Shaped plastic articles having replicated microstructure surfaces

• US 4,576,850 A
• Filed: 07/20/1978
• Issued: 03/18/1986
• Est. Priority Date: 07/20/1978
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Martens, John A.
• Primary Examiner(s): Kittle, John E.
• Application Number:
  US05/926,325
• Time in Patent Office: 2,798 Days
• Field of Search: 427/44, 204/159.16, 204/159.19, 204/159.13, 204/159.23, 264/1, 264/22, 264/DIG. 42, 264/1.1, 264/1.3, 264/1.4, 156/272, 428/156, 528/28
• US Class Current: 428/156
• CPC Class Codes: B29D 11/00605 Production of reflex reflectors
• CPC Class Codes: C08G 18/672 Esters of acrylic or alkyl acrylic acid having only one group containing active hydrogen
• CPC Class Codes: G02B 1/04 made of organic materials, e.g. plastics G02B1/08 takes precedence
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: Y10T 428/24479 including variation in thickness

Abstract

An article comprising a shaped, plastic layer or body comprising crosslinked polymer with hard and soft segments or moieties and having a microstructure-bearing surface is prepared by a process comprising filling a mold master, bearing or encoded with the microstructure to be replicated, with a fluid, castable, one-part, preferably solvent-free, radiation addition-polymerizable, crosslinkable, synthetic, organic oligomeric composition (or precursors thereof) having "hard" segments and "soft" segments, exposing the resulting cast composition to radiation, preferably actinic radiation such as ultraviolet radiation, and thereby forming said article, e.g., a retroreflective cube-corner sheeting, Fresnel lens or video disc.

Claims

1. An article, useful for an optical purpose, comprising a shaped, plastic, optically homogeneous, cast, monolithic layer having a replicated microstructure-bearing surface whose configuration contains a plurality of utilitarian discontinuities which characterize said optical purpose of said article, said layer comprising crosslinked polymer composed of (1) a plurality of hard segments of mono- or polyvalent moieties containing one or more carbocyclic and/or heterocyclic groups, wherein each of said moieties of said hard segments, when their valences are satisfied by protons, has at least one major transition temperature above 250°

K., and (2) a plurality of soft segments of mono- or polyvalent moieties, wherein each of said moieties of said soft segments has a number average molecular weight of about 500 to 5000 and homopolymers thereof have a glass transition temperature below 250°

K.

2. An article according to claim 1 wherein said crosslinked polymer has a gel swell within the range of 35 to 200 weight percent.

3. An article according to claim 1 wherein said crosslinked polymer has 10 to 80 weight percent of said hard segments and 10 to 60 weight percent of said soft segments.

4. An article according to claim 1 wherein said crosslinked polymer has dynamic shear moduli, over the temperature range of 23°

C. to 120°

C., which fall on or within the boundary of A-B-C-D of FIG. 1.

5. An article according to claim 1 wherein a diffraction grating of said crosslinked polymer has a first order diffraction efficiency which changes less than 15% when heated at 130°

C. for 1 hour as compared to the first order diffraction efficiency before heating.

6. An article according to claim 1 wherein said microstructure-bearing surface has an average profile which is plano, convex, concave, aspheric, or combinations thereof, the heights of said discontinuities deviating from said average profile by ±

0.005 μ

m to ±

750 μ

m, said discontinuities being the same or different and spaced apart or contiguous in a random or ordered manner.

7. An article according to claim 1 in the form of a retroreflective sheet comprising an array of cube-corner prism elements.

8. An article according to claim 1 wherein said crosslinked polymer is formed upon radiation of an oligomeric composition comprising one or more oligomers having (1) one or more like or different hard segments each comprising a mono- or poly-valent moiety containing one or more carbocyclic and/or heterocyclic groups, (2) one or more like or different soft segments each comprising a mono- or poly-valent moiety selected from the group consisting of polyester, polyacrylate, polyether and polyolefin, and (3) one or more like or different monovalent moieties containing a radiation sensitive, addition-polymerizable, functional group selected from the group consisting of acrylyl, methacrylyl, allyl, and vicepoxy.

