JP7572207B2 - Photocurable resin composition and method for producing photo-modeled object using same - Google Patents

Description

The present invention relates to a photocurable resin composition and a method for producing a photo-modeled object using the same.

With the development of three-dimensional photo-fabrication technology such as 3D printers, there is an increasing demand for improved heat resistance and mechanical strength of photo-fabricated objects. For example, Patent Document 1 proposes a curable composition for a sheet used in three-dimensional molding, which contains a compound such as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate, a bifunctional or higher (meth)acrylate compound, and a photoradical polymerization initiator, does not contain a urethane (meth)acrylate compound, or the content of the urethane (meth)acrylate compound is more than 0 mass% and less than 4 mass% with respect to the total mass of the curable composition, and the molecular weight between crosslinking points of the obtained cured product is 50 g/mol or more and 2,000 g/mol or less. It also teaches that a bifunctional or higher (meth)acrylate compound having an isocyanuric ring structure can be used as the bifunctional or higher (meth)acrylate compound.

JP 2019-19276 A

The present inventors have found that by using a triacrylate compound having an isocyanuric ring and three (meth)acryloyl groups, a photocurable resin composition can be obtained that gives a photo-modeled object with significantly improved heat resistance and mechanical strength. On the other hand, a triacrylate compound having an isocyanuric ring and three (meth)acryloyl groups has a high crystallinity at room temperature, and therefore there is a problem that a part or all of the photocurable resin composition solidifies during low-temperature storage.

One aspect of the present invention relates to a photocurable resin composition comprising a polymerizable compound and a photopolymerization initiator, the polymerizable compound comprising a first compound and a second compound each containing nitrogen, the first compound being a triacrylate compound having an isocyanuric ring and three (meth)acryloyl groups, the second compound being at least one selected from the group consisting of a diacrylate compound having an isocyanuric ring and two (meth)acryloyl groups and a monoacrylamide compound having one (meth)acryloyl group, and the proportion of the first compound in the total mass of the first compound and the second compound being 50% by mass or more and 90% by mass or less.

Another aspect of the present invention relates to a method for producing a photo-modeled object, comprising the steps of forming a photo-modeled object using the photo-curable resin composition, the step of forming the photo-modeled object comprising the steps of (i) forming a liquid film of the photo-curable resin composition and photo-curing the liquid film to form a pattern, (ii) forming another liquid film in contact with the pattern, and (iii) photo-curing the other liquid film on the pattern to laminate the other pattern.

We provide a photocurable resin composition that has excellent stability during low-temperature storage and can produce photo-modeled objects with excellent heat resistance and mechanical strength.

FIG. 2 is a schematic diagram for explaining a process of forming a stereolithography object using a photocurable resin composition according to one embodiment of the present invention.

The photocurable resin composition according to the embodiment of the present invention will be specifically described below, but the present invention is not limited to the following embodiment, and various changes and modifications are possible.

The term "(meth)acryloyl group" means an acryloyl group, a methacryloyl group, or both. Similarly, the term "(meth)acrylate" means an acrylate, a methacrylate, or both. Similarly, the term "(meth)acrylic" means "acrylic" or "methacrylic", or both.

A photo-modeled object needs heat resistance and mechanical strength necessary to express the function of the photo-modeled object. On the other hand, a photo-curable resin composition that gives such a photo-modeled object by curing is required to have not only photo-curability but also excellent workability and reactivity. A triacrylate compound having an isocyanuric ring and three (meth)acryloyl groups contributes greatly to improving the heat resistance and mechanical strength of a photo-modeled object, but may crystallize during low-temperature storage and solidify at least a part of the photo-curable resin composition. When a photo-curable resin composition solidifies, not only does its workability decrease, but the curing reaction of the solidified part is restricted, and the expected physical properties of the photo-modeled object may not be obtained. There is often a trade-off between the heat resistance and mechanical strength of the photo-modeled object and the stability of the photo-curable resin composition during low-temperature storage, and it is difficult to achieve both. In addition, a photo-modeled object is required to have low shrinkage during curing and shape accuracy. A photo-curable resin composition is required to have low viscosity and a fast curing speed.

The photocurable resin composition according to an embodiment of the present invention (hereinafter also referred to as "photocurable resin composition A") and the photo-fabricated object formed using the same can satisfy the various requirements described above with a high degree of satisfaction.

[Photocurable resin composition A]
The photocurable resin composition A includes a polymerizable compound and a photopolymerization initiator. The polymerizable compound includes a first compound and a second compound, each of which contains nitrogen.

The first compound is a triacrylate compound having an isocyanuric ring and three (meth)acryloyl groups, which significantly contributes to improving the heat resistance and mechanical strength of the photo-fabricated object. Meanwhile, the second compound is at least one selected from the group consisting of a diacrylate compound having an isocyanuric ring and two (meth)acryloyl groups and a monoacrylamide compound having one (meth)acryloyl group, which contributes to improving the heat resistance and mechanical strength of the photo-fabricated object and suppresses the solidification of the photocurable resin composition A during low-temperature storage caused by the first compound.

Here, the ratio of the first compound to the total mass of the first compound and the second compound is 50% by mass or more and 90% by mass or less. Photocurable resin composition A having this composition is resistant to solidification during low-temperature storage and has excellent storage stability, despite containing a fairly large amount of the first compound.

If the proportion of the first compound in the total mass of the first compound and the second compound is less than 50 mass%, it is difficult to achieve both the heat resistance and mechanical strength of the photo-modeled object with sufficient satisfaction. Also, if the proportion of the first compound in the total mass of the first compound and the second compound exceeds 90 mass%, it is difficult to ensure the stability of the photocurable resin composition A during low-temperature storage. In order to achieve both the heat resistance and mechanical strength of the photo-modeled object and the stability of the photocurable resin composition A during low-temperature storage with a higher degree of satisfaction, it is desirable to set the proportion of the first compound in the total mass of the first compound and the second compound to 60 mass% or more and 87 mass% or less.

