SHAPED BODY HAVING A VOLUME HOLOGRAM AND METHOD FOR PRODUCTION THEREOF

Abstract

The present invention concerns a method for the production of a moulded body containing at least one volume hologram by means of injection moulding, comprising the following method steps: provision of a hologram film composite having two sides comprising at least one photopolymer layer with at least one volume hologram, a shear protective layer and a substrate layer, and optionally, further composite film layers, insertion of the hologram film composite into a metallic injection mould, such that one side of the hologram film composite is at least partially in contact with the injection mould wall, introduction of a molten thermoplastic polymer for the production of the moulded body, wherein at least the outermost layer of the hologram film composite on the side of the hologram film composite coming into contact with the molten polymer contains essentially the same polymer raw materials as the molten thermoplastic polymer, and extrusion coating of the hologram film composite with the molten thermoplastic polymer, and solidification of the molten thermoplastic polymer.

The invention also concerns a moulded body produced in this manner and advantageous applications of this moulded body.

Claims

1.-15. (canceled)

16. A method for the production of a moulded body containing at least one volume hologram by means of injection moulding, comprising the following method steps: provision of a hologram film composite having two sides comprising at least one photopolymer layer with at least one volume hologram, a shear protective layer and a substrate layer, and optionally, further composite film layers, insertion of the hologram film composite into a metallic injection mould, such that one side of the hologram film composite is at least partially in contact with the injection mould wall, introduction of a molten thermoplastic polymer for the production of the moulded body, wherein at least the outermost layer of the hologram film composite on the side of the hologram film composite coming into contact with the molten polymer contains essentially the same polymer raw materials as the molten thermoplastic polymer, extrusion coating of the hologram film composite with the molten thermoplastic polymer, and solidification of the molten thermoplastic polymer.

17. The method according to claim 16, wherein the hologram film composite is inserted into the metallic injection mould such that the substrate layer is inserted facing the metallic injection mould with its side that faces away from the photopolymer layer, such that the substrate layer is at least partially in contact with the injection mould wall.

18. The method according to claim 16, wherein the shear protective film is formed by a protective lacquer.

19. The method according to claim 16, wherein the hologram film composite is inserted into the metallic injection mould such that the photopolymer layer is inserted with its free surface facing the metallic injection mould, such that the photopolymer layer is at least partially in contact with the injection mould wall.

20. The method according to claim 19, wherein the substrate layer and the shear protective layer are integrally configured.

21. The method according to claim 16, wherein the substrate layer contains a polymer from the group PC, PMMA, PET, PBT, PA, PS and PC/ABS.

22. The method according to claim 16, wherein the thermoplastic polymer contains a polymer from the group PC, PMMA, PET, PBT, PA, PS and PC/ABS.

23. The method according to claim 16, wherein the thermoplastic polymer contains additives, more particularly solvents, polymeric mixed substances or design-providing particles, dyes or absorbent pigments.

24. The method according to claim 23, wherein the additives contained in the thermoplastic polymer have a volume percentage of less than 20%, preferably less than 10% and particularly preferably less than 5%.

25. The method according to claim 16, wherein the thermoplastic polymer contains reinforcing agents, more particularly glass or carbon fibres or fabric.

26. The method according to claim 16, wherein the hologram film composite, before insertion of said hologram film composite into the metallic injection mould, is cut such that all layers of the hologram film composite have the same dimensions, with common cut edges that are oriented essentially perpendicularly to the extension of the hologram film composite.

27. The method according to claim 16, wherein the wall of the metallic injection mould does not exceed a maximum temperature of 100 C., preferably 90 C. and particularly preferably 80 C.

28. The method according to claim 16, wherein the internal mould pressure is a maximum of 1000 bar, preferably a maximum of 800 bar and more particularly a maximum of 700 bar, wherein the cycle time is a maximum of 30 s, preferably a maximum of 25 s and more particularly a maximum of 20 s.

29. A moulded body containing at least one volume hologram produced by the method according to claim 16.

30. A method comprising utilizing the moulded body containing at least one volume hologram according to claim 29 as a beam-guiding and/or beam-forming optical component for 3-dimensional imaging or as a security hologram in documents and for product protection and product labelling.

