2. Produkte
Offset
Sheet- Heatset Coldset
Gravure Flexo Digi
fed
Magazines,
Magazine,
catalogues X X X
Kataloge
Brochures, annual
Broschüren,
reports etc. X X
Jahresberichte etc.
Direct marketing
Directmarketing X X X X X
Books
Bücher X X X
Newspapers
Zeitungen X X
Packages, wrappers
Verpackungen X X X
2
3. Warum?
Ein besseres Verständnis der
Endanwendung unserer Papiere hilft
Ihnen, Ihre Kunden besser zu beraten
und Ihrem Verkauf Mehrwert zu
verleihen
3
4. Zusammenfassung
Offsetdruck
Was ist Farbe?
Grundlagen des Offsetdrucks
Bogenoffsetdruck
Heatset-Rollenoffsetdruck
Andere Druckverfahren
Konventionelle Verfahren
Tiefdruck
Flexografie
Siebdruck
Digitaldruckverfahren
Laser (Elektrofotografie)
Inkjet
Schlussfolgerung
4
8. Was ist nötig, um Farben zu sehen?
Eine Lichtquelle (Sonne, Glühbirne, Kerze)
Ein Empfänger und ein
Prozessor (Auge +
Gehirn)
Ein Objekt, das mit der Lichtquelle interagiert
8
9. Das menschliche Auge
• Licht trifft durch die Linse auf das Auge und wird auf der Netzhaut
gebündelt
Die Fotorezeptoren in der Netzhaut sind lichtempfindlich und leiten die
Signale an das Gehirn weiter, das diese Signale in Farbwahrnehmung
umwandelt.
Es gibt zwei Arten von Zellen:
-> Stäbchen = schwarz & weiß -> Zäpfchen = Farben
Es gibt drei verschiedene Typen von
Zapfenzellen; diese reagieren auf die
Wellenlänge von
=> rotem Licht
=> grünem Licht
=> blauem Licht
Licht stimuliert das Auge dreidimensional!!
9
12. Wie entstehen Farben : die additive Methode
Additiv Licht: rot + blau + grün = weiß
Zum Beispiel ein Fernseher oder ein Computer-
Bildschirm
12
13. Wie entstehen Farben?
Bei der additiven Farbmischung (grün + blau = CYAN, grün
+ rot = YELLOW, blau + rot = MAGENTA) können wir aus 3 ausgewählten Farbstoffen alle
möglichen Farbnuancen erzeugen.
Jeder Farbstoff spricht eine Grundfarbe des Spektrums an (rot, grün oder blau)
Wenn wir Rot erzeugen wollen, benötigen wir einen Farbstoff, der nur rot absorbiert, nicht
aber grün oder blau. Das ist CYAN
Farbe die
rotes Licht absorbiert
blaues Licht reflektiert blau + grün = Cyan-Druckfarbe
grünes Licht reflektiert
13
14. Wie entstehen Farben : die subtraktive Methode
elektive Absorption bestimmter Wellenlängen durch die Farbschicht
Magenta Druckfarbe Cyan Druckfarbe Yellow Druckfarbe
reflektiert rot absorbiert rot reflektiert rot
reflektiert blau reflektiert blau absorbiert blau
absorbiert grün reflektiert grün reflektiert grün
14
15. Primärfarben im Druck
Das Mischen der drei Primärfarben ergibt theoretisch schwarz.
=> tatsächlich ist das Ergebnis braun!
=> Um dieses Problem zu lösen, wird Schwarz als vierte Primärfarbe verwendet
(K von blacK)
CMY blacK CMYK
CMY Schwarz CMYK
+ =
15
16. Zusammenfassung
Offsetdruck
Was ist Farbe?
Grundlagen des Offsetdrucks
Bogenoffsetdruck
Heatset-Rollenoffsetdruck
Andere Druckverfahren
Konventionelle Verfahren
Tiefdruck
Flexografie
Siebdruck
Digitaldruckverfahren
Laser (Elektrofotografie)
Inkjet
Schlussfolgerung
16
17. Grundlagen des Offsetdrucks
Auf einer Druckplatte gibt es zwei Bereiche:
• Bereiche, die Druckfarbe annehmen und Wasser abweisen =
druckende Bereiche ( = hydrophob)
• Bereiche, die Wasser annehmen
= nicht druckende Bereiche (= hydrophil).
Diese Bereiche werden durch Wasser abgedeckt.
Aufgrund der unterschiedlichen Oberflächenspannung mischen sich Wasser und
Farbe nicht.
Das Verhalten der druckenden und der nicht druckenden Bereiche wird durch eine
komplexe Chemie erzielt.
17
18. Wie erhalten wir druckende und nicht druckende
Bereiche?
Farbe = hydrophob Wasser = hydrophil
DRUCKEND NICHT DRUCKEND
Funktion der Offset-Druckplatte
18
19. Wie erhalten wir druckende und nicht druckende
Bereiche?
Druckend
Nicht druckend
Vergrößerung (15x) einer Offset-Druckplatte
19
20. Wie erhalten wir druckende und nicht druckende
Bereiche?
Nicht
druckend
Druckend
Vergrößerung (1000x) Bild einer Offset-Druckplatte
20
21. Wie erhalten wir druckende und nicht druckende
Bereiche?
Substrat
= Direktübertragung
DRUCKEND NICHT DRUCKEND
Funktion der Offset-Druckplatte
21
22. Wie erhalten wir druckende und nicht druckende
Bereiche?
