Acrylate-terminated urethane polybutadienes from low-monomer 1:1 monoadducts from reactive olefinic compounds and diisocyanates and hydroxy-terminated polybutadienes for liquid optically clear adhesives (LOCAs)

1. A method to make a liquid optically clear adhesive comprising from 20 to 80 wt.-% of acrylate-terminated urethane polybutadienes 1) in formulations in combination with at least one liquid component selected from 30 to 70 wt.-% plasticizer and/or from 5 to 30 wt.-% reactive (meth)acrylates 2), wherein

the acrylate-terminated urethane polybutadienes 1) is made by the method comprising the steps of

A) at least one low-monomer 1:1 monoadduct with a free diisocyanate content below 2.0 wt. %

from

a1) at least one aliphatic, cycloaliphatic, and/or araliphatic diisocyanate

and

a2) at least one reactive olefinic compound having at least one methacrylate group and/or acrylate group and/or vinyl ether group and exactly one OH group

B) with at least one hydroxy-terminated polybutadiene and/or one at least partially or completely hydrogenated hydroxyterminated polybutadiene, and

C) with of at least one polymerization inhibitor

wherein the at least one low-monomer 1:1 monoadduct with a free diisocyanate content below 2.0 wt. % comprises a NCO group wherein the liquid optically clear adhesive is substantially transparent for optical applications wherein the liquid optically clear adhesive has at least 90% transmittance when air is used as a blank measured following the DIN 5033.

2. The method according to claim 1 , wherein the ratio of the NCO groups of component A) to the OH groups of component B) ranges from 1.2:1 and 1:40 wherein the liquid optically clear adhesive is substantially transparent for optical applications wherein, after 150° C. for 60 minute, the liquid optically clear adhesive has at least 90% transmission over the range of from 380 to 780 nm and a haze % of from 0.40 to 0.65.

3. The method according to claim 1 , wherein the low-content-monomer 1:1 monoadducts A) are prepared, from, as starting compounds,

a1) at least one aliphatic, cycloaliphatic and/or araliphatic diisocyanate in an amount of 1-20 mol, and

a2) 1 mol of at least one reactive olefinic compound having at least one methacrylate group and/or acrylate group and/or vinyl ether group and exactly one OH group, obtained by reaction in a temperature range of 40-120° C., the unreacted diisocyanate being separated off subsequently by a short-path distillation at 80-220° C./0.01-10 mbar from the reaction product,

wherein the short-path distillation takes place in the presence of

a3) at least one inhibitor which possesses at least one functional group reactive toward NCO groups

wherein the liquid optically clear adhesive is substantially transparent for optical applications wherein, after 200° C. for 60 minute, the liquid optically clear adhesive has at least 90% transmittance when air is used as a blank measured following the DIN 5033 and a haze % of from 0.40 to 0.80, and a viscosity at 25° C. of from 2450 cP to 10,800 cP.

4. A liquid optically clear adhesive comprising

1) from 20 to 80 wt.-% of acrylate terminated urethane polybutadienes, wherein the acrylate terminated urethane polybutadienes are obtained by the reaction of

A) a low-monomer-content 1:1 monoadduct, having a free diisocyanate content of less than 2 wt. %, the monoadduct being based on at least one aliphatic, cycloaliphatic and/or araliphatic diisocyanate a1) and at least one reactive olefinic compound having at least one methacrylate group and/or acrylate group and/or vinyl ether group and exactly one OH group a2), and

B) at least one hydroxyterminated polybutadiene and/or one at least partially or completely hydrogenated hydroxyterminated polybutadiene,

C) in the presence of at least one polymerization inhibitor and

2) a liquid component selected from 30 to 70 wt.-% plasticizer and/or from 5 to 30 wt.-% reactive (meth)acrylates, and

3) from 0.5 to 5 wt.-% of a photo-polymerization initiators

wherein the liquid optically clear adhesive is substantially transparent for optical applications wherein the liquid optically clear adhesive has at least 90% transmittance when air is used as a blank measured following the DIN 5033.

