EP3497521A1

EP3497521A1 - Shaped body having a volume hologram and method for production thereof

Info

Publication number: EP3497521A1
Application number: EP17751734.9A
Authority: EP
Inventors: Rainer Hagen; Thomas Fäcke; Enrico Orselli; Ute FLEMM; Ulrich Grosser
Original assignee: Covestro Deutschland AG
Current assignee: Covestro Deutschland AG
Priority date: 2016-08-12
Filing date: 2017-08-10
Publication date: 2019-06-19
Also published as: JP2019526823A; US20190171160A1; TWI775767B; TW201817578A; WO2018029294A1; KR20190039207A; CN109564402A

Abstract

The invention relates to a method for producing a shaped body containing at least one volume hologram by means of injection molding, comprising the following method steps: providing a hologram film composite having two sides and comprising at least one photopolymer layer having at least one volume hologram, a shear protection layer, and a substrate layer, and optionally further connected film layers; inserting the hologram film composite into a metallic injection mold, in such a way that one side of the hologram film composite is at least partially in contact with the injection mold wall; introducing a molten thermoplastic polymer for creating the shaped 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 polymeric basic materials as the molten thermoplastic polymer, and overmolding the hologram film composite with the molten thermoplastic polymer; and solidifying the molten thermoplastic polymer. The invention further relates to a shaped body produced in this way and to advantageous uses of said shaped body.

Description

Molded body with volume hologram and method for its production

The invention relates to a method for producing a shaped body containing at least one volume hologram by means of injection molding. The invention further relates to a molded body produced by injection molding formed by a thermoplastic polymer and containing at least one volume hologram, wherein the volume hologram is embedded in the molding and the molding is at least partially optically transparent in the area of action of the volume hologram. Volume holograms are known from the literature and are also referred to as thick holograms or Bragg holograms. According to the definition of a volume hologram, its thickness is much larger than the wavelength of light used to record the hologram. There are two types of volume holograms, so-called volume abstraction holograms and volume phase holograms. In this application, holograms are always volume phase holograms.

Recording materials for holograms are, for example, metal halide emulsions, dichromated gelatins and photopolymers. Their operation, chemical composition and applications are described in the literature ["Optical Holography", by P. Hariharan, Cambridge University Press (1996), ISBN 0 521 43348 7].

Relevant to the present invention are photopolymers. Holograms are stored in the layers of these photopolymers as volume phase gratings. Holograms are usually present as a film composite, comprising an optically clear

Carrier film (substrate) and a holographic photopolymer film thereon.

Injection molding is an established and cost-effective method for processing film composites. It can also be applied to a film composite with a hologram (s) stored in a photopolymer layer, for example to shape an originally flat hologram or to mechanically stabilize it, or even against external influences such as UV light , Moisture, mechanical stress, dirt or attacking chemicals. In injection molding, the hologram film composite is usually placed in an injection mold and back-injected or overmoulded with a thermoplastic polymer which has been brought into the molten state at elevated temperatures. Examples of known transparent engineering thermoplastics include polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), amorphous polyamide (PA) and amorphous polyesters, polyvinyl chloride (PVC), polyethylene terephthalate (PET), PC PET and polybutylene terephthalate (PBT). Known opaque engineering thermoplastics include crystalline polyamide (PA), acrylonitrile-butadiene-styrene (ABS), polyethylene (PE), PC / ABS, polypropylene (PP) and polyetheretherketone (PEEK).

Holographically exposed photopolymers are comparatively soft, shear-sensitive materials. The photopolymer layer, including the structure of the volume phase grids contained therein, must not change during processing in the injection molding process, e.g. warp, displace or wave. Since the hologram properties arise from the geometric orientation and the period of the lattice structures, a change in the lattice structure also means a change or even destruction of the hologram function. Fig. 1 shows a back-injected hologram foil composite according to the prior art.

This comprises a holographic photopolymer 101, which is embedded in the molded body 100. The carrier film 102 lies outside and covers the photopolymer 101 completely, so that a barrier and protective function is provided. This shaped body 100 is produced by an injection molding process in which the photopolymer and thus also the holographic lattice structures present in it are back-injected, i. Have contact with the hot thermoplastic melt. It is known that the melt flows into the cavity as it flows from the gate, thereby forcing forces, e.g. Shearing forces, applied to the inserted into the mold film composite, which can lead to damage of the photopolymer layer. This method is disadvantageous for this reason.

It is therefore an existing challenge to keep the lattice structures of the hologram unchanged during processing by injection molding, and thus to obtain a shaped body with defined optical and holographic-optical properties. These holographic-optical properties include the Bragg diffraction condition, measurable via the average reconstruction angle as well as the central reconstruction wavelength, the color value and the intensity of the diffracted light given observation position. The extended optical properties include, for example, the quality of the surface of the hologram, the transparency of the hologram out of the diffraction condition, measurable by the Haze value, the small angle scattering, and the absorption.

