JPS6356878B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel offset plate containing a tin-copper alloy, more particularly a speculum alloy, as a hydrophilic layer. The use of the hydrophilicity and surface potential of the tin surface in realizing offset plates is already known. However, in reality, this type of offset plate (i.e., an offset plate with a hydrophilic layer of tin component) is difficult to apply. -On the other hand, tin is not hard enough and can be scratched very easily, so it was never commercialized. The present invention relates to an offset plate consisting of a steel plate and a tin-based hydrophilic surface, which makes it possible to overcome all or some of the obstacles encountered to date in the use of tin. It has been found that of the metals that can be mixed with tin to provide greater surface hardness, copper is the preferred metal. Also - on the one hand, tin containing up to about 45-55% copper -
Copper binary metal compounds can be deposited very easily in matte or semi-bright form - on the other hand, tin containing up to about 45-60% copper -
Copper binary metal compounds retain the hydrophilicity and ink repellency of tin, despite copper's known hydrophilic properties; -Finally, of the available tin-copper binary metal compounds, speculum is the most important. It has been found that this constitutes a preferred product of the invention. Speculum has a base of copper and tin, about 60-55%
is a known alloy that can contain about 40-45% copper and about 40-45% tin. This alloy has hitherto been used primarily to achieve various desired surfaces using the surface hardness, constancy and appearance (i.e. color) of the product. Therefore, the present invention contains 40-90% by weight of tin and 10-90% by weight of tin.
It relates to an offset plate exhibiting a hydrophilic surface and more particularly a speculum surface based on a tin-copper alloy containing 60% by weight of copper. If the hydrophilic surface according to the invention is a tin-copper binary metal surface, this surface may contain a third component selected from zinc, cobalt, nickel and cadmium. This third component is present in a relatively small amount, less than 20%, preferably less than 5%. However, the preferred alloy for use in accordance with the present invention is speculum. This alloy actually has a complete set of favorable properties when using said alloy in offset plates. These properties are essentially as follows. - Sufficient surface hardness for the intended implementation; - Appreciable surface appearance (matte); - Good compatibility with metallic and optionally organic layers that can be used for the intended implementation; - the technology Outstanding resistance to corrosive solutions commonly used in the field, - near-zero electrical potential, - and the ability to trap moisture and repel ink. Two methods can be used for the hydrophilic speculum layer. (a) First of all, when using a printing plate, it can be used as a hydrophilic layer, ie a layer that traps moisture but not traps ink. To realize an offset plate of this kind, a speculum layer deposited on a suitable support is coated by a known method with a layer of a known ink-philic metal (or alloy) (e.g. copper) or a known photosensitive material. Cover with a resin layer. (b) However, it is likewise possible in particular to use this speculum layer as an underlayer of a hydrophilic metal layer.
It is therefore possible to deposit a chromium layer or a tin-nickel layer on the speculum layer. In this type of implementation, when the plate is used for printing, the water-trapping layer is not the speculum layer but a hydrophilic layer covering it. However, even in such implementations, the hydrophilicity of the speculum layer is of great importance, since very thin layers of hydrophilic metals can be deposited in the speculum layer mentioned above. Assuming that the hydrophilic metal layer on the surface is porous or unfinished, it has been found that the hydrophilicity of a portion of the surface of the offset plate is ensured. A second possibility of using speculum as an underlayer of a hydrophilic metal layer is the property of speculum, which can have a matte appearance (a feature found on the surface of a hydrophilic metal layer deposited on speculum) on the one hand, and on the other hand At the same time, the properties of speculum in resisting corrosive solutions used, especially when using two-element metal plates, are recognized at the same time. To realize an offset plate of this type, the speculum layer deposited on a suitable support is coated with a hydrophilic metal layer (for example chromium or tin-copper) in a known manner, and the said hydrophilic layer is made ink-philic. Coating with a metal layer and/or a photosensitive resin layer. The hydrophilic alloys of the invention, and in particular speculum, can be deposited and fixed on many surfaces, but as a support the so-called iron (or steel) whose surface is coated with a very thin layer of