Dr. Larisa von Riewel Heraeus Noblelight. Physical analysis of Ink-Radiation Interaction in drying processes

Transcription

1 Dr. Larisa von Riewel Heraeus Noblelight Physical analysis of Ink-Radiation Interaction in drying processes

2 Agenda topics and workflow 1 SHORT COMPANY INTRODUCTION APPLICATIONS PRINTING INDUSTRY 4 BLACK-YELLOW BEHAVIOR IN NIR AND MIDDLE WAVE RANGE 2 TECHNICAL LIGHT SOURCES BASICS 5 LAB SYSTEM BLACK.INFRARED 3 OPTICAL BEHAVIOR OF INKS WITH VARIABILITY OF WAVELENGTH 6 SUMMARY

3 Powerful solutions across the whole spectrum UV and Infrared emitters and systems, analytical lamps, flash lamps Staff: 762 (2017)

4 Specialty light solutions by Heraeus Noblelight First choice worldwide for reliable UV process solutions Stable analytical lamps support precise analysis High performance arc and flash lamps customized for reliable processes Intelligent heating solutions save energy

5 Print & packaging Innovative solutions for Drying with IR Curing of UV ink Disinfection of surfaces for packaging materials System solutions from one source for conductive surfaces Your benefits Environmentally friendly and reliable UV disinfection for efficient processes IR is used to shrink foils efficiently and reliably Depending on the type of ink, adhesive or coating, UV or IR emitters are used for drying and curing

6 Overall technical light sources 1 kw m kw m kw m kw m -2 Excimer Medium Pressure UV LED Visible Flash Lamps Halogen Short wave Carbon Medium wave Gas catalytic 100 nm nm nm

7 BEHAVIOR OF HERAEUS IR SOURCES (STANDARD) Thermal radiation is energy transfer without a medium emitted by hot matter transported by radiation Spectral distribution depends on source temperature (Planck s law) 2hπc dp( λ,t) = 5 λ C dp = λ dλ C2 exp( ) 1 Tλ 2 1 dλ hc exp( ) 1 ktλ Where: With: C1= x 10 8 Wµm 4 /m 2 C2= x 10 4 µmk

8 Behaviour of IR sources The emitted radiation varies continuously with wavelength. At any wavelength the magnitude of the emitted radiation increases with increasing temperature. The spectral region in which the radiation is concentrated depends on temperature, with comparatively more radiation appearing at shorter wavelengths as the temperature increases. Emissivity The spectral emissivity of each material is function of temperature and wavelength The emitted power is given by emissivity multiplied with the theoretical black body spectral distribution. P Object ( T, λ) * P ( λ, ) ( λ, T ) = ε T BlackBody

9 Bolzmann law for black body and the deviation of it for tungsten _= 4 where = W/m2K4

10 Wien displacement s law and the deviation of it for Wolfram When the temperature of a blackbody radiator increases, the overall radiated energy increases and the peak of the radiation curve moves to shorter wavelengths. When the maximum is evaluated from the Planck radiation formula, the product of the peak wavelength and the temperature is found to be a constant. λ max = C 3 / T λ max = wavelength of maximum intensity T = body temperatue = Third Radiation Constant (2898 µm*k) C 3

11 Optical behavior of inks Different absorption behavior of black and yellow inks in the visible, NIR up to mid infrared ranges; black absorbs significantly more energy than yellow For the same level of emitter output power an image printed with black can be completely dry but if printed with yellow this image may smear and transfer it to the paper transport rollers.

12 Optical behavior of water related to industrial light sources

13 Optical behavior of ink for different wavelengths and energy densities (yellow) Based on heating rate measurements one can choose the right wavelength for each ink type WBInk2: water based ink (95% water)

14 Heraeus solution infradry lab systems with variability of wavelength Modular construction system Scalable in printing width Scalable in drying length [IR- & AIR-shower-units] Controlled air-flow Air-Blade as kick-off for drying-process & closing process-room Air-pinching: In- & Outlet integrated in Infrared-field Air-Shower: Air-Exhaust for excellent evaporation & closing process-room High variability of wavelength: IR-Emitter from short- to medium-wave Easy & quick lamp exchange Variability of Air supply (external or internal) Position of exhaust-socket Position of electrical connection

15 Optical behavior of ink for different wavelengths and paper type (yellow) Based on heating rate measurements one can choose the right wavelength for each ink type WBInk5: water based ink high viscosity

16 Optical behavior of black and yellow ink Different absorption behavior of black and yellow inks in the visible and mid wave regions is pointed out by different values of heating rate WBInk1: water based ink (80% water)

17 Heraeus solution Black Infrared Emitter (BIR) High Power density emitter in wave spectrum up to 200 kw/m 2 for 1000 C (2560nm) up to 100 kw/m 2 for 700 C (3000nm) Outstanding infrared homogeneity (see additional slide) High emissivity of black quartz glass: great efficiency Suitable for vacuum applications, contact free Fast response time Flexible geometries: modular, scalable No cooling needed High purity ( only silicon & oxygen) Sizes: from 100 x 100 mm to 400 x 50 mm, thickness 2-4 mm 400 x 400 panels with highly customized emitter fields, thickness 2-4 mm Lifetime actual: approx h

18 Heraeus solution Black Infrared Emitter Conventional Infrared quartz tubes black.infrared panels H // I Homogeneity H // I Homogeneity operating point operating point Intensity Intensity Distance Distance emitter-substrate emitter-substrate Homogeneity dependent from distance: Operating point is a trade-off between homogeneity and intensity Homogeneity independent from distance: Operating point very close to IR source high efficiency 18

19 Optical behavior of black and yellow ink under BIR The BIR at 700 C is a black body with 3000nm wavelength that overlaps the region were black and yellow pigments have the same absorption WBInk1: water based ink (80% water)

20 Optical behavior of black and yellow ink under BIR (measurements) The BIR at 700 C is a black body with 3000nm wavelength that overlaps the region were black and yellow pigments have the same absorption WBInk1: water based ink (80% water) for thermal print heads WBInk3 and WBInk4 water based ink high viscosity

21 Lab System Black.Infrared with optimized Framework (steady)

22 SUMMARY 1 DRYING PROCESS OF WATER BASED INK DEPENDS ON WAVELENGTH AND INK RECIPIES; THERE IST NO GENERAL SOLUTION FOR OPTIMAL DRYING RATE OR IMAGE QUALITY 2 IN NEAR AND SHORT WAVE RADIATION SPECTRUM THE ABSORPTION OF BLACK AND YELLOW VARIES SIGNIFICANT AND THE HEATING RATES RESPECTIVELY. 3 A NEW TECHNICAL SOLUTION, BLACK INFRARED EMITTER, CAN OVERCOME THIS DRAWBACK AND LEVEL THE HEATING RATES

23 Apendix : Spectral measurements of different types of printing Paper