TWI760824B - Photopolymerization process using light beams of different wavelengths and applications thereof - Google Patents

Abstract

The present invention involves using a projector to project three light beams of different wavelengths, namely, a patterning light beam, an inhibitory light beam and an accelerating light beam, towards a liquid light-sensitive material which contains a first absorption peak activatable by the patterning light beam, a second absorption peak activatable by the inhibitory light beam, a third absorption peak activatable by the accelerating light beam, and at least one monomer. The liquid light-sensitive material is pre-illuminated with the accelerating light beam, thereby activating the third absorption peak to generate singlet oxygen. The patterning light beam and the inhibitory light beam are irradiated to the material subsequently, wherein the patterning light beam activates the first absorption peak to generate reactive free radicals, and the inhibitory light beam activates the second absorption peak to create polymerizing free radicals and inhibitory free radicals. The singlet oxygen, the reactive free radicals, the polymerizing free radicals and the at least one monomer are crosslinked to initiate photopolymerization, whereas the inhibitory free radicals bind to the reactive free radicals to inhibit the crosslinking reaction, thus quenching the photopolymerization.

Description

Method and application of multi-wavelength photopolymerization

The invention relates to a multi-wavelength photopolymerization method that can control the start and stop of photopolymerization, consume oxygen in advance to improve the photopolymerization efficiency, and control the photopolymerization inhibition zone to increase the photopolymerization rate and its application.

Photopolymerization can be carried out in the air under low light intensity light sources (such as halogen lamps, fluorescent lamps or fluorescent lamps, etc.), and light sources with wavelengths ranging from 200-810nm ultraviolet light to infrared light have been used for photoinitiated polymerization and cross-linking reaction. Photoinitiated polymerization and crosslinking reactions have many advantages, including fast and controllable reaction rates, and spatial and temporal control for material formation without the need for high temperatures or harsh conditions. Studies have shown that tissue engineering techniques using scaffold-based methods to chemically modify polymers can improve their mechanical properties by cross-linking or polymerizing with UV or visible light to produce gels or high molecular weight polymers.

Photopolymerization usually includes the following types: light-induced free radical polymerization (FRP), cationic and anionic catalyzed polymerization (CP and AP), free radical promoted cationic polymerization (FRPCP), thiol-ene polymerization, redox polymerization Aggregation and Controlled Aggregation. Controlled photocurable resins require the presence of photoinitiators (PI), photosensitizers (PS) or multi-component photoinitiator systems such as PI/hydrogen donors, PI/electron donors, PS/PI or PS/PI/additives, They generate free radicals, acids, free radical cations and/or photosensitive bases. Free radical polymerization is particularly sensitive to the presence of oxygen, which can effectively react with free radicals, thereby reducing polymerization efficiency by quenching the initiated and diffusing free radicals.

However, conventional photocurable resins only use a specific light beam of a single wavelength to initiate polymerization and cross-linking reactions, but the single-wavelength radiation will lose the polymerization inhibition zone due to untargeted cumulative irradiation. That is, irradiating a single wavelength on non-target regions makes it possible to polymerize regions where polymerization is not desired.

In view of this, the present invention provides a multi-wavelength photopolymerization method and its application, which can control the start and stop of photopolymerization, and can increase the photopolymerization rate, and its main purpose.

For the purpose disclosed above, the method for multi-wavelength photopolymerization of the present invention at least comprises the following steps: providing a liquid photosensitive material, the liquid photosensitive material comprises at least a photoinitiator and at least one monomer, and the at least one photoinitiator has the first 1. The second and third absorption peaks; provide a projection structure suitable for providing at least three shaped beams with different wavelengths, namely shaped image beams, shaped suppression beams and shaped acceleration beams, the first absorption peak can be The shaping image beam is excited, the second absorption peak can be excited by the shaping suppression beam, and the third absorption peak can be excited by the shaping acceleration beam; first, the liquid photosensitive material is pre-irradiated with the shaping acceleration beam to excite the liquid photosensitive material. The third absorption peak generates excited singlet oxygen ( ¹ O ₂ ) through triplet energy transfer; the liquid photosensitive material is then irradiated with the shaped image beam and the shaped suppression beam, and the shaped image beam excites the first An absorption peak forms reactive radicals, and the shaped suppression beam excites the second absorption peak to generate polymerization radicals and suppression radicals. The singlet oxygen, the reactive radical, the polymerization radical and the monomer generate crosslinking to initiate photopolymerization, and the inhibitory radical combines with the reactive radical to inhibit the crosslinking to stop the photopolymerization.

