METHOD FOR TRANSFERRING AN EMBOSSED STRUCTURE TO THE SURFACE OF A COATING AND COMPOUND STRUCTURE CONTAINING SAID COATING

Abstract

The present disclosure relates to a method for transferring an embossed structure to at least a part of a surface of a coating (B2), using a composite (F1B1) composed of a substrate (F1) and of an at least partially embossed and at least partially cured coating (B1), where the coating (B2) and the coating (B1) of the composite (F1B1) have embossed structures which are mirror images of one another. Also described herein is a composite (B2B1F1). Further described herein is a use of this composite for producing an at least partially embossed coating (B2) in the form of a free film or a composite (B2KF2) composed of a substrate (F2), at least one adhesive (K), and the coating (B2).

Claims

1. A method for transferring an embossed structure to at least a part of a surface of a coating (B2), using a composite (F1B1) composed of a substrate (F1) and of an at least partially embossed and at least partially cured coating (B1), where the coating (B2) and the coating (B1) of the composite (F1B1) have embossed structures which are mirror images of one another, the method comprising: (1) applying a coating composition (B2a) to at least a part of an at least partially embossed surface of a composite (B1F1) comprising the substrate (F1), and the at least partially embossed and at least partially cured coating (B1), to give a composite (B2aB1F1), and (2) at least partially curing the applied coating composition (B2a) to give a composite (B2B1F1) comprising the substrate (F1), the at least partially embossed and at least partially cured coating (B1), and the at least partially cured coating (B2), and (3) optionally removing the coating (B2) from the composite (B2B1F1) to restore the composite (B1F1) used in step (1), where the coating (B2), on its surface previously facing the coating (B1) within the composite (B2B1F1), has a mirror image of the at least partially embossed surface of the coating (B1) of the composite (B1F1) used in step (1) and restored in that step, where the coating composition (B1a) used for producing the coating (B1) of the composite (B1F1) used in step (1) and restored in step (3) is a radiation-curable coating composition, wherein the radiation-curable coating composition (B1 a) comprises at least one component (a) in an amount in a range from 40 to 95 wt %, at least one additive as component (b) in an amount in a range from 0.01 to 5 wt %, at least one photoinitiator as component (c) in an amount in a range from 0.01 to 15 wt %, and at least one 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 the formula (I) within the component (a).

2. The method as claimed in claim 1, wherein the coating (B2) in step (3) is obtained as a free film by peeling from the composite (B2B1F1) with additional restoration of the composite (B1F1).

3. The method as claimed in claim 1, wherein the coating (B2) is obtained in step (3) in three stages in a form of a composite (B2KF2), the method further comprising: (3a) applying an adhesive (K) to at least a part of a surface of the composite (B2B1F1), on its side having the coating (B2), to give a composite (KB2B1F1), (3b) applying a substrate (F2) to the composite (KB2B1F1) obtained after stage (3a), to at least a part of its surface having the adhesive (K), or vice-versa, to give a composite (F2KB2B1F1), and (3c) peeling the composite (B1F1) from the composite (F2KB2B1F1) to give a composite (F2KB2), where the coating (B2) of this composite has on its surface at least partially the mirror image of the at least partially embossed surface of the coating (B1) of the composite (B1F1).

4. The method as claimed in claim 3, wherein the coating (B2) is obtained as a free film by peeling from the composite (F2KB2) obtained after stage (3c).

5. The method as claimed in claim 1, wherein the at least partially embossed and at least partially cured coating (B1) of the composite (F1B1) used in step (1) has embossments in a micrometer and/or nanometer range.

6. The method as claimed in claim 1, wherein the composite (B1F1) used in step (1) 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.

7. The method as claimed in claim 1, wherein the composite (B1F1) used in step (1) and restored after step (3) is reusable and can be used repeatedly for transferring at least one embossed structure.

8. The method as claimed in claim 1, wherein the composite (F1B1) which is used in step (1) and which is composed of the substrate (F1) and of an at least partially embossed and at least partially cured coating (B1) is at least obtainable by (4) applying the radiation-curable coating composition (B1a) to at least a part of a surface of the substrate (F1), (5) 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), (6) 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 a 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 (7) removing the composite (F1B1) from the embossing tool (P1).

