WO2025134281A1 - Photocurable composition for support material formed by inkjet 3d printer and use thereof, and support material and optically built-up article production method using said photocurable composition - Google Patents

Abstract

The present invention addresses the problem of providing a photocurable composition capable of enhancing water solubility, support property, and transparency of a support material formed by an inkjet 3D printer. A photocurable composition for a support material formed by an ink jet 3D printer according to the present invention and solving said problem is characterized by containing a polymerizable monomer (A) having an oxyalkylene group and a water-soluble polymerizable monomer (B) other than the polymerizable monomer (A).

Description

Photocurable composition for a support material formed by an inkjet 3D printer, use thereof, and method for producing a support material and a photo-modeled object using the photocurable composition

The present invention relates to a photocurable composition for a support material formed by an inkjet 3D printer, its use, and a method for producing a support material and a photo-modeled object using the photocurable composition.

In recent years, a photo-lithography method using an inkjet 3D printer has been proposed, in which a liquid photo-curable composition ejected from an inkjet nozzle is cured and layered to produce a model. The inkjet 3D printer inks used in this photo-lithography method include a photo-curable composition for forming a molded body (model material) and a photo-curable composition for forming a support material used to prevent the model material from collapsing when stacking the model material in three dimensions. By layering a photo-cured model material on top of the photo-cured support material and then removing the support material, it becomes possible to form an overhang structure, hollow structure, etc.

Patent Document 1 describes a photocurable composition for a support material that contains a water-soluble ethylenically unsaturated monomer that contains an ionic group and a counter ion, and a photopolymerization initiator, and discloses that the support material formed from the composition has excellent water solubility and sufficient hardness (i.e., sufficient supportability).

Patent Document 2 describes a photocurable composition for a support material that contains a water-soluble ethylenically unsaturated monomer that contains an ionic group and a counter ion, and has a water content of 10 mass% or less relative to 100 mass% of the photocurable composition. It discloses that the composition has excellent curing properties, and that a support material formed from the composition has sufficient hardness and excellent solubility in a solvent.

International Publication No. 2018/043582 International Publication No. 2019/167948

Photocurable compositions for support materials formed by inkjet 3D printers are required to have better water solubility and supportability after curing, as well as improved transparency of the cured product after curing.
Therefore, an object of the present invention is to provide a photocurable composition that can enhance the solubility in water, supportability, and transparency of a cured product (support material) formed by an inkjet 3D printer.

As a result of extensive research to solve the above problems, the inventors discovered that by using a photocurable composition containing a polymerizable monomer (A) having an oxyalkylene group and a water-soluble polymerizable monomer (B) other than the polymerizable monomer (A), it is possible to improve the solubility in water, supportability, and transparency of a cured product (support material) formed by an inkjet 3D printer, and thus completed the present invention.

That is, the present invention is as follows.
[1] A photocurable composition for a support material formed by an inkjet 3D printer, comprising a polymerizable monomer (A) having an oxyalkylene group and a water-soluble polymerizable monomer (B) other than the polymerizable monomer (A).
[2] The photocurable composition according to [1], wherein the polymerizable monomer (B) is an ionic monomer having an ionic group.
[3] The photocurable composition according to [2], wherein the ionic monomer includes an ionic monomer having a polyvalent metal ion that forms a pair with the ionic group.
[4] The photocurable composition according to [3], wherein the content of the ionic monomer having a polyvalent metal ion is 50 mass% or more in 100 mass% of the polymerizable monomer (B).
[5] The photocurable composition according to any one of [1] to [4], wherein a total content of the polymerizable monomer (A) and the polymerizable monomer (B) is less than 50 mass% in 100 mass% of the photocurable composition.
[6] The photocurable composition according to any one of [1] to [5], wherein the polymerizable monomer (A) is a monomer represented by the following formula (1):
Z-(R ^a -O) _n -R ^b ...(1)
[In formula (1), Z represents an ethylenically unsaturated bond-containing group, R ^a represents an alkylene group, R ^b represents a hydrogen atom or a hydrocarbon group which may have a substituent, and n represents an integer of 1 or more. When n is an integer of 2 or more, the multiple R ^a 's may be the same or different.]
[7] In the formula (1),
Z is a group represented by CH ₂ ═C(R ¹ )-C(═O)-O-* or CH ₂ ═C(R ¹ )-(CH ₂ ) _m -O-* (R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent, m represents an integer of 0 to 6, and * represents a bond),
R ^a represents an alkylene group having 1 to 4 carbon atoms;
R ^b represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms;
The photocurable composition according to [6], wherein n is an integer from 1 to 100.
[8] The photocurable composition according to any one of [1] to [7], further comprising a photopolymerization initiator.
[9] The photocurable composition according to any one of [1] to [8], in which when a piece of a cured product (2 cm × 2 cm × 3 mm) obtained by irradiating the piece with light at 100 mW/ ^cm2 for 3 minutes is added to 50 mL of water at 25°C and allowed to stand for 3 hours, 50 mass% or more of the cured product piece dissolves.
[10] A method for producing a support material, comprising irradiating the photocurable composition according to any one of [1] to [9] with light.
[11] A process for forming a photo-modeled object precursor, comprising: a process A for forming a supporting material layer by irradiating the photocurable composition according to any one of [1] to [9] with light; and a process B for forming a model material layer carried out at the same timing and/or at a different timing from the process A, each of which is repeated multiple times;
and removing the supporting material composed of the supporting material layer from the optically shaped object precursor.
[12] Use of the photocurable composition according to any one of [1] to [9] for forming a support material by an inkjet 3D printer.
[13] A photocurable composition (I) according to any one of [1] to [9],
a photocurable composition (II) different from the photocurable composition (I),
A method of using the photocurable composition (I) by ejecting it from different ejection heads in an inkjet 3D printer.

The present invention provides a photocurable composition that can improve the water solubility, supportability, and transparency of the cured product (support material) formed by an inkjet 3D printer.

One embodiment of the present invention will be described below, but the present invention is not limited thereto. In this specification, unless otherwise specified, "A to B" indicating a numerical range means "A or more, B or less." In addition, "(meth)acrylic acid" means acrylic acid or methacrylic acid, and "(meth)acrylate" means acrylate or methacrylate. The same applies to terms such as "(meth)acryloxy" and "(meth)acryloyl."

1. Photocurable composition for a support material formed by an inkjet 3D printer The photocurable composition for a support material formed by an inkjet 3D printer of the present invention (hereinafter, may be simply referred to as "photocurable composition") contains a polymerizable monomer (A) having an oxyalkylene group and a water-soluble polymerizable monomer (B) other than the polymerizable monomer (A). By containing the polymerizable monomers (A) and (B) in the photocurable composition of the present invention, a support material with improved solubility in water, supportability, and transparency can be obtained.

The photocurable composition described below is used for forming a support material by an inkjet 3D printer. In other words, it is a composition for use in an inkjet 3D printer, and the photocurable composition may be used as is as ink for an inkjet 3D printer, or may be a composition containing each component at a high concentration so that the photocurable composition can be used as ink for an inkjet 3D printer by mixing the photocurable composition with a solvent when used. The content of each component in the photocurable composition described below indicates the content in the photocurable composition when used as ink for an inkjet 3D printer, unless otherwise specified.

1-1. Polymerizable monomer having an oxyalkylene group (A)
The photocurable composition of the present invention contains a polymerizable monomer (A) having an oxyalkylene group. When the photocurable composition contains a polymerizable monomer (A) having an oxyalkylene group, the solubility in water, supportability, and transparency of the obtained cured material (support material) are improved, and the transparency tends to be particularly improved. In this specification, the term "polymerizable monomer" refers to a compound having one or more ethylenically unsaturated groups and polymerizing by light or the like.

The number of oxyalkylene groups in one molecule of polymerizable monomer (A) is 1 or more, and is preferably 1 to 100, more preferably 2 to 80, even more preferably 4 to 60, and even more preferably 5 to 30.

The polymerizable monomer (A) is preferably a monomer represented by the following formula (1x), and more preferably a monomer represented by the following formula (1).
Z-((R ^a -O) _n -R ^b ) _x ...(1x)
Z-(R ^a -O) _n -R ^b ...(1)
[In the formula, Z represents an ethylenically unsaturated bond-containing group, R ^a represents an alkylene group, R ^b represents a hydrogen atom or a hydrocarbon group which may have a substituent, n represents an integer of 1 or more, and x represents an integer of 1 to 4. When n or x is an integer of 2 or more, a plurality of R ^a's and R ^b 's may be the same or different.]

The ethylenically unsaturated bond-containing group represented by Z is a monovalent to tetravalent group having one or more ethylenically unsaturated bonds. The valence corresponds to the number of bonds that the ethylenically unsaturated bond-containing group has for bonding to R ^a , and when x is 1 in formula (1x), Z is a monovalent group, and when x is 2 in formula (1x), Z is a divalent group. In formula (1), Z is a monovalent group.
The number of ethylenically unsaturated bonds contained in the ethylenically unsaturated bond-containing group is preferably 1 to 3, and more preferably 1.

The ethylenically unsaturated bond-containing group is preferably one having one ethylenically unsaturated group, for example, an alkene mono-, di-, tri-, or tetrayl group having about 2 to 10 carbon atoms, or a group in which the alkene mono-, di-, tri-, or tetrayl group is bonded to one or more divalent groups (such as a carbonyl group, -O-). The ethylenically unsaturated bond-containing group having one ethylenically unsaturated group more preferably has an ethylenically unsaturated bond at a terminal, even more preferably has a group represented by CH ₂ ═C(R ¹ )-*, even more preferably a group represented by CH ₂ ═C(R ¹ )-C(═O)-O-* or CH ₂ ═C(R ¹ )-(CH ₂ ) _m -O-*, and particularly preferably a group represented by CH ₂ ═C(R ¹ )-C(═O)-O-*.
In addition, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent, m represents an integer of 0 to 6, and * represents a bond.

Specific examples of the alkyl group having 1 to 4 carbon atoms represented by R ¹ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group.

