KIT-OF-PARTS CONTAINING A SEALING LAYER AND A PHOTOPOLYMER

Abstract

The invention relates to a kit-of-parts comprising at least one sealing layer C and a photopolymer B, a process for producing an at least partly interconnected layered setup formed of at least 2 layers, the use of the at least one sealing film C to protect the photopolymer B, the use of the kit-of-parts for the process referred to, a sealed holographic medium comprising the photopolymer and optical displays and security document comprising the sealed holographic medium.

Claims

1.-15. (canceled)

16. A kit-of-parts comprising at least one sealing layer C and an areal photopolymer B.

17. A process for producing an at least partly interconnected setup formed of at least 2 layers comprising a) an areal photopolymer B containing a volume hologram, and b) at least one at least partly actinically cured sealing layer C, wherein the photopolymer B containing a volume hologram comprises a crosslinked matrix; the sealing layer C is less than 50 m in thickness and has a viscosity of 2000 Pa s to 2 million Pa s, preferably 4000 Pa s to 1.6 million Pa s and comprises a physically drying resin C1, an acryloyl- or methacryloyl-functional reactive diluent C2 and a photoinitiator C3; and the sealing layer C is laminated onto the photopolymer B and thereafter cured with actinic radiation.

18. The kit-of-parts according to claim 16, wherein the photopolymer B is in the form of a layer, preferably on a preferably transparent thermoplastic substrate film A or on some other support.

19. The kit-of-parts according to claim 16, wherein the sealing layer C is present on a supporting film D.

20. The process according to claim 17, wherein a further sealing layer C is laminated onto the reverse side of the both-sidedly areal photopolymer B.

21. The process according to claim 17, wherein an at least partly interconnected setup formed of at least 3 layers comprising an areal photopolymer B containing a volume hologram, at least one at least partly actinically cured sealing layer C and a supporting film D is produced.

22. The process according to claim 17, wherein an at least partly interconnected setup formed of at least 4 layers comprising a layer B consisting of a photopolymer, containing a volume hologram and applied atop a substrate film A, at least one at least partly actinically cured sealing layer C and a supporting film D is produced.

23. The process according to claim 17, wherein the sealing layer C post lamination onto the photopolymer layer B is at least partly actinically cured within 60 minutes, preferably within 5 minutes, more preferably within less than 60 seconds.

24. The process according to claim 17, wherein the layer D or the layers D are at least partly delaminated post the at least partial curing of sealing layer C.

25. Use of sealing layer C to protect a photopolymer B according to claim 16.

26. Use of the kit-of-parts according to claim 16 for producing an at least partly interconnected setup formed of at least 2 layers comprising c) an areal photopolymer B containing a volume hologram, and d) at least one at least partly actinically cured sealing layer C, wherein the photopolymer B containing a volume hologram comprises a crosslinked matrix; the sealing layer C is less than 50 m in thickness and has a viscosity of 2000 Pa s to 2 million Pa s, preferably 4000 Pa s to 1.6 million Pa s and comprises a physically drying resin C1, an acryloyl- or methacryloyl-functional reactive diluent C2 and a photoinitiator C3; and the sealing layer C is laminated onto the photopolymer B and thereafter cured with actinic radiation.

27. A sealed holographic medium comprising a photopolymer B according to claim 16.

28. An optical display comprising a sealed holographic medium according to claim 27.

29. An autostereoscopic and/or holographic displays, projection screens, projection lenses, displays having switchable restricted emission characteristics for privacy filters and bidirectional multiuser screens, virtual displays, head-up displays, head-mounted displays, illumination symbols, warning lamps, signalling lamps, floodlights and display panels comprising a sealed holographic medium according to claim 27.

30. A security document comprising a sealed holographic medium according to claim 27.

31. The process according to claim 17, wherein the photopolymer B is in the form of a layer, preferably on a preferably transparent thermoplastic substrate film A or on some other support.

32. The process according to claim 17, wherein the sealing layer C is present on a supporting film D.

Description

EXAMPLES

[0143] The invention will now be more particularly described by means of examples.

[0144] FIG. 1 shows the transmission spectrum of a reflection hologram recorded at 532 nm.

