Method for Making an Object

Abstract

This invention describes a method for making a three dimensional (3D) image by additive manufacturing using, as a light source, an off-the-shelf visual display screen. The invention also relates to apparatus for carrying out said methods.

Claims

1-41. (canceled)

42. A method for creating a 3-dimensional object, the method comprising forming more than two layers of a cured polymer by exposing liquid photopolymer to light emitted by a single liquid crystal display screen, wherein none of the light emitted by the screen is UV light, and wherein the photopolymer contains a visible light photoinitiator, the photoinitiator being organometallic or metallocene.

43. The method of claim 42, wherein the liquid crystal display screen is backlit by LEDs.

44. The method of claim 42, wherein the photoinitiator is a titanocene.

45. The method of claim 44, wherein the photoinitiator is bis(.eta.5-2,4-cylcopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) titanium.

46. The method of claim 42, wherein a transparent low surface energy coating is on the liquid crystal display screen.

47. The method of claim 46, wherein the coating is a silicone film.

48. The method of claim 46, wherein the coating is a film of transparent plastic.

49. The method of claim 42, wherein the photopolymer is in direct contact with the liquid crystal display screen or, where present, with a coating on the screen.

50. The method of claim 42, wherein the photopolymer is separated from the liquid crystal display screen by either a liquid layer or a gaseous layer.

51. The method of claim 42, wherein the visual display screen is comprised in a handheld device.

52. The method of claim 42, wherein the liquid crystal display screen is the screen of a device selected from: television, computer, tablet computer and mobile phone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

[0033] FIG. 1 shows an exemplary apparatus suitable for carrying out the methods of the invention.

[0034] FIG. 2 shows an alternative exemplary apparatus suitable for carrying out the methods of the invention.

[0035] FIG. 3 shows products made according to the methods of the invention and in particular according to the Examples.

[0036] FIG. 4 shows graphically the time to grow a 0.1 mm layer and time required to hold smallest possible detail with different % additions of titanocene (Irgacure 784).

DETAILED DESCRIPTION

[0037] The wavelength of the light is a length suitable to create polymerisation in the liquid polymer.

[0038] The electromagnetic radiation selectively exposes an area of a thin layer of the liquid, solidifying it to form the relevant layer of the shape that is being created. At the end of this process the solidified layer is recoated with more resin and the process is repeated to harden another layer of resin on the previous layer. The process is repeated until the three-dimensional object is complete. The shape of the cured polymer is determined by the shape of the images sequentially created on the screen.

[0039] When initially formed, the three-dimensional object may not be fully cured and may require post-curing by heat, immersion in a curative liquid or electromagnetic radiation, or a combination thereof.

[0040] Each new layer of cured polymer is formed, therefore, by applying uncured polymer to the previously formed cured layer, e.g. the partially cured layer. The uncured polymer may be applied by lowering the build platform into a vat of the liquid photopolymer and allowing it to cover the previous layer, by spraying the polymer onto the previous layer or by retracting the build platform from the imaging source in a vat of resin or other methods familiar to those skilled in the art. Typically, the object is moved away from the imaging source by a greater distance than a layer then returned to a distance of a single layer. It is possible to retract the build platform in one direction only, away from the imaging source by only the build layer thickness each time.

[0041] If new layers are formed at the top surface of the growing object, then after each irradiation step the object under construction is lowered into the vat, a new layer of resin is coated on top and a new irradiation step takes place. An example of this technique is described in U.S. Pat. No. 5,236,637 to Hull, herein incorporated by reference in its entirety. In this process the vat or container of liquid polymer must be at least as deep as the tallest object being created. After the final layer has been created the entire object will be below the level of the liquid.

[0042] If new layers are formed at the bottom of the growing object, then after each irradiation step, the object under construction must be separated from the bottom print platform in the vat, as a natural attraction will occur. An example of such a technique is described in U.S. Pat. No. 5,236,637 to Hull, herein incorporated by reference in its entirety. This technique eliminates the need for a deep vat in which the object is submerged, by instead lifting the object out of a relatively shallow tank. Care should be taken when separating the solidified layer from the bottom print platform due to physical and chemical interactions between the polymer and the base of the container. In small format printers this can attraction can be overcome by the use of low surface energy release layers based on silicone or fluorinated ethylene propylene film or similar.

[0043] FIG. 1. shows this configuration where 100 is a build platform upon which a 3D object 102 is being built from a liquid polymer 101, contained in a vat 105, illuminated with light from an LCD screen 103 which is separated from the polymer by a low surface energy (or release) layer 104. Here the build platform moves up away from the screen.

[0044] FIG. 2. shows the configuration where the build platform 200 supports the 3D object 202 which is built from the liquid polymer 201, contained in the vat 205, illuminated with light from the LCD screen 203 which is separated from the polymer by the release layer 204.

[0045] The adhesion of the object to the base of the container occurs in stereolithographic printers that build from the bottom upwards. U.S. Pat. No. 7,438,846 to Hendrik, herein incorporated by reference in its entirety, describes a method of overcoming this with an elastic separation layer used to achieve non-destructive separation of solidified material from the bottom print platform.

[0046] Commonly a coating that comprises or is polydimethylsiloxane (PDMS) can be applied to the base of the container, usually acrylic sheet. The PDMS coating creates a thin lubricating film of un-polymerized resin through its action as a polymerization inhibitor. This is thought to be caused by ability for silicones to retain oxygen in their surface which is a known inhibitor of photoinitiation. Alternatively, another polymerisation inhibitor, stabiliser or a combination of them may be applied to the base of the container.

[0047] It is also possible to use low surface energy films tightened over a frame or open-bottomed tray. These films can be any clear plastic such as polypropylene, polyester, polycarbonate, polyethylene etc with silicone particles that are grafted or nano-coated onto their surface. It is also possible to use transparent polytetrafluoroethylene (PTFE), a perfluoroalkoxy copolymer (PFA) film, a ethylene-chloro-trifluoro-ethylene film (ECTFE), a copolymer of ethylene & tetrafluoroethylene (ETFE) film, a polyvinylidene fluoride (PVDF) film.

[0048] It is possible to use a FEP film as the release layer applied tightly to a frame which also acts as the vat.

