Additive manufacturing of transparent optical articles

Abstract

This disclosure provides an optical composition for trench photopolymerization, comprising: a photocurable monomer or a blend of monomers; a photoinitiator; a UV absorber; and a hindered amine light stabilizer. A method of forming an optical article includes printing the optical article using trench photopolymerization and the optical composition, wherein the optical surface of the optical article extends along a z-axis perpendicular to a printed surface on which the optical article is printed.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 558,684, entitled “Additive Manufacturing of Transparent Optical Articles,” filed February 28, 2024, pursuant to 35 USC § 119(e), the entire disclosure of which is incorporated herein by reference.

[0003] Government licensing rights

[0004] This invention was made with government support under Government Contract No. W911NF-17-2-0227, granted by the U.S. Army Contract Command on behalf of the U.S. Army Research Laboratory (ARL). The government may own certain rights to this invention. Technical Field

[0005] This disclosure relates to an optical composition and a method for manufacturing objects using slotted photopolymer additive manufacturing. Background Technology

[0006] Photopolymers are widely used in additive manufacturing processes such as trench photopolymerization and material jetting. Trench photopolymerization enables fine printing resolution. However, due to printing parameters, hardware limitations, and / or support structures, printed objects may have surface defects such as layer steps and surface roughness.

[0007] In the case of optical lenses, surface roughness and material composition can hinder lens sharpness and reduce lens functionality. Therefore, there is a need for a composition and method of use to produce smooth and sharp objects using slotted photopolymerization printing, as well as a post-processing method. Summary of the Invention

[0008] This disclosure provides an optical composition for trough photopolymerization, comprising, based on the total mass of the optical composition, a monomer or monomer blend comprising at least one of (meth)acrylate and thio-(meth)acrylate functional groups; 0.20% to 3.0% by mass of a photoinitiator; 0.40% to 2.2% by mass of a UV absorber; and 0.40% to 2.2% by mass of a hindered amine light stabilizer (HALS).

[0009] This disclosure further provides a method for forming an optical article comprising an optical surface defining an optical geometry, the method comprising printing the optical article having predetermined curved or flat boundaries using a trench photopolymerization. The curved or flat boundaries define the optical geometry. The optical article is printed such that the optical surface of the optical article extends along a z-axis perpendicular to the printed surface on which the optical article is printed. The trench photopolymerization comprises an optical composition. Based on the total mass of the optical composition, the optical composition comprises a monomer or blend of monomers containing at least one of (meth)acrylate and thio-(meth)acrylate functional groups; 0.20% to 3.0% by mass of a photoinitiator; 0.40% to 2.2% by mass of a UV absorber; and 0.40% to 2.2% by mass of a hindered amine light stabilizer (HALS). Attached Figure Description

[0010] The above and other features and advantages of this disclosure, as well as the ways in which they are obtained, will become more apparent from the following description taken in conjunction with the accompanying drawings, and the disclosure itself will be better understood. The above and other features of this disclosure can be used in any combination or arrangement.

[0011] Figure 1A This is a diagram illustrating the orientation of the lenses in the grooved photopolymerization printing process disclosed herein;

[0012] Figure 1B Is using Figure 1A Illustration of two views of a lens printed using the slotted photopolymerization process;

[0013] Figure 2 This is a diagram illustrating the different printing orientations of the -4 lens geometry on the Z-axis on the construction platform according to this disclosure;

[0014] Figure 3A It is an image of a -4 lens printed using the method of this disclosure;

[0015] Figure 3B yes Figure 3A The image shows a -4 lens, where the lens is located between the mold and another monomer, which is added to smooth the lens during curing.

[0016] Figure 4 This is a flowchart of a method for printing objects using slotted photopolymerization according to this disclosure; and

[0017] Figure 5 This is an image showing the birefringence of an optical article comprising the optical composition disclosed herein.

[0018] In the various views, corresponding reference numerals denote corresponding parts. The examples illustrated herein illustrate this disclosure, and such examples should not be construed as limiting the scope of this disclosure in any way. Detailed Implementation

[0019] This disclosure provides an optical monomer composition and a method for additively manufacturing 3D objects comprising the optical monomer composition using slotted photopolymerization.

[0020] I. Definition

[0021] For the purposes of the following detailed description, it should be understood that this disclosure may take various alternative variations and sequences of steps unless the contrary is explicitly stated. Furthermore, except in any operational instance, or where otherwise indicated, all figures used in the specification and claims to indicate, for example, the quantity of an ingredient, should be understood to be modified by the term “about” in all cases. For example, numerical ranges provided for the weight percentage of a component or the amount of added component should be interpreted as being modified by the term “about.” Therefore, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending on the desired properties to be obtained through this disclosure. At least, and not in an attempt to limit the application of the doctrine of equivalence to the scope of the claims, each numerical parameter should be interpreted at least according to the number of significant figures reported and by applying common rounding techniques.

[0022] Although the numerical ranges and parameters described in this disclosure are approximate, the values ​​illustrated in specific examples are reported as precisely as possible. However, any numerical value inherently contains some error that is necessarily caused by the standard deviation found in its corresponding test measurement results.

[0023] Although specific examples of this disclosure have been described above for illustrative purposes, it will be apparent to those skilled in the art that many changes may be made to the details of this disclosure without departing from the scope of the disclosure as defined in the appended claims.

[0024] Furthermore, it should be understood that any numerical range described herein is intended to include all subranges included therein. For example, the range “1 to 10” is intended to include all subranges from the described minimum value of 1 to the described maximum value of 10 (and include both the minimum and maximum values), that is, a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0025] Unless otherwise specified, the use of the singular includes the plural, and the plural encompasses the singular. Furthermore, unless otherwise specified, the use of "or" means "and / or," even if "and / or" may be explicitly used in certain instances.

[0026] As used in this article, “bottom exposure time” refers to the length of time that the first set of layers of a 3D printed object is exposed to UV light to ensure that the polymer substrate adheres to the build plate. Bottom exposure time can be many times the conventional exposure time required to print subsequent layers.

[0027] As used in this article, “substrate” refers to the number of substrates that are adhered to the build plate and follow the bottom exposure time.

[0028] As used in this article, “exposure time” refers to the UV light exposure time on each layer when 3D printing an object, and it may be different from “bottom exposure time”.

[0029] As used in this article, “closing time” refers to the amount of time between each movement of the elevator up and down the building plate to allow material to flow back between the membrane and the building plate.

[0030] As used herein, “ultraviolet light” or “UV light” means any light having a wavelength of 100 to 405 nm and including each of UVA (e.g., 315 to 405 nm), UVB (e.g., 280 to 315 nm), and UVC (e.g., 100 to 280 nm) ultraviolet (UV) light.

[0031] As used herein, “vertical orientation” describes the position of a three-dimensional article in which the optical and / or flat surface of the object is oriented in a substantially perpendicular position (e.g., in a substantially normal direction) relative to the print bed / print surface of an additive manufacturing apparatus (e.g., a 3D printer).

[0032] II. Optical compositions for slotted photopolymerization printing

[0033] This disclosure provides an optical composition for printing optical articles, such as lenses, disks, or any other suitable three-dimensional (3D) additively manufactured objects, with low haze, high transmittance, and low color density using slotted photopolymerization additive manufacturing. The composition may comprise a photocurable monomer / monomer blend, a UV absorber, a photoinitiator, and a hindered amine light stabilizer (HALS).

[0034] The type and relative proportions (e.g., mass %, weight %, and / or PPM) of the photocurable monomer / monomer blend, UV absorber, photoinitiator, HALS component, and / or additional additives can be selected and / or adjusted to allow objects to be additively manufactured using the methods described herein, and in particular, to channel photopolymerization additive manufacturing, wherein the object is printed such that the optical surfaces of the ophthalmic object are oriented in a substantially vertical orientation. For example, the weight percentage of each of the photocurable monomer / monomer blend, UV absorber, photoinitiator, and HALS component can be adjusted in combination to allow the ophthalmic object to be printed via channel polymerization, wherein the optical surfaces of the object are oriented in a vertical direction (e.g., normal to / perpendicular to the print bed / print surface of the channel polymerization 3D printer). Vertical orientation printing results in additively manufactured objects exhibiting optical properties similar to those of ophthalmic objects manufactured via casting / molding methods, and superior optical properties compared to ophthalmic objects printed with a horizontal orientation relative to the print bed / print surface, as described further in detail herein.

