Stereolithography apparatus

Abstract

The purpose of the present disclosure is to suppress deviation that may occur between a plan view shape of a region which is irradiated with light and a plan view shape of a region in which a photocurable resin is cured. A stereolithography apparatus according to the present disclosure is provided with an irradiation unit which irradiates a first region (A1) of a modeling surface (P) set inside a photocurable resin that contains a monomer and a polymerization initiator with first light having a wavelength that is included in the absorption wavelength of the polymerization initiator and having a time average of the intensity higher than the modeling threshold (Th), and which irradiates a second region (A2) of the modeling surface (P) with second light having a wavelength that is included in the absorption wavelength of the polymerization initiator and having a time average of the intensity lower than the modeling threshold (Th). In a light exposure apparatus according to the present disclosure, an outer edge (A21) of a second region (A2) surrounds an outer edge (A11) of a first region (A1) on a modeling surface (P).

Description

Stereolithography device

[0001] The present invention relates to a stereolithography apparatus using a liquid phase polymerization method.

[0002] For example, as described in Patent Document 1, a stereolithography device (referred to as a three-dimensional modeling device in Patent Document 1) using a liquid phase polymerization method is known. In a stereolithography device using a liquid phase polymerization method, a polymerization initiator and a monomer of a photocurable resin (ultraviolet curable resin in Patent Document 1) are filled into a liquid tank, and light (ultraviolet light in Patent Document 1) is irradiated onto a point or surface at a predetermined depth inside the liquid tank, thereby initiating a polymerization reaction in the photocurable resin and hardening the photocurable resin from a liquid to a solid (see, for example, FIG. 1 of Patent Document 1).

[0003] International Publication No. 2017 / 170475

[0004] In such a photopolymerization apparatus, it is ideal for the size of the area where the photocurable resin is cured to roughly match the size of the area irradiated with light. However, it has been found that when the size of the area irradiated with light is reduced, the area where the photocurable resin is cured becomes smaller than the area irradiated with light. It has also been found that this tendency is more pronounced when the length of one side of the area irradiated with light is less than 10 μm.

[0005] One aspect of the present invention has been developed in consideration of the above-mentioned problems, and its purpose is to suppress, more than ever before, the discrepancy that can occur between the planar shape of the area irradiated with light and the planar shape of the area where the photocurable resin has hardened in a photopolymerization device using a liquid phase polymerization method.

[0006] To solve the above-mentioned problems, a photo-lithography apparatus according to one aspect of the present invention includes an irradiation unit that irradiates a first region of a modeling surface set inside a photocurable resin containing a monomer and a polymerization initiator with first light having a wavelength included in the absorption wavelength of the polymerization initiator and a time-averaged intensity higher than a modeling threshold, and that irradiates a second region of the modeling surface with second light having a wavelength included in the absorption wavelength of the polymerization initiator and a time-averaged intensity lower than the modeling threshold. This exposure apparatus employs a configuration in which the outer edge of the second region on the modeling surface surrounds the outer edge of the first region.

[0007] According to one aspect of the present invention, in a photopolymerization device using a liquid phase polymerization method, the discrepancy that may occur between the planar shape of the area irradiated with light and the planar shape of the area where the photocurable resin has hardened can be suppressed more than in the past.

[0008] 5 is a schematic diagram showing the configuration of a stereolithography apparatus according to a first embodiment of the present invention; (a) is a plan view showing an irradiation pattern of acceleration light imaged on the modeling surface of the exposure apparatus shown in FIG. 1; (b) is a graph showing the intensity distribution of acceleration light shown in (a); and (b) is a graph in which oxygen concentration distribution and oxygen flow rate distribution are added to the graph shown in (b) of FIG. 2; (a) is a plan view showing a modified example of the irradiation pattern of acceleration light shown in FIG. 2; (b) is a graph showing the intensity distribution of acceleration light shown in (a); and (b) is a schematic diagram showing the configuration of an exposure apparatus according to a second embodiment of the present invention; (a) is a plan view showing the irradiation patterns of acceleration light and inhibitory light imaged on the modeling surface of the exposure apparatus shown in FIG. 5; (b) is a graph showing the intensity distribution of acceleration light and inhibitory light shown in (a); and (b) are graphs showing the intensity distribution of acceleration light, oxygen concentration distribution, and oxygen flow rate distribution imaged on the modeling surface of a stereolithography apparatus according to a comparative example of the present invention. 10 is a schematic graph showing the dependence of the degree of polymerization of a photocurable resin on light irradiation time when irradiating with promotion light using a photopolymerization apparatus according to a comparative example of the present invention and when irradiating with promotion light using a reference example in which it is assumed that oxygen is not present.