5. The liquid optically clear adhesive according to claim 4 , wherein the plasticizer is selected from the group consisting of polyisoprene resin, polybutadiene resin, hydrogenated polybutadiene, xylene polymer, hydroxyl-terminated polybutadiene and/or hydroxyl-terminated polyolefin, terpene polymer resin, phthalates, trimellitates, adipates, benzoate ester, hexanoate and dicarboxylate.

6. The liquid optically clear adhesive according to claim 4 , wherein the reactive (meth)acrylate is selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n- or iso-propyl (meth)acrylate, n- or iso- or tert-butyl (meth)acrylate, 2-(2-ethoxyethoxy) ethyl acrylate, tetrahydrofurfury (meth)acrylate, lauryl acrylate, isooctyl acrylate, isodecyl acrylate, 2-phenoxyethyl acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, caprolactone acrylate, morpholine (meth)acrylate, hexanediol di(meth)acrylate, ethyleneglycol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate and combinations thereof.

7. The liquid optically clear adhesive according to claim 4 , wherein the photo-polymerization initiator is selected from the group consisting of 1-Hydroxy-cyclohexyl-phenyl-ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenyl phosphinate, Bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide, 2-Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-Dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl) butan-1-one, 1-[4-(Phenylthio)phenyl]-1,2-octanedione 2-(O-benzoyloxime), and 1-[9-Ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-ethanone-1-(O-acetyloxime).

8. The liquid optically clear adhesive according to claim 4 , comprising

1) from 30 to 70 wt.-% of acrylate terminated urethane polybutadienes, wherein the acrylate terminated urethane polybutadienes are obtained by reaction of

A) at least one low-monomer-content 1:1 monoadduct, having a free diisocyanate content of less than 2% by weight, the monoadduct being based on at least one aliphatic, cycloaliphatic and/or araliphatic diisocyanate a 1) and at least one reactive olefinic compound having at least one methacrylate group and/or acrylate group and/or vinyl ether group and exactly one OH group a2), and

B) at least one hydroxyterminated polybutadiene

C) optionally in the presence of at least one polymerization inhibitor and

2) a liquid component selected from 30 to 70 wt.-% of at least one plasticizer and/or from 10 to 25 wt.-% of reactive (meth)acrylates, and

3) from 2 to 5 wt.-% of photo-polymerization initiators

wherein the liquid optically clear adhesive is substantially transparent for optical applications wherein, after 150° C. for 60 minute, the liquid optically clear adhesive has at least 90% transmittance when air is used as a blank measured following the DIN 5033 and a haze % of from 0.40, to 0.65, and a viscosity at 25° C. of from 2450 cP to 10,800 cP.

9. A process for binding a top substrate to a base substrate, in which

(a) the formulations according to claim 4 , is applied onto the top side of the base substrate,

(b) the top substrate is attached on the adhesive layer of step (a),

(c) the adhesive is hardened by exposure to electromagnetic radiation comprising a wavelength ranging from 200 nm to 700 nm.

10. The process according to claim 9 , wherein the base substrate is a display panel, selected from a liquid crystal display, a plasma display, a light-emitting diode (LED) display, an electrophoretic display, and a cathode ray tube display.

11. The process according to claim 9 , wherein the top substrate is selected from a reflector, cover lens, touch panel, retarder film, retarder glass, a LCD, a lenticular lens, a mirror, an anti-glare or anti-reflective film, an anti-splinter film, a diffuser, or an electromagnetic interference filter.

12. The process for binding a top substrate to a base substrate, in which

(a) the formulations according to claim 4 , is applied onto the top side of the base substrate,

(b) the top substrate is attached on the adhesive layer of step (a),

(c) the adhesive is hardened by exposure to electromagnetic radiation comprising a wavelength ranging from 250 nm to 500 nm.

13. The process according to claim 10 , wherein the top substrate is selected from a reflector, cover lens, touch panel, retarder film, retarder glass, a LCD, a lenticular lens, a mirror, an anti-glare or anti-reflective film, an anti-splinter film, a diffuser, or an electromagnetic interference filter.

