Title: Radiation- Curable Liquid Resin Composition for Additive

Fabrication and Three-Dimensional Object made Therefrom

Background of the Invention

An additive fabrication method is known, in which a

three-dimensional object is formed by repetition of a process of forming a cured resin layer by selectively applying light to a radiation- curable liquid substance (liquid resin composition), and thereby integrally laminating said cured resin layers (please see Japanese Unexamined Patent Application Publication Nos. H02-28261, H02-75618, and H6-2284). To explain a typical example of this additive fabrication method, a cured resin layer having a prescribed pattern is formed by selectively applying light, such as an ultraviolet light, to the liquid surface of a radiation-curable liquid resin composition. Then, one layer's worth of radiation-curable liquid resin composition is supplied adjacent to this cured resin layer, and by selectively applying light to its liquid surface, a new cured resin layer is integrally laminated adjacent to the previously-formed cured resin layer so as to be continuous with it. Then, by repeating the above process a prescribed number of times while varying or without varying the pattern in which the light is applied, a three-dimensional object in which a plurality of cured resin layers are integrally laminated is formed. By this additive fabrication method, the intended three-dimensional object can be obtained easily and in a short time, even if its shape is complex. This technique is very useful in the prototyping process in development of new products in the automotive and consumer electronics industries, and it is becoming an indispensible means of reducing development time and cutting costs.

An example of an additive fabrication process is stereolithography. In stereolithography, three-dimensional CAD data is loaded into a computer which controls a laser beam that traces the pattern of a cross section through a liquid resin contained in a vat, thereby solidifying a thin layer of the resin corresponding to the cross section. The solidified layer is recoated with resin and the laser beam traces another cross section to harden another layer of resin on top of the previous layer. The process is repeated layer by layer until the three-dimensional object is completed. When initially formed, the three-dimensional object is, in general, not fully cured and therefore may be subjected to post curing, if required. Stereolithography processes are described in, for example, U.S. Patent No. 4,575,330 and Paul F. Jacobs, Rapid

Prototyping & Manufacturing 69 110 (1992).

Many resin compositions have been known as radiation-curable liquid resin compositions useful in additive fabrication processes. From the viewpoint of balancing high curability and shape stability of the object, resin compositions containing radical-polymerizable organic compounds and cationically-polymerizable organic compounds have been widely used (please see Japanese Unexamined Patent Application Publication Nos. H02-28261, H02-75618, and H6-2284, Hll-310626, Hll-228610, and Hll-240939).

Three-dimensional objects obtained by such additive fabrication methods have been widely used as prototype models to study the design of mechanical parts. However, in recent market trends, there are increasing demands for the parts obtained by additive fabrication processes to be transparent so that internal mechanical operations are visible, and resins that are colorless, highly transparent and heat resistant have become required.

Throughout this patent application the term color is defined as follows: color (or colour, alternative spelling) is the visual perceptual property corresponding in humans to the categories called red, yellow, green, etc. Black is the visual perception of absence of all color, whereas white is the visual perception of all colors. Color derives from the spectrum of light (distribution of light energy versus wavelength) interacting in the eye with the spectral sensitivities of the light receptors. Color categories and physical specifications of color are also associated with objects, materials, light sources, etc., based on their physical properties such as light absorption, reflection, or emission spectra. Typically, only features of the composition of light that are detectable by humans (wavelength spectrum from 400 nm to 700 nm, roughly) are included, thereby objectively relating the psvchological phenomenon of color to its physical specification.

Color and transparency are two distinct principles. For instance, something may visually appear perfectly clear and still colored. For instance, certain colored glass is entirely transparent to the eye and possesses a color. Similarly, something may be colorless and also clear or opaque. Colorless is defined as lacking all color. For instance, pure liquid water is clear and colorless. An article that is visually perceived as perfectly clear and as a color, for instance, blue, is reflecting the blue color while allowing all other wavelengths of light to pass through. When a viewer perceives white, the article will appear less transparent because all colors are being reflected back at the viewer and thus not passing through the article.

In compositions of the past, even though resins judged as having excellent transparency from values such as total light transmittance and the like were obtained, there was the drawback that the three-dimensional objects exhibited a yellow or blue color because their transmittance was highly wavelength- dependent, and they could not be called colorless and transparent. Guidance for formulating radiation-curable liquid resin compositions with improved clarity can be found in published application US20030104313, although achieving a colorless appearance is not mentioned. In other compositions, color masking agents, such as pigments or dyes, are used to improve the colorless appearance of the formed three-dimensional objects. Please see, for example, US20090004579.

Photoacid generators containing antimony atoms having excellent curing functionality have been widely used as cationic polymerization initiators, but resins which use photoacid generators that do not contain antimony atoms have also been reported, due to considerations of safety to humans and impact on the environment. However, when a photoacid generator that does not contain antimony atoms is used as a cationic polymerization initiator, curability is often worse than when a photoacid generator having antimony atoms is used, and therefore the heat resistance of the obtained three-dimensional object tends to be reduced.

It would thus be useful to have a high-precision antimony-free radiation-curable liquid resin composition that attains a transparent and substantially colorless appearance while attaining excellent heat resistance.

Summary of the Invention

The first aspect of the instant claimed invention is a radiation- curable liquid resin composition for additive fabrication comprising components (A)-(E) below, where the total quantity of the composition is 100 mass%:

(A) 3-20 mass % of a compound having the structure represented by formula (1) below.

[Compound 1]

(in formula (1), R¹ is an organic group of valence n; R² is a single bond, methylene group or alkylene group having 2-4 carbons; each m, in the case where there is more than one m, is independently an integer from 1 to 10; n is an integer from 1 to 6),

(B) 15-85 mass% of a cationically-polymerizable compound other than

component (A) above,

(C) 0.1-25 mass% of a radical-polymerizable compound,

(D) 0.1-10 mass% of an onium salt consisting of a monovalent sulfonium ion having an aromatic structure and an anion represented by (PR¾)" (wherein each R³ is independently a fluorine atom or fluorinated alkyl group, and at least one R³ is a fluorinated alkyl group), (E) 0.01-10 mass% of a radical polymerization initiator,

wherein the content of divalent sulfonium salt having an aromatic structure is at most 1/20 (mass ratio) the content of the aforementioned component (D).

