Method of forming an object in a volume of a photocurable composition

Abstract

The present invention includes a method for forming an object in a volume including a photocurable composition described herein, the photocurable composition including a photocurable resin component and a photoconvertible photoinitiator, the photoconvertible photoinitiator comprising a P-type photochromic molecule. The present invention also includes a photo-convertible photoinitiator, the photo-convertible photoinitiator comprising a P-type photochromic molecule, preferably comprising a P-type diarylethene molecule; and photocurable compositions and methods including such photoconvertible photoinitiators.

Description

[0001] Claiming priority

[0002] This application claims priority to 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 which is hereby incorporated by reference in its entirety for all purposes. Technical Field

[0003] The present invention relates to the technical field of three-dimensional printing and related compositions, materials, methods, and products thereof. Summary of the invention

[0004] The present invention includes methods for forming an object in a volume of a photohardenable composition comprising a photohardenable resin component and a photoswitchable photoinitiator comprising a P-type photochromic molecule. The present invention also includes a photoswitchable photoinitiator comprising a P-type diarylethene molecule represented by the formula described herein; and photohardenable compositions and methods comprising any such photoswitchable photoinitiator.

[0005] According to one aspect of the present invention, there is provided a method of forming an object in a volume of a photohardenable composition, the method comprising:

[0006] (a) providing a volume including a photohardenable composition, the photohardenable composition comprising a photohardenable resin component and a photoconvertible photoinitiator, the photoconvertible photoinitiator comprising a P-type photochromic molecule,

[0007] (b) irradiating one or more selected locations within the volume of the photohardenable composition with light having a first wavelength and light having a second wavelength simultaneously or sequentially, wherein the light having the first wavelength and the light having the second wavelength activate a photoconvertible photoinitiator at the one or more selected locations to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength at the one or more selected locations within the volume, thereby at least partially forming the object; and

[0008] (c) optionally repeating step (b) irradiating the photohardenable composition at one or more selected locations in the volume that are the same as or different from one or more previously selected locations until the object is partially or completely formed.

[0009] The method preferably also includes separating the partially or fully formed object from the photohardenable composition.

[0010] The preferred photoconvertible photoinitiator included in the method of the present invention comprises a substituted or unsubstituted P-type photochromic molecule, which preferably comprises a P-type diarylethene molecule, wherein the P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

[0011] A more preferred photoconvertible photoinitiator included in the method of the present invention comprises a P-type photochromic molecule, which preferably comprises a P-type diarylethene molecule and includes one or more substituents, at least one substituent comprising a carbonyl group, wherein the P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

[0012] Examples of substituent groups comprising 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 α-diketones (such as, but not limited to, substituted or unsubstituted benzil groups, etc.), polycyclic groups comprising at least two fused atom rings, wherein at least one fused atom ring comprises one or more substituents, wherein at least one substituent comprises a double bonded oxygen connected to a carbon atom ring member included in one of the fused rings (such as, but not limited to, acenaphthylene-1,2-dione groups, polycyclic groups comprising at least two fused atom rings comprising thiochroman-4-one groups, 9-fluorenone groups, anthraquinone groups, benzanthrone groups, 9,10-phenanthrenequinone groups, etc., and derivatives thereof). Substituents on substituted functional groups comprising a carbonyl group may also optionally include one or more additional substituents.

[0013] Preferred P-type diarylethene molecules include P-type diarylcycloolefin molecules. Such molecules may desirably include one or more substituents. More preferably, such molecules include one or more substituents, at least one of which contains a carbonyl group.

[0014] Examples of more preferred photoconvertible photoinitiators for inclusion in the photohardenable compositions and methods described herein include, but are not limited to, P-type photochromic molecules comprising one or more substituents, at least one of which comprises a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atomic rings, at least one of which comprises one or more substituents, at least one of which comprises a double-bonded oxygen attached to a carbon atom ring member included in one of the fused rings.

[0015] More preferred photohardenable compositions for inclusion in the methods described herein include a photoswitchable photoinitiator according to another aspect of the invention.

[0016] According to another aspect of the present invention, a photoconvertible photoinitiator is provided, which comprises a P-type photochromic molecule, which comprises one or more substituents, wherein at least one substituent comprises a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atomic rings, wherein at least one of the fused atomic rings comprises one or more substituents, wherein at least one substituent comprises a double-bonded oxygen connected to a carbon atom ring member included in one of the fused rings, wherein the P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in a photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

[0017] The photo-switchable photoinitiator according to the present invention preferably comprises a P-type photochromic molecule.

[0018] Non-limiting examples of preferred photo-switchable photoinitiators include photo-switchable photoinitiators comprising a diarylcycloolefin molecule represented by the general formula (I):

[0019]

[0020] in:

[0021] A represents a substituted or unsubstituted cycloolefin ring structure,

[0022] X represents the following formula (X a )、(X b )、(X c ), or (X d ) represented by a heteroaryl group:

[0023]

[0024] in:

[0025] E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide (sulfur anhydride) group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ),

[0026] Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8 ), or a cyano (CN) group,

[0027] G is a ring member and represents a ring having R 9 The carbon atom of the substituent group (CR 9 ) or a nitrogen atom (N);

[0028] L is a ring member and represents a ring having R 1 The carbon atom of the substituent group (CR 1 ) or a nitrogen atom (N), and

[0029] R 1 , R 6 -R 9 and are substituents, are the same or different, and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0030]

[0031] in:

[0032] E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ),

[0033] Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8 ), or a cyano (CN) group,

[0034] G is a ring member and represents a carbon atom with an R substituent group (CR 9 ) or a nitrogen atom (N);

[0035] L is a ring member and represents a ring having R 1 The carbon atom of the substituent group (CR 1 ) or a nitrogen atom (N), and

[0036] R 1 and R 6 -R 9 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0037]

[0038] in:

[0039] E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ),

[0040] Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8 ), or a cyano (CN) group, and

[0041] R 2 -R 8 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0042]

[0043] E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ),

[0044] Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8), or a cyano (CN) group, and

[0045] R 2 -R 8 are substituents, are the same or different, and independently represent, 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 a substituted 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group;

[0046] Y represents the formula (Y a )、(Y b ), (Yc) or (Y d ) represented by a heteroaryl group:

[0047]

[0048] in:

[0049] E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ),

[0050] Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group,

[0051] G' is a ring member and represents a ring having R 18 The carbon atom of the substituent group (CR 18 ) or a nitrogen atom (N);

[0052] L' is a ring member and represents a ring having R 10 The carbon atom of the substituent group (CR 10 ) or a nitrogen atom (N), and

[0053] R 10 and R 15 -R 18 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0054]

[0055] in:

[0056] E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ),

[0057] Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group,

[0058] G' is a ring member and represents a ring having R 18 The carbon atom of the substituent group (CR 18 ) or a nitrogen atom (N);

[0059] L' is a ring member and represents a ring having R 10 The carbon atom of the substituent group (CR 10 ) or a nitrogen atom (N), and

[0060] and

[0061] R 10 and R 15 -R 18 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0062]

[0063] in:

[0064] E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ),

[0065] Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group, and

[0066] R 11 -R 17The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0067]

[0068] in:

[0069] E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ),

[0070] Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group, and

[0071] R 11 -R 17are substituents, are the same or different, and independently represent, 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 a substituted 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group;

[0072] wherein at least one of X and Y includes at least one R substituent comprising a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atom rings, wherein at least one of the fused atom rings comprises one or more substituents, wherein at least one substituent comprises a double bonded oxygen attached to a carbon atom ring member included in one of the fused rings; and

[0073] The P-type photochromic molecules are activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

[0074] It may be desirable for at least one R substituent to be present in X by (X a ) or (X b ) indicates that it is located at position R 1 or R 9 At one place, in X, by the formula (X c ) or (X d ) indicates that it is located at position R 2 -R 5 One place, in Y by (Y a ) or (Y b ) indicates that it is located at position R 10 or R 18 One of the places, or in Y by (Y c ) or (Y d ) indicates that it is located at position R 11 -R14 At one of the above, the R substituent comprises a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atom rings, wherein at least one of the fused atom rings comprises one or more substituents, wherein at least one of the substituents comprises a double bonded oxygen attached to a carbon atom ring member included in one of the fused rings.

[0075] Preferred examples of A include those represented by the following formula (A a )、(A b )、(A c ) and (A d ) represents the structure.

[0076] Optionally, the R groups on any two adjacent ring members of X and / or Y may include atoms for completing the ring structure that connects two adjacent substituent groups together. Such ring structures may be substituted or unsubstituted, and may optionally be part of a polycyclic substituted or unsubstituted ring structure. In addition to the carbon atoms in the ring structure, such ring structures, or (if applicable) the polycyclic structures of which such ring structures are a part, may optionally include one or more heteroatoms.

[0077] More preferably, at least one R substituent on X and / or Y comprises a substituted or unsubstituted benzophenone group, a substituted or unsubstituted benzil group, a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted naphthylenedione-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-indandione group, a substituted or unsubstituted chromone group, a substituted or unsubstituted 1,4-naphthoquinone group, and the like.

[0078] It may be desirable that X and Y each include at least one R substituent comprising a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atom rings, wherein at least one of the fused atom rings comprises one or more substituents, wherein at least one substituent comprises a double bonded oxygen connected to a carbon atom ring member included in one of the fused rings. In this case, such substituents on X and Y may be the same or different.

[0079] Optionally, X and Y may be symmetrical in that one or more R substituents on X and one or more R substituents on Y match each other.

[0080] Optionally, X and Y are asymmetric, wherein each of X and Y includes one or more different substituents on each of X and Y.

[0081] It may be particularly desirable that at least one R substituent on X and / or at least one R substituent on Y comprises a substituted or unsubstituted benzophenone group, a substituted or unsubstituted benzil group, a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted naphthylenedione-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-indandione group, a substituted or unsubstituted chromone group, a substituted or unsubstituted 1,4-naphthoquinone group, and the like.

[0082] According to another aspect of the present invention, a photohardenable composition is provided, which comprises a photohardenable resin component and a photoconvertible photoinitiator, wherein the photoconvertible photoinitiator comprises a P-type photochromic molecule, preferably a P-type diarylethene molecule, which molecule includes one or more substituents, wherein at least one substituent comprises a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atomic rings, wherein at least one fused atomic ring comprises one or more substituents, wherein at least one substituent comprises a double-bonded oxygen connected to a carbon atom ring member included in one of the fused rings, wherein the P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

[0083] The preferred photohardenable composition comprises a photohardenable resin component and a photoconvertible photoinitiator, the photoconvertible photoinitiator comprising a P-type diarylethene molecule represented by general formula (I) as described herein. The photohardenable composition may also preferably include a sensitizer. It may be desirable that the photohardenable composition exhibits non-Newtonian rheological behavior.

[0084] It is particularly contemplated that the photohardenable composition according to the present invention is used in volumetric 3D printing for forming an object in the volume of the photohardenable composition.

[0085] It should be understood by those skilled in the art to which the present invention relates that any feature described herein with respect to any particular aspect and / or embodiment of the present invention may be combined with one or more of any other features of any other aspect and / or embodiment of the present invention described herein, with appropriate modifications to ensure compatibility of the combination. Such combinations are considered part of the present invention contemplated by the present disclosure.

[0086] The foregoing, as well as other aspects and embodiments described herein and contemplated by the present disclosure, constitute embodiments of the present invention.

[0087] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

[0088] Other embodiments will be apparent to those skilled in the art from consideration of the specification, claims, and practice of the invention disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] In the accompanying drawings,

[0090] Figure 1A , 1B and 1C show photographs of front, rear and side views of a part generally printed according to the procedure set forth in this Example 5; Figure 1D , 1E 1F and 1F show the corresponding front view, back view and side view of the 3D model to be printed.

[0091] Figure 2A , 2B and 2C show photographs of front, rear and side views of a part generally printed according to the procedure set forth in this Example 6; Figure 2D , 2E 2F and 2F show the corresponding front view, back view and side view of the 3D model to be printed.

[0092] Figure 3A , 3B and 3C show photographs of front, rear and side views of a part generally printed according to the procedure set forth in this Example 7; Figure 3D , 3E 3F and 3D show the corresponding front view, back view and side view of the 3D model to be printed.

[0093] The drawings are simplified representations presented for purposes of illustration only; actual structures may differ in several respects including particularly the relative proportions of the depicted articles and aspects thereof.

[0094] For a better understanding of the present invention, together with other advantages and capabilities thereof, reference is made to the following disclosure and appended claims taken in conjunction with the above-described drawings. DETAILED DESCRIPTION

[0095] Various aspects and embodiments of the invention are further described in the following detailed description.

[0096] The present invention includes a method for forming an object in a volume of a photohardenable composition, the photohardenable composition comprising a photohardenable resin component and a photoconvertible photoinitiator, the photoconvertible photoinitiator comprising a P-type photochromic molecule. The present invention also includes a photoconvertible photoinitiator comprising a P-type diarylethene molecule represented by the formula described herein; and a photohardenable composition and method comprising the photoconvertible photoinitiator of the present invention.

[0097] A schematic diagram of the ring closure and photoreversal of a P-type photochromic molecule (A') containing a diarylethene is provided in Formula 1 (Eq1):

[0098]

[0099] When exposed to light of a first wavelength, the P-type photochromic molecule A' undergoes a 6π electrocyclization ring closure reaction to give B' when exposed to light of a first wavelength (usually in the UV range). This reaction can be easily reversed by exposure to light of a longer wavelength (photoreversal). However, compound B' does not readily undergo thermal reversibility to the open ring form (A') (while the example shown in Eq. 1 shows R A1 and R A2 As a substituent, alternatively, R A1 and R A2 Atoms in a ring structure may be included that link the two groups together (not shown).

[0100] For typical 3D printing, P-type photochromic molecules typically exhibit minimal or no thermal reversibility on time scales that are typically less than an hour.

[0101] Although the thermal reversal reaction of dual-color photoinitiators has been reported to be essential for their use in 3D printing, it has been surprisingly found that P-type photochromic molecules are effective and advantageous for use as photo-switchable photoinitiators in 3D printing.

[0102] According to one aspect of the present invention, there is provided a method of forming an object in a volume of a photohardenable composition, the method comprising:

[0103] (a) providing a volume including a photohardenable composition, the photohardenable composition comprising a photohardenable resin component and a photoconvertible photoinitiator, the photoconvertible photoinitiator comprising a substituted or unsubstituted P-type photochromic molecule,

[0104] (b) irradiating one or more selected locations within the volume of the photohardenable composition with light having a first wavelength and light having a second wavelength simultaneously or sequentially, wherein the light having the first wavelength and the light having the second wavelength activate a photoconvertible photoinitiator at the one or more selected locations to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength at the one or more selected locations within the volume, thereby at least partially forming the object; and

[0105] (c) optionally repeating step (b) irradiating the photohardenable composition at one or more selected locations in the volume that are the same as or different from one or more previously selected locations until the object is partially or completely formed.

[0106] A preferred method of forming an object in a volume of a photohardenable composition according to the present invention comprises:

[0107] (a) providing a volume including a photohardenable composition, the photohardenable composition comprising a photohardenable resin component and a photoconvertible photoinitiator, the photoconvertible photoinitiator comprising a P-type photochromic molecule,

[0108] (b) projecting an optical image generated by the second excitation light to a selected position in the volume along a projection axis, wherein the optical image is oriented perpendicular to the projection axis;

[0109] (c) generating a light sheet comprising a first excitation light, and directing the light sheet through the volume along a light sheet illumination axis such that the optical image intersects the light sheet at a selected location within a common plane, and wherein the light sheet overlaps the projected optical image in the volume at the selected location; and

[0110] (d) optionally repeating steps (b) and (c) one or more times to partially or completely form the object, wherein for a set of repeated steps (b) and (c), the selected location is the same or different from a previous selected location and the optical image is the same or different from a previous optical image.

[0111] Preferably, the intersection of the light sheet and the optical image in a common plane is coplanar or substantially coplanar.

[0112] The method according to the invention preferably further comprises separating the partially or fully formed object from the photohardenable composition.