Gummi Gummi
erste Übertragung zweite Übertragung
Substrat
DRUCKEND NICHT-DRUCKEND DRUCKEND NICHT DRUCKEND
Funktion des Gummituches = indirekte Übertragung
22
28. Feuchtmittel
Die Oberflächenspannung des Feuchtmittels muss niedriger sein als die
Oberflächenenergie der Fläche, um eine rasche Verteilung zu
gewährleisten.
•Wasser 85-98 %
•IPA (Isopropanol) 0-20 %
•Zusatzstoffe 2-4 %
schwache organische Säure(n), Puffer, Filmbildner,
Netzmittel, Chelatbildner, Biocide, Entschäumer,
Befeuchtungsmittel, Glykole, Korrosionshemmstoffe
Reinwasser,
72 mN/m Wasser + 6% IPA,
45 mN/m
Oberflächenenergie des nichtdruckenden Bereiches, 50 mJ/m2
28
29. Aufrasterung
Ein Rasterbild kann
tausende verschiedene
Farbtöne enthalten...
29
30. Verschiedene Rasterarten
Konventioneller Raster Stochastischer Raster
Der Abstand zwischen den Der Farbton wird durch die Änderung der
Punktmitten ist konstant Punktanordnung und des Punktabstands
bzw. die Anzahl der Punkte erzeugt
30
31. Stochastischer Raster
Die Punktgröße Die Punktgröße
bleibt konstant, und die Anzahl der
aber die Anzahl Punkte ändert
der Punkte sich.
variiert.
31
32. Rasterweite - konventionelles Raster
helle Töne ~ kleine Punkte Die Punkte sind so klein, dass sie vom
dunkle Töne ~ größere Punkte menschlichen Auge als eine Farbe
wahrgenommen werden.
Tonwert 75%
Tonwert 25%
40l/cm
Tonwert 50%
60l/cm
80l/cm
Tonwert 100%
Rasterweite (L/cm oder lpi)
32
33. Das Menschliche Auge
Beim Vierfarbendruck werden die Farben beim Betrachten sozusagen
im Auge gemischt, da das Auge nicht zwischen kleinen, engen
Bildelementen unterscheiden kann.
Normale Rasterfläche Stark vergrößerte Rasterfläche
33
34. Druckdichte
Die Druckdichte (dunkle Flächen) wird durch Erhöhung des
bedruckten Bereiches erzielt (Halbtonanteil)
Schwarz 20% Schwarz 40% Schwarz 60% Schwarz 80%
34
35. Druckfarbe
Farben (Farbton) werden durch Mischen von Prozessfarben zu bestimmten
Prozentsätzen erzielt
C80%/M20% C60%/M40% C40%/M60% C20%/M80%
35
45. Druckbestäubungspuder
zur Vermeidung von Ablegen der Druckfarbe
Distanzhalter zwischen den Bögen
erhöht die Sauerstoffzufuhr und verbessert damit den oxidativen
Trocknungsprozess
Spray
10 bis 80 Mikron
Calciumcarbonat
organisches, pflanzliches Druckbestäubungspuder aus natürlicher Stärke
45 300x - CaCo3
46. Lackierwerk
Warum?
Höherer Glanz
Schutzfunktion
Geringere Trockenzeit vor der Weiterverarbeitung
Gelegentlich zwei Lackiereinheiten
Hochglanz und Mattlack in einem Durchgang
Erste und UV-Lackierung bei Verwendung konventioneller Farben
Höherer Glanz als bei Auftrag mit einem Werk
46
47. Zusammenfassung
Offsetdruck
Was ist Farbe?
Grundlagen des Offsetdrucks
Bogenoffsetdruck
Heatset-Rollenoffsetdruck
Andere Druckverfahren
Konventionelle Verfahren
Tiefdruck
Flexografie
Siebdruck
Digitaldruckverfahren
Laser (Elektrofotografie)
Inkjet
Schlussfolgerung
47
48. Aufbau einer Heatset-Druckmaschine
Rollenbreiten: ~50- (über) 200 cm
Rollengeschwindigkeit: ~4-15 m/s
Rollenspannung: ~600-800 N/m
Trockentemperatur (der Rolle): ~110-140 °C
Falzen: üblicherweise inline Silikonisierungswerk
Rollenständer Druckwerke Trockner Kühlaggregat
Einzug
Falzapparat
48
56. Heatset Trockner
Verzögerung der Bahngeschwindigkeit im Trockner ~1 s
Trocknerlänge wird durch Maschinengeschwindigkeit bestimmt (10 m/s 10 m)
Der Trockner verfügt über mehrere Module
Heiße Luft aus den Düsen befördert die Papierbahn durch den Trockner
Abluft wird entweder zurückgeleitet oder nach entsprechender Behandlung in die
Atmosphäre abgegeben (z. B. in Nachbrennanlage)
56
57. Temperaturprofile im Trockner
Rollenaustrittstemperatur üblicherweise 100-140° C (90-180)
Abnehmendes Temperaturprofil
Rollentemperatur steigt rascher und Lösungsmittelverdampfung
°C beginnt früher
300
255°C
195°C
200
165°C
130°C
100
Temperatur der Trocknerluft
Bahntemperatur
Erster Zweiter Dritter Vierter
57
58. Kühlwalzen
Thermoplastisches Farbbindemittel ist nach dem Trockner weich
Kühlwalzen kühlen die Papierbahn und härten das Bindemittel aus (bessere
Scheuerfestigkeit)
Stahlzylinder (3 - 6), durch die kaltes Wasser gepumpt wird
Walzenspannung muss hoch genug sein, um guten Kontakt sicherzustellen
58
65. Ausschießen und Plattenherstellung
Ausschießen
Wird üblicherweise vom Drucker erledigt
Hängt davon ab, welche
Druckmaschine im Einsatz ist
16/32/48/64 Seiten
Verwendung spezieller Software
Plattenherstellung
Basierend auf Ausschießschema
65
69. Klebebindung
Arbeitsschritte
Die Druckbögen werden auf dem Förderband zusammengeklebt
Die Druckbögen werden mittels Förderband zur
Schneidmaschine befördert
Die Schneidmaschine beschneidet die
Bindekante, sodass der Klebstoff zwischen
den einzelnen Seiten verteilt werden kann
Das Magazin wird zur Umschlag-Station t
ransportiert
Das Magazin wird mittels Dreimesserautomat
beschnitten
Ein separater Umschlag ist erforderlich
Stehendes
Format
=MD
69
70. Sattelhefter
Arbeitsschritte
Die Druckbögen werden auf einem weiterlaufenden "Sattel" geordnet.