9. An article according to claim 1 in the form of a video disc.

10. An article according to claim 1 in the form of a diffraction grating.

11. An article according to claim 1 in the form of an ophthalmic lens.

12. An article according to claim 1 wherein said hard segments are represented by one of the following formulas:

##STR112## where each A is independently --NH-- or --O--, each R² is independently hydrogen or a lower alkyl,

each R³ is independently a di-valent carbocyclic-containing radical derived from benzene, napthalene, cyclohexane, dicyclohexylmethane, diphenylmethane, or norbornene, and their lower alkyl-substituted derivatives, by removal of two of their hydrogen atoms,

each R⁴ is independently an alkylene moiety with 2 to 10 carbon atoms, or a cycloalkylene moiety with 6 to 10 carbon atoms,

g is zero or a number up to 5,

h is an integer of 1 to 10,

h'"'"' is zero or an integer of 1 to 10,

each d, d'"'"' and d" is independently zero or 1, with the proviso that if either one of d'"'"' or d" is 1, then the other is zero,

and said soft segments are represented by one of the following formulas;

##STR113## where r'"'"' is a number of 1 to 10 and e'"'"' is 2 or 3, ##STR114## where r'"'"' is a number of 1 to 10 and s is 2 or 3, and R⁹ is oxyalkylene, polyoxyalkylene, or alkanetriyl.

13. An article according to claim 1 wherein said hard segments are represented by the formula:

##STR115## where each A is independently --NH-- or --O--, each R³ is independently a di-valent carbocyclic-containing radical derived from benzene, napthalene, cyclohexane, dicyclohexylmethane, diphenylmethane, or norbornene, and their lower alkyl-substituted derivatives, by removal of two of their hydrogen atoms,

each R⁴ is independently an alkylene moiety with 2 to 10 carbon atoms, or a cycloalkylene moiety with 6 to 10 carbon atoms,

g is zero or a number up to 5, and each d is independently zero or 1.

14. An article according to claim 1 wherein said hard segments comprise those represented by the formula ##STR116## and said soft segments comprise those represented by one of the following formulas ##STR117##

15. An article according to claim 1 wherein said hard segments comprise those represented by the formula:

##STR118## and said soft segments comprise those represented by the formula;

##STR119##

16. An article according to claim 1 wherein the heights of said discontinuities deviate from the average profile of said surface by ±

0.1 μ

m to ±

750 μ

m, said discontinuities being the same or different and spaced apart or contiguous in a random or ordered manner, and wherein said polymer has optical homogenity manifested by at least 91% transmission of light, haze of less than 5%, and birefringence, Δ

η

, of less than 0.002.

17. An article according to claim 1 in the form of a Fresnel lens element.

18. An article according to claim 1 in the form of an echelon lens element.

19. An optical article according to claim 1 wherein said optical purpose is that of refraction, said surface is that replicated from a mold master having a microstructure-bearing surface, and said layer consists essentially of said plastic.

20. An optical article according to claim 1 wherein said optical purpose is that of diffraction, said surface is that replicated from a mold master having a microstructure-bearing surface, and said layer consists essentially of said plastic.

21. A shaped plastic article, useful for an optical purpose, comprising a shaped, plastic, cast, monolithic layer having a replicated microstructure-bearing surface whose configuration contains a plurality of utilitarian discontinuities which characterizes said optical purpose of said article, said layer comprising crosslinked polymer composed of (1) a plurality of hard segments of mono- or polyvalent moieties containing one or more carbocyclic and/or heterocyclic groups and difunctional linking groups with hydrogen bonding capability, and (2) a plurality of soft segments of mono- or polyvalent moieties, wherein each of said moieties of said hard segments, when their valences are satisfied by protons, has at least one major transition temperature above 250°

K., and wherein each of said moieties of said soft segments has a number average molecular weight of about 500 to 250 and homopolymers thereof have a glass transition temperature below 250°

K., said crosslinked polymer having a gel swell within the range of 35 to 200 weight percent, 10 to 80 weight percent of said hard segments and 10 to 60 weight percent of said soft segments, and dynamic shear moduli, over the temperature range of 23°

C. to 120°

C., which fall on or within the boundary of A-B-C-D of FIG. 1, and wherein a diffraction grating of said crosslinked polymer has a first order diffraction efficiency which changes less than 15% when heated to 130°

C. for 1 hour as compared to the first order diffraction efficiency before heating.

22. An article according to claim 21 wherein difunctional linking groups are carbonyldioxy, carbamato, ureylene, amido or oxy.