[0035] A. Photocurable monomers and monomer blends

[0036] The optical composition may comprise a photocurable monomer or a blend of photocurable monomers. The monomer may comprise any suitable UV-curable ophthalmic monomer complex, including combinations of olefinically unsaturated monomers of olefinically bonded unsaturated monomers.

[0037] Ophthalmic monomers can be olefinically unsaturated monomers and may contain one or more (meth)acrylate functional groups and / or thio-(meth)acrylate functional groups, or combinations thereof. Suitable monomers may include acrylic acid, methacrylic acid, esters of acrylic acid (such as methyl acrylate, butyl acrylate, and 2-hydroxyethyl acrylate), esters of methacrylic acid (such as methyl methacrylate, phenoxyethyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, butyl methacrylate, and 2-hydroxyethyl methacrylate), and blends thereof.

[0038] Suitable polyfunctional (meth)acrylate monomers may include commercially available dimethacrylates, such as 1,6-hexanediol di(meth)acrylate, bisphenol A di(meth)acrylate, polyethylene glycol di(meth)acrylate, and polycaprolactone di(meth)acrylate.

[0039] Furthermore, (meth)acrylate functional monomers can be prepared by reacting a polyol precursor with an acrylate esterifying agent using methods well-known in the art. Suitable acrylate esterifying agents include (meth)acryloyl chloride and (meth)acrylic anhydride. Transesterification using methyl (meth)acrylate can also be performed. Suitable polyol precursors may include straight-chain alkylene glycols, such as ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, or diethylene glycol and triethylene glycol; branched-chain alkylene glycols, such as 1,2-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 2,3-butanediol; hydroquinones, such as o-dihydroxybenzene, m-dihydroxybenzene, and p-dihydroxybenzene; alkyl-substituted hydroquinones, such as 2,6-dihydroxytoluene, 3-methylcatechol, 4-methylcatechol, 2-hydroxybenzyl alcohol, 3-hydroxybenzyl alcohol, 4-hydroxybenzyl alcohol, and 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzyl alcohol; and dihydroxybiphenyls, such as 4,4'-dihydroxybiphenyl and 2,2'-dihydroxybiphenyl. Biphenyl; bisphenols, such as 4,4'-isopropylidene diphenol; 4,4'-oxybisphenol; 4,4'-dihydroxybenzophenone; 4,4'-thiobisphenol; phenolphthalein; bis(4-hydroxyphenyl)methane; 4,4'-(1,2-vinylene)bisphenol; and 4,4'-sulfonylbisphenol; halogenated bisphenols, such as 4,4'-isopropylidene bis(2,6-dibromophenol), 4,4'-isopropylidene bis(2,6-dichlorophenol), and 4,4'-isopropylidene bis(2,3,5,6-tetrachlorophenol); and dicyclohexanol, which can be prepared by hydrogenating the corresponding bisphenols, such as 4,4'-isopropylidene dicyclohexanol; 4,4'-oxybiscyclohexanol; 4,4'-thiobiscyclohexanol; and bis(4-hydroxycyclohexanol)methane.

[0040] The ethoxylated forms of any of the aforementioned polyols can be prepared first, such as by reacting the alcohol groups with an ethoxylating agent such as ethylene oxide under conditions recognized in the art. Polyols such as trimethylolpropane react with ethylene oxide-containing substances such as ethylene oxide, propylene oxide, α-epoxybutane, or β-epoxybutane to form ethoxylated, propoxylated, or butoxylated polyols, commonly referred to as hydroxyl-functionalized polyols. The average number of alkoxylated groups in each alcohol group of the starting polyol can range from 1 to 9. These can be used to prepare the corresponding poly(meth)acrylates by reacting with acrylate esterifying agents as described above.

[0041] Any of the above-mentioned polyol precursors can be reacted with the acrylate esterifying agent described above to form the corresponding (meth)acrylate.

[0042] Suitable monomers with thio(meth)acrylate functional groups include bis(2-methacryloylthioethyl) sulfide, bis(2-acryloylthioethyl) sulfide, 2,5-bis(methacryloylthiomethyl)1,4-dithiane, 2-ethyl-2-((meth)acryloylthiomethyl)-1,3-bis[(meth)acryloylthio]propane, 1,2,3-tris[(meth)acryloylthio]propane, 2,2-bis[(meth)acryloylthiomethyl]-1,3-bis[(meth)acryloylthio]propane, 4-(methyl Acryloylthiomethyl-3,6-dithia-1,8-bis[(meth)acryloylthio]octane, 7-[2-(meth)acryloyloxyethyl]-3,6,8,11-tetrathia-1,13-bis[(meth)acryloylthio]tetane, 4,8-bis[(meth)acryloylthiomethyl]-3,6,9-trithia-1,11-bis[(meth)acryloylthio]undecane or their regioisomers, such as 4,7- or 5,7-regioisomers, and 2,5-bis(methacryloylthiomethyl)1,4-dithiaane.

[0043] Suitable monomers containing (meth)acrylate and thio(meth)acrylate functional groups include: 2-acryloyloxyethyl-2'-acryloylthioethyl sulfide, 2-methacryloyloxyethyl-2'-methacryloylthioethyl sulfide, 1,3-bis[(meth)acryloylthio]-2-(meth)acryloyloxypropane, 1-(meth)acryloylthio-2,3-bis[(meth)acryloyloxy]propane, 1,2-bis[(meth)acryloylthio]-3-(meth)acryloyloxypropane and 7-(meth)acryloyloxymethyl-3,6,9,12-tetrathia-1,14-bis[(meth)acryloylthio]tetradecane.

[0044] Any mixture of the above-mentioned (meth)acrylate and / or thio(meth)acrylate functional monomers can be used to achieve the desired refractive index and hardness of the polymer.

[0045] Similar to the polyols mentioned above, polythiols and polythiols-alcohols can be esterified (meth)acrylated by reacting with an excess of acrylate esterifying agents (such as those mentioned above).

[0046] Based on the total mass of the composition, the optical composition may contain 95%, 96%, 97% to 98%, 98.5% or 99% by mass percentage, or any range (such as 95% to 99%, 96% to 98.5% or 97% to 98%) of a photocurable monomer / monomer blend containing one or more (meth)acrylate or thio-(meth)acrylate functional groups, using any of the foregoing values ​​as endpoints.

[0047] B. Photoinitiator

[0048] The optical composition may include a photoinitiator or a combination of photoinitiators. The photoinitiator can be activated by photochemical radiation, which applies energy that effectively generates the initiating material from the photopolymerization initiator upon irradiation, such as ultraviolet (UV) light (including the UVA, UVB, and UVC spectra), visible light, and blue light. The photoinitiator may be a UV photoinitiator activated by UV light in the UVA, UVB, and / or UVC spectra. The activation wavelength may be in the range of 300 to 450 nm.

[0049] Suitable UV photoinitiators may include acylphosphine oxide type 1 photoinitiators. Additionally, suitable photoinitiators may include α-hydroxy ketones, benzophenone, α,α-diethoxyacetophenone, 4,4-diethylaminobenzophenone, 2,2-dimethoxy-2-phenylacetophenone, 4-isopropylphenyl-2-hydroxy-2-propyl ketone, 1-hydroxycyclohexylphenyl ketone, isoamyl p-dimethylaminobenzoate, methyl 4-dimethylaminobenzoate, methyl O-benzoylbenzoate, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-hydroxy-2-methyl-1-phenylprop-1-one, 2-isopropylthioxanthone, dibenzocycloheptanone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bicyclophosphine oxide, benzophenone photoinitiators, oxime photoinitiators, phosphine oxide photoinitiators, and combinations of any of the foregoing substances.