Description

[0046] In the following, the invention will be explained in greater detail with reference to a drawing present embodiments. The figures show the following:

[0047] FIG. 1 a hologram film composite according to the prior art,

[0048] FIG. 2 a moulded body containing at least one volume hologram produced by means of injection moulding in a first embodiment,

[0049] FIG. 3 a moulded body containing at least one volume hologram produced by means of injection moulding in a second embodiment,

[0050] FIG. 4 a moulded body containing at least one volume hologram by means of injection moulding in a third embodiment,

[0051] FIG. 5 a moulded body containing at least one volume hologram by means of injection moulding in a fourth embodiment,

[0052] FIG. 6 a moulded body containing at least one volume hologram by means of injection moulding in a fifth embodiment,

[0053] FIG. 7 the basic structure of a holographic film, and

[0054] FIG. 8 the transmission spectrum of a reflection hologram contained in a moulded body produced by injection moulding.

[0055] FIG. 2 shows a moulded body 200 containing at least one volume hologram produced by means of injection moulding in a first embodiment. More particularly, the moulded body 200 comprises a hologram film composite 20, which in turn comprises a photopolymer layer 101 and a substrate layer 102 lying thereunder. It can be specifically seen that the holographic photopolymer 101, which contains the at least one volume hologram, is open on one side. The substrate layer 102 is arranged on the opposite side. With respect to the injection moulding process carried out using an injection mould (not shown), this means that the hologram film composite 20 comprising the photopolymer layer 101 and a substrate layer 102 were inserted into the metallic injection mould such that the photopolymer layer 101 was oriented with its free surface facing the metallic injection mould, such that the photopolymer layer 101 was at least partially in contact with the injection mould wall (not shown). The substrate layer 102 protects the sensitive photopolymer layer 101 during the injection moulding process from the hot inflowing thermoplastic polymer and the resulting shear forces by functioning as a shear protective film. Accordingly, in the present case, the substrate layer 102 and the shear protective layer are configured as a single piece.

[0056] In the present case, moreover, the hologram film composite 20, before insertion in the metallic injection mould, is cut in such a way that all of the layers of the hologram film composite 20 have the same dimensions, with common cut edges that are oriented essentially perpendicularly to the extension of the hologram film composite.

[0057] The dimensions of the hologram film composite 20 are selected relative to the injection mould is such a way that by means of the extrusion coating of the hologram film composite 20 with the molten, thermoplastic polymer, only one further layer 103 is built up on the back side of the substrate layer 102. Although the injection mould thus constitutes only a cuboid cavity, a side surface of the cavity is completely covered by the inserted hologram film composite 20, wherein the photopolymer layer 101 is in planar contact with the injection mould wall. Accordingly, during the injection moulding process, the hologram film composite 20 is not insert-moulded, but only overmoulded.

[0058] Because of the fact that the outermost layer of the hologram film composite 20, in the present case the substrate layer 102, contains essentially the same polymer raw material as the molten thermoplastic polymer 103 on the side of the hologram film composite 20 coming into contact with the molten polymer 103, a stable compound is produced between the molten thermoplastic polymer and the substrate layer 102.

[0059] FIG. 3 shows a moulded body 300 containing at least one volume hologram produced by means of injection moulding in a second embodiment. In contrast to the moulded body 200, the dimensions of the hologram film composite 30 of the moulded body 300 are selected to be smaller than the lateral surface of the cavity of the injection mould used (not shown), which comes into contact with the photopolymer layer 101 before the molten thermoplastic polymer is introduced. Accordingly, this side surface is not completely covered by the hologram film composite 30 during extrusion coating with the molten thermoplastic polymer. This in turn causes the hologram film composite 30 to be insert-moulded with the melt, i.e. the edges of the hologram film composite 30 also come into contact with the molten thermoplastic polymer 103. The hologram film composite 30, before insertion into the metallic injection mould, is again cut so that all layers of the hologram film composite 30 have the same dimensions. A stable compound is produced between the molten, thermoplastic polymer and the substrate layer 102, without requiring mechanical clamping of the hologram film composite 30 with the molten thermoplastic polymer 103.

