Aromatic glycol ethers as writing monomers in holographic photopolymer formulations

Abstract

The invention relates to a photopolymer formulation comprising specific aromatic glycol ethers as writing monomers, matrix polymers and a photoinitiator. The invention further provides an unexposed holographic medium obtainable using an inventive photopolymer formulation, and an exposed holographic medium obtainable by exposing a hologram into an inventive unexposed holographic medium. The invention likewise provides a visual display comprising an inventive exposed holographic medium, for the use of an inventive exposed holographic medium for production of chip cards, identification documents, 3D images, product protection labels, labels, banknotes or holographic optical elements, and specific aromatic glycol ethers.

Claims

1. A photopolymer formulation comprising D) as writing monomer at least one aromatic glycol ether of the general formula (I) ##STR00012## in which Aryl is a substituted aromatic radical, wherein R1 is a radical of formula (II) and R2 is a radical of formula (III), or wherein R1 is a radical of formula (III) and R2 is a radical of formula (II) ##STR00013## in which R3 is an organic radical which has up to 6 carbon atoms and may contain oxygen and/or sulphur atoms, and R4 is a radical selected from the group of H, CH3; E) matrix polymers; F) a photoinitiator, and wherein the Aryl radical is substituted by 1 to 5 identical or different substituents selected from the group consisting of n-alkyl, branched alkyl, alkyloxy, phenyl, methylphenyl, ethylphenyl, thiomethylphenyl, methoxyphenyl, biphenyl, benzyl, phenylalkyl, naphthyl, methylthiyl, ethylthiyl, alkylthiyl, alkylthioalkyl, phenoxy, phenylthiyl, napthylthiyl, fluorine, chlorine, bromine and iodine.

2. The photopolymer formulation according to claim 1, wherein the Aryl radical comprises 5 to 21 carbon atoms and/or heteroatoms in the aromatic system.

3. The photopolymer formulation claim 1, wherein the Aryl radical is selected from the group consisting of phenyl, methylphenyl, ethylphenyl, thiomethylphenyl, methoxyphenyl, biphenyl and naphthyl.

4. The photopolymer formulation according to claim 1, wherein R3 is a radical selected from the group consisting of CH2-, CH2CH2-, CH(CH3)CH2-, CH2CH(CH3)-, CH2CH2CH2-, CH2CH2CH2CH2-, CH2CHOCH2CH2-, CH2CH2OCH2CH2OCH2CH2-.

5. The photopolymer formulation according to claim 1, wherein the R1 radical is a radical of the formula (II) and the R2 radical is a radical of the formula (III), where the R3 radical is aCH2CH2- radical.

6. The photopolymer formulation according to claim 1, wherein the R1 radical is a radical of the formula (III) and the R2 radical is a radical of the formula (II), where the R3 radical is aCH2CH2- radical.

7. The photopolymer formulation according to claim 1, wherein the matrix polymers B) have been crosslinked.

8. The photopolymer formulation according to claim 1, wherein the matrix polymers are polyurethanes.

9. The photopolymer formulation according to claim 1, wherein it additionally comprises a monomeric fluoroethane.

10. The photopolymer formulation according to claim 9, wherein the fluorourethane comprise at least one compound of the formula (IV) ##STR00014## in which m1 and m8 and R7, R8, R9 are each independently hydrogen or linear, branched, cyclic or heterocyclic organic radicals which are unsubstituted or else optionally substituted by heteroatoms, where preferably at least one of the R7, R8, R9 radicals is substituted by at least one fluorine atom and, more preferably, R7 is an organic radical having at least one fluorine atom.

11. A holographic medium comprising the photopolymer formulation according to claim 1.

12. The holographic medium according to claim 11 into which at least one hologram has been exposed.

13. The holographic medium according to claim 12, wherein the hologram is a reflection, transmission, in-line, off-axis, full-aperture transfer, white light transmission, Denisyuk, off-axis reflection or edge-lit hologram, or else a holographic stereogram, preferably a reflection, transmission or edge-lit hologram.

14. A visual display comprising a holographic medium according to claim 12.

15. The holographic medium according to claim 12 which is applied to chip cards, identification documents, 3D images, product protection labels, labels, banknotes, holographic optical elements, or visual displays.

Description

EXAMPLES

(1) The invention is illustrated in detail hereinafter by examples.

(2) The drawings show:

(3) FIG. 1 the geometry of a holographic media tester (HMT) at =532 nm (DPSS 1a-ser=diode pumped solid state laser) and

(4) FIG. 2 the measured diffraction efficiency as circles plotted against the angle detuning and the fit to the Kogelnik theory as a solid line. The figure shows example 4.4.

(5) FIG. 3 the measured diffraction efficiency as circles plotted against the angle detuning and the fit to the Kogelnik theory as a solid line. The figure shows example 4.8.

TEST METHODS

(6) Determination of Viscosity:

(7) Viscosity was determined with a Physica MCR 51 (from Anton Paar) viscometer. For this purpose, the sample was equilibrated and a ball was suspended (for low viscosities <10 000 mPas: 23 C., ball diameter 25 mm (CP-25) and for high viscosities >10 000 mPas: 50 C., ball diameter 60 mm (CP-60)). About 0.5-1 g of product was placed onto the plate, and the ball was allowed to drop down, such that the ball was fully wetted with product. Excess product was wiped off. The shear rate (about 500 l/s at lower viscosities and about 100 l/s at higher viscosities) was set automatically by the instrument. 20 measurements were made in each case and the mean was determined.