[Polymerizable compound]
The polymerizable compound is not particularly limited, but refers to a compound that undergoes chain polymerization, and chain polymerization includes addition polymerization, ring-opening polymerization, etc. Load polymerization includes radical polymerization, cationic polymerization, anionic polymerization, coordination polymerization, etc. The polymerization reaction may be photosensitized polymerization. The polymerizable compound includes polymerizable monomers, polymerizable oligomers, etc.

The term "polymerizable" in polymerizable monomers and polymerizable oligomers means that the monomer or oligomer has a polymerizable group that participates in a curing reaction that utilizes a photopolymerization initiator. A polymerizable oligomer is one that contains at least a repeating portion of a structural unit (the number of repeats is two or more), and is distinguished from a polymerizable monomer.

The viscosity of the photocurable resin composition A at 25°C is, for example, 10 mPa·s or more and 3000 mPa·s or less. In order to easily ensure high photo-modeling properties, the viscosity at 25°C is preferably 2000 mPa·s or less, and more preferably 1000 mPa·s or less. The viscosity of the photocurable resin composition A can be measured, for example, using a cone-plate type E-type viscometer at a rotation speed of 20 rpm.

The polymerizable compound can be separated from the photocurable resin composition A by using a known separation method such as centrifugation, extraction, crystallization, column chromatography, or recrystallization. The polymerizable compound can be identified by analyzing the photocurable resin composition A by gas chromatography, liquid chromatography, mass spectrometry, or the like.

[First Compound]
The first compound is a triacrylate compound having an isocyanuric ring and three (meth)acryloyl groups (hereinafter also referred to as "triacrylate compound A"). The triacrylate compound A is classified as a polymerizable monomer. A cured product containing the triacrylate compound A as a main component has a Tg of, for example, 230°C or higher. Here, the main component means that 50% by mass or more (for example, 70% by mass or more) of the cured product is derived from the first compound. The first compound is a component that greatly contributes to improving the heat resistance and mechanical strength of the stereolithography object.

On the other hand, the first compound alone is solid at room temperature and has high crystallinity, which significantly affects the storage stability of the photocurable resin composition. In order to sufficiently improve the heat resistance and mechanical strength of the photofabricated object while ensuring the stability of the photocurable resin composition during low-temperature storage, it is necessary to use the first compound in combination with at least the second compound.

Triacrylate compound A has three substituents bonded to the three nitrogen atoms of the isocyanuric ring. Each of the three substituents has a (meth)acryloyl group. Triacrylate compound A is, for example, represented by formula (1):

Here, R1, R2, and R3 are each an independent organic group. The organic group is preferably a linear or branched aliphatic group, and at least one of the hydrogen atoms of the aliphatic group may be substituted. Among them, a linear alkylene group is preferable because it has small steric hindrance and is easy to ensure a high Tg. That is, the triacrylate compound A may contain a tris(acryloyloxyalkyl)isocyanurate having three acryloyloxyalkyl groups as three substituents. Here, the number of carbon atoms in the alkylene chain of the three acryloyloxyalkyl groups is preferably 1 to 4, and may be 2 to 3, each independently, because it has smaller steric hindrance and is easy to ensure a high Tg. For example, the acryloyloxyalkyl group may be an acryloyloxyethyl group. Specifically, the triacrylate compound A is represented by the formula (2):

The triacrylate compound A may be tris(2-acryloyloxyethyl)isocyanurate (or tris2-hydroxyethylisocyanuratetriacrylate) represented by the formula: The triacrylate compound A may be used alone or in combination of two or more kinds, and 70% by mass or more, further 90% by mass or more, or 100% of the triacrylate compound A may be tris(acryloyloxyalkyl)isocyanurate or tris(2-acryloyloxyethyl)isocyanurate.

[Second Compound]
The second compound is at least one selected from the group consisting of a diacrylate compound having an isocyanuric ring and two (meth)acryloyl groups (hereinafter also referred to as "diacrylate compound A") and a monoacrylamide compound having one (meth)acryloyl group (hereinafter also simply referred to as "monoacrylamide compound A"). The second compound containing nitrogen has a high affinity with the first compound containing nitrogen and is difficult to solidify, so that by coexisting with the first compound which is easy to solidify, it has the effect of highly suppressing the solidification of the first compound.

(Diacrylate Compound A)
The diacrylate compound A has a structure in which one of the three substituents of the triacrylate compound A is replaced with a substituent or atom (e.g., hydrogen, fluorine, etc.) that does not have a (meth)acryloyl group. A cured product mainly composed of the diacrylate compound A has high heat resistance and mechanical strength. Here, the main component means that 50% by mass or more (e.g., 70% by mass or more) of the cured product is derived from the diacrylate compound A.

Examples of the substituent not having a (meth)acryloyl group include a hydroxyalkyl group and an allyl group (CH ₂ ═CH—CH ₂ —). The number of carbon atoms in the alkylene chain of the hydroxyalkyl group is preferably 1 to 4, and may be 2 to 3, in terms of smaller steric hindrance and easier securing of a higher Tg. For example, the hydroxyalkyl group may be a 2-hydroxyethyl group. The diacrylate compound A may be used alone or in combination of two or more kinds, and 70% by mass or more, further 90% by mass or more, or 100% of the diacrylate compound A may be trishydroxyalkylisocyanurate diacrylate or tris2-hydroxyethylisocyanurate diacrylate.