The alkyl group having 1 to 4 carbon atoms represented by ^R1 may have a substituent, and examples of the substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom, hydroxyl group, thiol group, group represented by *-C(=O)-R, group represented by *-O-R, group represented by *-S-R, etc. In addition, * represents a bond and R represents a hydrocarbon group.
Examples of the hydrocarbon group represented by R include the groups exemplified as the hydrocarbon group represented by R ^b described below. Among them, an alkyl group or an aromatic hydrocarbon group is preferable, and an alkyl group having 1 to 4 carbon atoms or an aromatic hydrocarbon group having 6 to 10 carbon atoms is more preferable.

R ¹ is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group, or an ethyl group, and particularly preferably a hydrogen atom or a methyl group.

The m is preferably an integer from 1 to 6, more preferably an integer from 1 to 4, and even more preferably 1 or 2.

Among these, the ethylenically unsaturated bond-containing group represented by Z is preferably a group represented by _CH2 =C(H)-C(=O)-O-*, a group represented by _CH2 =C( _CH3 )-C(=O)-O-*, a group represented by _CH2 =C(H)-( _CH2 ) _m1 -O-*, or a group represented by _CH2 =C( _CH3 )-( _CH2 ) _m1 -O-* (m1 represents an integer of 1 to 4).

From the viewpoint of further enhancing the transparency of the obtained cured product, it is preferable to contain a compound in which Z in the above formula (1) is a group represented by CH ₂ ═C(R ¹ )-C(═O)-O-*. The content of the compound in the above formula (1) in which Z is a group represented by CH ₂ ═C(R ¹ )-C(═O)-O-* is preferably 30% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and may even be 100% by mass, in 100% by mass of polymerizable monomer (A).

The alkylene group represented by R ^a may be linear or branched, but is preferably linear.
The alkylene group represented by R ^a preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and further preferably 2 or 3 carbon atoms.
Specific examples of the alkylene group represented by R ^a include linear alkylene groups such as a methylene group, an ethylene group, a 1,3-propylene group, a 1,4-butylene group, a 1,5-pentylene group, and a 1,6-hexylene group; and branched alkylene groups such as a 1,2-propylene group, a 1,2-butylene group, a 1,3-butylene group, a 2,3-butylene group, and a 1,2-hexylene group.
The alkylene group represented by R ^a is preferably an alkylene group having 1 to 4 carbon atoms, more preferably a linear alkylene group having 1 to 4 carbon atoms, and even more preferably a linear alkylene group having 2 or 3 carbon atoms.

In addition, in formula (1x) or formula (1), when n is an integer of 2 or more and the compound contains two or more alkylene groups represented by R ^a , that is, when the compound represented by formula (1x) or formula (1) contains two or more alkyleneoxy groups, those alkyleneoxy groups may be added by random addition, block addition, alternating addition, or the like.

The hydrocarbon group represented by R ^b may be an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof.

Examples of the aliphatic hydrocarbon group include
Alkyl groups (preferably alkyl groups having 1 to 4 carbon atoms), such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, or a tert-butyl group;
alkenyl groups (preferably alkenyl groups having 2 to 6 carbon atoms) such as a vinyl group, an n-propenyl group, an isopropenyl group, a 1-butenyl group, a 2-butenyl group, a 1-pentenyl group, a 2-pentenyl group, a 2-methyl-1-butenyl group, a 2-methyl-2-butenyl group, or a 3-methyl-1-butenyl group;
cycloalkyl groups (preferably cycloalkyl groups having 3 to 8 carbon atoms) such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, 3-methylcyclohexyl group, 4-methylcyclohexyl group, and 4-ethylcyclohexyl group; and the like.
Among these, an alkyl group is preferable, an alkyl group having 1 to 4 carbon atoms is more preferable, a methyl group or an ethyl group is even more preferable, and a methyl group is particularly preferable.

The aromatic hydrocarbon group may, for example, be a phenyl group, a methylphenyl group, a dimethylphenyl group, a trimethylphenyl group, a 4-tert-butylphenyl group, a naphthyl group, etc., and is preferably an aromatic hydrocarbon group having 6 to 10 carbon atoms.

Examples of groups that combine the aliphatic hydrocarbon group and the aromatic hydrocarbon group include aralkyl groups such as benzyl and phenethyl groups, and preferably aralkyl groups having 7 to 12 carbon atoms.

The hydrocarbon group represented by R ^b may have a substituent. Examples of the substituent include the groups exemplified as the substituent that the alkyl group having 1 to 4 carbon atoms represented by R ¹ may have, and the preferred embodiments thereof are also the same.

R ^b is preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, further preferably a hydrogen atom, a methyl group, or an ethyl group, and particularly preferably a hydrogen atom or a methyl group.

n is preferably an integer of 1 to 100, more preferably an integer of 2 to 80, even more preferably an integer of 4 to 60, and still more preferably an integer of 5 to 30.
When the polymerizable monomer (A) is a mixture of monomers having different values of n in the above formula (1), the above n can be the average value thereof.

The compound represented by the formula (1) is
It is preferable that Z is a group represented by CH ₂ ═C(R ¹ )-C(═O)-O-* or CH ₂ ═C(R ¹ )-(CH ₂ ) _m -O-* (R ¹ , m, and * are the same as above), R ^a is an alkylene group having 1 to 4 carbon atoms, R ^b is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 100;
It is more preferable that Z is a group represented by _CH2 =C( ^R2 )-C(=O)-O-* or _CH2 =C( ^R2 )-( _CH2 ) _m2 -O-* ( ^R2 is a hydrogen atom or a methyl group, m2 is an integer of 1 to 4, and * is a bond), R ^a is an alkylene group having 2 or 3 carbon atoms, R ^b is a hydrogen atom or a methyl group, and n is an integer of 5 to 30.

Specific examples of the polymerizable monomer (A) include:
(meth)acrylate compounds having an oxyethylene group, such as ethylene glycol (meth)acrylate, ethylene glycol methyl ether (meth)acrylate, polyethylene glycol (meth)acrylate having a repeat number of ethylene glycol (i.e., a repeat number of oxyethylene groups) of 2 to 100, and polyethylene glycol methyl ether (meth)acrylate having a repeat number of ethylene glycol (i.e., a repeat number of oxyethylene groups) of 2 to 100;
(meth)acrylate compounds having an oxypropylene group, such as propylene glycol (meth)acrylate, propylene glycol monomethyl ether (meth)acrylate, polypropylene glycol (meth)acrylate having a propylene glycol repeat number (i.e., the oxypropylene group repeat number) of 2 to 100, and polypropylene glycol monomethyl ether (meth)acrylate having a propylene glycol repeat number (i.e., the oxypropylene group repeat number) of 2 to 100;
Ethylene oxide adducts of unsaturated alcohols such as vinyl alcohol ethylene oxide (hereinafter EO) adducts (EO added mole number 1 to 100 moles), (meth)allyl alcohol EO adducts (EO added mole number 1 to 100 moles), 3-buten-1-ol EO adducts (EO added mole number 1 to 100 moles), isoprene alcohol EO adducts (EO added mole number 1 to 100 moles), 3-methyl-2-buten-1-ol EO adducts (EO added mole number 1 to 100 moles), 2-methyl-3-buten-2-ol EO adducts (EO added mole number 1 to 100 moles), 2-methyl-2-buten-1-ol EO adducts (EO added mole number 1 to 100 moles), and 2-methyl-3-buten-1-ol EO adducts (EO added mole number 1 to 100 moles);
Examples of propylene oxide adducts of unsaturated alcohols include vinyl alcohol propylene oxide (hereinafter referred to as PO) adducts (number of moles of PO added: 1 to 100 moles), (meth)allyl alcohol PO adducts (number of moles of PO added: 1 to 100 moles), 3-buten-1-ol PO adducts (number of moles of PO added: 1 to 100 moles), isoprene alcohol PO adducts (number of moles of PO added: 1 to 100 moles), 3-methyl-2-buten-1-ol PO adducts (number of moles of PO added: 1 to 100 moles), 2-methyl-3-buten-2-ol PO adducts (number of moles of PO added: 1 to 100 moles), 2-methyl-2-buten-1-ol PO adducts (number of moles of PO added: 1 to 100 moles), and 2-methyl-3-buten-1-ol PO adducts (number of moles of PO added: 1 to 100 moles).

As the polymerizable monomer (A), commercially available products can also be used. Examples of commercially available products include NK Ester M-20G, M-40G, M-90G, M-130G, M-230G, M-450G, AM-90G, AM-130G, and AM-230G manufactured by Shin-Nakamura Chemical Co., Ltd.; and Blenmar (registered trademark) PME-100, PME-200, PME-400, PME-1000, PME-4000, and AME-400 manufactured by NOF Corporation.

The photocurable composition of the present invention may contain one type of polymerizable monomer (A) alone, or two or more types of polymerizable monomers.

One preferred embodiment is to use two or more types of polymerizable monomer (A).

When two or more kinds of polymerizable monomers (A) are used in combination, it is preferable to use polymerizable monomers (A) having different numbers of oxyalkylene groups in combination.
The above-mentioned combined use may be, for example, a mixture of two or more polymerizable monomers (A) having adjacent numbers of oxyalkylene groups, such as a mixture of a polymerizable monomer (A) having 3 oxyalkylene groups, a polymerizable monomer (A) having 4 oxyalkylene groups, and a polymerizable monomer (A) having 5 oxyalkylene groups (for example, a mixture of compounds in which n is 3, 4, and 5 in formula (1x) or formula (1)), or may be a combined use of two or more polymerizable monomers (A) having different average numbers of oxyalkylene groups, as described below.

In the photocurable composition of the present disclosure, the polymerizable monomer (A) preferably has a molecular weight distribution with a certain width, the molecular weight distribution is preferably unimodal or multimodal, and the molecular weight distribution of the polymerizable monomer (A) is more preferably unimodal or bimodal. The molecular weight distribution of the polymerizable monomer (A) can be measured by gel permeation chromatography (GPC), specifically, it can be measured under the same conditions as the measurement method of the weight average molecular weight of the polymerizable monomer (A) described later.
In either case, the photocurable composition of the present invention tends to have excellent photocurability.

