Peelable adhesive polymeric film

Abstract

Peelable polymeric film, in particular, peelable polymeric film which comprises a polymeric substrate layer and a coating layer of adhesive, and which is of particular use in the manufacture of electronic devices is described. The adhesive layer is derived from an aqueous composition which comprises an aliphatic polyurethane and is switchable.

Claims

1. A method for manufacturing an electronic device comprising: (a) heating a laminate comprising (i) a polyester film substrate having a first surface and a second surface, (ii) an adhesive coating derived from an aqueous composition comprising an aliphatic polyurethane and (iii) a glass or silicon wafer substrate, wherein the adhesive coating is disposed between the polyester film substrate and the glass or silicon wafer substrate, to a temperature of at least 150 C. for a period of at least two minutes; and (b) peeling the polyester film substrate from the glass or silicon wafer substrate to leave the adhesive coating on the glass or silicon wafer substrate.

2. The method according to claim 1 comprising the steps of: (c) providing a polyester film comprising (i) a polyester film substrate having a first surface and a second surface and (ii) an adhesive coating derived from an aqueous composition comprising an aliphatic polyurethane wherein said adhesive coating is disposed on a first surface of said polyester film substrate; (d) laminating a glass or silicon wafer substrate to the first surface of the polyester film substrate such that the adhesive coating is disposed between the polyester film substrate and the glass or silicon wafer substrate; (e) processing the laminate by subjecting it to a temperature of at least 150 C. for a period of at least 2 minutes and disposing one or more electronic components on the second surface of the polyester film substrate; and (f) peeling the polyester film substrate from the glass or silicon wafer substrate to leave the adhesive coating on the glass or silicon wafer substrate.

3. The method according to claim 1, wherein following the step of peeling the polyester film substrate from the glass or silicon wafer substrate, the first surface of the polyester film substrate is free from adhesive coating.

4. The method according to claim 1, wherein the electronic device is an electronic display device, or is a photovoltaic cell or a semiconductor device.

5. The method of claim 1, wherein said temperature is no more than 200 C.

6. The method according to claim 1, wherein following the step of peeling the polyester film substrate from the glass or silicon wafer substrate, the polyester film substrate is used as a substrate in said electronic device.

7. The method according to claim 1, wherein the change in the glass transition temperature (at onset) of the aqueous coating after drying and heating to 150 C. for two minutes, is no more than about 15 C., as measured by modulated differential scanning calorimetry (DSC).

8. The method according to claim 1, wherein the adhesive coating exhibits a CO.sub.2 peak relative intensity of less than 0.2, wherein CO.sub.2 peak relative intensity is defined as the intensity of the CO.sub.2 asymmetric stretching absorption in the region of 2200 to 2400 cm.sup.1 of the infrared spectrum as measured by FTIR-TGA analysis at 18 minutes during a temperature cycle which consists of heating the adhesive coating at 10 C./min from 40 C. to an isothermal hold at 200 C. for 5 minutes, relative to the intensity of the same CO.sub.2 asymmetric stretching absorption of atmospheric air in the same temperature cycle, and/or wherein the adhesive coating evolves no more than 31 g of CO.sub.2 per 25 mg of the adhesive coating as measured by FTIR-TGA analysis of the CO.sub.2 asymmetric stretching absorption in the infrared spectrum at 18 minutes during a temperature cycle which consists of heating the adhesive coating at 10 C./min from 40 C. to an isothermal hold at 180 C. for 5 minutes.

9. The method according to claim 1, wherein the aqueous composition further comprises acrylic monomers, wherein the acrylic monomers are selected from the group consisting of methyl methacrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, butyl methacrylate, pentaerythritol acrylate type materials and hydroxyethyl methacrylate (HEMA).

10. The method according to claim 9, wherein the aqueous composition is a Type 1 urethane-acrylic hybrid polymer dispersion.

11. The method according to claim 9, wherein the aqueous composition is a Type 2 urethane-acrylic hybrid polymer dispersion.

