WO2018118832A1

WO2018118832A1 - Adhesive sheet for securing 3d object to carrier platform and method of using same

Info

Publication number: WO2018118832A1
Application number: PCT/US2017/067172
Authority: WO
Inventors: Xinyu Gu
Original assignee: Carbon, Inc.
Priority date: 2016-12-23
Filing date: 2017-12-19
Publication date: 2018-06-28

Abstract

Provided herein is a method of forming a three-dimensional object (31) from a light-polymerizable resin (32) by advancing a carrier (22) for the growing three-dimensional object away from an optically transparent window (24) while projecting patterned light through the window to polymerize the resin and form the object on the carrier, the method comprising: adhering a flexible release sheet to the carrier, to which release sheet the growing three-dimensional object is adhered, the release sheet comprising(i)a flexible polymer sheet (11),(ii)an adhesive coating (12) on said sheet by which said sheet is adhered to the carrier; and(iii)a resin-compatible surface on said sheet to which said growing three-dimensional object is adhered.

Description

ADHESIVE SHEET FOR SECURING 3D OBJECT TO

CARRIER PLATFORM AND METHOD OF USING SAME Xinyu Gu

Related Applications

This application claims the benefit of United States provisional patent application serial no. 62/438,657, filed December 23, 2016, the disclosure of which is incorporated by reference herein in its entirety.

Field of the Invention

The present invention concerns additive manufacturing, particularly stereolithography, and materials and methods useful to facilitate release of a three- dimensional object from a carrier platform on which it is grown.

Background of the Invention

A. Ermoshkin et al, PCT Publication No. WO 2016/025599 (Feb 18, 2016) describes release mechanisms for carriers during continuous liquid interface production at Figures 30- 38 and associated text at pages 38-40. For additional background, see also H. Maaldernik, EP1876012 (also published as US Patent No. 9,205,599); Comb et al, US Patent No. 5,939,008; Burns et al., US 5,879,489, and 3D Systems, EP 2143552 (also published as Partanen et al, US Patent No. 7,906,061) (all cited in the Written Opinion of the International Searching Authority in A. Ermoshkin et al., above).

Summary of the Invention

The present invention provides a method of forming a three-dimensional object from a light-polymerizable resin (typically a viscous resin), which method includes the steps of advancing a carrier for the growing three-dimensional object away from an optically transparent window while projecting patterned light through the window to polymerize the resin and form the object on the carrier (e.g., by stereolithography, such as by continuous liquid interface production or "CLIP"). The method includes adhering a flexible release sheet to the carrier, to which release sheet the growing three-dimensional object is, in turn, adhered. The release sheet includes (i) a flexible polymer sheet, (ii) an adhesive coating on the sheet by which the sheet is adhered to the carrier; and (in) a resin-compatible surface on the sheet to which the growing three-dimensional object is, in turn, adhered.

In some embodiments, the method further includes separating the three-dimensional object from said carrier by separating said release sheet from said carrier, and optionally separating said release sheet from said object.

In some embodiments, the method further includes washing the object with a wash liquid while the object remains on the release sheet after the object is formed, but before separating the object from the release sheet (and either before or after separating said release sheet from said carrier, for example, with the release sheet providing a securement member for the object during wash, or a retrieval handle for the object after wash).

Among other things, it is surprising that a pressure-sensitive adhesive provides sufficient securement to a carrier without failing (itself separating) during a process like continuous liquid interface production, where the liquid interface between a (generally viscous) resin on the window while the carrier is advanced away itself exerts a separating force between the object and the carrier (here, through the release sheet).

In some embodiments, advantages of the present invention include some or all of the following:

The clean and fresh surface of the release sheet aids in consistent adhesion of objects to the carrier. The adhesion strength can be even higher that observed to anodized aluminum, stainless steel, or glass, due to the resin-compatible surface.

After each object is made, the release sheet can be easily peeled off for nearly effortless part removal. This obviates the need to forcefully apply a sharp metal scraper, which is both dangerous to the operator and non-manufacturing viable.

The release sheet is applied to the carrier platform through pressure sensitive adhesives that do not leave excessive residue adhesives upon peeling off. Such adhesives reduce the need for further cleaning and preparation of carrier platform for the next fabrication job.