[0049] U.S. Pat. No. 5,569,349 to Almquist et al., herein incorporated by reference in its entirety discloses an apparatus and method for providing 3D objects through the principles of stereolithography using flowable materials. This patent also describes the use of support materials that are easily removable from the finished part. The apparatus directs a nozzle to selectively dispense polymer in the desired areas to form the object. The flow is then blocked, allowing the material to harden, and the next section is formed in the same manner. If the object requires support, a second material such as a wax, thermoplastic or hot melt glue can be used to fill the voids. By using a second material with a different melting point, the second material can be readily removed from the final part.

[0050] Stereolithographic 3D printers typically require relatively low viscosity polymer to enable the new layer of liquid polymer coating the object to be applied evenly and easily. This viscosity may be less than 5,000 cps at 25° C. and desirably less than 500 cps at 25° C. In practice as low a viscosity as possible is advantageous for ease of re-covering the build platform.

[0051] The use of photoinitiators in 3D printing that are responsive to visible light has been described in EP 2502728 to Kangtai et al herein incorporated by reference in its entirety. This describes light sources emitting visible light e.g., from about 475 nm to about 900 nm and gives examples of suitable photoinitiators that include: camphorquinone, 4,4′-bis(diethylamino) benzophenone, 4,4′-bis(N,N′-dimethylamino) benzophenone, bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide, metallocenes such as bis(ela 5-2-4-cyclopentadien-1-yl) bis[2,6-difluoro-3-(1H-pyrrol-1-yl) phenyl] titanium, and the visible light photoinitiators from Spectra Group Limited, Inc. such as H-Nu 470, H-Nu-535, H-Nu-635, H-Nu-Blue-640, and H-Nu-Blue-660.

[0052] Photoinitiators used in 3D printing typically act by free radical transfer or by cationic transfer of light energy. The polymers used in 3D printing, sometimes also referred to as resins, inks or polymers, are typically either urethane acrylate or epoxy acrylate chemistry. Urethane acrylates can include monomers and/or free radical polymerizable monomers, and a suitable initiator such as a free radical initiator, and combinations thereof. Examples include, but are not limited to, acrylics, methacrylics, acrylamides, styrenics, olefins, halogenated olefins, cyclic alkenes, maleic anhydride, alkenes, alkynes, carbon monoxide, functionalized oligomers, functionalized polyethylene glycols, etc., including combinations thereof. Examples of liquid resins, monomers and initiators include, but are not limited to those described in U.S. Pat. No. 8,232,043 to Bishop, herein incorporated by reference in its entirety, which references the use of liquid bis(acyl)phosphine oxide as a photoinitiator.

[0053] In some embodiments the polymerizable liquid comprises a free radical polymerizable liquid in which case an inhibitor may be oxygen, in other embodiments the polymerizable liquid comprises an acid catalyzed, or cationically polymerized polymerizable liquid. In such embodiments the polymerizable liquid comprises monomers containing groups suitable for acid catalysis, such as epoxide groups and vinyl ether groups. Suitable monomers include olefins such as methoxyethene, 4-methoxystyrene, styrene, 2-methylprop-1-ene, 1,3-butadiene, etc.; heterocyclic monomers (including lactones, lactams, and cyclic amines) such as oxirane, thietane, tetrahydrofuran, oxazoline, 1,3, dioxepane, oxetan-2-one, etc., and combinations thereof. A suitable photoacid generator (PAG) is included in the acid catalyzed polymerizable liquid, examples of which include, but are not limited to onium salts, sulfonium and iodonium salts, etc., such as diphenyl iodide hexafluorophosphate, diphenyl iodide hexafluoroarsenate, diphenyl iodide hexafiuoroantimonate, diphenyl p-methoxyphenyl triflate, diphenyl p-toluenyl triflate, diphenyl p-isobutylphenyl triflate, diphenyl p-tert-butylphenyl triflate, triphenylsulfonium hexafluororphosphate, triphenylsulfonium hexafluoroarsenate, triphenylsulfonium hexafiuoroantimonate, triphenylsulfonium triflate, dibutylnaphthylsulfonium triflate, etc., including mixtures thereof. U.S. Pat. No. 7,824,839 to Ober et al, herein incorporated by reference in its entirety which describes various PAGs.

[0054] Preferably, the screen used in the methods of the invention is an LCD screen. An LCD typically consists of an array of pixels. Each pixel consists of a layer of liquid crystal molecules aligned between two transparent electrodes and two polarizing filters (parallel and perpendicular), the axes of transmission of which are, in most of the cases, perpendicular to each other. Before an electric field is applied, the orientation of the liquid-crystal molecules is determined by the alignment at the surfaces of electrodes. In the most commonly used twisted nematic device, the surface alignment directions at the two electrodes are perpendicular to each other and so the molecules arrange themselves in a helical structure. This induces the rotation of the polarization of the incident light, and the device appears grey. If the applied voltage is large enough, the liquid crystal molecules in the centre of the layer are almost completely untwisted and the polarization of the incident light is not rotated as it passes through the liquid crystal layer. This light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, light can be allowed to pass through in varying amounts thus constituting different levels of grey.

[0055] Other than the visual display screen, the apparatus of the 3D printer used in this invention may in principle be the same as any machine commonly used in stereolithographic printers. The process of creating the layers may in principle be the same as in existing stereolithography systems, but has been modified for the invention.

[0056] Thus, the invention may provide an apparatus for creating a 3-dimensional object (i.e. a 3D printer), the apparatus comprising: [0057] a visual display screen suitable for human viewing; [0058] a vat for liquid photopolymer; [0059] a build platform having a build surface for use in the vat whilst stereolithographically printing a 3D object; and [0060] an actuator for varying the separation of the build surface and the visual display screen.

[0061] The apparatus may also comprise an image processor configured to control the visual display screen to display a sequence of photolithographic images. The apparatus may also comprise an actuation controller configured to control the actuator; wherein the image processor and actuation controller are configured to communicate to synchronise the display of photolithographic images and the varying the separation of the build surface and the visual display screen. It may be that the actuation controller is configured to monotonically increase the separation of the build surface and the visual display screen between successive stereolithographic exposures by a distance corresponding with a layer thickness of a 3D object to be printed. Alternatively, it may be that the actuation controller is configured to increase the separation of the build surface and the visual display screen between successive stereolithographic exposures by a distance greater than a layer thickness of a 3D object to be formed, and subsequently to reduce the separation by a second distance to provide a net increase in separation corresponding with a layer thickness of a 3D object to be formed. Where the screen forms part of a handheld device, the actuation controller that controls the actuator could be the processor in the handheld device (i.e. same processor as the image processor), or it could be a separate part of the printer, which communicates with the phone's processor to synchronise varying the separation and making the image exposures.

