JP3805749B2 - Thin film curing stereolithography equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a regulated liquid level optical modeling apparatus that thinly cures and cures a photocurable resin.
[0002]
[Prior art]
Proposed a stereolithography method and equipment using a regulated liquid surface method that irradiates the photocurable resin in the tank with light energy from below the resin tank and forms a cured resin layer on the bottom surface of the modeling base plate placed in the resin liquid. Has been.
This stereolithography apparatus uses a liquid crystal panel driven based on shape data corresponding to a target shape as an optical shutter, and passes light from a surface light source as a parallel light beam to a photo-curing resin through a light-transmitting portion of the liquid crystal panel. Irradiate, cure the irradiated surface-shaped divided pattern portion to form the first-layer shaped object of the target shape, then move the liquid crystal panel to the next predetermined position by moving means, and perform the same process Repeatedly, a multilayered model is obtained.
[0003]
However, since this prior art irradiates the entire liquid crystal panel with the light of the surface light source at once, the entire liquid crystal panel is always exposed to heat rays and overheated, and the molding accuracy is lowered due to deformation and malfunction of the liquid crystal mask, Since the light from the surface light source passes through the translucent part of the liquid crystal panel from all directions, the part that should not be irradiated is irradiated with the light that has been obliquely transmitted through the translucent part. There was a problem that could not be obtained.
Furthermore, since the surface light source also irradiates the periphery of the liquid crystal mask, the light use efficiency of the light source is extremely low. For this reason, a large amount of power is required to maintain a predetermined illuminance on the light-cured resin irradiation surface. There was a problem.
[0004]
Moreover, the prior art irradiates the light curable resin with light close to parallel rays, and therefore, the thickness control of the cured layer depends solely on the sensitivity of the light curable resin. Since the sensitivity of the photo-curing resin is adjusted so that it does not cure even when some light hits the resin, the thickness of the cured layer of each layer is about 1000 microns, even if it is thin, it is about 100 microns. Since the thickness of the thin hardened layer below this could not be obtained, a step was produced in the optical modeling product, and the accuracy was deteriorated.
[0005]
In addition, the thickness of the hardened layer can be easily judged to be controllable by the amount of movement of the modeling base plate, but since the light used is close to parallel rays, the depth of the effect is one layer of the size of the modeled object. When it was larger than the layer, the thickness of the cured layer became as thick as about 100 microns due to the characteristics of the resin, and additive fabrication could not be performed.
[0006]
As another stereolithography method and apparatus, it is also known to irradiate a photocurable resin with a laser beam based on shape data. However, there is a drawback that it takes a long time to model one model. It was. Further, the lamination pitch is usually 100 microns, and it is difficult to make it thinner.
[0007]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and the object of the present invention is to make the thickness of a cured product layer of each layer formed on the surface of the modeling base plate as ultrathin, for example, 20 microns or less. It is possible to provide an optical modeling apparatus capable of easily modeling an optical modeling object with high accuracy within a relatively short time.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the thin-film curable optical modeling apparatus of the present invention stores a photocurable resin in a resin tank whose bottom surface is made of a transparent plate, and makes the modeling base plate disposed in the resin tank approach the transparent plate. An optical modeling apparatus using a regulated liquid level system that irradiates light from below the resin tank to the resin in the resin tank and forms a cured product layer having a predetermined thickness on the lower surface of the modeling base plate. A main optical system composed of a multi-point condensing spot lens using a minute lens having a focal point in the vicinity, and each of irradiating light from a light source as parallel light to the minute lens constituting the main optical system is tiltable. A digital micromirror device with a large number of micromirrors, and a digital micromirror device placed between the digital micromirror device and the main optical system. An intermediate optical system comprising a lens that outputs light as parallel light expanded in accordance with the pitch of the main optical system, means for sequentially moving the optical system in the X direction or Y direction, and means for moving the modeling base plate in the vertical direction It has.
[0009]
Preferably, in the thin-film curing type optical shaping apparatus of the present invention, the size of the microlens is larger than that of the micromirror constituting the digital micromirror device, and the intermediate optical system is provided for each microlens with respect to one micromirror. It is comprised so that reflected light may be expanded according to a magnitude | size.