[0060] FIG. 4 shows a further modified embodiment of a moulded body 400 containing at least one volume hologram by means of injection moulding. In this embodiment, a covering layer 401 that covers the entire surface of the photopolymer layer 101 and the substrate layer 102 is provided, wherein the covering layer 401 is preferably a protective film with a scratch protecting function. In a further embodiment, the covering layer 401 is an absorbent decorative layer. Moreover, the covering layer 401 may be coloured. For example, the moulded body 400 can be configured such that the decoration provided by the covering layer 401 lies outside the hologram surface(s) of the photopolymer layer 101, wherein the volume hologram is in the form of a reflection hologram that is visible through the decorative layer 401. For example, the covering layer can be applied to the photopolymer layer 101 by means of the in-mould decoration (IMD) method known from the prior art. This means that the covering layer 401 is first positioned in the injection mould (not shown) together with the hologram film composite 40, wherein the dimensions of the covering layer 401 extend beyond the dimensions of the two other layers 101, 102. More particularly, the covering layer 401 can be dimensioned such that it completely fills a flat base area in the injection mould. The layered composite with the hologram film composite 40 and covering layer 401 is then insert-moulded with the molten thermoplastic polymer, resulting in the geometry of the moulded body 400 shown. Moreover, the covering layer 401 can be subsequently applied to the moulded body 400 by lamination or gluing.

[0061] FIG. 5 shows a further moulded body 500 containing at least one volume hologram produced by injection moulding in a fourth embodiment. As can be seen, the photopolymer layer 101 having at least one volume hologram is now arranged internally. This means that the substrate layer 102 of the hologram film composite 50 is positioned in the metallic injection mould with its side facing away from the photopolymer layer 101 facing the metallic injection mould (not shown) such that the substrate layer 102 is at least partially in contact with the injection mould wall. This also means that the during introduction of the molten thermoplastic monomer, the photopolymer layer 101 is no longer protected by the substrate layer 102 from the effects of the molten thermoplastic polymer. Accordingly, a shear protective film 501 is provided that completely covers the side of the photopolymer layer 101 facing away from the substrate layer 102 and thus provides effective shear protection.

[0062] In the embodiment of the moulded body according to FIG. 6, the particular characteristics of the embodiments of FIGS. 4 and 5 are combined, as it were. The moulded body of FIG. 6 thus has a covering layer completely covering the moulded body, more particularly with a decorative or scratch protection function, while the hologram film composite 60 in turn comprises a photopolymer layer 101, a substrate layer 102 and a separate shear protective layer 501. Specifically, the photopolymer layer 101 is in turn arranged in the interior and is protected by the shear protective layer 501 from the effects of the shear forces of the molten thermoplastic polymer.

[0063] FIG. 7 shows as an example of the basic structure of a holographic film B100, for example Bayfol HX from Covestro Deutschland AG. In a preferred embodiment, this holographic Film B100 comprises an approx. 125 m thick transparent substrate film 102 of polycarbonate on which an approx. 16 m thick photopolymer film 101 is arranged. This is covered by an approx. 40 m thick laminating film, which can easily be removed for further processing of the holographic Film B100.

[0064] Finally, FIG. 8 shows the transmission spectrum of a reflection hologram contained in a moulded body produced by means of injection moulding and exposed in a photopolymer layer of the type Bayfol HX (manufacturer: Covestro Deutschland AG). The x value of the diagram is equivalent to the measurement wavelength in nm; the y value is equivalent to the transmission in [%]; value a entered in the diagram is equivalent to the transmission in [%] of the sample without a volume hologram at the wavelength at which the transmission spectrum of the volume hologram reaches its minimum; b is equivalent to the transmission in [%] at the wavelength at which the transmission spectrum of the volume hologram reaches its minimum; c is equivalent to the entire half width of the transmission minimum of the volume hologram [nm].

