Method for transferring an embossed structure to the surface of a coating means and compound structure usable as an embossing die

Abstract

The present disclosure relates to a method for transferring an embossed structure to a surface of a coating composition (B2a), which includes the steps (1-i) and (2-i) or (1-ii) and (2-ii) and also the steps (3) and optionally (4), where the steps (1-i) and (2-i) or (1-ii) and (2-ii) are performed using a composite (F1B1) which is employed as an embossing die (p2) of an embossing tool (P2) and which is composed of a substrate (F1) and of an at least partially embossed and at least partially cured coating (B1), and the coating composition (B1a) used for producing (B1) of the composite (F1B1) is a radiation-curable coating composition of defined constitution. Also described herein is a composite (F1B1).

Claims

1. A method for transferring an embossed structure to at least a part of a surface of a coating composition (B2a), the method comprising: (1-i) applying a coating composition (B2a) to at least a part of a surface of a substrate (F2) and (2-i) at least partially embossing the coating composition (B2a), applied at least partially to the surface of the substrate (F2), by means of at least one embossing tool (P2) comprising at least one embossing die (p2), where the embossing die (p2) comprises a composite (B1F1) composed of a substrate (F1) and of an at least partially embossed and at least partially cured coating (B1), to give a composite (F2B2aB1F1) after the at least partial embossing, or (1-ii) applying a coating composition (B2a) to at least a part of an at least partially embossed surface of a composite (B1F1) which is used as an embossing die (p2) of an embossing tool (P2) and which is composed of a substrate (F1) and of an at least partially embossed and at least partially cured coating (B1), to give a composite (B2aB1F1), and (2-ii) applying a substrate (F2) to at least a part of the surface, formed by (B2a), of the composite (B2aB1F1), to give a composite (F2B2aB1F1), and (3) at least partially curing the coating composition (B2a) within the composite (F2B2aB1F1), to give a composite (F2B2B1F1), where throughout a duration of the at least partial curing, the coating composition (B2a) is in contact with the composite (B1F1), used as embossing die (p2) within the composite (F2B2aB1F1), and (4) optionally removing the composite (F2B2) within the composite (F2B2B1F1) from the composite (B1F1) used as the embossing die (p2), where the coating composition (B1a) used for producing the coating (B1) of the composite (B1F1) used as the embossing die (p2) is a radiation-curable coating composition, wherein the coating composition (B1a) comprises: at least a component (a) in an amount in a range from 40 to 95 wt %, at least an additive as component (b) in an amount in a range from 0.01 to 5 wt %, at least a photoinitiator as component (c) in an amount in a range from 0.01 to 15 wt %, and at least a component (d), comprising at least one carbon double bond, in an amount in a range from 0 to 45 wt %, where (i) the components (a), (b), (c), and (d) are each different from one another, (ii) the stated amounts of the components (a), (b), (c), and (d) are each based on a total weight of the coating composition (B1a), and (iii) the amounts of all components present in the coating composition (B1a) add up to 100 wt %, and where component (a) comprises at least three structural units, each different from one another or at least partially identical, of formula (I) ##STR00007## in which radicals R.sup.1 in each case independently of one another are a C.sub.2-C.sub.8 alkylene group, radicals R.sup.2 in each case independently of one another are H or methyl, and m each independently of one another are an integral parameter in a range from 1 to 15, but with proviso that m is at least 2 in at least one of the structural units of formula (I) within the component (a).

2. The method according to claim 1, wherein the substrate (F2) is a moving film web.

3. The method according to claim 1, wherein micro- and/or nanostructures are transferred as embossed structure to the coating composition (B2a) by step (2-i) or by steps (1-ii) and (2-ii).

4. The method according to claim 1, wherein the embossing die (p2) of the embossing tool (P2) that is used in step (2-i) and (1-ii) is reusable and can be used repeatedly for transferring at least one embossed structure when step (4) of the method is carried out.

5. The method according to claim 1, wherein the composite (B1F1) used as an embossing die (p2) in step (2-i) and (1-ii) is a composite composed of a film web (F1) and of a coating (B1) which is applied thereto and is at least partially embossed and at least partially cured.