The foregoing and other objects and aspects of the present invention are explained in greater detail in the drawings herein and the specification set forth below. The disclosures of all United States patent references cited herein are to be incorporated herein by reference. Brief Description of the Drawings

Figure 1 is a side sectional schematic view of one embodiment of a release sheet of the invention, before being applied to a carrier.

Figure 2 schematically illustrates an object being formed by continuous liquid interface production, including a release sheet of the invention.

Figure 3 is a bottom plan view schematically illustrating the extent of contact of the release sheet to a carrier, the extent of contact of a release sheet to that portion of the three- dimensional object immediately adhered to the release sheet, and the adhesive perimeter thereby formed around the object (which may be of varying depths).

Figure 4 illustrates a release sheet and object being separated from a carrier, with an optional tool.

Detailed Description of Illustrative Embodiments

The present invention is now described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.

As used herein, the term "and/or" includes any and all possible combinations or one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative ("or").

1. PRODUCTION OF OBJECTS; GENERAL

The three-dimensional object is preferably formed from polymerizable resins by additive manufacturing, typically bottom-up additive manufacturing, generally known as stereolithography. Such methods are known and described in, for example, U.S. Patent No. 5,236,637 to Hull, US Patent Nos. 5,391,072 and 5,529,473 to Lawton, U.S. Patent No. 7,438,846 to John, US Patent No. 7,892,474 to Shkolnik, U.S. Patent No. 8,110,135 to El- Siblani, U.S. Patent Application Publication No. 2013/0292862 to Joyce, and US Patent Application Publication No. 2013/0295212 to Chen et al.

In some embodiments, the three-dimensional object is formed by continuous liquid interface production (CLIP). CLIP is known and described in, for example, PCT Application Nos. PCT7US2014/015486 (published as US Patent No. 9,211,678 on December 15, 2015); PCT/US2014/015506 (also published as US Patent No. 9,205,601 on December 8, 2015), PCT/US2014/015497 (also published as US Patent No 9,216,546 on December 22, 2015), and in J. Tumbleston, D. Shirvanyants, N. Ermoshkin et al., Continuous liquid interface production of 3D Objects, Science 347, 1349-1352 (published online 16 March 2015). See also R. Janusziewcz et al., Layerless fabrication with continuous liquid interface production, Proc. Natl. Acad. Sci. USA 113, 11703-11708 (October 18, 2016). In some embodiments, CLIP employs features of a bottom-up three-dimensional fabrication as described above, but the irradiating and/or advancing steps are carried out while also concurrently maintaining a stable or persistent liquid interface between the growing object and the build surface or window, such as by: (i) continuously maintaining a dead zone of polymerizable liquid in contact with said build surface, and (ii) continuously maintaining a gradient of polymerization zone (such as an active surface) between the dead zone and the solid polymer and in contact with each thereof, the gradient of polymerization zone comprising the polymerizable resin in partially cured form. In some embodiments of CLIP, the optically transparent member comprises a semipermeable member (e.g., a fluoropolymer), and the continuously maintaining a dead zone is carried out by feeding an inhibitor of polymerization through the optically transparent member, thereby creating a gradient of inhibitor in the dead zone and optionally in at least a portion of the gradient of polymerization zone. Other approaches for carrying out CLIP that can be used in the present invention and potentially obviate the need for a semipermeable "window" or window structure include utilizing a liquid interface comprising an immiscible liquid (see L. Robeson et al, WO 2015/164234, published October 29, 2015), generating oxygen as an inhibitor by electrolysis (see I Craven et al, WO 2016/133759, published August 25, 2016), and incorporating magnetically positionable particles to which the photoactivator is coupled into the polymerizable liquid (see J. Rolland, WO 2016/145182, published September 15, 2016).

In some embodiments, an intermediate object is formed from a dual cure stereolithography resin. Such resins are described in, for example, J. Rolland et al., PCT Applications PCT/US2015/036893 (see also US Patent Application Pub. No. US 2016/0136889), PCT/US2015/036902 (see also US Patent Application Pub. No. US 2016/0137838), PCT/US2015/036924 (see also US Patent Application Pub. No. US 2016/0160077), and PCT/US2015/036946 (see also US Patent No. 9,453,142). 2. RELEASE SHEET.