[0113] The preferred photoconvertible photoinitiator included in the method of the present invention comprises a substituted or unsubstituted P-type photochromic molecule, which preferably comprises a P-type diarylethene molecule, wherein the P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

[0114] A more preferred photoconvertible photoinitiator included in the method of the present invention comprises a P-type photochromic molecule, preferably comprising a P-type diarylethene molecule, the molecule comprising one or more substituents, at least one of which comprises a carbonyl group, wherein the P-type photochromic molecule is activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength. Preferably, the at least one substituent comprising a carbonyl group is attached to the P-type diarylethene molecule. The substituent comprising a carbonyl group may also optionally include one or more additional substituents or moieties in addition to the C=O moiety.

[0115] The P-type diarylethene molecule to which the at least one substituent comprising a carbonyl group is attached may preferably comprise a P-type diarylcycloolefin or diarylcycloheteroolefin molecule. Examples of preferred P-type diarylcyclopentene or diarylcycloolefin molecules include, but are not limited to, a P-type dithienylcyclopentene molecule. It may be desirable that in addition to the at least one substituent comprising a carbonyl group, one or both of the two thienyl groups and / or the cyclopentene rings to which the thienyl groups are attached further comprise one or more substituents.

[0116] Examples of substituent groups comprising a carbonyl group include, but are not limited to, substituent groups comprising: substituted or unsubstituted benzoyl groups, substituted or unsubstituted thioxanthone groups, substituted or unsubstituted diaryl ketone groups (such as, but not limited to, substituted or unsubstituted benzophenone groups, etc.), substituted or unsubstituted α-diketones (such as, but not limited to, substituted or unsubstituted benzil groups, etc.), polycyclic groups comprising at least two fused atom rings, wherein at least one fused atom ring comprises one or more substituents, wherein at least one substituent comprises a double bonded oxygen connected to a carbon atom ring member included in one of the fused rings (such as, but not limited to, 1,2-dione groups, polycyclic groups comprising at least two fused atom rings comprising thiochroman-4-one groups, 9-fluorenone groups, anthraquinone groups, benzanthrone groups, 9,10-phenanthrenequinone groups, etc., and derivatives thereof).

[0117] Additional examples of substituent groups comprising a carbonyl group include, but are not limited to, substituted or unsubstituted thioxanthone groups, substituted or unsubstituted diaryl ketone groups (such as, but not limited to, substituted or unsubstituted benzophenone groups, etc.), substituted or unsubstituted α-diketones (such as, but not limited to, substituted or unsubstituted benzil groups, etc.), substituted or unsubstituted α-diketones (such as, but not limited to, substituted or unsubstituted benzil groups, etc.), polycyclic groups comprising at least two fused atom rings, wherein at least one of the fused atom rings comprises one or more substituents, wherein at least one substituent comprises a double bonded oxygen attached to a carbon atom ring member included in one of the fused rings (such as, but not limited to, 1,2-dione groups, polycyclic groups comprising at least two fused atom rings comprising thiochroman-4-one groups, 9-fluorenone groups, anthraquinone groups, benzanthrone groups, 9,10-phenanthrenequinone groups, etc., and derivatives thereof).

[0118] Examples of photoconvertible photoinitiators preferably included in the method of the present invention include the photoconvertible photoinitiators described below according to another aspect of the present invention, including but not limited to photoconvertible photoinitiators represented by any formula (I), including but not limited to those represented by any of the following formulas (III) to (XIII) and (XV) to (XXX), and their derivatives (the prepared photoconvertible photoinitiator represented by formula (XIV) does not exhibit coloration).

[0119] The substituent including a carbonyl group (C=O) may be a substituent connected to the P-type photochromic molecule via a bond. Alternatively, the carbonyl group may be indirectly connected to the ring, for example, to another substituent or moiety connected to the ring.

[0120] Preferred photohardenable compositions for inclusion in the methods of the present invention include the photohardenable compositions described herein.

[0121] In the methods described herein, a volume of the photohardenable composition is preferably contained within a container, wherein at least one or more portions of the container are optically transparent so that the photohardenable composition is accessible to light for irradiating the photohardenable composition. It may be desirable that the optically transparent portion of the container is also optically flat.

[0122] Examples of first and second wavelength ranges used in the methods described herein include a first wavelength in the range of 300 nm to about 550 nm, such as but 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 nm to about 455 nm, about 375 nm to about 445 nm, about 375 nm to about 410 nm, and about 375 nm to about 405 nm, and a second wavelength in the range of about 450 nm to about 1000 nm, such as but not limited to about 450 nm to about 850 nm, most typically about 450 nm to about 700 nm.

[0123] Examples of the power density of the first wavelength light include about 0.01 to about 100,000 W / cm 2 Examples of the power density of the second wavelength light include about 0.01 to about 100,000 W / cm 2 power density within the range of .

[0124] Examples of exposure energy of the first wavelength light include about 0.001 to about 1,000 mJ / cm 2 Examples of the exposure energy of the second wavelength light include about 0.01 to about 100,000 mJ / cm 2 exposure energy within the range of .

[0125] The method according to the present invention preferably includes a photohardenable composition that exhibits non-Newtonian rheological behavior. The photohardenable composition including a photohardenable resin component and a P-type photochromic molecule that exhibits non-Newtonian rheological behavior can facilitate the formation of an object, preferably a three-dimensional object, that is completely suspended in a volume of the photohardenable composition during formation. The ability to completely suspend an object in a volume during formation advantageously eliminates the need for support structures of the type used in stereolithography to maintain the geometry / shape of the object during formation (which is sometimes referred to as printing or 3D printing).

[0126] For use in forming an object (e.g., a three-dimensional object), it is desirable that the photohardenable composition does not harden (e.g., the photohardenable resin component does not undergo polymerization or crosslinking) when the photohardenable composition is exposed to only the first wavelength or only the second wavelength. In other words, a photohardenable composition that is not hardened in a volume by exposure to two radiations simultaneously or nearly simultaneously (e.g., due to close sequential exposure in time) will not polymerize. In particular, in scanning a volume of photohardenable medium, as the light beams pass through previously exposed areas or planes, there will be many such points in the volume: these points are scanned successively in an arbitrary order by the first wavelength radiation and the second wavelength radiation as the structure of the object is defined in the volume of the medium by the intersection of the light beams. Some points may also undergo multiple exposures to the first wavelength light and / or the second wavelength light. Preferably, points that receive such multiple sequential (non-simultaneous) exposures do not polymerize.

[0127] Preferably, when only one of the first wavelength and the second wavelength is present, the amount of time that one or more selected locations within the volume are simultaneously or sequentially exposed to the first wavelength light and the second wavelength light is insufficient to initiate hardening of the photohardenable composition at the one or more selected locations, and is insufficient to cause the photohardenable composition to harden.

[0128] Preferably, light of the first wavelength and light of the second wavelength are directed into the volume as separate optical projections.

[0129] Preferably, the projection direction of the light of the first wavelength is orthogonal to the projection direction of the light of the second wavelength.

[0130] Preferably, the projection of light of the first wavelength comprises a light sheet.The light sheet may ideally comprise a planar arrangement of light having opposing major faces, wherein the major faces are parallel to the direction in which the light sheet is directed into the volume.

[0131] Preferably, the projection of light of the second wavelength comprises the optical image perpendicular to the direction in which the optical image is projected into the volume.A digital micromirror device (DMD) is preferably used for the projection of the optical image.

[0132] Preferably, the light sheet and the optical image intersect in a common plane. Desirably, the intersection of the light sheet and the optical image is coplanar or substantially coplanar.

[0133] The optical image may include any optical projection generated by the optical projection system. Examples of optical images include, but are not limited to, patterned or unpatterned two-dimensional images, light, or a single light spot. The two-dimensional image may include a cross-sectional plane of the printed three-dimensional image. The two-dimensional image may represent a cross-sectional slice of the object to be printed. Such cross-sectional slices are typically generated using slice software, as discussed elsewhere herein.

[0134] Examples of light sources that may be suitable for the excitation light of the methods described herein include, for example, but not limited to, lasers, laser diodes, light emitting diodes, light emitting diodes (LEDs), micro-LED arrays, vertical cavity lasers (VCLs), and filter lamps. Such light sources are commercially available, and a person of ordinary skill in the relevant art can easily select a suitable light source. LEDs of the type such as Phlatlight LED (available from Luminus) can be used for DMDs, and laser light sources may be preferred. Other suitable light sources may also be useful.

[0135] Optionally, the excitation light may be modulated in time and / or space. Optionally, the intensity of the excitation light may be modulated.

[0136] Examples of projection devices for use with 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”) (such as, but not limited to, 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”).

[0137] Preferred projection devices include digital light processors, such as SLM and DMD, with DMD being more preferred.

[0138] Preferably, the projection device irradiates with laser light.

[0139] The optical image projection system may also optionally include one or more optical components (e.g., projection optics, illumination optics, lenses, lens systems, reflectors, prisms, etc.). The optical image projection system may also optionally include one or more light sources as a part of the projection system or outside the projection system for irradiating the projection device. The use of an external light source may facilitate the flexibility of being able to easily replace the light source with a light source generating different wavelengths and / or a light source of different power capabilities.

[0140] Other information that may be useful related to one or more aspects and / or embodiments of the present invention includes International Application No. PCT / US2022 / 039766 filed by Quadratic 3D, Inc. on August 9, 2022, International Patent Application No. PCT / US2022,052157 filed by Quadratic3D, Inc. 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 which is hereby incorporated by reference in its entirety.

[0141] Optionally, the excitation light may be modulated in time and / or space. Optionally, the intensity of the excitation light may be modulated. Optionally, source drive modulation may be used to adjust the absolute power of the light beam.

[0142] Spatially modulated excitation light can be created by known spatial modulation techniques including, for example, a liquid crystal display (LCD), a digital micromirror device (DMD), or a micro-LED array. Other known spatial modulation techniques can be readily determined by a person of ordinary skill in the relevant art.

[0143] The light sheet generation system and / or the optical image projection system (if applicable) can be configured to apply continuous excitation light. Such a system can be configured to apply intermittent excitation light. Intermittent excitation can include random intermittent application of light or periodic application of light. Examples of periodic application of light include pulses. 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 applying intermittent excitation light before or after irradiation with continuous light. Intermittent light can be advantageous for increasing printing speeds using higher instantaneous light intensities.

[0144] As discussed above, in addition to the projection device, the projection system may include additional components including, but not limited to, projection optics, and one or more translation stages for moving the system or its components.

[0145] The methods of the invention described herein may also include post-processing. Examples of post-processing steps that may be further included in the methods according to the invention include, but are not limited to, one or more of the following: separation of at least a portion of the hardened composition from the unhardened composition, washing, post-curing (e.g., by light, heat, ionizing radiation, pressure, or a simultaneous or sequential combination of these techniques), metering, freeze drying, critical point drying, and packaging.

[0146] In the method for forming a three-dimensional object according to the present invention, it is desirable to select a photoconvertible photoinitiator molecule whose first excitation wavelength has significant absorption in the first form and in which the second form of the photoinitiator has minimal absorption in the first excitation wavelength. This has two advantages, first, it simplifies exposure because activation of the photoconvertible photoinitiator can occur without activating its second form to initiate a crosslinking or polymerization reaction in the photohardenable resin component. When there is a large amount of overlap, the intensity of the two radiations must be carefully controlled so as to activate the photoconvertible photoinitiator molecules while minimizing activation of its second form. Second, it can allow deeper penetration into the volume or layer of the composition because the conversion of the photoconvertible photoinitiator to its second form has the effect of "bleaching" the photoconvertible photoinitiator molecule or making it transparent to the first wavelength radiation.

[0147] The photoconvertible photoinitiator included in the methods and photohardenable compositions described herein will preferably absorb the first wavelength of light in the range of about 300 nm to about 550 nm. Other examples of the range in which the photoconvertible photoinitiator absorbs the first wavelength of light 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 photoconvertible photoinitiator, the conversion to the second form can be initiated by exposure to any source (e.g., laser, light emitting diode, mercury lamp) emitting within this range. A filter 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 radiation source for generating the first wavelength radiation.

[0148] The second form of the photoconvertible photoinitiator will preferably absorb in the range of about 450 to 1000 nm and most typically 450 to 850 nm. Other examples of the range in which the second form of the photoconvertible photoinitiator will preferably absorb include 450 to about 700 nm. The form can be activated by a second excitation light to directly generate free radicals or to generate excitons, which undergo electron transfer or hydrogen abstraction (optionally via electrons, hydrogen, or energy to the co-initiator (including one or more co-initiators) of various aspects of the present invention) by exposure to any second wavelength in the range. For the second excitation, exposure can be achieved using a laser source, an LED or LED array, filtered emission from an arc lamp, or other suitable sources with emission in the desired wavelength range, argon ions, He-Ne, laser diodes, krypton, frequency-doubled Nd-YAG, etc. Other light sources, such as light emitting diodes, incandescent lamps, halogen lamps, mercury lamps, arc lamps, etc., optionally with filters to limit the output wavelength, can be used.

[0149] Optionally, the photohardenable composition included in the method according to the present invention may also include a light-activated photoinitiator that preferably does not respond significantly to light of the first wavelength or the second wavelength. In any post-processing of the printed object, it may be desirable to include such a light-activated photoinitiator in connection with an optional post-curing step with UV light after printing. If the photoinitiator is included in the photohardenable resin for post-curing purposes, the method may also include a post-curing step that includes exposing the object to light of a third wavelength to further harden the object, the third wavelength being different from the first wavelength and the second wavelength. When the photoinitiator is UV-activatable, the third wavelength is preferably in the ultraviolet wavelength range.

[0150] Separation of the at least partially hardened object from the unhardened composition may be performed by a variety of means known in the art, such as gravity drainage, screening, air knife, centrifugation, vibration, or ultrasonic agitation.

[0151] Preferably, after separation, at least part of the hardened object is washed.

[0152] Washing can be carried out with any suitable organic or aqueous washing liquid or a combination thereof, including solutions, suspensions, emulsions, microemulsions, etc. Examples of suitable washing liquids include, but are not limited to, water, alcohols (e.g., methanol, ethanol, isopropanol, etc.), glycol ethers, benzene, toluene, etc. Washing liquids comprising a mixture of two or more liquids (e.g., water and an alcohol (e.g., isopropanol)) may also be suitable. Such washing solutions may optionally contain additional ingredients, such as surfactants, etc.

[0153] The methods according to various aspects of the present invention may further comprise post-processing of the formed one or more three-dimensional objects.

[0154] In addition to washing, other examples of post-treatment include, but are not limited to, post-curing (e.g., by light, electron beam, heat, non-ionizing radiation, ionizing radiation, time (aging), pressure, humidity, or a simultaneous or sequential combination of these techniques), metering, labeling or tracking (e.g., by barcodes, QR codes, or RFID tags), freeze-drying, critical point drying, and packaging.

[0155] In the methods described herein including light sheets, the light sheets can be constructed by means known in the art, including, for example but not limited to, technologies including lasers and Powell prisms, galvanometers, and / or polygonal scanning mirrors. Alternatively, one or more LEDs can be used as light sources.

[0156] Optionally, the methods described herein may also include using an additional different wavelength to force the second form of the photo-switchable photoinitiator to back-react to the original / starting form to help avoid hardening of undesirable areas.

[0157] As used herein, a first wavelength, a second wavelength, or other additional wavelengths may refer to a range of wavelengths.

[0158] In the methods described herein, the first wavelength and the second wavelength are preferably generated by different light sources or optical projection systems.

[0159] As mentioned above, the method according to the present invention preferably comprises providing a volume of the photohardenable composition described herein contained in a container, wherein at least a portion of the container is optically transparent so that the photohardenable composition is accessible to the excitation light. Optionally, the entire container is optically transparent.

[0160] The optically transparent portion of the container can be constructed of materials including, for example, but not limited to, glass, quartz, fluoropolymers (e.g., Teflon FEP, Teflon AF, Teflon PFA), cyclic olefin copolymers, polymethyl methacrylate (PMMA), polynorbornene, sapphire, or transparent ceramics.