Die zusammengesetzten Druckbögen erhalten auf dieselbe Weise einen
Umschlag und gelangen dann unter die Heftköpfe, wo Heftklammern angebracht
werden
Das Magazin wird mittels Dreimesserautomat beschnitten
Wird üblicherweise nur für Druckschriften mit weniger als
96 Seiten verwendet
70
71. Zusammenfassung
Offsetdruck
Was ist Farbe?
Grundlagen des Offsetdrucks
Bogenoffsetdruck
Heatset-Rollenoffsetdruck
Andere Druckverfahren
Konventionelle Verfahren
Tiefdruck
Flexografie
Siebdruck
Digitaldruckverfahren
Laser (Elektrofotografie)
Inkjet
Schlussfolgerung
71
80. Zusammenfassung
Offsetdruck
Was ist Farbe?
Grundlagen des Offsetdrucks
Bogenoffsetdruck
Heatset-Rollenoffsetdruck
Andere Druckverfahren
Konventionelle Verfahren
Tiefdruck
Flexografie
Siebdruck
Digitaldruckverfahren
Laser (Elektrofotografie)
Inkjet
Schlussfolgerung
80
81. Was ist Digitaldruck?
Beim DIGITAL-Druck wird direkt von digitalen Daten gedruckt
Das Original liegt in digitaler Form vor
es werden keine Filme benötigt
es werden keine Druckplatten benötigt
81
82. Pro und Con Digitaldruck
Pro
einfach zu ändernder Content
Design und Farben
Text
Kein Einrichten
-> kleine Auflagen zu vernünftigen Preisen
Personalisierung
Versionierung
On-Demand-Druck
dezentralisierter Druck
einfach zu handeln im Vergleich zu Offsetdruck
"unbegrenzte" Wiederholung
Con
Druckqualität noch immer geringer als im Offsetdruck
Geringe Druckgeschwindigkeit im Vergleich zu konventionellen Druckmaschinen
Formateinschränkungen (kleine Rollen/Bögen)
Nur wenige oder keine Spot- und Metallfarben
Konventionelle Weiterverarbeitung
Kosten (Toner etc.)
82
83. Anwendungen
Produktionsvariable Daten
Direct Marketing
Individualisierte Anschreiben
kundenadressierte Kataloge,
Broschüren etc.
Akzidenzdruck
On-Demand-Druck und
Kleinauflagen von Büchern
Kleinauflagen von Broschüren
83
84. Zusammenfassung
Offsetdruck
Was ist Farbe?
Grundlagen des Offsetdrucks
Bogenoffsetdruck
Heatset-Rollenoffsetdruck
Andere Druckverfahren
Konventionelle Verfahren
Tiefdruck
Flexografie
Siebdruck
Digitaldruckverfahren
Laser (Elektrofotografie)
Inkjet
Schlussfolgerung
84
85. Grundlagen Elektrofotografie
1. Der Fotoleiter wird geladen
2. Ein latentes Bild wird
durch Entladung der - -
- - - - -- - -
- -
Trommel mittels Laser --
--
oder LED gebildet +
++ 6. Überschüssiger
--
-
-+
-
Toner
+
--
-
wird weggewischt
3. Ein latentes Bild wird
mittels Toner entwickelt 5. Der Toner wird
auf dem Papier
durch Hitze fixiert
= Verschmelzung
+ ++
+
4. Toner (Bild) wird im elektrischen Feld
auf das Papier übertragen; gegensätzliche
Ladung zieht sich an
85
86. Zusammenfassung
Offsetdruck
Was ist Farbe?
Grundlagen des Offsetdrucks
Bogenoffsetdruck
Heatset-Rollenoffsetdruck
Andere Druckverfahren
Konventionelle Verfahren
Tiefdruck
Flexografie
Siebdruck
Digitaldruckverfahren
Laser (Elektrofotografie)
Inkjet
Schlussfolgerung
86
87. Continuous Inkjet
1. Continuous Stream, CS, CIJ
Die Farbtröpfchen werden aus dem kontinuierlichen Tintenstrahl selektiv ausgewählt
Die Tröpfchen weisen ähnliche Größen auf
hohe Geschwindigkeit
z. B. Scitex VersaMark
87
88. Inkjet : Drop on demand
2. Drop-on-demand, DOD
Jeder Farbtropfen wird gedruckt
hohe Auflösung
geringere Geschwindigkeit
z. B. Aprion
88
89. Zusammenfassung
Offsetdruck
Was ist Farbe?
