Composite comprising a substrate and a photopolymer film

Abstract

The invention relates to an assembly comprising a substrate and a photopolymer film, which are joined to one another partably at least in sections, the substrate comprising polyethylene terephthalate, and the photopolymer film comprising three-dimensionally crosslinked polyurethane matrix polymers, a writing monomer and a photoinitiator, characterized in that the substrate, after seven-day incubation at 23 C. in a 0.5 volume percent butyl acetate solution of the dye of formula (I) ##STR00001##
has an L value L1 and before the incubation an L value of L0, the L values being determined by CieLAB measurements, and the difference between the L values L1 and L0 satisfying the formula (II)
L1L0>0.25(formula II).

Claims

1. An assembly comprising a substrate and a photopolymer film, which are joined to one another partably at least in sections, the substrate comprising polyethylene terephthalate, and the photopolymer film comprising three-dimensionally crosslinked polyurethane matrix polymers, a writing monomer and a photoinitiator, wherein the substrate, after seven-day incubation at 23 C. in a 0.5 volume percent butyl acetate solution of the dye of formula (I) ##STR00007## has an L value L1 and before the incubation an L value of L0, the L values being determined by CieLAB measurements, and the difference between the L values L1 and L0 satisfying the formula (II)
L1L0<0.25(formula II), and wherein the substrate has a surface tension of 28 mN/m and 42.5 mN/m.

2. The assembly according to claim 1, wherein the difference between the L values L1 and L0 satisfies the formula (III)
L1L00.30(formula Ill).

3. The assembly according to either of claim 1, wherein the substrate is a foil, and more particularly a foil having a thickness of 10 m to 375 m.

4. The assembly according to any of claim 1, wherein the photopolymer film has a thickness of 5 m to 100 m.

5. The assembly according to claim 1, wherein the photopolymer film is detachable from the substrate with a peel force of 0.05 to 0.75 N/10 mm, the peel force being measured in accordance with DIN Standard EN ISO 11339.

6. The assembly according to claim 1, wherein the substrate has a surface roughness of Rz600 nm.

7. The assembly according to claim 1, wherein the writing monomer comprises or consists of at least one mono- and/or one polyfunctional writing monomer, preferably at least one mono- and/or polyfunctional acrylate writing monomer and more preferably at least one monofunctional and/or one polyfunctional urethane (meth)acrylate.

8. The assembly according to claim 1, wherein the photopolymer film comprises urethanes of the general formula (IV) ##STR00008## in which m is 1 and m is 8 and R.sub.1 is a linear, branched, cyclic or heterocyclic organic radical, optionally substituted by heteroatoms, and R.sub.2 and R.sub.3 independently of one another are hydrogen.

9. The assembly according to claim 1, wherein a hologram has been exposed into the photopolymer film.

10. A method for producing an assembly according to claim 1, comprising applying a photopolymer formulation comprising a polyisocyanate component, an isocyanate-reactive component, a writing monomer and a photoinitiator to the substrate and curing the photopolymer formulation to form the photopolymer film.

11. A method for producing an isolated photopolymer wherein the photopolymer film and the substrate of an assembly according to claim 1 are separated completely from one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows schematically the construction of the foil coating line for the production of the photopolymer films.

(2) FIG. 2 shows the spectrum of a UV lamp used for bleaching (manufacturer data).

EXAMPLES

(3) Measurement Methods:

(4) Measurement of the Dry Film Thickness of the Photopolymer Film

(5) The physical layer thickness was determined using commercial white-light interferometers, such as the FTM-Lite NIR layer thickness measuring instrument from Ingenieursbro Fuchs.

(6) The layer thickness was determined in principle on the basis of interference phenomena at thin layers. Light waves reflected from two interfaces with different optical densities were superimposed on one another. The undistorted superimposition of the reflected component beams leads to periodic brightening and extinction in the spectrum of a white continuum emitter (e.g., halogen lamp). This superimposition is called interference by the skilled person. The interference spectra were measured and evaluated mathematically.

