EP0255251A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Retroreflective sheet with enhanced brightness
Assignee: 3M Co
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Filing: 1987-07-08
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Granted: —
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Expires: 2007-07-08
Abstract
Abstract Retroreflective construction comprising a monolayer of microspheres (2) with associated dielectric mirrors (10) which are hemispherically surrounded by tangentially-oriented, preferably contour-conforming, reflective pigment nacreous flakes. The dielectric mirrors (10) and reflective nacreous pigment flakes cooperate additively substantially without interfering with each other to provide a high brightness retroreflective sheet. The novel sheets retain much of their reflectivity after several launderings or drycleanings and, in some embodiments, can be made very flexible, making them well-suited for use as reflective fabrics.
Inventors
- 👤 Wallace K. C/O Minnesota Mining And Bingham
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 10:42
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/12; G02B5/126; G02B5/128
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
142 words
A retroreflective sheet characterized in that said sheet comprises: (A) a monolayer of transparent microspheres having a refractive index n₂; and (B) transparent specular reflectors associated with said microspheres in optical connection therewith, said specular reflectors comprising a transparent layer of refractive index n₁, the faces of said layer being in contact with materials of refractive index n₂ and n₃, wherein n₂ and n₃ are both at least 0.1 either higher or lower than n₁, said transparent layer having an optical thickness corresponding to an odd numbered multiple of about one quarter wavelength of light in the wavelength range of about 3,800 to 10,000 angstroms; partially embedded in (C) a base layer comprising a substantially transparent binder material and reflective nacreous pigment flakes which are arranged about the embedded portion of said microspheres and said specular reflectors in approximately tangential orientation thereto.
Claim 2
Dependent Claim
142 words
A retroreflective sheet characterized in that said sheet comprises: (A) a monolayer of transparent microspheres having a refractive index n₂; and (B) transparent specular reflectors associated with said microspheres in optical connection therewith, said specular reflectors comprising a transparent layer of refractive index n₁, the faces of said layer being in contact with materials of refractive index n₂ and n₃, wherein n₂ and n₃ are both at least 0.1 either higher or lower than n₁, said transparent layer having an optical thickness corresponding to an odd numbered multiple of about one quarter wavelength of light in the wavelength range of about 3,800 to 10,000 angstroms; partially embedded in (C) a base layer comprising a substantially transparent binder material and reflective nacreous pigment flakes which are arranged about the embedded portion of said microspheres and said specular reflectors in approximately tangential orientation thereto.
Claim 3
Dependent Claim
44 words
A sheet as defined in claim 1 further characterized in that said sheet comprises: (D) a transparent spacer layer disposed between said microspheres and said transparent specular reflectors; and (E) a flattop transparent layer in which the front surfaces of said microspheres are embedded.
Claim 4
Dependent Claim
15 words
A sheet as defined in claim 1 further characterized in that said microspheres are glass.
Claim 5
Dependent Claim
23 words
A sheet as defined in claim 1 further characterized in that said microspheres have a refractive index between about 1.4 and about 2.7.
Claim 6
Dependent Claim
24 words
A sheet as defined in claim 1 further characterized in that said microspheres have an average diameter between about 30 and about 150 microns.
Claim 7
Dependent Claim
25 words
A sheet as defined in claim 1 further characterized in that said base layer further comprises a coloring agent incorporated in said transparent binder material.
Claim 8
Dependent Claim
51 words
A sheet as defined in claim 1 further characterized in that said reflective nacreous pigment flakes have a thickness less than about 200 millimicrons, and have a maximum dimension which falls within the range of about 5 to about 80 microns, inclusive, which is less than the diameter of said microspheres.
Claim 9
Dependent Claim
34 words
A sheet as defined in claim 1 further characterized in that the concentration of said reflective nacreous flakes is at least about 15 percent by weight of the total solids in said base layer.
Claim 10
Dependent Claim
30 words
A sheet as defined in claim 1 further characterized in that said reflective nacreous pigment flakes conform to the contours of said microspheres and said specular reflectors in cup-like fashion.
Claim 11
Dependent Claim
18 words
A sheet as defined in claim 1 further characterized in that said reflective nacreous pigment flakes are transparent.
Claim 12
Dependent Claim
107 words
A sheet as defined in claim 1 further characterized in that (1) said microspheres are g|ass, have a refractive index between about 1.8 and 2.0 and have an average diameter between about 30 and 150 microns; (2) said base layer further comprises a coloring agent incorporated in said transparent binder material; (3) said reflective nacreous pigment flakes have a maximum dimension which falls within the range between about 8 and 30 microns, inclusive, which is less than the diameter of said microspheres, and have a thickness between about 30 and 60 millimicrons, and conform to the contours of said microspheres and said specular reflectors in cup-like fashion.
Claim 13
Dependent Claim
32 words
A sheet as defined in claim 1 further further characterized in that said sheet comprises: (D) a layer of adhesive disposed on the side of said base layer opposing said monolayer microspheres.
Claim 14
Dependent Claim
19 words
A sheet as defined in claim 16 further characterized in that said sheet is adhesively bonded to a fabric.
Claim 15
Dependent Claim
67 words
A sheet as defined in claim 1 further further characterized in that said sheet comprises: (D) a cover film disposed in spaced arrangement in front of said microspheres; and (E) a network of narrow intersecting bonds extending between said cover film and said base layer to adhere said cover film and said base layer together and form a plurality of cells within which microspheres are hermetically sealed.
References Cited (Backward Citations)
No citation records indexed.
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