9. The method as claimed in claim 1, wherein a solids content of the coating composition (B1a) is ≥90 wt %, based on a total weight of the coating composition (B1a).

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

11. The method as claimed in claim 1, wherein a fraction of ether segments —[O—R.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).

12. A composite (B2B1F1) comprising: a substrate (F1), an at least partially embossed and at least partially cured coating (B1), and an at least partially cured coating (B2) applied to (B1), where the coating (B1) 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 coating composition (B1a) comprises: at least one component (a) in an amount in a range from 40 to 95 wt %, at least one additive as component (b) in an amount in a range from 0.01 to 5 wt %, at least one photoinitiator as component (c) in an amount in a range from 0.01 to 15 wt %, and at least one 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## wherein 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 the formula (I) within the component (a).

13. The composite (B2B1F1) as claimed in claim 12, wherein a composite (B1F1) in the composite (B2B1F1) is obtainable by (4) applying the radiation-curable coating composition (B1a) to at least a part of a surface of the substrate (F1), (5) 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), (6) 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 a 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 (7) removing the composite (F1B1) from the embossing tool (P1).

14. The composite (B2B1F1) as claimed in claim 12, wherein the composite (B2B1F1) is obtainable by (1) applying a coating composition (B2a) to at least a part of an at least partially embossed surface of a composite (B1F1) composed of comprising: the substrate (F1), and the at least partially embossed and at least partially cured coating (B1), to give a composite (B2aB1F1), and (2) at least partially curing the applied coating composition (B2a) to give a composite (B2B1F1) composed of comprising the substrate (F1), the at least partially embossed and at least partially cured coating (B1), and the at least partially cured coating (B2).

15. A method for producing a coating (B2), embossed at least partially on one of its surfaces, in the form of a free film, using the composite (B2B1F1) as claimed in claim 12.

16. A method for producing a composite (B2KF2) comprising a substrate (F2), at least one adhesive (K), and the coating (B2), using the composite (B2B1F1) as claimed in claim 12.

Description

INVENTIVE AND COMPARATIVE EXAMPLES

[0247] The inventive and comparative examples below serve to illustrate the invention, but should not be interpreted as imposing any restriction.

[0248] Unless otherwise indicated, the amounts in parts are parts by weight and amounts in percent are in each case percentages by weight.

[0249] 1. Ingredients and Materials Used

[0250] Hostaphan® GN—commercially available PET film with a layer thickness of 125 μm.

[0251] Laromer® UA 9033 (L UA 9033)—aliphatic urethane acrylate from BASF SE, employable as component (d) Hexanediol diacrylate (HDDA)—employable as component (d)

[0252] Sartomer® 395 (SR 395)—isodecyl acrylate from Sartomer, employable as component (d)

[0253] Sartomer® 502 (SR 502)—TMPTA (trimethylolpropane triacrylate) with 9-fold ethoxylation, from Sartomer, employable as component (a)

[0254] Sartomer® 499 (SR 499)—TMPTA (trimethylolpropane triacrylate) with 6-fold ethoxylation, from Sartomer, employable as component (a)

[0255] Sartomer® 454 (SR 454)—TMPTA (trimethylolpropane triacrylate) with 3-fold ethoxylation, from Sartomer, employable as comparative component (a)

[0256] TMPTA (trimethylolpropane triacrylate)—employable as comparative component (a)

[0257] GPTA (glyceryl propoxytriacrylate)—glyceryl triacrylate with 3-fold propoxylation, employable as comparative component (a)

[0258] Irgacure® 184 (I-184)—commercially available photoinitiator from BASF SE, employable as component (c)

[0259] Irgacure® TPO-L (I-TPO-L)—commercially available photoinitiator from BASF SE, employable as component (c)

[0260] Tego® Rad 2500 (TR 2500)—lubricity and antiblocking additive from Evonik (silicone acrylate), employable as component (b)

[0261] Byk-SILCLEAN 3710 (BS 3710)—surface additive from BYK Chemie GmbH (polyether-modified acrylic-functional polydimethylsiloxane), employavle as component (b)

2. Examples

[0262] 2.1 Production of Coating Compositions (B1a) and Corresponding Comparative Coating Compositions

[0263] The coating compositions were produced in accordance with tables 1a and 1b below. Coating compositions E1a to E3a as well as E4a to E6a 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 Ela to E3a and V1a to V5a.