Grundlagen des Offsetdrucks
Bogenoffsetdruck
Heatset-Rollenoffsetdruck
Andere Druckverfahren
Konventionelle Verfahren
Tiefdruck
Flexografie
Siebdruck
Digitaldruckverfahren
Laser (Elektrofotografie)
Inkjet
Schlussfolgerung
89
90. Die Definition hängt von der Papierqualität ab
LWC Zeitungsdruck
60l/cm 48l/cm
Gestrichenes SC,
Feinpapier 54l/cm
70l/cm
90
91. Verschiedene Druckverfahren, verschiedene
Ergebnisse
Offsetdruck Flexografie Tiefdruck
(20%, 75 l/cm) (20%, 60 l/cm) (20%, 100 l/cm)
• Punkte werden • Druckfarbe wird an • Bei hellen Schattierungen
gleichmäßig mit die Ränder gepresst, sind gebrochene Formen
Farbe bedeckt die Druckdichte in und fehlende Punkte typisch
• Die Ränder sind den Punkten variiert • Doughnut-förmige Punkte
ausgefranst • Glatte Ränder • Der Text ist gerastert, die
(ungestrichene • Schatten am Ränder gezackt
Papiere) Textrand
• Gleichmäßiger Text
91
92. Beispiele für Rasterpunkte und Text
Inkjet Elektrofotografie
(20%) (~20%)
• Die Punkte sind recht • Die Punkte sind recht
gleichmäßig gleichmäßig
mit Farbe bedeckt mit Toner bedeckt
• Ein Punkt besteht aus mehreren • Die Ränder sind
Farbtröpfchen ausgefranst
• Die Kanten sind ausgefranst oder • Einzelne Tonerpartikel (bei
gleichmäßig, je nach Papier Trockentoner)
• Satelliten, Ausreißer • Gleichmäßiger Text
92
93. ?
Wir beantworten gerne Ihre technischen Fragen:
Françoise Accou, +32 492.582.287, francoise.accou@sappi.com
Fragen?
93
Hinweis der Redaktion
These products are different because they have different levels of printing quality and their circulation is also different : Ikea magazine is printed in …….so printed in gravure when customer magazine like Air France for example have a circulation of 300 000 ex or books have a circulation of a few thousands ….. Qualität Niedrig Mittel Hoch Ink-jet Elektrofoto- grafie Tiefdruck Heatsetoffset Bogenoffset
So let’s have an overview of our program : Offset printing is the most common printing method applied to Sappi products so we’ll spend much more time on this process . Lithography Method was invented by Alois Senefelder in 1798 Then we’ll have a quick view on other technics
In this slide there is the print quality level and suitable job size for different printing methods. The first two bubbles are desktop office printing and colour copying, third is DIGITAL printing, and then the conventional printing methods of which offset is the major one.
PLAN A FAIRE SUR PAPERBOARD First of all, printing is applying colors on a substrate; so it is important to understand what’s make the color ?
Colour is not a physical reality; colour is in the brain and not in the material. Colour is an interpretation made by the brain of perceptions coming from the eye. Colour is different from one to the other. If there is no light or no electromagnetic radiation, no colour can be seen!
SLIDE A FAIRE SUR PAPERBOARD We only see material without colour. Material has the property to reflect more or less some rays which the human eye are sensible to. What do we need to see colours ? 3 elements : A light source, an object and a processor which is the eyes It is a complex mechanism to explain how electromagnetic radiations are turned into the coloured sensation for the human being :
All humans perceive color in a similar manner, but not all perceive them identically.Light enters the eye through the lens and is focused on to the retina. There, an array of photoreceptor cells respond to light and pass the signals on to the brain.The light receptors are called rods and cones.Rods are not sensitive to color and work at low levels of illumination.3 kinds of cones:long (RedRed), ), medium (GreenGreen))short (BlueBlue) wavelengths.) wavelengths. The eye is picking up the photons * The retina is coding the photons This code is sent to the brain which translates in coloured sensation Because of rods, we can see in the dark but only black and white. Because of the three cone cells, light stimulates the eye three dimensionnally. Furthermore this is the basis for multi colour printing using three primary colours. Multi colour reproduction does not imitate the spectral distribution of the original colour but it stimulates similar colour perception in the human eye. This is possible because physically different spectrums can cause the same colour perception.
We are exposed to lots of electromagnetic rays. Only a small part can be seen. Light can be from a physical perspective, small particles of energy called photons which move at 00000km/heure or electromagnetic waves who move at the same speed. When the wavelength is between 400 and 700, the ray can be seen as visible light; these rays mainly comes from the sun. Visible light is about 80% of the rays tranmsitted by the sun. UV is making a reaction on lignin which makes the paper becoming yellow. OBA turn the UV light into visible blue light (fluorescence). Every colour group represents third of the spectrum. White light is a mixture of all the colours. Die Geschwindigkeit, mit der sich die Wellen bewegen, wird als Frequenz bezeichnet und die Länge einer Welle ist die Wellenlänge Faire dessin au tableau
They are technically 2 ways to mix colours : substractive and additive. With the substractive mixing, white light is filtered by coloured filters. With the additive method, the required colour is generated by mixing lights of different colours (like television).