[0145] FIG. 2 shows the transmission spectrum of the FIG. 1 reflection hologram after adhesive bonding with an OCA (OCA-69604 UV-curing optically clear adhesive from Tesa SE, Norderstedt, Germany).

[0146] FIG. 3 shows the transmission spectrum of the test hologram for Example 1 of table 2 before sealing.

[0147] FIG. 4 shows the transmission spectrum of the test hologram for Example 1 of table 2 after sealing.

[0148] FIG. 5 shows the transmission spectrum of the test hologram for Example 1 of table 2 after sealing and after a thermal stress period of 24 hours/60 C.

VISCOSITY MEASUREMENT

[0149] Sample preparation for determining the viscosity of sealing layer C took the form of pouring a corresponding solution from table 1, consisting of physically drying resin C1 and reactive diluent C2 dissolved in the organic solvent indicated therein, out onto a small plane-parallel Teflon pan. This was followed by drying in a vacuum drying cabinet at up to 60 C. The resulting film, about 1 mm in thickness and free from solvent odour, was cut out and measured on an Ares viscometer from Rheometrics. The viscosity was measured in the frequency sweep mode and in the plate-plate setup (14 mm diameter for measuring plates) sealed in a chamber temperature-regulated to 25 C. and reported for 1 Hz.

Chemicals:

[0150] CAS numbers are reported where known between angular parentheses.

Raw Materials of Photopolymer Layer B

[0151]

TABLE-US-00001 2-hydroxyethyl acrylate [818-61-1]-Sigma-Aldrich Chemie GmbH Steinheim, Germany 2,6-di-tert-butyl-4-methylphenol [128-37-0]-Merck KGaA, Darmstadt, Germany 3-(methylthio)phenyl isocyanate [28479-19-8]-Sigma-Aldrich Chemie GmbH Steinheim, Germany Desmodur RFE tris(p-isocyanatophenyl) thiophosphate, 27% strength in ethyl acetate, product from Covestro DeutschlandAG, Leverkusen, Germany dibutyltin dilaurate [77-58-7]-Sigma-Aldrich Chemie GmbH Steinheim, Germany Fomrez UL 28 Momentive Performance Chemicals, Wilton, CT, USA. Borchi Kat 22 [85203-81-2]-OMG Borchers GmbH, Langenfeld, Germany. BYK-310 BYK-Chernie GmbH, Wesel, Germany Desmodur N 3900 Covestro DeutschlandAG, Leverkusen, DE, hexane diisocyanate-based polyisocyanate, at least 30% proportion of iminooxadiazinedione, NCO content: 23.5%. Desmorapid SO [301-10-0]-Rhein Chemie Rheinau GmbH, Mannheim, Germany CGI-909 tetrabutylammonium tris(3-chloro-4- methylphenyl)-(hexyl)borate, [1147315-11-4], BASF SE trimethylhexamethylene diisocyanate [28679-16-5]-ABCR GmbH & Co KG, Karlsruhe, Germany 1H,1H-7H-perfluoroheptan-1-ol [335-99-9]-ABCR GmbH & Co KG, Karlsruhe, Germany Astrazone Pink FG 200% [3648-36-0]-DyStar Colours Deutschland GmbH, Frankfurt am Main, Germany sodium bis(2-ethylhexyl) sulphosuccinate [45297-26-5] Sigma-Aldrich Chemie GmbH, Steinheim, Germany polytetrahydrofuran polyether polyol

Raw Materials of Sealing Layer C

Physically Drying Resins C1

[0152]

TABLE-US-00002 Ebecryl 1200-resin 1 An approximately 10-tuply acryloyl-functional polyacrylate from Allnex, Brussels, Belgium. Degalan M920-resin 2 A linear thermoplastic amorphous polymethyl methacrylate with Mw = 300000 from Evonik Industries, Marl, Germany APEC 1895-resin 3 A linear thermoplastic cyclohexanone-bisphenol polycarbonate from Covestro Deutschland AG, Leverkusen, Germany.

