JP7665444B2 - Photocurable resin composition - Google Patents

Description

The present invention relates to a method for producing a photocurable resin composition, a cured product, and an article.

In recent years, additive manufacturing (AM) has been increasingly used as a means of manufacturing products, against the backdrop of diversification of modeling materials and evolution of equipment technology. Among these, there are modeling methods called liquid layer photopolymerization and stereolithography. This modeling method forms a three-dimensional shape by hardening a liquid photocurable resin with a laser beam or lamp, and is characterized by the ability to model with high precision and accuracy. On the other hand, models made of photocurable resin are required to have high mechanical strength and environmental resistance, and improvements in material properties such as flexural modulus, impact resistance, and heat resistance are being made.
Patent Literature 1 describes that a curable composition having flexibility, high hardness, and heat resistance can be obtained by using a curable composition consisting of a radically polymerizable monomer and a polyfunctional radically polymerizable compound. Patent Literature 2 describes that a molded object having mechanical properties similar to those of a thermoplastic resin can be obtained by using an ink containing a cyclopolymerizable monomer and an oligomer curable material for modeling with a 3D printer.

JP 2014-40585 A Special Publication No. 2020-505255

However, depending on the application of the product, further improvement in mechanical properties is required, specifically, both impact resistance and flexural modulus are required. In addition, when used for high-definition and high-precision modeling, low liquid viscosity is also required from the viewpoint of preventing bubble entrapment and liquid leveling. The composition of Patent Document 1 can achieve low liquid viscosity, but does not provide sufficient impact resistance. The composition of Patent Document 2 produces a cured product with excellent mechanical properties such as flexural modulus, but the liquid viscosity is not sufficiently low and is not suitable for high-definition and high-precision modeling. The present invention aims to provide a curable resin composition that can produce a cured product with excellent impact resistance and flexural modulus, and has a low viscosity.

Means for Solving the Problems The present inventors have conducted intensive research in order to achieve the above-mentioned object, and have thus completed the present invention, which relates to a photocurable resin composition containing a monofunctional acrylic monomer (component (A)) that forms a polymer containing a five-membered cyclic ether by radical polymerization, and a polyfunctional radically polymerizable compound (component (B)) that contains an ethyleneoxy group or a propyleneoxy group.
Component (A) and component (B) form a copolymer structure by radical polymerization. In the cured product after polymerization, the 5-membered ring ether formed by polymerization of component (A) and the ethyleneoxy group or propyleneoxy group in component (B) have the function of absorbing impact, and the crosslinked structure formed by the polyfunctional radical polymerizable compound such as component (B) realizes high elastic modulus of the polymer. In particular, it was found that the number of the 5-membered ring ether and the ethyleneoxy group or propyleneoxy group and the distance between the crosslinking points are necessary factors for achieving both the free volume required for impact absorption and a high elastic modulus.
The photocurable resin composition according to the present embodiment is
A photocurable resin composition comprising component (A), component (B) and component (C),
The component (A) is a compound represented by the following general formula (1):

［一般式（１）中、Ｒは、水素または炭素数１以上４以下の炭化水素基である。前記炭化水素基は、置換基を有していても良い。］
前記成分（Ｂ）は、一分子内に、エチレンオキシ基またはプロピレンオキシ基を３個以上１５個以下有し、かつ、ラジカル重合性基を２個以上有する化合物であり、
前記成分（Ｃ）はラジカル重合開始剤であり、
前記光硬化性樹脂組成物中のエチレンオキシ基またはプロピレンオキシ基数Ｘは、下記式（ｉ）により算出され、
前記光硬化性樹脂組成物中の架橋基数Ｙは、下記式（ｉｉ）により算出され、
Ｘ＝ｘ_Bｎ_B／（ｘ_A＋ｘ_Bｎ_B＋ｘ_Bｍ_B）×１００ ・・・（ｉ）
Ｙ＝ｘ_Bｍ_B／（ｘ_A＋ｘ_Bｎ_B＋ｘ_Bｍ_B）×１００ ・・・（ｉｉ）
［ｘ_A：前記成分（Ａ）のモル分率
ｘ_B：前記成分（Ｂ）のモル分率
ｎ_B：前記成分（Ｂ）１分子内のエチレンオキシ基またはプロピレンオキシ基数
ｍ_B：前記成分（Ｂ）１分子内のラジカル重合性基数］
前記Ｘは３０以上４５以下、前記Ｙは１０以上１９以下の範囲にあることを特徴とする。

[In the general formula (1), R is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. The hydrocarbon group may have a substituent.]
The component (B) is a compound having 3 to 15 ethyleneoxy groups or propyleneoxy groups and 2 or more radical polymerizable groups in one molecule,
The component (C) is a radical polymerization initiator,
The number X of ethyleneoxy groups or propyleneoxy groups in the photocurable resin composition is calculated by the following formula (i):
The number Y of crosslinking groups in the photocurable resin composition is calculated by the following formula (ii):
X= _xBnB / _{( xA} + _xBnB + _{xBmB )} ×100 _... (i)
Y= _{xBmB / (xA+xBnB+xBmB ) × 100 ...} (ii)
[x _A : mole fraction of the component (A), x _B : mole fraction of the component (B), n _B : number of ethyleneoxy groups or propyleneoxy groups in one molecule of the component (B), m _B : number of radically polymerizable groups in one molecule of the component (B)]
The X is in the range of 30 or more and 45 or less, and the Y is in the range of 10 or more and 19 or less.

The present invention provides a photocurable resin composition that is suitable for molding and has low liquid viscosity before curing, and can produce molded objects with excellent impact resistance and flexural modulus.

FIG. 1 is a schematic diagram showing an example of the configuration of a molding apparatus using a free surface method.

The photocurable resin composition (hereinafter sometimes referred to as the "composition") according to this embodiment will be described in detail.