[0161] Examples of container shapes include, but are not limited to, cylindrical containers with circular or oval cross-sections, containers with straight sides and polygonal cross-sections, or rectangular or square cross-sections.

[0162] As mentioned above, it may be desirable for one or more optically transparent portions of the container to also be optically flat.

[0163] Optionally, one or more filters are added to at least one surface of any optically transparent portion of the container to block undesirable light, such as room light, to prevent unintended curing.

[0164] Optionally, the photohardenable composition is filtered to remove particles before being introduced into the container. Optionally, bubbles are removed from the photohardenable composition before or after being introduced into the container. Optionally, the photohardenable composition is degassed, purged or bubbled with an inert gas before or after being introduced into the container. Optionally, the photohardenable composition is maintained under inert conditions, e.g., an inert atmosphere, during printing. This can prevent oxygen from being introduced into the container while the object is being printed or formed.

[0165] In the methods described herein, the container can be rotated to provide additional angles for irradiation or projection of the excitation light into the volume of the photohardenable composition contained therein. This can help to more accurately pattern an object volume or surface, or it can be used as a means to provide multiple exposures of a given feature from different angles.

[0166] In the methods described herein, the container can be stationary while the beam or optical projection of activating light is directed into the photohardenable composition.

[0167] The methods disclosed herein may also include systems that use commercially available light projection and filtering techniques or employ two or more light projection methods simultaneously.

[0168] The methods described herein are generally used in combination with computers and software. For example, the light sheet generation system, optical image projection system, and projection device that may be included in the methods described herein may be used in combination with computers and software. Software may be used to coordinate optical projections (e.g., point illumination, line illumination, two-dimensional pattern, or light sheet) generated at various positions along respective projection directions from their corresponding optical projection systems or projection devices so as to generate components plane by plane. The plane of the projected optical image is preferably orthogonal to its projection direction into the photohardenable composition. When two optical projections are projected into the volume of the photohardenable 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 range of ordinary technicians in the relevant field. Other components may also be optionally included or used with the system.

[0169] The method according to the invention also advantageously does not require the printed object to be adhered to a fixed substrate (eg a build plate) at the beginning of the printing process, thereby avoiding a post-processing step of detaching the printed object from the fixed substrate.

[0170] The methods described herein are particularly useful for forming or "printing" three-dimensional objects.

[0171] Before printing, obtain the digital file of the object to be printed. If the digital file is not in a format that can be used to print the object, the digital file is converted into 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 a three-dimensional slicer software and converted into G-Code or a set of machine commands, which facilitates the construction of the object. See B. Redwood et al., "The 3D Printing Handbook—Technologies, designs applications", 3D HUBS BV2018.

[0172] The excitation light may be directed into the volume of the photohardenable composition in a continuous or intermittent manner. Intermittent excitation may include random intermittent application of light or periodic application of light. Examples of periodic application of light include pulses. Excitation may alternatively be applied as a combination of both continuous excitation light and intermittent light, including, for example, applying intermittent excitation light before or after irradiation with continuous light.

[0173] Other information on optical systems that may be useful in connection with various aspects of the present invention includes Texas Instruments Application Report DLPA022-July 2010 entitled "DLP TM System Optics"; Texas Instruments" TIDL R Technology for 3D Printing–Design scalable high-speedstereolithography[sic]systems using TIDLP technology” 2016; Texas Instruments “DLP6500 0.65 1018p MVSP Type A DMD”, DLP6500, DLPS040A-October 2014-Revised October 2016; and YH 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.

[0174] According to another aspect of the present invention, a photoconvertible photoinitiator is provided, which comprises a P-type photochromic molecule, which comprises one or more substituents, wherein at least one substituent comprises a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atomic rings, wherein at least one fused atomic ring comprises one or more substituents, wherein at least one substituent comprises a double-bonded oxygen connected to a carbon atom ring member included in one of the fused rings, wherein the P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in a photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

[0175] The substituent including the carbonyl group may be a substituent connected to the P-type photochromic molecule via a bond. Alternatively, the carbonyl group may be indirectly connected to the ring.

[0176] It can be expected that the photoconvertible photoinitiator comprises a P-type photochromic molecule, which preferably comprises a P-type diarylethene molecule, which molecule includes one or more substituents, at least one of which is a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group including at least two fused atomic rings, at least one of which includes one or more substituents, at least one of which includes a double-bonded oxygen connected to a carbon atom ring member included in one of the fused rings, wherein the P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

[0177] The photo-switchable photoinitiator according to the present invention preferably comprises a P-type photochromic molecule.

[0178] Non-limiting examples of preferred photo-switchable photoinitiators include photo-switchable photoinitiators comprising a diarylcycloolefin molecule represented by the general formula (I):

[0179]

[0180]

[0181] in:

[0182] A represents a substituted or unsubstituted cycloolefin ring structure,

[0183] X represents the following formula (X a )、(X b )、(X c ), or (X d ) represented by a heteroaryl group:

[0184]

[0185] in:

[0186] E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ),

[0187] Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8 ), or a cyano (CN) group,

[0188] G is a ring member and represents a ring having R 9 The carbon atom of the substituent group (CR 9 ) or a nitrogen atom (N);

[0189] L is a ring member and represents a ring having R 1 The carbon atom of the substituent group (CR 1 ) or a nitrogen atom (N), and

[0190] R 1 and R 6 -R 9 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0191]

[0192] in:

[0193] E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ),

[0194] Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8 ), or a cyano (CN) group,

[0195] G is a ring member and represents a carbon atom with an R substituent group (CR 9 ) or a nitrogen atom (N);

[0196] L is a ring member and represents a ring having R 1 The carbon atom of the substituent group (CR 1 ) or a nitrogen atom (N), and

[0197] R 1 and R 6 -R 9 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0198]

[0199] in:

[0200] E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ),

[0201] Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8 ), or a cyano (CN) group, and

[0202] R 2 -R 8The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0203]

[0204] E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ),

[0205] Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, SR 7 Group, OR 8 group, or a cyano (CN) group, and

[0206] R 2 -R 8are substituents, are the same or different, and independently represent, 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 a substituted 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group;

[0207] Y represents the formula (Y a )、(Y b ), (Yc) or (Y d ) represented by a heteroaryl group:

[0208]

[0209] in:

[0210] E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ),

[0211] Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group,

[0212] G' is a ring member and represents a ring having R 18 The carbon atom of the substituent group (CR 18 ) or a nitrogen atom (N);

[0213] L' is a ring member and represents a ring having R 10 The carbon atom of the substituent group (CR 10 ) or a nitrogen atom (N), and

[0214] R 10 and R 15 -R 18 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0215]

[0216] in:

[0217] E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ),

[0218] Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group,

[0219] G' is a ring member and represents a ring having R 18 The carbon atom of the substituent group (CR 18 ) or a nitrogen atom (N);

[0220] L' is a ring member and represents a ring having R 10 The carbon atom of the substituent group (CR 10 ) or a nitrogen atom (N), and

[0221] and

[0222] R 10 and R 15 -R 18 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0223]

[0224] in:

[0225] E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ),

[0226] Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, SR 16 Group, OR 17 group, or a cyano (CN) group, and

[0227] R 11 -R 17The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or

[0228]

[0229] in:

[0230] E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ),

[0231] Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group, and

[0232] R 11 -R 17are substituents, are the same or different, and independently represent, 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 a substituted 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group;

[0233] wherein at least one of X and Y includes at least one R substituent comprising a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atom rings, wherein at least one of the fused atom rings comprises one or more substituents, wherein at least one substituent comprises a double bonded oxygen attached to a carbon atom ring member included in one of the fused rings; and

[0234] The P-type photochromic molecules are activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

[0235] Optionally, the R groups on any two adjacent ring members of X and / or Y may include atoms for completing the ring structure that connects the two adjacent groups together. Such ring structures may be substituted or unsubstituted, and may optionally be part of a polycyclic substituted or unsubstituted ring structure. In addition to the carbon in the ring structure, such ring structures, or (if applicable) the polycyclic structures of which such ring structures are a part, may also optionally include one or more heteroatoms.

[0236] Preferred examples include those wherein at least one R substituent on X and / or Y comprises a substituted or unsubstituted benzophenone group, a substituted or unsubstituted benzil group, a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted naphthylenedione-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 wherein R 1 -R 18 At least one of, and most preferably R 1 -R 6 At least one of the above represents a substituted or unsubstituted benzophenone group, a substituted or unsubstituted benzil group, a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted naphthylenedione-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-indandione group, a substituted or unsubstituted chromone group, a substituted or unsubstituted 1,4-naphthoquinone group, and the like.

[0237] It can be expected that X and Y each include at least one substituent, the substituent includes a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group including at least two fused atom rings, wherein at least one fused atom ring includes one or more substituents, wherein at least one substituent includes a double bond oxygen connected to a carbon atom ring member included in one of the fused rings. In this case, such substituents on X and Y can be the same or different. For example, it can be expected that 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 α-diketone group, or a polycyclic group including at least two fused atom rings, wherein at least one fused atom ring includes one or more substituents, wherein at least one substituent includes a double bond oxygen connected to a carbon atom ring member included in one of the fused rings.

[0238] Optionally, X and Y may be symmetrical in that any one or more R substituents on X and any one or more R substituents on Y are compatible with each other.

[0239] Optionally, X and Y are asymmetric, wherein each of X and Y includes one or more different R substituents on each of X and Y.

[0240] It may be desirable for at least one R substituent on X and / or at least one R substituent on Y to contain a substituted or unsubstituted benzophenone group, a substituted or unsubstituted benzil group, a substituted or unsubstituted thioxanthone group, a substituted or unsubstituted naphthylenedione-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-indandione group, a substituted or unsubstituted chromone group, a substituted or unsubstituted 1,4-naphthoquinone group, and the like.

[0241] In the general formula (I), E in X and E' in Y are optionally independently the same or different.

[0242] In the general formula (I), G in X and G' in Y are optionally independently the same or different.

[0243] In the general formula (I), Z in X and Z' in Y are optionally independently the same or different.

[0244] In the general formula (I), L in X and L' in Y are optionally independently the same or different.

[0245] Optionally, X and Y may be the same or different.

[0246] Examples of preferred substituted or unsubstituted diaryl ketone groups include those represented by the general formula (DAK):

[0247]

[0248] wherein Ar and Ar' are the same or different and independently comprise a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.

[0249] Examples of substituted or unsubstituted aryl groups included as Ar and / or Ar' in the general formula (DAK) include, but are not limited to, substituted or unsubstituted substituents or functional groups derived from aromatic rings, including, but not limited to, benzene rings, naphthalene rings, anthracene rings, indene rings, fluorene rings, and the like.

[0250] Examples of substituted or unsubstituted heteroaryl groups included as Ar or Ar' in the general formula (DAK) include, but are not limited to, substituted or unsubstituted substituents or functional groups derived from a heteroaryl ring, including, but not limited to, a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, an isoxazole ring, a thiazole ring, an isothiazole ring, an imidazole ring, a pyrazole ring, a pyran ring, a pyridine ring, a pyrazine ring, an indole ring, a quinoline ring, an isoquinoline ring, a xanthene ring, a carbazole ring, an acridine ring, an indeline ring, a julolidine ring, and the like.

[0251] In a substituted aryl or heteroaryl group, examples of substituents that may replace a hydrogen atom attached to the aryl or heteroaryl group include, but are not limited to, a halogen atom, an alkyl group, an alkoxy group, an alkylamino group, a dialkylamino group, an alkylthio group, a heterocyclic group, more specifically a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a phenyl group, a trifluoromethyl group, a cyano group, an acetyl group, an ethoxycarbonyl group, a carboxyl group, a carboxylate group, an amino group, a methylamino group, a dimethylamino group, an ethylamino group, a diethylamino group, an isopropylamino group, a diisopropylamino group, a cyclohexylamino group, a dicyclohexylamino group, an ethylamino group, a Amido group, piperidinyl group, pyrrolidinyl group, --PO3H, methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, pentyloxy group, phenoxy group, hydroxyl group, acetoxy group, methylthio group, ethylthio group, isopropylthio group, mercapto group, acetylthio group, thiocyano group, methylsulfinyl group, methylsulfonyl group, dimethylsulfonyl group, sulfonate group, fluorine atom, chlorine atom, bromine atom, iodine atom, trimethylsilyl group, triethylsilyl group, furyl group, thienyl group, pyridyl group, piperidinyl group, morpholinyl group, pyrrolidinyl group and the like.

[0252] Examples of preferred substituted or unsubstituted α-diketone groups include those represented by the general formula (ADK):

[0253] Ar 1 -C(=O)-C(=O)-Ar 2

[0254] (ADK)

[0255] Among them, Ar 1 and Ar 2 are the same or different and are independently a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.

[0256] Examples of substituted or unsubstituted aryl groups included as Ar and / or Ar' in the general formula (ADK) include, but are not limited to, substituted or unsubstituted substituents or functional groups derived from aromatic rings, including, but not limited to, benzene rings, naphthalene rings, anthracene rings, indene rings, fluorene rings, and the like.

[0257] Examples of the substituted or unsubstituted heteroaryl group contained as Ar or Ar' in the general formula (ADK) include substituted or unsubstituted substituents or functional groups derived from a heteroaryl ring, including but not limited to a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, an isoxazole ring, a thiazole ring, an isothiazole ring, an imidazole ring, a pyrazole ring, a pyran ring, a pyridine ring, a pyrazine ring, an indole ring, a quinoline ring, an isoquinoline ring, a xanthene ring, a carbazole ring, an acridine ring, an indoline ring, a julolidine ring and the like.

[0258] In a substituted aryl or heteroaryl group, examples of substituents that may replace a hydrogen atom attached to the aryl or heteroaryl group include, but are not limited to, a halogen atom, an alkyl group, an alkoxy group, an alkylamino group, a dialkylamino group, an alkylthio group, a heterocyclic group, more specifically a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a phenyl group, a trifluoromethyl group, a cyano group, an acetyl group, an ethoxycarbonyl group, a carboxyl group, a carboxylate group, an amino group, a methylamino group, a dimethylamino group, an ethylamino group, a diethylamino group, an isopropylamino group, a diisopropylamino group, a cyclohexylamino group, a dicyclohexylamino group, an ethylamino group, a Amido group, piperidinyl group, pyrrolidinyl group, --PO3H, methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, pentyloxy group, phenoxy group, hydroxyl group, acetoxy group, methylthio group, ethylthio group, isopropylthio group, mercapto group, acetylthio group, thiocyano group, methylsulfinyl group, methylsulfonyl group, dimethylsulfonyl group, sulfonate group, fluorine atom, chlorine atom, bromine atom, iodine atom, trimethylsilyl group, triethylsilyl group, furyl group, thienyl group, pyridyl group, piperidinyl group, morpholinyl group, pyrrolidinyl group and the like.

[0259] Specific examples of the α-diketone group represented by the formula ADK include, but are not limited to, the following compounds represented by the formulas (ADK-1) to (ADK-11):

[0260]

[0261]

[0262]

[0263] Optionally, Ar in the general formula ADK and any compound represented by formula (ADK-1) to (ADK-11) 1 and / or Ar 2One or more substituents may be included on one or both of the aryl or heteroaryl groups, and these substituents may be the same or different. Examples of substituents include, but are not limited to, 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 carbamate groups, substituted or unsubstituted urea groups, substituted or unsubstituted tetrazine groups, substituted or unsubstituted amino groups, iodine, bromine, chlorine, fluorine, cyano groups, nitro groups, hydroxyl groups, thiols, alkyl thioethers, aryl thioethers, substituted or unsubstituted alcohol groups, and those listed above.

