HIDING OPTICAL DEFECT LINES ON PARTS OF FDM PRINTED LUMINAIRES WITH METALLIC LOOK

Abstract

The application relates to a method for 3D printing a 3D item (10) on a substrate (1550), the method comprising providing a filament (320) of 3D printable material (201) and printing during a printing stage said 3D printable material (201) to provide the 3D item (10) comprising 3D printed material (202), wherein the 3D printable material (201) comprises light transmissive polymeric material and wherein the polymeric material has a glass transition temperature, wherein the 3D printable material during at least part of the printing stage further comprises plate-like particles (410), wherein the plate-like particles (410) have a metallic appearance, wherein the plate-like particles (410) have a longest dimension length (L1) selected from the range of 50 m-2 mm and a largest thickness (L2) selected from the range of 0.05-20 m, and wherein the method further comprises subjecting the 3D printed material (202) on the substrate (1550) to a temperature of at least the glass transition temperature.

Claims

1. A method for manufacturing a reflector by 3D printing on a substrate, the method comprising providing a filament of 3D printable material and printing during a printing stage the 3D printable material, to provide said reflector comprising 3D printed material, wherein the 3D printable material comprises light transmissive polymeric material and wherein the polymeric material has a glass transition temperature, wherein the 3D printable material during at least part of the printing stage further comprises plate-like particles, wherein the plate-like particles have a metallic appearance, wherein the plate-like particles have a longest dimension length (L1) selected from the range of 40 m-2 mm and a largest thickness (L2) selected from the range of 0.05-20 m, and wherein the method further comprises at least temporarily heating the substrate to a temperature of at least 5 C. above the glass transition temperature at least during deposition and/or after deposition of a first layer of 3D printable material on the substrate executed until essentially the deposited first layer is conformal with the substrate.

2. The method according to claim 1, wherein the plate-like particles have a longest dimension length (L1) selected from the range of 100 m-1 mm and a largest thickness (L2) selected from the range of 0.10-10 m, and wherein the plate-like particles comprise one or more of dollar like particles, flake-like particles, and particles with straight edges.

3. The method according to claim 1, wherein the method comprises at least temporarily heating the substrate to a temperature below the melting temperature.

4. The method according to claim 1, wherein the 3D printable material comprises in the range of 0.1-5 wt % of the plate-like particles, relative to the total weight of the 3D printable material.

5. The method according to claim 1, wherein the 3D printable material comprises one or more of polystyrene (PS), polycarbonate (PC), polyethylenetelepthalate (PET), polymethylmethacrylate (PMMA), and copolymers of two or more of these, and wherein the particles comprise one or more of metal particles and metal coated particles, wherein the metal coated particles comprise silver or aluminum coated mica particles or glass particles.

6. The method according to claim 1, wherein the 3D printable material comprises the plate-like particles when 3D printing on a substrate and wherein the 3D printable material optionally comprises the plate-like particles when 3D printing on already 3D printed material.

7. The method according to claim 1, the method comprising printing during the printing stage said 3D printable material on a substrate, wherein the substrate has one or more of a curved face, a facetted face, and faces configured relative to each under an angle.

8. A 3D printed reflector (1) obtainable by a method according to claim 1, wherein the 3D printed reflector (1) comprises 3D printed material, wherein at least a first layer of the 3D printed material comprises light transmissive polymeric material, wherein the polymeric material has a glass transition temperature, wherein the 3D printed material further comprises plate-like particles, wherein the plate-like particles have a metallic appearance, wherein the plate-like particles have a longest dimension length (L1) selected from the range of 40 m-2 mm and a largest thickness (L2) selected from the range of 0.05-20 m, wherein the first layer is an outer layer, and wherein the first layer comprises a repetitive arrangement of the polymer comprising plate-like particles.

9. The 3D printed reflector according to claim 8, wherein the particles having a coating, wherein the coating comprises one or more of a metal coating and a metal oxide coating, and wherein the plate-like particles have a longest dimension length (L1) selected from the range of 100 m-1 mm and a largest thickness (L2) selected from the range of 0.10-10 m.