Examples of injection-molded holograms in which the photopolymer is protected against contact with the melt by a foil laminate are shown in the application JP 2008- 170852 (A). However, the internal laminate has the disadvantage that it does not combine in the injection molding with the polymer melt. To make a positive connection, additional measures are necessary, such as. the production of an inner laminate with supernatant or a laterally chamfered multi-layer structure. These layer structures with hologram are overmolded and thereby connected to the molded body. Disadvantages are the increased expense for producing the hologram film composite suitable for injection molding and the limitation with regard to the shape design and process freedom in injection molding.

The object of the present invention was to provide a simplified process for producing a shaped body containing at least one volume hologram by means of injection molding and to provide a dimensionally stable, mechanically robust thermoplastic injection molded body containing at least one volume hologram, wherein both the optical quality, such. the Haze value, the Kl inwinkel scattering or the absorption of the volume hologram remain unchanged as well as the holographic-optical properties, such as the diffraction efficiency and the reconstruction wavelength of the volume hologram remain within narrow limits unchanged.

The object according to the present invention is achieved by a method for producing a shaped body containing at least one volume hologram by means of injection molding of the aforementioned type, wherein the method is characterized by the following steps: providing a two-sided hologram film composite comprising at least one photopolymer layer having at least one volume hologram, a shear protective layer and a substrate layer and optionally further connected film layers, Inserting the hologram film composite into a metallic injection mold, such that one side of the hologram film composite is at least partially in contact with the injection mold wall,

Introducing a molten thermoplastic polymer to produce the shaped body, wherein at least the outermost layer of the hologram foil composite on the side of the hologram foil composite in contact with the molten polymer essentially contains the same polymeric base materials as the molten polymer, and encapsulating the hologram foil composite with the molten polymer, and

- Solidification of the molten thermoplastic polymer.

The hologram film composite provided according to the invention comprises at least one photopolymer layer having at least one volume hologram, a protective layer to which the at least one photopolymer layer adheres, and a substrate layer.

The substrate layer performs the function of a stable carrier layer for the soft, flexible photopolymer layer during the injection molding process. The protective effect is intended to prevent contact between the photopolymer layer and the hot melt flowing into the injection mold as far as possible. Da / u the shear protection film covers the photopolymer layer preferably over the entire surface. Optionally, additional layers can be added to the hologram film composite. Thus, the substrate layer or the shear protection layer may consist of film composites. These can be e.g. by lamination, multi-layer coextrusion or by wet-coating method. It is also possible to laminate more than one holographic photopolymer layer to each other, which is particularly advantageous when several holographic-optical

Functions should be prepared separately and then combined with each other. Other possible layers are scratch-resistant layers, decorative layers, contrast-producing layers or the like. The substrate layer has a layer thickness of 5 to 500 μιη, preferably from 10 to 300 μιη and particularly preferably from 25 to 200 μηι. It is characterized by at least one smooth, shiny surface. Preferably, the substrate layer is transparent and optically clear, but may also be at least partially opaque, in particular printed. If it is provided that the substrate layer comes into contact with the molten thermoplastic polymer during the injection molding process, it is preferably at least partially on its side facing the melt oberfiächenstrukturiert. In particular, in this case it is preferred that the substrate layer contains a polymer from the group consisting of PC, PMMA, PET, PBT, PA, PS and PC / ABS. Preferably, the molten thermoplastic polymer contains polycarbonate (PC). Furthermore, the polymer of the substrate layer may contain additives, in particular solvents, polymeric mixed substances or design-giving particles, dyes or absorbent pigments. These preferably have a volume fraction of less than 20%, preferably less than 10% and particularly preferably less than 5%.

The photopolymers used in the process according to the invention can be formed at least from photoinitiator systems and polymerizable writing monomers.

Preferably, the photopolymers may comprise plasticizers and / or thermoplastic binders and / or crosslinked matrix polymers. It is particularly preferred if the photopolymers are formed from a photoinitiator system, one or more random monomers, plasticizers and crosslinked matrix polymers. The photopolymer layer itself has a layer thickness of 0.5 to 1000 μπι and preferably from 1 to 200 μπι and particularly preferably 2 to 100 μπι on.

If, in the case of the hologram film composite, the shear protection film is in direct contact with the photopolymer layer, good adhesion is achieved. As the Applicant's experiments have shown, the adhesion between the photopolymer layer and the protective film can preferably be characterized in such a way that it is lower by a cross-hatch test (according to DIN EN ISO 2409 2013 (6.2), when the characteristic value is determined eight times and arithmetic averaging) with a characteristic number lower, ie is rated better than 3.