[0264] Examples of preferred polycyclic groups comprising at least two fused atom rings (wherein at least one fused atom ring comprises one or more substituents, wherein at least one substituent comprises a double bonded oxygen connected to a carbon atom ring member included in one of the fused rings) include, but are not limited to, polycyclic groups represented by:

[0265] Thioxanthone group represented by the general formula (PG-A):

[0266]

[0267]

[0268] · A 1,2-dione group represented by the general formula (PG-B):

[0269]

[0270] ●Thiochroman-4-one group represented by the general formula (PG-C):

[0271]

[0272] ·9-fluorenone group represented by the general formula (PG-D):

[0273]

[0274] Anthraquinone group represented by the general formula (PG-E):

[0275]

[0276] ●Benzanthrone group represented by the general formula (PG-F):

[0277] ●9,10-phenanthrenequinone group represented by the general formula (PG-G):

[0278]

[0279] Examples of additional polycyclic groups that may be suitable for inclusion in the second unit include, but are not limited to: - A xanthone group represented by the general formula (PG-H):

[0280]

[0281] · 1,3-indandione group represented by the general formula (PG-I):

[0282]

[0283] Chromone group represented by the general formula (PG-J):

[0284]

[0285] · 1,4-naphthoquinone group represented by the general formula (PG-K):

[0286]

[0287]

[0288] Coumarin group represented by the general formula (PG-L):

[0289]

[0290] A ketocoumarin group represented by the general formula (PG-M):

[0291]

[0292] The aryl group may be substituted or unsubstituted and may optionally include one or more heteroatoms.

[0293] Optionally, the polycyclic group including any one of PG-A to PG-M may be further substituted with one or more additional substituents or functional groups.

[0294] Preferred examples of A include those represented by the formula (A a )、(A b )、(A c ) and (A d ) represents the structure:

[0295]

[0296] in:

[0297] X 1 , X 2 , X 3 , X 4 , X 5 and X 6 are the same or different and are independently hydrogen (H), fluorine (F), chlorine (Cl), or a substituted or unsubstituted alkyl or heteroalkyl group,

[0298]

[0299] in:

[0300] J is a ring member and represents oxygen O or has R 25 The nitrogen of the substituent group (NR 25 ), where R 25 represents hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl,

[0301]

[0302] in:

[0303] E" is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 23 The nitrogen atom (NR 23 ),

[0304] G" is a ring member and represents a ring having R 24 The carbon atom of the substituent group (CR 24 ) or a nitrogen atom (N); and

[0305] R 22 -R 24The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group, or

[0306]

[0307] in:

[0308] 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.

[0309] Other examples of A include substituted or unsubstituted 6-membered ring structures and substituted and unsubstituted polycyclic ring structures containing an ethylene bridge, wherein X and Y are attached to carbons at opposite ends of the double bond of the ethylene bridge.

[0310] In the general formula (I), it may be desirable that at least one functional group containing a carbonyl group contains a ketone. In the general formula (I), it may be desirable that at least one functional group containing a carbonyl group is a ketone.

[0311] Examples of preferred photo-switchable photoinitiators according to the present invention include those represented by the following formulae (III)-(XXX):

[0312]

[0313]

[0314]

[0315]

[0316] In formulae (III) to (XXX) above, a bare line 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).

[0317] The photo-switchable photoinitiator according to the present invention also includes a derivative of the compound represented by any one of structures (III) to (XXX).

[0318] Among the above examples, it may be particularly desirable that the photo-switchable photoinitiators represented by formula (VI), (XIX) and (XXI) are included in the method according to the present invention.

[0319] The photoconvertible photoinitiators described herein will preferably absorb a first wavelength of light in the range of about 300 to 550 nm. Other examples of other ranges of first wavelengths of light that the photoconvertible photoinitiators described herein will absorb include, but are not limited to, about 350 to about 460 nm, about 350 to about 455 nm, about 350 to about 445 nm, about 350 to about 410 nm, about 350 to about 405 nm, about 375 to about 460 nm, about 375 to 455 nm, about 375 to 445 nm, about 375 to 410 nm, about 375 to about 405 nm, about 375 nm ± 10 nm, about 405 nm ± 10 nm, about 410 + nm. Depending on the extinction coefficient of the specific photoconvertible photoinitiator, the conversion to the second form can be initiated by exposure to any source (e.g., laser, light emitting diode, mercury lamp) emitting within this range. Filters can be used to limit the output wavelength. Non-limiting examples of filtered light include filtered emissions from mercury arc lamps, etc.

[0320] The second form of the photoconvertible photoinitiator will preferably absorb in the range of about 450 to 1000 nm and most typically 450 to 850 nm. Other examples of the range in which the second form of the photoconvertible photoinitiator will preferably absorb include 450 to about 700 nm. The form can be activated by a second excitation light to directly generate free radicals or to generate excitons, which undergo electron transfer or hydrogen abstraction (optionally via electrons, hydrogen, or energy to the co-initiator (including one or more co-initiators) of various aspects of the present invention) by exposure to any second wavelength in the range. For the second excitation, exposure can be achieved using a laser source, an LED or LED array, filtered emission from an arc lamp, or other suitable sources with emission in the desired wavelength range, argon ions, He-Ne, laser diodes, krypton, frequency-doubled Nd-YAG, etc. Other light sources, such as light emitting diodes, incandescent lamps, halogen lamps, mercury lamps, arc lamps, etc., optionally with filters to limit the output wavelength, can be used.

[0321] According to another aspect of the present invention, a photohardenable composition is provided, which comprises a photohardenable resin component and a photoconvertible photoinitiator, wherein the photoconvertible photoinitiator comprises a P-type photochromic molecule, preferably a P-type diarylethene molecule, which molecule includes one or more substituents, wherein at least one substituent comprises a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atomic rings, wherein at least one fused atomic ring comprises one or more substituents, wherein at least one substituent comprises a double-bonded oxygen connected to a carbon atom ring member included in one of the fused rings, wherein the P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

[0322] Preferred photo-switchable photoinitiators for inclusion in the photohardenable composition include diarylcycloolefin molecules represented by the general formula (I) described herein:

[0323]

[0324] Examples of preferred P-type photo-switchable photoinitiators contained in the photohardenable composition and method according to the present invention include those represented by formulas (III) to (XIII) and (XV-XXX) set forth above, and derivatives thereof.

[0325] Among the above examples, it may be particularly desirable that the photo-switchable photoinitiators represented by formula (VI), (XIX) and (XXI) are contained in the photohardenable composition used in the method according to the present invention.

[0326] As discussed herein, photohardenable compositions that exhibit non-Newtonian rheological behavior may be desirable or preferred.

[0327] The photohardenable composition may also optionally include a co-initiator.

[0328] The photohardenable composition may also optionally include a sensitizer.

[0329] Optionally, the photohardenable composition may include a combination comprising one or more co-initiators and / or one or more sensitizers.

[0330] Several considerations in selecting a particular photoconvertible photoinitiator for inclusion in a photohardenable composition or method according to the present invention include, for example, but not limited to, the absorption spectra of the molecule and its second form and the Δ max , the solubility of the photoconvertible photoinitiator in the photohardenable resin component, the photosensitivity of the second form of the photoconvertible photoinitiator, the amount of the initial concentration of the second form in the monomer solution, the stability of the photoconvertible photoinitiator, and the reduction and oxidation potentials of the second form of the photoconvertible photoinitiator.

[0331] The photohardenable composition according to the present invention is particularly suitable for use in the method for forming a three-dimensional object according to the present invention because the photoconvertible photoinitiator molecule in its initial open form (which is generally colorless for the initial form of the p-type diarylethene) and the photoinitiator molecule in its second closed form (which is generally colored) have sufficiently distinct absorption spectra that, once the open form of the molecule is converted to its closed form, the closed form absorbs in a wavelength region that the open form does not substantially absorb. In this way, the closed form can be independently excited with the second wavelength without causing the open form to be accidentally excited by the second wavelength. Once the closed form is generated by exposure to the first wavelength, the second wavelength can excite the closed form to generate free radicals or otherwise initiate the desired hardening of the photohardenable resin component.

[0332] The photohardenable resin component may optionally include one or more multifunctional acrylate monomers. Dipentaerythritol pentaacrylate (a pentafunctional acrylic monomer available from Sartomer as SR399) is an example of a photohardenable resin component.

[0333] It is also desirable to use aliphatic urethane acrylates as the photohardenable resin component.

[0334] Mixtures of multifunctional acrylate monomers such as dipentaerythritol pentaacrylate (eg, SR399 from Sartomer) with aliphatic urethane acrylates may also be used.

[0335] An acrylamide monomer may also be included in the photohardenable resin composition to serve as a solvent for mixing the photoinitiator in the first resin component.

[0336] Preferably, the photohardenable resin component included in the photohardenable composition is selected to achieve an optically transparent or clear liquid, which is desirable in methods and systems in which light (eg, excitation light) is directed into the composition.

[0337] As provided herein, photohardenable compositions according to the present invention may optionally include one or more co-initiators.

[0338] Suitable co-initiators include co-initiators that are reducing agents, oxidizing agents, or hydrogen donating compounds.

[0339] Examples of potentially useful co-initiators may be selected from those known in the art, and more particularly tertiary amines and organic borates. Ionium salts are also useful, particularly in combination with borates. In certain embodiments, iodonium salts in combination with tertiary amines may also be included. Examples of other useful electron donating co-initiators are discussed by Eaton, DF in "Dye Sensitized Photopolymerization", Advances in Photochemistry, Vol. 13, pp. 427-486.

[0340] Representative examples of useful N,N-dialkylanilines 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-dimethylthioanicidine, 4-amino-N,N-dimethylaniline, 3-hydroxy-N,N-dimethylaniline, N,N,N,'N,-tetramethyl-1,4-diphenylamine, 4-acetamido-N,N-dimethylaniline, 2,6-diethyl-N,N-dimethylaniline, N,N,2,4,6-pentanethylaniline (PMA) and p-tert-butyl-N,N-dimethylaniline.

[0341] Certain other tertiary amines are also useful co-initiators, including triethylamine, triethanolamine, N-methyldiethanolamine, 2-ethyl-4-(dimethylamino)benzoate, 2-ethylhexyl-4-(dimethylamino)benzoate, and the like.

[0342] Another class of useful co-initiators are alkyl borates, such as those of formula BR a R b Rc R d The ammonium salt of the borate anion, wherein R a -R d R is independently selected from alkyl, aryl, alkaryl, allyl, aralkyl, alkenyl, alkynyl, alicyclic and saturated or unsaturated heterocyclic groups. a -R d Representative examples of alkyl groups represented by are methyl (Me), ethyl, propyl, butyl, pentyl, hexyl, octyl, stearyl, etc. The alkyl group may be substituted, for example, with one or more halogen, cyano, acyloxy, acyl, alkoxy or hydroxyl groups. a -R d Representative examples of aryl groups represented by include phenyl, naphthyl, and substituted aryl groups (such as anisyl) and alkaryl groups (such as methylphenyl, dimethylphenyl, etc.). a -R d Representative examples of aryl groups represented by include benzyl. Representative alicyclic groups include cyclobutyl, cyclopentyl and cyclohexyl groups. Examples of alkynyl groups are arylpropynyl and ethynyl, and examples of alkenyl groups include vinyl groups. Preferably, R a , R d , R c and R d At least one but not more than three of R are alkyl groups. a , R b , R c and R d Each may contain up to 20 carbon atoms, and they typically contain 1 to 7 carbon atoms. More preferably, R a -R d It is a combination of one or more alkyl groups and one or more aryl groups or one or more aralkyl groups, and more preferably a combination of three aryl groups and one alkyl group, that is, alkyl triphenyl borate, such as but not limited to butyl triphenyl borate.

[0343] As mentioned herein, the photohardenable composition according to the present invention may optionally include a coinitiator (a coinitiator may also be referred to as a synergist). Non-limiting examples of coinitiators include amines, thiols, thioethers, mercaptans, silanes, organic borate compounds, diaryliodonium salts, triarylsulfonium salts. A preferred example of a suitable coinitiator is butyrylcholine butyltriphenylborate. Another preferred example of a suitable coinitiator is N-methyldiethanolamine. When included in a photohardenable composition, the combination of a coinitiator and a photoconvertible photoinitiator can promote photoinitiation through the active form of the photoconvertible photoinitiator via, for example, electron transfer or hydrogen transfer.

[0344] The photohardenable compositions and methods according to the present invention preferably exhibit non-Newtonian rheological behavior, advantageously wherein such rheological behavior facilitates forming an object in a volume of the photohardenable composition described herein when exposed to at least two different wavelengths of excitation light, wherein during formation, the object remains in a fixed position or is minimally displaced in the volume of the unhardened photohardenable composition. Minimal displacement refers to displacement of the object within the volume during its formation that is acceptable for accurately producing the desired part geometry.

[0345] The photohardenable compositions and methods according to the present invention preferably exhibit non-Newtonian rheological behavior, which can also advantageously facilitate separation of the formed object from the unhardened photohardenable composition upon application of stress. While not being bound by theory, upon application of stress, the apparent viscosity of the non-Newtonian photohardenable composition can drop to a value (e.g., a steady shear viscosity) lower than a static value (e.g., a zero shear viscosity or a yield stress), which allows the unhardened photohardenable composition to flow out and separate from the object more easily. Examples of such non-Newtonian rheological behavior include, but are not limited to, pseudoplastic fluids, yield pseudo (Bingham) plasticity, Bingham plasticity, or Bingham pseudoplasticity.

[0346] By further including one or more reactive components (e.g., urethane acrylate oligomers, urethane methacrylate oligomers, acrylated or methacrylated polyurethanes, acrylated or methacrylated polyurethane-ureas, acrylated or methacrylated polyesters, acrylated or methacrylated polyamides, acrylate- or methacrylate-functional block copolymers, alkenyl- or alkynyl-functional urethane oligomers, alkenyl- or alkynyl-functional polyurethanes, alkenyl- or alkynyl-functional polyamides) in the photohardenable resin component, the photohardenable resin component can be further modified to obtain a photohardenable resin. The photohardenable composition may be provided with non-Newtonian rheological behavior by further adding one or more non-reactive additives (such as, but not limited to, one or more thixotropic agents and / or rheology modifiers) to the photohardenable composition. The selection of one or more reactive components and the amount thereof added to the photohardenable resin component to impart non-Newtonian rheological behavior thereto is within the skill of a person skilled in the relevant art without undue experimentation. Similarly, the selection of non-reactive additives and the amount thereof added to the photohardenable composition to impart non-Newtonian rheological behavior thereto is within the skill of a person skilled in the relevant art without undue experimentation.

[0347] For photohardenable compositions 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 (steady shear viscosity refers to the viscosity after the thixotropic agent network is broken).

[0348] additive

[0349] As mentioned above, the photohardenable composition according to the present invention may include one or more additives. Examples of additives include, but are not limited to, thixotropic agents / rheology modifiers, defoamers, stabilizers, deoxidizers, and non-reactive solvent diluents. Any additive may be a single additive or a mixture of additives. For example, the thixotropic agent may include a single thixotropic agent or a mixture of two or more thixotropic agents.

[0350] The additives are preferably selected such that they do not react with the photohardenable resin component, the photoswitchable photoinitiator, the thixotropic agent, or any other additive that may be included in the photohardenable composition.

[0351] filler

[0352] Optionally, the photohardenable composition according to the present invention may also include one or more fillers. Fillers may be included in an amount greater than 0 to about 90 weight percent, the amount being determined by the purpose of the filler and the desired end-use characteristics of the intended three-dimensional object. Advantageously, the filler may be selected to maintain the optical transparency of the photohardenable composition, for example, by controlling the particle size to be significantly smaller than the excitation wavelength, or by matching the refractive index of the filler and the matrix to reduce light scattering.

[0353] Fillers can be used to modify the properties of the hardened photohardenable composition, such as stiffness, strength, toughness, impact resistance, creep resistance, fatigue resistance, mechanical energy return, mechanical loss tangent, glass transition temperature, thermal degradation temperature, thermal conductivity, heat resistance, water absorption, electrical conductivity, static dissipation, dielectric constant and loss tangent, density, refractive index, light dispersion, opacity to ionizing radiation, and resistance to ionizing radiation. Fillers can also be used to modify the properties of the liquid photohardenable composition, such as rheological properties (e.g., viscosity and thixotropy) and optical properties (e.g., refractive index). Examples of fillers include, but are not limited to, silica, alumina, zirconium oxide; 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 lithophane, montmorillonite, bentonite, kaolinite, hectorite and halloysite; calcium phosphate minerals such as hydroxyapatite, mineral fillers such as chalk, rock dust, slag dust, fly ash, hydraulic cement, loess, limestone, 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 (particularly less than about 100 nm) can be beneficial in providing high optical clarity of the liquid composition to better facilitate printing. Controlling the particle size distribution (eg, monodisperse, bimodal, or trimodal distribution of particle sizes) can be beneficial in controlling rheological properties, increasing filler weight percentage, or otherwise altering the properties of the photohardenable composition.