<Component (A): Monofunctional 2-(allyloxymethyl)acrylic acid or its ester>
The component (A), monofunctional 2-(allyloxymethyl)acrylic acid or its ester, is represented by the following general formula (1).

In the general formula (1), R is hydrogen or a hydrocarbon group having 1 to 4 carbon atoms, and the hydrocarbon group may be a saturated or unsaturated hydrocarbon group and may have a substituent. The hydrocarbon group having 1 to 4 carbon atoms may be linear, branched, or cyclic, and may contain an ether bond. Examples of the hydrocarbon group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a vinyl group, an allyl group, a methallyl group, a crotyl group, a cyclopropyl group, a cyclobutyl group, a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an ethoxyethyl group, a vinyloxyethyl group, an epoxy group, and an oxetanyl group. As the hydrocarbon group having 1 to 4 carbon atoms, a hydrocarbon group having 1 to 2 carbon atoms is particularly preferably used. Examples of the substituents that the hydrocarbon group may have include linear unsaturated hydrocarbon groups such as vinyl, allyl, methallyl, and crotyl groups; cyclic ether structures such as epoxy, glycidyl, and oxetanyl groups; alkoxy groups such as methoxy, ethoxy, and methoxyethoxy groups; alkylthio groups such as methylthio and ethylthio groups; acyl groups such as acetyl and propionyl groups; acyloxy groups such as acetyloxy and propionyloxy groups; alkoxycarbonyl groups such as methoxycarbonyl and ethoxycarbonyl groups; alkylthiocarbonyl groups such as methylthiocarbonyl and ethylthiocarbonyl groups; halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; ureido groups; amide groups; cyano groups; hydroxyl groups; and trimethylsilyl groups.

Component (A) can be a commercially available product, such as AOMA (manufactured by Nippon Shokubai Co., Ltd.).

The inclusion of a 5-membered ring ether formed by polymerization of component (A) improves the impact resistance of the cured product. Therefore, the content of component (A) is preferably 50% by mass or more and 95% by mass or less, more preferably 60% by mass or more and 85% by mass or less, even more preferably 60% by mass or more and 80% by mass or less, and even more preferably 65% by mass or more and 75% by mass or less, based on the total amount of the composition.

<Component (B): Polyfunctional radically polymerizable compound>
The polyfunctional radically polymerizable compound of component (B) has 3 to 15 ethyleneoxy groups or propyleneoxy groups and 2 or more radically polymerizable groups in one molecule.

Component (B) may be any of a linear compound, a branched compound, and a cyclic compound, and the ethyleneoxy group or propyleneoxy group contained in component (B) may be contained in the main chain, the side chain, or in a cyclic chain. The ethyleneoxy group or propyleneoxy group may form a repeating structure such as a polyoxyethylene or polyoxypropylene structure in the molecule. The ethyleneoxy group or propyleneoxy group may exist apart from each other. Specifically, for example, in a structure derived from a branched or cyclic compound such as pentaerythritol, dipentaerythritol, trimethylolpropane, ditrimethylolpropane, isocyanurate, etc., the ethyleneoxy group or propyleneoxy group may exist apart from each other. The propyleneoxy group may be linear or branched.

The radically polymerizable group contained in component (B) is preferably a group having a carbon-carbon double bond, and more preferably an acryloyl group.

The number of ethyleneoxy groups or propyleneoxy groups in one molecule, n _B , is 3 or more and 15 or less. When n _B is small, the number of ethyleneoxy groups or propyleneoxy groups X in the composition is small, or in order to increase X, the number of radical polymerizable groups in the composition is increased, which leads to an increase in the number of crosslinking groups Y in the composition, and therefore the impact resistance tends to decrease. When n _B is less than 3, impact resistance sufficient for practical use cannot be obtained. On the other hand, when n _B is large, X is more than Y in the composition, so that the composition exhibits properties similar to those of a rubber component, and the elastic modulus tends to decrease. When n _B is more than 15, the elastic modulus decreases rapidly. The range of n _B is preferably 3 to 14, more preferably 6 to 14.

As component (B), commercially available products can be used, such as SR454, SR492, SR499, SR502, SR9035, SR494, SR344, CD561, SR602, SR610, SR205, SR209, SR252, SR480, SR603, SR644 (all manufactured by SARTOMER), A-200, A-400, A-600, APG200, APG400, APG700, A Examples include BE-300, A-BPE-4, ABPE-10, A-TMPT-3EO, A-TMPT-9EO, A-TMPT-3PO, A-TMPT-9PO, A-GLY-3E, A-GLY-6E, A-GLY-9E, A-GLY-6P, A-GLY-9PA, A-DPH-12E, 3G, 4G, 9G, 14G, 3PG, 9PG, GLY-6E, GLY-9E (all manufactured by Shin-Nakamura Chemical Co., Ltd.), KAYARAD PEG400DA, R551, R712, RP1040, DPEA-12 (all manufactured by Nippon Kayaku Co., Ltd.), Viscoat #310, #700HVHP (all manufactured by Osaka Organic Chemical Industry Co., Ltd.), etc.

<Number of Ethyleneoxy Groups or Propyleneoxy Groups X and Number of Crosslinking Groups Y in Photocurable Resin Composition>
Component (B) is preferably contained so that the number X of ethyleneoxy groups or propyleneoxy groups in the photocurable resin composition is in the range of 30 to 45, and the number Y of crosslinking groups in the photocurable resin composition is in the range of 10 to 19. The methods for calculating X and Y are described below.