Acryloyl-Functional Reactive Diluents C2

(Reactive Diluent Abbreviated RD)

[0153]

TABLE-US-00003 Miramer M410-RD 1 [94108-97-1] ditrimethylolpropane tetraacrylate from Miwon Specialty Chemical Co., Ltd., Gyeonggi-do, Korea. Miramer M4004-RD 2 [51728-26-8] 5-tuply ethoxylated pentaerythritol tetraacrylate from Miwon Specialty Chemical Co., Ltd., Gyeonggi-do, Korea. Sartomer SR494-RD 3 4-tuply ethoxylated pentaerythritol tetraacrylate (PPTTA) from SARTOMER Division of CRAY VALLEY, Paris, France. Ebecryl 110-RD 4 Acrylate of ethoxylated phenol having an average degree of ethoxylation of about 2.5, from Allnex, Brussels, Belgium. Desmolux XP2740- RD 5 Flexible aliphatic allophanate-based urethane acrylate having an acrylate functionality of three, from Allnex, Brussels

Photoinitiators C3

[0154]

TABLE-US-00004 Irgacure 2022-initiator 1 An 80:20 mixture of 2-hydroxy-2-methyl-1- phenyl-1-propanone and bis(2,4,6- trimethylbenzoyl)-phenylphosphine oxide from BASF, SE, Ludwigshafen, Germany. Irgacure 1173-initiator 2 2-Hydroxy-2-methyl-1-phenyl-1-propanone from BASF, SE, Ludwigshafen, Germany.

Additives

[0155]

TABLE-US-00005 BYK 310-flow agent Silicone-containing surface additive from BYK-Chemie GmbH, Wesel, Germany Tinuvin 292-light stabilizer A sterically hindered amine from BASF SE, Ludwigshafen, Germany. Irganox 1135-antioxidant A phenolic antioxidant from BASF SE, Ludwigshafen, Germany.

Solvents

[0156]

TABLE-US-00006 butyl acetate (BA) Butyl acetate from Brenntag GmbH, Mlheim an der Ruhr, Germany. methoxypropanol (MP) 1-Methoxy-2-propanol from Brenntag GmbH, Mlheim an der Ruhr, Germany. MPA-EEP (M/E) A 50:50 wt % mixture of 1-methoxy-2-propanol acetate (DOWANOL PMA GLYCOL ETHER ACETATE) from DOW Deutschland Anlagengesellschaft mbH, Schwalbach, Germany and ethyl 3-ethoxypropionate from Brenntag GmbH, Mlheim an der Ruhr, Germany.

Urethane Acrylate 1: phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethan-2,1-diyl) trisacrylate

[0157] A 500 mL round-bottom flask was initially charged with 0.1 g of 2,6-di-tert-butyl-4-methylphenol, 0.05 g of dibutyltin dilaurate and also 213.1 g of a 27% solution of tris(p-isocyanatophenyl) thiophosphate in ethyl acetate (Desmodur RFE, product from Covestro DeutschlandAG, Leverkusen, Germany), followed by heating to 60 C. Subsequently, 42.4 g of 2-hydroxyethyl acrylate were added dropwise and the mixture was further maintained at 60 C. until the isocyanate content had fallen below 0.1%. This was followed by cooling and complete removal of the ethyl acetate in vacuo. The product was obtained as a partly crystalline solid.

Urethane Acrylate 2: 2-({[3-(methylsulphanyl)phenyl]carbamoyl}oxy)ethyl prop-2-enoate

[0158] A 100 mL round-bottom flask was initially charged with 0.02 g of 2,6-di-tert-butyl-4-methylphenol, 0.01 g of dibutyltin dilaurate and 11.7 g of 3-(methylthio)phenyl isocyanate, followed by heating to 60 C. Subsequently, 8.2 g of 2-hydroxyethyl acrylate were added dropwise and the mixture was maintained at 60 C. until the isocyanate content had fallen below 0.1%. This was followed by cooling. The product was obtained as a colourless liquid.

Polyol Component:

[0159] A 1 L flask was initially charged with 0.037 g of Desmorapid SO, 374.8 g of -caprolactone and 374.8 g of a difunctional polytetrahydrofuran polyether polyol, followed by heating to 120 C. and maintenance of this temperature until the solids content (the proportion of non-volatile constituents) was 99.5 wt % or thereabove. This was followed by cooling, and the product was obtained as a waxy solid.

