Method for forming an object within the volume of a photocurable composition

Abstract

The present invention includes a method for forming an object within a volume containing a photocurable composition described herein, the photocurable composition including a photocurable resin component and a photoswitchable photoinitiator including a P-type photochromic molecule. The present invention also includes a photoswitchable photoinitiator including a P-type photochromic molecule, preferably including a P-type diarylethene molecule, and a photocurable composition and method including such a photoswitchable photoinitiator.

Description

Technical Field

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 341,594, filed May 13, 2022; U.S. Provisional Patent Application No. 63 / 438,280, filed Jan. 11, 2023; U.S. Provisional Patent Application No. 63 / 440,085, filed Jan. 19, 2023; and U.S. Provisional Patent Application No. 63 / 450,931, filed Mar. 8, 2023, each of which is hereby incorporated by reference in its entirety for any purpose.

Background Art

[0002] The present invention relates to the technical field of three-dimensional printing and related compositions, materials, methods, and products.

Summary of the Invention

Means for Solving the Problems

[0003] (Summary of the Invention) The present invention includes a method for forming an object within the volume of a photocurable composition, the method including a photocurable resin component and a photoswitchable photoinitiator including a P-type photochromic molecule. The present invention also includes a photoswitchable photoinitiator including a P-type diarylethene molecule represented by the formula described herein, a photocurable composition including any of such photoswitchable photoinitiators, and a method.

[0004] According to one aspect of the present invention, a method for forming an object within the volume of a photocurable composition, comprising: (a) providing a volume containing a photocurable composition, the photocurable composition including a photocurable resin component and a photoswitchable photoinitiator including a P-type photochromic molecule; (b) irradiating, simultaneously or sequentially, light having a first wavelength and light having a second wavelength at one or more selected locations within the volume of the photocurable composition, wherein the light having the first wavelength and the light having the second wavelength activate a light-switchable photoinitiator at the one or more selected locations to induce a crosslinking or polymerization reaction in the photocurable composition at the intersection of the first and second wavelengths, thereby at least partially forming an object, and (c) optionally repeating step (b) of irradiating the photocurable composition at one or more selected locations within the volume that are the same as or different from the previous one or more selected locations until the object is partially or fully formed. A method is provided.

[0005] The method preferably further comprises separating the partially or fully formed object from the photocurable composition.

[0006] A preferred light-switchable photoinitiator for inclusion in the method of the present invention comprises a substituted or unsubstituted P-type photochromic molecule, preferably a P-type diarylethene molecule. The P-type photochromic molecule is activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and induces a crosslinking or polymerization reaction in the photocurable composition at the intersection of the first and second wavelengths. The first wavelength is shorter than the second wavelength.

[0007] A more preferred light-switchable photoinitiator for inclusion in the method of the present invention comprises a P-type photochromic molecule, preferably a P-type diarylethene molecule, which contains one or more substituents, at least one of which contains a carbonyl group. The P-type photochromic molecule is activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and induces a crosslinking or polymerization reaction in the photocurable composition at the intersection of the first and second wavelengths. The first wavelength is shorter than the second wavelength.

[0008] Examples of substituents containing a carbonyl group include, but are not limited to, substituted or unsubstituted thioxanthone groups, substituted or unsubstituted diaryl ketone groups, substituted or unsubstituted benzophenone groups, substituted or unsubstituted alpha-diketones (e.g., but not limited to, substituted or unsubstituted benzyl groups, etc.), polycyclic groups containing at least two fused rings of atoms, at least one of the fused rings of atoms contains one or more substituents, and at least one of the substituents contains a double bond oxygen bonded to a carbon atom ring member contained in one of the fused rings (e.g., but not limited to, acenaphthylene-1,2-dione groups, polycyclic groups containing at least two fused rings of atoms include thiochroman-4-one groups, 9-fluorenone groups, anthraquinone groups, benzanthrone groups, 9,10-phenanthrenequinone groups, etc. and their derivatives). Substituents on a substituted functional group containing a carbonyl group may optionally further include one or more additional substituents.

[0009] Preferred P-type diarylethene molecules include P-type diarylcycloalkene molecules. Such molecules may desirably contain one or more substituents. More preferably, such molecules contain one or more substituents, at least one of which contains a carbonyl group.

[0010] Examples of more preferred photoswitchable photoinitiators for inclusion in the photocurable compositions and methods described herein include P-type photochromic molecules that contain one or more substituents, at least one of which contains a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group containing at least two fused rings of atoms, at least one of the fused rings of atoms contains one or more substituents, and at least one of the substituents contains a double bond oxygen bonded to a carbon atom ring member contained in one of the fused rings, but are not limited thereto.

[0011] A more preferred photocurable composition for inclusion in the methods described herein contains a photoswitchable photoinitiator according to another aspect of the present invention.

[0012] According to another aspect of the present invention, a photo-switchable photoinitiator comprising a P-type photochromic molecule is provided, the molecule comprising one or more substituents, at least one of the substituents comprising a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group comprising at least two fused rings of atoms, at least one of the fused rings of atoms comprising one or more substituents, at least one of the substituents comprising a double bond oxygen bonded to a carbon atom ring member contained in one of the fused rings, the P-type photochromic molecule being activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and at the intersection of the first and second wavelengths, inducing a crosslinking or polymerization reaction in the photocurable composition, the first wavelength being shorter than the second wavelength.

[0013] The photo-switchable photoinitiator according to the present invention preferably comprises a P-type photochromic molecule.

[0014] Non-limiting examples of preferred photo-switchable photoinitiators are of general formula (I)

[0015]

Chemical formula

[0016]

Chemical formula

[0017] [Chemical formula] (wherein E is a ring member, an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or R 6 A nitrogen atom having a substituent (NR6 ) represents Z is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R 7 a sulfur atom having a substituent (SR 7 ), R 8 an oxygen atom having a substituent (OR 8 ), or a cyano (CN) group, and G is a member of the ring and represents a carbon atom having an R substituent (CR 9 ), or a nitrogen atom (N), L is a member of the ring and represents an R 1 carbon atom having a substituent (CR 1 ), or a nitrogen atom (N), R 1 and R 6 ~R 9 are substituents, which may be the same, different, or independent, and for example, hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkylaryl group, a substituted or unsubstituted heteroalkyl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted ester group, a substituted or unsubstituted carbonate group, a substituted or unsubstituted ketone group, a substituted or unsubstituted aldehyde group, a substituted or unsubstituted imine group, a substituted or unsubstituted carboxyl group, a substituted or unsubstituted amide group, a substituted or unsubstituted urethane group, a substituted or unsubstituted urea group, a substituted or unsubstituted tetrazine group, a substituted or unsubstituted amino group, iodine, bromine, chlorine, fluorine, a cyano group (-CN), a nitro group (-NO2), a hydroxyl group (-OH), a thiol (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group. Or

[0018]

Chemical formula

[0019]

Chemical formula

[0020]

Chemical formula

[0021]

Chemical formula

[0022] [Chemical formula] (wherein E' is a member of the ring and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or R 15 a nitrogen atom having a substituent (NR 15 )) and Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R 16 a sulfur atom having a substituent (SR 16 ), R 17 an oxygen atom having a substituent (OR 17 ), or a cyano (CN) group, and R 11 ~R 17is a substituent, which may be the same or different and independently represents, for example, hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkylaryl group, a substituted or unsubstituted heteroalkyl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted ester group, a substituted or unsubstituted carbonate group, a substituted or unsubstituted ketone group, a substituted or unsubstituted aldehyde group, a substituted or unsubstituted imine group, a substituted or unsubstituted carboxyl group, a substituted or unsubstituted amide group, a substituted or unsubstituted urethane group, a substituted or unsubstituted urea group, a substituted or unsubstituted tetrazine group, a substituted or unsubstituted amino group, iodine, bromo, chloro, fluoro, a cyano group (-CN), a nitro group (-NO2), a hydroxyl group (-OH), a thiol (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group.) or

[0023]

Chemical formula

[0024] At least one R substituent includes a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group containing at least two fused rings of atoms, at least one of the fused rings of atoms includes one or more substituents, and at least one of the substituents includes a double bond oxygen bonded to a carbon atom ring member included in one of the fused rings, and when X is represented by (X a ) or (X b ), at one of positions R 1 or R 9 , when X is represented by the formula (X c ) or (X d ), at one of positions R 2 to R 5 , when Y is represented by (Y a ) or (Y b ), at one of positions R 10 or R 18 , or when Y is represented by (Y c ) or (Y d ), it may be desirable to be located at one of positions R 11 to R 14 .

[0025] Preferred examples of A include structures represented by the following formulas (A a ), (A b ), (A c ) and A( d ).

[0026] Optionally, the R groups on any two adjacent ring members of X and / or Y may include atoms for completing a ring structure that connects two adjacent substituents together. Such a ring structure may be substituted or unsubstituted and may optionally be part of a polycyclic substituted or unsubstituted ring structure. Such a ring structure, or, where applicable, the polycyclic structure of which the ring structure is a part, may optionally include one or more heteroatoms in addition to carbon atoms in the ring structure.

[0027] More preferably, at least one R substituent on X and / or Y is a substituted or unsubstituted benzophenone group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted acenaphthylene-1,2-dione group, a substituted or unsubstituted thiochroman-4-one group, a substituted or unsubstituted 9-fluorenone group, a substituted or unsubstituted anthraquinone group, a substituted or unsubstituted benzanthrone group, a substituted or unsubstituted 9,10-phenanthrenequinone group, a substituted or unsubstituted xanthone group, a substituted 1,2-indanedione group, a substituted or unsubstituted chromone group, a substituted or unsubstituted 1,4-naphthoquinone group, and the like.

[0028] Each of X and Y preferably contains a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group containing at least two fused rings of atoms, where at least one of the fused rings of atoms contains one or more substituents, and at least one of the substituents contains a double bond oxygen bonded to a carbon atom ring member contained in one of the fused rings, and may contain at least one R substituent. In such cases, such substituents on X and Y may be the same or different.

[0029] Optionally, X and Y may be symmetric in that the R substituents on X and the R substituents on Y are compatible with each other.

[0030] Optionally, X and Y are not symmetric with respect to each of X and Y containing one or more different substituents on each of X and Y.

[0031] At least one R substituent on X and / or at least one R substituent on Y may particularly preferably include a substituted or unsubstituted benzophenone group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted acenaphthylene-1,2-dione group, a substituted or unsubstituted thiochroman-4-one group, a substituted or unsubstituted 9-fluorenone group, a substituted or unsubstituted anthraquinone group, a substituted or unsubstituted benzanthrone group, a substituted or unsubstituted 9,10-phenanthrenequinone group, a substituted or unsubstituted xanthone group, a substituted 1,2-indanedione group, a substituted or unsubstituted chromone group, a substituted or unsubstituted 1,4-naphthoquinone group, and the like.

[0032] According to another aspect of the present invention, there is provided a photocurable composition containing a photocurable resin component and a P-type photochromic molecule, preferably a P-type diarylethene molecule, the molecule containing one or more substituents, at least one of the substituents containing a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group containing at least two condensed rings of atoms, at least one of the condensed rings of atoms containing one or more substituents, at least one of the substituents containing a double bond oxygen bonded to a carbon atom ring member contained in one of the condensed rings, the P-type photochromic molecule being activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and inducing a crosslinking or polymerization reaction in the photocurable composition at the intersection of the first and second wavelengths, the first wavelength being shorter than the second wavelength.

[0033] A preferred photocurable composition contains a photocurable resin component and a photo-switchable photoinitiator containing a P-type diarylethene molecule represented by the general formula (I) described herein. The photocurable composition may preferably further contain a sensitizer. The photocurable composition may desirably exhibit non-Newtonian rheological behavior.

[0034] The photocurable composition according to the present invention is particularly desirable for use in volume 3D printing for forming an object within the volume of the photocurable composition.

[0035] It should be recognized by those skilled in the art to which the present invention pertains that any of the features described herein with respect to any particular aspect and / or embodiment of the present invention can be modified, as necessary, to ensure compatibility in combination with any one or more of the other features of any other aspect and / or embodiment of the present invention described herein, and can be combined. Such combinations are considered to be part of the present invention contemplated by this disclosure.

[0036] All of the foregoing and other aspects and embodiments described herein and contemplated by this disclosure constitute embodiments of the present invention.

[0037] It should be understood that neither the foregoing summary nor the following detailed description is intended as a limitation on the claimed invention, but is merely exemplary and explanatory.

[0038] Other embodiments will be apparent to those skilled in the art from consideration of the description of the present invention, the claims, and practice disclosed herein.

Brief Description of the Drawings

[0039]

Figure 1A

Figure 1B

Figure 1C

Figure 1D

Figure 1E

Figure 1F

Figure 2A

Figure 2B

Figure 2C

Figure 2D

Figure 2E

Figure 2F

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 3E

Figure 3F

DETAILED DESCRIPTION OF THE INVENTION

[0040] The accompanying drawings are simplified representations presented for illustrative purposes only, and the actual structure differs in many respects including the relative scale of the articles depicted and their aspects.

[0041] To better understand the present invention, together with other advantages and capabilities, reference is made to the following disclosure in connection with the drawings described above and the appended claims.

[0042] Various aspects and embodiments of the present invention are further described in the following detailed description.

[0043] The present invention includes a method for forming an object within the volume of a photocurable composition, the photocurable composition including a photocurable resin component and a photoswitchable photoinitiator including a P-type photochromic molecule. The present invention also includes a photoswitchable photoinitiator including a P-type diarylethene molecule represented by the formulas described herein, and a photocurable composition and method including the photoswitchable photoinitiator of the present invention.

[0044] The display of a schematic diagram of the ring closure and photo-reversion of a P-type photochromic molecule including diarylethene (A’) is shown by Equation 1 (Eq1).

[0045]

Chemical formula

[0046] Upon exposure to light of a first wavelength, the P-type photochromic molecule A’ undergoes a 6π electron ring closure reaction upon exposure to light of the first wavelength (typically in the UV range), resulting in B’. The reaction can be readily reversed (photo-reversion) by exposure to light of a longer wavelength. However, compound B’ does not readily undergo thermal reversion to the open-ring form (A’) (the example shown in Eq1 shows substituents R A1 and R A2 but alternatively R A1 and R A2 may include atoms in a ring structure that links the two groups together (not shown).).

[0047] P-type photochromic molecules generally exhibit, or do not exhibit, minimal thermal reversibility on the time scale of typical 3D volume printing. Such typical time scales can generally be less than 1 hour.

[0048] The thermal back reaction of the two-color photoinitiator has been reported for its necessity in volume printing, but it has surprisingly been found that P-type photochromic molecules are effective and advantageous for use as photo-switchable photoinitiators in volume printing.

[0049] According to one aspect of the present invention, there is provided a method of forming an object within a volume of a photocurable composition, comprising: (a) providing a volume containing a photocurable composition, the photocurable composition comprising a photocurable resin component and a photo-switchable photoinitiator comprising a substituted or unsubstituted P-type photochromic molecule; (b) irradiating one or more selected locations within the volume of the photocurable composition simultaneously or sequentially with light having a first wavelength and light having a second wavelength, the light having the first wavelength and the light having the second wavelength activating the photo-switchable photoinitiator at the one or more selected locations to induce a crosslinking or polymerization reaction in the photocurable composition at the intersection of the first and second wavelengths at the one or more selected locations within the volume to at least partially form an object; and (c) optionally repeating step (b) of irradiating the photocurable composition until the object is partially or fully formed at one or more selected locations within the volume that are the same as or different from the previous one or more selected locations.

[0050] A preferred method of forming an object within a volume of a photocurable composition according to the present invention is: (a) providing a volume containing a photocurable composition, the photocurable composition comprising a photocurable resin component and a photo-switchable photoinitiator comprising a P-type photochromic molecule; (b) Projecting the optical image generated by the second excitation light along the projection axis onto a selected location in the volume, wherein the optical image is oriented perpendicular to the projection axis; (c) Generating an optical sheet containing the first excitation light and directing the optical sheet along the optical sheet illumination axis through the volume, such that the optical image and the optical sheet intersect at a selected location in a common plane, wherein the optical sheet overlaps the projected optical image at the selected location within the volume; and (d) Optionally repeating steps (b) and (c) one or more times to partially or fully form an object, wherein in the repeated set of steps (b) and (c), the selected location is the same as or different from a previous selected location, and the optical image is the same as or different from a previous optical image.

[0051] Preferably, the intersection of the optical sheet and the optical image in the common plane is in the same plane or a substantially the same plane.

[0052] The method according to the present invention preferably further comprises separating the partially or fully formed object from the photocurable composition.

[0053] A photo-switchable photoinitiator preferably included in the method of the present invention comprises a substituted or unsubstituted P-type photochromic molecule containing a P-type diarylethene molecule, wherein the P-type photochromic molecule is activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and at the intersection of the first and second wavelengths, induces a crosslinking or polymerization reaction in the photocurable composition, and the first wavelength is shorter than the second wavelength.

[0054] More preferably, the photo-switchable photoinitiator included in the method of the present invention preferably contains a P-type diarylethene molecule, the molecule contains one or more substituents, at least one of which contains a carbonyl group-containing P-type photochromic molecule, the P-type photochromic molecule is activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and at the intersection of the first and second wavelengths, it induces a cross-linking or polymerization reaction in the photocurable composition, and the first wavelength is shorter than the second wavelength. Preferably, at least one substituent containing a carbonyl group is bonded to the P-type diarylethene molecule. The substituent containing a carbonyl group may optionally further contain one or more additional substituents or moieties in addition to the C=O moiety.

[0055] The P-type diarylethene molecule to which at least one substituent containing a carbonyl group is bonded may preferably contain a P-type diarylcycloalkene or diarylcycloheteroalkene molecule. Examples of preferred P-type diarylcyclopentene or diarylcycloalkene molecules include, but are not limited to, P-type dithienylcyclopentene molecules. One or both of the two thienyl groups and / or the cyclopentene ring to which the thienyl group is bonded may desirably contain one or more substituents in addition to at least one substituent containing a carbonyl group.