6. The method according to claim 1, wherein during implementation of step (2-i), the composite (B1F1) used as embossing die (p2) in step (2-i) is guided via a first roll functioning as embossing tool (P2) and composite (F2B2a) is guided via a second roll, which lies opposite the first roll and is counter-rotatory thereto or co-rotatory therewith, and following application of the coating composition (B2a) to at least a part of its at least partially embossed surface to give the composite (B2aB1F1), during implementation of step (2-ii), the composite (B1F1) used as embossing die (p2) in step (1-ii) is guided via a first roll functioning as embossing tool (P2), and the substrate (F2) used within step (2-ii) is guided via a second roll, which lies opposite to the first roll and is counter-rotatory thereto or co-rotatory therewith.

7. The method according to claim 6, wherein the at least partial embossing of step (2-i) takes place at a level of a roll nip which is formed by two mutually opposing rolls, rotating counter-directionally or in a same direction, where the at least partially embossed coating (B1) of the composite (B1F1) is facing the coating composition (B2a) of the composite (F2B2a), and the at least partial embossing of step (2-ii) takes place at the level of the roll nip which is formed by the two mutually opposing rolls, rotating counter-directionally or in the same direction, where the coating composition (B2a) of the composite (B2aB1F1) is facing the substrate (F2).

8. The method according to claim 1, wherein a solids content of the coating composition (B1a) is 90 wt %, based on the total weight of the coating composition (B1a).

9. The method according to claim 1, wherein m is at least 2 in each of the at least three structural units of the formula (I) of component (a).

10. The method according to claim 1, wherein a fraction of ether segments [OR.sup.1].sub.m present in the structural units of formula (I) in the component (a) is at least 35 wt %, based on a total weight of component (a).

11. The method according to claim 1, wherein the composite (F1B1) which is used as embossing die (p2) of the embossing tool (P2) and which is composed of a substrate (F1) and of an at least partially embossed and at least partially cured coating (B1) is at least obtainable by: (5) applying the radiation-curable coating composition (B1a) to at least a part of a surface of a substrate (F1), (6) at least partially embossing the radiation-curable coating composition (B1a), applied at least partially to the surface of the substrate (F1), by means of at least one embossing tool (P1) having at least one embossing die (p1), (7) at least partially curing the radiation-curable coating composition (B1a), applied to at least a part of the surface of the substrate (F1) and at least partially embossed, by radiation curing, to give a composite (F1B1) composed of substrate (F1) and of at least partially embossed and at least partially cured coating (B1), where throughout the duration of the at least partial curing the coating composition (B1a) is in contact with the at least one embossing die (p1) of the at least one embossing tool (P1), and (8) removing the composite (F1B1) from the embossing tool (P1).

12. A composite (F1B1) comprising: a substrate (F1), and an at least partially embossed and at least partially cured coating (B1), and which is producible by at least partially curing a coating composition (B1a), applied to at least a part of a surface of the substrate (F1) and at least partially embossed, by radiation curing, where the coating composition (B1a) is a radiation-curable coating composition, wherein the radiation-curable coating composition (B1a) comprises: at least a component (a) in an amount in a range from 40 to 95 wt %, at least an additive as component (b) in an amount in a range from 0.01 to 5 wt %, at least a photoinitiator as component (c) in an amount in a range from 0.01 to 15 wt %, and at least a component (d), comprising at least one carbon double bond, in an amount in a range from 0 to 45 wt %, where (i) the components (a), (b), (c), and (d) are each different from one another, (ii) the stated amounts of the components (a), (b), (c), and (d) are each based on a total weight of the coating composition (B1a), and (iii) the amounts of all components present in the coating composition (B1a) add up to 100 wt %, and where component (a) comprises at least three structural units, each different from one another or at least partially identical, of formula (I) ##STR00008## in which radicals R.sup.1 in each case independently of one another are a C.sub.2-C.sub.8 alkylene group, radicals R.sup.2 in each case independently of one another are H or methyl, and m each independently of one another are an integral parameter in a range from 1 to 15, but with proviso that m is at least 2 in at least one of the structural units of formula (I) within the component (a); wherein the number of ether groups of the general formula OR.sup.1 within the component a) is in a range of from 4 to 18.

