Retroreflective sheeting and methods for making same

• US 4,618,518 A
• Filed: 06/20/1985
• Issued: 10/21/1986
• Est. Priority Date: 08/10/1984
• Status: Expired due to Term

• Current Assignee: Avery Dennison Corporation
• Original Assignee: Amerace Corporation (ABB Limited)
• Inventors: Pricone, Robert M., Roberts, William N., Zanotti, Richard
• Primary Examiner(s): Lesmes, George F.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/747,103
• Time in Patent Office: 488 Days
• Field of Search: 428/161, 428/323, 428/173, 428/338, 428/331, 428/339, 428/343, 428/352, 428/354, 428/542.6, 427/164, 427/180, 427/212, 350/102, 350/103, 350/105, 350/109
• US Class Current: 428/41.5
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: Y10T 428/1462 Polymer derived from material having at least one acrylic or alkacrylic group or the nitrile or amide derivative thereof [e.g., acrylamide, acrylate ester, etc.]
• CPC Class Codes: Y10T 428/24521 with component conforming to contour of nonplanar surface
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/259 Silicic material
• CPC Class Codes: Y10T 428/268 Monolayer with structurally defined element
• CPC Class Codes: Y10T 428/269 including synthetic resin or polymer layer or component
• CPC Class Codes: Y10T 428/28 Web or sheet containing structurally defined element or component and having an adhesive outermost layer
• CPC Class Codes: Y10T 428/2839 with release or antistick coating
• CPC Class Codes: Y10T 428/2848 Three or more layers

Abstract

A retroreflective relatively flexible laminate sheet construction has a thermoplastic web with a smooth light-receiving first side and a second side coextensive with said first side. A retroreflective pattern is formed on the second side. A slurry of granular material is deposited on the second side to cover selected portions of the formed pattern with remaining portions of the formed pattern devoid of the granular material, and said slurry is dried or cured to produce a well-defined pattern. A layer of backcoating material is deposited on the second side to overlay the granular material, the backcoating material contacting the thermoplastic web where no granular material has been deposited, thereby encapsulating the granular material between the second side and the backcoating layer. An added, outer layer provides additional weather protection for the thermoplastic web. Methods are detailed to manufacture the laminate, and compositions of backcoating mixtures also are disclosed.

Claims

1. A flexible retroreflective cube corner type laminate sheet construction including a thermoplastic web with a light-receiving and transmitting first side and a second side coextensive with said first side, and a cube corner type retroreflective pattern formed on at least a portion of said second side, said construction comprising:

a layer of hydrophobic granular material deposited on said second side to cover selected portions of said formed cube corner retroreflective pattern with remaining portions of said second side devoid of said hydrophobic granular material; and

a layer of backcoating material deposited on said second side to substantially completely overly said hydrophobic granular material without disturbing the pattern formed by said granular material, said backcoating material substantially fully contacting said portions of said second side devoid of said granular material and being fixedly secured thereto, thereby encapsulating said hydrophobic granular material between said second side and said backcoating layer, the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in the area devoid of said granular material.

2. The construction of claim 1, wherein said hydrophobic granular material is deposited so as to form a well-defined regular and repeating array.

3. The construction of claim 1, wherein said hydrophobic granular material is deposited so as to form a discrete, regularly-spaced array of pattern elements,

each said pattern element being surrounded by contiguous portions of said second side devoid of said granular material.

4. The construction set forth in claim 3, in which said array of elements repeats itself in regular intervals.

5. The construction of claim 1, wherein said hydrophobic granular material is hydrophobic silica.

6. The construction of claim 1, wherein said hydrophobic granular material has a primary particle size of about 18 nanometers.

7. The construction of claim 1, wherein said hydrophobic granular material is hydrophobic silica.

8. The construction of claim 1, wherein said backcoating consists essentially of a polymeric or copolymeric, water-based system.

9. The construction of claim 8, wherein said backcoating includes a major proportion of an acrylic/urethane copolymer.

10. The construction of claim 8, wherein said backcoating includes a major proportion of a polymeric acrylic water-borne system.

11. The construction of claim 8, wherein said backcoating comprises an acrylic/urethane copolymer, a coloring agent, and an acrylic-based thickening agent.

12. The construction of claim 11, wherein said backcoating includes a defoaming agent.

13. The construction of claim 8, wherein said backcoating comprises a polymeric acrylic system, a coloring agent, and a thickening agent.

14. The construction of claim 8, wherein said backcoating comprises an acrylic/urethane copolymer, a coloring agent, a thickener and a cross-linking agent.

15. The construction of claim 14, wherein said backcoating includes a defoaming agent.

16. The construction of claim 15, wherein said backcoating, when dried, comprises of about the following constituents by weight:

73.7% acrylic/urethane copolymer;

21.6% coloring agent;

0.8% thickening agent;

1.3% defoaming agent; and

2.6% cross-linking agent.

17. The construction of claim 1, further including a lamina of flexible thermoplastic material co-extensive with and secured to said light-receiving and transmitting side of said thermoplastic web,

said lamina including means for absorbing radiation in about the ultraviolet range.

