WO2023139025A1

WO2023139025A1 - Fdm 3d printed reflective material

Info

Publication number: WO2023139025A1
Application number: PCT/EP2023/050872
Authority: WO
Inventors: Rifat Ata Mustafa Hikmet; Ties Van Bommel
Original assignee: Signify Holding B.V.
Priority date: 2022-01-20
Filing date: 2023-01-16
Publication date: 2023-07-27

Abstract

The invention provides a method for producing a 3D item (1) by means of fused deposition modelling, the method comprising: (A) providing 3D printable material (201) comprising (i) a polymeric matrix material (211) that is transmissive for visible radiation, wherein the polymeric matrix material (211) comprises thermoplastic matrix material, and (ii) a reflective material (212) that is reflective for at least part of the visible radiation and that is at least partly enclosed by the polymeric matrix material (211); wherein the reflective material (212) comprises a microporous polymeric material (213) selected from the group of polycarbonate polymers and polyterephthalate polymers; and (B) depositing the 3D printable material (201), to provide the 3D item (1) comprising 3D printed material (202) comprising the matrix material (211) and the reflective material (212).

Description

FDM 3D printed reflective material

FIELD OF THE INVENTION

The invention relates to a method for manufacturing a 3D (printed) item. The invention also relates to the 3D (printed) item, such as obtainable with such method. Further, the invention relates to a lighting device including such 3D (printed) item.

BACKGROUND OF THE INVENTION

The use of a thermoplastic polymer comprising a particulate filler for preparing 3D articles is known in the art. W02017/040893, for instance, describes a powder composition, wherein the powder composition comprises a plurality of thermoplastic particles characterized by a bimodal particle size distribution, and wherein the powder composition may further comprise a particulate filler, antioxidant, heat stabilizer, light stabilizer, ultraviolet light stabilizer, ultraviolet light absorbing additive, near infrared light absorbing additive, infrared light absorbing additive, plasticizer, lubricant, release agent, antistatic agent, anti-fog agent, antimicrobial agent, colorant, laser marking additive, surface effect additive, radiation stabilizer, flame retardant, anti-drip agent, fragrance, fiber, or a combination comprising at least one of the foregoing, preferably a colorant or a metal particulate. This document further describes a method of preparing a three-dimensional article, the method comprising powder bed fusing the powder composition to form a three- dimensional article.

SUMMARY OF THE INVENTION

Within the next 10-20 years, digital fabrication will increasingly transform the nature of global manufacturing. One of the aspects of digital fabrication is 3D printing. Currently, many different techniques have been developed in order to produce various 3D printed objects using various materials such as ceramics, metals and polymers. 3D printing can also be used in producing molds which can then be used for replicating objects.

For the purpose of making molds, the use of polyjet technique has been suggested. This technique makes use of layer by layer deposition of photo-polymerisable material which is cured after each deposition to form a solid structure. While this technique produces smooth surfaces the photo curable materials are not very stable, and they also have relatively low thermal conductivity to be useful for injection molding applications.

The most widely used additive manufacturing technology is the process known as Fused Deposition Modeling (FDM). Fused deposition modeling (FDM) is an additive manufacturing technology commonly used for modeling, prototyping, and production applications. FDM works on an "additive" principle by laying down material in layers; a plastic filament or metal wire is unwound from a coil and supplies material to produce a part. Possibly, (for thermoplastics for example) the filament is melted and extruded before being laid down. FDM is a rapid prototyping technology. Other terms for FDM are “fused filament fabrication” (FFF) or “filament 3D printing” (FDP), which are considered to be equivalent to FDM. In general, FDM printers use a thermoplastic filament, which is heated to its melting point and then extruded, layer by layer, (or in fact filament after filament) to create a three-dimensional object. FDM printers are relatively fast, low cost and can be used for printing complicated 3D objects. Such printers are used in printing various shapes using various polymers. The technique is also being further developed in the production of LED luminaires and lighting solutions.

Optical elements, like reflectors, may not easily be made free-form. Further, materials used for optical elements, like reflectors, may not always have the desirable optical properties. When using materials that have desirable optical properties, such materials may be more difficult to process or may not easily be made free-form. Further, there may be a desire to 3D print objects having e.g. an improved reflection and/or to provide an improved method for providing an element, such as an optical element, having controllable optical properties.

Hence, it is an aspect of the invention to provide an alternative 3D printing method and/or 3D (printed) item which preferably further at least partly obviate(s) one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Herein, amongst others, solutions are provided to produce substantially freeform items, that may be suitable for reflection of visible radiation, using 3D printing, especially fused deposition modelling (though other options are herein not excluded).

In a first aspect, the invention provides a method for producing a 3D item (“3D printed item”) by means of fused deposition modelling. Especially, the method may comprise a 3D printing stage, wherein the 3D printing stage comprises a reflective material deposition stage, wherein the reflective material deposition stage may comprise depositing 3D printable material to provide the 3D printed item. Especially, the method for producing the 3D item by means of fused deposition modelling may comprise (a) providing 3D printable material and (b) depositing the 3D printable material. The 3D printable material may comprise (i) a polymeric matrix material (“polymeric matrix”) that may especially be transmissive for visible radiation. Further, the 3D printable material may comprise (ii) a reflective material that may especially be reflective for at least part of the visible radiation. Further, the reflective material may at least partly be enclosed by the polymeric matrix material. In embodiments, the polymeric matrix material may comprise thermoplastic matrix material (“thermoplastic matrix”).

In specific embodiments, the reflective material may comprise a microporous polymeric material (“reflective microporous polymeric material”). In further specific embodiments, the microporous polymeric material may be selected from the group of polycarbonate polymers and polyterephthalate polymers.

An example of a suitable reflective microporous polymeric material is a microcellular polymeric material, sometimes also referred to as a microcellular plastic or a microcellular foam. In other words, the term “microcellular polymeric material” refers to a species of the more generic term “microcporous polymeric material”.

A microcellular polymeric material is a microporous polymeric material that has been fabricated to contain pores in the form of bubbles or cells in a size range of 0.1 to 100 micrometers, typically at a concentration of billions per cubic centimeter (such as as least 10 billion per cubic centimeter), and/or with a porosity (volume void fraction) in a range of 5 % to 99 %.

Microcellular polymeric materials can be formed by dissolving a gas under high pressure into a polymer material. Removing the polymer material from the high pressure environment creates a thermodynamic instability. Heating the polymer material above the effective glass transition temperature (of the polymer/gas mixture) then causes the material to foam, thereby creating an arrangement of bubbles or cells.

Microcellular polymeric materials, and their methods of manufacturing, have become standardized since their original inception. Currently, manufacturers of microcellular polymeric materials use both injection molding and blow molding methods to create products for a wide range of different applications, including automotive, medical, packaging, consumer, and industrial applications. In the remainder of this description, wherever an embodiment is said to be implemented using a microporous polymeric material (having pores), the same embodiment can also be implemented using a microcellular material (having bubbles or cells) as example of a microporous polymeric material. In other words, the embodiment applies to microporous polymeric material as a genus, but also to microcellular polymeric material as a species of the aformentioned genus.

Further, as indicated above, the method may comprise depositing the 3D printable material, to provide the 3D item comprising 3D printed material comprising the matrix material and the reflective material.

Hence, in embodiments the invention provides 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 a reflective material deposition stage, wherein the reflective material deposition stage comprises): (A) providing 3D printable material comprising (i) a polymeric matrix material that is transmissive for visible radiation, wherein the polymeric matrix material comprises thermoplastic matrix material, and (ii) a reflective material that is reflective for at least part of the visible radiation and that is at least partly enclosed by the polymeric matrix material; wherein the reflective material comprises a microporous polymeric material selected from the group of polycarbonate polymers and polyterephthalate polymers; and (B) depositing the 3D printable material, to provide the 3D item comprising 3D printed material comprising the matrix material and the reflective material.

With such method, it may be possible to provide substantially free-form reflective 3D printed items. Further, in embodiments it may be possible to control reflectivity of the 3D item. Further, it may be possible to provide relatively highly reflective 3D items. Further, the use of at least two different materials may also allow choosing good combinations of mechanical and/or optical properties, and optionally also other properties. The reflective material may be used for its reflectivity and the matrix material may be used to host the reflective material and to provide mechanical strength to the 3D item. Further, the porosity of the filler may also have a positive effect in reducing the weight of the 3D printed item.

As indicated above, the invention provides amongst others a method for producing a 3D item comprising (A) providing 3D printable material and (B) depositing the 3D printable material, to provide the 3D item comprising 3D printed material. More especially, the invention provides a method for producing a 3D item comprising a 3D printing stage, wherein the 3D printing stage comprises a reflective material deposition stage, wherein the reflective material deposition stage comprises: (A) providing 3D printable material and (B) depositing the 3D printable material, to provide the 3D item comprising 3D printed material. Hence, especially a FDM based method may be applied. The 3D printable material (and thus also the 3D printed material) may comprise reflective material. Hence, the method may especially comprise a reflective material deposition stage.

Note that in embodiments the method may also comprise other stages, such as a stage wherein no reflective material is provided and/or a stage wherein reflective material is provided different from what is herein described and/or claimed (in addition to the reflective material deposition stage). Hence, the 3D printing stage may in embodiments also comprise other stages, such as a stage wherein 3D printable material is deposited that does not comprise the reflective material and/or does not comprise the polymeric matrix material. For instance, part of the 3D item may comprise 3D printed material essentially only consisting of the polymeric matrix material without reflective material. Hence, the material composition of different 3D printed layers may be different. Even, in specific embodiments the material composition of a 3D printed layer may vary over e.g. the layer length. Hence, if desirable, the composition of the 3D printed layers may vary over the 3D item. For instance, in the case of a hollow reflector, the surface of the hollow reflector that should be reflective may be produced during the reflective material deposition stage whereas an external part, or support elements for the surface of the hollow reflector that should be reflective, may be produced during a 3D printing stage where not necessarily reflective material is used.

In embodiments, the 3D printable material may thus comprise (i) a polymeric matrix material. Especially, the polymeric matrix material comprises thermoplastic matrix material. More especially, the polymeric matrix material may essentially consist of thermoplastic matrix material. In this way, the polymeric matrix material may be printable. As further described below, the polymeric (matrix) material may optionally further comprise fillers, like colorants, etc. Especially, 3D printability may be provided by at least the polymeric matrix material, more especially the thermoplastic matrix material.