Preferably, in the thin film curing type optical shaping apparatus of the present invention, the size of the micro lens is larger than that of the micro mirror constituting the digital micro mirror device, and a plurality of intermediate optical systems are provided for one micro lens. The reflection light transmitted from the individual micromirrors is configured to be enlarged.
[0010]
[Action]
In the present invention, light is radiated to the photocurable resin in the tank in a spot manner from a lower side of the resin tank through a fine lens group, and a cured layer is formed in a spot on the lower surface of the modeling base plate. Since a lens group in which a large number of fine lenses having a focal point are arranged in the very vicinity of the lens surface is used, the cured layer can be 20 microns or less. However, the hardened layer is scattered in an island shape and does not become a surface as it is. Therefore, the lens group and the cured layer are relatively moved in the horizontal direction, whereby the uncured photo-curing resin is sequentially cured and connected to form a surface property, thereby forming an extremely thin film. In addition, since a digital micromirror device is used, all the light is reflected and is not heated. As in the case of a liquid crystal mask, heat is generated by the liquid crystal being absorbed, resulting in malfunction. In addition, the shape of the micromirror can be created freely by turning the micromirror on and off, and it has an intermediate optical system. And can be appropriately incident on the main optical system as parallel light.
[0011]
When obtaining a three-dimensional shaped product, if the first layer is cured, the base plate is moved in the Z-axis direction by a predetermined amount by the Z-axis direction lifting device. Since the uncured photo-curing resin is under the first layer, the second layer integrated with the first layer is formed under the first layer when the above process is performed. By repeating the necessary number of times below, a three-dimensional stereolithography object is accurately created.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
1 to 9 show an example of a thin film curing type optical modeling apparatus according to the present invention.
In FIG. 1, reference numeral 1 denotes a resin modeling tank, which is composed of a side wall plate 1a having no light transmittance and a transparent bottom plate 1b made of quartz glass or the like, and is entirely supported by a support body (not shown). The photocurable resin 2 is stored with the bottom plate 1b as a bottom. A transparent peeling thin film 10 such as Teflon (registered trademark) or diamond-like carbon is coated on the inner surface of the bottom plate 1b, that is, the surface in contact with the photocurable resin 2, and the cured layer and the final shaped product can be easily peeled off. It can be done.
[0013]
Reference numeral 3 denotes a modeling base plate that is immersed in the photocurable resin 2 in the resin modeling tank 1, which is a light-shielding face plate that is larger than the maximum dimension of the modeled object to be modeled. The modeling base plate 3 is moved up and down at an arbitrary pitch by being provided integrally and moving the Z-axis stage 4.
[0014]
Reference numeral 5 denotes an airframe located below the resin modeling tank 1, which has an XY axis stage 6 movable in two horizontal directions and a base 7 fixed to the XY axis stage 6. The base 7 is a bottom plate of the resin modeling tank 1. A rigid base 7a is provided to face 1b.
The drive control units 4c and 6c of the Z-axis stage 4 and the XY-axis stage 6 are connected to a controller 8 including an external CPU. CAD data is input to the controller 8, and signals are sent to the drive control units 4c and 6c of the Z-axis stage 4 and the XY-axis stage 6 in accordance with the information, so that the moving direction and moving amount are automatically controlled. It has become.
[0015]
Reference numeral 9 denotes a main optical system mounted on a hard and transparent base 7 a such as quartz glass of the mount 7. The main optical system 9 is composed of a lens group capable of creating a multifocal light spot SP from parallel light.
Specifically, as shown in FIG. 3, a microlens array in which a large number of fine lenses 90 having a focal point near the lens surface such as a hemispherical lens or a ball lens are arranged in an array shape is used.
[0016]
The reason why the fine lens 90 is used in the present invention is to control the thickness of the hardened layer for one layer to 20 microns or less, and the unit lens preferably has a diameter of about 300 microns or less. This makes it possible to control the focal length from the lens surface to 20 microns or less from the surface of the bottom plate 1b when irradiated with parallel rays. The focal length can be finely adjusted by changing the lens material, that is, the refractive index. Also, it is possible to reduce the focal length in a similar manner by reducing the diameter of the lens.
