l
`I
`
`Ink Transfer in Image and
`Non-Image Areas in the
`Rotogravure Process
`
`By
`
`Andrew M. Clist
`BEng (Wales), M Sc (Wales)
`
`Thesis submitted to the University of Wales Swansea
`In Candidature for the degree of Doctor of Philosophy
`
`School of Engineeri-ng
`May 2004
`
`I
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`i
`I
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`I
`
`FAST FELT 2010 , pg. 1
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`Andrew M. Clist
`Flat 3/3, 294 Kilmarnock Road
`Glasgow,
`G22 5HZ, UK
`
`Tel: (+44) 07782 162323
`Email : amclist@hotmail.com
`
`Profi le
`
`Education
`
`Skilled research engineer with PhD in Rotogravure ink release. Strong background in manufactunng process
`development and in product improvement programs. Experienced in all major print processes and color
`measurement technology. Experienced in managing multiple projects from conception to completron.
`PhD, University of Wales Swansea (2004)
`"Ink Transfer in Image and Non-Image Areas in the Rotogravure Process"
`This was the first published work investigating the causes of scumming in the Rotogravure pnnting process.
`and the first work performed on commercial presses to measure the volume of ink released from engraved
`cells. The work developed interferometric techniques for accurately examining engraved cells, printed dot
`volumes. Various color measurement techniques and protocols were also developed.
`
`MSc, University of Wales Swansea (2000)
`''The Effects of Thermal Transients on Waterless Offset Can Decoration".
`Other projects included interferometric determination of ink film thicknesses and color measurement
`techniques, along with long term on-press trials and investigations
`
`(
`
`PGCE, University of Wales Swansea (1997)
`Secondary Science (Physics)
`
`BEng (Hons), University of Wales Swansea (1995)
`Chemical Engineering
`
`"The Influence of the Cylinder on Scumming" 2004 T AGA Conference
`"Measurement of Engraving Diamonds" 2002 Institute of Physics
`"Characterisatron of Gravure Cylinders" 2001 TAGA Conference
`
`Scientific Research Manager, Gavin Watson Ltd (2003- Current)
`Managed and carried out a variety of projects developing a printable environmentally sensrtrve rnk and
`developing anti-counterfeiting products for both brand owners and the UK government, usrng both
`Lithographic and Flexographic printing processes
`• Successfully completed courses in Project and Financial management
`• Developed new security products, as well as liaising with existing manufacturers
`• Managing projects from conception through development, planning, scheduling, supervisron of
`technicians/pressmen, carrying out trials, analysis of data, presentation of program highlights to senror
`management and government liaison groups
`
`Research Engineer, University of Wales Swansea (2000-2003)
`Managed and carried out projects for several externally sponsored research and development projects.
`• Used many measurement and analysis procedures, both traditional and novel, laboratory and site based
`• Devised a methodology for interferometric analysis of gravure/anilox cells in great detail, including
`accurate measurement of volume, depth, area etc.
`• Managed projects, including supervision of technicians/pressmen, carrying out trials, analysis of data
`presentation of program highlights at technology group meetings
`• Supervised undergraduate. MSc and Foreign exchange students projects
`• Carrying out groundbreaking research into ink release and the problem of scumming
`
`Physics Teacher, Pontllanfraith Comprehensive, Wales (1997 -1998)
`Classroom teacher for the 11-16 age group
`• Taught Scrence to years seven and eight, physics to years nine to eleven
`• Taught electronics to year 11
`• Managed projects. including writing schemes of work and planning, performing and marking coursework
`Rotogravure Printing Technology Group, 2000-2003
`Member of Steering committee
`
`•
`
`•
`
`I MechE -Associate Member
`Languages- German and French to GCSE standard
`Driving License- Full and Clean (UK)
`Interests- Music, Classic cars, Mountain biking
`
`Publications
`
`Experience
`
`Positions of
`Responsibility
`
`Additional
`Information
`
`FAST FELT 2010 , pg. 2
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`Summary
`
`Rotogravure printing is one of the oldest printing processes, yet little is understood
`about the fundamentals, which drive the ink transfer in the process. This is largely due
`to the difficulties in analysing the process. The quantities of ink being transferred are
`very small, necessitating novel means to analyse them, and the practicalities of
`carrying out an investigation like this are significant. As a result, this is the first study
`to investigate the effects of compression ratio and stylus angle.