12. The method according to claim 1, wherein the aliphatic polyurethane is derived from an aliphatic diisocyanate and a polyester polyol, and wherein the aliphatic diisocyanate is selected from the group consisting of 1,6-diisocyanatohexane (HDI), 1,4-diisocyanatobutane, 1-isocyanato-5-isocyanato-methyl-3,3,5-trimethyl-cyclohexane or isophorone diisocyanate (PIDI), bis(4-isocyanatocyclohexyl)methane, cyclohexane diisocyanate (CHDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), 1,3-bis(isocyanatomethyl)cyclohexane (H.sub.6XDI), 1,1 methylenebis(4-isocyanato)-cyclohexane (H.sub.12MDI) and mixtures thereof and/or the polyester polyol is selected from the group consisting of polycaprolactone diols, polycarbonate diols and mixtures thereof.

13. The method according to claim 1, wherein the aqueous composition further comprises a diluent, wherein the diluent is selected from the group consisting of N-ethyl pyrrolidone (NEP), and butyl diglycol.

14. The method according to claim 1, wherein the adhesive coating has a total nitrogen content in the range from about 2 to about 6 mol%.

15. The method according to claim 1, wherein the ratio of nitrogen to carbon in the adhesive coating is in the range from 0.01 to about 0.05.

16. The method according to claim 1, wherein the aqueous composition from which the adhesive coating is derived comprises aliphatic polyurethane, poly(butylmethacrylate), polycaprolactone and poly(hexamethylene carbonate).

17. The method according to claim 16, wherein the aliphatic polyurethane is present in an amount of about 5 to 15 mol%, the poly(butylmethacrylate) is present in an amount of about 40 to 80 mol%, the polycaprolactone is present in an amount of about 7 to 19 mol%, and the poly-(hexamethylene carbonate) is present at amount of about 5 to 15 mol%, based on the total content of carbonyl group-containing species present in the composition.

18. A laminate comprising (i) a polyester film substrate having a first surface and a second surface, (ii) an adhesive coating derived from an aqueous composition comprising an aliphatic polyurethane, and (iii) a glass or silicon wafer substrate, wherein the adhesive coating is disposed between the polyester film substrate and the glass or silicon wafer substrate, wherein there is a change in the plane of failure of the adhesive coating after heating to a temperature of at least 150 C.

19. The laminate according to claim 18, wherein the adhesion between the polyester film substrate and the adhesive coating is greater than the adhesion between the adhesive coating and the glass or silicon wafer substrate and wherein, following the change in the plane of failure of the adhesive coating, the adhesion between the glass or silicon wafer and the adhesive coating is greater than the adhesion between the adhesive coating and the polyester film substrate.

20. The laminate according to claim 18, wherein the change in the glass transition temperature (at onset) of the aqueous coating after drying and heating to 150 C. for two minutes, is no more than about 15 C. as measured by modulated differential scanning calorimetry (DSC).

21. The laminate according to claim 18, wherein the adhesive coating exhibits a CO.sub.2 peak relative intensity of less than 0.2, wherein CO.sub.2 peak relative intensity is defined as the intensity of the CO.sub.2 asymmetric stretching absorption in the region of 2200 to 2400 cm.sup.1 of the infrared spectrum as measured by FTIR-TGA analysis at 18 minutes during a temperature cycle which consists of heating the adhesive coating at 10 C./min from 40 C. to an isothermal hold at 200 C. for 5 minutes, relative to the intensity of the same CO.sub.2 asymmetric stretching absorption of atmospheric air in the same temperature cycle, and/or wherein the adhesive coating evolves no more than 31 g of CO.sub.2 per 25 mg of the adhesive coating as measured by FTIR-TGA analysis of the CO.sub.2 asymmetric stretching absorption in the infrared spectrum at 18 minutes during a temperature cycle which consists of heating the adhesive coating at 10 C./min from 40 C. to an isothermal hold at 180 C. for 5 minutes.