Dye 1:

[0160] 5.84 g of anhydrous sodium bis(2-ethylhexyl) sulphosuccinate were dissolved in 75 mL of ethyl acetate. 14.5 g of the dye Astrazone Pink FG 200%, dissolved in 50 mL of water, were added. The aqueous phase was separated off and the organic phase was extracted, three times, with 50 ml of fresh water at 50 C., the aqueous phase being separated off each time, the last one at room temperature. After the aqueous phase had been separated off, the solvent was distilled off in vacuo to obtain 8.6 g of 3H-indolium 2-[2-[4-[(2-chloroethyl) methylamino]phenyl]ethenyl]-1,3,3-trimethyl-1,4-bis(2-ethylhexyl) sulphosuccinate [153952-28-4] as a highly viscous oil.

Fluorinated Urethane: bis(2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl) (2,2,4-trimethylhexane-1,6-diyl)biscarbamate

[0161] In a 6 L round-bottom flask, 0.50 g of dibutyltin dilaurate and 1200 g of trimethylhexamethylene diisocyanate were initially charged and heated to 80 C. This was followed by the dropwise addition of 3798 g of 1H,1H,7H-perfluoroheptan-1-ol and the mixture was maintained at 80 C. until the isocyanate content had fallen below 0.1%. This was followed by cooling. The product was obtained as a colourless oil.

Producing Holographic Media (Photopolymer Film)

[0162] 7.90 g of the polyol component described above were melted and mixed with 7.65 g of the particular urethane acrylate 2, 2.57 g of the above-described urethane acrylate 1, 5.10 g of the above-described fluorinated urethane, 0.91 g of CGI 909, 0.232 g of dye 1, 0.230 g of BYK 310, 0.128 g of Fomrez UL 28 and 3.789 g of ethyl acetate to obtain a clear solution. This was followed by the addition of 1.50 g of Desmodur N 3900 and renewed mixing.

[0163] This solution was then applied, in a reel-to-reel coating rig, atop a 36 m thick PET film where a blade was used to apply the product in a wet film thickness of 19 m. The coated film was dried at a drying temperature of 85 C. for a drying period of 5 minutes and subsequently protected with a polyethylene film 40 m in thickness. This film was subsequently packed in a light-tight package.

Production and Characterization of Test Holograms

[0164] Test holograms were prepared as follows: the photopolymer films were, in the dark, cut to the desired size and laminated with a rubber roll onto a glass plate measuring 50 mm70 mm (3 mm thickness).

[0165] Test holograms are made by means of a test apparatus which creates Denisyuk reflection holograms by means of green (532 nm) laser radiation. The test apparatus consists of a laser source, an optical beam-guiding system and a holder for the glass coupons. The holder for the glass coupons is mounted at an angle of 13 relative to the beam axis. The laser source generated the radiation which was guided via a specific optical path, which expands at about 5 cm, to the glass coupon, which was in optical contact with the mirror. The holographed object was a mirror about 2 cm2 cm in size, so the wavefront of the mirror was reconstructed on reconstructing the hologram. The examples were all exposed with a green 532 nm laser (Newport Corp, Irvine, Calif., USA, cat. No. EXLSR-532-50-CDRH). A shutter was used to expose the recording film for 2 seconds in a defined manner. Subsequently, the samples were placed with the substrate side facing the lamp onto the conveyor belt of a UV source and exposed twice at a belt speed of 2.5 m/min. The UV source used was an iron-doped Hg lamp of the Fusion UV type D Bulb No. 558434 KR 85 with total power density of 80 W/cm.sup.2. The parameters corresponded to a dose of 22.0 J/cm.sup.2 (measured with an ILT 490 Light Bug).

[0166] This diffractive reflection is analysable in transmission by virtue of the high efficiency of the volume hologram with visible light with a VIS spectrometer (USB 2000, Ocean Optics, Dunedin, Fla., USA), and it appears in the transmission spectrum as a peak with reduced transmission. The transmission curve can be analysed to determine the quality of the hologram: the width of the peak was determined as the full width at half maximum (FWHM) in nanometers (nm), the depth of the peak (Tmin) was reported as 100% Tmin in percent, and the region with the lowest transmission indicates the wavelength (nm) where diffraction efficiency is highest.