[0017]
The fine lenses 90 are arranged on the base 7a directly or on another transparent plate in a staggered manner as shown in FIG. 3A or in a parallel manner as shown in FIG. It is fixed by a fixing medium such as a trademark resin. The lens group is disposed such that the surface thereof is close to or in contact with the lower surface of the bottom plate 1b.
[0018]
Reference numeral 11 denotes an intermediate optical system disposed behind the third optical system 9, and reference numeral 12 denotes a source optical system including a mirror device 14 disposed rearward on the optical axis of the intermediate optical system 11. Each optical system is mounted on the gantry 7 and is moved together with the gantry 7.
The source optical system 12 includes an arbitrary light source 12a having a wavelength of 350 to 450 mm, such as a metal halide lamp, and a lens 12b that irradiates the mirror device 14 with light from the light source 12a. A collimating lens or the like can be used as the lens 12b.
The intermediate optical system 11 includes lenses 11 a and 11 b that expand parallel light from the mirror device 14 in accordance with the pitch of the minute lenses 90 in the main optical system 9 and output parallel light. The lenses 11a and 11b are arbitrary, such as a Kepler type beam expander as shown in FIGS. 4 and 5, and a Galileo type beam expander as shown in FIGS.
[0019]
The mirror device 14 may be a normal mirror, but a digital micromirror device is preferably used. The digital micromirror device is a light modulation semiconductor chip composed of, for example, a very small mirror (micromirror) 14a of 16 × 16 μm. That is, as schematically shown in FIG. 8, the micromirror 14a is a MEMS element (a general term for a microsystem in which micro-sized sensors, actuators, and control circuits are integrated) arranged on a base 14b at fine intervals. Each of the micromirrors 14a is connected to the controller 8 and electromechanically controlled by digital signals from now on, and can be tilted so as not to collide with each other at angles of +10 degrees (on) and −10 degrees (off). It has become. Each of the micromirrors 14a can be switched on / off at an ultra-high speed of several thousand times per second.
Although only 3 × 3 mirrors are shown in FIG. 2, the same number of fine lenses 90, for example, 1280 × 1024 is actually used.
[0020]
When the light strikes, the light hitting the off-state micromirror 14 a ′ is directed outward and absorbed by a light absorbing plate (not shown), and only the light hitting the on-state micromirror 14 a passes through the intermediate optical system 11. To the fine lens 90 in the main optical system 9. Therefore, even when the planar shape of the shaped object A is a ring shape having an empty space a in place as shown in FIG. 12 or a shape with irregularities on the periphery, a predetermined micromirror is turned off correspondingly. It is possible to deal with it freely.
[0021]
Depending on the type of the microlens 90 to be used, the intermediate optical system 11 may be omitted and the main optical system 9 may be directly irradiated with the parallel light from the mirror device 14.
FIG. 9 and FIG. 10 show such an example, and FIG. 9 shows a case where the reflected light is sent as parallel light to each one of the fine lenses 90 for each mirror of the mirror device 14 without being enlarged. Is shown. In FIG. 10, reflected light from a plurality of micromirrors is sent to each microlens 90.
[0022]
However, when the micro lens 90 of the main optical system 9 is about the same as the size of the micro mirror, the focal length is too short. Therefore, the micro lens 90 having a size larger than that of the micro mirror is used, and one micro mirror is used. In order to adjust the reflected light to the size of one lens, it is preferable to use the intermediate optical system 11.
FIG. 11 and FIG. 12 show an example, and FIG. 11 enlarges the reflected light by the intermediate optical system 11 in accordance with the size of each micro lens 90 for one micro mirror. In FIG. 12, the reflected light of the plurality of micromirrors is enlarged by the intermediate optical system 11 in accordance with the size of one microlens 90.
9, 10, and 11, one micromirror is turned off and is not incident on the microlens 90, because this shows that it can cope with the modeling shape as described above.