The initially molten thermoplastic and after completion of the inventive method for producing a shaped body containing at least one Volumenhologramm cured thermoplastic polymer preferably contains a thermoplastic polymer from the group PC. PMMA, PET, PBT, PA, PS and PC / ABS. Preferably, the molten thermoplastic polymer contains polycarbonate (PC). Furthermore, the thermoplastic polymer preferably contains additives, in particular solvents, polymeric mixed substances or design-giving particles, dyes or absorbent pigments. These preferably have a volume fraction of less than 20%, preferably less than 10% and particularly preferably less than 5%. In a further embodiment of the invention, the thermoplastic polymer contains reinforcing agents, so that the shaped body produced remains dimensionally stable at high temperatures, as can occur, for example, in automotive applications. Suitable reinforcing agents may be, for example, glass or carbon fibers or fabrics.

According to the invention, at least the outermost layer of the hologram film composite essentially contains the same polymeric base materials as the molten polymer on its side which comes into contact with the molten thermoplastic polymer. The term "essentially identical polymeric base materials" or "essentially identical" is understood here to mean polymers which contain more than 10%, preferably more than 50% of the identical monomeric basic structures, with monomeric basic structures being both functional groups such as carbonate -O-CO-O-, Esters -O-CO-, ether O-, amides -NH-CO - as well as identical monomer bodies such as terephthalic-O-CO- (ara-phenyl) -CO-O-, isophthalo-O-CO- (meta-phenyl) - CO-O-, ethylene glycol 0-CH2-C H2-0-, butylene glycol -O-CH2-CH2-CH2-CH2-O- styrene -CH2-CH-phenyl-, methyl acrylate <H2-CH (() - C OC H3 ) -.

Methyl methacrylate CH 2-CCH 3 (O-C 0 -CH 3) -. Butyl acrylate CH2-CH (() - (O-CH2-CH2-CH2-CH3) -, butyl methacrylate € H2-CCH3 (0-C0-C H2-CH2-CH2-CH3) - bisphenol A - 0-phenyl- C (CH 3) 2-phenyl-O, hexamethylenediamine NH - ((H 2) 6 -NH, dodecanediamine-NH- (CH 2) 1 2-NH) It is particularly preferred if the polymers consist of more than 90% of identical basic structures and in this case differ in their average number average molecular weight not more than 50% from each other.

The at least one volume hologram contained in the photopolymer layer according to the method according to the invention is characterized in that it comprises lattice structures, so-called volume enphas engi tter. These as refractive index modulations in

Photopolymer-located grating structures deflect light from a suitable light source by Bragg diffraction and thus produce a predetermined illumination pattern or holographic or holographic stereogram or the like. The hologram is preferably formed as a holographic-optical element (HOE), the class of angles and color selective diffractive optical elements. The hologram may be a transmission hologram, a reflection hologram or an edge-lit hologram (i.e., a hologram having one of the two reconstruction angles in the substrate medium). The process according to the invention allows the person skilled in the art important

Injection molding process parameters, such as the melt temperature, the pressure curve, the Tool temperature and the cycle time to adapt so that it receives the best impression for its purpose in terms of surface quality, isotropy of the solidified polymer, but also in terms of labor and equipment costs. The person skilled in the art will not be restricted with regard to the use of special casting materials or other tools or substances, such as sheet molding compounds. The method according to the invention can thus be combined or extended by known methods, such as, for example, in-mold coating (IMC), in-mold decoration (IMD) or film insert molding (FIM). The procedural variation options are thus retained. According to the invention, the hologram foil composite is inserted into a metallic injection mold such that one side of the hologram foil composite is at least partially in contact with the injection mold wall. Contact in the sense of this invention means that the hologram foil composite is applied at one point to the wall of the injection molding or is connected to a selected location of the injection mold. Such a point can also be formed, for example, by an edge on which the hologram foil composite is clamped or glued. Likewise, the hologram foil composite may comprise a tab which is positioned outside the cavity of the injection mold. With regard to the individual layers of the hologram film composite, this may mean in detail according to a first embodiment of the method according to the invention that the substrate layer is placed facing away from the photopolymer layer facing the metallic injection mold, such that the substrate layer at least partially in contact, preferably in planar Contact, with the injection mold wall is. In this case, the photopolymer layer is located on the side of the substrate layer facing away from the injection mold. The protection of the sensitive photopolymer layer with respect to the polymer melt in this case preferably takes over the shear protective layer, which is arranged on the side remote from the substrate layer side of the photopolymer layer and in this case preferably as the outermost layer of Hologrammfolienverbunds according to the teachings of the invention essentially the same polymeric base materials as that contains molten polymer.