The second compound may be 50% by mass or more of the diacrylate compound A, or 70% by mass or more or 90% by mass or more of the diacrylate compound A. In this way, when the main component of the second compound is the diacrylate compound A, the total ratio of the first compound and the second compound to the mass of the polymerizable compound may be 30% by mass or more, 35% by mass or more, or 40% by mass or more. In addition, the total ratio of the first compound and the second compound to the mass of the polymerizable compound may be 60% by mass or less, 55% by mass or less, 50% by mass or less, or 45% by mass or less. When limiting the range, these upper and lower limits can be arbitrarily combined. For example, the total ratio of the first compound and the second compound to the mass of the polymerizable compound may be 30% by mass or more, 60% by mass or less, 30% by mass or more, 50% by mass or less, or 35% by mass or more, 55% by mass or less.

(Monoacrylamide compound A)
The monoacrylamide compound A can be in a low-viscosity liquid state at room temperature (25° C.). In addition, a cured product containing the monoacrylamide compound A as a main component can have a Tg of, for example, 130° C. or higher, and therefore a shaped product having high mechanical strength can be easily obtained. Here, the main component means that 50% by mass or more (for example, 70% by mass or more) of the cured product is derived from the monoacrylamide compound A.

The monoacrylamide compound A can be obtained, for example, as an acid amide of a nitrogen-containing compound and (meth)acrylic acid. Examples of the nitrogen-containing compound constituting the acid amide of (meth)acrylic acid include aliphatic amines (triethylamine, ethanolamine, etc.), alicyclic amines (cyclohexylamine, etc.), aromatic amines (aniline, etc.), and nitrogen-containing cyclic compounds. The nitrogen-containing cyclic compound has a heterocycle containing a nitrogen atom, and the heterocycle is preferably a 5-membered to 8-membered ring, and may be a 5-membered or 6-membered ring. The heterocycle may be a heterocycle containing ether oxygen or the like. Specific examples of the nitrogen-containing cyclic compound include pyrrole, pyrrolidine, piperidine, pyrimidine, morpholine, and thiazine. The heterocycle may be aromatic, but is preferably an alicyclic ring.

Among them, heterocyclic (meth)acrylamides having a heterocycle containing a nitrogen atom have a lower viscosity, have less steric hindrance, and are more likely to ensure a high Tg. Acryloylmorpholine may be used as the monoacrylamide compound A. 70% by mass or more, even 90% by mass or more, or 100% of the monoacrylamide compound A may be heterocyclic (meth)acrylamide or acryloylmorpholine.

As the monoacrylamide compound A other than acryloylmorpholine, for example, N-alkyl(meth)acrylamide, N,N-dialkyl(meth)acrylamide, etc. may be used. Here, the hydrogen atom of the alkyl group may be substituted with a hydroxy group, an amino group, etc. The number of carbon atoms of the alkyl group may be, for example, 1 to 6. More specifically, dimethylacrylamide, isopropylacrylamide, diethylacrylamide, hydroxyethylacrylamide, etc. may be used.

The second polymerizable compound may be 50% by mass or more of the monoacrylamide compound A, or may be 70% by mass or more or 90% by mass or more of the monoacrylamide compound A. In this way, when the main component of the second compound is monoacrylamide compound A, the total ratio of the first compound and the second compound to the mass of the polymerizable compound may be 50% by mass or more, 55% by mass or more, or 60% by mass or more. In addition, the total ratio of the first compound and the second compound to the mass of the polymerizable compound may be 80% by mass or less, 75% by mass or less, or 70% by mass or less. When limiting the range, these upper and lower limits can be arbitrarily combined. For example, the total ratio of the first compound and the second compound to the mass of the polymerizable compound may be 50% by mass or more, 80% by mass or less, 55% by mass or more, 75% by mass or less, or 60% by mass or more, 75% by mass or less.

[Third Compound]
The polymerizable compound contained in the photocurable resin composition A may further include a third compound different from the first compound and the second compound. Polymerizable compounds other than the first compound and the second compound are classified as third compounds. The content of the third compound in the photocurable resin composition is determined by the total content of the first compound and the second compound. The third compound will be described below.

(Polymerizable Monomer)
The polymerizable monomer that can be used as the third compound may be monofunctional or polyfunctional. The polymerizable group of the polymerizable monomer may be, for example, a group having a polymerizable carbon-carbon unsaturated bond such as a vinyl group, an allyl group, an acryloyl group, or a methacryloyl group, and the (meth)acryloyl group is preferred. In this case, a high curing speed is obtained, and it is suitable for modeling applications such as photo-modeling.

Examples of monofunctional polymerizable monomers (hereinafter also referred to as the first monomer) include vinyl monomers, allyl monomers, and acrylic monomers. Examples of vinyl monomers include monomers having a vinyl group, such as vinyl ethers of monohydric alcohols, aromatic vinyl monomers (styrene, etc.), alicyclic vinyl monomers, and heterocyclic compounds having a vinyl group (N-vinylpyrrolidone, etc.). Examples of allyl monomers include monomers having an allyl group, such as allyl ethers of monohydric alcohols. Examples of acrylic monomers include monomers having a (meth)acryloyl group, such as (meth)acrylic acid esters of monohydric alcohols, and (meth)acrylic acid. The first monomer may be used alone or in combination of two or more types.

