more of a resin having a softening point of 140° C. or higher.

Also drying oil, alkyd resin, amino alkyd resin,
Urethane resins, epoxy resins, urethane-modified alkyd resins, etc. can be used.

As the colorant that can be used in the present invention, those used in conventional ink compositions such as inorganic or organic pigments can be used, but organic pigments are preferable.
Especially Disazo Yellow, Disazo Orange, Palkan Orange, Lake Orange, Helioresin TD1 Lilly Red R, Calcium Lilly Red, Lake Leta 7 Tsudo D1 Mancan Red 52, Lake Red C, Rhodamine 6G Lake, Brilliant Cardin 6B, Rhodamine B Lake. , Rhodamine 3B Lake, Methyl Violet Lake, Crystal Violet Lake, Victoria Pure Blue 80 Lake, Reflex Blue 3G, Reflex Blue R, Diamond Green Lake, etc. are preferred.

The ink composition of the present invention can also be used as a transparent ink for overcoating without adding a colorant.

This transparent ink for overcoating can be used not only to overcoat printed matter produced by waterless lithographic printing but also to printed matter produced by lithographic printing using dampening water.

Coats, such as waxes, greases, desiccants, dispersants,
Fillers and other known materials may also be used.

As a method for adding titanium oxide, commonly used dispersion methods such as a roll mill, a sand mill, and a ball mill can be used.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto. Note that parts used in the examples are based on parts by weight. In addition, in the following explanation, soil stain resistance is measured by the following method.

Method for evaluating background stain resistance (measurement of background stain occurrence index) A printing machine modified to raise the temperature of the plate surface by passing hot water into the plate cylinder.
A waterless lithographic plate with a non-adhesive layer made of silicone rubber was attached, and printing was performed while increasing the temperature of the plate surface without supplying dampening water, and scumming occurred on the printed matter at a certain solid density. The plate surface temperature at the time of printing was used as the background stain occurrence index. Ink with a high scumming index is less likely to cause scumming in practical printing.

[Example] Example 1 40 parts of rosin-modified phenol resin with a softening point of 165°C (Pentalin DP-105, manufactured by Rika Vercules), 20 parts of linseed oil, 40 parts of hydrocarbon solvent (No. 5 Solvent, manufactured by Nippon Oil Co., Ltd.) The mixture was heated and stirred at 200° C. for 1 hour to obtain Varnish A.

Using the thus obtained varnish A, the following composition was kneaded using three rolls in a conventional manner to obtain ink A.

Ink A Disazo Yellow 12.0 parts Titanium oxide (TTO-55 manufactured by Ishihara Sangyo Co., Ltd., average particle size 0.0
2~0.05μ) 8.0 parts 5@solvent
3.0 parts varnish A
77.0 parts total 100.0 parts The scumming index of this ink A was 34.

Comparative Example] Using varnish A, ink B was obtained by kneading the following composition using three rolls in a conventional manner.

Ink B Disazo Yellow 12.0 parts Varnish A
88.0 parts Total 100.0 parts The scumming index of this ink A was 34.

Example 2 50 parts of cyclopentadiene petroleum resin with a softening point of 145° C. (Nisseki Neoresin 540 manufactured by Yasseki Kagaku Co., Ltd.), 10 parts of Alkyrado resin, and 40 parts of No. Varnish B was obtained by heating and stirring at 200° C. for 1 hour.

Using this varnish B, a transparent overcoat ink C was prepared with the following composition in a conventional manner.

Ink C Titanium oxide (TTO-55 manufactured by Ishihara Sangyo Co., Ltd. average particle size 0.02 to 0.05μ) 5.0 parts Varnish B
95. A total of 100.0 parts of this overcoat transparent ink C had a scumming index of 34.

Comparative Example 2 Using Varnish B, transparent ink D for overcoat was prepared in the same manner as in Example 2 with the following composition.

Ink D Titanium oxide (CR-EL manufactured by Ishihara Sangyo Co., Ltd., average particle size 0.2 to 0.4μ> 5.0 parts Varnish B
95.0 parts total 100.0 parts The scumming index of this transparent overcoat ink D was 33.

A waterless lithographic printing plate having a non-adhesive layer made of silicone rubber was prepared using the inks of Example 1 and Comparative Example 1 using a Komori sprint printing machine without supplying dampening water to the plate surface.
(manufactured by Toshiku Co., Ltd.) to obtain printed matter 1 and printed matter 2.

Further, on the printed matter printed using ink B of Comparative Example 1, ink C of Example 2 and ink D of Comparative Example 2 were printed in the same manner, respectively, to obtain printed matter 3 and printed matter 4.

All of these prints were in good condition with no background stains.

Next, these printed materials 1 to 4 were evaluated for light resistance and color clarity, and the results are shown in Table 1.

As is clear from Table 1, printed matter 2 using ink B that does not contain titanium oxide has significantly poor light resistance, and transparent overcoat ink using titanium oxide with an average particle size exceeding 0.1 μ Printed material 4 printed with D had poor color clarity. On the other hand, printed matter 1 and printed matter 3
There were no problems with light fastness or color clarity.

[Effects of the Invention] Since the ink composition for waterless lithographic printing of the present invention is configured as described above, it can be printed well without scumming in the non-image areas, and the obtained printed matter has excellent light resistance. .

Claims (1)

[Claims] An ink composition for waterless lithographic printing, comprising 1 to 20% by weight of titanium oxide having an average particle diameter of 0.1 μm or less.