Retroreflective materials

Details Retroreflective materials Retroreflective materials

1996-07-19

1999-05-04

Phan, James

Optical: systems and elements

Signal reflector

Including a curved refracting surface

359539, G02B 5128

Patent

active

059009780

DESCRIPTION:

BRIEF SUMMARY
This invention relates to retroreflective materials, to making the same and to making material retroreflective, which is to say, given a material, making it retroreflective.
The principles underlying retroreflective materials are well known--glass microspheres, silvered hemispherically, are applied to the surface of the material after some fashion. The microspheres, if the incident light is on the unsilvered half, tend to totally internally reflect the light off the silvered part and direct it back towards its source. If the microspheres are orientated randomly, about a third of them will retroreflect at least to some extent.
The microspheres are silvered while embedded in an adhesive layer, which exposes only one hemisphere for silvering. The hemispherically silvered microspheres can be removed from the adhesive layer, by one means or another, as individual microspheres which can then be applied to an adhesive surface on a material which is to be made retroreflective. Measures have been proposed, as by applying a magnetic coating with the silvering and subjecting the individual particles to magnetic alignment whilst being applied to the material, to improve upon the proportion of correctly aligned microspheres over and above what is achieved by the laws of chance.
According to U.S. Pat. No. 3,989,775 microspheres are fully silvered and applied to a surface leaving half of each microsphere exposed, which is then desilvered. The microspheres are applied to the surface of rigid and flexible plastics materials which are embossed to improve the retroreflective properties for light incident at a large angle to the perpendicular to the plane of the surface of the material. Flexible polyvinyl chloride is said to be a most preferred material since it is not only easily embossed in continuous manner but it may be plasticised with, for example, dioctyl phthalate and other well known plasticisers to give a material having drape properties that make it suitable for use in the manufacture of garments.
In JP 60-175004, an inexpensive retroreflector is produced by providing a transparent thermoplastic resin layer on a metallic film, glass microspheres are deposited in a layer thereon and pressed in to deform the metallic layer. A similar process using a thin reflective layer and microparticles is disclosed in WO 91/06880.
For providing retroreflection to clothing, especially outdoor and particularly protective clothing for night safety, strips of retroreflective tape are commercially available to be sewn or glued on to the material of the clothing. There is currently, however, no commercially viable method generally applicable to the coating of any desired fabric or other material surface with properly aligned microspheres to make it efficiently retroreflective. WO 88/07214, which uses magnetic or electrostatic orientation of magnetic or electric dipole particles only promises that 30% of the particles are correctly aligned, which is no more, or scarcely more, than would be expected by randomly scattering them.
The present invention provides a method by which hemispherically silvered microspheres can be applied to a surface of any desired material in correct orientation for maximum retroreflectivity.
The invention comprises a method for making a material retroreflective comprising the steps of: that a part of each bead is exposed and a part embedded in the adhesive layer; adhesive on the surface of the material; temporary adhesive layer and freed therefrom when attached to the permanent adhesive so that the coated parts of the beads are enclosed in the permanent adhesive.
The layer of beads may be applied to a temporary adhesive layer on a flexible substrate, such as a plastic film. A suitable such film for many applications is a clear adhesive tape such as that sold under the Registered Trade Mark "Sellotape".
The layer of beads may be applied by passing the substrate through a fluidised bed of the beads. The fluidised bed may be heated, which may have the effect of softening or making more tacky the adhesive layer--a p

REFERENCES:
patent: 3251704 (1966-05-01), Nellessen
patent: 5269840 (1993-12-01), Morris et al.
patent: 5358750 (1994-10-01), Brookfield

Affiliated with

Also associated with

Rating

Retroreflective materials does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Retroreflective materials, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Retroreflective materials will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1873843