The monohydric alcohol may be any of aliphatic alcohols, alicyclic alcohols, and aromatic alcohols. The aliphatic alcohols may have an aromatic ring, an aliphatic ring, or a heterocyclic ring. The aliphatic ring may be a crosslinked ring. Examples of the aliphatic alcohols include alkyl alcohols (C 1-20 alkyl alcohols such as methanol, ethanol, propanol, isopropanol, 2-hydroxypropyl alcohol, butanol, hexanol, nonyl alcohol, isononyl alcohol, lauryl alcohol, stearyl alcohol, and isostearyl alcohol), benzyl alcohol, phenethyl alcohol, monoesters of phthalic acid and ethylene glycol, phenoxyethyl alcohol, and cyclohexanemethanol. Examples of the alicyclic alcohols include alicyclic C _5-20 alcohols (alicyclic C _5-10 alcohols) such as cyclohexanol, menthol, borneol, isoborneol, and dicyclopentanyl alcohol. Examples of the aromatic alcohols include aromatic C _6-10 alcohols such as _phenol and naphthol. Examples of heterocyclic alcohols include aliphatic alcohols (C _1-4 aliphatic alcohols, etc.) having a heterocyclic group (such as a 4- to 8-membered heterocyclic group) containing nitrogen, oxygen, and/or sulfur as a ring-constituting atom. Examples of heterocyclic alcohols include furfuryl alcohol and tetrahydrofurfuryl alcohol.

It is preferable that the polymerizable monomer has an aliphatic ring. In this case, the curing reaction proceeds efficiently, a high-strength molded object is easily obtained, and distortion during curing is reduced. Specifically, it is preferable to use an ester of an alicyclic alcohol and (meth)acrylic acid as the polymerizable monomer.

When a polyfunctional polymerizable monomer (hereinafter also referred to as the second monomer) is used, a crosslinked structure is formed by curing, which makes it easier to further increase the strength of the cured product. As the second monomer, one having two or more polymerizable groups can be used. The number of polymerizable groups is, for example, 2 to 4, and may be 2 or 3. The second monomer may be used alone or in combination of two or more types. When multiple types of second monomers are used, the types of polymerizable groups in each second monomer may all be the same, some may be the same, or all may be different.

The second monomer may be, for example, a compound in which at least two hydroxyl groups of a polyol are replaced with at least one selected from the group consisting of a vinyl ether group, an allyl ether group, an acryloyloxy group, and a methacryloyloxy group. The polyol may be any of an aliphatic polyol, an alicyclic polyol, and an aromatic polyol. Examples of the alkylene glycol include C _2-10 alkylene glycols such as ethylene glycol, trimethylene glycol, 1,4-butanediol, and hexanediol. Aliphatic polyols also include those having an aromatic ring, an aliphatic ring, or a heterocyclic ring. Examples of such aliphatic polyols include cyclohexanedimethanol, benzenedimethanol, and dioxane glycol. It is preferable that the second monomer (specifically, the polyol that forms the second monomer) has an aliphatic ring or a heterocyclic ring. In this case, the curing reaction is likely to proceed efficiently. In addition, a molded object with high strength is likely to be obtained, and distortion during curing is small. More specifically, it is preferable to use, as the second monomer, a heterocyclic compound having a vinyl group, an ester of an alicyclic alcohol and (meth)acrylic acid, or an ester of a heterocyclic alcohol and (meth)acrylic acid (for example, dioxane glycol diacrylate).

Specific examples of preferable third compounds will be further described below.
(Polycyclic Aliphatic Di(meth)acrylates)
A cured product mainly composed of a polycyclic aliphatic di(meth)acrylate can have a Tg of, for example, 170° C. or higher, so that a shaped product having high mechanical strength is easily obtained, and distortion during curing is small. In addition, a polycyclic aliphatic di(meth)acrylate has a low viscosity and a fast curing speed. A polycyclic aliphatic refers to an aliphatic compound having two or more carbon rings among alicyclic compounds. Examples of a polycyclic aliphatic include bicycloundecane, decahydronaphthalene, and tricyclodecane dimethanol. A polycyclic aliphatic di(meth)acrylate has a structure in which at least two hydroxyl groups of a polycyclic aliphatic polyol are replaced with (meth)acryloyloxy groups, for example. A specific example of a typical polycyclic aliphatic di(meth)acrylate with a high Tg of the cured product is tricyclodecane dimethanol diacrylate. The structure of tricyclodecane dimethanol diacrylate is shown below.

(Poly(meth)acrylate having four or more (meth)acryloyl groups)
A cured product mainly composed of a poly(meth)acrylate having four or more (meth)acryloyl groups can have a Tg of, for example, 230° C. or higher, and therefore can easily produce a shaped product having high mechanical strength. In consideration of the shrinkage rate during curing, the number of (meth)acryloyl groups in the poly(meth)acrylate having four or more (meth)acryloyl groups is preferably 6 or less, and more preferably 5 or less.

A poly(meth)acrylate having four or more (meth)acryloyl groups has a structure in which at least four hydroxyl groups of an aliphatic polyol having four or more hydroxyl groups are replaced with (meth)acryloyloxy groups. Examples of aliphatic polyols having four or more hydroxyl groups include ditrimethylolpropane, pentaerythritol, dipentaerythritol, and sugar alcohols. Specific examples of poly(meth)acrylates having four or more (meth)acryloyl groups include ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate. Among these, ditrimethylolpropane tetraacrylate is preferred because it has a high Tg of the cured product, high low-temperature stability, low viscosity, and a relatively small shrinkage rate during curing. The structure of ditrimethylolpropane tetraacrylate is shown below.

It is desirable that the total proportion of the polycyclic aliphatic di(meth)acrylate and the poly(meth)acrylate having four or more (meth)acryloyl groups in the third compound is 90% by mass or more.