[0062] Further embodiments of the apparatus of the invention, and particularly of the visual display screen, are described elsewhere in this specification. In particular, it may be that the visual display screen is a liquid crystal display screen (LCD). It may be that the visual display screen is a single LCD screen. It may be that the visual display screen is backlit by LEDs. It may be that the visual display screen is selected from a light emitting diode type (LED), an organic light emitting diode type (OLED), a polymer light emitting diode type (PLED), an electroluminescent display type (ELD), and a plasma display panel type (PDP).

[0063] It may be that the visual display screen forms the base of the vat; and the 3D printer further comprises a low surface energy coating or film provided on the visual display screen. It may be that the vat is an open topped box in which the base of the box is the screen and in which four walls are arranged on top of the screen. It may be that the film is a silicone film. It may be that the film is a perfluoroalkoxy copolymer or a fluorinated ethylene propylene film. The film may be a perflouroalkoxy (PFA) film. PFA has a very low surface energy and provides high light transport with low levels of diffraction.

[0064] It may be that the a visual display screen is situated outside the vat whilst stereolithographically printing a 3D object, and the vat is transparent to at least part of the spectrum of light that is visible to the human eye or comprises a window that is transparent to at least part of the spectrum of light that is visible to the human eye. The build platform may comprise a plate having a surface, said surface being the build surface. The plate is typically made of a substance that has a considerably higher affinity for photopolymers than the base of the vat. The plate may, for example, be a glass plate. The plate is typically the same shape as the base of the vat. The plate may be the same size as the base of the vat. The plate may be slightly smaller than the base of the vat, e.g. from 85%-99% as large in one or all dimensions compared to the base of the vat.

[0065] The standard process of creating a 3D image is to take a digital 3D image using computer aided design/computer aided manufacturing (CAD/CAM) software, for example, Google's SketchUp or Caligari Corp's Truespace, which will then split this design into layers, typically 0.1 mm or smaller. It then sends a digital image of this layer to a display apparatus, in this case an LCD screen.

[0066] The length of time that the screen illuminates the image is determined by the rate of cure of the polymer. It is desirable that it is as short as time as possible, typically a number of seconds from 1 to 2520 seconds, more typically from 20 to 220 seconds or from 50 to 180 seconds. While exposure times of from 1 to 50 seconds (e.g. from 1 to 20 second) can generate images suitable for certain applications, these images are often underexposed for many applications. This invention typically uses longer times of the order of 60 to 180 seconds per layer 0.1 mm thick. Typically existing SLA machines require between 4 and 20 seconds to build a layer 0.1 mm thick. At the end of the illuminating sequence the print platform will move away from the screen in order to provide a space for the new layer to be created.

[0067] In practice it can be desirable to move the platform further away from the screen than the layer thickness to allow easy and fast passage of the polymer back into the gap. Here the platform will typically move away by the distance of small number of layers and then can optionally wait for a dwell time of a few seconds before returning to the separation distance of one build layer from the screen.

[0068] There are other methods used to enable easy screen detachment and to allow resin to flow back. It is possible to move the print platform away from the screen at an angle so the peel area is a line rather than the entire build area. It is possible that the build platform itself bends or is hinged so the detachment force is applied at an angle to the screen. It is possible to use a flexible inner lamina of transparent film that can be peeled back from the screen surface. It is also possible to inject resin to separate the platform from the screen with jets of liquid resin. The method of screen detachment is not critical to this invention and is not limited to these examples.

[0069] Typically the photosensitive resin is filled into a vat. The object will be created on a build platform which is immersed in the vat. The build platform can be moved in the vertical plane inside that vat of polymer. The build platform may be made from a light, strong and flexible material, suitably aluminium, stainless steel or rigid plastic. The build platform is typically made of a substance that has a considerably higher affinity for photopolymers than the base of the vat. The build platform may, for example, be made of glass. The surface of the build platform should be a material that the polymer will grow onto easily. The surface of the material may thus be roughened. It has been found that the good results can be obtained from using anodised aluminium with a surface that was slightly roughened. Alternatively the build platform could be formed from the same daylight active polymer that is used to make the 3D objects. In practice it has been found that it is desirable to exposes a number of solid layers first typically between 2 and 5 that will become an active base layer to grow the structure from.

[0070] Any suitable polymerisable compound can be used to construct the photopolymer in this invention. The photopolymer is typically a urethane acrylate or an epoxy acrylate, but could be any compound that is polymerisable under electromagnetic radiation. In this process a photopolymer was created by combining urethane oligomers with reactive monomers and photoinitiators. The photopolymer resin used in the formulation can be manufactured in a variety of manners known by anyone skilled in the art. The critical aspect is the addition of the correct photoinitiators in the correct concentrations so that they have the ability to absorb in the visible region of the electromagnetic spectrum and pass that energy on. The level of the photoinitiators can be at an amount, for example, from 0.1% to 10% by weight and more typically at levels of from 0.3 to 2.5% (e.g. from 0.3 to 1.3% or from 0.3 to 0.7%). More preferably, the photoinitiators will be present at an amount of from 0.7 to 1.5%, the percentages being calculated by weight of the total liquid photopolymer. It is desirable that the cure speed of the reaction is adjusted so that the rate of growth is as fast as practical. The rate of cure will determine the programmed time to create a layer of the desired thickness in the apparatus.