13. The composite (F1B1) according to claim 12, wherein the composite is obtainable by: (5) applying the radiation-curable coating composition (B1a) to at least a part of a surface of a substrate (F1), (6) at least partially embossing the radiation-curable coating composition (B1a), applied at least partially to the surface of the substrate (F1), by means of at least one embossing tool (P1) having at least one embossing die (p1), (7) at least partially curing the radiation-curable coating composition (B1a), applied to at least a part of the surface of the substrate (F1) and at least partially embossed, by radiation curing, to give a composite (F1B1) composed of substrate (F1) and of at least partially embossed and at least partially cured coating (B1), where throughout the duration of the at least partial curing the coating composition (B1a) is in contact with the at least one embossing die (p1) of the at least one embossing tool (P1), and (8) removing the composite (F1B1) from the embossing tool (P1).

14. The composite according to claim 12, wherein the substrate (F1) is a moving film web.

15. A method of transferring an embossed structure to at least a part of a surface of a coating composition (B2a) or to at least a part of a surface of a coating composition (B2a) which is at least partly applied on a substrate (F2), the method comprising using the composite (F1B1) according to claim 12 as an embossing die (p2) of an embossing tool (P2).

Description

INVENTIVE AND COMPARATIVE EXAMPLES

(1) The inventive and comparative examples below serve to illustrate the invention, but should not be interpreted as imposing any restriction.

(2) Unless otherwise indicated, the amounts in parts are parts by weight and amounts in percent are in each case percentages by weight.

1. Compounds and Materials Used

(3) Hostaphan GNcommercially available PET film with a layer thickness of 125 m.

(4) Laromer UA 9033 (L UA 9033)aliphatic urethane acrylate from BASF SE, employable as component (d)

(5) Hexanediol diacrylate (HDDA)employable as component (d)

(6) Sartomer 395 (SR 395)isodecyl acrylate from Sartomer, employable as component (d)

(7) Sartomer 502 (SR 502)TMPTA (trimethylpropane triacrylate) with 9-fold ethoxylation, from Sartomer, employable as component (a)

(8) Sartomer 499 (SR 499)TMPTA (trimethylpropane triacrylate) with 6-fold ethoxylation, from Sartomer, employable as component (a)

(9) Sartomer 454 (SR 454)TMPTA (trimethylpropane triacrylate) with 3-fold ethoxylation, from Sartomer, employable as comparative component (a)

(10) TMPTA (trimethylpropane triacrylate)employable as comparative component (a)

(11) GPTA (glyceryl propoxytriacrylate)glyceryl triacrylate with 3-fold propoxylation, employable as comparative component (a)

(12) Irgacure 184 (1-184)commercially available photoinitiator from BASF SE, employable as component (c)

(13) Irgacure TPO-L (1-TPO-L)commercially available photoinitiator from BASF SE, employable as component (c)

(14) Irgacure TPO (1-TPO)commercially available photoinitiator from BASF SE, employable as component (c)

(15) Tego Rad 2500 (TR 2500)lubricity and antiblocking additive from Evonik (silicone acrylate), employable as component (b)

(16) Byk-SILCLEAN 3710 (BS 3710)surface additive from BYK Chemie GmbH (polyether-modified polydimethylsiloxane with acrylic functionality), employable as component (b)

2. Examples

(17) 2.1 Production of Coating Compositions (B1a) and Corresponding Comparative Coating Compositions

(18) The coating compositions were produced in accordance with tables 1a and 1b below. Coating compositions E1a to E7a are inventive. Coating compositions V1a to V5a are comparative coating compositions. The flow times ascertained at room temperature (20 C.) are in the range from 26 to 172 s in the case of the production of E1a to E3a and V1a to V5a.