The second aspect of the instant claimed invention is the radiation- curable liquid resin composition for additive fabrication according to the first aspect of the instant claimed invention, wherein the aforementioned component (D) is a compound having a structure represented by formula (2) below:

[Compound 2]

(in formula (2), each R³ is independently a fluorine atom or fluorinated alkyl group, and at least one R³ is a fluorinated alkyl group), and the

aforementioned divalent sulfonium salt having an aromatic structure is a compound having a structure represented by formula (3) below:

[Compound 3]

(in formula (3), R³ is the same as in formula (2)). The third aspect of the instant claimed invention is the radiation- curable liquid resin composition for additive fabrication according to the first or second aspect of the instant claimed invention, which contains 10-18 mass% of the aforementioned component (A), where the total quantity of the composition is 100 mass%.

The fourth aspect of the instant claimed invention is the radiation- curable liquid resin composition for additive fabrication according to any of the first through third aspects of the instant claimed invention, wherein, in the aforementioned formula (2) and formula (3), (PR³6)^" is (PF6-m(C_nF2n+i)m)^" (where m is 1-5, and n is 1-4).

The fifth aspect of the instant claimed invention is the radiation- curable liquid resin composition for additive fabrication according to any of the first through fourth aspects of the instant claimed invention, wherein the aforementioned component (A) is a compound having a structure represented by formula (4) below:

Compound 4]

formula (4), m is the same as in formula (1)).

The sixth aspect of the instant claimed invention is the radiation- curable liquid resin composition for additive fabrication according to any of the first through fifth aspects of the instant claimed invention, wherein the aforementioned component (B) contains a compound having epoxy groups (Bl) and a compound having oxetanyl groups (B2).

The seventh aspect of the instant claimed invention is the radiation-curable liquid resin composition for additive fabrication according to any of the first through sixth aspects of the instant claimed invention, wherein the aforementioned component (Bl) is a compound having at least two alicyclic epoxy groups in the molecule.

The eighth aspect of the instant claimed invention is the radiation- curable liquid resin composition for additive fabrication according to any of the first through seventh aspects of the instant claimed invention,, which contains lxlO ⁵ - lxlO ² mass% of dye and/or pigment (F), where the total quantity of the composition is 100 mass%.

The ninth aspect of the instant claimed invention is a three- dimensional object obtained by applying light to the radiation-curable liquid resin composition for additive fabrication according to any of the first through eight aspects of the instant claimed invention.

Description of the Drawings

[FIG. 1] (1) is a perspective view of a warping test specimen, and (2) is an elevation view of a warping test specimen affixed to a horizontal stand. [Explanation of Reference Numerals]

10 Warping model

11, 12 Legs

20 Horizontal stand

Detailed Description of the Invention

The present invention relates to a radiation-curable liquid resin composition for additive fabrication and a three-dimensional object obtained by optically curing same. The first aspect of the instant claimed invention is a radiation-curable liquid resin composition for additive fabrication comprising components (A)-(E) below, where the total quantity of the composition is 100 mass%:

(A) 3-20 mass % of a compound having the structure represented by formula (1) below.

[Compound 1]

(in formula (1), R¹ is an organic group of valence n; R² is a single bond, methylene group or alkylene group having 2-4 carbons; each m, in the case where there is more than one m, is independently an integer from 1 to 10; n is an integer from 1 to 6),

(B) 15-85 mass% of a cationically-polymerizable compound other than

component (A) above,

(C) 0.1-25 mass% of a radical-polymerizable compound,

(D) 0.1-10 mass% of an onium salt consisting of a monovalent sulfonium ion having an aromatic structure and an anion represented by (PR³6)^" (wherein each R³ is independently a fluorine atom or fluorinated alkyl group, and at least one R³ is a fluorinated alkyl group),

(E) 0.01-10 mass% of a radical polymerization initiator,

wherein the content of divalent sulfonium salt having an aromatic structure is at most 1/20 (mass ratio) the content of the aforementioned component (D).

This specification discloses all feasible combinations for the skilled person exercising common sense and carrying out the embodiments disclosed herein. For instance, various combinations of the five essential components in the ranges for each component described herein are disclosed.

The radiation- curable liquid resin composition for additive fabrication of the present invention (called "composition of the present invention" hereinafter) has components (A) through (E) above as mandatory constituent components. The mandatory components and optional components are each described below.

Component (A) Component (A) used in the composition of the present invention is a compound having a structure represented by formula (1) below:

[Compound 5]

(in formula (1), R¹ is an organic group of valence n; R² is a single bond, methylene group or alkylene group having 2-4 carbons; each m, in the case where there is more than one m, is independently an integer from 1 to 10; n is an integer from 1 to 6). Similar components have been disclosed in, for example, Japanese Unexamined Patent Application Publication No.

2008-260812.

Due to the fact that it contains a compound having a structure represented by the above formula (1), the composition of the present invention can form a three-dimensional object having excellent heat resistance while maintaining a low yellow index and a color tone close to colorless. Specifically, a three-dimensional object having a high glass transition temperature (Tg) and high heat distortion temperature (HDT) can be obtained.

Preferred examples of compounds having a structure represented by the aforementioned formula (1) are compounds having a structure represented by formula (4) below:

[Compound 6]

(in formula (4), m is the same as in formula (1)).