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

TABLE-US-00002 TABLE 1b Coating composition Component (a) Component (b) Component (d) Component (c) E4a SR 499 (65 parts) TR 2500 (0.5 parts) L UA 9033 I-184 (3.5 parts) (13.5 parts) and and I-TPO-L (3.5 HDDA (13.5 parts) parts) E5a SR 499 (65 parts) TR 2500 (2 parts) L UA 9033 I-184 (3.5 parts) (13.5 parts) and and I-TPO-L (3.5 HDDA (13.5 parts) parts) E6a SR 499 (65 parts) BS 3710 (1 part) L UA 9033 I-184 (3.5 parts) (13.5 parts) and and I-TPO-L (3.5 HDDA (13.5 parts) parts)

[0264] 2.2 Production of Master Films (B1F1) Using Ela to E3a and V1a to V5a as Well as E4a to E6a

[0265] 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 Ela to E3a and V1a to V5a as well as E4a to E6a 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 partially 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).

[0266] Further, a master film is produced by using a roll-to-roll embossing apparatus having an embossing tool P1 made of nickel bearing the desired positive structure. For this purpose, the coating composition Ela described above is applied to a PET film (F1) (Hostaphan® GN) and passed over the embossing tool P1 with the aid of a pressing roll. Even while the embossing apparatus is in contact with the coating composition, the at least partial curing of the coating composition is effected by a UV-LED lamp. A 365 nm, 6 W UV-LED lamp from Easytec (100% lamp power, 5 m/min) is used. Subsequently, the at least partially cured coating together with the film is separated from the embossing apparatus with the negative structure by comparison with P1, and the structured film (master film) is obtained. The master film is subsequently post-exposed with a UVA lamp (Panacol-Elosal UV F-900).

[0267] 2.3 Master Films Produced

[0268] In the manner described in section 2.2, various sets of master films are obtained (E1F1 to E3F1 and V1F1 to V5F1 as well as E4F1 to E6F1), 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 [0269] 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 μm to the PET film employed), [0270] a microstructure M1 (two-dimensional triangle structure with a width and height of 33 μm and a space of 35 μm between the structures; the respective coating composition is applied in layer thicknesses of 20 μm to the PET film employed), [0271] a microstructure A (continuous two-dimensional triangular structure with a width of 45 μm and a height of 13 μm, the respective coating composition is applied in layer thicknesses of 20 μm to the PET film used), or with [0272] a microstructure B (two-dimensional triangular structure with a height of 80 μm and 115 μm space between the structures, the respective coating composition being applied to the employed PET film in layer thicknesses of 110 μm.

[0273] 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 M1 are used for determining the success of replication—see. Point 2.4—and also used for the production of transfer films as described below under points 2.5 to 2.7. The master films with the microstructures A or B are used for the production of transfer films as described in Section 2.8 below. For producing these master films, the coating composition Ela is used in each case and correspondingly master films E1F1 with microstructure A or B are obtained.

[0274] 2.4 Investigations on the Master Films

[0275] 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.

TABLE-US-00003 TABLE 2 DB Success of Modeling Master conversion replication accuracy film (%) Adhesion (%) (Δh, %) 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

[0276] 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%.

[0277] 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.

[0278] 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. Conversely, the investigated master films E1F1 and E2F1 exhibit a replication success of 100%.

[0279] 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 a contraction of 29% obtained, which is unacceptable.

[0280] 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).