[0009] [Embodiment 1] A photo-fabrication apparatus 10 according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic diagram showing the configuration of the photo-fabrication apparatus 10. FIG. 2(a) is a plan view showing the irradiation pattern of the acceleration light L1 imaged on the fabrication surface P of the photo-fabrication apparatus 10, and FIG. 2(b) is a graph showing the intensity distribution of the acceleration light L1. Note that FIG. 2(b) illustrates the intensity distribution along line A-A' shown in FIG. 2(a). FIG. 3 is a graph in which the oxygen concentration distribution and oxygen flow rate distribution are added to the graph shown in FIG. 2(b). FIG. 4(a) is a plan view showing a modified example of the irradiation pattern of the acceleration light L1 shown in FIG. 2. FIG. 4(b) is a graph showing the intensity distribution in the modified example of the irradiation pattern of the acceleration light L1.

[0010] The stereolithography device 10 is a stereolithography device that uses a liquid-phase polymerization method. In this embodiment, 1,4-butanediol dimethylacrylate is used as the monomer that constitutes the liquid photocurable resin R before curing. Camphorquinone is used as the polymerization initiator that absorbs the energy of the acceleration light L1 when irradiated with the acceleration light L1 and initiates the polymerization reaction. However, the combination of the polymer and the polymerization initiator is not limited to 1,4-butanediol dimethylacrylate and camphorquinone, and can be appropriately selected from existing combinations. Ethyl 4-(dimethylamino)benzoate may also be added to accelerate the polymerization reaction. In this embodiment, blue light with a wavelength λ1 of 470 nm is used as the acceleration light L1.

[0011] 1, the optical shaping device 10 includes a light source 11, a condenser lens 12, a DMD (Digital Mirror Device) 13, a tube lens 14, a mirror 15, and an objective lens 16. The optical shaping device 10 also includes a stage and a control unit, which are not shown in FIG.

[0012] The stage is a stage on whose mounting surface a liquid vat B filled with photocurable resin R is placed, and is a stage that can move in translation parallel to the three axial directions of a Cartesian coordinate system. The stage may be configured to be rotatable about an axis that is parallel to the perpendicular to the mounting surface.

[0013] The control unit controls the irradiation pattern of the acceleration light L1 that forms an image on the modeling surface P (described later) by switching the state of each micromirror that constitutes the DMD 13 (described later) between an on state and an off state. The control unit also controls the depth direction position of the modeling surface P inside the photocurable resin R by moving the positions of the tube lens 14 and the objective lens 16 (described later). The control unit also controls the position of the stage.

[0014] The light source 11 is a light source that generates acceleration light L1. The wavelength λ1 of the acceleration light L1 may be selected appropriately depending on the polymerization initiator used, as long as it is included in the absorption wavelength range of the polymerization initiator.

[0015] In this embodiment, an LED array in which a plurality of LEDs (light emitting diodes) are arranged in a matrix is ​​used as the light source 11. The light source 11 is configured to emit convergent light from a light-emitting region 111 having a predetermined area. However, the form of the light source 11 is not limited to an LED array and can be designed as appropriate. A laser or a mercury lamp may be used instead of the LED.

[0016] In Fig. 1 , among the chief rays constituting the convergent light, representative chief rays L11, L12, and L13 are shown by dashed-dotted lines. The chief ray L11 is a light ray emitted from the center of the light-emitting region 111 toward the normal direction of the light-emitting region 111. Note that in Fig. 1 , a light beam L11F represented by the chief ray L11 is shown by solid lines and hatching. The light beam L11F can be considered to be a light beam emitted from a point light source located in the center of the light-emitting region 111, and is a light beam that diverges at the time of emission. The chief ray L12 and the chief ray L13 are light rays that are emitted from the outer edge of the light-emitting region 111, and are light rays that converge to approach the chief ray L11 at the time of emission. Similar to the light beam L11F corresponding to the chief ray L11, there are light beams corresponding to the chief ray L12 and the chief ray L13, but these light beams are not shown in FIG.

[0017] Although not shown in FIG. 1 , the light source 11 may further include optical elements such as a diffuser (or integrator lens), a collector lens, and an aperture stop arranged downstream of the LED array in order to emit promotion light L1 whose chief ray becomes convergent light. These optical elements may be arranged inside or outside the housing of the light source 11. The types, number, and arrangement of these optical elements are not limited and can be designed as appropriate.

