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©Eastman Kodak Company, 2005
Thermal Printing Chemistry for Digital Output
David G. FosterEastman Kodak Company
Rochester, NY 14650
©Eastman Kodak Company, 2005
Overview of Talk
• A Definition of Thermal Printing• System Review• Media Design
– Dye donor– Receiver
• Image Quality• Applications• Wrap-Up/Questions
©Eastman Kodak Company, 2005
Resistive-Head Thermal Dye Transfer Printing
A digital printing method where thermal energy is used to make photographic quality output by the transfer of dyes from a donor ribbon to a receiver that are in intimate contact.– Used for over a decade– Consumer, government, professional, entertainment, commercial,
and home printing– Historically used in low-volume but expanding quickly to high-
volume applications– Both single- and multiple-printhead printers
©Eastman Kodak Company, 2005
Some Applications for Thermal Printing
• Kiosk printing from digital cameras • Home printing of images• ID Cards, passport photos• Studio portraits• Diagnostic imaging• Entertainment imaging (i.e., images from theme park
rides)• Color proofing in publishing industry• And the list continues to grow…
©Eastman Kodak Company, 2005
The Thermal Printing System
Donor Ribbon
Printer
Image
Firmware&
SoftwareReceiver Sheet
©Eastman Kodak Company, 2005
Simple Model of a Thermal Printer
Donor Take-Up Spool
Printhead
Donor Supply Spool
Donor RibbonReceiver Sheet
U.S. Patent 4,621,271
©Eastman Kodak Company, 2005
Printing Process Steps
• Electronic image is subjected to color separation and converted into electronic signals
• Yellow, magenta, and cyan electronic signals are transmitted to a thermal printer
• Images are created by printing yellow, magenta, cyan, and over-laminate patches from the donor to a receiver
Yellow first Magenta second
Cyan third Laminate last
©Eastman Kodak Company, 2005
Major Attributes ofThermal Dye Transfer Printing
• Reflective prints and transparencies of multiple formats
• Color and black & white• Simple and reliable
equipment
• Dry process• Continuous tone scale• High resolution• Ecologically clean
©Eastman Kodak Company, 2005
Media Design
©Eastman Kodak Company, 2005
Donor Design Considerations
• Raw stock keeping• Energy to print• Printing artifacts• Interaction with
hardware• Coating
• Dye• Polymeric binder• Dye-to-binder ratio• Dye diffusion• Additives/addenda• Interaction with
receiver
©Eastman Kodak Company, 2005
Engraving Pattern
Gravure CoatingIn gravure coating, the rigid coating cylinders have cells, grooves, and patterns of a specific volume engraved into the surface. These cells are filled with fluid and the pattern of the engraving is transferred to the substrate surface.*
* “Liquid Film Coating,” edited by S.F. Kistler and P.M. Schweizer, Chapman & Hall, NY 1997, Chapter 12c.
©Eastman Kodak Company, 2005
Multi-Station Gravure Printing Press
SupportPath
Dryer
CoatingStation
Cyan Station Magenta Station Yellow Station
©Eastman Kodak Company, 2005
Thermal Donor Basic Structure
Dye Side Coating (~0.4 µm)
AdhesiveLayer
(~0.1 µm)PET
(4.5 and 6 µm thickness)
Slip Layer/Heat Resistant Layer (~0.3 µm)
©Eastman Kodak Company, 2005
Thermal Donor Ribbon
YellowPatch
MagentaPatch
CyanPatch
LaminatePatch
YellowPatch
MagentaPatch
CyanPatch
Picture UnitSome Products Have
Registration Bars
A picture unit consists of patches of yellow, magenta, cyan, and laminate that repeat in the donor spool.
©Eastman Kodak Company, 2005
Dye Donor LayerPolymeric Binder
U.S. Patent Number 4,700,207
OO
OR
OR
CH2OR
nR = CH3CO, CH3CH2CO
• Dyes with desirable hue• Compatible with the
binder• Good adhesion to the
subbing layer• Non-interactive with the
slip layer• High dye transfer
efficiency• No sticking to the receiver
20 µm
Optical Image of Magenta PatchU.S. Patent Number 5,387,573
©Eastman Kodak Company, 2005
Dye Layer Chemistry
NN
N
O
N
O
O
NH
N
N
O
O
NH
N
N
SN
CN
NN
N
O
N
N
C
H
NN
O
N
SN
C
N
NN
NH O
N
Along with dyes:• Polymeric binder• Plasticizer• Spacing beads• Solvent• Other addenda
U.S. Patent Numbers 4,695,287; 4,698,651; 4,839,336; 4,743,582; 4,866,029; 5.340,789; and 5,340,790
O
O
NH
N
N
N N
N
N
O
©Eastman Kodak Company, 2005
Donor Film Base• Thickness affects heat
transfer efficiency• Thicker support
– Requires more heat to transfer an amount of dye
– May be more robust to printing
• Thinner supports – Requires less heat to
transfer an amount of dye
– Facilitates the transfer process
O CH2 CH2 O C
O
C
O
n
Support in this system is generally poly(ethylene terephthalate) (PET) ata thickness of either 4.5 or 6 µm.