In a form in which two or more polymerizable monomers (A) having different average numbers of oxyalkylene groups are used in combination as the polymerizable monomer (A), it is preferable to use two polymerizable monomers (A) having different average numbers of oxyalkylene groups in combination. In other words, among forms in which the molecular weight distribution of the polymerizable monomer (A) is multimodal, it is preferable that the molecular weight distribution of the polymerizable monomer (A) is bimodal.

When two or more polymerizable monomers (A) having different average numbers of oxyalkylene groups are used in combination, it is preferable that the difference between the average number of oxyalkylene groups of the polymerizable monomer (A) having the largest average number of oxyalkylene groups and the average number of oxyalkylene groups of the polymerizable monomer (A) having the smallest average number of oxyalkylene groups is 5 or more, and more preferably 5 to 20. For example, a combination of a polymerizable monomer (A) having an average number of oxyalkylene groups of 1 to 5 and a polymerizable monomer (A) having an average number of oxyalkylene groups of 10 or more, a combination of a polymerizable monomer (A) having an average number of oxyalkylene groups of 6 to 15 and a polymerizable monomer (A) having an average number of oxyalkylene groups of 20 or more are preferred, a combination of a polymerizable monomer (A) having an average number of oxyalkylene groups of 1 to 5 and a polymerizable monomer (A) having an average number of oxyalkylene groups of 10 to 20, and a combination of a polymerizable monomer (A) having an average number of oxyalkylene groups of 10 to 15 and a polymerizable monomer (A) having an average number of oxyalkylene groups of 20 to 30 are more preferred.

When a polymerizable monomer (A) having an average number of oxyalkylene groups of 1 to 5 (hereinafter, A1) and a polymerizable monomer (A) having an average number of oxyalkylene groups of 10 or more (hereinafter, A2) are used in combination, the usage ratio (A1:A2) is preferably 10:90 to 90:10, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40, on a mass basis.
In addition, when a polymerizable monomer (A) having an average number of oxyalkylene groups of 6 to 15 (hereinafter, A3) is used in combination with a polymerizable monomer (A) having an average number of oxyalkylene groups of 20 or more (hereinafter, A4), the usage ratio (A3:A4) is preferably 10:90 to 90:10, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40, on a mass basis.

When two or more types of polymerizable monomers (A) are used in combination, it is preferred that all of the ethylenically unsaturated bond-containing groups in those polymerizable monomers (A) are groups represented by _CH2 =C( ^R1 )-C(=O)-O-* or all are groups represented by _CH2 =C( ^R1 )-( _CH2 ) _m -O-*, it is more preferred that all are groups represented by _CH2 =C( ^R1 )-C(=O)-O-*, and it is even more preferred that all are groups represented by _CH2 =C(H)-C(=O)-O-* or all are groups represented by _CH2 =C( _CH3 )-C(=O)-O-*.

The weight average molecular weight of the polymerizable monomer (A) is not particularly limited, but is preferably 160 to 4500.

The weight average molecular weight of the polymerizable monomer (A) can be measured by gel permeation chromatography (GPC), specifically, under the following conditions.
Apparatus: Tosoh Corporation high-speed GPC apparatus (HLC-8320GPC)
Detector: RI
Column: Showa Denko SHODEX (registered trademark), Asahipak (registered trademark), GF-310-HQ, GF-710-HQ, GF-1G 7B
Column temperature: 40°C
Flow rate: 0.5ml/min
Calibration curve: Polyacrylic Acid Standard manufactured by Sowa Science Co., Ltd.
Eluent: 0.1N sodium acetate aqueous solution/acetonitrile = 3/1 (weight ratio)

The content of the polymerizable monomer (A) is preferably 3 to 60% by mass, more preferably 5 to 45% by mass, and even more preferably 8 to 30% by mass, based on 100% by mass of the photocurable composition.

The content of the polymerizable monomer (A) relative to 100% by mass of the total amount of polymerizable monomers contained in the photocurable composition of the present invention (i.e., the total amount of polymerizable monomers (A) to (C)) is preferably 15 to 85% by mass, more preferably 25 to 75% by mass, and even more preferably 35 to 70% by mass. By adjusting the content of the polymerizable monomer (A) to the above-mentioned specified value or more, the transparency and water solubility of the obtained cured product tend to be further improved, and by adjusting the content of the polymerizable monomer (A) to the above-mentioned specified value or less, the supportability of the obtained cured product tends to be further improved.

1-2. Water-soluble polymerizable monomer (B)
The photocurable composition of the present invention contains a water-soluble polymerizable monomer (B) other than the polymerizable monomer (A). By containing the polymerizable monomer (B), the curability of the photocurable composition is improved, and the supportability and solubility in water of the obtained cured product are improved. The photocurable composition of the present invention may contain one type of polymerizable monomer (B) alone or two or more types of polymerizable monomers (B) may be contained.
In this specification, the term "water-soluble polymerizable monomer" refers to a polymerizable monomer having a water solubility at 20°C (hereinafter, water solubility (20°C)) of 20 g/L or more. In this specification, in a thermo-hygroscopic chamber at 20°C, Xg of polymerizable monomer (temperature: 20°C) is added to 50 cc of ion-exchanged water (temperature: 20°C) in a 100 cc screw tube, and the solution is stirred for 5 minutes using a magnetic stirrer (rotor: length 10 mm x φ4 mm is used) and then allowed to stand for 10 minutes. When the solution obtained is visually confirmed as being uniformly transparent, the water solubility (20°C) of the polymerizable monomer is judged to be Yg/L or more (Y = 20X), and when the solution obtained is not uniformly transparent, the water solubility (20°C) of the polymerizable monomer is judged to be less than Yg/L (Y = 20X). That is, the polymerizable monomer (B) is a polymerizable monomer that, when 1 g of the polymerizable monomer is used in the measurement of the water solubility (20° C.), the resulting solution is uniform and transparent. Note that the term "uniform and transparent" means that no phase separation is observed by visual inspection and no cloudiness is observed.

The water solubility (20°C) of the polymerizable monomer (B) is preferably 100 g/L or more, more preferably 200 g/L or more, and even more preferably 500 g/L or more.

The content of the polymerizable monomer (B) is preferably 5 to 60 mass% in 100 mass% of the photocurable composition, more preferably 8 to 40 mass%, and even more preferably 10 to 25 mass%.

The content of the polymerizable monomer (B) relative to 100% by mass of the total amount of polymerizable monomers contained in the photocurable composition of the present invention (i.e., the total amount of polymerizable monomers (A) to (C)) is preferably 15 to 85% by mass, more preferably 25 to 75% by mass, and even more preferably 30 to 65% by mass. By adjusting the content of the polymerizable monomer (B) to be equal to or greater than the above-mentioned specified value, the supportability of the obtained cured product can be further improved, and by adjusting the content of the polymerizable monomer (B) to be equal to or less than the above-mentioned specified value, the solubility in water of the obtained cured product can be further improved.

The mass ratio (B/A) of the polymerizable monomer (B) to the polymerizable monomer (A) is preferably 0.1 to 5.0, more preferably 0.3 to 3.0, and even more preferably 0.5 to 2.0. By adjusting the mass ratio (B/A) to the above range, the resulting cured product tends to have better transparency and water solubility.

The polymerizable monomer (B) preferably contains an ionic monomer having an ionic group (hereinafter, sometimes simply referred to as an ionic monomer).

The ionic group may be an anionic group, and specifically may be a group obtained by removing a proton from an acidic group, such as a group obtained by removing a proton from a carboxy group, a group obtained by removing a proton from a phosphate group, or a group obtained by removing a proton from a sulfo group. Of these, the ionic group is preferably a group obtained by removing a proton from a carboxy group.

It is preferable that the ionic monomer further has an ion (hereinafter, sometimes referred to as a counter ion) that pairs with the ionic group. It is preferable that the charges of the ionic group and the counter ion are balanced as a whole, that is, the ionic monomer is neutral as a whole.

The counter ion is preferably a cation, specifically,
a monovalent counter ion such as an alkali metal ion, such as a sodium ion or a potassium ion, or an ammonium ion;
Polyvalent counter ions typified by polyvalent metal ions such as zinc ion, magnesium ion, calcium ion, aluminum ion, and neodymium ion; and the like.

In particular, from the viewpoint of further enhancing the supportability of the resulting cured product, the counter ion is preferably a polyvalent metal ion, i.e., the ionic monomer preferably contains an ionic monomer having a polyvalent metal ion that pairs with the ionic group (hereinafter, may be referred to as a polyvalent metal ion-containing ionic monomer). The counter ion constituting the polyvalent metal ion-containing ionic monomer is not particularly limited as long as it is a polyvalent metal ion, but among them, it is preferably a divalent metal ion such as a zinc ion, magnesium ion, calcium ion, or neodymium ion, more preferably a zinc ion, magnesium ion, or calcium ion, and particularly preferably a zinc ion.

It is also preferable to use, as the ionic monomer, a polyvalent metal ion-containing ionic monomer in combination with an ionic monomer having a monovalent cation as the counter ion (hereinafter, sometimes referred to as a monovalent cation-containing ionic monomer). The counter ion constituting the monovalent cation-containing ionic monomer is preferably an alkali metal ion or ammonium, more preferably a sodium ion, potassium ion or ammonium, and even more preferably a potassium ion.

The content of the ionic monomer (particularly the total content of the monovalent cation-containing ionic monomer and the polyvalent metal ion-containing ionic monomer) is preferably 30 to 100 mass% in 100 mass% of the polymerizable monomer (B), more preferably 50 to 100 mass%, even more preferably 80 to 100 mass%, and particularly preferably 95 to 100 mass%.

The content of the ionic monomer is preferably 5 to 60% by mass, more preferably 8 to 40% by mass, and even more preferably 10 to 25% by mass, based on 100% by mass of the photocurable composition.

The content of the ionic monomer relative to 100% by mass of the total amount of polymerizable monomers contained in the photocurable composition of the present invention (i.e., the total amount of polymerizable monomers (A) to (C)) is preferably 15 to 85% by mass, more preferably 25 to 75% by mass, and even more preferably 30 to 65% by mass. By adjusting the content of the ionic monomer to be equal to or greater than the above-mentioned specified value, the supportability of the obtained cured product can be further improved, and by adjusting the content of the polymerizable monomer (B) to be equal to or less than the above-mentioned specified value, the solubility in water of the obtained cured product can be further improved.

