JP3173088B2 - Optical stereoscopic image forming method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for selectively irradiating a photocurable resin with a laser beam to form a three-dimensional three-dimensional image and an apparatus therefor. An object of the present invention is to provide a method and an apparatus capable of making the liquid film thickness uniform.

[0002]

2. Description of the Related Art Molds are often used to produce molded articles made of synthetic resin. However, the mold forming method has problems that a large amount of cost is required for manufacturing a mold and that many steps are required until a molded product is obtained.

As a method of solving the above-mentioned problems of the mold molding method, a method of forming a desired three-dimensional image by exposing a photocurable resin to light with a predetermined exposure beam and curing the light-curable resin has recently been disclosed in Japanese Patent Application Laid-Open Publication No. HEI 9-163191. Japanese Patent Application Laid-Open No. 62-36966 and others have been proposed.

In this method, a predetermined portion of the surface of a liquid photocurable resin is irradiated with light to form a cured layer having a predetermined shape, and an uncured liquid resin is further supplied on the cured layer, and the light is again irradiated. Is repeated to form a cured layer, and then laminated on the previously cured layer to form a three-dimensional resin molded product. Laser light is used as light for curing the resin because of the photosensitive wavelength characteristics, beam directivity, and light condensing properties of the photocurable resin.

In this method, in order to control the thickness of each of the cured layers sequentially laminated, the thickness of the uncured resin liquid film supplied on the already-cured layer must be regulated. FIG. 4 is a schematic diagram illustrating a conventional method for regulating the thickness of a resin liquid. The resin cured product 1 shown in FIG. 4A is submerged in the resin liquid 2 as shown in FIG. At this time, the depth of the cured resin is set to be larger than a predetermined thickness. The resin liquid 2 is gradually supplied by natural flow onto the surface of the cured product, and the liquid level becomes horizontal. Next, as shown in FIG. 4C, the cured resin 1 is raised to a predetermined position. At this time, in general, the resin liquid surface is not horizontal, but rises over the entire surface or a part of the resin cured product 1, so that the film thickness of the resin liquid 2 on the resin cured product 1 becomes larger than a predetermined thickness. ing. Subsequently, FIG.
As shown in FIG. 4D, by moving the wiper 3 composed of a smooth plate standing perpendicular to the liquid surface, the excess resin liquid is scraped off, and as shown in FIG. The thickness of the resin liquid on the cured resin 1 is set to a specified thickness.

Further, Japanese Patent Application Laid-Open No. 61-114818 describes a method of obtaining a uniform film thickness by moving a wiper formed of a smooth plate perpendicular to the resin liquid surface while supplying the resin liquid. .

[0007]

However, in the above-mentioned method for regulating the film thickness, there was no problem in the case of a relatively thick laminated layer having a thickness of about 0.2 mm. In addition, it was found that a swelling of the liquid surface, which is considered to be caused by the viscosity and the surface tension of the resin liquid, occurred, and the layers could not be laminated properly. For example, when a wiper perpendicular to the liquid surface as shown in FIG. 4D is used, a lens-like swell gradually occurs in the cured layer corresponding to the swell of the liquid surface in each curing process. In the end, the resin cured product becomes higher than the liquid level, and the wiper comes into contact with this resin cured product, and in severe cases the molded product may be destroyed or conversely, the wiper will not move and molding will be stopped. Sometimes it became impossible. Moreover, even if the wiper does not come into contact, naturally, the accuracy in the height direction is not reliable at all. For example, a model molded under such conditions has a design shape shown in FIG. 5B with respect to the design shape shown in FIG. 5A, and is not practical.

In the stereolithography method, a step equal to the thickness of each lamination always occurs on a curved surface or an inclined surface.
It is desirable that the lamination thickness be as small as possible for the purpose of increasing the precision of the formed product. The thinner the lamination thickness, the smoother the surface, and the need for polishing in a later step becomes unnecessary or easy, which is desirable. From this viewpoint, the above-mentioned swelling phenomenon was a very inconvenient phenomenon.

The present invention solves such a conventional problem,
It is an object of the present invention to provide a method capable of precisely forming a three-dimensional image and an apparatus therefor.

[0010]

As a result of a detailed study of the above-mentioned swelling phenomenon, it has been found that a meniscus is formed by the contact angle between the wiper and the resin liquid, and the cause is that the resin liquid adheres to the wiper. . That is, FIG.
As shown in FIG. 5, in the wiper 3 perpendicular to the resin liquid surface, a meniscus is always formed unless the combination has a contact angle of 90 degrees, and the resin liquid 2 becomes higher than the liquid surface. The meniscus moves with the movement of the wiper 3, but as shown in FIG. 6B, the influence of the swelling remains even after the wiper 3 is separated from the surface of the cured resin 1.

