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Fogra screen printing inks as per ISO 28462846-4 and ISO 1264712647-5
Screen 2012 24. May
Fogra standards for use in flat-bed and cylinder screen printing
Table of contents 1.0 1.1 2.0 2.1
Fogra/AiF Process standards Standard series ISO 12647/12642 Screen printing standard ISO 12647-5
3.0 3.1 3.2 3.3 3.4 3.5
Standard series ISO 2846 Screen printing standard ISO 2846-4 Proof production Spectrophotometer Determination of colour coordinates Determination of transparency
4.0 4.1 4.2
Revision of standard Investigations and status Differentiation between ISO 2846-4 and 12647-5 Marabu recommendations Print parameters Results Summary Overview of standards
1.0 Fogra/AiF Fogra aims to promote printing technology in the fields of research and development and to make the results useable by the print industry. At the heart of Fogra are the eight technical advisory committees which represent different specialist areas. At meetings of these committees, experts from various companies and Fogra employees define real-life problems to be investigated. Technical advisory committees Printing inks Printing paper Print finishing Continuous printing Screen printing Newspaper printing Flat-bed printing Pre-press technology The aim of all Fogra research projects is to increase the reliability of the production process and to improve quality in companies.
Fogra in the AiF
5.0 5.1 5.2 5.3 6.0
In the Federal Republic of Germany there are more than one hundred medium-sized sectors where companies have grouped together to carry out joint industrial research. The umbrella organization of these research associations is the Arbeitsgemeinschaft industrieller Forschungsvereinigungen [AiF].
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In order to reconcile quality demands and quality control with the necessity to reduce production costs, several research and development projects were initiated by the Arbeitsgemeinschaft industrieller Forschungsvereinigungen/AiF (German Federation of Industrial Research Associations). These projects were funded by the Bundesverband Druck (German Printing Federation) and Deutsche Institut Druck (German Institute of Printing). Today, they form the basis of standardization schemes for offset, flexo, gravure, 4-colour screen, and digital printing.
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1.1 Process standards The aim of the formulation and definition of process and colour standards by Fogra and the German Printing and Media Federation is to achieve a practical quality standard which ensures reproducible results and enables fast production processes in companies. Goals: • Improved communication thanks to the use of the same colour language in both pre-press and production printing • Fast and reliable production processes • Fewer bad copies and reduced faulty stencil production • Narrower printing tolerances and improved reproducibility in copy preparation • Constant quality • The use of different printing ink sets which enable equivalent print results if printed onto similar substrates and with a suitable ink density/saturation
2.0 Standard series ISO 12647 ("processor standard") ISO (International Organization for Standardization) 12647 is a production standard for proc processors. essors It contains standard process specifica specifications, tions objectives, and tolerances for various print procedures and processes. It describes standards in the field of process control for offset, offset gravure, flexo, screen, and digital printing for press proofing and production printing in realreal-life conditions. For example, for the offset printing process standard [PSO, 1], the following standard series and standard parts apply: - ISO 12642-2 (Input data for charaterization of 4-colour process printing. - ISO 12647-1:2005: Graphic technology Process control for the production of half-tone colour separations, proof and production prints - Part 1: Parameters and measurement methods - ISO 12647-2 — Part 2 (Offset lithographic processes - sheet-fed and heat-set web printing) - ISO 12647-3 — Part 3 (Coldset offset lithography on newsprint) The basic principles of ISO 1264712647-2 and ISO 12647--3 focus on a traditional (i.e. film-based) 12647 workflow and build on the offset printing process standard, which was published in 1996. Specific pre-press process parameters, proofing values (measurement methods and conditions), and four-colour separation printing were defined here. These standards define the parame parameters necessary for press proofing and production printing. printing.
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Fogra is one of the founding members of this federation of industrial research associations.
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The basic principles required for the standardization of these processes were mainly developed by Fogra and the German Printing and Media Federation (bvdm). Significant changes in the graphics industry were not yet taken into account in previous versions of ISO 1264712647-2. This includes newly developed paper qualities, print conditions, the modification of colour tolerances, printing with UV-cured inks, the use of modern, nonperiodic (FM) screens, CtP (Computer-toPlate) technology, and waterless offset printing. Further research activities relating to the optimization of the various parts of ISO 12647 are ongoing.