Adhesively Bonding a Reflection Hologram with an Optical Clear Adhesive (OCA)

[0167] The display industry routinely employs films of optical clear adhesive (OCA) to bond glass layers to displays for touch functions for example. Any sealing of volume holograms of the type described above is thereby only possible at the cost of unacceptable changes in frequency. FIG. 1 thus shows the transmission spectrum of a reflection hologram recorded at 532 nm. After adhesive bonding with such an OCA (OCA-69604, UV-curing optically clear adhesive from Tesa SE, Norderstedt, Germany), FIG. 2 shows very distinct deviations in frequency, which do not permit any industrial use.

Production of Sealing Coating Layer C on Substrate D

[0168] The formulations reported in table 1 were produced by mixing the physically drying resins C1, dissolved in the organic solvent reported, with the reactive diluent C2. Then, the photoinitiator C3 and also 0.9% of flow assistant and 0.05% each of stabilizer 1 and stabilizer 2 were admixed in the dark. The solution was blade coated onto 36 m thick polyester film (RNK 36 from Mitsubishi Polyester Film GmbH, Wiesbaden, Germany) and dried at 60 C. for 20 minutes to obtain a film layer thickness of 3-10 m.

TABLE-US-00007 TABLE 1 Compositions of sealing layer C (inventive and non-inventive examples) Solids content and Viscosity solvent of of sealing Inventive Component Component Component coating layer examples C1 C2 C3 solution [Pa s] 1 69.5% 29.5% 0.7% initiator 30.0% 10800 resin 1 RD 2 1 and 0.3% in BA initiator 2 2 69.5% 29.5% 0.3% initiator 30.0% 10800 resin 1 RD 2 1 and 0.7% in BA initiator 2 3 94.5% 4.5% 1% initiator 1 30.0% 83800 resin 1 RD 4 in BA 4 89.5% 9.5% 1% initiator 1 63.3% 5000 resin 1 RD 4 in BA 5 60% 38% 1% initiator 1 21.2% 816400 resin 3 RD 1 in M/E 6 40% 58% 1% initiator 1 28.8% 16500 resin 3 RD 1 in M/E 7 50% 50% 3% initiator 1 24.5% 40100 resin 2 RD 1 in MP 8 35% 65% 1% initiator 1 26.2% 11400 resin 2 RD 1 in MP 9 30% 68% 1% initiator 1 29.3% 8500 resin 2 RD 1 in MP 10 25% 73% 1% initiator 1 33.2% 4800 resin 2 RD 1 in MP 11 99% 1% initiator 1 55.5% 1534700 resin 1 in BA 12 94% 5% 1% initiator 1 56.7% 257300 resin 1 RD 5 in BA 13 89% 10% 1% initiator 1 58.1% 401200 resin 1 RD 5 in BA 14 84% 15% 1% initiator 1 59.5% 279900 resin 1 RD 5 in BA 15 90% 10% 1% initiator 1 58.1% 202400 resin 1 RD 3 in BA 16 80% 20% 1% initiator 1 60.9% 68000 resin 1 RD 3 in BA 17 70% 30% 1% initiator 1 63.8% 11000 resin 1 RD 3 in BA Non- Solvent inventive Component Component Component and Viscosity examples C1 C2 C3 solids [Pa s] N1 10% 88% 1% initiator 1 55.4% 200 resin 2 RD 1 in MP N2 50% 50% 1% initiator 1 71.0% 30 resin 1 RD 4 in BA

[0169] Table 2, then, shows results of frequency stability measurements on test holograms involving sealing coatings 1-4 and 12-14. Holographic media containing test holograms characterized beforehand by VIS spectrometer (see the Before bonding column of table 2), were laminated together with the appropriate sealing lacquer to form the layered setup A-B-C-D. Curing took place within 60 seconds via UV light (layer side A oriented towards the UV lamp, belt speed 2.5 m/min, Hg lamp of the Fusion UV type D Bulb No. 558434 KR 85 with 80 W/cm.sup.2 total power density, dosage 2 J/cm2), before layer D was removed. When the sealing lacquer C stays behind on the photopolymer layer B and is easy to separate from D, the transferability is termed OK. A transmission spectrum is remeasured (see the After bonding column of table 2). The samples were subsequently stored at 60 C. for 24 hours and remeasured (see the After 1 d 60 C. storage column of table 2).