23. An article, useful for an optical purpose, comprising a shaped, plastic, optically homogeneous, cast, monolithic layer having a replicated microstructure-bearing surface whose configuration contains a plurality of utilitarian discontinuities which characterize said optical purpose of said article, said layer comprising crosslinked polymer composed of (1) a plurality of hard segments of mono- or polyvalent moieties containing one or more carbocyclic and/or heterocyclic groups, and (2) a plurality of soft segments of mono- or polyvalent moieties, wherein said hard segments are represented by one or more of the following formulas:

##STR120## where each A is independently --NH-- or --O--,

each B is ##STR121## where f is an integer of 2 to 5, each R² is independently hydrogen or a lower alkyl,

each R³ is independently a di-valent carbocyclic-containing radical derived from benzene, naphthalene, cyclohexane, dicyclohexylmethane, diphenylmethane or norbornene, and their lower alkyl-substituted derivatives, by removal of two of their hydrogen atoms,

each R⁴ is independently an alkylene moiety with 2 to 10 carbon atoms, or a cycloalkylene moiety with 6 to 10 carbon atoms,

each R⁵ is independently a phenyl moiety or methyl,

each R⁶ is independently a lower alkyl with 1 to 4 carbon atoms, g is zero or a number up to 5, h is an integer of 1 to 10, h'"'"' is zero or an integer of 1 to 10,

each d, d'"'"' and d" is independently zero or 1, with the proviso that if either one of d'"'"' or d" is 1, then the other is zero,

and wherein said soft segments are residues remaining from removal of the active hydrogen atoms of one or more of the following;

poly(oxyalkylene) polyols, polyester polyols, polyether polyester polyols, polyolefin polyols, poly(alkylacrylate) polyols, and polyamines.

24. An article according to claim 23 wherein said soft segments are represented by one or more of the following formulas:

##STR122## where each A is independently --NH-- or --O--,

(OR⁷)_i is oxyalkylene or poly(oxyalkylene),

R⁷ is an alkylene of 2 to 4 carbon atoms,

R⁸ is a saturated aliphatic radical free of active hydrogen atoms and which can contain 1 or 2 non-vicinal catenary oxygen or nitrogen atoms, R⁸ having a valence equal to j and 2 to 10 carbon atoms,

i is a number of 1 to 20,

j is an integer of 1 to 3, and

d and c are each independently zero or 1 with the provisos that when d is 1, then c is zero and j is 2 or 3, and when d is zero, then j is 1, ##STR123## where R⁹ is a saturated aliphatic radical free of active hydrogen atoms and can contain 1 or 2 nonvicinal catenary oxygen or nitrogen atoms, R⁹ having a valence equal to s and 2 to 10 carbon atoms,

each a, o, p and q is independently zero or 1,

each e'"'"' is independently an integer of 2 to 10,

each r is independently a number of 1 to 20,

each s is independently an integer of 1 to 3 with proviso that

when q is 1, then s is 2 or 3 and o is zero and either a and p are both zero or both 1, and

when q is zero, then s and o are 1 and either a and p are both zero or both 1, ##STR124## where t is a number of 7 to 35, ##STR125## where the groups enclosed by the single brackets with the subscripts u and v are repeating units randomly distributed within the double brackets and u and v are integers whose sum is from 2 to 20 and u/v is a ratio of 1/4 to 4/1, s is 2 or 3, and R¹⁰ is a polyvalent carbocyclic-containing radical derived from benzene, naphthalene, or a phenyl-substituted benzene by removal of 2 or more hydrogen atoms, ##STR126## where each R¹¹ is independently hydrogen or methyl,

R¹² is independently an alkyl of 2 to 10 carbon atoms,

R¹³ is independently, --C(O)OCH₃, --CN or phenyl,

R¹⁴ is --SR¹⁵ H, --SR¹⁵ O--, --SCH₂ C(O)OR¹⁵ H or H, where R¹⁵ is an alkylene having 1 to 12 carbon atoms,

f is an integer of 2 to 5

and the groups enclosed by the single brackets with subscripts x, y and z are repeating units randomly distributed within the double brackets, and sum of x, y and z being such that the number average molecular weight of the totality of said repeating units is about 500 to 5000, the units enclosed by brackets with subscripts x and y always being present and the units enclosed by the bracket with subscript z being optionally present.