With the additive method, the required colour is generated by mixing lights of different colours (like television). Green + Blue = CYAN Green _+ Red = YELLOW Blue + Red = MAGENTA
With the additive method, the required colour is generated by mixing lights of different colours (like television). Green + Blue = CYAN Green _+ Red = YELLOW Blue + Red = MAGENTA
In printing the colour mixing method is mainly substractive. The printing of colours is based on the selective absorption by the ink of a certain wave length area. If the blue spectrum is absorbed by the ink, the reflected light is seen as yellow; furthermore absorption of the green produces magenta and absorption of the red gives cyan. Colour mixing in printing is also partly additive when the half tone dots of different primary colours are near each other in the light tones. The three primary colours used in printing are Cyan, Magenta and Yellow.
In principle it would be possible to make black by mixing all the 3 primary colours Mixing the 3 primary colours theoretically results in black. ->In practice the result is brown ! => To remedy this, black is used as the fourth primary colour. It improves the quality and is also cheaper than coloured inks
There are 3 typical charcteristics defining offset : a flat plate, a fountain solution and a rubber blanket On a printing plate there are two areas: 1. Areas accepting water and due to that being repulsive to ink = Non-Image areas (= hydrophilic) 2. Areas accepting ink and at being repulsive to water = Image areas (= hydrophobic) The behavior of the image and non-image areas is caused by a complex chemistry. The distinction between image areas and non image areas is based on differences in surface energies and hydrophilicity. The image area is a friend of grease and repellent to water. The non image area is a friend of water but a repellent to grease. Grease means ink and water is fountain solution. The netire process is based on the property that grease and water do not mix.
Two things are very important: 1.Image areas are hydrophobic and non-image areas are hydrophilic . Reason: Special chemistry of printing plates 2.Dampening water and ink do not mix. -> In the hydrophobic areas a ink layer will stay on the plate -> In the hydrophilic are a water film stay on the plate
Image areas are hydrophobic and non-image areas are hydrophilic … … here to be seen on a magnified picture of a of set plate.
Theoretically it is possible to transfer the ink directly to substrate. = Direct transfer. The direct ink transfer is not in practical use.
The ink layer on the image area of the plate is... ...transferred to the rubber blanket… … from the rubber blanket the ink is transferred to the substrate. Warum wird ein Gummituch verwendet? 2. Höhere Geschwindigkeit (Gummi erlaubt Rotationsdruck) 1. Höhere Druckauflagen (harte Platte und weicher Gummi) 3. Gummi erlaubt Druck auch auf unebenen Oberflächen
The plate is wetted by fountain solution before it is inked Water forms a film on the non image areas. When ink is fed to the plate it is unable to transfer to the damped areas and it will only be taken up by the water free image areas. The principle of offset is indirect : this is how offset got his name. Many ink rollers are needed to spread the tacky ink into a thin layer. – La couche d'encre sur le matériel est entre 0.7 et 1.1μm Now let’s go into more details about the different elements
How does a printing plate work ? It is an assembly of several chemical layers stacked on an aluminium basis. The thickness of the alu plate can vary from 0,15 to 0,4 mm . Then we have at least 2 layers One layer of aluminium oxide which attracts water on non image areas of the plate and another layer which is light sensitive and whose formula is kept secret which attracts ink on image areas. The action of light destroys the coating on non –image areas . Détruire à la lumière la couche imprimante Dans le cas d'une plaque traditionnelle positive, l'action de la lumière d'insolation détruit la couche imprimante sur les zones non masquées par le film, c'est-à-dire sur les zones ne devant pas être imprimées. Dans le cas d'une plaque négative, la lumière, au contraire, solidifie la couche imprimante sur les zones non masquées par le film, qui sont cette fois-ci, les zones à imprimer. Une image positive après insolation En CTP, le principe est le même : le laser de l'imageuse vient détruire la couche imprimante sur les zones vierges de la page ou solidifier la couche sur les zones à imprimer. C'est pourquoi il existe des plaques CTP positives ou négatives. Dans tous les cas, les plaques portent une image positive après insolation et développement. The printing plate has a light sensitive coating. We expose the plate to light through either a positive or negative film. Most plate making is now filmless with the image being directly exposed on the plate. CTP (computer to plate) can be used when the plates are on the press.
How does a printing plate work ? It is an assembly of several chemical layers stacked on an aluminium basis. The thickness of the alu plate can vary from 0,15 to 0,4 mm . Then we have at least 2 layers One layer of aluminium oxide which attracts water on non image areas of the plate and another layer which is light sensitive and whose formula is kept secret which attracts ink on image areas. The action of light destroys the coating on non –image areas . Détruire à la lumière la couche imprimante Dans le cas d'une plaque traditionnelle positive, l'action de la lumière d'insolation détruit la couche imprimante sur les zones non masquées par le film, c'est-à-dire sur les zones ne devant pas être imprimées. Dans le cas d'une plaque négative, la lumière, au contraire, solidifie la couche imprimante sur les zones non masquées par le film, qui sont cette fois-ci, les zones à imprimer. Une image positive après insolation En CTP, le principe est le même : le laser de l'imageuse vient détruire la couche imprimante sur les zones vierges de la page ou solidifier la couche sur les zones à imprimer. C'est pourquoi il existe des plaques CTP positives ou négatives. Dans tous les cas, les plaques portent une image positive après insolation et développement. The printing plate has a light sensitive coating. We expose the plate to light through either a positive or negative film. Most plate making is now filmless with the image being directly exposed on the plate. CTP (computer to plate) can be used when the plates are on the press.
