US4763985A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Retroreflective sheet with enhanced brightness
Assignee: 3M Co
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Filing: 1986-08-01
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Granted: 1988-08-16
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Expires: 2006-08-01
Abstract
Abstract Retroreflective construction comprising a monolayer of microspheres with associated dielectric mirrors which are hemispherically surrounded by tangentially-oriented, preferably contour-conforming, reflective pigment nacreous flakes. The dielectric mirrors 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. Bingham
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:29
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/12; G02B5/126; G02B5/128
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
148 words
A retroreflective sheet comprising: (A) a monolayer of transparent microspheres having a refractive index n 2 ; and (B) transparent specular reflectors associated with said microspheres in optical connection therewith, said specular reflectors comprising a transparent layer of refractive index n 1 , the faces of said layer being in contact with materials of refractive index n 2 and n 3 , wherein n 2 and n 3 are both at least 0.1 either higher or lower than n 1 , 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
148 words
A retroreflective sheet comprising: (A) a monolayer of transparent microspheres having a refractive index n 2 ; and (B) transparent specular reflectors associated with said microspheres in optical connection therewith, said specular reflectors comprising a transparent layer of refractive index n 1 , the faces of said layer being in contact with materials of refractive index n 2 and n 3 , wherein n 2 and n 3 are both at least 0.1 either higher or lower than n 1 , 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
39 words
A sheet as defined in claim 1 further comprising: (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
12 words
A sheet as defined in claim 1 wherein said microspheres are glass.
Claim 5
Dependent Claim
20 words
A sheet as defined in claim 1 wherein said microspheres have a refractive index between about 1.4 and about 2.7.
Claim 6
Dependent Claim
19 words
A sheet as defined in claim 4 wherein said microspheres have a refractive index between about 1.8 and 2.0.
Claim 7
Dependent Claim
17 words
A sheet as defined in claim 5 wherein said microspheres have a refractive index of about 1.91.
Claim 8
Dependent Claim
21 words
A sheet as defined in claim 1 wherein said microspheres have an average diameter between about 30 and about 150 microns.
Claim 9
Dependent Claim
21 words
A sheet as defined in claim 7 wherein said microspheres have an average diameter between about 60 and about 75 microns.
Claim 10
Dependent Claim
22 words
A sheet as defined in claim 1 wherein said base layer further comprises a coloring agent incorporated in said transparent binder material.
Claim 11
Dependent Claim
48 words
A sheet as defined in claim 1 wherein 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 12
Dependent Claim
31 words
A sheet as defined in claim 10 wherein said maximum dimension is between about 8 and about 30 microns, inclusive, and said thickness is between about 30 and about 60 millimicrons.
Claim 13
Dependent Claim
31 words
A sheet as defined in claim 1 wherein the concentration of said reflective nacreous flakes is at least about 15 percent by weight of the total solids in said base layer.
Claim 14
Dependent Claim
26 words
A sheet as defined in claim 1 wherein reflective nacreous pigment flakes conform to the contours of said microspheres and said specular reflectors in cup-like fashion.
Claim 15
Dependent Claim
15 words
A sheet as defined in claim 1 wherein said reflective nacreous pigment flakes are transparent.
Claim 16
Dependent Claim
104 words
A sheet as defined in claim 1 wherein (1) said microspheres are glass, 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 17
Dependent Claim
26 words
A sheet as defined in claim 1 further comprising: (D) a layer of adhesive disposed on the side of said base layer opposing said monolayer microspheres.
Claim 18
Dependent Claim
14 words
A sheet as defined in claim 16 which is adhesively bonded to a fabric.
Claim 19
Dependent Claim
61 words
A sheet as defined in claim 1 further comprising: (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.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-08-16 | 1992-02-15 | 1992-08-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-08-16 | 1996-02-15 | 1996-08-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-08-16 | 2000-02-15 | 2000-08-16 | $7700.00 | Window Closed / Lapsed |