The content of the polyvalent metal ion-containing ionic monomer is, for example, 20 to 100% by mass, preferably 35% by mass or more, more preferably 50% by mass or more, even more preferably 65% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on 100% by mass of the polymerizable monomer (B). By adjusting the content of the polyvalent metal ion-containing ionic monomer to the above range, the supportability of the obtained cured product can be further improved. In particular, by adjusting the content of the polyvalent metal ion-containing ionic monomer to 50% by mass or more, the effect of improving the supportability tends to be further enhanced. In addition, by adjusting the content of the polyvalent metal ion-containing ionic monomer to 50% by mass or more (preferably 65% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more), the viscosity of the photocurable composition can be reduced. By reducing the viscosity of the photocurable composition, ejection defects in an inkjet 3D printer, such as clogging of the ejection head, are less likely to occur, that is, ejection stability is improved.

The content of the monovalent cation-containing ionic monomer may be, for example, 10% by mass or more, or 20% by mass or more, in 100% by mass of the polymerizable monomer (B). The content of the monovalent cation-containing ionic monomer may be 100% by mass in 100% by mass of the polymerizable monomer (B), but from the viewpoint of lowering the viscosity of the photocurable composition and further increasing the supportability of the obtained cured product, it is preferably 80% by mass or less, more preferably 50% by mass or less, even more preferably 35% by mass or less, even more preferably 20% by mass or less, particularly preferably 10% by mass or less, and may be 0% by mass.

The mass ratio of the polyvalent metal ion-containing ionic monomer to the monovalent cation-containing ionic monomer contained in the photocurable composition (polyvalent metal ion-containing ionic monomer/monovalent cation-containing ionic monomer) is, for example, 20/80 to 100/0, preferably 35/65 to 100/0, more preferably 50/50 to 100/0, even more preferably 60/40 to 100/0, and particularly preferably 80/20 to 100/0. In particular, from the viewpoint of reducing the viscosity of the photocurable composition, it is preferable to adjust the above mass ratio to 50/50 to 100/0, more preferably 60/40 to 100/0, and even more preferably 80/20 to 100/0.

The ionic monomer containing a group obtained by removing a proton from a carboxy group as the ionic group is preferably a salt of an ethylenically unsaturated carboxylic acid.
Examples of the salt of the ethylenically unsaturated carboxylic acid include monovalent salts such as alkali metal salts, such as sodium salts and potassium salts, and ammonium salts of the unsaturated carboxylic acid; and polyvalent salts represented by polyvalent metal salts, such as zinc salts, magnesium salts, calcium salts, aluminum salts, and neodymium salts.
The ethylenically unsaturated carboxylic acid constituting the salt of the ethylenically unsaturated carboxylic acid is a carboxylic acid compound having an ethylenically unsaturated group, and specific examples thereof include aliphatic unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, fumaric acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxyethylsuccinic acid, N-(meth)acryloylaspartic acid, and ω-(meth)acroylalkane-1,1-dicarboxylic acid; and aromatic unsaturated carboxylic acids such as 2-(meth)acryloyloxybenzoic acid, 3-(meth)acryloyloxybenzoic acid, 4-(meth)acryloyloxybenzoic acid, 2-(meth)acryloyloxyethylphthalic acid, 2-vinylbenzoic acid, 3-vinylbenzoic acid, and 4-vinylbenzoic acid; and among these, aliphatic unsaturated carboxylic acids are preferable.
The number of carbon atoms in the ethylenically unsaturated carboxylic acid constituting the salt of the ethylenically unsaturated carboxylic acid is preferably 3 to 15, more preferably 3 to 12, further preferably 3 to 9, and particularly preferably 3 to 6. By using a salt of an ethylenically unsaturated carboxylic acid having a small number of carbon atoms, the hydrophobic portion in the molecule can be made smaller, and the solubility of the obtained cured product in water can be further increased.

The ionic monomer containing, as the ionic group, a group obtained by removing a proton from a phosphate group, is preferably a salt of an ethylenically unsaturated phosphate.
Examples of the salt of the ethylenically unsaturated phosphate include monovalent salts such as alkali metal salts, such as sodium salts and potassium salts, and ammonium salts of ethylenically unsaturated phosphate; and polyvalent salts represented by polyvalent metal salts, such as zinc salts, magnesium salts, calcium salts, aluminum salts, and neodymium salts.
The ethylenically unsaturated phosphoric acid constituting the salt of the ethylenically unsaturated phosphoric acid is a phosphoric acid compound having an ethylenically unsaturated group, and specific examples thereof include mono(2-(meth)acryloyloxyethyl) acid phosphate, phenyl(2-(meth)acryloyloxyethyl) phosphate, acid phosphooxyethyl (meth)acrylate, (meth)acryloyloxypropyl acid phosphate, (meth)acryloyloxy-2-hydroxypropyl acid phosphate, (meth)acryloyloxy-3-hydroxypropyl acid phosphate, (meth)acryloyloxy-3-chloro-2-hydroxypropyl acid phosphate, vinyl phosphoric acid, and p-vinylbenzene phosphoric acid.

The ionic monomer containing a group obtained by removing a proton from a sulfo group as the ionic group is preferably a salt of an ethylenically unsaturated sulfonic acid.
Examples of the salt of the ethylenically unsaturated sulfonic acid include monovalent salts such as alkali metal salts, such as sodium salts and potassium salts, and ammonium salts of ethylenically unsaturated sulfonic acids; and polyvalent salts represented by polyvalent metal salts, such as zinc salts, magnesium salts, calcium salts, aluminum salts, and neodymium salts.
The ethylenically unsaturated sulfonic acid constituting the salt of the ethylenically unsaturated sulfonic acid is a sulfonic acid compound having an ethylenically unsaturated group, and specific examples thereof include allylsulfonic acid, isoprene sulfonic acid, 2-(meth)acrylamide ethyl sulfonic acid, 3-(meth)acrylamide propyl sulfonic acid, 4-(meth)acrylamide butyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, p-vinylbenzenesulfonic acid, and vinylsulfonic acid.

The ionic monomer is preferably a salt of an ethylenically unsaturated carboxylic acid, more preferably a monovalent salt and/or a polyvalent metal salt of an ethylenically unsaturated carboxylic acid, even more preferably a polyvalent metal salt of an ethylenically unsaturated carboxylic acid, still more preferably a divalent metal salt such as a zinc salt, magnesium salt, calcium salt or neodymium salt of an ethylenically unsaturated carboxylic acid, particularly preferably a zinc salt, magnesium salt or calcium salt of an ethylenically unsaturated carboxylic acid, and most preferably a zinc salt of an ethylenically unsaturated carboxylic acid.
It is also preferable to use the polyvalent metal salt of the ethylenically unsaturated carboxylic acid in combination with a monovalent salt of the ethylenically unsaturated carboxylic acid. The monovalent salt of the ethylenically unsaturated carboxylic acid is preferably an alkali metal salt or an ammonium salt of the ethylenically unsaturated carboxylic acid, more preferably a sodium salt, a potassium salt or an ammonium salt of the ethylenically unsaturated carboxylic acid, and even more preferably a potassium salt of the ethylenically unsaturated carboxylic acid.

The ethylenically unsaturated carboxylic acid constituting the salt of the ethylenically unsaturated carboxylic acid is most preferably (meth)acrylic acid.That is, the ionic monomer is preferably a salt of (meth)acrylic acid, more preferably a monovalent salt and/or a polyvalent metal salt of (meth)acrylic acid, even more preferably a polyvalent metal salt of (meth)acrylic acid, even more preferably a divalent metal salt such as zinc salt, magnesium salt, calcium salt, or neodymium salt of (meth)acrylic acid, particularly preferably a zinc salt, magnesium salt, or calcium salt of (meth)acrylic acid, and most preferably a zinc salt of (meth)acrylic acid.
It is also preferable to use the polyvalent metal salt of (meth)acrylic acid in combination with a monovalent salt of (meth)acrylic acid. The monovalent salt of (meth)acrylic acid is preferably an alkali metal salt or ammonium salt of (meth)acrylic acid, more preferably a sodium salt, potassium salt or ammonium salt of (meth)acrylic acid, and even more preferably a potassium salt of (meth)acrylic acid.

The content of the salt of the ethylenically unsaturated carboxylic acid (particularly the salt of (meth)acrylic acid) is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, even more preferably 80 to 100% by mass, and particularly preferably 90 to 100% by mass, based on 100% by mass of the polymerizable monomer (B).

The content of the salt of the ethylenically unsaturated carboxylic acid (particularly the salt of (meth)acrylic acid) is preferably 5 to 60 mass %, more preferably 8 to 40 mass %, and even more preferably 10 to 25 mass %, based on 100 mass % of the photocurable composition.

The content of the salt of the ethylenically unsaturated carboxylic acid (particularly the salt of (meth)acrylic acid) relative to 100% by mass of the total amount of polymerizable monomers contained in the photocurable composition of the present invention (i.e. the total amount of polymerizable monomers (A) to (C)) is preferably 15 to 85% by mass, more preferably 25 to 75% by mass, and even more preferably 30 to 65% by mass. By adjusting the content of the salt of the ethylenically unsaturated carboxylic acid to the above-mentioned specified value or more, the supportability of the obtained cured product can be further improved, and by adjusting the content of the polymerizable monomer (B) to the above-mentioned specified value or less, the solubility in water of the obtained cured product can be further improved.

The content of the polyvalent metal salt of the ethylenically unsaturated carboxylic acid (particularly, the polyvalent metal salt of (meth)acrylic acid) is, for example, 20 to 100% by mass, preferably 35% by mass or more, more preferably 50% by mass or more, even more preferably 65% by mass or more, and even more preferably 80% by mass or more, based on 100% by mass of the polymerizable monomer (B). By adjusting the content of the polyvalent metal salt of the ethylenically unsaturated carboxylic acid to the above range, the supportability of the obtained cured product can be further improved. In particular, by adjusting the content of the polyvalent metal salt of the ethylenically unsaturated carboxylic acid (particularly, the polyvalent metal salt of (meth)acrylic acid) to 50% by mass or more, the effect of improving the supportability tends to be further enhanced. In addition, by adjusting the content of the polyvalent metal salt of the ethylenically unsaturated carboxylic acid (particularly, the polyvalent metal salt of (meth)acrylic acid) to 50% by mass or more (preferably 65% by mass or more, more preferably 80% by mass or more), the viscosity of the photocurable composition can be reduced.