A commercially-available product of a compound having a structure represented by the aforementioned formula (1) is EHPE3150

(epoxy-4-(2-oxiranyl)cyclohexene adduct of 2,2-bis(hydroxymethyl)-l-butanol, manufactured by Daicel Chemical Industries, Ltd.). The use of this component in radiation-curable liquid resin compositions for additive fabrication is disclosed in, for example, US Patent US6287745.

The content of component (A) in the present invention is normally 3-20 mass%, preferably 10-18 mass%, more preferably 12-17 mass%, where the total quantity of the composition is 100 mass%. In another embodiment the quantity of component (A) in the present invention is 3-18 mass %, preferably 3-17 mass%. In another embodiment the quantity of component (A) in the present invention is 10-20 mass %, preferably 10-18 mass%, and more preferably 10-17 mass%. In another embodiment the quantity of component (A) in the present invention is 12-20 mass %, preferably 12-18 mass%, and more preferably 12-17 mass%. Due to the fact that the content of component (A) is 3 mass% or above, a three-dimensional object having excellent heat resistance can be obtained. If the content of component (A) exceeds 20 mass%, the yellow index of the three-dimensional object tends to increase and the color tone tends to exhibit a strong yellow tint, and in addition, curing shrinkage of the three-dimensional object is noticeable and the precision of the

three-dimensional object is reduced. Component (B) Component (B) used in the composition of the present invention is not particularly limited provided that it is a cationically-polymerizable compound other than component (A).

Due to the fact that the composition of the present invention contains component (B), the heat resistance, yellow index and color tone of the three-dimensional object can be finely adjusted in conjunction with component (A) and component (C). If component (A) is not used and only component (B) is used as a cationically-polymerizable compound, heat resistance can be maintained by raising the crosslink density, but this tends to result in a higher yellow index and a more yellow color tone.

The cationically-polymerizable compound (B) is not particularly limited provided that it is something other than component (A), but it preferably contains a compound having epoxy groups (Bl) and a compound having oxetanyl groups (B2).

Specific examples of component (Bl) are bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S diglycidyl ether, epoxy novolac resin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether,

3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexyl carboxylate,

2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane, bis(3,4-epoxycyclohexylmethyl)adipate,

bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,

3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy-6'-methyl-cyclohexane carboxylate, ε-caprolactone- modified 3, 4- epoxycyclohexylmethyl- 3', 4'- epoxycyclohexane carboxylate, trimethylcaprolactone-modified

3, 4- epoxycyclohexylmethyl- 3', 4'- epoxycyclohexane carboxylate,

-methyl-5-valerolactone-modified

3, 4- epoxycyclohexylmethyl- 3', 4'- epoxycyclohexane carboxylate, methylenebis(3,4-epoxycyclohexane), di(3,4-epoxycyclohexylmethyl)ether of ethylene glycol, ethylenebis(3,4-epoxycyclohexane carboxylate), dioctyl epoxycyclohexahydro phthalate, di-2-ethylhexyl epoxycyclohexahydro phthalate, 1,4-butane diol diglycidyl ether, 1,6-hexane diol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, glycerol triglycidyl ether and

polypropylene glycol diglycidyl ether; polyglycidyl ethers of polyether polyols obtained by the addition of one or more alkylene oxides to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerol; diglycidyl esters of aliphatic long- chain dibasic acids; monoglycidyl ethers of aliphatic higher alcohols; monoglycidyl ethers of polyether alcohols obtained by the addition of phenols, cresols, butylphenols or alkylene oxides; glycidyl esters of higher fatty acids; epoxidated soybean oil; butyl epoxy stearate; octyl epoxy stearate; epoxidated linseed oil; epoxidated polybutadiene and the like. The above cationically-polymerizable compounds may be used either individually or in combinations of two or more as component (Bl).

Among these, preferred cationically-polymerizable compounds are 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexyl carboxylate,

bis(3,4-epoxycyclohexylmethyl)adipate, ε-caprolactone-modified

3, 4- epoxycyclohexylmethyl- 3', 4'- epoxycyclohexane carboxylate,

trimethylcaprolactone-modified

3, 4- epoxycyclohexylmethyl- 3', 4'- epoxycyclohexane carboxylate,

-methyl-5-valerolactone-modified

3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerol triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether and the like. Even more preferred are compounds having at least two alicyclic epoxy groups in the molecule, such as

3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexyl carboxylate and

bis(3,4-epoxycyclohexylmethyl)adipate. To maintain good curing speed and mechanical strength, it is preferred that this epoxy compound is contained in component (Bl) in a proportion of at least 50 mass%.

Examples of commercially- available products of the

cationically-polymerizable compound having epoxy groups (Bl) are UVR-6100, UVR-6105, UVR-6110, UVR-6128, UVR-6200, UVR-6216 (manufactured by Union Carbide Corp.), Celoxide 2021, Celoxide 2021P, Celoxide 2081, Celoxide 2083, Celoxide 2085, Epolead GT-300, Epolead GT-301, Epolead GT-302, Epolead GT-400, Epolead 401, Epolead 403 (manufactured by Daicel Chemical Industries, Ltd.), KRM-2100, KRM-2110, KRM-2199, KRM-2400, KRM-2410, KRM-2408, KRM-2490, KRM-2200, KRM-2720, KRM-2750 (manufactured by Asahi Denka Kogyo Co., Ltd.), CER-4221, CER-4221-E, CER-4221-H

(manufactured by Dalian Trico Chemical Co., Ltd.), Rapi-Cure DVE-3, CHVE, PEPC (manufactured by ISP Corp.), Epikote 828, Epikote 812, Epikote 1031, Epikote 872, Epikote CT508 (manufactured by Japan Epoxy Resin Co., Ltd.), XDO (manufactured by Toagosei Co., Ltd.), VECOMER 2010, 2020, 4010, 4020 (manufactured by Allied Signal Corp.) and the like.