According to an advantageous embodiment of the invention, the shear protection layer can be formed for example by a protective lacquer. Due to the fact that according to the invention at least the outermost layer of the hologram film composite, in the embodiment described above, the shear protection film essentially contains the same polymeric base materials as the molten polymer on its side in contact with the molten polymer, is not only avoided in the process according to the invention. that the sensitive photopolymer layer comes into contact with the polymer melt, so that in the results no shear forces act on the photopolymer layer. On the contrary, as a result of the matched material composition of the outermost layer of the hologram film composite and of the molten polymer, good adhesion of the hologram film composite to the solidified melt is ensured. If the hologram foil composite is positioned in the injection molding s such that not only a flat side of the hologram foil composite, but also at least in part the opposing planar side during the injection molding process comes into contact with the thermoplastic melt, then it goes without saying that this side too must be covered with a material-adapted layer with respect to the melt.

According to an alternative advantageous embodiment of the invention, it is provided that the photopolymer layer is placed pointing with its free surface facing the metallic injection mold, such that the photopolymer layer is at least partially in, preferably flat, contact with the injection mold wall. This means that both the substrate layer and the shear protection film are arranged on the side of the photopolymer layer facing away from the wall of the metallic injection mold.

In a particular embodiment, the hologram sheet composite containing the photopolymer layer is formed by a thermoforming process (e.g.

Vacuum thermoforming, (high) -druckthermoformen and their various manifestation variants) preformed so that it can take a good fit with the injection mold. According to a further advantageous embodiment of the invention can be provided that the substrate layer and the shear protection layer are integrally formed. The substrate layer formed integrally with the protective layer, in particular, represents the outermost layer of the hologram film composite on its side in contact with the molten polymer and thus simultaneously performs the function of the protective film. It then contains essentially the same polymeric base materials as the molten polymer, in particular it is chemically mixed with the injection molding polymer Essentially matching thermoplastic film. In the case of injection molding, the film and the melt mechanically bond stably and, owing to the matched material composition of the outermost layer of the hologram film composite and the molten polymer, good adhesion of the hologram film composite to the solidified melt is ensured.

According to a further particularly advantageous embodiment of the invention, it is provided that the hologram foil composite is cut into the metallic injection mold in such a way that all layers of the hologram foil composite have the same dimensions such that they are common, substantially perpendicular to the extent of the hologram foil composite Hologrammfolienverbunds aligned cutting edges have. Due to the good adhesion between the hologram film composite and the surrounding (initially molten) thermoplastic polymer, it is not necessary in the inventive method as in the prior art, for example JP 2008-170852 A, a mechanical clamping between the film composite and the surrounding polymer by bevel the edges, stepped sequence of layers or similar mechanical measures. In particular, in the case of a direct contacting of the wall of the metallic injection mold by the sensitive photopolymer layer is provided according to a further advantageous embodiment of the invention that the wall of the metal injection mold a maximum temperature of 100 ° C, preferably of 90 ° C, particularly preferably of 80 ° C does not exceed.

According to an advantageous embodiment of the invention, it is provided that the cavity pressure during the injection molding process is at most 1000 bar, preferably at most 800 bar and in particular at most 700 bar, the cycle time being a maximum of 30 s, preferably a maximum of 25 s and in particular a maximum of 20 s.

Preferably, the Spritzgus s form is made of polished steel. Furthermore, the injection mold preferably has at least one essentially flat surface. Preferably, this surface has a surface roughness less than 50 μπι, preferably less than 20 μπι and particularly preferably less than 10 μπι. The method is suitable for thin-walled and thick-walled molded parts. The injection mold is furthermore preferably planar or continuous, wherein "continuous" in the sense of the present invention means that a curvature in the area of the volume hologram illuminated in the photopolymer layer contains no edges and a curvature also has an averaged radius of greater than 3 cm, preferably greater than 5 cm, where expressly with curvature also forms are meant, which are not exclusively spherically shaped, but are also constructed with variable curvature.

With regard to the preservation of the holographic-optical properties of the at least one hologram inscribed in the photopolymer layer, the Applicant's investigations on a molded article produced by the process according to the invention revealed that the spectral diffraction efficiency of the hologram as a result of thermal and mechanical stress during injection molding in the case of a flat film geometry in the region of the hologram, preferably changed by less than 2%. Likewise, the spectral half-width of the hologram is changed, in particular, by less than 1 nm. In addition, the spectral peak position, i. the wavelength at which the hologram reaches its maximum efficiency is shifted by less than 10 nm, in part by less than 5 nm and, ideally, by less than 2 nm in the long-wave or short-wave range. In a preferred embodiment, the hologram is oriented parallel to the steel mold, of course, with a bent steel mold, the hologram is in an equidistant position to the steel mold. The distance of the hologram to the steel mold is defined by its substrate or by one or more layers. This distance is less than 300 μιη, preferably less than 100 μπι, and most preferably less than 70 μιη.

A further aspect of the present invention relates to a shaped body comprising at least one volume hologram produced by a method according to one of claims 1 to 13. The above statements apply correspondingly to the advantages of this shaped body.