(8) Determination of Refractive Index:

(9) For high-viscosity and solid products, the refractive index was determined at a wavelength of 589 nm by obtaining the refractive index n from the transmission and reflection spectra as a function of the wavelength of the sample. For this purpose, films of the samples of thickness about 100-300 mm were spun onto quartz glass slides from a five percent by weight solution in ethyl acetate. The transmission and reflection spectrum of this layer assembly was measured with a CD-Measurement System ETA-RT spectrometer from STEAG ETA-Optik, and then the layer thickness and the spectral profile of n were fitted to the measured transmission and reflection spectra. This was done with the spectrometer's internal software and additionally required the n data of the quartz glass substrate, which were determined beforehand in a blank measurement.

(10) For liquid products, an Abbe refractometer was used to determine the refractive index at 589 nm. This was done by applying 3 drops of the product onto the cleaned measurement prism of the instrument, folding down the illumination prism and then equilibrating to 20 C. within 2 minutes. Subsequently, in the observation field, the light/dark boundary was positioned precisely onto the crosshairs of the refractometer. Once there was no longer any variation in the value set, the refractive index was read off on the instrument to four decimal places. A double determination was conducted. Differences of up to 0.0002 scale division were permissible.

(11) Measurement of Haze

(12) Haze was measured to ASTM D 1003. The haze is the percentage of light transmitted which deviates by more than 2.5 on average from the light beam emitted. To measure the haze, the holographic coupons were cleaned on the outside prior to the measurement, in order to avoid distortion of the result by fingerprints and dirt on the glass surfaces. Then the coupons were inserted into a Byk-Gardner Haze-Gard-Plus instrument for analysis. The layer thickness of the coupon was measured as described below in the section Measurement of the holographic properties DE and n of the holographic media by means of twin beam interference in transmission arrangement in the simulation of the theoretical Bragg curve according to Kogelnik.

(13) Measurement of Time for Dissolution of Writing Monomers

(14) 1.47 g of the polyol component were introduced into a tablet tube, a stirrer bar was added and the tablet tube was positioned on a magnetic stirrer. Subsequently, 1.00 g of the writing monomer to be tested was added while stirring and the time taken for a visually clear, homogeneous solution to form was determined.

(15) Isocyanate Content

(16) Reported NCO values (isocyanate contents) were determined to DIN EN ISO 11909.

(17) The full conversion of NCO groups, i.e. the absence thereof, in a reaction mixture was detected by IR spectroscopy. Thus, complete conversion was assumed when no NCO band (2261 cm.sup.1) was visible in the IR spectrum of the reaction mixture.

(18) Solids Content

(19) An unpainted tin can lid and a paperclip were used to ascertain the tare weight. Then about 1 g of the sample to be analysed was weighed out and then distributed homogeneously in the tin can lid with the suitably bent paperclip. The paperclip remained in the sample for the measurement. The starting weight was determined, then the assembly was heated in a laboratory oven at 125 C. for 1 hour, and then the final weight was determined. The solids content was determined by the following equation: Final weight [g]*100 starting weight [g]=% by weight of solids.

(20) Measurement of the Holographic Properties DE and n of the Holographic Media by Means of Twin Beam Interference in Transmission Arrangement

(21) The media produced were tested for their holographic properties by means of a measurement setup according to FIG. 1 as follows:

(22) FIG. 1 shows the holographic test setup with which the diffraction efficiency (DE) of the media was measured, with the following labels: M=mirror, S=shutter, SF=spatial filter, CL=collimator lens, /2=/2 plate, PBS=polarization-sensitive beam splitter, D=detector, I=iris diaphragm, .sub.0=22.3, .sub.0=22.3 are the angles of incidence of the coherent beams measured outside the sample (outside the medium). RD=reference direction of the turntable.

(23) The beam of a DPSS laser (emission wavelength 532 nm) was converted to a parallel homogeneous beam with the aid of the spatial filter (SF) and together with the collimation lens (CL). The final cross sections of the signal and reference beam are fixed by the iris diaphragms (I). The diameter of the iris diaphragm opening is 0.4 cm. The polarization-dependent beam splitters (PBS) split the laser beam into two coherent beams of identical polarization. By means of the /2 plates, the power of the reference beam was set to 2.0 mW and the power of the signal beam to 2.0 mW. The powers were determined using the semiconductor detectors (D) with the sample removed. The angle of incidence (.sub.0)) of the reference beam is 22.3; the angle of incidence (.sub.0) of the signal beam is 22.3. The angles are measured proceeding from the sample normal to the beam direction. According to FIG. 1, therefore, .sub.0 has a negative sign and .sub.0 a positive sign. At the location of the sample (medium), the interference field of the two overlapping beams produced a pattern of light and dark strips parallel to the angle bisectors of the two beams incident on the sample (transmission hologram). The strip spacing A, also called grating period, in the medium is 700 nm (the refractive index of the medium assumed to be 1.504).

(24) Holograms were recorded in the medium in the following manner: Both shutters (S) are opened for the exposure time t. Thereafter, with the shutters (S) closed, the medium is allowed 5 minutes for the diffusion of the as yet unpolymerized writing monomers.

(25) The holograms recorded were then reconstructed in the following manner. The shutter of the signal beam remained closed. The shutter of the reference beam was opened. The iris diaphragm of the reference beam was closed to a diameter of <1 mm. This ensured that the beam was always completely within the previously recorded hologram for all angles of rotation () of the medium. The turntable, under computer control, swept over the angle range from .sub.min to .sub.max with an angle step width of 0.05. is measured from the sample normal to the reference direction of the turntable. The reference direction (=0) of the turntable is obtained when the angles of incidence of the reference beam and of the signal beam have the same absolute value on recording of the hologram, i.e. .sub.0=22.3 and .sub.0=22.3. In general, the following is true of the interference field in the course of writing (recording) of a symmetric transmission hologram (.sub.0=.sub.0):
.sub.0=.sub.0
.sub.0 is the semiangle in the laboratory system outside the medium. Thus, in this case, .sub.0=22.3. At each setting for the angle of rotation , the powers of the beam transmitted in the zeroth order were measured by means of the corresponding detector D, and the powers of the beam diffracted in the first order by means of the detector D. The diffraction efficiency was calculated at each setting of angle as the quotient of:

(26) $=\frac{P_D}{P_D+P_T}$

(27) P.sub.D is the power in the detector for the diffracted beam and P.sub.T is the power in the detector for the transmitted beam.

