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
1997-04-14
2001-03-13
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
C522S096000, C522S097000, C528S075000, C528S076000, C528S077000, C264S401000, C560S209000, C560S205000
Reexamination Certificate
active
06200732
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a photocurable resin position, a production method thereof and an urethane acrylate used in the photocurable resin composition. More specifically, it relates to a photocurable resin composition which can provide moldings and stereolithographed objects, i.e., three-dimensionally shaped object, having excellent dimensional accuracy with a small volume shrinkage factor at the time of photo-curing and excellent heat resistance with a high thermal deformation temperature as well as excellent transparency and mechanical properties such as tensile strength; a production method thereof; and an urethane acrylate used in the photocurable resin composition.
Generally speaking, a liquid photocurable resin composition is widely used as a coating agent (especially hard coating agent), photoresist, dental material and the like. In recent years, particular attention has been paid to a method for optically shaping a photocurable resin composition three-dimensionally based on data input into a three-dimensional CAD system. As for optical stereolithography technology, JP-A 56-144478 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses an optical stereolithography which comprises supplying a required amount of controlled optical energy to a liquid photocurable resin to cure it into a thin layer, further supplying a liquid photocurable resin onto the layer, irradiating the resin with light under control to cure it into a thin layer in a laminate manner and repeating this procedure to produce a stereolithographed object. A practical basic method therefor is proposed in JP-A 60-247515. Thereafter, 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 propose also technologies related with an optical stereolithography.
A typical method for optically producing a stereolithographed object comprises selectively irradiating a liquid surface of a liquid photocurable resin composition in a container with light from an ultraviolet laser controlled by a computer to cure it to a predetermined thickness so as to obtain a desired pattern, supplying one layer of the liquid photocurable resin composition on the cured layer, irradiating it with light from the ultraviolet laser similarly to cure it to form a unitarily continuous cured layer and repeating this laminating procedure to produce a stereolithographed object having the final shape. This method is widely employed, and since this method makes it possible to produce a target stereolithographed object having a complex shape in a relatively short period of time with ease, it has been attracting special attention these days.
As the photocurable resin composition used as a coating, photoresist, dental material or the like, curable resins such as unsaturated polyesters, epoxy (meth)acrylate, urethane (meth)acrylate and (meth)acrylic acid ester monomers, to which a photopolymerization initiator is added, are widely used.
Illustrative examples of the photocurable resin composition used in the optical stereolithography include those containing as an essential component at least one photopolymerizable compound such as an photopolymerizable modified (poly)urethane (meth)acrylate compound, oligoester acrylate compound, epoxy acrylate compound, epoxy compound, polyimide compound, aminoalkyd compound or vinyl ether compound and a photopolymerization initiator. In recent years, JP-A 1-204915, JP-A 1-213304, JP-A 2-28261, JP-A 2-75617, JP-A 2-145616, JP-A 104626/1991, JP-A 3-114732 and JP-A 3-1147324 disclose various technologies for improving the photocurable resin composition.
It is necessary that the photocurable resin composition used in the optical stereolithography be a liquid having a low viscosity and have a small volume shrinkage factor at the time of curing from viewpoints of handling properties, stereolithographing speed and stereolithographing accuracy, and that it give a stereolithographed object having excellent mechanical properties when it is photo-cured. In recent years, along with expanding demands and applications of optical stereolithographed objects, stereolithographed objects having excellent heat resistance with a high thermal deformation temperature and transparency in addition to the above characteristics are desired in some applications. For instance, in optical stereolithographed objects used in the design of a complex heating medium circuit and in optical stereolithographed objects used for the analysis of the behavior of a heating medium having a complex structure, great importance is attached to small volume shrinkage factor at the time of photo-curing, high thermal deformation temperature and excellent transparency.
Heretofore, for the purpose of obtaining an optical stereolithographed object having improved heat resistance, there have been studied a method for introducing a benzene ring into the molecule of a photocurable resin, a method for increasing crosslinking density in photo-cured products, and the like. However, the thermal deformation temperatures under high load of stereolithographed objects obtained by these methods are around 70 to 80° C. at best, and the heat resistances thereof are not satisfactory. In addition, when the heat resistance of a photo-cured product is attempted to be improved, the volume shrinkage factor at the time of curing becomes large undesirably, resulting in deterioration in dimensional accuracy. Therefore, a photocurable resin composition which has both improved heat resistance and reduced volume shrinkage factor at the time of curing has not been obtained yet.
Generally, when the crosslinking density in a photo-cured product is increased, improvement in heat resistance is expected, but the volume shrinkage is liable to become large by increasing the crosslinking density at the same time. Therefore, the improvement of heat resistance and the reduction of volume shrinkage factor are antinomic to each other. Although a huge number of photocurable resin compositions have been proposed as described above, a photocurable resin composition which has high heat resistance with a thermal deformation temperature under high load of higher than 100° C. and a small volume shrinkage factor at the time of curing at the same time and further can provide moldings and stereolithographed objects having excellent transparency and mechanical properties has not been provided yet.
It is therefore an object of the present invention to provide a photocurable resin composition which is a liquid having low viscosity and excellent handling properties, can be cured in a short period of irradiation time, and can provide moldings, stereolithographed objects and other cured products having excellent dimensional accuracy with a small volume shrinkage factor at the time of curing, excellent heat resistance with a high thermal deformation temperature and excellent transparency and mechanical properties such as tensile strength; as well as a production method thereof.
It is another object of the present invention to provide a novel urethane acrylate which is used in the above photocurable resin composition.
Other objects and advantages of the present invention will become clear from the following description.
The inventors of the present invention have conducted studies to attain the above objects and as a result, have found that a novel urethane acrylate having a specific chemical structure synthesized by the inventors is extremely effective in achieving the above objects and when this urethane acrylate is mixed with another radical polymerizable compound and a photopolymerization initiator, a liquid photocurable resin composition having low viscosity and excellent handling properties can be obtained, and that the photocurable resin composition can be cured in a short period of time when it is exposed to light and have small volume shrinkage at the time of curing, and hence, a stereolithographed object having a desired shape and size can be produced with a high dim
Hagiwara Tsuneo
Tamura Yorikazu
Anderson Kill & Olick P.C.
Hamilton Cynthia
Teijin Seikei Co., Ltd.
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