18. The construction of claim 17, wherein said lamina is formed from polymethyl methacrylate in a thickness from about 0.2 mil to 0.4 mil.

19. The construction of claim 17 wherein said lamina is formed from a rubber-based cross-linked thermoplastic acrylic polymer composition, and

said absorbing means is 2-(2H-benzotriazol-2-yl)-4-methyl-phenol.

20. The construction of claim 19, wherein said lamina is from about 0.5 mil to about 2.3 mil in thickness.

21. The construction of claim 1, further including a lamina of flexible thermoplastic material co-extensive with and secured to said light-receiving and transmitting side of said thermoplastic web,

said lamina including a rubber-based cross-linked thermoplastic acrylic polymer composition.

67. The construction of claim 1, 22 on 55, wherein substantially the entire second side is formed to contain cube corner elements therein and said backcoating adheres directly to portions of said cube corner elements devoid of said hydrophobic granular material.

22. A retroreflective cube corner laminate sheet construction comprising:

a thermoplastic web having a light-receiving and transmitting first side, and a second side coextensive with said first side;

said second side having a repeating retroreflective cube corner pattern formed on at least a portion thereof;

a layer of hydrophobic granular material disposed on said second side to cover selected portions of said formed cube corner pattern and leaving remaining area of said second side devoid of said hydrophobic granular material;

a layer of backcoating material deposited on said second side to overlay said hydrophobic granular material;

said backcoating material also contacting substantially all of said remaining area of said second side devoid of said hydrophobic granular material;

the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material, whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in said remaining area devoid of said granular material;

said backcoating material being in secure attachment to said second side at said remaining area, thereby encapsulating said granular material between said second side and said backcoating material;

a layer of adhesive applied to and generally co-extensive with said backcoating material; and

a release sheet releably secured to said adhesive layer.

23. The construction of claim 22, wherein said hydrophobic granular material is deposited on said second side so as to form a regular and repeating array.

24. The construction of claim 23, wherein said array includes discrete, regularly-spaced pattern elements of selected geometric shape;

and

each said pattern element is surrounded by contiguous portions of said second side devoid of said hydrophobic granular materials.

25. The construction of claim 24, wherein said array comprises an array of square pattern elements;

said pattern elements defining therebetween a series of paths devoid of said hydrophobic granular material.

26. The construction of claim 22, wherein said hydrophobic granular material has a particle size of about 18 nanomters.

27. The construction of claim 22, wherein said hydrophobic granular material is hydrophobic silica.

28. The construction of claim 22, wherein said backcoating includes a major proportion of a water-borne acrylic-urethane copolymer.

29. The construction of claim 22, wherein said backcoating includes a major proportion of a polymeric acrylic water-borne system.

30. The construction of claim 24, wherein said hydrophobic granular material is hydrophobic silica.

31. The construction of claim 22, further including a lamina of flexible thermoplastic material co-extensive with and secured to said light-receiving and transmitting side of said thermoplastic web,

said lamina including means for absorbing radiation in about the ultraviolet range.

32. The construction of claim 31, wherein said lamina is formed from a rubber-based cross-liked thermoplastic acrylic polymer composition, and

said absorbing means is 2-(2H-benzotriazol-2-yl)-4-methyl-phenol.

34. The construction of claim 22, wherein said lamina is formed from polymethyl methacrylate in a thickness from about 0.2 mil to 0.4 mil.

35. A method for producing a cube corner type retroreflective laminate sheet construction, said method comprising the steps of:

(a) applying a layer of hydrophobic granular material to a web of thermoplastic material having a retroreflective cube corner formed pattern on at least a portion of one side, said granular material deposited so as to form a regular and repeating array on said retroreflective pattern;

(b) forming, as part of said array a plurality of paths on said one side devoid of said hydrophobic granular material;

(d) applying a layer of backcoating material to overlay said hydrophobic granular material and to fill said paths; and

(d) adhering said backcoating material to encapsulate said hydrophobic granular material between said formed side and said backcoating material,

the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in the area devoid of said granular material.

33. The construction of claim 40, wherein said lamina is from about 0.5 mil to about 2.0 mil in thickness.

36. The method of claim 35 wherein said layer of hydrophobic granular material consists initially of a slurry comprising a hydrophobic granular material, a polar solvent, and a non-polar solvent, said polar solvent and said non-polar solvent present in relative proportions sufficient to allow deposition of said hydrophobic granular material in said well-defined array on said thermoplastic web.

37. The method of claim 36, wherein said polar solvent is an aliphatic alcohol.

38. The method of claim 36, wherein said polar solvent is n-butanol.

39. The method of claim 36, wherein said non-polar solvent comprises low odor mineral spirits.

40. The method of claim 36, wherein said polar solvent is present in an amount from about 10% to about 30% of said slurry, and said non-polar solvent is present in an amount from about 40% to about 70% of said slurry.

41. The method of claim 36, wherein said polar solvent is present in an amount of about 15% of said slurry.

42. The method of claim 36, wherein said slurry consists of from about 15% to about 35% of said hydrophobic granular material, from about 10% to about 30% of said polar solvent, and from about 40% to about 70% of said non-polar solvent.