(28) By means of the process described above, the Bragg curve, which describes the diffraction efficiency as a function of the angle of rotation for the recorded hologram, was measured and saved on a computer. In addition, the intensity transmitted into the zeroth order was also recorded against the angle of rotation and saved on a computer.

(29) The central diffraction efficiency (DE=0) of the hologram was determined at =0.

(30) The refractive index contrast n and the thickness d of the photopolymer layer were now fitted to the measured Bragg curve by means of coupled wave theory (see: H. Kogelnik, The Bell System Technical Journal, Volume 48, November 1969, Number 9 page 2909-page 2947). The evaluation process is described hereinafter:

(31) For the Bragg curve () of a transmission hologram, according to Kogelnik:

(32) $=\frac{{\sin }^2\left(\sqrt{v^2+{}^2}\right)}{1+\frac{{}^2}{v^2}}\mathrm{with}\text{:}$$v=\frac{.Math.n.Math.}{.Math.\sqrt{.Math.c_s.Math.c_r.Math.}}=-\frac{}{2.Math.c_s}.Math.\mathrm{DP}$$c_s=\cos \left(\right)c_r=\cos \left(\right)$$\mathrm{DP}=\frac{}{}.Math.\left(-2.Math.\sin \left(\right)-\frac{}{n.Math.}\right)$$=-\frac{}{2.Math.n.Math.\sin \left(\right)}$

(33) In the reconstruction of the hologram, as explained analogously above:
.sub.0=.sub.0+
sin(.sub.0)=n.Math.sin()

(34) Under the Bragg condition, the dephasing DP=0. And it follows correspondingly that:
.sub.0=.sub.0
sin(.sub.0)=n.Math.sin()

(35) v is the grating thickness and is the detuning parameter of the refractive index grating which has been recorded. n is the mean refractive index of the photopolymer and was set to 1.504. is the wavelength of the laser light in the vacuum.

(36) The central diffraction efficiency (DE=0), when =0, is then calculated to be:

(37) $\mathrm{DE}={\sin }^2\left(v\right)={\sin }^2\left(\frac{.Math.n.Math.}{.Math.\cos \left(\right)}\right)$

(38) The measured data for the diffraction efficiency and the theoretical Bragg curve are plotted against the angle of rotation , as shown in FIG. 2 and FIG. 3.

(39) Since DE is known, the shape of the theoretical Bragg curve, according to Kogelnik, is determined only by the thickness d of the photopolymer layer. n is corrected via DE for a given thickness d such that measurement and theory for DE are always in agreement. d is thus adjusted until the angle positions of the first secondary minima and the heights of the first secondary maxima of the theoretical Bragg curve correspond to the angle positions of the first secondary minima and the heights of the first secondary maxima of the measured Bragg curve.

(40) FIG. 2 and FIG. 3 show the theoretically calculated Bragg curves fitted to the experimental data by the coupled wave theory (also called Kogelnik theory) as a solid line, and shows, for comparison, the experimentally determined diffraction efficiency (in circle symbols) plotted against the angle of rotation .

(41) For a formulation, this procedure was repeated, possibly several times, for different exposure times t on different media, in order to find the mean energy dose of the incident laser beam in the course of recording of the hologram at which n reaches the saturation value. The mean energy dose E is calculated as follows from the powers of the two component beams assigned to the angles .sub.0 and .sub.0 (reference beam where P.sub.r=2.00 mW and signal beam where P.sub.s=2.00 mW), the exposure time t and the diameter of the iris diaphragm (0.4 cm):

(42) $E\left(\mathrm{mJ}/{\mathrm{cm}}^2\right)=\frac{2.Math.\left[P_r+P_s\right].Math.t\left(s\right)}{.Math.{0.4}^2{\mathrm{cm}}^2}$
Chemicals:

(43) In each case, the CAS number, if known, is stated in square brackets.