[0354] Thixotropic Agents / Rheology Modifiers

[0355] Thixotropic agents and rheology modifiers suitable for inclusion in the photohardenable compositions described herein include, for example, but are not limited to, urea derivatives; modified urea compounds such as Rheobyk 410 and Rheobyk-D available from BYK-Chemie GmbH (part of the ALTANA Group); 410; fumed metal oxides (also known as pyrogenic metal oxides), including, for example, but not limited to, fumed silica, fumed alumina; zirconium oxide; precipitated metal oxides, including, for example, but not limited to, precipitated silica, precipitated alumina; unmodified and organically modified layered silicate clays; dimerized and trimerized fatty acids; polyether phosphates; oxidized polyolefins; oxidized polyolefins blended 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; polyalkylene oxide-terminated polyamides; polyether amides; acrylamidomethyl-substituted cellulose ester polymers; polyethylene imines; polyureas; organoclays; hydrogenated castor oil; organic alkali salts of clay minerals (e.g., montmorillonite) and other silicate-type materials; aluminum, calcium and zinc salts of fatty acids (e.g., lauric acid or stearic acid).

[0356] For information related to urea derivatives that can be used as thixotropic agents, see U.S. Patent No. 6,548,593 to Merz et al., issued on April 15, 2003, and U.S. Patent No. 9,376,602 to Walther et al., issued on June 28, 2016, which are hereby incorporated by reference in their entirety.

[0357] Thermoreversible gelling agents such as ester-terminated polyamides, tertiary amide-terminated polyamides, polyalkyleneoxy-terminated polyamides, and polyetheramides and combinations thereof may be desirable to us as thixotropic agents. 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 thixotropic agent.

[0358] It may be desirable to use a metal oxide that has been surface-treated to impart dispersibility characteristics compatible with the photohardenable resin component as a thixotropic agent.

[0359] The thixotropic agent can be included in the photohardenable composition described herein in an amount ranging from about 0.05% to about 15%, from about 0.5% to about 15%, from about 0.5% to about 10%, from about 1% to about 10% by weight of the composition, for example. Other amounts may also be determined to be useful.

[0360] The thixotropic agent is preferably included in the photohardenable composition in an amount effective to at least partially restrict movement of the three-dimensional object or one or more regions thereof in the photohardenable composition during formation.

[0361] More preferably, the thixotropic agent is included in the photohardenable composition in an amount effective to at least partially restrict movement of a three-dimensional object suspended in the volume of the photohardenable composition (not in contact with a container surface) during formation. Most preferably, the position of the object in the volume of the photohardenable composition remains a fixed position during formation of the object.

[0362] Defoaming agent

[0363] Defoamers may be included to aid in the removal of air bubbles introduced during processing and handling.A preferred defoamer is BYK 1798 (a silicone based defoamer), available from BYK-Chemie GmbH (part of the ALTANA Group).

[0364] Stabilizer

[0365] Stabilizers may be included to improve the shelf life of the photohardenable composition and / or to control the level of cure and / or spatial resolution during printing. An example of a preferred stabilizer is TEMPO (2,2,6,6-tetramethylpiperidinyloxy free radical, available from Sigma-Aldrich). Examples of other stabilizers include, but are not limited to, hindered phenols such as butylated hydroxytoluene; hydroquinone and its derivatives such as hydroquinone methyl ether; hindered amine light stabilizers; alkylated diphenylamines; and phosphites.

[0366] Deoxidizer

[0367] Oxygen scavengers may be included to react with oxygen (eg, singlet oxygen, dissolved oxygen) present in the photohardenable composition.

[0368] Non-reactive solvent diluent

[0369] Non-reactive solvent diluents may be included. Examples include, but are not limited to, acetone, amyl acetate, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, butyl acetate, cyclohexanone, decane, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, dipropylene glycol, dipropylene glycol methyl ether, ethanol, ethyl acetate, ethylene glycol, glycerine, heptane, isopropyl alcohol, isopropyl acetate, methyl ethyl ketone, N-methylpyrrolidone, propylene carbonate, propylene glycol, propylene glycol diacetate, tetrahydrofuran, tripropylene glycol methyl ether, toluene, water, xylene.

[0370] Thermally activated free radical initiators

[0371] It may also be desirable to include a thermally activated free radical initiator in the photohardenable composition. Examples of thermally activated free 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, peroxodisulfates.

[0372] When a thermally activated free radical initiator is included in the photohardenable composition, the composition may also include a resin component that is hardenable by a heat-driven reaction, in which case the component resulting from exposure to the first wavelength and the second wavelength may be heat treated to further harden the component. Examples of suitable heat-hardenable resin components include, but are not limited to, polyurethane, polyurethane-urea, and polyurea precursors; epoxy resins and epoxy curing agents; cyanate resins and phthalonitrile resins; maleimide resins, such as bismaleimide resins, used alone or with allyl curing agents; polyimide and polyamideimide precursors, including but not limited to polyamic acid (e.g., poly(pyromellitic dianhydride-co-4,4'-diaminodiphenyl ether)amic acid), polyamideamic acid (e.g., Torlon AI-30 and Torlon AI-50, available from Solvay), amines, anhydrides, and isocyanates; norbornene resins, such as nadic anhydride-terminated resins; phenolic resins; and the like. Examples of preferred thermally driven reactions or mechanisms include, but are not limited to, heating (eg, direct or indirect application of heat or thermal energy, microwave irradiation, irradiation with UV, visible light, or infrared light for heating purposes).

[0373] Inclusion of one or more resin components that can be hardened by a heat-driven reaction or mechanism in the photohardenable compositions described herein can facilitate or enable the formation of articles having features and / or performance properties that can be suitable for end-use applications that may not be suitable for articles formed from resins that include photohardenable compositions that do not contain the resin components. Examples of additional properties that can be altered by the inclusion of a second resin component include, for example, but are not limited to, mechanical, thermal, electrical, dielectric, chemical resistance, moisture resistance, and biocompatibility properties. Examples include improved mechanical properties, including increased tensile strength and modulus, flexural strength and modulus, compressive strength and modulus, impact strength, hardness, wear resistance, fatigue resistance, fracture toughness; improved thermal properties, including increased glass transition temperature, increased heat distortion temperature, increased thermal degradation temperature, or reduced coefficient of thermal expansion; reduced moisture or solvent absorption; improved radiation resistance; improved fire resistance, flame retardancy, or char yield; improved dielectric properties (e.g., reduced dielectric constant, reduced dielectric loss constant, or increased breakdown voltage); or improved optical properties (e.g., increased refractive index).

[0374] Examples of suitable resin components include, but are not limited to, polyurethanes, polyurethane-ureas, and polyurea precursors; epoxy resins and epoxy curing agents; cyanate resins and phthalonitrile resins; maleimide resins, such as bismaleimide resins, used alone or with allyl curing agents; polyimide and polyamideimide precursors, including, but not limited to, polyamic acids (e.g., poly(pyromellitic dianhydride-co-4,4'-diaminodiphenyl ether)amic acid), polyamideamic acids (e.g., Torlon AI-30 and Torlon AI-50, available from Solvay), amines, anhydrides, and isocyanates; norbornene resins, such as nadic anhydride-terminated resins; phenolic resins; and benzoxazine resins.

[0375] The photohardenable composition according to the present invention, which also includes a resin component that can be hardened by a heat-driven reaction, may include, for example, but not limited to, about 0.5 to about 95, preferably about 40 to about 95 weight % of the photohardenable resin component; about 0.0001 to about 0.5, including but not limited to about 0.0001 to about 0.05, 0.0001 to about 0.02, about 0.0001 to less than about 0.02 weight % of a photoconvertible photoinitiator; about 0.0001 to about 25 weight % of a second light-activated photoinitiator, and about 0.5 to about 95, and preferably about 15 to about 95 weight % of the resin component.

[0376] When a method includes a photohardenable composition described herein that also includes a resin component that is hardenable by a thermally driven reaction, once an object is formed by irradiation with a first wavelength and a second wavelength, the object can be removed from the volume in which it was formed, optionally washed, and then subjected to a sufficient thermally driven reaction or mechanism (e.g., heating and / or microwave irradiation) to further harden (e.g., by further reaction, further polymerization, further chain growth) the thermally hardenable resin component and form an article.

[0377] Separation of at least a portion of the hardenable object from the unhardened composition may be performed by a variety of means known in the art, such as gravity drainage, screening, air knives, centrifugation, vibration, or ultrasonic agitation.

[0378] Washing can be carried out with any suitable organic or aqueous washing liquid or a combination thereof, including solutions, suspensions, emulsions, microemulsions, etc. Examples of suitable washing liquids include, but are not limited to, water, alcohols (e.g., methanol, ethanol, isopropanol, etc.), glycol ethers, benzene, toluene, etc. Washing liquids comprising a mixture of two or more liquids (e.g., water and an alcohol (e.g., isopropanol)) may also be suitable. Such washing solutions may optionally contain additional ingredients, such as surfactants, etc.

[0379] After the object is formed, optionally washed, etc. (as described above), it can be further hardened by a heat-driven reaction or mechanism. Hardening can include heating and / or microwave irradiation to further cure it. Heating can be active heating (e.g., in an oven, such as an electric stove, a gas stove, or a solar cooker), or passive heating (e.g., at ambient temperature). Active heating can be faster than passive heating, and in some embodiments can be preferred. Passive heating (e.g., by maintaining the intermediate at ambient temperature for a time sufficient to achieve further curing) can also be desirable. Optionally, heating can include heating a first time period at a first temperature, then heating a second time period at a second temperature, then heating a third time period at a third temperature, etc., to achieve any number of temperatures and time periods. Temperatures and time periods can be selected to promote volatiles to evaporate from the product without causing damage (e.g., cracks); promote more complete curing of one or more lower temperature curing components to stabilize the product shape before the subsequent curing of one or more higher temperature curing components; or develop higher thermomechanical properties. Differential scanning calorimetry can help determine the temperature and time period suitable for curing by indicating that the curing reaction begins and reaches the temperature of its maximum rate (for example, in a temperature increase experiment) and indicating how much time is needed to complete the curing reaction (for example, in an isothermal experiment). The time period can be the same length or different. In certain embodiments, the first temperature can be ambient temperature or higher than ambient temperature, and each subsequent temperature can be higher than the previous temperature. Preferably, the maximum temperature is enough to completely or substantially completely harden or solidify the hardenable resin composition, but below the degradation temperature, for example, as measured by a 5% mass loss temperature of thermogravimetric analysis. When using multiple temperatures, the temperature can be ramped, for example, by progressively increasing.

[0380] Second light activated photoinitiator

[0381] Optionally, the photohardenable composition may further include a light activated photoinitiator. Preferably, such photoinitiator does not significantly respond to light of the first wavelength or the second wavelength. It may be desirable to include a photoinitiator in connection with optional post-processing, including, for example, a post-curing step involving exposing the printed object to UV light after printing.

[0382] If a second light-activated photoinitiator is included in the photohardenable resin composition, the method may further include a post-curing step comprising exposing the object to light of a third wavelength to further harden the object, the third wavelength being different from the first wavelength and the second wavelength. The irradiation with the third wavelength is preferably performed after the partially hardened component is removed or separated from the volume in which it is formed. It may also be desirable to wash the separated or removed component before irradiating with the third wavelength post-cure. When the second light-activated photoinitiator is UV-activatable, the third wavelength is preferably in the ultraviolet wavelength range. A third wavelength in the range of, for example, 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 wavelength and the second wavelength may be useful.

[0383] The selection of the second photoinitiator generally takes into account the absorption band of the second photoinitiator and the wavelength of the radiation or light used to activate the second photoinitiator, as well as the first wavelength and the second wavelength used to activate the photoconvertible photoinitiator, so as to avoid undesired polymerization. As a non-limiting example, a second photoinitiator that can be activated by UV or visible wavelength light is available. In the selection process, other factors such as absorption coefficient, rate constant of primary free radicals to photohardenable resin components, possible side reactions, and light intensity may also be considered and balanced. See, for example, A, Eibel et al., "Choosing the ideal photoinitiator for free-radical photopolymerizations: predictions based on simulations using established data", Polym. Chem., 2018, 9, 5107-5115.

[0384] It is desirable that the second photoinitiator exhibits no or minimal absorption at the first wavelength and the second wavelength.

[0385] Preferably, the third wavelength is not directed into the volume during formation of the partially hardened object therein.

[0386] Preferably, the third wavelength is smaller than the first wavelength and the second wavelength.

[0387] The second photoinitiator preferably comprises a photoinitiator (also referred to herein as a free radical photoinitiator) that initiates polymerization or crosslinking of the photohardenable resin component by a free radical reaction. The second photoinitiator may comprise a Type I photoinitiator (Type I photoinitiators may also be referred to as Norrish Type I photoinitiators in the art). The second photoinitiator may comprise a Type II photoinitiator (Type II photoinitiators may also be referred to as Norrish Type II photoinitiators in the art). It may be preferred to comprise a single-component second photoinitiator, such as a Type I photoinitiator, that does not significantly absorb light of the first wavelength or the second wavelength.

[0388] Examples of the second photoinitiator include, but are not limited to, acetophenone, anisole, anthraquinone, benzil, benzoin, benzoin ethyl ether, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, 4,4'-bis(diethylamino)benzophenone, thioxanthone, 2-chlorothioxanthone, dibenzosuberenone, 2,2'-diethoxyacetophenone, 4,4'-dihydroxybenzophenone, 2, 2-Dimethoxy-2-phenylacetophenone, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO), 4'-ethoxyacetophenone, 3'-hydroxyacetophenone, 4'-hydroxyacetophenone, 3-hydroxybenzophenone, 1-hydrocyclohexylphenyl ketone, 2-hydroxy-2-methylpropiophenone, methyl benzoylformate, 2-methyl-4'-(methylthio)-2-morpholinopropiophenone, phenanthrenequinone, 4'-phenoxyacetophenone.

[0389] An example of a preferred second photoinitiator comprising a free radical photoinitiator is Omnirad 184 (1-hydroxycyclohexyl-phenyl ketone) available from IGM.

[0390] Exposure of the second photoinitiator to light of a third wavelength can advantageously initiate a change or alter at least one chemical or physical property of the previously unaltered photohardenable composition included in the object, typically through a crosslinking or polymerization reaction in the photohardenable composition, to further harden the initial print or partially hardened object.

[0391] Preferably, the second photoinitiator exhibits no or minimal absorption at the first wavelength and the second wavelength.

[0392] It may be desirable for the second photoinitiator to not be activated or significantly activated by either the first wavelength or the second wavelength to avoid undesired reactions in the photohardenable composition without exposure to the third wavelength.

[0393] Post-curing of the initial print or partially hardened object can be performed with light of a third wavelength to further harden (e.g., further polymerize or crosslink). Preferably, exposure to the third wavelength is performed after the partially hardened object is separated from the volume in which it was formed. It may be desirable to wash the separated object before irradiating the object with light of the third wavelength.

[0394] The nature of the monomers, the amount of photoconvertible photoinitiator, and, where applicable, co-initiator and / or sensitizer in the photohardenable compositions according to the present invention will vary depending on the specific use of the composition, the emission characteristics of the exposure source, the development procedure, the physical properties desired in the polymerized product, and other factors.

[0395] Examples of photohardenable compositions including one or more co-initiators and / or sensitizers according to certain aspects of the present invention generally have a composition in parts by weight [based on 100 parts total] falling within the following composition ranges:

[0396] Photocurable resin component: about 10 to 99.9999

[0397] Photoconvertible photoinitiator: about 0.0001 to about 0.5, including, for example 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.

[0398] Coinitiator (optional): about 0.001 to about 10, including for example 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.

