PRINTED STRUCTURE WITH METALLIC APPEARANCE

Abstract

The invention provides a method for 3D printing a 3D item (1), the method comprising (i) providing 3D printable material (201) comprising particles (410) embedded in the 3D printable material (201), wherein the particles (410) are reflective for at least part of the visible light, wherein the particles (410) have a particle length (L1), a particle height (L2), and an aspect ratio AR defined as the ratio of the particle length (L1) and the particle height (L2), wherein AR>5, and (ii) layer-wise depositing the 3D printable material (201) to provide the 3D item (10) with layers (322) of the 3D printed material (202) with a layer height (H) and a layer width (W), and wherein the 3D printable material (201) has a particle concentration C selected from the range of 0.001-30 vol. % of the particles (410) relative to the total volume of the 3D printable material (201).

Claims

1. A method for 3D printing a 3D item, the method comprising the steps of: providing a 3D printable material, and layer-wise depositing the 3D printable material to provide the 3D item with layers of a 3D printed material, wherein the 3D printable material comprises particles embedded in the 3D printable material at a particle concentration, wherein the particles are metallic particles or particles coated with one or more of a metal coating and a metal oxide coating, wherein each of the particles has a shape selected from the group of coin shapes and flake shapes, with a particle length (L1), a particle height (L2), and a first particle aspect ratio defined as the ratio of the particle length (L1) and the particle height (L2), the first particle aspect ratio being equal to or larger than 5, wherein each layer of the 3D printed material has a layer height (H), a layer width (W) and a layer aspect ratio defined as the ratio of the layer width (W) and the layer height (H), and wherein, when the layer aspect ratio is larger than 2, the particle concentration is in a range of 4-13 vol. % relative to the total volume of the 3D printable material, and when the layer aspect ratio is equal to or smaller than 2 and equal to or larger than 1, the particle concentration is in a range of 0.004-4% vol. % relative to the total volume of the 3D printable material.

2. The method according to claim 1, wherein, for at least 50 wt % of the particles, the particle length (L1) is in a range of 5-100 μm and the particle height (L2) is in a range of 0.1-20 μm, and wherein the layer height (H) is in a range of 0.05-5 mm.

3. The method according to claim 1, wherein the particles have a particle width (L3) in a range of 5-100 μm, wherein the particles have a second aspect ratio defined as the ratio of the particle width (L3) and the particle height (L2), and wherein the second particle aspect ratio is equal to or larger than 5.

4. (canceled)

5. The method according to claim 1, wherein each of the particles comprises one or more of a silver coating and an aluminum coating.

6. The method according to claim 1, wherein the 3D printable material comprises one or more of acrylonitrile butadiene styrene, polystyrene, polycarbonate, polyethylene terephthalate, polyethylene, polypropylene, polymethylmethacrylate, and copolymers of two or more of these.

7. The method according to claim 1, wherein the step of layer-wise depositing the 3D printable material to provide the 3D item with layers of a 3D printed material is performed with a fused deposition modeling 3D printer, wherein the fused deposition modeling 3D printer comprises a printer head, and wherein the printer head comprises a printer nozzle having an equivalent circular diameter that is larger than the particle length.

8. A 3D item comprising layers of a 3D printed material wherein the 3D printed material comprises particles embedded in the 3D printed material at a particle concentration, wherein the particles are metallic particles or particles coated with one or more of a metal coating and a metal oxide coating, wherein each of the particles has a shape selected from the group of coin shapes and flake shapes, with a particle length (L1), a particle height (L2), and a first particle aspect ratio defined as the ratio of the particle length (L1) and the particle height (L2), the first particle aspect ratio being equal to or larger than 5, wherein each layer of the 3D printed material has a layer height (H), a layer width (W) and a layer aspect ratio defined as the ratio of the layer width (W) and the layer height (H), and wherein the layer aspect ratio is larger than 2 and the particle concentration is in a range of 4-13 vol. % relative to the total volume of the 3D printable material, or the layer aspect ratio is equal to or smaller than 2 and equal to or larger than 1 and the particle concentration is in a range of 0.004-4% vol. % relative to the total volume of the 3D printable material.