D.G. Foster & M.L. Gray, “Media and Equipment Advances in Dye Diffusion Thermal Transfer to Facilitate a Multihead Printer System”, IS&T’s NIP 18: 2004 International Conference on Digital Printing Technologies, October 2002
©Eastman Kodak Company, 2005
Ti OR
OR
OR
H2OTi
OR
OR
Ti(OR)4 Ti
OR
OR
O Ti OR
OR
OR
H2OTi(OR)4Hydrolysis of Ti(OR)4
Donor Adhesive/Subbing Layer
RORO RO OH
• High adhesion to support & dye layer
• Impermeable to dyes• Low affinity to dyes• Antistatic
OTi
OR
OR OR
Ti OR
OR
OR
1. U.S. Patent Number 4,737,4862. S. Neuman, “Titanium Alkoxide Subbing Layer Chemistry,” 10th International Congress on Advances in Non-Impact Printing, Oct 1994
Ti
OR
OROH2O(RO)n(TiO)y(TiO2)zTi(OR)4
©Eastman Kodak Company, 2005
Slipping/Heat Resistant Layer
Rough Surface Cleans Printhead.
• Low & constant friction over entire printing temperature range
• Non-contaminating to print head
• Not abrasive to printhead• Good adhesion to the
subbing layer• Non-interactive with dye
layer when spooled
Slip layers contain lubricants, polymeric binders, solvents, and other addenda to achieve printing.
U.S. Patent Application Publication No. 2005 0009699, Jan 13, 2005U.S. Patent Application Publication No. 2005 0009799, Jan 13, 2005
©Eastman Kodak Company, 2005
Laminate – Over Protective Layer
• Thermal dye transfer prints without a protective laminate layer are susceptible to density loss due to – faster light fade of dyes near the surface– attack by ozone, nitrogen dioxide, or sulfur dioxide– other organic chemicals such as those from human fingerprints– dye retransfer to other surfaces in contact especially to materials
like PVC
• A thin protective layer laminated on the final print at the last step of printing has proven to be a very robust method to eliminate or greatly minimize these problems
©Eastman Kodak Company, 2005
Two Laminate Options: Glossy and Matte
Dye Receiving Layer
Paper Support
Glossy Surface
Expancel beads are hollow beads that are thermally expanded during the lamination step, interrupting the gloss of the surface.
Matte Surface
Clear Laminate
U.S. Patent Numbers 6,362,132 and 6,184,181
©Eastman Kodak Company, 2005
Matte DonorSEM photos of microspheres in donorSEM photos of microspheres in donor
Higher magnification showshow far out of the polymer
layer the microspheres protrude
Rows ofmicrospheres
from gravure coating
J.J. Hastreiter and W.H. Simpson, “Matte Finish on Thermal Prints”, IS&T’s NIP 20: 2004 International Conference on Digital Printing Technologies, October 2004, page 976
©Eastman Kodak Company, 2005
Thermal Receivers
• Thermal transfer can take many forms– Label stock– Transparency (loosing ground due to video projectors)– An intermediate receiver that is laminated to a final surface
• For all thermal applications, the receiver must be smooth, because thermal printing is a contact process– The receiver is either a card or has the look and feel of a
photograph. Other kinds of receivers have met with limited success
– Receiver has a big role in thermal management
©Eastman Kodak Company, 2005
Thermal ReceiverBasic Structure Schematic
Requirements
U.S. Patent Numbers 6,362,131; 5,853,965; 5,866,282; 5,874,205; 5,888,643; 5,888,681; 5,888,683; and 5,888,714
• High dye uptake• Compatible with dyes• Not easily deformed by heat
and pressure• No sticking to dye donor
during printing• Insensitive to humidity• Good scratch and abrasion
resistant• No stack blocking• Good image stability: light
fade, dark fade, dye retransfer, smear, fingerprint, etc.
• Robust picking & transport
Support Requirements• Smooth surface• No curl at most environmental conditions• Compliant to give good uniformity• Thermal insulating• Antistatic
Paper support
Tie layer
Dye Receiving Layer (~3µm)
Micro-voided film
Tie layer
Anti-curl layer
©Eastman Kodak Company, 2005
Thermal Receiver Cross Linking
R NCO + R' OH R N CO
O R'H
isocyanate alcohol urethane
©Eastman Kodak Company, 2005
Thermal Receiver Cross Linking
C
CH3
CH3
O C OCH2CH2OCH2CH2O
O
O HCOCH2CH2OCH2CH2O
O
H
n=5 to 6
C
CH3
CH3
O C OCH2CH2OCH2CH2O
O
OCOCH2CH2OCH2CH2O
O
n=5 to 6
N
N
N
O
OO
(CH2)6NN(CH2)6 CC
H H OO
(CH2)6N
H
C
O
N
N
N
O
OO
(CH2)6NCOOCN(CH2)6
(CH2)6NCO
+
LMW Bisphenol A diethyleneglycol polycarbonate
HDI trimer
Crosslinked polyurethane
Advantages: Image density, Tg influenced by plasticizer, Compatibility with Dyes, Light Stability.
