RETROREFLECTIVE SURFACE USING 3D PRINTING

Abstract

A method for producing a 3D item by means of fused deposition modelling, the method comprising a 3D printing stage, wherein the 3D printing stage comprises layer-wise depositing 3D printable material (201) to provide the 3D item (1) comprising 3D printed material (202), wherein: (a) the 3D printable material (201) comprises 3D printable core material (1351) and 3D printable shell material (1361); the 3D item (1) comprises a core-shell layer (1322) of the 3D printed material (202), wherein the core-shell layer (1322) comprises (i) a core (330) comprising 3D printed core material (1352) and (ii) a shell (340) comprising 3D printed shell material (1362); wherein the shell (340) at least partly encloses the core (330); (b) the 3D printable core material (1351) is reflective or absorbing for a wavelength (21) in the visible wavelength range; and (c) the 3D printable shell material (1361) comprises shell particles (430) which are transmissive for the wavelength (21) and wherein at least part of a total number of shell particles (430) protrude from the shell (340) of the 3D printed material (202).

Claims

1. A method for producing a 3D item by means of fused deposition modelling, the method comprising a 3D printing stage, wherein the 3D printing stage comprises: layer-wise depositing 3D printable material to provide the 3D item comprising 3D printed material, wherein: the 3D printable material comprises 3D printable core material and 3D printable shell material; wherein the 3D item comprises a core-shell layer of the 3D printed material, wherein the core-shell layer comprises (i) a core comprising 3D printed core material and (ii) a shell comprising 3D printed shell material; at least partly encloses the core; and the 3D printable shell material comprises shell particles which are transparent for a wavelength in the visible wavelength range, and wherein at least part of a total number of shell particles of the 3D printed material.

2. The method according to claim 1, wherein the 3D printable shell material is light transparent for the wavelength; and wherein the shell particles are transparent for wavelengths in a wavelength range of at least 100 nm.

3. The method according to claim 1, wherein the shell particles have an equivalent spherical diameter D1 selected from the range of 30 μm≤D1≤2000 μm, and wherein the shell has a shell width W2, wherein 0.5≤D1/W2≤1.5.

4. The method according to claim 1, wherein the 3D printable shell material comprises a thermoplastic material, with the shell particles, wherein the shell particles have a first refractive index and the thermoplastic material has a second refractive index, wherein the first refractive index and second refractive index differ with at least 0.15.

5. The method according to claim 1, wherein the shell particles comprise one or more of (i) glass beads, and (ii) polymer spheres.

6. The method according to claim 1, wherein the 3D printable core material is reflective or absorbing for the wavelength, wherein the 3D printable core material comprises core particles, wherein the core particles are each individually described by a smallest rectangular prism circumscribing the respective particles, wherein the rectangular prism has a length L.sub.1, a width L.sub.2 and a height L.sub.3, wherein L.sub.1≥L.sub.2≥L.sub.3, wherein the rectangular prism has a first aspect ratio is AR.sub.1=L.sub.1/L.sub.2, a second aspect ratio is AR.sub.2=L.sub.1/L.sub.3, and a third aspect ratio is AR.sub.3=L.sub.2/L.sub.3, wherein: the shell particles are described by a length L.sub.2,1, a first aspect ratio AR.sub.2,1, a second aspect ratio AR.sub.2,2, and a third aspect ratio AR.sub.2,3 wherein length L.sub.2,1 is in the range from 30-2000 μm and wherein AR.sub.2,1≤2, AR.sub.2,2≤2, and AR.sub.2,3≤2.

7. The method according to claim 6, wherein the core particles are reflective for the wavelength, wherein the core particles are described by a length L.sub.1,1 and a second aspect ratio AR.sub.1,2, wherein length L.sub.1,1 is in the range from 1 μm, wherein AR.sub.1,2≥10.

8. The method according to claim 6, wherein the core particles are absorbing for the wavelength, wherein the core particles are described by a length L.sub.1,1 and a first aspect ratio AR.sub.1,1, a second aspect ratio AR.sub.1,2 and a third aspect ratio AR.sub.1,3, wherein length L.sub.1,1 is in the range from 1-100 μm, and wherein AR.sub.1,1≤2, AR.sub.1,2≤2, and AR.sub.1,3≤2.

9. The method according to claim 1, wherein a shrinkage of the 3D printed shell material is higher than a shrinkage of the 3D printed core material.