(44) TABLE-US-00001 m-Cresol [108-39-4]ABCR GmbH & Co KG, Karls- ruhe, Germany 3-Ethylphenol [620-17-7]Fluka/Sigma-Aldrich Chemie GmbH, Steinheim, Germany 3-(Methylthio)phenol [1073-29-6]ABCR GmbH & Co KG, Karlsruhe, Germany 4-(Methylthio)phenol [1073-72-9]Sigma-Aldrich Chemie GmbH, Steinheim, Germany Potassium carbonate Sigma-Aldrich Chemie GmbH, Steinheim Germany Epibromohydrin [3132-64-7]Sigma-Aldrich Chemie GmbH, Steinheim, Germany Phenyl glycidyl ether Denacol EX141; Nagase ChemteX Corpo- ration, Osaka, Japan Triphenylphosphine [603-35-0] ABCR GmbH & Co KG, Karls- ruhe, Germany Acrylic acid [79-10-7] Acros Organics, Geel, Belgium Methacrylic acid [79-41-4] Acros Organics, Geel, Belgium Ionol [128-37-0] Merck KGaA, Darmstadt, Ger- many 2-[(Biphenyl-2- Denacol EX142; Nagase ChemteX Corpo- yloxy)methyl]oxirane ration, Osaka, Japan 2-[(2- [2210-79-9] Sigma-Aldrich Chemie GMbH, Methyl- Steinheim, Germany phenoxy)methyl]oxirane 2-Isocyanatoethyl acrylate [13641-96-8]Karen AOI, SHOWA DENKO K.K., Fine Chemicals Group, Spe- cialty Chemicals Department, Chemicals Division, Japan 2-Isocyanatoethyl [30674-80-7]Karenz MOI, SHOWA methacrylate DENKO K.K., Fine Chemicals Group, Spe- cialty Chemicals Department, Chemicals Division, Japan 1,2-Cyclohexanamino- [672306-06-8] ABCR GmbH & Co KG, N,N-bis (3,5-di- Karlsruhe, Germany t-butylsalicylidene)cobalt(III) p-toluenesulphonate monohydrate 1-Isocyanato-3- [28479-19-8]Sigma-Aldrich Chemie (methylsulphanyl)benzene GmbH, Steinheim, Germany Tris(p-isocyanatophenyl) Desmodur RFE, product from Bayer thiophosphate MaterialScience AG, Leverkusen, Germany Dibutyltin dilaurate [77-58-7]urethanization catalyst Desmorapid Z, Bayer MaterialScience AG, Leverkusen, Germany Fomrez UL 28 urethanization catalyst, commercial product from Momentive Performance Chemicals, Wilton, CT, USA. Addocat SO a tin-based catalyst from RheinChemie, Mannheim, Germany Desmodur N 3900 product from Bayer MaterialScience AG, Leverkusen, DE, hexane diisocyanate-based polyisocyanate, proportion of iminooxadia- zinedione at least 30%, NCO content: 23.5%. CGI-909 tetrabutylammonium tris(3-chloro-4- methylphenyl)(hexyl)borate [1147315-11-4] is a product from BASF SE (formerly Ciba Inc.). Trimethylhexamethylene [28679-16-5]ABCR GmbH & Co KG, diisocyanate Karlsruhe, Germany 1H,1H-7H- [335-99-9]ABCR GmbH & Co KG, Perfluoroheptan-1-ol Karlsruhe, Germany Crystal violet [548-62-9] Sigma-Aldrich Chemie GmbH, Steinheim, Germany Irgacure 250 [344562-80-7], iodonium, (4- methylphenyl)[4-(2-methylpropyl)phenyl]-, hexafluorophosphate(1-) product from BASF SE
Inventive Writing Monomers:

General Method for Preparation of the Oxiranes (Examples 1.5 to 1.7; Other Oxiranes Used are Commercially Available)

(45) 1 equivalent of phenol and 2.4 equivalents of potassium carbonate were initially charged in 2-butanone. Then 3 equivalents of epibromohydrin were added gradually at room temperature. The amount of 2-butanone corresponded to 50 percent by weight of the total amount. There was a preliminary check of whether the phenol dissolves sufficiently in 2-butanone. The potassium carbonate suspension was then boiled under reflux.

(46) Once full conversion had been attained, was checked by .sup.1H NMR spectroscopy (see below for statement of time), the potassium carbonate was filtered off and the mixture was concentrated on a rotary evaporator. This gave the liquid, clear products, some of which were coloured, without further workup. The yield based on the phenol used was quantitative.

Example 1.5 2-[(3-methylphenoxy)methyl]oxirane

(47) Reactants: 11.9 g m-cresol 45.2 g epibromohydrin 36.4 g potassium carbonate 93.5 g 2-butanone

(48) Conditions: 16.5 h at 86 C. and 49.5 hours at 70 C.

(49) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=7.18 (t, 1H), 6.77 (d; 1H), 6.68-6.75 (m, 2H), 4.18 (dd, 3.95 (dd, 1H), 3.24 (m, 1H), 2.89 (dd, 1H), 2.73 (dd, 1H), 2.32 (s, 3H).

Example 1.6 2-[(3-ethylphenoxy)methyl]oxirane

(50) Reactants: 12.2 g 3-ethylphenol 41.1 g epibromohydrin 33.1 g potassium carbonate 86.4 g 2-butanone

(51) Conditions: 19.3 h at 86 C. and 50 hours at 70 C.

(52) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=7.40 (t, 1H), 6.80 (dd, 1H), 6.77 (m, 2H), 6.70 (dd, 1H), 4.40 (dd, 1H), 3.95 (dd, 1H), 3.35 (m, 1H), 2.85 (dd, 1H), 2.75 (dd, 1H), 2.65 (q, 2H), 1.25 (t, 3H).

Example 1.7 2-{[4-(methylsulphanyl)phenoxy]methyl}oxirane

(53) Reactants: 15.4 g 4-(methylthio)phenol 45.2 g epibromohydrin 36.4 g potassium carbonate 97.1 g 2-butanone

(54) Conditions: 16.3 h at 86 C. and 50.2 hours at 70 C.

(55) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=7.25 (AABB, 2H), 6.88 (AABB, 2H), 4.20 (dd, 1H), 3.90 (dd, 1H), 3.40 (m, 1H), 2.85 (dd, 1H), 2.73 (dd, 1H), 2.40 (s, 3H).

General Method for Preparation of the (Meth)Acrylic Acid-Oxirane Adducts (Examples 2.1-2.11)

(56) The oxirane, the catalyst, stabilizer and the (meth)acrylic acid were initially charged in a three-neck flask equipped with precision glass stirrer and stirrer motor, and also a drying tube. The mixture was heated to 90 C., and stirring was continued at this temperature until, in the .sup.1H NMR spectrum, a conversion of the oxirane group of >95% was apparent or no oxirane groups were detectable any longer. (MC=main components, SC=secondary component)

Example 2.1+2.2 Mixture of 2-hydroxy-3-phenoxypropyl acrylate and 1-hydroxy-3-phenoxypropan-2-yl acrylate (about 85:15)

(57) Reactants: 75.3 g phenyl glycidyl ether (Denacol EX141) 328 mg triphenylphosphine 36.0 acrylic acid 1.1 mg ionol

(58) Conditions: Reaction time 37 hours A clear, colourless, viscous liquid was obtained.