[0018] The condenser lens 12 is a convex lens that converts the luminous flux L11F, which is divergent light, into convergent light and focuses the promotion light L1 emitted from the light-emitting region 111 onto the light-receiving surface of the DMD 13.

[0019] The DMD 13 is an example of a spatial light modulator, and its light receiving surface is composed of a plurality of micromirrors arranged in a matrix. An example of a spatial light modulator other than a DMD is a liquid crystal on silicon (LCOS). When an LCOS is used as the spatial light modulator, the LCOS may be either a reflective type or a transmissive type.

[0020] In the DMD 13, the propagation direction of the acceleration light L1 incident on each micromirror is switched by switching the direction of the reflective surface of each micromirror. In this embodiment, as shown in Figure 1, the state in which the acceleration light L1 reflected by each micromirror travels toward the tube lens 14, mirror 15, and objective lens 16 is called the "on state," and states other than the "on state" are called the "off state." Only when a certain micromirror is in the "on" state, the acceleration light L1 reflected by that micromirror is imaged on the modeling surface P set inside the photocurable resin R.

[0021] The DMD 13 switches the state of each micromirror between an on state and an off state in response to a control signal generated by the control unit, thereby generating an irradiation pattern when irradiating the acceleration light L1 onto the printing surface P. The DMD 13 also controls the duty ratio, which is the ratio between the time that each micromirror is in the on state and the time that it is in the off state, for each micromirror, thereby controlling the intensity of the acceleration light in the area of ​​the printing surface P that corresponds to that micromirror. In this case, the DMD 13 generates an irradiation pattern on the printing surface P in which the intensity of the acceleration light L1 changes over time.

[0022] Here, the irradiation pattern shown in FIG. 2 is used as an example of the irradiation pattern of the acceleration light L1. As shown in FIGS. 2A and 2B, the DMD 13 irradiates a first region A1 of the printing surface P with acceleration light L1 whose time-averaged intensity is higher than the printing threshold Th, and irradiates a second region A2 of the printing surface P with acceleration light L1 whose time-averaged intensity is lower than the printing threshold Th. The DMD 13, together with the tube lens 14 and objective lens 16 described below, constitutes an irradiation unit. The acceleration light L1 irradiated to the first region A1 and the acceleration light L1 irradiated to the second region A2 are examples of first light and second light, respectively. In this embodiment, the first light and the second light are generated using light emitted from the light source 11, and therefore the wavelengths of the first light and the second light are the same. Note that the wavelengths of the first light and the second light may be different from each other as long as they are at least included in the absorption wavelength of the polymerization initiator. The modeling threshold Th is not a threshold that determines whether or not the monomer initiates a polymerization reaction, but a threshold that determines whether or not the polymer generated by the polymerization reaction will not flow away in the subsequent cleaning process and will remain fixed in the intended position as a stereolithography object. In this embodiment, the acceleration light intensity at which the average normalized degree of polymerization (see FIG. 8) reaches 70% is used as the modeling threshold Th.

[0023] In this irradiation pattern, the first region A1 is a region in which the outer edge A11 is square, and the second region A2 is a region in which the outer edge A21 and the inner edge A22 are each square. As can be seen from (a) and (b) of Figures 2A and 2B, in this irradiation pattern, the outer edge A21 surrounds the outer edge A11. Also, in this irradiation pattern, the inner edge A22 surrounds the outer edge A11 while being in contact with the outer edge A11. Hereinafter, the time-averaged intensity of the promotion light, rather than the instantaneous intensity of the promotion light at a certain point in time, is referred to as the promotion light intensity.

[0024] In this embodiment, the diffusion coefficient of oxygen in the photocurable resin R is defined as D [cm ２ s －１ ], the consumption rate of oxygen concentration in the photocurable resin when irradiated with the second light is ν [s －１], and the distance L between the outer edge of the first region and the outer edge of the second region on the modeling surface is 4(D / ν) １／２ The second area A2 is designed so that D=1×10 －８ cm ２ s －１ , and ν=4×10 －３ s －１ Assuming this, L=64 μm.

[0025] The coefficient 4 that defines the interval L is the oxygen concentration in the state where the accelerating light L1 is not irradiated. ０ The oxygen concentration n at the outer edge A11 is the oxygen concentration n ０ This coefficient is determined by ln(2 / 100) assuming that the desired oxygen concentration n ０ The oxygen concentration n can be appropriately determined depending on the ratio of the oxygen concentration n to the desired oxygen concentration n ０ The ratio of the oxygen concentration n to the oxygen concentration n can be determined according to the size of the object to be stereolithographically fabricated. The size of an object whose shape in plan view is irregular can be defined as the square root of the area obtained when the object is viewed in plan view. The size of an object whose shape in plan view is rectangular may be defined by the length of its short side. The size of an object whose shape in plan view is circular may be defined by the length of its diameter.