10. A 3D item comprising 3D printed material, wherein the 3D item comprises a plurality of layers of 3D printed material, wherein at least one of the layers comprises a core-shell layer of 3D printed material; wherein the core-shell layer, comprises (i) a core comprising a 3D printed core material, and (ii) a shell comprising a 3D printed shell material; wherein the shell at least partly encloses the core, wherein the 3D printed shell material comprises shell particles which are transparent for a wavelength in the visible wavelength range and wherein at least part of a total number of shell particles protrude from the shell of the 3D printed material.

11. The 3D item according to claim 10, wherein the shell particles have an equivalent spherical diameter D1, wherein 30 μm≤D1≤2000 μm, and wherein the shell has a shell width W2, wherein 0.5≤D1/W2≤1.5, wherein the 3D printed shell material comprise a thermoplastic material with the shell particles, wherein the shell particles have a first refractive index and the thermoplastic material has a second refractive index, wherein the first refractive index and second refractive index differ with at least 0.15.

12. The 3D item according to claim 10, wherein the 3D printed core material is reflective or absorbing for the wavelength, wherein the 3D printed core material comprises core particles, wherein the core particles and shell particles are each individually described by a smallest rectangular prism circumscribing the respective particles, wherein the rectangular prism has a length L.sub.1, a width L.sub.2 and a height L.sub.3, wherein L.sub.1≥L.sub.2≥L.sub.3, wherein the rectangular prism has a first aspect ratio is AR.sub.1=L.sub.1/L.sub.2, a second aspect ratio is AR.sub.2=L.sub.1/L.sub.3, and a third aspect ratio is AR.sub.3=L.sub.2/L.sub.3, wherein: the shell particles are described by a length L.sub.2,1, a first aspect ratio AR.sub.2,1, a second aspect ratio AR.sub.2,2, and a third aspect ratio AR.sub.2,3 wherein length L.sub.2,1 is in the range from 30-2000 μm and wherein AR.sub.2,1≤2, AR.sub.2,2≤2, and AR.sub.2,3≤2; the core particles comprise reflective particles, wherein the core particles are described by a length L.sub.1,1 and a second aspect ratio AR.sub.1,2, wherein length L.sub.1,1 is in the range from 1-1000 μm and wherein AR.sub.1,2≥10.

13. The 3D item according to claim 10, wherein the shell particles comprise glass beads, and wherein the 3D printed shell material is light transparent for the wavelength.

14. A lighting device comprising the 3D item according to claim 10, wherein the 3D item is configured as one or more of (i) at least part of a lighting device housing, (ii) at least part of a wall of a lighting chamber, and (iii) an optical element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0115] 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:

[0116] FIGS. 1a-1c schematically depict some general aspects of the 3D printer and of an embodiment of 3D printed material;

[0117] FIGS. 2a-2d schematically depict some further aspects of the method and of the 3D printed material of the invention;

[0118] FIGS. 3a-3c schematically depict some aspects of embodiments of particles;

[0119] FIG. 4 schematically depicts the mechanism for retroreflection;

[0120] FIG. 5 schematically depicts an application;

[0121] FIG. 6 is a photograph of a 3D printed item according to the present invention; and

[0122] FIG. 7 is a photograph of a 3D printed item according to the present invention.

[0123] The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0124] 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 an 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 (see below). 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). Reference 321 indicates extrudate (of 3D printable material 201).

[0125] 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 layers 322 wherein each layers 322 comprises 3D printable material 201, 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). By deposition, the 3D printable material 201 has become 3D printed material 202. 3D printable material 201 escaping from the nozzle 502 is also indicated as extrudate 321. Reference 401 indicates thermoplastic material.

[0126] The 3D printer 500 may be configured to heat the filament 320 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.

[0127] 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 an extrudate 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 extrudate 321 downstream of the nozzle 502 is reduced relative to the diameter of the filament 322 upstream of the printer head 501. Hence, the printer nozzle is sometimes (also) indicated as extruder nozzle. Arranging layer 322 by 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.

[0128] Reference Ax indicates a longitudinal axis or filament axis.

[0129] 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.

[0130] 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.

[0131] Alternatively, the printer can have a head that can also rotate during printing. Such a printer has an advantage that the printed material cannot rotate during printing.

[0132] Layers are indicated with reference 322, and have a layer height H and a layer width W.

[0133] 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.

[0134] Reference D indicates the diameter of the nozzle (through which the 3D printable material 201 is forced).

[0135] 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. Reference H indicates the height of a layer. Layers are indicated with reference 322. The layers may have an essentially circular cross-section. Often, however, they may be flattened, such as having an outer shape resembling a flat oval tube or flat oval duct (i.e. a circular shaped bar having a diameter that is compressed to have a smaller height than width, wherein the sides (defining the width) are (still) rounded).