The term “polymeric matrix material”, and similar terms, may refer to a polymeric material that may form a matrix (for another material). Hence, the term “thermoplastic matrix material”, and similar terms, refer to thermoplastic (polymeric) material that may form a matrix (for another material). The term “matrix” is applied, as the polymeric matrix material may at least partially enclose reflective material. For this reason, the polymeric matrix material especially is transmissive for visible radiation. Herein, visible radiation may especially refer to radiation having a wavelength selected from the range of 380-780 nm. Hence, visible radiation may refer to white light, but also to colored light. Hence the phrase “the polymeric matrix material is transmissive for visible radiation”, and similar phrases, may especially indicated that the polymeric matrix material is transmissive for radiation having one or more wavelengths within the 380-780 nm wavelength range, even more especially at least selected from the range of 400-680 nm.

The light transmissive material may have a light transmission in the range of 50-100 %, especially in the range of 70-100%, for light having a wavelength selected from the visible wavelength range.

The transmission (or light permeability) can be determined by providing light at a specific wavelength with a first intensity to the light transmissive material under perpendicular radiation and relating the intensity of the light at that wavelength measured after transmission through the material, to the first intensity of the light provided at that specific wavelength to the material (see also E-208 and E-406 of the CRC Handbook of Chemistry and Physics, 69th edition, 1088-1989).

In specific embodiments, a material may be considered transmissive when the transmission of the radiation at a wavelength or in a wavelength range, especially at a wavelength or in a wavelength range of radiation generated by a source of radiation as herein described, through a 1 mm thick layer of the material, especially even through a 5 mm thick layer of the material, under perpendicular irradiation with said radiation is at least about 20%, such as at least 40%, like at least 60%, such as especially at least 80%, such as at least about 85%, such as even at least about 90%.

The light transmissive material has light guiding or wave guiding properties. Hence, the light transmissive material is herein also indicated as waveguide material or light guide material. The light transmissive material will in general have (some) transmission of one or more of (N)UV, visible and (N)IR radiation, such as in embodiments at least visible light, in a direction perpendicular to the length of the light transmissive material. Without the activator (dopant) such as trivalent cerium, the internal transmission in the visible might be close to 100%.

The transmission of the light transmissive material (as such) for one or more luminescence wavelengths may be at least 80%/cm, such as at least 90%/cm, even more especially at least 95%/cm, such as at least 98%/cm, such as at least 99%/cm. This implies that e.g. a 1 cm³ cubic shaped piece of light transmissive material, under perpendicular irradiation of radiation having a selected luminescence wavelength (such as a wavelength corresponding to an emission maximum of the luminescence of the luminescent material of the light transmissive material), will have a transmission of at least 95%.

Herein, values for transmission especially refer to transmission without taking into account Fresnel losses at interfaces (with e.g. air). Hence, the term “transmission” especially refers to the internal transmission. The internal transmission may e.g. be determined by measuring the transmission of two or more bodies having a different width over which the transmission is measured. Then, based on such measurements the contribution of Fresnel reflection losses and (consequently) the internal transmission can be determined. Hence, especially, the values for transmission indicated herein, disregard Fresnel losses.

In embodiments, an anti-reflection coating may be applied to the luminescent body, such as to suppress Fresnel reflection losses (during the light incoupling process).

In addition to a high transmission for the wavelength(s) of interest, also the scattering for the wavelength(s) may especially be low. Hence, the mean free path for the wavelength of interest only taking into account scattering effects (thus not taking into account possible absorption (which should be low anyhow in view of the high transmission), may be at least 0.5 times the length of the body, such as at least the length of the body, like at least twice the length of the body. For instance, in embodiments the mean free path only taking into account scattering effects may be at least 5 mm, such as at least 10 mm. The wavelength of interest may especially be the wavelength at maximum emission of the luminescence of the luminescent material. The term “mean free path” is especially the average distance a ray will travel before experiencing a scattering event that will change its propagation direction.

In embodiments, the element comprising the light transmissive material may essentially consist of the light transmissive material. In specific embodiments, the element comprising the light transmissive material may be a light transparent element.

Especially, the light transmissive element, such as the light transparent element, may in embodiments have an absorption length and/or a scatter length of at least the length (or thickness) of the light transmissive element, such as at least twice the length of the light transmissive element. The absorption length may be defined as the length over which the intensity of the light along a propagation direction due to absorption drops with 1/e. Likewise, the scatter length may be defined as the length along a propagation direction along which light is lost due to scattering and drops thereby with a factor 1/e.

As the light transmissive material may at least partially enclose the reflective material, the transmission of the light transmissive material as well as a thickness of the enclosing layer may be selected such, that at least part of the visible light is transmitted through the light transmissive material, reaches the reflective material, is reflected by the reflective material, propagates through the light transmissive material, and escapes from the light transmissive material to external of the 3D printed material (or 3D printable material). In specific embodiments, the light transmissive material as well as a thickness of the enclosing layer may be selected such that for one or more wavelengths in the visible wavelength range, at least 50% of the light that entered the 3D printed material (or 3D printable material) also escapes form the 3D printed material (or 3D printable material) after reflection at the reflective material.

Hence, the 3D printable material (and the 3D printed material) may also comprise a reflective material that is reflective for at least part of the visible radiation and that is at least partly enclosed by the polymeric matrix material. Hence, at least part of the visible light that is transmitted through the polymeric matrix material reaching the reflective material is reflected thereby. At least part of the reflected light may (again) escape from the polymeric matrix material. Further, especially at least part of visible radiation having one or more wavelengths selected from the range of 380-780 nm, even more especially at least selected from the range of 400-680 nm, may be reflected by the polymeric matrix material.

Especially, assuming perpendicular irradiation, the reflection of the reflective material for the visible radiation may be larger than the transmission and absorption of the visible radiation by the reflective material. Likewise, assuming perpendicular irradiation, especially the transmission of the visible radiation by the polymeric matrix material may be larger than the reflection or absorption of the visible radiation by the polymeric matrix material. Note that these definitions do not necessarily imply that (only) perpendicular irradiation is applied; this formulation is used to define e.g. reflection or transmission.

The term “reflective material” may also refer to a combination of two or more different materials; together they may form the reflective material.

The reflective material may comprise a microporous polymeric material, such as e.g. selected from the group of polycarbonate polymers and polyterephthalate polymers. In specific embodiments, the term “polymer” may also refer to a copolymer of a polycarbonate polymer with another polymer or a polyterephthalate polymer and another polymer, respectively.

Alternatively or additionally, the reflective material may comprise a microporous polymeric material, such as e.g. selected from the group of polytetrafluoroethylene) (PTFE), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly(ethylene-alt-tetrafluoroethylene) (ETFE), poly(chlorotrifluoroethylene) (PCTFE), poly(vinylidene fluoride )(PVDF), poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PF A), poly(vinylidene fluori de-co-hexafluor opropylene) (PVDF-co-HFP), and poly(vinyl fluoride) (PVF). Fluorothermoplastics typically are copolymers of tetrafluoroethylene (TFE) with one or more other perfluorinated, partially fluorinated or non-fluorinated comonomers. Copolymers of TFE and perfluorinated alkyl or allyl ethers are known in the art as PFA's (perfluorinated alkoxy polymers). Copolymers of TFE and hexafluoropropylene (HFP) with or without other perfluorinated comonomers are known in the art as FEP's (fluorinated ethylene propylene). Copolymers of TFE, HFP and vinylidenefluoride (VDF) are known in the art as THV. Other types of melt-processable fluoropolymers are based on vinylidenefluoride homo- or copolymers, known in the art as PVDF. Other class of fluorothermoplastic is fluorinated ethylenic-cyclo oxyaliphatic substituted ethylenic copolymer is a family of amorphous fluoropolymers based on copolymers of 2,2- bistrifluoromethyl-4,5-difluoro-l,3-dioxole (PDD. Some fluoropolymers are known by their commercial names such as Teflon, Aflas, Vitom, Fluorel, Cytop, Karlez. Especially such fluoropolymers may be used as microporous polymeric material.

Especially, in embodiments the microporous polymeric material may comprise a microporous polycarbonate polymer. Alternatively or additionally, in embodiments the microporous polymeric material may comprise a microporous polyterephthalate polymer. The term “microporous polymeric material” may also refer to a combination of two or more different microporous polymeric materials. The reflectivity for visible radiation of the microporous polymeric material may especially be relatively high. In embodiments, the reflective material may have a porosity, such as due to air gaps between the fibers within the agglomerates. The microporous polymeric material may be in the form of continuous or cut ribbons and or fibers. The fibers may form agglomerates. In that case, the air gaps within the agglomerates may lead to light scattering.

In embodiments, the microporous polymeric material may be in the form of particles (particulate material).

Especially, in embodiments the microporous polymeric material may comprise pores having one or more dimensions selected from the range of 0.1-100 pm, such from the range of 1-100 pm , or from the range of 1-40 pm. For instance, pore sizes may be determined on the basis of mercury pressure porosimetry. More especially, in embodiments the microporous polymeric material may comprise pores having one or more dimensions selected from the range of 1-30 pm, such as selected from the range of 1-20 pm, like selected from the range of 1-10 gm. In specific embodiments, the median pore diameter may be selected from the range of about 0.1-10 pm, such as selected from the range of 0.5-10 pm. In other embodiments, the pore size of the pores of the microporous polymeric material may be selected from the range of 1-100 pm, such as selected from the range of 10-100 pm. In yet further embodiments, the average pore size may be selected from the range of 11-100 pm, such as selected from the range of 10-100 pm. Instead of the term “average pore size”, also the term “average pore diameter” may be applied. For an evaluation of the pore size of pore diameter, methods know in the art may be applied, such as mercury intrusion porosimetry. Especially, in embodiments the microporous polymeric material may have a porosity (volume void fraction) selected from the range of 5-99 %, such as from the range of 20-70%, like especially selected from the range of 30-60%, more especially selected from the range of about 35-50%. A porosity of about 35-45%, such as 37-43% may give a relatively high reflection.

In embodiments, the microporous polymeric material may substantially be white. Hence, in embodiments the reflectivity as function of the wavelength over the wavelength range of 400-680 nm, more especially over the wavelength range of 380-780 nm, may in average be over 75%, such as in average at least 80%, such as in average above 85%, such as especially at least 90% in average. Yet, in further specific embodiments the reflectivity may be in average at least 95% over the wavelength range of 400-680 nm, more especially within the wavelength range of 380-780 nm. Hence, here the term “average” may especially refer to the wavelength average of the reflectivity over the indicated wavelength range. The reflectivity may differ as function of the wavelength. However, especially within the wavelength range of 400-680 nm, a deviation of the average value is not larger than 15% (percentage points), such as not larger than 10% (percentage points). Hence, assuming an average reflectivity of 90%, the range within the reflectivity may vary assuming a deviation to be not larger than 15% would be 75-100% reflectivity (assuming the reflectivity cannot be larger than 100%). Especially, the reflectivity of the microporous polymeric material may be diffuse reflective.