(59) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=7.23-7.32 (m, 2H), 6.92-7.00 (m, 1H), 6.84-6.92 (m, 2H), 6.46 (d, 1H), 6.16 (dd, 1H), 5.97 (d, 1H), 5.28 (p, 1H from SC), 3.9-4.45 (m, 5H), 2.72 (t, 1H from SC, OH), 2.60 (s, broad, 1H, OH).

Example 2.3 Mixture of 2-hydroxy-3-phenoxypropyl methacrylate and 1-hydroxy-3-phenoxypropan-2-yl methacrylate (about 85:15)

(60) Reactants: 37.7 g phenyl glycidyl ether (Denacol EX141) 164 mg triphenylphosphine 21.5 g methacrylic acid 0.6 mg ionol

(61) Conditions: Reaction time 34.5 hours A clear, colourless, viscous liquid was obtained.

(62) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=7.25-7.32 (m, 2H), 6.96 (t, 1H), 6.91 (d, 2H), 6.14 (s, 1H), 5.60 (s, 1H), 5.28 (p, 1H from SC), 3.35 (in, 2H from MC), 4.29 (p, 1H from MC), 4.20 (d, 2H from SC), 4.0-4.1 (m, 2H from MC), 3.94 (m, 2H from SC), 2.69 (s, broad, 1H, OH), 1.95 (s, 3H).

Example 2.4 Mixture of 2-hydroxy-3-(2-methylphenoxy)propyl acrylate and 1-hydroxy-3-(2-methylphenoxy)propan-2-yl acrylate (about 85:15)

(63) Reactants: 16.4 g 2-[(2-methylphenoxy)methyl]oxirane 66 mg triphenylphosphine 7.2 g acrylic acid 11.8 mg ionol

(64) Conditions: Reaction time 17 hours A clear, colourless, viscous liquid was obtained.

(65) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H) 7.1-7.2 (m, 2H), 6.88 (t, 1H), 6.80 (d, 1H), 6.44 (d, 1H), 6.18 (dd, 1H), 5.88 (d, 1H), 5.32 (p, 1H from SC), 4.35-4.45 (m, 2H from MC), 4.29 (p, 1H from MC), 4.19 (d, 2H from SC), 4.0-4.1 (m, 2H from MC), 3.96 (m, 2H from SC), 2.93 (s, broad, 1H, OH), 2.22 (s, 3H from MC), 2.20 (s, 3H, from SC).

Example 2.5 Mixture of 2-hydroxy-3-(3-methylphenoxy)propyl acrylate and 1-hydroxy-3-(3-methylphenoxy)propan-2-yl acrylate (about 85:15)

(66) Reactants: 16.5 g Example 1.5 66 mg triphenylphosphine 7.3 g acrylic acid 11.9 mg ionol

(67) Conditions: Reaction time 17 hours A clear, colourless, viscous liquid was obtained.

(68) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=7.13-7.20 (t, 1H), 6.78 (d, 1H), 6.68-6.75 (m, 2H), 6.45 (d, 1H), 6.18 (dd, 1H), 5.87 (d, 1H), 5.28 (p, 1H from SC), 4.3-4.4 (m, 2H from MC), 4.28 (p, 1H from MC), 4.15-4.25 (m, 2H from SC), 3.98-4.08 (m, 2H from MC), 3.94 (m, 2H from SC), 2.90 (s, broad, 1H, OH), 2.30 (s, 3H).

Example 2.6 Mixture of 2-hydroxy-3-(3-ethylphenoxy)propyl acrylate and 1-hydroxy-3-(3-ethylphenoxy)propan-2-yl acrylate (about 85:15)

(69) Reactants: 15.3 g Example 1.6 56 mg triphenylphosphine 6.2 g acrylic acid 10.8 mg ionol

(70) Conditions: Reaction time 17 hours A clear, colourless, viscous liquid was obtained.

(71) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=7.13-7.20 (m, 1H), 6.80 (d, 1H), 6.75 (s, 1H), 6.71 (dd, 1H), 6.45 (d, 1H), 6.18 (dd, 1H), 5.85 (d, 1H), 5.28 (p, 1H from SC), 4.3-4.4 (m, 2H from MC), 4.25 (p, 1H from MC), 4.19 (d, 2H from SC), 3.99-4.07 (m, 2H from MC), 3.93 (d, 2H from SC), 3.35 (s, broad, 1H, OH), 2.60 (q, 2H), 1.21 (t, 3H).

Example 2.7 Mixture of 2-hydroxy-3-[4-(methylsulphanyl)phenoxy]propyl acrylate and 1-hydroxy-3-[4-(methylsulphanyl)phenoxy]propan-2-yl acrylate (about 85:15)

(72) Reactants: 35.7 g Example 1.7 119 mg triphenylphosphine 13.1 g acrylic acid 24.4 mg ionol

(73) Conditions: Reaction time 39 hours at 70 C.

(74) GC-MS (EI) Retention time (from acetonitrile solution, only all the secondary components that appear >10% relative to the main component in the GC are mentioned): 1. 100%: 17.59 min (MS-EI: m/e=55, 125, 129, 140, 268): isomeric main products (M=268) 2. 17.8%: 3.03 min (MS-EI: m/e=27, 45, 55, 72) acrylic acid (M=72) 3. 11.2%: 21.30 min (MS-EI: m/e=55, 57, 115, 129, 353, 382) 3-({4-[3-(acryloyloxy)-2-hydroxypropoxy]phenyl}sulphanyl)-2-hydroxypropyl acrylate (M=382)

Example 2.8 Mixture of 3-(biphenyl-2-yloxy)-2-hydroxypropyl acrylate and 1-(biphenyl-2-yloxy)-3-hydroxypropan-2-yl acrylate (about 85:15)

(75) Reactants: 191.2 g 2-[(biphenyl-2-yloxy)methyl]oxirane (Denacol EX 142) 0.525 g triphenylphosphine 57.6 g acrylic acid 2.5 ionol

(76) Conditions: Reaction time 24.5 hours at 90 C. A clear, colourless, viscous liquid was obtained.