25. An article according to claim 24 wherein said soft segments are represented by one or more of the following formulas:

##STR127## where each f'"'"' is independently 2 to 4 and i'"'"' is 5 to 10, ##STR128## where f'"'"' is 2 to 4, i'"'"' is 5 to 10, and k is 2 or 3 and is the valence of R⁸, ##STR129## where the groups enclosed by the single brackets with subscripts m and n are repeating units randomly distributed, m is zero or 1 to 4, n is 4 to 20, with the proviso that n/m is at least 4, and ##STR130## where the groups enclosed by the brackets with subscripts m and n are repeating units randomly distributed within the double brackets, m, n, and n/m are as defined above, and k is 2 or 3 and is the valence of R⁸.

26. An article according to claim 24 wherein said soft segments are represented by one or more of the following formulas:

##STR131## where r'"'"' is a number of 1 to 10 and e'"'"' is 2 or 3, ##STR132## where r'"'"' is a number of 1 to 10 and s is 2 or 3, and R⁹ is oxyalkylene, polyoxyalkylene, or alkanetriyl, ##STR133## where each e'"'"' is independently a number of 2 to 5 and r'"'"' is a number of 1 to 10, and ##STR134## where e'"'"' is a number of 2 to 5, r'"'"' is a number of 1 to 10, R⁹ is as defined above, and s is 2 or 3.

27. A plastic diffraction grating comprising a shaped, plastic, monolithic layer having a diffraction grating-bearing surface and comprising crosslinked polymer composed of (1) 20 to 50 weight percent of a plurality of hard segments selected from those represented by one or both of the formulas ##STR135## where each A is --NH-- or --O--,

A'"'"' is --NH--,

each R³ is independently a di-valent carbocyclic-containing radical derived from benzene, naphthalene cyclohexane, dicyclohexylmethane, or diphenylmethane, and their lower alkyl-substituted derivatives, by removal of two of their hydrogen atoms,

each R⁴ is independently an alkylene moiety with 2 or 4 carbon atoms, or a cycloalkylene moiety with 6 to 10 carbon atoms,

each R⁵ is phenyl,

each d is independently zero or 1

g is zero or a number having an average of 1 to 3, and

h'"'"' is zero or an integer of 1 to 10

(2) 15 to 45 weight percent of a plurality of soft segments selected from those represented by one or more of the formulas:

##STR136## where r'"'"' is a number of 1 to 5 and e'"'"' is 2 or 3, ##STR137## and where r'"'"' is a number of 1 to 5 and s is 2 or 3, and R⁹ is oxyalkylene, polyoxyalkylene, or alkanetriyl,

said crosslinked polymer having a gel swell within the range of 35 to 200 weight %, and dynamic shear moduli, over a temperature range of 23°

to 120°

C., which fall on or within the boundary of A-B-C-D of FIG. 1, and wherein the first order diffraction efficiency of said grating changes less than 5% when heated at 130°

C. for 1 hour as compared to the first order diffraction efficiency before heating.

28. A plastic retroreflective sheet comprising a shaped, plastic, cast, mono-lithic layer having a surface with an array of a plurality of contiguous trihedral or tetrahedral prism elements and comprising optically homogeneous crosslinked polymer composed of (1) 20 to 50 weight percent of a plurality of hard segments represented by the formula ##STR138## where each A is independently --NH-- or --O--,

A'"'"' is --NH--,

each R³ is independently a di-valent carbocyclic-containing radical derived from cyclohexane or dicyclohexylmethane, and their lower alkyl-substituted derivatives, by removal of two of their hydrogen atoms,

each R⁴ is independently an alkylene moiety with 2 to 10 carbon atoms, or a cycloalkylene moiety with 6 to 10 carbon atoms,

d is 1, and

g is zero or a number up to 5,

(2) 15 to 45 weight percent of soft segments selected from one of the following formulas ##STR139## where r'"'"' is a number of 1 to 10 and e'"'"' is 2 or 3, ##STR140## where r'"'"' is a number of 1 to 10 and s is 2 or 3 and R⁹ is oxyalkylene, polyoxyalkylene or alkanetriyl, ##STR141## where each R¹¹ is independently hydrogen or methyl,