[0050] The concentration of photoinitiator can be directly proportional to the curing speed, with higher concentrations resulting in faster curing. However, photoinitiator concentration can also negatively affect the haze percentage and increase the yellowing color of the final product. Therefore, the photoinitiator concentration can be optimized to control the curing speed and reduce the haze percentage.

[0051] Based on the total mass of the composition, the optical composition may contain a photoinitiator in the following weight percentages: 0.20 wt.%, 0.35 wt.%, 0.40 wt.%, 0.45 wt.% to 0.50 wt.%, 0.60 wt.%, 1 wt.%, 1.5 wt.%, 2.0 wt.%, 2.5 wt.%, or 3 wt.%, or any range using any of the foregoing values ​​as endpoints (such as 0.20 wt.% to 0.60 wt.%, 0.35 wt.% to 0.50 wt.%, 0.40 wt.% to 0.45 wt.%, 1.0 wt.% to 3.0 wt.%, 1.5 wt.% to 3.0 wt.%, or 2.0 wt.% to 3.0 wt.%).

[0052] C. Ultraviolet (UV) absorbers

[0053] Optical compositions may contain UV absorbers (i.e., UVA). UV absorbers limit the penetration of UV light into the composition by absorbing and dissipating the energy of incident UV radiation. This prevents UV light from reaching deeper layers of the composition during additive manufacturing, which can control or limit polymerization. Specifically, when an optical composition is exposed to UV light, a portion of the UV radiation is absorbed by the UV absorber, preventing the absorbed light from penetrating the optical composition. This limited penetration allows control over the amount and rate of polymerization in the optical composition, thereby allowing control over the depth of curing and surface properties.

[0054] For a trough photopolymerization system with a wavelength of 405 nm, a suitable UV absorber can absorb ultraviolet light in the range of 300 nm to 405 nm. For any other trough photopolymerization system with different wavelengths, a UV absorber can be selected to absorb ultraviolet light within 5 nm of the wavelength of the light source used to initiate photopolymerization.

[0055] Suitable UV absorbers may include benzophenones such as 2-hydroxybenzophenone, benzotriazoles such as 2-hydroxyphenylbenzotriazole, triazines such as 2-hydroxyphenyltriazine, oxaloylaniline, 2-hydroxyphenyltriazine, cinnamate, salicylates, formamidinium and / or any suitable commercially available UV absorber.

[0056] UV absorbers protect printed objects containing optical compositions from environmental conduction and prevent color changes such as yellowing. The concentration of UV absorbers in the composition can affect printing speed; higher concentrations result in slower polymerization rates. Therefore, the amount of UV absorber in this composition can be optimized to reduce yellowing and regulate printing speed.

[0057] Based on the total mass of the composition, the optical composition may contain a UV absorber in the following mass percentages: 0.40 wt.%, 0.45 wt.%, 0.50 wt.% to 0.55 wt.%, 0.58 wt.%, 0.60 wt.%, or 2.2 wt.%, or any range (such as 0.4 wt.% to 2.2 wt.%, 0.45 wt.% to 0.60 wt.%, 0.50 wt.% to 0.5 wt.%, or 0.50 wt.% to 0.58 wt.%).

[0058] D. Hindered amine light stabilizers

[0059] Optical compositions may contain light stabilizers, such as UV light stabilizers, which may include hindered amine light stabilizer (HALS) components. HALS are a class of chemical compounds used to protect polymers from degradation caused by exposure to ultraviolet (UV) light. HALS work by scavenging free radicals generated during UV irradiation, thereby preventing the deterioration of the physical and mechanical properties of the polymer. Specifically, the HALS component may include amine functional groups configured to inhibit the degradation of polymer blends by removing free radicals generated by the photo-oxidation of the polymer. Suitable HALS components include the following: 1-(methyl)-8-(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethylpiperidin-4-yl)3,5-di-tert-butyl-4-hydroxybenzylmalonate n-butyl ester; bis(1,2,2,6,6-pentamethylpiperidinyl)-2-n-butyl-2- (2-hydroxy-3,5-di-tert-butylbenzyl)malonate; 2-chloro-4,6-bis(4-n-butylamino-1,2,2,6,6-pentamethylpiperidinyl)-1,3,5-triazine; 3-dodecyl-1-(1,2,2,6,6-pentamethylpiperidin-4-yl)pyrrolidine-2,5-dione; N-(1,2,2,6,6-pentamethylpiperidin-4-yl)-n-dodecylsuccinimide; and combinations thereof.

[0060] High concentrations of HALS in a composition can affect the printing speed, haze percentage, and color of the cured composition. Therefore, the amount of HALS in an optical composition can be optimized to target these optical features.

[0061] Based on the total mass of the composition, the optical composition may contain HALS in the following mass percentages: 0.40%, 0.45%, 0.50% to 0.55%, 0.60%, 0.85 wt.%, 2.0 wt.%, or 2.2%, or any range (such as 0.4% to 2.2%, 0.45% to 0.60%, 0.50% to 0.55%, or 0.85 wt.% to 2.0 wt.%).

[0062] E. Other additives

[0063] Additives, such as pigments or fixing dyes, can be added to optical compositions to achieve the correct color required for transparent applications. Suitable pigments / dyes may include anthraquinone dye derivatives, such as the following commercial dyes: Morplas Blue 2R (Soluble Blue 128) 9,10-anthraquinone-1,4-bis(2-bromo-4,6-dimethylphenyl)amino; Morplas Violet 3B (Soluble Violet 38) 9,10-anthraquinone-1,4{(2,6-dibromo-4-methylphenyl)amino}; Morplas Yellow GS (Soluble Yellow 163) 9,10-anthraquinone-1,4-bis(phenylthio); Morplas Violet 14 (Soluble Violet 14) 9,10-anthraquinone-1,8-bis(methylphenyl)amino; Morplas Blue E (Soluble Blue 101) 9,10-anthraquinone-1,4-bis(alkylphenyl)amino; PylakromeBlue LX-9704 (Soluble Blue 58) manufacturer undisclosed; pyrazolone derivatives; Pylakrome Yellow LX-10124, manufacturer undisclosed; Pylam Liquid Oil Yellow LO-2112 1-Phenyl-3-methyl-4-(alkylphenylazo)-5(solvent yellow)pyrazolone; and combinations thereof.

[0064] Other suitable additives may include antioxidants (such as triphenyl phosphite), polymerization modifiers (chain transfer agents), photosensitizers (such as isopropylthioxanthrone), and internal release agents (such as MOLDWIZ 4681, SELEC UN, etc.).

[0065] Based on the total mass of the composition, the coating composition may contain additives in the following mass percentages: 0.0001 wt.%, 0.0002%, 0.00025 wt.% to 0.0003%, 0.0004 wt.%, or 0.0005 wt.%, or any range (such as 0.0001 wt.% to 0.0005 wt.%, 0.0002 wt.% to 0.0004 wt.%, or 0.0003 wt.% to 0.0004 wt.%).

[0066] As previously described, the type and relative weight percentage (e.g., PPM) of each of the photocurable monomer / monomer blends, photoinitiators, UV absorbers, and HALS components can be combined to produce ophthalmic objects that are slotted in a substantially vertical orientation and manufactured (e.g., 3D printable) with optical properties similar to those of optical articles manufactured via casting methods (e.g., with equally good performance). For example, 1) the type and relative weight percentage (e.g., PPM) of the photoinitiator can be selected to control the curing rate and reduce the haze percentage, which can be combined with 2) the type and relative weight percentage (e.g., PPM) of the UV absorber that can absorb UV light in a given frequency range and reduce yellowing and regulate the printing rate, which can be combined with 3) the type and relative weight percentage (e.g., PPM) of the HALS components that can affect the printing rate, haze percentage, and color of the cured composition, each selected according to 4) the optical monomer / monomer blends used in the ophthalmic composition.