The present invention utilizes the pre-irradiation of the shaping accelerating beam to consume oxygen in advance to improve the photopolymerization efficiency, and the shaping image beam initiates crosslinking between reactive free radicals and monomers to initiate photopolymerization, while the shaping inhibiting beam initiates the inhibition of free radicals. The inhibitory radical is combined with the reactive radical to inhibit the crosslinking to close the photopolymerization, thereby controlling the progress and stop of the photopolymerization, and the photopolymerization inhibition zone can be controlled to improve the photopolymerization efficiency.

In a preferred aspect, the shaping image beam is 470 nm blue light, the shaping suppressing beam is 365 nm ultraviolet light, and the shaping accelerating beam is 635 nm red light.

In another aspect, the shaping image beam is green light, the shaping inhibiting beam is ultraviolet light, and the shaping accelerating beam is red light; or, the shaping image beam is red light, and the shaping inhibiting beam is red light. The light beam is ultraviolet light, and the shaped accelerating light beam is infrared light.

The present invention provides another kind of multi-wavelength photopolymerization applied to the production of three-dimensional three-dimensional finished products.

In a preferred aspect, a container is included for accommodating the liquid photosensitive material, the bottom of the container has at least one light-transmitting window, and a forming platform is adapted to move toward and away from the light-transmitting window at the bottom of the container .

In a better aspect, the shaped image beam, the shaped suppression beam and the shaped acceleration beam penetrate the light-transmitting window from the bottom of the container to illuminate the liquid photosensitive material.

In another preferred aspect, the shaped image beam and the shaped suppression beam penetrate the light-transmitting window from the bottom of the container to irradiate the liquid photosensitive material, and the shaped accelerating beam irradiates the liquid from the top or side of the container photosensitive material.

In order to help the examiners to understand the technical features, content and advantages of this creation and the effects that can be achieved, this creation is hereby combined with the accompanying drawings, and is described in detail as follows in the form of embodiment. The subject matter is only for illustration and auxiliary instructions, and may not necessarily be the real proportion and precise configuration after the implementation of this creation. Therefore, the proportion and configuration relationship of the attached drawings should not be interpreted or limited to the scope of rights of this creation in actual implementation. Together first to describe.

Referring to FIG. 1, it is a schematic diagram of the photochemical paths of the two shaping beams according to the first embodiment of the present invention. Wherein, the dual-wavelength (blue light and ultraviolet light) radical-mediated system is composed of two kinds of first and second photoinitiators A and B, and the first photoinitiator A has a first absorption peak and the third photoinitiator The diphotoinitiator B has a second absorption peak, and the wavelengths of the first and second absorption peaks are different from each other. The shaping image beam 41 is blue light (wavelength 470 nm) to excite the first absorption peak in the first photoinitiator A to generate the excited triplet state A*; and the shaping suppressing beam 42 is ultraviolet light (wavelength 365 nm) that excites The second absorption peak in the second photoinitiator B can generate inhibitory radicals N and polymerization radicals X, which can interact with monomer M to generate crosslinking. The triplet (A*) action of the first photoinitiator A reacts with the first photoinitiator A to chain growth and generate more reactive radicals R, which lead to crosslinking. The reorganization of the reactive radical R and the inhibition of the interaction between the reactive radical N and the reactive radical R may lead to the termination of the polymerization. In a preferred embodiment, camphorquinone (CQ) (initial concentration 0.05~0.4%) and 4-(dimethylamino) ethyl benzoate (ethyl 4-(dimethylamino)benzoate; EDAB) (initial concentration 0.5 ~3%) mixed as the first photoinitiator A, and butyl nitrite (BN) (initial concentration 0~3%) as the second photoinitiator B, the photopolymerization of the prepared methacrylate resin . Photochemical decomposition of butyl nitrite (BN) produces nitric oxide (N) and alkoxy (X), N is a potent inhibitor of reactive radical R, and X can initiate additional polymerization. In the first embodiment as shown in the figure, the cross-linking effect is formed through two paths, namely, the first absorption peak (illuminated by blue light) of the first photoinitiator A to initiate the reaction radical R, and the second The polymerization radical X formed by the second absorption peak of the photoinitiator B (illuminated by ultraviolet light) is cross-linked with the monomer M; while the inhibitory radical N reduces the conversion efficiency by reducing the reactive radical R. Of course, the dual-wavelength radical-mediated system in this embodiment can also have only a single photoinitiator, and the single photoinitiator has two different absorption peaks.

In the dual-wavelength system of the first embodiment, the penetration depth of blue light (1~200 mW/cm ² ) in the methacrylate resin is greater than the penetration depth of ultraviolet light (1~200 mW/cm ² ), and the photopolymerization surface And the thickness of the inhibition zone can be adjusted by the light intensity, which increases the printing speed as the thickness of the inhibition zone between the polymerization surface and the projection window increases.