Further, as indicated above, especially the reflective material may at least partly be enclosed by the polymeric matrix material. For instance, this may in embodiments be the reflective material being embedded as particulate material in the polymeric matrix material and/or this may in (other) embodiments be the reflective material being enclosed as core by a shell of the polymeric matrix material; see further also below. As indicated above, the method may further comprise depositing the 3D printable material, to provide the 3D item comprising 3D printed material comprising the matrix material and the reflective material. Therefore, in embodiments the polymeric matrix material and (ii) a reflective material may be provided, such as to a nozzle of a 3D printer (especially a FDM printer). This material may be deposited, such as on a substrate (or receiver item) (or on 3D printed material earlier printed on the substrate). Hence, the reflective material deposition stage may further comprise: depositing the 3D printable material, especially on a substrate (or receiver item) (or on 3D printed material earlier printed on the substrate). In this way, the method may provide the 3D item comprising 3D printed material comprising the matrix material and the reflective material. Hence, the 3D printable material has in this way been printed and essentially thereby become 3D printed material.

Basically there may be two options. In a first option, it is substantially not attempted to extrude the microporous polymeric material, but the microporous polymeric material is simply fed as fiber through the printer nozzle, e.g. in a core part of the nozzle. This can be done with a core-shell nozzle, but also with a nozzle with a single opening. The fiber may be guided through the nozzle and the 3D printable matrix material may substantially surround the microporous polymeric material (fiber). In a second option, the microporous polymeric material may be made more 3D printable, substantially without losing its reflectivity, by embedding microporous polymeric material particles in another matrix.

Hence, in embodiments the reflective material deposition stage may comprise (a) guiding a fiber (comprising the microporous polymeric material) through a 3D printer nozzle, while also (b) providing the polymeric matrix material to the 3D printer nozzle to provide core-shell 3D printed material. In such embodiments, the fiber may be guided through the 3D printer nozzle without melting and/or without substantial softening of the microporous polymeric material (e.g. by surpassing a possible melting temperature of the microporous polymeric material). This may be executed with a core-shell nozzle, or with a nozzle with a single opening; the former may allow an easier control of the reflective material deposition stage. The fiber may essentially consist of the microporous polymeric material, such as at least 90 vol.% of the fiber consisting of microporous polymeric material. In yet other embodiments, the fiber may have a core of a different material, and a coating or cladding of microporous polymeric material.

Alternatively or additionally, in embodiments the 3D printable material may comprise particulate material comprising the reflective material, wherein the particulate material may be embedded in the matrix material. The particles may e.g. have dimensions selected from the range of 1 pm - 1 mm, such as especially selected from the range of 1-500 pm. In specific embodiments, one or more dimensions may be selected from the range of 2- 100 pm. Especially, the particles may be smaller than the smallest dimension of a 3D printer nozzle opening through which the particles have to be transported. Further, especially the particles may have dimensions smaller than a height and/or a width of a 3D printed layer (to be printed) wherein the particles will be available, such as equal to or less than 80% of the height and/or a width of a 3D printed layer (to be printed) wherein the particles will be available. The term particulate material may especially refer to plurality of particles.

Especially, in embodiments the reflective material may comprise particulate material having particle lengths (LI), particle heights (L2) and/or particle widths (L3), with aspect ratios (i) Ll/L2>5, (ii) L3/L2>5, and Ll/L3<5. Further, especially also L3/L1<5. Hence, 0.2<Ll/L3<5. Especially, 0.5<Ll/L3<2. Hence, the particles of the particulate material may in embodiments be precision cut platelets.

Especially, LI and L3 may each individually be chosen from at least 20 pm, such as more especially at least 50 pm. Further, LI and L3 may each individually be chosen from at maximum 5 mm, such as more especially at maximum 2 mm, like at maximum 1 mm. Yet further, L2 may be chosen from at least 5 pm, such as at least 10 pm. Yet further, L2 may be chosen from at maximum 500 pm, such as at maximum 400 pm.

Especially, the herein indicated dimensions and/or ratios may apply to at least 50 weight% of the particulate reflective material, like at least 70 weight%, such as at least 80 weight%.

When using particulate material, it may be available in the entire 3D printable (and 3D printed material), like throughout the entire cross-section of a filament. However, it may also be concentrated in a core part, with a higher concentration in a core of the 3D printable material and 3D printed material, than in a shell. There may essentially be no microporous polymeric material comprising material in a shell of the 3D printable material and 3D printed material. This may allow using less microporous polymeric material while still having a good reflection. Hence, in embodiments the method may comprise depositing 3D printable material comprising a core and a shell, wherein the core may comprise the reflective material and wherein the shell may comprise the matrix material. In such embodiments, the core may comprise thermoplastic material, with reflective particulate material embedded therein. The thermoplastic material of the core and the shell may be the same or may be different.

Note that in embodiments the fiber of microporous polymeric material or the particles of microporous polymeric material may comprise agglomerates of fibers.

In embodiments, a fiber of microporous polymeric material may define the core of a filament. In embodiments, a fiber of microporous polymeric material may define the core of 3D printed layer.

The 3D printable material and the 3D printed material may consist for at least 90 vol% of the reflective material and the matrix material, such as at least 95 vol.%, more especially essentially 100 vol%. The 3D printable material and the 3D printed material may consist for at least 20 vol% of the reflective material and/or for at least 20 vol% of the matrix material, more especially for at least 30 vol% of the reflective material and/or for at least 30 vol% of the matrix material. Even more especially, the 3D printable material and the 3D printed material may consist for at least 40 vol% of the reflective material and/or for at least 30 vol% of the matrix material.

In embodiments, a layer of the 3D printed material may have a width (wl) and a height (hl). Especially, the width (wl) and a height (hl) may individually be selected from the range of 100 - 5000 pm, such as especially selected from the range of 100-3000 pm. Especially, the width (wl) and a height (hl) may individually be selected from the range 0.1- 10 mm, like at maximum 8 mm, such as in embodiments 0.1-3 mm.

Further, in specific embodiments the shell may have a largest shell width (wsmi). Especially, in embodiment the largest shell width (w_smi) may be selected from the range of 1-25% of the width (wl), even more especially, 2-15% of the width (wl), like in embodiments selected from the range of 5-15%. The core-shell option also allows providing better adhering layers, which adhere better to each other, while having a good reflection for visible radiation.

Layers may be stacked. In this way the 3D item may get a height (relative to the printing stage) of one or more, especially a plurality of layers stacked one on another. It is also possible to configure layers adjacent to each other. In this way, the 3D item or 3D item part, may get a thickness, which may be at least a layer thickness, such as the thickness of two or more layers. Part of at least one of the layers, such as an entire layer, may essentially consist of the matrix material and reflective material. Hence, part of at least one of the layers may comprise (other) 3D printed material. In embodiments, such part(s) of may be light absorbing, though this is not necessarily the case. Such part of at least one of the layers may comprise does thus not necessarily comprise the herein described reflective material. Such part of at least one of the layers may be available for support of the part of at least one of the layers, essentially consisting of the matrix material and reflective material. However, other functions may also possible. It may not be necessary that the entire 3D item is reflective for visible light.

As indicated above, the polymeric matrix material may be transmissive for visible radiation having one or more wavelengths selected from the range of 380-780 nm. Further, in embodiments the reflective material may be reflective for the visible radiation having the one or more wavelengths selected from the range of 380-780 nm. Especially, the polymeric matrix material, the reflective material, the relative amounts, the thickness of the 3D printed layer, etc. may be selected such that under perpendicular radiation with the visible radiation having the one or more wavelengths selected from the range of 380-780 nm a layer comprising the 3D printed material reflects at least 40% of the visible radiation having the one or more wavelengths selected from the range of 380-780 nm. Hence, in embodiments the polymeric matrix material may be transmissive for visible radiation having one or more wavelengths selected from the range of 380-780 nm, and wherein the reflective material is reflective for the visible radiation having the one or more wavelengths selected from the range of 380-780 nm; wherein polymeric matrix material, the reflective material, the relative amounts, the thickness of the 3D printed layer, etc. are selected such that under perpendicular radiation with the visible radiation having the one or more wavelengths selected from the range of 380-780 nm a layer comprising the 3D printed material reflects at least 40% of the visible radiation having the one or more wavelengths selected from the range of 380-780 nm. Percentage may refer to percentage of the spectral power (e.g. in Watts) of the visible radiation. In embodiments, the reflective material may be provided with a coating. This may prevent that the cavities of the reflective material are at least partly filled with the surrounding (thermoplastic) material. Especially, such reflective coating is light transmissive for at least part of the visible radiation. More especially, such reflective coating is light transparent for at least part of the visible radiation. Therefore, in embodiments the reflective material comprises a light transmissive coating (412) at least partly enclosing the microporous polymeric material, wherein the light transmissive coating (412) is light transmissive for at least part of the visible radiation. In embodiments, the particles may have such coating. Alternatively or additionally, when the reflective material is provided as core, the core may have such light transmissive coating. In embodiments, the coating may be provided via atomic layer deposition (ALD) and/or via a sol-gel coating process. Hence, in embodiments, the light transmissive coating may comprise one or more of an ALD coating and a sol-gel coating.

Alternatively or additionally, the light transmissive coating (412) may comprise a polymeric coating, wherein the polymeric coating (412) may in embodiments comprises thermoplastic material identical to the thermoplastic matrix material. Of course, the polymeric coating may alternatively (also) comprise thermoplastic material different from the thermoplastic matrix material. In specific embodiments, the polymeric coating may (alternatively) (also) comprise a thermoplastic material having a higher glass transition temperature than a glass transition temperature of the thermoplastic matrix material.

In specific embodiments, the light transmissive coating (412) may comprise an inorganic coating. For instance, the inorganic coating may in embodiments comprise one or more of alumina (AI2O3) and titania (TiCL). Such coatings may be provided via ALD and/or sol-gel synthesis. Especially, the inorganic coating may have a thickness selected from the range of 0.4-40 nm, such as especially 0.5-20 nm, like e.g. 1.5-20 nm. Therefore, in specific embodiments the light transmissive coating (412) may comprise an inorganic coating, wherein the inorganic coating comprises one or more of alumina and titania, and wherein the inorganic coating has a thickness selected from the range of 0.5-20 nm.

In other embodiments, the light transmissive coating may have a layer thickness selected from the range of up to about 100 pm, such as selected from the range of 0.4 nm - 100 pm. For instance, the light transmissive coating may have a layer thickness of at least 20 nm, such as at least 50 nm, like at least 100 nm. In specific embodiments, the light transmissive coating may have a thickness selected from the range of 0.01-100 pm, like 0.05- 100 pm, such as up to about 50 pm. Especially in the case of a polymeric light transmissive coating, the layer thickness may be at least 50 nm.