[0067] Here, it has been surprisingly found that, based on the selection of ophthalmic monomers / monomer blends containing olefinically unsaturated functional groups, 1) containing 0.20 wt.% to 3.0 wt.% of a photoinitiator, 2) containing 0.40 wt.% to 2.2 wt.% of a UV absorber, and 3) 0.40 wt.% to 2.2 wt.% of a HALS component, additively manufactured objects with performance as good as those produced by casting methods are produced, since the resulting optical compositions are malleable additively manufactured, wherein the optical surfaces of the objects are oriented in a substantially vertical direction (e.g., substantially normal to the print bed / print surface of a malleable additive 3D printer).

[0068] III. Printing process and post-curing process

[0069] This disclosure provides a method for additive manufacturing of objects using a trough photopolymerization and post-curing process.

[0070] Tank photopolymerization is an additive manufacturing process that uses bottom-up, top-down, or volumetric methods. The bottom-up method is the most common in the vast majority of commercial desktop and industrial systems. This bottom-up method performs the printing operation while the build platform moves upwards after each layer has cured to allow for resin liquid backflow, and then moves downwards to prepare for the next layer. Separation or peeling steps are required between each layer to separate it from the bottom of the tank.

[0071] The process of slotted photopolymer system can include different light sources, such as lasers, LEDs with DLP chips, and LEDs with LCD screens.

[0072] The resolution of slot-type light aggregation in the XY plane is limited by the pixel size of the light source. In the case of a laser light source, the beam spot size can be the smallest pixel size. For an LED light source, it can be the smallest light image per square meter of a DLP or LCD screen.

[0073] like Figure 4 As shown, method 40 includes printing an object 41 using a slotted photopolymerization process, optionally removing a support structure 42, sealing the object in a mold 43, filling the mold with additional monomers and securing the mold 44, exposing the mold to light and heat 45, and removing the object from the mold with a solvent 46. All steps 41 to 46 are further described below.

[0074] The printed object can be referred to as an optical article, lens, disc, or any suitable ophthalmic object manufactured using slotted photopolymer additive manufacturing in step 41. (Reference) Figure 1A The elevator 17 can lower the build platform 18 into the slot 14 containing the optical composition. A light source 16 can be projected into the bottom of the slot, opposite the build platform 18, thereby activating the optical composition so that the object 12 is printed onto the build platform 18. The light source 16 can emit UV light within a specific UV wavelength range, such as UV A light in the range of 315 to 405 nm, and particularly an LED with a narrow emission of 405 nm or 385 nm.

[0075] Light source 16 can emit light of specific wavelengths, such as 405 nm or 385 nm, with an irradiance of 3 mW / cm². 2 5 mW / cm 2 7 mW / cm 2 Up to 9 mW / cm 2 11 mW / cm 2 Or 13 mW / cm 2 Or any range using any of the aforementioned values ​​as endpoints, such as 3 mW / cm 2 Up to 13 mW / cm 2 5 mW / cm 2 Up to 11 mW / cm 2 Or 7 mW / cm 2 Up to 9 mW / cm 2 .

[0076] Printing parameters for trough photopolymerization can vary depending on the geometry of the object being printed and / or the printable composition. Printing parameters may include bottom exposure time, bottom layer, exposure time, shutdown time, and layer thickness.

[0077] In trough polymerization, the bottom exposure time refers to the duration during which the optical composition at the bottom of the trough is exposed to UV / curing light, which determines the solidification and quality of the printed layer in the additive manufacturing process. Here, the bottom exposure time of the printed optical composition can be at least 20 seconds, at least 22 seconds, at least 24 seconds, at least 26 seconds, at least 28 seconds, at least 30 seconds, or at least 32 seconds, or any range using any of the foregoing values ​​as endpoints, such as 20 to 32 seconds, 22 to 30 seconds, or 24 to 28 seconds.

[0078] In trough polymerization, the underlayer / base layer refers to the initial layer of the additively manufactured object, which adheres to the build platform, serves as the foundation for subsequent layers, and affects the overall structural integrity and accuracy of the printed product. Here, when forming the printed object, the printed optical composition may include at least two, at least three, at least four, at least five, at least six, or at least seven underlayers.

[0079] In tank polymerization, exposure time refers to the duration for which each layer of liquid resin is exposed to curing / UV light. It determines the degree of solidification and complexity in the additive manufacturing process, affecting the final quality of the printed object. Here, exposure time can vary depending on the layer thickness. Specifically, the thicker the desired layer, the longer the exposure time. If the exposure time is too low for a large area within a thin layer, polymerization will be insufficient, and the exposure time should be adjusted. Here, when forming a printed object, the printed optical composition may include exposure times of at least 2 seconds, 3 seconds, 4 seconds, 5 seconds, 6 seconds, 7 seconds, 8 seconds, 9 seconds, 10 seconds, or 11 seconds.

[0080] In trough polymerization, the off-time refers to the duration for which the ultraviolet (UV) light source is deactivated or paused, allowing for a temporary interruption of the curing process. This can be used to manage layer-by-layer polymerization in trough photopolymerization. In the case of bottom-up systems, the off-time can also be used to separate the printed layer from the membrane or thin film of the trough photopolymerization system. For all SLA, DLP, and LCD trough photopolymerization systems, the off-time can also be used to allow the optical composition to flow back to cover the printed surface and to allow the composition to polymerize further in the next layer. Here, when forming the printed object, the printed optical composition may include an off-time of at least 0.5 seconds, 1 second, 1.5 seconds, or 2 seconds, or 3 seconds.

[0081] Printed objects can have a maximum layer thickness of 10 µm or less. In some cases, a layer thickness of 10 µm or less can be considered “layerless” or “continuously printed.” Layer thickness is determined based on the partitioning of the object relative to the Z-axis, where material is polymerized on a layer-by-layer basis to produce a given layer thickness. Here, during additive manufacturing, the additive manufacturing system stops and moves the printed layer away from the printing area after each layer is exposed to light to polymerize, allowing unpolymerized material to flow and cover subsequent printing areas. As an alternative, continuous printing relies on fine layer partitioning, where the printing device may not stop printing between added layers. Volumetric printing processes can also utilize multiple projection planes and selective photopolymerization. Depending on the build orientation of the object in the slotted photopolymerization system, the layer thickness can be proportional to the surface roughness of the final article. This is due to steps generated on any curved surfaces on the same planar surface as the build area.

[0082] The printed object can have a maximum layer thickness of 10 µm or less, such as 0.1 µm, 1 µm, 4 µm to 6 µm, 8 µm or 10 µm, or any range of layer thicknesses using any of the foregoing values ​​as endpoints (such as 0.1 µm to 10 µm, 1 µm to 10 µm or 4 µm to 10 µm). Small layer thicknesses result in increased hardness in the resulting optical articles and reduced haze and surface defects.

[0083] As described above, the type and weight percentage of each of the photocurable monomers / monomer blends, UV absorbers, photoinitiators, and HALS components in the optical composition can be adjusted in combination to allow ophthalmic objects to be printed via slot polymerization, wherein the optical surfaces of the object are oriented in the vertical direction (e.g., normal to the print bed / print surface of the slot polymerization 3D printer). Here, the selection of printing parameters (e.g., bottom exposure time, bottom layer, exposure time, shutdown time, layer thickness) can directly affect the optical composition, and the optical composition can directly affect the 3D slot polymerization printing behavior. In this case, it has been surprisingly found that, based on the combined selection / optimization of each of the following: a bottom exposure time of 20 to 32 seconds, a bottom layer number of 2 to 7 layers, an exposure time of 2 to 11 seconds, a shutdown time of 0.5 to 3 seconds, and a layer thickness of 10 µm or less, the aforementioned optical composition can be selected to be additively manufactured in a vertical orientation via slot polymerization.

[0084] A. Vertical orientation printing

[0085] Printable objects can be designed using suitable computer-aided design software. Slotted photopolymer printers can be used with UV light and a z-axis pitch of 10 µm or less.