22. The laminate according to claim 18 wherein the aqueous composition further comprises acrylic monomers, wherein the acrylic monomers are selected from the group consisting of methyl methacrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, butyl methacrylate, pentaerythritol acrylate type materials and hydroxyethyl methacrylate (HEMA).

23. The laminate according to claim 22, wherein the aqueous composition is a Type 1 urethane-acrylic hybrid polymer dispersion.

24. The laminate according to claim 22, wherein the aqueous composition is a Type 2 urethane-acrylic hybrid polymer dispersion.

25. The laminate according to claim 18, wherein the aliphatic polyurethane is derived from an aliphatic diisocyanate and a polyester polyol, and wherein the aliphatic diisocyanate is selected from the group consisting of 1,6-diisocyanatohexane (HDI), 1,4-diisocyanatobutane, 1-isocyanato-5-isocyanato-methyl-3,3,5-trimethyl-cyclohexane or isophorone diisocyanate (PIDI), bis(4-isocyanatocyclohexyl)methane, cyclohexane diisocyanate (CHDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), 1,3-bis(isocyanatomethyl)cyclohexane (H.sub.6XDI), 1,1 methylenebis(4-isocyanato)-cyclohexane (H.sub.12MDI) and mixtures thereof and/or the polyester polyol is selected from the group consisting of polycaprolactone diols, polycarbonate diols and mixtures thereof.

26. The laminate according to claim 18, wherein the aqueous composition further comprises a diluent, wherein the diluent is selected from the group consisting of N-ethyl pyrrolidone (NEP) and butyl diglycol.

27. The laminate according to claim 18, wherein the adhesive coating has a total nitrogen content in the range from about 2 to about 6 mol% %.

28. The laminate according to claim 18, wherein the ratio of nitrogen to carbon in the adhesive coating is in the range from 0.01 to about 0.05.

29. The laminate according to claim 18, wherein the aqueous composition from which the adhesive coating is derived comprises aliphatic polyurethane, poly(butylmethacrylate), polycaprolactone and poly(hexamethylene carbonate).

30. The laminate according to claim 29, wherein the aliphatic polyurethane is present in an amount of about 5 to 15 mol%, the poly(butylmethacrylate) is present in an amount of about 40 to 80 mol%, preferably about 68 mol%, the polycaprolactone is present in an amount of about 7 to 19 mol%, and the poly(hexamethylene carbonate) is present at amount of about 5 to 15 mol%, based on the total content of carbonyl group-containing species present in the composition.

31. A polyester film comprising a polyester film substrate and an adhesive coating, wherein the adhesive coating is derived from an aqueous composition comprising an aliphatic polyurethane and wherein the change in the glass transition temperature at onset (Tg (onset)) of the adhesive coating after heating to 150 C. for two minutes, is no more than about 15 C. as measured by modulated differential scanning calorimetry (DSC).

32. The film according to claim 31, wherein the adhesive coating exhibits a CO.sub.2 peak relative intensity of less than 0.2 wherein CO.sub.2 peak relative intensity is defined as the intensity of the CO.sub.2 asymmetric stretching absorption in the region of 2200 to 2400 cm.sup.1 of the infrared spectrum as measured by FTIR-TGA analysis at 18 minutes during a temperature cycle which consists of heating the adhesive coating at 10 C./min from 40 C. to an isothermal hold at 200 C. for 5 minutes, relative to the intensity of the same CO.sub.2 asymmetric stretching absorption of atmospheric air in the same temperature cycle, and/or wherein the adhesive coating evolves no more than 31 g of CO.sub.2 per 25 mg of the adhesive coating as measured by FTIR-TGA analysis of the CO.sub.2 asymmetric stretching absorption in the infrared spectrum at 18 minutes during a temperature cycle which consists of heating the adhesive coating at 10 C./min from 40 C. to an isothermal hold at 180 C. for 5 minutes.