[0399] Sensitizer (optional): about 0.1 to 1, including, for example 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, and the like.

[0400] Examples of photohardenable compositions according to certain aspects of the present invention that do not include one or more co-initiators and / or sensitizers generally have a composition in parts by weight [based on 100 parts total] that falls within the following composition ranges:

[0401] Photocurable resin component: about 10 to about 99.9999

[0402] Photoconvertible photoinitiator: about 0.0001 to about 0.5, including, for example 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.

[0403] When a coinitiator is optionally further included in the photohardenable composition, it may be included in the composition range as set forth above in parts by weight [based on 100 parts in total].

[0404] The weight percentage of the photohardenable resin component in the above exemplary composition can be less than 10 weight percent, for example less than 5 weight percent, less than 3 weight percent, less than 2 weight percent, or 1 weight percent or less, in some cases such as printing of hydrogels, where the remainder of the resin is composed of non-reactive components suspended in the final photohardening resin.

[0405] Optionally, the photohardenable composition according to the present invention may also include a second light-activated photoinitiator that preferably does not respond significantly to light of the first wavelength or the second wavelength. Inclusion of such a light-activated photoinitiator in connection with an optional post-curing step with UV light after printing may be desirable in any post-processing of the printed object.

[0406] When a second photoactivated photoinitiator is further included in the photohardenable composition, it may be included, for example, in a composition range ranging from about 0.0001 to about 25% by weight [based on a total of 100 parts], including, for example, but not limited to, 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, and the like.

[0407] The photohardenable compositions according to the present invention can be prepared using known or conventional procedures.

[0408] If a second light-activated photoinitiator is included in the photohardenable resin for post-curing purposes, the method may further include a post-curing step comprising exposing the object to light at a third wavelength to further harden the object, the third wavelength being different from the first wavelength and the second wavelength. When the photoinitiator is UV-activatable, the third wavelength is preferably in the ultraviolet wavelength range.

[0409] Example

[0410] Example 1

[0411] Preparation of Photoconvertible Photoinitiators

[0412] All photoswitchable photoinitiators reported herein were obtained using different Suzuki coupling reactions as depicted in Scheme 1. The structures and characterizations of (III)-(XXX) are shown in Table 1. For the synthesis of photoswitchable photoinitiators (III)-(XXI) (Scheme 1a), halide-functionalized diarylethenes (1–4) and boronated sensitizers (5–13) were combined. A complementary approach was adopted to synthesize photoswitchable photoinitiators (XXII)-(XXX) (Scheme 1b), where the final step placement of a series of heterocycles could be achieved by cross-coupling of boronates 14 and 15 with commercially available heterocyclic halides.

[0413] 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.

[0414]

[0415] Route 1. Different synthetic routes for photo-switchable photoinitiators (III)-(XXX).

[0416] General procedure for the synthesis of photo-switchable photoinitiators (III)-(XXX) as depicted in Scheme 1:

[0417] Halide and borate substrates *, Pd XPhos G3 (0.03 equivalents), potassium phosphate (5.0 equivalents) and a magnetic stirring bar were added to a 4 mL amber vial. The vial was sealed with a Teflon-lined cap and placed under a N2 atmosphere for three vacuum / N2 cycles. Then, a 5:1 mixture (v / v) (2 mL) of deoxygenated dioxane: water was added to the vial via a syringe. The vial was sealed with electrical tape and placed on a heating block set to 90° C., and the mixture was then stirred for 2 hours. The mixture was distributed between CH2Cl2 (4 mL) and water (4 mL), the organic layer was dried and filtered with Na2SO4, and the volatiles were then removed at 40° C. via rotary evaporation. The residue was subjected to preparative thin layer chromatography (hexane / CH2Cl2 or CH2Cl2 / EtOAc solvent system) to obtain the desired diarylethene photoconvertible photoinitiator (III)-(XXX). In several cases, both mono- and di-substituted analogs were isolated as part of a statistical mixture from the same reaction (eg, (III) and (IV)). The isolated compounds and characterization data are summarized in Table 1 below.

[0418] *For the synthesis of III-XXI (Scheme 1a), the substrates were halide functionalized diarylethenes 1, 2, 3, or 4 (50 mg) and boronated sensitizers (5-13, 1 eq.). For the synthesis of XXII-XXX (Scheme 1b), the substrates were boronate esters 14 or 15 (50 mg, 1 eq.) and commercially available heteroaryl halides (2 eq.).

[0419] Table 1

[0420]

[0421]

[0422]

[0423]

[0424]

[0425]

[0426]

[0427]

[0428]

[0429]

[0430]

[0431]

[0432] Synthesis of diarylethene starting material 4

[0433]

[0434] 3-bromo-5-chloro-2-methylthiophene (2.33 g, 11.0 mmol, 1.1 equivalents), anhydrous diethyl ether (30 mL) and a magnetic stirring bar were loaded into a 100 mL flame-dried Schlenk flask. The stirred solution was cooled to -78 ° C with a dry ice / acetone bath, and n-BuLi (2.5 M in hexane, 4.0 mL, 10.0 mmol, 1.0 equivalents) was then added dropwise via a syringe within 3-5 minutes. The mixture was stirred at -78 ° C for 30 minutes, and perfluorocyclopentene (4.2 g, 20 mmol, 2.0 equivalents) was then added quickly via a syringe. After being kept at -78 ° C for another 3-5 minutes, the cooling bath was removed, and the mixture was allowed to warm to room temperature. After 1 hour at room temperature, the mixture was quenched with saturated NH4Cl aqueous solution (30 mL). The layers were separated and the organic layer was washed with saturated aqueous NaCl solution (30 mL), dried over Na2SO4, filtered, and the solvent was removed from the filtrate via rotary evaporation. The residue was purified by column chromatography (100% hexanes) to give compound 16 (1.62 g, 50%) as a colorless liquid. The liquid was used directly in the next step without characterization.

[0435] 2-Bromo-3,5-dimethylthiophene (540mg, 2.83mmol, 1.2 equivalents), anhydrous diethyl ether (10mL) and a magnetic stirring bar were loaded into a 25mL flame-dried Schlenk flask. The stirred solution was cooled to -78°C with a dry ice / acetone bath, and n-BuLi (2.5M in hexane, 1.04mL, 2.59mmol, 1.1 equivalents) was then added dropwise via a syringe in about 1 minute. The mixture was placed in an ice / water bath for 15 minutes, and then placed back in a -78°C bath for about 5 minutes. Compound 16 (765mg, 2.36mmol, 1.0 equivalents) was added dropwise via a syringe in about 1 minute. After being kept at -78°C for another 3-5 minutes, the cooling bath was removed, and the mixture was allowed to warm to room temperature. After 1 hour at room temperature, the mixture was quenched with a saturated NH4Cl aqueous solution (20mL) and extracted with EtOAc (20mL). The organic layer was washed with saturated aqueous NaCl solution (30 mL), dried over Na2SO4, filtered, and the solvent was removed from the filtrate via rotary evaporation. The residue was purified by column chromatography (100% hexanes) to give Compound 4 (0.57 g, 58%) as a colorless crystalline solid.

[0436] Synthesis of borate esters 5-13

[0437]

[0438] Commercially available aryl halides (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 stirring bar were added to a 40 mL screw cap vial. The vial was sealed and placed under a N2 atmosphere for three vacuum / N2 cycles. Anhydrous deoxygenated dioxane (10 mL) was added via a syringe and the vial was sealed with electrical tape. The mixture was stirred at 90°C (heating block temperature) for 12-24 hours, then the mixture was allowed to reach room temperature and diluted with CH2Cl2 (30 mL). The mixture was filtered through a solvent-equilibrated silica gel plug (20 g). The plug was rinsed with CH2Cl2 containing 20% ​​EtOAc until the product was no longer observed by thin layer chromatography. The filtrate was concentrated via rotary evaporation, and the crude boronate was recrystallized from hexane or used without further purification. The following boronated polycyclic compounds were prepared and isolated using this procedure:

[0439]

[0440] Synthesis of building blocks 14 and 15.

[0441]

[0442] (a) Pd(dppf)Cl2 (0.03 eq.), K2CO3 (5 eq.), dioxane / water, 90°C; (b) (Bpin)2 (1.1 eq.), Pd(dppf)Cl2 (0.03 eq.), KOAc (2.5 eq.), dioxane, 90°C; (c) AlCl3 (1.5 eq.), CH2Cl2

[0443] Example 2

[0444] Base resin preparation

[0445] 10.0g thixotropic agent (Crystasense HP-5, Croda) is loaded into the 100-mL round-bottom flask containing a magnetic stirring bar. Then 50.0g N, N-dimethylacrylamide (DMAA, Rahn) is added to the flask via a syringe. The flask is sealed with a rubber septum, and a 1-inch 22G needle is inserted for ventilation. The flask is placed on a preheated (105°C) aluminum heating block, and the mixture is stirred at 250-300rpm until the thixotropic agent is completely dissolved (10-15 minutes). Next, 50.0g DMAA is loaded into a 0.6-gallon polypropylene bucket equipped with a polypropylene cap via a syringe. Then, 200g of Genomer 4259 (Rahn) and 650g of Genomer 4247 (Rahn) are added to the bucket via a large-bore syringe. The contents of the bucket were rapid mixed (DAC 2800-1000, Flacktek) at 1100 rpm for 1 minute. The HP-5 solution was then poured into the bucket and the contents of the bucket were rapid mixed at 1100 rpm for another 1 minute.

[0446] Example 3

[0447] Preparation of Resin Formulation 1 Comprising One of Compounds (III)-(XXX) and a Polymerization Enhancer for Voxelization Studies

[0448] First, a stock solution of one of the photoconvertible photoinitiators (III)-(XXX) was prepared by dissolving the photoconvertible photoinitiator in N,N-dimethylacrylamide (DMAA, Rahn) in a 4 mL amber vial to a final concentration of 1.00 mg / g photoconvertible photoinitiator in DMAA. Then, 0.60 g of the photoconvertible photoinitiator stock solution (20 ppm by mass of photoconvertible photoinitiator) and 0.90 g of N-methyldiethanolamine (3% by mass of polymerization synergist) were added to a 40 mL amber vial containing 28.5 g of the base resin (described above). The contents of the vial were rapidly mixed (DAC 2800-1000, Flacktek) at 3500 rpm for 1 minute to obtain resin formulation 1. The preparation was transferred into 1 cm plastic cuvettes (Einmal-Küvetten), which were capped and centrifuged at 4000 rpm for 3 minutes (5804R, Eppendorf) to remove trapped air bubbles.

[0449] Example 4

[0450] Evaluation of Photo-Switchable Photoinitiation in Resin Formulation 1 under Intersecting Beams of UV and Visible Illumination Light

[0451] A centrifuged bubble-free cuvette containing Resin Formulation 1 (prepared as described above) was placed in a setup featuring two intersecting, nearly 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 0.6W / cm 2 (“Condition 2”), and the irradiance of the 520nm light source was 1.7W / cm 2 (all cases). The sources were orthogonal to each other and intersected at the center of a 1 cm x 1 cm square cuvette. The time taken for the convergence point to form was recorded and this served as a proxy for part formation in the printer ("voxel time"). In separate experiments, different cuvettes were subjected to an irradiance of only 0.22 W / cm 2 (“Condition 1”) or 0.6W / cm 2 ("Condition 2") 408 nm irradiation. The time taken for polymerized areas to form was recorded and this served as a proxy for curing by the UV light sheet in the printer ("Light Sheet Time"). The times reported in Table 1 are the average of 2-3 measurements.

[0452] In this study, two indicators were used to predict the performance of photoconvertible photoinitiators for 3D printing: (1) the ratio of "light sheet time" to "voxel time"; (2) the value of "voxel time". Larger values ​​of 1 and smaller values ​​of 2 contribute to better performance. For example, it has been found that under the conditions of Example 4, the ratio of (UV light curing time) / (voxel curing time) is at least one (1) and the voxel curing time is 30 seconds or less, and preferably the ratio of (UV curing time / voxel curing time) is at least 1.2 and the voxel curing time is less than 15 seconds can be used to screen preferred photoconvertible photoinitiators for 3D printing.

[0453] Without being bound by theory, it is believed that a ratio of (UV light curing time) / (voxel curing time) of no greater than one or a curing time of greater than 30 seconds should not be interpreted as a particular photoconvertible photoinitiator being unsuitable for three-dimensional printing. However, it is expected that these results can be used as an indication of changing one or more printing conditions (e.g., photoconvertible photoinitiator and / or synergist concentration, power level of one or both excitation lights, printing temperature, and / or one or both excitation wavelengths) to obtain better printability. Such adjustments are routine for one of ordinary skill in the art without undue experimentation.

[0454] Example 5

[0455] Example of the procedure for printing an object with AE4

[0456] A. Preparation of Resins

[0457] A stock solution was prepared by dissolving 80 mg of Compound No. AE4 (prepared as described in Example 1) in 25 mL of N,N-dimethylacrylamide.

[0458] Separately, 25 ml of N,N-dimethylacrylamide was mixed with 70 ml of isobornyl acrylate and 5.5 g of Crystalsense HP5 (Croda). The solution was stirred at 80°C to completely dissolve and homogenize the components.

[0459] A third solution was prepared by mixing 650 grams of Genomer 4247 (Rahn) and 200 grams of Genomer 4259 (Rahn) in a Flaktek high speed mixer bucket at 60°C. To this warm solution was added a solution containing Crystalsense HP5 and the resulting mixture was rapidly mixed at 1000 RPM for 1 minute (DAC 2800-1000, Flaktek). Then, a solution containing a photo-switchable photoinitiator was added and the mixture was rapidly mixed at 1000 RPM for another minute. Finally, 60 grams of N-methyldiethanolamine was added to the bucket and the entire mixture was rapidly mixed at 1000 RPM for another minute.

[0460] The mixture was then centrifuged to remove air bubbles and dispensed by pouring into a 20 mm long, 20 mm wide, 45 mm high glass cuvette and allowed to cool to room temperature before printing.

[0461] B. Printing process

[0462] A cuvette of the photohardenable composition was placed in a holder on a motorized stage. A digital micromirror device (Texas Instruments) was illuminated using green laser (532 nm CW diode laser, 20 W operating power) to form a pattern that was projected into the cuvette along the z-axis to generate approximately 1.6 W / cm 2 Green light pattern. Violet light (405nm CW diode laser, 50-365mW operating power) is used to form a light sheet that passes through the cuvette orthogonal to the projected pattern to illuminate a single xy plane that is nominally 100 microns thick. The light sheet passes through two lenses and reflects from a mirror so that it passes through the resin a second time in the opposite direction in approximately the same beam path as the forward propagating sheet to combine to form a forward and reverse propagating combined light sheet (generally as described in International Patent Application No. PCT / US2022 / 052157 filed by Quadratic 3D, Inc. on December 7, 2022), but the photoconvertible photoinitiators described herein can be used for stereoscopic printing using a variety of different light sheets and projector geometries. In this printing experiment, the violet laser diode was operated at 200mW to produce approximately 0.66W / cm 2 irradiance of . The platform is advanced in 14 micron increments at 250 millisecond intervals, with the violet light forming a light sheet and the green light pattern changing at each advance corresponding to a slice of the computer-generated three-dimensional object. In areas exposed to both wavelengths of light simultaneously or nearly simultaneously, the photohardenable composition hardens. In this way, three-dimensional solid objects are formed without displacement (e.g., sinking or floating) and without the need for support structures or build platform attachments due to the high zero shear viscosity or yield stress of the non-Newtonian photohardenable composition. The parts are removed from the resin using a scraper, washed by stirring in isopropyl alcohol for 2 minutes, allowed to dry for 10 minutes, and then further post-cured for 10 minutes using Formlabs Form Cure.

[0463] Typically, a photograph of a part printed according to the procedure described in this Example 5 is shown in Figure 1A , 1B and 1C. The printed part reproduces the features of the target object in all three dimensions. Figure 1D , 1E 1F and 1F show the front view, back view, and side view of the 3D model shape targeted for printing.