Another aspect of the present invention relates to the use of a shaped body containing at least one volume hologram according to claim 14 as a beam-guiding and / or beam-shaping optical component for 3-dimensional imaging or as a security hologram in documents and for product protection and the Product identification or as spectacle lens in correction glasses and electronic spectacles (so-called Augmented Reality (AR) spectacles)

Examples of applications for holographic-optical elements are holographic, machine-readable data memories, transparent display devices in the automobile (such as head-up displays), transparent displays for point-of-sales and points of interest, transparent displays for TV and for mobile IT applications, Light-guiding and light-conducting elements for general and automotive lighting as well as light-directing and light-conducting elements for spectacles with special holographic-optical integrated functions.

In the following, we will explain the invention with reference to an exemplary embodiments illustrative drawing. 1 shows a hologram film composite according to the prior art,

2 shows a shaped body containing at least one volume hologram produced by injection molding in a first embodiment, FIG. 3 shows a shaped body containing at least one volume hologram produced by means of injection molding in a second embodiment, FIG.

4 shows a shaped body containing at least one volume hologram by means of

Injection molding in a third embodiment,

5 shows a shaped body containing at least one volume hologram by means of

Injection molding in a fourth embodiment,

6 shows a shaped body containing at least one volume hologram by means of

Injection molding in a fifth embodiment,

Fig. 7 shows the basic structure of a holographic film, and

8 shows the transmission spectrum of a reflection hologram in a molded article produced by means of injection molding. FIG. 2 shows a shaped body 200 containing at least one volume hologram produced by means of injection molding in a first embodiment. In detail, the molded body 200 comprises a hologram film composite 20, which in turn comprises a photopolymer layer 101 and an underlying substrate layer 102. In detail, it is shown that the holographic photopolymer 101 in which the at least one volume hologram is contained is unilaterally exposed. On the opposite side, the substrate layer 102 is arranged. Based on the injection molding process performed using an injection mold (not shown), this means that the photopolymer layer 101 and a substrate layer 102 were introduced into the metal injection mold in such a way that the photopolymer layer 101 was oriented with its free surface facing the metal injection mold such that the photopolymer layer 101 is at least partially in contact with the injection mold wall (not shown). The substrate layer 102 protects the sensitive photopolymer layer 101 during the injection molding process from the hot inflowing thermoplastic polymer and the shear forces occurring thereby by acting as a shear protection film. Accordingly, in the present case, the substrate layer 102 and the shear protective layer are integrally formed.

In the present case, the hologram foil composite 20 is further cut before insertion into the metallic injection mold in such a way that all layers of the hologram foil composite 20 have the same dimensions, such that they have common, substantially perpendicular to the extension of the hologram foil composite aligned cutting edges. The dimensions of the hologram film composite 20 are selected relative to the injection mold such that the encapsulation of the hologram film composite 20 with the molten thermoplastics polymer is merely a further layer 103 on the back of the substrate layer 102 is constructed. Thus, the injection mold comprises only a cuboid cavity, so in particular a side surface of the cavity is completely covered by the inserted hologram foil composite 20, wherein the photopolymer layer 101 is in surface contact with the injection mold wall. Accordingly, the hologram film composite 20 is not encapsulated during the injection molding process, but merely back-injected. Due to the fact that the outermost layer of the hologram foil composite 20, in the present case the substrate layer 102, on the side of the hologram foil composite 20 that comes into contact with the molten polymer 103, essentially the same polymeric base materials as the contains molten thermoplastic polymer 103, a stable bond is created between the molten thermoplastic polymer and the substrate layer 102. FIG. 3 shows a shaped body 300 containing at least one volume hologram produced by means of Spntzguss in a second embodiment. In contrast to the shaped body 200, the dimensions of the hologram foil composite 30 of the shaped body 300 are selected to be smaller than the side area of the cavity of the injection mold used (not shown), which is contacted with the photopolymer layer 101 before the introduction of the molten thermoplastic polymer. Accordingly, this side surface is not completely covered by the hologram foil composite 30 during extrusion with the molten thermoplastic polymer. This in turn means that the hologram film composite 30 is "overmolded" with the melt, ie that the edges of the hologram film composite 30 likewise come into contact with the molten thermoplastic polymer 103. Again, the hologram film composite 30 is in front of the metallic injection mold in FIG in a manner such that all of the layers of the hologram film composite 30 have the same dimensions A stable bond is created between the molten thermoplastic polymer and the substrate layer 102 without requiring mechanical interlocking of the hologram film composite 30 with the molten thermoplastic polymer 103.