[0086] refer to Figure 1A and1B Object 12 can be printed using thin printing layers (0.1 µm to 10 µm, as previously described) such that the optical surface 12d of the object is in the z-axis direction. The optical surface 12d of the printed object 12 refers to a curved or flat boundary that plays a role in the manipulation of light as it passes through the object 12. The curvature of the optical surface 12d defines the optical geometry of the object 12, which will be discussed further below. The optical surface 12d of the printed object 12 can define the height of the object 12. When printing each thin layer of object 12 using a slotted photopolymerization process, object 12 extends from the build platform 18 in the z-direction such that object 12 is supported by support structures 13 along the bottom / peripheral edge 12c of object 12 onto the build platform 18. Once the object is printed, any existing support structures 13 can be removed. In some cases, object 12 can be printed at an angle relative to the z-axis, such as and referencing Figure 2 The angle is between 1 degree and 65 degrees. Printing at an angle allows for additive manufacturing of larger object diameters compared to printing in the normal direction.

[0087] Conventional additive manufacturing of objects similar to object 12 is limited to printing optical articles on top of a prefabricated surface (e.g., a substrate), and further limited to printing in a substantially horizontal orientation (e.g., printing on a build platform), such that the width of the object extends in the z-direction. Specifically, prefabricated lenses (such as precursor lenses) can be used as substrates on which subsequent material layers are deposited / built to produce three-dimensional optical articles that can be post-processed into optical lenses. Due to the limitations of slot-polymer additive manufacturing, when building continuous layers, the additive manufacturing process must occur when the substrate is oriented in a substantially horizontal orientation (e.g., across the build platform).

[0088] Using substrates and / or horizontal printing presents numerous drawbacks that adversely affect the optical performance of the resulting lenses. Specifically, when objects are printed in a horizontal orientation (e.g., the optical surface is horizontal with the printing surface / bed of the 3D printer), the layer thickness of the composition is proportional to the height of concentric circular defects present within the lens. Concentric circular defects refer to optical defects that manifest as a series of circular or ring-shaped patterns on the lens surface. These defects cause birefringence, and in some cases, circular birefringence, because multiple layers of material split light into different wavelengths and produce a rainbow effect. Specifically, circular birefringence can occur when the lens material introduces a phase difference between the two circularly polarized components of light. Such defects may be directly related to the layer-by-layer lines of the printed object, exhibiting a rainbow effect when the optical article is tilted relative to the light source. Therefore, optical articles manufactured using horizontally oriented additive manufacturing (such as those dependent on substrates) include many concentric circles (e.g., due to horizontal deposition methods), resulting in relatively high (if not very high) birefringence (e.g., birefringence defects). These birefringence defects negatively impact the optical performance of the lens, affecting its visual quality and clarity, and potentially affecting the wearer's vision.

[0089] Furthermore, the limitations of slot-type additive manufacturing necessitate the use of support structures to hold the substrate to the build platform. Based on the horizontal orientation of the additive manufacturing process, this build platform must be attached to the article across the front or rear surface of the printed object to build subsequent layers. For example, when using a lens precursor (e.g., a substrate), the substrate must be held to the build platform by a support structure attached to a flat / optical surface of the lens precursor. Alternatively, if no substrate is used, a support structure is required to attach the object to the build platform during formation, which is also attached to a flat / optical surface in a horizontal orientation. Such support structures adversely affect the overall quality of the object because the support structure is attached to a flat surface (or, in the case of ophthalmic articles, an optical surface), leaving numerous surface defects or ridges after the support structure is removed, resulting in undesirable defects in the object. For example, the front and rear optical surfaces may be blocked due to surface defects caused by the support structure, rendering the lens unusable / defective. The surface roughness of the resulting object may also increase due to the attachment of the support structure.

[0090] Vertical additive manufacturing of optical articles is substrate-independent (e.g., substrate-free). Therefore, vertically oriented printing significantly reduces the impact of circular defects compared to horizontal printing. Specifically, any circular defects in an object printed in a vertical orientation are related to the pixel size of the projected image or the vector tracked by the 3D printer. These variables can therefore be tuned to minimize circular defects depending on their orientation along the Z-axis, resulting in ophthalmic articles that are superior to those additively manufactured in a horizontal orientation.

[0091] Furthermore, vertical additive manufacturing of optical articles avoids the support structure 13 contacting the front surface 12a and / or the rear surface 12b, but instead only contacts the outer periphery of the object 12, such as along the bottom surface 12c. In this case, any defects or ridges can be easily removed from the outer periphery (e.g., compared to the front surface 12a and / or the rear surface 12b), and in the case of ophthalmic lenses / objects, adverse effects on the optical surface of the lens are avoided, as well as... Figure 4 As shown in step 42.

[0092] B. Post-curing process

[0093] In trough photopolymerization, a post-curing process is performed to enhance the structural and functional properties of the printed object. The post-curing cycle uses UV light with the same or substantially similar irradiance as that used during the trough photopolymerization printing process. Some post-curing systems / processes utilize post-heating (e.g., via heating elements), which provides a thermal cycle before or during the post-curing cycle to enhance the mechanical properties and drying of the printed part.

[0094] refer to Figure 3A and 3B This illustrates the post-curing process 30. The mold 34 can be placed on either side of the lens 12, and also... Figure 4 As described in step 43. The mold 34 can be a rigid, semi-rigid, or flexible mold. The mold 34 can be made of materials such as plastic, glass, or any other suitable material. The mold 34 can have a hollow region with a geometry substantially similar to the desired geometry of the printed object. Figure 4 In step 44, additional monomers 32 can be added to the printed lens 12 and mold 34, such that the total volume of the hollow region of mold 34 is filled with the lens 12 and the additional monomers 32. The amount of additional monomers added can be directly related to the surface area to be covered and the pressure applied to the monomers to find the optimal amount. The lens 12 can be clamped in the middle by mold 34, and mold 34 is secured together by fasteners (such as transparent tape, clamps, or other suitable devices) to keep the position and pressure on the lens 12 constant. Figure 4 Step 44). The amount of additional monomer 32 added can be selected to fill the volume created by the gap between the printed surfaces of the lens 12 and the mold 34.

[0095] Once the mold is closed, the lens and additional monomer are inside the mold, which can be exposed to UV light, such as at temperatures between 60°C and 120°C for 1 hour, 2 hours, or 3 hours. Figure 4 Step 45). The curing time and temperature can be proportional to the UV light source irradiance. The optical composition is prepared with an LED UV light source and 9.1 mW / cm². 2The post-curing oven with appropriate irradiance can cure at 80°C for 2 hours. However, the optical composition is not cured under conditions with a mercury bulb and 964 mW / cm². 2 The lens can be cured at 80°C for 1 minute in a post-curing oven with high irradiance. In the event of grooves and / or other surface defects on the surface of the lens 12 (e.g., during 3D printing), the monomer 32 fills such features, and once cured, produces a lens 12 with a smooth optical surface.

[0096] After heat and UV exposure, the fasteners are removed and the mold 34 can be opened. To separate the printed lens 12 from the mold 34, a solvent can be used to lift the lens 12 and release it from the mold 34. Figure 4 Step 46). Lens 12 does not require cleaning solvents to remove haze (e.g., the process is essentially solvent-free).

[0097] IV. Properties of Additively Manufactured Objects Using Groove Photopolymerization

[0098] A wide variety of objects can be printed using the compositions and methods described herein. For example, and as described above, ophthalmic objects (e.g., ophthalmic lenses) comprising optical compositions can be formed via the trench polymerization-based additive manufacturing and curing process of the present invention, which can result in ophthalmic objects exhibiting surprisingly high-performance properties and / or characteristics compared to similar additive manufacturing techniques. Specifically, the type and weight percentage of each of the photocurable monomers / monomer blends, UV absorbers, photoinitiators, and HALS components in the optical composition can be combined to allow the ophthalmic object to be printed via trench polymerization, wherein the optical surfaces of the object are oriented in a vertical direction (e.g., normal to the print bed / print surface of the trench polymerization 3D printer), as based on the selection / adjustment of various printing parameters including bottom exposure time, bottom layer, exposure time, shut-off time, and layer thickness. After curing, the optical articles can exhibit surprisingly high-performance characteristics compared to articles obtained by other additive manufacturing techniques (e.g., trench polymerization with substrate / horizontal orientation). The performance characteristics are directly generated by the selection of any of the components of the optical composition and the printing parameters used. Therefore, and in light of the foregoing discussion, the printing method and optical composition can be considered optimized to result in additively manufactured objects, and particularly ophthalmic objects, that exhibit performance comparable to molded lenses, representing a significant improvement over similar additive manufacturing technologies.