(19) TABLE-US-00001 TABLE 1a Component (a) Coating or comparative composition component (a) Component (b) Component (d) Component (c) E1a SR 499 (65 parts) TR 2500 (1 part) L UA 9033 I-184 (3.5 parts) and (13.5 parts) and I-TPO-L (3.5 parts) HDDA (13.5 parts) E2a SR 499 (92 parts) TR 2500 (1 part) I-184 (3.5 parts) and I-TPO-L (3.5 parts) E3a SR 502 (65 parts) TR 2500 (1 part) L UA 9033 I-184 (3.5 parts) and (13.5 parts) and I-TPO (3.5 parts) HDDA (13.5 parts) V1a SR 499 (65 parts) L UA 9033 I-184 (3.5 parts) and (13.5 parts) and I-TPO-L (3.5 parts) HDDA (13.5 parts) V2a SR 454 (65 parts) TR 2500 (1 part) L UA 9033 I-184 (3.5 parts) and (13.5 parts) and I-TPO (3.5 parts) HDDA (13.5 parts) V3a TMPTA (50 parts) TR 2500 (1 part) L UA 9033 I-184 (3.5 parts) and (26 parts) and I-TPO-L (3.5 parts) SR 395 (16 parts) V4a GPTA (50 parts) TR 2500 (1 part) L UA 9033 I-184 (3.5 parts) and (26 parts) and I-TPO-L (3.5 parts) SR 395 (16 parts) V5a SR 499 (32 parts) TR 2500 (1 part) L UA 9033 I-184 (3.5 parts) and (30 parts) and I-TPO-L (3.5 parts) HDDA (30 parts)

(20) TABLE-US-00002 TABLE 1b Component (a) Coating or comparative composition component (a) Component (b) Component (d) Component (c) E4a SR 499 (63 parts) TR 2500 (0.5 part) L UA 9033 I-184 (3.5 parts) and (13.5 parts) and I-TPO (3.5 parts) HDDA (13.5 parts) E5a SR 499 (63 parts) TR 2500 (1 part) L UA 9033 I-184 (3.5 parts) and (13.5 parts) and I-TPO (3.5 parts) HDDA (13.5 parts) E6a SR 499 (63 parts) TR 2500 (2 parts) L UA 9033 I-184 (3.5 parts) and (13.5 parts) and I-TPO (3.5 parts) HDDA (13.5 parts) E7a SR 499 (63 parts) BS 3710 (1 part) L UA 9033 I-184 (3.5 parts) and (13.5 parts) and I-TPO (3.5 parts) HDDA (13.5 parts)

(21) 2.2 Production of Master Films (B1F1) Using E1a to E3a and V1a to V5a

(22) A number of different master films are produced using a roll-to-plate embossing apparatus with a nickel embossing tool P1 bearing the desired positive structure. For this purpose, one each of the above-described coating compositions E1a to E3a and V1a to V5a is applied to P1, and a PET film (F1) is applied over it (Hostaphan GN). The resulting stack of film and respective coating composition then runs through beneath a pressing roll and, still while the embossing apparatus is in contact with the coating composition of the respective stack, the coating compositions are at least partly cured by means of a UV-LED lamp. The lamp used in this case is a 365 nm, 6 W UV-LED lamp from Easytec (100% lamp power, 2 m/min, 2 passes). The at least partially cured coating together with film, with the negative structure by comparison with P1, is subsequently separated from the embossing apparatus, to give the structured film (master film). The master films are subsequently post-exposed with a UVA lamp (Panacol-Elosal UV F-900).

(23) Furthermore, a master film is produced using a roll-to-roll embossing apparatus with a nickel embossing tool P1 bearing the desired positive structure. For this purpose, the above-described coating composition E1a is applied to a PET film (F1) (Hostaphan GN) and guided over the embossing tool P1 with the aid of a pressing roll. Still while the embossing apparatus is in contact with the coating composition, the coating composition is at least partly cured by means of a UV-LED lamp. The lamp used in this case is a 365 nm, 6 W UV-LED lamp from Easytec (100% lamp power, 5 m/min). The at least partially cured coating together with film, with the negative structure by comparison with P1, is subsequently separated from the embossing apparatus, to give the structured film (master film). The master film is subsequently post-exposed with a UVA lamp (Panacol-Elosal UV F-900).