X is calculated by the following formula (i), and Y is calculated by the following formula (ii).
X= _xBnB / _{( xA} + _xBnB + _{xBmB )} ×100 _... (i)
Y= _{xBmB / (xA+xBnB+xBmB ) × 100 ...} (ii)
[x _A : mole fraction of component (A) x _B : mole fraction of component (B) n _B : number of ethyleneoxy groups or propyleneoxy groups in one molecule of component (B) m _B : number of radically polymerizable groups in one molecule of component (B)]

When the composition contains, as component (D), a polyfunctional radically polymerizable compound different from component (B), X is calculated by the following formula (iii), and Y is calculated by the following formula (iv).
X= _xBnB / _{(xA+xBnB+xBmB + xDmD ) × 100 ... (} iii)
Y= _{xBmB + xDmD / (xA+xBnB + xBmB + xDmD )} ×100 _... (iv)
[ _xA : mole fraction of component (A) _xB : mole fraction of component (B) _xD : mole fraction of component (D) _nB : number of ethyleneoxy groups or propyleneoxy groups in one molecule of component (B) _mB : number of radically polymerizable groups in one molecule of component (B) _mD : number of radically polymerizable groups in one molecule of component (D)]

When the composition contains, as component (E), a monofunctional radically polymerizable compound different from component (A), X is calculated by the following formula (v), and Y is calculated by the following formula (vi).
X _{= xBnB} / _{( xA} + _xE + _xBnB + _xBmB )×100 _... (v)
Y= _{xBmB / (xA+xE+xBnB+xBmB ) × 100 ... (} vi)
[x _A : mole fraction of component (A) x _B : mole fraction of component (B) x _E : mole fraction of component (E) n _B : number of ethyleneoxy groups or propyleneoxy groups in one molecule of component (B) m _B : number of radically polymerizable groups in one molecule of component (B)]

The mole fraction of each component is calculated from the amount (mass) of each compounded component added and its molecular weight. Molar fraction is the ratio of the amount of substance of each component to the sum of the amounts of substance of all the components, and is a dimensionless quantity with no units.

When multiple types of compounds are contained as component (B), x _B n _B and x _B m _B are the sums of the products of the mole fractions calculated for each compound and the number of ethyleneoxy groups or propyleneoxy groups or the number of radically polymerizable groups in one molecule. The same applies to x _D m _D when multiple types of compounds are contained as component (D).

The range of X that can produce a molded object with impact resistance and elastic modulus sufficient for practical use is 30 or more and 45 or less. The ethyleneoxy group or propyleneoxy group contained in component (B) has the effect of absorbing impact, but if X is below 30, the impact resistance decreases, and if X exceeds 45, the properties become similar to those of a rubber component, resulting in a decrease in the elastic modulus.

The range of Y that can be used to obtain a molded object with impact resistance and elastic modulus sufficient for practical use is 10 or more and 19 or less. A high flexural modulus can be achieved when Y is 10 or more, but if it exceeds 19, the number of breaking points when an impact is applied increases, resulting in reduced impact resistance.

By satisfying both the X and Y ranges, it is possible to obtain a cured product with little deformation under load while ensuring the free volume necessary for shock absorption after radical polymerization. In particular, when the range of X is 30 to 45 and the range of Y is 10 to 19, it is possible to obtain a cured product with particularly excellent flexural modulus and impact resistance.

<Component (C): Radical Polymerization Initiator>
The radical polymerization initiator can be appropriately selected depending on the curing conditions (irradiation wavelength, irradiation amount) of the curable resin.

Polymerization initiators that generate radical species upon irradiation with light include, but are not limited to, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 4-phenylbenzophenone, 4-phenoxybenzophenone, 4,4'-diphenylbenzophenone, and 4,4'-diphenoxybenzophenone.

In addition, examples of polymerization initiators that generate radical species by heat include azo compounds such as azobisisobutylnitrile (AIBN), and peroxides such as benzoyl peroxide, tert-butyl peroxypivalate, tert-butyl peroxyneohexanoate, tert-hexyl peroxyneohexanoate, tert-butyl peroxyneodecanoate, tert-hexyl peroxyneodecanoate, cumyl peroxyneohexanoate, and cumyl peroxyneodecanoate, but are not limited to these.

The radical polymerization initiator may be used alone or in combination of two or more kinds. The amount of radical polymerization initiator added is preferably in the range of 0.01 parts by mass to 10.00 parts by mass to 100 parts by mass of the radical polymerizable compound. The ratio of the radical polymerization initiator added may be appropriately selected depending on the amount of light irradiation and further the additional heating temperature. It may also be adjusted depending on the target average molecular weight of the resulting polymer.

<Component (D): Polyfunctional radically polymerizable compound different from component (B)>
A polyfunctional radically polymerizable compound different from component (B) can be added as component (D) to the photocurable resin composition of the present invention, within the range that does not significantly deteriorate the performance of the cured product.

Component (D) may be any of the following polyfunctional (meth)acrylates. For example, 1,4-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, trimethylolpropane triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, penta Examples of the component (D) include, but are not limited to, erythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, dioxane glycol diacrylate, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene diacrylate, cyclohexane-1,4-dimethanol di(meth)acrylate, cyclohexane-1,3-dimethanol di(meth)acrylate, dioxane glycol diacrylate, and dicyclopentanyl di(meth)acrylate. In addition, the component (D) may be used alone or in combination with multiple components, as long as the mechanical properties of the cured product are not reduced.

<Component (E): Monofunctional radically polymerizable compound different from component (A)>
To the photocurable resin composition of the present invention, a monofunctional radically polymerizable compound different from component (A) can be added as component (E) to the extent that a significant decrease in the performance of the cured product does not occur.