`
`It has been shown that traditional methods of volume calculation are extremely
`inaccurate, never getting within 20% of the actual cell volume. A new method has
`been suggested which is accurate for the calculation of cell volume at 80% coverage.
`It has been demonstrated that measurement and calculation of ink release are possible,
`and the
`techniques required
`to analyse the release are detailed,
`including
`interferometric analysis to examine the cells and printed dots in detail and TDGCMS
`analysis to quantify the retained solvents in the ink. It has been identified that 18.3%
`±2.5% of the total cell volume is released. This shows considerable agreement with
`previous work once calculation has been corrected for actual cell volume.
`
`Additionally, the project has analysed the effects of several variables ofthe process on
`ink release. It is shown that by increasing the screen ruling, compression ratio or
`stylus angle, a higher percentage of the ink contained within the cell is released to the
`substrate, with the most significant effects observed with screen ruling and stylus
`angle, where variation within common ranges cause a 2% variation in ink release.
`
`The effects of several variables on the levels of scumming (ink release from non(cid:173)
`image regions) observed were also calculated, demonstrating that several variables
`will affect scumming. Changing substrates not only changes the levels of scumming
`observed, but also changes the form observed. Varying blade load has been shown to
`affect scumming levels, but may increase or decrease the scumming level depending
`on the hydrodynamic conditions affecting the blade. Surface finish has a small effect
`on the scumming, but provided normal levels of roughness are maintained this effect
`is minimal. Varying the ink however, caused significant changes in the levels of
`scumming observed. Interactions were observed between blade load, surface finish,
`ink type/viscosity and substrate type. Additionally it was shown that although surface
`finish is a primary factor affecting scumming levels, the roughness values do not
`critically affect the scumming within normal ranges. The surface form and structure
`were examined and found to be critical factors in controlling the levels, with cylinders
`polished with emery paper causing the highest levels of scumming. Significant
`correlations were drawn to blade coating with similar results obtained when compared
`with the blade coating film thickness I blade load characteristic curve.
`
`c
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`c
`
`FAST FELT 2010, pg. 3
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`\
`
`Declaration
`
`This work has not previously been accepted in substance for any degree and is not
`being concurrently submitted in candidature for any degree.
`
`Signed 1 f L-v (Candidate)
`Date !M4
`
`Statement 1
`
`This thesis is a result of my own investigations, except where otherwise stated. Other
`sources are acknowledged, giving explicit references. A bibliography is appended at
`the end of the thesis
`
`Signed d t -=-., _alandidate)
`Date I/( /(;4
`
`7
`
`,
`
`Statement 2
`
`I hereby give consent for my thesis, if accepted to be available for photocopying and
`for inter-library load, and for the title and the summary to be made available to
`outside organisations
`
`II
`
`FAST FELT 2010 I pg. 4
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`Acknowledgements
`
`I would like to take this opportunity to thank the variety of people who have assisted
`me in the preparation of this work. In particular I would like to thank Dr Tim
`Claypole and Prof. David Gethin for their assistance and direction during this project.
`I would also like to particularly thank Dr Mark Bohan for his untiring assistance,
`guidance, second-guessing and especially, calm during moments of stress. I would
`also like to thank my colleagues in the Welsh Centre for Printing and Coating for their
`acceptance of my short temper during the closing stages of this project.
`
`In addition I would like to thank those members of the Rotogravure Printing
`Technology Group for their donations of time and equipment to the cause.