Specific examples of component (B2) include compounds having at least two oxetanyl groups, such as

l,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene (XDO) and

di[2-(3-oxetanyl)butyl] ether (DOX), and compounds having one oxetanyl group, such as 3-ethyl-3-(phenoxymethyl)oxetane (POX) and

3-ethyl-3-hydroxymethyloxetane (OXA). When oxetane compounds having an aromatic structure such as the aforementioned XDO are used, the obtained three-dimensional object tends to exhibit a yellow color, and therefore it is preferred that the content of oxetane compound not having an aromatic structure is at least 50 mass%, more preferably 100 mass%, of the total quantity of component (B2).

The content of component (B) in the composition of the present invention is normally 15-85 mass%, preferably 30-80 mass%, more preferably 40-75 mass%, where the total quantity of the composition is 100 mass%. If the content of component (B) exceeds 85 mass%, deformation such as warping of the three-dimensional object tends to be large. On the other hand, if it is less than 15 mass%, the three-dimensional object tends not to have sufficient mechanical strength or thermal characteristics.

The content of component (Bl) in the composition of the present invention is normally 10-65 mass%, preferably 20-55 mass%, more preferably 25-50 mass%, where the total quantity of the composition is 100 mass%. On the other hand, the content of component (B2) is normally 5-30 mass%, preferably 10-25 mass%, more preferably 15-25 mass%, where the total quantity of the composition is 100 mass%.

Component (C)

Component (C) used in the composition of the present invention is a radical-polymerizable compound. Specifically, it is a compound having ethylenically unsaturated bonds (C=C), such as compounds having one ethylenically unsaturated bond in the molecule (monofunctional

radical-polymerizable compounds) and compounds having two or more ethylenically unsaturated bonds in the molecule (polyfunctional

radical-polymerizable compounds) .

It is preferred that a polyfunctional radical-polymerizable compound which is at least trifunctional - that is, which has at least three ethylenically unsaturated bonds in the molecule - is contained in a proportion of at least 60 mass% in component (C), where the total quantity of component (C) is 100 mass%. A more preferred proportion of this polyfunctional

radical-polymerizable compound which is at least trifunctional is 70 mass% or above, even more preferably 80 mass% or above, and most preferably 100 mass%. If the proportion of this polyfunctional radical-polymerizable compound which is at least trifunctional is at least 60 mass%, the radiation curability of the obtained resin composition is further improved, and deformation of the obtained three-dimensional object tends not to occur over time.

Specific examples of monofunctional radical-polymerizable compounds of component (C) are (meth)acryloylmorpholine,

7-amino-3,7-dimethyloctyl (meth)acrylate, isobornyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyldiethylene glycol (meth)acrylate, t-octyl (meth)acrylamide, dimethylaminoethyl (meth)acrylate, lauryl (meth)acrylate, dicyclopentadiene (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl

(meth)acrylate, vinyl caprolactam, N-vinylpyrrolidone, phenoxyethyl

(meth)acrylate, butoxyethyl (meth)acrylate, polyethylene glycol

mono(meth)acrylate, polypropylene glycol mono(meth)acrylate and the like.

Specific examples of polyfunctional radical-polymerizable compounds of component (C) are ethylene glycol di(meth)acrylate,

dicyclopentenyl di(meth)acrylate, triethylene glycol diacrylate, tetraethylene glycol di(meth)acrylate, tricyclodecanediyldimethylene di(meth)acrylate, tris(2-hydroxyethyl)isocyanurate di(meth)acrylate,

tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, caprolactone-modified tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene oxide- (called "EO" hereinafter) modified

trimethylolpropane tri(meth)acrylate, propylene oxide- (called "PO"

hereinafter) modified trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, di-terminal (meth)acrylate adduct of bisphenol A diglycidyl ether, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate,

pentaerythritol tetra(meth)acrylate, polyester di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipentaerythritol hexa(meth)acrylate,

dipentaerythritol penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate,

caprolactone-modified dipentaerythritol penta(meth)acrylate,

ditrimethylolpropane tetra(meth)acrylate, EO-modified bisphenol A

di(meth)acrylate, PO-modified bisphenol A di(meth)acrylate, EO-modified hydrogenated bisphenol A di(meth)acrylate, PO-modified hydrogenated bisphenol A di(meth)acrylate, EO-modified bisphenol F di(meth)acrylate, (meth)acrylate of phenol novolac polyglycidyl ether and the like.

Preferred among these are the tri(meth)acrylate compounds, tetra(meth)acrylate compounds, penta(meth)acrylate compounds,

hexa(meth)acrylate compounds and the like that are shown above as examples of polyfunctional radical-polymerizable compounds which are at least trifunctional. Among these, tris(acryloyloxyethyl) isocyanurate,

trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate and ditrimethyolopropane tetra(meth)acrylate are particularly preferred.

Examples of commercially- available products of the monofunctional radical-polymerizable compound of component (C) are ARONIX M-101, M-102, M-lll, M-113, M-117, M-152, TO-1210 (manufactured by Toagosei Co., Ltd.), KAYARAD TC-110S, R-564, R-128H (manufactured by Nippon Kayaku Co., Ltd.), Viscoat 192, Viscoat 220, Viscoat 2311HP, Viscoat 2000, Viscoat 2100, Viscoat 2150, Viscoat 8F, Viscoat 17F (manufactured by Osaka Organic Chemical Industry Ltd.) and the like.