Component (E) may be the following monofunctional (meth)acrylates. For example, 4-tert-butylcyclohexanol (meth)acrylate, 3,3,5-trimethylcyclohexanol (meth)acrylate, isobornyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, 3-hydroxy-1-(meth)acryloyloxyadamantane, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, dicyclopentaenyl (meth)acrylate, 2-isopropyladamantan-2-yl (meth)acrylate, Acrylate, tetrahydrodicyclopentadienyl (meth)acrylate, α-(meth)acryloxy γ-butyrolactone, 2-hydroxy-o-phenylphenolpropyl (meth)acrylate, acryloylmorpholine, diethylacrylamide, isopropylacrylamide, hydroxyethylacrylamide, cyclohexyl (meth)acrylate, methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isooctyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, phenylglycidyl (meth)acrylate, lauryl (meth)acrylate, isodecyl (meth)acrylate, stearyl (meth)acrylate, isooctyl (meth)acrylate Examples of the component (E) include, but are not limited to, tridecyl (meth)acrylate, tridecyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxyditripropylene glycol (meth)acrylate, tricyclodecane (meth)acrylate, dicyclopentadieneoxyethyl (meth)acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, dicyclopentenyloxy methacrylate, dicyclopentanyl acrylate, and dicyclopentanyl methacrylate. In addition, the component (E) may be added alone or in combination with multiple types, as long as the mechanical properties of the cured product are not reduced.

<Component (F): Other Polymerizable Compounds>
Other polymerizable materials may be added as component (F) for viscosity adjustment or functionality. There are no particular limitations on the other polymerizable compounds, and examples of such compounds include cationic polymerizable compounds such as monofunctional or bifunctional or higher functional epoxy or oxetane compounds.

Examples of monofunctional or bifunctional or higher functional epoxy and oxetane compounds include hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol AD diglycidyl ether, hydrogenated bisphenol Z diglycidyl ether, cyclohexane dimethanol diglycidyl ether, tricyclodecane dimethanol diglycidyl ether, 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, 3,4-epoxy-1-methylcyclohexyl-3,4-epoxy-1-methyl ... carboxylate, 6-methyl-3,4-epoxycyclohexylmethyl-6-methyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-3-methylcyclohexylmethyl-3,4-epoxy-3-methylcyclohexanecarboxylate, 3,4-epoxy-5-methylcyclohexylmethyl-3,4-epoxy-5-methylcyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-metadioxane, bis(3,4-epoxycyclohexylmethyl)adipate, 3,4-epoxy-6-methyl ...3-methylcyclohexylmethyl-3,4-epoxy-3-methylcyclohexanecarboxylate, 3,4-epoxy-3-methylcyclohexylmethyl ethylcyclohexyl carboxylate, dicyclopentadiene diepoxide, ethylene bis(3,4-epoxycyclohexane carboxylate), dioctyl epoxyhexahydrophthalate, di-2-ethylhexyl epoxyhexahydrophthalate, ε-caprolactone modified 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate, 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol, bis(3,4-epoxycyclohexyl)methane, 2,2-bis(3,4-epoxycyclohexane Examples of the cyclohexyl)propane, 1,1-bis(3,4-epoxycyclohexyl)ethane, alpha-pinene oxide, camphalenic aldehyde, limonene monoxide, limonene dioxide, 4-vinylcyclohexene monoxide, 4-vinylcyclohexene dioxide, 3-hydroxymethyl-3-methyloxetane, 3-hydroxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-propyloxetane, 3-hydroxymethyl-3-normal butyloxetane, 3-hydroxymethyl-3-propyloxetane, etc., but are not limited to these.

In addition, when a cationic polymerizable compound is added, a polymerization initiator that generates cationic species upon light irradiation, a photoacid generator, or a photobase generator may be added to the composition to promote the polymerization reaction of the cationic polymerizable compound. A suitable polymerization initiator that generates cationic species upon light irradiation is, but is not limited to, iodonium (4-methylphenyl) [4-(2-methylpropyl)phenyl]-hexafluorophosphate. Examples of photoacid generators include, but are not limited to, triarylsulfonium hexafluoroantimonate, triphenylphenacylphosphonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate, bis-[4-(diphenylsulfonio)phenyl]sulfide bisdihexafluoroantimonate, bis-[4-(di4'-hydroxyethoxyphenylsulfonio)phenyl]sulfide bisdihexafluoroantimonate, bis-[4-(diphenylsulfonio)phenyl]sulfide bisdihexafluorophosphate, and diphenyliodonium tetrafluoroborate.

<Other additives>
To the composition of the present invention, a polymerization inhibitor, a photosensitizer, a light stabilizer, a heat stabilizer, an antioxidant, a chain transfer agent, a curing aid, etc. can be added within a range that does not significantly deteriorate the performance of the cured product.

Examples of polymerization inhibitors include hydroquinone-based polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, hydroquinone monoethyl ether, hydroquinone monopropyl ether, hydroquinone monobutyl ether, hydroquinone monopentyl ether, hydroquinone monohexyl ether, hydroquinone monooctyl ether, and hydroquinone monoheptyl ether, and phenol-based polymerization inhibitors having a substituent such as 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. However, hydroquinone-based polymerization inhibitors such as hydroquinone and benzoquinone-based polymerization inhibitors such as benzoquinone may turn yellow when exposed to UV light, so they are suitable for obtaining thin-film cured products such as coatings. Examples of polymerization inhibitors include, but are not limited to, those mentioned above as polymerization inhibitors during reaction and storage. The amount of addition is preferably in the range of 0.01% by mass to 1.00% by mass of the composition. In addition, only one polymerization inhibitor may be used, or two or more polymerization inhibitors may be used in combination. Considering the lack of coloring, it is preferable to use a hydroquinone-based polymerization inhibitor in combination.

Examples of photosensitizers include benzophenone, 4,4-diethylaminobenzophenone, 1-hydroxycyclohexyl phenyl ketone, isoamyl p-dimethylaminobenzoate, methyl 4-dimethylaminobenzoate, benzoin, benzoin ethyl ether, benzoin isobutyl ether, benzoin isopropyl ether, 2,2-diethoxyacetophenone, methyl o-benzoylbenzoate, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and acylphosphine oxide. The amount of the photosensitizer added is preferably in the range of 0.01% by mass to 10.00% by mass of the composition.