[0071] Experimentation has shown that organometallic and metallocene photoinitiators are suitable for the invention. These photoinitiators react mainly to the photons emitted from the blue pixels of the visual display screen. Other initiators tried so far have been unsuitable. Examples of suitable photoinitiators in certain embodiments include titanocene compounds, e.g. bis(cyclopentadienyl)titanium dichloride, bis(cyclopentadienyl)diphenyltitanium, bis(cyclopentadienyl)bis(2,3,4,5,6-pentafluoro-phen-1-yl)titanium, bis(cyclopenta-dienyl)bis(2,3,5,6-tetrafluorophen-1-yl)titanium, bis-(cyclopentadienyl) bis(2,4,6-trifluoropheny-1-yl)titanium, bis(cyclopentadienyl)bis(2,6-difluorophen-1-yl)titanium, bis(cyclopentadienyl)bis(2,4-difluorophen-1-yl)titanium, bis(methylcyclopenta-dienyl)bis(2,3,4,5,6-pentafluorophen-1-yl)titanium, bis(methyl-cycxlopentadienyl)-bis(2,3,5,6-tetrafluorophen-1-yl)titanium, bis(methylcyclopenta-dienyl)bis(2,4-difluoropheny-1-yl)titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(pyr-1-yl)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(methylsulfonamido)-phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-butylbiaroylamino)-phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-ethylacetylamino)phenyl]-titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-methylacetylamino)phenyl]-titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-ethylpropionylamino)phenyl]-titanium, bis(cy-clopentadienyl)bis[2,6-difluoro-3-(N-ethyl-(2,2-dimethylbutanoyl)-amino)phenyl]-titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-butyl-(2,2-dimethyl-butanoyl)-amino)phenyl-]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-pentyl-(2,2-dimethyl-butanoyl)amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-hexyl)-(2,2-dimethylbutanoyl)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-methylbutyrylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-methylpentanoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-ethylcyclohexylcarbonylamino)phenyl]titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(N-ethylisobutyrylamino)phenyl]titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2,2,5,5-tetramethyl-1,2,5-azadisilolidin-1-yl)phenyl]titanium, bis-(cyclo-pentadienyl)bis[2,6-difluoro-3-(octylsulfonamido)phenyl]titanium bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(4-tolylsulfonamido)phenyl]titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(4-dodecylphenylsulfonylamido)-phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(4-(1-pentylheptyl)phenylsulfonyl-amido)phenyl]titanium, bis-(cyclopentadienyl)bis[2,6-difluoro-3-(ethylsulfonylamido)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-((4-bromophenyl)sulfonylamido)-phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2-naphthylsulfonylamido)phenyl]titanium, bis-(cyclopentadienyl)bis[2,6-difluoro-3-(hexadecylsulfonylamido)phenyl]titanium, bis-(cyclopentadienyl)bis[2,6-difluoro-3-(N-methyl-(4-dodecylphenyl)sulfonylamido)-phenyl-]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-methyl-4-(1-pentylheptyl)-phenyl)sulfonylamido)]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-hexyl-(4-tolyl)sulfonylamido)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(pyrrol-idine-2,5-dion-1-yl)phenyl-]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3,4-dimethyl-3-pyrroli-dine-2,5-dion-1-yl)phenyl]titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(phthalimido)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-isobutoxycarbonylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(ethoxycarbonylamino)phenyl-]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-((2-chloroethoxy)carbonylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(phenoxycarbonylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3-phenylthioureido)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3-butyl-thioureido)phenyl-]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3-phenylureido)-phenyl]-titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3-butylureido)phenyl]tit-anium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N,N-diacetylamino)phenyl]-titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3,3-dimethylureido)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(acetylamino)phenyl]titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(butyrylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(decanoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(octadec-anoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(isobutyryl-amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2-ethylhexanoyl-amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2-methylbutanoyl-amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(pivaloylamino)-phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2,2-dimethylbutanoyl-amino-)phenyl-]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2-ethyl-2-methyl-heptan-oylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(cyclohexylcar-bonylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2,2-dimethyl-3-chloropropanoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3-phenylpropanoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2-chloromethyl-2-methyl-3-chloropropanoylamino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(3,4-xyloylamino)phenyl]titanium, bis(cyclopentadienyl)bis-[2,6-difluoro-3-(4-ethylbenzoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2,4,6-mesitylcarbonylamino)phenyl]titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(benzoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(3-phenylpropyl)benzoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(3-ethylheptyl)-2,2-dimethylpentanoylamino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-isobutyl-(4-toluyl)amino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-isobutylbenzoylamino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-cyclohexylmethylpivaloy-lamino)phenyl]titanium, bis-(cyclopentadienyl)bis[2,6-difluoro-3-(N-(oxolan-2-ylmethyl)benzoylamino)phenyl]-titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(3-ethylheptyl)-2,2-dimethyl-butanoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(3-phenyl-propyl-(4-toluyl)amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(oxolan-2-ylmethyl)-(4-toluyl)-amino)phenyl)titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(4-toluylmethyl)benzoylamino)phenyl]titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(N-(4-toluylmethyl)-(4-toluyl)amino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-butylbenzoylamino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-butyl-(4-toluyl)amino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-hexyl-(4-toluyl)amino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-(2,4-dimethylpentyl)-2-,2-dimethylbutanoylamino) phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2,4-dimethylpentyl)-2,2