Deliverable [11.9]

ML² – Multi Layer Micro Lab

D11.9 - Demonstration of coating materials

1. Introduction ......................................................................................................................................... 2

2. UV embossing lacquer chemistry ....................................................................................................... 2

2.1. The main components in UV embossing lacquer composition .................................................. 2

2.2. UV Curing Polymerization Process ............................................................................................ 3

3. UV cured polymer materials properties .............................................................................................. 4

3.1. UV Curing Lacquer: Primary Properties..................................................................................... 4

3.2. UV Curing Lacquer: Secondary Properties ................................................................................ 4

4. UV lacqer testing method ................................................................................................................... 5

4.1. Coating adhesion test ................................................................................................................ 5

5. The embossing lacquer developed ..................................................................................................... 8

5.1. Lentex 50, general purpose UV lacquer .................................................................................... 8

5.2. Lentex 700, general purpose UV lacquer .................................................................................. 9

5.3. AntiK 51, hydrophilic UV lacquer ............................................................................................. 10

5.4. MIL587 High refractive index UV embossing lacquer .............................................................. 11

5.5. MIL587-3 High refractive index UV embossing lacquer........................................................... 12

5.6. YKLJ-A PMMA UV Embossing Lacquer .................................................................................. 13

5.7. YKLJ-B PMMA UV Embossing Lacquer .................................................................................. 14

1. Introduction

UV embossing technology is able to replicate nano and micro structure precisely on the substrate surface. The process can fabricate the structure with depths from as small as few nanometers to several hundred microns. The principle can be further applied indirectly and directly to produce optical components, including microfluidic channels of lab-on chips. Roll to roll UV embossing replication is a continuous manufacturing method which is able to produce large volume high quality nano and micro surface structure at relatively low cost. Direct embossing is another way to produce nano, micro and smooth flat surface on to the optical components.

The advantages of the technology are including that refractive index matching, super transparency, higher Tg and low birefringence. The properties required by the optical application can be achieved by formulating UV curing lacquer.

This report will cover the key elements of UV curing lacquer materials and substrates, also mould tooling, and embossing process. The discussion will be focused on primary and secondary material property requirements, and also the application examples.

2. UV embossing lacquer chemistry

There are two main category of UV curable lacquer, one is based on the free radical acrylate polymerization and another is cationic epoxy/acrylate hybrid polymerization. Since the cationic polymerization is relative slower chain reaction, it is not suited for a roll to roll embossing process. Contrast to cationic polymerization, free radical polymerization is fast which provided possibility to have the roll to roll process line spend to maintain at speed up to 30-50 meter per minute.

2.1. The main components in UV embossing lacquer composition

The main components in a free radical acrylate lacquer composition:

Oligomer

Monomer

Pigment

Additives

Photo initiator

The main components in a cationic epoxy/acrylate hybrid lacquer composition:

Epoxy

Polyol

Oligomer

Monomer

Pigment

Additives

Photo initiator

Some commonly used monomers and oligomers in the formulation:

2.2. UV Curing Polymerization Process

The free radical acrylate polymerization is started from a free radical which is generated by a photo initiator exposed to the UV light.

3. UV cured polymer materials properties

The UV curing technology was widely used in verity industry, coating, printing, imprint, microelectronic,….. Depending on the applications, especially for the roll to roll microfluidic channels application, we define them as primary properties which are required in general all the application, and secondary properties which are special required for special application.

3.1. UV Curing Lacquer: Primary Properties

Good adhesion to substrate surface

Good peeling from mould surface

High transparency, low haze, low colour

High Tg

Good anti-scratch

Refractive index RI= 1.50 -1.56

Low birefringency

Good surface wetting

Right viscosity

Shrinkage control

Curing speed

Chemical resistant: alcohols, acid, bases, polar solvent

Halogen free

3.2. UV Curing Lacquer: Secondary Properties

Antistatic

Conductive

Super - hydrophilic

Super - hydrophobic

Good weathering stability

Good metallization adhesion

Refractive index RI 1.56

Food contact applicable

High purity, low extractable

Biocompatible

Biodegradable

Low odour

Colour

4. UV lacqer testing method

4.1. Coating adhesion test

The cross hatch adhesion test was used to evaluate the coating adhesion on the substrate. This test method follows American standard test method (ASTM) – D3002 and D3359.This test is fast and simple to perform with an inexpensive cross-hatch cutter test kit. A lattice pattern is cut into the finish film down to the substrate using a cross-hatch cutter. The test area is then brushed diagonally five times in each direction to remove any loose film finish particles. A special tape for testing adhesion is then firmly applied over the crosshatch test area and removed quickly by pulling the tape back off of the test area to reveal the amount of coating lifted off by the test tape. The cross-hatched test area is then visually compared to ASTM standards D3002 and D3359. In the standard list, there are five charts with visual diagrams of varying degrees of film pull-off. ASTM class 5B illustrates no film pull-off, representing the highest level of adhesion. ASTM class 1B illustrates between 35% and 65% of the film removed, representing the poorest adhesion. Class 2B-4B represent varying degrees of adhesion properties that fall between class 1B and 5B. (See illustration provided.) By the nature of this visual comparison, the results are sometimes somewhat subjective and not always definitive with a numerical value associated with this test. Complete test methods may be found on ASTM website (www.astm.org).

Figure 4.1 Cross hatch addesion testing kits

Figure 4.2 Cross hatch addesion testing failure illustration patterns.

5. The embossing lacquer developed

5.1. Lentex 50, general purpose UV lacquer

Lentex 50 is a low viscosity UV lacquer specially formulated for nano and micro

structures of depth around microns.. It is no yellowing, high Tg(100°C).

5.2. Lentex 700, general purpose UV lacquer

Lentex 700 is a medium viscosity UV lacquer specially formulated for micro structures of

depth around 1- 150 microns.. It is no yellowing, high Tg(115°C).

5.3. AntiK 51, hydrophilic UV lacquer

Antik 51 is a super hydrophilic UV lacquer specially formulated for antistatic surface and it also offers good capillary force for aqueous solution.

5.4. MIL587 High refractive index UV embossing lacquer

MIL587 is a medium viscosity high refractive index UV lacquer specially formulated for micro optics structures.

5.5. MIL587-3 High refractive index UV embossing lacquer

MIL587-3 is a high viscosity high refractive index UV lacquer specially formulated for micro optics structures.

5.6. YKLJ-A PMMA UV Embossing Lacquer

YKLJ-A is formulated for micro structure embossing on PMMA substrate.

5.7. YKLJ-B PMMA UV Embossing Lacquer

YKLJ-B is formulated for micro structure embossing on PMMA substrate.