The pigment gives the color to the ink; they are mostly organic ones but sometimes inorganic are used too (carbon black). The binders are hard resins and drying oils; the main function of the binder is to key pigments to the paper; Thin mineral oils are used as solvents in inks; their function is to solve the binders. Additive are used in the ink to adjust the performance at the press; we can add driers for example which are cobalt and manganese; waxes are usually polyethylene Lots of changes these last years due to speed increased and environment
Blankets are mainly characterized by the following properties : release, hardness, compressibility and surface Hardness Harder blankets have better release properties and they are more durable Softer blankets have better contact with paper/board and better ink transfer properties
Requirements of a fountain solution : Quick spreading over non-image area of the plate Desensitization of the non-image area of the plate Good transfer on rollers Stable pH Minimal corrosive effects No bacterial spoilage No foaming Lubrication of the blanket Requirements: Quick spreading over non-image areas of the plate Emulsion with the ink Stable pH Protection of the non-image areas of the plate Cooling of the inking unit Properties pH 4.5-5.5 If too low ink does not dry If too high emulsification increases Surface tension Low surface tension improves wetting of the plate Viscosity Higher viscosity improves the fountain solution transfer in the rollers Hardness Conductivity Temperature
Because one half tone image may contain thousands of different shades, it would be impossible to print the tones without screening. Screening means changing the colours into dots, the size and/or amount of which varies according to the shade. There are 2 types of screens : Conventional screen Stochastic screen
In stochastic screening, the image is reproduced from small, almost randomly distributed dots. Therefore there is no screen ruling at all. By stochastic screen it is possible to produce superior details and a continuous-tone-like appearance.
Because the dot size in the stochastic screening is very small (15 - 40 µm) it is possible to print sharper images.
In conventional screening the size of the dots varies according to the tone. Light tones need small dots and dark tones need bigger dots. The dots are so small that the human eye sees them as a single colour. In conventional screening the dot size varies, but their distance from dot center to dot center is constant. The distance is determine by screen ruling. It shows how many lines of dots there are per centimeter or per inch.
The eye has limits ...
Speeds ~ 5 000 - 20 000 copies/h One side printed in one unit (both sides 4+4 units) Extra colour units (PMS-colours) or varnishing units Sizes A3 (2/4 pages) A2 (4/8 pages) A1 (8/16 pages) A0 (16/32 pages) XXL (64 A4) Sheet offset printing: Sizes from DIN A4 to 120 x 162 cm 1 - 12 printing units max. 18,000 sheets / h One or two-sided printing Basis weight from 70 - 400 g/m² usual
Why more than 4 colours ? Spot Colours Brand Colours Metallic printing inks Heavy ink layers Solid areas
A SRA = Supplement Raw format A (refers to untrimmed paper formats)
The sheets are taken one by one by suction
This picture shows how the sheet is transferred from one printing group to another one
Heat Set Web Offset (HSWO) Paper in reels normally from 28gsm to 150gsm both coated and uncoated A major difference Is that Both sides are printed in one pass in four or more colours. The web runs between two blanket cylinders (no impression cylinder) on each unit. The ink dries through absorption in to the paper and through evaporation as the web travels through an oven. Usually the web is cut and folded in to signatures. Sometimes it is sheeted or is reel to reel. Reels in various widths Blanket- to-blanket Heatset ink: solvents evaporate in dryer Inline folding / finishing Cut-off length depends on press Limitations in colours/ grammages Fluting / more printing gloss 8-16-24-32-48-64-72-80 pages Delivery in signatures / reels / sheets
1970 : Single web press 100 m/min ou 2m/sec Laize 1 meter 20% wate Today Double web presees 1000 m/min ou 18m/sec 2,86 m de large 2 a 5 % waste automation
As many other industries, HSWO is more and more automated… Press console From this place they can adjust ink levels, register, pressure between cylinders, etc etc …. The press console provides electronic control for register, image control, ink and dampening easily. The press operator monitors the console and, if neceseasily. The press operator monitors the console and, if necessary, makes press adjustment by adjusting switches on the console, which cause the appropriate adjustments to be made on the press. Today, computer controlled consoles are the norm for process control and providing a consistent printed product. The color control console is where the printer will add or subtract color across the entire sheet or in localized areas. On the console are keys which correspond to "zones" in the inking system. Electronically the operator can select the color unit they want to change at the console. This will correspond at the selected print unit. If the printer wants more ink across the whole sheet, the ductor roll will contact the "feed" or "ball" roller longer. If the printer wants to only add color to a localized area, small plates at the ink fountain will open allowing more ink to pass at that spot only. This gives the printer great flexibility!