When using a coating, the pores may be protected from intrusion of the polymeric matrix material. Further, when using a coating, the reflective material may be protected - at least to some extend - against higher temperatures. Hence, the 3D printable material may in embodiments be 3D printed at higher temperatures than a glass transition temperature of the microporous polymeric material.

When using a polymeric coating, the polymeric coating may have a higher Tg than a glass transition temperature of the (reflective) microporous polymeric material. Alternatively, the polymeric coating may be a cross-linked material. Therefore, in embodiments the polymeric coating (412) may comprise one or more of (a) thermoplastic material having a higher glass transition temperature than a glass transition temperature of the thermoplastic matrix material, and (b) a cured polymer. Yet further, in embodiments the polymeric coating may in embodiments be selected such and a nozzle temperature may be selected such, that at the nozzle temperature, the polymeric coating is (substantially) not melted.

In embodiments, the coating may be a multi-layer coating, which may comprise two or more polymeric layers, or two or more inorganic layers, or a combination of one or more polymeric layers and one or more organic layers.

The reflection may be tuned by adding a colorant to the polymeric matrix material, such as a dye or a colorant. In this way the reflected light may have another spectral power distribution of the impinging (visible) light. The term “dye” may especially refer to an organic light absorbing material. For instance, in embodiments a dye may be molecularly dispersed in the thermoplastic matrix material. The term “colorant” may especially refer to a particulate light absorbing material, especially an inorganic material. Further, the terms “dye” and “colorant” may especially refer to materials that do not convert the absorbed light into visible luminescence, though in other embodiments this may be possible. However, especially the dye or a colorant may essentially be non-luminescent under irradiation with the visible light. By using a dye or a colorant, the polymeric matrix material may have a wavelength dependent transmission for the visible radiation. In this way, the 3D printed material may thus have a wavelength dependent reflection for the visible radiation. Hence, in embodiments the polymeric matrix material comprises one or more of a pigment and a dye, wherein the polymeric matrix material has a wavelength dependent transmission for the visible radiation. In embodiments, the microporous polymeric material has a porosity selected from the range about 35-45% (see also above).

Especially, in embodiments the microporous polymeric material may have a glass transition temperature T_r,_g, wherein the polymeric matrix material has one or more of a glass transition temperature T_m,g and a melting temperature T_m,m, wherein one or more of the following applies: (a) T_m,g< T_r,_g, and (b) T_m,g< T_r,_m. For instance, in embodiments one or more of the following applies: (a) T_m,_g< T_r,_g-10°C, and (b) T_m,_g< T_r,m-10°C, such as especially one or more of the following applies: (a) T_m,_g< T_r,_g-15°C, and (b) T_m,_g< T_r,m-15°C, more especially one or more of the following applies: (a) T_m,_g< T_r,_g-20°C, and (b) T_m,_g< T_r,_m- 20°C.

Yet, in further embodiments, (during operation) the nozzle temperature may be lower than the glass transition temperature T_r,_g of the microporous polymeric material but higher than the glass transition temperature T_m,g and/or the melting temperature T_m,m of the polymeric matrix material.

In embodiments, the polymeric matrix material may in embodiments be selected such that a glass transition temperature thereof is not larger than 50°C higher than a glass transition temperature of the microporous polymeric material. Further, the polymeric matrix material may in embodiments be selected such and a nozzle temperature may be selected such, that at the nozzle temperature, the polymeric matrix material is (substantially) not melted.

In specific embodiments the microporous polymeric material may have a glass transition temperature T_r,_g, selected from the range of 100-250 °C, such as especially selected from the range of 150-200 °C.

For instance, when microporous polyterephthalate polymer is applied, then especially the microporous polymeric material may have a glass transition temperature T_r,_g, selected from the range of 100-250 °C, more especially selected from the range of 150-200 °C.

In embodiments, the microporous polymeric material comprises a polyterephthalate polymer and the polymeric matrix material comprises a polymer having a relative low melting point, such as a low density polymer. In embodiments, the polymeric matrix material may comprise Tafrner, which may have a relatively low melting temperature and/or low glass transition temperature, and a good light transmission for light having a wavelength in the visible. In specific embodiments, one or more of the following applies, especially all of the following may apply: (A) the microporous polymeric material has a porosity selected from the range about 35-45%; (B) the reflective material comprises particulate material having particle lengths (LI), and particle heights (L2) and/or particle widths (L3), with aspect ratios (i) Ll/L2>5, (ii) L3/L2>5, and Ll/L3<5; (C) the polymeric matrix material comprises one or more of polycarbonate (PC), polyethylene (PE), high-density polyethylene (HDPE), polypropylene (PP), polyoxymethylene (POM), polyethylene naphthalate (PEN), styreneacrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), and semicrystalline polytethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), poly(methyl methacrylate) (PMMA), polystyrene (PS), and styrene acrylic copolymers (SMMA); and (D) the microporous polymeric material has a glass transition temperature T_r,_g, wherein the polymeric matrix material has one or more of a glass transition temperature T_m,g and a melting temperature T_m,m, wherein one or more of the following applies: (a) T_m,g< T_r,_g, and (b) Tm,g< Tr,m.

In specific embodiments, the microporous polymeric material may comprise a polycarbonate polymer and the polymeric matrix material comprises one or more of polymethylmethacrylate, polyethylene terephthalate, polystyrene, and a copolymer of one of these with polyethylene (PE). The polyethylene may especially be selected from LLDPE and LLDPE.

As indicated above, the reflective material may be comprised by particulate material or by a fiber. The particulate material may be embedded in the entire matrix material, or may be embedded in a core matrix material. The fiber may be proved as such, and thus be at least partly enclosed by the matrix material, or may in specific embodiments be enclosed by a core matrix material (which is on its turn at least partly enclosed by the matrix material.

Hence, in a first type of embodiments (the reflective material deposition stage of) the method comprises (a) guiding a fiber comprising the reflective material (especially without melting) through a 3D printer nozzle, while also (b) providing the polymeric matrix material to the 3D printer nozzle to provide core-shell 3D printed material.

Hence, in a second type of embodiments the 3D printable material may comprise particulate material comprising the reflective material, wherein the particulate material may be embedded in the thermoplastic matrix material. Such material may be 3D printed (extruded) via a single nozzle. In yet further specific embodiments, the method may comprise depositing 3D printable material comprising a core and a shell, wherein the core comprises the reflective material and a core thermoplastic material (optionally different from the thermoplastic matrix material), and wherein the shell comprises the matrix material.

Further, as indicated above, a layer of the 3D printed material may have a width (wl) and a height (hl), individually selected from the range of 0.1-10 mm; wherein the shell may have a largest shell width (w_smi), wherein the largest shell width (w_smi) is selected from the range of 2-15% of the width (wl).

The method may be used to produce reflectors, like hollow reflectors. Hence, in embodiments the 3D item may comprise a hollow reflector. The method may (thus) be used to produce a collimator, such as a hollow collimator. The 3D item may be a reflective collimator, like a hollow reflective collimator.

Here below, some further embodiments are described.

In embodiments of a core-shell filament or a core-shell layer, a cross-sectional parameter of the core of a core-shell filament or a core-shell layer may be selected from the range of 0.7-0.95 times the cross-sectional parameter of the filament or layer, respectively. The cross-section parameters may be defined along coinciding lines. This may provide a relatively high reflection but also a relatively good adhesion.

The cross-sectional parameter of the core of a core-shell filament or a coreshell layer may in embodiments be at least 0.5 mm and/or the cross-sectional parameter of the filament or layer, respectively, may be at maximum 3 mm. This may provide sufficient UV reflection, but may also allow acceptable material usage. A cross-sectional dimension of the core may in embodiments be selected from the range of 1.5-2.5, such as about 1.75-2.25 mm.

As indicated above, the method comprises depositing during a printing stage 3D printable material. Herein, the term “3D printable material” refers to the material to be deposited or printed, and the term “3D printed material” refers to the material that is obtained after deposition. These materials may be essentially the same, as the 3D printable material may especially refer to the material in a printer head or extruder at elevated temperature and the 3D printed material refers to the same material, but in a later stage when deposited. In embodiments, the 3D printable material may be printed as a filament and deposited as such. The 3D printable material may be provided as filament or may be formed into a filament. Hence, whatever starting materials are applied, a filament comprising 3D printable material may be provided by the printer head and 3D printed. The term “extrudate” may be used to define the 3D printable material downstream of the printer head, but not yet deposited. The latter may be indicated as “3D printed material”. In fact, the extrudate may be considered to comprises 3D printable material, as the material is not yet deposited. Upon deposition of the 3D printable material or extrudate, the material may thus be indicated as 3D printed material. Essentially, the materials may be the same material, as the thermoplastic material upstream of the printer head, downstream of the printer head, and when deposited, may essentially be the same material(s).

Herein, the term “3D printable material” may also be indicated as “printable material”. The term “polymeric material” may in embodiments refer to a blend of different polymers, but may in embodiments also refer to essentially a single polymer type with different polymer chain lengths. Hence, the terms “polymeric material” or “polymer” may refer to a single type of polymers but may also refer to a plurality of different polymers. The term “printable material” may refer to a single type of printable material but may also refer to a plurality of different printable materials. The term “printed material” may refer to a single type of printed material but may also refer to a plurality of different printed materials.

Hence, the term “3D printable material” may also refer to a combination of two or more materials. In general, these (polymeric) materials have a glass transition temperature T_g and/or a melting temperature T_m. The 3D printable material will be heated by the 3D printer before it leaves the nozzle to a temperature of at least the glass transition temperature, and in general at least the melting temperature. Hence, in a specific embodiment the 3D printable material comprises a thermoplastic polymer having a glass transition temperature (T_g) and /or a melting point (T_m), and the printer head action may comprises heating the 3D printable material above the glass transition and in embodiments above the melting temperature (especially when the thermoplastic polymer is a semi-crystalline polymer). In yet another embodiment, the 3D printable material comprises a (thermoplastic) polymer having a melting point (T_m), and the 3D printing stage may comprise heating the 3D printable material to be deposited on the receiver item to a temperature of at least the melting point. The glass transition temperature is in general not the same thing as the melting temperature. Melting is a transition which may occur in crystalline polymers. Melting may happen when the polymer chains fall out of their crystal structures, and become a disordered liquid. The glass transition may be a transition which happens to amorphous polymers; that is, polymers whose chains are not arranged in ordered crystals, but are just strewn around in any fashion, even though they are in the solid state. Polymers can be amorphous, essentially having a glass transition temperature and not a melting temperature or can be (semi) crystalline, in general having both a glass transition temperature and a melting temperature, with in general the latter being larger than the former. The glass temperature may e.g. be determined with differential scanning calorimetry. The melting point or melting temperature can also be determined with differential scanning calorimetry.