(Third compound having an isocyanuric ring)
The third compound may include, for example, a monoacrylate compound having an isocyanuric ring and one (meth)acryloyl group (hereinafter also referred to as "monoacrylate compound A"). The monoacrylate compound A has a structure in which two of the three substituents of the triacrylate compound A are substituted with a substituent or atom (e.g., hydrogen, fluorine, etc.) that does not have a (meth)acryloyl group. The substituent that does not have a (meth)acryloyl group is the same as in the case of the diacrylate compound A. Specific examples of the monoacrylate compound A include trishydroxyalkylisocyanurate monoacrylate and tris2-hydroxyethylisocyanurate monoacrylate.

The third compound may contain triallyl isocyanurate. Triallyl isocyanurate has an isocyanuric ring and three allyl groups, and is therefore expected to have improved heat resistance and mechanical strength similar to those of the first and second compounds.

Preferred embodiments of the present invention are listed below.
First Embodiment
A polymerizable compound and a photopolymerization initiator are included,
the polymerizable compound includes a first compound and a second compound each containing nitrogen,
the first compound is a triacrylate compound A having an isocyanuric ring and three (meth)acryloyl groups;
the second compound is at least one selected from the group consisting of a diacrylate compound A having an isocyanuric ring and two (meth)acryloyl groups and a monoacrylamide compound A having one (meth)acryloyl group,
a ratio of the first compound to a total mass of the first compound and the second compound is 50 mass% or more and 90 mass% or less,
a total mass ratio of the first compound and the second compound in the polymerizable compound is 20 mass % or more and 80 mass % or less.

Second Embodiment
In the first embodiment, 50% by weight or more, further 70% by weight or more, and further 90% by weight or more of the second compound is the diacrylate compound A;
a total ratio of the first compound and the second compound to the mass of the polymerizable compound is 35 mass% or more and 60 mass% or less, or 35 mass% or more and 55 mass% or less, or 40 mass% or more and 50 mass% or less.

Third Embodiment
In the first embodiment, 50% by mass or more, further 70% by mass or more, and further 90% by mass or more of the second polymerizable compound is the monoacrylamide compound A,
a total ratio of the first compound and the second compound to the mass of the polymerizable compound is 50 mass% or more and 80 mass% or less, or 55 mass% or more and 75 mass% or less, or 60 mass% or more and 70 mass% or less.

Fourth Embodiment
In a first embodiment, the photocurable resin composition further includes a polycyclic aliphatic di(meth)acrylate, and a proportion of the polycyclic aliphatic di(meth)acrylate in the mass of the polymerizable compound is 15 mass% or more and 60 mass% or less.

Fifth Embodiment
In a second embodiment, the photocurable resin composition, wherein the polymerizable compound further contains a polycyclic aliphatic di(meth)acrylate, and a proportion of the polycyclic aliphatic di(meth)acrylate in the mass of the polymerizable compound is 30 mass% or more and 60 mass% or less, or 35 mass% or more and 55 mass% or less.

Sixth Embodiment
In a third embodiment, the photocurable resin composition, wherein the polymerizable compound further contains a polycyclic aliphatic di(meth)acrylate, and a proportion of the polycyclic aliphatic di(meth)acrylate in the mass of the polymerizable compound is 15 mass% or more and 40 mass% or less, or 20 mass% or more and 35 mass% or less.

Seventh Embodiment
In a fourth embodiment, the polymerizable compound further includes a poly(meth)acrylate having four or more (meth)acryloyl groups, and the proportion of the poly(meth)acrylate having four or more (meth)acryloyl groups in the mass of the polymerizable compound is 5 mass% or more and 20 mass% or less.

Eighth embodiment
In a fifth or sixth embodiment, the polymerizable compound further comprises a poly(meth)acrylate having four or more (meth)acryloyl groups, and the proportion of the poly(meth)acrylate having four or more (meth)acryloyl groups in the mass of the polymerizable compound is 5 mass% or more and 15 mass% or less.

[Photopolymerization initiator]
The photopolymerization initiator contained in the photocurable resin composition A is activated by the action of light to initiate polymerization of the polymerizable compound. Examples of the photopolymerization initiator include radical polymerization initiators that generate radicals by the action of light, as well as those that generate acids (or cations) by the action of light (specifically, cation generators). The photopolymerization initiator may be used alone or in combination of two or more. The photopolymerization initiator is selected depending on the type of the polymerizable compound, for example, whether it is radically polymerizable or cationic polymerizable. Examples of the radical polymerization initiator (radical photopolymerization initiator) include alkylphenone-based photopolymerization initiators and acylphosphine oxide-based photopolymerization initiators. Examples of photopolymerization initiators are shown below, but are not limited to these.

Examples of alkylphenone photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, and the like.

Examples of the acylphosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide, and the like.
(others)
The photocurable resin composition A may further contain other known additives, such as a thiol compound, an amine compound, a colorant, a UV absorber, an antioxidant, a polymerization inhibitor, a defoamer, a filler, and a stabilizer.

(Storage Stability)
It is desirable for the photocurable resin composition A to satisfy at least condition 1 of the following <Conditions 1 to 3>, it is more desirable for the photocurable resin composition A to satisfy conditions 1 and 2, and it is most desirable for the photocurable resin composition A to satisfy all of conditions 1 to 3.

<Condition 1>
Photocurable resin composition A is cooled at −30° C. for 72 hours, then heated to 23° C., and then allowed to stand at 23° C. for 48 hours, at which point the entire photocurable resin composition A becomes liquid. After cooling at −30° C. for 72 hours, photocurable resin composition A may be in a solidified state.

<Condition 2>
When the photocurable resin composition A, which is entirely liquid, is allowed to stand at 5° C. for one month, the photocurable resin composition A remains entirely liquid thereafter.