[0026] The tube lens 14 is a convex lens that collimates the acceleration light L1 having a desired pattern that is reflected by the DMD 13. The tube lens 14 also cooperates with the objective lens 16 when changing the working distance of the objective lens 16 (described later) to control the depth-wise position of the modeling surface P within the photocurable resin R. More specifically, the tube lens 14 adjusts the distance from the DMD 13 in synchronization with changes in the working distance of the objective lens 16, thereby adjusting the modeling surface P and the DMD 13 (more specifically, the light-receiving surface of the DMD 13) to be conjugate with respect to the tube lens 14 and the objective lens 16. In FIG. 1 , the modeling surface P and the DMD 13, which are conjugate with respect to the tube lens 14 and the objective lens 16, are indicated by filled triangles.

[0027] The mirror 15 is a mirror that bends the optical path of the promotion light L1 collimated by the tube lens 14 by reflecting it.

[0028] The objective lens 16 is a convex lens that is spatially intensity modulated by the DMD 13 and focuses the acceleration light L1 having a desired pattern onto the modeling surface P. The objective lens 16 adjusts the working distance from the photocurable resin R contained in the liquid tank B, thereby adjusting the depthwise position of the modeling surface P within the photocurable resin R. By being able to adjust the depth, the stereolithography device 10 can perform three-dimensional stereolithography using a liquid phase polymerization method.

[0029] As described above, the optical molding device 10 includes, as an irradiation unit, a DMD 13 (an example of a spatial light modulator) that generates the acceleration light L1 to be irradiated onto the first area A1 and the acceleration light L1 to be irradiated onto the second area A2 (an example of first light and second light) by spatially intensity-modulating the acceleration light L1 from the light source 11, and a tube lens 14 and an objective lens 16 (an example of a lens) that focus the acceleration light L1 to be irradiated onto the first area A1 and the acceleration light L1 to be irradiated onto the second area A2 onto the molding surface P, and the molding surface P and the DMD 13 are arranged in a conjugate position with respect to the tube lens 14 and the objective lens 16.

[0030] <Regarding Oxygen Inhibition> The inventors of the present application have discovered that oxygen contained in a liquid photocurable resin can inhibit the polymerization reaction of the photocurable resin. Here, we will first explain the inhibition of the polymerization reaction by oxygen with reference to FIGS. 7 and 8 , and then explain the effect of the optical shaping device 10 with reference to FIG. 3 . FIG. 7 is a graph showing the intensity distribution of the acceleration light intensity, the oxygen concentration distribution, and the oxygen flow rate distribution imaged on the shaping surface of a photocurable resin shaping device according to a comparative example of the present invention. FIG. 8 is a schematic graph showing the dependence of the degree of polymerization of the photocurable resin on the light irradiation time when the acceleration light is irradiated using a comparative example of the present invention and when the acceleration light is irradiated using a reference example in which oxygen is assumed not to be present. Note that in FIG. 8 , the values ​​are normalized by the value at which the degree of polymerization saturates in the comparative example.

[0031] The comparative example of the present invention uses the same configuration as the optical shaping apparatus 10 shown in FIG. 1 , but the irradiation pattern of the promotion light formed by the DMD 13 is different from the irradiation pattern shown in FIG. 2 . The irradiation pattern formed by the DMD 13 in the optical shaping apparatus 10 includes a first region A1 and a second region A2, as shown in FIGS. 2A and 2B . On the other hand, the irradiation pattern formed by the DMD 13 in the comparative example includes the first region A1′ but does not include the second region A2, as shown in FIG. 7 . Note that, like the optical shaping apparatus 10, the comparative example also irradiates the first region A1′ with promotion light L1 whose time average intensity is higher than the shaping threshold.

[0032] In the comparative example, oxygen present in the first region A1' irradiated with the acceleration light L1 is consumed by the polymerization initiator activated by the acceleration light L1. Therefore, as shown in FIG. 7, the oxygen concentration within the first region A1' decreases, although there is some distribution. However, outside the first region A1', there is a large amount of photocurable resin R that has not been irradiated with the acceleration light L1, and this photocurable resin R remains in a state containing a large amount of oxygen. Therefore, a large amount of oxygen diffuses from the outside of the first region A1' into the inside of the first region A1' where oxygen has been consumed (see the oxygen flux in FIG. 7).