There are no particular limitations on the light resistance stabilizer as long as it does not significantly affect the properties of the cured product, and examples of such stabilizers include 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol, and 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol. Benzotriazole compounds such as 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)]-4-(1,1,3,3-tetramethylbutyl)phenol, and 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol; cyanoacrylate compounds such as ethyl 2-cyano-3,3-diphenylacrylate and 2-ethylhexyl 2-cyano-3,3-diphenylacrylate; triazine compounds; and benzophenone compounds such as octabenzone and 2,2'-4,4'-tetrahydrobenzophenone. The light resistance stabilizer may also function as a photosensitizer, in which case the photosensitizer need not be added. The amount of the additive is preferably in the range of 0.01% by mass to 10.00% by mass relative to the composition.

There are no particular limitations on the heat stabilizer as long as it does not significantly affect the properties of the cured product, and examples thereof include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, alkyl esters of 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanoic acid having a side chain and a carbon number of 7 to 9, 4,6-bis(octylthiomethyl)-o-cresol, Examples of such compounds include hindered phenol compounds such as 4,6-bis(dodecylthiomethyl)-o-cresol, ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)]propionate, and hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, phosphorus compounds such as tris(2,4-di-tert-butylphenyl)phosphite, and sulfur compounds such as dioctadecyl-3,3'-thiodipropionate. The amount of the compound added is preferably in the range of 0.01% by mass to 10.00% by mass of the composition.

There are no particular limitations on the antioxidant as long as it does not significantly affect the properties of the cured product, and examples include hindered amine compounds such as bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate and bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate. The amount added is preferably in the range of 0.01% by mass to 10.00% by mass of the composition.

Examples of chain transfer agents and curing aids include β-mercaptopropionic acid, 2-ethylhexyl-3-mercaptopropionate, n-octyl-3-mercaptopropionate, methoxybutyl-3-mercaptopropionate, stearyl-3-mercaptopropionate, 1-butanethiol, cyclohexanethiol, cyclohexyl 3-mercaptopropionate, 1-decanethiol, 2,4-diphenyl-4-methyl-1-pentene, 1-dodecanethiol, dodecyl 3-mercaptopropionate, 2-ethylhexyl mercaptoacetate, 3-mercaptopropionate, 2-Ethylhexyl mercaptoate, ethyl mercaptoacetate, 1-hexadecanethiol, hexyl 3-mercaptopropionate, 2-mercaptoethanol, 3-mercapto-1,2-propanediol, mercaptoacetic acid, sodium 2-mercaptoethanesulfonate, 3-mercaptopropionic acid, methyl mercaptoate, mercaptosuccinic acid, methyl 3-mercaptopropionate, octadecyl 3-mercaptopropionate, octyl 3-mercaptopropionate, 1-octanethiol, 1-octadecanethiol, tridecyl 3-mercaptopropionate, thiophene As polyfunctional thiols, bis(2-mercaptoethyl)sulfide, 3,6-dioxa-1,8-octanedithiol, trimethylolpropane tris(3-mercaptopropionate), 1,4-butanediol bis(thioglycolate) pentaerythritol tetra(3-mercaptopropionate), 1,4-benzenethiol, 3,7-dithia-1,9-nonanol, DL-1,4-dimercapto-2,3-butanediol, 1,5-dimercaptonaphthalene, dithioerythritol, ethylene bisthioglycolate, pentaerythritol tetrakismethyl Mercaptoacetate, tris-[(3-mercaptopropionyloxyethyl)-isocyanurate, tetraethylene glycol bis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), 3,3'-thiodipropionic acid, dithiodipropionic acid, laurylthiopropionic acid (dodecylthiopropionic acid), and commercially available products include TS-G, C3TS-G, TA-G, LDAIC (manufactured by Shikoku Chemical Industry Co., Ltd.), Karenz MTPE1, BD1, NR1, TPMB, (manufactured by Showa Denko K.K.), etc.

Furthermore, pigments, fillers, etc. may be added to adjust viscosity or impart functionality. There are no particular limitations on the filler, and it is sufficient that it does not deteriorate the mechanical properties of the cured product. Types of fillers include metal salts, metal oxides, polymer fine particles, rubber particles, inorganic fibers, organic fibers, carbon, etc. Metal oxides include, but are not limited to, silicon oxide, titanium oxide, aluminum oxide, etc. Polymer fine particles include, but are not limited to, acrylic fine particles, polystyrene fine particles, nylon particles, etc. Rubber particles include, but are not limited to, butadiene rubber particles, styrene-butadiene rubber copolymer particles, acrylonitrile-butadiene copolymer rubber particles, or saturated rubber particles obtained by hydrogenating or partially hydrogenating these diene rubbers, crosslinked butadiene rubber particles, isoprene rubber particles, chloroprene rubber particles, natural rubber particles, silicone rubber particles, ethylene/propylene/diene monomer terpolymer rubber particles, acrylic rubber particles, acrylic/silicone composite rubber particles, etc. Organic fibers include, but are not limited to, nylon fibers, cellulose nanofibers, etc.

<Viscosity>
If the viscosity (liquid viscosity of the uncured composition measured in an atmosphere at 23 ° C.) is less than 1,000 cps (mPa · s), modeling by liquid layer photopolymerization method or photolithography method is possible. However, if the viscosity is 200 cps or more, bubbles may be mixed into the cured product, or time may be required for leveling of the resin liquid surface. Therefore, the composition of the present invention achieves a viscosity of less than 200 cps (liquid viscosity of the uncured composition measured in an atmosphere at 23 ° C.). More preferably, the viscosity is 100 cps or less, and even more preferably, 10 cps or less. The low liquid viscosity can suppress the mixing of bubbles, and further improves the handling properties, such as shortening the leveling time of the resin liquid surface and simplifying the cleaning process performed after modeling. It can also be suitably used in spraying such as inkjet method.