[0099] A. Layer thickness

[0100] As previously mentioned, the printed object may have a minimum layer thickness of 0.1 µm, 1 µm, 4 µm to 6 µm, 8 µm, or 10 µm, or any range (such as 0.1 µm to 10 µm, 1 µm to 8 µm, or 4 µm to 6 µm) using any of the aforementioned values ​​as endpoints. As previously mentioned, layer thickness can directly affect the surface roughness of the printed article (e.g., in a proportional manner). Smaller layer thicknesses increase the hardness of the resulting optical article and reduce haze and surface defects.

[0101] B. Optical geometry

[0102] Optical articles printed using the compositions and methods of this disclosure may have planar, plano-convex, biconvex, plano-concave, biconcave, achromatic, and / or aspherical geometries. Alternatively, optical articles may have square, circular, or elliptical geometries.

[0103] Optical articles may have optical lens geometries of -1, -2 to -3 or -4, or any range (such as -1 to -4 or -2 to -3) using any of the aforementioned values ​​as endpoints.

[0104] C. Total thickness of optical products

[0105] Optical articles may have a total thickness of at least 1 mm, at least 2 mm, at least 2.5 mm, at least 3 mm, at least 3.5 mm or at least 4 mm, or any range (such as 1 mm to 4 mm, 2 mm to 3.5 mm or 2.5 mm to 3 mm) using any of the foregoing values ​​as endpoints.

[0106] D. Surface roughness

[0107] Surface roughness of a printed object (such as an ophthalmic lens) refers to the microscopic irregularities on its outer surface, influencing factors such as visual acuity, comfort, and the likelihood of light scattering. Lower surface roughness is associated with smoother lenses, which contributes to improved optical performance and wearer satisfaction. The surface of a printed object can be determined by printing variables, including but not limited to illumination pixel size. Printed objects may have roughness measured using a confocal laser scanning microscope. Before adding the object to the mold and adding additional monomers, the object printed according to the method of this disclosure may have a root mean square height (Sq) of surface roughness less than 0.250 µm, less than 0.200 µm, less than 0.150 µm, less than 0.100 µm, less than 0.080 µm, less than 0.060 µm, less than 0.040 µm, or less than 0.020 µm, or any range using any of the foregoing values ​​as endpoints (such as 0.020 µm to 0.250 µm, 0.040 µm to 0.200 µm, 0.060 µm to 0.150 µm, or 0.080 µm to 0.100 µm).

[0108] Horizontally printed objects may have a root mean square height of surface roughness greater than 0.250 µm, which is caused by the staircase effect in the optical surface located on the printed surface.

[0109] E. Microhardness

[0110] The microhardness of additively manufactured objects (such as ophthalmic lenses) describes their resistance to indentation or surface deformation at the microscopic level, thus providing in-depth knowledge of the lens's durability and ability to withstand external forces without compromising its optical performance. Objects additively manufactured according to the methods of this disclosure can have a microhardness of at least 90 N / mm². 2 At least 100 N / mm 2 At least 110 N / mm 2 At least 120 N / mm 2 At least 130 N / mm 2 Or at least 180 N / mm 2 Or any range using any of the aforementioned values ​​as endpoints (such as 90 N / mm). 2 Up to 180 N / mm 2 100 N / mm 2 Up to 130 N / mm 2 Or 110 N / mm 2 Up to 120 N / mm 2 The microhardness of the material, as determined by DIN EN ISO 14577-1.

[0111] F. Refractive index

[0112] The refractive index (RI) of an additively manufactured object (such as an ophthalmic lens) refers to the degree to which the lens can bend and slow down light, thus affecting its optical power; a higher refractive index indicates more efficient light bending, making it possible to manufacture thinner and lighter lenses with enhanced vision correction. Additively manufactured objects according to the methods of this disclosure may have a refractive index of 1.0, 1.1, 1.3 to 1.5, 1.6, or 1.7, or any range (such as 1.0 to 1.7, 1.1 to 1.6, or 1.3 to 1.5) using any of the foregoing values ​​as endpoints, as measured according to ASTM C1648.

[0113] G. Abbe value

[0114] The Abbe value of an additively manufactured object (such as an ophthalmic lens) refers to its ability to disperse light, indicating how much chromatic aberration or color distortion occurs when light passes through the lens; a higher Abbe value means lower chromatic aberration and better optical quality. Additively manufactured objects according to the methods of this disclosure may have Abbe values ​​of 28, 30, 32 to 35, 36, or 38, or any range (such as 28 to 38, 30 to 36, or 32 to 35) using any of the foregoing values ​​as endpoints, as measured according to ASTM C1648.

[0115] H. Transmittance percentage (%)

[0116] The transmittance percentage (%) of an additively manufactured object (such as an ophthalmic lens) represents the percentage of light that passes through the lens, indicating its optical transparency; a higher transmittance value (%) corresponds to a greater amount of light transmitted, thus contributing to clear vision and visual comfort. Additively manufactured objects according to the methods of this disclosure can have transmittance (%) of 86%, 88%, 90% to 92%, 94% to 95%, or any range using any of the foregoing values ​​as endpoints (such as 86% to 95%, 88% to 94%, or 90% to 92%), as measured according to ASTM D1003-9.

[0117] I. Haze value percentage

[0118] The percentage (%) of haze in an additively manufactured object (such as an ophthalmic lens) describes the turbidity of the lens caused by light scattering. The higher the value, the greater the visible turbidity in the object. Additively manufactured objects according to the methods of this disclosure may have a haze percentage of less than 10%, less than 8%, less than 6%, less than 4%, less than 2%, or less than 1%, or any range (such as 1% to 10%, 2% to 8%, or 4% to 6%) using any of the foregoing values ​​as endpoints, as determined by ASTM D1003.

[0119] J. Yellowing Index

[0120] The yellowing index (also known as YIE313) of additively manufactured objects (such as ophthalmic lenses) at a wavelength of 313 nanometers is a measure of the degree of yellow tint in the lens material when exposed to ultraviolet light, providing insight into its potential to filter harmful ultraviolet rays and improving visual comfort by reducing glare and enhancing contrast. Additively manufactured objects according to the methods of this disclosure can have YIE313 values ​​greater than 6, 8, 10, 12, 14, or 16, as measured according to ASTM E313.

[0121] K. Birefringence

[0122] As previously stated, birefringence in additively manufactured objects (such as ophthalmic lenses) is an optical property of the lens that occurs when a beam of light passes through an optical material and is split into different wavelengths, resulting in a rainbow effect. Specifically, circular birefringence can occur when the lens material introduces a phase difference between the two circularly polarized components of light. As previously stated, objects additively manufactured according to the methods of this disclosure can significantly reduce birefringence effects compared to similar articles manufactured by similar techniques (e.g., horizontally / with a substrate), and in some cases, can significantly reduce circular birefringence effects because the ophthalmic articles of this disclosure are additively manufactured with a substantially vertical orientation. Therefore, objects additively manufactured according to the methods of this disclosure can have low (e.g., 2, as relevant to Working Example 6) or no (e.g., 1, as relevant to Working Example 6) birefringence effects.

[0123] Example

[0124] The aspects of this disclosure are further illustrated by the following examples. It will be apparent to those skilled in the art that many modifications can be made to the materials and methods without departing from the scope of this disclosure.

[0125] Example 1: Formulation of monomer optical compositions for trough photopolymerization technology

[0126] In this example, a first additively fabricable (e.g., 3D printable) optical composition is mixed to achieve optimal printing. The components of the formulation are constructed using the following composition.