[0033] When comparing the case where the comparative example was irradiated with accelerating light with the case where the reference example was irradiated with accelerating light, which assumed the absence of oxygen, the rise in polymerization degree in the comparative example was significantly slower than in the reference example, indicating that the presence of oxygen inhibits the progress of the polymerization reaction. In the comparative example, the inhibition of the polymerization reaction by oxygen makes it difficult for the photocurable resin to harden. Therefore, when comparing the planar shape of the region irradiated with the first light with the planar shape of the region where the photocurable resin has hardened, the area of ​​the region where the photocurable resin has hardened is smaller, resulting in a significant discrepancy between the two. Furthermore, the inhibition of the polymerization reaction by oxygen is more pronounced with shorter light irradiation times, and it was found that the finer the steps per layer in the stereolithography process, the greater the susceptibility to this effect.

[0034] In contrast, in the irradiation pattern used by the optical shaping apparatus 10 of this embodiment, the second region A2 is arranged so that its outer edge A21 surrounds the outer edge A11 of the first region A1. Furthermore, the second region A2 is irradiated with acceleration light L1 whose time-average intensity is lower than the shaping threshold value, thereby consuming oxygen in the second region A2. Therefore, diffusion of oxygen from the second region A2 to the first region A1 can be suppressed (more preferably, prevented).

[0035] As in this irradiation pattern, the second region A2 preferably has a closed annular shape in plan view, and preferably surrounds the first region A1 seamlessly. The closed annular shape of the second region A2 can suppress (more preferably prevent) oxygen diffusion from outside the second region A2 to the first region A1 without passing through the second region A2.

[0036] In this irradiation pattern, oxygen diffusing from outside the second region A2 into the second region A2 may exist near the outer edge A21 of the second region A2 (see the oxygen flux in FIG. 3 ). However, by making the distance L longer than the diffusion length of oxygen, the amount of oxygen that can reach the outer edge A11 of the first region A1 from the second region A2 can be significantly reduced (see the oxygen concentration in FIG. 3 ).

[0037] In this way, the photopolymerization device 10 can reduce the inhibition of the polymerization reaction by oxygen, thereby making it possible to suppress more than ever before the discrepancy that may occur between the planar shape of the area irradiated with the first light and the planar shape of the area where the photocurable resin has hardened.

[0038] In the irradiation pattern of the promotion light L1 shown in Fig. 2, the inner edge A22 of the second region A2 is in contact with the outer edge A11 of the first region A1 and surrounds the outer edge A11. However, the relationship between the inner edge A22 and the outer edge A11 is not limited thereto. For example, as shown in Fig. 4, the first region A1 and the second region A2 may be defined such that the inner edge A22 surrounds the outer edge A11 while being spaced apart from the outer edge A11.

[0039] In this way, even if a gap is formed between the first region A1 and the second region A2 where the promotion light L1 is not irradiated, the planar shape of the second region A2 is a closed ring, so that the possibility of oxygen being supplied to this gap region from outside the second region A2 is very low.

[0040] Furthermore, since a gap is formed between the first area A1 and the second area A2, even if the focus of the promotion light L1 becomes blurred for some reason, the promotion light L1 in the second area A2 is unlikely to overlap with the promotion light L1 in the first area A1, thereby reducing unexpected curing.

[0041] [Embodiment 2] A photo-fabrication apparatus 20 according to Embodiment 2 of the present invention will be described with reference to Figures 5 and 6. Figure 5 is a schematic diagram showing the configuration of the photo-fabrication apparatus 20. Figure 6(a) is a plan view showing the irradiation pattern of the promotion light L1 and the inhibitory light L2 imaged on the fabrication surface P of the photo-fabrication apparatus 20, and Figure 6(b) is a graph showing the intensity distribution of the promotion light L1 and the inhibitory light L2. Note that Figure 7(b) illustrates the intensity distribution along the line A-A' shown in Figure 2(a).

[0042] The optical shaping apparatus 20 is an optical shaping apparatus that uses a liquid-phase polymerization method, similar to the optical shaping apparatus 10. As with the optical shaping apparatus 10, the optical shaping apparatus 20 also uses 1,4-butanediol dimethacrylate as a monomer that constitutes the photocurable resin R. Camphorquinone is also used as a polymerization initiator that absorbs the energy of the acceleration light L1 when irradiated with the acceleration light L1 and starts the polymerization reaction, and the wavelength λ1 of the acceleration light L1 is also 470 nm, the same as that of the optical shaping apparatus 10. However, the optical shaping apparatus 20 uses ultraviolet light with a wavelength λ2 of 375 nm as the inhibitory light L2 that inhibits the polymerization reaction of the photocurable resin R.