[0056] Examples of substituents containing a carbonyl group include, but are not limited to, substituted or unsubstituted benzoyl groups, substituted or unsubstituted thioxanthone groups, substituted or unsubstituted diaryl ketone groups (e.g., but not limited to, substituted or unsubstituted benzophenone groups, etc.), substituted or unsubstituted alpha-diketones (e.g., but not limited to, substituted or unsubstituted benzyl groups, etc.), substituents containing polycyclic groups containing at least two fused rings of atoms, at least one of the fused rings of atoms contains one or more substituents, and at least one of the substituents is a double-bonded oxygen bonded to a carbon atom ring member contained in one of the fused rings (e.g., but not limited to, acenaphthylene-1,2-dione groups, polycyclic groups containing at least two fused rings of atoms include thiochroman-4-one groups, 9-fluorenone groups, anthraquinone groups, benzanthrone groups, 9,10-phenanthrenequinone groups, etc. and their derivatives).

[0057] Examples of additional substituents containing a carbonyl group include, but are not limited to, substituted or unsubstituted thioxanthone groups, substituted or unsubstituted diaryl ketone groups (e.g., but not limited to, substituted or unsubstituted benzophenone groups, etc.), substituted or unsubstituted alpha-diketones (e.g., but not limited to, substituted or unsubstituted benzyl groups, etc.), substituted or unsubstituted alpha-diketones (e.g., but not limited to, substituted or unsubstituted benzyl groups, etc.), substituents containing polycyclic groups containing at least two fused rings of atoms, at least one of the fused rings of atoms contains one or more substituents, and at least one of the substituents is a double-bonded oxygen bonded to a carbon atom ring member contained in one of the fused rings (e.g., but not limited to, acenaphthylene-1,2-dione groups, polycyclic groups containing at least two fused rings of atoms include thiochroman-4-one groups, 9-fluorenone groups, anthraquinone groups, benzanthrone groups, 9,10-phenanthrenequinone groups, etc. and their derivatives).

[0058] Examples of photo-switchable photoinitiators that are preferably included in the method of the present invention include photo-switchable photoinitiators according to another aspect of the present invention as described below, which include, but are not limited to, those represented by any of the following formulas (III) to (XIII) and (XV) to (XXX), and derivatives thereof, and include, but are not limited to, photo-switchable photoinitiators represented by any of formula (I) (photo-switchable photoinitiators represented by formula (XIV) prepared without showing color).

[0059] A substituent containing a carbonyl group (C=O) can be a substituent bonded to the P-type photochromic molecule by a bond. Alternatively, the carbonyl group can be indirectly attached to the ring, for example, attached to another substituent or moiety bonded to the ring.

[0060] Preferred photocurable compositions for inclusion in the method of the present invention include the photocurable compositions described herein.

[0061] In the method described herein, the volume of the photocurable composition is preferably contained within a container, and at least one or more portions of the container are optically transparent so that light used to irradiate the photocurable composition can reach the photocurable composition. It may be desirable for the optically transparent portion of the container to also be optically flat.

[0062] Examples of ranges of the first and second wavelengths for use in the method described herein include from 300 nm to about 550 nm, for example, but not limited to, from about 350 to about 460 nm, from about 350 to about 455 nm, from about 350 nm to about 445 nm, from about 350 nm to about 410 nm, from about 375 nm to about 455 nm, from about 375 nm to about 445 nm, from about 375 nm to about 410 nm, and from about 375 nm to about 405 nm for the first wavelength, and from about 450 nm to about 1000 nm, for example, but not limited to, from about 450 nm to about 850 nm, most typically from about 450 nm to about 700 nm for the second wavelength.

[0063] Examples of the output density at the first wavelength light include an output density in the range of about 0.01 to about 100,000 W / cm 2 Examples of the output density at the second wavelength light include an output density in the range of about 0.01 to about 100,000 W / cm 2 Examples of the exposure energy at the first wavelength light include an exposure energy in the range of about 0.001 to about 1,000 mJ / cm

[0064] Examples of the exposure energy at the second wavelength light include an exposure energy in the range of about 0.01 to about 100,000 mJ / cm 2 Examples of the exposure energy at the second wavelength light include an exposure energy in the range of about 0.01 to about 100,000 mJ / cm 2 The method according to the present invention preferably includes a photocurable composition exhibiting non-Newtonian rheology behavior. A photocurable composition containing a photocurable resin component and a P-type photochromic molecule, which exhibits non-Newtonian rheology behavior, can promote the formation of an object, preferably a three-dimensional object, that is completely suspended in the volume of the photocurable composition during formation. The ability to completely suspend an object in volume advantageously eliminates the need to include the type of support structure used in stereolithography for maintaining the outer shape / shape of the object during formation (sometimes referred to as printing or 3D printing).

[0065]

[0066] For use during the formation of an object, for example a three-dimensional object, it is desirable that when the photocurable composition is exposed to only the first wavelength or only the second wavelength, the photocurable composition does not cure (for example, the photocurable resin component does not undergo polymerization or crosslinking). In other words, the curing of the photocurable composition in volume that is not exposed to both radiations simultaneously or almost simultaneously (for example, for sequential exposure at close time intervals) does not polymerize. Specifically, in the scanning of the volume of the photocurable medium, as a result of the beam passing through the previously exposed area or surface, the structure of the object is defined within the volume of the medium by the intersection of the beams, so there are a number of points in the volume that are sequentially scanned in any order using radiation of the first wavelength and radiation of the second wavelength. Some points may be subjected to multiple exposures to the first wavelength light and / or the second wavelength light. Preferably, points that have received such multiple sequential (not simultaneous) exposures do not polymerize.​

[0067] Preferably, the amount of time during which one or more selected locations within the volume are exposed to the first wavelength light and the second wavelength light either simultaneously or sequentially is sufficient to induce curing of the photocurable composition at the one or more selected locations and insufficient to cause curing of the photocurable composition if only one of the first and second wavelengths is present.

[0068] Preferably, the first light and the light of the second wavelength are directed into the volume as separate optical projections.

[0069] Preferably, the direction in which the light of the first wavelength is projected is orthogonal to the direction in which the light of the second wavelength is projected.

[0070] Preferably, the projection of the light of the first wavelength includes an optical sheet. The optical sheet may desirably include a planar structure of light having opposing major surfaces, the major surfaces being parallel to the direction in which the optical sheet is directed into the volume.

[0071] Preferably, the projection of the light of the second wavelength includes an optical image perpendicular to the direction in which the optical image is projected into the volume. A digital micromirror device (DMD) is preferably utilized for the projection of the optical image.

[0072] Preferably, the optical sheet and the optical image intersect at a common plane. The intersection of the optical sheet and the optical image is desirably in the same plane or substantially the same plane.

[0073] The optical image can include any optical projection generated by an optical projection system. Examples of optical images include, but are not limited to, patterned or unpatterned two-dimensional images, lines of light, or single points of light. The two-dimensional image can include a cross-section of a three-dimensional image to be printed. The two-dimensional image can represent a cross-sectional slice of an object to be printed. Such cross-sectional slices are typically generated using slicing software as discussed elsewhere in this specification.

[0074] Examples of light sources for the excitation light that may be suitable for use in the methods described herein include, by way of example and not limitation, lasers, laser diodes, light emitting diodes, light emitting diodes (LEDs), micro-LED arrays, vertical cavity lasers (VCLs), and filtered lamps. Such light sources are commercially available, and the selection of a suitable light source can be readily made by one of ordinary skill in the art. This type of LED, such as the Phlatlight LED available from Luminus, may be useful for DMDs, and a laser light source may sometimes be preferred. Other suitable light sources may also be useful.

[0075] Optionally, the excitation light may be temporally and / or spatially modulated. Optionally, the intensity of the excitation light may be modulated.

[0076] Examples of projection devices for use in the methods described herein may include, but are not limited to, laser projection systems, liquid crystal displays (also referred to herein as "LCDs"), spatial light modulators (also referred to herein as "SLMs") (e.g., digital micromirror devices (also referred to herein as "DMDs")), micro-LED arrays, vertical cavity laser arrays (also referred to herein as "VCLs"), vertical cavity surface emitting laser arrays (also referred to herein as "VCSELs"), liquid crystal on silicon (also referred to herein as "LCoS") projectors, and scanning laser systems (light emitting diodes are also referred to herein as "LEDs").

[0077] Preferred projection devices include digital light processors, such as SLMs and DMDs, with DMDs being more preferred.

[0078] Preferably, the projection device is illuminated with a laser.

[0079] An optical image projection system may optionally further include one or more optical components (e.g., projection optical elements, illumination optical elements, lenses, lens systems, mirrors, prisms, etc.). The optical image projection system may optionally further include one or more light sources, either as parts of the projection system or external to the projection system for illuminating the projection device. Using an external light source can facilitate the flexibility to easily change the light source to a light source for generating different wavelengths and / or a light source with different output performance.

[0080] Other information that may be useful in connection with one or more aspects and / or embodiments of the present invention includes International Application No. PCT / US2022 / 039766 of Quadratic 3D, Inc., filed on August 9, 2022, International Patent Application No. PCT / US2022 / 052157 of Quadratic 3D, Inc., filed on December 7, 2022, U.S. Provisional Patent Application No. 63 / 341,594, filed on May 13, 2022, U.S. Provisional Patent Application No. 63 / 438,280, filed on January 11, 2023, U.S. Provisional Patent Application No. 63 / 440,085, filed on January 19, 2023, and U.S. Provisional Patent Application No. 63 / 450,931, filed on March 8, 2023, each of the foregoing applications being incorporated herein by reference in its entirety.

[0081] Optionally, the excitation light can be modulated temporally and / or spatially. Optionally, the intensity of the excitation light can be modulated. Optionally, the absolute output of the light beam can be adjusted using source drive modulation.

[0082] Spatially modulated excitation light can be created by known spatial modulation techniques including, for example, liquid crystal displays (LCDs), digital micromirror devices (DMDs), or micro-LED arrays. Other known spatial modulation techniques can be readily identified by those skilled in the art.

[0083] A system for generating a light sheet and / or an optical image projection system can be configured to apply continuous excitation light, if applicable. Such a system can be configured to apply intermittent excitation light. Intermittent excitation can include random on and off application of light or periodic application of light. An example of periodic application of light includes pulsing. Such a system can be configured to apply a combination of both continuous excitation light and intermittent light, including, for example, an irradiation step that includes application of intermittent excitation light preceded or followed by continuous light irradiation. The intermittent light can use a higher instantaneous light intensity to facilitate an increase in printing speed.

[0084] As discussed above, in addition to the projection device, the projection system can further include additional components including, but not limited to, projection optics, and one or more translation stages for moving the system or its components.

[0085] The method of the invention described herein can further include post-processing. Examples of post-processing steps that can further be included in the method according to the invention include, but are not limited to, one or more of the following: separation of at least partially cured composition from uncured composition, washing, post-curing (e.g., by light, heat, ionizing radiation, pressure or a combination of simultaneous or sequential techniques), metrology, freeze-drying treatment, critical point drying and packaging.

[0086] In the method according to the invention for forming a three-dimensional object, it is desirable to select a photo-switchable photoinitiator molecule, in which first form, the wavelength of the first excitation has significant absorption and the second form of the photoinitiator has minimal absorption of the first excitation wavelength. This has two advantages. The first is that the exposure is simplified, i.e., the activation of the photo-switchable photoinitiator occurs without the activation of its second form and can induce a cross-linking or polymerization reaction in the photocurable resin component. If there is significant overlap, the intensities of the two radiations must be carefully controlled such that the photo-switchable photoinitiator activates the molecules while its second form is minimally activated. Second, the conversion of the photo-switchable photoinitiator to its second form has a "bleaching" effect on the photo-switchable photoinitiator molecule or makes it transmissive to the first wavelength radiation, enabling deeper penetration of the volume of the composition or the layer.

[0087] The photo-switchable photoinitiators for inclusion in the methods and photocurable compositions described herein preferably absorb light of a first wavelength in the range of about 300 nm to about 550 nm. Other examples of ranges in which the photo-switchable photoinitiator absorbs light of the first wavelength include, but are not limited to, about 350 to about 460 nm, about 350 to about 455 nm, about 350 nm to about 445 nm, about 350 nm to about 410 nm, about 375 to about 455 nm, about 375 to about 445 nm, about 375 nm to about 405 nm. Depending on the extinction coefficient of the specific photo-switchable photoinitiator, the conversion to the second form can be induced by exposure to any source that emits in this range, such as a laser, a light-emitting diode, a mercury lamp, etc. Filters can be used to limit the output wavelength. Non-limiting examples of filtered light include filtered emission from a mercury arc lamp, etc. A laser can be a preferred source of radiation that generates radiation of the first wavelength.

[0088] The second form of the photo-switchable photoinitiator preferably absorbs in the range of about 450 to 1000 nm, most typically 450 to 850 nm. Other examples of ranges that the second form of the photo-switchable photoinitiator preferably absorbs include 450 to about 700 nm. This form can be activated by the second excitation light to directly generate free radicals, or can generate excitons that undergo electron transfer or hydrogen abstraction upon exposure to any second wavelength within this range (optionally, via electron, hydrogen or energy transfer to a co-initiator in embodiments of the present invention that include one or more co-initiators). In the second excitation, the exposure can be achieved using a laser source, an LED or LED array, light filtered from an arc lamp, or other suitable source that emits within the desired wavelength range. Argon ion, He-Ne, laser diode, krypton, frequency-doubled Nd-YAG, etc. Other light sources with optional filters, such as light-emitting diodes, incandescent lamps, halogen lamps, mercury lamps, arc lamps, etc., can be used to limit the output wavelength.

[0089] Optionally, the photocurable composition included in the method according to the present invention can further include a photoinitiator that is activated by light, which preferably does not respond well to light of the first wavelength or the second wavelength. The inclusion of such a photoinitiator that is activated by light may be desirable in any post-treatment of the printed object, in relation to an optional post-curing step carried out using UV light after printing. When the photoinitiator is included in the photocurable resin for post-curing purposes, the method can further include a post-curing step that includes exposing the object to light of a third wavelength to further cure the object, where the third wavelength is different from the first and second wavelengths. If the photoinitiator is UV-activatable, the third wavelength is preferably a wavelength in the ultraviolet range.

[0090] Separation of the at least partially cured object from the uncured composition can be carried out by several means known in the art, such as gravity drainage, sieving, air blade, centrifugation, vibration or ultrasonic agitation.

[0091] Preferably, the at least partially cured object is washed after separation.

[0092] The washing can be carried out with any suitable organic or aqueous cleaning liquid, including but not limited to solutions, suspensions, emulsions, microemulsions, etc., or combinations thereof. Examples of suitable cleaning liquids include, but are not limited to, water, alcohols (such as methanol, ethanol, isopropanol, etc.), glycol ethers, benzene, toluene, etc. Cleaning liquids containing mixtures of two or more liquids (such as a mixture of water and an alcohol (such as isopropanol)) can also be suitable. Such cleaning solutions can optionally contain additional components, such as surfactants, etc.

[0093] The methods according to various aspects of the present invention can further include post-treatment of the formed three-dimensional object.

[0094] In addition to washing, examples of other post-treatments include post-curing (e.g., by light, e-beam, heating, non-ionizing radiation, ionizing radiation, time (aging), pressure, humidity, or a combination of simultaneous or sequential techniques), metrology, labeling or tracking (e.g., by barcodes, QR codes, or RFID tags), freeze-drying treatment, critical point drying, and packaging, but are not limited thereto.

[0095] In the methods described herein that include a light sheet, the light sheet can be constructed by means known in the art, including but not limited to techniques that include lasers and power lenses, galvanometers, and / or polygonal scanning mirrors. Alternatively, one or more LEDs can be used as the light source.

[0096] Optionally, the methods described herein can further include the use of an additional different wavelength to promote the reverse reaction of the second form of the photo-switchable photoinitiator back to its original / starting form, helping to avoid curing in unwanted areas.

[0097] The first wavelength, the second wavelength, or any other additional wavelength used herein may refer to a range of wavelengths.

[0098] In the methods described herein, the first wavelength and the second wavelength are preferably generated by different light sources or optical projection systems.

[0099] As mentioned above, the method according to the invention preferably includes the step of providing a volume of the photocurable composition described herein contained within a container, at least a portion of the container being optically transparent such that the excitation light is reachable by the photocurable composition. Optionally, the entire container is optically transparent.

[0100] The optically transparent parts of the container can be constructed from materials including, but not limited to, for example, glass, quartz, fluoropolymers (such as Teflon FEP, Teflon AF, Teflon PFA), cyclic olefin copolymers, polymethyl methacrylate (PMMA), polynorbornene, sapphire, or transparent ceramics.

[0101] Examples of container shapes include, but are not limited to, cylindrical containers having a circular or elliptical cross-section, containers having straight sides and a polygonal cross-section or a rectangular or square cross-section.

[0102] As mentioned above, it may be desirable for the optically transparent portion of the container to also be optically flat.

[0103] Optionally, one or more filters can be added to at least the surface of any optically transparent part of the container to block unwanted light, such as room light, to prevent unintentional curing.

[0104] Optionally, the photocurable composition is filtered to remove particulates prior to introduction into the container. Optionally, air bubbles are removed from the photocurable composition before and after introduction into the container. Optionally, the photocurable composition is degassed, purged or sparged with an inert gas before and after introduction into the container. Optionally, the photocurable composition is maintained under inert conditions, such as in an inert atmosphere, during printing. Thereby, while an object is printed or formed, introduction of oxygen into the container can be prevented.

[0105] In the method described herein, the container can be rotated to obtain an additional angle of illumination or projection of the excitation light into the volume of the photocurable composition contained therein. This can assist in more accurately patterning the volume or surface of the object, or can be used as a means to expose a given feature multiple times from different angles.

[0106] In the method described herein, the container may be fixed while a beam or optical projection of excitation light is directed into the photocurable composition.

[0107] The method disclosed herein may also include the use of commercially available optical projection and filtering techniques or systems that employ two or more optical projection methods at once.

[0108] The methods described herein are typically used in combination with a computer and software. For example, a light sheet generation system, an optical image projection system, and a projection device that may be included therein and may be included in the methods described herein may be used in combination with a computer and software. The software may be used to coordinate the generation (e.g., point illumination, line illumination, two-dimensional pattern, or light sheet) at each position along each projection direction of the optical projection from its respective optical projection system or projection device such that the resulting portion unfolds plane by plane. The plane of the projected optical image is preferably orthogonal to its projection direction into the photocurable composition. When two optical projections are projected into the volume of the photocurable composition, the projection directions of the two projections are preferably orthogonal to each other. The selection of computer control and software is within the skill of one of ordinary skill in the art. Other components may also optionally be included or used with the system.

[0109] The method according to the invention advantageously further does not require adhering the object to be printed to a fixed substrate (e.g., build plate) at the beginning of the printing process and avoids a post-treatment step of separating the printed object from the fixed substrate.