From the above, the present invention has been made based on the idea that, if the meniscus is not generated, the swelling phenomenon does not occur. FIG. 7 shows the contact angle θ between the wiper 3 and the resin liquid 2. In the combination of the resin liquid having the contact angle θ and the wiper as shown in FIG. 7, when the liquid surface and the wiper are positioned vertically as shown in FIG. 7A, a meniscus is formed. And the liquid level rises.

FIG. 7B shows the contact angle when the resin liquid 2 is on the smooth plate 3.

On the other hand, as shown in FIG.
When the wiper 3 is tilted and the angle between the liquid surface and the smooth plate is exactly equal to the contact angle θ, at least one of the smooth plates has an apparently horizontal liquid surface, and the resin liquid is higher than the liquid surface. Never. That is, if the wiper is moved in such a direction that the liquid level is horizontal, the surface formed after the movement is smooth and has a uniform film thickness.

According to the present invention, a three-dimensional image is formed by irradiating the liquid photocurable resin contained in the resin container with light to selectively form a photocurable layer. In the method of forming a three-dimensional image, a wiper is disposed on the resin container, and the wiper is moved in a direction perpendicular to the length direction to form a resin liquid layer having a smooth and uniform film thickness. The angle between the rear surface with respect to the moving direction of the wiper and above the resin liquid surface and the resin liquid surface behind with respect to the moving direction of the wiper is an obtuse angle, and at an angle that does not substantially generate meniscus. Yes,
And an angle formed between a front surface of the resin liquid in the moving direction of the wiper and above the surface of the resin liquid and a surface of the resin liquid rearward in the moving direction of the wiper is a right angle or an obtuse angle. This method of the present invention enables precise lamination of 0.1 mm or less.

Further, the three-dimensional image forming apparatus according to the present invention comprises:
A liquid photocurable resin contained in a resin collecting container is irradiated with light to selectively form a photocurable layer, and a plurality of such photocurable layers are stacked to form a three-dimensional stereoscopic image. A wiper arranged on the container, and means for moving the wiper in a direction perpendicular to the length direction thereof,
Here, the angle formed between the rear surface in the moving direction of the wiper and above the resin liquid surface and the resin liquid surface behind the moving direction of the wiper is an obtuse angle and substantially generates a meniscus. And the angle between the front surface of the wiper in the moving direction of the wiper and above the resin liquid surface and the rear surface of the liquid resin with respect to the moving direction of the wiper is a right angle or an obtuse angle. I do.

The wiper desirably has a smooth surface, that is, a smooth plate, and the angle between the smooth plate and the resin liquid varies depending on the type of resin and the combination of materials used for the smooth plate, and is ideally used. The contact angle is desirably set equal to the contact angle uniquely determined by the combination of the members, but may be shifted from the contact angle as long as the meniscus is not substantially formed.

The angle between the wiper and the resin liquid is 30.
Degree or higher is desirable. If the angle is less than 30 degrees, if the resin liquid is on the slope due to some action, the resin liquid may gradually fall and have an adverse effect.

For this reason, it is desirable that the material used for the wiper has as low a surface energy as possible. A material having a low surface energy has a larger contact angle with the resin liquid, which can increase the inclination angle of the smooth plate, and the resin liquid adheres to the wiper surface due to poor wettability with the resin liquid. Can be prevented. Specifically, a material obtained by coating or laminating another material such as a fluorine-containing polymer such as Teflon or polyvinylidene fluoride, a silicon resin, or a metal with these resins is preferable.

As the structure of the wiper, the inclined wiper according to the present invention may be used alone, or a plurality of wipers may be used. When a plurality of wipers are used, if the last wiper in the traveling direction of the wiper is the inclined wiper of the present invention, the previous wiper may be a vertical wiper or a brush-like one. It doesn't matter.