[0023]
As another aspect of the present invention, the film side, that is, the resin modeling tank 1 may be moved in the XY axes instead of moving the optical system. In this case, the gantry 7 is fixed in position, and the resin modeling tank 1 is mounted on the outer frame-shaped XY axis stage and driven by the controller 8.
[0024]
The thin film curing type optical modeling method using the apparatus of the present invention will be described. First, the shape and dimensions to be modeled are converted into data by CAD, and the data is input to the controller 8. The controller 8 determines the number and position of the micromirrors of the mirror device 14 to be turned off according to the shape and dimensions to be shaped, and determines the amount of movement in the XY axis direction, the amount of movement in the Z axis direction, and the light amount of the light source. To do.
The photo-curing resin 2 is optional. For example, as an epoxy system, an SCR 7001 with a critical exposure Ec of 33 mJ / cm ^2, an SCR 710 with 13 mJ / cm ^{2, and} an SCR 9120 with 10.9 J / cm ² are used. 1 is stored.
[0025]
When a signal from the controller 8 is sent to the mirror device 14, the micromirror 14a at a position corresponding to the shape and size to be shaped is turned on / off. In the case where the modeling shape has no unevenness in the plane or when there is no empty portion, the micromirror in the modeling outline is turned on, but the modeling shape has no unevenness in the plane or as illustrated in FIG. If there is a void a, the micromirror at the position corresponding to it is turned off. Of course, the micromirror outside the modeling contour is also turned off.
The signal from the controller 8 is also sent to the drive control unit 4 c of the Z-axis stage 4, whereby the Z-axis stage 4 is lowered and the modeling base plate 3 is held at a position close to the bottom plate 1 b of the resin modeling tank 1. Further, a signal from the controller 8 is sent to the light source 12a, and light is irradiated with an appropriate amount of light.
[0026]
The light from the light source 12a is applied to the mirror device 14, and parallel light is reflected by each micromirror. The parallel light from the on-state micromirror 14a is enlarged by the intermediate optical system 11 in accordance with the size and pitch of the fine lens 90 of the main optical system 9, and is incident on the main optical system 9 as parallel light. Since the main optical system 9 is composed of a lens group in which a large number of fine lenses 90 having a focal point are arranged in the vicinity of the lens surface, the light is irradiated as shown in FIGS. 13 (a) and 14 (a). The curable resin 2 is cured at a time with multiple spots condensed so as to be equal to or greater than the critical exposure amount. SP is a condensing spot, and 20 is a spot-like (island-like) hardened portion.
[0027]
In surface exposure, it is necessary to irradiate the resin with light that is larger than the exposure amount of the photocuring resin, so a powerful light source is required, but this light must be collected at a sharp angle with a multipoint lens. This makes it possible to cure only the portion of the resin whose light energy density is increased. By making an acute angle, the curing depth is shallow and it is possible to cure thinly to 20 microns or less. That is, the curing depth can be reliably controlled.
Since the light is collected by the lens to produce light that exceeds the sea exposure amount and the resin is cured, even if the resin is irradiated with the light that has passed through the gaps between the fine lenses, the portion is not cured.
[0028]
Next, a signal from the controller 8 is sent to the drive unit 6c of the XY axis stage 6, whereby the XY axis stage 6 and the optical system mounted thereon move horizontally. As a result, the condensing spot SP from the lens group in which a large number of fine lenses 90 having a focal point in the vicinity of the lens surface are arranged continuously translates in the X or Y direction by one pitch of the lens group.
FIG. 13B shows the middle of movement, and FIG. 13C and FIG. 14B show a state where the lens is moved by the lens interval. In this example, the condensing spot SP moves to the right to connect the spot-like hardened portions 20 and 20 ′ to form a surface 200 having a predetermined width of 20 μm or less.
[0029]
FIGS. 15A to 15D show a state in which one layer is formed. As shown in FIG. 15A, the condensing spot is moved in the X direction to form a predetermined surface 200, and then the Y direction. After moving to the spot diameter or a moderately smaller amount than that, it moves to the left, and is connected so that it becomes the surface 200 'of the second row as shown in (b). Then, after moving in the Y direction by a spot diameter or a modest amount smaller than that, it moves to the right and connects to the surface 200 ″ of the third row as shown in (c). A necessary surface is formed as shown in (d) by the same movement path, and the first hardened layer A is completed.