The content of the monovalent salt of the ethylenically unsaturated carboxylic acid (particularly, the monovalent salt of (meth)acrylic acid) may be, for example, 10% by mass or more, or 20% by mass or more, in 100% by mass of the polymerizable monomer (B). The content of the monovalent salt of the ethylenically unsaturated carboxylic acid (particularly, the monovalent salt of (meth)acrylic acid) may be 100% by mass in 100% by mass of the polymerizable monomer (B), but from the viewpoint of lowering the viscosity of the photocurable composition and further increasing the supportability of the obtained cured product, it is preferably 80% by mass or less, more preferably 50% by mass or less, even more preferably 35% by mass or less, even more preferably 20% by mass or less, particularly preferably 10% by mass or less, and may be 0% by mass.

In addition, the mass ratio of the polyvalent metal salt of an ethylenically unsaturated carboxylic acid to the monovalent salt of an ethylenically unsaturated carboxylic acid (polyvalent metal salt of an ethylenically unsaturated carboxylic acid/monovalent salt of an ethylenically unsaturated carboxylic acid) contained in the photocurable composition is, for example, 20/80 to 100/0, preferably 35/65 to 100/0, more preferably 50/50 to 100/0, even more preferably 60/40 to 100/0, and particularly preferably 80/20 to 100/0. In addition, it is also preferable to adjust the mass ratio of the polyvalent metal salt of (meth)acrylic acid to the monovalent salt of (meth)acrylic acid (polyvalent metal salt of (meth)acrylic acid/monovalent salt of (meth)acrylic acid) contained in the photocurable composition to the above range. In particular, from the viewpoint of reducing the viscosity of the photocurable composition, it is preferable to adjust the above mass ratio (i.e., polyvalent metal salt of ethylenically unsaturated carboxylic acid/monovalent salt of ethylenically unsaturated carboxylic acid, preferably polyvalent metal salt of (meth)acrylic acid/monovalent salt of (meth)acrylic acid) to 50/50 to 100/0, more preferably 60/40 to 100/0, and even more preferably 80/20 to 100/0.

Examples of polymerizable monomers (B) other than the above ionic monomers include (meth)acrylic acid; methyl (meth)acrylate; (meth)acryloylmorpholine; N-vinylpyrrolidone; acrylamides such as (meth)acrylamide, N,N-dimethylacrylamide, N-hydroxyethylacrylamide, and N-isopropylacrylamide; and the like.

The total content of polymerizable monomer (A) and polymerizable monomer (B) relative to 100% by mass of the total amount of polymerizable monomers contained in the photocurable composition of the present invention (i.e., the total amount of polymerizable monomers (A) to (C)) is preferably 50 to 100% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 98% by mass or more.

1-3. Polymerizable monomer (C)
The photocurable composition of the present invention may contain a polymerizable monomer (C) other than the above-mentioned polymerizable monomers (A) and (B) (for example, a polymerizable monomer having a water solubility (20° C.) of less than 20 g/L). Examples of the polymerizable monomer (C) include:
Ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, n-stearyl (meth)acrylate alicyclic hydrocarbon group-containing (meth)acrylates such as cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, etc.; aromatic hydrocarbon group-containing (meth)acrylates such as phenyl (meth)acrylate, benzyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, etc.; (meth)acrylate compounds such as tetrahydrofurfuryl (meth)acrylate, etc.;
Allyl ether compounds such as phenyl allyl ether, o-, m-, p-cresol monoallyl ether, biphenyl-2-ol monoallyl ether, biphenyl-4-ol monoallyl ether, butyl allyl ether, cyclohexyl allyl ether, and cyclohexanemethanol monoallyl ether;
Vinyl ether compounds such as butyl vinyl ether, butyl propenyl ether, butyl butenyl ether, hexyl vinyl ether, ethylhexyl vinyl ether, phenyl vinyl ether, benzyl vinyl ether, acetylethoxyethoxy vinyl ether, cyclohexyl vinyl ether, and adamantyl vinyl ether;
Maleimide compounds such as phenylmaleimide, cyclohexylmaleimide, and n-hexylmaleimide; and the like.
These may be used alone or in combination of two or more.

The content of the polymerizable monomer (C) is preferably 30% by mass or less, more preferably 10% by mass or less, and particularly preferably less than 2% by mass, based on 100% by mass of the photocurable composition. By adjusting the content of the polymerizable monomer (C) to the above range, the odor of the photocurable composition can be further suppressed.

The total content of the polymerizable monomer (A), the polymerizable monomer (B), and the polymerizable monomer (C) (particularly the total content of the polymerizable monomers (A) and (B)) is preferably 80% by mass or less, more preferably 60% by mass or less, even more preferably less than 50% by mass, even more preferably 45% by mass or less, and particularly preferably 40% by mass or less, in 100% by mass of the photocurable composition. By adjusting the total amount of the polymerizable monomers (particularly the total content of the polymerizable monomers (A) and (B)) to the above range, it is possible to reduce the viscosity of the photocurable composition, and also to increase the thermal stability of the photocurable composition (specifically, the effect of suppressing thickening when stored under high temperature conditions).
The total content of the polymerizable monomer (A), the polymerizable monomer (B), and the polymerizable monomer (C) (particularly the total content of the polymerizable monomers (A) and (B)) is preferably 8% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of the photocurable composition. By adjusting the total amount of the polymerizable monomers (particularly the total content of the polymerizable monomers (A) and (B)) within the above range, the supportability of the obtained cured product can be further improved.
That is, the total content of the polymerizable monomer (A), the polymerizable monomer (B), and the polymerizable monomer (C) (particularly the total content of the polymerizable monomers (A) and (B)) is preferably 8 to 80 mass%, more preferably 15 to 60 mass%, even more preferably 20 mass% or more and less than 50 mass%, still more preferably 20 to 45 mass%, and particularly preferably 20 to 40 mass%, in 100 mass% of the photocurable composition.

In addition, by increasing the proportion of the polyvalent metal ion-containing ionic monomer in the polymerizable monomer (B), the supportability of the resulting cured product can be increased even if the total amount of polymerizable monomers in the photocurable composition is at least. That is, an embodiment in which the total content of polymerizable monomer (A), polymerizable monomer (B), and polymerizable monomer (C) (particularly the total content of polymerizable monomers (A) and (B)) is 8% by mass or more and less than 50% by mass (preferably 15 to 45% by mass, more preferably 20 to 45% by mass, and even more preferably 20 to 40% by mass) in 100% by mass of the photocurable composition, and the content of the polyvalent metal ion-containing ionic monomer (preferably a polyvalent metal salt of an ethylenically unsaturated carboxylic acid, more preferably a polyvalent metal salt of (meth)acrylic acid) is 50 to 100% by mass in 100% by mass of polymerizable monomer (B) is preferable from the viewpoint of achieving both the thermal stability of the photocurable composition and the supportability of the resulting cured product.

In addition, by increasing the proportion of the polyvalent metal ion-containing ionic monomer in the polymerizable monomer (B), the viscosity of the photocurable composition can be kept low even if the content of the polymerizable monomer in the photocurable composition is high. That is, even if the total content of the polymerizable monomer (A), polymerizable monomer (B), and polymerizable monomer (C) (particularly the total content of the polymerizable monomers (A) and (B)) is, for example, 15% by mass or more (preferably 20 to 45% by mass) in 100% by mass of the photocurable composition, the viscosity of the photocurable composition can be kept low by adjusting the content of the polyvalent metal ion-containing ionic monomer (preferably a polyvalent metal salt of an ethylenically unsaturated carboxylic acid, more preferably a polyvalent metal salt of (meth)acrylic acid) to 50 to 100% by mass in 100% by mass of the polymerizable monomer (B).

1-4. Organic acid and/or salt thereof The photocurable composition of the present invention may contain an organic acid and/or a salt thereof. By containing an organic acid and/or a salt thereof, storage stability is further improved. Note that the organic acid and/or a salt thereof is a compound that does not have a polymerizable unsaturated group, that is, the above polymerizable monomers (A) to (C) are not included.

Examples of the organic acid include organic carboxylic acids, organic sulfonic acids, and organic phosphoric acids.
Examples of the organic carboxylic acid include aliphatic carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, octylic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, tridecanoic acid, pentadecanoic acid, heptadecanoic acid, lactic acid, malic acid, citric acid, oxalic acid, malonic acid, succinic acid, fumaric acid, adipic acid, glycine, polyacrylic acid, and polylactic acid; and aromatic carboxylic acids such as benzoic acid, phthalic acid, and salicylic acid.
Specific examples of the organic sulfonic acid include p-toluenesulfonic acid.
Specific examples of the organic phosphoric acid include phenylphosphonic acid.
Among these, organic carboxylic acids are preferred, aliphatic carboxylic acids are more preferred, and lactic acid, propionic acid, and polyacrylic acid are even more preferred.

The salt of the organic acid is preferably a metal salt of the organic acid, and specific examples thereof include alkali metal salts such as lithium salts, sodium salts, and potassium salts of the organic acids described above; and alkaline earth metal salts such as magnesium salts, calcium salts, strontium salts, and barium salts of the organic acids described above. Of these, alkali metal salts of the organic acids described above are preferred, and potassium salts of the organic acids described above are more preferred.

These organic acids and/or salts thereof may be contained in the photocurable composition of the present invention either alone or in combination of two or more kinds.

The organic acid and/or its salt are preferably an organic carboxylic acid or a metal salt of an organic carboxylic acid, more preferably an aliphatic carboxylic acid or a metal salt of an aliphatic carboxylic acid, and even more preferably lactic acid, a metal salt of lactic acid, propionic acid, a metal salt of propionic acid, polyacrylic acid, or a metal salt of polyacrylic acid.

The content of the organic acid and/or its salt is, for example, 0 to 20% by mass in 100% by mass of the photocurable composition. In particular, from the viewpoint of improving storage stability, the content is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 5% by mass.