[0127] Table 1: First Formulation of Medium Refractive Index Monomer Optical Compositions

[0128]

[0129] 1 A mixture of monofunctional and difunctional methacrylates was prepared to obtain a polymer with a refractive index of 1.56.

[0130] Example 2: Formulation of optical compositions for trough photopolymerization technology

[0131] In this example, a second additively fabricable (e.g., 3D printable) optical composition is blended to achieve optimal printing. The components of the formulation are constructed using the same method described with respect to Example 1.

[0132] Table 2: Formulations of high refractive index monomer optical compositions

[0133]

[0134] 2 A mixture of 40% difunctional methacrylate and 60% difunctional and trifunctional thiomethacrylate (by weight) was prepared to obtain a polymer with a refractive index of 1.60.

[0135] Example 3: Formulation of optical compositions for trough photopolymerization technology

[0136] In this example, a third additively fabricable (e.g., 3D printable) optical composition is blended to achieve optimal printing. The components of the formulation are constructed using the same method described with respect to Example 1.

[0137] Table 3: Formulations of medium refractive index monomer optical compositions

[0138]

[0139] 3 A mixture of monofunctional and difunctional methacrylates was prepared to obtain a polymer with a refractive index of 1.56.

[0140] Example 4: Formulation of optical compositions for trough photopolymerization technology

[0141] In this example, a fourth additively fabricable (e.g., 3D printable) optical composition is blended to achieve optimal printing. The components of the formulation are constructed using the same method described with respect to Example 1.

[0142] Table 4: Formulations of Medium Refractive Index Monomer Optical Compositions

[0143]

[0144] 4 A mixture of monofunctional and difunctional methacrylates was prepared to obtain a polymer with a refractive index of 1.56.

[0145] Example 5: Printing of formulations for medium and high refractive index monomer compositions for channel photopolymerization technology

[0146] For additive manufacturing processes (e.g., 3D printing), computational-aided designs are generated for 3D printing and appropriate orientation, allowing slices to be digitally generated and all this information, including other parameters, to generate physical objects in the 3D printer. Various lenses, including the optical composition of Example 1, are printed using different layer thicknesses.

[0147] The computer-aided design (CAD) lens geometry should be precisely exported from the CAD software package and imported into the additive manufacturing slicer software package to orient the part, generate the support structure geometry, and set the manufacturing parameters as described below:

[0148] Table 5: Printing parameters (irradiance = 3.2 nW / cm) 2 )

[0149]

[0150] When surface roughness results are established directly from additive manufacturing equipment, the orientation of the lens geometry is important. Therefore, a vertical orientation of the optical surface that does not face the bottom or top of the printing area is an important design aspect for achieving optimal printability of these functional surfaces.

[0151] Example 6: Smoothing the outer surface of a 3D-printed -4 lens

[0152] The contrast lens (Sample Comparison C) was cast using conventional methods and the same optical composition as in Example 1. This involved using a glass mold for a plane lens, which was assembled with tape to create a gap of approximately 2 mm thickness. The liquid monomer composition was then poured into the cavity of the molded lens and finally sealed using the same tape that held the mold in place. The encapsulated lens (Comparison C) did not undergo the post-curing process described in Example 7.

[0153] Example 7: Smoothing the outer surface of a 3D-printed -4 lens

[0154] Each of the printed lenses is placed between two glass mold parts, each corresponding to the exact same geometry placed on each surface. Additionally, further 3D printing formulations (e.g., monomers) are added between the glass molds and the printed surfaces, and between the molds and the lenses, to further aid in the smoothing of the printed surfaces. Transparent tape is used to hold the glass molds to the printed object. The tape holds the components in place and applies pressure between the mold surfaces and the printed surfaces to ensure that the liquid formulation makes full contact with all surfaces upon curing.

[0155] The printed lenses in the mold are exposed to both heat and UV light to cure the added monomers into any grooves on the object produced by the trench photopolymerization process. The post-curing cycle includes exposure to 9.12 mW / cm² irradiance at 80°C. 2 Expose to UV light for 2 hours.

[0156] Post-cured lenses appear completely transparent. However, three main defects can still be seen when backlit. The first defect is the presence of concentric circles, almost invisible to the naked eye but clearly visible under backlight. The same figure A shows a diagonal line, or birefringence, passing through the center of the backlit lens. This birefringence can be caused by multiple exposures during the layer-by-layer process. The location of the birefringence varies depending on the lens's viewing angle, reflecting multiple layer lines during the additive process. The final defect is the incomplete filling of portions of the lens with additional monomers during post-curing, as shown in part B of the same figure, resulting in a less transparent surface. This defect is affected by the pressure applied to the mold and the amount of additional monomers used.

[0157] Example 8: Characteristics of 3D Printed Lenses

[0158] The data in Table 6 show a comparison of typical optical properties and hardness of the optical compositions. Table 7 shows similar information, but for the stained version of the optical composition. Table 8 shows similar information, but for compositions with higher refractive indices. In both cases, the properties shown for the printed instance, particularly at lower layer thicknesses, are the same as those for the cast sample (Comparison C). Table 9 shows the optical properties of formulations with different photoinitiators, taking higher loadings of the element and their effects as an example. Only small differences exist in the haze percentage, which decreases progressively with smaller layer thicknesses. For birefringence, a qualitative evaluation was performed on all tested samples. The standard followed was to place each sample on a white background at a certain height, with light shining through the top. If a set of rainbow lines is observed on the white paper, the birefringence effect is recorded. If the rainbow effect is relatively thin, it will be recorded as low birefringence, but if it is thick, it will be recorded as high birefringence. Figure 5 An example is shown below.

[0159] Table 6: Characteristics of Printed Lenses (including Composition 1)

[0160]

[0161] Table 7: Characteristics of Printed Lenses (with Dyes) with Medium Refractive Index Formulas

[0162]

[0163] Table 8: Characteristics of Printed Lenses with High Refractive Index Formulations

[0164]

[0165] Table 9: Characteristics of Printed Lenses with Medium Refractive Index Formulation

[0166]

[0167] The cast samples serve as a baseline for comparison with any printed samples. All samples with a layer thickness of 25 µm or less exhibit consistent characteristic performance, with the haze percentage changing most significantly as the layer thickness decreases.

[0168] The lenses produced after the post-curing process have a smoother surface than the same lenses used immediately after printing and the contrast cast lens (Sample I). The cast samples were made with disc or plane lenses, while the printed and post-processed lenses are of -4 geometry. The lenses were measured on the stage of a Keyence VK-X260K / X250K confocal scanning laser microscope. The samples were imaged using a 20x magnifying lens. Once the images were captured, they were fed into the VK File Analyzer program, where surface roughness was obtained using general software parameters. The height maps were normalized so that the central region of each sample was 0 micrometers.

[0169] Table 10 shows the smoothness characteristics of post-cured lens sample F relative to cast lens and sample F printed without a post-curing process. These results demonstrate how post-processing methods can provide surfaces as good as casting or conventional manufacturing methods.

[0170] Table 10: Surface Roughness of Lenses

[0171]

[0172] While specific examples of the invention have been described above for illustrative purposes, it will be apparent to those skilled in the art that various changes may be made to the details of the invention without departing from the invention as defined by the appended claims. Therefore, this disclosure is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Furthermore, this disclosure is intended to cover any such departures from this disclosure within known or conventional practice in the art to which this disclosure pertains, and which fall within the limitations of the appended claims.

[0173] aspect

[0174] Aspect 1 is an optical composition for trough photopolymerization, wherein, based on the total mass of the optical composition, the optical composition comprises: a monomer or blend of monomers comprising at least one of (meth)acrylate and / or thio-(meth)acrylate functional groups; 0.20% to 3% by mass of a photoinitiator; 0.40% to 2.2% by mass of a UV absorber; and 0.40% to 2.2% by mass of a hindered amine light stabilizer (HALS).

[0175] Aspect 2 is an optical composition according to aspect 1, wherein the monomer or blend of the monomer comprises two or more (meth)acrylate and / or thio-(meth)acrylate functional groups.