[0110] The methods described herein are particularly useful for the formation or "printing" of three-dimensional objects.

[0111] Before printing, a digital file of the object to be printed is obtained. If the digital file is not in a format that can be used to print the object, the digital file is then converted to a format that can be used to print the object. Examples of typical formats that can be used for printing include, but are not limited to, STL files. Typically, the STL file is then sliced into two-dimensional layers using three-dimensional slicer software and converted into G-code or a series of machine commands that facilitate the assembly of the object. See B. Redwood et al., "The 3D Printing Handbook - Technologies, designs applications", 3D HUBS B.V. 2018.

[0112] The excitation light can be directed into the volume of the photocurable composition in a continuous or intermittent manner. Intermittent excitation can include random on and off application of light or periodic application of light. An example of periodic application of light includes pulsing. The excitation can alternatively be applied as a combination of both continuous excitation light and intermittent light, including, for example, application of intermittent excitation light preceded or followed by continuous light irradiation.

[0113] Other information related to optical systems that may be useful in connection with various aspects of the present invention can be found in Texas Instruments Application Report DLPA022 entitled "DLP (trademark) System Optics", July 2010; Texas Instruments "TI DL R"Technology for 3D Printing - Design scalable high-speed stereolithography [sic] systems using TI DLP technology", 2016; Texas Instruments, "DLP6500 0.65 1018p MVSP Type A DMD", DLP6500, DLPS040A, October 2014, Revised October 2016; and Y-H Lee et al., "Fabrication of Periodic 3D Nanostructuration for Optical Surfaces by Holographic Two-Photon-Polymerization", Int'l Journal of Information and Electronics Engineering, Vol. 6, No. 3, May 2016, each of which is hereby incorporated by reference in its entirety.

[0114] According to another aspect of the present invention, a photo-switchable photoinitiator comprising a P-type photochromic molecule is provided, the molecule comprising one or more substituents, at least one of the substituents comprising a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group comprising at least two fused rings of atoms, at least one of the fused rings of atoms comprising one or more substituents, at least one of the substituents comprising a double bond oxygen bonded to a carbon atom ring member included in one of the fused rings, the P-type photochromic molecule being activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and at the intersection of the first and second wavelengths, inducing a crosslinking or polymerization reaction in the photocurable composition, the first wavelength being shorter than the second wavelength.

[0115] A substituent containing a carbonyl group can be a substituent bonded to the P-type photochromic molecule by a bond. Alternatively, the carbonyl group can be indirectly attached to the ring.

[0116] The photo-switchable photoinitiator includes a P-type photochromic molecule, and preferably may desirably include a P-type diarylethene molecule, the molecule includes one or more substituents, and at least one substituent is a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group including at least two condensed rings of atoms, at least one of the condensed rings of atoms includes one or more substituents, and at least one of the substituents includes a double bond oxygen bonded to a carbon atom ring member included in one of the condensed rings, the P-type photochromic molecule is activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), at the intersection of the first and second wavelengths, it induces a crosslinking or polymerization reaction in the photocurable composition, and the first wavelength is shorter than the second wavelength.

[0117] The photo-switchable photoinitiator according to the present invention preferably includes a P-type photochromic molecule.

[0118] Non-limiting examples of preferred photo-switchable photoinitiators are of general formula (I)

[0119]

Chemical formula

[0120]

Chemical formula

[0121]

Chemical formula

[0122]

Chemical formula

[0123]

Chemical formula

[0124]

Chemical formula

[0125]

Chemical formula

[0126] [Chemical formula] (wherein E' is a member of the ring and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or R 15 a nitrogen atom having a substituent (NR 15 ), Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, an SR 16 group, an OR 17 group or a cyano (CN) group, R 11 ~R 17is a substituent, which may be the same or different and independently represents, for example, hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkylaryl group, a substituted or unsubstituted heteroalkyl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted ester group, a substituted or unsubstituted carbonate group, a substituted or unsubstituted ketone group, a substituted or unsubstituted aldehyde group, a substituted or unsubstituted imine group, a substituted or unsubstituted carboxyl group, a substituted or unsubstituted amide group, a substituted or unsubstituted urethane group, a substituted or unsubstituted urea group, a substituted or unsubstituted tetrazine group, a substituted or unsubstituted amino group, iodine, bromine, chlorine, fluorine, a cyano group (-CN), a nitro group (-NO2), a hydroxyl group (-OH), a thiol (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group.) or

[0127] [Chemical formula] (wherein E' is a member of the ring and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or R 15 a nitrogen atom having a substituent (NR 15 ), and Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R 16 a sulfur atom having a substituent (SR 16 ), R 17 an oxygen atom having a substituent (OR 17 ), or a cyano (CN) group, and R 11 ~R 17is a substituent, which may be the same or different and independently represents, for example, hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkylaryl group, a substituted or unsubstituted heteroalkyl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted ester group, a substituted or unsubstituted carbonate group, a substituted or unsubstituted ketone group, a substituted or unsubstituted aldehyde group, a substituted or unsubstituted imine group, a substituted or unsubstituted carboxyl group, a substituted or unsubstituted amide group, a substituted or unsubstituted urethane group, a substituted or unsubstituted urea group, a substituted or unsubstituted tetrazine group, a substituted or unsubstituted amino group, iodine, bromo, chloro, fluoro, a cyano group (-CN), a nitro group (-NO2), a hydroxyl group (-OH), a thiol (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group.); At least one of X and Y contains at least one R substituent including a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group containing at least two condensed rings of atoms, and at least one of the condensed rings of atoms contains one or more substituents, and at least one of the substituents contains a double bond oxygen bonded to a carbon atom ring member contained in one of the condensed rings, The P-type photochromic molecule is activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and at the intersection of the first and second wavelengths, induces a crosslinking or polymerization reaction in the photocurable composition, and the first wavelength is shorter than the second wavelength, and contains a light-switchable photoinitiator.

[0128] Optionally, the R groups on any two adjacent ring members of X and / or Y may contain atoms for completing a ring structure that connects two adjacent groups together. Such a ring structure may be substituted or unsubstituted and may optionally be part of a polycyclic substituted or unsubstituted ring structure. Such a ring structure, or, where applicable, the polycyclic structure of which the ring structure is a part, may optionally contain one or more heteroatoms in addition to carbon in the ring structure.

[0129] Preferred examples include those in which at least one R substituent on X and / or Y is a substituted or unsubstituted benzophenone group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted acenaphthylene-1,2-dione group, a substituted or unsubstituted thiochroman-4-one group, a substituted or unsubstituted 9-fluorenone group, a substituted or unsubstituted anthraquinone group, a substituted or unsubstituted benzanthrone group, a substituted or unsubstituted 9,10-phenanthrenequinone group, a substituted or unsubstituted xanthone group, a substituted 1,2-indanedione group, a substituted or unsubstituted chromone group, a substituted or unsubstituted 1,4-naphthoquinone group, and the like. Additional preferred examples include those in which 1 ~R 18 at least one of, most preferably 1 ~R 6 at least one of represents a substituted or unsubstituted benzophenone group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted acenaphthylene-1,2-dione group, a substituted or unsubstituted thiochroman-4-one group, a substituted or unsubstituted 9-fluorenone group, a substituted or unsubstituted anthraquinone group, a substituted or unsubstituted benzanthrone group, a substituted or unsubstituted 9,10-phenanthrenequinone group, a substituted or unsubstituted xanthone group, a substituted 1,2-indanedione group, a substituted or unsubstituted chromone group, a substituted or unsubstituted 1,4-naphthoquinone group, and the like.

[0130] Each of X and Y includes a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group containing at least two condensed rings of atoms, with at least one of the condensed rings of atoms containing one or more substituents, and it may be desirable for at least one of the substituents to include a double bond oxygen bonded to a carbon atom ring member included in one of the condensed rings. In such cases, such substituents on X and Y may be the same or different. For example, at least one R substituent on X and at least one R substituent on Y include a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group containing at least two condensed rings of atoms, with at least one of the condensed rings of atoms containing one or more substituents, and it may be desirable for at least one of the substituents to include a double bond oxygen bonded to a carbon atom ring member included in one of the condensed rings.

[0131] Optionally, X and Y may be symmetric in that any R substituent on X and any R substituent on Y are compatible with each other.

[0132] Optionally, X and Y are not symmetric in each of X and Y that contain one or more different R substituents on each of X and Y.

[0133] It may be desirable for at least one R substituent on X and / or at least one R substituent on Y to include a substituted or unsubstituted benzophenone group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted acenaphthylene-1,2-dione group, a substituted or unsubstituted thiochroman-4-one group, a substituted or unsubstituted 9-fluorenone group, a substituted or unsubstituted anthraquinone group, a substituted or unsubstituted benzanthrone group, a substituted or unsubstituted 9,10-phenanthrenequinone group, a substituted or unsubstituted xanthone group, a substituted 1,2-indanedione group, a substituted or unsubstituted chromone group, a substituted or unsubstituted 1,4-naphthoquinone group, etc.

[0134] In general formula (I), E in X and E' in Y can optionally and independently be the same or different.

[0135] In general formula (I), G in X and G' in Y can optionally and independently be the same or different.

[0136] In general formula (I), Z in X and Z' in Y can optionally and independently be the same or different.

[0137] In general formula (I), L in X and L' in Y can optionally and independently be the same or different.

[0138] Optionally, X and Y can be the same or different.

[0139] Examples of preferred substituted or unsubstituted diaryl ketone groups include those represented by general formula (DAK)

[0140]

Chemical formula

[0141] Examples of substituted or unsubstituted aryl groups for inclusion in general formula (DAK) as Ar and / or Ar' include, but are not limited to, substituted or unsubstituted substituents or functional groups derived from aromatic rings such as benzene ring, naphthalene ring, anthracene ring, indene ring, fluorene ring, etc.

[0142] Examples of substituted or unsubstituted heteroaryl groups for inclusion as Ar or Ar' in general formula (DAK) include, but are not limited to, substituted or unsubstituted substituents or functional groups derived from heteroaryl rings including furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, pyran ring, pyridine ring, pyrazine ring, indole ring, quinoline ring, isoquinoline ring, xanthene ring, carbazole ring, acridine ring, indoline ring, julolidine ring, etc.

[0143] Examples of substituents that can substitute the hydrogen atoms bonded to the aryl group or heteroaryl group in the substituted aryl or heteroaryl group include halogen atom, alkyl, alkoxy, alkylamino, dialkylamino, alkylthio, heterocyclic group, more specifically methyl, ethyl, isopropyl, tert-butyl, phenyl, trifluoromethyl, cyano, acetyl, ethoxycarbonyl, carboxyl, carboxylate, amino, methylamino, dimethylamino, ethylamino, diethylamino, isopropylamino, diisopropylamino, cyclohexylamino, dicyclohexylamino, acetylamino, piperidino, pyrrolidyl, --PO3H, methoxy, ethoxy, propoxy, isopropoxy, butoxy, pentyloxy, phenoxy, hydroxyl, acetoxy, methylthio, ethylthio, isopropylthio, mercapto, acetylthio, thiocyano, methylsulfinyl, methylsulfonyl, dimethylsulfonyl, sulfonate group, fluorine atom, chlorine atom, bromine atom, iodine atom, trimethylsilyl, triethylsilyl, furyl, thienyl, pyridyl, piperidino, morpholino, pyrrolidyl group, etc., but are not limited to them.

[0144] Examples of preferred substituted or unsubstituted alpha-diketone groups are general formula (ADK) Ar 1 -C(=O)-C(=O)-Ar 2 (ADK) (wherein Ar 1 and Ar 2is the same as or different from, and independently, a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.) including those represented by

[0145] Examples of the substituted or unsubstituted aryl group for inclusion in the general formula (ADK) as Ar and / or Ar’ include, but are not limited to, substituted or unsubstituted substituents or functional groups derived from aromatic rings such as benzene ring, naphthalene ring, anthracene ring, indene ring, fluorene ring, etc.

[0146] Examples of the substituted or unsubstituted heteroaryl group for inclusion in the general formula (ADK) as Ar or Ar’ include, but are not limited to, substituted or unsubstituted substituents or functional groups derived from heteroaryl rings such as furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, pyran ring, pyridine ring, pyrazine ring, indole ring, quinoline ring, isoquinoline ring, xanthene ring, carbazole ring, acridine ring, indoline ring, julolidine ring, etc.

[0147] Examples of substituents that can be substituted with a hydrogen atom bonded to an aryl group or heteroaryl group in a substituted aryl or heteroaryl group include halogen atoms, alkyl, alkoxy, alkylamino, dialkylamino, alkylthio, heterocyclic groups, more specifically methyl, ethyl, isopropyl, tert-butyl, phenyl, trifluoromethyl, cyano, acetyl, ethoxycarbonyl, carboxyl, carboxylate, amino, methylamino, dimethylamino, ethylamino, diethylamino, isopropylamino, diisopropylamino, cyclohexylamino, dicyclohexylamino, acetylamino, piperidino, pyrrolidyl, --PO3H, methoxy, ethoxy, propoxy, isopropoxy, butoxy, pentyloxy, phenoxy, hydroxyl, acetoxy, methylthio, ethylthio, isopropylthio, mercapto, acetylthio, thiocyano, methylsulfinyl, methylsulfonyl, dimethylsulfonyl, sulfonate groups, fluorine atom, chlorine atom, bromine atom, iodine atom, trimethylsilyl, triethylsilyl, furyl, thienyl, pyridyl, piperidino, morpholino, pyrrolidyl groups, etc., but are not limited thereto.

[0148] Specific examples of the alpha-diketone group represented by formula ADK include, but are not limited to, the following compounds represented by formulas (ADK-1) to (ADK-11).

[0149]

Chemical formula

[0150] Optionally, Ar in the general formula ADK 1 and / or Ar 2, and any of the compounds represented by formulas (ADK-1) to (ADK-11) may contain one or more substituents on one or both of the aryl or heteroaryl groups, and the substituents may be the same or different. Examples of substituents include substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, substituted or unsubstituted heteroaryl groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted ester groups, substituted or unsubstituted carbonate groups, substituted or unsubstituted ketone groups, substituted or unsubstituted aldehyde groups, substituted or unsubstituted imine groups, substituted or unsubstituted carboxyl groups, substituted or unsubstituted amide groups, substituted or unsubstituted urethane groups, substituted or unsubstituted urea groups, substituted or unsubstituted tetrazine groups, substituted or unsubstituted amino groups, iodine, bromo, chloro, fluoro, cyano groups, nitro groups, hydroxyl groups, thiol, alkylthioethers, arylthioethers, substituted or unsubstituted alcohol groups, and those listed above, but not limited thereto.

[0151] Examples of polycyclic groups include those containing at least two fused rings of atoms, at least one of the fused rings of atoms containing one or more substituents, at least one of the substituents being attached to a carbon atom ring member contained in one of the fused rings, preferably containing a double bond oxygen, and including, but not limited to, polycyclic groups represented by the following · General formula (PG-A)

[0152]

Chemical formula

[0153]

Chemical formula

[0154]

Chem.

[0155]

Chem.

[0156]

Chem.

[0157]

Chem.

[0158]

Chem.

[0159] Examples of additional polycyclic groups that may be suitable for inclusion in the second unit include, but are not limited to, the following · General formula (PG-H)

[0160]

Chem.

[0161]

Chem.

[0162]

Chem.

[0163]

Chem.

[0164]

Chem.

[0165]

Chem.

[0166] Optionally, the polycyclic group containing any one of PG-A to PG-M may be further substituted with one or more additional substituents or functional groups.

[0167] Preferred examples of A are the formulas (A a ), (A b ), (A c ) and (A d )

[0168]

Chem.

[0169] [Chemical formula] (wherein J is a member of the ring and is oxygen (O) or R 25 nitrogen with a substituent (NR 25 ), and R 25 represents hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl.).

[0170] [Chemical formula] (wherein E'' is a member of the ring and is an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or R 23 nitrogen atom with a substituent (NR 23 ), and G'' is a member of the ring and is a carbon atom with a substituent (CR 24 ), or a nitrogen atom (N), and 24 R ~R 22 ~R 24is a substituent, which may be the same or different and independently represents, for example, hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkylaryl group, a substituted or unsubstituted heteroalkyl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted ester group, a substituted or unsubstituted carbonate group, a substituted or unsubstituted ketone group, a substituted or unsubstituted aldehyde group, a substituted or unsubstituted imine group, a substituted or unsubstituted carboxyl group, a substituted or unsubstituted amide group, a substituted or unsubstituted urethane group, a substituted or unsubstituted urea group, a substituted or unsubstituted tetrazine group, a substituted or unsubstituted amino group, iodine, bromine, chlorine, fluorine, a cyano group (-CN), a nitro group (-NO2), a hydroxyl group (-OH), a thiol (-SH), a thioether group (R-X-R' where R or R' may independently represent an aryl or alkyl group), or a substituted or unsubstituted alcohol group.) or

[0171] [Chemical formula] (wherein X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 and X 8 are the same or different and independently represent hydrogen (H), fluorine (F), chlorine (Cl) or a substituted or unsubstituted alkyl or heteroalkyl group.) contains a structure represented by

[0172] Other examples of A include a substituted or unsubstituted 6-membered ring structure containing an ethene bridge with X and Y bonded to carbon on opposite sides of the double bond of the ethene bridge, and substituted and unsubstituted polycyclic ring structures.

[0173] In general formula (I), it may be desirable for at least one functional group containing a carbonyl group to include a ketone. In general formula (I), it may be desirable for at least one functional group containing a carbonyl group to be a ketone.

[0174] Examples of preferred photoswitchable photoinitiators according to the present invention include those represented by the following formulas (III) to (XXX).

[0175] [Table 1] TIFF2025520023000042.tif232161TIFF2025520023000043.tif200161TIFF2025520023000044.tif95161

[0176] In the above formulas (III) to (XXX), a bare line without a symbol attached to the ring structure represents a methyl group, and where no substituent or line is shown at a ring position, the substituent is H (hydrogen).

[0177] The photoswitchable photoinitiator according to the present invention also includes derivatives of the compounds represented by any of structures (III) to (XXX).

[0178] Among the above examples, the photoswitchable photoinitiators represented by formulas (VI), (XIX), and (XXI) may be particularly desirable for inclusion in the method according to the present invention.