In order to obtain the central space a in FIG. 15, the micro mirror 14 a that forms a pair with the minute lens 90 corresponding to the space a may be set in the OFF state, which can be easily handled.
[0030]
FIG. 16A schematically shows a state where the first hardened layer A is formed, and the first hardened layer A having a thickness t of 20 microns or less is bonded to the lower surface of the forming base plate 3. ing.
Next, the irradiation of light from the light source 12 a is once stopped, and the Z-axis stage 4 is raised by a predetermined amount by a signal from the controller 8. Since the lower surface of the first hardened layer A is in contact with the transparent peeling thin film 10, it easily peels off and rises along with the modeling base plate 3 as shown in FIG.
[0031]
This state is confirmed, and light is again emitted from the light source 12a. As a result, the bottom surface of the first hardened layer A is used as a modeling base plate, and a spot-like hardened portion is formed by the condensing spot SP as in the case of the first layer, and the condensing spot SP is formed in the XY axis direction. It moves and connects the spot-like hardened parts to form the second hardened layer. The second hardened layer is bonded and laminated to the first hardened layer A. By repeating the above steps as many times as necessary, a highly accurate stereolithography object having a desired shape can be obtained.
[0032]
In addition, in this invention, all the some hardened layers are not limited to the aspect which produces and laminates | stacks by the equivalent thickness. Films with different thicknesses may be created and laminated. This includes, for example, a portion that requires accuracy of the optically shaped object and a portion that does not.
This is achieved by changing the Z-axis direction moving distance of the modeling base plate 3, that is, the pitch of the stacking interval, and sending a signal from the controller 8 to the light source 12a to control the amount of light under the condition that the focal point of the lens is fixed. What is necessary is just to change the critical exposure amount to resin.
[0033]
FIG. 17 schematically shows this. When a layer corresponding to a portion requiring accuracy is formed, the moving distance of the forming base plate 3 in the Z-axis direction is reduced, and light energy is irradiated with a suitable critical exposure amount. A thin first cured layer A is formed. When the next layer is a layer corresponding to a portion that does not require accuracy, as shown in (a), the Z-axis direction moving distance of the modeling base plate 3 to which the first hardened layer A is bonded is relatively large. At the same time, the amount of light from the light source 12a is increased to greatly irradiate light energy (intensity), thereby changing the critical exposure amount to the resin. This deepens the solidification depth, and a thick hardened layer A2 is laminated as shown in (b). When the third layer is also thickened, the Z-axis direction moving distance of the modeling base plate 3 may be increased as shown in the figure.
[0034]
In the case where the unevenness and the empty portion have a shape that does not penetrate in the thickness direction of the optical modeling object, the micromirror of the mirror device 14 is switched to the on state at the stage of forming the corresponding layer, and the light source 12a is in that state. Then, light may be irradiated and condensed by a fine lens 90. Therefore, even complex shapes can be easily optically modeled.
Moreover, what is necessary is just to set it as a finished product in the said 1st layer, when obtaining a thin sheet-like optical modeling thing.
[0035]
The present invention uses a mirror device 14 such as a digital micromirror device and does not use a liquid crystal mask. For this reason, since all the light is reflected, it is hardly heated, and generation of heat and failure due to absorption of light by the liquid crystal as in the case of the liquid crystal mask can be prevented.