[0043] 5 includes the light source 11, the condenser lens 12, the DMD 13, the tube lens 14, the mirror 15, and the objective lens 16, as does the light source 10 shown in Fig. 1, and further includes a light source 21, a condenser lens 22, the DMD 23, a mirror 24, and a dichroic mirror 25. Note that in this embodiment, descriptions of the light source 11, the condenser lens 12, the DMD 13, the tube lens 14, the mirror 15, and the objective lens 16 will be omitted, and only the light source 21, the condenser lens 22, the DMD 23, the mirror 24, and the dichroic mirror 25 will be described.

[0044] The light source 21 is a light source that generates an inhibiting light L2, which is an example of a third light. The wavelength λ2 of the inhibiting light L2 may be any wavelength that inhibits polymerization of the monomer contained in the photocurable resin, and may be appropriately selected depending on the monomer used.

[0045] In this embodiment, similar to the light source 11, the light source 21 is an LED array in which multiple LEDs (light emitting diodes) are arranged in a matrix. The light source 21 has the same configuration as the light source 11, except that the wavelength λ2 is 375 nm instead of 470 nm. That is, the chief ray L21, the chief ray L22, the chief ray L23, and the luminous flux L21F of the inhibiting light L2 emitted by the light source 21 correspond to the chief ray L11, the chief ray L12, the chief ray L13, and the luminous flux L11F of the promoting light L1 emitted by the light source 11, respectively. Furthermore, the light-emitting region 211 of the light source 21 corresponds to the light-emitting region 111 of the light source 11. Therefore, a description of these chief rays and luminous fluxes will be omitted here.

[0046] The condenser lens 22 is a convex lens that converts the divergent light beam L21F into convergent light and focuses the inhibiting light L2 emitted from the light-emitting region 211 onto the light-receiving surface of the DMD 23 via the mirror 24.

[0047] The mirror 24 is a mirror that bends the optical path of the inhibiting light L2 converted into convergent light by the condenser lens 22 toward the DMD 23 by reflecting it.

[0048] The DMD 23 is an example of another spatial light modulator, and its light receiving surface is formed by a plurality of micromirrors arranged in a matrix. An example of a spatial light modulator other than the DMD is LCOS (Liquid Crystal on Silicon). When an LCOS is used as the spatial light modulator, the LCOS may be either a reflective type or a transmissive type.

[0049] The DMD 23 has the same configuration as the DMD 13 and is controlled by the control unit, except that the DMD 23 generates an inhibiting light L2 having a different pattern from the promoting light L1.

[0050] 6A shows the irradiation pattern of the acceleration light L1 generated by the DMD 13 on the printing surface P, and the irradiation pattern of the inhibition light L2 generated by the DMD 23 on the printing surface P. Also, FIG. 6B shows the intensity distribution of the acceleration light L1 and the inhibition light L2. According to FIGS. 6A and 6B, the irradiation pattern of the acceleration light L1 is the same as the irradiation pattern of the acceleration light L1 shown in FIG. 2. That is, the outer edge A21 of the second region A2 surrounds the outer edge A11 of the first region A1, and the inner edge A22 of the second region A2 surrounds the outer edge A11 while being in contact with the outer edge A11.

[0051] 6A and 6B, the third region A3 is located around the first region A1 on the printing surface P. In this embodiment, the third region A3 has a closed annular shape in plan view. The third region A3 is defined such that the outer edge A31 surrounds the outer edge A11 of the first region A1, and the inner edge A32 surrounds the outer edge A11. In this embodiment, the inner edge A32 surrounds the outer edge A11 while being in contact with the outer edge A11.

[0052] In this way, the DMD 23 irradiates the third area A3 located around the first area A1 with the inhibiting light L2 that inhibits the polymerization reaction of the monomer on the modeling surface P. The DMD 23 constitutes another irradiation unit together with the tube lens 14 and the objective lens 16 described in the first embodiment.

[0053] The dichroic mirror 25 transmits the promotion light L1, which has been spatially intensity modulated by the DMD 13 and has a desired pattern, and reflects the inhibition light L2, which has been spatially intensity modulated by the DMD 23 and has a desired pattern, thereby combining the promotion light L1 and the inhibition light L2 on a common optical axis. To this end, the dichroic mirror 25 is configured so that the wavelength λ1 of the promotion light L1 (λ1 = 470 nm in the first and second embodiments) is included in its transmission band and the wavelength λ2 of the inhibition light L2 (λ2 = 375 nm in this embodiment) is included in its reflection band. Note that in FIG. 5 , only the principal ray L11 of the promotion light L1 is illustrated by a two-dot chain line.