<Method of preparing the composition>
The method for preparing the composition of the present invention is not particularly limited, and the simplest method is to weigh all the materials and then heat and stir them. However, if there is a concern that polymerization may occur due to heating, a polymerization inhibitor may be added as appropriate. If it is difficult to mix uniformly by heating alone, the composition may be prepared by dissolving all the materials in a solvent such as acetone and then distilling off the solvent. Furthermore, stirring using a dispersing machine such as an ultrasonic homogenizer, a ball mill, or a disk mill may be used.

<Method of forming an article>
In the curing step of the composition, the shape of the cured product and the curing method are not particularly limited. Examples of the curing method include a method of applying the composition onto a substrate and then irradiating the composition with light, a method of injecting the composition into a mold and then irradiating the composition with light, and a photolithography method (stereolithography) in which thin films of cured products are stacked.

The method for applying the composition to the substrate is not particularly limited. For example, the composition may be applied to the substrate to a desired thickness using a contact transfer type coating device such as a roll coater, reverse coater, bar coater, or slit coater, or a non-contact type coating device such as a spinner (rotary coating device) or curtain flow coater to form a coating film.

Any of the conventionally known photo-fabrication methods and devices can be used for the method of photo-fabrication using the composition of the present invention. A preferred method is a method of stacking layers of photo-cured composition at a predetermined thickness. A representative example of a preferred photo-fabrication method is a method having a step of repeatedly placing and curing a curable resin composition at a predetermined thickness based on slice data generated based on three-dimensional shape data of the object to be manufactured (three-dimensional model).

There are two main types of stereolithography: the free surface method and the controlled surface method.

Figure 1 shows an example of the configuration of a modeling device 100 using the free liquid surface method. The modeling device 100 has a tank 11 that contains a liquid curable resin composition 10. Inside the tank 11, a modeling stage 12 is provided so that it can be driven vertically by a drive shaft 13. The active energy beam 15 for curing the curable resin composition 10, which is emitted from a light source 14, is scanned over the surface of the tank 11 by changing the irradiation position using a galvanometer mirror 16 controlled by a control unit 18 according to slice data. In Figure 1, the scanning range is indicated by a thick dashed line.

The thickness d of the photocurable resin composition 10 cured by the active energy beam 15 is a value determined based on the settings made when the slice data was generated, and affects the precision of the resulting article (the reproducibility of the three-dimensional shape data of the article to be molded). The thickness d is achieved by the control unit 18 controlling the drive amount of the drive shaft 13.

First, the control unit 18 controls the drive shaft 13 based on the settings, and the curable resin composition is supplied to a thickness d on the stage 12. The liquid curable resin composition on the stage 12 is selectively irradiated with active energy rays 15 based on slice data so as to obtain a cured layer having the desired pattern, and a cured layer is formed. Next, the stage 12 is moved in the direction of the white arrow, and uncured curable resin composition is supplied to a thickness d on the surface of the cured layer. Then, active energy rays 15 are irradiated based on the slice data, and a cured product integrated with the previously formed cured layer is formed. By repeating this layered curing process, the desired three-dimensional object 17 can be obtained.

When irradiating a surface made of a curable resin composition with active energy rays to form a cured layer of a predetermined shape pattern, the resin can be cured by a pointillist or line drawing method using light energy rays focused in a dotted or line shape. Alternatively, the resin can be cured by irradiating the active energy rays in a planar manner through a planar drawing mask formed by arranging multiple microscopic light shutters such as liquid crystal shutters or digital micromirror shutters.

Like the free liquid level method, modeling by the regulated liquid level method is also preferred. A modeling device using the regulated liquid level method is configured such that the stage 12 of the modeling device 100 in FIG. 1 is arranged to raise the model 17 above the liquid level, and the light irradiation means is arranged below the tank 11. A typical modeling example by the regulated liquid level method is as follows. First, the support surface of the support stage, which is arranged to be freely raised and lowered, and the bottom surface of the tank containing the curable resin composition are installed so as to be at a predetermined distance, and the curable resin composition is supplied between the support surface of the support stage and the bottom surface of the tank. Next, light is selectively irradiated from the bottom surface side of the tank containing the curable resin composition to the curable resin composition between the stage support surface and the bottom surface of the tank according to slice data by a laser light source or a projector. The curable resin composition between the stage support surface and the bottom surface of the tank is cured by the irradiation of light, and a solid cured layer is formed. After that, the support stage is raised, and the cured layer is peeled off from the bottom surface of the tank.

Then, the height of the support stage is adjusted so that a predetermined distance is formed between the cured layer formed on the support stage and the bottom surface of the tank. Then, as before, a curable resin composition is supplied between the bottom surface of the tank and the cured layer, and a new cured layer is formed between the cured layer and the bottom surface of the tank by irradiating light according to the slice data. By repeating this process multiple times, a molded object 17 consisting of multiple cured layers stacked together can be obtained.

The shaped object 17 thus obtained is removed from the tank 11, and any unreacted curable resin composition remaining on its surface is removed. After that, the desired article can be obtained by carrying out post-processing as necessary.

Post-processing includes cleaning, post-curing, cutting, polishing, and assembly.

As a cleaning agent used for cleaning, an alcohol-based organic solvent such as isopropyl alcohol or ethyl alcohol can be used. In addition, a ketone-based organic solvent such as acetone, ethyl acetate, or methyl ethyl ketone, or an aliphatic organic solvent such as terpenes can also be used.

