Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive...
Reexamination Certificate
2000-04-24
2003-09-30
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
C430S273100, C430S005000, C264S401000, C425S112000, C425S174400, C425S375000
Reexamination Certificate
active
06627376
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to stereolithographic apparatus and method for optically manufacturing a three-dimensional object by using photohardenable resin, and particularly the present invention relates to stereolithographic apparatus and method for exposing the overall surface of a photohardenable resin layer to light through a mask at a time to optically manufacture a three-dimensional object, and also to stereolithographic apparatus and method for optically manufacturing a three-dimensional object having a complicated shape such as an overhang portion, portions which are separately mounted, plural leg portions which are different in length, or the like by using specific photohardenable resin composition. In the following description, “stereolithographic process” is defined as a process of exposing photohardenable resin or photohardenable resin composition to light to form a photohardened layer, and repeating the light exposing operation on photohardenable resin (composition) to laminate photohardened layers on a layer basis, thereby optically forming a desired three-dimensional object.
2. Description of the Related Art
In general, liquid photohardenable resin composition (hereinafter referred to as “photohardenable resin”) has been widely used as coating (particularly, hard coating), photoresist, dental materials, etc. Recently, much attention has been paid to a so-called stereolithography technique which optically forms a three-dimensional object on the basis of data output from a controller such as a three-dimensional CAD system or the like by using photohardenable resin because a three-dimensional object can be optically formed in desired shape and size with high precision even when it has a complicated structure. With respect to the stereolithography technique, Japanese Laid-open Patent Application No. Sho-56-144478 discloses a stereolithographic method for repeating a process of applying a required amount of optical energy to liquid photohardenable resin under control to harden the photohardenable resin as a thin layer, further supplying liquid photohardenable resin onto the hardened resin layer and then exposing the liquid photohardenable resin to light controlled on the basis of stereolithographic data from a controller to harden the liquid photohardenable resin and laminate the thin hardened photohardenable resin layer on the preceding hardened resin layer, whereby a subsequent hardened photohardenable resin layer is successively laminated on a preceding hardened photohardenable resin layer to manufacture a desired three-dimensional object. Further, a practical use method of the stereolithographic method disclosed in the above publication is proposed in Japanese Laid-open Patent Application No. Sho-60-247515, and then various proposals on the stereolithography technique have been made. As a method of optically manufacturing a three-dimensional object has been generally and widely used a method of selectively irradiating laser beams such as ultraviolet laser beams or the like to the liquid surface of liquid photohardenable resin put in a stereolithographic bath under the control of a computer to harden the photohardenable resin so that a photohardened resin layer having a predetermined thickness and a desired pattern is obtained, then supplying a layer of liquid photohardenable resin onto the photohardened resin layer and then likewise exposing a laser beam such as an ultraviolet laser beam or the like to the liquid photohardenable resin layer to harden the photohardenable resin layer, and repeating the lamination/photohardening operations until a targeted three-dimensional object is obtained.
In general, it takes a long time to irradiate laser beams to a layer of photohardenable resin until the photohardenable resin layer is hardened, and for the purpose of increasing the stereolithographic process speed, an apparatus for forming a mask and irradiating the overall surface of a photohardenable resin layer through the mask pattern by an ultraviolet lamp at a time (hereinafter referred to as “plane-exposure”) has been proposed.
According to such a plane-exposing apparatus, a mask having a predetermined pattern formed on the surface thereof is formed and superposed on a unhardened photohardenable resin layer, and then the overall surface of the unhardened photohardenable resin layer is exposed to ultraviolet rays through the mask at a time (i.e, plane-exposed), thereby hardening the photohardenable resin layer in accordance with the mask pattern.
In the plane-exposing apparatus, however, since the mask is not brought into close contact with the unhardened photohardenable resin layer in the exposure process, uneven portions are formed on the surface of the hardened resin layer and thus it is required to cut out these uneven portions layer by layer after the hardening operation of the photohardenable resin is completed.
Furthermore, in a process of forming a photohardenable resin layer, a solid surrounding member is beforehand formed and fixed so as to surround the photohardenable resin layer, and then unhardened photohardenable resin is supplied into the inside of the fixed solid surrounding member. Therefore, unhardened photohardenable resin remains in the solid surrounding member. If the uneven portions on the surface of the hardened resin layer are cut out while the residual unhardened photohardenable resin is left, the comer portions of the hardened resin layer may be defected. In order to avoid this disadvantage, after the photohardenable resin layer is hardened, the unhardened photohardenable resin is scraped up, wax is filled into the scraped portions to prevent defects and then the uneven portions on the surface of the hardened resin layer are cut out. Therefore, extra wax, etc. are required.
Still furthermore, three-dimensional objects having complicated shapes such as overhang portions, separately-mounted portions, plural leg portions which are different in length, uneven portions, etc. have been widely manufactured by using the conventional stereolithography technique. Individual hardened layers which are successively formed by light irradiation are extremely thin, and thus a laminate obtained by laminating these thin layers is also thin. Therefore, the laminate thus finally obtained has a lower shape holding performance. In addition, photohardenable resin in a stereolithographic bath is liquid, and it has little capability of supporting a photohardened layer. Therefore, when a three-dimensional object having a complicated shape such as overhand portions, separately mounted portions, leg portions which are different in length, uneven portions or the like is manufactured, there is liable to occur such problems as hang-down, deformation, dimensional deviation, positional shift, etc. of stereolithographically-formed sites formed by photohardening during the stereolithographic process. Accordingly, in order to avoid these problems, there has been generally adopted a method of disposing a separately-formed support in a stereolithographic bath and stereolithographically forming a desired three-dimensional object while the object being formed is supported by the support (hereinafter referred to as “support basing method”), or a method of stereolithographically forming a desired three-dimensional object while an extra support portion is simultaneously formed together with the desired three-dimensional object (hereinafter referred to as “support attaching method”).
In the following description, the support-based supporting method and the support-attached supporting method will be described; in detail with reference to
FIGS. 1
to
4
F particularly when these methods are applied to the stereolithographic process of forming three-dimensional objects having specific structures.
In the case of a three-dimensional object having a disc portion
202
between upper and lower cylindrical portions
201
a
,
201
b
as shown in
FIG. 1
, when the stereolithographic operation is carried out on a layer basis from the lower
Baxter Janet
Darby & Darby
Lee Sin J.
Teijin Seiki Co. Ltd.
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