<Condition 3>
When 0.1 mass % of crystals of tris(2-acryloyloxyethyl)isocyanurate (triacrylate compound A) is added to photocurable resin composition A, which is liquid as a whole, and the composition is allowed to stand at 5° C. for 72 hours, the entire photocurable resin composition A (excluding the added crystals) remains liquid even after the addition.

Even if at least a portion of the photocurable resin composition A that satisfies condition 1 solidifies at extremely low temperatures, it will return to a stable liquid state when it is subsequently returned to room temperature (23°C), and therefore can be stored, for example, in a freezer.

Photocurable resin composition A that satisfies condition 2 always maintains a stable liquid state throughout, even when stored for a long period of time at low temperatures (5°C), so that photocurable resin composition A can be used safely in winter or in cold regions.

Photocurable resin composition A that satisfies condition 3 has extremely high stability, even if seed crystals are added, because the seed crystals do not induce solidification and the liquid state can be maintained.

Photocurable resin composition A is suitable for curing by light irradiation to form a three-dimensional photo-modeled object (also called a "photo-modeled object" or "cured object"). The present invention also includes a photo-modeled object made of photocurable resin composition A. A photo-modeled object has, for example, a layered structure in which multiple layered cured patterns formed by photocuring are stacked. Such a photo-modeled object can be manufactured by a 3D printer. In other words, photocurable resin composition A is suitable as a material for three-dimensional photo-modeling for a 3D printer.

[Light modeling]
Stereolithography is used in a variety of applications that require high heat resistance and mechanical strength, such as electronic devices, electrical devices, medical devices, electrical appliances, robot-related products, and vehicle-related products.

A photo-fabricated object can be produced, for example, by a production method including a step (i) of forming a liquid film of a photocurable resin composition and curing the liquid film to form a pattern, a step (ii) of forming another liquid film in contact with the pattern, and a step (iii) of curing the other liquid film on the pattern to laminate another pattern. Usually, steps (ii) and (iii) are then repeated several times.

(Head deflection temperature (HDT))
The deflection temperature under load (HDT) of the cured product of the photocurable resin composition A is measured by the edgewise method at a load of 0.45 MPa in accordance with ASTM D648. The HDT is, for example, 200° C. or higher, and depending on the composition of the photocurable resin composition A, an HDT of 240° C. or higher or 280° C. or higher can be achieved. Such a cured product can be said to have extremely high heat resistance.

The deflection temperature under load (HDT) is measured using a test piece formed from a cured product of photocurable resin composition A or a photo-fabricated product. A test piece having a height of 12.7 mm, a width of 6.4 mm, and a length of 127 mm is used. The deflection temperature under load (HDT) is measured for multiple test pieces (e.g., five) and the values are averaged to obtain an average value. HDT is the temperature at which the deflection amount is 2.6 mm.

(Tensile strength)
The tensile strength of the cured product of the photocurable resin composition A is measured in accordance with ASTM D638. The tensile strength is, for example, 50 MPa or more, and can reach 60 MPa or more or 70 MPa or more depending on the composition of the photocurable resin composition A. Such a cured product can be said to have extremely high mechanical strength.

The tensile strength is measured using a test piece formed from a cured product of photocurable resin composition A or a photo-fabricated product. A test piece with a thickness of 4 mm, a parallel part width of 6 mm, a total length of 115 mm, and a parallel part length of 33 mm (Type IV) is usually used. The measurement is performed under conditions of 23°C, a chuck distance of 65 mm, and a tensile speed of 5 mm/min. A commercially available tensile tester is used for the measurement. The tensile strength is the maximum stress measured before the test piece breaks. The tensile strength is measured for multiple (e.g., five) test pieces, and the average value is calculated by averaging.

Test pieces for HDT and tensile strength are produced, for example, by a method for producing a stereolithography object by repeating steps (i) to (iii) described below. The thickness of the liquid film or two-dimensional pattern per layer is 25 μm to 100 μm.

[Method of manufacturing a photo-modeled object]
The method for producing a stereolithography product includes a step of forming a stereolithography product using a photocurable resin composition A. The step of forming a stereolithography product includes a step (i) of forming a liquid film of the photocurable resin composition A and photocuring the liquid film to form a pattern, a step (ii) of forming another liquid film so as to be in contact with the pattern, and a step (iii) of photocuring the other liquid film on the pattern to laminate another pattern.

The procedure for bat-type stereolithography is illustrated below.
1 shows an example of forming a three-dimensional object using a photo-fabrication apparatus (patterning apparatus) equipped with a resin tank (vat). In the illustrated example, a suspension-type modeling is shown, but there is no particular limitation as long as it is a method capable of three-dimensional photofabrication using a photocurable resin composition. In addition, there is no particular limitation on the type of light irradiation (exposure), and it may be point exposure or surface exposure.

The patterning device 1 includes a platform 2 having a pattern forming surface 2a, a resin tank 3 containing a photocurable resin composition 5, and a projector 4 as a light source for the surface exposure method.

(i) Step of forming a liquid film and curing it to form a pattern In step (i), as shown in (a), first, the pattern-forming surface 2a of the platform 2 is immersed in the photocurable resin composition 5 contained in the resin tank 3 while facing the projector 4 (i.e., the bottom surface of the resin tank 3). At this time, the height of the pattern-forming surface 2a (or the platform 2) is adjusted so that a liquid film 7a (liquid film a) is formed between the pattern-forming surface 2a and the projector 4 (or the bottom surface of the resin tank 3). Next, as shown in (b), the liquid film 7a is photocured by irradiating light L from the projector 4 (surface exposure) to form a pattern 8a (pattern a).