9. The 3D item according to claim 8, wherein, for at least part of the total number of particles, the particle length (L1) is in a range of 5-200 μm and the particle height (L2) is in a range of 0.1-100 μm, and wherein the layer height (H) is in a range of 0.05-5 mm.

10. The 3D item according to claim 8, wherein, for at least 50 wt % of the particles, the particle length (L1) is in a range of 10-100 μm and the particle height (L2) is in a range of 0.1-20 μm, wherein the particles have a particle width (L3) in a range of 5-100 μm, wherein the particles have a second particle aspect ratio defined as the ratio of the particle width (L3) and the particle height (L2), wherein the second particle aspect ratio is equal to or larger than 5, and wherein the particles comprise one or more of a silver coating and an aluminum coating.

11. The 3D item according to claim 8, wherein the 3D printed material comprises one or more of acrylonitrile butadiene styrene, polystyrene, polycarbonate, polyethylene terephthalate, polyethylene, polypropylene, polymethylmethacrylate, and copolymers of two or more of these.

12. A luminaire or a lamp comprising the 3D item according to claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0105] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0106] FIGS. 1a-1b schematically depict some general aspects of the 3D printer and/or printing process;

[0107] FIG. 2a-2f schematically depict some aspects of embodiments of particles, with some of the shapes being depicted for reference purposes;

[0108] FIGS. 3a-3b schematically depict some further aspects of the invention; and

[0109] FIG. 4 schematically depicts a lamp or luminaire.

[0110] FIG. 5 shows examples of dollar shaped flakes;

[0111] FIG. 6-9 show results with such flakes;

[0112] FIG. 10 shows examples of corn-flake type of flakes; and

[0113] FIGS. 11-12 show results with such flakes.

[0114] The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0115] FIG. 1a schematically depicts some aspects of the 3D printer. Reference 500 indicates a 3D printer. Reference 530 indicates the functional unit configured to 3D print, especially FDM 3D printing; this reference may also indicate the 3D printing stage unit. Here, only the printer head for providing 3D printed material, such as a FDM 3D printer head is schematically depicted. Reference 501 indicates the printer head. The 3D printer of the present invention may especially include a plurality of printer heads, though other embodiments are also possible. Reference 502 indicates a printer nozzle. The 3D printer of the present invention may especially include a plurality of printer nozzles, though other embodiments are also possible. Reference 321 indicates a filament of printable 3D printable material (such as indicated above). For the sake of clarity, not all features of the 3D printer have been depicted, only those that are of especial relevance for the present invention (see further also below).

[0116] The 3D printer 500 is configured to generate a 3D item 1 by layer-wise depositing on a receiver item 550, which may in embodiments at least temporarily be cooled, a plurality of filaments 321 wherein each filament 20 comprises 3D printable material, such as having a melting point T.sub.m. The 3D printable material 201 may be deposited on a substrate 1550 (during the printing stage).

[0117] The 3D printer 500 is configured to heat the filament material upstream of the printer nozzle 502. This may e.g. be done with a device comprising one or more of an extrusion and/or heating function. Such device is indicated with reference 573, and is arranged upstream from the printer nozzle 502 (i.e. in time before the filament material leaves the printer nozzle 502). The printer head 501 may (thus) include a liquefier or heater. Reference 201 indicates printable material. When deposited, this material is indicated as (3D) printed material, which is indicated with reference 202.

[0118] Reference 572 indicates a spool or roller with material, especially in the form of a wire, which may be indicated as filament 320. The 3D printer 500 transforms this in a filament 321 downstream of the printer nozzle which becomes a layer 322 on the receiver item or on already deposited printed material. In general, the diameter of the filament 321 downstream of the nozzle is reduced relative to the diameter of the filament 322 upstream of the printer head. Hence, the printer nozzle is sometimes (also) indicated as extruder nozzle. Arranging layer 322 by layer 322 and/or layer 322t on layer 322, a 3D item 1 may be formed. Reference 575 indicates the filament providing device, which here amongst others include the spool or roller and the driver wheels, indicated with reference 576.