2.1
Screen printing standard ISO 1264712647-5
Standard series 12647 constitutes the basis for the screen printing standard ISO 1264712647-5-First Edition 20012001-1212-15 for the screen print printing field: International standard Graphic technology - Process control for the manufacture of half-tone colour separations, proof and production prints -- Part 5: Screen printing This standard incorporates the process parameters for screen printing, from the quality of colour separation films and the type of screening to screen printing on the printing machine. It defines the characterization data, target values, tolerances for the colour appearance of the substrate material, and the dot gains of a print run. The standard also specifies the CIELAB coordinates (L*a*b colour space) of a total of three colour gamut classes. These colour spaces are classified as follows with regard to colour saturation for the following applications: - Gamut class 1 - Gamut class 2 - Gamut class 3
Low colour saturation Medium colour saturation High colour saturation
The currently valid version of the ISO standard for sheet-fed and web offset printing, ISO 1264712647-2 AMD 1:20071:2007-04, 04 was defined as an amendment in 2007 and has the following description: ISO 1264712647-2 AMD 1:20071:2007-04 Graphic technology - Process control for the production of half-tone colour separations, proof and production prints - Part 2: Offset lithographic processes; Amendment 1
If screen printing 4-colour process shades are likened to half-tone images produced in other print procedures such as offset printing, the use of gamut class 2 is recommended. Further characterization data that are specific to this prevalent gamut class 2 (medium colour saturation/reflected light density) appear in Fogra table 9. Gamut class 3 should be used for applications in the display or point of sale field. In this field, transparent materials with background lighting are often used, requiring a high colour density and saturation.
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Offset range/colour gamut of 5 paper classes
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Colour gamut classes as per ISO 1264712647-5 Edition 20012001-1212-15 12647-5 CIELAB coordinates of solid colours
Gamut class 1 a
Gamut class 2
The first edition of the currently valid standard for screen printing, printing ISO 28646-4-First Edition2000-12-15, was published in English in December 2000. International standard Graphic technology - Colour and transparency of printing ink sets for four-colour printing Part 4: Screen printing
Gamut class 3
3.1 Screen printing standard ISO 28462846-4 First EditionEdition-20002000-1212-15
Characterization of the substrate material to be used and checked for ISO 12467-5 compliance 100 ≥ L* ≥ 90 -3 ≥ a* ≥ 3 -5 ≥ b* ≥ 5 Measured as per ISO 12647-1:1996; 5.6
For the 12647-5 standard check, it is recommended that screen printing 4-colour process shades as per ISO 2846-4 be used.
3.0 Standard series ISO 2846 ("manufacturer standard") This international standard defines a printing ink set of colour chart inks for four-colour printing. ISO 2846 and its associated parts are laboratory standards that are targeted primarily at manufacturers of printing inks. inks This standard describes the procedure for checking printing ink sets. The results are based on proof printing machines. This requires defined conditions and a characteristic curve of printing whereby printing inks are printed onto speci specified paper qualities. qualities Standard series 2846 is the successor of the so-called Euroscale.
In an initial step, the attainability of colour coordinates and printing ink dot gains intended for offset printing were checked for the screen printing field. The tests were carried out on a selected and defined substrate (APCO II/II). II/II) The "Handbuch zur Standardisierung des "Handbuch Raster Rastersiebdrucks" (4-Colour Screen Printing Standardization Handbook), which was published by the German Printing Federation in October 1996, was used as the basis for a standardized test and procedure. Handbook research work: • Process influences on print quality in 4colour screen printing • Standardization of stencil copying in 4colour screen printing • Print standardization in 4-colour screen printing • Colour gamut for 4-colour screen printing The ISO standard demonstrates the corresponding procedure, test methods, and measurement methods for the checking of printing inks and the determination of standard printing inks. The colourmetric properties of the colour gamut constitute an important component in this process. The stipulations relate to screen printing inks for conventional drying and UV curing.
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b
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ISO 2846-4 defines the following parameters: • Colour coordinate • Transparency • Defined test paper/material • Test procedure • Measurement methods The aim is to use similar inks when printing as follows: • With printing ink sets from different manufacturers • In the usual layer thickness range • On similar substrates 3.2 Proof production The universal CIELAB colour space was chosen for the definition of the reference paper for the colourmetric test (colour coordinate). Phoenix Imperial APCO II/II paper from Scheufelen, Lenningen, Germany was stipulated here. Coated paper with a black overprint should be used to determine the transparency. The L" value of the black ink should not be higher than 6. This test card can either be produced in house or acquired as Leneta card 105 C from Leneta Corp. Mahwah, N.J., USA.
Different ink concentrations printed onto APCO II/II
To determine the transparency, the same shades are printed onto Leneta cards or the test cards produced in house. 3.3 Spectrophotometer All prints are subjected to spectral measurement with a spectrophotometer and a measurement geometry of 45°/0° or 0°/45°. The colour space distance dE is measured as per ISO 13655 with illuminant D50 and a 2º observer. The annex to ISO 2846-4 prescribes target colour coordinate values for spectrophotometers with diffuse/8º and 8º/diffuse measurement geometry.