R¹² is independently an alkyl of 2 to 10 carbon atoms,

R¹³ is independently --C(O)OCH₃, --CN or phenyl,

R¹⁴ is --SR¹⁵ H, --SR¹⁵ O--, --SCH₂ C(O)OR¹⁵ H or H, where R¹⁵ is an alkylene having 1 to 12 carbon atoms,

f is an integer of 2 to 5

the groups enclosed by the single brackets with subscripts x, y and z are repeating units randomly distributed within the double brackets, the sum of x, y and z being such that the number average molecular weight of the totality of said repeating units is about 500 to 5000, the units enclosed by brackets with subscripts x and y always being present and the units enclosed by the bracket with subscript z being optionally present, said crosslinked polymer having a gel swell within the range of 35 to 200 weight percent, said crosslinked polymer in the form of a diffraction grating having a first order diffraction efficiency which changes less than 5% when heated at 130°

C. for 1 hour as compared to the first order diffraction efficiency before heating, said retroreflective sheet having a brightness of at least 600 candles per lumen at 0.2°

divergence angle.

29. A plastic lens element comprising a shaped, plastic, cast, monolithic layer having on its surface a linear Fresnel or echelon pattern, and comprising optically homogeneous crosslinked polymer composed of (1) 20 to 50 weight percent of a plurality of hard segments represented by the formula ##STR142## where each A is independently --NH-- or --O--,

A'"'"' is --NH--

each R³ is independently a di-valent carbocyclic-containing radical derived from cyclohexane or dicyclohexylmethane, and their lower alkyl-substituted derivatives, by removal of two of their hydrogen atoms,

each R⁴ is independently an alkylene moiety with 2 to 10 carbon atoms, or a cycloalkylene moiety with 6 to 10 carbon atoms,

d is 1, and

g is zero or a number up to 5,

(2) 15 to 45 weight percent of soft segments selected from one of the following formulas ##STR143## where r'"'"' is a number of 1 to 10 and e'"'"' is 2 or 3, ##STR144## where r'"'"' is a number of 1 to 10 and s is 2 or 3, and R⁹ is oxyalkylene, polyoxyalkylene, or alkanetriyl, ##STR145## where each R¹¹ is independently hydrogen or methyl,

R¹² is independently an alkyl of 2 to 10 carbon atoms,

R¹³ is independently --C(O)OCH₃, --CN or phenyl,

R¹⁴ is --SR¹⁵ H, --SR¹⁵ O--, --SCH₂ C(O)OR¹⁵ H or H, where R¹⁵ is an alkylene having 1 to 12 carbon atoms,

f is an integer of 2 to 5

the groups enclosed by the single brackets with subscripts x, y and z are repeating units randomly distributed within the double brackets, the sum of x, y and z being such that the number average molecular weight of the totality of said repeating units is about 500 to 5000, the units enclosed by brackets with subscripts x and y always being present and the units enclosed by the bracket with subscript z being optionally present, said crosslinked polymer having a gel swell of 35 to 200% and dynamic shear moduli, over a temperature range of 23°

to 120°

C., which fall on or within the boundary of A-B-C-D of FIG. 1, said crosslinked polymer in the form of a diffraction grating having a first order diffraction efficiency which changes less than 5% when heated at 130°

C. for 1 hour as compared to the first order diffraction efficiency before heating.

30. A video disc comprising a shaped, plastic, cast, monolithic layer having on its surface information-bearing microstructure in the form of a predetermined array or pattern of spaced-apart depressions and comprising crosslinked polymer composed of (1) 20 to 50 weight percent of a plurality of hard segments represented by the formula ##STR146## where each A is independently --NH-- or --O--,

A'"'"' is --NH--

each R³ is independently a di-valent carbocyclic containing radical derived from cyclohexane or dicyclohexylmethane, and their lower alkyl-substituted derivatives, by removal of two of their hydrogen atoms,

each R⁴ is independently an alkylene moiety with 2 to 10 carbon atoms, or a cycloalkylene moiety with 6 to 10 carbon atoms,

d is 1, and

g is zero or a number up to 5,

(2) 15 to 45 weight percent of soft segments represented by the formula:

##STR147## where R⁹ is a saturated aliphatic radical free of active hydrogen atoms and can contain 1 or 2 non-vicinal catenary oxygen or nitrogen atoms, R⁹ having a valence equal to s and 2 to 10 carbon atoms,

each a, o, p and q is independently zero or 1,

each e'"'"' is independently an integer of 2 to 10,

each r is independently a number of 1 to 20, and

each s is independently an integer of 1 to 3, with proviso that

when q is 1, then s is 2 or 3 and o is zero and either a and p are both zero or both 1, and

when q is zero, then s and o are 1 and either a and p are both zero or both 1,

said crosslinked polymer having a gel swell of 35 to 200 weight percent and in the form of a diffraction grating having a first order diffraction efficiency which changes less than 15% when heated at 130°

C. for 1 hour as compared to the first order diffraction efficiency before heating.

31. A process for making a shaped plastic article comprising a shaped, plastic, monolithic layer having a microstructure-bearing surface and comprising crosslinked polymer, comprising the steps of filling a mold master with a fluid, castable, one-part radiation addition-polymerizable, crosslinkable, oligomeric composition or precursors thereof, said oligomeric composition comprising one or more oligomers having (1) one or more like or different hard segments each comprising a mono- or poly-valent moiety containing one or more carbocyclic and/or heterocyclic groups, wherein each of said moieties of said hard segments, when their valences are satisfied by protons, has at least one major glass transition temperature above 250°

K., (2) one or more like or different soft segments each comprising a mono- or poly-valent moiety selected from the group consisting of polyester, polyacrylate, polyether and polyolefin, and (3) one or more like or different monovalent moieties containing a radiation sensitive, addition-polymerizable, functional group selected from the group consisting of acrylyl, methacrylyl, allyl, and vic-epoxy, exposing the resulting cast oligomeric composition, or precursors thereof, to radiation, and recovering said shaped plastic article.

32. The process according to claim 31 wherein said oligomeric composition contains 10 to 80 weight percent of said hard segments and 10 to 60 weight percent of said soft segments, said hard segments containing difunctional linkages with hydrogen-bonding capability, each of said moieties of said hard segments, said crosslinked polymer having a gel swell within the range of 35 to 200 weight percent and having dynamic shear moduli, over the temperature range of 23°

to 120°

C., which fall on or within the boundary of A-B-C-D of FIG. 1, and wherein a diffraction grating of said crosslinked polymer has a first order diffraction efficiency which changes less than 15% when heated at 130°

C. for 1 hour as compared to the first order diffraction efficiency before heating.

33. The process according to claim 31 wherein said microstructure-bearing surface has an average profile which is plano, convex, concave, aspheric, or combinations thereof, said surface having discontinuities whose heights deviate from said average profile by ±

0.005 μ

m to ±

750 μ

m, said surfaces being free of utilitarian discontinuities or having one or a plurality of utilitarian discontinuities which are the same or different and spaced apart or contiguous in a random or ordered manner.

34. The process according to claim 31 wherein said article is in the form of a diffraction grating.

35. The process according to claim 31 wherein said article is in the form of a retroreflective sheet comprising an array of cube-corner prism elements.

36. The process according to claim 31 wherein said article is in the form of a Fresnel or echelon lens element.

37. The process according to claim 31 wherein said article is in the form of a video disc.

38. The process according to claim 31 wherein said article is in the form of a precision optical element.

39. The process according to claim 31 wherein said article is in the form of an ophthalmic lens.

40. A shaped, plastic article made by the process of claim 31.

41. An article, useful for an optical purpose, comprising a shaped, plastic, optically homogeneous, cast, monolithic layer having a replicated microstructure-bearing surface whose configuration contains a plurality of utilitarian discontinuities which characterize said optical purpose of said article, said layer comprising crosslinked polymer composed of (1) a plurality of hard segments comprising those represented by the formula:

##STR148## and (2) a plurality of soft segments comprising those represented by the formula;

##STR149##

42. A process for making a shaped plastic article comprising a shaped, plastic, monolithic layer having a microstructure-bearing surface and comprising crosslinked polymer, comprising the steps of filling a mold master with a fluid, castable, one-part radiation addition-polymerizable, crosslinkable, oligomeric composition or precursors thereof, said oligomeric composition comprising one or more oligomers represented by the formula:

##STR150## where each α

is independently 1 or 2

β

is zero or a number up to 20 and has an average value up to about 5

"γ

" is 2 or 3

"E" is represented by the formulas;

