JP-2026074538-A - Manufacturing method for three-dimensional stereolithography

Abstract

[Problem] To provide a method for producing high-strength three-dimensional stereolithography by a liquid bath photopolymerization method using a liquid photocurable composition containing 100 parts by mass of a radical polymerizable monomer, 5.0 to 400 parts by mass of an inorganic filler, 0.05 to 10.0 parts by mass of a photopolymerization initiator, and 0.01 to 5.0 parts by mass of a polymerization inhibitor, wherein a molded body made of a primary cured body is obtained by a liquid bath photopolymerization method, and then the molded body is washed and subjected to a postpolymerization step of additional activation light irradiation and heat treatment, and the method can prevent the occurrence of fine cracks in the interior and surface of the target object. [Solution] The additional irradiation of activation light is performed by applying a solution containing an oxygen-blocking substance such as polyvinyl alcohol to the surface of the molded body after cleaning, and while the surface and the solution are in contact. [Selection Diagram] None

Inventors

• 坂田 英武
• 中島 慶

Assignees

• 株式会社トクヤマデンタル

Dates

Publication Date

20260507

Application Date

20241021

Claims (3)

1. A molding process to obtain a molded body consisting of a cured liquid photocurable resin composition having a shape corresponding to the shape of the three-dimensional object, and comprising a cured liquid photocurable resin composition containing an effective amount of the photopolymerization initiator, by sequentially forming and stacking molded layers having shapes corresponding to the two-dimensional shapes at each height in the order of the sequence, based on the two-dimensional shape data; and using a liquid bath photopolymerization method in which the height direction of the three-dimensional object is digitized and sequenced from three-dimensional shape data showing the shape of the three-dimensional object, and two-dimensional shape data showing the cross-sectional shape of the three-dimensional object at each sequenced height; and sequentially forming and stacking molded layers having shapes corresponding to the two-dimensional shapes at each height in the order of the sequence, based on the two-dimensional shape data; A washing step of washing the molded body obtained in the above step with an organic solvent; and a post-polymerization step of irradiating the molded body washed in the above step with the activation light at an irradiation intensity of 10 to 10,000 mW/ cm² and then heating the molded body irradiated with the activation light at a temperature of 50°C or higher and less than 110°C to polymerize the unpolymerized components contained in the molded body; A method for manufacturing a three-dimensional object, including As the liquid photocurable resin composition, use a composition comprising: radical polymerizable monomer (A): 100 parts by mass, inorganic filler (B): 5.0 to 400 parts by mass, (C) photopolymerization initiator that absorbs the activation light and generates radicals: 0.05 to 10.0 parts by mass, and polymerization inhibitor (D): 0.01 to 5.0 parts by mass. The irradiation of the activation light in the post-polymerization step is performed in a state in which the surface of the molded article is in contact with an oxygen-blocking substance or a solution in which the oxygen-blocking substance is dissolved. A method for manufacturing a three-dimensional stereolithographic object, characterized by the following features.
2. A method for producing a three-dimensional stereolithographic object according to claim 1, using the liquid photocurable resin composition comprising 20 to 350 parts by mass of the inorganic filler (B), and further comprising 0.1 to 3.0 parts by mass of (E) an activating light absorber {excluding (C)}.
3. A method for manufacturing dental restorations, characterized by manufacturing dental restorations using the method for manufacturing three-dimensional stereolithography described in claim 1.

Description

This invention relates to a method for manufacturing three-dimensional stereolithographic objects. The technique of forming three-dimensional objects by curing a photocurable composition (sometimes called a "photocurable resin" or "photocurable resin composition") containing a polymerizable monomer and a photopolymerization initiator by irradiating it with light that activates the photopolymerization initiator (activating light) is known as stereolithography. Several methods of stereolithography are known, but the vat photopolymerization method is widely used because the equipment is relatively inexpensive and it can produce objects with smooth surfaces with high precision. In the liquid-bath photopolymerization method, three-dimensional shape data representing the shape of a three-dimensional object to be manufactured is used to digitize and serialize the height direction of the three-dimensional object, and two-dimensional shape data representing the cross-sectional shape of the three-dimensional object at each serialized height is generated. The liquid photocurable composition held in the bath (here, liquid means a dispersion in which liquid or inorganic powders, etc., are dispersed under the usage environment) is irradiated with the activation light at predetermined positions determined in advance based on the two-dimensional shape data, thereby selectively primary curing the liquid photocurable composition present at those positions to form a molded layer having the aforementioned cross-sectional shape. In addition, molded layers having the cross-sectional shape at each height are sequentially formed and stacked according to the serialization order to obtain a laminate with a shape corresponding to the shape of the three-dimensional object. After washing this laminate with an organic solvent as necessary, secondary curing (also called "post-polymerization") is performed to obtain the target product. This secondary curing is generally performed to improve the polymerization rate and increase its strength by applying additional light irradiation and/or heat treatment to the laminate. In the field of dentistry, there is a growing interest in manufacturing dental restorations such as dentures and crowns, which require high precision to produce unique shapes tailored to the individual oral conditions of each patient. These restorations are being developed using CAD data designed with digital data obtained from intraoral scans, and manufactured using stereolithography via a photopolymerization method (see, for example, Patent Document 1). When manufacturing dental restorations for use in the oral cavity, a photocurable resin composition containing a large amount of inorganic filler in a radically polymerizable monomer is sometimes used to increase strength. However, in such cases, if sufficient curing is performed during secondary curing to achieve high precision for fitting the restoration to the individual patient's oral cavity, it is known that deformation due to polymerization shrinkage and the resulting stress between the fabricated layers during photopolymerization can easily cause (microscopic) cracks to form inside and/or on the surface of the three-dimensional object. Techniques to prevent such problems are also known. In other words, Patent Document 1 discloses a method for manufacturing a three-dimensional object, wherein the photocurable resin composition that hardens upon irradiation with activation light comprises: 100 parts by mass of a radical polymerizable monomer, 5.0 to 400 parts by mass of an inorganic filler, 0.05 to 10.0 parts by mass of a photopolymerization initiator that absorbs the activation light and generates radicals, 0.01 to 2.7 parts by mass of an activation light absorber that absorbs the activation light, and 0.01 to 5.0 parts by mass of a polymerization inhibitor. The method involves obtaining a molded body of a three-dimensional object (consisting of a laminate of primary cured products of the photocurable resin composition) containing an effective amount of the photopolymerization initiator by a liquid bath photopolymerization method, and then performing a postpolymerization step (secondary curing step) by irradiating the molded body with activation light at an irradiation intensity of 10 to 10,000 mW/ cm² and then heating the molded body irradiated with activation light to a temperature of 50°C or higher and less than 110°C. International Publication No. 2023/008233 brochureJapanese Patent Application Publication No. 9-241304Japanese Patent Publication No. 2000-128723 This figure is an optical microscope image (magnification 50x) of the surface of the three-dimensional stereolithography object obtained in Example 1.This figure is an optical microscope image (magnification 50x) of the surface of the three-dimensional stereolithographic object obtained in Comparative Example 2. The manufacturing method of the present invention solves the aforementioned problems. A key feat