[0119] Reference A indicates a longitudinal axis or filament axis.

[0120] Reference C schematically depicts a control system, such as especially a temperature control system configured to control the temperature of the receiver item 550. The control system C may include a heater which is able to heat the receiver item 550 to at least a temperature of 50° C., but especially up to a range of about 350° C., such as at least 200° C.

[0121] Alternatively or additionally, in embodiments the receiver plate may also be moveable in one or two directions in the x-y plane (horizontal plane). Further, alternatively or additionally, in embodiments the receiver plate may also be rotatable about z axis (vertical). Hence, the control system may move the receiver plate in one or more of the x-direction, y-direction, and z-direction.

[0122] Layers are indicated with reference 322, and have a layer height H and a layer width W.

[0123] Note that the 3D printable material is not necessarily provided as filament 320 to the printer head. Further, the filament 320 may also be produced in the 3D printer 500 from pieces of 3D printable material.

[0124] FIG. 1b schematically depicts in 3D in more detail the printing of the 3D item 1 under construction. Here, in this schematic drawing the ends of the filaments 321 in a single plane are not interconnected, though in reality this may in embodiments be the case.

[0125] Hence, FIGS. 1a-1b schematically depict some aspects of a fused deposition modeling 3D printer 500, comprising (a) a first printer head 501 comprising a printer nozzle 502, (b) a filament providing device 575 configured to provide a filament 321 comprising 3D printable material 201 to the first printer head 501, and optionally (c) a receiver item 550. In FIGS. 1a-1b, the first or second printable material or the first or second printed material are indicated with the general indications printable material 201 and printed material 202. Directly downstream of the nozzle 502, the filament 321 with 3D printable material becomes, when deposited, layer 322 with 3D printed material 202.

[0126] FIG. 1b schematically depicts filaments have been deposited comprising particles. However, Not all layers need to include the particulate material, though this may of course be the case.

[0127] FIG. 2a schematically depicts for the sake of understanding particles and some aspects thereof. Note that the particles used in the present invention are especially elative flat, see e.g. FIG. 2d, 2e, FIG. 5, and FIG. 10.

[0128] The particles comprise a material 411, or may essentially consist of such material 411. The particles 410 have a first dimension or length L1. In the left example, L1 is essentially the diameter of the essentially spherical particle. On the right side a particle is depicted which has non spherical shape, such as an elongated particle 410. Here, by way of example L1 is the particle length. L2 and L3 can be seen as width and height. Of course, the particles may comprise a combination of differently shaped particles.

[0129] FIGS. 2b-2f schematically depict some aspects of the particles 410. Some particles 410 have a longest dimension A1 having a longest dimension length L1 and a shortest dimension A2 having a shortest dimension length L2. As can be seen from the drawings, the longest dimension length L1 and the shortest dimension length L2 have a first aspect ratio larger than 1. FIG. 2b schematically depicts a particle 410 in 3D, with the particle 410 having a length, height and width, with the particle (or flake) essentially having an elongated shape. Hence, the particle may have a further (minor or main) axis, herein indicated as further dimension A3. Essentially, the particles 410 are thin particles, i.e. L2<L1, especially L2<<L1, and L2<<L3. L1 may e.g. be selected from the range of 5-200 μm; likewise L3 may be. L2 may e.g. be selected from the range of 0.1-20 μm.

[0130] FIG. 2c schematically depicts a particle that has a less regular shape such as pieces of broken glass, with a virtual smallest rectangular parallelepiped enclosing the particle.

[0131] Note that the notations L1, L2, and L3, and A1, A2 and A3 are only used to indicate the axes and their lengths, and that the numbers are only used to distinguish the axis. Further, note that the particles are not essentially oval or rectangular parallelepiped. The particles may have any shape with at least a longest dimension substantially longer than a shortest dimension or minor axes, and which may essentially be flat. Especially, particles are used that are relatively regularly formed, i.e. the remaining volume of the fictive smallest rectangular parallelepiped enclosing the particle is small, such as less than 50%, like less than 25%, of the total volume.