[0179] The photo-switchable photoinitiators described herein preferably absorb first wavelength light in the range of about 300 - 550 nm. Other examples of other ranges in the photo-switchable photoinitiators described herein include, but are not limited to, about 350 - about 460 nm, about 350 - about 455 nm, about 350 - about 445 nm, about 350 - about 410 nm, about 350 - about 405 nm, about 375 - about 460 nm, about 375 - 455 nm, about 375 - 445 nm, about 375 - 410 nm, about 375 - about 405 nm, about 375 nm ± 10 nm, about 405 nm ± 10 nm, about 410+ nm. Depending on the extinction coefficient of the specific photo-switchable photoinitiator, the conversion to the second form can be induced by exposure to any source that emits in this range, such as a laser, light emitting diode, mercury lamp, etc. Filters can be used to limit the output wavelength. Non-limiting examples of filtered light include filtered emission from a mercury arc lamp, etc.

[0180] The second form of the photo-switchable photoinitiator preferably absorbs in the range of about 450 - 1000 nm, most typically 450 - 850 nm. Other examples of ranges that the second form of the photo-switchable photoinitiator preferably absorbs include 450 - about 700 nm. This form can be activated by the second excitation light to directly generate free radicals, or can generate excitons that undergo electron transfer or hydrogen abstraction upon exposure to any second wavelength within this range (optionally, via electron, hydrogen or energy transfer to a co-initiator in embodiments of the present invention that include one or more co-initiators). For the second excitation, the exposure can be achieved using a laser source, an LED or LED array, filtered emission from an arc lamp, or other suitable source that emits within the desired wavelength range. Argon ion, He-Ne, laser diode, krypton, frequency-doubled Nd-YAG, etc. Other light sources that optionally have filters can be used to limit the output wavelength, such as light emitting diodes, incandescent lamps, halogen lamps, mercury lamps, arc lamps, etc.

[0181] According to another aspect of the present invention, there is provided a photocurable composition containing a photocurable resin component and a P-type photochromic molecule, preferably a P-type diarylethene molecule, the molecule containing one or more substituents, at least one of the substituents containing a substituted or unsubstituted diarylketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group containing at least two condensed rings of atoms, at least one of the condensed rings of atoms containing one or more substituents, at least one of the substituents containing a double bond oxygen bonded to a carbon atom ring member contained in one of the condensed rings, the P-type photochromic molecule being activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and at the intersection of the first and second wavelengths, inducing a crosslinking or polymerization reaction in the photocurable composition, the first wavelength being shorter than the second wavelength, a photocurable composition containing a photoswitchable photoinitiator is provided.

[0182] A photoswitchable photoinitiator preferably included in the photocurable composition is of the general formula (I) described herein

[0183]

Chemical formula

[0184] Examples of P-type photoswitchable photoinitiators preferably included in the photocurable composition and the method according to the present invention include those represented by formulas (III) to (XIII) and (XV to XXX) and their derivatives as specified above.

[0185] Among the above examples, the photoswitchable photoinitiators represented by formulas (VI), (XIX) and (XXI) may be particularly desirable to be included in the photocurable composition for use in the method according to the present invention.

[0186] As discussed herein, photocurable compositions exhibiting non-Newtonian rheology behavior may be desirable or preferred.

[0187] The photocurable composition may optionally further contain a co-initiator.

[0188] The photocurable composition may optionally further contain a sensitizer.

[0189] Optionally, the photocurable composition may contain a combination comprising one or more co-initiators and / or one or more sensitizers.

[0190] Some of the problems in the selection of a specific photoswitchable photoinitiator for inclusion in the photocurable composition or the method according to the invention are, by way of example, the absorption spectra of the molecule and its second form and Δ max , the solubility of the photoswitchable photoinitiator in the photocurable resin component, the photosensitivity of the second form of the photoswitchable photoinitiator, the amount of the initial concentration of the second form in the monomer solution, the stability of the photoswitchable photoinitiator, and the reduction and oxidation potentials of the second form of the photoswitchable photoinitiator, including but not limited to these.

[0191] The photocurable composition according to the invention is particularly suitable for use in the method according to the invention for forming a three-dimensional object, because the photoswitchable photoinitiator molecules in the initial open form (typically colorless in the initial form of the P-type diarylethene), and the second closed form of the photoinitiator molecules (typically colored) have sufficiently different absorption spectra, and when the open form of the molecule is converted to its closed form, the closed form absorbs in a wavelength region where the open form is substantially non-absorbing. Thus, the closed form can be independently excited at the second wavelength without causing unintentional excitation of the open form by the second wavelength. The second wavelength can excite the closed form to generate free radicals, or otherwise, if the closed form is generated by exposure to the first wavelength, it can induce the desired curing of the photocurable resin component.

[0192] The photocurable resin component may optionally contain one or more polyfunctional acrylate monomers. The pentafunctional acrylic monomer, dipentaerythritol pentaacrylate, available from Sartomer as SR399, is an example of a photocurable resin component.

[0193] Aliphatic urethane acrylates may also be desirable for use as a photocurable resin component. Mixtures of polyfunctional acrylate monomers such as dipentaerythritol pentaacrylate (e.g., SR399 from Sartomer) and aliphatic urethane acrylates may also be used.

[0194] Acrylamide monomers may also be included in the photocurable resin composition and act as a solvent for mixing photoinitiators in the first resin component.

[0195] Preferably, the photocurable resin component included in the photocurable composition is selected to obtain an optically transparent, or clear liquid, which is desirable for processes and systems in which light, e.g., actinic light, is directed into the composition.

[0196] The photocurable composition according to the invention provided herein may optionally contain one or more coinitiators.

[0197] Suitable coinitiators include coinitiators that are reducing agents, oxidizing agents or hydrogen donating compounds.

[0198] Examples of coinitiators that may be useful can be selected from those known in the art, and more particularly, from tertiary amines and organic borates. Iodonium salts may also be useful, particularly in combination with borates. In certain embodiments, iodonium salts may also be included in combination with tertiary amines. Examples of other useful electron donating coinitiators are discussed by Eaton, D. F., "Dye Sensitized Photopolymerization", Advances in Photochemistry, Vol. 13, pp. 427 - 486.

[0199] Typical examples of N,N-dialkylanilines useful as co-initiators in the present invention include 4-cyano-N,N-dimethylaniline, 4-acetyl-N,N-dimethylaniline, 4-bromo-N,N-dimethylaniline, 4-methyl-N,N-dimethylaniline, 4-ethoxy-N,N-dimethylaniline, N,N-dimethylthioanisidine, 4-amino-N,N-dimethylaniline, 3-hydroxy-N,N-dimethylaniline, N,N,N',N'-tetramethyl-1,4-dianiline, 4-acetamido-N,N-dimethylaniline, 2,6-diethyl-N,N-dimethylaniline, N,N,2,4,6-pentaethylaniline (PMA), and p-t-butyl-N,N-dimethylaniline.

[0200] Certain other tertiary amines, including triethylamine, triethanolamine, N-methyldiethanolamine, 2-ethyl-4-(dimethylamino)benzoate, 2-ethylhexyl-4-(dimethylamino)benzoate, etc., are also useful co-initiators.

[0201] Another class of useful co-initiators are alkyl borates, such as the ammonium salts of borate anions of the formula BR a R b R c R d (wherein R a ~R d are independently selected from the group consisting of alkyl, aryl, alkaryl, allyl, aralkyl, alkenyl, alkynyl, alicyclic, and saturated or unsaturated heterocyclic groups). Representative examples of the alkyl groups represented by R a ~R d are methyl (Me), ethyl, propyl, butyl, pentyl, hexyl, octyl, stearyl, etc. The alkyl group may be substituted, for example, by one or more halogen, cyano, acyloxy, acyl, alkoxy, or hydroxy groups. Representative examples of the aryl groups represented by R a ~R d include phenyl, naphthyl, and substituted aryl groups, such as anisyl and alkaryl, for example methylphenyl, dimethylphenyl, etc. R a ~Rd Typical examples of the aryl group represented by include benzyl. Typical alicyclic groups include cyclobutyl, cyclopentyl and cyclohexyl groups. Examples of alkynyl groups, aryl, propynyl and ethynyl, examples of alkenyl groups include vinyl groups. Preferably, R a , R d , R c and R d Of these, at least 1, but 3 or less, are alkyl groups. R a , R b , R c and R d Each of can contain up to 20 carbon atoms, which typically contain 1 to 7 carbon atoms. More preferably, R a ~R d Is a combination of an alkyl group and an aryl group or an aralkyl group, even more preferably a combination of 3 aryl groups and 1 alkyl group, that is, an alkyl triphenyl borate, for example, but not limited to, butyl triphenyl borate.

[0202] As mentioned herein, the photocurable composition according to the present invention can optionally contain a co-initiator (the co-initiator is also referred to as a synergistic additive). Non-limiting examples of co-initiators include amines, thiols, thioethers, mercaptans, silanes, organic borate compounds, diaryliodonium salts, triarylsulfonium salts. A preferred example of a suitable co-initiator is butyrylcholine butyl triphenyl borate. Another preferred example of a suitable co-initiator is N-methyldiethanolamine. When the co-initiator is included in the photocurable composition, it can be combined with a photo-switchable photoinitiator to promote photoinitiation by the active form of the photo-switchable photoinitiator, for example, via electron transfer or hydrogen transfer.

[0203] The photocurable compositions and methods according to the present invention preferably exhibit advantageously non-Newtonian rheological behavior which, upon exposure to at least two different wavelengths of excitation light, can promote the formation of an object within the volume of the photocurable composition described herein, the object remaining in a fixed position or displacing minimally within the volume of the uncured photocurable composition during formation. The minimal displacement refers to an object being formed and being able to be tolerated to displace within the volume during its formation in order to accurately produce the intended outer shape of the part.

[0204] The photocurable compositions and methods according to the present invention preferably, advantageously, exhibit non-Newtonian rheological behavior which, upon application of stress, can also promote the separation of the formed object from the uncured photocurable composition. Without wishing to be bound by theory, upon application of stress, the apparent viscosity of the non-Newtonian photocurable composition can drop to a value lower than the static value (e.g., zero shear viscosity or yield stress) (e.g., steady shear viscosity), and the uncured photocurable composition can flow out more easily and be separated from the object. Examples of such non-Newtonian rheological behavior include, but are not limited to, pseudoplastic fluids, yield pseudoplastics, Bingham plastics or Bingham pseudoplastics.

[0205] Non-Newtonian rheological behavior can be imparted to a photocurable composition by further including one or more reactive components (e.g., urethane acrylate oligomer, urethane methacrylate oligomer, acrylated or methacrylated polyurethane, acrylated or methacrylated polyurethane-urea, acrylated or methacrylated polyester, acrylated or methacrylated polyamide, acrylate- or methacrylate-functional block copolymer, alkenyl- or alkynyl-functional urethane oligomer, alkenyl- or alkynyl-functional polyurethane, alkenyl- or alkynyl-functional polyurethane-urea, alkenyl- or alkynyl-functional polyester, alkenyl- or alkynyl-functional polyamide, alkenyl- or alkynyl-functional block copolymer, thiol-functional urethane oligomer, thiol-functional polyurethane, thiol-functional polyurethane-urea, thiol-functional polyester, thiol-functional polyamide, thiol-functional block copolymer) and / or by further adding one or more non-reactive additives (e.g., but not limited to, one or more thixotropes and / or rheology modifiers) to the photocurable composition. The selection of the amount of one or more of the reactive components and its addition to the photocurable resin component to impart non-Newtonian rheological behavior is within the skill of one of ordinary skill in the art without undue experimentation. Similarly, the selection of the amount of the non-reactive additive and its addition to the photocurable composition to impart non-Newtonian rheological behavior is within the skill of one of ordinary skill in the art without undue experimentation.

[0206] In the photocurable composition according to the present invention, the preferred steady-shear viscosity is less than 30,000 centipoise, more preferably less than 10,000 centipoise, and most preferably less than 1,000 centipoise (the steady-shear viscosity refers to the viscosity after the thixotropic network structure is broken).

[0207] Additive As mentioned above, the photocurable composition according to the present invention may include one or more additives. Examples of additives include, but are not limited to, thixotropes / rheology modifiers, defoamers, stabilizers, deoxidizers, and non-reactive solvent diluents. Any additive can be a single additive or a mixture of additives. For example, a thixotrope can include a single thixotrope or a mixture of two or more thixotropes.

[0208] The additive is preferably selected so as not to react with the photocurable resin component, the photo-switchable photoinitiator, the thixotrope, or any other additive that may be included in the photocurable composition.

[0209] Filler Optionally, the photocurable composition according to the present invention may further include one or more fillers. The filler can be included in an amount of from 0 to greater than about 90 weight percent, the amount being determined by the purpose of the filler and the desired end-use properties of the intended three-dimensional object. Advantageously, the filler can be selected to maintain the optical transparency of the photocurable composition, for example, by controlling the particle size to be substantially below the excitation wavelength or by matching the refractive indices of the filler and the matrix to reduce light scattering.

[0210] Fillers can be used to modify the properties of the cured photocurable composition, such as degree of cure, strength, toughness, impact resistance, creep resistance, fatigue resistance, mechanical energy return, mechanical loss tangent, glass transition temperature, thermal decomposition temperature, thermal conductivity, heat resistance, moisture absorption, conductivity, electrostatic dissipation, dielectric constant and loss tangent, density, refractive index, optical dispersion, opacity to ionizing radiation, and resistance to ionizing radiation. Fillers can also be used to modify the properties of the liquid photocurable composition, such as rheological properties, for example viscosity and thixotropy, and optical properties, for example refractive index. Examples of fillers include, but are not limited to, silica, alumina, zirconia; silicate glasses, such as soda lime glass, borosilicate glass, sodium silicate glass, lead glass, aluminosilicate glass, barium glass, thorium glass, glass ceramics; chalcogenide glasses; glass microspheres and microbubbles; nanoclays, such as laponite, montmorillonite, bentonite, kaolinite, hectorite, and halloysite; calcium phosphate inorganics, such as hydroxyapatite, inorganic fillers, for example chalk, rock powder, slag dust, fly ash, hydraulic cement, rice husk, lime, kaolin, talc, and wollastonite. Examples of particle size ranges include, but are not limited to, less than 10 microns, less than 1 micron, 10 nm to 500 nm, 10 nm to 90 nm, 40 nm to 70 nm. Smaller particle sizes, more particularly those less than about 100 nm in size, can be beneficial in obtaining a high optical clarity of the liquid composition and promoting better printing. Controlling the particle size distribution, such as a monodisperse, bimodal, or trimodal distribution of size, can be beneficial in controlling rheological properties, increasing the weight percentage of filler, or modifying the properties of the photocurable composition.

[0211] Thixotrope / Rheology Modifier Thixotropes and rheology modifiers suitable for inclusion in the photocurable compositions described herein include, for example, urea derivatives; modified urea compounds such as Rheobyk 410 and Rheobyk-D 410 available from BYK-Chemie GmbH, which is part of the ALTANA group; fumed metal oxides (also called exothermic metal oxides) including, but not limited to, fumed silica, fumed alumina; zirconia; precipitated metal oxides including, but not limited to, precipitated silica, precipitated alumina; unmodified and organically modified phyllosilicate clays; dimer and trimer fatty acids; polyether phosphates; oxidized polyolefins; hybrid oxidized polyolefins with polyamides; alkali-soluble / swellable emulsions; cellulose ethers; hydrophobically modified alkali-soluble emulsions; hydrophobically modified ethylene oxide-based urethanes; sucrose benzoate; ester-terminated polyamides; tertiary amide-terminated polyamides; polyalkyleneoxy-terminated polyamides; polyether amides; acrylamide methyl-substituted cellulose ester polymers; polyethyleneimine; polyureas; organoclays; hydrogenated castor oil; organic base salts of clay minerals (e.g., montmorillonite) and other silicate-based materials; and aluminum, calcium, and zinc salts of fatty acids such as lauric acid or stearic acid, among others.

[0212] Reference is made to the information on urea derivatives that may be useful as thixotropes in U.S. Patent No. 6,548,593 to Merz et al., issued April 15, 2003, and U.S. Patent No. 9,376,602 to Walther et al., issued June 28, 2016, which are hereby incorporated by reference in their entirety.

[0213] Thermoreversible gelling agents, such as ester-terminated polyamides, tertiary amide-terminated polyamides, polyalkyleneoxy-terminated polyamides, and polyetheramides, and combinations thereof, may be desirable to the authors as thixotropes. Examples include Crystasense LP1, Crystasense LP2, Crystasense LP3, Crystasense MP, Crystasense HP4, Crystasense HP5, Rheoptima X17, Rheoptima X24, Rheoptima X38, Rheoptima X58, Rheoptima X73, and Rheoptima X84 available from Croda. Crystasense HP-5 is a preferred example of a thixotrope.

[0214] Metal oxides surface-treated to impart dispersibility properties and compatible with the photocurable resin component may be desirable for use as thixotropes.

[0215] Thixotropes may be included in the photocurable compositions described herein in an amount in the range of, for example, about 0.05 weight percent to about 15 weight percent, about 0.5 weight percent to about 15 weight percent, about 0.5 weight percent to about 10 weight percent, about 1 to about 10 weight percent of the composition. Other amounts may also be determined to be useful.

[0216] The thixotrope is preferably included in the photocurable composition in an amount effective to at least partially restrict the movement of the three-dimensional object or one or more of its regions during formation.

[0217] More preferably, the thixotrope is included in the photocurable composition in an amount effective to at least partially restrict the movement of the suspended three-dimensional object (not in contact with the container surface) during formation in the volume of the photocurable composition. Most preferably, the position of the object in the volume of the photocurable composition remains fixed during object formation.

[0218] Antifoaming agent Defoamers may be included to assist in removing bubbles introduced during processing and handling. A preferred defoamer is BYK 1798 (a silicone-based defoamer) available from BYK-Chemie GmbH, which is part of the ALTANA group.

[0219] Stabilizer Stabilizers may be included to improve the shelf life of the photocurable composition and / or to control the level of curing and / or spatial resolution during printing. Examples of preferred stabilizers are TEMPO (2,2,6,6-tetramethylpiperidinooxy free radical available from Sigma-Aldrich). Examples of other stabilizers include, but are not limited to, hindered phenols such as butylhydroxytoluene; hydroquinone and its derivatives such as hydroquinone methyl ether; hindered amine light stabilizers; alkylated diphenylamines; and phosphite esters.

[0220] Oxygen scavenger Oxygen scavengers may be included to react with oxygen (e.g., singlet oxygen, dissolved oxygen) present in the photocurable composition.

