TECHNICAL FIELD

The present invention relates to an ultraviolet-curable silicone composition for stereolithography and to a cured product thereof.

BACKGROUND ART

With the ongoing growth in 3D printer technology, stereolithography materials for 3D printers are also being actively developed. The stereolithography materials that are widely distributed on the market today are generally acrylic resin compositions or urethane-acrylic resin compositions (Patent Document 1).

However, the great majority of these resin compositions give a hard cured product when irradiated with ultraviolet light, and so a widespread desire exists for ultraviolet-curable compositions that yield rubbery cured products such as silicone rubber. Silicone resins, because they have a high durability compared with general organic resins such as acrylate resins, are expected to see increased use in a broad range of stereolithographic applications.

Silicone compositions containing a light-activated platinum catalyst (Patent Document 2) and silicone compositions that cure by way of a thiol-ene reaction (Patent Document 3) are already being developed as silicone compositions applicable to stereolithographic systems.

Yet, in the case of bottom-up 3D printers, the stereolithography material used must have a low viscosity; the foregoing materials are unsuitable for this purpose. Hence, these exists a desire for the development of a silicone material which has a low viscosity and also exhibits good rubber properties after ultraviolet curing.

PRIOR ART DOCUMENTS

Patent Documents

Patent Document 1: JP-A 2012-111226Patent Document 2: JP-A 2012-506933Patent Document 3: JP-A 2006-2087

SUMMARY OF INVENTION

Technical Problem

In view of the above circumstances, one object of this invention is to provide an ultraviolet-curable silicone composition which has a viscosity suitable for use in stereolithography systems such as a bottom-up system and gives a cured product having excellent rubber properties. Another object is to provide such a cured product.

Solution to Problem

The inventors have conducted extensive investigations aimed at achieving these objects and have found as a result that by using a specific organopolysiloxane having (meth)acryloyloxy-containing groups and a given organopolysiloxane resin having (meth)acryloyloxy-containing groups, an ultraviolet-curable silicone composition that has a viscosity suitable for use in stereolithography systems and gives a cured product having good rubber properties can be obtained. This discovery ultimately led to the present invention.

Accordingly, the present invention provides:

1. An ultraviolet-curable silicone composition for stereolithography which includes:

(A) 100 parts by weight of an organopolysiloxane having two groups of formula (1) below per molecule


(wherein each R1is independently a monovalent hydrocarbon group of 1 to 20 carbon atoms, R2is an oxygen atom or an alkylene group of 1 to 20 carbon atoms, each R3is independently an acryloyloxyalkyl group, methacryloyloxyalkyl groups, acryloyloxyalkyloxy group or methacryloyloxyalkyloxy group, “p” is a number that satisfies 0≤p≤10, and “a” is a number that satisfies 1≤a≤3);

(B) from 5 to 200 parts by weight of an organopolysiloxane resin consisting of (a) units of formula (2) below


(wherein R1, R2, R3, “a” and “p” are as defined above), (b) R43SiO1/2units (wherein each R4is independently a monovalent hydrocarbon group of 1 to 10 carbon atoms) and (c) SiO4/2units, the molar ratio of the sum of (a) units and (b) units to (c) units being in the range of 0.6:1 to 1.2:1; and

(C) from 0.01 to 20 parts by weight of a photopolymerization initiator;

2. The ultraviolet-curable silicone composition for stereolithography of 1 above which has a viscosity at 23° C. of not more than 10,000 mPa·s;

3. The ultraviolet-curable silicone composition for stereolithography of 1 or 2 above, further including (D) from 0.01 to 20 parts by weight of an ultraviolet absorber having a light absorption at wavelengths of 360 to 410 nm;

4. The ultraviolet-curable silicone composition for stereolithography of any of 1 to 3 above, further including (E) from 0.01 to 20 parts by weight of a colorant; and

5. A cured product of the ultraviolet-curable silicone composition for stereolithography of any of 1 to 4 above.

Advantageous Effects of Invention

The ultraviolet-curable silicone composition for stereolithography of the invention has a viscosity suitable for use in stereolithography systems such as a bottom-up system. Also, the cured product obtained after ultraviolet curing exhibits good rubber properties.