33. The film according to claim 31, wherein the aqueous composition further comprises acrylic monomers, wherein the acrylic monomers are selected from the group consisting of methyl methacrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, butyl methacrylate, pentaerythritol acrylate type materials and hydroxyethyl methacrylate (HEMA).

34. The film according to claim 33, wherein the aqueous composition is a Type 1 urethane-acrylic hybrid polymer dispersion.

35. The film according to claim 33, wherein the aqueous composition is a Type 2 urethane-acrylic hybrid polymer dispersion.

36. The film according to claim 31, wherein the aliphatic polyurethane is derived from an aliphatic diisocyanate and a polyester polyol, and wherein the aliphatic diisocyanate is selected from the group consisting of 1,6-diisocyanatohexane (HDI), 1,4-diisocyanatobutane, 1-isocyanato-5-isocyanato-methyl-3,3,5-trimethyl-cyclohexane or isophorone diisocyanate (PIDI), bis(4-isocyanatocyclohexyl)methane, cyclohexane diisocyanate (CHDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), 1,3-bis(isocyanatomethyl)cyclohexane (H.sub.6XDI), 1,1 methylenebis(4-isocyanato)-cyclohexane (H.sub.12MDI) and mixtures thereof and/or the polyester polyol is selected from the group consisting of polycaprolactone diols, polycarbonate diols and mixtures thereof.

37. The film according to claim 31, wherein the aqueous composition further comprises a diluent, wherein the diluent is selected from the group consisting of M-ethyl pyrrolidone (NEP) and butyl diglycol.

38. The film according to claim 31, wherein the adhesive coating has a total nitrogen content in the range from about 2 to about 6 mol%.

39. The film according to claim 31, wherein the ratio of nitrogen to carbon in the adhesive coating is in the range from 0.01 to about 0.05.

40. The film according to claim 31, wherein the aqueous composition from which the adhesive coating is derived comprises aliphatic polyurethane, poly(butylmethacrylate), polycaprolactone and poly(hexamethylene carbonate).

41. The film according to claim 40, wherein the aliphatic polyurethane is present in an amount of about 5 to 15 mol%, the poly(butylmethacrylate) is present in an amount of about 40 to 80 mol%, the polycaprolactone is present in an amount of about 7 to 19 mol%, and the poly(hexamethylene carbonate) is present at amount of about 5 to 15 mol%, based on the total content of carbonyl group-containing species present in the composition.

42. A polyester film comprising a polyester film substrate and an adhesive coating, wherein the adhesive coating is derived from an aqueous composition comprising an aliphatic polyurethane and wherein the adhesive coating exhibits a CO.sub.2 peak relative intensity of less than 0.2, wherein CO.sub.2 peak relative intensity is defined as the intensity of the CO.sub.2 asymmetric stretching absorption in the region of 2200 to 2400 cm.sup.1 of the infrared spectrum as measured by FTIR-TGA analysis at 18 minutes during a temperature cycle which consists of heating the adhesive coating at 10 C./min from 40 C. to an isothermal hold at 200 C. for 5 minutes, relative to the intensity of the same CO.sub.2 asymmetric stretching absorption of atmospheric air in the same temperature cycle, and/or wherein the adhesive coating evolves no more than 31 g of CO.sub.2 per 25 mg of the adhesive coating as measured by FTIR-TGA analysis of the CO.sub.2 asymmetric stretching absorption in the infrared spectrum at 18 minutes during a temperature cycle which consists of heating the adhesive coating at 10 C./min from 40 C. to an isothermal hold at 180 C. for 5 minutes.

43. The film according to claim 42, wherein the aqueous composition further comprises acrylic monomers, wherein the acrylic monomers are selected from the group consisting of methyl methacrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, butyl methacrylate, pentaerythritol acrylate type materials and hydroxyethyl methacrylate (HEMA).

44. The film according to claim 43, wherein the aqueous composition is a Type 1 urethane-acrylic hybrid polymer dispersion.