[0136] 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, respectively. Directly downstream of the nozzle 502, the filament 321 with 3D printable material becomes, when deposited, layer 322 with 3D printed material 202.

[0137] FIG. 1c schematically depicts a stack of 3D printed layers 322, each having a layer height H and a layer width W. Note that in embodiments the layer width and/or layer height may differ for two or more layers 322. Reference 252 in FIG. 1c indicates the item surface of the 3D item (schematically depicted in FIG. 1c).

[0138] Referring to FIGS. 1a-1c, the filament of 3D printable material that is deposited leads to a layer having a height H (and width W). Depositing layer 322 after layer 322, the 3D item 1 is generated. FIG. 1c very schematically depicts a single-walled 3D item 1. FIGS. 2a-2e schematically depicts some further aspects of the method of the invention. FIGS. 2a-2b depict some embodiments of a (core-shell) filament 320 that may be used in the method. The filaments 320 may be used in a printer 500, e.g. as depicted in FIG. 1a-1b, having a nozzle 502 with a single opening. The geometry, especially the width of the core W1F, height of the core H1F and the width (or thickness) of the shell W2F in the filaments are indicated. In the embodiment of FIG. 2b, the shell material 341 comprising shell polymeric material 345 completely enclosing the core material 331 (comprising core polymeric materials 335) (W2F is non-zero at all locations along the perimeter of the filament 320).

[0139] In embodiments depicted in FIG. 2a-b, the filament 320 comprises (i) core material 331 comprising a printable core material 1351, comprising core particles 420 and (ii) a shell material 341 comprising a printable shell material 1361, comprising shell particles 430. In the embodiment of FIG. 2a, the shell material 341 only partly encloses the core material 331. The shell material 341 does not enclose the core material 331 at the two locations indicated by the arrows; at these locations W2F is zero (0 μm). As such, the shell material 341 of the filament 320 covers (encloses) the core material 331 of the filament 320 at two continuous sections arranged at a surface of the filament 320, where W2F is non-zero. Using the filament 320 of FIG. 2b in the 3D printing stage may in embodiments result in the 3D item 1 depicted in FIG. 2d.

[0140] Referring to FIGS. 2a-2b, the shell may partly enclose the core (see FIG. 2a) or fully enclose the core (see FIG. 2b).

[0141] Additionally to or as an alternative to using core-shell filaments, a core-shell nozzle 502 may be used as is schematically illustrated in FIG. 2c. Filaments 320 comprising 3D printable core material 1351 and shell printable material 1361 enter printing head 501 in the core nozzle 5025 and shell nozzle 5026, respectively. The 3D printable core material 1351 may comprise particles 420, the shell printable material 1361 may comprise particles 430. After extrusion, a core-shell layer 1322 is deposited comprising a core 330 comprising core material 331, comprising core printed material 1352; and a shell 340 comprising shell material 341, comprising shell printed material 1362.

[0142] In embodiments, the particle sizes are selected such that the core particles 420 can pass through the core nozzle 5025 and that the shell particles 430 can pass through the shell nozzle 5026 without clog formation. Relative extrusion rates of core printing material 1351, shell printing material 1361 and substrate 550 may be selected such that shell width W2 is controlled in relation to the particle equivalent spherical diameter D1 in a first stage following 0.5≤D1/W2≤1.5 resulting in shell particles 430 protruding from the shell 340 to obtain a retroreflective 3D item 1.

[0143] FIG. 2d schematically depicts a stack of 3D printed core-shell layers 1322. The layers comprise core-shell layer 1322 of 3D printed material 202 and comprising a core 330 and a shell 340. The core 330 comprises a core material 331 comprising a first composition. The shell 340 comprises a shell material 341 comprising a second composition different from the first composition, e.g. in physical, chemical, and/or optical properties. In embodiments, the core printed material 1352 comprises core particles 420. The core particles may be absorbing or reflective. Different types of core particles 420 may be combined in one 3D item 1. FIG. 2d depicts a stack of four core-shell layers 1322 printed according to the present invention, resulting in core-shell layers 1322 with shell particles 430 protruding from the shell 340 of the 3D printed item 1. In embodiments, the core particles 420 in the two top layers 322 may be reflective whereas the core particles 420 in the two bottom layers 332 may be absorbing.

[0144] In the exemplary layers of FIG. 2d, the shell fully encloses the core.

[0145] In embodiments, the shell printed material 1362 comprises particles 430. Further, the core height of the core 330 is indicated with reference H1, and the width of the core is indicated with reference W1. The shell 340 has a shell width W2. The shell width W2 may herein also be referred to as thickness W2 of the shell 340. FIG. 2d depicts an embodiment wherein (in each core-shell layer 1322) the shell 340 substantially completely encloses the core 330.