100% ink content 90% ink content (10% mixing compound) 80% ink content (20% mixing compound) 70% ink content (30% mixing compound) 60% ink content (40% mixing compound) 50% ink content (50% mixing compound) The various concentrations are printed onto the full area of the reference substrate APCO paper II/II on a flat-bed screen printing machine. Solvent inks must be made ready for printing beforehand.
The inks are spectrophotometer ISO/DIS. 13655.
measured with a in accordance with
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For the colourmetric test, the following shades of each colour must be created through the addition of mixing compound:
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3.4 Colourmetric assessment (colour coor coordinate)
3.5 Determination of transparency
The following CIELAB reference values and tolerances are currently valid for screen print printing as per ISO 28462846-4, printed on APCO II/II paper: Colour L* a* b* E* Yellow 91.0 -5.1 95.00 6.0 Magenta 50.0 76.0 -3.00 7.0 Cyan 57.0 -39.2 -46.00 5.0 Black 18.0 0.8 L*≤18
Transparency is determined by marking a small section of the black area on each non-printed colour card and measuring it. All shades of each colour are then printed onto the previously marked black background. The printed area is then measured against the previously determined values for the black, non-printed background in each case and the dE colour space distance is determined. For each colour, a diagram which plots the measured dE value against the concentration is created. Bestimmung der Transparenz bei Magenta UVAR 435
30
25
DEab*
20
15
10
The printed colour sequences must be measured on APCO II/II paper and compared with the defined CIELAB reference values for each colour. The dE colour space distance of at least one sample for each colour sequence must be below the defined dE tolerance. The diagram below shows ink concentration against delta E value. Farbmetrische Prüfung UVAR 435
5
0 50
60
70
80
90
100
Prozentanteil druckfertige Farbe
The points are connected by a line of best fit. The gradient of the line is calculated. The reciprocal of the coefficient yields the transparency (T). In order to meet transparency criteria, the printing ink must have a T value higher than the values in the table below. In the case of highly transparent inks, the reciprocal of the coefficient can be 0 or a negative value. Target transparency values for chromatic col colours: Colour Transparency (T) Yellow 4.0 Magenta 6.0 Cyan 5.0
20
DE ab*
15
10
5
0 50
60
70
80
90
100
Prozentanteil Druckfarbe
If the tolerance range is not reached, the printed ink film thickness and thus the colour coordinate/ transparency and dE colour space distance can be affected.
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25
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INFO This current research project aims to define afresh and consistently in relation to each other the colourmetric guidelines for half-tone screen printing inks on a reference substrate [ISO 2846-4] and on production substrates [ISO 12647-5] in accordance with current market conditions. The characteristic printing curves for UV and solvent-based inks are to be checked and updated if necessary. The substrates on which the required target values and tolerances can be achieved are also to be divided into groups.
Transparency measurement: Printing onto Leneta card 105 C/UVAR 435
A printing ink is standard-compliant when at least one sample print in the colour sequence falls within the tolerances for the colourmetric test as per ISO 2846-4 and also observes transparency stipulations.
4.0 Revision of standards
screen
printing
Fogra research study 34.017 Foundations for the revision of ISO 2846 Part 4: Screen printing Planned duration: 01.12.2007 to 30.11.2009 Funding: Funded by the Federal Ministry of Economics and Technology as part of the programme to promote joint industrial research via the German Federation of Industrial Research Associations (AiF). The investigations carried out at Fogra as part of the AiF "Proof Production and Colour Management Suitable for Screen Print Printing" project [34.014] have shown that many screen printing inks do not comply with ISO 2846-4.
In August 2009, investigations and sample printing began with the aim of revising the standard with the following remit: To redefine the colourmetric guidelines for light-fast screen printing inks on a reference substrate (for ISO 2846-4) and on defined production substrates (for ISO 12647-5) in accordance with current market conditions for colour gamut classes 2 (medium saturation) and 3 (high saturation). The following tests were carried out: • Test prints with various screen geometries and screen rulings • Test prints with various EOM and RZ values • Test prints with various sets of solvent-based inks and UV inks from various manufacturers • The tests took place with a special test stencil. • The test prints were made in different print shops. • Test prints with various selected PVC film qualities and paper qualities • Investigations on colour sequence, tonal value range, and colourmetric target values
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4.1 Investigations and status for 34.017
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In offset standard 12647-2, a total of 5 different paper types are defined with regard to the material colour. The CIELAB colour spaces are then again defined per paper type. The chromaticities specified in the ISO 12647 standard parts are processor standards and should be achieved in production conditions with ISO 2846-4-compliant screen printing inks. However, in our experience this is not always necessarily the case. The research work aims to improve the level of agreement between the two standards.