[0221] Non-reactive solvent diluent Non-reactive solvent diluents may be included. Examples include, but are not limited to, acetone, amyl acetate, n-butanol, sec-butanol, tert-butanol, butyl acetate, cyclohexanone, decane, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, dipropylene glycol, dipropylene glycol methyl ether, ethanol, ethyl acetate, ethylene glycol, glycerol, heptane, isopropanol, isopropyl acetate, methyl ethyl ketone, N-methylpyrrolidone, propylene carbonate, propylene glycol, propylene glycol diacetate, tetrahydrofuran, tripropylene glycol (glygol) methyl ether, toluene, water, xylene.

[0222] Thermally activated radical initiator It may also be desirable for the photocurable composition to contain a thermally activated radical initiator. Examples of thermally activated radical initiators include, but are not limited to, 2,2'-azobis(2-methylpropionitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] n-hydrate, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], organic peroxides, inorganic peroxides, and peroxydisulfates.

[0223] When a thermally activated radical initiator is included in the photocurable composition, the composition may further include a resin component curable by a heat-driven reaction. In this case, heat treatment of the part resulting from exposure to the first and second wavelengths can be carried out to further cure the part. Examples of suitable heat-curable resin components include, but are not limited to, polyurethanes, polyurethane-ureas and polyurea precursors; epoxy resins and epoxy curing agents; cyanate ester resins and phthalonitrile resins; maleimide resins with or without allyl curing agents, such as bismaleimide resins; polyamic acids (e.g., poly(pyromellitic dianhydride-co-4,4'-oxydianiline) amic acid), polyamideamic acids (e.g., Torlon AI-30 and Torlon AI-50 available from Solvay), polyimides and polyamideimide precursors containing amines, acid anhydrides and isocyanates; norbornene resins, such as nadic anhydride-terminated resins; phenolic resins, etc. Examples of preferred heat-driven reactions or mechanisms include, but are not limited to, heating (e.g., direct or indirect application of heat or thermal energy, irradiation with microwaves for heating purposes, irradiation with UV, visible light or infrared light).

[0224] The inclusion of one or more resin components that can be cured by a heat-driven reaction or mechanism in the photocurable compositions described herein can facilitate or enable the formation of an article that has properties and / or performance characteristics suitable for the end-use applications of articles formed from resins comprising photocurable compositions that may not have suitable resin components. Examples of properties that can be modified by the inclusion of a second resin component include, but are not limited to, mechanical properties, thermal properties, electrical properties, dielectric properties, chemical resistance, moisture resistance, and biocompatibility. Examples include improved mechanical properties including increased tensile strength and modulus, flexural strength and modulus, compressive strength and modulus, impact strength, hardness, abrasion resistance, fatigue resistance, fracture toughness; improved thermal properties including elevated glass transition temperature, elevated heat deflection temperature, elevated thermal decomposition temperature or reduced coefficient of thermal expansion; reduced moisture or solvent uptake; improved radiation resistance; improved fire resistance, flame retardancy or char yield values; improved dielectric performance (e.g., reduced dielectric constant, reduced dielectric loss constant, or elevated breakdown voltage); or improved optical properties (e.g., elevated refractive index).

[0225] Examples of suitable resin components include, but are not limited to, polyurethanes, polyurethane-ureas and polyurea precursors; epoxy resins and epoxy curing agents; cyanate ester resins and phthalonitrile resins; maleimide resins with or without allyl curing agents, such as bismaleimide resins; polyamic acids (e.g., poly(pyromellitic dianhydride-co-4,4'-oxydianiline) amic acid), polyamideamic acids (e.g., Torlon AI-30 and Torlon AI-50 available from Solvay), polyimide and polyamideimide precursors including amines, acid anhydrides and isocyanates; norbornene resins, such as nadic anhydride-terminated resins; phenolic resins; and benzoxazine resins, among others.

[0226] The photocurable composition according to the present invention further comprising a resin component curable by a heat-driven reaction may comprise, for example, from about 0.5 to about 95, preferably from about 40 to about 95 weight percent of a photocurable resin component; from about 0.0001 to about 0.05, from 0.0001 to about 0.02, including but not limited to from about 0.0001 to less than about 0.02, from about 0.0001 to about 0.5 weight percent of a photoswitchable photoinitiator; from about 0.0001 to about 25 weight percent of a second photoactivating photoinitiator, and from about 0.5 to about 95, preferably from about 15 to about 95 weight percent of a resin component, including but not limited thereto.

[0227] When the method involves a photocurable composition described herein further comprising a resin component curable by a heat-driven reaction, the object can be removed from the volume where it is formed upon irradiation with the first and second wavelengths, where the object is formed and optionally washed, and then the resin component thermally curable is further cured (e.g., by further reacting, polymerizing, chain extending), and also subjected to a heat-driven reaction or mechanism sufficient to form the article (e.g., heated and / or microwave irradiated).

[0228] Separation of the at least partially curable object from the uncured composition can be carried out by several means known in the art, such as gravity drainage, sieving, air blade, centrifugation, vibration or ultrasonic agitation.

[0229] Washing can be carried out with any suitable organic or aqueous cleaning liquid, including but not limited to solutions, suspensions, emulsions, microemulsions, etc., or combinations thereof. Examples of suitable cleaning liquids include, but are not limited to, water, alcohols (e.g., methanol, ethanol, isopropanol, etc.), glycol ethers, benzene, toluene, etc. Cleaning liquids containing a mixture of two or more liquids (e.g., a mixture of water and an alcohol (e.g., isopropanol)) can also be suitable. Such cleaning solutions can optionally contain additional components, such as surfactants, etc.

[0230] The object is formed as described above and can be further cured by a heat-driven reaction or mechanism, optionally after washing or the like. Curing can include heating and / or microwave irradiation to further solidify the object. The heating can be active heating (e.g., in an oven, such as an electric, gas, or solar oven as an example) or passive heating (e.g., at ambient temperature). Active heating can be faster than passive heating and may be preferred in some embodiments. Passive heating, for example, by maintaining the intermediate at ambient temperature for a time sufficient to cause further solidification, may also be desirable. Optionally, the heating can include heating at a first temperature for a first period, then heating at a second temperature for a second period, then heating at a third temperature for a third period, and so on for any number of temperatures and periods. The temperature and period are selected to promote evaporation of volatile substances from the article without causing damage (e.g., cracks); to promote more complete solidification of the lower temperature solidifying component before solidification of the higher temperature solidifying component to stabilize the shape of the article; or to generate higher thermomechanical properties. Differential scanning calorimetry can assist in determining the appropriate temperature and period for curing by indicating the temperature at which the curing reaction starts and reaches its maximum rate (e.g., in a temperature ramp experiment), and by indicating how much time is required to complete the curing reaction (e.g., in an isothermal experiment). The periods can be of the same length or different. In some embodiments, the first temperature can be ambient temperature or can exceed ambient temperature, and each subsequent temperature can exceed the previous one. Preferably, the maximum temperature is sufficient to complete or substantially complete the curing or solidification of the curable resin composition, but is below the decomposition temperature, e.g., the 5% mass loss temperature measured by thermogravimetric analysis. When multiple temperatures are used, the temperature can ramp, for example, in a stepwise manner.

[0231] The second photoactivatable photoinitiator Optionally, the photocurable composition may further comprise a photoactivatable photoinitiator. Preferably, such a photoinitiator does not respond significantly to light of the first wavelength or the second wavelength. Inclusion of a photoinitiator may be desirable in connection with an optional post-treatment, for example, including a post-curing step involving exposure of the printed object to UV light after printing.

[0232] When a second photoactivatable photoinitiator is included in the photocurable resin composition, the method includes exposing the object to light of a third wavelength to further cure the object, and the third wavelength may further include a post-curing step different from the first and second wavelengths. Irradiation with the third wavelength is preferably performed after removing or separating the partially cured part from the volume in which it was formed. It may also be desirable to wash the separated or removed part before post-curing irradiation with the third wavelength. When the second photoactivatable photoinitiator is UV-activatable, a third wavelength in the ultraviolet range is preferred. For example, a third wavelength in the range of about 240 to about 455 nm, about 240 nm to about 445 nm, about 240 nm to about 410, or other ranges less than the first and second wavelengths may be useful.

[0233] The selection of the second photoinitiator is generally made taking into account the absorption band of the second photoinitiator, the wavelength of the radiation or light used to activate the second photoinitiator, and the first and second wavelengths to avoid unwanted polymerization to activate a photoswitchable photoinitiator. As a non-limiting example, a second photoinitiator that can be activated by UV or visible wavelength light can be utilized. Other factors, such as extinction coefficient, rate constant of primary radicals with respect to the photocurable resin component, possible side reactions, and light intensity, can also be taken into account and balanced in the selection process. See, for example, A, Eibel et al., "Choosing the ideal photoinitiator for free-radical photopolymerizations: predictions based on simulations using established data", Polym. Chem., September 2018, pp. 5107-5115.

[0234] The second photoinitiator desirably shows no absorption or minimal absorption at the first wavelength and the second wavelength.

[0235] Preferably, the third wavelength is not directed into the volume during the formation of the partially cured object in the volume.

[0236] Preferably, the third wavelength is less than the first and second wavelengths.

[0237] The second photoinitiator preferably includes a photoinitiator that initiates the polymerization or crosslinking of the photocurable resin component by a free radical reaction (also referred to herein as a free radical photoinitiator). The second photoinitiator may include a type I photoinitiator (a type I photoinitiator may sometimes be referred to as a Norrish type I photoinitiator in the art). The second photoinitiator may include a type II photoinitiator (a type II photoinitiator may sometimes be referred to as a Norrish type II photoinitiator in the art). The second photoinitiator may preferably be a single component, for example, a type I photoinitiator that does not absorb much light at the first or second wavelength.

[0238] Examples of the second photoinitiator include, but are not limited to, acetophenone, anisoin, anthraquinone, benzyl, benzoin, benzoin ethyl ether, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, 4,4'-bis(diethylamino)benzophenone, thioxanthone, 2-chlorothioxanthone, dibenzosuberone, 2,2'-diethoxyacetophenone, 4,4'-dihydroxybenzophenone, 2,2-dimethoxy-2-phenylacetophenone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), 4'-ethoxyacetophenone, 3'-hydroxyacetophenone, 4'-hydroxyacetophenone, 3-hydroxybenzophenone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methylpropiophenone, methyl benzoylformate, 2-methyl-4'-(methylthio)-2-morpholinopriopiophenone, phenanthraquinone, 4'-phenoxyacetophenone.

[0239] An example of a preferred second photoinitiator that includes a free radical photoinitiator is Omnirad 184 (1-hydroxycyclohexyl-phenyl ketone) available from IGM.

[0240] Exposure of the second photoinitiator to light at the third wavelength typically advantageously induces or can alter at least one chemical or physical property of the previously unaltered photocurable composition contained in the object to further cure the initial print or partially cured object by a crosslinking or polymerization reaction in the photocurable composition.

[0241] Preferably, the second photoinitiator shows no or minimal absorption at the first and second wavelengths.

[0242] The second photoinitiator desirably may not be activatable or may not be very activatable by the first or second wavelength so as to avoid unwanted reactions in the photocurable composition without exposure to the third wavelength.

[0243] Post-curing of the initial print or the partially cured object can be carried out with light of a third wavelength for further curing (e.g., for further polymerization or crosslinking). Preferably, exposure to the third wavelength is carried out after separating the partially cured object from the volume in which it was formed. It may be desirable to wash the separated object before irradiating it with light of the third wavelength.

[0244] The nature of the monomers, the amount of the photoswitchable photoinitiator, and, where applicable, the co-initiator and / or sensitizer in the photocurable composition according to the present invention vary depending on the specific use of the composition, the emission characteristics of the exposure light source, the development procedure, the physical properties desired for the polymerized product, and other factors.

[0245] Examples of photocurable compositions according to certain embodiments of the present invention containing one or more co-initiators and / or sensitizers generally have a composition falling within the following compositional ranges in parts by weight [relative to a total of 100 parts by weight]: Photocurable resin component: about 10 to 99.9999 Photoswitchable photoinitiator: about 0.0001 to about 0.5, such as including, but not limited to, about 0.0001 to about 0.1, about 0.0001 to about 0.05, about 0.0001 to about 0.01, about 0.0001 to about 0.009, about 0.0001 to about 0.005, about 0.0001 to about 0.0025, etc. Co-initiator (optional): about 0.001 to about 10, such as including, but not limited to, about 0.001 to about 7.5, about 0.001 to about 5, about 0.001 to about 2.5, about 0.001 to about 1, about 0.001 to about 0.5, about 0.0001 to about 0.25, etc. Sensitizer (optional): about 0.1 to 1, such as including, but not limited to, about 0.1 to about 0.75, about 0.1 to about 0.5, about 0.1 to about 0.25, etc.

[0246] Examples of the photocurable compositions according to certain embodiments of the present invention that do not contain one or more co-initiators and / or sensitizers generally have a composition falling within the following compositional ranges, in parts by weight [relative to a total of 100 parts by weight]: Photocurable resin component: about 10 to about 99.9999 Light-switchable photoinitiator: about 0.0001 to about 0.5, including, but not limited to, for example, about 0.0001 to about 0.1, about 0.0001 to about 0.05, about 0.0001 to about 0.01, about 0.0001 to about 0.009, about 0.0001 to about 0.005, about 0.0001 to about 0.0025, etc.

[0247] When a co-initiator is optionally further included in the photocurable composition, it may be included within the compositional ranges, in parts by weight [relative to a total of 100 parts by weight], specified above.

[0248] In some cases, such as in the printing of hydrogels that float within the final resin after photocuring where the remainder of the resin consists of non-reactive components, the weight percentage of the photocurable resin component in the exemplary composition above may be less than 10 weight percent, for example, less than 5 weight percent, less than 3 weight percent, less than 2 weight percent, or less than or equal to 1 weight percent.

[0249] Optionally, the photocurable composition according to the present invention may further include a second photoactivatable photoinitiator that preferably does not respond significantly to light of the first wavelength or the second wavelength. The inclusion of such a photoactivatable photoinitiator may be desirable in relation to any post-treatment of the printed object and any optional post-curing step carried out using UV light after printing.

[0250] When the second photoactivatable photoinitiator is further included in the photocurable composition, it may be included within a compositional range, for example, in parts by weight [relative to a total of 100 parts by weight], of about 0.0001 to about 25%, including, but not limited to, for example, about 0.0001 to about 10, about 0.0001 to about 7.5, about 0.0001 to about 5, about 0.0001 to about 2.5, about 0.0001 to about 1, about 0.0001 to about 0.5, etc.

[0251] The photocurable composition according to the present invention can be prepared using known or conventional procedures.

[0252] When a second photoactivatable photoinitiator is included in the photocurable resin for post-curing purposes, the method includes exposing the object to light of a third wavelength to further cure the object, and the third wavelength may further include a post-curing step different from the first and second wavelengths. When the photoinitiator is UV-activatable, a third wavelength in the ultraviolet range is preferred.

Examples

[0253] [Example 1] Preparation of Photo-Switchable Photoinitiators All photo-switchable photoinitiators reported herein are obtained using the versatile Suzuki coupling reactions depicted in Scheme 1. The structures and characteristics of (III) - (XXX) are shown in Table 1. To synthesize the photo-switchable photoinitiators (III) - (XXI) (Scheme 1a), halide-functionalized diarylethenes (1 - 4) and borylated sensitizers (5 - 13) were combined. A complementary approach was employed for the synthesis of the photo-switchable photoinitiators (XXII) - (XXX) (Scheme 1b), and the incorporation of various heterocycles in the final step can be achieved by cross-coupling of borylates 14 and 15 with commercially available heterocyclic halides.

[0254] The diarylethene halide starting material 1 was purchased from Ambeed (Cat. No. A992492), and 2 - 3 were synthesized as described in the academic literature. The remaining starting materials (4 - 15) were synthesized as described below.

[0255]

Chemical formula

[0256] General procedure for synthesizing the photo-switchable photoinitiators (III) - (XXX) depicted in Scheme 1: In a 4 mL amber vial, a halide and a borate substrate * , Pd XPhos G3 (0.03 eq), potassium phosphate (5.0 eq), and a magnetic stir bar were added. The vial was sealed with a Teflon-lined cap, placed under a N2 atmosphere, and subjected to 3 vacuum / N2 cycles. To this vial, a deoxygenated 5:1 mixture (v / v) of dioxane:water (2 mL) was then added via syringe. The vial was sealed with insulating tape and placed on a heating block set at 90 °C, and then the mixture was stirred for 2 h. The mixture was partitioned between CH2Cl2 (4 mL) and water (4 mL), the organic layer was dried over Na2SO4, filtered, and then the volatiles were removed by rotary evaporation at 40 °C. The residue was subjected to preparative thin layer chromatography (hexane / CH2Cl2 or CH2Cl2 / EtOAc solvent systems) to afford the desired diarylethene photoswitchable photoinitiators (III)–(XXX). In some cases, both the mono- and disubstituted analogues were isolated as part of a statistical mixture from the same reaction (e.g., (III) and (IV)). The isolated compounds and characterization data are summarized in Table 1 below. * For the synthesis of III–XXI (Scheme 1a), the substrates were halide-functionalized diarylethenes 1, 2, 3, or 4 (50 mg) and a borated photosensitizer (5–13, 1 eq). For the synthesis of XXII–XXX (Scheme 1b), the substrates were borates 14 or 15 (50 mg, 1 eq) and a commercially available heteroaryl halide (2 eq).

[0257]

Table 2

[0258] Synthesis of diarylethene starting material 4

[0259]

Chem.

[0260] Into a flame-dried 100 mL Schlenk flask were placed 3-bromo-5-chloro-2-methylthiophene (2.33 g, 11.0 mmol, 1.1 equiv), dry diethyl ether (30 mL), and a magnetic stir bar. The stirred solution was cooled to -78 °C in a dry ice / acetone bath, and then n-BuLi (2.5 M in hexanes, 4.0 mL, 10.0 mmol, 1.0 equiv) was added dropwise via syringe over 3 - 5 min. The mixture was stirred at -78 °C for 30 min, and then perfluorocyclopentene (4.2 g, 20 mmol, 2.0 equiv) was added rapidly via syringe. After an additional 3 - 5 min at -78 °C, the cooling bath was removed and the mixture was warmed to room temperature. After 1 h, at room temperature, the mixture was quenched with saturated aqueous NH4Cl solution (30 mL). The layers were separated, the organic layer was washed with saturated aqueous NaCl solution (30 mL), dried over Na2SO4, filtered, and the solvent was removed from the filtrate by rotary evaporation. The residue was purified by column chromatography (100% hexanes) to give compound 16 (1.62 g, 50%) as a colorless liquid. This liquid was used directly without characterization in the next step.