[0176] Aspect 3 is an optical composition according to aspect 1 or aspect 2, wherein the UV absorber comprises at least one of benzophenone and triazine.

[0177] Aspect 4 is an optical composition according to any one of aspects 1 to 3, wherein the photoinitiator comprises an acylphosphine oxide type 1 photoinitiator.

[0178] Aspect 5 is an optical composition according to any one of Aspects 1 to 4, wherein the UV absorber comprises an absorption range of 300 nm to 405 nm.

[0179] Aspect 6 is an optical composition according to any one of aspects 1 to 5, further comprising 0.0001 wt.% to 0.0005 wt.% of at least one additive; wherein the at least one additive is one of pigment, fixing dye, antioxidant, polymerization modifier, photosensitizer and internal release agent.

[0180] Aspect 7 A method of forming an optical article, the optical article comprising an optical surface defining an optical geometry, the method comprising: printing the optical article having a predetermined curved or flat boundary using a trench photopolymerization, the curved or flat boundary defining the optical geometry; wherein the optical article is printed such that the optical surface of the optical article extends along a z-axis perpendicular to a printed surface on which the optical article is printed; and wherein the trench photopolymerization comprises an optical composition, the optical composition comprising, based on the total mass of the optical composition: a monomer or blend of monomers comprising at least one of (meth)acrylate and thio-(meth)acrylate functional groups; 0.20% to 3% by mass of a photoinitiator; 0.40% to 2.2% by mass of a UV absorber; and 0.40% to 2.2% by mass of a hindered amine light stabilizer (HALS).

[0181] Aspect 8 is the method according to aspect 7, further comprising printing a support structure for the optical article, the support structure anchoring the optical article to the printed surface along the peripheral edge of the optical article.

[0182] Aspect 9 is the method according to aspect 8, which further includes removing the support structure from the optical article.

[0183] Aspect 10 is a method according to any one of aspects 7 to 9, further comprising: encapsulating the optical article in a mold having a hollow portion defining a mold optical geometry, wherein the mold optical geometry is substantially similar to the optical geometry of the optical article; filling the mold with an excess of optical composition; securing the mold with fasteners; exposing the mold to UV light and heat; and removing the optical article from the mold.

[0184] Aspect 11 is the method according to aspect 10, wherein filling the mold with an excess optical composition comprises filling the mold with a certain amount of optical composition such that any grooves or defects on the surface of the optical article are filled with the excess optical composition; wherein exposing the mold to UV light and heat causes the excess optical composition in the grooves or defects on the surface of the optical article to cure.

[0185] Aspect 12 is the method according to any one of Aspects 10 to 11, wherein the optical article removed from the mold has a haze percentage of less than 2%, as determined by ASTM D1003.

[0186] Aspect 13 is the method according to any one of aspects 10 to 12, wherein the optical article removed from the mold has a strength of at least 120 N / mm. 2 The hardness, as measured by DIN EN ISO 14577-1.

[0187] Aspect 14 is the method according to any one of aspects 10 to 13, wherein the optical article removed from the mold has a surface roughness of less than 0.2 µm.

[0188] Aspect 15 is the method according to any one of Aspects 10 to 14, wherein the optical article comprises a transmittance value of more than 80%, as measured according to ASTM D1003-9.

[0189] Aspect 16 is the method according to any one of aspects 10 to 15, wherein the optical geometry of the optical article includes at least one of planar, plano-convex, biconvex, plano-concave, biconcave, positive achromatic, and aspherical geometry.

[0190] Aspect 17 is the method according to any one of aspects 7 to 16, wherein printing the optical article comprises printing continuous layers, each having a layer thickness of 0.1 µm to 10 µm.

[0191] Aspect 18 is the method according to any one of aspects 7 to 17, wherein the optical article is printed using a slotted photopolymerization method, comprising a bottom exposure time of 20 to 32 seconds.

[0192] Aspect 19 is the method according to any one of aspects 7 to 18, wherein printing the optical article using slotted photopolymerization includes a shut-off time of 0.1 seconds to 5 seconds.

[0193] Aspect 20 is the method according to any one of aspects 7 to 19, wherein printing the optical article using slotted photopolymerization includes printing 2 to 7 substrates of the optical article.

Claims

1. An optical composition for channel photopolymerization, wherein, based on the total mass of the optical composition, the optical composition comprises: Monomers or blends of monomers containing at least one of (meth)acrylate and / or thio-(meth)acrylate functional groups; 。 2. The optical composition according to claim 1, wherein the monomer or blend of the monomer comprises two or more (meth)acrylate and / or thio-(meth)acrylate functional groups.

3. The optical composition according to claim 1 or claim 2, wherein the UV absorber comprises at least one of benzophenone and triazine.

4. The optical composition according to any one of claims 1 to 3, wherein the photoinitiator comprises an acylphosphine oxide type 1 photoinitiator.

5. The optical composition according to any one of claims 1 to 4, wherein the UV absorber comprises an absorption range of 300 nm to 405 nm.

6. The optical composition according to any one of claims 1 to 5, further comprising 0.0001 wt.% to 0.0005 wt.% of at least one additive; The at least one additive is one of pigment, fixing dye, antioxidant, polymerization modifier, photosensitizer and internal release agent.

7. A method of forming an optical article, the optical article comprising an optical surface defining an optical geometry, the method comprising: The optical article is printed using a slotted photopolymerization process and has a predetermined curved or flat boundary, which defines the optical geometry. The optical article is printed such that the optical surface of the optical article extends along the z-axis, which is perpendicular to the printed surface on which the optical article is printed. and The aforementioned slotted photopolymerization includes an optical composition, which, based on its total mass, comprises: Monomers or blends of monomers containing at least one of (meth)acrylate and thio-(meth)acrylate functional groups; 。 8. The method of claim 7, further comprising printing a support structure for the optical article, the support structure anchoring the optical article to the printed surface along the peripheral edge of the optical article.

9. The method of claim 8, further comprising removing the support structure from the optical article.

10. The method according to any one of claims 7 to 9, further comprising: The optical article is sealed in a mold having a hollow portion defining the optical geometry of the mold, wherein the optical geometry of the mold is substantially similar to the optical geometry of the optical article; The mold is filled with an excess of optical composition; Secure the mold with fasteners; The mold was exposed to UV light and heat; Remove the optical article from the mold.

11. The method of claim 10, wherein filling the mold with an excess of optical composition comprises filling the mold with a certain amount of optical composition such that any grooves or defects on the surface of the optical article are filled with the excess optical composition; The mold is exposed to UV light and heat to cure the excess optical composition within the grooves or defects on the surface of the optical article.

12. The method according to any one of claims 10 to 11, wherein the optical article removed from the mold has a haze percentage of less than 2%, as determined by ASTM D1003.

13. The method according to any one of claims 10 to 12, wherein the optical article removed from the mold has a strength of at least 120 N / mm. 2 The hardness, as measured by DIN EN ISO 14577-1.

14. The method according to any one of claims 10 to 13, wherein the optical article removed from the mold has a surface roughness of less than 0.2 µm.

15. The method according to any one of claims 10 to 14, wherein the optical article comprises a transmittance value of more than 80%, as measured according to ASTM D1003-9.

16. The method according to any one of claims 10 to 15, wherein the optical geometry of the optical article comprises at least one of planar, plano-convex, biconvex, plano-concave, biconcave, positive achromatic, and aspherical geometry.

17. The method according to any one of claims 7 to 16, wherein printing the optical article comprises printing continuous layers, each having a layer thickness of 0.1 µm to 10 µm.

18. The method according to any one of claims 7 to 17, wherein printing the optical article using a slotted photopolymerization method includes a bottom exposure time of 20 to 32 seconds.

19. The method according to any one of claims 7 to 18, wherein printing the optical article using slotted photopolymerization includes a shut-off time of 0.1 seconds to 5 seconds.

20. The method according to any one of claims 7 to 19, wherein printing the optical article using slotted photopolymerization comprises printing two to seven substrates of the optical article.

Images