OPTICAL BONDING SILICONE WITH UV BLOCKER FOR OUTDOOR APPLICATION

Abstract

A silicone composition along with uses and processes for preparing the same. Where the silicone composition is used as an optical binder for outdoor display applications.

Claims

1-4. (canceled)

5. A hydrosilylation curable silicone composition for optical bonding outdoor application, comprising: a component (A) having at least one organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule; a component (B) having at least one organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule, in an amount such that an amount of silicon-bonded hydrogen atoms in this component being from 0.1 to 20 mol per 1 mol of silicon-bonded alkenyl groups in the component (A); a component (C) having at least one hydrosilylation reaction catalyst, in an amount which accelerates the curing of the present composition; and a component (D) that is from 0.5 wt % to 3.0 wt % of the UV-blocker: 2-(2H-Benzotriazol-2-yl)-6-dodecyl-4-methylphenol based on the total weight of the composition.

6. The composition of claim 5, wherein the composition is transparent.

7. The composition of claim 5, wherein the composition is used as a glue for the optical bonding of the glass to the top surface of a display for outdoor application.

8. A process for preparing a display for outdoor application, comprising: providing a hydrosilylation curable silicone composition comprising a component (A), a component (B), a component (C) and a component (D); wherein the component (A) has at least one organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule; wherein the component (B) has at least one organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule, in an amount such that an amount of silicon-bonded hydrogen atoms in this component being from 0.1 to 20 mol per 1 mol of silicon-bonded alkenyl groups in the component (A); wherein the component (C) has at least one hydrosilylation reaction catalyst, in an amount which accelerates the curing of the present composition; and wherein the component (D) that is from 0.5 wt % to 3.0 wt % of the UV-blocker: 2-(2H-Benzotriazol-2-yl)-6-dodecyl-4-methylphenol based on the total weight of the composition; and utilizing the composition as an optical bonding glue of the glass to the top surface of the display.

Description

EXAMPLES

[0056] In the examples described below, all of the data for parts and percentages are based on the weight, unless stated otherwise. Unless stated otherwise, the examples below are carried out at a pressure of the ambient atmosphere, i.e. about at 1000 hPa, and at room temperature, i.e. at about 20° C., or at a temperature which is established upon combining the reactants at room temperature without additional heating or cooling. Hereinbelow, all of the viscosity data refer to a temperature of 25° C. The examples below illustrate the invention without having a limiting effect.

[0057] Optical and Mechanical Properties

[0058] Method to Determine Yellowing Index:

[0059] The yellowing index (YI) was determined with a KONICA MINOLTA CM-5 in the L*a*b* color space for initial samples according to ASTM E313-73. In the L*a*b* color space, L*indicates lightness and a*and b*are chromaticity coordinates. a*and b*are color directions: +a*is the red axis, −a*is the green axis, +b*is the yellow axis and −b*is the blue axis.

[0060] Method to determine light transmittance: The light transmittance was determined with an Analytikjena SPECORD 200.

[0061] Lap Shear Strength Test:

[0062] The sample size is 7.0 cm.sup.2 on soda lime glass substrate with bond-line thickness of 300 microns. The pull test speed is 300 mm/min at room temperature. The maximum force measured is reported as adhesion strength.

[0063] Used products: [0064] TINUVIN® 171 from BASF AG, Germany as compound (D) [0065] LUMISIL® 100 A/B from Wacker Chemie AG, Germany a (1:1) 2-part addition heat curing silicone gel composition, comprising at least the compounds (A), (B) and (C).

[0066] Its features include: [0067] protect outdoor display form UVA & UVB in sun light [0068] Self-leveling with low viscosity [0069] Fast cure at low temperature [0070] Good optical performance [0071] Low shrinkage

Example 1: LUMISIL® 100+0.5% by Weight TINUVIN® 171

[0072] 9995 g of LUMISIL® 100 A and 5 g of TINUVIN® 171 were charged into a reaction vessel equipped with a stirrer. The mixture can also be transferred into a container for SpeedMix equipment. 9995 g of LUMISIL® 100 B and 5 g of TINUVIN® 171 were charged into a reaction vessel equipped with a stirrer. The mixture can also be transferred into a container for SpeedMix equipment. The mixture was stirred for 0.1-0.5 hours while controlling the temperature at 20° C. to prepare a hydrosilylation curable silicone compositions in A and B sides. The A and B sides were mixed as 1:1 ratio to make the final optical bonding silicone with UV blocking capability. The mixture can be cured as room temperature with regular reaction speed or elevated temperature for high reaction speed. Test specimens were prepared and the yellowing index and tansmittance was determined according to the above-mentioned test methods. The UV cutoff starts from 365 nm and initial yellow index is about 0.18.

[0073] The light transmittance is 99.78% at 550 nm.