[0261] Into a flame-dried 25 mL Schlenk flask were placed 2-bromo-3,5-dimethylthiophene (540 mg, 2.83 mmol, 1.2 equiv), dry diethyl ether (10 mL), and a magnetic stir bar. The stirred solution was cooled to -78 °C in a dry ice / acetone bath, and then n-BuLi (2.5 M in hexanes, 1.04 mL, 2.59 mmol, 1.1 equiv) was added dropwise via syringe over about 1 min. The mixture was placed on an ice / water bath for 15 min and then placed back on the -78 °C bath for about 5 min. Compound 16 (765 mg, 2.36 mmol, 1.0 equiv) was added dropwise via syringe over about 1 min. After an additional 3 - 5 min at -78 °C, the cooling bath was removed and the mixture was warmed to room temperature. After 1 h at room temperature, the mixture was quenched with saturated aqueous NH4Cl (20 mL) and extracted with EtOAc (20 mL). The organic layer was washed with saturated aqueous NaCl (30 mL), dried over Na2SO4, filtered, and the solvent was removed from the filtrate by rotary evaporation. The residue was purified by column chromatography (100% hexanes) to afford Compound 4 (0.57 g, 58%) as a colorless crystalline solid.

[0262] Synthesis of Boronic Acid Esters 5 - 13

[0263] [Chemical formula]

[0264] To a 40 mL vial with a screw cap, a commercially available aryl halide (2.5 g), bis(pinacolato)diboron (1.1 molar equivalents), XPhos Pd G2 (0.02 - 0.03 equivalents), potassium acetate (2.5 equivalents), and a stir bar were added. The vial was sealed, placed under an N2 atmosphere, and subjected to 3 vacuum / N2 cycles. Anhydrous, deoxygenated dioxane (10 mL) was added via syringe, and the vial was sealed with insulating tape. The mixture was stirred at 90 °C (heating block temperature) for 12 - 24 h, then the mixture was brought to room temperature and diluted with CH2Cl2 (30 mL). The mixture was filtered through a plug of silica gel (20 g) equilibrated with the solvent. The plug was flashed with 20% EtOAc in CH2Cl2 by thin layer chromatography until no further product was observed. The filtrate was concentrated by rotary evaporation, and the crude boronic ester was recrystallized from hexane or used without further purification. The following borolated polycyclic compounds were prepared and isolated using this procedure:

[0265] [Chemical formula]

[0266] Synthesis of Components 14 and 15.

[0267] [Chemical formula] (a) Pd(dppf)Cl2 (0.03 equivalents), K2CO3 (5 equivalents), dioxane / water, 90 °C; (b) (Bpin)2 (1.1 equivalents), Pd(dppf)Cl2 (0.03 equivalents), KOAc (2.5 equivalents), dioxane, 90 °C; (c) AlCl3 (1.5 equivalents), CH2Cl2

[0268] [Example 2] Preparation of the Base Resin A 100-mL round-bottom flask containing a magnetic stir bar was charged with 10.0 g of a thixotrope (Crystasense HP-5, Croda). To this flask, 50.0 g of N,N-dimethylacrylamide (DMAA, Rahn) was then added via a syringe. The flask was sealed with a rubber septum and a 1-in 22G needle was inserted for ventilation. The flask was placed on a preheated (105 °C) aluminum heating block and the mixture was stirred at 250 - 300 rpm until the thixotrope was completely dissolved (10 - 15 min). Next, 50.0 g of DMAA was placed via a syringe into a 0.6 gallon polypropylene pail equipped with a polypropylene lid. To this pail, 200 g of Genomer 4259 (Rahn) and 650 g of Genomer 4247 (Rahn) were then added via a large-bore syringe. The contents of the pail were mixed at high speed for 1 min at 1100 rpm (DAC 2800-1000, Flacktek). The HP-5 solution was then poured into the pail and the contents of the pail were mixed at high speed for an additional 1 min at 1100 rpm.

[0269] [Example 3] Preparation of Resin Composition 1 Containing One of Compounds (III)-(XXX) and a Polymerization Synergist for Use in Voxelization Studies One stock solution of one of the photo-switchable photoinitiators (III) - (XXX) was first prepared by dissolving the photo-switchable photoinitiator in N,N-dimethylacrylamide (DMAA, Rahn) in a 4 mL amber vial to a final concentration of 1.00 mg of photo-switchable photoinitiator per DMAA. To a 40 mL amber vial containing 28.5 g of the base resin (above), 0.60 g of the photo-switchable photoinitiator stock solution (20 ppm with respect to the mass of the photo-switchable photoinitiator) and 0.90 g of N-methyldiethanolamine (3% with respect to the mass of the polymerization synergist) were then added. The contents of the vial were mixed at high speed at 3500 rpm for 1 min (DAC 2800-1000, Flacktek) to obtain resin formulation 1. The formulation was transferred to a 1 cm plastic cuvette (Einmal-Kuvetten), capped, and centrifuged at 4000 rpm for 3 min (5804R, Eppendorf) to remove trapped air bubbles.

[0270] [Example 4] Evaluation of Photo-Switchable Photoinitiation in Resin Formulation 1 under Crossed Beams of UV and Visible Illumination Light A centrifuge tube containing resin formulation 1 (prepared as above) and free of air bubbles was placed in a configuration that characterized two crossed, approximately collimated, coherent light sources (408 nm and 520 nm). The irradiance of the 408 nm light source was 0.22 W / cm 2 ("Condition 1") or 0.6 W / cm 2 ("Condition 2"), and the irradiance of the 520 nm light source was 1.7 W / cm 2 (in all cases). The light sources were orthogonal and crossed at the center of a 1 cm x 1 cm square cuvette. The time taken to form the polymerized spot was noted, which serves as a proxy for part formation in a printer ("voxel time"). In another experiment, different cuvettes were exposed to 408 nm irradiation only, at 0.22 W / cm 2 ("Condition 1") or 0.6 W / cm 2It was irradiated with the irradiation amount of (「Condition 2」). Attention was paid to the time required to form the polymerized region, which serves as a proxy for curing derived from the UV light sheet in the printer (「light sheet time」). The times reported in Table 1 are the averages of 2 to 3 measurements.

[0271] In this operation, two metrics are used to predict the performance of a photo-switchable photoinitiator for volume printing: (1) the ratio of 「light sheet time」 to 「voxel time」; (2) the value of 「voxel time」. A larger value in 1 and a smaller value in 2 contribute to better performance. For example, under the conditions of Example 4, a ratio of at least 1 of (time until UV light curing) / (time until voxel curing) and a voxel curing time of 30 seconds or less, preferably a ratio of at least 1.2 of (time of UV curing / time of voxel curing), and a voxel curing time of less than 15 seconds were found to be useful for screening photo-switchable photoinitiators preferred for volume printing.

[0272] Although not wishing to be bound by theory, a ratio of (time until UV light curing) / (time until voxel curing) not exceeding 1, or a curing time exceeding 30 seconds, should not be construed as indicating that a particular photo-switchable photoinitiator is not suitable for use in volume printing. However, such results may be useful as an indicator for varying one or more printing conditions (e.g., the concentration of the photo-switchable photoinitiator and / or synergistic additive, the output level of one or both of the excitation lights, the printing temperature, and / or one or both of the excitation wavelengths) for better printability. Such adjustments are routine for those skilled in the art without the need for undue experimentation.

[0273] [Example 5] Example of a procedure for printing an object using AE4

[0274] A. Preparation of Resin The stock solution is prepared by dissolving 80 milligrams of Compound No. AE4 (prepared as specified in Example 1) in 25 milliliters of N,N-dimethylacrylamide.

[0275] Separately, 25 milliliters of N,N-dimethylacrylamide are mixed with 70 milliliters of isobornyl acrylate and 5.5 grams of Crystasense HP5 (Croda). This solution is stirred at 80 degrees Celsius until completely dissolved to homogenize the components.

[0276] The third solution is prepared by mixing 650 grams of Genomer 4247 (Rahn) and 200 grams of Genomer 4259 (Rahn) in a Flaktek speed mixer bucket at 60 degrees Celsius. To this warm solution, the solution containing Crystasense HP5 is added, and the resulting mixture is mixed at high speed for 1 minute at 1000 RPM (DAC 2800-1000, Flacktek). Then, the solution containing the photo-switchable photoinitiator is added, and the mixture is mixed at high speed again for 1 minute at 1000 RPM. Finally, 60 grams of N-methyldiethanolamine are added to the bucket, and the entire mixture is mixed at high speed once more for 1 minute at 1000 RPM.

[0277] This mixture is then centrifuged to remove bubbles, dispensed by pouring into a glass cuvette 20 mm in length, 20 mm in width, and 45 mm in height, and cooled to room temperature before printing.

[0278] B. Printing Process The cuvette of the photocurable composition is placed in a holder on a motorized stage. Using a green laser light (532 nm CW diode laser, 20 W operating power), a digital micromirror device (Texas Instruments) is illuminated to form a pattern projected into the cuvette along the z-axis, at approximately 1.6 W / cm 2Generate a pattern of green light. Use purple light (405nm CW diode laser, 50 - 365mW operating power) to form a light sheet that passes orthogonally through the cuvette into the projected pattern, illuminating a single x - y plane nominally 100 microns thick. This light sheet passes through two lenses and is reflected by a mirror, as generally described in International Patent Application No. PCT / US2022 / 052157 of Quadratic 3D, Inc. filed on December 7, 2022, and as a result, in a beam path almost identical to the forward - propagating sheet, it passes through the resin once again in the reverse direction and is combined to form one light sheet that propagates in both the forward and reverse directions. However, the photo - switchable photoinitiators described herein can be used for volume printing using a variety of different light sheets and projector profiles. In this printing experiment, the purple laser diode is operated at 200mW to generate an irradiance of approximately 0.66W / cm 2 . The stage is advanced in 14 - micron increments at 250 - ms intervals. The purple light forms the light sheet, and the green light changes the pattern with each advance corresponding to a computer - generated slice of the three - dimensional object. In the region where simultaneous or almost - simultaneous exposure to the wavelengths of both lights occurs, the photocurable composition is cured. In this way, a three - dimensional solid object is formed without displacement (e.g., sedimentation or drift) and without the need for attachment to an assembly platform due to a high zero - shear viscosity or yield stress of the support structure or non - Newtonian photocurable composition. The parts are removed from the resin using a spatula, washed for 2 minutes by agitation in isopropyl alcohol, dried for 10 minutes, and then post - cured for an additional 10 minutes using Formlabs Form Cure.

[0279] Photographs of the parts printed generally following the procedure specified in Example 5 are shown in FIGS. 1A, 1B, and 1C. The printed parts reproduce all the features of the target in three dimensions. FIGS. 1D, 1E, and 1F illustrate the front, back, and side views of the 3D model shape to be printed.

[0280] [Example 6] Example of the procedure for printing an object using AE32 The printing experiment was carried out using Compound No. AE32 as the photo-switchable photoinitiator detailed in this Example 6, as generally specified in Example 5.

[0281] A. Preparation of Resin The preparation of the resin was carried out generally as described in Example 5 above, except that 20 milligrams of Compound No. AE32 (prepared as specified in Example 1) was used instead of 80 milligrams of Compound No. AE4.

[0282] B. Printing Process Printing was carried out at 40 degrees Celsius, the stage was advanced in 28-micron units at intervals of 150 milliseconds, the UV irradiation dose was 0.50 W / cm 2 and the green irradiation dose was 1.0 W / cm 2 Printing was carried out generally as described in Example 5 above, except for the above, and parts using the resin prepared as described in Paragraph 6A of this Example were printed.

[0283] Photographs of the parts printed generally according to the procedure described in this Example 6 are shown in Figures 2A, 2B, and 2C. The parts faithfully reproduce the features of the target object in all three dimensions. Figures 2D, 2E, and 2F illustrate the front view, rear view, and side view of the 3D model shape of the object to be printed.

[0284] [Example 7] Example of the procedure for printing an object using AE39 The printing experiment generally specified in Example 5 was carried out using Compound No. AE39 as the photo-switchable photoinitiator detailed in this Example 7.

[0285] A. Preparation of Resin The preparation of the resin was carried out generally as described in Example 5 above, except that 40 milligrams of AE39 (prepared as specified in Example 1) was used instead of 80 milligrams of AE4.

[0286] B. Printing Process The printing was carried out at 40 degrees Celsius, the stage was advanced in 28 - micron units at 280 - millisecond intervals, the UV irradiation amount was 1.0 W / cm 2 , and the green irradiation amount was 1.6 W / cm 2 Except for the above, the printing was executed generally as described in Example 5 above, and parts using the resin prepared as described in Paragraph 7A of this example were printed.

[0287] Photographs of the parts printed generally according to the procedure described in Example 7 of this document are shown in Figures 3A, 3B, and 3C. The parts faithfully reproduce all the features of the target object in three dimensions. Figures 3D, 3E, and 3F illustrate the front view, rear view, and side view of the 3D model shape of the object to be printed.

[0288] [Example 8] Example of object printing in a photocurable composition containing a photocurable photoinitiator represented by the above formula XXI (Compound No. AE32) and with or without a second photoinitiator

[0289] A. Preparation of the photoswitchable photoinitiator Compound No. AE32. Compound AE32 was prepared according to the procedure described in Example 1.

[0290] B. Preparation of the base resin Mix 25 milliliters of N,N - dimethylacrylamide with 70 milliliters of isobornyl acrylate and 5.5 grams of Crystasense HP5 (Croda). Stir this solution at 80 degrees Celsius until completely dissolved to homogenize the components.

[0291] The second solution was prepared by mixing 650 grams of Genomer 4247 (Rahn) and 200 grams of Genomer 4259 (Rahn) in a Flaktek speed mixer bucket at 60 degrees Celsius.

[0292] To this warm solution, a solution containing Crystasense HP5 is added, and the resulting mixture is rapidly mixed at 1000 RPM for 1 minute (DAC 2800-1000, Flacktek). Finally, 60 grams of N-methyldiethanolamine is added to the speed mixer bucket, and the entire mixture is rapidly mixed again at 1000 RPM for 1 minute.

[0293] C. Preparation of Resin Formulation Containing Compound No. AE32 The stock solution of the photoswitchable photoinitiator was prepared by dissolving the photoswitchable photoinitiator prepared generally as described in Example 1 in a 1:1 v / v mixture of 25 mL of N,N-dimethylacrylamide (DMAA, Rahn) and benzyl acrylate (Beantown chemical) in a 40 mL amber vial, resulting in a final concentration of approximately 0.75 mg / mL of the photoswitchable photoinitiator in the solvent. 0.30 mL of this photoswitchable photoinitiator stock solution was added to 14.7 grams of the above base resin to create a resin formulation containing 15 ppm of the photoswitchable photoinitiator. This resin formulation was rapidly mixed at 3000 rpm for 1 min (DAC 2800-1000, Flacktek).

[0294] D. Preparation of Test Samples Two test samples were prepared as specified below, one containing a second photoinitiator and the other not containing a second photoinitiator.

[0295] To prepare the test sample containing the second photoinitiator, 0.6 wt% of 1-hydroxycyclohexyl-phenyl ketone (Omnirad 184, IGM Resins, CAS NO. 947-19-3) was added to 1 kilogram of the prepared resin as generally specified in Example 8C, and the mixture was stirred until all solids were dissolved. This was centrifuged at 4500 rpm for 5 minutes (5804R, Eppendorf) to remove bubbles and poured into a custom quartz cuvette with an inner dimension of 2×2×4 cm for printing.

[0296] In the case of the test sample without the second photoinitiator, 500 grams of the base resin formulation (prepared as generally described in Example 8C) was centrifuged at 4500 rpm for 5 minutes (5804R, Eppendorf) to remove bubbles and poured into a custom quartz cuvette with an inner dimension of 2×2×4 cm for printing.

[0297] E. Printing of objects in resins containing Compound No. AE32 with and without the second photoactivating photoinitiator Two cuvettes were prepared for printing, each containing one of the two samples described in Example 8D, one containing the second photoinitiator and the other not containing the second photoinitiator.

[0298] One cuvette containing the sample described in Example 8D containing the second photoinitiator and the other cuvette containing the sample described in Example 8D without the second photoinitiator were used for printing 7×7×7 mm cubes as generally described in this Example 8E.

[0299] These cuvettes were separately subjected to the following printing settings: Purple light (408 nm mW diode laser, 365 mW maximum operating power) was illuminated outside the scanning galvanometer to generate an optical sheet approximately 130 microns thick, reflected by a mirror, and a combined double-path optical sheet was achieved following a similar optical beam path (generally described in International Patent Application No. PCT / US2022,052157 of Quadratic 3D, Inc. filed on December 7, 2022), and the irradiation dose of the purple light was 0.50 W / cm 2 It was. This light was crossed orthogonally to the projected green light with an irradiation dose of 1.0 W / cm 2 of the projected green light (532 nm laser, continuous wave diode laser with a maximum operating power of 18 watts) using a Texas Instruments DMD to pattern the green light projected in space orthogonally to the optical sheet.

[0300] 7×7×7 mm cubes were printed in each cuvette using the following printing settings: 40 degrees Celsius, 28 micron stage movement interval, 150 milliseconds exposure per slice. In each case, the correctly printed cubes were then washed for 1 minute by stirring in isopropyl alcohol, dried for 10 minutes, and then post-cured under nitrogen in a form that solidified in 10 minutes (396 nm, LED irradiation center at 9.1 watts).

[0301] With these cubes, hardness was tested using a Shore D durometer to compare the conversion from resin to polymer. For cubes printed in resin without any second photoinitiator, the Shore D hardness after this post-curing protocol was 65D, while for resin containing a second photoinitiator, the printed cubes had a Shore hardness of 87D.

[0302] Observation: Inclusion of a second photoinitiator activatable at wavelengths shorter than 405 nm was found to be substantially inactive at the two printing wavelengths, resulting in more complete post-curing without substantially affecting the printing settings.

[0303] The light sheet can be constructed by means known in the art including, but not limited to, techniques involving a laser and a Powell lens, galvanometer, and / or polygonal scanning mirror. Alternatively, one or more LEDs can be used as the light source.