In the patterning apparatus 1, the resin tank 3 serves as a supply unit for the photocurable resin composition 5. It is desirable that at least the portion of the resin tank between the liquid film and the projector 4 (the bottom surface in the illustrated example) is transparent to the exposure wavelength so that the liquid film is irradiated with light from the light source. There are no particular limitations on the shape, material, size, etc. of the platform 2.

After the liquid film a is formed, the liquid film a is photocured by irradiating light from a light source toward the liquid film a. The light irradiation can be performed by a known method. There is no particular limitation on the exposure method, and it may be point exposure or surface exposure. As the light source, a known light source used for photocuring can be used. In the case of the point exposure method, for example, a plotter type, a galvano laser (or galvano scanner) type, an SLA (stereolithography) type, etc. can be mentioned. In the case of the surface exposure method, it is convenient to use a projector as the light source. Examples of projectors include an LCD (transmissive liquid crystal) type, an LCoS (reflective liquid crystal) type, and a DLP (registered trademark, Digital Light Processing) type. The exposure wavelength can be appropriately selected depending on the components of the photocurable resin composition (especially the type of initiator).

(ii) Step of forming a liquid film between the pattern a and the light source In step (ii), a photocurable resin composition is supplied between the pattern a obtained in step (i) and the light source to form a liquid film (liquid film b). That is, the liquid film b is formed on the pattern a formed on the pattern formation surface. For the supply of the photocurable resin composition, the explanation for step (i) can be referred to.

For example, in step (ii), as shown in FIG. 1(c), after forming the two-dimensional pattern 8a (two-dimensional pattern a), the pattern forming surface 2a may be raised together with the platform 2. Then, by supplying a photocurable resin composition 5 between the two-dimensional pattern 8a and the bottom surface of the resin tank 3, a liquid film 7b (liquid film b) can be formed.

(iii) Step of laminating another pattern b on pattern a In step (iii), the liquid film b formed in step (ii) is exposed to light from a light source to photocure the liquid film b, and another pattern (pattern b obtained by photocure of the liquid film b) is laminated on the pattern a. By laminating the patterns in the thickness direction in this manner, a three-dimensional modeling pattern can be formed.

For example, as shown in FIG. 1D, the liquid film 7b (liquid film b) formed between the pattern 8a (pattern a) and the bottom surface of the resin tank 3 is exposed to light from the projector 4 to photo-cure the liquid film 7b. This photo-cure converts the liquid film 7b into the pattern 8b (pattern b). In this way, the pattern 8b can be laminated on the pattern 8a.
For the light source, exposure wavelength, etc., see the description of step (i).

(iv) Step of repeating step (ii) and step (iii) The first step may include step (iv) of repeating step (ii) and step (iii) multiple times. This step (iv) results in multiple patterns b being stacked in the thickness direction, resulting in a more three-dimensional shaping pattern. The number of repetitions may be appropriately determined depending on the shape and size of the desired three-dimensional object (three-dimensional shaping pattern).

For example, as shown in FIG. 1(e), the platform 2 is raised with the pattern 8a (pattern a) and the pattern 8b (pattern b) stacked on the pattern forming surface 2a. At this time, a liquid film 7b (liquid film b) is formed between the pattern 8b and the bottom surface of the resin tank 3. Then, as shown in FIG. 1(f), the projector 4 exposes the liquid film 7b to light, causing the liquid film 7b to photo-cure. As a result, another pattern 8b (pattern b) is formed on the pattern 8b. Then, by alternately repeating (e) and (f), multiple patterns 8b (two-dimensional patterns b) can be stacked.

If uncured photocurable resin composition remains on the three-dimensional pattern obtained in step (iii) or step (iv), a cleaning treatment with a solvent may be performed.

The three-dimensional pattern obtained in step (iii) or step (iv) may be post-cured as necessary. Post-curing can be performed by irradiating the pattern with light. The light irradiation conditions can be appropriately adjusted depending on the type of photocurable resin composition and the degree of curing of the obtained pattern. Post-curing may be performed on a part of the pattern or on the entire pattern.

[Example]
The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

(1) Preparation of Photocurable Resin Composition The components shown in Table 1 were mixed in the mass ratios shown in Tables 2 and 3, and heated in an oven at 80° C. for 3 hours or more while stirring to dissolve the solid components, thereby preparing a homogeneous liquid photocurable resin composition A.

(2) Evaluation The photocurable resin composition obtained in (1) above was subjected to the following evaluations.

(a) Viscosity The viscosity of the photocurable resin composition was measured at 25° C. and a rotation speed of 20 rpm using an E-type viscometer (TVE-20H, Toki Sangyo Co., Ltd.).

(b) HDT
Using a 3D printer (Sonic mini manufactured by Phrozen), the above-mentioned test piece was produced under the conditions of an irradiation time of 5 seconds per layer and a pitch of 50 μm in the z-axis (height direction). Using this test piece, the HDT (° C.) was measured under the above-mentioned conditions in accordance with ASTM D648.

(c) Tensile strength The above-mentioned test specimen was produced using a 3D printer (Sonic mini manufactured by Phrozen) under conditions of an irradiation time of 5 seconds per layer and a pitch of 50 μm in the z-axis (height direction). The tensile strength (MPa) of this test specimen was measured under the above-mentioned conditions in accordance with ASTM D638.

The HDT and tensile strength test pieces were post-cured by irradiating each side with light for 10 minutes (total of 20 minutes) using an EeezCure 180 manufactured by XYZ PRINTING. The test pieces were then annealed in an oven at 230°C for 30 minutes.

(d) Low temperature stability: Check whether the above conditions 1 to 3 are satisfied.
If all conditions 1 to 3 are met, ◎
If condition 1 and condition 2 are met, mark them with a circle.
If only condition 1 is satisfied, it is marked as △.
Cases where all of conditions 1 to 3 were not satisfied were evaluated as ×.