(7) Solids Content

(8) About 1 g of the respective sample was applied in an uncoated can lid and spread out effectively by means of a paperclip. Can lid and paperclip were weighed beforehand. The sample together with paperclip and can lid was then dried in an oven at 125 C. for an hour. The solids content was obtained as follows: (final tare mass)*100/(initial tare mass).

(9) Viscosity

(10) The viscosities were determined in accordance with DIN EN ISO 32191A.3 at 23 C. with a shear rate of 40

(11) Isocyanate Content (NCO Content)

(12) The NCO values (isocyanate contents) were determined in accordance with DIN EN ISO 11909.

(13) Production of the Test Specimens for the LAB Measurement:

(14) Two foil samples of each of the substrates under investigation were cut to an approximate size of 2 cm3 cm. One foil sample was then incubated in a 0.5 volume percent butyl acetate solution of C.I. Basic Blue 3 in the form of the bis(2-ethylhexyl)sulphosuccinate at 23 C. for 7 days. Thereafter the sample was taken from the solution, dabbed dry with a paper cloth and dried in the air.

(15) Measurement of the L Value According to the CIELAB System

(16) The measurements were conducted on a sphere spectrometer of the Hunter Ultrascan Pro type from Hunter Lab, FMS Jansen GmbH & Co. KG, Murnau am Staffelsee, Germany, based on the standard ASTM E 308 for L*a*b*, The measurement was carried out using the D65 illuminant at an observation angle of 10. The measurement range went from 350 nm 1100 nm, with measurement only up to 850 nm for the colorimetric determination. For the purpose of calibration, a measurement in air was carried out, and the transmittance of this measurement was set at 100%.

(17) For each substrate under investigation, determinations were made both of the L0 value of the unincubated foil sample, and of the L1 value of the incubated foil sample.

(18) The difference was then formed between the L1 and L0 values. If this difference was less than or equal to 0.25, the substrate was classed as suitable in accordance with the invention.

(19) Measurement of the Surface Tension on Substrates

(20) The measurement took place using an instrument of type OCA 20 from DataPhysics Instruments GmbH, Filderstadt, Germany. The surface tension was calculated from the contact angles by the method of Owens-Wendt using the SCA21 software. For the measurement of the contact angles, 3 l of a measuring liquid was applied to each of the substrates under investigation. A USB-CCIR camera took pictures of the droplet at a frequency of 20 images per second. 4 seconds following application of the droplet, the contact angle was evaluated automatically. At least 5 individual measurements per substrate and measuring liquid were carried out, in order to obtain a sufficient statistical base. Measuring liquids used were double-distilled water, fresh diiodmethane and ethylene glycol.

(21) The instrument-specific measurement accuracy for the contact angle was 0.1 according manufacturer data.

(22) Measurement of the Peel Forces

(23) The measurement took place using a tensile testing machine in accordance with DIN EN ISO 527-1. Measurements were made of the tensile force and travel of the tensile traverse. The tensile force was defined as peel force or bonding force, and the traverse travel as peel travel, represented graphically in the form of a tensile force/peel travel diagram. The bonding force was the average value of the tensile forces between 20 and 100 mm peel travel. In accordance with DIN EN ISO 11339 (180 peel test, T-peel test), the peel strength was defined as peel force relative to the overall sample width. The sample was at least 80 mm long, with the clamped length in the tensioning clamps being 20 mm. The peel travel was 60 mm, corresponding to a travel of the tensile traverse of 120 mm. The tensioning rate was 100 mm/min. The tensile force was measured with a 50 N force transducer.

(24) Materials Employed

(25) Overview of the Substrates Used:

(26) Substrate foil 1 is Hostaphan GN 50 CT01B (=37.9 mN/m) and was obtained from Mitsubishi Polyester Film GmbH, Wiesbaden, Germany.