4 shows a further modified embodiment of a shaped body 400 containing at least one volume hologram by means of injection molding. In this embodiment, one covering the entire area of the photopolymer layer 101 and the substrate layer 102 is

Cover layer 401 is provided, wherein the cover layer 401 is preferably by a protective film with scratch protection function. In another embodiment, the cover layer 401 is an absorbent decorative layer. Further, the cover layer 401 may be colored. For example, the molded body 400 may be configured such that the decoration provided by the cover layer 401 is outside the hologram surface (s) of the photopolymer layer 101, the volume hologram being a reflection hologram that is visible through the decoration layer 401. The cover layer can be applied to the photopolymer layer 101, for example, by means of the in-mold decoration (IMD) method known from the prior art. This means that the cover layer 401 together with the hologram foil composite 40 is first positioned in the injection mold (not shown), the dimensions of the cover layer 401 being the dimensions The other two layers 101, 102 project beyond. In particular, the cover layer 401 may be dimensioned so that it completely fills a flat base in the injection mold. Then, the layer composite with hologram film composite 40 and cover layer 401 is injected with the molten thermoplastic polymer, resulting in the illustrated geometry of the molded article 400. Furthermore, the cover layer 401 can be subsequently applied to the molded body 400 by lamination or gluing.

FIG. 5 shows a further shaped body 500 containing at least one volume hologram by means of injection molding in a fourth embodiment. As can be seen, the photopolymer layer 101 having the at least one volume hologram is now arranged on the inside. This means that the substrate layer 102 of the hologram foil composite 50 has been positioned, with its side facing away from the photopolymer layer 101, toward the metallic injection mold (not shown) in the metallic injection mold such that the substrate layer 102 is at least partially in contact with the injection mold wall. This also means that during the introduction of the molten thermoplastic polymer, the photopolymer layer 101 is no longer protected by the substrate layer 102 from the action of the shear forces of the molten thermoplastic polymer. Consequently, a shear protection film 501 is provided, which covers the side of the photopolymer layer 101 facing away from the substrate layer 102 over its entire area and thus provides effective shear protection.

In the embodiment of the shaped body according to FIG. 6, the special features of the embodiments of FIGS. 4 and 5 are as it were combined. Thus, the shaped body of FIG. 6 has a covering layer which completely covers the molding body, in particular with decoration or scratch protection function, while the hologram film bond 60 in turn comprises a photopolymer layer 101, a substrate layer 102 and a separate shear protection layer 501. Specifically, the photopolymer layer 101 is again disposed inboard and protected by the shear protective layer 501 from exposure to the shear forces of the molten thermoplastic polymer.

7 shows by way of example 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 a transparent substrate foil 102 of polycarbonate about 1 .mu.m thick, on which an approximately 16 μm thick photopolymer film 101 is arranged. This is covered by an approximately 40 μηι thick laminating film, which can be easily deducted before further processing of the holographic film B100.

Finally, FIG. 8 shows the transmission spectrum of a reflection hologram contained in a molded body produced by injection molding and imprinted into a

Photopolymer layer of the type Bayfol® HX (manufacturer: Covestro Deutschland AG). The x-value of the diagram corresponds to the measuring wavelength in nm; the y-value corresponds to the transmission in [%]; the value a entered in the diagram corresponds to the transmission in [%] of the sample without volume hologram at the wavelength at which the transmission spectrum of the volume hologram reaches its minimum; b corresponds to the transmission in [%] at the wavelength at which the transmission spectrum of the volume hologram reaches its minimum; c corresponds to the full half width of the transmission minimum of the volume hologram [nm].

Examples

Example 1: Production of a sample for the hologram exposure

A photopolymer-based holographic recording film from Covestro Deutschland AG (formerly Bayer MaterialScience AG) of the Bayfol® HX (B100) type is used, see FIG. 6. It is a 16 μιη thicker photosensitive photopolymer film (B101), which adheres to a transparent 125 μπι polycarbonate carrier film (B102) and with removable polyethylene film (B103) is laminated. In the dark lab, a 60 x 30 mm piece of foil is cut out of it. Subsequently, the lamination is removed and the photopolymer with its free side by means of a hand roller, which is equipped with a high-quality rubberized pressure roller, laminated bubble-free on a 1 mm thick glass slide from SCHOTT without supernatant. The photopolymer is now embedded between polycarbonate carrier (B102) and glass carrier. This sample is packed in a light-tight aluminum bag and is thus prepared for a subsequent hologram exposure.

Example 2: Recording a hologram

For the exposure ("recording") of a hologram, a Coherent diode-pumped solid-state laser is used, with wavelength = 532 nm and output power _max = 50 mW, which is integrated into a vibration-damped illumination outlet.

The sample prepared according to Example 1 (B100) is clamped in a sample holder, which is tilted relative to the collimated laser beam by 13 °. The poly carbonate sub strate lies outside, on the light incident side. The laser is widened to a diameter of approx. 25 mm and homogenized. The laser is switched on for 2 s and hits the sample centrally and also centrally on the approx. 15 x 1 5 mm mirrored surface of the sample holder. The back reflection from the mirror and the incident beam interfere in the photopolymer and produce a sinusoidal intensity grating during the exposure time, which reproduces in the photopolymer material as a phase grating. The phase grating represents the hologram. It remains after the laser exposure as a stable lattice structure in the photopolymer film obtained.