10. The 3D printed reflector according to claim 8, wherein the 3D printed material comprises up to 40 wt % of the plate-like particles relative to the total weight of the 3D printed material.

11. The 3D printed reflector according to claim 8, wherein the 3D printed material comprises in the range of 0.1-5 wt % of the plate-like particles relative to the total weight of the 3D printed material, wherein the 3D printed material 4024 comprises one or more of polystyrene (PS), polycarbonate (PC), polyethylenetelepthalate (PET), polymethylmethacrylate (PMMA), and copolymers of two or more of these, and wherein the plate-like particles comprise one or more of metal flakes, coated mica flakes, and coated glass flakes.

12. The 3D printed reflector according to claim 8, wherein at least a part of the first layer of 3D printed material of the 3D printed reflector comprises the plate-like particles at a first average content c1, and wherein one or more other parts of the 3D printed reflector comprise the plate like particles at a second average c1, wherein c2/c10.8.

13. The 3D printed reflector according to claim 8, wherein the reflector is an ellipse-shaped reflector, a parabola-shaped reflector, or a hyperbola-shaped reflector.

14. A lighting system comprising (a) a light source configured to generate light source light and (b) a reflector according to claim 13 configured to reflect at least part of said light source light.

15. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] 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:

[0073] FIGS. 1a-1b schematically depict some general aspects of the 3D printer;

[0074] FIGS. 2a-2d schematically depict some aspects of the particles, such as flakes, that can be used herein;

[0075] FIGS. 3a-3d schematically depict some applications, including 3D printed items;

[0076] FIGS. 4a-4d further schematically depict some applications, including 3D printed items; and

[0077] FIG. 5 schematically depicts some further aspects.

[0078] The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0079] 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 320 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).

[0080] The 3D printer 500 is configured to generate a 3D item 10 by depositing on a substrate 1550, such as a receiver item 550, which may in embodiments at least temporarily be heated and cooled, a plurality of filaments 320 wherein each filament 20 comprises 3D printable material, such as having a melting point T.sub.m. 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.

[0081] Reference 572 indicates a spool or roller with material, especially in the form of a wire. The 3D printer 500 transforms this in a filament or fiber 320 on the substrate 1550 or on already deposited printed material. In general, the diameter of the filament downstream of the nozzle is reduced relative to the diameter of the filament upstream of the printer head. Hence, the printer nozzle is sometimes (also) indicated as extruder nozzle. Arranging filament by filament and filament on filament, a 3D item 10 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.

[0082] Reference A indicates a longitudinal axis or filament axis.

[0083] Reference C schematically depicts a control system, such as especially a temperature control system configured to control the temperature of the substrate 1550. The control system C may include a heater which is able to heat the substrate 1550 to at least a temperature of 50 C., but especially up to a range of about 350 C., such as at least 200 C.

[0084] FIG. 1b schematically depicts in 3D in more detail the printing of the 3D item 10 under construction. Here, in this schematic drawing the ends of the filaments 320 in a single plane are not interconnected, though in reality this may in embodiments be the case.

[0085] 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 320 comprising 3D printable material 201 to the first printer head 501, and optionally (c) a substrate 1550. 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.

[0086] FIGS. 2a-2d schematically depict some aspects of the particles 410. Some particles 410 have a longest dimension A1 having a longest dimension length L1 and a minor axis A2 having a minor axis length L2. As can be seen from the drawings, the longest dimension length L1 and the minor axis length L2 have a first aspect ratio larger than 1. FIG. 2a 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 axis A3. Essentially, the particles 410 are elongated thin particles, i.e. L2<L1, especially L2<<L1, and L2<L3, especially L2<<L3. L1 may e.g. be selected from the range of 1-500 m; likewise L3 may be. L2 may e.g. be selected from the range of 0.1 m-10 m. Also L3 may e.g. be selected from the range of 0.1 m-10 m. However, L2 and/or L3 may also be longer, such as up to 5 mm, such as up to 1 mm, like up to 100 m.

[0087] FIG. 2b 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.

[0088] 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 minor axis 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.