[0074] The adhesion strength on glass is 2.15 kgf/cm.sup.2 with cohesive failure mode.

Example 2: LUMISIL® 100+1.0% by Weight TINUVIN® 171

[0075] 9990 g of LUMISIL® 100 A and 10 g of TINUVIN® 171 were charged into a reaction vessel equipped with a stirrer. The mixture can also be transferred into a container for SpeedMix equipment. 9990 g of LUMISIL® 100 B and 10 g of TINUVIN® 171 were charged into a reaction vessel equipped with a stirrer. The mixture can also be transferred into a container for SpeedMix equipment. The mixture was stirred for 0.1-0.5 hours while controlling the temperature at 20° C. to prepare a hydrosilylation curable silicone compositions in A and B sides. The A and B sides were mixed as 1:1 ratio to make the final optical bonding silicone with UV blocking capability. The mixture can be cured as room temperature with regular reaction speed or elevated temperature for high reaction speed. Test specimens were prepared and the yellowing index and tansmittance was determined according to the above-mentioned test methods. The UV cutoff starts from 370 nm and initial yellow index is about 0.24.

Example 3: LUMISIL® 100+1.5% by Weight TINUVIN® 171

[0076] 9985 g of LUMISIL® 100 A and 15 g of TINUVIN® 171 were charged into a reaction vessel equipped with a stirrer. The mixture can also be transferred into a container for SpeedMix equipment. 9985 g of LUMISIL® 100 B and 15 g of TINUVIN® 171 were charged into a reaction vessel equipped with a stirrer. The mixture can also be transferred into a container for SpeedMix equipment. The mixture was stirred for 0.1-0.5 hours while controlling the temperature at 20° C. to prepare a hydrosilylation curable silicone compositions in A and B sides. The A and B sides were mixed as 1:1 ratio to make the final optical bonding silicone with UV blocking capability. The mixture can be cured as room temperature with regular reaction speed or elevated temperature for high reaction speed. Test specimens were prepared and the yellowing index and tansmittance was determined according to the above-mentioned test methods. The UV cutoff starts from 378 nm and initial yellow index is about 0.3.

Example 4: LUMISIL® 100+2.5% by Weight TINUVIN® 171

[0077] 9975 g of LUMISIL® 100 A and 25 g of TINUVIN® 171 were charged into a reaction vessel equipped with a stirrer. The mixture can also be transferred into a container for SpeedMix equipment. 9975 g of LUMISIL® 100 B and 25 g of TINUVIN® 171 were charged into a reaction vessel equipped with a stirrer. The mixture can also be transferred into a container for SpeedMix equipment. The mixture was stirred for 0.1-0.5 hours while controlling the temperature at 20° C. to prepare a hydrosilylation curable silicone compositions in A and B sides. The A and B sides were mixed as 1:1 ratio to make the final optical bonding silicone with UV blocking capability. The mixture can be cured as room temperature with regular reaction speed or elevated temperature for high reaction speed. Test specimens were prepared and the yellowing index and tansmittance was determined according to the above-mentioned test methods. The UV cutoff starts from 385 nm and initial yellow index is about 0.45. The light transmittance is 99.84% at 550 nm. The adhesion strength on glass is 1.96 kgf/cm2 with cohesive failure mode.

Comparative Example 1: LUMISIL® 100 Alone

[0078] The LUMISIL 100 A and B sides were mixed as 1:1 ratio to make the final optical bonding silicone with UV blocking capability. The mixture can be cured as room temperature with regular reaction speed or elevated temperature for high reaction speed. Test specimens were prepared and the yellowing index and tansmittance was determined according to the above-mentioned test methods. The UV cutoff starts from ˜215 nm and initial yellow index is typically less than 0.2. The light transmittance is over 99% at 550 nm. The adhesion strength on glass is 2.2 kgf/cm2 with cohesive failure mode.

[0079] Discussion of the Results:

[0080] It is known from above examples that UV blocking material will have effects on UV cutoff, yellow index, and adhesion strength.

[0081] The effect on UV cutoff means the UV blocking material can be used as a method to adjust UV cutoff according to different applications.

[0082] In the diagram according to FIG. 1 the relationship between yellow index (YI) and UV block material concentrations can be seen. As can be seen in FIG. 1 the use of UV blocker has only minor influence on the measured YI and b*of the initial samples.

[0083] The effect on yellow index means the UV blocking material can affect the transparency of optical silicone slightly. Good news is for most outdoor applications the change of yellow index could be ignored, especially when we consider UV blocking materials effectively protect the electronics and lower the device temperature significantly.

[0084] The effect on adhesion strength means the UV blocking material can affect the pull strength for optical silicone on glass. However, all the adhesion strength in all these examples are still cohesive failure mode, which is the key requirement for most applications.