-dimethyl-pentanoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-((4-toluyl)amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2,2-dimethyl-pentanoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2,2-dimethyl-3-ethoxypropanoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(2,2-dimethyl-3-allyloxypropanoylamino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-allylacetylamino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(2-ethylbutanoylamino)phenyl]titanium, bis(cyclopenta-dienyl)bis(2,6-difluoro-3-(N-cyclohexylmethylbenzoy-lamino)phenyl]titanium, bis-(cyclopentadienyl)bis[2,6-difluoro-3-(N-cyclohexylmethyl-(4-toluyl)amino)phenyl]-titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(2-ethylhexyl)benzoylamino)-phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-isopropylbenzoylamino-)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-phenylpropyl)-2,2-dime-thylpentanoyl)amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-hexylbenzoylamino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-cyclohexylmethyl-2,2-dimethylpentanoyl)amino)phenyl-]titanium, bis(cyclopean-tadienyl)bis[2,6-difluoro-3-(N-butylbenzoyl-amino)-phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-(2-ethylhexyl)-2,2-dimethylpentanoyl)amino)phenyl]-titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-hexyl-2,2-dimethylpentanoyl-amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-isopropyl-2,2-dimethylpentanoylamino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-3-phenylpropyl)pivaloylamino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-butyl-2,2-dimethylpentanoylamino)phenyl]titanium, bis (cyclopentadienyl)bis[2,6-difluoro-3-(N-(2-methoxyethyl)benzoylamino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-benzylbenzoylamino)phenyl]titanium, bis-(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-benzyl-(4-toluyl)amino)phenyl]titanium, bis-(cyclopean-tadienyl)bis[2,6-difluoro-3-(N-(2-methoxyethyl)-(4-toluyl)amino)phenyl-]titan-ium, bis-(cyclopentadienyl)bis[2,6-difluoro-3-(4-methylphenylmethyl)-2,2-dimethyl-pentan-oylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(2-methoxyethyl)-2,2-dimethylpentanoylamino)phenyl]titanium, bis(cyclopentadienyl) bis[2,6-difluoro-3-(N-cyclohexylmethyl-(2-ethyl-2-methylheptanoyl)aminophenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-butyl-(4-chlorobenzoyl)amino)phenyl]titanium, bis-(cyclopentadienyl)bis[2,6-difluoro-3-(N-hexyl-(2-ethyl-2-methylbutanoyl-)amino)-phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-cyclohexyl-2,2-dimethyl-pentanoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(oxolan-2-ylmethyl)-2,2-dimeth-ylpentanoyl)amino)phenyl]titanium, bis(cyclopentadienyl)-bis-[2,6-difluoro-3-(N-cyclohexyl-(4-chlorobenzoyl)am-ino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-cyclohexyl-(2-chlorobenzoyl)amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3,3-dimethyl-2-azetidinon-1-yl)phenyl]tit-anium, bis(cyclopentadienyl)bis(2,6-difluoro-3-isocyanatophenyl)titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-ethyl-(4-tolylsulfonyl)amino)phenyl]titanium, bis-(cyclopentadienyl)bis[2,6-difluoro-3-(N-hexyl-(4-tolylsulfonyl)amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-butyl-(4-tolylsulfonyl)amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-isobutyl-(4-tolylsulfonyl)amino)phenyl]-titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-butyl-(2,2-dimethyl-3-chloropr-opanoyl)amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(3-phenyl-propanoyl)-2,2-dimethyl-3-chloropropanoyl)amino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-cyclohexylmethyl-(2,2-dimethyl-3-chloro-propan-oyl)amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-isobutyl-(2,2-dimethyl-3-chloropropanol)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-butyl-(2-chloromethyl-2-methyl-3-chloropropanoyl)amino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(butylthiocarbonylamino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(phenylthiocarbonylamino)phenyl)titanium, bis(methyl-cyclopentadienyl)bis[2,6-difluoro-3-(N-hexyl-2,2-dimethylbutanoyl)amino-)phenyl]tit-anium, bis(methylcyclopentadienyl)bis[2,6-difluoro-3-(N-hexyl-2,2-dimethylpenta-noylamino)phenyl)titanium, bis(methylcyclopentadienyl)bis[2,6-difluoro-3-(N-ethyl-acetytlamino)phenyl-]titanium, bis(methylcyclopentadienyl)bis[2,6-difluoro-3-(N-ethylpropionylamino)phenyl]titanium, bis(trimethylsilylpentadienyl)bis[2,6-difluoro-3-(N-butyl-2,2-dimethylpro-panoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(2-methoxyethyl)-trimethylsilylamino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-butylhexyldimethylsilylamino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-ethyl-(1,1,2-trimethylpropyl)dimethylsilylamino)-phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3-ethoxymethyl-3-methyl-2-azethi-odinon-1-yl)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3-allyl-oxymethyl-3-methyl-2-azet-idinon-1-yl)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(3-chloromethyl-3-methyl-2-azetid-inon-1-yl)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-benzyl-2,2-dimethylpropanoylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(5,5-dimethyl-2-pyrrodininon-1-yl)phenyl-]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(6,6-diphenyl-2-piperidinon-1-yl)-phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(2,3-dihydro-1,2-benzo-isothiaz-ol-3-one(1,1-dioxide)-2-yl)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-hexyl-(4-chlorobenzoyl)amino)phenyl]titanium, bis(cyclopenta-dienyl)-bis[2,6-difluoro-3-(N-hexyl-(2-chlorobenzoyl)amino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-isopropyl-(4-chlorobenzoyl)amino)phenyl]titanium, bis-(cyclopentadienyl)bis[2,6-difluoro-3-(N-(4-methylphenylmethyl)-(4-chlorobenzoyl)-amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(4-methylphenyl-methyl)-(2-chlorobenzoyl)amino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-benzyl-2,2-dimethylpentanoylamino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-(2-ethylhexyl)-4-tolyl-sulfonyl)amino)phenyl]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-(3-oxaheptyl)benzoylamino)phenyl-]titanium, bis(cyclopenta-dienyl)bis[2,6-difluoro-3-(N-(3,6-dioxadecyl)benzo-ylamino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(trifluoromethyl-sulfonyl)amino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(trifluoro-acetylamino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(2-chloro-benzo-yl)amino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(4-chlorobenzoyl)-amino)phenyl]titanium, bis(cyclo-pentadienyl)bis[2,6-difluoro-3-(N-(3,6-dioxadecyl)-2,2-dim-ethylpenta-noylamino)phenyl]titanium, bis(cyclopentadienyl)bis[2,6-difluoro-3-(N-(3,7-dimethyl-7-methoxyoctyl)benzoylamino)phenyl]titanium, and bis(cyclo-pentadienyl)bis[2,6difluoro-3-(N-cyclohexylbenzoylamino)phenyl]titanium.