After washing, post-curing may be performed as necessary by light irradiation, heat irradiation, or both. Post-curing can harden any unreacted curable resin composition that may remain on the surface and inside of the object, suppressing stickiness on the surface of the three-dimensional object and improving the initial strength of the three-dimensional object.

Examples of active energy rays include ultraviolet rays, electron beams, X-rays, radiation, and high frequency waves. Among these, ultraviolet rays having a wavelength of 300 nm to 430 nm are preferably used from an economical point of view, and as a light source, ultraviolet lasers (e.g., semiconductor-pumped solid-state lasers, Ar lasers, He-Cd lasers, etc.), high-pressure mercury lamps, ultra-high-pressure mercury lamps, mercury lamps, xenon lamps, halogen lamps, metal halide lamps, ultraviolet LEDs (light-emitting diodes), fluorescent lamps, etc. can be used. Among these, ultraviolet lasers are preferably used because they have excellent light-collecting properties, can increase the energy level to shorten the modeling time, and can obtain high modeling precision.

<Applications>
The composition of the present invention can be suitably used in three-dimensional additive manufacturing, particularly in photolithography. In addition, the cured product of the present invention and the molded product obtained by a 3D printer can be widely used in the field of optical three-dimensional molding. The application fields are not limited in any way, but representative fields include prototype models of industrial products, design models, working models, base models for producing molds, direct molds for prototype molds, service parts, housings, parts of industrial products, etc. In particular, the composition of the present invention can be used to manufacture housings and parts of industrial products because it has both elastic modulus and impact resistance.

Examples 1 to 12 and Comparative Examples 1 to 7
<Ingredients>
Each component used in the examples and comparative examples is shown in Table 1 together with its molecular weight, the number of ethyleneoxy or propyleneoxy groups in one molecule, and the number of radically polymerizable groups in one molecule.

<Production of Composition>
The components were blended in the blending ratios (mass ratios) shown in Table 2 and mixed uniformly to prepare compositions.

<Production of Cured Test Pieces>
The prepared composition was used to prepare a cured product by the following method. First, a mold with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm was sandwiched between two pieces of quartz glass, and the composition was poured into the mold. The poured composition was irradiated with 10 mW/cm ² ultraviolet light for 120 seconds using an ultraviolet irradiator (EX250 manufactured by HOYA CANDEO OPTRONICS Co., Ltd.) and an illuminometer (UIT-250 manufactured by Ushio Inc.) for a total of six times, with the irradiated surface being reversed, and then demolded to obtain a cured product (total irradiated energy was 7200 mJ/cm ² ). The obtained cured product was then placed in a heating oven at 50° C. for 1 hour and then in a heating oven at 100° C. for 1 hour, and a cured product for test specimens was obtained.

<Evaluation of flexural modulus>
The flexural modulus of the obtained test specimen was measured using a universal material testing machine (5581, manufactured by INSTRON) in accordance with JIS K 7171. The flexural modulus was calculated from the stress gradient in the specified strain range (0.05% to 0.25%) under the condition of 2 mm/min. The flexural modulus was also evaluated according to the following criteria. The results are shown in Table 2.
A (very good): Flexural modulus of elasticity is 2.0 GPa or more.
B (good): Flexural modulus is 1.5 GPa or more and less than 2.0 GPa.
C (poor): Flexural modulus is less than 1.5 GPa.

<Evaluation of impact resistance>
The obtained test specimen was subjected to a 2 mm deep, 45° notch in the center using a notch forming machine (manufactured by Toyo Seiki Seisakusho, product name "Notching Tool A-4") in accordance with JIS K 7111. Then, using an impact tester (manufactured by Toyo Seiki Seisakusho, product name "IMPACT TESTER IT"), the test specimen was broken with an energy of 2 J from the back of the notch. The energy required for breaking was calculated from the angle at which the hammer swung up to 150° after the test specimen was broken, and this Charpy impact strength was used as an index of impact resistance. In addition, impact resistance was evaluated according to the following criteria. The results are shown in Table 2.
A (very good): Charpy impact strength is 6 kJ/ ^m2 or more.
B (good): Charpy impact strength is 5 kJ/ ^m2 or more and less than 6 kJ/ ^m2 .
C (poor): Charpy impact strength is less than 5 kJ/ ^m2 .

<Measurement of Liquid Viscosity>
The liquid viscosity of the uncured composition was measured in an atmosphere of 23° C. using an ultrasonic vibration viscometer (manufactured by Sekonic Corporation, product name "VM-10A-L"). The liquid viscosity was evaluated according to the following criteria. The results are shown in Table 2.
A (very good): Liquid viscosity is less than 200 cps.
B (Good): Liquid viscosity is 200 cps or more and less than 1,000 cps.

<Light Prototyping>
For the composition of Example 4, a 3D printer (ML-48, manufactured by Mutoh Engineering Co., Ltd.) was used to create a model with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm by stereolithography under conditions of a layer pitch of 0.1 mm and an exposure time of 60 seconds per layer. The resulting model was subjected to a secondary curing treatment at a temperature of 60° C. for 60 minutes using a secondary curing tool (Formcure, manufactured by Formlabs). The impact resistance and flexural modulus of the resulting cured product were evaluated in the same manner as for the test specimen cured product. The evaluation results of the cured product obtained by stereolithography and the test specimen cured product are shown in Table 3.

As can be seen from Table 2, when Examples 1 to 6, which use a compound (component (B)) having 3 to 15 ethyleneoxy or propyleneoxy groups in one molecule and having 2 or more radically polymerizable groups as a polyfunctional radically polymerizable compound, are compared with Comparative Example 9, which uses a polyfunctional radically polymerizable material D-1 that does not have an ethyleneoxy or propyleneoxy group in its molecule, the cured products of Examples 1 to 6 have high impact resistance. On the other hand, compared to Comparative Example 14, which uses D-3 that has more than 15 ethyleneoxy or propyleneoxy groups in one molecule, the cured products of Examples 1 to 6 have a high flexural modulus.