(24) 2.3 Production of Master Films (B1F1) Using E4a to E7a

(25) A number of different master films are produced using a nickel embossing tool P1 bearing the desired positive structure. For this purpose, one each of the above-described coating compositions E4a to E7a is applied to P1, and a PET film is applied over it (Hostaphan GN). The resulting stack of film and respective coating composition is then pressed on with a rubber roller and, still while the embossing apparatus is in contact with the coating composition of the respective stack, the coating compositions are at least partly cured by means of a UV-LED lamp. The lamp used in this case is a 365 nm, 6 W UV-LED lamp from Easytec (100% lamp power, 2 m/min, 2 passes). The at least partially cured coating together with film, with the negative structure by comparison with P1, is subsequently separated from the embossing apparatus, to give the structured film (master film).

(26) 2.4 Master Films Produced

(27) In the manner described in sections 2.2 and 2.3, various sets of master films are obtained (E1F1 to E7F1 and V1F1 to V5F1), additionally differing in their embossing according to the nature of the positive structure. In this case, embossing apparatuses of nickel with different positive structures were used, specifically with a nanostructure (lattice structure with a period of 430 nm and a depth of 140 nm; the respective coating composition is applied in layer thicknesses between 5-10 m to the PET film employed), a microstructure A (two-dimensional triangle structure with a width and height of 33 m and a space of 35 m between the structures; the respective coating composition is applied in layer thicknesses between 20 m to the PET film employed), a microstructure B (continuous two-dimensional triangle structure with a width of 43 m and a height of 10 m; the respective coating composition is applied in layer thicknesses of 20 m to the PET film employed), or with a microstructure C (two-dimensional triangle structure with a height of 80 m and a space of 115 m between the structures; the respective coating composition is applied in layer thicknesses of 110 m to the PET film employed).

(28) The master films with the nanostructure are used for determining the modeling accuracy, the double bond conversions, and the adhesion. The master films with the microstructure A are used for determining the success of replication in the case of those master films produced using one of the coating compositions E1a to E3a and V1a to V5a (cf. Point 2.5 below) and also used as embossing die as described below under Point 2.6. The master films with the microstructure B are used for determining the success of replication in the case of those master films produced using one of the coating compositions E4a to E7a (cf. Point 2.5 below) and also used as embossing die as described below under Point 2.6. The master film with the microstructure C is used as embossing die as described below under Point 2.7. In order to produce this master film the coating composition E1a is used and a master film E1F1 with microstructure C is correspondingly obtained.

(29) 2.5 Investigations on the Master Films

(30) Table 2 below summarizes the investigations conducted. The investigations were each conducted in accordance with the methods described above. The symbol within the table denotes that the particular investigation was not carried out.

(31) TABLE-US-00003 TABLE 2 Modeling Master DB conversion Success of accuracy film (%) Adhesion replication (%) (h, %) E1F1 92 3.5 100 4 E2F1 90 0.5 100 4 E3F1 95 2.5 4 V1F1 93 5 100 3 V2F1 85 1.5 85 2 V3F1 89 5 85 5 V4F1 92 5 100 4 V5F1 87 5 85 29 E4F1 100 E5F1 100 <1 E6F1 100 E7F1 100 <1

(32) The data show that in the case of V2F1, V3F1 and V5F1 there is no attainment of sufficient DB conversion (DB conversion <90). With too low a DB conversion, problems may occur in the embossing both of the coating composition (B1a) and also, later on, of the coating composition (B2a). The master films E1F1, E2F1 and E3F1, conversely, show DB conversions of at least 90%.

(33) In the case of V1F1 and V4F1, the DB conversions are indeed >90%, but the adhesion achieved with these master films, just as with V3F1 and V5F1 is inadequate (cross-cut test evaluated with a rating of 5). If adhesion of the master coating on the PET film is insufficient, problems may occur during embossing both of the coating composition (B1a) and also, later on, of the coating composition (B2a). The master films E1F1, E2F1 and E3F1, conversely, all exhibit good to sufficient adhesion properties.

(34) The data additionally show that in the case of V2F1, V3F1 and V5F1, only values of 85% are obtained in the assessment of the success of replication, since 15% of the respective coating V2, V3 and V5 could not be removed from the embossing tool.