Among the common types of photopolymerization is "photo-induced free radical polymerization (FRP)", wherein the free radical polymerization is particularly sensitive to the presence of oxygen, because oxygen can effectively react with free radicals, thus initiating and diffusing through quenching Therefore, if oxygen inhibition can be reduced and polymerization can be initiated, the photopolymerization efficiency can be improved; irradiation with red light can consume oxygen but not initiate photopolymerization. Figure 2 shows the red light pretreatment. The effect of illumination time (Tp) on the distribution of oxygen concentration, the red light pre-illumination can consume the oxygen of the photoinitiator. Curve 1 shows the oxygen concentration curve for red light only, and also defines the initial value of oxygen at the start of photopolymerization. Curve 2 shows the oxygen characteristic curve for photopolymerization initiation without red light irradiation (or Tp = 0). Curves 3 and 4 are the oxygen characteristic curves of photopolymerization initiation after pre-illumination Tp = 200 s and 450 s with red light I ₁₀ =34 mW/cm ² , respectively. The longer the Tp, the smaller the remaining oxygen concentration, which also shortens the induction time (T _ID ) for the oxygen concentration to drop to the critical value of polymerization. The dual light source pre-irradiation system has a faster oxygen consumption rate and higher light source than the single light source. Aggregation efficiency. Figure 2 shows the induction times (T _ID2 , T _ID3 and T _ID4 ) for pre-illumination Tp = 0 s, 200 s and 450 s (curves 2, 3 and 4).

Referring to FIG. 3, it is a schematic diagram of the photochemical paths of three shaped beams in the second embodiment of the present invention. Wherein, a liquid photosensitive material is provided first, and the liquid photosensitive material includes first, second and third photoinitiators A, B, C and at least one monomer, and the first, second and third photoinitiators respectively have The first, second and third absorption peaks are different from each other; and a projection structure is provided, and the projection structure is suitable for providing at least three shaped beams with different wavelengths, namely the shaped image beam, the shaped suppression beam and the shaped acceleration beam. In this embodiment, the wavelength of the shaping suppressing beam is the shortest, the wavelength of the shaping image beam is centered, and the wavelength of the shaping accelerating beam is the longest, wherein the shaping suppressing beam is ultraviolet light, and the shaping image beam is blue light , the shaping acceleration beam is preferably red light. The liquid photosensitive material is pre-irradiated with red light (wavelength 635 nm), the red light excites the third absorption peak in the third photoinitiator C and generates excited singlet oxygen ( ¹ O ₂ ) through triplet energy transfer Reducing the inhibition of oxygen enhances the blue light conversion rate of the monomer M; then irradiates the liquid photosensitive material with blue light (wavelength 470 nm) and ultraviolet light (wavelength 365 nm), the blue light excites the first absorption in the first photoinitiator A The second absorption peak in the second photoinitiator B will be excited by ultraviolet light to generate the inhibitory radical N and the polymerization radical X, which can interact with the monomer M to generate cross-linking. The triplet (A*) action of the first photoinitiator A reacts with the first photoinitiator A to chain growth and generate more reactive radicals R, which lead to crosslinking. The reorganization of reactive radicals R, the inhibition of radicals [N] and the interaction of reactive radicals R may lead to the termination of polymerization. In a preferred embodiment, zinc 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (ZnTTP) (initial concentration 0.05~1%) and ethyl 4-(dimethylamino)benzoate (EDAB) ( Initial concentration 0.5~3%) mixed as the first photoinitiator A, butyl nitrite (butyl nitrite, BN) (initial concentration 0~3%) as the second photoinitiator B, camphorquinone (CQ) as the third photoinitiator Photopolymerization of methacrylates formulated with initiator C. The photochemical decomposition of butyl nitrite (BN) produces nitric oxide (N) and alkoxy (X), where N is an effective inhibitor of the reactive radical R, and X is used to initiate additional polymerization. In the second embodiment as shown in the figure, the cross-linking effect is formed through three paths, namely, the first absorption peak (illuminated by blue light) of the first photoinitiator A to initiate the reaction radical R, and the second photoinitiator to initiate the reaction. The polymerization radical X formed by the second absorption peak of the agent B (in UV light) and the [ ¹ O ₂ ] formed by the third absorption peak of the third photoinitiator C (in red light) are cross-linked with the monomer M; The inhibition of free radical N reduces the conversion efficiency by reducing the reactive radical R. Of course, the second embodiment can also have at least one photoinitiator (for example, a single photoinitiator or two photoinitiators), and the at least one photoinitiator has three mutually different first, second, and third absorption peak.