##STR151## where R¹ is a hydrogen atom or methyl,

each A is independently --NH-- or --O--,

a, b, c and d are each independently zero or 1, with the provisos that

(1) at least one of b and d must be 1,

(2) if b and c are both zero, than a and d must be 1,

(3) if b and d are both 1, then a and c must be 1, and e is at least 2, and

(4) if d is 1 and a and b are both zero, then c must be 1,

e is an integer of 1 to 5, ##STR152## where d is zero or 1,

e is an integer of 1 to 5, ##STR153## where R² is hydrogen or a lower alkyl,

B is ##STR154## where each f is a integer of 2 to 5, and each d is independently zero or 1,

"H" is represented by one or more of the formulas;

##STR155## where each A is independently --NH-- or --O--,

each B is ##STR156## where f is an integer of 2 to 5, each R² is independently hydrogen or a lower alkyl,

each R³ is independently a polyvalent carbocyclic-containing radical derived from benzene, naphthalene, cyclohexane, dicyclohexylmethane, diphenylmethane or norbornene, and their lower alkyl-substituted derivatives, by removal of two or more of their hydrogen atoms,

each R⁴ is independently an alkylene moiety with 2 to 10 carbon atoms, or a cycloalkylene moiety with 6 to 10 carbon atoms,

each R⁵ is independently a phenyl moiety or methyl,

each R⁶ is independently a lower alkyl with 1 to 4 carbon atoms,

g is zero or a number up to 5,

h is an integer of 1 to 10,

h'"'"' is zero or an integer of 1 to 10,

each d, d'"'"' and d" is independently zero or 1, with the proviso that if either one of d'"'"' or d" is 1, then the other is zero, and

"S" is the residue remaining after removal of the active hydrogen atoms of one or more of the following;

poly(oxyalkylene)polyols, polyester polyols, polyether polyester polyols, polyolefin polyols, poly(alkylacrylate)polyols, and polyamines.

43. The process according to claim 42 wherein "E" is represented by one of the formulas:

##STR157## where R¹ is methyl and A is --O--, ##STR158## where R¹ is methyl, A is --O--, and e is 2, ##STR159## where R¹ is hydrogen and A is --O--, and "S" is represented by one of the formulas ##STR160## where each A is independently --NH-- or --O--,

(OR⁷)_i is oxyalkylene or poly(oxyalkylene),

R⁷ is an alkylene of 2 to 4 carbon atoms,

R⁸ is a saturated aliphatic radical free of active hydrogen atoms and which can contain 1 or 2 nonvicinal caternary oxygen or nitrogen atoms, R⁸ having a valence equal to j and 2 to 10 carbon atoms,

i is a number of 1 to 20,

j is an integer of 1 to 3, and

d and c are each independently zero or 1 with the provisos that when d is 1, then c is zero and j is 2 or 3, and when d is zero, then j is 1, ##STR161## where R⁹ is a saturated aliphatic radical free of active hydrogen atoms and can contain 1 or 2 nonvicinal catenary oxygen or nitrogen atoms, R⁹ having a valence equal to s and 2 to 10 carbon atoms,

each a, o, p and q is independently zero or 1,

each e'"'"' is independently an integer of 2 to 10,

each r is independently a number of 1 to 20,

each s is independently an integer of 1 to 3 with proviso that

when q is 1, then s is 2 or 3 and o is zero and either a and p are both zero or both 1, and

when q is zero, then s and o are 1 and either a and p are both zero or both 1, ##STR162## where t is a number of 7 to 35, ##STR163## where the groups enclosed by the single brackets with the subscripts u and v are repeating units randomly distributed within the double brackets and u and v are integers whose sum is from 2 to 20 and u/v is a ratio of 1/4 to 4/1, s is 2 or 3, and R¹⁰ is a polyvalent carbocyclic-containing radical derived from benzene, naphthalene, or a phenyl-substituted benzene by removal of 2 or more hydrogen atoms, ##STR164## where each R¹¹ is independently hydrogen or methyl,

R¹² is independently an alkyl of 2 to 10 carbon atoms,

R¹³ is independently --C(O)OCH₃, --CN or phenyl,

R¹⁴ is --SR¹⁵ H, --SR¹⁵ O--, --SCH₂ C(O)OR¹⁵ H or H, where R¹⁵ is an alkylene having 1 to 12 carbon atoms,

f is an integer of 2 to 5

the groups enclosed by the single brackets with subscripts x, y and z are repeating units randomly distributed within the double brackets, the sum of x, y and z being such that the number average molecular weight of the totality of said repeating units is about 500 to 5000, the units enclosed by brackets with subscripts x and y always being present and the units enclosed by the bracket with subscript z being optionally present.