43. The method of claim 36, wherein said slurry includes a thixotropic thickener.

44. The method of claim 35 wherein said backcoating consists of the following constituents:

(a) a water-borne mixture of an acrylic/urethane copolymer in a proportion from about 70 perent to about 90 percent;

(b) a coloring agent in a proportion from about 6 percent to about 24 percent;

(c) a defoamer in a proportion from about 0.4 percent to about 0.9 percent;

(d) an acrylic-based thickening agent in a proportion from about 1.5 percent to about 3.5 percent;

(e) deionized water in a proportion from none to about 5 percent; and

(f) a pH-adjusting agent in a proportion from none to about 0.3 percent.

45. The method of claim 44, wherein said backcoating includes:

(g) an aqueous solution of a cross-linking agent in a proportion from about 0.5 percent to about 1.5 percent, by weight, of constituents (a)-(d).

46. The method of claim 35, wherein said backcoating consists of the following constituents:

(a) a water-borne polymeric acrylic system in a proportion from about 42 percent to about 62 percent;

(b) water in a proportion from about 2 percent to about 12 percent;

(c) an anti-skinning agent in a proportion from about 1.5 percent to about 2.5 percent;

(d) a coloring agent in a proportion from about 5 percent to about 36 percent;

(e) a flatting agent in a proportion from about 3 percent to about 5 percent;

(f) a pH-adjusting agent in a proportion from about 0.3 percent to about 0.5 percent;

(g) a defoamer in a proportion from about 0.6 percent to about 1.0 percent;

(h) a coalescent solvent in a proportion from about 1.0 percent to 1.6 percent; and

(i) a thickener in a proportion from 0 percent to 3.6 percent.

47. The method of claim 35, wherein said slurry includes a polar solvent and a non-polar solvent.

48. The method of claim 47, wherein said polar solvent is an aliphatic alcohol.

49. The method of claim 47, wherein said polar solvent is n-butanol.

50. The method of claim 47, wherein said non-polar solvent comprises low odor mineral spirits.

51. The method of claim 35, further including the step of:

(e) securing an overlayer of weather-resistant thermoplastic material containing absorbers of radiation in about the ultra-violet range, to that side of said web opposite to the side on which said cube corner type pattern is formed.

52. The method of claim 35, interposing between steps (b) and (c) the step of:

(b₁) drying said layer of hydrophobic granular material.

53. The method of claim 35, wherein said hydrophobic granular material is hydrophobic silica.

54. The method of claim 35, wherein substantially said entire second side is formed to contain cube corner elements therein and said backcoating adheres directly to portions of said cube corner elements devoid of said hydrophobic granular material.

55. A flexible cube corner type retroreflective laminate sheet construction including a retroreflective web with a light-receiving and transmitting first side and a second side co-extensive with said first side, and a cube corner type retroreflective pattern formed on at least a portion of said second side, said construction comprising:

a layer of hydrophobic granular material deposited on said second side to cover selected portions of said cube corner pattern, with the uncovered portions of said second side forming paths devoid of said granular material;

a layer of backcoating material deposited on said second side to overlay said hydrophobic granular material, said backcoating material contacting said uncovered portions of said cube corner pattern on said second side and being fixedly secured thereto, thereby encapsulating said granular material between said second side and said backcoating layer, the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material wherein said backcoating material is unable to penetrate said granular material and interact with said second side pattern except in said uncovered portions; and

said paths being sized and shaped to cover a selected portion of the surface area of said cube corner pattern found in said second web side thereby to control the amount of incident light reflected from said first side of said retroreflective web, without changing said formed cube corner pattern on said second side.

56. The construction of claim 55, wherein said hydrophobic granular material is deposited so as to form a regularly-spaced array of discrete pattern elements,

each said pattern element being surrounded by contiguous portions of said paths.

57. The construction of claim 56, wherein said pattern elements are square.

58. The construction of claim 56, wherein each said pattern element is a square having sides of 0.200 inch and each said path is 0.015 inch wide.

59. The construction of claim 56, wherein each said pattern element is a square having sides of 0.138 inch wide and each said path is 0.127 inch wide.

60. The construction of claim 56, wherein each said element is a square having sides of 0.096 inch and each said path is 0.029 inch wide.

61. The construction of claim 56, wherein each said pattern element is a square having sides of 0.170 inch wide and each said path is 0.030 inch wide.

62. The construction of claim 55, wherein said paths define rectangular pattern elements.

63. The construction of claim 55, including a lamina co-extensive with and secured to said first side of said retroreflective web,

said lamina including means to absorb radiation in about the ultraviolet range on said retroreflective web.

64. The construction of claim 63, wherein said lamina is formed of polymethyl methacrylate in a thickness of about 0.2 mil to about 0.4 mil.

65. The construction of claim 63, wherein said lamina is formed from a rubber-based, cross-linked thermoplastic acrylic polymer composition.

66. The construction of claim 63, wherein said absorbing means is 2-(2H-benzotriazol-2-yl)-4-methyl-phenol.