Retroreflective articles and devices having viscoelastic lightguide

• US 9,551,475 B2
• Filed: 02/11/2014
• Issued: 01/24/2017
• Est. Priority Date: 07/10/2008
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Sherman, Audrey A., Boulos, Marie A., Schaffer, Kevin R., Meis, Michael A., Tran, Thu-Van T., Aeling, Ellen O., Widagdo, Soemantri
• Primary Examiner(s): Patel, Ashok
• Application Number:
  US14/177,332
• Publication Number:
  US 20140160764A1
• Time in Patent Office: 1,078 Days
• US Class Current: 1/1
• CPC Class Codes: B42D 2035/20 Optical effects
• CPC Class Codes: B42D 25/29 Securities; Bank notes
• CPC Class Codes: B42D 25/324 Reliefs
• CPC Class Codes: B42D 25/328 Diffraction gratings; Holograms
• CPC Class Codes: B44F 1/045 having mirrors or metallic or reflective layers at the back side
• CPC Class Codes: F21V 13/04 the elements being reflectors and refractors for vehicle rear lights F21S43/40
• CPC Class Codes: G02B 5/12 Reflex reflectors
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• 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 6/0063 for extracting light out both the major surfaces of the light guide
• CPC Class Codes: G09F 13/18 Edge-illuminated signs

Abstract

Disclosed herein is an optical device having a light source, a viscoelastic lightguide and a retroreflective film suitable for retroreflecting light. Light from the light source enters the viscoelastic lightguide and is transported within the lightguide by total internal reflection. The transported light is extracted from the lightguide and retroreflected at a structured surface of the retroreflective film. The optical device may have a “front lit” or a “back lit” configuration depending on the relative positioning of the lightguide and the retroreflective film. The retroreflective film may include prismatic retroreflective sheeting, holographic film or film structured with diffraction gratings. The optical device may be used, for example, as a sign or marking, a license plate assembly, a tail light assembly for vehicles, a security laminate for protection of documents against tampering, or an illumination device.

Claims

1. An electronic device comprising a keypad, the keypad comprising:

a light source;

a viscoelastic lightguide, comprising a pressure sensitive adhesive core, wherein light emitted by the light source enters the pressure sensitive adhesive core and is transported within the core by total internal reflection; and

a retroreflective film suitable for retroreflecting light, wherein light being transported within the viscoelastic lightguide is extracted from the lightguide and retroreflected from a structured surface of the retroreflective film.

2. An electronic device comprising a button, the button comprising:

a light source;

a viscoelastic lightguide, comprising a pressure sensitive adhesive core, wherein light emitted by the light source enters the pressure sensitive adhesive core and is transported within the core by total internal reflection; and

a retroreflective film suitable for retroreflecting light, wherein light being transported within the viscoelastic lightguide is extracted from the lightguide and retroreflected from a structured surface of the retroreflective film.

3. An optical device, comprising:

a light source;

a viscoelastic lightguide, comprising a pressure sensitive adhesive core, wherein light emitted by the light source enters the pressure sensitive adhesive core and is transported within the core by total internal reflection; and

a retroreflective film suitable for retroreflecting light, wherein light being transported within the viscoelastic lightguide is extracted from the lightguide and retroreflected from a structured surface of the retroreflective film;

wherein the retroreflective film includes diffraction gratings.

4. An optical device, comprising:

a light source;

a viscoelastic lightguide, comprising a pressure sensitive adhesive core, wherein light emitted by the light source enters the pressure sensitive adhesive core and is transported within the core by total internal reflection; and

a retroreflective film suitable for retroreflecting light, wherein light being transported within the viscoelastic lightguide is extracted from the lightguide and retroreflected from a structured surface of the retroreflective film;

wherein the viscoelastic lightguide includes a structured surface including a plurality of features.

5. The optical device of claim 4, wherein an areal density of the plurality of features changes over at least one of the length or width of the viscoelastic lightguide.

6. The optical device of claim 4, wherein the plurality of features are arranged to provide an image.