LIGHT CURABLE RESIN COMPOSITION

Abstract

The present application relates to a resin composition and in particular to a light-curable resin composition.

It is known to achieve a thixotropic behavior of an adhesive composition by adding an inorganic additive like fumed silica. Adding inorganic additives results in significant particle problems as fumed silica is a solid particle and affects the optical performance of the adhesive composition.

In accordance with the invention a particle free resin composition with a thixotropic behavior is provided. The inventive composition comprises a) 30 to 90 wt % of a urethane acrylate oligomer with a molecular weight greater than 15000, b) 2 to 40 wt % of a (meth)acrylate monomer having a benzene ring, and c) 0.2 to 10 wt % of a photo initiator.

Claims

1. A light-curable resin composition, comprising a) 30 to 90 wt % of a urethane acrylate oligomer with a molecular weight greater than 15000, b) 2 to 40 wt % of a (meth)acrylate monomer having a benzene ring, c) 0.2 to 10 wt % of a photo initiator.

2. The light-curable resin composition according to claim 1, wherein the urethane acrylate oligomer is an aliphatic urethane acrylate.

3. The light-curable resin composition according to claim 1, wherein the (meth)acrylate monomer having a benzene ring is selected from a group comprising benzyl acrylate, phenoxyethyl acrylate, nonylphenoxypolyethylene glycol acrylate, ethoxylated bisphenol A diacrylate, phenoxyethyl methacrylate, ethoxylated bisphenol A dimethacrylate, benzyl methacrylate, 1-phenylethyl methacrylate, 2-phenoxyethyl methacrylate, 2-phenylethyl methacrylate, 3-phenylpropyl methacrylate, 3-phenylpropyl acrylate and 2-phenoxyethyl acrylate and combinations thereof.

4. The light-curable resin composition according to claim 3, wherein the (meth)acrylate monomer having a benzene ring is selected from a group comprising ##STR00002##

5. The light-curable resin composition according to claim 1, wherein the photoinitiator is selected from a group comprising phenylglyoxylates, -hydroxyketones, -aminoketones, benzildimethylketal, monoacylphosphinoxides, bisacylphosphinoxides, benzophenones, oxime esters, titanocene and combinations thereof.

6. The light-curable resin composition according to claim 1, comprising a) 40 to 80 wt % of a urethane acrylate oligomer with a molecular weight of more than 15000, b) 5 to 30 wt % of a (meth)acrylate monomer having a benzene ring, and c) 0.5 to 6w t % of a photo initiator.

7. The light-curable resin composition according to claim 1, wherein the composition further comprises up to 40 wt %, deformer, ultra-violet light absorber, light stabilizer, silane coupling agent, antioxidant and combinations thereof.

8. The light-curable resin composition according to claim 7, wherein the deformer is based on silicones.

9. The light-curable resin composition according to claim 7, wherein the antioxidant is selected from a group comprising phenolic, aminic, sulphur-based antioxidants and multifunctional antioxidants or combinations thereof.

10. The light-curable resin in accordance with claim 7, wherein the ultra-violet light absorber is a benzotriazole type ultra-violet light absorber.

11. Use of said light-curable resin composition of claim 1 for bonding parts of optical assemblies.

12. Use of said light-curable resin composition of claim 1 for touch panel sensor assemblies.

13. Use of said light-curable resin composition of claim 1 for cover lens bonding.

14. Use of said light-curable resin composition of claim 1 for directly bonding the cover lens to a LCD module.

15. Use of said light-curable resin composition of claim 1 on liquid crystal, displays to fix the touch screen on the base substrate, wherein the base substrate is a display panel selected from a liquid crystal display, a plasma display, light-emitting diode (IED) display, an electrophoretic display, and a cathode ray tube display.

16. Use of said light-curable resin composition of claim 15, wherein the base substrate is selected from a liquid crystal display, a plasma display, a light-emitting diode (LED) display, an electrophoretic display, and a cathode ray tube display.

Description

DESCRIPTION OF EMBODIMENTS

[0011] The term (meth)acrylate as used herein refers to either acrylates or (meth)acrylates.

[0012] The benzene ring of the (meth)acrylate can comprise one or more substituent(s)/group(s) other than hydrogen.

