LIGHT DIFFUSIVE PRESSURE SENSITIVE ADHESIVE

• US 20100068421A1
• Filed: 09/16/2009
• Published: 03/18/2010
• Est. Priority Date: 09/17/2008
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Purgett, Mark D., Everaerts, Albert I., Cheng, Ming, Tse, Kiu-Yuen, Satrijo, Andrew, Xia, Jianhui
• Application Number:
  US12/560,646
• Publication Number:
  US 20100068421A1
• Time in Patent Office: Days
• US Class Current: 428/1.540
• CPC Class Codes: C09J 4/00 Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
• CPC Class Codes: C09K 2323/057 Ester polymer, e.g. polycarbonate, polyacrylate or polyester

Abstract

The present disclosure provides for a light diffusing pressure sensitive adhesive and a method of making the same. In applications where there is a point light source such as a light bulb or an light emitting diode (LED), or a series of such point light sources, and it is desirable to diffuse the light from the point source to produce a desirable background brightness. The light diffusive PSA disclosed herein is reworkable; has a luminous transmission of grater than 80%, as measured according to ASTM D 1003-95-5; has a haze value not less than 20%; and has a depolarization of less than about 10%, as measured using wavelength in the visible spectrum.

Claims

1. A light diffusing pressure sensitive adhesive comprising:

an adhesive matrix having a first refractive index n₁ and comprising no greater than about 20 parts by weight of at least one of a radically polymerizable hydroxyl-containing monomer and a radically polymerizable acid-containing monomer and less than about 100 parts by weight of an alkyl (meth)acrylate momoner, wherein the alkyl groups comprise from about 4 to 12 carbon atoms; and

no greater than about 75 parts light diffusing particles dispersed in the adhesive matrix and having a second refractive index n₂ that differs from n₁;

wherein the light diffusing adhesive has a luminous transmission of great than about 80% as measured according to ASTM D 1003-95-5, has a haze value not less than 20%, and has a depolarization of less than about 10% as measured using wavelength in the visible spectrum of about 400 to 700 nanometer.

2. The adhesive of claim 1, wherein the adhesive matrix further comprises about 0.1 to 10 parts of an antistatic agent based on the weight of the adhesive matrix.

3. The adhesive of claim 2, wherein the antistatic agent is lithium bis(trifluoromethanesulfonyl)imide.

4. The adhesive of claim 1, wherein the acid containing monomer is acrylic acid.

5. The adhesive of claim 1, wherein the adhesive matrix further comprises a plasticizer.

6. The adhesive of claim 1 having a backscatter of less than about 20% as measured using wavelength in the visible spectrum of about 400 to 700 nanometer.

7. The adhesive of claim 1 having 180°

peel adhesion value of less than about 60 ounces per inch (16.4N/25 mm) at a peel rate of about 12 inches per minute after about 48 hours of dwell at 50°

C. on glass.

8. The adhesive of claim 1, wherein the alkyl (meth)acrylate momoner is selected from the group consisting of n-butyl acrylate, 2-ethyl hexyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl acrylate, and mixtures thereof.

9. The adhesive of claim 1, wherein the light diffusing particles are polymethyl methacrylate.

10. The adhesive of claim 1 attached to at least one of a polarizer and a liquid crystal cell of a display of an electronic device.

11. A method of making a light diffusing pressure sensitive adhesive comprising the steps of:

(a) providing a solventless polymer syrup having a first refractive index n₁ and comprising (i) a monomer mixture having no greater than about 20 parts by weight of at least one of a radically polymerizable hydroxyl-containing monomer and a radically polymerizable acid-containing monomer and (ii) less than about 100 parts by weight of an alkyl (meth)acrylate monomer, wherein the alkyl group comprises from about 4 to 12 carbon atoms;

(b) providing no greater than about 75 parts light diffusing particles having a second refractive index n₂ that differs from n₁, the particles dispersed in the monomer mixture;

(c) providing from about 0.1 to 5 parts of a photoinitiator;

(d) providing from about 0.01 to 20 parts crosslinker;

wherein the parts of the light diffusing particles, photoinitiator, and crosslinker are based on the weight of the monomer mixture;

(e) mixing the solventless polymer syrup, light diffusing particles, photoinitiator, and crosslinker to yield an adhesive composition;

(f) coating the adhesive composition on a first side of a first backing; and

(g) curing the adhesive composition using actinic radiation to yield a light diffusing pressure sensitive adhesive.

12. The method of claim 11 further comprising a step of providing from about 0.1 to 10 parts of an antistatic agent prior to the mixing step (e).

13. The method of claim 12, wherein the antistatic agent is lithium bis(trifluoromethanesulfonyl)imide.

14. The method of claim 11 further comprising a step of providing a plasticizer prior to the mixing step (e).

15. The method of claim 11, the light diffusing adhesive has a backscatter of less than about 20% as measured using wavelength in the visible spectrum of about 400 to 700 nanometer.

16. The method of claim 11, wherein the light diffusing adhesive has a luminous transmission of greater than about 80% as measured according to ASTM D 1003-95-5.

17. The method of claim 11, wherein the light diffusing adhesive has 180°

peel adhesion value of less than about 60 ounces per inch (16.4N/25 mm) at a peel rate of about 12 inches per minute after about 48 hours of dwell at 50°

C. on glass.

18. The method of claim 11, wherein the light diffusing adhesive has a haze not less than 20%.

19. The method of claim 11, wherein the light diffusing adhesive as a depolarization of less than about 10% as measured using wavelength in the visible spectrum of about 400 to 700 nanometer.

20. The method of claim 11, wherein the light diffusing particles are polymethyl methacrylate.