The evaluation results of the examples and comparative examples are shown in Tables 2 and 3. Entry Nos. 1 to 5 are examples, and 6 to 14 are comparative examples. If the test piece cracked during annealing and the measurement was stopped, an * is indicated in Tables 2 and 3. If the measurement was not performed, a - is indicated.

The ingredients in Table 1 are as follows.
"ACMO": acryloylmorpholine (second compound)
"SR833NS": Tricyclodecane dimethanol diacrylate (polycyclic aliphatic diacrylate)
"M370": Tris 2-hydroxyethyl isocyanurate triacrylate (triacrylate compound A (first compound))
"M-313": A mixture of the following triacrylate compound A (first compound) and diacrylate compound A (second compound) Tris 2-hydroxyethyl isocyanurate triacrylate 65% by mass (first compound)
Tris 2-hydroxyethyl isocyanurate diacrylate 35% by mass (second compound)
"M-923": a mixture of the following triacrylate compound A (first compound), diacrylate compound A (second compound), and monoacrylate compound A (third compound) Tris 2-hydroxyethyl isocyanurate triacrylate 40% by mass
Tris 2-hydroxyethyl isocyanurate diacrylate 50% by mass
Tris 2-hydroxyethyl isocyanurate monoacrylate 10% by mass
"AD-TMP": ditrimethylolpropane tetraacrylate (polyacrylate having four acryloyl groups)
"Omnirad TPO-H": diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (photopolymerization initiator)
"Omnirad 819": phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (photopolymerization initiator)

While the present invention has been described with respect to the presently preferred embodiments, such disclosure should not be interpreted as limiting. Various modifications and alterations will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. Accordingly, the appended claims should be construed to embrace all such modifications and alterations without departing from the true spirit and scope of the invention.

The photocurable resin composition of the present invention is suitable as a material for forming three-dimensional objects in photolithography applications.

1: Photopolymerization device, 2: Platform, 2a: Pattern formation surface, 3: Resin tank, 4: Projector, 5: Photocurable resin composition, 6: Release agent layer, 7a: Liquid film a, 7b: Liquid film b, 8a: Two-dimensional pattern a, 8b: Two-dimensional pattern b, L: Light

Claims (12)

The composition includes a polymerizable compound (excluding a silicon-containing α,β-unsaturated double bond group-containing compound) and a photopolymerization initiator,
the polymerizable compound includes a first compound and a second compound each containing nitrogen,
the first compound is a triacrylate compound having an isocyanuric ring and three (meth)acryloyl groups;
the second compound is at least one selected from the group consisting of a diacrylate compound having an isocyanuric ring and two (meth)acryloyl groups and a monoacrylamide compound having one (meth)acryloyl group;
a ratio of the first compound to a total mass of the first compound and the second compound is 50 mass% or more and 90 mass% or less,
a total mass ratio of the first compound and the second compound in the polymerizable compound is 20 mass% or more and 80 mass% or less,
the polymerizable compound further comprises a poly(meth)acrylate having four or more (meth)acryloyl groups;
A photocurable resin composition used for forming a three-dimensional photo-modeled object having a layered structure in which layered cured patterns formed by photocuring are stacked in multiple layers, wherein the proportion of the poly(meth)acrylate having four or more (meth)acryloyl groups in the mass of the polymerizable compound is 5 mass% or more and 25 mass% or less. 50% by mass or more of the second compound is the diacrylate compound,
2 . The photocurable resin composition according to claim 1 , wherein a total ratio of the first compound and the second compound to a mass of the polymerizable compound is 30 mass % or more and 60 mass % or less. 50% by mass or more of the second compound is the monoacrylamide compound,
2 . The photocurable resin composition according to claim 1 , wherein a total ratio of the first compound and the second compound to a mass of the polymerizable compound is 50 mass % or more and 80 mass % or less. The photocurable resin composition according to any one of claims 1 to 3, wherein the triacrylate compound includes tris(acryloyloxyalkyl)isocyanurate. The photocurable resin composition according to any one of claims 1 to 4, wherein the monoacrylamide compound includes a heterocyclic acrylamide having a heterocycle containing a nitrogen atom. The photocurable resin composition according to any one of claims 1 to 5, wherein the polymerizable compound further comprises a polycyclic aliphatic di(meth)acrylate. The photocurable resin composition according to claim 6, wherein the proportion of the polycyclic aliphatic di(meth)acrylate in the mass of the polymerizable compound is 15% by mass or more and 70% by mass or less. The photocurable resin composition according to any one of claims 1 to 7 , wherein the photocurable resin composition is cooled at -30°C for 72 hours, heated to 23°C, and then allowed to stand at 23°C for 48 hours, and the entire composition is liquid. The photocurable resin composition according to any one of claims 1 to 8 , wherein when the photocurable resin composition is entirely liquid and left to stand at 5°C for one month, the photocurable resin composition remains entirely liquid thereafter. The photocurable resin composition according to any one of claims 1 to 9 , wherein a deflection temperature under load of the cured product of the photocurable resin composition is 280°C or higher, as measured by an edgewise method at a load of 0.45 MPa in accordance with ASTM D648. The photocurable resin composition according to any one of claims 1 to 10 , which is for use in a 3D printer. A process for forming a stereolithography object using the photocurable resin composition according to claim 1,
The step of forming a stereolithography object includes:
(i) forming a liquid film of the photocurable resin composition and photocuring the liquid film to form a pattern;
(ii) forming another liquid film in contact with the pattern;
and (iii) photocuring the other liquid film on the pattern to laminate another pattern.

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