[0036]
【The invention's effect】
According to claim 1 of the present invention described above, a photocurable resin is stored in a resin tank whose bottom surface is made of a transparent plate, and a modeling base plate arranged in the resin tank is brought close to the transparent plate, and the resin tank Is a stereolithography apparatus based on a regulated liquid level system that irradiates the resin in the resin tank from below and forms a cured product layer having a predetermined thickness on the bottom surface of the modeling base plate, and has a focal point near the lens surface. A main optical system composed of a multi-point condensing spot lens using a fine lens and a number of micromirrors each capable of tilting to irradiate light from a light source as parallel light to the fine lens constituting the main optical system. Digital micromirror device equipped, and between the digital micromirror device and the main optical system, the parallel light from the micromirror device is the main light An intermediate optical system composed of lenses that output as parallel light expanded in accordance with the pitch of the system, means for sequentially moving the optical system in the X direction or Y direction, and means for moving the modeling base plate in the vertical direction Therefore, with a relatively small and simple structure, it is possible to easily form a highly accurate optically shaped object in which the layer thickness is thinly stacked in a short time.
In addition, since a digital micromirror device is used, all the light is reflected, and the parallel light from the micromirror device is output as parallel light expanded in accordance with the pitch of the main optical system in the intermediate optical system. Therefore, it is possible to obtain an excellent effect that a shape to be shaped can be freely created with high accuracy by turning on / off the micromirror.
[Brief description of the drawings]
FIG. 1 is a longitudinal side view showing an example of a thin film curing type optical shaping apparatus according to the present invention.
FIG. 2 is a perspective view of a modeling state.
FIGS. 3A and 3B are plan views showing examples of a main optical system, respectively.
FIG. 4 is a side view showing a state in which modeling is performed using a Kepler type beam expander as an intermediate optical system.
FIG. 5 is a partially enlarged view of FIG. 4;
FIG. 6 is a side view of a state in which a Galileo beam expander is used as an intermediate optical system.
FIG. 7 is a partially enlarged view of FIG. 6;
FIG. 8 is a perspective view showing an outline of a digital micromirror device.
FIG. 9 is a side view showing a first example of a form of forming a focused spot.
FIG. 10 is a side view showing a second example of the formation mode of the focused spot.
FIG. 11 is a side view showing a third example of the formation mode of the condensed spots.
FIG. 12 is a side view showing a fourth example of the formation mode of the condensed spots.
FIGS. 13A, 13B and 13C are schematic cross-sectional views showing the thin film forming process in the present invention step by step.
14 (a) and 14 (b) are schematic plan views showing the thin film formation process in the present invention step by step.
FIGS. 15 (a), 15 (b), 15 (c) and 15 (d) are schematic plan views showing the thin film formation process in the present invention step by step.
FIGS. 16A and 16B are schematic cross-sectional views showing stepwise the lamination method in the present invention.
17 (a) and 17 (b) are schematic cross-sectional views showing stepwise examples of the lamination method in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Resin modeling tank 2 Photocurable resin 3 Modeling base plate 4 Z-axis stage 6 YY-axis stage 9 Main optical system 90 Fine lens 11 Intermediate optical system 14 Mirror device 14a Micro mirror

Claims (3)

A photocurable resin is stored in a resin tank whose bottom surface is made of a transparent plate, a modeling base plate arranged in the resin tank is brought close to the transparent plate, and light is applied to the resin in the resin tank from below the resin tank. A multi-point condensing spot lens that uses a fine lens that irradiates and forms a cured layer having a predetermined thickness on the lower surface of the modeling base plate, using a fine lens having a focal point near the lens surface. A digital micromirror device having a plurality of micromirrors each capable of tilting to irradiate light from a light source as parallel light onto a minute lens constituting the main optical system, Arranged between the micromirror device and the main optical system, the parallel light from the micromirror device is output as parallel light expanded according to the pitch of the main optical system. An intermediate optical system including a lens for the optical system successively and means for moving, the thin film curing stereolithography apparatus characterized in that it comprises means for moving the shaping base plate in the vertical direction in the X or Y direction. The microlens is larger in size than the micromirror constituting the digital micromirror device, and the intermediate optical system is configured to expand the reflected light in accordance with the size of each microlens with respect to one micromirror. The thin-film curable stereolithography apparatus according to claim 1.   The micro lens is larger in size than the micro mirror constituting the digital micro mirror device, and the intermediate optical system is configured to expand the reflected light transmitted from the plurality of micro mirrors to one micro lens. The thin film curing type optical modeling apparatus according to claim 1.

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