Examples of commercially- available products of the polyfunctional radical-polymerizable compound of component (C) are SA1002 (manufactured by Mitsubishi Chemical Corp.), Viscoat 195, Viscoat 230, Viscoat 260, Viscoat 215, Viscoat 310, Viscoat 214HP, Viscoat 295, Viscoat 300, Viscoat 360, Viscoat GPT, Viscoat 400, Viscoat 700, Viscoat 540, Viscoat 3000, Viscoat 3700 (manufactured by Osaka Organic Chemical Industry Ltd.), KAYARAD R-526, HDDA, NPGDA, TPGDA, MANDA, R-551, R-712, R-604, R-684, PET-30, GPO-303, TMPTA, THE-330, DPHA, DPHA-2H, DPHA-2C, DPHA-2I, D-310, D-330, DPCA-20, DPCA-30, DPCA-60, DPCA-120, DN-0075, DN-2475, T-1420, T-2020, T-2040, TPA-320, TPA-330, RP-1040, RP-2040, R-011, R-300, R-205 (manufactured by Nippon Kayaku Co., Ltd.), ARONIX M-210, M-220, M-233, M-240, M-215, M-305, M-309, M-310, M-315, M-325, M-400, M-6200, M-6400 (manufactured by Toagosei Co., Ltd.), Lite Acrylate BP-4EA, BP-4PA, BP-2EA, BP-2PA, DCP-A (manufactured by Kyoeisha Chemical Co., Ltd.), New Frontier BPE-4, BR-42M, GX-8345 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), ASF-400 (manufactured by Nippon Steel Chemical Co., Ltd.), Ripoxy SP-1506, SP-1507, SP-1509, VR-77, SP-4010, SP-4060 (manufactured by Showa

Highpolymer Co., Ltd.), NK Ester A-BPE-4 (manufactured by Shin-Nakamura Chemical Co., Ltd.) and the like.

The content of component (C) in the composition of the present invention is normally 0.1-25 mass%, preferably 0.1-15 mass%, where the total quantity of the composition is 100 mass%. By the addition of component (C), the radiation curability of the obtained resin composition is improved, and deformation of the obtained three-dimensional object tends not to occur over time. However, if the content exceeds 25 mass%, there is the problem that impact resistance and fracture toughness of the three-dimensional object are reduced.

Component (D)

Component (D) used in the composition of the present invention is an onium salt consisting of a monovalent sulfonium ion having an aromatic structure and an anion represented by (PR³6)^". Here, each R³ is independently a fluorine atom or fluorinated alkyl group, and at least one R³ is a fluorinated alkyl group. Component (D) is a photoacid generator which absorbs radiation and generates acid. It is added in order to polymerize the

cationically-polymerizable compounds of component (A) and component (B).

Because component (D) is a photoacid generator that does not contain antimony atoms but contains phosphorus atoms, it has the advantages of low toxicity to humans and a small load on the environment. If a photoacid generator having antimony atoms is used, the obtained three-dimensional object tends to strongly exhibit a yellow color, but by using component (D), an object can be obtained which has a lower yellow index and is close to colorless.

There are cases where component (D) obtained as a

commercially-available product contains a large quantity of divalent sulfonium salt having an aromatic structure made up of dimers and so forth of component (D). Divalent sulfonium salt having an aromatic structure tends to cause the liquid resin composition to become more viscous over time and to reduce storage stability. For this reason, the content of divalent sulfonium salt having an aromatic structure contained in the composition of the present invention must be at most 1/20 (mass ratio) the content of the aforementioned

component (D).

Component (D) is a compound having a structure represented by formula (2) below.

[Compound 7]

(In formula (2), each R³ is independently a fluorine atom or fluorinated alkyl group, and at least one R³ is a fluorinated alkyl group.) In formula (2), (PR³6)^" is preferably (PF6-m(C_nF2n+i)m)^" (where m is an integer from 1 to 5, and n is an integer from 1 to 4).

If component (D) is a compound having a structure represented by formula (2) above, the content of compound having a structure represented by formula (3) below contained in the composition of the present invention must be at most 1/20 (mass ratio) the content of the compounding having a structure represented by formula (2) above.

[Compound 8]

(In formula (3), R³ is the same as in formula (2).)

Also, due to the fact that its anion part has a fluorinated alkyl group, component (D) has excellent optical curability similar to photoacid generators having antimony atoms, and therefore a three-dimensional object having excellent heat resistance can be obtained. In the case where, unlike component (D), the anion part of formula (2) above is PF6, curability is lower than in the case where the photoacid generator of component (D) is used, and therefore curing of the obtained three-dimensional object is insufficient, and heat resistance is reduced.

Examples of commercially- available products of component (D) are CPI-200K and CPI-200S (manufactured by San-Apro Ltd.). Such compounds have been used in additive fabrication processes. Please see US patent application publication US20090295003 and Japanese Unexamined Patent Application Publication No. 2007-169423. The content of component (D) in the present invention is normally 0.1-10 mass%, preferably 0.2-8 mass%, more preferably 1-8 mass%, where the total quantity of the composition is 100 mass%. In another embodiment the amount of component (D) is 2-10 mass%, more preferably 2-8 mass%, and more preferably 2-7 mass%. In another embodiment the amount of component (D) is

3- 10 mass%, more preferably 3-8 mass%, and more preferably 3-7 mass%. If the contained proportion of component (D) is less than 0.1 mass%, the radiation curability of the obtained resin composition is reduced, and a three-dimensional object having sufficient mechanical strength cannot be produced. On the other hand, if it exceeds 10 mass%, suitable transparency is not obtained and it is difficult to control the curing depth when the obtained resin composition is submitted to additive fabrication, and the shape precision of the obtained three-dimensional object tends to be reduced. Component (E)

Component (E) used in the composition of the present invention is a radical polymerization initiator, and is a compound (radical

photopolymerization initiator) which decomposes by receiving radiation such as light, and by the radicals thereby produced, initiates a radical

polymerization reaction of component (C).

