Ultraviolet luminescent retroreflective sheeting

• US 5,759,671 A
• Filed: 08/15/1996
• Issued: 06/02/1998
• Est. Priority Date: 12/16/1994
• Status: Expired due to Term

• Current Assignee: Nippon Carbide Kogyo Kabushiki Kaisha (Nippon Carbide Industries Company Incorporated)
• Original Assignee: Nippon Carbide Kogyo Kabushiki Kaisha (Nippon Carbide Industries Company Incorporated)
• Inventors: Fushimi, Hidenori, Tanaka, Osamu, Hiromitsu, Kiyohito
• Primary Examiner(s): WATKINS III, WILLIAM P
• Application Number:
  US08/693,292
• Time in Patent Office: 656 Days
• Field of Search: 428/141, 428/143, 428/156, 428/195, 428/201, 428/203, 428/204, 428/207, 428/325, 428/913, 428/166, 428/178, 359/529, 359/530, 359/531, 359/532, 359/533, 359/534, 359/536, 40/612, 40/442, 40/542, 40/543, 40/582, 250/461.1, 250/486.1
• US Class Current: 428/166
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: G02B 5/128 transparent spheres being embedded in matrix
• CPC Class Codes: G09F 13/0472 Traffic signs
• CPC Class Codes: G09F 13/16 Signs formed of or incorporating reflecting elements or surfaces, e.g. warning signs having triangular or other geometrical shape
• CPC Class Codes: Y10S 428/913 Material designed to be responsive to temperature, light, moisture
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/24372 Particulate matter
• CPC Class Codes: Y10T 428/24479 including variation in thickness
• CPC Class Codes: Y10T 428/24562 Interlaminar spaces
• CPC Class Codes: Y10T 428/24661 Forming, or cooperating to form cells
• CPC Class Codes: Y10T 428/24802 Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
• CPC Class Codes: Y10T 428/24851 Intermediate layer is discontinuous or differential
• CPC Class Codes: Y10T 428/24868 Translucent outer layer
• CPC Class Codes: Y10T 428/24876 Intermediate layer contains particulate material [e.g., pigment, etc.]
• CPC Class Codes: Y10T 428/24901 including coloring matter
• CPC Class Codes: Y10T 428/252 Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]

Abstract

Ultraviolet luminescent retroreflective sheeting includes a retroreflective portion containing retroreflective elements and an ultraviolet luminescent portion to facilitate nighttime viewing by persons not located at or near a source of light being retroreflected by the retroreflective portion. At least part of the ultraviolet luminescent portion is provided as the bonding lines for bonding the transparent cover sheet to the support sheet to form a series of sealed cells in which the retroreflective elements, which may be of the encapsulated lens-type or the encapsulated cube-corner-type, are disposed. The ultraviolet luminescenct portion includes fluorescent agent which emits light when irradiation by ultraviolet irradiation. The ultraviolet luminescent retroreflective sheeting may be used in a display device, such as a roadside sign, in combination with a source of ultraviolet radiation means which may be formed integrally with the sheeting or spaced therefrom and which will, in operation, emit ultraviolet rays in the direction of the retroreflective sheeting.

Claims

1. Ultraviolet luminescent retroreflective sheeting comprising a retroreflective region having retroreflective elements and an ultraviolet luminescent region which emits light under ultraviolet radiation;

wherein the retroreflective region comprises

an encapsulated lens retroreflective region comprising a support layer, a substantial monolayer of transparent microspheres partially embedded in one surface of the support layer, a light reflective layer coating on the portion of the transparent microspheres which are embedded in the one surface of the support layer, a transparent surface protective film facing in spaced relationship to the one surface of the support layer, and a series of bonding lines bonding the protective film to the one surface of the support layer to thereby form a plurality of sealed, small compartment cells, each of the sealed cells containing therein a part of the substantial monolayer of transparent microspheres, the non-embedded portions of which are exposed to the atmosphere within the sealed cell, or

said retroreflective region comprises

an encapsulated cube-corner retroreflective region comprising a support layer;

a light-transmitting cover layer spaced apart from the support layer;

a layer of cube-corner retroreflective elements disposed on one surface of the cover layer facing the support layer, a series of bonding lines bonding the surface layer to the layer of cube-corner retroreflective elements and forming a plurality of sealed, small compartment cells, each of the sealed cells containing therein cube-corner retroreflective elements which are exposed to the atmosphere within the sealed cell, and

wherein the bonding lines comprise a fluorescent agent which emits light under ultraviolet radiation and a resin, wherein said bonding lines form at least a portion of the ultraviolet region, and,

wherein when the ultraviolet luminescent region is illuminated with a fluorescent lamp which emits near-ultraviolet rays of main wavelength around 360 nm at a light-receiving intensity of 0.8 mW/cm², the luminance is at least 10 cd/m².

2. The ultraviolet luminescent retroreflective sheeting according to claim 1, wherein the fluorescent agent comprises inorganic fluorescent agent.

3. The ultraviolet luminescent retroreflective sheeting according to claim 2, wherein the inorganic fluorescent agent is at least one member selected from the group consisting of red light-emitting inorganic fluorescent agent, green light-emitting inorganic fluorescent agent and blue light-emitting inorganic fluorescent agent.

4. The ultraviolet luminescent retroreflective sheeting according to claim 2, wherein the inorganic fluorescent agent has a particle size distribution such that at least 80% by weight of the particles have a size not greater than 25 μ

m.

5. The ultraviolet luminescent retroreflective sheeting according to claim 1, wherein the fluorescent agent emits light under irradiation of ultraviolet rays having a wavelength within the range of 250-400 nm.