5.0 Marabu recommendations To date, the Marabu application technology department (AWETA) has tested various colour systems on its own initiative and in collaboration with Fogra. This includes Ultra Ultragraph UVAR ink types, which are used on a wide spectrum of materials in the graphics sector. This colour system has been successfully tested in our AWETA department to check its compliance with the currently valid ISO 28462846-4 screen printing specification with the following print parameters.
5.1 Print parameters Print parameter
Fogra test value
Mesh
150-31 Y
Screen tension
> 15 N/cm
Squeegee type/
Triplex 75-90-75
profile
Right-angled sharpening
Squeegee angle
80°
Squeegee
1,0
pressure in bar Floodbar
Setting 13
squeegee pressure Test motif Printing machine
Solid print as per FOGRA guidelines Thieme ¾ automatic printing machine/AWETA Print and floodbar squeegee
Printing speed Curing (UV ink) Substrate(s)
250 mm/sec - 2 x 120 W/cm / 25 m/min. - APCO II/II paper; 150 gr. - Leneta test card no. 105C
5.2 Results The following screen printing inks comply with ISO 2846-4: UVAR 425 Yellow UVAR 435 Magenta UVAR 455 Cyan UVAR 488 Black
Reflected light density: 1.4 Reflected light density: 1.4 Reflected light density: 1.4 Reflected light density: 2.3
The ink series has the requisite weather resistance and light fastness for use outside (in Central Europe) for two years. Fogra Certification according to ISO 28642864-4 On June 8th 2010, the following, specifically developed Ultraboard UVBR formulations have been certified by Fogra according to ISO 2846-4:2000 with regard to colour coordinates and transparency: UVBR 702 66 424 RZX RZX UVBR 702 67 434 RZX RZX UVBR 702 68 455 RZX RZX UVBR 702 69 485 RZX RZX
Yellow Magenta Cyan Black
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4.2 Differentiat Differentiation ion between ISO 28462846-4 and 1264712647-5/-2 When comparing CIELAB guidelines (colour space guidelines), it can be seen that the values stated in standards ISO 2864-4 and ISO 12647-5/ISO 12647-2 do not match. In the case of the manufacturer standard - 2846-4 the colour coordinates to be achieved are dimensioned for a defined test paper (APCO II/II). In the case of ISO 12647-5, the material colour is defined with a tolerance window and the colour spaces for the screen printing shades are divided into 3 saturation classes.
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The Certification is based on the parameters mentioned below: Print parameter
Fogra test value
Mesh
150-34 Y PW 0°
Screen tension
> 17 N/cm
Squeegee type/
Triplex 75-90-75
profile
Right-angled sharpening
Squeegee angle Squeegee pressure in bar Floodbar squeegee pressure Test motif Printing machine
Printing speed Curing (UV ink) Substrate(s)
80° 1,0
Setting 3,4 Solid print as per FOGRA guidelines Thieme ¾- automatic printing machine 3010 Print and floodbar squeegee 250 mm/sec - 2x 120 W/cm / 25 m/Min. - medium-pressure mercury lamp - APCO-Papier II/II; 150 gr. - Leneta test card No. 105C
Characteristic curve of printing: Standardized parameters or a characteristic curve of printing from the pre-press stage to printing on the machine are basic prerequisites for reproducible print jobs and process control. This characteristic curve is to be adjusted in line with the corresponding material quality or qualities used. Parameters which influence layer thickness and thus thus the colour coordinate and transparency: • • • • •
Mesh selection Kind of thread / ink release Stencil quality Squeegee selection/quality Squeegee sharpening
• • • • •
Squeegee angle Squeegee pressure Floodbar squeegee/pressure/edge Printing speed Substrate
Pigment quality/selection quality/selection The pigment selection influences the formula of an ink with regard to the following main factors: • Light fastness • Weather resistance • Colour coordinate/index • Transparency/print sequence • Reflected light density • Transmitted light density • Opacity/contrast • Adhesion/surface bonding strength • Price 5.3 Summary It is challenging to formulate standard guidelines for screen printing since it uses a very broad range of materials and has diverse application possibilities. The extent to which customers such as advertising agencies, designers, and marketing departments are able and willing to take the material definitions and qualities defined in the ISO standards in conjunction with the listed colour gamut classes depending on the saturation/density of the colours into account will become apparent in the future. However, this reconciliation is also a prerequisite for meeting ISO guidelines with corresponding screen settings. Screen printing has a wider range of applications than other print procedures. Inks must be specially formulated to meet the needs of a range of materials and tasks with regard to technical print, adhesion, weathering, and price considerations. In order to enable colour space guidelines to be met, special pigment qualities must be used. These restrictions can result in an impairment of other properties such as adhesion, weather
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These formulations are weather and fade resistant for a permanent outdoor exposure of 6 months, referred to the middle European climate.