45. The film according to claim 44, wherein the aqueous composition is a Type 2 urethane-acrylic hybrid polymer dispersion.

46. The film according to claim 42, wherein the aliphatic polyurethane is derived from an aliphatic diisocyanate and a polyester polyol, and wherein the aliphatic diisocyanate is selected from the group consisting of 1,6-diisocyanatohexane (HDI), 1,4-diisocyanatobutane, 1-isocyanato-5-isocyanato-methyl-3,3,5-trimethyl-cyclohexane or isophorone diisocyanate bis(4-isocyanatocyclohexyl)methane, cyclohexane diisocyanate (CHDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), 1,3-bis(isocyanatomethyl)cyclohexane (H.sub.6XDI), 1,1 methylenebis(4-isocyanato)-cyclohexane (H.sub.12MDI) and mixtures thereof and/or the polyester polyol is selected from the group consisting of polycaprolactone diols, polycarbonate diols and mixtures thereof.

47. The film according to claim 42, wherein the aqueous composition further comprises a diluent, preferably wherein the diluent is selected from the group consisting of N-ethyl pyrrolidone (NEP) and butyl diglycol.

48. The film according to claim 42, wherein the adhesive coating has a total nitrogen content in the range from about 2 to about 6 mol%.

49. The film according to claim 42, wherein the ratio of nitrogen to carbon in the adhesive coating is in the range from 0.01 to about 0.05.

50. The film according to claim 42, wherein the aqueous composition from which the adhesive coating is derived comprises aliphatic polyurethane, poly(butylmethacrylate), polycaprolactone and poly(hexamethylene carbonate).

51. The film according to claim 50, wherein the aliphatic polyurethane is present in an amount of about 5 to 15 mol%, the poly(butylmethacrylate) is present in an amount of about 40 to 80 mol%, the polycaprolactone is present in an amount of about 7 to 19 mol%, and the poly(hexamethylene carbonate) is present at amount of about 5 to 15 mol%, based on the total content of carbonyl group-containing species present in the composition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1(a) and (b) are modulated DSC traces for NeoRad R440;

(2) FIG. 1(c) is a plot of Heat Capacity vs temperature for NeoRad 440 as determined by modulated DSC;

(3) FIGS. 2(a) and (b) are modulated DSC traces for Alberdingk Lux 399;

(4) FIG. 2(c) is a plot of heat capacity vs temperature for Alberdingk Lux 399 as determined by modulated DSC;

(5) FIGS. 3(a) and (b) are modulated DSC traces for Alberdingk U8001;

(6) FIG. 3(c) is a plot of heat capacity vs temperature for Alberdingk U8001 as determined by modulated DSC;

(7) FIGS. 3(d) and 3(e) are DMA traces for Alberdingk U8001;

(8) FIGS. 4(a) and (b) are modulated DSC traces for Incorex W2205;

(9) FIG. 4(c) is a plot of heat capacity vs temperature for Incorez W2205 as determined by modulated DSC;

(10) FIGS. 4(d) and (e) are DMA traces for Incorez W2205;

(11) FIG. 5 shows TGA curves for NeoRad R440, Alberdingk Lux 399, Alberdingk U8001 and Incorez W2205 at a temperature of 180 C.;

(12) FIG. 6 shows TGA curves for NeoRad R440, Alberdingk Lux 399, Alberdingk U8001 and Incorez W2205 at a temperature of 200 C.;

(13) FIG. 7 shows TGA curves for NeoRad R440, Alberdingk Lux 399, Alberdingk U8001 and Incorez W2205 at a temperature of 220 C.;

(14) FIG. 8 shows chemigrams for NeoRad R440, Alberdingk Lux 399, Alberdingk U8001 and Incorez W2205 at a temperature of 180 C.;

(15) FIG. 9 shows chemigrams for NeoRad R440, Alberdingk Lux 399, Alberdingk U8001 and Incorez W2205 at a temperature of 200 C.; and

(16) FIG. 10 shows chemigrams for NeoRad R440, Alberdingk Lux 399, Alberdingk U8001 and Incorez W2205 at a temperature of 220 C.