1-5. Photopolymerization initiator The photocurable composition of the present invention may contain a photopolymerization initiator. Specific examples of the photopolymerization initiator include:
Benzoin compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, and benzoin isobutyl ether;
Acetophenone compounds such as acetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-methylpropanone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one;
Anthraquinone compounds such as 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-chloroanthraquinone, and 2-amylanthraquinone;
Thioxanthone compounds such as 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, and [3-(3,4-dimethyl-9-oxothioxanthen-2-yl)oxy-2-hydroxypropyl]-trimethylazanium chloride;
Ketal compounds such as acetophenone dimethyl ketal, benzil dimethyl ketal, and benzil diethyl ketal;
Benzophenone compounds such as benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 4,4'-bismethylaminobenzophenone;
Phosphine oxide compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; and the like.
These may be used alone or in combination of two or more.

Among them, the photopolymerization initiator is
Benzoin compounds, acetophenone compounds, ketal compounds, and phosphine oxide compounds are preferred;
Benzoin compounds; α-hydroxyacetophenone compounds such as 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-methylpropanone; α-aminoacetophenone compounds such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one; benzyl ketal compounds such as benzyl dimethyl ketal and benzyl diethyl ketal; acylphosphine oxide compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide are more preferred, and α-hydroxyacetophenone compounds are particularly preferred.

The content of the photopolymerization initiator is preferably 0.05 to 10.0% by mass, more preferably 0.1 to 7.0% by mass, and even more preferably 0.2 to 5.0% by mass, based on 100% by mass of the photocurable composition. By adjusting the content of the photopolymerization initiator within the above range, the curability can be further improved.
The content of the photopolymerization initiator is preferably 0.5 to 20 parts by mass, more preferably 1.0 to 15 parts by mass, and even more preferably 3.0 to 10 parts by mass, relative to 100 parts by mass of the total of the polymerizable monomers (A) to (C) (particularly, the total of the polymerizable monomer (A) and the polymerizable monomer (B)).

1-6. Polymerization Inhibitor The photocurable composition of the present invention may contain a polymerization inhibitor within a range that does not impair the effects of the present invention. By containing a polymerization inhibitor, the thermal stability of the photocurable composition is improved.

Polymerization inhibitors include:
Phenols with a molecular weight of less than 300, such as hydroquinone, catechol, resorcin, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 2,4-dihydroxybenzophenone, 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, and 2,6-di-t-butyl-4-ethylphenol; 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3 bisphenols such as 4,4'-(2,3-dimethyl-tetramethylene)dipyrocatechol; stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 3,4, 5-Trihydroxybenzoic acid propyl ester, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene (Irganox (registered trademark) 1330, manufactured by BASF Corporation), tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)propionate]methane, phenolic antioxidants such as polymeric phenols having a molecular weight of 300 or more, such as 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-s-triazine-2,4,6-(1H,3H,5H)trione, tocopherol, tocopherol derivatives, and 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl=acrylate (Sumilizer (registered trademark) GS, manufactured by Sumitomo Chemical Co., Ltd.);
sulfur-based antioxidants such as 2-mercaptobenzimidazole, dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, 2-mercaptobenzimidazole, tetrakismethylene-3-(laurylthio)propionate methane, and stearylthiopropylamide;
Triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl ditridecyl)phosphite, cyclic neopentane tetrayl bis(octadecyl)phosphite, tris(nonylphenyl)phosphite, tris(mono- and/or dinonylphenyl)phosphite, diisodecyl pentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide phosphorus-based antioxidants such as tetrakis(2,4-di-t-butylphenyl)phosphite, 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, tris(2,4-di-t-butylphenyl)phosphite, cyclic neopentanetetraylbis(2,4-di-t-butylphenyl)phosphite, cyclic neopentanetetraylbis(2,6-di-t-butyl-4-methylphenyl)phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, distearyl pentaerythritol diphosphite, di(2,4-di-t-butylphenyl)phosphite, and tetrakis(2,4-di-t-butylphenyl)-4,4-biphenylenephosphonite;
hindered amine antioxidants such as 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate, dimethyl succinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine and condensates thereof, and 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4,5]decane-2,4-dione;
Alkoxyamine radicals such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radicals;
Examples of the oxime include 1,1-diphenyl-2-picrylhydrazyl, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cupferron, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N-(3-oxyanilino-1,3-dimethylbutylidene)aniline oxide, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime, and cyclohexanone oxime.

These polymerization inhibitors may be used alone or in combination of two or more types.

The polymerization inhibitor is preferably at least one selected from the group consisting of a phenol-based antioxidant, a sulfur-based antioxidant, a phosphorus-based antioxidant, a hindered amine-based antioxidant, and an alkoxyamine radical, and is more preferably a phenol-based antioxidant and/or an alkoxyamine radical.
In 100% by mass of the polymerization inhibitor, the total amount of the phenol-based antioxidant, the sulfur-based antioxidant, the phosphorus-based antioxidant, the hindered amine-based antioxidant, and the alkoxyamine radical (preferably the total amount of the phenol-based antioxidant and the alkoxyamine radical) is preferably 50 to 100% by mass, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

The content of the polymerization inhibitor is preferably 0.01 to 5.0% by mass, more preferably 0.03 to 3.0% by mass, and even more preferably 0.05 to 1.0% by mass, based on 100% by mass of the photocurable composition.
The content of the polymerization inhibitor is preferably 0.03 to 14.0 parts by mass, more preferably 0.08 to 9.0 parts by mass, and even more preferably 0.14 to 3.0 parts by mass, relative to 100 parts by mass of the total of the polymerizable monomers (A) to (C) (particularly, the total of the polymerizable monomer (A) and the polymerizable monomer (B)).

The photocurable composition of the present invention may contain a solvent within a range that does not impair the effects of the present invention. Examples of the solvent include water, monohydric alcohol, glycol, glycol ether, glycol ether acetate, and trihydric alcohol.

Specific examples of the monohydric alcohol include methanol, ethanol, and propanol, and preferably have 1 to 5 carbon atoms.

Specific examples of the glycol include:
Alkylene glycols such as ethylene glycol, propylene glycol, 1,3-butylene glycol, hexylene glycol, and 1,2-hexanediol (preferably, C _2-6 alkylene glycol);
Polyalkylene glycols having a total number of repeating alkylene glycol units (i.e., the number of repeating oxyalkylene groups) of 2 or more (preferably 2 to 20, more preferably 2 to 10), such as diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, and a copolymer of ethylene glycol and propylene glycol.

Specific examples of the glycol ether include propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, and propylene glycol monopropyl ether, and preferably (poly)C _2-3 alkylene glycol C _1-4 alkyl ether.

Specific examples of the glycol ether acetate include propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate, and preferably (poly)C _2-3 alkylene glycol mono C _1-4 alkyl ether acetate.

Specific examples of the trihydric alcohol include glycerol.

The above solvents may be used alone or in combination of two or more.

The solvent preferably contains at least one selected from the group consisting of glycol, glycol ether, glycol ether acetate, and glycerol, more preferably contains at least one selected from the group consisting of glycol and glycerol, and particularly preferably contains glycol.
The total content of glycol, glycol ether, glycol ether acetate, and glycerol (particularly, the total content of glycol and glycerol) is preferably 50 to 100 mass%, more preferably 80 to 100 mass%, and even more preferably 95 to 100 mass%, based on 100 mass% of the solvent.
The content of the glycol is preferably 50 to 100% by mass or more, more preferably 70 to 100% by mass, and further preferably 90 to 100% by mass, based on 100% by mass of the solvent.

Among glycols, (poly) _C2-6 alkylene glycols containing an alkylene chain having 2 to 6 carbon atoms as the alkylene chain constituting the glycol molecule are preferred, (poly) _C2-3 alkylene glycols containing an alkylene chain having 2 and/or 3 carbon atoms are more preferred, and (poly)propylene glycols containing an alkylene chain having 3 carbon atoms are even more preferred.

From the viewpoint of improving the thermal stability of the photocurable composition, the above glycol preferably contains at least a _C2-6 alkylene glycol, more preferably contains at least ethylene glycol and/or propylene glycol, and even more preferably contains at least propylene glycol.

The content of C _2-6 alkylene glycol (particularly the content of propylene glycol) is preferably from 20 to 100% by mass, more preferably from 30 to 95% by mass, and even more preferably from 40 to 90% by mass, based on 100% by mass of the solvent.

The glycol preferably contains a C _2-6 alkylene glycol and a poly C _2-6 alkylene glycol, more preferably contains ethylene glycol and/or propylene glycol and polyethylene glycol and/or polypropylene glycol, further preferably contains ethylene glycol and/or propylene glycol and a polyethylene glycol having an ethylene glycol repeat number (i.e., the number of oxyethylene group repeats) of 2 to 20 and/or a polypropylene glycol having a propylene glycol repeat number (i.e., the number of oxypropylene group repeats) of 2 to 20, and particularly preferably contains propylene glycol and a polyethylene glycol having an ethylene glycol repeat number (i.e., the number of oxyethylene group repeats) of 2 to 10 and/or a polypropylene glycol having a propylene glycol repeat number (i.e., the number of oxypropylene group repeats) of 2 to 10. By using such a glycol as a solvent, the compatibility between the polymer obtained by curing the photocurable composition of the present invention and the solvent becomes good, probably because of the good compatibility with the polymerizable monomer (A), and the transparency of the obtained support material is enhanced. As a result, the surface properties of the resulting stereolithographic object tend to be improved.

The total content of the C _2-6 alkylene glycol and poly C _2-6 alkylene glycol is preferably from 50 to 100% by mass, more preferably from 70 to 100% by mass, and even more preferably from 80 to 100% by mass, in 100% by mass of the solvent.
The content of poly _C2-6 alkylene glycol per 100 parts by mass of _C2-6 alkylene glycol is preferably 5 to 200 parts by mass, more preferably 10 to 150 parts by mass, and even more preferably 20 to 120 parts by mass. In particular, it is preferable to adjust the total content of polyethylene glycol and polypropylene glycol per 100 parts by mass of propylene glycol to be within the above range.
The content of the polyC _2-6 alkylene glycol per 100 parts by mass of the polymerizable monomer (A) is preferably from 10 to 500 parts by mass, more preferably from 30 to 450 parts by mass, and even more preferably from 50 to 400 parts by mass.