[0132] FIG. 2d schematically depicts in cross-sectional view a particle 410 including a coating 412. The coating may comprise light reflective material. For instance, the coating may comprise a (white) metal oxide. In other embodiments, the coating may essentially consist of a metal, such as an Ag coating. In other embodiments the coatings may only be on one or both of the large surfaces and not on the thin side surfaces of the particles.

[0133] FIG. 2e schematically depicts a relatively irregularly shaped particle. The particulate material that is used may comprise e.g. small broken glass pieces. Hence, the particulate material that is embedded in the 3D printable material or is embedded in the 3D printed material may include a broad distribution of particles sizes. A rectangular parallelepiped can be used to define the (orthogonal) dimensions with lengths L1, L2 and L3.

[0134] FIG. 2f schematically depicts cylindrical, spherical, and irregularly shaped particles, which will herein in general not be used (see also above).

[0135] As shown in FIGS. 2b-2f the terms “first dimension” or “longest dimension” especially refer to the length L1 of the smallest rectangular cuboid (rectangular parallelepiped) enclosing the irregular shaped particle. When the particle is essentially spherical the longest dimension L1, the shortest dimension L2, and the diameter are essentially the same.

[0136] FIG. 3a schematically depicts a filament 321, such as when escaping from a printer nozzle (not depicted), which comprises 3D printable material 201. The 3D printable material comprise thermoplastic material 401 with particles 410 embedded therein.

[0137] FIG. 3b schematically depicts a 3D item 1, showing the ribbed structures (originating from the deposited filaments), having heights H. This height may also be indicated as width. Here, layers 322 with printed material 202, with heights H and widths W are schematically depicted. FIG. 3b can be seen as a stack of layers 322 of which a plurality adjacent stacks are shown in FIG. 1b.

[0138] FIG. 4 schematically depicts an embodiment of a lamp or luminaire, indicated with reference 1, which comprises a light source 10 for generating light 11. The lamp may comprise a housing or shade or other element, which may comprise or be the 3D printed item 2. The possible transmissivity of the material may provide additional optical effects and appearance (in the off state of the lamp or luminaire) may appear mat.

[0139] In experimental work, polycarbonate provided with aluminum dollar like flakes or coins with a size of 20 μm (1 μm thick) shown in FIG. 5. FIGS. 6-9 show the effect of layer thickness on the reflectivity of the direction perpendicular to the printed surface for respectively 0.2, 2, 10, and 20 wt % of the flakes, relative to the total weight (respectively 0.09, 0.9, 4.4, and 8.9 vol. %, relative to the total volume) of the PC-based 3D printable material (including the flakes). The diameter of the nozzle diameter of 1.8 mm which also corresponds to layer width was used to print the structures which were used in the reflectivity measurements shown in FIGS. 6-9.

[0140] Flakes of so called corn flakes type shown in FIG. 10 were also used. These flakes are 45 μm large flakes (1 μm thick). In FIG. 11 the side reflectivity of 3D printed PC containing about 1.4 wt. % is shown.

[0141] In FIG. 12 the side reflectivity of PC with such flakes at about 0.1 wt % (0.04 vol. %). Here, the sizes of the flakes are 20 μm largest length and only 30 nm thick. These flakes were obtained with physical vapor deposition.

[0142] The term “substantially” herein, such as “substantially consists”, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” includes also embodiments wherein the term “comprises” means “consists of”. The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term “comprising” may in an embodiment refer to “consisting of” but may in another embodiment also refer to “containing at least the defined species and optionally one or more other species”.

[0143] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0144] The devices herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

[0145] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0146] The invention also provides a control system that may control the apparatus or device or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the apparatus or device or system, controls one or more controllable elements of such apparatus or device or system.

[0147] The invention further applies to a device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

[0148] The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.

[0149] It goes without saying that one or more of the first (printable or printed) material and second (printable or printed) material may contain fillers such as glass and fibers which do not have (to have) influence on the on T.sub.g or T.sub.m of the material(s).