In the three-wavelength system of the second embodiment, the red light (635 nm) (1~200 mW/cm ² ) has the deepest penetration depth in the methacrylate resin, and the blue light (470 nm) (1~200 mW/cm ² ) followed by ultraviolet light (365 nm) (1~200 mW/cm ² ) is the shallowest. The red light can pre-illuminate the liquid photosensitive material in various directions to consume oxygen to increase the polymerization rate; the thickness of the photopolymerization surface and the inhibition zone can be adjusted by the intensity of blue light and ultraviolet light, which increases with the increase of the thickness of the inhibition zone between the polymerization surface and the projection window. Printing rate.

Furthermore, the above shaped beam can be extended to the following spectral ranges, as long as the absorption spectra of the three wavelengths can be effectively separated and have corresponding absorption peaks. For example: (i) the shaping acceleration beam is red (635 nm), the shaping image beam is green (532 nm) and the shaping suppression beam is ultraviolet (365 nm); (ii) the shaping acceleration beam It is infrared light, the shaping image beam is red light (635 nm), and the shaping suppression beam is ultraviolet light (365 nm); these bands can all come from semiconductor light sources.

The multi-wavelength photopolymerization method of the present invention can be applied to a three-dimensional printing device to produce a three-dimensional finished product. As shown in FIG. 4 , it further includes a container 1 for accommodating the liquid photosensitive material 2 , and the bottom of the container 1 has at least A light-transmitting window 11 , the forming image beam 41 and the forming-inhibiting beam 42 penetrate the light-transmitting window 11 from the bottom of the container 1 to illuminate the liquid photosensitive material 2 , and the forming accelerating beam 43 passes from the top or side of the container 1 While irradiating the liquid photosensitive material 2, the forming plane 51 is on the fixed plane of the container 1, and another forming platform 5 can be moved from the forming plane 51 to the direction away from the container 1 through a vertical moving device (not shown). The initial position of the molding platform 5 is at the position of the molding surface 51 for the cured body 6 to be attached. The projection structure 3 provides the shaping image beam 41 and the shaping suppression beam 42 to promote the absorption peak of the specific photoinitiator in the liquid photosensitive material 2 and the monomer to form photopolymerization on the shaping surface 51, and this is the image projected by the shaping image beam The image is a two-dimensional image and moves upward on the forming platform 5 to form the solidified body 6 , and the inhibition zone 52 provides a supplementary flow channel for the liquid photosensitive material 2 . Next, move the forming platform 5 from the initial position in the direction of the container 1 on the forming surface 51 , and use the time-varying forming image beam 41 to accumulate the surface formed by photopolymerization into a three-dimensional finished product over time.

In addition, the shaping image beam 41 , the shaping suppression beam 42 and the shaping acceleration beam 43 can also penetrate the light-transmitting window 11 from the bottom of the container 1 to illuminate the liquid photosensitive material 2 , as shown in FIG. The surfaces formed by photopolymerization are combined with the time-varying shaped image beam 41 to form a three-dimensional finished product over time.

The method for multi-wavelength photopolymerization of the present invention has the following advantages and effects: 1. Two competing factors of photopolymerization: the generation of free radicals required to suppress free radicals to eliminate photopolymerization, and the consumption of oxygen to suppress photopolymerization, can be independently and selectively tuned. 2. Using the pre-irradiation of the forming accelerated beam, the oxygen is consumed in advance to improve the photopolymerization efficiency; the light conversion efficiency of the forming image beam can be improved, and the conversion characteristic curve of the forming image beam can be determined by controlling the induction time of the oxygen concentration. 3. The forming image beam induces free radicals and monomers to cross-link to form photopolymerization, while the forming inhibiting beam induces the formation of inhibiting free radicals, and the inhibiting free radicals combine with the reaction free radicals to inhibit cross-linking to stop photopolymerization. 4. Control the progress and stop of photopolymerization through the shaping restraint beam. 5. Control the forming image beam to project a two-dimensional image, and the forming restraint beam controls the photopolymerization area, which can directly print a two-dimensional plane. With a movable forming platform, a three-dimensional printed product is formed, and the three-dimensional finished product is formed continuously in all directions during the forming process. 6. The increase of the photopolymerization inhibition zone is controlled by the shaping inhibition beam, which makes the supplementary material easy to reflow, and effectively improves the speed of three-dimensional printing.

The above embodiments are only for the purpose of illustrating the present invention, and are not intended to limit the present invention. Those skilled in the relevant art, various modifications or changes made without departing from the technical scope of the present invention should also belong to the protection category of the present invention.