Relation colour / water / paper : The paper quality plays an important roll in relation to the water and the colour absorption capability in the printing result and has to meet several requirements, among which you can find: A good absorption to support drying and adhesion of the colour. The paper has to absorb the water quickly and uniformly to avoid that the following colour is badly printed after printing the first colour as the water film coming onto the paper when printing the single colours is not completely absorbed by the paper (repelling of the colour). If insufficient water is absorbed by the paper, the colour may start to emulsify (= to mix with water), influencing the printing quality and the drying properties extremely in a negative way. The paper has to be resistant against fountain solution with a pH of approx. 5 (the coating layer should not detach). In case of a contact with moisture the paper should practically not deform . The paper surface has to be resistant against the forces being released during cracking of the colour if the paper loosens from the rubber blanket.
Hot air Inlet temperature > 200°C Web temperature approx. 120°C The length of the oven is very important
Falzbruch vermeiden Die Aufbringung eines dünnen Wasser-/Silikonfilms soll "Schmierstellen" beim Falzen ungestrichener Papiere verringern. Gestrichene Papiere können aufgrund der Latexbeschichtung Abdrücke hinterlassen, wenn sie das Farzwerk passieren. Bei ungestrichenen Papieren ist es vorteilhaft, wenn der Drucker in den trockenen Wintermonaten dem Wasser einen Weichmacher hinzufügt, der die statische Aufladung der Papierbahn verringert.
Signature = group of pages
There are three basic types of folders: former folders, jaw (= machoire) folders, and chopper, or quater folders. Often, all three folding devices are incorporated into a combination folder. A former folder folds the web by passing it over a triangular-shaped former board. This action makes a "with the grain" fold by folding the web along it length. Additional folds after the former fold are made with jaw and chopper folders. A jaw folder folds the web across its width (cross grain) by allowing it to travel around a cylinder equipped with a tucker blade that forces the paper into a jaw (opening) on an opposing cylinder. After passing through the folding jaw, the web is automatically cut into individual signatures and, if necessary, passes to a chopper folder. In the chopper folder each signature is forced between two rotating fold rollers that make the final fold, against with the grain.
Gravure- Widely used printing process- suited for long runs, where a high quality reproduction is required. Cells of varying shape, depth, and area are chemically etched, electromechanically engraved, and/or laser beam engraved into copper image carrier. (Laser engraved into the zinc layer). The engraved image is later chromium coated to increase the durability of image carrier. • Variation in depth enables different volumes of ink to be delivered. Compared with other printing processes (except screen), the ink film thickness delivered by the cells is high, up to 6 micron for most work on paper The cylinder is engraved. When the print job is finished or the cylinder is worn out the copper bracket is stripped off. The copper cylinder can be chrome plated to make it longer lasting. Gravure - Main strengths Very high quality colour reproduction is possible Waste levels are relatively low, Print quality is very consistent, Inks are relatively volatile liquids and key to a wide range of substrates without requiring a lot of energy, It is possible to print continuous designs, Very high production speeds are achieved, Running costs are relatively low Gravure - Main weaknesses High cost of producing cylinders compared to plates for other processes.Lead times for producing cylinders are comparatively long. Corrections are more difficult.Only really cost efficient for longer runs. Print quality can be very poor if the substrate roughness is not within the minimum specification The ink is picked up in the engraved cylinder cells, the excess is removed by the doctor blade; the paper passes through the nip between the printing cylinder and the impression cylinder; the ink is transferred to the paper as a series of dots; electrostatic assistance helps the transfer of ink from cylinder to paper (YMCK = ink sequuence).
4, 32 metres 18 ribbons
PACKAGING AND CONVERTING • Packages- 6% of total value of all manufactured goods • Beverage packaging- food products- spent approx. • $1 billion/year on packaging • Folding cartons, flexible packaging, labels, wrappers, composite cans, metal, glass GRAVURE FOLDING CARTONS • Wet, dry foods, beverage carriers, bakery, candy boxes; • Gravure- used by 65 North American folding carton producers • 29% share on the market- gravure FLEXIBLE PACKAGING • Flexible packaging- 5% annual growth (as a whole) • About 1/3 market share- gravure • Flexible packaging – package products weighting less than 25 lb. • Paper, plastic film, foil laminates, different combinations • Fully printed packaging materials, combination materials, (converted wrap) • Single- serving food packages4 GRAVURE LABELS AND WRAPPERS • Roll, sheet labels applied to cans, cartons, bottles, tags, self-adhesive products, • Most of them printed on paper substrate PRODUCT GRAVURE • Narrow width plastic films- to vinyl shower curtains, wall covering, decorative laminates, floor coverings, tissue products GIFT WRAPS • 90% of all gift wraps- printed; Gravure- dominant 70% of all production • Christmas wrapping paper • Decorative laminates- general purpose- horizontal surfaces .050in • Vertical surfaces- as thin as .028 in FLOOR COVERINGS Sheet vinyl coverings 18 in. to 6,12,15-ft width • Inventories of engraved cylinders – hundreds of patterns • 84% vinyl floor coverings printed gravure TISSUE PRODUCTS • Paper towels, bathroom tissue • ¾ of all tissue product are printed with patterns, • ¼ of bathroom tissue printed; 1/8 of all napkins- printed • Sanitary tissue- flexo, gravure declines OTHER PRODUCTS • Cigarette filter tips, heat transfer paper, marbled book end papers, pill and candy trademarking, auto windshield tinting GRAVURE WALLCOVERINGS • Traditional gravure • Gravure- 40-45% of all wall coverings- almost entirely on vinyl GRAVURE VINYL PRINTING • Curtains, shower curtains, tablecloth, ceiling tiles, automobile upholstery, vinyl fabrics for outdoor furniture (umbrellas, chairs) • Unsupported vinyl, vinyl backed with paper, fabrics. • Some- printed on paper and vinyl coated. DECORATIVE LAMINATES • Thermoset laminates in furniture, construction – wood grain – used in furniture. High pressure laminates- formed by high pressure- 1,000-1500 psi • Contains up to 18 layers of polymer saturated paper • Top sheet-translucent- melamine impregnated Magazines and catalogues (45%); Flexible packaging (50%) and confectionery wrappings Folding box cartons (34%), liquid cartons and cigarette packets (75%);
Where gravure has the dots engraved in the cylinder, with Flexography the dots are raised above the surface. A wide range of substrates can be used from foils to paper. It has many applications such as the printing of – Newspapers Wallpaper Food and hygiene packaging Self adhesive labels Corrugated boxes Très présente dans le domaine de l'emballage, la flexographie est utilisée pour l'impression de supports aussi variés que le film polyéthylène, le papier , le carton ondulé et le carton plat. Longtemps, les clichés étaient composés de caoutchouc, avant l'apparition des plaques photopolymères dans les années 70. A flexo print unit consist of a plate cylinder carrying the flexible plate. A C ounter I mpression cylinder is used to back the substrate for the printing. The liquid flexo ink is transported out of the ink pan by the ANILOX ROLLER; The excess of ink is wiped off the surface of the anilox roller by means of a DOCTOR BLADE
The application ranges for Flexo are various. Flexo is the printing process with the highest rates of increase.
