US3700305A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Retroreflective microspheres having a dielectric mirror on a portion of their surface and retroreflective constructions containing such microspheres
Assignee: 3M Co
•
Filing: 1970-12-14
•
Granted: 1972-10-24
•
Expires: 1990-12-14
Abstract
Abstract Retroreflective constructions containing microspheres with adjacent dielectric mirrors. Also microspheres having a plurality of coatings on a portion of their surface to form a dielectric mirror thereon.
Inventors
- 👤 Wallace Karl Bingham
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 08:05
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/12; G02B5/126; G02B5/128
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
27 words
The retroreflective construction of claim 1 in which said specular reflectors comprise a plurality of transparent layers having successively alternating refractive indices of at least 0.1 difference.
Claim 2
Dependent Claim
18 words
The retroreflective construction of claim 2 wherein the said successively alternating refractive indices have at least 0.3 difference.
Claim 3
Dependent Claim
24 words
The retroreflective construction of claim 2 in which the plurality of transparent layers comprises from two to seven layers adjacent said spherical lens elements.
Claim 4
Dependent Claim
21 words
The retroreflective construction of claim 1 wherein said material of refractive index n2 is the material of said spherical lens elements.
Claim 5
Dependent Claim
21 words
The retroreflective construction of claim 5 in which said material of refractive index n3 is a binder for said lens elements.
Claim 6
Dependent Claim
31 words
The retroreflective construction of claim 5 in which the material of refractive index n3 is a second transparent layer having an optical thickness corresponding to that of the other transparent layer.
Claim 7
Dependent Claim
28 words
The retroreflective construction of claim 1 in which n1 is in the 1.7 to 4.9 range and n2 and n3 are both in the 1.2 to 1.7 range.
Claim 8
Dependent Claim
28 words
The retroreflective construction of claim 1 in which n1 is in the 1.2 to 1.7 range and n2 and n3 are both in the 1.7 to 4.9 range.
Claim 9
Dependent Claim
27 words
The retroreflective construction of claim 1 in which said spherical lens elements and adjacent specular reflectors are partially embedded in a binder containing a diffuse reflecting material.
Claim 10
Dependent Claim
95 words
Retroreflective microspheres having a diameter between 10 and 200 microns and a refractive index n2 and having on about a hemispherical portion of the surface thereof at least two transparent layers with 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, the transparent layer most adjacent said microsphere having a refractive index of n1 and the next adjacent transparent layer having a refractive index of n3, n1 being at least 0.1 greater or less than both n2 and n3.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-24 | 1976-04-24 | 1976-10-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-24 | 1980-04-24 | 1980-10-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-24 | 1984-04-24 | 1984-10-24 | $7700.00 | Window Closed / Lapsed |