Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2000-01-06
2002-07-02
Hamilton, Cynthia (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S285100, C522S096000, C522S097000, C522S092000, C560S183000, C560S209000, C560S221000, C560S222000, C560S115000
Reexamination Certificate
active
06413698
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a novel urethanated acrylic compound, a photohardenable resin composition containing the compound, a process for producing the composition, and a process for producing a three-dimensional object using the composition. More particularly, it relates to a photohardenable resin composition which hardens on irradiation with minimized volume shrinkage to provide a molded part or a three-dimensional object having high dimensional accuracy, a high heat distortion temperature (i.e., high heat resistance), high transparency, and excellent mechanical characteristics, such as tensile strength; a process for producing the photohardenable resin composition; a process for producing a three-dimensional object by stereolithography using the photohardenable resin composition; and a urethanated acrylic compound used in the photohardenable resin composition.
BACKGROUND OF THE INVENTION
Liquid photohardenable resin compositions are generally in wide use as a coating material, especially a hard coating material, a photoresist, a dental material, and the like. In recent years attention has been paid to stereolithography for building up a three-dimensional object from a photohardenable resin composition based on the data put in three-dimensional CAD. In this regard, JP-A-56-144478 discloses a process comprising applying a requisite amount of controlled light energy to a liquid photohardenable resin to harden the irradiated resin in a thin layer, supplying the liquid photohardenable resin on the hardened layer, followed by irradiation under control to harden the resin in a thin layer to be integrally superposed on the previously formed layer, and repeating these steps until a desired solid object is built up. Fundamental materialization of this technique is suggested in JP-A-60-247515. Thereafter, a large number of proposals have been made on the stereolithographic techniques, as disclosed, e.g., in JP-A-62-35966, JP-A-1-204915, JP-A-2-113925, JP-A-2-145616, JP-A-2-153722, JP-A-3-15520, JP-A-3-21432, and JP-A-3-41126.
A typical and commonly used process for producing a three-dimensional object by stereolithography comprises selectively applying a computer-controlled ultraviolet (UV) laser beam to the liquid surface of a liquid photohardenable resin composition in a container according to a designed pattern to harden the resin to a prescribed depth (thickness), supplying the liquid resin composition on the hardened layer to the thickness corresponding to one layer, applying a UV laser beam thereto to successively form a hardened layer on the preceding layer, and repeating these steps until an entire three-dimensional object is built up. This process has recently been attracting attention because three-dimensional objects having complicated shapes can be obtained easily in a relatively short time.
Photohardenable resin compositions which are widely employed as a coating material, a photoresist or a dental material generally comprise a photohardenable compound, such as an unsaturated polyester, epoxy (meth)acrylate, urethane (meth)acrylate or a (meth)acrylic ester monomer, and a photosensitive polymerization initiator.
Photohardenable resin compositions used in stereolithography generally comprise at least one photopolymerizable compound, such as a modified (poly)urethane (meth)acrylate compound, an oligoester acrylate compound, an epoxyacrylate compound, an epoxy compound, a polyimide compound, an aminoalkyd compound, and a vinyl ether compound, as a main component, and a photosensitive polymerization initiator. More recently, various improvements have been added as disclosed, e.g., in JP-A-1-204915, JP-A-1-213304, JP-A-2-28261, JP-A-2-75617, JP-A-2-145616, JP-A-3-104626, JP-A-3-114732, and JP-A-3-1147324.
From the standpoint of handling properties, formation speed and formation accuracy, a photohardenable resin composition to be used in stereolithography is required to be low-viscosity liquid, to show a low level of volume shrinkage on hardening, and to provide a three-dimensional object with satisfied mechanical characteristics. With the increasing demand for, and broadening application of, stereolithography, three-dimensional objects for some uses as intended have now been required to exhibit excellent heat resistance having a high heat distortion temperature and transparency in addition to the above-described properties. For example, three-dimensional objects for use in designing complicated heating medium circuits or analyzing the behavior of a heating medium having a complicated structure are particularly required to have low shrinkage on photohardening, a high heat distortion temperature, and excellent transparency.
In order to obtain three-dimensional objects with improved heat resistance, it has been studied to incorporate a benzene ring into the molecule of a photohardenable resin or to increase the crosslinking density of the photohardened product. However, the heat resistance achieved by these techniques of related arts is insufficient, and the possible highest heat distortion temperature is no higher than about 70 to 80° C. under a high load applied. Moreover, the so far proposed improvement on heat resistance of a photohardened product has been accompanied with increased shrinkage on photohardening, resulting in reduced dimensional accuracy. For example, an increase in crosslinking density in a photohardenable resin composition is generally expected to bring about improved heat resistance. However, an increased crosslinking density tends to lead to increased shrinkage on hardening. That is, an improvement on heat resistance and a reduction in hardening shrinkage are inconsistent with each other, and none of the above-mentioned photohardenable resin compositions of the related arts has succeeded in resolving this inconsistency. It has therefore been demanded to develop a photohardenable resin composition which simultaneously satisfies both requirements of improved heat resistance and reduced volume shrinkage on photohardening.
The present inventors have previously found that the inconsistency experienced between an improvement in heat resistance and a reduction in volume shrinkage can be eliminated by compounding a specific filler into a specific photohardenable resin composition (JP-A-9-227640). In the course of further investigations based on this finding, they have recognized that it is urgent necessity for the practice in the art to develop a photohardenable resin composition which would provide a hardened product exhibiting not only improved heat resistance and reduced volume shrinkage but improved mechanical properties in strength, elongation and toughness.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a photohardenable resin composition which is low-viscosity liquid easy to handle and hardens in a short time on irradiation with minimized volume shrinkage to provide, with excellent dimensional accuracy, a molded part, a three-dimensional object or any other hardened product that has a high heat distortion temperature, i e., high heat resistance, high transparency, and excellent mechanical characteristics, such as tensile strength, elongation, and toughness.
Another object of the invention is to provide a process for producing the photohardenable resin composition.
Still another object of the invention is to provide a process for producing a three-dimensional object by stereolithography using the photohardenable resin composition.
Yet another object of the invention is to provide a novel urethanated acrylic compound which provides the photohardenable resin composition.
As a result of extensive studies, the present inventors have found that a novel urethanated acrylic compound having a specific chemical structure is extremely effective at accomplishment of the above objects. They have ascertained that the urethanated acrylic compound combined with a radical polymerizable compound and a polymerization initiator provides a liquid photohardenable resin composition which has a low viscosity and has excellent handl
Hagiwara Tsuneo
Ishihama Yasushi
Nakamura Takayuki
Ohtake Makoto
Ozaki Tatsuhiko
Akin Gump Strauss Hauer & Feld L.L.P.
Hamilton Cynthia
Teijin Seiki Co. Ltd.
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