(17) FIG. 11 shows the apparatus used to measure the amount of carbon dioxide evolved in the FTIR-TGA experiments, and the calibration thereof.

(18) FIG. 12 shows the data collected from the apparatus of FIG. 11 used to calibrate the experiment.

(19) In the Figures, the terms Rev Cp and Nonrev Cp refer to reversing heat flow and non-reversing heat flow, respectively; the former thermal effects relate to the measurement of Tg and Tm, and the latter kinetic effects to crystallisation, as will be appreciated by the skilled person.

EXAMPLES

(20) In the examples, adhesive coated polyester films were prepared, laminated to a glass slide and heated to a temperature of 150 C. for 2 minutes. The peel strength of the polyester film substrate from the glass or silicon wafer substrate was assessed. The laminates were also analysed for any sign of bubbling of the adhesive coating. The adhesive coatings used in each case are detailed in the specific examples.

Example 1

(21) Coated films were prepared as follows. Polyethylene terephthalate was melt extruded, cast onto a cooled rotating drum and stretched in the direction of extrusion to approximately 3 times its original dimensions at a temperature of 150 C. The film was passed into a stenter oven at a temperature of 120 C. where the film was dried and stretched in the transverse direction to approximately 3 times its original dimensions and heat-set at a temperature of about 200 C. The heat-set biaxially stretched film was then unwound and then further heat-stabilised in a roll-to-roll process by passing the film through an additional set of ovens, of which the maximum temperature was above 150 C., for a duration of no more than 2 seconds. The film was transported through the ovens under a low line tension, allowing it to relax and stabilize further. The heat-stabilised film was coated on its upper surface with an adhesive coating composition as described in Table 1 below in an amount sufficient (about 50 m wet-coat thickness) to provide the desired final dry thickness (which is from 7-15 m). The polyester film substrate had a thickness of 125 m in the final film.

(22) The coated film was then laminated to a glass slide substrate (7.5 cm in length) by passing through a laminator nip roller at a speed of 25.4 cm/minute at a temperature of 80 C. and a pressure of 172 kPa. The laminates obtained were then heated to a temperature of 150 C. for 2 minutes and assessed for peel strength and bubbling.

(23) TABLE-US-00001 TABLE 1 Adhesive Observations Supplier Description Alberdingk AC2523 Bubbling during thermal cure. Alberdingk Boley GmbH Self-crosslinking acrylic copolymer Neocryl XK176 Bubbling during thermal cure. DSM Neoresins Acrylic copolymer emulsion Butvar BR Did not laminate to glass at all. Solutia Inc. Poly vinyl butyral Alberdingk LUX 250 Extensive bubbling during thermal cure. Alberdingk Boley GmbH Solvent-free, hard-elastic, UV-curable Cohesive failure during peels. polyurethane dispersion. Alberdingk LUX 515 Bubbling during thermal cure. Cohesive Alberdingk Boley GmbH Aqueous anionic UV-crosslinkable dispersion failure during peels. based on an acrylic acid esters copolymer. Neocryl XK-90 Bubbling during thermal cure. Non-clean DSM Neoresins Acrylic copolymer emulsion. peels at incorrect interface. Alberdingk LUX 3381 Extensive bubbling during thermal cure. Alberdingk Boley GmbH Aqueous, UV crosslinkable, solvent-free Peels not clean. polymer dispersion based on a copolymer of acrylic acid esters. Alberdingk LUX 399 Some bubbling during thermal cure. Alberdingk Boley GmbH Aqueous, anionic, UV-crosslinkable dispersion based on an aliphatic polyurethane & acrylic acid esters copolymer. Alberdingk U8001 Performed well at 150 C., but bubbling at Alberdingk Boley GmbH Aqueous, anionic, solvent-free, low viscous 180 C. dispersion of an aliphatic polyester- polyurethane without free isocyanate groups, (contains triethylamine) Incorez W2205 Performed very well Incorez Ltd. Polyurethane acrylic hybrid dispersion with a polycarbonate backbone Neorad R440 Cracking during thermal cure. Cohesive DSM Aliphatic urethane dispersion failure at peel.