[0013] Urethane acrylates are well known to a person skilled in the art, they may for example be obtained by reaction of diisocyanates, preferably aliphatic diisocyanates, with hydroxyacrylates, or may for example be obtained by reaction of diisocyanates, preferably aliphatic diisocyanates, with hydroxyacrylates and polyols.

[0014] Preferred urethane acrylates, which can be used according to this invention, are for example UVA-002 and UVA-004 from Osaka Organic Chemical Co., Ltd. Other urethane acrylates can be used provided their molecular weight is greater than 15000.

[0015] The properties of the preferred urethane acrylates are as follows:

TABLE-US-00001 UVA-002 UVA-004 Mw 20000 20000 Viscosity (m * Pa * s) 200000 170000 Transmittance (%) 99 99 Haze (%) 0.1 0.1

[0016] The (meth)acrylate monomer having a benzene ring can be selected from a group comprising benzyl acrylate, phenoxyethyl acrylate, nonylphenoxypolyethylene glycol acrylate, ethoxylated bisphenol A diacrylate, phenoxyethyl methacrylate, ethoxylated bisphenol A dimethacrylate, benzyl methacrylate, 1-phenylethyl methacrylate, 2-phenoxyethyl methacrylate, 2-phenylethyl methacrylate, 3-phenylpropyl methacrylate, 3-phenylpropyl acrylate and 2-phenoxyethyl acrylate and combinations thereof. The use of benzyl acrylate as (meth)acrylate monomer is preferred.

[0017] In particular, the (meth)acrylate monomer having a benzene ring can be selected from a group comprising

##STR00001##

[0018] While the inventive composition must contain at least one (meth)acrylate monomer having a benzene ring, the composition in accordance with the present invention can comprise one or more additional monomers like, for example, isobornyl acrylate, 4-hdroxybutyl acrylate and tricylodecane dimethanol diacrylate, wherein an additional monomer may be used to fine tune the properties of the resulting cured composition.

[0019] The composition in accordance with the present invention comprises at least one photoinitiator. A photoinitiator initiates the reaction and has a great influence on the curing of the composition, wherein different kinds of photoinitiators have different issues and advantages. For example, some photoinitiators cause discoloration of the cured compositions while others are particularly well suited for pigmented systems.

[0020] In accordance with the present invention it is preferred to select a photoinitiator from a group comprising phenylglyoxylates, -hydroxyketones, -aminoketones, benzildimethylketal, monoacylphosphinoxides, bisacylphosphinoxides, benzophenones, oxime esters, titanocene and combinations thereof.

[0021] It is preferred that the light-curable resin composition comprises [0022] a) 40 to 80 wt % of a urethane acrylate oligomer with a molecular weight of more than 15000, [0023] b) 5 to 30 wt % of a (meth)acrylate monomer having a benzene ring, [0024] c) 0.5 to 6 wt % of a photo initiator.

[0025] It is more preferred that the light-curable resin composition comprises [0026] a) 45 to 80 wt % of a urethane acrylate oligomer with a molecular weight of more than 15000, [0027] b) 5 to 28 wt % of a (meth)acrylate monomer having a benzene ring, [0028] c) 0.5 to 6 wt % of a photo initiator.

[0029] It is most preferred that the light-curable resin composition comprises [0030] a) 50 to 80 wt % of a urethane acrylate oligomer with a molecular weight of more than 15000, [0031] b) 5 to 25 wt % of a (meth)acrylate monomer having a benzene ring, [0032] c) 0.5 to 6 wt % of a photo initiator.

[0033] The light-curable resin composition might comprise 0 to 40 wt %, preferably 0 to 30 wt %, other components such as deformer, ultra-violet light absorber, light stabilizer, silane coupling agents, an antioxidant or a combination thereof.

[0034] With regard to the other components it is preferred that the deformer (defoamer or an anti-foaming agent) is based on silicones and polymers. The antioxidant is preferably selected from a group comprising phenolic, aminic, sulphur-based antioxidants and multifunctional antioxidants or combinations thereof. The ultra-violet light absorber is preferably a benzotriazole type ultra-violet light absorber, and in particular 2-(5-t-butyl-2-hydroxyphenyl)benzotriazole.