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On the basis of our experience, it will not be possible to use such specially adjusted ISOcompliant screen printing inks for all tasks or ink requirement profiles.
Calculation of colour differences as per Delta E and Delta E 2000 The CIELAB colour space does not offer sufficiently constant colour space distances for practical applications. In the case of brilliant and heavily saturated colours, differences between two samples are visually perceived as being less than indicated by the calculated dE*ab-value. The DE2000 formula achieves a result that is nearer to what is visually perceived. Depending on the location of the colours being compared in the CIELAB colour space, an appropriate correction is carried out. Although it is recognized that the CIELAB formula is inadequate, the DE2000 formula is not yet particularly widespread in the industry. It is important to encourage this formula to be used more in the future. The Marabu ColorFormulator formula and quality control software provides a choice of all mentioned formulas. For important and detailed further information, see our TechInfo "Farbabstands "Farbabstandsformeln in der Praxis" ("Practical Colour Space Distance Formulas").
Overview of standards ISO 12642, Edition: 19961996-12 Graphic technology - Prepress digital data exchange - Input data for characterization of 4colour process printing ISO 1264212642-2, Edition: 20062006-12 Graphic technology - Prepress digital data exchange - Input data for characterization of 4colour process printing ISO (International Organization for Standardi Standardization) 12467 offers process standardization, target observers, and tolerances for various print procedures and processes. ISO 12647 consists of the following parts and has the general title Graphic technology -Process control for the production of half-tone colour separations, proof and production prints: ISO 1264712647-1:20041:2004-08: Graphic technology Process control for the production of half-tone colour separations, proof and production prints - Part 1: Parameters and measurement methods ISO 1264712647-2:20042:2004-11: Graphic technology Process control for the production of half-tone colour separations, proof and production prints - Part 2: Flat-bed printing ISO 1264712647-2 AMD 1:20071:2007-04: 04 Graphic technology - Process control for the production of half-tone colour separations, proof and production prints - Part 2: Offset lithographic processes; Amendment 1 ISO 1264712647-3:20053:2005-10: Graphic technology Process control for the production of half-tone colour separations, proof and production prints -- Part 3: Coldset offset lithography on newsprint
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resistance, light fastness, and resistance against abrasion. The cost aspect of pigment selection must also be remembered.
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ISO 1264712647-4:20054:2005-11: Graphic technology Process control for the production of half-tone colour separations, proof and production prints -- Part 4: Publication gravure printing ISO 1264712647-5:20015:2001-12: Graphic technology Process control for the production of half-tone colour separations, proof and production prints -- Part 5: Screen printing ISO 1264712647-6:20066:2006-04: Graphic technology Process control for the production of half-tone colour separations, proof and production prints -- Part 6: Flexographic printing ISO 1264712647-7:20077:2007-12: Graphic technology Process control for the production of half-tone colour separations, proof and production prints -- Part 7: Proofing processes working directly from digital data
ISO 28462846-4:20004:2000-12 Graphic technology - Colour and transparency of printing ink sets for four-colour-printing Part 4: Screen printing
ISO 28462846-5:20055:2005-03 Graphic technology - Colour and transparency of printing ink sets for four-colour-printing Part 5: Flexographic printing Ink measurement technology ISO 1365513655-19961996-10 Graphic technology -- Spectral measurement and colorimetric computation for graphic arts images
ISO/DIS 12647Graphic 12647-8:20108:2010-06: technology - Process control for the production of half-tone colour separations, proof and production prints -- Part 8: Validation print processes working directly from digital data
ISO 28462846-2:20072:2007-12 Graphic technology - Colour and transparency of printing ink sets for four-colour printing Part 2: Coldset offset lithographic printing ISO 28462846-3:20023:2002-10 Graphic technology - Colour and transparency of printing ink sets for four-colour-printing Part 3: Publication gravure printing
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Euro ISO 28462846-1:20061:2006-11 (previously Eur oscale/ DIN 16539) Graphic technology - Colour and transparency of printing ink sets for four-colour printing Part 1: Sheet-fed and heat-set web offset lithographic printing