After the end of the holographic exposure, the sample is photocured and photocured by means of UV / VIS light. A mercury arc lamp by Dr. Ing. Hönle AG of the type MH emitter UV-400 H. At a mean intensity at the location of the sample of about 40 mW / cm ² is exposed for 4 min.

Example 3: Reconstruction of the hologram

The reconstruction of the hologram produced according to Example 2 takes place by means of an industry-established method according to ISO 17901, "Optics and Photonics Holography", Part 1 and Part 2, which makes it possible to determine the spectral diffraction efficiency in transmission (see FIG ).

The spectral diffraction efficiency is defined as the fractional ratio of the decrease in the zeroth diffraction order in the holographic film [%] and the transmission of the film without hologram [%], the decrease in the zeroth diffraction order being in transmission with the strength of the reconstructed, i. Correlated at the grating diffracted wave.

The mirror or reflection hologram is read out with a reconstruction light wave. The hologram generates a signal wave in the direction of reflection by Bragg diffraction. A portion of the reconstruction light wave, the so-called zeroth order, is detected in transmission.

The practical experiment uses a fiber optic spectrometer from Ocean Optics with light source Di l -min i, optical light guides, sample holder with sample plate and detector USB2000 +. The detector is based on a rotating grating element and a CCD sensor array. This acts like a monochromator, with the advantage that the spectrum is measured in-situ.

The measuring method consists of the following steps:

a) switching on the light source

b) inserting the sample into the assembly c) adjustment of the collimating lens, so that the light beam corresponds to a well-collimated beam, ie largely a plane wave.

d) Positioning of the sample so that the light beam falls into the hologram e) Recording of the spectrum in the visible wavelength range in transmission f) Evaluation of the spectrum by determination of the values a, b and c acc. Fig. 8

It is observed that the hologram causes a significant "peak" in the green spectral range of the transmission spectrum, see the spectrum in Fig. 8. The spectral width is determined experimentally with c = 16 nm Achieved peak wavelength, which is determined to be 529 nm The mathematically determined spectral diffraction efficiency = (ab) la is rounded to 96%.

Example 4: Integration of Ho! Ogrammproben by Pol carbonate injection molding a) construction HX / PC / melt

In example 4a, a holographic sample of the type Bayfol® HX (manufacturer: Covestro Deutschland AG) is placed in an injection molded body in an injection mold. The sample corresponds to an approximately 2 x 2 cm ² piece of film with 2-layer structure, consisting of a 16 μπι thick photopolymer film (HX) containing a green test hologram of the type Denisjuk mirror hologram, and a transparent 125 μπι thick polycarbonate carrier film (PC ). The adhesion between I IX and PC was evaluated by means of cross-cut test (DIN EN ISO 2409 2013 (6.2)) with a ratio of 0. The sample is positioned so that the HX side is aligned with the steel wall of the injection mold while the PC side is aligned with the cavity. The injection mold is closed and the sample is back-injected with a hot polycarbonate melt of the type Makroion 2647 (manufacturer: Covestro Deutschland AG) at about 270 ° C and 800 bar pressure. After 30 seconds, the sample is ready and the injection mold is opened.

This injection-molded body shows a good stability, recognizable by the good bond between sample and solidified melt.

The hologram is then characterized spectrometrically. It shows an unchanged high spectral diffraction efficiency. The peak wavelength has shifted only by 4 nm. b) Construction HX / TAC / melt (non-inventive example)

In Example 4b, another holographic sample of a Bayfol® HX photopolymer (manufacturer: Covestro Deutschland AG) is placed in an injection molded article. The sample

4b differs from the sample 4a by the carrier film, which now consists of 50 μιη cellulose triacetate (TAC). The sample is positioned and processed according to Example 4a.

It can be observed that TAC and polycarbonate bodies did not form-fit. The back-injected HX and its TAC film can be completely removed without effort from the polycarbonate body.

c) Setup PC / HX / T AC / Enamel (not according to the invention) in Example 4c, another holographic sample of a Bayfol® HX photopolymer (manufacturer: Covestro Deutschland AG) is placed in an injection molded article. 4a, the sample is oriented with the PC support film to the steel wall while the photopolymer is laminated with a cellulose triacetate shear release (TAC) film and aligned with the cavity. The adhesion between HX and TAC was evaluated by means of cross-cut test (DIN EN ISO 2409 2013 (6.2)) with a ratio of 5. The sample is positioned and processed according to Example 4a.

