Dimensionally stabilized diffuse reflective articles

• US 20010036546A1
• Filed: 01/12/2001
• Published: 11/01/2001
• Est. Priority Date: 08/03/1999
• Status: Abandoned Application

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Caswell, Warren P., Kretman, Wade D., Kaytor, Scott R.
• Application Number:
  US09/759,929
• Publication Number:
  US 20010036546A1
• Time in Patent Office: Days
• US Class Current: 428/316.6
• CPC Class Codes: C08J 2323/02 not modified by chemical after treatment
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: F21S 41/37 characterised by their material, surface treatment or coatings
• CPC Class Codes: F21V 7/24 characterised by the material
• CPC Class Codes: F21V 7/28 characterised by coatings
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• CPC Class Codes: G02B 5/0247 by means of voids or pores
• CPC Class Codes: G02B 5/0284 used in reflection
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02B 6/0096 the lights guides being of the hollow type
• CPC Class Codes: Y10T 428/249958 Void-containing component is synthetic resin or natural rubbers
• CPC Class Codes: Y10T 428/249981 Plural void-containing components
• CPC Class Codes: Y10T 428/249991 Synthetic resin or natural rubbers
• CPC Class Codes: Y10T 428/249995 Constituent is in liquid form

Abstract

Diffuse reflective articles having a first layer formed by thermally induced phase separation of a thermoplastic polymer and a diluent, plus a second layer containing a dimensionally stabilizing polymer are described. Such materials find a wide variety of applications, including in combinations with various light management films. The diffuse reflective articles are useful in applications where high reflectivity is desired, such as backlight units of liquid crystal displays, lights, copy machines, projection system displays, facsimile apparatus, electronic blackboards, diffuse white standards, and photographic lights.

Claims

1. A diffuse reflective article comprising:

a diffuse reflective layer containing a polymeric network having voids therein, the network including a polymeric component and a diluent component, said diluent component being miscible with the polymeric component at a temperature above the melting point of the polymeric component; and

a dimensionally stabilizing polymeric layer.

2. The diffuse reflective article of

claim 1

, wherein the diffuse reflective layer contains a polymer selected from the group consisting of polypropylene, polyethylene, and combinations thereof.

3. The diffuse reflective article of

claim 1

, wherein the diffuse reflective layer comprises:

(a) at least about 20 parts by weight of the polymer component; and

(b) less than about 80 parts by weight of the diluent component.

4. The diffuse reflective article of

claim 1

, wherein the dimensionally stabilizing polymeric layer has a glass transition temperature greater than 40°

C.

5. The diffuse reflective article of

claim 1

, wherein the dimensionally stabilizing polymeric layer has a glass transition temperature greater than 70°

C.

6. The diffuse reflective article of

claim 1

, wherein the dimensionally stabilizing polymeric layer comprises an acrylic coating.

7. The diffuse reflective article of

claim 1

, wherein the dimensionally stabilizing polymeric layer contains particles.

8. The diffuse reflective article of

claim 7

, wherein the particles are white pigments.

9. The diffuse reflective article of

claim 1

, wherein the dimensionally stabilizing polymeric layer contains absorbing dyes or pigments.

10. The diffuse reflective article of

claim 1

, wherein the dimensionally stabilizing layer comprises at least one polymer selected from the group consisting of polyethylene terephthalate, polycarbonate, polymethylmethacrylate, and combinations thereof.

11. The diffuse reflective article of

claim 1

, wherein the dimensionally stabilizing polymeric layer contains voids.

12. The diffuse reflective article of

claim 1

, wherein the combined thickness of the diffuse reflective layer and the dimensionally stabilizing polymeric layer is less than 350 microns.

13. The diffuse reflective article of

claim 1

, wherein the diffuse reflective layer is from 2 to 40 times as thick as the dimensionally stabilizing polymeric layer.

14. The diffuse reflective article of

claim 1

, wherein the diffuse reflective layer is from about 2 to about 5 times as thick as the dimensionally stabilizing polymeric layer

15. The diffuse reflective article of

claim 1

, wherein the dimensionally stabilizing polymeric layer is laminated to the diffuse reflective layer with an adhesive. The diffuse reflective article of

claim 13

, wherein the adhesive contains a white pigment.

16. The diffuse reflective article of

claim 1

, further comprising surface elements configured to reduce optical coupling.

17. The diffuse reflective article of

claim 1

, wherein the diffuse reflective article has a reflectivity greater than 92% at a wavelength of 550 nm according to ASTM E 1164-94 using a spectrophotometer with an integrating sphere.

24. A display containing the diffuse reflective article of

claim 1

.

25. The diffuse reflective article of

claim 1

, used in association with light management films selected from reflective polarizing films, turning films, brightness enhancing films, diffusers, and films including hemispheres, cylindrical structures or lenslets.

18. A diffuse reflective article comprising:

a diffuse reflective material proximate to a structure wherein said diffuse reflective material is made of a porous polyolefin sheet comprising a network of polymer domains and fibrils interconnecting the domains, and

a dimensionally stabilizing polymeric layer.

19. The diffuse reflective article of

claim 18

, wherein the porous polymeric sheet has a reflectivity greater than 92% at a wavelength of 550 nm according to ASTM E 1164-94 using a spectrophotometer with an integrating sphere.

20. The diffuse reflective article of

claim 18

, wherein the diffuse reflective material comprises:

(a) at least 20 parts by weight of a polymer component; and

(b) less than about 80 parts by weight of a diluent component.

21. The diffuse reflective article of

claim 20

, wherein the polymer component is substantially non-absorbing to light at a wavelength between 380 and 730 nanometers.

22. The diffuse reflective article of

claim 20

, wherein the polymer component is selected from the group consisting of polypropylene and polyethylene.

23. The diffuse reflective article of

claim 20

, wherein the diluent component is mineral oil.

26. A method of making a diffuse reflecting article configured for positioning proximate to a structure, the method comprising:

providing a polymer component;

providing a diluent component, said diluent component being miscible with the polymer component at a temperature above the melting point of the polymer component;

combining the polymer component and diluent component to form a porous polymeric sheet; and

securing a dimensionally stabilizing polymeric layer to the polymeric sheet.