`Particularly John Broadhurst (of Tecnograv Ltd) for the engraving of a multitude of
`cylinders, John Dallison (of Teich Flexibles Ltd) for the use of a press, Peter Watson
`(of Daetwyler UK) for his experience and assistance in running trials and Mark
`Worthington (ex. of BASF) for the loan of a press, manufacture of several inks, and
`cleaning up after the 'Andy drops a gallon of ink' incident.
`
`I would also like to thank my family and friends for their ongoing support, in
`particular Simon Harnblyn and Ian Fox for helping beat Microsoft Word into
`submission. In addition, I would like to thank Stuart Whittaker for carrying out my
`TDGCMS measurements. Finally, I would like to thank Tom Axon - my headmaster
`of many years ago for telling me I'd never achieve anything, and thus forcing me to,
`in order to prove him wrong.
`
`(
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`c
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`,., .
`111
`
`FAST FELT 2010 I pg. 5
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`Table of Contents
`
`Sutnrnary ......................................................................................................................... i
`Declaration ..................................................................................................................... ii
`Acknowledgements ...................................................................................................... iii
`Table ofContents .......................................................................................................... iv
`Table of Figures ......................................................................................................... viii
`Figure A5.1 - Schematic of Compression Ratios .. ...... ...... .. ... . . . . . . . .. . . . . . .. .. 175
`
`(
`
`........................................................................................................................................ X
`Figure A5.2 - Examples of Moire........................................................ 177
`
`1.1.2
`
`1.2
`
`1.3
`
`(.
`
`1.3.3
`
`........................................................................................................................................ X
`Figure A5.3 Line Ruling Examples ................................................... .
`178Table of graphs ........................................................................................................ x
`Table of graphs ............................................................................................................. xi
`Introduction ............................................................................................................ 1
`1.1
`The Printing Industry ..................................................................................... I
`1.1.1
`Introduction ............................................................................................ 1
`The Printing Industry ............................................................................. 1
`1.1.3
`The printing processes ........................................................................... 3
`History of the rotogravure process ................................................................ .4
`Components ................................................................................................... 6
`1.3.1
`Cylinder .................................................................................................. 6
`1.3.1.1 Gamma Curves ................................................................................... 7
`1.3.2
`Ink .......................................................................................................... 7
`Doctor Blade .......................................................................................... 8
`1.3.4
`Impression Roller ................................................................................. 10
`1.4 Motivation .................................................................................................... 10
`1.5
`Closure ......................................................................................................... 11
`2 Review of literature .............................................................................................. 13
`2. 1
`Introduction .................................................................................................. l3
`Experimental Measurement Techniques ...................................................... l3
`2.2.1
`Colour Measurement. ........................................................................... l4
`Surface Profiling and Volume measurement ....................................... 18
`Ink transfer measurement ..................................................................... 22
`
`2.2
`
`2.2.2
`
`2.2.3
`
`IV
`
`FAST FELT 2010 I pg. 6
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`(
`
`(
`
`2.3
`
`2.3.2
`
`2.3.3
`
`2.3.4
`
`2.3.4.1
`
`2.4
`
`2.5
`
`3.2
`
`Experimental Results ................................................................................... 25
`2.3. 1
`Inks ....................................................................................................... 25
`Substrates ............................................................................................. 26
`Cylinder analysis ........... ....................................................................... 28
`Ink Transfer .......................................................................................... 28
`Scumming ........................................................................................ 31
`Numerical Modelling Experirnents .............................................................. 32
`Closure ......................................................................................................... 33
`3 Methodologies ...................................................................................................... 34
`3.1
`Introduction .................................................................................................. 34