Specific examples of the radical polymerization initiator of component (E) are acetophenone, acetophenone benzyl ketal, anthraquinone, l-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-l-one, carbazole, xanthone,

4- chlorobenzophenone, 4,4'-diaminobenzophenone,

1,1-dimethoxydeoxybenzoin, 3,3'- dimethyl-4-methoxybenzophenone, thioxanthone-based compounds,

2 - methyl- 1 - [4- (methylt hi o) phenyl] - 2- morpholino-pr opan- 2 - one,

2 -benzyl- 2 - dimethylamino- 1 - (4-morpholinophenyl) -butan- 1 -one,

triphenylamine, 2,4,6-trimethylbenzoyldiphenylphosphine oxide,

bis(2,6-dimethoxybenzoyl-2,4,4-tri-methylpentylphosphine oxide, benzyl dimethyl ketal, 1-hydroxycyclohexylphenyl ketone,

2- hydroxy-2-methyl-l-phenylpropan-l-one, fluorenone, fluorene, benzaldehyde, benzoin ethyl ether, benzoin propyl ether, benzophenone, Michler's ketone,

3- methylacetophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone (BTTB), combinations of BTTB and dye sensitizers such as xanthene, thioxanthene, cumarin and ketocumarin and the like. Of these, benzyl dimethyl ketal, 1-hydroxycyclohexylphenyl ketone,

2,4,6-trimethylbenzoyldiphenylphosphine oxide,

2-benzyl-2-dimethylamino-l-(4-morpholinophenyl)-butan-l-one and the like are particularly preferable. The above radical polymerization initiators can be used either individually or in combinations of two or more as component (E).

The content of component (E) in the composition of the present invention is normally 0.01-10 mass%, preferably 0.1-5 mass%, where the total quantity of the composition is 100 mass%. If the contained proportion of component (E) is less than 0.01 mass%, the radical polymerization reaction rate (curing rate) of the obtained resin composition is low, time is required in forming the three-dimensional object, and resolution tends to be reduced. On the other hand, if the contained proportion of component (E) exceeds 10 mass%, the excessive quantity of polymerization initiator causes the curing characteristics of the resin composition to be reduced, and may adversely affect the moisture resistance and heat resistance of the three-dimensional object.

Component (F)

Dyes and/or pigments may be added as component (F) to the composition of the present invention, to an extent that does not hinder the effect of the present invention. By adding component (F), the color tone of the obtained three-dimensional object is compensated for, and can be made nearly colorless. In order not to reduce the transparency of the obtained

three-dimensional object, dyes that do not have light scattering characteristics, unlike pigments, are preferred. As the dyes and/or pigments of component (F), commercially-available products in many color tones can be suitably selected depending on the color tone of the resin composition. Many varieties of commercially-available products are provided by Clariant, Lanxess, BASF and the like.

The contained proportion of component (F) in the composition of the present invention is preferably lxlO ⁵ - lxlO ² mass% (0.1-100 ppm), more preferably lxlO ⁴ - lxlO ³ mass% (1-10 ppm), where the total quantity of the composition is 100 mass%.

Various additives may be added to the radiation- curable liquid resin composition for additive fabrication of the present invention as other optional components, within a range such that as the objectives and effects of the present invention are not impaired. Examples of such additives are

photosensitizers, polymerization inhibitors, polymerization initiation adjuvants, leveling agents, wettability improvers, surfactants, plasticizers, UV absorbents, silane coupling agents, organic or inorganic fillers and the like.

The composition of the present invention can be produced by putting appropriate quantities of the above components (A)-(F) and other components (various additives) in a stirring container, and stirring at a temperature of normally 30-70 °C, preferably 50-60 °C, for a time of normally 1-6 hours, preferably 1-2 hours.

The radiation- curable liquid resin composition for additive fabrication obtained in this way is ideally used as a radiation- curable liquid resin composition in additive fabrication. That is, a three-dimensional object of a desired shape can be produced by additive fabrication, wherein the energy required for curing is supplied by selectively applying light such as visible light, ultraviolet light or infrared light or other radiation to the

radiation-curable liquid resin composition of the present invention.

If the radiation-curable liquid resin composition for additive fabrication of the present invention is used, the storage stability of the resin liquid is good, and a three-dimensional object having high shape precision, a low yellow index, a color tone close to colorless, high transparency, and excellent heat resistance can be obtained. The ninth aspect of the instant claimed invention is a

three-dimensional object obtained by applying light to the radiation- curable liquid resin composition for additive fabrication according to any of the first through eight aspects of the instant claimed invention.

The three-dimensional object of the present invention can be obtained by applying light to the aforementioned composition of the present invention.

As a means for selectively applying light to the composition of the present invention, various means may be employed without particular limitation. Examples of means which may be employed include a means for applying light to the composition by scanning with laser beams or focused rays converged by a lens, mirror or the like, a means for applying unfocused rays to the composition via a mask having a phototransmission area with a specific pattern, and a means for applying light to the composition via optical fibers corresponding to a specific pattern of a photoconductive material formed by bundling a plurality of optical fibers. Furthermore, light can be applied with LEDs or a lamp. Also, in the case of a means which uses a mask, a mask which optoelectrically forms a mask image consisting of a phototransmission area and a non-phototransmission area according to a specific pattern by using the same principle as that of a liquid crystal display apparatus may be used. In the case where the intended three-dimensional object is something having a finely- detailed section or which requires high dimensional accuracy, a means for scanning with laser beams with a small spot diameter is preferably employed as the means for selectively applying light to the composition. The irradiated surface of the resin composition held in a container (for example, the scanning plane of focused rays) may be the liquid surface of the resin composition, or the contact surface between the resin composition and the wall of a transparent container. In the case where light is applied to the liquid surface of the resin composition or the contact surface with the wall of the container, light may be applied to the composition either directly from outside the container or indirectly through the wall of the container.