14. The method according to claim 2 , wherein the low-content-monomer 1:1 monoadducts A) are prepared, from, as starting compounds,

a1) at least one aliphatic, cycloaliphatic and/or araliphatic diisocyanate in an amount of 1-20 mol, and

a2) 1 mol of at least one reactive olefinic compound having at least one methacrylate group and/or acrylate group and/or vinyl ether group and exactly one OH group, obtained by reaction in a temperature range of 40-120° C., the unreacted diisocyanate being separated off subsequently by a short-path distillation at 80-220° C./0.01-10 mbar from the reaction product,

wherein the short-path distillation takes place in the presence of

a3) at least one inhibitor which possesses at least one functional group reactive toward NCO groups.

15. The liquid optically clear adhesive according to claim 5 , wherein the reactive (meth)acrylates are chosen from methyl (meth)acrylate, ethyl (meth)acrylate, n- or iso-propyl (meth)acrylate, n- or iso- or tert-butyl (meth)acrylate, 2-(2-ethoxyethoxy) ethyl acrylate, tetrahydrofurfury (meth)acrylate, lauryl acrylate, isooctyl acrylate, isodecyl acrylate, 2-phenoxyethyl acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, caprolactone acrylate, morpholine (meth)acrylate, hexanediol di(meth)acrylate, ethyleneglycol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate and combinations thereof.

16. The liquid optically clear adhesive according to claim 5 , wherein the photo-polymerization initiator is selected from the group consisting of 1-Hydroxy-cyclohexyl-phenyl-ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenyl phosphinate, Bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide, 2-Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-Dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl) butan-1-one, 1-[4-(Phenylthio)phenyl]-1,2-octanedione 2-(O-benzoyloxime), 1-[9-Ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-ethanone-1-(O-acetyloxime).

17. The liquid optically clear adhesive according to claim 5 , comprising

1) from 30 to 70 wt.-% of acrylate terminated urethane polybutadienes, wherein the acrylate terminated urethane polybutadienes are obtained by reaction of

A) at least one low-monomer-content 1:1 monoadduct, having a free diisocyanate content of less than 2% by weight, the monoadduct being based on at least one aliphatic, cycloaliphatic and/or araliphatic diisocyanate a 1) and at least one reactive olefinic compound having at least one methacrylate group and/or acrylate group and/or vinyl ether group and exactly one OH group a2), and

B) at least one hydroxyterminated polybutadiene

C) optionally in the presence of at least one polymerization inhibitor and

2) a liquid component selected from 30 to 70 wt.-% of at least one plasticizer and/or from 10 to 25 wt.-% of reactive (meth)acrylates, and

3) from 2 to 5 wt.-% of photo-polymerization initiators

wherein the liquid optically clear adhesive is substantially transparent for optical applications wherein, after 200° C. for 60 minute, the liquid optically clear adhesive has at least 90% transmittance when air is used as a blank measured following the DIN 5033 and a haze % of from 0.40 to 0.80 and a viscosity at 25° C. of from 2450 cP to 10,800 cP.

18. A process for binding a top substrate to a base substrate, in which

(a) the formulation, as described in claim 5 , is applied onto the top side of the base substrate,

(b) the top substrate is attached on the adhesive layer of step (a),

(c) the adhesive is hardened by exposure to electromagnetic radiation comprising a wavelength ranging from 200 nm to 700 nm.

19. The process according to claim 18 , wherein the base substrate is a display panel, selected from a liquid crystal display, a plasma display, a light-emitting diode (LED) display, an electrophoretic display, and a cathode ray tube display.

20. The process according to claim 19 , wherein the top substrate is selected from a reflector, cover lens, touch panel, retarder film, retarder glass, a LCD, a lenticular lens, a mirror, an anti-glare or anti-reflective film, an anti-splinter film, a diffuser, or an electromagnetic interference filter.

21. The method according to claim 1 , wherein the polybutadiene B) has terminal hydroxyl groups, where the polybutadiene comprises the 1,3-butadiene-derived monomer units

where the proportion of (I) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 10 to 60 mol percent, and where the sum of the proportions of (II) and (III) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 40 to 90 mol percent.

22. The liquid optically clear adhesive according to claim 4 , wherein the polybutadiene B) has terminal hydroxyl groups, where the polybutadiene comprises the 1,3-butadiene-derived monomer units

where the proportion of (I) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 10 to 60 mol percent, and where the sum of the proportions of (II) and (III) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 40 to 90 mol percent.