In addition, when comparing Examples 1 to 6, in which X is in the range of 30 to 45 and Y is in the range of 10 to 19, with Comparative Examples 1 to 15, in which X and Y are not in this range, it is clear that Examples 1 to 6 can achieve both high flexural modulus and impact resistance. In addition, the liquid viscosity was 10 cps or less in all cases.

In addition, Table 3 shows that the test pieces obtained by stereolithography have the same performance as molded products.

These results demonstrate that the composition of the present invention can produce a cured product that has both high impact resistance and flexural modulus, and that the composition has low liquid viscosity in the uncured state, making it suitable for use in optical three-dimensional modeling.

10: Curable resin composition, 12: Stage, 15: Active energy beam, 17: Model, 100: Modeling device

Claims (20)

A photocurable resin composition comprising component (A), component (B) and component (C),
The component (A) is a compound represented by the following general formula (1):

[In the general formula (1), R is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. The hydrocarbon group may have a substituent.]
The component (B) is a compound having 3 to 15 ethyleneoxy groups or propyleneoxy groups and 2 or more radical polymerizable groups in one molecule,
The component (C) is a radical polymerization initiator,
The number X of ethyleneoxy groups or propyleneoxy groups in the photocurable resin composition is calculated by the following formula (i):
The number Y of crosslinking groups in the photocurable resin composition is calculated by the following formula (ii):
X= _xBnB / _{( xA} + _xBnB + _{xBmB )} ×100 _... (i)
Y= _{xBmB / (xA+xBnB+xBmB ) × 100 ...} (ii)
[x _A : mole fraction of the component (A), x _B : mole fraction of the component (B), n _B : number of ethyleneoxy groups or propyleneoxy groups in one molecule of the component (B), m _B : number of radically polymerizable groups in one molecule of the component (B)]
A photocurable resin composition, wherein X is in the range of 30 or more and 45 or less, and Y is in the range of 10 or more and 19 or less. The photocurable resin composition according to claim 1, characterized in that the content of component (A) is 60% by mass or more and 80% by mass or less. The photocurable resin composition according to claim 1, characterized in that the content of component (A) is 65% by mass or more and 75% by mass or less. 4. The photocurable resin composition according to claim 1, which has a viscosity of less than 200 cps. The photocurable resin composition according to any one of claims 1 to 4, characterized in that component (B) has 6 to 14 ethyleneoxy groups or propyleneoxy groups in one molecule. The photocurable resin composition according to any one of claims 1 to 5, characterized in that component (B) contains a group having a carbon-carbon double bond as the radical polymerizable group. The photocurable resin composition according to claim 6, characterized in that the group having a carbon-carbon double bond is an acryloyl group. A photocurable resin composition comprising component (A), component (B), component (C) and component (D),
The component (A) is a compound represented by the following general formula (1):

[In the general formula (1), R is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. The hydrocarbon group may have a substituent.]
The component (B) is a compound having 3 to 15 ethyleneoxy groups or propyleneoxy groups and 2 or more radical polymerizable groups in one molecule,
The component (C) is a radical polymerization initiator,
The component (D) is a polyfunctional radical polymerizable compound different from the component (B),
The number X of ethyleneoxy groups or propyleneoxy groups in the photocurable resin composition is calculated by the following formula (iii):
The number Y of crosslinking groups in the photocurable resin composition is calculated by the following formula (iv):
X= _xBnB / _{(xA+xBnB+xBmB + xDmD ) × 100 ... (} iii)
Y= _{xBmB + xDmD / (xA+xBnB + xBmB + xDmD )} ×100 _... (iv)
[ _xA : molar fraction of the component (A), _xB : molar fraction of the component (B), _xD : molar fraction of the component (D), _nB : number of ethyleneoxy groups or propyleneoxy groups in one molecule of the component (B), _mB : number of radically polymerizable groups in one molecule of the component (B), _mD : number of radically polymerizable groups in one molecule of the component (D)]
A photocurable resin composition, wherein X is in the range of 30 or more and 45 or less, and Y is in the range of 10 or more and 19 or less. The photocurable resin composition according to claim 8, characterized in that the content of component (A) is 60% by mass or more and 80% by mass or less. The photocurable resin composition according to claim 8, characterized in that the content of component (A) is 65% by mass or more and 75% by mass or less. 11. The photocurable resin composition according to claim 8, which has a viscosity of less than 200 cps. The photocurable resin composition according to any one of claims 8 to 11, characterized in that component (B) has 6 to 14 ethyleneoxy groups or propyleneoxy groups in one molecule. The photocurable resin composition according to any one of claims 8 to 12, characterized in that component (B) contains a group having a carbon-carbon double bond as the radical polymerizable group. The photocurable resin composition according to claim 13, characterized in that the group having a carbon-carbon double bond is an acryloyl group. A cured product obtained by curing the photocurable resin composition according to any one of claims 1 to 14. The cured product according to claim 15, characterized in that the cured product has a flexural modulus of elasticity of 1.5 GPa or more. The Charpy impact strength of the cured product is 6 kJ/m ² The cured product according to claim 15 or 16, characterized in that A method for manufacturing an article, comprising repeating a step of photocuring the photocurable resin composition according to any one of claims 1 to 14 to a predetermined thickness to form a cured layer multiple times. disposing a curable resin composition at a predetermined thickness;
a step of irradiating the curable resin composition with light energy based on slice data of a three-dimensional model to cure the composition;
20. The method of claim 18 , comprising: The method for manufacturing an article according to claim 19, further comprising a step of washing or post-curing a shaped object obtained by repeating a step of disposing the curable resin composition to a predetermined thickness and a step of irradiating the curable resin composition with light energy to cure the composition multiple times.

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