[0072] In certain embodiments, the composition further comprises an activator which can be used together with a photoinitiator to enhance curing efficiency. In one embodiment, the activators may comprise tertiary amine and sulfinate compounds. Examples of activators which could be used in the present invention include, but are not limited to, e.g. ethyl 4-(N,N-dimethylamino) benzoate, 2-(ethylhexyl)-4-(N,N-dimethylamino) benzoate, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminophenethyl alcohol, sodium benzenesulfinate, and sodium toluenesulfinate. In another embodiment the metallocene compound was used in conjunction with Eosin Y or 2′,4′,5′,7′-Tetrabromofluorescein acid to enhance its reactivity to photons emitted from the green pixels.

[0073] It was found desirable to use a metallocene composition containing bis(.eta.5-2,4-cylcopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) titanium.

[0074] In certain embodiments, the composition further comprises one or more performance-enhancing additives including, for example, esters of acrylic or methacrylic acid, stabilisers, defoamers, dyes and high molecular weight fatty acids. Examples of fatty acids which are particularly effective in ensuring a dry, tack-free surface after post-curing of the washed plate include, for example, myristic acid.

EXAMPLES

[0075] Various aspects of the invention will now be particularly described with reference to the following examples:

Example 1—Exemplary Apparatus and Method

[0076] A 3D printer was constructed in the following manner, a central processing unit was programmed with the driver software and connected to a drive motor that vertically raised or declined a platform by small increments, typically 0.1 mm. The image to be printed was a detailed chess piece which was scanned using 3D scanning software such as reconstructme.net from Profactor and created using Google SketchUp from Google Inc. The resultant computer image file was stored in stereolithography format (STL).

[0077] The image was split into slices that were 0.1 mm thick and these images were sent sequentially to the screen as black and white files. The length of time the image was displayed on the screen, the illuminating time, was a constant for all the image slices after the first layer. This was calculated as the time required for the chosen screen to polymerise 0.1 mm of the liquid polymer.

[0078] A VGA type 4:3 resolution 8″ LCD colour monitor with VGA BNC AV Port, manufactured by Samsung was used, this screen provided a 800 (horizontal)×600 pixel resolution (vertical) with a viewing area of 162 mm wide by 121.5 mm high and a viewing angle of 130 degrees high by 115 degrees vertically. The brightness of the screen was 300 cd/sqm.

[0079] To create a release layer on the surface of the LCD screen a total of 60 g of Silguard 184 manufactured by Dow, a 2 part reactive silicone, was mixed thoroughly, de-aerated and poured over the screen to create a low surface energy surface for easy detachment of the polymer from the screen. This gave a thickness of 1 mm evenly cured over the screen. The screen was left at 40 C for 48 hours to fully cure.

[0080] A flat aluminium platform 75 mm×45 mm perforated with holes was mounted onto a belt driven motor so that it could be raised and lowered in the vertical plane by increments of 0.1 mm. An open-topped and open-bottomed polymer containment vessel or vat was sealed around the edge of the top of the LCD screen which could contain liquid in a leak-proof manner. The vat was large enough to take the print platform.

[0081] 500 g of the light polymerisable compound was composed in the following manner. A glass vessel was loaded with 325 g of Genomer 4302, an aliphatic polyester triurethane, manufactured by Rahn AG of Switzerland, 130 g of TEDGMA (tri-ethylene dimethacrylate) a reactive diluent manufactured by Sartomer under the trade SR205 to it, 40 g of TMPTMA (trimethylolpropane trimethacrylate) a reactive diluent manufactured by Sartomer under the trade SR350 and 5.0 g of (bis(.eta.5-2,4-cylcopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) titanium) a photoinitiator manufactured by BASF under the trade name Irgacure 784. They were mixed at 60° C. for a total of 3 hours and allowed to cool.

[0082] The photopolymer liquid was poured into the vat. The print platform with the adhesive sheet on, with its sticky side facing down, was lowered down onto the screen and this point was taken as the zero point. It was then backed off by 0.5 mm by the motor and the first exposure was commenced. The first image was an extended exposure time to ensure that any fine detail is formed and adhered to the print platform. This first time was set to 2 minutes. After this the normal exposure cycle was started.

[0083] The print platform was lowered from its previous exposure position by 0.5 mm to allow polymer to re-fill the cavity. It can be lowered in the motor's fast setting to save time. The motor then stopped and reversed to bring the platform back up to the same position as before, but 0.1 mm lower, i.e. a reversal of 0.4 mm. The second image was exposed on the screen for 15 seconds, the print platform was again lowered by 0.5 mm and the process repeated.

[0084] The 3D printer could be positioned in two orientations, with the LCD screen at the top with the build platform below where the platform moves sequentially lower and further away from the screen as the image grows. It could also be positioned with the LCD screen at the bottom with the build platform above it where the build platform moves upwards away from the LCD screen. In both formats the build platform is immersed in a vat of liquid polymer.

[0085] Thus the image could be formed in layers, each one being created in proximity to the screen. The print platform is then moved away by a multiple of the layers or separation distance and the cavity created is replaced by liquid polymer. This method is repeated until the final slice of the image was exposed and the image is completed. The print platform and 3D object was removed from the polymer vat. The 3D image was washed in water and detergent to remove liquid polymer and was treated to post treatment of 10 minutes post curing by immersing the object in water and subjecting it to UV exposure of an intensity of 1.5 mW/cm2. The chess piece was composed of 657 0.1 mm layers and is shown in FIG. 3A.

[0086] While a satisfactory image was generated using the above conditions, at a level of curing that would be satisfactory for certain applications, the chess piece made in this example was found to be underexposed showing no evidence of the internal helical staircase for example. The above process was repeated, except the layer exposure time was set to 55 seconds. This resulted in a perfectly exposed version of the tower showing the external brickwork and the internal staircase and helix as shown in FIG. 3B.

Example 2—Faster Formulation

[0087] To investigate the optimised rate of growth of the polymer under LCD illumination with different levels of addition of bis(.eta.5-2,4-cylcopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) titanium (titanocene made by BASF under the tradename Irgacure 784), 500 g of a standard polymer formulation was made to test it in. A glass vessel was loaded with 325 g of Genomer 4302, an aliphatic polyester triurethane, manufactured by Rahn AG of Switzerland, 130 g of TEDGMA (tri-ethylene dimethacrylate) a reactive diluent manufactured by Sartomer under the trade SR205 to it, 45 g of TMPTMA (trimethylolpropane trimethacrylate) a reactive diluent manufactured by Sartomer under the trade SR350. To this, the following percentages of bis(.eta.5-2,4-cylcopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) titanium) were separately added, 0.1%, 0.2%, 0.3%. 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% and 1.5%. Each composition was mixed at 60° C. for a total of 3 hours and allowed to cool.

[0088] Each compound was filled into the vat and using the standard 3D method described in example 1, the amount of time required to fully create a 1 mm build layer was found. This time was the minimum time to create a layer successfully and was found by iterative experimentation. These results are shown in tabular format in Table 1 below:

TABLE-US-00001 Effect of varying addition concentration of Titanocene with time Minimum time to hold detail Time to hold all % addition at 0.1 mm thickness possible detail of Titanocene (underexposed) at 0.1 mm thickness 0.1 42 175 0.2 27 152 0.3 21 129 0.4 18 116 0.5 16 97 0.6 19 85 0.7 22 73 0.8 25 69 0.9 29 55 1 34 57 1.1 39 67 1.2 45 77 1.3 48 80 1.4 50 90 1.5 60 100

[0089] These results are shown in graphical format in FIG. 4.