It can be observed that the photopolymer and its PC carrier film can be completely removed from the polycarbonate body without any effort. e) Composition PC / HX / melt - Comparative Example

In Example 4e, a holographic sample is placed analogously to Example 4a in an injection molded article. The sample is unlike in Fig. 4a with the PC side to

Steel wall and the HX side to the cavity, i. without protective foil, aligned. The sample was cut to a size of about 2 cm x 2 cm smaller than the cavity to allow the edges to flow around and bond to the melt. The injection mold is closed and the sample is back-injected with a hot polycarbonate melt of the type Makroion 2647 (manufacturer: Covestro Deutschland AG) at about 260 ° C. and 650 bar pressure. To

The sample is ready for 30 seconds and the injection mold is opened. This injection-molded article shows a large-scale destruction in the form of a wave pattern in the photopolymer film; in these places the hologram is no longer visible.

f) Structure Hardcoat / HX / PC / melt - example according to the invention

In Example 4f, a 3-layer holographic is placed in an injection molded body. The adhesion between the photopolymer film and the polycarbonate carrier film was evaluated by means of a cross hatch test (DIN EN ISO 2409 2013 (6.2)) with a ratio of 0. The sample is positioned this time so that the hardcoat side faces the steel wall of the injection mold while the PC side is aligned with the cavity. The injection mold is closed and the sample with a hot polycarbonate melt of the type Makroion 2647 (manufacturer: Covestro Germany AG) at about 300 ° C and 800 bar

Pressure behind injection. After 30 seconds, the sample is ready and the mold is opened.

The hologram is then characterized spectrometrically. It shows an unchanged high spectral diffraction efficiency. The peak wavelength has shifted by only 1 nm.

Claims

claims

Process for producing a shaped body containing at least one

Volume hologram by injection molding, comprising the following process steps:

Providing a two-sided hologram film composite comprising at least one photopolymer layer having at least one

Volume hologram, a shear protective layer and a substrate layer and optionally further connected film layers,

Inserting the hologram film composite into a metal injection mold, such that one side of the hologram film composite is at least partially in contact with the injection mold wall,

Introducing a molten thermoplastic polymer to produce the

Shaped body, wherein at least the outermost layer of the Hologrammfolienverbunds on the side in contact with the molten polymer of the hologram foil composite contains essentially the same polymeric base materials as the molten thermoplastic polymer, and encapsulating the

Hologram film composite with the molten thermoplastic polymer, and

Solidification of the molten thermoplastic polymer.

Method according to claim 1,

characterized in that

the hologram foil composite is inserted into the metallic injection mold in such a way that the substrate layer with its side facing away from the photopolymer layer facing the metallic injection mold is inserted, such that the substrate layer is at least partially in contact with the injection mold wall.

Method according to claim 1,

characterized in that

the protective film is formed by a protective varnish.

Method according to claim 1,

characterized in that

the hologram film composite is inserted into the metallic injection mold in such a way that the photopolymer layer with its free surface faces the metallic injection molding is placed in a manner pointing, so that the Photo olymers chi cht at least partially in contact with the injection mold wall.

Method according to claim 4,

characterized in that

the substrate layer and the shear protective layer are integrally formed.

Method according to one of claims 1 to 5,

characterized in that.

the substrate layer contains a polymer from the group consisting of PC, PMMA, PET, PBT, PA, PS and PC ABS.

7. The method according to any one of claims 1 to 6,

characterized in that

the thermoplastic polymer is a polymer from the group PC, PMMA, PET, PBT, P A,

PS and PC / ABS contains.

Method according to one of claims 1 to 7,

characterized in that

the thermoplastic polymer contains additives, in particular solvents, polymeric mixed substances or design-giving particles, dyes or absorbent pigments.

Method according to claim 8,

characterized in that

the additives contained in the thermoplastic polymer have a volume fraction of less than 20%, preferably less than 10% and particularly preferably less than 5%.

Method according to one of claims 1 to 9,

characterized in that

The thermoplastic polymer reinforcing agent, in particular glass or carbon fibers or fabric, contains iL method according to one of claims 1 to 10,

characterized in that.

the hologram film composite prior to the insertion of the hologram film composite ^' metallic injection mold is cut in such a way that all layers of the hologram foil composite have the same dimensions, such that they have common, aligned substantially perpendicular to the extension of the hologram foil composite cutting edges.

12. The method according to any one of claims 1 to 11,

characterized in that.

the wall of the metallic injection mold does not exceed a maximum temperature of 100 ° C, preferably of 90 ° C, more preferably of 80 ° C.

13. The method according to any one of claims 1 to 12,

characterized in that

the cavity pressure is a maximum of 1000 bar, preferably a maximum of 800 bar and in particular a maximum of 700 bar, wherein the cycle time is a maximum of 30 s, preferably a maximum of 25 s and in particular a maximum of 20 s.

14. Shaped body containing at least one volume hologram prepared by a method according to any one of claims 1 to 13. 15. Use of a shaped body containing at least one volume hologram according to

Claim 14 as a beam-guiding and / or beam-shaping optical component for 3-dimensional imaging or as a security hologram in documents and for product protection and product labeling.