[0146] Further, as shown in FIG. 2d, the width W1 of the core and the width W2 of the shell may be determined essentially perpendicular to the stacking height. Further, the height of the core H1 may be determined essentially parallel to the stacking height. The term “shell width” may especially refer to the largest shell width. The term “core height” may also especially refer to the largest core height. The term “core width” may also especially refer to the largest core width. Especially, the largest shell width is the width of the shell in the same plane as the largest core width.

[0147] FIGS. 3a-3c schematically depict embodiments of particles 410. FIG. 3a depicts a spherical particle 410 and ellipsoid particle 410. The length L.sub.1, width L.sub.2, and height L.sub.3 of the spherical particle 410 are all equal to its diameter. The length L.sub.1, width L.sub.2, and height L.sub.3 of the ellipsoid particle 410 are defined by a virtual smallest rectangular prism 415 enclosing the particle. The rectangular prism 415 has a length L.sub.1, a width L.sub.2 and a height L.sub.3 wherein L.sub.1≥L.sub.2≥L.sub.3. FIG. 3b depicts a particle 410 that has a rectangular prism shape, wherein the rectangular prism 415 has a length L.sub.1, a width L.sub.2 and a height L.sub.3 wherein L.sub.1≥L.sub.2≥L.sub.3. FIG. 3c schematically depicts a particle that has a curved shape, with a virtual smallest rectangular prism 415 enclosing the particle. The rectangular prism 415 has a length L.sub.1, a width L.sub.2 and a height L.sub.3 wherein L.sub.1≥L.sub.2≥L.sub.3.

[0148] Further, note that the particles are not essentially oval or rectangular prismoids. Of course, the particles may comprise a combination of differently shaped particles.

[0149] Shell particle dimensions and core particle dimensions are defined analogously to the particle dimensions described above by a virtual smallest rectangular prism 415 enclosing the core or shell particle. Core particles 420 may thus be described by a length L.sub.1,1, a width L.sub.1,2, a height L.sub.1,3, a first aspect ratio AR.sub.1,1, a second aspect ratio AR.sub.1,2 and a third aspect ratio AR.sub.1,3. Hence, shell particles 430 may be described a length L.sub.2,1, a width L.sub.2,2, a height L.sub.2,3, a first aspect ratio AR.sub.2,1, a second aspect ratio AR.sub.2,2 and a third aspect ratio AR.sub.2,3. Also, 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.

[0150] FIG. 4 depicts the mechanism of retroreflection by 3D item 1. Shell particles 430 are partially embedded in 3D printed material 202 and partially protruding from a surface of the 3D printed item 1. Light with a wavelength 21 in the visible wavelength range is transmitted through the shell particle 430 and reflected by the 3D printed material 202. The shell particle 430 acts as a lens and in combination with the reflective 3D printed material reflects the light in its original direction, thus is retroreflecting the wavelength 21.

[0151] FIG. 5 schematically depicts an embodiment of a lamp or luminaire, indicated with reference 2, which comprises a light source 10 for generating light 11. The lamp may comprise a housing or shade or another element, which may comprise or be the 3D printed item 1. Here, the half sphere (in cross-sectional view) schematically indicates a housing or shade. The lamp or luminaire may be or may comprise a lighting device 1000 (which comprises the light source 10). Hence, in specific embodiments the lighting device 1000 comprises the 3D item 1. The 3D item 1 may be configured as one or more of (i) at least part of a lighting device housing, (ii) at least part of a wall of a lighting chamber, and (iii) an optical element. Hence, the 3D item may in embodiments be reflective for light source light 11 and/or transmissive for light source light 11. Here, the 3D item may e.g. be a housing or shade.

[0152] FIG. 6 depicts a photograph of the surface of a retroreflective 3D printed item wherein the core of the 3D printed item is light reflective.

[0153] FIG. 7 depicts a photograph of the surface of a retroreflective 3D printed item wherein the core of the 3D printed item is light absorbing.

[0154] The term “plurality” refers to two or more.

[0155] The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. . . . . Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” 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%.

[0156] The term “comprise” also includes embodiments wherein the term “comprises” means “consists of”.

[0157] 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”.

[0158] 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.

[0159] The devices, apparatus, or systems may herein amongst others be 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, apparatus, or systems in operation.

[0160] 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.

[0161] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0162] 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. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

[0163] The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

[0164] The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system 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.

[0165] The invention also provides a control system that may control the device, apparatus, 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 device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

[0166] The invention further applies to a device, apparatus, or system 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.

[0167] 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.

[0168] 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).