`The Cylinders ............................................................................................... 36
`3.2.1
`Cylinder Production ............................................................................. 36
`Cylinder Design ................................................................................... 38
`Ink Release from lmage Areas ......................................................... 38
`lnk release from Non-Image areas ................................................... 42
`Cylinder Measurement Techniques .................................................... .43
`Surface Roughness ............................................................................... 45
`'Masking' ......................................................................................... 46
`Cell Volume ......................................................................................... 46
`Cell length, width depth and open area ................................................ 51
`Cell offset ............................................................................................. 52
`Cell wall roughness .............................................................................. 53
`3.2.9
`Example calculation ............................................................................. 54
`3.2.10 Comparison with traditional methods .................................................. 63
`3.2.11
`Blade load measurement.. .................................................................... 63
`Running the Press Trials .............................................................................. 64
`3.3.1
`Ink Release From Image Areas ............................................................ 64
`3.3.1.1 Trial Methodology ........................................................................... 65
`3.3.2
`Ink Release From Non-Image Areas ................................................... 66
`Ink Selection .................................................................................... 66
`3.3.2.2 Substrate selection ........................................................................... 66
`3.3.2.3 Trial Methodology ........................................................................... 67
`Print Measurement Techniques .................................................................... 67
`3.4.1
`Printed Density and colour ................................................................... 67
`
`3.2.2
`
`3.2.2.1
`
`3.2.2.2
`
`3.2.3
`
`3.2.4
`
`3.2.4.1
`
`3.2.5
`
`3.2.6
`
`3.2. 7
`
`3.2.8
`
`3.3
`
`3.4
`
`3.3.2.1
`
`v
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`FAST FELT 2010 I pg. 7
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`3.5
`
`3.6
`
`4.3
`
`4.3.3.1
`
`4.3 .4
`
`4.4
`
`3 .4.1.1 Density calculation ........................................................................... 68
`3.4.1.2 Optical Tone gain calculations ......................................................... 68
`3.4.1.3 Colour difference calculations ......................................................... 69
`3.4.2
`Scumming level measurement ............................................................. 69
`3.4.3
`Printed dot volume ............................................................................... 69
`3.4.3.1 Dot volume measurement ................................................................ 70
`Thermal Desorption - Gas Chromatography - Mass Spectrometry ............ 71
`Statistical Confidence Confirmation ............................................................ 72
`3.7
`Closure ......................................................................................................... 75
`4 Results- Ink release from image areas ................................................................. 77
`4.1
`Introduction .................................................................................................. 77
`4.2
`Comparison - Traditional volume analysis with interferometric volume
`analysis ..................................................................................................................... 78
`4.2.1
`Summary .............................................................................................. 82
`Cylinder Analysis ......................................................................................... 82
`4.3 .1
`Screen ruling ........................................................................................ 83
`4.3 .1.1 Screen ruling summary .................................................................... 96
`4.3 .2
`Compression ratio ................................................................................ 97
`4.3 .2.1 Compression ratio summary .......................................................... 104
`4.3.3
`Stylus angle ........................................................................................ l05
`Stylus angle summary .................................................................... 110
`Summary of geometric parameters effects ........................................ 110
`Calculation of printed dot volumes ............................................................ 112
`4.4.1
`TDGCMS results ............................................................................... 112
`Inks ................................................................................................. ll2
`4.4.1.1
`4.4.1.2 Substrate ......................................................................................... 114
`Interferometry results ......................................................................... 115
`4.4.2
`4.4.2.1 Optimisation of sample size ........................................................... l17
`4.4.2.2 Solid ink volumes effects of cell characteristics ......................... 117
`4.4.2.3 Effects of Ink .................................................................................. 118
`4.4.2.4 Dot volumes and printed density ................................................... 120
`4.4.2.5 Total released volume .................................................................... 122