In the aforementioned additive fabrication method, normally, after curing a specified area of the resin composition, the irradiation position (irradiated surface) is moved continuously or step-wise from the cured area to the uncured area to form layers of cured areas, thereby forming the desired three-dimensional shape. The irradiation position may be changed by various methods, such as moving the light source, the resin composition or the cured area of the resin composition, or by additionally providing resin composition to a container. A typical example of the aforementioned additive fabrication method is described as follows. A supporting stage installed such that it can freely move in the vertical direction in a container is minutely lowered

(dropped) from the liquid surface of the resin composition, thereby forming a thin layer (1) of the resin composition on the supporting stage. Then, the thin layer (1) is selectively irradiated with light, thereby forming a solid cured resin layer. Next, the supporting stage is again minutely lowered (dropped), thereby forming a thin layer (2) of the radiation-curable liquid resin composition on the cured resin layer (1), and the thin layer (2) is selectively irradiated with light, so as to continuously and integrally laminate it on top of the aforementioned cured resin layer (1) and form a new cured resin layer (2). Then, by repeating the above process a prescribed number of times while varying or without varying the pattern in which the light is applied, a three-dimensional object in which a plurality of cured resin layers (n) are integrally laminated is formed.

The resulting three-dimensional object is then removed from the container, and the residual unreacted resin composition remaining on the surface is removed, after which the three-dimensional object is washed as necessary. Examples of the washing agent used include alcohol-based organic solvents typified by alcohols such as isopropyl alcohol and ethyl alcohol;

ketone-based organic solvents typified by acetone, ethyl acetate, methyl ethyl ketone and the like; aliphatic organic solvents typified by terpenes; and heat-curable resins or radiation- curable resins of low viscosity. Furthermore, after the three-dimensional object is washed with a washing agent, it may be post-cured as necessary by heat or light irradiation. Post curing can cure unreacted resin composition remaining inside and on the surfaces of the three-dimensional object, can control stickiness of the surface of the object, and can improve the initial strength of the object.

The three-dimensional object of the present invention has high shape precision, a low yellow index, a color tone close to colorless and excellent heat resistance.

Examples

The present invention is described more specifically below by giving examples, but the present invention is not in any way limited by these examples.

[Preparation of liquid resin composition]

Liquid resin compositions of examples 1-8 and comparative examples 1-6 were prepared by putting the components in a stirring container according to the recipes shown in Table 1, and stirring at 60 °C for 3 hours. The recipes of Table 1 are shown in parts by mass unless otherwise stated.

Using the liquid resin compositions of examples 1-8 and comparative examples 1-6, tests were conducted to evaluate glass transition temperature, heat distortion temperature, yellow index, color tone, warping and resin liquid storage stability. The evaluation results are shown in Table 1.

Evaluation methods [Ratio of component (D) and divalent sulfonium salt having an aromatic structure contained in the composition]

Resin liquid and methanol were mixed well in a volume ratio of 20:80, and after letting stand for 1 hour, the supernatant liquid was filtered using a 0.45- μηι filter, and this was used as the sample liquid. This sample was analyzed by high-performance liquid chromatography (column: Inertsil Ph-3, GL Sciences Inc.; carrier: methanol/water = 95/5 (0.15% sodium perchlorate)), and the content ratio of component (D) (compound having a structure represented by the aforementioned formula (2)) and the divalent sulfonium salt having an aromatic structure (compound having a structure represented by the aforementioned formula (3)) was calculated from the area ratio of the peaks originating from the two compounds (detected by a diode array detector, analyzed at 300nm). [Glass transition temperature (Tg)J

(1) Creation of test specimen

A glass plate was coated with liquid resin composition in a thickness of 200 μηι, it was irradiated with ultraviolet rays at 1 J/cm² (220mW/cm2 X 4.55sec) using a metal halide lamp (Model M03-L31 from Eye Graphics Co., Ltd.), and a cured film was obtained. After that, it was left to stand for 24 hours in a thermo-hygrostat chamber at temperature 23°C and humidity 50%.

(2) Measurement

A test specimen of dimensions 8 cm x 0.6 cm was cut from the cured film created in this way. Measurement was performed at a heating rate of

20°C/minute using a DSC measurement apparatus (model 8230, manufactured by Rigaku).

[Heat distortion temperature (HOT)]

(1) Creation of test specimen

Using a solid creator SCS-300P (manufactured by D-MEC Ltd.), a three- dimensional object (length 120 mm, width 10 mm, thickness 4 mm) was created according of the flat-wise method specified in JIS K7191. Then, this three-dimensional object was removed from the solid creator, and resin composition attached to the outer surface was washed off. It was left to stand for 24 hours in a thermo-hygrostat chamber at temperature 23°C and humidity 50%, and then heat-treated for 2 hours at 80°C, after which measurement was performed using this as a test specimen.

(2) Measurement

HDT of the test specimen created in this way was measured using a heat distortion tester manufactured by Yasuda Seiki Seisakusho Ltd., according to flat-wise method b specified in JIS K7191. The measurement load was fixed at 0.45 MPa.

[Yellow index]

(1) Creation of test specimen

A test specimen was created in the same way as that for heat distortion temperature except that the thickness was 10 mm.

(2) Measurement

The yellow index of the test specimen created in this way was measured using a differential colorimeter VSS-300H manufactured by Nippon Denshoku Industries Co., Ltd. (measurement: transmission mode) against a white background. The colorimeter is calibrated against a white background by calibrating the tristimulus values (X, Y and Z) of the XYZ-Colorimetric system. Acceptable ranges are X=92.85±2.79, Y=94.76±2.84, Z=112.17±3.37. [Color tone]

Color tone was judged visually.

[Warping]

(1) Creation of test specimen

Using a solid creator SCS-300P (manufactured by D-MEC Ltd.), the three- dimensional object shown in FIG. 1-(1) was created (called "warping model 10" hereinafter). Then, this warping model 10 was removed from the solid creator, and resin composition attached to the outer surface was washed off. It was left to stand for 24 hours in a thermo-hygrostat chamber at temperature 23°C and humidity 50%, after which measurement was performed using this as a test specimen.