[0304] Information that may be useful in connection with the inventions disclosed herein includes International Patent Application No. PCT / US2021 / 035791, filed on June 3, 2021, by Quadratic 3D, Inc., entitled "Volumetric Three-Dimensional Printing Methods Including A Light Sheet And Systems", and U.S. Patent No. 10,843,410, issued to Lippert et al., entitled "System And Method For A Three-Dimensional Optical Switch Display (OSD) Device"; International Application No. PCT / US2022 / 039766, filed on August 9, 2022, by Quadratic 3D, Inc., entitled "Methods And Systems For Forming An Object In A Volume Of A Photohardenable Composition", Masahiro Irie, "Diarylethene Molecular Photoswitches - Concepts and Functionalities", 2021, Wiley-VCH, Boschstr. 12, 69469, Weinheim, Germany, and H. Durr and H. Bouas-Laurent, "Photochromism: Molecules and Systems", Elsevier (2003).

[0305] As used herein, "alkyl" refers to a branched or straight-chain fully saturated aliphatic hydrocarbon group, or a monocyclic or polycyclic saturated aliphatic hydrocarbon ring system, unless otherwise indicated. Examples include alkyl groups having from 1 to 20 (more typically 1 to 10) carbon atoms, which can be linear, branched, or cyclic alkyl groups, but are not limited thereto. An alkyl group may contain only carbon and hydrogen atoms, or may further incorporate one or more heteroatoms, such as Si, N, O, or S, as part of the alkyl group (sometimes referred to as a heteroalkyl group).

[0306] As used herein, "alkoxy", unless otherwise indicated, refers to a straight or branched chain alkyl moiety covalently bonded to the parent molecule via an -O- linkage. Examples include alkoxy groups having from 1 to 20 (more typically 1 to 10) carbon atoms, which can be straight, branched or cyclic alkoxy groups, but are not limited thereto, and examples thereof include, but are not limited to, methoxy (MeO), ethoxy (EtO), and the like.

[0307] As used herein, "aralkyl" or "arylalkyl" can also refer to an aryl-substituted alkyl moiety, unless otherwise indicated. Examples include aralkyl groups having from 7 to 20 carbon atoms, but are not limited thereto, and examples thereof include, but are not limited to, benzyl, methylphenyl, ethylphenyl, and the like.

[0308] As used herein, "cycloalkyl" can also refer to a saturated aliphatic ring system moiety having at least 3 carbon atoms, unless otherwise indicated. Examples include, but are not limited to, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and the like. A cycloalkyl group can contain a saturated aliphatic ring system containing only carbon atoms, or can further incorporate one or more heteroatoms, such as Si, N, O or S, as part of the ring group (sometimes referred to as a heteroalkyl group).

[0309] As used herein, "heteroalkyl" can also refer to an alkyl group containing one or more heteroatoms, unless otherwise indicated. When two or more heteroatoms are present, they can be the same or different. Examples of heteroalkyl groups include, but are not limited to, CH2-OH, O-C n H .2n+1 where n is any integer of 1 or more, but is not limited thereto.

[0310] As used herein, "aryloxy", unless otherwise indicated, refers to an aryl moiety covalently bonded to the parent molecule via an -O- linkage.

[0311] As used herein, "heteroatom" refers to any atom other than hydrogen or carbon, unless otherwise indicated. Typical heteroatoms include, but are not limited to, S (sulfur), N (nitrogen), O (oxygen), P (phosphorus), Cl (chlorine), Br (bromine), I (iodine), F (fluorine), etc.

[0312] As used herein, "alkenyl" refers to a monovalent straight-chain or branched hydrocarbon chain containing a carbon double bond, such as having 2 to 20 carbon atoms, or a monocyclic or polycyclic hydrocarbon ring moiety, unless otherwise indicated. Examples include, but are not limited to, 1-propenyl, 2-propenyl, 2-methyl-1-propenyl, 1-butenyl, 2-butenyl, etc. A cycloalkenyl group may contain only carbon and hydrogen atoms, or may further incorporate one or more heteroatoms, such as Si, N, O, or S, as part of the alkyl group (sometimes referred to as a heteroalkenyl group).

[0313] As used herein, "cycloalkenyl" may also refer to a monocyclic or polycyclic hydrocarbon ring system moiety having at least 3 carbon atoms, unless otherwise indicated. Examples include, but are not limited to, cyclopropenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, etc. A cycloalkenyl group may contain a monocyclic or polycyclic hydrocarbon ring system consisting of only carbon, or may further incorporate one or more heteroatoms, such as Si, N, O, or S, as part of the ring group (sometimes referred to as a heterocycloalkenyl group).

[0314] As used herein, "amide" refers to -NRC(=O)R', where R and R' may be the same or different, and R and R' independently may represent, for example, hydrogen, alkyl, or aryl, but are not limited thereto.

[0315] As used herein, "amino" refers to -NRR', where R and R' independently may represent, for example, hydrogen, alkyl, or aryl, but are not limited thereto.

[0316] As used herein, "carboxyester", unless otherwise indicated, may also refer to -C(=O)O. Examples include groups having the structure -COOR or -OCOR, where R may represent, for example, but is not limited to, hydrogen, alkyl, or aryl.

[0317] As used herein, "carboxyl", unless otherwise indicated, may also refer to -COOH.

[0318] As used herein, "carbonyl" refers to any group containing a -C(=O) moiety, where C is bonded to two other atoms. Examples of carbonyl groups include groups containing a carbonyl moiety, or a moiety containing a carbonyl moiety. For example, a carbonyl group may include a group containing an aldehyde (-C(=O)H) moiety, a ketone (-C-C(=O)-C moiety, an ester (-C(=O)-O-C') moiety, an acyl (-C-C(=O)-) moiety, a carboxyl (-C(=O)OH group, a thioester (-C(=)OSR') moiety, a primary amide (-C-C(=O)N(non-C)2 moiety (where N is bonded to one C), a secondary amide (-C-C(=O)NHC- moiety (where N is bonded to two Cs), a tertiary amide (-C(=O)NCC moiety (where N is bonded to three Cs), and the like.

[0319] As used herein, "aryl" refers to any aromatic carbocyclic or heterocyclic group containing unsaturated C-C bonds conjugated to each other, whether a single ring or multiple fused rings, unless otherwise indicated. Examples of aryl groups include, but are not limited to, aryl groups containing 5 to 20 carbon atoms, such as phenyl, naphthyl, phenanthryl, etc. Examples of "aryl" substituents include phenyl, naphthyl, anthranyl, naphthacenyl, fluorenyl, pyrenyl, etc., or any aromatic heterocyclic group, such as pyridine, pyrazine, indole, purine, furan, thiophene, pyrrole, etc., but are not limited thereto. An aryl group may contain only carbon and hydrogen atoms, or may further incorporate one or more heteroatoms, such as Si, N, O or S, as part of the alkyl group (sometimes referred to as a heteroaryl group).

[0320] As used herein, "heteroaryl" may also refer to an aromatic ring system moiety in which one or more ring atoms are heteroatoms, whether a single ring or multiple fused rings, unless otherwise indicated. When two or more heteroatoms are present, they may be the same or different. In a fused ring system, one or more heteroatoms may be present in only one of the rings. Examples of heteroaryl groups include, but are not limited to, benzothiazyl, benzoxadiazyl, quinazolinyl, quinolinyl, isoquinolinyl, quinoxalinyl, pyridinyl, pyridazinyl, pyrimidinyl, pyrazinyl, pyrrolyl, oxazolyl, indolyl, thiazyl, etc.

[0321] As used herein, a group, moiety or molecule can be substituted or unsubstituted unless otherwise indicated. A “substituted” group, moiety or molecule refers to a group, moiety or molecule having at least one hydrogen substituted by a group of atoms or a non-hydrogen atom (the group of atoms or non-hydrogen atom replacing hydrogen is typically also referred to as a substituent). When substituted, the substituents are one or more groups selected individually and independently. Examples of various substituents include, but are not limited to, alkyl, cycloalkyl, alkenyl, cycloalkenyl, ether, aryl, heteroaryl, heterocycloalkyl, hydroxyl, oxy, alkoxyl, ester, thioester, acyl, carboxyl, carbonyl, cyano, nitro, amino, amide, halo (e.g., fluoro, chloro, bromo, iodo) or sulfur. When a substituted group contains more than one substituent, the substituted group can be attached to the same atom or two or more different atoms in the group. Substituents containing a group of atoms can also be optionally substituted.

[0322] When used as a property of a container or a part of a build chamber, “optically transparent” refers to having high optical transmissivity with respect to the wavelength of the light used, and “optically flat” refers to being free of distortion (e.g., the wavefront of the light wave entering a part of the container or build chamber remains mostly unaffected).

[0323] As used herein, the singular forms “a”, “an” and “the” include the plural unless the context clearly indicates otherwise. Thus, for example, a reference to a luminescent material includes a reference to one or more such materials.

[0324] The applicant specifically incorporates the entire contents of all patents, patent applications, publications, and other documents cited or referred to in this disclosure. Further, when a quantity, concentration, or other value or parameter is shown as a range, a list of preferred ranges, or preferred upper and lower limits, this is to be understood as specifically disclosing the range, as well as all ranges formed from any pair of an upper limit or preferred value of a range, and a lower limit or preferred value of a range, regardless of whether the upper and lower limits of each range are separately disclosed. When a numerical range is recited herein, unless otherwise specified, the range is intended to include its endpoints and all integers and fractions within the range. When defining a range, it is not intended that the scope of the invention be limited to the specific values recited.

[0325] Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The specification and examples are considered to be exemplary only, and the true scope and spirit of the invention are indicated by the following claims and their equivalents.

Claims

1. A method for forming an object within the volume of a photocurable composition, (a) A step of preparing the volume containing the photocurable composition, wherein the photocurable composition contains a photocurable resin component and a photoswitchable photoinitiator containing a P-type photochromic molecule, (b) A step of simultaneously or sequentially irradiating one or more selected locations within the volume of the photocurable composition with light having a first wavelength and light having a second wavelength, wherein the light having the first wavelength and light having the second wavelength activate the photoswitchable photoinitiator at the one or more selected locations, thereby inducing a crosslinking or polymerization reaction in the photocurable composition at the intersection of the first and second wavelengths at the one or more selected locations within the volume, thereby forming the object at least partially, and (c) A method comprising optionally repeating step (b) of irradiating the photocurable composition until the object is partially or completely formed in one or more selected locations in the volume that are the same as or different from the previously selected locations.

2. A method for forming an object within the volume of a photocurable composition, (a) A step of preparing the volume containing the photocurable composition, wherein the photocurable composition contains a photocurable resin component and a photoswitchable photoinitiator containing a P-type photochromic molecule, (b) A step of projecting an optical image generated by a second excitation light onto a selected location within the volume along a projection axis, wherein the optical image is oriented perpendicular to the projection axis. (c) A step of generating a light sheet containing a first excitation light, directing the light sheet through the volume along the light sheet illumination axis, such that the optical image and the light sheet intersect at the selected location on a common plane, wherein the light sheet overlaps the projected optical image at the selected location within the volume, and (d) A method comprising the step of optionally repeating steps (b) and (c) one or more times to partially or completely form the object, wherein in the repeated set of steps (b) and (c), the selected location is the same as or different from a previously selected location, and the optical image is the same as or different from a previous optical image.

3. The method according to claim 1, wherein the photocurable composition comprises a photocurable resin component and a P-type photochromic molecule, the molecule comprising one or more substituents, at least one of which comprises a carbonyl group.

4. The method according to claim 2, wherein the photocurable composition comprises a photocurable resin component and a P-type photochromic molecule, the molecule comprising one or more substituents, at least one of which comprises a carbonyl group.

5. The method according to any one of claims 1 to 4, wherein the P-type photochromic molecule is activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and a crosslinking or polymerization reaction is induced in the photocurable composition at the intersection of the first and second wavelengths, and the first wavelength is shorter than the second wavelength.

6. The method according to any one of claims 1 to 4, wherein the first wavelength is in the range of about 300 to about 550 nm, and the second wavelength is in the range of about 450 to about 1000 nm.

7. The method according to any one of claims 1 to 4, wherein the first wavelength is in the range of about 350 to about 460 nm, and the second wavelength is in the range of about 450 to about 700 nm.

8. The method according to any one of claims 1 to 4, wherein the first wavelength is in the range of about 350 to about 410 nm, and the second wavelength is in the range of about 450 to about 850 nm.

9. The method according to any one of claims 1 to 4, wherein the first wavelength is approximately 405 nm ± 10 nm, and the second wavelength is in the range of approximately 450 to approximately 700 nm.

10. The method according to any one of claims 1 to 4, wherein the first wavelength is approximately 375 nm ± 10 nm, and the second wavelength is in the range of approximately 450 to approximately 850 nm.

11. The method according to any one of claims 1 to 4, wherein the first wavelength is approximately 405 nm ± 10 nm, and the second wavelength is in the range of approximately 450 to approximately 850 nm.

12. The method according to any one of claims 1 to 4, wherein the amount of time during which one or more selected locations within the volume are simultaneously or sequentially exposed to the first wavelength light and the second wavelength light to induce curing of the photocurable composition at the one or more selected locations is insufficient to cause curing of the photocurable composition when only one of the first and second wavelengths is present.

13. The method according to any one of claims 1 to 4, wherein the light of the first wavelength and the light of the second wavelength are directed separately into the volume.

14. The method according to claim 13, wherein the light of the first wavelength includes a light sheet.

15. The method according to claim 13, wherein the light of the second wavelength includes an optical image.

16. The method according to claim 14, wherein the light of the second wavelength includes an optical image.

17. The method according to claim 16, wherein the light sheet is directed through the volume in a first direction, and the optical image is projected into the volume in a second direction perpendicular to the first direction, so that the light sheet and the optical image intersect at one or more selected locations on a common plane.

18. The method according to any one of claims 1 to 4, wherein the object, at least partially formed in the photocurable composition, remains in a fixed position in the uncured photocurable composition during formation, or is minimally displaced.

19. The method according to claim 16, wherein the optical image includes two-dimensional cross-sectional slices of an object to be printed, and the optical images of repeated steps include continuous two-dimensional cross-sectional slices of the object.

20. The method according to any one of claims 1 to 4, wherein the P-type photochromic molecule comprises a P-type photochromic diarylethene molecule.

21. The method according to any one of claims 1 to 4, wherein the P-type photochromic molecule comprises a P-type photochromic diarylcycloalkene molecule.

22. The method according to claim 3 or 4, wherein the at least one substituent comprising a carbonyl group comprises a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted diarylketone group, a substituted or unsubstituted alpha-diketone, or a polycyclic group comprising at least two fused rings of atoms, wherein at least one of the fused rings comprises one or more substituents, and at least one of the substituents comprises a double bond oxygen bonded to a carbon atom ring member included in one of the fused rings.

23. The method according to claim 3 or 4, wherein the at least one substituent comprising a carbonyl group is a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted diarylketone group, a substituted or unsubstituted alpha-diketone, or a polycyclic group comprising at least two fused rings of atoms, wherein at least one of the fused rings comprises one or more substituents, and at least one of the substituents comprises a double bond oxygen bonded to a carbon atom ring member included in one of the fused rings.

24. The photoswitchable photoinitiator is Formula (VI), formula (XIX), formula (XXI), or derivatives thereof: 【Chemistry 1】 【Chemistry 2】 【Transformation 3】 The method according to claim 1 or 2, comprising a P-type photochromic molecule represented by [formula].

25. A photoswitchable photoinitiator comprising a P-type photochromic molecule, wherein the molecule comprises one or more substituents, at least one substituent comprising a substituted or unsubstituted diarylketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group comprising at least two fused rings of atoms, at least one of the fused rings of atoms comprising one or more substituents, at least one of the substituents comprising a double bond oxygen bonded to a carbon atom ring member included in one of the fused rings, the P-type photochromic molecule being activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), inducing a crosslinking or polymerization reaction in a photocurable composition at the intersection of the first and second wavelengths, the first wavelength being shorter than the second wavelength, the photoswitchable photoinitiator.

26. A photoswitchable photoinitiator comprising a p-type photochromic molecule containing a p-type diarylethene molecule, wherein the molecule comprises one or more substituents, at least one of which substituents is a substituted or unsubstituted diarylketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group comprising at least two fused rings of atoms, at least one of which of which fused rings comprises one or more substituents, at least one of which substituents comprises a double bond oxygen bonded to a carbon atom ring member included in one of the fused rings, the p-type photochromic molecule is activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2), and at the intersection of the first and second wavelengths, a crosslinking or polymerization reaction is induced in the photocurable composition, wherein the first wavelength is shorter than the second wavelength.