Figure 1 is a side sectional schematic view of one embodiment of a release sheet of the invention, before being applied to a carrier. A protective sheet (15) is included, which is removed to expose the adhesive (generally a pressure sensitive adhesive (12)) so that the sheet can then be applied to a carrier.

The carrier (22) typically includes a flat surface, generally a metal surface {e.g., aluminum, such as anodized aluminum), to which the release sheet is adhered for formation of the object (31), such as illustrated (in a non-limiting embodiment) in Figure 2.

The release sheet, itself, is generally formed of a flexible polymer sheet (11), which is, in turn, comprised of polyethylene terephthalate, polyvinyl chloride, high density polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyimide, or a combination thereof. In some embodiments, the flexible polymer sheet has a thickness of 10, 20 or 30 microns, to 300, 400 or 500 microns. In some embodiments, the flexible polymer sheet has a tensile strength of 30 or 40 MPa to 300 or 400 MPa, or more. In some embodiments, the flexible polymer sheet has a Young's Modulus of 1 or 2 GPa to 80 or 100 GPa, or more. Polyethylene terephthalate (PET) is currently preferred for the flexible polymer sheet, at a thickness of about 5 mil (about 130 microns); a tensile strength of about 55 MPa, and a Young's Modulus of about 3 GPa.

The flexible polymer sheet may, in some embodiments, itself, be a material to which the resin will bind. In such a case, the polymer sheet may have a surface that is uncoated, and/or have surface features formed therein {e.g., a roughened or abraded surface) that facilitates adhesion of the resin to the sheet as the resin is polymerized. In other cases, the polymer sheet may be coated with a material (13) that facilitates adhesion of the resin to the sheet. Numerous options for such coating are known {See, for example, S. Malhotra, Ink Jet Transparencies, US Patent No. 5,672,424; see also H. Nakane and J. Ito, UV-Curable InkJet Ink Composition, US Patent Application Pub. No. US2014/0118451; P. Odell and E. Toma, Radiation Curable Inks, US Patent Application Pub. No. US 2006/0158492; I. Hutchinson, Raw Materials for UV Curable Inks (Chapter 10 in The Chemistry of ^'Inkjet Inks, 2009); and S. Edison, Formulating UV Curable Inkjet Inks (Chapter 9 in The Chemistry of Inkjet Inks, 2009)). In some embodiments, the coating may be an organic compound or material, such as an acrylate-based coating formulation that adheres to the plastic yet can adhere a resin. In other embodiments, the coating may be an inorganic compound or material, such as a porous inorganic filler like fumed silica or diatomaceous earth (in which case the resin is absorbed into the inorganic particles and form an IPN for adhesion).

Pressure sensitive adhesives that may be used to carry out the present invention are known. Examples include, but are not limited to, those set forth in US Patent Nos. 9,523,023; 9,521,803; 9,505,197; 9,493,680; 9,492,338, and numerous others. Examples of suitable pressure sensitive adhesives include, but are not limited to, silicone static cling adhesives, glass beads filled with adhesives, repositionable/removable adhesives, permanent adhesives, etc.

Examples of commercially available materials from which release sheets as described herein may be formed include, but are not limited to, VIZIPRTNT® Impress PET films, VIZIPRINT® Illuminate PET films, and RETAC® PVC films (all available from Drytac Corporation, 5601 Eastport Boulevard, Richmond, Virginia, USA), FLEXMARK® printable vinyl films (available from FLEXcon, 1 FLEXcon Industrial Park, Spencer, MA, 01562-2642 USA) and other film materials available from Nova Films & Foils, Inc. (11 Industry Drive, Bedford, OH 44146 USA), TEKTRA Division of EIS, Inc. (16700 West Lincoln Avenue, New Berlin, WI 53151 USA), and Feyong Digital Technology Ltd. (02, Block A, Nanxian Commercial Square, Meilong Road, Longhua, Shenzhen, China, 518000).

In some embodiments, the release sheet may include a release tab (14), which is a portion of the polymer sheet that does not have adhesive. The release tab can protrude out from the edge of the carrier when adhered thereto, allowing ease of gripping for the user's removal of the release sheet from the carrier and/or object.