As described above, the solvent may contain water, but the content is preferably small. The content of water is preferably 0 to 10% by mass, more preferably 5% by mass or less, and even more preferably 3% by mass or less, based on 100% by mass of the photocurable composition. By adjusting the content of water to the above range, the supportability can be further improved.
The water content in the photocurable composition can be calculated from the water content of each compound added, or can be determined by Karl Fischer measurement.

In 100% by mass of the photocurable composition of the present invention, the total content of the above solvents is preferably 20 to 90% by mass, more preferably 30 to 85% by mass, even more preferably 40 to 80% by mass, and even more preferably 50 to 80% by mass or 55 to 80% by mass.

1-8. Other Additives The photocurable composition of the present invention may contain other additives as necessary within the range that does not impair the effects of the present invention. Examples of the additives include known additives such as photoinitiator assistants, surfactants, colorants, chain transfer agents, fillers, emulsion stabilizers, penetration promoters, UV absorbers, preservatives, antifungal agents, rust inhibitors, pH adjusters, surface tension adjusters, antifoaming agents, viscosity adjusters, dispersants, dispersion stabilizers, chelating agents, drying inhibitors (wetting agents), discoloration inhibitors, resistivity adjusters, and film adjusters.

Examples of photoinitiator assistants include tertiary amine compounds such as N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-toluidine, N,N-dimethylamino-p-benzoic acid ethyl ester, N,N-dimethylamino-p-benzoic acid isoamyl ethyl ester, N,N-dihydroxyethylaniline, triethylamine, and N,N-dimethylhexylamine.

Surfactants include PEG-type nonionic surfactants such as 1-40 mole ethylene oxide (hereinafter abbreviated as EO) adduct of nonylphenol and 1-40 mole EO adduct of stearic acid; polyhydric alcohol-type nonionic surfactants such as sorbitan palmitate monoester, sorbitan stearate monoester, and sorbitan stearate triester; fluorine-containing surfactants such as 1-50 mole EO adduct of perfluoroalkyl, perfluoroalkyl carboxylate, and perfluoroalkyl betaine; modified silicone oils such as polyether-modified silicone oil and (meth)acrylate-modified silicone oil; etc.

Colorants include toluidine red, permanent carmine FB, fast yellow G, disazo yellow AAA, disazo orange PMP, soluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine blue, indanthrone blue, quinacridone red, dioxazine violet, basic dyes, acid dyes, aniline black, daylight fluorescent pigments, nitroso pigments, nitro pigments, natural pigments, metal oxides as inorganic pigments, carbon black, etc.

Chain transfer agents include hydroquinone, diethylmethylamine, diphenylamine, diethyl disulfide, di-1-octyl disulfide, toluene, xylene, 1-butene, 1-nonene, dichloromethane, carbon tetrachloride, methanol, 1-butanol, ethyl thiol, 1-octyl thiol, acetone, methyl ethyl ketone, 2-methyl-2-propyl aldehyde, 1-pentyl aldehyde, phenol, m-cresol, p-cresol, and o-cresol.

Fillers include alumina powder, silica powder, talc, mica, clay, aluminum hydroxide, calcium carbonate, calcium silicate, aluminum powder, copper powder, carbon fiber, glass fiber, cotton fiber, nylon fiber, acrylic fiber, rayon fiber, microballoons, carbon black, metal sulfides, and wood powder.

The above additives may be used alone or in combination of two or more kinds.
The content of the additives may be appropriately adjusted depending on the additives used, but is preferably 0 to 30 mass%, more preferably 0.05 to 20 mass%, and even more preferably 0.05 to 10 mass% or 0.05 to 5 mass%, relative to 100 mass% of the photocurable composition.

1-9. Method for preparing photocurable composition The photocurable composition of the present invention can be prepared using the various components described above, and the preparation means and conditions are not particularly limited, but examples thereof include a method of stirring and mixing using a mixing or stirring device such as a general stirring blade or ultrasonic homogenizer, a high-speed homogenizer, a high-pressure homogenizer, a planetary stirring device, a three-roll mill, a ball mill, a Kitty mill, a disk mill, a pin mill, a Dyno mill, etc. The mixture obtained by stirring and mixing may be filtered using various filters.

1-10. Physical Properties of Photocurable Composition From the viewpoint of improving the ejection properties from the ejection head of an inkjet 3D printer, the photocurable composition of the present invention preferably has a viscosity of 20 mPa·s or less at the ejection temperature.
Moreover, from the viewpoint of discharge stability, the photocurable composition of the present invention preferably has a low viscosity at 25°C. Specifically, the viscosity is preferably 300 mPa·s or less, more preferably 200 mPa·s or less, even more preferably 150 mPa·s or less, and particularly preferably 100 mPa·s or less. The lower limit is not particularly limited, but is, for example, 5 mPa·s or more, preferably 20 mPa·s or more.
The viscosity of the photocurable composition can be measured using an E-type viscometer in accordance with JIS Z 8803.

The photocurable composition of the present invention preferably has a surface tension of 25 to 70 mN/m at 25°C. The surface tension of the photocurable composition can be measured, for example, using a bubble pressure type dynamic surface tensiometer BP100 (manufactured by KRUSS).

The photocurable composition of the present invention has excellent curability. The photocurable composition of the present invention is preferably cured by irradiation with ultraviolet light of 100 to 3000 mJ/ ^cm2 . Here, curing means that the composition is no longer liquid and loses fluidity.

The cured product obtained by using the photocurable composition of the present invention has excellent supportability. Here, the supportability refers to the ability of the cured product obtained by curing the photocurable composition to support a model material. The higher the hardness of the cured product obtained by curing the photocurable composition, the higher the supportability. When the hardness of a plate-shaped cured product (thickness 3 mm) obtained by irradiating the photocurable composition of the present invention with ultraviolet light of 100 mW/cm ² for 3 minutes is measured using a type E durometer, the hardness 0 seconds after the start of measurement is preferably 65 or more, more preferably 75 or more, even more preferably 80 or more, and particularly preferably 85 or more or more than 85.

The cured product formed from the photocurable composition of the present invention preferably has a property of being easily removable by water. When a piece of the cured product (2 cm x 2 cm x 3 mm thick) obtained by irradiating the photocurable composition of the present invention with 100 mW/ ^cm2 ultraviolet light for 3 minutes is added to 50 mL of water at 25°C and left to stand for 3 hours, preferably 50% by mass or more of the cured product piece dissolves, more preferably 80% by mass or more of the cured product piece dissolves, and particularly preferably all of the cured product piece dissolves.

The cured product formed from the photocurable composition of the present invention has excellent transparency. The present inventors have discovered that the more transparent the cured product formed from the photocurable composition for supporting material is (specifically, the lower the haze of the cured product is), the cleaner (less rough) the surface state of the resulting photomodeled product (model material) is. Although the mechanism is unclear, when the supporting material is made of a photocurable composition in which a polymerizable monomer with high water solubility is dissolved or dispersed (i.e., a photocurable composition with water affinity), and the model material is made of a photocurable composition in which a polymerizable monomer with low water solubility is dissolved or dispersed (i.e., a photocurable composition with low water affinity), the more transparent the cured product (supporting material) formed from the photocurable composition for supporting material with water affinity is, the more difficult it is for the photocurable composition for supporting material to mix with the photocurable composition for model material with low water affinity. As a result, when both the photocurable composition for supporting material and the photocurable composition for model material are discharged, the separation of the interface between them is enhanced, and it is considered that a photomodeled product (model material) with a clean surface derived from the interface is obtained.
When the photocurable composition of the present invention is irradiated with ultraviolet light at 100 mW/ ^cm2 for 3 minutes to obtain a plate-shaped cured product piece (thickness: 2 mm) and the haze is measured using a turbidity meter, the haze is preferably 70% or less, more preferably 50% or less, even more preferably 10% or less, and particularly preferably less than 5%.

2. Cartridge for inkjet 3D printer The photocurable composition is used as an ink for inkjet 3D printers. The photocurable composition is usually filled into a cartridge for inkjet 3D printers for use. The inkjet 3D printer cartridge may be filled with the photocurable composition, and any cartridge for inkjet 3D printers may be used in the form of a known cartridge.

3. Method for manufacturing a support material The support material of the present invention is manufactured by irradiating the photocurable composition with light. That is, the method for manufacturing a support material of the present invention may include a step of irradiating the photocurable composition with light, and specifically, it is preferable to include a step of discharging the photocurable composition from the discharge head of an inkjet 3D printer (discharge step a) and a step of irradiating the discharged photocurable composition with light (light irradiation step a) to form a support material layer A. By repeatedly performing this support material layer formation step A, the support material layers can be laminated to produce a support material of the desired shape. In the discharge step a, a known method can be used other than using the photocurable composition.

The light irradiation step a can also be carried out by a known method. The light to be irradiated to the photocurable composition can be ultraviolet light, near ultraviolet light, visible light, infrared light, far infrared light, electron beams, alpha rays, gamma rays, X-rays, etc., with ultraviolet light being preferred.

The exposure dose during light irradiation is preferably from 100 mJ/cm ² to 3000 mJ/cm ² , more preferably from 100 to 2000 mJ/cm ² , and even more preferably from 100 to 1000 mJ/cm ² .

4. Method for Producing a Photo-Modeled Object The method for producing a photo-modeled object of the present invention includes the steps of:
a forming step of a modeled object precursor, in which a forming step A of a supporting material layer in which the photocurable composition is irradiated with light and a forming step B of a model material layer carried out at the same timing and/or different timing as the forming step A are each repeated multiple times;
and removing the support material formed of the support material layer from the optically shaped object precursor.

In the above-mentioned method for producing a photo-cured object, a known method can be used in addition to using the above-mentioned photocurable composition (hereinafter sometimes referred to as photocurable composition (I)) in the step A of forming the support material layer. Specifically, the step A of forming the support material layer preferably includes a step of ejecting the above-mentioned photocurable composition (I) from the ejection head of an inkjet 3D printer (ejection step a) and a step of irradiating the ejected photocurable composition (I) with light (light irradiation step a). By repeatedly performing the step A of forming the support material layer, the support material layers can be stacked to produce a support material of the desired shape. The preferred aspects of the ejection step a and the light irradiation step a are the same as those described above.