[0054] The inhibiting light L2, which is combined with the promoting light L1 by the dichroic mirror 25 and has the desired pattern, is focused onto the forming surface P via the tube lens 14, mirror 15, and objective lens 16, which are arranged downstream of the dichroic mirror 25.

[0055] As described above, the optical shaping device 20 includes, as other irradiation units, the DMD 23 (an example of a spatial intensity modulator) that generates the inhibitory light L2 that is irradiated onto the third region A3 by spatially intensity modulating the inhibitory light L2 from the light source 21, and the tube lens 14 and objective lens 16 (an example of a lens) that focus the inhibitory light L2 irradiated onto the third region A3 onto the shaping surface P, and the shaping surface P and the DMD 23 are arranged in a conjugate position with respect to the tube lens 14 and the objective lens 16. Note that in FIG. 5, the shaping surface P and the DMD 23, which are in a conjugate position with respect to the tube lens 14 and the objective lens 16, are marked with black triangles.

[0056] [Summary] In a stereolithography device using a liquid-phase polymerization method, in order to suppress, more than conventional methods, the discrepancy that may occur between the planar shape of a region irradiated with light and the planar shape of a region where the photocurable resin is cured, a stereolithography device according to a first aspect of the present invention includes an irradiation unit that irradiates a first region of a modeling surface set inside a photocurable resin containing a monomer and a polymerization initiator with first light having a wavelength included in the absorption wavelength of the polymerization initiator and a time-averaged intensity higher than a modeling threshold, and irradiates a second region of the modeling surface with second light having a wavelength included in the absorption wavelength of the polymerization initiator and a time-averaged intensity lower than the modeling threshold. In this exposure device, a configuration is adopted in which the outer edge of the second region on the modeling surface surrounds the outer edge of the first region.

[0057] The inventors of the present application have discovered that oxygen contained in a liquid photocurable resin can inhibit the polymerization reaction of the photocurable resin.

[0058] According to the above configuration, since the second region is irradiated with the second light having a time-averaged intensity lower than the modeling threshold, oxygen diffusing from outside the outer edge of the first region into the first region can be reduced, and therefore, inhibition of the polymerization reaction by oxygen can be reduced, thereby making it possible to more effectively suppress the discrepancy that may occur between the planar shape of the region irradiated with the first light and the planar shape of the region where the photocurable resin is cured.

[0059] In addition, in the optical shaping apparatus according to the second aspect of the present invention, in addition to the configuration of the optical shaping apparatus according to the first aspect described above, a configuration is adopted in which the inner edge of the second region on the shaping surface surrounds the outer edge of the first region.

[0060] According to the above configuration, since the first region and the second region do not overlap with each other, the exposure amount in the first region, which is irradiated with first light whose time average intensity is higher than the modeling threshold, can be set independently, regardless of the exposure amount of the second light.

[0061] In addition to the configuration of the optical shaping apparatus according to the first or second aspect of the present invention, the optical shaping apparatus according to the third aspect of the present invention further comprises a step of setting the diffusion coefficient of oxygen in the photocurable resin to D [cm２ s －１ ], the consumption rate of oxygen concentration in the photocurable resin when irradiated with the second light is ν [s －１ ], and the distance between the outer edge of the first region and the outer edge of the second region on the modeling surface is 4(D / ν) １／２ The above configuration has been adopted.

[0062] According to the above configuration, by irradiating the second region with the second light, the oxygen concentration in the first region can be reduced to 2% or less of the oxygen concentration in the initial state (a state in which neither the first light nor the second light is irradiated). Therefore, it is possible to reliably suppress a discrepancy that may occur between the region irradiated with the first light and the region in which the photocurable resin is cured.

[0063] Furthermore, in the optical shaping apparatus according to the fourth aspect of the present invention, in addition to the configuration of the optical shaping apparatus according to any one of the first to third aspects described above, a configuration is adopted in which the wavelength of the first light and the wavelength of the second light are common.

[0064] According to the above configuration, the first light and the second light can be generated using one common light source.