[0464] Example 6

[0465] Example of a procedure for printing an object with AE32

[0466] Printing experiments generally as described in Example 5 were carried out using Compound No. AE32 as the photo-switchable photoinitiator, as detailed in this Example 6.

[0467] A. Preparation of Resins

[0468] The resin preparation was carried out generally as described above in Example 5, except that 20 mg of Compound No. AE32 (prepared as described in Example 1) was used instead of 80 mg of Compound No. AE4.

[0469] B. Printing process

[0470] Printing was generally performed as described in Example 5 above to print parts using the resin prepared as described in paragraph 6A of this example, except that printing was performed at 40°C, the platform was advanced in 28 micron increments at intervals of 150 milliseconds, and the UV irradiance was 0.50 W / cm 2 , and the green light irradiance is 1.0W / cm 2 .

[0471] Typically, a photograph of a part printed according to the procedure described in Example 6 is shown in Figure 2A , 2B and 2C. The component faithfully reproduces the features of the target object in all three dimensions. Figure 2D , 2E 2F and 2F show the front view, back view, and side view of the 3D model shape targeted for printing.

[0472] Example 7

[0473] Example of a procedure for printing an object with AE39

[0474] Printing experiments generally as described in Example 5 were carried out using Compound No. AE39 as the photo-switchable photoinitiator, as detailed in this Example 7.

[0475] A. Preparation of Resins

[0476] The resin preparation was carried out generally as described above in Example 5, except that 40 mg of AE39 (prepared as described in Example 1) was used in place of 80 mg of AE4.

[0477] B. Printing process

[0478] Printing was generally performed as described in Example 5 above to print parts using the resin prepared as described in paragraph 7A of this example, except that printing was performed at 40°C, the platform was advanced in 28 micron increments at intervals of 280 milliseconds, and the UV irradiance was 1.0 W / cm 2 , and the green light irradiance is 1.6W / cm 2 .

[0479] Typically, a photograph of a part printed according to the procedure described in this Example 7 is shown in Figure 3A , 3B and 3C. The component faithfully reproduces the features of the target object in all three dimensions. Figure 3D , 3E 3F and 3F show the front view, back view and side view of the 3D model shape targeted for printing.

[0480] Example 8

[0481] Examples of printing an object in a photohardenable composition comprising a photohardenable photoinitiator represented by Formula XXI above (Compound No. AE32) and a photohardenable resin component with and without a second photoinitiator

[0482] A. Preparation of photoconvertible photoinitiator compound No.AE32.

[0483] Compound AE32 was prepared according to the procedure described in Example 1.

[0484] B. Preparation of base resin

[0485] 25 ml of N,N-dimethylacrylamide was mixed with 70 ml of isobornyl acrylate and 5.5 g of Crystalsense HP5 (Croda). The solution was stirred at 80° C. to completely dissolve and homogenize the components.

[0486] A second solution was prepared by mixing 650 grams of Genomer 4247 (Rahn) and 200 grams of Genomer 4259 (Rahn) in the bucket of a Flaktek high speed mixer at 60°C.

[0487] To this warm solution was added the solution containing Crystasense HP5 and the resulting mixture was speed mixed at 1000 RPM for 1 minute (DAC 2800-1000, Flacktek).Finally, 60 grams of N-methyldiethanolamine was added to the high speed mixer bowl and the entire mixture was speed mixed at 1000 RPM for another 1 minute.

[0488] C. Preparation of Resin Formulation Containing Compound No.AE32

[0489] A stock solution of the photoconvertible photoinitiator was prepared by dissolving the photoconvertible photoinitiator (prepared as described in Example 1) in 25 mL of a 1:1 v / v mixture of N,N-dimethylacrylamide (DMAA, Rahn) and benzyl acrylate (Beantown chemical) in a 40 mL amber vial to a final concentration of approximately 0.75 mg / mL of the photoconvertible photoinitiator in the solvent. 0.30 mL of the photoconvertible photoinitiator stock solution was added to 14.7 grams of the above base resin to create a resin formulation containing 15 ppm of the photoconvertible photoinitiator. The resin formulation was rapidly mixed (DAC 2800-1000, Flacktek) at 3000 rpm for 1 minute.

[0490] D. Preparation of Test Samples

[0491] Two test samples were prepared as set forth below: one including the second photoinitiator, and one not including the second photoinitiator.

[0492] To prepare test samples including a second photoinitiator, 0.6 wt% 1-hydroxycyclohexyl-phenyl ketone (Omnirad 184, IGM Resins, CAS No. 947-19-3) was added to 1 kg of resin prepared generally as described in Example 8C, and the mixture was stirred until all solids dissolved. It was centrifuged at 4500 rpm for 5 minutes (5804R, Eppendorf) to remove bubbles and poured into a custom quartz cuvette with internal dimensions of 2×2×4 cm for printing.

[0493] In the case of test samples that did not include a second photoinitiator, 500 grams of the base resin formulation (prepared generally as described in Example 8C) was centrifuged at 4500 rpm for 5 minutes (5804R, Eppendorf) to remove air bubbles and poured into a custom quartz cuvette with an internal dimension of 2×2×4 cm for printing. E. Printing of objects in resin containing compound No. AE32 with and without a second light-activated photoinitiator

[0494] Two cuvettes (each containing one of the two samples described in Example 8D) were prepared for printing: one containing the second photoinitiator and the other not containing the second photoinitiator.

[0495] One cuvette including the sample described in Example 8D containing the second photoinitiator and another cuvette including the sample described in Example 8D without the second photoinitiator were used to print a 7×7×7 mm cube as generally described in this Example 8E.

[0496] These cuvettes are loaded into the following printing devices:

[0497] Purple light (408 nm mW diode laser, 365 mW maximum operating power) is irradiated from a scanning galvanometer to generate a light sheet approximately 130 microns thick, and is reflected from a mirror and folded back a similar beam path to achieve a combined double-pass light sheet (generally as described in International Patent Application No. PCT / US2022,052157 filed by Quadratic 3D, Inc. on December 7, 2022), with an irradiance of 0.50 W / cm 2 The light was projected at 1.0 W / cm2 orthogonally to the light sheet using a Texas Instruments DMD. 2 The projected green light green irradiation (532 nm laser, 18 watt maximum operating power continuous wave diode laser) intersects orthogonally so that the projected green light is spatially patterned.

[0498] Print a 7×7×7 mm cube in each cuvette using the following print settings:

[0499] 40 degrees Celsius, 28 micron stage movement interval, 150 milliseconds exposure per slice. In each case, the cube was successfully printed and then washed by agitation in isopropanol for 1 minute and allowed to dry for 10 minutes, and then post-cured in a cured form under nitrogen for 10 minutes (9.1 watt 396nm center LED irradiation).

[0500] For these cubes, the hardness was tested using a Shore D hardness tester to compare the conversion of the resin to the polymer. In the cube printed in the resin without any second photoinitiator, the Shore D hardness after this post-curing protocol was 65D, while in the resin containing the second photoinitiator, the cube printed had a Shore D hardness of 87D.

[0501] Observation: The inclusion of a second photoinitiator activatable at wavelengths shorter than 405 nm appears to be substantially inactive at both printing wavelengths and results in a more complete post-cure without substantially affecting the print setup.

[0502] The light sheet may be constructed by means known in the art, including, for example but not limited to, techniques including lasers and Powell prisms, galvanometers, and / or polygonal scanning mirrors. Alternatively, one or more LEDs may be used as the light source.

[0503] Information that may be useful related to the invention disclosed in this article includes International Patent Application No. PCT / US2021 / 035791 of Quadratic 3D, Inc., “Volumetric Three-Dimensional Printing Methods Including A LightSheet And Systems” filed on June 3, 2021, and U.S. Patent No. 10,843,410 of Lippert et al., “System And Method For A Three-Dimensional Optical Switch Display (OSD) Device”; International Application No. PCT / US2022 / 039766 of Quadratic 3D, Inc., “Methods And Systems ForForming An Object In AVolume Of APhotohardenable Composition” filed on August 9, 2022, 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).

[0504] As used herein, unless otherwise provided, "alkyl" refers to a branched or straight chain fully saturated aliphatic hydrocarbon group or a monocyclic or polycyclic saturated aliphatic hydrocarbon ring system. Examples include, but are not limited to, alkyl groups having 1 to 20 (more typically 1 to 10) carbon atoms, which may be straight chain, branched, or cyclic alkyl groups. Alkyl groups may contain only carbon and hydrogen atoms, or may also introduce one or more heteroatoms such as Si, N, O or S as part of the alkyl group (which may also be referred to as a heteroalkyl group).

[0505] As used herein, unless otherwise provided, "alkoxy" refers to a straight or branched chain alkyl moiety covalently bonded to the parent molecule through an -O- bond. Examples include, but are not limited to, alkoxy groups having 1 to 20 (more typically 1 to 10) carbon atoms, which may be straight chain, branched, or cyclic alkoxy groups, examples of which include, but are not limited to, methoxy (MeO), ethoxy (EtO), and the like.

[0506] As used herein, unless otherwise provided, "aralkyl" or "arylalkyl" may also refer to an alkyl moiety substituted with an aryl group. Examples include, but are not limited to, aralkyl groups having 7 to 20 carbon atoms, examples of which include, but are not limited to, benzyl, methylphenyl, ethylphenyl, and the like.

[0507] As used herein, unless otherwise provided, "cycloalkyl" may also refer to a saturated aliphatic ring system portion having at least three carbon atoms. Examples include, but are not limited to, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and the like. A cycloalkyl group may contain a saturated aliphatic ring system containing only carbon atoms, or may also introduce one or more heteroatoms such as Si, N, O, or S as part of the ring group (which may also be referred to as a heteroalkyl group).

[0508] As used herein, unless otherwise provided, "heteroalkyl" may also refer to an alkyl group containing one or more heteroatoms. When two or more heteroatoms are present, they may be the same or different. Examples of heteroalkyl groups include, but are not limited to, CH2-OH, OC n H .2n+1 , where n is any integer greater than or equal to 1.

[0509] As used herein, unless otherwise provided, "aryloxy" refers to an aryl moiety covalently bonded to the parent molecule through an -O- linkage.

[0510] As used herein, unless otherwise provided, "heteroatom" refers to any atom that is not hydrogen or carbon. 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.

[0511] As used herein, unless otherwise provided, "alkenyl" refers to a monovalent straight or branched hydrocarbon chain or monocyclic or polycyclic hydrocarbon ring moiety containing, for example, two to twenty carbon atoms, containing a carbon double bond. Examples include, but are not limited to, 1-propenyl, 2-propenyl, 2-methyl-1-propenyl, 1-butenyl, 2-butenyl, and the like. Cycloalkenyl groups may contain only carbon and hydrogen atoms, or may also introduce one or more heteroatoms such as Si, N, O, or S as part of an alkyl group (which may also be referred to as a heteroalkenyl group).

[0512] As used herein, unless otherwise provided, "cycloalkenyl" may also refer to a monocyclic or polycyclic hydrocarbon ring system moiety having at least three carbon atoms. Examples include, but are not limited to, cyclopropenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, and the like. A cycloalkenyl group may contain a monocyclic or polycyclic hydrocarbon ring system containing only carbon rings, or may also introduce one or more heteroatoms such as Si, N, O, or S as part of the ring group (which may also be referred to as a heterocycloalkenyl group).

[0513] As used herein, unless otherwise provided, "amido" refers to -NRC(=O)R', wherein R and R' may be the same or different, wherein R and R' may independently represent, for example but not limited to, hydrogen, alkyl, or aryl.

[0514] As used herein, unless otherwise provided, "amino" refers to -NRR', wherein R and R' may independently represent, for example but not limited to, hydrogen, alkyl, or aryl.

[0515] As used herein, unless otherwise provided, "carboxyl ester" may also refer to -C(=O)O. Examples include groups of the structure -COOR or -OCOR, where R may represent, for example, but not limited to, hydrogen, alkyl, or aryl.

[0516] As used herein, unless otherwise provided, "carboxy" may also refer to -COOH.

[0517] As used herein, "carbonyl" refers to any group comprising a -C(═O) moiety, wherein C is bonded to two other atoms. Examples of carbonyl groups include groups comprising a carbonyl moiety or a moiety comprising a carbonyl moiety. For example, a carbonyl group may include a group comprising an aldehyde (-C(═O)H) moiety, a ketone (-CC(═O)-C moiety, an ester (-C(═O)-OC') moiety, an acyl (-CC(═O)-) moiety, a carboxyl (-C(═O)OH group, a thioester (-C(═)OSR') moiety, a primary amide (-CC(═O)N(non-C)2 moiety (where N is attached to one C), a secondary amide (-CC(═O)NHC- moiety (where N is attached to two Cs), a tertiary amide (-C(═O)NCC moiety (where N is attached to three Cs), and the like.

[0518] As used herein, unless otherwise provided, "aryl" refers to any aromatic carbocyclic or heterocyclic group containing unsaturated C-C bonds conjugated to each other, whether one ring or multiple fused rings. Examples of aryl groups include, but are not limited to, aryl groups including, for example, 5 to 20 carbon atoms, examples of which include, but are not limited to, phenyl, naphthyl, phenanthrenyl, etc. Examples of "aryl" substituents include, but are not limited to, phenyl, naphthyl, anthracene, tetraphenyl, fluorenyl, pyrenyl, etc., or any aromatic heterocyclic group such as pyridine, pyrazine, indole, purine, furan, thiophene, pyrrole, etc. The aryl group can contain only carbon and hydrogen atoms, or one or more heteroatoms such as Si, N, O or S can also be introduced as part of the alkyl group (which can also be referred to as a heteroaryl group).

[0519] As used herein, unless otherwise provided, "heteroaryl" may also refer to an aromatic ring system portion, wherein one or more ring atoms are heteroatoms, whether one ring or multiple fused rings. When there are two or more heteroatoms, they may be the same or different. In a fused ring system, one or more heteroatoms may be present only in one ring. Examples of heteroaryl groups include, but are not limited to, benzothiazolyl, benzoxazolyl, quinazolinyl, quinolyl, isoquinolyl, quinoxalinyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, pyrrolyl, oxazolyl, indolyl, thiazolyl, etc.

[0520] As used herein, unless otherwise provided, a group, part or molecule can be substituted or unsubstituted. "Substituted" group refers to a group, part or molecule (atomic group or non-hydrogen atomic group replacing hydrogen) having at least one hydrogen substituted by an atomic group or a non-hydrogen atomic group. When substituted, one or more substituent groups 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, alkoxy, ester, thioester, acyl, carboxyl, carbonyl, cyano, nitro, amino, amide, halogen (e.g., fluorine, chlorine, bromine, iodine) or sulfur. When the substituted group includes more than one substituent, the substituent can be bonded to the same atom or two or more different atoms in the group. The substituent including the atomic group can also be optionally substituted.

[0521] When used as a feature of a portion of a container or build chamber, "optically transparent" means having high optical transmittance for the wavelength of light used, and "optically flat" means being distortion-free (e.g., an optical wavefront entering a portion of a container or build chamber is largely unaffected).

[0522] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an emissive material includes reference to one or more of such materials.

[0523] The applicant has introduced the full contents of all patents, patent applications, publications and other references cited or referenced in the disclosure in particular. In addition, when equivalent, concentration or other values ​​or parameters are given with a list of scope, preferred range or preferred upper limit and preferred lower limit, this should be understood as specifically disclosing all ranges (regardless of whether scope is disclosed separately) formed by any pair of any upper range or preferred value and any lower range or preferred value, and the upper and lower limits of each scope. In the case of the scope of numerical values ​​listed herein, unless otherwise noted, the scope is intended to include its endpoints, and all integers and fractions within the scope. It is not intended that the scope of the present invention is limited to the specific value listed when defining the scope.

[0524] Considering the detailed description and practice of the invention disclosed herein, other embodiments of the present invention will be obvious to those skilled in the art. It is meant that the description and examples are considered to be exemplary only, and the true scope and spirit of the present invention are represented by the following claims and their equivalents.

