Backlit display composite film

• US 6,251,505 B1
• Filed: 04/01/1999
• Issued: 06/26/2001
• Est. Priority Date: 04/01/1999
• Status: Expired due to Term

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Brabbs, Noel Stephen, Rakos, Karl, Logan, Moira, Mills, Paul David Alan
• Primary Examiner(s): Hess, Bruce H.
• Assistant Examiner(s): SHEWAREGED, BETELHEM
• Application Number:
  US09/283,426
• Time in Patent Office: 817 Days
• Field of Search: 428/212, 428/327, 428/213, 428/480, 428/482, 428/325, 428/332, 428/331, 428/446
• US Class Current: 428/212
• CPC Class Codes: B32B 2307/412 Transparent
• CPC Class Codes: B32B 2309/105 Thickness
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: B41M 5/502 characterised by structural details, e.g. multilayer materials supports, backcoats or intermediate layers for thermal dye transfer donor and receiver sheets B41M5/41, B41M5/42
• CPC Class Codes: C08J 2367/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds; C08J2367/06 takes precedence
• CPC Class Codes: C08J 7/0427 with only one layer of a composition containing a polymer binder with more layers C08J7/042
• CPC Class Codes: C08J 7/043 Improving the adhesiveness of the coatings per se, e.g. forming primers adhesives in the form of films or foils characterised by the primer layers between the polymer carriers and the adhesives C09J7/50
• CPC Class Codes: C08J 7/044 Forming conductive coatings; Forming coatings having anti-static properties
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/2495 Thickness [relative or absolute]
• CPC Class Codes: Y10T 428/252 Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]
• CPC Class Codes: Y10T 428/254 Polymeric or resinous material
• CPC Class Codes: Y10T 428/259 Silicic material
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]
• CPC Class Codes: Y10T 428/31794 Of cross-linked polyester

Abstract

A composite film is described which consists of a primary unfilled polyester layer and a secondary polyester layer containing from 1 to 8% by weight, based on the weight of the secondary polyester layer, of finely divided silica particles having a volume weighted mean particle size diameter D[4,3] of from 2.3 to 6.2 micrometers. The composite film is used in backlit displays such as illuminated signboards and provides uniform light transmission while maintaining the same strength of illumination at all points over the area of the display.

Claims

1. A polyester composite film comprising a primary transparent, unfilled polyester layer and a secondary filled polyester layer formed on at least one surface of the primary polyester layer, wherein the secondary polyester layer has a thickness of from 2.5 to 35 micrometers and comprises from 5 to 20% of the total thickness of the primary and the secondary polyester layers and comprises from 1 to 8% by weight, based on the weight of the secondary polyester layer of finely divided silica particles having a volume weighted mean particle diameter D[4,3] of from 2.3 to 6.2 micrometers, a porosity of from 0.44 to 1.6 ml/g and a surface area of from 300 to 700 m²/g, coated on one or both exposed polyester surfaces with an adhesion promoting and/or antistatic aqueous or solvent based emulsion or solution polymer coating, said coating comprising a polyester resin and a polymer containing amino groups or a styrene containing acrylic polymer and a melamine-formaldehyde cross-linking agent, wherein said polyester composite film has (a) a total luminous transmission (TLT) of at least 30% measured according to ASTM Method D1003 and (b) an angular light scattering ratio (I₂/I₀) of at least 0.02 wherein I₂ and I₀ are the light intensities measured at an angle of 2 degrees and 0 degrees, respectively, from a line perpendicular to the plane of the time.

2. The polyester composite film of claim 1 wherein the coating comprises an aqueous dispersion of a polyester resin and a polymer containing amino groups.

3. The polyester composite film of claim 1 wherein the coating comprises an aqueous coating of a styrene containing acrylic polymer and a melamine-formaldehyde cross-linking agent.

4. The polyester composite film of claim 1 wherein the adhesion promoting and/or antistatic coating is applied to the surface of the primary polyester layer remote from the secondary polyester layer.