As indicated above, the invention may thus provide a method comprising providing a filament of 3D printable material and printing during a printing stage said 3D printable material on a substrate, to provide said 3D item.

Materials that may especially qualify as 3D printable materials may be selected from the group consisting of metals, glasses, thermoplastic polymers, silicones, etc. Especially, the 3D printable material comprises a (thermoplastic) polymer selected from the group consisting of ABS (acrylonitrile butadiene styrene), Nylon (or polyamide), Acetate (or cellulose), PLA (poly lactic acid), terephthalate (such as PET polyethylene terephthalate), Acrylic (polymethylacrylate, Perspex, polymethylmethacrylate, PMMA), Polypropylene (or polypropene), Polycarbonate (PC), Polystyrene (PS), PE (such as expanded- high impact- Polythene (or poly ethene), Low density (LDPE) High density (HDPE)), PVC (polyvinyl chloride) Polychloroethene, such as thermoplastic elastomer based on copolyester elastomers, polyurethane elastomers, polyamide elastomers polyolefine based elastomers, styrene based elastomers, etc.. Optionally, the 3D printable material may comprise a 3D printable material selected from the group consisting of Urea formaldehyde, Polyester resin, Epoxy resin, Melamine formaldehyde, thermoplastic elastomer, etc... Optionally, the 3D printable material may comprise a 3D printable material selected from the group consisting of a polysulfone. Elastomers, especially thermoplastic elastomers, may especially be interesting as they are flexible and may help obtaining relatively more flexible filaments comprising the thermally conductive material. A thermoplastic elastomer may comprise one or more of styrenic block copolymers (TPS (TPE-s)), thermoplastic polyolefin elastomers (TPO (TPE-o)), thermoplastic vulcanizates (TPV (TPE-v or TPV)), thermoplastic polyurethanes (TPU (TPU)), thermoplastic copolyesters (TPC (TPE-E)), and thermoplastic polyamides (TPA (TPE-A)).

Suitable thermoplastic materials, such as also mentioned in W02017/040893, may include one or more of polyacetals (e.g., polyoxyethylene and polyoxymethylene), poly(Ci-6 alkyl)acrylates, polyacrylamides, polyamides, (e.g., aliphatic polyamides, polyphthalamides, and polyaramides), polyamideimides, polyanhydrides, polyarylates, polyarylene ethers (e.g., polyphenylene ethers), polyarylene sulfides (e.g., polyphenylene sulfides), poly aryl sulfones (e.g., polyphenylene sulfones), polybenzothiazoles, polybenzoxazoles, polycarbonates (including polycarbonate copolymers such as polycarbonate-siloxanes, polycarbonate-esters, and polycarbonate-ester-siloxanes), polyesters (e.g., polycarbonates, polyethylene terephthalates, polyethylene naphtholates, polybutylene terephthalates, polyarylates), and polyester copolymers such as polyester-ethers), polyetheretherketones, polyetherimides (including copolymers such as polyetherimidesiloxane copolymers), polyetherketoneketones, polyetherketones, polyethersulfones, polyimides (including copolymers such as polyimide- siloxane copolymers), poly(Ci-6 alkyl)methacrylates, polymethacrylamides, polynorbornenes (including copolymers containing norbornenyl units), polyolefins (e.g., polyethylenes, polypropylenes, polytetrafluoroethylenes, and their copolymers, for example ethylene- alpha- olefin copolymers), polyoxadiazoles, polyoxymethylenes, polyphthalides, polysilazanes, polysiloxanes, polystyrenes (including copolymers such as acrylonitrile-butadiene-styrene (ABS) and methyl methacrylate-butadiene-styrene (MBS)), poly sulfides, poly sulfonamides, polysulfonates, polysulfones, polythioesters, polytriazines, polyureas, polyurethanes, polyvinyl alcohols, polyvinyl esters, polyvinyl ethers, polyvinyl halides, polyvinyl ketones, polyvinyl thioethers, polyvinylidene fluorides, or the like, or a combination comprising at least one of the foregoing thermoplastic polymers. Embodiments of polyamides may include, but are not limited to, synthetic linear polyamides, e.g., Nylon-6, 6; Nylon-6, 9; Nylon-6, 10; Nylon-6, 12; Nylon-11; Nylon-12 and Nylon-4, 6, preferably Nylon 6 and Nylon 6,6, or a combination comprising at least one of the foregoing. Polyurethanes that can be used include aliphatic, cycloaliphatic, aromatic, and polycyclic polyurethanes, including those described above. Also useful are poly(Ci-6 alkyl)acrylates and poly(Ci-6 alkyl)methacrylates, which include, for instance, polymers of methyl acrylate, ethyl acrylate, acrylamide, methacrylic acid, methyl methacrylate, n-butyl acrylate, and ethyl acrylate, etc. In embodiments, a polyolefine may include one or more of polyethylene, polypropylene, polybutylene, polymethylpentene (and co-polymers thereof), polynorbornene (and co-polymers thereof), poly 1 -butene, poly (3 -methylbutene), poly(4-m ethylpentene) and copolymers of ethylene with propylene, 1 -butene, 1 -hexene, 1 -octene, 1 -decene, 4-methyl-l -pentene and 1- octadecene.

In specific embodiments, the 3D printable material (and the 3D printed material) may comprise one or more of polycarbonate (PC), polyethylene (PE), high-density polyethylene (HDPE), polypropylene (PP), polyoxymethylene (POM), polyethylene naphthalate (PEN), styrene-acrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), and semi-crystalline polytethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), poly(m ethyl methacrylate) (PMMA), polystyrene (PS), and styrene acrylic copolymers (SMMA).

The term 3D printable material is further also elucidated below, but may especially refer to a thermoplastic material, optionally including additives, to a volume percentage of at maximum about 60%, especially at maximum about 30 vol.%, such as at maximum 20 vol.% (of the additives relative to the total volume of the thermoplastic material and additives).

The printable material may thus in embodiments comprise two phases. The printable material may comprise a phase of printable polymeric material, especially thermoplastic material (see also below), which phase is especially an essentially continuous phase. In this continuous phase of thermoplastic material polymer additives such as one or more of antioxidant, heat stabilizer, light stabilizer, ultraviolet light stabilizer, ultraviolet light absorbing additive, near infrared light absorbing additive, infrared light absorbing additive, plasticizer, lubricant, release agent, antistatic agent, anti-fog agent, antimicrobial agent, colorant, laser marking additive, surface effect additive, radiation stabilizer, flame retardant, anti-drip agent may be present. The additive may have useful properties selected from optical properties, mechanical properties, electrical properties, thermal properties, and mechanical properties (see also above).

The printable material in embodiments may comprise particulate material, i.e. particles embedded in the printable polymeric material, which particles form a substantially discontinuous phase. The number of particles in the total mixture may especially not be larger than 60 vol.%, relative to the total volume of the printable material (including the (anisotropically conductive) particles) especially in applications for reducing thermal expansion coefficient. For optical and surface related effect number of particles in the total mixture is equal to or less than 20 vol.%, such as up to 10 vol.%, relative to the total volume of the printable material (including the particles). Hence, the 3D printable material may especially refer to a continuous phase of essentially thermoplastic material, wherein other materials, such as particles, may be embedded. Likewise, the 3D printed material especially refers to a continuous phase of essentially thermoplastic material, wherein other materials, such as particles, are embedded. The particles may comprise one or more additives as defined above. Hence, in embodiments the 3D printable materials may comprises particulate additives.

The printable material may be printed on a receiver item. Especially, the receiver item can be the building platform or can be comprised by the building platform. The receiver item can also be heated during 3D printing. However, the receiver item may also be cooled during 3D printing.

The phrase “printing on a receiver item” and similar phrases include amongst others directly printing on the receiver item, or printing on a coating on the receiver item, or printing on 3D printed material earlier printed on the receiver item. The term “receiver item” may refer to a printing platform, a print bed, a substrate, a support, a build plate, or a building platform, etc... Instead of the term “receiver item” also the term “substrate” may be used. The phrase “printing on a receiver item” and similar phrases include amongst others also printing on a separate substrate on or comprised by a printing platform, a print bed, a support, a build plate, or a building platform, etc... Therefore, the phrase “printing on a substrate” and similar phrases include amongst others directly printing on the substrate, or printing on a coating on the substrate or printing on 3D printed material earlier printed on the substrate. Here below, further the term substrate is used, which may refer to a printing platform, a print bed, a substrate, a support, a build plate, or a building platform, etc., or a separate substrate thereon or comprised thereby.

Layer by layer printable material may be deposited, by which the 3D printed item may be generated (during the printing stage). The 3D printed item may show a characteristic ribbed structures (originating from the deposited filaments). However, it may also be possible that after a printing stage, a further stage is executed, such as a finalization stage. This stage may include removing the printed item from the receiver item and/or one or more post processing actions. One or more post processing actions may be executed before removing the printed item from the receiver item and/or one more post processing actions may be executed after removing the printed item from the receiver item. Post processing may include e.g. one or more of polishing, coating, adding a functional component, etc... Postprocessing may include smoothening the ribbed structures, which may lead to an essentially smooth surface.

Further, the invention relates to a software product that can be used to execute the method described herein. Therefore, in yet a further aspect the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by a fused deposition modeling 3D printer, is capable of bringing about the method as described herein.

Hence, in an aspect the invention (thus) provides a software product, which, when running on a computer is capable of bringing about (one or more embodiments of) the method (for producing a 3D item by means of fused deposition modelling) as described herein.

The herein described method provides 3D printed items. Hence, the invention also provides in a further aspect a 3D printed item obtainable with the herein described method. In a further aspect a 3D printed item obtainable with the herein described method is provided. Especially, the invention provides a 3D item comprising 3D printed material, wherein the 3D item comprises one or more layers of 3D printed material. Especially, at least part of the one or more layers may comprise 3D printed material comprising (i) a polymeric matrix material and (ii) a reflective material. Especially, the polymeric matrix material is transmissive for visible radiation. Further, in embodiments the polymeric matrix material may comprise thermoplastic matrix material. Especially, the reflective material may be reflective for at least part of the visible radiation. Yet further, the reflective material may at least partly enclosed by the polymeric matrix material. In specific embodiments, the reflective material may comprise a microporous polymeric material selected from the group of polycarbonate polymers and polyterephthalate polymers. Therefore, in embodiments the invention also provides a 3D item comprising 3D printed material, wherein the 3D item comprises a plurality of layers of 3D printed material, wherein at least part of the plurality of layers comprises 3D printed material comprising (i) a polymeric matrix material that is transmissive for visible radiation, wherein the polymeric matrix material comprises thermoplastic matrix material, and (ii) a reflective material that is reflective for at least part of the visible radiation and that is at least partly enclosed by the polymeric matrix material; wherein the reflective material comprises a microporous polymeric material selected from the group of polycarbonate polymers and polyterephthalate polymers.