(77) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=7.45 (d, 2H), 7.38 (t, 2H), 7.2-7.35 (m, 3H), 7.15 (t, 2H), 6.96 (d, 2H), 6.37 (dd, 1H), 6.13 (dd, 1H), 5.81 (d, 1H), 5.28 (p, 1H from SC), 4.37 (t, 1H from SC, OH), 4.28-4.35 (m, 2H), 4.15 (m, 2H from MC), 4.13 (p, 1H), 3.95-4.06 (m, 2H), 3.75 (m, 2H from SC), 2.74 (s, broad, 1H, OH).

(78) GC-MS 1.1% acrylic acid, 7.8% 2-[(biphenyl-2-yloxy)methyl]oxirane (reactant), 1.5% reactant+HCl, 2.7% reactant+H2O, 73.2% products (isomers), 2.2% product+acrylic acid, 2.7% reactant+biphenylphenol, 3.3% product+reactant

Example 2.9 Mixture of 2-hydroxy-3-(1-naphthyloxy)propyl acrylate and 1-hydroxy-3-(1-naphthyloxy)propan-2-yl acrylate (about 85:15)

(79) Reactants: 46.0 g 2-[(1-naphthyloxy)methyl]oxirane 0.151 g triphenylphosphine 16.6 g acrylic acid 0.6 mg ionol

(80) Conditions: Reaction time 22.7 hours A clear, colourless, viscous liquid was obtained.

(81) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=8.18-8.25 (m, 1H), 7.73-7.80 (m, 1H), 7.38-7.49 (m, 3H), 7.29-7.35 (2t, 1H), 6.76 (d, 1H), 6.44 (2d, 1H), 6.15 (2dd, 1H), 5.82 (d, 1H), 5.43 (p, 1H from SC), 4.35-4.50 (m, 3H from MC), 4.30 (d, 2H from SC), 4.13-4.18 (m, 2H from MC), 3.98 (d, 2H from SC), 3.32 (s, broad, 1H, OH), 2.70 (t, 1H from SC, OH).

Example 2.10 Mixture of 2-hydroxy-3-(2-methoxyphenoxy)propyl acrylate and 1-hydroxy-3-(2-methoxyphenoxy)propan-2-yl acrylate (about 85:15)

(82) Reactants: 10.8 g 1,2-epoxy-3-(2-methoxyphenoxy)propane 0.039 g triphenylphosphine 4.3 g acrylic acid 7.6 mg ionol

(83) Conditions: Reaction time 29.3 hours A clear, colourless, viscous liquid was obtained.

(84) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=6.82-7.01 (m, 4H), 6.44 (2d, 1H), 6.15 (2dd, 1H), 5.82 (d, 1H), 5.28 (p, 1H from SC), 4.30-4.42 (m, 2H from MC), 4.27 (m, 1H from MC), 4.12 (dd, from MC, ABX), 4.04 (dd, 1H from MC, ABX), 3.98 (d, 2H from SC), 3.78-3.85 (m, 3H, OMe from MC and from SC+2H from SC), 3.21 (s, broad, 1H, OH).

Example 2.11 2-Hydroxy-3-phenoxypropyl acrylate

(85) Reactants: 8.3 g phenyl glycidyl ether 0.030 g 1,2-cyclohexanamino-N,N-bis (3,5-di-t-butylsalicylidene)cobalt(III) p-toluenesulphonate monohydrate 3.9 g acrylic acid 0.1 mg ionol

(86) Conditions: Reaction time 40 hours at room temperature

(87) Workup: 5 g of the crude product were diluted with 25 g of a mixture of butyl acetate and toluene and then freed of the cobalt catalyst by means of a gravity column and, with addition of 0.005 mg of ionol, freed of the solvent mixture in a rotary evaporator.

(88) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H) 7.28 (m, 2H), 6.98 (tt, 1H), 6.92 (dd, 2H), 6.46 (dd, 1H), 6.17 (dd, 1H), 5.87 (dd, 1H), 4.32-4.42 (m, 2H), 4.28 (m, 1H), 4.00-4.09 (m, 2H), 2.65 (d, 1H, OH). Purity by NMR>92%.

General Method for Preparation of the Inventive Aromatic Glycol Ether Writing Monomers (Examples 3.1-3.11)

(89) The precursor (Example 2.1-2.11), dibutyltin dilaurate and 2,6-di-tert-butyl-4-methylphenol were initially charged in a three-neck flask which was equipped with a precision glass stirrer and stirrer motor, gas inlet and drying tube. Subsequently, the mixture was heated to 60 C., air was passed over slowly, and the 2-isocyanatoethyl (meth)acrylate was added dropwise while stirring within about half an hour. Stirring was continued until it was no longer possible to observe any NCO band (2261 cm.sup.1) in the IR spectrum. Table 1 shows details of the reaction conditions and the characterization of the inventive writing monomers:

(90) TABLE-US-00002 TABLE 1 Preparation conditions and characterizations of the inventive writing monomers Reac- Fingerprint Ex- tion Product (IR, strong, ample Reactant 1 Reactant 2 DBTL Ionol Temp time Viscosity appearance cm1) 3.1 33.4 g Example 2.1 21.2 g AOI 27 mg 27 mg 60 C. 4.5 h 6350 mPas clear, yellowish 984, 888, 810, 757, 693 3.2 33.4 g Example 2.2 23.3 g MOI 28 mg 28 mg 60 C. 3.7 h 4630 mPas clear, yellow 985, 948, 887, 811, 756, 693 3.3 58.2 g Example 2.3 38.8 g MOI 49 mg 49 mg 60 C. 4.7 h 3830 mPas clear, orange- 945, 887, 815, brown 756, 693 3.4 23.6 g Example 2.4 14.1 g AOI 19 Mg/m3 19 mg 60 C. 9.2 h 8790 mPas clear, colourless 983, 808, 751 3.5 23.6 g Example 2.5 14.1 g AOI 19 mg 19 mg 60 C. 15.5 h 5150 mPas clear, amber 989, 809, 777 3.6 21.5 g Example 2.6 12.1 g AOI 17 mg 17 mg 60 C. 15.5 h 2670 mPas clear, amber 984, 814, 778 3.7 25.2 g Example 2.7 13.3 g AOI 19 mg 19 mg 60 C. 19.5 h 174700 mPas clear, yellowish 987, 812, 775 3.8 140.7 g Example 2.8 62.6 g AOI 102 mg 102 mg 60 C. 13.5 h 240000 mPas clear, colourless 984, 826, 809, 756, 734, 701, 667 3.9 54.5 g Example 2.9 28.2 g AOI 60 C. 21.5 h 176000 mPas clear, red brown 984, 809, 794, 773, 738 3.10 15.1 g Example 2.10 8.4 g AOI 12 mg 12 mg 60 C. 14 h 13190 mPas clear, colourless 988, 811 3.11 12.2 g Example 2.11 7.7 g AOI 10 mg 10 mg 60 C. 103 h 2640 mPas clear, colourless 978, 814, 756

(91) ##STR00008## ##STR00009## ##STR00010## ##STR00011##

Comparative Example C1: Phosphorothioyltris(oxybenzene-4,1-diylcarbamoyloxyethane-2,1-diyl) trisacrylate [1072455-04-9]

(92) 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 and 213.07 g of a 27% solution of tris(p-isocyanatophenyl) thiophosphate in ethyl acetate, which were heated to 60 C. Subsequently, 42.37 g of 2-hydroxyethyl acrylate were added dropwise and the mixture was still kept at 60 C. until the isocyanate content had fallen below 0.1%. This was followed by cooling and complete removal of the ethyl acetate under reduced pressure. The product was obtained as a semicrystalline solid. The product obtained has an n.sup.D.sub.20=1.5430 (589 nm).

Comparative Example C2: Benzene-1,3-diylbis[oxy-3-(biphenyl-4-yloxy)propan-1,2-diyl]bisacrylate

(93) Comparative example 2 is prepared in a first stage from a dithiol and an oxirane (cf. also Example 4a+b in WO 2012/020061 A1).

(94) The oxirane and the catalyst were initially charged in a three-neck flask equipped with precision glass stirrer and stirrer motor, and also a drying tube. The mixture was heated to 60 to 80 C. and then the dithiol was added dropwise. Subsequently, stirring was continued at the temperature specified until, in the .sup.1H NMR spectrum, a conversion of the oxirane group of >95% was apparent or no oxirane groups were detectable any longer.

Stage 1 3,3-(Butane-2,3-diyldisulphanediyl)bis[1-(biphenyl-2-yloxy)propan-2-ol]

(95) Reactants: 14.3 g 2-[(biphenyl-2-yloxy)methyl]oxirane (Denacol EX 142) 36 mg 1-butyl-3-methylimidazolium bromide 3.7 g 2,3-butanedithiol

(96) Conditions: Reaction temperature 60 C. on dropwise addition, 80 C., reaction time 48.5 h A clear, colourless, viscous liquid was obtained.

(97) .sup.1H NMR (CDCl.sub.3, 400 MHz): (1H)=7.45 (d, 2H), 7.38 (t, 2H), 7.32 (m, 3H), 7.16 (t, 1H), 6.97 (d, 1H), 4.05 (d, 2H), 3.95 (m, 1H), 2.65 (dd, 1H), 2.58 (dd, 1H), 2.4-2.55 (m, 2H), 1.5-4.65 (m, 2H).

Stage 2: 6,13-Bis[(biphenyl-2-yloxy)methyl]-9,10-dimethyl-4,15,20-trioxo-5,14,19-trioxa-8,11-dithia-3,16-diazadocos-21-en-1-yl acrylate

(98) Stage 1, dibutyltin dilaurate and 2,6-di-tert-butyl-4-methylphenol were initially charged in a three-neck flask which was equipped with a precision glass stirrer and stirrer motor, gas inlet and drying tube. Subsequently, the mixture was heated to 60 C., air was passed over slowly, and the 2-isocyanatoethyl acrylate was added dropwise within about half an hour. Stirring was continued until it was no longer possible to observe any NCO band (2261 cm.sup.1) in the IR spectrum.

(99) Reactants: 18.0 g product from Stage 1 8.5 g 2-isocyanatoethyl acrylate 13 mg dibutyltin dilaurate 3 mg 2,6-di-tert-butyl-4-methylphenol

(100) Conditions: dropwise addition (exothermic!) in 35 minutes at 60 C., then reaction time of 16 h at 60 C. A clear, almost colourless product of high viscosity was obtained.

(101) n.sup.20;.sub.D 1.5840 (589 nm)

Comparative Examples C3-C5

(102) Comparative Examples 4-6 were produced analogously to Comparative Example 3 from WO 2012/020061A1, and the viscosity thereof was measured. The results are shown in Table 2.