La sérigraphie permet de réaliser des impressions sur papier, carton, plastique souple ou rigide, métal, textile, verre, bois et sur les auto-collants. Called screen printing because the ink is forced through a screen. More suitable for solid colours and thought to have been with us for about 4,000 years and now used for many applications such as – Clothing & Textiles Product labels Printed electronics , including circuit boards Large formats, i.e. posters and balloons Medical devices Signs and Displays
There are sometimes problems to understand what people mean by digital printing. The "real" digital printing is printing without films and plates ; computer-to-press printing occurs where the data is in digital form but plates are made at the press.
Here are the main pros and cons today - tomorrow they might be different. PROS: The possibility of digital printing is in small runs that can mean either short run lengths or personalisation. Personalisation is the real benefit. It does not only mean some text such as names, addresses etc, but personalising the content. Versioning means e.g. different language versions. On-demand printing happens when e.g. 10 copies are printed today, 20 tomorrow etc. Decentralised printing is delivering digital data to different printing plants to be printed near the distribution area. A digital printer needs different skills compared to a conventional printer. He works mainly by a computer. Run length in conventional printing is defined by the circumference of the print cylinder. In digital printing there is a possibility to print several metres long images. This is useful e.g. in wallpaper borders. CONS: Even though digital print quality has improved a lot, it is still not as good as offset in general. Typical faults are stripes and mottling especially in solid areas. Printing speed in sheetfed offset is, calculated in m/min, around 150 m/min as in digital printing it is e.g. in Xeikon 7,35 m/min (or 15 m/min). Small reels (width 32 or 50 cm) /sheets (SRA3) mean limitations to the printed products and also difficulties to board mills in converting. In Xeikon-based machines there are only four primary colours available, but in Indigo also two additional colours are possible. However, in digital toners the colour space is wider than with offset inks. The further converting, diecutting etc is not digitised at all. After the latest printing technology, very conventional converting methods come in the picture. There is, however, work going on in laser diecutting where cutting is not a problem, but creasing is! Today e.g. the toners are expensive and so is the unit price of a copy. Only one series of toners is available per press. Of course for short runs the price is also high in offset and personalised products in offset are impossible in practice.
Electrophotographic method works in the following way: 1. The drum is covered by a photoconductor material which maintains charges in darkness but discharges in light. The photoconductor drum is first charged with even charge. 2. A latent image is formed by discharging the drum by laser or LED (light emitting diode). 3. The latent image is developed by toner (ink). It sticks to the opposite charges. 4. Then the toner image is transferred on the board in an electric field, again opposite charge attracts. 5. The last step is fusing where toner is fixed to the board by heat and/or pressure. The same principle as in laser printers and copying machines, but in printers the speed and resolution are lower in copying machines the original is a hardcopy possibility to print on reels Negatively charged toner particles stick on the positively charged image areas until transfereed to paper. A strong electrical dischare on reverse side of the paper The electric field (corona) and toner particles have opposite charges Important chraacteristic of pare is Resistivity and dielectricity IR fusing without pressure for xeikon
There are two principle ink jet methods: continuous stream and drop-on-demand. In CIJ (continuous ink jet) the droplets are formed continuously and the printing droplets are selected from the stream. The non-printing droplets are returned to the ink circulation. All the droplets have similar size. By this method very high speeds are possible. CIJ is largely used in b&w marking. The new 4-colour press of Scitex belongs to the VersaMark family (in the picture).
In DOD ink jet drops are formed only in need, so every drop is printing. Resolution in principle is higher, but speed lower than in continuous stream. E.g. Aprion (separated from Scitex) is concentrating in this technology. Their DPS-65 in seen in the picture. Weiter Anwendungsbereich z. B. für Codierung (Addressierung, Haltbarkeitsdatum), Poster, Plakate, Büro- und Heimanwendung, Korrekturabzüge, Textildruck.... In Zukunft... Wandbeläge (z. B. Bordüren) Wellpappe