1、 Reference number ISO/TR 12705:2011(E) ISO 2011TECHNICAL REPORT ISO/TR 12705 First edition 2011-10-15 Graphic technology Laboratory test method for chemical ghosting in lithography Technologie graphique Mthode dessai en laboratoire pour impression fantme chimique en lithographie ISO/TR 12705:2011(E)
2、 COPYRIGHT PROTECTED DOCUMENT ISO 2011 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address
3、below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2011 All rights reservedISO/TR 12705:2011(E) ISO 2011 All rights rese
4、rved iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for w
5、hich a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all
6、 matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are c
7、irculated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. In exceptional circumstances, when a technical committee has collected data of a different kind from that which is normally published as an Inte
8、rnational Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have to be reviewed until the data it provides are considered to be no longer va
9、lid or useful. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TR 12705 was prepared by Technical Committee ISO/TC 130, Graphic technology. ISO/T
10、R 12705:2011(E) iv ISO 2011 All rights reservedIntroduction This Technical Report describes a test method to evaluate the susceptibility of a particular ink, substrate and printing procedure to produce chemical ghosting in sheet-fed offset lithographic printing. Chemical ghosting occurs only in shee
11、t-fed offset lithographic printing and appears mostly in dark areas of a print. A related phenomenon, mechanical ghosting, can appear in both sheet-fed and web offset. This is due to the ink supply limitations of some inking unit designs for sheet-fed offset presses; its origin is unknown in web-off
12、set presses. Chemical ghosting occurs during storage of freshly printed sheets in the output stack. Inks formulated from natural fatty acids liberate volatile chemicals during oxidative drying. These might cause either image-wise yellowing of the back side of the adjacent sheet in the stack (in eith
13、er single side or perfecting printing), or variation in the drying speed of ink layers that are subsequently over-printed, which results in an image- wise variation in gloss. In both cases “ghost image artefacts” might be visible. Complete suppression of these artefacts can be achieved by strictly s
14、eparating the sheets. The effect of chemical ghosting depends on the nature and film thickness of the printing inks, the substrate, climatic conditions, the time intervals between face and reverse printing, and printing and converting. The severity of chemical ghosting that manifests itself by diffe
15、rences in gloss may be reduced by: a) measures that result in faster ink drying; b) lower ink film thicknesses; c) moderate temperatures; d) medium relative humidity; e) very short or very long intervals between face and reverse printing; f) short converting intervals 3 . If prints are surface-finis
16、hed by dispersion, UV lacquers, and sometimes oil lacquers, this tends to achieve a homogeneous gloss level and therefore to suppress chemical ghosting 3 . Optical measurements like densitometry, colorimetry and gloss measurement at constant and variable angles of illumination and detection have pro
17、ven unsatisfactory in the evaluation of the severity of image-wise gloss artefacts. These effects are better evaluated visually. The reliability of the test method described in this Technical Report was validated by printing trials on a sheet- fed offset printing press 34 . TECHNICAL REPORT ISO/TR 1
18、2705:2011(E) ISO 2011 All rights reserved 1Graphic technology Laboratory test method for chemical ghosting in lithography 1 Scope This Technical Report describes a laboratory method, using a printability tester, for the preparation of specimens in order to evaluate the tendency of a particular ink,
19、substrate and printing procedure to produce chemical ghosting in sheet-fed offset lithography on coated papers or foils. A test procedure to induce ghosting using these specimens is also included. The presence of chemical ghosting is determined by visual evaluation of test images. Chemical ghosting
20、can appear either as reverse-side yellowing on single-side and perfect printing, or as image-wise gloss variations in perfect printing. This method applies only to oxidative drying inks on coated papers or foils and it evaluates a particular ink and substrate combination. 2 Terms and definitions For
21、 the purposes of this document, the following terms and definitions apply. 2.1 chemical ghosting reverse-side and image-wise yellowing and/or gloss variations in face and reverse printing, typically in the form of a mirror image 2.2 face and reverse printing perfect printing printing on both sides o
22、f a print substrate, either in the same run or in two subsequent runs 3 Test method 3.1 Principle Two test prints are prepared, according to the procedures defined in ISO 2834-1, using the ink and substrate combination to be evaluated. One of the test prints should have a large area of uniform cover
23、age. The second test print should have a smaller area of uniform coverage that will lie within the area (or width) of coverage of the larger area test print when the two printed areas are placed facing each other. These test prints are then placed with the printed areas facing each other, for a defi
24、ned time interval, in a condition that simulates the pressure and environment associated with storage of freshly printed sheets in the output stack of a production press. ISO/TR 12705:2011(E) 2 ISO 2011 All rights reserved3.2 Apparatus 3.2.1 Printability tester A printability tester meeting the requ