Example 2

(24) Further analysis was conducted on three coatings from Example 1 which exhibited at least some aspects of the required property profile, together with a coating (Neorad R440) which did not exhibit the required properties. The following coatings were thus identified: (i) Neorad R440 (ii) Alberdingk Lux 399 (iii) Alberdingk U8001; and (iv) Incorez W2205

(25) Coatings (iii) and (iv) exhibited the best switchability in the experiments of Example 1. Coated films were prepared using these four adhesive compositions and they were analysed by modulated DSC and DMA as described above. The results are presented in FIGS. 1 to 4. The data for the glass transition temperatures (at onset) as measured by modulated DSC is provided in Table 2 below. The reheat conditions were 150 C. for 2 minutes in air.

(26) TABLE-US-00002 TABLE 2 As received Reheat Tg Tg Adhesive Tg Onset Tg End Tg Onset Tg End Onset End Coating ( C.) ( C.) ( C.) ( C.) ( C.) ( C.) Neorad 46.05 33.61 16.16 +4.91 29.89 38.52 R440 Alberdingk 47.89 34.10 17.63 +10.64 30.26 44.82 Lux 399 Alberdingk 50.42 43.34 50.04 43.14 0.38 0.20 U8001 Incorez 60.20 56.44 58.07 51.65 2.13 4.79 W2205

(27) The results demonstrate that the adhesive coatings which showed the most effective switching are those where the change in Tg following heating to high temperatures is less than 15 C. i.e. the Alberdingk U8001 and the Incorez0 W2205 adhesive coatings.

Example 3

(28) Further analysis of adhesive coatings (i) to (iv) from Example 2 was performed using FTIR-TGA. The samples were analysed as described herein with a heating rate of 10 C./minute using three different final temperatures (180 C., 200 C. and 220 C.) for the 5-minute isothermal hold. Visual inspection of the sample pans after heating showed that the Neorad R440 adhesive coating had bubbled by 180 C. The Alberdingk U8001 coating had bubbled by 200 C. The Incorez W2205 coating exhibited almost no bubbling up to 200 C.

(29) The FTIR-TGA plots and chemigrams obtained are presented in FIGS. 5 to 10. In each spectrum recorded and illustrated in FIGS. 5, 6 and 7 (which used 180, 200 and 220 C. final isothermal holds, respectively), the upper lines correspond to the TGA curves, while the lower lines are the chemigrams of the CO.sub.2 region (2400-2200 cm.sup.1). The chemigrams are also shown in FIGS. 8, 9 and 10. The spike recorded at 180 C. in the TGA curves is an anomaly and can be ignored. Any spikes observed towards the end of the chemigram sample are associated with opening the furnace and so can be ignored because they are not representative of the sample result. The initial loss which was evident in all of the TGA curves was due to the loss of water from the sample (all samples were made up with distilled water in order to be analysed by FTIR-TGA).

(30) The CO.sub.2 peak relative intensity data, as measured by the FTIR-TGA analysis described herein, are presented in Table 3 below.

(31) TABLE-US-00003 TABLE 3 Relative Relative Relative intensity of intensity of intensity of Adhesive CO.sub.2 peak CO.sub.2 peak CO.sub.2 peak composition at 180 C. at 200 C. at 220 C. Neorad R440 0.1 0.2 0.6 Alberdingk Lux 399 0.2 0.3 0.5 Alberdingk U8001 0.1 0.5 0 Incorez W2205 0.1 0 0.5