[0281] 2.5 Production of Transfer Films:

[0282] The master films obtained respectively with the microstructure are then each used in a roll-to-plate embossing apparatus, and a coating composition (B2a) is applied with a wet layer thickness of 20 μm to the structured surface of the respective master film. The resulting stack of master film and coating composition (B2a) is lined with a TAC film to protect against oxygen. The stack obtained in turn, comprising master film, coating composition (B2a) applied thereto, and TAC film applied to the coating composition, then runs through beneath a pressing roll, in a process simultaneous with the at least partial curing of the coating composition (B2a) 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). In this way, following removal of the TAC film, a composite (B2B1F1) is obtained as a transfer film stack.

[0283] The coating composition (B2a) employed is a commercial, radiation-curing coating composition which comprises at least one urethane acrylate, at least one photoinitiator and also commercial additives.

[0284] 2.6 Production of Bonded Composites and Free Structured Films:

[0285] The unstructured, coated side of the coating (B2) of the transfer film (B2B1F1) is then adhered by means of a laminating film (mount laminating film S-4705 WSA 120P from ATP; polyacrylate) to a coated steel plate. The laminating film used consists of an adhesive film K, lined on either side initially in each case with a silicone paper in order to protect against unintended sticking. For this purpose, the silicone paper is first of all peeled from one of the sides and, parallel to the direction of peeling of the silicone paper, the adhesive film is brought, with its now exposed adhesive side, onto the coated side of the coating (B2) of the transfer film (B2B1F1), by pressing the adhesive film onto B2 with a rubber roller. Similarly, then, the silicone paper is peeled off from the other side and, parallel to the direction of peeling of the silicone paper, the adhesive film is pressed by its final adhesive side, now exposed, onto a surface of the steel plate as substrate F2, using a rubber roller. The resulting composite (F2KB2B1F1) is first stored at 50° C. for 12 hours. Following this storage, the respective master film (B1F1) is peeled from the aforesaid composite, to give not only the master film but also the composite (F2KB2).

[0286] In order to obtain a free structured film, the coating (B2) can be separated from the bonded steel plate (F2KB2).

[0287] 2.7 Investigations on the Bonded Composites (F2KB2) or on the Free Structured Film (B2)

[0288] Table 3 below summarizes the results of the investigations of the success of replication performed on the resultant transfer 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.

TABLE-US-00004 TABLE 3 Success of replication of the embossed structure Success of Master film used replication (%) E1F1 100 E2F1 100 E3F1 100 E5F1 100 E6F1 100 V1F1  52* V2F1 100 V3F1  17 V4F1  <1 V5F1  86 * = Average value of two determinations

[0289] The data show that, in the case where V3F1 and V4F1 are used, replication is only inadequate. When using V1F1 and V5F1, as well, values of only <100% are obtained when assessing the success of replication, since in these cases parts of the coating B2 could not be removed from the coatings V1 and V5 of the respective master films. Conversely, when using the investigated master films E1F1 to E3F1 and E5F1 and E6F1, a replication success of 100% is achieved.

[0290] 2.8 Production of Further Transfer Films:

[0291] A thermally curable coating composition (B2a) is applied with a wet layer thickness of 200 μm to the structured surface of the respective master film E1F1, which carries one of the microstructures A or B. The at least partial curing of the thus obtained stack of master film and coating composition (B2a) takes place after a flash-off time of 10 minutes at room temperature (23° C.) in a commercial oven from Heraeus at 80° C. oven temperature (45 min). It is thus obtained as a stack a composite (B2B1F1) as a transfer film.

[0292] The used thermally curable coating composition (B2a) is a commercially available thermosetting 2K coating composition. The mixing ratio between component 1 and component 2 is 2:1. Component 1 contains at least one polyol and commercial additives. Component 2 contains at least one polyisocyanate and commercially available additives.

[0293] From the transfer films thus obtained, composites (F2KB2) are obtained by means of the procedure described under point 2.6.

[0294] Table 4 below summarizes the results of the tests of the success of replication performed on the obtained transfer films taking into account each master film used for embossing.

TABLE-US-00005 TABLE 4 Success of replication of the embossed structure Success of Master film used replication (%) E1F1 (with microstructure A) 100 E1F1 (with microstructure B) 100

[0295] The data show that in the case of the use of the investigated master films E1F1 a replication success of 100% is achieved, even if a thermosetting coating composition is used as the coating composition (B2a).