(103) TABLE-US-00003 TABLE 2 Noninventive Comparative Examples 4-6 Com- Example parative from WO Exam- 2012/020061 ple Noninventive Compound A1 Viscosity C3 6,16-Bis[(biphenyl-2-yloxy) 6b >1 000 000 mPas methyl]-4,18,23-trioxo- 5,11,17,22-tetraoxa-8,14-dithia- 3,19-diazapentacos-24-en-1-yl acrylate C4 6,13-Bis[(biphenyl-2-yloxy) 10b >1 000 000 mPas methyl]-4,15,20-trioxo-10-[({[2- (phenylsulphanyl)phenyl] car- bamoyl}oxy)methyl]-5,14,19- trioxa- 8,11-dithia-3,16- diazadocos-21-en-1-yl acrylate C5 6,19-Bis[(bipbenyl-2-yloxy) 7b >1 000 000 mPas methyl]-4,21,26-trioxo- 5,11,14,20,25-pentaoxa-8,17- dithia-3,22-diazaoctacos-27-en- 1-yl acrylate ,
Polyol Component:

(104) A 1 l flask was initially charged with 0.18 g of Addocat SO, 374.8 g of -caprolactone and 374.8 g of a difunctional polytetrahydrofuran polyether polyol (equivalent weight 650 g/mol OH), which were heated to 120 C. and kept at this temperature until the solids content (proportion of nonvolatile constituents) was 99.5% by weight or higher. Subsequently, the mixture was cooled and the product was obtained as a waxy solid.

Urethane acrylate 1: 2-({[3-(Methylsulphanyl)phenyl]carbamoyl}oxy)ethyl prop-2-enoate

(105) 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 Desmorapid Z, 11.7 g of 3-(methylthio)phenyl isocyanate, and the mixture was heated to 60 C. Subsequently, 8.2 g of 2-hydroxyethyl acrylate were added dropwise and the mixture was still kept 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.

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

(106) A 6 l round-bottom flask was initially charged with 0.50 g of Desmorapid Z and 1200 g of trimethylhexamethylene diisocyanate, and the mixture was heated to 80 C. Subsequently, 3798 g of 1H,1H,7H-perfluoroheptan-1-ol were added dropwise and the mixture was still kept 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.

Production of the Inventive and Noninventive Media (Coupons) (Examples 4.1 to 4.11 and Comparative Examples C4.1-C4.5)

(107) 2.940 g of the above-described polyol component were mixed with 2.000 g of the respective writing monomer (Examples 3.1 to 3.11 and Comparative Examples C4.1-C4.5), 2.000 g of the above-described urethane acrylate 1, 2.000 g of the above-described fluorinated urethane, 0.15 g of CGI 909, 15 mg of crystal violet, 15 mg of Irgacure 250, 15 mg of glass beads of size 9.18 m and 0.517 g of N-ethylpyrrolidone, so as to obtain a clear (in some cases slightly hazy) solution. This was followed by cooling to 30 C., admixture of 545 mg of Desmodur N 3900 and renewed mixing. This was finally followed by admixture of 6 mg of Fomrez UL 28 and renewed brief mixing. The resulting liquid mixture was then applied to a glass slide (from Corning, N.Y. 14831, USA, Micro slide plane: thickness 0.96-1.06 mm, 75 mm50 mm, type: 2947-7550) and covered with a second glass slide thereon. This test specimen was stored at room temperature for 12 hours and cured in the process. Subsequently, the media were packaged with exclusion of light.

(108) Determination of the Physical Data of the Inventive and Noninventive Media

(109) The measurement of the holographic properties DE and n was conducted by the process described above in the Test methods section.

(110) The measurement of haze was likewise conducted by the process described above in the Test methods section, except that the measurement was preceded by bleaching of the respective medium initially at room temperature under ambient light for about 15-30 minutes until the colour was no longer visually perceptible.

(111) The results of the measurements are shown in Table 3.

(112) TABLE-US-00004 TABLE 3 Holographic and optical performance of the inventive examples of the photopolymer formulations 4.1-4.11 and of the comparative examples C4.1 to C4.5 Inventive Dissolu- n at Haze Ex- Writing tion time 16 mJ/cm.sup.2 d in % amples monomer [min] [-] [m] [%] 4.1 3.1 0.50 0.0310 9.6 0.6 4.2 3.2 0.50 0.0275 10.8 0.7 4.3 3.3 0.33 0.0278 10.2 0.9 4.4 3.4 0.50 0.0370 7.9 0.4 4.5 3.5 1.00 0.0250 12.0 0.8 4.6 3.6 0.75 0.0250 10.7 2.0 4.7 3.7 2.00 0.0265 10.8 0.9 4.8 3.8 2.00 0.0358 9.4 1.1 4.9 3.9 0.50 0.0365 11.2 0.9 4.10 3.10 0.75 0.0310 11.8 0.6 4.11 3.11 0.75 0.0300 6.5 1.4 Comparative Examples C4.1 C1 >2800 0.0240 9.2 54.9 C4.2 C2 480 0.0315 10.0 1.0 C4.3 C3 70 0.0292 12.2 1.4 C4.4 C4 >480 0.0280 13.7 3.5 C4.5 C5 25 0.0290 10.0 0.9

(113) As apparent from Table 3, the holographic media consisting of inventive formulations comprising a writing monomer of formula (1) exhibited comparable or better holographic performance for transmission holograms of more than n>0.02. Furthermore, the inventive examples are suitable for production of low-haze holographic media and, at layer thicknesses greater than 6 m, exhibit a haze of less than 5%. In Inventive Examples 4.1-4.11, the writing monomers dissolve quickly and easily without addition of solvents within much less than 5 minutes, whereas the writing monomers of Comparative Examples C1-C5 took much longer to dissolve completely. Consequently, the production of the photopolymer formulations is as much more time-consuming in the comparative examples.