[0020]

In the present invention, since the inclined wiper having the inclined angle at which the meniscus is not substantially generated is used, 0.1 is used.
mm or less, and the surface of the modeled object can be made smooth. For this reason, not only the appearance of the modeled object is improved, but also the polishing in the post-processing step becomes easy or unnecessary, the model creation can be sped up, and the resolution in the height direction of the modeled object can be improved. it can.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic perspective view showing the structure of an example of a three-dimensional image forming apparatus which can be used in the present invention. This apparatus is provided with an optical system that irradiates a laser beam onto the surface of a liquid photocurable resin and scans it, and a resin housing system that houses the liquid resin and moves up and down a cured layer of the resin. Photocurable resin liquid g
Is accommodated in a resin liquid tank h, and the liquid tank h is provided with an elevating table f for raising and lowering the curing tank i on the surface of the resin liquid, a smooth plate k, and a pump m for returning the overflowed resin liquid to the tank.

The optical system rotates the mirror e with a laser beam j focused on the surface of the resin liquid g by a laser oscillator a, mirrors b and e, a shutter c and a Z-focus lens d, thereby changing the resin liquid level. Scan. At this time, an optical path difference occurs when the laser beam irradiates the liquid surface vertically and when the laser beam irradiates obliquely at a certain angle, and the in-focus position shifts. And the focus position can always be adjusted to the liquid level. The focus position can be adjusted by providing a correction lens that moves along the path of the laser beam instead of the Z focus lens.

In order to form a three-dimensional image, for example, a cross-sectional shape obtained by thinly slicing the three-dimensional image to be formed is stored in a storage device, and the rotation of the mirror e is controlled by a control device such as a computer. Make a hardened layer of a predetermined shape for each
In addition, the molded product is lowered into the resin liquid by the thickness of the hardened layer by controlling the lifting / lowering table f. However, the storage device, the control device, and the like may be the same as those in the conventional example, and are not illustrated. The smoothing plate k is moved by the motor controlled by the same control device at the required time in the direction indicated by the arrow in the figure and in the opposite direction. The drive system of the smoothing plate may be the same as that of the conventional device, and is not shown.

As a device for forming a three-dimensional image, in addition to a device for scanning a laser beam using a movable mirror as shown in FIG. 1, a device for scanning by moving an optical fiber by an NC table or a liquid crystal shutter or the like It is also possible to use an apparatus or the like for performing a batch exposure using a mask.

The photo-curable resin to be used is not particularly limited as long as it is a commonly used liquid photo-curable resin, and is a radical polymerizable photo-curable resin containing urethane acrylate, epoxy acrylate or the like as a main component. Examples thereof include a resin and a photocurable resin utilizing photocationic polymerization of an epoxy resin.

Next, a method for forming a three-dimensional stereoscopic image using the wiper according to the present invention will be described. FIG. 2 shows the basic structure of the wiper according to the present invention. In this structure, the lower surface of a smooth thin plate is cut so as to be equal to the contact angle θ, and the lower surface of the smooth plate 4 is moved along the liquid surface. FIG. 3 shows an example of the structure of a wiper according to the present invention. FIG. 3 (a) shows a structure in which a vertical portion 4A is provided on the upper part of the basic structure shown in FIG. (B) shows a structure in which one surface is kept vertical. (C) is an example of combination with a conventional vertical wiper 3. (D) is an example in which the brush 5 is combined. In the examples of (c) and (d), the vertical wiper 3 and the brush 5 are provided forward of the wiper 4 in the traveling direction.

Example 1 An apparatus having the structure shown in FIG. 1 was used in the experiment. This apparatus is an example in which an overflow method is used for level control of a liquid level. The liquid level is always kept constant by constantly circulating the resin liquid by a circulation pump m. Using this apparatus, a model having the shape shown in FIG. 5A was created with a layer thickness of 50 μm for each layer. FIG. 5A shows the dimensions of the model in mm.

The wiper used was a 2 mm thick Teflon plate processed into the shape shown in FIG. 3 (a). The photocurable resin is urethane acrylate resin Desolite S
CR-200 (manufactured by Nippon Synthetic Rubber Co., Ltd.) was used. The contact angle between the resin and the Teflon plate was 60 degrees. Therefore, the wiper inclination angle θ was adjusted to be 60 degrees.

The lamination was performed in the same manner as shown in FIG. That is, after the curing of the n-th layer by the laser irradiation is completed, the lift f is lowered by 1.5 mm, and
Move to the end of the layer in the direction opposite to the arrow in. Next, it is allowed to stand for 5 seconds, the resin liquid is placed on the n-th layer, and then the lifting platform is raised to a predetermined height (a position 50 μm below the initial position). Next, the smooth plate is moved in the direction of the arrow in the figure to make the liquid level uniform. Next, after leaving still for 5 seconds, laser irradiation of the (n + 1) th layer was performed. Hereinafter, the same operation was repeated to complete the model.