`Calculation of ink release ratio .................................................................. 123
`Closure ....................................................................................................... 130
`
`(
`
`4.5
`
`4.6
`
`Vl
`
`FAST FELT 2010, pg. 8
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`(
`
`(
`
`5
`
`5.2
`
`5.3
`
`5.3.2
`
`5.4
`
`5.5
`
`5.6
`
`5.7
`
`5.8
`
`Ink release from non-image areas ...................................................................... 131
`5 .l
`Introduction ................................................................................................ 131
`Existing theory ........................................................................................... 131
`Effect of surface finishes ........................................................................... 134
`5.3.1
`Evolution of surface finish ................................................................. l35
`Effect of surface finish ....................................................................... l39
`Effect ofblade load .................................................................................... l46
`Effect of Substrate ...................................................................................... 149
`Effect of ink type ....................................................................................... 151
`Effect ofviscosity ...................................................................................... 153
`Closure ....................................................................................................... 156
`6 Conclusions and further work ............................................................................ l57
`6.1
`Conclusions ................................................................................................ 158
`6.1.1
`Ink release from image areas ............................................................. 158
`Ink release from non-image areas ...................................................... 159
`Recommendations for further work ........................................................... 160
`References .................................................................................................................. 162
`A l
`Appendix l - Diamond Measurements .......................................................... 166
`A1.1 Diamond ana1ysis ....................................................................................... 166
`A 1.1.1
`Stylus Angle Calculation ................................................................... 167
`A 1.1.2 Tip Wear Calculation ......................................................................... 169
`A 1. 1.3
`Summary of Diamond Measurements ............................................... 170
`A2 Appendix 2
`Image Specifications ..................................................................... 172
`A3 Appendix 3 - Raw data example (cell volume analysis) ..................................... 173
`A4 Appendix 4 - List of publications and presentations ........................................... l74
`
`6.1.2
`
`6.2
`
`vii
`
`FAST FELT 2010 I pg. 9
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`Table of Figures
`
`Figure 1-1 - The gravure process ................................................................................... 5
`Figure 1-2 - Types of doctor blade ................................................................................ 9
`Figure 1-3 - Doctor Blade Mounting ......................................................................... 9
`Figure 1-4 - Doctor Blade nip, indicating forces .......................................................... 9
`Figure 1-5 - Impression roller application ................................................................... IO
`Figure 2-1 -Spectrophotometer ................................................................................... 14
`Figure 2-2 - CIELAB colour space [ 18). ..................................................................... 15
`Figure 2-3 - Densitometer ............................................................................................ 16
`Figure 2-4 - Colour filters ........................................................................................... 16
`Figure 2-5 - Interferometer .......................................................................................... 21
`Figure 2-6 - Blade coating response (From Kistler and Schweizer [29]) ................... 31
`Figure 3-1 - Variables in the Gravure process ............................................................ 34
`Figure 3-2 - Test image ............................................................................................... 36
`Figure 3-3 - Test image with identifiers ...................................................................... 37
`Figure 3-4 - L9 array ................................................................................................... 40
`Figure 3-5 - L9 array. Compression ratio and Screen ruling ..................................... .40
`Figure 3-6 Cylinder layout ........................................................................................ 43
`Figure 3-7 - Cylinder 3 Layout ................................................................................... 43
`Figure 3-8 - Rollscope ................................................................................................. 45
`Figure 3-9 - Masked and unmasked images ............................................................... .46
`Figure 3-10 - Microscope image of cell ..................................................................... .4 7
`Figure 3-11 - Interferometric measurement of gravure cells ................................ .48
`Figure 3-12- Diagram of Surface and Cell ............................................................. 49
`Figure 3-13 Width and Length calculation ............................................................... 52
`Figure 3-14 - Engraving Diamond ................................................................ , ............. 53