Claims

1. A method of forming an object in a volume of a photohardenable composition, the method comprising: (a) providing a volume including the photohardenable composition, the photohardenable composition comprising a photohardenable resin component and a photoconvertible photoinitiator, the photoconvertible photoinitiator comprising a P-type photochromic molecule, (b) irradiating one or more selected locations within the volume of the photohardenable composition with light having a first wavelength and light having a second wavelength simultaneously or sequentially, wherein the light having the first wavelength and the light having the second wavelength activate the photoconvertible photoinitiator at the one or more selected locations within the volume to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength at the one or more selected locations to at least partially form an object; as well as (c) optionally repeating step (b) irradiating the photohardenable composition at one or more selected locations in the volume that are the same as or different from one or more previously selected locations until the object is partially or completely formed.

2. A method of forming an object in a volume of a photohardenable composition, the method comprising: (a) providing a volume including the photohardenable composition, the photohardenable composition comprising a photohardenable resin component and a photoconvertible photoinitiator, the photoconvertible photoinitiator comprising a P-type photochromic molecule, (b) projecting an optical image generated by a second excitation light onto a selected position in the volume along a projection axis, wherein the optical image is oriented perpendicular to the projection axis; (c) generating a light sheet comprising a first excitation light, and directing the light sheet through the volume along a light sheet illumination axis such that the optical image intersects the light sheet at the selected location within a common plane, and wherein the light sheet overlaps the projected optical image in the volume at the selected location; as well as (d) optionally repeating steps (b) and (c) one or more times to partially or completely form the object, wherein for each group of repetitions 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.

3. The method of claim 1, wherein the photohardenable composition comprises a photohardenable 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 of claim 2, wherein the photohardenable composition comprises a photohardenable 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 1-4, wherein the P-type photochromic molecules are activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

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

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

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

12. The method of any one of claims 1-4, wherein the power density of the first wavelength light at the one or more selected locations is between about 0.01 and about 100,000 W / cm 2 and the power density of the second wavelength light at the one or more selected locations is between about 0.01 and about 100,000 W / cm 2 within the range.

13. The method of any one of claims 1-4, wherein the exposure energy of the first wavelength light at the one or more selected locations is between about 0.001 and about 1,000 mJ / cm 2 and the exposure energy of the second wavelength light at the one or more selected locations is between about 0.01 and about 100,000 mJ / cm 2 within the range.

14. The method of any one of claims 1-4, wherein when only one of the first wavelength and the second wavelength is present, the amount of time that 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 hardening of the photohardenable composition at the one or more selected locations is insufficient to cause the photohardenable composition to harden.

15. The method of any one of claims 1-4, wherein the light at the first wavelength and the light at the second wavelength are separately directed into the volume. The method of claim 15 , wherein the light at the first wavelength comprises a light sheet. The method of claim 15 , wherein the light at the second wavelength comprises an optical image. The method of claim 16 , wherein the light at the second wavelength comprises an optical image.

19. The method of claim 18, 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 orthogonal to the first direction such that the light sheet and optical image intersect at the one or more selected locations within a common plane.

20. The method of any one of claims 1-4 and 19, wherein the object at least partially formed in the photohardenable composition is maintained at a fixed position or is minimally displaced in the unhardened photohardenable composition during forming.

21. The method of claim 18, wherein the optical image comprises a two-dimensional cross-sectional slice of the object to be printed, and the optical images of the repeated steps comprise sequential two-dimensional cross-sectional slices of the object.

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

23. The method of any one of claims 1-4, wherein the P-type photochromic molecule comprises a P-type photochromic diarylcycloolefin molecule.

24. The method of 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 diaryl ketone group, a substituted or unsubstituted α-diketone, a polycyclic group comprising at least two fused atom rings, wherein at least one of the fused atom rings comprises one or more substituents, wherein at least one of the substituents comprises a double bonded oxygen attached to a carbon atom ring member included in one of the fused rings.

25. The method of 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 diaryl ketone group, a substituted or unsubstituted α-diketone, a polycyclic group comprising at least two fused atom rings, wherein at least one of the fused atom rings comprises one or more substituents, wherein at least one of the substituents comprises a double bonded oxygen attached to a carbon atom ring member included in one of the fused rings.

26. The method of claim 1 or 2, wherein the photo-switchable photoinitiator comprises a P-type photochromic molecule represented by formula (VI) or a derivative thereof:

27. The method of claim 1 or 2, wherein the photo-switchable photoinitiator comprises a P-type photochromic molecule represented by formula (XIX) or a derivative thereof:

28. The method of claim 1 or 2, wherein the photo-switchable photoinitiator comprises a P-type photochromic molecule represented by formula (XXI) or a derivative thereof:

29. A photoconvertible photoinitiator comprising a P-type photochromic molecule, the molecule comprising one or more substituents, at least one of which comprises a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atomic rings, at least one of which comprises one or more substituents, at least one of which comprises a double-bonded oxygen connected to a carbon atom ring member included in one of the fused rings, wherein the P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in a photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

30. A photoconvertible photoinitiator comprising a P-type photochromic molecule, wherein the P-type photochromic molecule comprises a P-type diarylethene molecule, wherein the molecule includes one or more substituents, wherein at least one substituent is a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group including at least two fused atomic rings, wherein at least one of the fused atomic rings includes one or more substituents, wherein at least one of the substituents includes a double-bonded oxygen connected to a carbon atom ring member included in one of the fused rings, wherein the P-type photochromic molecule can be activated by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in a photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

31. A photo-switchable photoinitiator comprising a diarylcycloolefin molecule represented by the general formula (I): in: A represents a substituted or unsubstituted cycloolefin ring structure, X represents the following formula (X a )、(X b )、(X c ), or (X d ) represented by a heteroaryl group: in: E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ), Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8 ), or a cyano (CN) group, G is a ring member and represents a ring having R 9 The carbon atom of the substituent group (CR 9 ) or a nitrogen atom (N); L is a ring member and represents a ring having R 1 The carbon atom of the substituent group (CR 1 ) or a nitrogen atom (N), and R 1 and R 6 -R 9 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or in: E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ), Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8 ), or a cyano (CN) group, G is a ring member and represents a carbon atom with an R substituent group (CR 9 ) or a nitrogen atom (N); L is a ring member and represents a ring having R 1 The carbon atom of the substituent group (CR 1 ) or a nitrogen atom (N), and R 1 and R 6 -R 9 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or in: E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ), Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8 ), or a cyano (CN) group, and R 2 R 8 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or E is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 6 The nitrogen atom (NR 6 ), Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 7 The sulfur atom of the substituent group (SR 7 ), with R 8 The oxygen atom of the substituent group (OR 8 ), or a cyano (CN) group, and R 2 -R 8 are substituents, are the same or different, and independently represent, 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 a substituted 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; Y represents the formula (Y a )、(Y b ), (Yc) or (Y d ) represented by a heteroaryl group: in: E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ), Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group, G' is a ring member and represents a ring having R 18 The carbon atom of the substituent group (CR 18 ) or a nitrogen atom (N); L' is a ring member and represents a ring having R 10 The carbon atom of the substituent group (CR 10 ) or a nitrogen atom (N), and R 10 and R 15 -R 18 are substituents, are the same or different, and independently represent, 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 a substituted 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; in: E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ), Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group, G' is a ring member and represents a ring having R 18 The carbon atom of the substituent group (CR 18 ) or a nitrogen atom (N); L' is a ring member and represents a ring having R 10 The carbon atom of the substituent group (CR 10 ) or a nitrogen atom (N), and R 10 and R 15 -R 18 are substituents, are the same or different, and independently represent, 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 a substituted 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; in: E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ), Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group, and R 11 -R 17 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; or in: E' is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 15 The nitrogen atom (NR 15 ), Z' represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkynyl group, 16 The sulfur atom of the substituent group (SR 16 ), with R 17 The oxygen atom of the substituent group (OR 17 ), or a cyano (CN) group, and R 11 -R 17 are substituents, are the same or different, and independently represent, 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 a substituted 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group; wherein at least one of X and Y includes at least one R substituent comprising a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atom rings, wherein at least one of the fused atom rings comprises one or more substituents, wherein at least one of the substituents comprises a double bonded oxygen attached to a carbon atom ring member included in one of the fused rings; and The P-type photochromic molecules are activatable by light having a first wavelength (λ1) and light having a second wavelength (λ2) to initiate a crosslinking or polymerization reaction in the photohardenable composition at the intersection of the first wavelength and the second wavelength, wherein the first wavelength is shorter than the second wavelength.

32. A photo-switchable photoinitiator according to claim 31, wherein at least one R substituent on X and at least one R substituent on Y comprises a substituted or unsubstituted diaryl ketone group, a substituted or unsubstituted α-diketone group, or a polycyclic group comprising at least two fused atom rings, wherein at least one of the fused atom rings comprises one or more substituents, wherein at least one of the substituents comprises a double bonded oxygen connected to a carbon atom ring member included in one of the fused rings, wherein the R substituent on X and the R substituent on Y are independently the same or different.

33. The photo-switchable photoinitiator according to claim 31 or 32, wherein A comprises a a )、(A b )、(A c ), or (A d ) represents the structure: in: X 1 , X 2 , X 3 , X 4 , X 5 and X 6 are the same or different and are independently hydrogen (H), fluorine (F), chlorine (Cl), or a substituted or unsubstituted alkyl or heteroalkyl group, in: J is a ring member and represents oxygen O or has R 25 The nitrogen of the substituent group (NR 25 ), where R 25 represents hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl, in: E" is a ring member and represents an oxygen atom (O), a sulfur atom (S), a sulfur dioxide group (SO2), a selenium atom, or a ring having R 23 The nitrogen atom (NR 23 ), G" is a ring member and represents a ring having R 24 The carbon atom of the substituent group (CR 24 ) or a nitrogen atom (N); and R 22 -R 24 The substituents are the same or different and independently represent, 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 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 carbamate 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-R', wherein R or R' may independently represent an aryl group or an alkyl group), or a substituted or unsubstituted alcohol group, or in: 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.

34. A photo-switchable photoinitiator according to claim 31 or 32, wherein the R groups on any two adjacent ring members of X and / or Y may comprise atoms which complete a ring structure linking the two adjacent groups together.

35. The photo-switchable photoinitiator of claim 31 or 32, wherein the ring structure is substituted.

36. The photo-switchable photoinitiator of claim 31 or 32, wherein the ring structure is part of a polycyclic substituted or unsubstituted ring structure.

37. The photo-switchable photoinitiator according to claim 31 or 32, wherein the ring structure or the polycyclic structure of which the ring structure is a part comprises one or more carbon atoms and one or more heteroatoms.

38. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-A) or a derivative thereof:

39. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-B) or a derivative thereof:

40. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-C) or a derivative thereof:

41. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-D) or a derivative thereof:

42. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-E) or a derivative thereof:

43. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-F) or a derivative thereof:

44. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-G) or a derivative thereof:

45. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-H) or a derivative thereof:

46. ​​The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-I) or a derivative thereof:

47. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-J) or a derivative thereof:

48. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-K) or a derivative thereof:

49. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-L) or a derivative thereof:

50. The photo-switchable photoinitiator according to any one of claims 29 to 32, wherein the polycyclic group is represented by the general formula (PG-M): The aryl group may be substituted or unsubstituted and may optionally include one or more heteroatoms.

51. The photo-switchable photoinitiator according to claim 31 or 32, wherein in the general formula (I), A is represented by the formula (A d ) indicates that X 1 -X 6 is hydrogen or fluorine, X is represented by (X a ) indicates that R 1 is iodine, bromine, chlorine, fluorine, or an alkyl group, E is sulfur, Z is an alkyl or phenyl group, and G is CR 9 , and Y is given by (Y a ) represents, wherein E' is sulfur, Z' is an alkyl or phenyl group, and G' is CR 15 , and R 10 refers to a polycyclic group comprising at least two fused atom rings, wherein at least one of said fused atom rings comprises one or more substituents, wherein at least one of said substituents comprises a double bonded oxygen attached to a carbon atom ring member comprised in one of said fused rings.

52. The photo-switchable photoinitiator according to claim 31 or 32, wherein in the general formula (I), A is represented by the formula (A d ) indicates that X 1 -X 6 is hydrogen or fluorine, X is represented by (X b ) indicates that R 1 is iodine, bromine, chlorine, fluorine, or an alkyl group, E is sulfur, Z is an alkyl or phenyl group, and G is CR 9 , and Y is given by (Y a ) represents, wherein E' is sulfur, Z' is an alkyl or phenyl group, and G' is CR 15 , and R 10 refers to a polycyclic group comprising at least two fused atom rings, wherein at least one of said fused atom rings comprises one or more substituents, wherein at least one of said substituents comprises a double bonded oxygen attached to a carbon atom ring member comprised in one of said fused rings.

53. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (III):

54. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (IV):

55. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (V):

56. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (VI):

57. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (VII):

58. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (VIII):

59. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (IX):

60. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (X):

61. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XI):

62. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XII):

63. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XIII):

64. The photo-switchable photo-initiator according to claim 31 or 32, wherein the photo-switchable photo-initiator is represented by formula (XV):

65. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XVI):

66. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XVII):

67. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XVIII):

68. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XIX):

69. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XX):

70. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XXI):

71. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XXII):

72. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XXIII):

73. The photo-switchable photo-initiator according to claim 31 or 32, wherein the photo-switchable photo-initiator is represented by formula (XXIV):

74. The photo-switchable photo-initiator according to claim 31 or 32, wherein the photo-switchable photo-initiator is represented by formula (XXV):

75. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XXVI):

76. The photo-switchable photo-initiator according to claim 31 or 32, wherein the photo-switchable photo-initiator is represented by formula (XXVII):

77. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XXVIII):

78. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XIX):

79. The photo-switchable photoinitiator according to claim 31 or 32, wherein the photo-switchable photoinitiator is represented by formula (XXX):

80. A photohardenable composition comprising a photohardenable resin component and a photoconvertible photoinitiator, wherein the photoconvertible photoinitiator is activatable by exposure to light having a first wavelength and light having a second wavelength to initiate a crosslinking or polymerization reaction in the photohardenable resin component at the intersection of the two wavelengths of light, wherein the first wavelength and the second wavelength are different, and wherein the photoconvertible photoinitiator comprises a photoconvertible photoinitiator according to any one of claims 29-32.

81. The photohardenable composition of claim 80, further comprising a co-initiator.

82. The photohardenable composition of claim 80, wherein the photohardenable composition exhibits non-Newtonian rheological behavior.

83. A method of forming an object in a volume of a photohardenable composition, the method comprising: (a) providing a volume comprising the photohardenable composition, the photohardenable composition comprising a photohardenable resin component and a photo-switchable photoinitiator according to any one of claims 29 to 32, (b) projecting an optical image generated by a second excitation light onto a selected position in the volume along a projection axis, wherein the optical image is oriented perpendicular to the projection axis; (c) generating a light sheet comprising a first excitation light, and directing the light sheet through the volume along a light sheet illumination axis such that the optical image intersects the light sheet at the selected location within a common plane, and wherein the light sheet overlaps the projected optical image in the volume at the selected location; as well as (d) optionally repeating steps (b) and (c) one or more times to partially or completely form the object, wherein for each group of repetitions 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.

84. A method according to claim 83, wherein the optical image comprises a two-dimensional cross-sectional slice of the object to be printed, and the optical image of the repeated step comprises sequential two-dimensional cross-sectional slices of the object, and wherein the optical image is oriented perpendicular to the direction in which it is irradiated or projected into the volume.

85. A method according to claim 1, wherein the photohardenable composition further includes a resin component that is hardenable by a heat-driven reaction, and wherein the method further includes separating the object from the volume in which it is formed and heating the separated object to further harden the object.

86. The method of claim 85, wherein the separated objects are washed prior to heating.

87. A method according to claim 1, wherein the photohardenable composition further includes a second light-activated photoinitiator, and wherein the method further includes separating the object from the volume in which it was formed and irradiating the separated object with light of a third wavelength to further harden the object, wherein the third wavelength is shorter than the first wavelength and the second wavelength.

88. The method of claim 87, wherein the separated objects are washed prior to irradiation with light of a third wavelength.

89. New, usable and non-obvious processes, machines, articles of manufacture, and compositions of matter as herein shown and described.

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