Especially, the 3D item comprises one or more layers of 3D printed material. More especially, the 3D item comprises a plurality of layers of 3D printed material. The 3D item may comprise two or more, like at least 5, such as at least 10, like in embodiments at least 20 layers of 3D printed material.

The 3D printed item may comprise a plurality of layers on top of each other, i.e. stacked layers. The width (thickness) and height of (individually 3D printed) layers may e.g. in embodiments be selected from the range of 100 - 5000 pm, such as 200-2500 pm, with the height in general being smaller than the width. For instance, the ratio of height and width may be equal to or smaller than 0.8, such as equal to or smaller than 0.6.

Layers may be core-shell layers or may consist of a single material. Within a layer, there may also be a change in composition, for instance when a core-shell printing process was applied and during the printing process it was changed from printing a first material (and not printing a second material) to printing a second material (and not printing the first material).

At least part of the 3D printed item may include a coating.

Some specific embodiments in relation to the 3D printed item have already been elucidated above when discussing the method. Below, some specific embodiments in relation to the 3D printed item are discussed in more detail.

As indicated above, in embodiments the reflective material may comprise a light transmissive coating (412) at least partly enclosing the microporous polymeric material, wherein the light transmissive coating (412) may be light transmissive for at least part of the visible radiation. In specific embodiments, the light transmissive coating (412) may comprise a polymeric coating, wherein the polymeric coating (412) comprises thermoplastic material identical to the thermoplastic matrix material. In embodiments the inorganic coating may comprise one or more of alumina and titania, and wherein the inorganic coating may have a thickness selected from the range of 0.5-20 nm.

In embodiments, the polymeric matrix material may comprise one or more of a pigment and a dye, wherein the polymeric matrix material has a wavelength dependent transmission for the visible radiation (and wherein the 3D printed material has a wavelength dependent reflection for the visible radiation).

In specific embodiments, the microporous polymeric material may have a porosity selected from the range about 35-45%. In embodiments, an average pore size of pores of the microporous polymeric material may be selected from the range of 1-100 pm.

In embodiments, the microporous polymeric material may have a reflectivity of at least 80%, such as at least 85%. Especially, the microporous polymeric material may have an average reflectivity of at least 80% over the 400-680 nm wavelength range.

In embodiments, the reflective material may comprise particulate material having particle lengths (LI), and particle heights (L2) and/or particle widths (L3), with aspect ratios (i) Ll/L2>5, (ii) L3/L2>5, and Ll/L3<5.

In embodiments, the polymeric matrix material may comprise one or more of polycarbonate (PC), polyethylene (PE), high-density polyethylene (HDPE), polypropylene (PP), polyoxymethylene (POM), polyethylene naphthalate (PEN), styrene-acrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), and semi-crystalline polytethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), poly(m ethyl methacrylate) (PMMA), polystyrene (PS), and styrene acrylic copolymers (SMMA) In embodiments, the microporous polymeric material may have a glass transition temperature T_r,_g, wherein the polymeric matrix material has one or more of a glass transition temperature T_m,g and a melting temperature T_m,m, wherein one or more of the following applies: (a) T_m,g< T_r,_g, and (b) T_m,g< T_r,_m.

In embodiments, the microporous polymeric material may comprise a polycarbonate polymer and the polymeric matrix material may comprise one or more of polymethylmethacrylate, polyethylene terephthalate, polystyrene, and a copolymer of one of these with polyethylene.

In specific embodiments, at least part of the plurality of layers may comprise one or more of (i) core-shell 3D printed material comprising a core and a shell, wherein the core comprises a fiber comprising the reflective material, and wherein the shell comprises the polymeric matrix material, (ii) 3D printed material comprising particulate material, wherein the particulate material comprise the reflective material, wherein the particulate material is embedded in the thermoplastic matrix material; and (iii) core-shell 3D printed material comprising a core and a shell, wherein the core comprises the reflective material and a core thermoplastic material (optionally different from the thermoplastic matrix material), and wherein the shell comprises the matrix material.

When the particulate material is embedded in the thermoplastic matrix material, the particulate material may be distributed over the thermoplastic matrix. In embodiments, at least a part of the total number of particles of the particulate may be fully enclosed by the thermoplastic matrix. However, in embodiments a number of particles may also extend from the thermoplastic matrix.

The (with the herein described method) obtained 3D printed item may be functional per se. For instance, the 3D printed item may be a lens, a collimator, a reflector, etc... The thus obtained 3D item may (alternatively) be used for decorative or artistic purposes. The 3D printed item may include or be provided with a functional component. The functional component may especially be selected from the group consisting of an optical component, an electrical component, and a magnetic component. The term “optical component” especially refers to a component having an optical functionality, such as a lens, a mirror, a light transmissive element, an optical filter, etc... The term optical component may also refer to a light source (like a LED). The term “electrical component” may e.g. refer to an integrated circuit, PCB, a battery, a driver, but also a light source (as a light source may be considered an optical component and an electrical component), etc. The term magnetic component may e.g. refer to a magnetic connector, a coil, etc... Alternatively, or additionally, the functional component may comprise a thermal component (e.g. configured to cool or to heat an electrical component). Hence, the functional component may be configured to generate heat or to scavenge heat, etc...

As indicated above, the 3D printed item maybe used for different purposes. Amongst others, the 3D printed item maybe used in lighting. Hence, in yet a further aspect the invention also provides a lighting device comprising the 3D item as defined herein. In a specific aspect the invention provides a lighting system comprising (a) a light source configured to provide (visible) light source light and (b) the 3D item as defined herein, wherein 3D item may be configured as one or more of (i) at least part of a housing, (ii) at least part of a wall of a lighting chamber, and (iii) a functional component, wherein the functional component may be selected from the group consisting of an optical component, a support, an electrically insulating component, an electrically conductive component, a thermally insulating component, and a thermally conductive component. Hence, in specific embodiments the 3D item 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. As a relative smooth surface may be provided, the 3D printed item may be used as mirror or lens, etc... In embodiments, the 3D item may be configured as shade. A device or system may comprise a plurality of different 3D printed items, having different functionalities.

Returning to the 3D printing process, a specific 3D printer may be used to provide the 3D printed item described herein. Therefore, in yet a further aspect the invention also provides a fused deposition modeling 3D printer, comprising (a) a printer head comprising a printer nozzle, and (b) a 3D printable material providing device configured to provide 3D printable material to the printer head, wherein the fused deposition modeling 3D printer is configured to provide said 3D printable material according to the herein described method.

The printer nozzle may include a single opening. In other embodiments, the printer nozzle may be of the core-shell type, having two (or more) openings. The term “printer head” may also refer to a plurality of (different) printer heads; hence, the term “printer nozzle” may also refer to a plurality of (different) printer nozzles.

The 3D printable material providing device may provide a filament comprising 3D printable material to the printer head or may provide the 3D printable material as such, with the printer head creating the filament comprising 3D printable material. Hence, in embodiments the invention provides a fused deposition modeling 3D printer, comprising (a) a printer head comprising a printer nozzle, and (b) a filament providing device configured to provide a filament comprising 3D printable material to the printer head, wherein the fused deposition modeling 3D printer is configured to provide said 3D printable material to a substrate, according to the herein described method.

Especially, the 3D printer comprises a controller (or is functionally coupled to a controller) that is configured to execute in a controlling mode (or “operation mode”) the method as described herein. Instead of the term “controller” also the term “control system” (see e.g. above) may be applied.

The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior to the element (determining the behavior or supervising the running of an element), etc., such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc.. Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as “controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and element may not be physically coupled. Control can be done via wired and/or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which e.g. one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface.

The control system may also be configured to receive and execute instructions form a remote control. In embodiments, the control system may be controlled via an App on a device, such as a portable device, like a Smartphone or I-phone, a tablet, etc.. The device is thus not necessarily coupled to the lighting system, but may be (temporarily) functionally coupled to the lighting system.

Hence, in embodiments the control system may (also) be configured to be controlled by an App on a remote device. In such embodiments the control system of the lighting system may be a slave control system or control in a slave mode. For instance, the lighting system may be identifiable with a code, especially a unique code for the respective lighting system. The control system of the lighting system may be configured to be controlled by an external control system which has access to the lighting system on the basis of knowledge (input by a user interface of with an optical sensor (e.g. QR code reader) of the (unique) code. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, WIFI, LiFi, ZigBee, BLE or WiMAX, or another wireless technology.

The system, or apparatus, or device may execute an action in a “mode” or “operation mode” or “mode of operation”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operation mode” or “mode of operation” or “operational mode”. The term “mode” may also be indicated as “controlling mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and/or after executing the mode one or more other modes may be executed.

However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e. “on”, without further tunability).

Hence, in embodiments, the control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and/or a predetermined time scheme.

In yet a further aspect, the invention provides a method for producing a 3D item by means of 3D printing, such as fused deposition modelling (FDM, with a fused deposition modelling printer), or stereolithography (SL) printing (with a stereolithographic apparatus SLA), the method comprising a 3D printing stage, wherein the 3D printing stage may comprise a reflective material deposition stage, wherein the reflective material deposition stage may comprise: (A) providing 3D printable material comprising (i) a polymeric matrix material that is transmissive for UV radiation, especially wherein the polymeric matrix material may comprise thermoplastic material, and (ii) a reflective material that is reflective for the UV radiation and that is at least partly enclosed by the polymeric matrix material; wherein the reflective material may comprise a microporous polymeric material; and (B) depositing the 3D printable material, to provide the 3D item comprising 3D printed material comprising the matrix material and the reflective material. In yet a further aspect (or in yet further embodiments), the invention provides a method for producing a 3D item by 3D printing, such as fused deposition modelling or SLA printing, the method comprising (i) a 3D printing stage comprising layer-wise depositing (an extrudate comprising) 3D printable material, to provide the 3D item comprising 3D printed material (on a receiver item), wherein the 3D item may comprise a plurality of layers of 3D printed material, wherein the 3D printing stage may comprise a reflective material deposition stage, wherein the reflective material deposition stage may comprise: (A) providing 3D printable material comprising (i) a polymeric matrix material that is transmissive for UV radiation, especially wherein the polymeric matrix material may comprise thermoplastic material, and (ii) a reflective material that is reflective for the UV radiation and that is at least partly enclosed by the polymeric matrix material; wherein the reflective material may comprise a microporous polymeric material; and (B) depositing the 3D printable material, to provide the 3D item comprising 3D printed material comprising the matrix material and the reflective material. Stereolithography may be based on using light, such as UV radiation, to cure liquid resin into a solid object, in general one layer at a time. In this way, layer by layer a 3D item can be printed.