EXAMPLES

Example 1: Production of a Sample for Hologram Exposure

[0065] A photopolymer-based holographic recording film from Covesiro Deutschland AG (formerly Bayer MaterialScience AG) of the type Bayfol HX (B100) is used, see FIG. 6. It is a 16 m thick light-sensitive photopolymer film (B101) that adheres to a transparent 125 m polycarbonate carrier film (B102) and is lined with a detachable polyethylene film (B103). A piece of this film measuring approx. 6030 mm is cut out in the dark laboratory. The lining is then removed, and the free side of the photopolymer is laminated blister-free without residue onto a 1 mm thick glass carrier from SCHOTT by means of a hand roller equipped with a high-quality rubberized pressing roll. The photopolymer is now embedded between the polycarbonate carrier (B102) and the glass carrier. This sample is packed in a light-proof aluminium bag and is thus ready for a subsequent hologram exposure.

Example 2: Recording of a Hologram

[0066] For the exposure (recording) of a hologram, a diode-pumped solid-state laser from Coherent is used, with a wavelength =532 nm and an output power P.sub.max=50 mW. This is integrated into a vibration-damped exposure structure.

[0067] The sample produced according to example 1 (B100) is clamped into a sample holder that is tilted by 13 relative to the collimated laser beam. The polycarbonate substrate is located externally on the side on which light is incident. The laser is widened to a diameter of approx. 25 mm and homogenized. The laser is switched on for 2 s, striking the centre of the sample and also the centre of the approx. 1515 mm mirrored surface of the sample holder. The back reflection of the mirror and the incident beam interfere in the photopolymer and generate a sinusoidal intensity grating during the exposure time that is reproduced in the photopolymer material as a phase grating. The phase grating represents the hologram. After laser exposure, it remains in the photopolymer film as a stable grating structure.

[0068] After the end of the holographic exposure, the sample is photobleached and photocured by means of UV/VIS light. A mercury arc lamp from Dr. Mlle AG of the type MH-Strahler UV-400 H is used. Exposure is carried out for 4 min with an average intensity at the location of the sample of approx. 40 mW/cm.sup.2.

Sample 3: Reconstruction of the Hologram

[0069] Reconstruction of the hologram produced according to example 2 is carried out by means of a method established in the industry according to ISO 17901, Optics and Photonics Holography, Part 1 and Part 2, that makes it possible to determine spectral diffraction efficiency in transmission (cf. FIG. 8).

[0070] In this case, spectral diffraction efficiency is defined as the fractional ratio of the decrease in the zeroth diffraction order in the holographic film [%] to the transmission of the film without hologram [%], wherein the decrease in the zeroth diffraction order in transmission correlates with the strength of the reconstructed wave, i.e. the wave diffracted on the grating.

[0071] In this case, the mirror or reflection is read using a reconstruction light source. By means of Bragg diffraction, the hologram produces a signal wave in the reflection direction. A portion of the reconstruction light wave, the so-called zeroth order, is detected in transmission.

[0072] In the practical experiment, a fibre spectrometer from Ocean Optics with a DH-mini light source, optical light guides, a sample holder with a sample plate and a USB2000+ detector is used. The detector is based on a rotating grating element and a CCD sensor array. This functions like a monochromator, with the advantage that the spectrum is measured in situ.

[0073] The measuring method comprises the following steps: [0074] a) switching on of the light source [0075] b) placement of the sample in the structure [0076] c) adjustment of the collimating lens so that the light beam corresponds to a well-collimated beam, i.e. as flat a wave as possible [0077] d) positioning of the sample so that light beam falls in the hologram [0078] e) recording of the spectrum in the visible wavelength range in transmission [0079] f) evaluation of the spectrum by determining the values a, b and c according to FIG. 8.

[0080] It is observed that the hologram causes a clear break (peak) in the green spectral range of the transmission spectrum, cf. the spectrum in FIG. 8. The spectral width is experimentally determined at c=16 nm. The minimum of the spectrum is reached at the so-called peak wavelength, which is determined at 529 nm. The mathematically determined spectral diffraction efficiency =(ab)/a is rounded off to 96%.