(2) Measurement

As shown in FIG. l-(2), the bottom end of a leg 11 of the test specimen obtained from warping model 10 was affixed to a horizontal stand 20, and the distance Ah from the horizontal stand 20 to the bottom end of a leg 12 was evaluated as the amount of warping, and was given the mark O, Δ or X in order of least amount of warping.

[Resin liquid storage stability]

100 g of each resin liquid was measured out in a sample bottle, and left to stand in an 80°C thermostat apparatus. After 10 days had elapsed, resin liquid storage stability was judged as X if the viscosity of the resin liquid was at least 1.5 times the initial value, or judged as O if less than 1.5 times the initial value.

[Table 1]

1) EHPE3150: epoxy-4-(2-oxiranyl)cyclohexene adduct of 2,2-bis(hydroxymethyl)- l-butanol, compound of formula (4) with m = 5

2) 2021P: 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexyl carboxylate

3) Epolite 4000: hydrogenated bisphenol diglycidyl ether

4) XDO: l,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene

5) OXA: 3-ethyl-3-hydroxymethyloxetane

6) DPHA: dipentaerythritol hexaacrylate

7) 399E: dipentaerythritol pentaacrylate

8) CPI-200K: compound in which (PR¾)- of formula (2) is (PF3(C2FB)3)", and the content of compound represented by formula (3) is at most 1/20 that of compound represented by formula (2)

9) CPI- 100P: compound in which (PR¾)" of formula (2) is substituted with PFe\ and the content of compound represented by formula (3) is at most 1/20 that of compound represented by formula (2)

10) UVI-6992: compound in which (PR¾)" of formula (2) is substituted with PF6^~, and the content of compound represented by formula (3) exceeds 1/20 that of compound represented by formula (2)

11) CPI-lOlA: compound in which (PR¾)- of formula (2) is substituted with SbF6", and the content of compound represented by formula (3) is at most 1/20 that of compound represented by formula (2)

12) Irgacure 184: 1-hydroxycyclohexyl phenyl ketone

13) Dye: violet-based dye

EHPE3150: epoxy-4-(2-oxiranyl)cyclohexene adduct of 2,2- bis(hydroxymethyl)-l-butanol (compound of formula (4) with m = 5

(manufactured by Daicel Chemical Industries, Ltd.))

2021 P : 3,4- epoxycyclohexylmethyl- 3', 4'- epoxycyclohexyl carboxylate

(manufactured by Daicel Chemical Industries, Ltd.)

Epolite 4000: hydrogenated bisphenol diglycidyl ether (manufactured by

Kyoeisha Chemical Co., Ltd.)

XD 0: 1, 4-bis{[(3- ethyl- 3-oxetanyl) methoxy] methyl}benzene

OXA: 3-ethyl-3-hydroxymethyloxetane (manufactured by Toagosei Co., Ltd.),

DPHA: dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co.,

Ltd.)

399E: dipentaerythritol pentaacrylate (Sartomer 399E, manufactured by

Nippon Kayaku Co., Ltd.)

CPI-200K: compound in which (PR³6)^" of the aforementioned formula (2) is (PF3(C2F5)3)^" (manufactured by San-Apro Ltd.); the content of compound having a structure represented by the aforementioned formula (3) is at most 1/20 that of the compound represented by formula (2)

CPI-100P: compound in which (PR¾)- of formula (2) is substituted with PF6" (manufactured by San-Apro Ltd.); the content of the compound having a structure in which (PR³6)^" of formula (3) is substituted with PF6" is at most 1/20 that of the compound represented by formula (2)

UVI-6992: compound in which (PR³6)^" of formula (2) is substituted with PF6"

(manufactured by Dow Chemical Corp.); the content of the compound having a structure in which (PR³6)^" of formula (3) is substituted with PF6" exceeds 1/20 that of the compound represented by formula (2)

CPI-101A: compound in which (PR³6)^" of formula (2) is substituted with SbF6" (manufactured by San-Apro Ltd.); the content of the compound having a structure in which (PR³6)^" of formula (3) is substituted with SbF6^" is at most 1/20 that of the compound represented by formula (2)

Irgacure 184: 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba

Specialty Chemicals Ltd.)

Dye: violet-based dye (Hostaperm, manufactured by Clariant)

From the results in Table 1, in each example, a three-dimensional object having good heat resistance as expressed by Tg (glass transition temperature) and HDT (heat distortion temperature), good transparency as expressed by yellow index and color tone, low warping and high precision was obtained, and resin liquid storage stability was also good. In example 5, in which color tone was compensated for by adding pigments/dyes and the like, the value of the yellow index was reduced, and the color tone changed from light yellow to light violet. On the other hand, in comparative examples 1-2, in which the content of component (A) was zero or very small, heat resistance was maintained to a certain extent by replacing component (A) with component (B), but transparency was poor. In comparative example 3, in which the content of component (A) was large, a trend of reduced transparency was seen, and the crosslink density in the three-dimensional object was large, and a large amount of warping of the object was seen. Comparative examples 4-6 are examples in which the photoacid generator did not correspond to component

(D). In comparative example 4, in which the photoacid generator used was non- antimony-based but the structure of the anion part was different, curability was insufficient, and as a result, crosslink density in the three-dimensional object was low and heat resistance was reduced. In comparative example 5, the structure of the photoacid generator was the same as in comparative example 4, but since the content of dimers of photoacid generator was high, not only was heat resistance reduced, but resin liquid storage stability was also reduced. In comparative example 6, in which an antimony-based photoacid generator was used, since curability was high, heat resistance was maintained, but the yellow index increased and the color tone tended toward yellow. [Possible Industrial Uses]

The composition of the present invention is ideally used in additive fabrication applications.

The composition of the present invention has good storage stability of the resin liquid and can produce a high-precision three-dimensional object, and is ideally used in applications for obtaining three-dimensional objects having a low yellow index (YI), a color tone close to colorless, high

transparency and excellent heat resistance.