Photopolymer formulation having ester-based writing monomers
View Patent ↗The invention relates to a photopolymer formulation comprising matrix polymers, writing monomers, and photoinitiators, wherein the writing monomers comprise compounds of formula (I), where at least one of the radicals R1, R2, R3, R4, R5, R6 is a radical bonded to the aromatic ring via X of formula (II), where, in formula (II), A is a linear or branched hydrocarbon, optionally comprising oxygen or nitrogen, the remaining radicals R1, R2, R3, R4, R5, R6 are, independent of each other, hydrogen or an organic radical, and R7 is hydrogen or methyl. The invention further relates to the use of the photopolymer formulation for producing holographic media.
1. A photopolymer formulation comprising matrix polymers, writing monomers, photoinitiators, and urethanes as plasticizers, where the urethanes as plasticizers are substituted by at least one fluorine atom, the matrix polymers being polyurethanes obtainable by reacting an isocyanate component a) with an isocyanate-reactive component b) having an average of at least 1.5 isocyanate-reactive groups per molecule, characterized in that the writing monomers comprise aromatic compounds of the formula (I)
in which at least one of the R 1 , R 2 , R 3 , R 4 , R 5 , R 6 radicals is a radical which is bonded to the aromatic ring at the point X of the formula (II)
where X in the formula (II) is a point of attachment, where A in the formula (II) is a linear or branched hydrocarbyl chain optionally containing oxygen or nitrogen, the other R 1 , R 2 , R 3 , R 4 , R 5 , R 6 radicals are each independently hydrogen or an organic radical and R 7 is hydrogen or methyl.
2. The photopolymer formulation of claim 1 , wherein two or three of the R 1 , R 2 , R 3 , R 4 , R 5 , R 6 radicals are radicals which are bonded to the aromatic ring at the point X of the formula (II).
3. The photopolymer formulation of claim 2 , wherein, when two radicals of the formula (II) are present, they are bonded in the meta or para positions on the aromatic ring, and, when three radicals of the formula (II) are present, these are each bonded in meta positions.
4. The photopolymer formulation of claim 1 , wherein the organic radical has a radiation-curing group.
5. The photopolymer formulation of claim 4 , wherein the radiation-curing group is an acrylate or methacrylate group.
6. The photopolymer formulation of claim 1 , wherein A is —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —, —CH 2 —CH(CH 3 )—CH 2 — or —CH 2 —CH 2 —CH 2 —CH 2 —.
7. The photopolymer formulation of claim 1 , wherein the photoinitiators comprise an anionic, cationic or uncharged dye and a coinitiator.
8. The photopolymer formulation of claim 1 , wherein the urethanes as plasticizers have the general formula (III)
in which n≧1 and n≦8 and R 8 , R 9 , R 10 are each independently hydrogen, linear, branched, cyclic or heterocyclic organic radicals which are unsubstituted or optionally substituted by heteroatoms, provided at least one of the R 8 , R 9 , R 10 radicals is substituted by at least one fluorine atom.
9. The photopolymer formulation of claim 8 , wherein R 8 is an organic radical containing at least one fluorine atom.
10. The photopolymer formulation of claim 1 , wherein the writing monomers additionally comprise a further mono- or polyfunctional writing monomer.
11. The photopolymer formulation of claim 10 , wherein the further mono- or polyfunctional writing monomer is a mono- or polyfunctional acrylate.
12. A holographic medium produced from the photopolymer formulation of claim 1 .
13. The holographic medium of claim 12 , wherein said holographic medium is selected from the group consisting of inline holograms, off-axis holograms, full-aperture transfer holograms, white light transmission holograms, Denisyuk holograms, off-axis reflection holograms, edge-lit holograms, and holographic stereograms.