TABLE-US-00008 TABLE 2 Test results on transferability and colour shifts or firmly adherent sealing coatings After 1 d Before After 60 C. Shift Shift through bonding bonding storage through 1 d 60 C. .sub.peak .sub.peak .sub.peak bonding storage (dry) Example [nm] Transferability [nm] [nm] .sub.peak [nm] .sub.peak [nm] 1 529.62 OK 534.59 531.68 4.97 2.06 2 530.45 OK 534.24 528.18 3.79 2.27 3 529.62 OK 532.16 529.00 2.54 0.62 4 530.45 OK 533.89 531.89 3.44 1.44 12 529.42 OK 527.56 524.26 1.86 5.16 13 528.18 OK 527.15 523.44 1.03 4.74 14 527.77 OK 527.97 523.85 0.20 3.92

[0170] Table 2, then, shows that the process of the present invention proceeds with very good frequency stability on the part of the holograms. The sealing ensures good protection of the hologram and good handleability.

[0171] FIGS. 3 to 5 show the transmission spectra of the test holograms for Example 1 of table 2, which were produced from a kit-of-parts of sealing film and photopolymer film by the process of the present invention and measured before sealing (FIG. 3), after sealing (FIG. 4) and after a thermal stress period of 24 hours/60 C. (FIG. 5). The transmission spectra show the high stability of the hologram without disadvantageous colour shift (apparent from the position of the transmission minimum, which is likewise reported in table 2).

[0172] Table 3 shows further test results of thermally adherent sealing coatings. What is important for the industrial utility of sealing films formed from layer C and layer D is the film property after winding the films. To this end, a lamination film can be used to protect the sealing layer C. This is no longer successful in the non-inventive examples N1 and N2, since the uncured layer C starts to undulate as the films are being laminated and/or wound. This leads to undesirable irregular protective layer thicknesses, which is unacceptable. Similarly, an excessive tackiness (tacky) proves to be unsuitable to obtain a consistent lamination result. The Rating of film property column in table 3 reports an assessment on a scale of German school grades (1very good, 2good, 3fair, 4satisfactory, 5unsatisfactory).

TABLE-US-00009 TABLE 3 Processability test of Examples 5-19 and of non-inventive examples N1 and N2. Frequency stability was spectroscopically determined and reported in some examples. Rating Assessment Shift [nm] Film of film of film Layer thickness of after 1 d 60 C. Example properties property property sealing layer C Transferability storage 5 clear, dry 1 OK 2-3 m OK 1.44 6 clear, 2 OK 2-3 m OK 1.44 very slightly tacky 7 clear, 2 OK not determined OK not determined very slightly tacky 8 clear, 2 OK 2-4 m OK 6.18 very slightly tacky 9 clear, 3 OK 3-4 m OK 6.60 slightly tacky 10 clear, 3 OK 4-6 m OK 4.12 slightly tacky 11 clear, dry 1 OK not determined OK not determined 12 clear, dry 1 OK not determined OK 5.16 13 clear, dry 1 OK not determined OK 4.74 14 clear, dry 1 OK not determined OK 3.92 gummy 15 clear, dry 1 OK not determined OK not determined 16 clear, 1 OK not determined OK not determined very slightly tacky 17 clear, 2 OK not determined OK not determined slightly tacky N1 clear, 5 not OK 5-8 m OK 5.19 tacky N2 clear, 5 not OK not determined OK not determined slightly tacky, orange peel effect

[0173] A comparison of tables 1, 2 and 3 reveals that the sealing coatings which are suitable have a viscosity within from 2000 Pa s to 2 million Pa s, preferably 4000 Pa s to 1.6 million Pa s, and are readily transferable to the photopolymer layer B and have good adherence.