44. The process of claim 42 where "S" is represented by one of the formulas:

##STR165## where each f'"'"' is independently 2 to 4, and i'"'"' is 5 to 10, ##STR166## where f'"'"' is 2 to 4, i'"'"' is 5 to 10, and k is 2 or 3 ##STR167## where the groups enclosed by the single brackets with subscripts m and n are repeating units randomly distributed, m is zero or 1 to 4, n is 4 to 20, with the proviso that n/m is at least 4, ##STR168## where the groups enclosed by the brackets with subscripts m and n are repeating units randomly distributed within the double brackets, m, n, and n/m are as defined above, and k is 2 or 3 and is the valence of R⁸, ##STR169## where r'"'"' is a number of 1 to 10 and e'"'"' is 2 or 3, ##STR170## where r'"'"' is a number of 1 to 10 and s is 2 or 3, and R⁹ is oxyalkylene, polyoxyalkylene, or alkanetriyl, ##STR171## where each e'"'"' is independently a number of 2 to 5 and r'"'"' is a number of 1 to 10, ##STR172## where e'"'"' is a number of 2 to 5, r'"'"' is a number of 1 to 10, R⁹ is as defined above, and s is 2 or 3.

45. A process for making a retroreflective sheet comprising a shaped, plastic, monolithic layer of crosslinked polymer and having a microstructure-bearing surface comprising an array of trihedral or tetrahedral prism elements, said process comprising the steps of filling a metal mold master with a fluid castable, one-part radiation sensitized, crosslinkable, composition comprising an oligomer of the formula:

##STR173## where each α

is independently 1 or 2

β

is zero or a number up to 20 and has an average value up to about 5

γ

is 2 or 3

"E" is ##STR174## "H" is a hard segment of the formula;

##STR175## and "S" is a soft segment of the formula;

##STR176## said composition further comprising 2-(N-butylcarbamyl)ethyl methacrylate as a diluent monomer, exposing the rsulting cast composition to ultraviolet radiation to cure the same, and removing from said mold master said retroreflective sheet, the latter having a brightness of at least 600 candles per lumen at 0.2°

divergence angle, said crosslinked polymer having a gel swell within the range of 35 to 200 weight percent and having dynamic shear moduli, over the temperature range of 23°

to 120°

C., which fall on or within the boundary of A-B-C-D of FIG. 1, and wherein a diffraction grating of said crosslinked polymer has a first order diffraction efficiency which changes less than 15% when heated at 130°

C. for 1 hour as compared to the first order diffraction efficiency before heating.

46. An article, useful for an optical purpose, comprising a shaped, plastic, optically homogeneous, cast, monolithic layer having a replicated microstructure-bearing surface whose configuration contains a plurality of utilitarian discontinuities which characterize said optical purpose of said article, said layer comprising crosslinked polymer composed of (1) a plurality of hard segments comprising those represented by the formula:

##STR177## and (2) a plurality of soft segments comprising those represented by the formula;

##STR178##

47. An article, useful for an optical purpose, comprising a shaped, plastic, optically homogeneous, cast, monolithic layer having a replicated microstructure-bearing surface whose configuration contains a plurality of utilitarian discontinuities which characterize said optical purpose of said article, said layer comprising crosslinked polymer composed of (1) a plurality of hard segments comprising those represented by the formula:

##STR179## and (2) a plurality of soft segments comprising those represented by one or more of the following formulas;

##STR180##

48. An article, useful for an optical purpose, comprising a shaped, plastic, optically homogeneous, cast, monolithic layer having a replicated microstructure-bearing surface whose configuration contains a plurality of utilitarian discontinuities which characterize said optical purpose of said article, said layer comprising crosslinked polymer composed of (1) a plurality of hard segments comprising those represented by the formula:

##STR181## and (2) a plurality of soft segments comprising those represented by the formula;

##STR182##