[0065] Furthermore, in a photo-polymerization apparatus according to a fifth aspect of the present invention, in addition to the configuration of the photo-polymerization apparatus according to any one of the first to fourth aspects described above, a configuration is adopted in which the irradiation unit includes a spatial light modulator that generates the first light and the second light by spatial intensity modulating light from a light source, and a lens that focuses the first light and the second light, and the molding surface and the spatial light modulator are arranged in a conjugate position with respect to the lens.

[0066] According to the above configuration, the first light and the second light, the intensity of which has been spatially modulated by the spatial light modulator, can be focused on the modeling surface, allowing the patterns of the first and second regions to be determined arbitrarily. Therefore, optically modeled objects of various shapes can be easily manufactured. Furthermore, compared to when optical modeling is performed by scanning a modeling light with a point focus, the time required for optical modeling can be shortened because a wide area can be exposed simultaneously.

[0067] Furthermore, the optical shaping apparatus according to the sixth aspect of the present invention, in addition to the configuration of the optical shaping apparatus according to any one of the first to fifth aspects described above, further includes another irradiation unit that irradiates a third region located around the first region on the shaping surface with third light that inhibits polymerization of the monomer.

[0068] According to the above configuration, it is possible to prevent the periphery of the first region from being unintentionally cured by unintended light of the first light, and therefore it is possible to sharpen the edge of the stereolithographic object that corresponds to the outer edge of the first region.

[0069] Furthermore, in the optical shaping apparatus according to the seventh aspect of the present invention, in addition to the configuration of the optical shaping apparatus according to the sixth aspect described above, the other irradiation unit includes another spatial light modulator that generates the third light by spatial intensity modulating light from a light source, and another lens that focuses the third light, and the shaping surface and the other spatial light modulator are arranged in a conjugate position with respect to the lens.

[0070] According to the above configuration, the third light whose intensity has been spatially modulated by the spatial light modulator can be focused on the object to be formed, so that the pattern of the third region can be determined arbitrarily, and therefore, sharp edges can be easily obtained in optically shaped objects of various shapes.

[0071] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0072] DESCRIPTION OF SYMBOLS 10, 20 Optical shaping device 11, 21 Light source 12, 22 Condenser lens 13, 23 DMD (spatial light modulator, other spatial light modulator, irradiation unit and part of other irradiation unit) 14 Tube lens (irradiation unit and part of other irradiation unit) 15, 24 Mirror 16 Objective lens (irradiation unit and part of other irradiation unit) 25 Dichroic mirror 111, 211 Light-emitting area A1 First area A11, A21, A31 Outer edge A2 Second area A22, A32 Inner edge A3 Third area L1 Promotion light (first light, second light) L11, L12, L13, L21, L22, L23 Chief light L11F, L21F Light beam L2 Inhibition light (third light)

Claims

1. A photopolymerization device comprising an irradiation unit that irradiates a first region of a modeling surface set inside a photocurable resin containing a monomer and a polymerization initiator with first light, the wavelength of which is included in the absorption wavelength of the polymerization initiator and the time-average intensity of which is higher than the modeling threshold, and that irradiates a second region of the modeling surface with second light, the wavelength of which is included in the absorption wavelength of the polymerization initiator and the time-average intensity of which is lower than the modeling threshold, wherein the outer edge of the second region on the modeling surface surrounds the outer edge of the first region.

2. The optical shaping apparatus according to claim 1, wherein the inner edge of the second region on the shaping surface surrounds the outer edge of the first region.

3. The diffusion coefficient of oxygen in the photocurable resin is D [cm ２ s －１ ], the consumption rate of oxygen concentration in the photocurable resin when irradiated with the second light is ν [s －１ ], and the distance between the outer edge of the first region and the outer edge of the second region on the modeling surface is 4(D / ν) １／２ The optical shaping apparatus according to claim 1 or 2, wherein:

4. The optical shaping apparatus according to any one of claims 1 to 3, wherein the first light and the second light have the same wavelength.

5. The optical shaping device according to any one of claims 1 to 4, wherein the irradiation unit includes a spatial light modulator that generates the first light and the second light by spatially intensity modulating light from a light source, and a lens that focuses the first light and the second light, and the shaping surface and the spatial light modulator are arranged in a conjugate position with respect to the lens.

6. The optical shaping device according to any one of claims 1 to 5, further comprising another irradiation unit that irradiates a third area located around the first area on the shaping surface with third light that inhibits polymerization of the monomer.

7. The optical shaping device according to claim 6, wherein the other irradiation unit includes another spatial light modulator that generates the third light by spatially intensity modulating light from a light source, and another lens that focuses the third light, and the shaping surface and the other spatial light modulator are arranged in a conjugate position with respect to the lens.

Images