tin or a layer of tin-based alloy Of particular interest is the use of the present invention utilizing tinplate. Such materials (tinplate) are commonly used, especially in the packaging industry. The present invention will be explained below using examples. Example 1 Deposition of speculum (1) Electrolytic cell for speculum precipitation Currently known electrolytic cells for speculum precipitation are described in the literature, and their basic characteristics are as follows. (a) Composition (average) Tin 40g / Copper 8g / Free cyanide 16g / Free sodium hydroxide 15g / (b) Operating conditions Operate at a temperature of 65°C. The anode is partly electrolytic copper and partly pure tin. Each anode is fed into a special circuit. This circuit is 2-3 volts ^OA , 62 amps/dm ² for copper and 3-5 volts 1 ^A , 8 amps/dm ² for tin. The deposition rate of speculum under these conditions is about 3 microns per 5 minutes. (2) Plate A 3 micron thick speculum layer (copper 58% and tin
After depositing 42%), washing, rinsing, polishing, and rinsing again were performed. The appearance of the speculum layer was a matte milky color. After rinsing and drying, a printing photosensitive layer of approximately 1.8 microns (PR12 layer from La Société PCAS) was coated by rotating the coating plate at approximately 80 tr/min. The layer was dried with hot air for 5 minutes and then in a drying oven. After exposure to sunlight, it was developed with a developer compatible with the photosensitive layer used. The soluble portion was removed to expose the speculum layer. After rinsing, excess water was pushed out with a spatula and a 3% phosphoric acid solution was poured over the finish for 2 minutes. After rinsing and drying, the board was then coated with rubber. This board used in machinery did not interfere with operation under any circumstances due to oil, and was able to be used even after more than 10,000 trials. Example 2 Speculum Precipitation The following plates were produced in a manner similar to that described above (with respect to speculum layer precipitation). (A) Steel (support) Speculum 1.9 micron (water absorption layer) Printed photosensitive layer (B) Steel (support) Speculum 2.5 micron (water absorption layer) Copper 0.09 micron (intermediate protective layer) Printed photosensitive layer (C) Steel (support Speculum 2.5 micron (water absorption layer) Copper 2.5 micron (ink-friendly layer) (D) Steel (support) Speculum 1.5 micron (intermediate layer) Chromium 0.5 micron (water absorption layer) Printed photosensitive layer (E) Steel (support) Speculum 1 micron (intermediate layer) Chromium 1 micron (water absorbing layer) Copper 0.09 micron (intermediate layer) Printed photosensitive layer In plates A, B, C, D and E, the steel support is made of non-oxidized steel or tin plate (i.e. tin). A support of steel coated with a thin layer of aluminum or an aluminum support suitably treated, for example by a tinning method, can be substituted. In plates D and E, the water-absorbing layer (chromium) can be replaced by another water-absorbing metal layer, such as a tin-nickel layer. The thickness of the speculum layer can be varied depending on the conditions (support, action of the speculum layer, etc.) and, especially in the case of intermediate layers, it is possible to have layers from only 0.005 microns thick to 5 microns thick. However, if the thickness is greater than this, no properties that can be evaluated will be exhibited. EXAMPLE 3 A known bath based on copper and tin cyanide (in particular a bath containing equal amounts of potassium pyrophosphate and potassium cyanide) deposits about 60% tin and 40% tin on the shiny smooth surface of a steel sheet. A copper-containing alloy was deposited. The resulting surface is completely hydrophilic and ink-phobic so that (after coating with a suitable photosensitive layer) the plate can be used as an offset plate. Example 4 A steel sheet was coated with a bimetallic tin-copper compound following a similar electrolytic deposition method. The hardness and hydrophilicity (+) of the resulting layer were measured. The results are shown in the table below.

[Table] It is considered that the hydrophilicity of the two-element metal layer can be evaluated to be extremely clear, and a Cu-Sn alloy containing up to about 40% by weight of tin can be used.

Claims (1)

[Scope of Claims] 1. The offset plate is made of 40 to 90% by weight of tin and 10 to 90% by weight of tin.
1. An offset plate characterized in that it exhibits a hydrophilic surface of a two-element metal compound containing 60% by weight of copper. 2. Offset plate according to claim 1, in which the hydrophilic surface can contain up to 20% by weight of other metals chosen from zinc, cobalt, nickel and cadmium. 3. The offset plate according to claim 1, wherein the surface is a speculum. 4. Offset plate according to claim 3, in which the speculum layer is used as an underlayer of a hydrophilic metal layer, preferably a chromium layer or a tin-nickel layer.