(35) Conversely, the investigated master films E1F1 and E2F1 exhibit a replication success of 100%.

(36) Apart from V5F1, all of the master films investigated exhibit sufficient modeling accuracy, since very low contraction values are obtained consistently. Only in the case of V5F1 is the contraction obtained 29%, which is unacceptable.

(37) In summary it can be stated that only the master films E1F1, E2F1 and E3F1 furnish good results in respect of all of the properties investigated (DB conversion, adhesion, modeling accuracy, and success of replication).

(38) 2.6 Use of the Master Films as Embossing Die for Producing Embossed Product Films

(39) The master films obtained respectively with the microstructure A or B are then each used as embossing die of an embossing tool. For this purpose, the master film is used in a roll-to-plate embossing apparatus. A coating composition (B2a) is applied with a wet layer thickness of 20 m to the respective master film. Moreover, a PET film as substrate F2 (Hostaphan GN) is contacted with the coating composition (B2a). The resulting stack of film and coating composition (B2a) then runs through beneath a pressing roll and, while the embossing device is still in contact with the coating composition of the respective stack, the coating composition (B2a) is at least partially cured by a UV-LED lamp. The lamp used in this case is a 365 nm, 6 W UV-LED lamp from Easytec (100% lamp power, 2 m/min, 2 passes). The at least partially cured coating B2 together with film F2 with the desired final embossed structure is subsequently parted from the embossing die, in other words from the particular master film used, of the embossing tool, and the structured product film (B2F2) is obtained.

(40) The coating composition (B2a) employed is a commercial, radiation-curing coating composition which comprises at least one urethane acrylate and at least one photoinitiator and also commercial additives.

(41) Table 3a below summarizes the results of the investigations of the success of replication performed on the resultant product films, taking account of the particular master film used for embossing. The symbol within the table denotes that the particular investigation was not carried out.

(42) TABLE-US-00004 TABLE 3a Success of replication of the embossed structure of the product film Master film used Success of replication (%) E1F1 100 E2F1 100 E3F1 E4F1 100 E5F1 100 E6F1 100 E7F1 100 V1F1 42* V2F1 100 V3F1 85 V4F1 100 V5F1 100 *= Average from two determinations

(43) The data show that in the case where V1F1 and V3F1 were used as the embossing die, values of only <100% are obtained when assessing the success of replication, since in these cases 15% or 58% of the coating B2 could not be removed from the coatings V1 and V3 of the respective master films. Conversely, when using the investigated master films E1F1, E2F1 and E4F1 to E7F1 as embossing die, a replication success of 100% of the coating B2 of the product film is achieved.

(44) 2.7 Further Use of the Master Films as Embossing Die for Producing Embossed Product Films

(45) The master film obtained with the microstructure C (E1F1) is used as embossing die. A coating composition (B2a) is applied with a wet layer thickness of 100 m to the master film. Moreover, a PET film as substrate F2 (Hostaphan GN) is contacted with the coating composition (B2a) and pressed on. The resulting stack of film (F1), coating (B1, i.e. E1), coating composition (B2a) and film (F2) is cured at room temperature (23 C.) for a period of 24 hours. The at least partially cured coating (B2) together with film (F2) with the desired final embossed structure is subsequently parted from the embossing die, in other words from the master film (E1F1) used with the microstructure C and the structured product film (B2F2) is thus obtained.

(46) The coating composition (B2a) employed is a commercial, thermally curing two component epoxy resin (Epofix from Struers GmbH). The mixing ratio between component 1 and component 2 is 9:1. Component 1 comprises at least one bisphenol epichlorohydrin. Component 2 comprises at least one polyamine.

(47) Table 3b below summarizes the results of the investigation of the success of replication performed on the resultant product film, taking account of the master film used for embossing.

(48) TABLE-US-00005 TABLE 3b Success of replication of the embossed structure of the product film Master film used Success of replication (%) E1F1 100

(49) With the use of the master film E1F1 as embossing die, a replication success of 100% of the coating B2 of the product film is achieved, even when a thermally curing coating composition is used as coating composition (B2a).