Example 4: Integration of Hologram Samples by Means of Polycarbonate Injection Moulding

[0081] a) Structure of HX/PC/Melt

[0082] In example 4a, a holographic sample of the type Bayfol HX (manufacturer: Covestro Deutschland AG) is inserted into an injection moulded body in an injection mould. The sample is equivalent to a film measuring approx. 22 cm.sup.2 with a 2-layer structure composed of a 16 m thick photopolymer film (HX) containing a green test hologram of the Denisjuk mirror hologram type and a transparent 125 m thick polycarbonate carrier film (PC). The adhesion between HX and PC was evaluated by means of the cross-cut test (DIN EN ISO 2409 2013 (6.2)) with a reference number of 0. The sample is positioned such that the HX side is aligned in the direction of the steel wall of the injection mould, while the PC side is aligned in the direction of the cavity. The injection mould is closed, and the sample is overmoulded with a hot polycarbonate melt of the type Makrolon 2647 (manufacturer: Covestro Deutschland AG) at approx. 270 C. and 800 bar. After 30 seconds, the sample is finished and the injection mould is opened.

[0083] This injection moulded body shows favourable stability, as can be seen by the good adhesive bond between the sample and the solidified melt.

[0084] The hologram is then characterized by spectrometry. It shows an unchanged high spectral diffraction efficiency. The peak wavelength has shifted by only 4 nm.

[0085] b) Structure of HX/TAC/Melt (not an Example According to the Invention)

[0086] In example 4b, a further holographic sample of a Bayfol HX photopolymer (manufacturer: Covestro Deutschland AG) is placed in an injection moulded body. The sample 4b differs from sample 4a in the carrier film, which here is composed of 50 m cellulose triacetate (TAC). The sample is positioned and processed according to example 4a.

[0087] It is to be observed that TAC and the polycarbonate body have not formed an integral whole. The overmoulded HX and its TAC film can be completely peeled off the polycarbonate body without using any strength.

[0088] c) Structure of PC/HX/TAC/Melt (not According to the Invention)

[0089] In example 4c, a further holographic sample of a Bayfol HX photopolymer (manufacturer: Covestro Deutschland AG) is placed in an injection moulded body. In contrast to 4a, the sample is aligned with the PC carrier film in the direction of the steel wall, while the photopolymer is laminated with a cellulose triacetate shear protective film (TAC) and the film is aligned in the direction of the cavity. The adhesion between the HX and TAC was evaluated by means of the cross-cut test (DIN EN ISO 2409 2013 (6.2)) with a reference number of 5. The sample is positioned and processed according to example 4a.

[0090] It is to be observed that the photopolymer and its PC carrier film can be completely peeled off the polycarbonate body without using any strength.

[0091] e) Structure of PC/HX/MeltComparative Example

[0092] In example 4e, a holographic sample is placed in an injection moulded body analogously to example 4a. In contrast to 4a, the sample is aligned with the PC side facing the steel wall and the HX side facing the cavity, i.e. without shear protective film. The sample was cut to dimensions approx. 2 cm2 cm less than the cavity so as to allow flow around the edges and binding to the melt. The injection mould is closed, and the sample is overmoulded with a hot polycarbonate melt of the type Makrolon 2647 (manufacturer: Covestro Deutschland AG) at approx. 260 C. and 650 bar. After 30 seconds, the sample is finished and the injection mould is opened.

[0093] This injection moulded body shows destruction over a large area in the form of a wave pattern in the photopolymer film; the hologram is no longer visible at these sites.

[0094] f) Structure of Hardcoat/HX/PC/MeltExample According to the Invention

[0095] In example 4f, a 3 layer holographic [sample] is placed in an injection moulded body. The adhesion between the photopolymer film and the polycarbonate carrier film was evaluated by means of the cross-cut test (DIN EN ISO 2409 2013 (6.2)) with a reference number of 0. The sample is positioned in this case such that the hardcoat side is aligned in the direction of the steel wall of the injection mould, while the PC side is aligned in the direction of the cavity. The injection mould is closed, and the sample is overmoulded with a hot polycarbonate melt of the type Makrolon 2647 (manufacturer: Covestro Deutschland AG) at approx. 300 C. and 800 bar overmoulded. After 30 seconds, the sample is finished and the injection mould is opened.

[0096] This injection moulded body shows favourable stability, as can be seen by the favourable adhesive bond between the sample and the solidified melt.

[0097] The hologram is then spectrometrically characterized. It shows unchanged high spectral diffraction efficiency. The peak wavelength has now shifted by 1 nm.