(32) The FTIR-TGA experiments demonstrated that CO.sub.2 evolution increases with increasing temperature. In particular, the Neorad R440 and the Alberdingk Lux 399 coatings gave off increasing amounts of CO.sub.2 as the temperature increased. In addition, for Alberdingk Lux 399, the onset of CO.sub.2 evolution occurred at a much lower starting temperature compared to the other resins. The Alberdingk U8001 coating exhibited reasonable performance up to 180 C. but evolved significant amounts of CO.sub.2 at 200 C. For Incorez W2205, the coating exhibits excellent performance within the target temperature range of no more than 200 C. in that only very small amounts of CO.sub.2 were evolved. While the Incorez W2205 coating did exhibit a relatively large % weight loss in the range of 180-220 C., this is due to the evolution of water (as demonstrated by the infra-red spectra of the coating at these temperatures).

(33) The mass (in g) of carbon dioxide evolved at 18 minutes during the temperature cycle of the FTIR-TGA analysis described herein, as measured for the relatively more intense, higher wavenumber absorption peak at 2364 cm.sup.1 of the multiplet observed for the asymmetric stretching absorption of CO.sub.2, is presented in Table 4 below.

(34) TABLE-US-00004 TABLE 4 Amount of Amount of Amount of Adhesive CO.sub.2 evolved CO.sub.2 evolved CO.sub.2 evolved composition at 180 C. at 200 C. at 220 C. Neorad R440 31.21 36.81 31.06 Alberdingk Lux 399 34.24 4.09 3.64 Alberdingk U8001 30.61 31.82 9.39 Incorez W2205 27.73 32.58 15.6

(35) The results in Table 4 indicate that the Alberdingk Lux 399 coating has degraded (or cured) and that the large fall in CO.sub.2 with temperature can be attributed to that effect, as supported by the modulated DSC and DMA analysis. The Neorad R440 continues to generate CO.sub.2 during the temperature rise and the significant Tg change in the modulated DSC and DMA analysis shows that there is degradation or other significant change in the system. Both Incorez W2205 and Alberdingk U8001 gave superior performance across all temperature ranges, but within the target temperature range of from 150 to 200 C., and specifically at 180 C., the Incorez W2205 coating exhibited significantly reduced CO.sub.2 generation, and therefore provided significantly superior performance.

Example 4

(36) The analytical results for Incorez W2205 are set out below.

(37) NMR

(38) The carbonyl group-containing species present in Incorez W2205 are demonstrated as follows. A sample of Incorez W2205 was dissolved in deuterated pyridine and analysed by NMR techniques. The NMR spectrum demonstrates the presence of N-ethyl pyrrolidone and butyl diglycol solvents in the composition. The NMR spectrum further demonstrates the presence of poly(butylmethacrylate), polycaprolactone, poly(hexamethylenecarbonate) and aliphatic polyurethane. The approximate quantification of the composition based on the distribution of carbonyl species is shown in Table 5 below.

(39) TABLE-US-00005 TABLE 5 Carbonyl type Mole % Polycarbonate: O(CO)O 9 Polyurethane: O(CO)NHRNH(CO)O 9 Polycaprolactone: O(CO) 14 Acrylic: O(CO) 68 Total CO integral 100
FTIR/Raman

(40) A film of the adhesive Incorez W2205 was cast and left to dry overnight on a glass slide at room temperature, and the sample was then subjected to FTIR and Raman analysis. The Raman and FTIR analyses demonstrate that the dried film comprises poly(butylmethacrylate) as a major fraction. No unreacted isocyanate was observed in the dry film.

(41) Inorganic Analysis

(42) Inorganic elemental analysis was carried after drying the adhesive composition at 200 C. for 3 hours. The average % w/w was 2.4% N, 66.4% C and 9.5% H, i.e. an N/C molar ratio of 0.03.

(43) XPS

(44) A drop of the adhesive composition was dried overnight at approximately 40 C. on a piece of clean PET film. The bulk and surface of the dried sample were analysed using XPS and found to have the same composition which means that no detectable macroscopic separation occurred during drying. The XPS analysis confirmed an N/C molar ratio of 0.03.