6. The ultraviolet luminescent retroreflective sheeting according to claim 1, wherein the ultraviolet luminescent region contains 10-600 parts by weight of said fluorescent agent, per 100 parts by weight of the resin component.

7. The ultraviolet luminescent retroreflective sheeting according to claim 1, wherein the resin component comprises at least one resin selected from the group consisting of acrylic resins, urethane resins, polyester resins, vinyl chloride resins and fluorine-containing resins.

8. The ultraviolet luminescent retroreflective sheeting according to claim 1, wherein the luminance of the ultraviolet luminescent region is at least 20 cd/m².

9. The ultraviolet luminescent retroreflective sheeting according to claim 3, wherein the inorganic fluorescent agent comprises at least one red light-emitting agent selected from the group consisting of Y₂ O₃ :

Eu, Y(P,V)O₄ ;

Eu, Y₂ O₂ S;

Eu, 0.5MgF₂.3.5MgO.GeO₂ ;

Mn, YVO₄ ;

Eu and (Y,Gd)BO₃ ;

Eu.

10. The ultraviolet luminescent retroreflective sheeting according to claim 3, wherein the inorganic fluorescent agent comprises at least one green light-emitting agent selected from the group consisting of Zn₂ GeO₄ :

Mn, ZnO;

Zn, ZnS;

Cu, ZnS;

(Cu, Al), (Zn,Cd)S;

(Cu,Al), ZnS;

(Cu,Au,Al), Zn₂ SiO₄ ;

Mn, ZnS;

(Cu,Ag), (Zn,Cd)S;

Cu, Gd₂ O₂ S;

Tb, La₂ O₂ S;

Tb, Y₂, SiO₅ ;

(Ce,Tb), CeMgAl₁₁ O₁₉ ;

Tb, ZnS;

(Cu,Co), LaOBr;

(Tb,Tm), La₂ O₂ S;

Tb and BaMg₂ Al₁₆ O₂₇ ;

(Eu,Mu).

11. The ultraviolet luminescent retroreflective sheeting according to claim 3, wherein the inorganic fluorescent agent comprises at least one blue light-emitting agent selected from the group consisting of Sr₅ (PO₄)₃ Cl:

Eu, BaMg₂ Al₁₆ O₂₇ ;

Eu, BaMgAl₁₀ O₁₇ ;

Eu, ZnS;

Ag, CaWO₄, Y₂ SiO₅ ;

Ce, ZnS;

(Ag,Ga,Cl), Sr₂ P₂ O₇ ;

Eu, CaS;

Bi and CaSrS;

Bi.

12. The ultraviolet luminescent retroreflective sheeting according to claim 1, wherein said retroreflective region comprises said encapsulated lens retroreflective region.

13. The ultraviolet luminescent retroreflective sheeting according to claim 12, which further comprises an ultraviolet luminescent region on the support layer-facing surface of the light-transmitting cover layer or on the microspherical lens-embedding surface of the support layer.

14. The ultraviolet luminescent retroreflective sheeting according to claim 1, wherein said bonding lines are formed by printing.

15. The ultraviolet luminescent retroreflective sheeting according to claim 12, wherein, with respect to 100% of the incident side surface area of the sheeting, the areal ratio of the retroreflective region is within a range of 20-70%, the areal ratio of the ultraviolet luminescent region is within a range of 30-80%, and the sum of the areal ratios is 100%.

16. The ultraviolet luminescent retroreflective sheeting according to claim 1, wherein the retroreflective region comprises said encapsulated cube-corner retroreflective region.

17. The ultraviolet luminescent retroreflective sheeting according to claim 16, wherein, with respect to 100% of the incident side surface area of the sheeting, the areal ratio of the retroreflective region is within a range of 15-80%, the areal ratio of the ultraviolet luminescent region is within a range of 20-85%, and the sum of the areal ratios is 100%.

18. A display device comprising ultraviolet luminescent retroreflective sheeting according to claim 1, in combination with an ultraviolet radiation means for radiating ultraviolet rays in the direction of said sheeting.

19. The display device according to claim 18, wherein said ultraviolet luminescent retroreflective sheeting forms a display portion comprising one or more of characters, figures or signs.

20. The display device according to claim 19, which further comprises a background portion for said display portion, wherein the background portion comprises retroreflective sheeting having a color different from the color of the display portion.

21. The display device according to claim 19, which further comprises a background portion for said display portion, wherein the background portion comprises ultraviolet luminescent retroreflective sheeting having a different color tone from the color tone of the display portion.

22. The display device according to claim 19 wherein the sheeting and the ultraviolet radiation means are integrally combined.

23. The display device according to claim 20 wherein the sheeting and the ultraviolet means are installed at a distance one from the other.

24. Ultraviolet luminescent retroreflective sheeting comprising a retroreflective portion and an ultraviolet luminescent portion adjacent to but not substantially overlapping with the retroreflective portion,

wherein said retroreflective portion comprises retroreflective elements encapsulated within sealed cells, said sealed cells being formed by a support layer and a light transparent cover layer and bond lines connecting the support layer to the transparent cover layer;

and further wherein,

said bond lines comprise particles of fluorescent agent which emits light when irradiated by ultraviolet radiation, said particles being dispersed in a resin component, whereby said bond lines form said adjacent but non-overlapping ultraviolet luminescent portion;

wherein when the ultraviolet luminescent region is illuminated with a fluorescent lamp which emits near-ultraviolet rays of main wavelength around 360 nm at a light-receiving intensity of 0.8 mW/cm², the luminance is at least 10 cd/m².