Figure 3 is a bottom plan view schematically illustrating the extent of contact of the release sheet to a carrier (41), the extent of contact of a release sheet to that portion of the three-dimensional object immediately adhered to the release sheet (42), and the adhesive contact area perimeter (43) thereby formed by the release sheet around the contact portion of the three-dimensional object, around the entire circumference of that contact portion (which perimeter may be of varying lateral depth, but typically at least 1, 2, or 3 millimeters).

It will also be appreciated that the release sheet is preferably continuous or unperforated, so that it forms a protective barrier between the carrier and the polymerizable resin (or other extraneous materials that might otherwise contaminate the carrier contact surface and deleteriously affect adhesion of the object, or subsequent objects, to the carrier). Hence, the surface area of the release sheet that is adhered to the carrier is typically greater than the surface area of the release sheet that is adhered to the three-dimensional object (and preferably forms an extended adhesively securing perimeter completely around the attachment portion of the three-dimensional object, as noted above).

Figure 4 illustrates a release sheet and object being separated from a carrier, with an optional tool. The figure is highly schematic, as a bending or curving of the sheet would more accurately reflect actual appearance of a currently preferred embodiment. The tool (51) is optional, and in some embodiments is configured to engage an optional tool access feature (23) on the carrier, if present (see Figure 2). While in Figure 4 the object (31) is being shown as separating from the release sheet at substantially the same time as the release sheet is separating from the carrier (22), in other situations the object (31) may remain adhered to the release sheet after the release sheet has been separated from the carrier, such as to facilitate handling during washing, as discussed below. Indeed, the object may remain attached to the carrier through the release sheet during a wash step (thereby protecting the surface of the carrier from contamination that might adversely affect adhesion, similarly to as noted above).

3. WASHING

In general, objects formed from resins as described above by additive manufacturing have residual, unpolymerized or partially polymerized, resin on the surface thereof, which must be cleaned or washed from the object.

In some embodiments, the object remains adhered to the carrier through the release sheet for this wash step (with the carrier serving as a handle or mount for the object during washing); in other embodiments, the object may be separated from the carrier but remain adhered to the release sheet for the wash step (with the release sheet optionally serving as a handle or mount during washing). Note that wash steps may include agitation of the object and/or the wash liquid, such as with an impeller, a sonicator, mounting of the object on a rotor or spinner, etc.

Wash liquids that may be used to carry out the present invention include, but are not limited to, water, organic solvents, and combinations thereof (e.g., combined as co-solvents), optionally containing additional ingredients such as surfactants, chelants (ligands), enzymes, borax, dyes or colorants, fragrances, etc., including combinations thereof. The wash liquid may be in any suitable form, such as a solution, emulsion, dispersion, etc.

In some embodiments, the wash liquid consists of a 50:50 (volume: volume) solution of water and isopropanol. In some embodiments, the wash liquid comprises a hydrofluorocarbon solvent, examples of which include, but are not limited to, 1,1, 1,2,3,4,4,5, 5, 5-decafluoropentane (Vertrel XF, DuPont Chemours), 1,1,1,3,3-Pentafluoropropane, 1,1,1,3,3-Pentafluorobutane, etc.

In some embodiments, the wash liquid comprises a hydrochlorofluorocarbon solvent, examples of which include, but are not limited to, 3, 3 -Dichloro- 1,1, 1,2,2- pentafluoropropane, 1 ,3 -Dichloro- 1 , 1 ,2,2,3 -pentafluoropropane, 1 , 1 -Dichloro- 1 - fluoroethane, etc., including mixtures thereof.

In some embodiments, the wash liquid comprises a hydrofluoroether solvent, examples of which include, but are not limited to, methyl nonafluorobutyl ether (HFE-7100), methyl nonafluoroisobutyl ether (HFE-7100), ethyl nonafluorobutyl ether (HFE-7200), ethyl nonafluoroisobutyl ether (HFE-7200), l,l,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, etc., including mixtures thereof. Commercially available examples of this solvent include Novec 7100 (3M), Novec 7200 (3M).

In some embodiments, the wash liquid comprises a volatile methylsiloxane solvent, examples of which include, but are not limited to, hexamethyldisiloxane (OS- 10, Dow Corning), octamethyltrisiloxane (OS-20, Dow Corning), decamethyltetrasiloxane (OS-30, Dow Corning), etc., including mixtures thereof.