[0035] A further aspect of the invention relates to the use of said light-curable resin composition for bonding parts of optical assemblies.

[0036] A further aspect of the invention relates to the use of said light-curable resin composition for touch panel sensor assemblies

[0037] A further aspect of the invention relates to the use of said light-curable resin composition for cover lens bonding.

[0038] A further aspect of the invention relates to the use of said light-curable resin composition for directly bonding the cover lens to a LCD module.

[0039] Finally, a further aspect of the invention relates to the use of said light-curable resin composition on liquid crystal displays to fix the touch screen on the base substrate, wherein the base substrate can be a display panel, preferably selected from a liquid crystal display, a plasma display, a light-emitting diode (LED) display, an electrophoretic display, and a cathode ray tube display.

EXAMPLES

[0040] The following table 1 shows four compositions which were prepared by mixing all ingredients to obtain a homogeneous mixture away from light.

[0041] The first example comprises all essential components of the inventive composition, namely 30 to 90 wt % (67.7 wt %) of a urethane acrylate oligomer with a molecular weight greater than 15000 (UVA-002 has a molecular weight of 20000), 2 to 40 wt % (15.0 wt %) of a (meth)acrylate monomer having a benzene ring (benzyl acrylate) and 0.2 to 10 wt % (3.5 wt % in total) of a photo initiator (combination of TPO and Irgacure 184).

[0042] The table also comprises three comparative compositions which do not comprise all of the essential components.

[0043] As can be seen from table 2, only the composition in accordance with the present invention shows a significantly enhanced thixotropic ratio of 1.7. The compositions in accordance with prior art all show a thixotropic ratio of 1.0.

TABLE-US-00002 TABLE 1 Different light-curable resin compositions Components Example Comparison 1 Comparison 2 Comparison 3 Oligomer UVA-002* 67.6 67.6 urethane acrylate UC203* 67.6 isoprene acrylate UT5141* 67.6 urethane acrylate Monomer Benzyl acrylate 15.0 15.0 15.0 0.8 Isobornyl acrylate 5.2 5.2 5.2 15.0 4-hydroxybutyl 5.2 5.2 5.2 9.6 acrylate Tricylodecane 2.1 2.1 2.1 2.1 dimethanol Diacrylate Deformer BYK-088* 0.5 0.5 0.5 0.5 Antioxidant Irganox 1520L* 0.6 0.6 0.6 0.6 light TINUVIN PS* 0.4 0.4 0.4 0.4 stabilizer Photoinitiator TPO* 0.9 0.9 0.9 0.9 Irgacure 184* 2.6 2.5 2.5 2.5 100.0 100.0 100.0 100.0

TABLE-US-00003 TABLE 2 Characteristics of the light-curable resin compositions Example Comparison 1 Comparison 2 Comparison 3 Viscosity 150,000 mPa .Math. s 60,000 mPa .Math. s 20,000 mPa .Math. s 160,000 mPa .Math. s Thixotropic ratio, 1 sec.sup.1/ 1.7 1.0 1.0 1.0 10 sec.sup.1 Transmittance (%) 99.0 99.0 99.0 99.0 @550 nm Y.I. (b*) 0.22 0.10 0.08 0.18 Haze (%) 0.1 0.1 0.1 0.1 [0044] *UC203: isoprene acrylate oligomer with MW of 50008000, from Kuraray Co. Ltd. [0045] *UT5141: urethane acrylate oligomer with MW of 600010000, by Nipon Gosei Co., Ltd. [0046] *UVA002: urethane acrylate oligomer with MW of 20000, by Osaka Organic Chemical Ind., Ltd. [0047] *BYK-088: by BYK [0048] *Irganox 1520L, TINUVIN PS, TPO and Irgacure: all from BASF
For viscosity and thixotropic ratio (ratio of viscosity@1 Sec1 and 10 Sec1 shear rate), HAAKE Reometer was used according to ASTM D 1084.

[0049] Transmittance and Y.I (b*) were measured with UV-Vis spectrometer according to ASTM E 903 and ASTM D1003, respectively.

[0050] Haze was measured with Haze detector according to ASTM D 1003.