Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1993-05-24
1995-05-30
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524423, 524425, 524431, 524444, 524447, 524451, 428211, 428331, 428323, 428530, 4285375, C08K 334, B32B 300, B32B 700, B32B 516
Patent
active
054201900
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF INVENTION
This invention relates to gravure printing and, more particularly but not exclusively, is concerned with a paper coating composition for use in preparing a coated paper for gravure printing, to a coated paper prepared using said composition, and to a gravure printing process using the coated paper.
Three main methods exist for applying printing ink to a paper surface, namely gravure, offset and letterpress. In theory, any of the three methods could be used to print any grade of paper, but in practice the quality of the print obtained depends significantly on the nature of the paper surface to which it is applied; and to achieve acceptable print quality the paper must normally possess certain properties which differ according to the method of printing to be used. Gravure printing is a form of intaglio printing, i.e. printing which uses a plate or cylinder constituting a former into the surface of which the subject matter to be printed is etched or engraved. A liberal film of fluid printing ink is supplied to the whole printing surface and the surface is then wiped, for example by a doctor blade, in order to remove all the ink from the unindented parts of the surface leaving ink only in the indentations or cells. Paper in a continuous web or in separate sheets is then pressed into contact with the inked surface in order to receive an impression of the subject matter.
In the most widely used kind of gravure printing, which is known as the rotogravure process, the subject matter, which may be textual or pictorial, is etched into the printing surface in the form of a matrix of cells which vary in depth and/or in surface area, so that the cells corresponding to the darker parts of the subject matter have a greater capacity for ink than the cells which correspond to the lighter parts of the subject mater. An image of the subject matter is formed by a photographic process on a sheet of carbon tissue which is impregnated with gelatine containing a light sensitive reagent. There is first formed on the sheet of carbon tissue a rectilinear grid having from about 50 to about 160 lines to the centimeter. The grid is formed by placing a screen consisting of small opaque squares separated by fine transparent lines in contact with the impregnated carbon tissue and exposing the screen to light so that the gelatine in the tissue immediately below the lines is rendered insoluble.
The image of the subject matter to be printed is then superimposed on the image of the screen by placing in contact with the carbon tissue a positive photographic transparency of the subject matter for the colour to be printed, and exposing the transparency to light. Again, the gelatine in areas of the carbon tissue lying immediately beneath clear areas of the transparency is rendered insoluble and in other areas the solubility of the gelatine is inversely proportional to the amount of light transmitted by the transparency. The carbon tissue is then placed over the surface of a specially prepared colour roller; those parts of the gelatine which are still soluble are washed away, and the surface of the roller is etched with a suitable reagent such as ferric chloride. The result is that the surface of the cylinder is etched in a pattern composed of a very large number of cells defined by a rectilinear grid, the depth of the cells in a particular area being dependant on the solubility of the gelatine in the carbon tissue overlying that area and thus on the amount of light transmitted through the transparency in that area.
Although the choice of a suitable paper for gravure printing is largely empirical and results can be obtained on a wide variety of different types of paper, ranging from newsprint to the finest matt paper, for best results the paper should generally be absorbent enough to take the ink without the exertion of undue pressure. It is not, however, essential that the paper is absorbent, although the surface of the paper should at least be wettable by the ink solvent. The surface to which the ink is applied must also
REFERENCES:
patent: 3714107 (1973-01-01), Smith
patent: 4575477 (1986-03-01), Werkema et al.
DeWitt La Vonda
ECC International Limited
Michl Paul R.
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