In yet an aspect, the invention also provides a filament, wherein the filament comprises (i) a polymeric matrix material that is transmissive for visible radiation, wherein the polymeric matrix material comprises thermoplastic matrix material, and (ii) a reflective material that is reflective for at least part of the visible radiation and that is at least partly enclosed by the polymeric matrix material; wherein the reflective material comprises a microporous polymeric material selected from the group of polycarbonate polymers and polyterephthalate polymers. Especially, in embodiments the reflective material is provided as particulate material or as a fiber. In specific embodiments, also a combination may be possible.

Instead of the term “fused deposition modeling (FDM) 3D printer” shortly the terms “3D printer”, “FDM printer” or “printer” may be used. The printer nozzle may also be indicated as “nozzle” or sometimes as “extruder nozzle”.

BRIEF DESCRIPTION OF THE DRAWINGS

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: Figs, la-lc schematically depict some general aspects of the 3D printer and of an embodiment of 3D printed material;

Fig. 2a-2b schematically depict some further aspects;

Fig. 3a-3g schematically depict some aspects of embodiments of particles, with some of the shapes being depicted for reference purposes;

Fig. 4 schematically depicts an application; and

Fig. 5 schematically depicts a further embodiment. The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. la 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).

Instead of a filament also pellets may be used as 3D printable material. Both can be extruded via the printer nozzle.

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).

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 may comprise 3D printable material 201, such as having a melting temperature T_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.

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.

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 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.

Reference Ax indicates a longitudinal axis or filament axis.

Reference 300 schematically depicts a control system. The control system may be configured to control the 3D printer 500. The control system 300 may be comprised or functionally coupled to the 3D printer 500. The control system 300 may further comprise or be functionally coupled to a temperature control system configured to control the temperature of the receiver item 550 and/or of the printer head 501. Such temperature control system 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.

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.

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

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

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 201. Reference D indicates the diameter of the nozzle (through which the 3D printable material 201 is forced). However, the nozzle is not necessarily circular.

Fig. lb 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 layers 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. Here, the layers have a flattened (circular) cross-section, 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).

Hence, Figs, la-lb 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, la-lb, 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. Downstream of the nozzle 502, the 3D printable material 201 becomes, when deposited, layer 322 with 3D printed material 202.

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. The layer width and/or layer height may also vary within a layer. Reference 252 in Fig. 1c indicates the item surface of the 3D item (schematically depicted in Fig. 1c).

Referring to Figs, la-lc, 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.

Fig. 2a very schematically depicts a number of embodiments how 3D printable material can be printed.

Amongst others, the invention provides a method for producing a 3D item 1 by means of fused deposition modelling. The method may comprise a 3D printing stage, wherein the 3D printing stage may comprise a reflective material deposition stage. Especially, the reflective material deposition stage may comprise: (a) providing 3D printable material 201 comprising (i) a polymeric matrix material 211 that is transmissive for visible radiation, wherein the polymeric matrix material 211 may comprise thermoplastic material, and (ii) a reflective material 212 that is reflective for the visible radiation and that is at least partly enclosed by the polymeric matrix material 211. Especially, the reflective material 212 may comprise a microporous polymeric material 213. Further, the reflective material deposition stage may comprise: (b) depositing the 3D printable material 201, to provide the 3D item 1 comprising 3D printed material 202 comprising the matrix material 211 and the reflective material 212.

The microporous polymeric material 213 may comprise microporous polymeric material 213 comprising pores having one or more dimensions selected from the range of 1-40 pm. For instance, the medial pore size may be 1-10 pm.

Referring to embodiments I-III in Fig. 2a, the reflective material deposition stage may comprise a guiding a fiber 240 (without melting) through a 3D printer nozzle 502, while also b providing the polymeric matrix material 211 to the 3D printer nozzle 502 to provide core-shell 3D printed material 202.

Referring to embodiments IV-VI, the 3D printable material 201 may comprise particulate material 250 comprising the reflective material 212, wherein the particulate material 250 is embedded in the matrix material 211. The term “particulate material” may especially refer to plurality of particles.

As schematically depicted, the method may comprise depositing 3D printable material 201 comprising a core 260 and a shell 270, wherein the core 260 may comprise the reflective material 212 (wherein the core 260 may comprise thermoplastic material,) and wherein the shell 270 may comprise the matrix material 211; wherein a layer 322 of the 3D printed material 202 has a width wl and a height hl, in embodiments individually selected from the range of 0.1-10 mm, like at maximum 8 mm, such as in embodiments 0.1-3 mm; wherein the shell 270 has a largest shell width w_smi, wherein the largest shell width w_smi may be selected from the range of 2-15% of the width wl. There may also be a minimum width, which is indicated with reference w_sm2. The minimum with may be zero, but may also be non-zero, like at least 10% of w_smi. Referring to embodiment VI of Fig. 2a, the cross-section parameters may be defined along coinciding lines.

Further, referring to Fig. 2a, embodiment VI, optionally the matrix material 211 may comprise a (particulate) filler material. Hence, the polymeric matrix material 211 may essentially consist of the thermoplastic material, but may in embodiments also comprise other materials, lile fillers, pigments, etc.

Embodiments VII and VIII schematically depict some further embodiments. In embodiment VII the 3D printable material 201 is provided as printable material pellets, which may be deformed in the printer head, especially the printer nozzle 502. The pellets of 3D printable material 201 may comprise the matrix material 211 that may comprise thermoplastic material, more especially may consist of thermoplastic material, with reflective material 212 in the form of particles embedded therein. In this way, a layer 322 of 3D printed material 202 is provided, wherein the particulate reflective material 212 may be available. In embodiment VIII a filament 320 is provided, which may comprise the matrix material 211 that may comprise thermoplastic material, more especially may consist of thermoplastic material, with reflective material 212 in the form of particles embedded therein.

The polymeric matrix material 211 may be transmissive for visible radiation having one or more wavelengths selected from the range of 380-780 nm, and the reflective material 212 may be reflective for the visible radiation having the one or more wavelengths selected from the range of 380-780 nm; wherein the polymeric matrix material, the reflective material, the relative amounts, the thickness (i.e. the width wl) of the 3D printed layer are selected such that under perpendicular radiation with the visible radiation having the one or more wavelengths selected from the range of 380-780 nm a layer 322 comprising the 3D printed material 202 reflects at least 40% of the visible radiation having the one or more wavelengths selected from the range of 380-780 nm.

Referring to Fig. 2b, the 3D item 1 may comprise a hollow reflector, such as a reflective collimator. Reference 11 indicates radiation, such as visible radiation. Reference O indicates an optical axis. The 3D item 1 may e.g. collimate the radiation 11. Fig. 2b also schematically depicts an embodiment wherein part of the 3D printed item is printed according to the reflective material deposition stage. The result thereof is (are) layer(s) 322. These may provide the inner surface of the 3D items 1 reflectivity for visible radiation 11. Another part of the 3D item may comprise a different type of 3D printed material 202. This layer / these layer(s) are indicated with reference 322’. The width wl (and/or the heights) may be different, but may also be the same. The width of the layer 322 printed according to the reflective material deposition stage is indicated with reference wl and the width of the layer 322’ not printed according to the reflective material deposition stage is indicated with reference wl’. For instance, the layer 322’ not printed according to the reflective material deposition stage may be (visible) light absorbing and/or may have other optical properties than the layers 322 printed according to the reflective material deposition stage.

Referring to e.g. Fig. 2b, the invention also provides a 3D item 1 comprising 3D printed material 202, wherein the 3D item 1 may comprise a plurality of layers 322 of 3D printed material 202, wherein at least part of the plurality of layers 322 may comprise 3D printed material 202 comprising (i) a polymeric matrix material 211 that is transmissive for visible radiation, and (ii) a reflective material 212 that is reflective for the visible radiation and that is at least partly enclosed by the polymeric matrix material 211; wherein the reflective material 212 may comprise a microporous polymeric material (213).

The microporous polymeric material (213) may comprise a microporous polytetrafluoroethylene, and wherein the microporous polymeric material (213) may comprise pores having one or more dimensions selected from the range of 1-40 pm.

In embodiments, at least part of the plurality of layers 322 may comprise coreshell 3D printed material 202, wherein the core-shell 3D printed material 202 may comprise a core 260 and a shell 270, wherein the core 260 may comprise a fiber 240 comprising the reflective material 212, and wherein the shell 270 may comprise the polymeric matrix material 211.

Hence, the thus obtained 3D printed material 202 may comprise a core 260 and a shell 270, wherein the core 260 may comprise the reflective material 212 and wherein the shell 270 may comprise the matrix material 211; and wherein one or more of the plurality of layers 322 of the 3D printed material 202 have a width wl and a height hl, individually selected from the range of 0.1-10 mm, like at maximum 8 mm, such as in embodiments 0.1-3 mm; wherein the shell 270 has a largest shell width w_smi, wherein the largest shell width w_smi is selected from the range of 2-15% of the width wl.

Fig. 3a schematically depicts for the sake of understanding particles and some aspects thereof.

The particles comprise a material 411, or may essentially consist of such material 411. The particles 410 have a first dimension or length LI. In the left example, LI 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 LI is the particle length. L2 and L3 can be seen as height and width. Of course, the particles may comprise a combination of differently shaped particles.

Figs 3b-3g schematically depict some aspects of the particles 410 and/or fibers 260. Some particles 410 have a longest dimension Al having a longest dimension length LI and a shortest dimension A2 having a shortest dimension length L2. As can be seen from the drawings, the longest dimension length LI and the shortest dimension length L2 have a first aspect ratio larger than 1. Fig. 3b 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.

Fig. 3c 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.

Note that the notations LI, L2, and L3, and Al, 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.

Fig. 3d schematically depicts in cross-sectional view a particle 410 including a coating 412. Especially, the coating is light transmissive for the visible light.

Fig. 3e 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 LI, L2 and L3.

Fig. 3f schematically depicts cylindrical, spherical, and irregularly shaped particles, which will herein in general not be used (see also above).