(27) Substrate foil 2 is Excel XG 532 (=38.5 mN/m) and was obtained from Toray International Europe GmbH, Neu-Isenburg, Germany.

(28) Substrate foil 3 is Excell XG6SF2 (36.9 mN/m) and was obtained from Toray International Europe GmbH, Neu-Isenburg, Germany.

(29) Substrate foil 4 is Lumirror U32 (36.4 mN/m) and was obtained from Toray International Europe GmbH, Neu-Isenburg, Germany.

(30) Substrate foil 5 is Lumirror U40 (=37.3 mN/m) and was obtained from Toray International Europe GmbH, Neu-Isenburg, Germany.

(31) Substrate foil C1 is Hostaphan RNK 36 (=48.3 mN/m) and was obtained from Mitsubishi Polyester Film GmbH, Wiesbaden, Germany.

(32) Substances Employed for the Photopolymer Films:

(33) Component A: experimental product of Bayer MaterialScience AG, Leverkusen, Germany; its preparation is described below.

(34) Component B1 (phosphorothioyltris(oxy-4,1-phenyleniminocarbonyloxyethane-2,1-diyl)triacrylate): experimental product of Bayer MaterialScience AG, Leverkusen, Germany; its preparation is described below,

(35) Component B2 (2-({[3-(methylsulphanyl)phenyl]carbamoyl}oxy)ethyl prop-2-enoate): experimental product of Bayer MaterialScience AG, Leverkusen, Germany; its preparation is described below.

(36) Component C (bis(2,2,3,3,4,4,5,5,6,6,7,7-dodeeafluoroheptyl) (2,2,4-trimethylhexane-1,6-diyl)biscarbamate): experimental product of Bayer MaterialScience AG, Leverkusen, Germany; its preparation is described below.

(37) Component D: Fascat 4102 0.07%, urethanization catalyst, butyltin tris(2-ethylhexanoate), product of Arkema Dsseldorf, Germany.

(38) BYK 310: silicone-based surface additive from BYK-Chemie GmbH, Wesel, 25% strength solution in xylene.

(39) Component E: C.I. Basic Blue 3 (converted to bis(2-ethylhexyl)sulphosuccinate salt) 0.26%, Safranin O (converted to bis(2-ethylhexyl)sulphosuccinate salt) 0.13% and Astrazone Orange G (converted to bis(2-ethylhexyl)sulphosuccinate salt) 0.13% with CGI 909, experimental product of BASF SE, Basel, Switzerland, 1.5%, as solution in 5.8% ethyl acetate. Percentages are based on the overall formulation of the medium.

(40) Component F: ethyl acetate (CAS No. 141-78-6).

(41) Component G: Desmodur N 3900, commercial product of Bayer MaterialScience AG, Leverkusen, Germany, hexane diisocyanate-based polyisocyanate, iminooxadiazinedione fraction at least 30%, NCO content: 23.5%.

(42) Preparation Protocols for the Substances Employed:

(43) Preparation of Component A:

(44) A 1 L flask was charged with 0.18 g of tin octoate, 374.8 g of -caprolactone and 374.8 g of a difunctional polytetrahydrofuran polyether polyol (equivalent weight 500 g/mole OH), and this initial charge was heated to 120 C. and held at that temperature until the solids content (fraction of the nonvolatile constituents) was 99.5 wt % or above. Subsequently it was cooled and the product was obtained as a waxy solid.

(45) Preparation of Component B1 (phosphorothioyltris(oxy-4,1-phenyleniminocarbonyl-oxyethane-2,1-diyl) triacrylate):

(46) A 500 mL round-bottomed flask was charged with 0.1 g of 2,6-di-tert-butyl-4-methylphenol, 0.05 g of dibutyltin dilaurate (Desmorapid Z, Bayer MaterialScience AG, Leverkusen, Germany) and with 213.07 g of a 27% strength solution of tris(p-isocyanatophenyl) thiophosphate in ethyl acetate (Desmodur RFE, product of Bayer MaterialScience AG, Leverkusen, Germany) and this initial charge was heated to 60 C. Then 42.37 g of 2-hydroxyethyl acrylate were added dropwise and the mixture was held further at 60 C. until the isocyanate content had dropped below 0.1%. Thereafter it was cooled and the ethyl acetate was removed in full under vacuum. The product was obtained as a partially crystalline solid.