[0089] FIG. 2c 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.

[0090] FIG. 2d 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.

[0091] FIG. 3a schematically depicts a lighting system 1000 comprising a) a light source 1010 configured to generate light source light 1011 and b) a reflector 1, such as defined above, configured to reflect at least part of said light source light 1011.

[0092] In yet another embodiment, the reflector shaped substrate(s) can produce reflectors with 10, 25 and 40 degrees full width half maximum. In an embodiment, the reflector shaped support may thus have the shape and smoothness of a smooth reflector (see e.g. FIG. 3b, wherein schematically a reflector is depicted, with a (specular) reflective surface 405, such as a specular reflective surface). In another embodiment, the reflector shaped table might have the shape and smoothness of a faceted reflector. The facets may have areas of larger than 16 mm.sup.2, such as in the range of 16-1600 mm.sup.2. However, the facets may also be smaller, such as in the range of 1-16 mm.sup.2, or even smaller, such as in the range of 0.01-1 mm.sup.2. Such fine facets or structures provide smoother beams.

[0093] In yet another embodiment, we suggest a reflector shaped table which has a shape and smoothness of a spiral faceted reflector. The fine facets in a tight spiral are desired to achieve a smooth beam. In yet another embodiment, we suggest a reflector shaped table which has a shape and smoothness of a hybrid reflector. It comprises facets near the light source in order to obtain a beam without a black hole (see FIG. 3c). More remote from the light source, the reflector may not be facetted. In yet another embodiment, we suggest a reflector shaped table which has a shape and smoothness of an engineered structure including but not limited to including a textured, orange peel and stochastic design. Hence, essentially any reflector 1 may include one or more 3D parts comprising the herein described 3D item 10 having reflective properties. Hence, parts of the reflectors 1 in FIGS. 3b-3c are 3D printed, and include the 3D item 10.

[0094] For printing lamps and luminaires, we suggest the use of a reflector shape which is placed on the print platform. The reflector shape is in this example used as substrate 1550. Note that other shapes, including textured shapes, may be applied as well. Subsequently, the printer can print on top of such a surface of the substrate 1550, replicating the shape and surface texture thereof (FIG. 3d). Reference 220 indicates the surface of the 3D item 10 (under construction) that is in contact with the substrate 1550.

[0095] Here we suggest using metal and or glass flakes with a metal or a metal oxide coating. Such glass flakes show specular reflection and act as small mirrors. Here we suggest using glass flakes with a metal, metal oxide coating. For obtaining glitter effect the flakes have an aspect ratio (size/thickness) of 20 or larger. The average size of the flakes is in the range 20 m-1 mm. The flakes can be brought into a polymer such as PC, PMMA, and PET at a concentration up to 40 wt %. The host polymer is preferentially a transparent polymer. It is also possible to combine with dyes to maintain glittering effect without inducing scattering. In may also comprise a luminescent or absorbing dye.

[0096] FIG. 4a very schematically depicts an embodiment as well as variants of the 3D printing process, wherein by way of example printable material 201 without plate like particles 401 (left) and with such particles (right) is provided. Such materials may be provided as filament or mixture to the printer head(s), whereby filaments 320 may be produced, of which some options are schematically depicted, with from left to right: filament 320 without plate-like particles, filament 320 with part comprising plate like particles 410 and with part without such particles (of course, a plurality of such different regions may be available), and a filament 320 with plate like particles 401. One or more of such type of filaments may be used for printing, either with a single printer head or with two or more printer heads, and provide a 3D printed item 10. Here, by way of example part of the item does not comprise the herein defined plate like particles. This part is indicated with reference 25. However, another part, herein indicated as outer layer 15, does comprise the particle 410. Here, this is by way of example the right side face, which was thus the part of the 3D item 10 that was first deposited on the substrate. As indicated above, the item 1, or at least part thereof is heated on the substrate. The outer surface of the item 10 that was in contact with the surface is due to the heating to about or (slightly) above the glass transition temperature, essentially become conformal to the shape of the substrate. Assuming a flat substrate, a flat outer layer is obtained, as schematically depicted in FIG. 4a. Hence, the characteristic rib structure with ribs 19 which is often seen for 3D printed items 10, is essentially not present in this outer layer. However, such layers above the outer layer that was in contact with the substrate, and outer layers that were not in contact with the substrate, may include such ribs 19. This leads to elongated shallow cavities 217. These are herein also indicated as mechanical defect lines 217. Reference 216 refers to optical defect lines, which are further explained in relation to FIG. 5. Reference 220 refers to a surface of the 3D item 10, especially to the surface of the outer layer 15. This surface may thus have a shape essentially conformal to the earlier used substrate during 3D printing. FIG. 4d shows a comparison in one photo of the examples shown in FIGS. 4b and 4c.