25、irements of ISO 2834-1 should be used. All of its settings should be recorded as defined in ISO 2834-1. 3.2.2 Printing forme Two different printing formes are required. The inkable area of the first printing forme should represent a significantly smaller area than the second printing forme. For easy
26、 visual detection, the printing forme with the smaller area should have more than just one contrast edge. This can be achieved by printing two symmetrically located stripes spaced by the width of the stripes (typically about 10 mm). Figure 1 shows an example of a pair of printing formes for a typica
27、l printability tester meeting the criteria defined. Figure 1 Example of a pair of printing forms meeting the criteria of 4.2.2 3.3 Materials 3.3.1 Printing ink This test is appropriate for use with all oxidative drying printing inks intended for sheet-fed offset printing. Since the drying speed of t
28、he ink plays an important role, any drying inhibitors that may have been applied to the ink surface while in the can should be completely removed prior to the test. 3.3.2 Print substrate This test is appropriate for use with all coated papers or foils compatible with sheet-fed offset printing. Each
29、test requires two pieces of substrate. 3.3.3 Output stack simulation Prints should be stored in way that simulates the pressure and environment associated with storage of freshly printed sheets in the output stack of a production press. The use of the test substrate as the material for the stack is
30、not necessary. Common office copy paper with a grammage of 80 g/m 2may be used. The stack height above each pair of test images in contact with each other should be at least 5 cm. ISO/TR 12705:2011(E) ISO 2011 All rights reserved 33.4 Test conditions 3.4.1 Climatic conditions Samples should be condi
31、tioned, and tests should be conducted, under the standard conditions of ISO 187. 3.4.2 Settings for the printability tester The printability tester should be used with a printing pressure of 200N/cm and a printing speed of 1 m/s. 4 Procedure The steps in the testing procedure are as follows. a) Cond
32、ition the printability tester, the ink and the printing substrate for a sufficient period of time (e.g. 2 h) so that temperature and humidity will come to equilibrium. b) Create a test print using the test form with the smaller area at an ink film thickness specified for the intended printing condit
33、ion to be simulated. NOTE 1 A unified ink film thickness of 2,5 g/m 2is suggested. c) Allow the first test print to set for an initial time period that is long enough that set-off from the printed sheet to the second sheet does not occur. Limit the ink setting time to 15 min at the maximum. NOTE 2 A
34、n ink setting test according to the manuals or instructions of the manufacturer of the printability tester can be used to determine the appropriate time interval to be used. d) Place a second sample of the substrate in contact with the first test print with the intended printing side facing the firs
35、t test print. e) Place these sheets within a simulated output stack of paper for a time interval that compares well to the expected time between face and reverse printing. f) Remove the sample sheets from the simulated output stack of paper and separate the unprinted test sheet from the printed test
36、 sheet. g) Examine the unprinted test sheet for any evidence of yellowing in the areas that were in contact with the printed area of the first test sheet. h) Using the unprinted test sheet and the test form with the larger area prepare a second test print. Be sure hat the printing is performed on th
37、e side designated as the intended printing side when the unprinted sheet was placed in contact with the first test print. i) Allow the second test print to set for an initial time period that is long enough that set-off from the printed sheet to the second sheet does not occur. Limit the ink setting
38、 time to 15 min at the maximum. j) Place this second test print in contact with the first test print in the same position and orientation that was initially used. k) Place these sheets within a simulated output stack of paper for a time interval that compares well to the expected time between face a
39、nd reverse printing. l) Remove the sample sheets from the simulated output stack of paper and separate the second test sheet from the first test sheet. m) Visually evaluate the second test print for variations in gloss. ISO/TR 12705:2011(E) 4 ISO 2011 All rights reserved5 Test report The report shou
40、ld contain: a) a reference to this Technical Report, i.e. ISO/TR 12705:2011; b) any deviation from this Technical Report; c) type of printability tester used and all its settings; d) climatic conditions during the test; e) designations and brands of both paper and ink; f) design and ink film thickne
41、ss of the first test print; g) time interval between first and second test print; h) ink film thickness of the second test print; i) time interval between second test print and evaluation; j) result of visual inspection; k) any operations not specified in this Technical Report which might have influ
42、enced the result. ISO/TR 12705:2011(E) ISO 2011 All rights reserved 5Bibliography 1 ISO 187, Paper, board and pulps Standard atmosphere for conditioning and testing and procedure for monitoring the atmosphere and conditioning of samples 2 ISO 2834-1, Graphic technology Laboratory preparation of test
43、 prints Part 1: Paste inks 3 SOMMER, G., BERTHOLDT, U, Causes of matt/gloss effects (“ghosting”) in sheet-fed offset; Research Report; Fogra; Munich 2008 4 BERTHOLDT, U., SOMMER, G, Causes of matt/gloss effects (“ghosting”) in sheet-fed offset; Advances in Printing and Media Technology Vol. 35; Darmstadt 2008, pp. 421-428 ISO/TR 12705:2011(E) ICS 37.100.01 Price based on 5 pages ISO 2011 All rights reserved
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