First Photoinitiator A Second Photoinitiator B Third Photoinitiator C Monomer M Reactive Radical R Polymerization Radical X Inhibition Radical N Ground State Oxygen ³ O ₂ Singlet Oxygen ¹ O ₂ Induction Time T _ID Pre-illumination Time Tp Container 1 Light-transmitting window 11 Liquid photosensitive material 2 Molding surface 21 Photopolymerization inhibition zone 22 Filtering mirror group 3 Image forming beam 41 Forming inhibition beam 42 Forming acceleration beam 43 Forming platform 5 Forming surface 51 Inhibition zone 52 Cured body 6

FIG. 1 is a schematic diagram of the photochemical paths of two shaped beams in the first embodiment of the present invention; Figure 2 is a schematic diagram of the influence of red light pre-illumination time (Tp) on the distribution of normalized oxygen concentration; Fig. 3 is a schematic diagram of the photochemical paths of the photopolymerization formed by three shaped beams in the present invention; FIG. 4 is a schematic diagram of the structure of the present invention applied to a three-dimensional printing device, and FIG. 5 is a schematic diagram of another structure of the present invention applied to a three-dimensional printing device.

First Photoinitiator A Second Photoinitiator B Third Photoinitiator C Monomer M Reactive Radical R Polymerization Radical X Inhibition Radical N Ground State Oxygen ³ O ₂ Singlet Oxygen ¹ O ₂ Shaping Image Beam 41 Shaping Suppressing Beam 42 Shaping Accelerating Beam 43

Claims (10)

A method for multi-wavelength photopolymerization, comprising at least the following steps: providing a liquid photosensitive material, the liquid photosensitive material comprises at least one photoinitiator and at least one monomer, and the at least one photoinitiator has mutually different first and second 2. The third absorption peak; providing a projection structure suitable for providing at least three shaped beams with different wavelengths, namely, a shaped image beam, a shaped suppression beam and a shaped acceleration beam; first, the shaped acceleration beam is used to The liquid photosensitive material is pre-irradiated to excite the third absorption peak, and through triplet energy transfer, the oxygen that inhibits photopolymerization is consumed, and the excited singlet oxygen ( ¹ O ₂ ) is generated; then the shaping image beam and the shaping The liquid photosensitive material is irradiated with an inhibiting beam, the shaped image beam excites the first absorption peak to form reactive radicals, and the shaped inhibiting beam excites the second absorption peak to generate polymerization free radicals and inhibited free radicals, the singlet state Oxygen, the reactive radical, the polymerization radical and the monomer are cross-linked to form photopolymerization, and the inhibitory radical is combined with the reactive radical to inhibit the cross-linking to stop the photopolymerization. The method for multi-wavelength photopolymerization according to claim 1, wherein the wavelength of the shaping suppression beam is the shortest, the wavelength of the shaping image beam is centered, and the wavelength of the shaping accelerating beam is the longest. The method for multi-wavelength photopolymerization according to claim 2, wherein the shaping suppressing beam is ultraviolet light, the shaping image beam is blue light, and the shaping accelerating beam is red light. The method for multi-wavelength photopolymerization according to claim 2, wherein the shaping image beam is green light, the shaping suppressing beam is ultraviolet light, and the shaping accelerating beam is red light; or, the shaping image beam It is red light, the shaping inhibiting beam is ultraviolet light, and the shaping accelerating beam is infrared light. The method for multi-wavelength photopolymerization according to any one of claims 1 to 4, wherein the penetration depth of the shaping suppression beam in the liquid photosensitive material is the shallowest, and the penetration depth of the shaping image beam at the liquid photosensitive material In the center, the penetration depth of the shaped accelerating beam is the deepest in the liquid photosensitive material. An application of multi-wavelength photopolymerization, which at least includes the method of any one of claims 1 to 4, can be used to produce three-dimensional finished products. The application according to claim 6, further comprising a container for accommodating the liquid photosensitive material, the container has at least one light-transmitting window at the bottom, and a forming platform is adapted to move toward and away from the container . The application according to claim 7, wherein the shaped image beam, the shaped suppression beam and the shaped acceleration beam penetrate the light-transmitting window from the bottom of the container to irradiate the liquid photosensitive material. The application of claim 7, wherein the shaped image beam and the shaped suppression beam penetrate the light-transmitting window from the bottom of the container to irradiate the liquid photosensitive material, and the shaped accelerating beam is irradiated from the top or side of the container the liquid photosensitive material. The application according to claim 6, wherein the image projected by the shaping image beam is a two-dimensional image.

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