[0097] Hence, printing starts always by deposition of layers on a flat platform, here indicate with the broader term substrate. The area printed on the platform can form the front decorative surface of a luminaire. Objects showing metallic appearance are highly appreciated. For this purpose one can make use of polymers filled with plate like particles with a metallic appearance such as metal flakes. During the deposition using FDM printing metallic flakes can get oriented within the polymer, parallel to the surface showing metallic appearance. However when such layers are placed next to each other to produce a flat surface, optical defect lines start to appear in regions between the subsequently deposited layers next to each other. In order to avoid the appearance of mechanical defect lines it is important to heat up the platform to a temperature close or above the glass transition temperature of the polymer. FIG. 4b shows such optical defect lines obtained during the printing of a polymer containing A1 flakes with (lateral) dimensions about 20 micron on a flat platform. Such optical defect lines tend to disturb uniform metallic appearance of the surface. It was surprisingly found that the visibility of the optical defect lines is very much related to the size of the metal particles. We used various plate-shaped particles which were disc or flake shaped ranging from 20 m and up. When particles with lateral dimensions up to around 100 m were used optical defects were clearly visible. When particles with larger dimensions were used the optical defect lines became less visible. When particles with lateral dimensions above 200 m were used optical defect lines totally disappeared. Over about 1-2 mm, the surface texture may become too rough or particles may protrude from the surface. FIG. 4c shows a photo obtained after the printing of a polycarbonate containing 4% A1 dollar type flakes with dimensions about 240 m on a flat platform which was heated to 150 C. through a printer nozzle (at 290 C. with a diameter of 1.8 mm. In FIG. 4c it can be seen that the optical defect lines disappear. FIG. 4d shows a comparison in a single figure of the same items as shown in FIGS. 4b and 4c, respectively. In FIG. 4d, also optical defect lines 216 are depicted, which are due to some orientation of the particles at interfaces of two 3D printed filaments. Hence, even though the ribbed structure may be removed due to heating of the substrate, a kind of ribbed structure is still visible due to the orientation of the particles within the printed filaments. However, these optical defect lines 216 are hardly visible in the lower embodiment shown in FIG. 4d (and also shown in FIG. 4c).

[0098] Hence, it is herein suggest using transparent polymer containing plate like particles with a metallic appearance having lateral dimensions larger than 40 m, especially larger than about 100 m for using FDM to obtain metallic appearance without optical defects upon printing on a flat surface. Such polymers may also contain other additives such as colorants. Plate like particles may be metal flake such as aluminum, copper, nickel etc. They may also have disc like shape such as so-called dollar shape, or coin shape.

[0099] FIG. 5 schematically depicts a few layers of 3D printed material 200 on the substrate 1550. The structure with ribs 219, and mechanical defect lines 217 is shown at the edges and on the substrate. Upon heating the substrate, these mechanical defect lines 217 essentially disappear at the surface 220 of the first layer 15. Hence, here a flat surface 220 of the outer layer 15 is shown, as this part of the external surface of the 3D printed item 10 was in contact with the substrate 1550.

[0100] As shown in FIG. 5, there is a repetitive arrangement with an orientation of the particles 410 at the (original) boundaries between filaments that were deposited adjacent to each other. As the polymeric material is light transmissive, and thus the particles 410 are visible through the polymeric material, this orientation lead to optical defect lines 216.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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).