As shown in Figs. 3b-3f the terms “first dimension” or “longest dimension” especially refer to the length LI of the smallest rectangular cuboid (rectangular parallelepiped) enclosing the irregular shaped particle. When the particle is essentially spherical the longest dimension LI, the shortest dimension L2, and the diameter are essentially the same.

In embodiments, the reflective material comprises particulate material having particle lengths LI, and particle heights L2 and/or particle widths L3, with aspect ratios (i) Ll/L2>5, (ii) L3/L2>5, and Ll/L3<5.

Hence, the invention provides amongst others a method for producing a 3D item 1 by means of fused deposition modelling. The method may comprise (a 3D printing stage, wherein the 3D printing stage comprises a reflective material deposition stage, wherein the reflective material deposition stage comprises): providing 3D printable material 201 comprising (i) a polymeric matrix material 211 that is transmissive for visible radiation, wherein the polymeric matrix material 211 comprises thermoplastic matrix material, and (ii) a reflective material 212 that is reflective for at least part of the visible radiation and that is at least partly enclosed by the polymeric matrix material 211; wherein the reflective material 212 comprises a microporous polymeric material 213 e.g. selected from the group of polycarbonate polymers and polyterephthalate polymers; and depositing the 3D printable material 201, to provide the 3D item 1 comprising 3D printed material 202 comprising the matrix material 211 and the reflective material 212.

Especially, in embodiments the reflective material 212 comprises a light transmissive coating 412 at least partly enclosing the microporous polymeric material 213. The light transmissive coating 412 is especially light transmissive for at least part of the visible radiation. An embodiment of a coating 412 on particulate material 250 comprising the reflective material 212 is schematically depicted in embodiment I of Fig. 3g. An embodiment of a coating 412 on a fiber 240 comprising the reflective material 212 is schematically depicted in embodiment II of Fig. 3g. The coating thickness is indicated with reference dl.

In embodiments, the light transmissive coating 412 comprises a polymeric coating. Especially, the polymeric coating may comprise thermoplastic material having a higher glass transition temperature than a glass transition temperature of the thermoplastic matrix material, or wherein the polymeric coating comprises a cured polymer. In embodiments, the polymeric coating has a layer thickness selected from the range of 0.05- 100 pm. Alternatively or additionally, the light transmissive coating 412 may comprise an inorganic coating, wherein the inorganic coating may in specific embodiments comprise one or more of alumina and titania. The inorganic coating may have a thickness selected from the range of 0.5-20 nm.

The polymeric matrix material 211 may in embodiments comprises one or more of a pigment and a dye. Especially, the polymeric matrix material 211 may (thereby) have a wavelength dependent transmission for the visible radiation (and wherein the 3D printed material 202 has a wavelength dependent reflection for the visible radiation).

In embodiments, the microporous polymeric material 213 may have a porosity selected from the range about 35-45%. In embodiments, an average pore size of pores of the microporous polymeric material may be selected from the range of 1-100 pm. In embodiments, the microporous polymeric material 213 may have an average reflectivity of at least 80% over the 400-680 nm wavelength range. In embodiments, the method may comprise guiding a fiber 240 comprising the reflective material 212 (without melting) through a 3D printer nozzle 502, while also providing the polymeric matrix material 211 to the 3D printer nozzle 502 to provide coreshell 3D printed material 202.

In embodiments, the 3D printable material 201 may comprise particulate material 250 comprising the reflective material 212, wherein the particulate material 250 is embedded in the thermoplastic matrix material.

The invention also may thereby provide a 3D item 1 comprising 3D printed material 202, wherein the 3D item 1 comprises a plurality of layers 322 of 3D printed material 202, wherein at least part of the plurality of layers 322 comprises 3D printed material 202 comprising (i) a polymeric matrix material 211 that is transmissive for visible radiation, wherein the polymeric matrix material 211 comprises thermoplastic matrix material, and (ii) a reflective material 212 that is reflective for at least part of the visible radiation and that is at least partly enclosed by the polymeric matrix material 211; wherein the reflective material 212 comprises a microporous polymeric material 213 selected from the group of polycarbonate polymers and polyterephthalate polymers.

Fig. 4 schematically depicts an embodiment of a lamp or luminaire, indicated with reference 2, which may comprise 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 may comprise the light source 10). Hence, in specific embodiments the lighting device 1000 may comprise 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.

However, the 3D item 1 may also be a (hollow) reflector, like a collimator. An example is shown in Fig. 5.

The term “plurality” refers to two or more. 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%. The term “comprise” also includes 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". 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.

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.

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. 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”. 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 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. 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. 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.

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.

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_g or T_m of the material(s).

Claims

CLAIMS:

1. A method for producing a 3D item (1) by means of fused deposition modelling, the method comprising: providing 3D printable material (201) comprising (i) a polymeric matrix material (211) that is transmissive for visible radiation, wherein the polymeric matrix material (211) comprises thermoplastic matrix material, and (ii) a reflective material (212) that is reflective for at least part of the visible radiation and that is at least partly enclosed by the polymeric matrix material (211); wherein the reflective material (212) comprises a microcellular polymeric material (213) selected from the group of polycarbonate polymers and polyterephthalate polymers; and depositing the 3D printable material (201), to provide the 3D item (1) comprising 3D printed material (202) comprising the matrix material (211) and the reflective material (212).

2. The method according to claim 1, wherein the reflective material (212) comprises a light transmissive coating (412) at least partly enclosing the microcellular polymeric material (213), wherein the light transmissive coating (412) is light transmissive for at least part of the visible radiation.

3. The method according to claim 2, wherein the light transmissive coating (412) comprises a polymeric coating, wherein the polymeric coating comprises thermoplastic material having a higher glass transition temperature than a glass transition temperature of the thermoplastic matrix material, or wherein the polymeric coating comprises a cured polymer.

4. The method according to any one of the preceding claims 2-3, wherein the light transmissive coating (412) has a thickness selected from the range of up to 100 pm.

5. The method according to any one of the preceding claims, wherein the polymeric matrix material (211) comprises one or more of a pigment and a dye, wherein the polymeric matrix material (211) has a wavelength dependent transmission for the visible radiation.

6. The method according to any one of the preceding claims, wherein: the microcellular polymeric material (213) has a porosity selected from the range about 35-45%; wherein an average pore size of pores of the microcellular polymeric material is selected from the range of 1-100 pm; and wherein the microcellular polymeric material (213) has an average reflectivity of at least 80% over the 400-680 nm wavelength range; the reflective material (212) comprises particulate material having particle lengths (LI), and particle heights (L2) and/or particle widths (L3), with aspect ratios (i) Ll/L2>5, (ii) L3/L2>5, and Ll/L3<5; the polymeric matrix material (211) comprises one or more of polycarbonate (PC), polyethylene (PE), high-density polyethylene (HDPE), polypropylene (PP), polyoxymethylene (POM), polyethylene naphthalate (PEN), styrene-acrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), and semi-crystalline polytethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), poly(m ethyl methacrylate) (PMMA), polystyrene (PS), and styrene acrylic copolymers (SMMA); the microcellular polymeric material (213) has a glass transition temperature T_r,_g, wherein the polymeric matrix material (211) has one or more of a glass transition temperature T_m,g and a melting temperature T_m,m, wherein one or more of the following applies: (a) Tm,g< E-.g, and (b) Tm,g< Tr,m.

7. The method according to any one of the preceding claims, wherein the microcellular polymeric material (213) comprises a polycarbonate polymer and the polymeric matrix material (211) comprises one or more of polymethylmethacrylate, polyethylene terephthalate, polystyrene, and a copolymer of one of these with polyethylene.

8. The method according to any one of the preceding claims 1-7, wherein the method comprises (a) guiding a fiber (240) comprising the reflective material (212) through a 3D printer nozzle (502), while also (b) providing the polymeric matrix material (211) to the 3D printer nozzle (502) to provide core-shell 3D printed material (202).

9. The method according to any one of the preceding claims 1-7, wherein the 3D printable material (201) comprises particulate material (250) comprising the reflective material (212), wherein the particulate material (250) is embedded in the thermoplastic matrix material.

10. The method according to any one of the preceding claims 8-9, comprising depositing 3D printable material (201) comprising a core (260) and a shell (270), wherein the core (260) comprises the reflective material (212) and a core thermoplastic material, and wherein the shell (270) comprises the matrix material (211); wherein a layer (322) of the 3D printed material (202) has a width (wl) and a height (hl), individually selected from the range of 0.1-10 mm; wherein the shell (270) has a largest shell width (w_smi), wherein the largest shell width (w_smi) is selected from the range of 2-15% of the width (wl).

11. A 3D item (1) comprising 3D printed material (202), wherein the 3D item (1) comprises a plurality of layers (322) of 3D printed material (202), wherein at least part of the plurality of layers (322) comprises 3D printed material (202) comprising (i) a polymeric matrix material (211) that is transmissive for visible radiation, wherein the polymeric matrix material (211) comprises thermoplastic matrix material, and (ii) a reflective material (212) that is reflective for at least part of the visible radiation and that is at least partly enclosed by the polymeric matrix material (211); wherein the reflective material (212) comprises a microcellular polymeric material (213) selected from the group of polycarbonate polymers and polyterephthalate polymers.

12. The 3D item (1) according to claim 11, wherein the reflective material (212) comprises a light transmissive coating (412) at least partly enclosing the microcellular polymeric material (213), wherein the light transmissive coating (412) is light transmissive for at least part of the visible radiation.

13. The 3D item (1) according to any one of the preceding claims 11-12, wherein the polymeric matrix material (211) comprises one or more of a pigment and a dye, wherein the polymeric matrix material (211) has a wavelength dependent transmission for the visible radiation.

14. The 3D item (1) according to any one of the preceding claims 11-13, wherein at least part of the plurality of layers (322) comprises one or more of (i) core-shell 3D printed material (202) comprising a core (260) and a shell (270), wherein the core (260) comprises a fiber (240) comprising the reflective material (212), and wherein the shell (270) comprises the polymeric matrix material (211), (ii) 3D printed material (202) comprising particulate material (250), wherein the particulate material (250) comprise the reflective material (212), wherein the particulate material (250) is embedded in the thermoplastic matrix material; and (iii) core-shell 3D printed material (202) comprising a core (260) and a shell (270), wherein the core (260) comprises the reflective material (212) and a core thermoplastic material, and wherein the shell (270) comprises the matrix material (211).

15. A lighting device (1000) comprising the 3D item (1) according to any one of the preceding claims 11-14, wherein the 3D item (1) 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, wherein the lighting device (1000) comprises a light source (10) configured to generate visible radiation (11) having the one or more wavelengths selected from the range of 380-780 nm wherein the 3D item (1) is configured downstream of the light source (10).