T.M. Kung, D. Bailey, B. Pope & G. Bodem, “Development of a Cross-Linked Imaging Layer for Thermal Dye Transfer Receiver”, IS&T’s NIP 20: 2004 International Conference on Digital Printing Technologies, October 2004, page 988
©Eastman Kodak Company, 2005
Dye Receiving Layer Components Goal:Curve Shape and Robust Performance
• Polyols– Molecular weight– Composition– End group (aliphatic alcohol vs. phenol)
• Cross linking agents
• Catalysts
• Solvents
• Other addenda – surfactants, plasticizers, release agents, etc.
©Eastman Kodak Company, 2005
Image Quality
©Eastman Kodak Company, 2005
Image Quality Depends Upon…
• Resolution • Density Range
High Resolution Low Resolution Low DensityHigh Density
©Eastman Kodak Company, 2005
Image Quality Depends Upon…
• Tone Scale Continuous Tone
Print Density
Input Signal to PrinterRed – Continuous Tone (Thermal Dye Transfer)Green – Bimodal (Wax Transfer & Inkjet)Blue – Multilevel Inkjet
Half Tone
©Eastman Kodak Company, 2005
Image Quality Depends Upon…
• Color Gamut• Image stability• Print surface• Print durability• Physical
appearance
SmallLarge
©Eastman Kodak Company, 2005
Thermal Printing Media:PVC Retransfer Test (7 days, 50°C/50% RH)
Unlaminated Laminated
©Eastman Kodak Company, 2005
Possible Printing Artifacts
• Ribbon folds and “smiles”• Burned pixel or change in resistance → streak• Dirt (on media or printhead) • Dropout (non-printed area) or streak• Thermal smear – buildup of heat in printhead that can
affect the image down the page– Aggravated by fast printing– Can be compensated with algorithms
• Parasitic resistance• Misregistration – in the case of multicolor printing
©Eastman Kodak Company, 2005
Customized images have been created/discovered to create artifacts for robustness testing.
©Eastman Kodak Company, 2005
Thermal Printer Speed IncreasesKodak 4 x 6 Print
0102030405060708090
100
1999 2000 2001 2002 2003 2004 2005
Year
Prin
t Tim
e in
Sec
onds
4720 printer
4700 printer (90 sec)
6800 printer (11 sec)
6400 printer
6850 (8 sec)
©Eastman Kodak Company, 2005
Early Thermal Printers
1989 First page-sized printer• 8 dots/min• 20 msec/line• 8.5 × 11 or 11 × 11 in.
Kodak XLS 8600 PS printer• Introduced in 1994• 4 msec/line• 12 dots/min• Clear protective laminate
©Eastman Kodak Company, 2005
Kodak Thermal Printer Portfolio
Kodak Professional 4700 photo printer Kodak Professional 8670 PS thermal printer
– 4 × 6 & 4 × 7 inch – Photo grade &
sticker prints– Cartridge load
donor
– Page size – Prints mono,
RGB & CMYK
Kodak Professional 8660 thermal printer Kodak Professional 8500 digital photo printer– Cartridge load
donor– Multiple
output sizes– Network
connectivity
– First Kodak pageprinter under$1000
©Eastman Kodak Company, 2005
Two Roll-Fed PrintersIntroduced in 2002
Kodak Photo Printer 6400thermal printer
Kodak Professional ML-500 digital photo print system
– Roll-fed receiver intended for kiosk application
– 4 × 6 inch print in 26 sec – Lower media cost
– 13 sec per 8 × 10 in. print (270 prints per hr) – 4 Printheads – Variable print length (Up to 500 ft)
©Eastman Kodak Company, 2005
Kodak EasyShare Printer Dock Plus(Announced – August 2004)
• Prints in 60 seconds• Exposure correction
built into the printer• Capability of printing
wirelessly (Bluetooth)• Built in memory card
slot
©Eastman Kodak Company, 2005
Kodak’s 2005 Thermal Printers and Kiosks
Kodak Photo Printer 6800• Roll fed receiver with a single
printhead, intended for kiosk applications
• 11 second prints, at a price that enables 2 printers/kiosk, for a net of pictures in 5.5 seconds
• Features higher productivity and somewhat lower media cost
Kodak Picture Kiosk G-3 Print Station
• Multiple configurations, with page size and 4 × 6 printers
• Can be equipped with Bluetooth and IR wireless capability for printing from PDAs or cell phone cameras
• Multiple digital inputs
©Eastman Kodak Company, 2005
Kodak Picture Maker G3 Print Station
• A bundled system of monitor, processor with CD-ROM, memory card reader, floppy disk, flat-bed scanner & thermal printer(s)
• Makes copies from original prints, CDs, picture cards from digital cameras, FLASHPIX CD & JPEG images on diskettes
• Zoom, crop, red-eye reduction, image restoration & text entry
• Touch-screen controls
©Eastman Kodak Company, 2005
People to Thank…Maurice GrayElaine BarrettJake Hastreiter
Teh-Ming KungBill Simpson
George BodemJohn CormanRob Gutierrez
Richard HenzelChuck Christ