(47) Preparation of Component B2 (2-({[3-(methylsulphanyl)phenyl]carbamoyl}oxy)ethyl prop-2-enoate):

(48) A 100 mL round-bottomed flask was 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 initially introduced and this initial charge was heated to 60 C. Then 8.2 g of 2-hydroxyethyl acrylate were added dropwise and the mixture was held further at 60 C. until the isocyanate content had dropped below 0.1%. Thereafter it was cooled. The product was obtained as a pale yellow liquid.

(49) Preparation of the additive C (bis(2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl) (2,2,4-trimethylhexane-1,6-diyl)biscarbamate):

(50) A 2000 mL round-bottomed flask was charged with 0.02 g of Desmorapid Z and 3.60 g of 2,4,4-trimethylhexane 1,6-diisocyanate (TMDI) and this initial charge was heated to 70 C. Then 11.39 g of 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptan-1-ol were added dropwise and the mixture was held further at 70 C. until the isocyanate content had dropped below 0.1%. Thereafter it was cooled. The product was obtained as a colourless oil.

(51) Preparation of Basic Blue 3 bis(2-ethylhexyl)sulphosuccinate

(52) 15.0 g of sodium bis(2-ethylhexyl)sulphosuccinate were dissolved in 350 ml of water at 50 C. 24.5 g of the dye of the formula

(53) ##STR00005##
(Basic Blue 3), as 53 wt % product, and 220 ml of butyl acetate were added and the mixture was stirred at 50 C. for 4 hours. The aqueous phase was removed and the organic phase was stirred three times with 50 ml of fresh water at 50 C. Finally the aqueous phase was removed each time, the last phase at room temperature. The deep-blue organic phase was dried initially with anhydrous magnesium sulphate, then filtered and freed from the remaining water by azeotropic distillation at 150 mbar. Addition of anhydrous butyl acetate, lastly, gave 250 g of deep-blue solution, containing 9.68 wt % of the dye of the formula

(54) ##STR00006##
(96.4% of theory).

(55) .sub.max in methanol: 643 nm.

(56) After appropriate dilution, this solution was used directly for testing in accordance with the invention.

(57) Producing the Assemblies of Substrate and Photopolymer Film on a Foil Coating Unit

(58) For production, the foil coating unit represented in FIG. 1 was used, with the individual components being assigned the following reference numerals: 1 First reservoir container 1 Second reservoir container 2 Metering device 3 Vacuum degassing device 4 Filter 5 Static mixer 6 Coating device 7 Forced-air dryer 8 Substrate foil 9 Liner layer

(59) To produce a photopolymer formulation, 304.3 g of Component A in a stirring vessel were admixed in steps with a writing monomer mixture of 138 g of Component B1 and 138 g of Component B2, with 191 g of Additive C, 0.60 g of Component D, 2.55 g of BYK 310 and 101 g of Component F, and these components were mixed. Then 66.5 g of Component E were added to the mixture in the dark and the composition was mixed so as to give a clear solution. If necessary, the formulation was heated at 60 C. for a short time in order to bring the ingredients into solution more rapidly.

(60) This mixture was subsequently introduced into the first reservoir container 1 of the coating unit. Introduced into the second reservoir container 1 was Component G (polyisocyanate). Both components were then conveyed to the vacuum degassing device 3, in each case by the metering devices 2, in a ratio of 942.2 (Components A to F) to 57.8 (Component G), and degassing was carried out. From there, they were then each passed through the filter 4 into the static mixer 5, where the components were mixed to form the photopolymer formulation. The liquid material obtained was then supplied in the dark to the coating device 6.