[0090] It was found that the optimal rate of cure was obtained when approximately 0.9% of the photopolymer was the initiator.

Example 3—Silicone Coated Screen

[0091] 500 g of the light polymerisable compound was composed in the following manner. A glass vessel was loaded with 325 g of Genomer 4302, an aliphatic polyester triurethane, manufactured by Rahn AG of Switzerland, 130 g of TEDGMA (tri-ethylene dimethacrylate) a reactive diluent manufactured by Sartomer under the trade SR205 to it, 41.25 g of TMPTMA (trimethylolpropane trimethacrylate) a reactive diluent manufactured by Sartomer under the trade SR350 and 3.75 g of (bis(.eta.5-2,4-cylcopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) titanium) a photoinitiator manufactured by BASF under the trade name Irgacure 784. They were mixed at 60° C. for a total of 3 hours and allowed to cool.

[0092] The LCD screen was a VGA type 4:3 resolution 8″ LCD colour monitor with VGA BNC AV Port, manufactured by Samsung. It provided a 800 (horizontal)×600 pixel resolution (vertical) with a viewing area of 162 mm wide by 121.5 mm high and a viewing angle of 130 degrees high by 115 degrees vertically. The brightness of the screen was 300 cd/sqm.

[0093] A release layer for the LCD screen was created covering it with a suitable curable silicone compound. A total of 60 g of Silgaurd 184, a 2 part reactive silicone, manufactured by Dow Corporation was mixed thoroughly, de-aerated and poured over the LCD screen to create a low surface energy surface for easy detachment of the polymer from the screen. This provided a 1 mm thickness of silicone evenly cured over the screen. The screen was left at 40 C for 48 hours to fully harden and be dry to touch.

[0094] A flat aluminium platform 75 mm×45 mm perforated with holes was mounted to a belt driven motor so that it could be elevated and declined in the vertical plane by increments of 0.1 mm.

[0095] A total of 16.9 g of the photopolymer was poured in a tray the size of the print platform. It was cured with daylight to form a level solid sheet of exposed polymer. It was not post exposed under water, so the upper surface contained open, not fully cross-linked chains. This sheet was attached to the print platform using 9088 double sided tape manufactured by 3M Corporation.

[0096] An open-topped and open-bottomed polymer containment vat was made from Perspex (trademark of Dupont) to the inner dimensions of the screen. It was sealed around its base to the top of the LCD screen with the same silicone, such that it could contain the liquid polymer in a leak-proof manner. The container was large enough to take the print platform and elevate it to a total of 10 cm high.

[0097] 500 g of the photopolymer liquid was poured into the container. The print platform with the adhesive sheet on, with the sticky side facing down, was lowered down onto the screen and this point was taken as the starting or zero point.

[0098] The object to be printed was an open lattice of a sphere. It was scaled by a half of its original size so that the final object would be 5 cm in diameter, comfortably within the dimensions of the print platform. The print platform was then moved 0.5 mm away from the screen and the first exposure was started. The first exposure was an extended exposure time to ensure that any fine detail is formed and successfully adhered. This first time was set to 2 minutes. After this the normal exposure cycle commenced.

[0099] The print platform was lowered from its previous exposure position by 0.5 mm to allow polymer to re-fill the cavity. It was lowered in the motor's fast setting to save time. The motor then stopped and reversed to bring the platform back up to the same position as before, but 0.1 mm lower, i.e. a reversal of 0.4 mm. The second image was exposed on the screen for 24 seconds, and the process was repeated.

[0100] A total of 347 layers were made and the resultant 3D image created was shown in FIG. 3C.

[0101] While a satisfactory image was generated using the above conditions, at a level of curing that would be satisfactory for certain applications, the sphere made in this example was found to be underexposed for many applications.

Example 4 Using FEP Film Instead of Silicone

[0102] 500 g of the light polymerisable compound was composed in the following manner. A glass vessel was loaded with 325 g of Genomer 4302, 130 g of TEDGMA to it, 40.5 g of TMPTMA and 4.5 g of titanocene They were mixed at 60° C. for a total of 3 hours and allowed to cool.

[0103] The LCD screen was a VGA type 4:3 resolution 8″ LCD colour monitor with VGA BNC AV Port. It provided a 800 (horizontal)×600 pixel resolution (vertical) with a viewing area of 162 mm wide by 121.5 mm high and a viewing angle of 130 degrees high by 115 degrees vertically. The brightness of the screen was 400 cd/sqm.

[0104] An open bottomed rectangular tray of base dimensions 162 mm by 121.5 mm was constructed from 4 mm thick clear cast acrylic sheet, the sheet was 100 mm wide, creating the depth of the vat. A sheet of 12 μm FEP film, manufactured by Dupont, was sealed around the frame to leave a taught, sealed base of the film. It could be sealed with adhesive, solvent or ultrasonic welding or adhesive tape. This tray was placed on top of the screen so that the clear film was resting on the LCD screen.

[0105] A flat aluminium platform 75 mm×45 mm perforated with holes was mounted to a belt driven motor so that it could be elevated and declined in the vertical plane by increments of 0.1 mm.

[0106] A total of 500 g of the photopolymer was poured into the tray. The print platform was lowered down onto the screen and this point was taken as the starting or zero point.

[0107] The object to be printed was a cylindrical spiral shape. The print platform was then elevated 0.1 mm away from the screen and the first exposure was started. The first exposure was an extended exposure time to ensure that any fine detail is formed and successfully adhered. This first time was set to 5 minutes. After this the normal exposure cycle commenced.

[0108] The print platform was raised from its previous exposure position by 0.5 mm to allow polymer to re-fill the cavity. It was lowered 0.4 mm to leave it 0.1 mm away from the screen. The second image was exposed on the screen for 55 seconds, and the process was repeated.

[0109] A total of 454 layers were made and the resultant 3D image created was shown in FIG. 3D.