27. A photoswitchable photoinitiator comprising a diarylcycloalkene molecule represented by general formula (I), 【Chemistry 4】 (In the formula, A represents a substituted or unsubstituted cycloalkene ring structure. X is given by the following equation (X ａ ), (X ｂ ), (X ｃ ) or (X ｄ Represents a heteroaryl group represented by: 【Transformation 5】 (In the formula, E is a member of the ring, consisting of an oxygen atom (O), a sulfur atom (S), and a sulfur dioxide group (SO) ２ ), selenium atom, or R ６ Nitrogen atom having substituents (NR ６ ) represents, Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R ７ a sulfur atom having a substituent (SR ７ ), R ８ an oxygen atom having a substituent (OR ８ ), or a cyano (CN) group, and G is a member of the aforementioned ring, and R ９ Carbon atoms having substituents (CR ９ ) or represents a nitrogen atom (N), L is a member of the ring, and R １ Carbon atoms having substituents (CR １ ) or represents a nitrogen atom (N), R １ and R ６ ~R ９ is a substituent, identical or different, independently of, for example, hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, substituted or unsubstituted heteroalkyl groups, substituted or unsubstituted heteroaryl groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted ester groups, substituted or unsubstituted carbonate groups, substituted or unsubstituted ketone groups, substituted or unsubstituted aldehyde groups, substituted or unsubstituted imine groups, substituted or unsubstituted carboxyl groups, substituted or unsubstituted amide groups, substituted or unsubstituted urethane groups, substituted or unsubstituted urea groups, substituted or unsubstituted tetrazine groups, substituted or unsubstituted amino groups, iodine, bromo, chloro, fluoro, cyano (-CN), nitro (-NO) ２ ), represents a hydroxyl group (-OH), a thiol group (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group), or 【Transformation 6】 (In the formula, E is a member of the ring, consisting of an oxygen atom (O), a sulfur atom (S), and a sulfur dioxide group (SO) ２ ), selenium atom, or R ６ Nitrogen atom having substituents (NR ６ ) represents, Z is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R ７ A sulfur atom having a substituent (SR ７ ), R ８ Oxygen atom having substituents (OR ８ ), or represents a cyano (CN) group, G is a member of the ring and is a carbon atom having an R9 substituent (CR ９ ) or represents a nitrogen atom (N), L is a member of the ring, and R １ Carbon atoms having substituents (CR １ ) or represents a nitrogen atom (N), R １ and R ６ ~R ９ is a substituent, identical or different, independently of, for example, hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, substituted or unsubstituted heteroalkyl groups, substituted or unsubstituted heteroaryl groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted ester groups, substituted or unsubstituted carbonate groups, substituted or unsubstituted ketone groups, substituted or unsubstituted aldehyde groups, substituted or unsubstituted imine groups, substituted or unsubstituted carboxyl groups, substituted or unsubstituted amide groups, substituted or unsubstituted urethane groups, substituted or unsubstituted urea groups, substituted or unsubstituted tetrazine groups, substituted or unsubstituted amino groups, iodine, bromo, chloro, fluoro, cyano (-CN), nitro (-NO) ２ ), represents a hydroxyl group (-OH), a thiol group (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group), or 【Transformation 7】 (In the formula, E is a member of the ring, consisting of an oxygen atom (O), a sulfur atom (S), and a sulfur dioxide group (SO) ２ ), selenium atom, or R ６ Nitrogen atom having substituents (NR ６ ) represents, Z is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R ７ A sulfur atom having a substituent (SR ７ ), R ８ Oxygen atom having substituents (OR ８ ), or represents a cyano (CN) group, R ２ R ８ is a substituent, identical or different, independently of, for example, hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, substituted or unsubstituted heteroalkyl groups, substituted or unsubstituted heteroaryl groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted ester groups, substituted or unsubstituted carbonate groups, substituted or unsubstituted ketone groups, substituted or unsubstituted aldehyde groups, substituted or unsubstituted imine groups, substituted or unsubstituted carboxyl groups, substituted or unsubstituted amide groups, substituted or unsubstituted urethane groups, substituted or unsubstituted urea groups, substituted or unsubstituted tetrazine groups, substituted or unsubstituted amino groups, iodine, bromo, chloro, fluoro, cyano (-CN), nitro (-NO) ２ ), represents a hydroxyl group (-OH), a thiol group (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group), or 【Transformation 8】 (In the formula, E is a member of the ring, consisting of an oxygen atom (O), a sulfur atom (S), and a sulfur dioxide group (SO) ２ ), selenium atom, or R ６ Nitrogen atom having substituents (NR ６ ) represents, Z is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R ７ A sulfur atom having a substituent (SR ７ ), R ８ Oxygen atom having substituents (OR ８ ), or represents a cyano (CN) group, R ２ ~R ８ is a substituent, identical or different, independently of, for example, hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, substituted or unsubstituted heteroalkyl groups, substituted or unsubstituted heteroaryl groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted ester groups, substituted or unsubstituted carbonate groups, substituted or unsubstituted ketone groups, substituted or unsubstituted aldehyde groups, substituted or unsubstituted imine groups, substituted or unsubstituted carboxyl groups, substituted or unsubstituted amide groups, substituted or unsubstituted urethane groups, substituted or unsubstituted urea groups, substituted or unsubstituted tetrazine groups, substituted or unsubstituted amino groups, iodine, bromo, chloro, fluoro, cyano (-CN), nitro (-NO) ２ ), a hydroxyl group (-OH), a thiol group (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group); Y is given by the formula (Y ａ ), (Y ｂ ), (Y ｃ ) or (Y ｄ Represents a heteroaryl group represented by: 【Chemistry 9】 (In the formula, E' is a member of the ring, consisting of an oxygen atom (O), a sulfur atom (S), and a sulfur dioxide group (SO) ２ ), selenium atom, or R １５ Nitrogen atom having substituents (NR １５ ) represents, Z' is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R １６ A sulfur atom having a substituent (SR １６ ), R １７ Oxygen atom having substituents (OR １７ ), or represents a cyano (CN) group, G' is a member of the aforementioned ring, R １８ Carbon atoms having substituents (CR １８ ) or represents a nitrogen atom (N), L' is a member of the aforementioned ring, R １０ Carbon atoms having substituents (CR １０ ) or represents a nitrogen atom (N), R １０ and R １５ ~R １８ is a substituent, identical or different, independently of, for example, hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, substituted or unsubstituted heteroalkyl groups, substituted or unsubstituted heteroaryl groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted ester groups, substituted or unsubstituted carbonate groups, substituted or unsubstituted ketone groups, substituted or unsubstituted aldehyde groups, substituted or unsubstituted imine groups, substituted or unsubstituted carboxyl groups, substituted or unsubstituted amide groups, substituted or unsubstituted urethane groups, substituted or unsubstituted urea groups, substituted or unsubstituted tetrazine groups, substituted or unsubstituted amino groups, iodine, bromo, chloro, fluoro, cyano (-CN), nitro (-NO) ２ ), represents a hydroxyl group (-OH), a thiol group (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group. 【Chemistry 10】 (In the formula, E' is a member of the ring, consisting of an oxygen atom (O), a sulfur atom (S), and a sulfur dioxide group (SO) ２ ), selenium atom, or R １５ Nitrogen atom having substituents (NR １５ ) represents, Z' is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R １６ A sulfur atom having a substituent (SR １６ ), R １７ Oxygen atom having substituents (OR １７ ), or represents a cyano (CN) group, G' is a member of the aforementioned ring, R １８ Carbon atoms having substituents (CR １８ ) or represents a nitrogen atom (N), L' is a member of the aforementioned ring, R １０ Carbon atoms having substituents (CR １０ ) or represents a nitrogen atom (N), R １０ and R １５ ~R １８ is a substituent, identical or different, independently of, for example, hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, substituted or unsubstituted heteroalkyl groups, substituted or unsubstituted heteroaryl groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted ester groups, substituted or unsubstituted carbonate groups, substituted or unsubstituted ketone groups, substituted or unsubstituted aldehyde groups, substituted or unsubstituted imine groups, substituted or unsubstituted carboxyl groups, substituted or unsubstituted amide groups, substituted or unsubstituted urethane groups, substituted or unsubstituted urea groups, substituted or unsubstituted tetrazine groups, substituted or unsubstituted amino groups, iodine, bromo, chloro, fluoro, cyano (-CN), nitro (-NO) ２ ), represents a hydroxyl group (-OH), a thiol group (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group. 【Chemistry 11】 (wherein, E' is a member of the ring, an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO ２ ), a selenium atom, or R １５ -substituted nitrogen atom (NR １５ ), and Z' is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R １６ A sulfur atom having a substituent (SR １６ ), R １７ Oxygen atom having substituents (OR １７ ), or represents a cyano (CN) group, R １１ to R １７ are substituents, which may be the same or different and are independently, for example, hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkenyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkylaryl group, a substituted or unsubstituted heteroalkyl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted ester group, a substituted or unsubstituted carbonate group, a substituted or unsubstituted ketone group, a substituted or unsubstituted aldehyde group, a substituted or unsubstituted imine group, a substituted or unsubstituted carboxyl group, a substituted or unsubstituted amide group, a substituted or unsubstituted urethane group, a substituted or unsubstituted urea group, a substituted or unsubstituted tetrazine group, a substituted or unsubstituted amino group, iodine, bromo, chloro, fluoro, a cyano group (—CN), a nitro group (—NO ２ ), a hydroxyl group (—OH), a thiol (—SH), a thioether group (R—X—R′ (where R or R′ may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group.) or 【Chemistry 12】 (In the formula, E' is a member of the ring, consisting of an oxygen atom (O), a sulfur atom (S), and a sulfur dioxide group (SO) ２ ), selenium atom, or R １５ Nitrogen atom having substituents (NR １５ ) represents, Z' is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, R １６ A sulfur atom having a substituent (SR １６ ), R １７ Oxygen atom having substituents (OR １７ ), or represents a cyano (CN) group, R １１ ~R １７ is a substituent, identical or different, independently of, for example, hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, substituted or unsubstituted heteroalkyl groups, substituted or unsubstituted heteroaryl groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted ester groups, substituted or unsubstituted carbonate groups, substituted or unsubstituted ketone groups, substituted or unsubstituted aldehyde groups, substituted or unsubstituted imine groups, substituted or unsubstituted carboxyl groups, substituted or unsubstituted amide groups, substituted or unsubstituted urethane groups, substituted or unsubstituted urea groups, substituted or unsubstituted tetrazine groups, substituted or unsubstituted amino groups, iodine, bromo, chloro, fluoro, cyano (-CN), nitro (-NO) ２ ), a hydroxyl group (-OH), a thiol group (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group); At least one of X and Y includes at least one R substituent which includes a substituted or unsubstituted diarylketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group which includes at least two fused rings of an atom, and at least one of the fused rings of the atom includes one or more substituents which includes at least one double bond oxygen bonded to a carbon atom ring member included in one of the fused rings, A photoswitchable photoinitiator in which a P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2), and at the intersection of the first and second wavelengths, a crosslinking or polymerization reaction is induced in the photocurable composition, wherein the first wavelength is shorter than the second wavelength.

28. The photoswitchable photoinitiator according to claim 27, wherein at least one R substituent on X and at least one R substituent on Y comprises a substituted or unsubstituted diarylketone group, a substituted or unsubstituted alpha-diketone group, or a polycyclic group comprising at least two fused rings of atoms, at least one of the fused rings of atoms comprises one or more substituents, at least one of the substituents comprises a double bond oxygen bonded to a carbon atom ring member included in one of the fused rings, and the R substituent on X and the R substituent on Y are independently the same or different.

29. A is the formula (A ａ ), (A ｂ ), (A ｃ A photoswitchable photoinitiator according to claim 27 or 28, comprising a structure represented by (A d): 【Chemistry 13】 (In the formula, X １ , X ２ , X ３ , X ４ , X ５ and X ６ These are the same or different, and independently hydrogen (H), fluorine (F), chlorine (Cl), or substituted or unsubstituted alkyl or heteroalkyl groups. 【Chemistry 14】 (In the formula, J is a member of the ring, and is oxygen O or R) ２５ Nitrogen having substituents (NR ２５ ) represents R ２５ (where represents hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl.) 【Chemistry 15】 (In the formula, E'' is a member of the ring, consisting of an oxygen atom (O), a sulfur atom (S), and a sulfur dioxide group (SO) ２ ), selenium atom, or R ２３ Nitrogen atom having substituents (NR ２３ ) represents, G'' is a member of the ring, R ２４ Carbon atoms having substituents (CR ２４ ) or represents a nitrogen atom (N), R ２２ ~R ２４ is a substituent, identical or different, independently of, for example, hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aryl groups, substituted or unsubstituted aralkyl groups, substituted or unsubstituted alkylaryl groups, substituted or unsubstituted heteroalkyl groups, substituted or unsubstituted heteroaryl groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted ester groups, substituted or unsubstituted carbonate groups, substituted or unsubstituted ketone groups, substituted or unsubstituted aldehyde groups, substituted or unsubstituted imine groups, substituted or unsubstituted carboxyl groups, substituted or unsubstituted amide groups, substituted or unsubstituted urethane groups, substituted or unsubstituted urea groups, substituted or unsubstituted tetrazine groups, substituted or unsubstituted amino groups, iodine, bromo, chloro, fluoro, cyano (-CN), nitro (-NO) ２ ), a hydroxyl group (-OH), a thiol group (-SH), a thioether group (R-X-R' (wherein R or R' may independently represent an aryl or alkyl group)), or a substituted or unsubstituted alcohol group.) or 【Chemistry 16】 (In the formula, X １ , X ２ , X ３ , X ４ , X ５ , X ６ , X ７ and X ８ These are identical or distinct, and independently represent hydrogen (H), fluorine (F), chlorine (Cl), or substituted or unsubstituted alkyl or heteroalkyl groups.

30. The photoswitchable photoinitiator according to claim 27 or 28, wherein the R groups on any two adjacent ring members X and / or Y may contain atoms to complete a ring structure linking the two adjacent groups together.

31. The photoswitchable photoinitiator according to claim 27 or 28, wherein the ring structure is substituted.

32. The photoswitchable photoinitiator according to claim 27 or 28, wherein the ring structure is part of a polycyclic substituted or unsubstituted ring structure.

33. The photoswitchable photoinitiator according to claim 27 or 28, wherein the ring structure or polycyclic structure in which the ring structure is a part comprises one or more carbon atoms and one or more heteroatoms.

34. The aforementioned polycyclic group is of the general formula (PG-A), general formula (PG-B), general formula (PG-C), general formula (PG-D), general formula (PG-E), general formula (PG-F), general formula (PG-G), general formula (PG-H), general formula (PG-I), general formula (PG-J), general formula (PG-K), general formula (PG-L), general formula (PG-M), or derivatives thereof: 【Chemistry 17】 [Chemistry 18] 【Chemistry 19】 【Chemistry 20】 【Chemistry 21】 【Chemistry 22】 【Chemistry 23】 【Chemistry 24】 【Chemistry 25】 【Chemistry 26】 【Chemistry 27】 【Chemistry 28】 【Chemistry 29】 (In the formula, the aryl group may be substituted or unsubstituted, and may optionally contain one or more heteroatoms.) A photoswitchable photoinitiator according to any one of claims 25 to 28, as represented by [the above].

35. In general formula (I), A is in formula (A ｄ ) is represented by X １ ~X ６ is hydrogen or fluorine, and X is (X ａ ) is represented by R １ The group is iodine, bromo, chloro, fluoro, or alkyl, E is sulfur, Z is an alkyl or phenyl group, and G is CR ９ And Y is ( Y ａ Represented by ), where E' is sulfur, Z' is an alkyl or phenyl group, and G' is CR １５ And R １０ The photoswitchable photoinitiator according to claim 27 or 28, wherein the photoinitiator represents a polycyclic group comprising at least two fused rings of an atom, at least one of the fused rings of the atom comprising one or more substituents, and at least one of the substituents comprising a double bond oxygen bonded to a carbon atom ring member included in one of the fused rings.

36. In general formula (I), A is in formula (A ｄ ) is represented by X １ ~X ６ is hydrogen or fluorine, and X is (X ｂ ) is represented by R １ The group is iodine, bromo, chloro, fluoro, or alkyl, E is sulfur, Z is an alkyl or phenyl group, and G is CR ９ And Y is ( Y ａ Represented by ), where E' is sulfur, Z' is an alkyl or phenyl group, and G' is CR １５ And R １０ The photoswitchable photoinitiator according to claim 27 or 28, wherein the photoinitiator represents a polycyclic group comprising at least two fused rings of an atom, at least one of the fused rings of the atom comprising one or more substituents, and at least one of the substituents comprising a double bond oxygen bonded to a carbon atom ring member included in one of the fused rings.

37. The aforementioned photoswitchable photoinitiator is formula (III), formula (IV), formula (V), formula (VI), formula (VII), formula (VIII), formula (IX), formula (X), formula (XI), formula (XII), formula (XIII), formula (XV), formula (XVI), formula (XVII), formula (XVIII), formula (XIX), formula (XX), formula (XXI), formula (XXII), formula (XXIII), formula (XXIV), formula (XXV), formula (XXVII), formula (XXVIII), formula (XXVIIII), formula (XXIX), or formula (XXX): 【Transformation 30】 【Chemistry 31】 【Chemistry 32】 【Transformation 33】 【Transformation 34】 【Chemistry 35】 【Transformation 36】 【Chemistry 37】 【Transformation 38】 【Chemistry 39】 【Chemistry 40】 【Chemistry 41】 【Chemistry 42】 【Chemistry 43】 【Chemistry 44】 【Chemistry 45】 【Chemistry 46】 【Chemistry 47】 【Chemistry 48】 【Chemistry 49】 [Transformation 50] 【Chemistry 51】 【Chemistry 52】 【Chemistry 53】 【Chemistry 54】 【Transformation 55】 【Transformation 56】 A photoswitchable photoinitiator according to claim 27 or 28, as represented by the above.

38. A photocurable composition comprising a photocurable resin component and a photoswitchable photoinitiator, wherein the photoswitchable photoinitiator is activatable by exposure to light having a first wavelength and light having a second wavelength, and at the intersection of the two wavelengths of light, it induces a crosslinking or polymerization reaction in the photocurable resin component, wherein the first and second wavelengths are different, and the photoswitchable photoinitiator comprises the photoswitchable photoinitiator described in any one of claims 25 to 28.

39. The photocurable composition according to claim 38, further comprising a co-initiator.

40. The photocurable composition according to claim 38, wherein the photocurable composition exhibits non-Newtonian rheological behavior.

41. A method for forming an object within the volume of a photocurable composition, (a) A step of preparing the volume containing the photocurable composition, wherein the photocurable composition contains a photocurable resin component and a photoswitchable photoinitiator according to any one of claims 25 to 28, (b) A step of projecting an optical image generated by a second excitation light onto a selected location within the volume along a projection axis, wherein the optical image is oriented perpendicular to the projection axis. (c) A step of generating a light sheet containing a first excitation light, directing the light sheet through the volume along the light sheet illumination axis, such that the optical image and the light sheet intersect at the selected location on a common plane, wherein the light sheet overlaps the projected optical image at the selected location within the volume, and (d) A method comprising the step of optionally repeating steps (b) and (c) one or more times to partially or completely form the object, wherein in the repeated set of steps (b) and (c), the selected location is the same as or different from a previously selected location, and the optical image is the same as or different from a previous optical image.

42. The method according to claim 41, wherein the optical image comprises two-dimensional cross-sectional slices of an object to be printed, and the optical image of repeated steps comprises continuous two-dimensional cross-sectional slices of the object, and the optical image is oriented perpendicular to the direction in which it is irradiated or projected into the volume.

43. The method according to claim 1, wherein the photocurable composition further comprises a resin component that is curable by a heat-driven reaction, and the method further comprises the steps of separating the object from the volume in which it is formed, and heating the separated object to further cure the object.

44. The method according to claim 43, wherein the separated object is washed before the heating step.

45. The method according to claim 1, wherein the photocurable composition further comprises a second photoactivating photoinitiator, and the method further comprises the steps of separating the object from the volume in which it is formed, and irradiating the separated object with light at a third wavelength to further cure the object, wherein the third wavelength is shorter than the first and second wavelengths.

46. The method according to claim 45, wherein the separated object is cleaned before being irradiated with light of the third wavelength.

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