(61) The coating device 6 is in the present case a slot die, with which the skilled person is familiar. Alternatively, however, a doctor blade system may also be employed. Using the coating device 6, the photopolymer formulation was applied to the respective substrate foil 8 at a processing temperature of 20 C., and dried in a forced-air dryer 7 at a crosslinking temperature of 80 C. for 5.8 minutes. This gave an assembly in the form of a film, which was then provided with a 40 m thick polyethylene-foil liner layer 9, and wound up.

(62) The layer thickness obtained for the film was 18 m1 m.

(63) Production of the Specimens for the Measurement of the Peel Forces of the Exposed and Unexposed Photopolymer

(64) If the adhesion between substrate foil and photopolymer film is less than that between liner layer and photopolymer film, the assembly can be measured as it is, without any need for the liner layer to be removed beforehand. For this purpose, a section measuring 10 cm20 cm was cut from the assembly and placed on the conveyor belt of a UV source, and exposed twice with a belt speed of 2.5 m/min. The UV source used was an iron-doped Hg lamp of type Fusion UV D Bulb No. 558434 KR 85 with an overall power density of 80 W/cm.sup.2. The spectrum of the lamp used is shown in FIG. 2 (manufacturer data). The parameters correspond to a dose of 22.0 J/cm.sup.2, measured with an ILT 490 light bug. By dose, generally, is meant in each case the quantity of light actually acting on the photopolymer film. Then strips with a width of 10 mm and a length of approximately 12 cm were cut from the exposed assembly, and then these strips were used for measurement, by the method described above, of the force needed to peel off the substrate foil.

(65) If the adhesion between liner layer and photopolymer film is less than that between substrate foil and photopolymer film, the liner layer was first of all removed manually. Then a section measuring 10 cm20 cm was cut from the assembly, consisting of photopolymer film and substrate foil, and was laminated to a glass plate and then exposed twice with the UV source, as described above. Thereafter the section of the assembly, using a roll laminator at 100 C. with the photopolymer film side, was adhered to the smooth side of a polycarbonate foil of type Makrofol DE 1-4 (product of Bayer MaterialScience AG, Leverkusen, Germany), using a hot-melt adhesive foil based on a thermoplastic polyurethane of type Platilon HU2 from Epurex Films GmbH & Co. KG, Walsrode, Germany. Strips with a width of 10 mm and a length of approximately 12 cm were then cut from the assembly, and then these strips were used, in accordance with the method described above, to measure the force required to peel off the substrate foil.

(66) Results of the Measurements of the Peel Forces to DIN EN ISO 11339:

(67) TABLE-US-00001 Peel force Substrate foil L1 L0 P exposed 1 0.75 0.12 * 2 0.97 0.10 * 3 0.30 0.15 * 4 0.48 0.16.sup. 5 3.51 0.17.sup. C1 0.04 3.6 Values in N/10 mm, * Sample measurement on 15 mm sample width.

(68) As is evident from the table above, peel forces needed for detachment of the photopolymer film were measured for substrate foils 1-8, and are situated in the region less than 0.25 N/mm. This shows that for the assemblies which comprise one of these substrate foils, the separation of substrate foil from photopolymer film is possible easily and in particular without damage to the photopolymer film.

(69) Furthermore, the differences between the L1 and L0 values were measured for each of the substrate foils 1-8. They are all less than 0.25. This demonstrates that the difference in the L values and the criterion of formula (II) is suitable for the identification of readily detachable substrate foils.

(70) Comparative Example C1 shows in turn that when the difference between L1 and L0 is greater than 0.25, the peel forces needed for detachment of the photopolymer film from the substrate foil are also considerably greater. These forces are so great that damage to the photopolymer film may occur during the operation. Consequently, the substrate foil C1 is not suitable for solving the problem addressed by the invention, as was already evident from the consideration of the difference between the L values.