In some embodiments, the wash liquid comprises an azeotropic mixture comprising, consisting of, or consisting essentially of a first organic solvent (e.g., a hydrofluorocarbon solvent, a hydrochlorofluorocarbon solvent, a hydrofluoroether solvent, a methylsiloxane solvent, or combination thereof; e.g., in an amount of from 80 or 85 to 99 percent by weight) and a second organic solvent (e.g., a C1-C4 or C6 alcohol such as methanol, ethanol, isopropanol, tert- butanol, etc.; e.g., in an amount of from 1 to 15 or 20 percent by weight). Additional ingredients such as surfactants or chelants may optionally be included. In some embodiments, the azeotropic wash liquid may provide superior cleaning properties, and/or enhanced recyclability, of the wash liquid.

Additional examples of suitable azeotropic wash liquids include, but are not limited to, those set forth in US Patent Nos. 6,008,179; 6,426,327; 6,753,304; 6,288,018; 6,646,020; 6,699,829; 5,824,634; 5,196,137; 6,689,734; and 5,773,403, the disclosures of which are incorporated by reference herein in their entirety.

When the wash liquid includes ingredients that are not desired for carrying into a further curing step, in some embodiments the initial wash with the wash liquid can be followed with a further rinsing step with a rinse liquid, such as water (e.g., distilled and/or deionized water), or a mixture of water and an alcohol such as isopropanol.

The foregoing is illustrative of the present invention, and is not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims

What is claimed is:

1. In a method of forming a three-dimensional object from a light-polymerizable resin by advancing a carrier for the growing three-dimensional object away from an optically transparent window while projecting patterned light through the window to polymerize the resin and form the object on the carrier, the improvement comprising:

adhering a flexible release sheet to the carrier, to which release sheet the growing three-dimensional object is adhered, the release sheet comprising (i) a flexible polymer sheet, (ii) an adhesive coating on said sheet by which said sheet is adhered to the carrier; and (Hi) a resin-compatible surface on said sheet to which said growing three-dimensional object is adhered.

2. The method of claim 1, the improvement further comprising: separating said three- dimensional object from said carrier by separating said release sheet from said carrier, and optionally separating said release sheet from said object.

3. The method of claim 1 or claim 2, the improvement further comprising: washing said object on said release sheet with a wash liquid after said object is formed, but before separating said object from said release sheet.

4. The method of claim 3, wherein said wash step is carried out before separating said release sheet from said carrier.

5. The method of claim 4, wherein said wash step is carried out by agitating said object {e.g., by rotating or spinning) in a wash liquid.

6. The method of any preceding claim, wherein said flexible polymer sheet is comprised of polyethylene terephthalate, polyvinyl chloride, high density polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyimide, or a combination thereof.

7. The method of any preceding claim, wherein said adhesive comprises a pressure sensitive adhesive.

8. The method of any preceding claim, wherein said light polymerizable resin is viscous.

9. The method of any preceding claim, further comprising maintaining a continuous liquid interface between said window and said three-dimensional object while said three- dimensional object is formed.

10. The method of any preceding claim, wherein said resin-compatible surface comprises (i) an uncoated surface portion of said flexible polymer sheet, or (ii) an additional organic or inorganic coating on said flexible polymer sheet.

11. The method of any preceding claim, wherein said release sheet is continuous and/or unperforated, and/or forms a protective barrier between said carrier and said polymerizable liquid.

12. The method of any preceding claim, wherein the surface area of said release sheet adhered to said carrier is greater than the surface area of said release sheet adhered to said three-dimensional object (and preferably forms an extended adhesively securing perimeter completely around the attachment portion of the three-dimensional object).

13. The method of any preceding claim, wherein said carrier comprises a metal surface portion (e.g., aluminum, such as anodized aluminum) to which said release sheet is adhered.

14. The method of any preceding claim, wherein said flexible polymer sheet has a thickness of 10, 20 or 30 microns, to 300, 400 or 500 microns.

15. The method of any preceding claim, wherein said flexible polymer sheet has a tensile strength of 30 or 40 MPa to 300 or 400 MPa, or more.

16. The method of any preceding claim, wherein said flexible polymer sheet has a Young's Modulus of 1 or 2 GPa to 80 or 100 GPa, or more.