During the molding, the smooth plate did not come into contact with the molded article, and the completed model did not show any swelling as shown in FIG. 5 (b), and exhibited a good appearance as designed.

Comparative Example 1 In the same manner as in Example 1, a model of FIG. 5A was created using a vertical wiper as shown in FIG. 6A. The material used was the same Teflon plate as in Example 1. In this case, it was observed that the wiper was in contact with the modeled object during molding because there was a portion that was higher than the design value.

Therefore, the completed model had a swell as shown in FIG. 5 (b).

Example 2 Using two smooth plates as shown in FIG.
The model of FIG. 5A was created with a layer thickness of μm. The material of the inclined flat plate was Teflon as in Example 1, and the vertical flat plate was a polyethylene plate having a thickness of 2 mm. Subsequent operation was performed in the same manner as in Example 1. There was no contact during molding and the finished model was as designed.

Example 3 A similar experiment was carried out with a lamination thickness of 30 μm using a smooth plate used in combination with a brush as shown in FIG. In this case, the operation of temporarily lowering the elevating table as in Example 1 was not performed, and the lamination was performed by submerging a predetermined lamination thickness of 30 μm from the beginning.

As the material of the inclined flat plate, a polyvinylidene fluoride plate having a thickness of 1 mm was used. The contact angle between this material and the resin liquid was 47 degrees, and the inclination angle was adjusted to 47 degrees.
The brush used was wool and had a hair length of 20 mm.

No contact was observed during molding, and the finished model was as designed.

[0038]

As described above, according to the present invention, a precise lamination of 0.1 mm or less can be achieved, and the surface of the modeled object can be made smooth. For this reason, not only the appearance of the modeled object is improved, but also the polishing in the post-processing step becomes easy or unnecessary, the model creation can be sped up, and the resolution in the height direction of the modeled object can be improved. it can.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an embodiment of an optical three-dimensional image forming apparatus according to the present invention.

FIG. 2 is a sectional view showing a basic structure of a wiper according to the present invention.

FIG. 3 is a cross-sectional view illustrating a structural example of a wiper according to the present invention.

FIG. 4 is a schematic view showing the smoothing of a liquid surface.

FIG. 5 is a perspective view showing a design model and a three-dimensional image formed by a conventional method.

FIG. 6 is a schematic view showing a meniscus generated in a conventional wiper and a swelling of a resin liquid caused by the meniscus.

FIG. 7 is a diagram showing a contact angle between a smooth plate and a resin liquid.

[Explanation of symbols]

 a Laser oscillator b Mirror c Shutter d Z focus lens e Mirror f Lifting table g Resin liquid h Resin liquid tank i Photocured material j Laser beam k Smooth plate m Pump 1 Resin cured material 2 Resin liquid 3,4 Smooth plate

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Katsushi Igarashi 2--11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (56) References JP-A-5-38762 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 67/00

Claims (2)

(57) [Claims] 1. A method for irradiating a liquid photocurable resin contained in a resin collection container with light to selectively form a photocurable layer, and stacking a plurality of such photocurable layers to form a three-dimensional stereoscopic image. In the above, when a wiper is arranged on the resin collecting container and the wiper is moved in a direction perpendicular to its length direction to form a resin liquid layer having a smooth and uniform film thickness, the moving direction of the wiper The angle between the rear surface of the wiper and the upper portion of the surface of the resin liquid and the surface of the resin liquid rearward with respect to the moving direction of the wiper is an obtuse angle, and the angle substantially does not generate a meniscus; Wherein the angle between the front surface in the moving direction of the wiper and above the surface of the resin liquid and the surface of the resin liquid behind the moving direction of the wiper is a right angle or an obtuse angle. 2. An apparatus for selectively forming a photocurable layer by irradiating light to a liquid photocurable resin contained in a resin collecting container, and stacking a plurality of such photocurable layers to form a three-dimensional stereoscopic image. A wiper arranged on the resin collecting container, and means for moving the wiper in a direction perpendicular to the length direction thereof, wherein a rear surface of the wiper in a moving direction and a resin liquid surface The angle between the upper portion and the surface of the resin liquid that is rearward with respect to the moving direction of the wiper is an obtuse angle, is an angle that does not substantially generate meniscus, and is the front surface with respect to the moving direction of the wiper. An optical three-dimensional image forming apparatus, wherein an angle between an upper part of the liquid surface and a resin liquid surface rearward with respect to a moving direction of the wiper is a right angle or an obtuse angle.