`Figure 3-15 - Inverted cell, showing offset.. ............................................................... 53
`Figure 3-16 - Cell wall quadrant, showing roughness ................................................ 54
`Figure 3-17 - Raw measurement of engraved surface ................................................. 55
`Figure 3-18 - Masked measurement of engraved surface ............................................ 56
`Figure 3-19 - Developed calculation screen ................................................................ 57
`Figure 3-20 - Histogram indicating peak .................................................................... 57
`Figure 3-21 - Histogram, indicating cell depth ........................................................... 58
`
`Vlll
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`(
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`FAST FELT 2010 I pg. 10
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`(
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`Figure 3-22 - Histogram indicating masking point and direction ............................... 58
`Figure 3-23 - Entire data for masked cell .................................................................... 59
`Figure 3-24 - Measurement of depth and width .......................................................... 60
`Figure 3-25 - Measurement of offset.. ......................................................................... 61
`Figure 3-26 - Cell wall roughness, isolating the quadrant .......................................... 62
`Figure 3-27 - Flattened quadrant.. ............................................................................... 62
`Figure 3-28 - 30 picture of gravure dot.. .................................................................... 70
`Figure 3-29 - 20 image and trace ................................................................................ 71
`Figure 3-30- Printed dots (40%, 70lpcm, 57° compression ratio, 130° stylus) ... 74
`Figure 3-31 Poor cell measurements ......................................................................... 74
`Figure 4-1- Screen ruling I compression ratio comparisons (20x magnification)
`.............................................................................................................................. 83
`Figure 4-2 - Screen ruling comparison .................................................................... 85
`Figure 4-3 - Channels between gravure cells ( 45° compression ratio, 140° stylus,
`80lpcm, 100% cells) ............................................................................................. 94
`Figure 4-4- Comparison of CSA of cells ............................................................... 106
`Figure 4-5 - TIC, magenta ink ................................................................................... 113
`Figure 4-6 - 30 image of gravure printed dot (40% coverage, 70lpcm, 45°
`compression ratio, 130° stylus angle) ................................................................ 116
`Figure 4-7 - Range of dot sizes ................................................................................. 116
`Figure 4-8 - Different viscosity dots (SO% coverage, 70lpcm, 45° Compression ratio,
`130° stylus angle) ............................................................................................... 120
`Figure 5-1 - The Stribeck curve ................................................................................ 132
`Figure 5-2 - Blade coating response (From Kistler and Schweizer [23]) ................. 133
`Figure S-3 - Matrix of surface finishes. Polished chrome surface, just before printing.
`Cylinders 1 and 2 ............................................................................................... 134
`Figure 5-4 - Cylinder surface finish after printing - image ...................................... 13 7
`Figure 5-5 - Surface height after printing- trace ...................................................... 137
`Figure 5-6 - Polishing surfaces, used materials ......................................................... 143
`Figure 5-7 - Copper surface after polishing .............................................................. 144
`Figure S-8 - Forms of scumming (60x magnification) .............................................. l50
`Figure A 1.0-1 Engraving Head and Diamond ........................................................ 166
`Figure A 1.0-2 - Cross Hatch Analysis ....................................................................... 167
`Figure A 1.0-3 - Angle evolution analysis ................................................................. 168
`
`IX
`
`FAST FELT 2010 I pg. 11
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`Figure A l.0-4 - Diamond tips ................................................................................... 169
`Figure Al.0-5 Tip analysis ..................................................................................... 169
`Figure Al.0-6 Schematic of effects of worn diamond on cell volume. Exaggerated
`for clarity ............................................................................................................ 170
`
`Figure A5.1 - Schematic of Compression Ratios . . . . . .. . . . . . . .. . . . .. .. .. .. .. .. .. .. .. . 175
`
`Figure A5.2 - Examples of Moire........................................................ 177
`
`Figure A5.3 Line Ruling Examples . . .. . ... . .. . . .. .. . ... . . . . . . ...... ... .. . .. . . . . . . . . . .. 178
`
`(
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`(
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`X
`
`FAST FELT 2010 I pg. 12
`Owens Corning v. Fast Felt
`IPR2015-00650
`
`

`
`Table of graphs
`
`Graph 1.1 - Market share value (UK) of various printing processes ............................ 2
`Graph 4.1 - Comparison of ideal volume and measured volume using traditional
`pyramidal calculation (Results for 60, 70, 80lpcm, 37, 45, 57° compression ratio,
`120, 130, 140° stylus angle - all combinations) .................................................. 79
`Graph 4.2 - Average deviation between measured and ideal volumes ......