Example 5—Faster Curing

[0110] To make a 3D object faster, a more active daylight was developed. 500 g of this daylight polymerisable compound was made by taking 190 g of Genomer 4302, an aliphatic polyester triurethane, 135 g of Genomer 4269 a urethane acrylate manufactured by Rahn AG of Switzerland, 150 g of HDDA (Hexane-1,6-diol diacrylate) a difunctional reactive monomer made by Rahn under the name Miramer M200, adding 22.75 g of TMPTMA (trimethylolpropane trimethacrylate) a reactive diluent manufactured by Sartomer under the trade SR350 and 2.25 g of (bis(.eta.5-2,4-cylcopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) titanium) manufactured by BASF under the trade name Irgacure 784. They were all added to a glass mixing vessel and were mixed at 60 C for a total of 3 hours and allowed to cool.

[0111] The LCD screen, 3D printing apparatus and procedure of operation was the same as in Example 3. The object to be printed was a scale model of the 101 Tower in Taipei. The print platform was moved 0.5 mm away from the screen to create a larger first layer to ensure that any fine detail is formed and adhered to the print platform. This first time was set to 90 secs. After this the normal exposure cycle commenced.

[0112] The print platform was lowered from its previous exposure position by 0.5 mm to allow polymer to re-fill the cavity. It can be lowered in the motor's fast setting to save time. The motor then stopped and reversed to bring the platform back up to the same position as before but 0.1 mm lower, i.e. a reversal of 0.4 mm. The second image was exposed on the screen for 15 seconds, and the process was repeated.

[0113] A total of 397 layers were made and the resultant 3D image created was shown in FIG. 3E.

[0114] While a satisfactory image was generated using the above conditions, at a level of curing that would be satisfactory for certain applications, the tower made in this example was found to be underexposed for many applications.

Example 6—Finer Resolution

[0115] It is possible to make objects with finer resolution if the layer thickness is thinner, in practice the limiting factor here is not the chemistry of the resin, but the accuracy of the engineering of the z-axis. This was demonstrated by making a high resolution test piece at 0.05 mm layers. 500 g of the daylight polymerisable compound used in example 4 was made.

[0116] The LCD screen, 3D printing apparatus and procedure of operation was the same as in Example 4. The object to be printed was a test plate with fine dots and lines. The print platform was moved 0.1 mm away from the screen to create a larger first layer to ensure that any fine detail is formed and adhered to the print platform. This first time was set to 5 mins. After this the normal exposure cycle commenced.

[0117] The print platform was raised from its previous exposure position by 0.5 mm to allow polymer to re-fill the cavity. It was then lowered by 0.45 mm, ie a separation of 0.05 mm or 50 μm. The second image was exposed on the screen for 28 seconds, and the process was repeated.

[0118] The resultant 3D image created was shown in FIG. 3F and FIG. 3G which is enlarged 200 times. The x:y resolution obtained was μm, the 0.05 mm wide lines and 0.05 mm diameter cylinders have all been held. This gives an overall resolution of μm.

Example 7—Lower Shrinkage

[0119] An adaption of the photopolymer formulation was made to exhibit lower shrinkage with the optimisation of reactive monomers and reactive acrylates. 500 g of this daylight polymerisable compound was made by taking 325 g of Genomer 4188, a high elongation and stress break, low yellowing acrylate manufactured by Rahn AG of Switzerland, 172.75 g of TEDGMA (triethyleneglycol dimethacrylate) a difunctional reactive monomer and 2.25 g of (bis(.eta.5-2,4-cylcopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) titanium) manufactured by BASF under the trade name Irgacure 784. They were all added to a glass mixing vessel and were mixed at 60 C for a total of 3 hours and allowed to cool.

[0120] The LCD screen, 3D printing apparatus and procedure of operation was the same as in Example 4. The object to be printed was a tower. The print platform was moved 0.5 mm away from the screen to create a larger first layer to ensure that any fine detail is formed and adhered to the print platform. This first time was set to 1 minute. After this the normal exposure cycle commenced.

[0121] The print platform was lowered from its previous exposure position by 0.5 mm to allow polymer to re-fill the cavity. It can be lowered in the motor's fast setting to save time. The motor then stopped and reversed to bring the platform back up to the same position as before but 0.1 mm lower, i.e. a reversal of 0.4 mm. The second image was exposed on the screen for 18 seconds, and the process was repeated.

[0122] A total of 230 layers were made and the resultant 3D image created was shown in FIG. 3H.

[0123] While a satisfactory image was generated using the above conditions, at a level of curing that would be satisfactory for certain applications, the tower made in this example was found to be underexposed for many applications.

Example 8

[0124] An alternative LCD screen was demonstrated using a versatile polymer with low shrinkage and fast rate of cure. 500 g of this daylight polymerisable compound was made by taking 215 g of Genomer 4188, a high elongation and stress break, low yellowing acrylate manufactured by Rahn AG of Switzerland, 119.25 g of Genomer 4302, an aliphatic polyester triurethane, manufactured by Rahn AG of Switzerland 163.5 of TEDGMA (triethyleneglycol dimethacrylate) a difunctional reactive monomer and 2.25 g of (bis(.eta.5-2,4-cylcopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) titanium) manufactured by BASF under the trade name Irgacure 784. They were all added to a glass mixing vessel and were mixed at 60° C. for a total of 3 hours and allowed to cool.

[0125] The LCD screen was a 7″ photo display screen made by Lumina. This had a display providing 480×234 pixels, a screen size of 15.8 cm×8.7 cm (6.2 inches×3.4 inches) with a viewing angle of 60° vertically and 40° horizontally and a brightness of 200 cd/m.sup.2. The 3D printing apparatus and procedure of operation was the same as in Example 5. The object to be printed was a lower human jaw or mandible. The print platform was moved 0.5 mm away from the screen to create a larger first layer to ensure that any fine detail is formed and adhered to the print platform. This first time was set to 2 minutes. After this the normal exposure cycle commenced.

[0126] The print platform was lowered from its previous exposure position by 0.5 mm to allow polymer to re-fill the cavity. It can be lowered in the motor's fast setting to save time. The motor then stopped and reversed to bring the platform back up to the same position as before but 0.1 mm lower, i.e. a reversal of 0.4 mm. The second image was exposed on the screen for 21 seconds, and the process was repeated.

[0127] A total of 272 layers were made and the resultant 3D image created was shown in FIG. 3I.

[0128] While a satisfactory image was generated using the above conditions, at a level of curing that would be satisfactory for certain applications, the jaw made in this example was found to be underexposed for many applications.