The model material layer forming process B preferably includes a process of irradiating light to a photocurable composition for the model material (hereinafter sometimes referred to as photocurable composition (II)). Specifically, it preferably includes a process (discharging process b) of discharging the photocurable composition (II) from the discharge head of the inkjet 3D printer, and a process (light irradiation process b) of irradiating the discharged photocurable composition (II) with light. By repeatedly performing this model material layer forming process B, model material layers can be stacked to produce a model material of the desired shape.

The ejection step b in the model material layer formation step B is a step of ejecting the photocurable composition (II) from the ejection head of the inkjet 3D printer. In the ejection step b, a known method can be used.

It is preferable that the ejection head that ejects the photocurable composition (I) in the ejection step a is different from the ejection head that ejects the photocurable composition (II) in the ejection step b. In other words, the inkjet 3D printer used in the present invention is preferably equipped with an ejection head for ejecting the photocurable composition (I) and an ejection head for ejecting the photocurable composition (II).

The light irradiation step b in the model material layer formation step B is a step of irradiating the photocurable composition (II) discharged in the discharge step b with light, and a known method can be used. The preferred embodiment of the light irradiation step b is the same as the preferred embodiment of the light irradiation step a.

The optically shaped object precursor composed of the supporting material and the model material is manufactured by repeating each of the forming steps A and B a plurality of times.
Specifically, the optically shaped object precursor can be manufactured by stacking layers of the desired optically shaped object precursor finely divided into thin pieces, and each layer can be a layer consisting of only a supporting material, a layer consisting of only a modeling material, or a layer consisting of a supporting material and a modeling material (i.e., a layer in which a supporting material and a modeling material are present on the same plane). When forming a layer consisting of only a supporting material, the forming step A is carried out, when forming a layer consisting of only a modeling material, the forming step B is carried out, and when forming a layer consisting of a supporting material and a modeling material, the forming step A and the forming step B can be carried out simultaneously. By appropriately repeating these steps, the desired optically shaped object precursor can be manufactured.
The order of forming step A, forming step B, and the step of simultaneously carrying out forming step A and forming step B, as well as the number of repetitions, may be appropriately adjusted according to the desired shape of the optically shaped object precursor.

When the formation step A and the formation step B are performed simultaneously, it is preferable to first perform the discharge step a and the discharge step b, place the photocurable composition (I) and the photocurable composition (II) on the same plane, and then perform the light irradiation step a and the light irradiation step b. In this case, the discharge step a and the discharge step b may be performed simultaneously, or may be performed at different times, such as performing the discharge step b after the discharge step a, or performing the discharge step a after the discharge step b. In the present invention, since a photocurable composition for the support material (i.e., the photocurable composition (I)) in which the transparency of the obtained cured product is increased is used, the separation of the interface between the photocurable composition (I) and the photocurable composition (II) discharged by the discharge step a and the discharge step b is increased. And since the light irradiation step a and the light irradiation step b can be performed while the separation of the interface is increased, a photo-molded object (model material) with a clean surface derived from the interface can be obtained.
When the supporting material layer forming step A and the model material layer forming step B are carried out simultaneously, it is more preferable to carry out the light irradiation steps a and b simultaneously.

The photocurable composition (II) used in the formation process B is preferably a composition containing a polymerizable monomer (D) and a photopolymerization initiator.

The polymerizable monomer (D) is not particularly limited as long as it is a compound having one or more ethylenically unsaturated groups and is polymerizable by light or the like. Specifically,
(Meth)acrylic acid;
Alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, isobutyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and t-butyl (meth)acrylate;
Hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate;
(meth)acrylates containing an alicyclic hydrocarbon group, such as cyclohexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, and adamantyl (meth)acrylate;
Aromatic hydrocarbon group-containing (meth)acrylates, such as phenyl (meth)acrylate and phenoxyethyl (meth)acrylate;
Heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, 4-(meth)acryloyloxymethyl-2-methyl-2-ethyl-1,3-dioxolane, 4-(meth)acryloyloxymethyl-2-cyclohexyl-1,3-dioxolane, cyclic trimethylolpropane formal (meth)acrylate, and glycidyl (meth)acrylate;
Alkyleneoxy group-containing (meth)acrylates such as tripropylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and 2-(2-vinyloxyethoxy)ethyl (meth)acrylate;
(Meth)acrylamides such as N-alkyl(meth)acrylamides having an alkyl group having 1 to 12 carbon atoms;
Vinyl compounds such as vinyl acetate, vinyl propionate, methyl vinyl ether, styrene, and N-vinyl caprolactam;
methyl allyloxymethylacrylate; and the like.

The polymerizable monomer (D) may be used alone or in combination of two or more kinds. In addition, the polymerizable monomer (D) is preferably a monomer that does not contain a metal component, and more preferably does not contain the above-mentioned polymerizable monomer (A) or polymerizable monomer (B) (particularly, an ionic monomer).

The polymerizable monomer (D) preferably contains a polymerizable monomer having a water solubility (20° C.) of less than 20 g/L, more preferably contains a polymerizable monomer having a water solubility (20° C.) of 10 g/L or less, and even more preferably contains a polymerizable monomer having a water solubility (20° C.) of 1 g/L or less.
The content of the polymerizable monomer having a water solubility (20° C.) of less than 20 g/L (preferably 10 g/L or less, more preferably 1 g/L or less) is preferably 50 to 100 mass%, and more preferably 60 to 100 mass%, based on 100 mass% of the polymerizable monomer (D), from the viewpoint of preventing the resulting cured product (model material) from dissolving in water.

The content of the polymerizable monomer (D) is preferably 15 to 90 mass% and more preferably 20 to 80 mass% in 100 mass% of the photocurable composition (II) from the viewpoint of improving the curability of the photocurable composition (II).

The photopolymerization initiator contained in the photocurable composition (II) may be any of the compounds exemplified as the photopolymerization initiator in the photocurable composition (I).

The content of the photopolymerization initiator is preferably 0.05 to 10.0% by mass, more preferably 0.1 to 7.0% by mass, and even more preferably 0.2 to 5.0% by mass, based on 100% by mass of the photocurable composition (II). By adjusting the content of the photopolymerization initiator within the above range, the curability can be further improved.
The content of the photopolymerization initiator is preferably 0.5 to 20 parts by mass, more preferably 1.0 to 15 parts by mass, and further preferably 3.0 to 10 parts by mass, based on 100 parts by mass of the polymerizable monomer (D).

The photocurable composition (II) may further contain a solvent. As the solvent, the solvents exemplified as the solvent for the photocurable composition (I) can be used. The content of the solvent is not particularly limited, and may be adjusted so that the photocurable composition (II) has a suitable viscosity. The photocurable composition (II) preferably has a viscosity of 5 to 300 mPa·s at 25°C. In addition, from the viewpoint of improving the ejection properties from the ejection head of the inkjet 3D printer, it is preferable that the viscosity of the photocurable composition (II) at the ejection temperature is 20 mPa·s or less.

The photocurable composition (II) may contain other additives as necessary, provided that the effects of the present invention are not impaired. Examples of the additives include known additives such as photoinitiator assistants, polymerization inhibitors, surfactants, colorants, chain transfer agents, fillers, emulsion stabilizers, penetration promoters, UV absorbers, preservatives, antifungal agents, rust inhibitors, pH adjusters, surface tension adjusters, antifoaming agents, viscosity adjusters, dispersants, dispersion stabilizers, chelating agents, drying inhibitors (wetting agents), discoloration inhibitors, resistivity adjusters, and film adjusters.

The model material formed from the photocurable composition (II) needs to be resistant to the support material removal process. When a cured piece (2 cm x 2 cm x 3 mm) obtained by irradiating the photocurable composition (II) with 100 mW/ ^cm2 ultraviolet light for 3 minutes is added to 50 mL of water at 25°C and allowed to stand for 3 hours, it is preferable that the cured piece does not dissolve at all.

Subsequently, a process of removing the support material composed of the support material layer from the obtained stereolithography precursor is carried out to obtain the desired stereolithography (stereolithography composed of model material). The support material can be easily removed using a polar solvent such as water, alcohol, acidic solution, or basic solution. From the viewpoints of safety and reducing environmental load, it is preferable to use water as the polar solvent. From the viewpoints of safety and cost, the support material removal process is preferably a method in which the stereolithography precursor is left to stand in a polar solvent (preferably water) to remove the support material. The standing time is not particularly limited, but from the viewpoint of workability, it is preferably 1 to 5 hours, more preferably 0.5 to 2 hours. In addition, the temperature of the polar solvent (preferably water) is preferably 10 to 40°C, more preferably 20 to 30°C.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples, and it is of course possible to carry out the invention with appropriate modifications within the scope of the intent described above and below, all of which are included in the technical scope of the present invention. In the following, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

[Example 1]
To a 20 mL brown screw tube, 20 parts of methoxypolyethylene glycol acrylate (average number of repeating oxyethylene groups: approximately 9, manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester AM-90G"), 15 parts of zinc acrylate, 30 parts of propylene glycol, 30 parts of triethylene glycol, 5 parts of glycerin, and 2 parts of a photopolymerization initiator (manufactured by IGM Resins B.V., product name "Omnirad2959") were added and mixed with stirring to obtain a photocurable composition.

[Examples 2 to 13, Comparative Examples 1 to 3]
Photocurable compositions were obtained in the same manner as in Example 1, except that the compositions were changed to those shown in Table 1.

The photocurable compositions obtained in the examples and comparative examples were evaluated using the following evaluation methods.

(1) Evaluation of Viscosity of Photocurable Composition The viscosity of the photocurable compositions of Examples 11 to 13 was measured at 25° C. using a TPE100 viscometer (manufactured by Toki Sangyo Co., Ltd.) according to a method in accordance with JIS Z 8803. The obtained viscosities (unit: mPa s) are shown in Table 1.

(2) Evaluation of curability The photocurable composition was irradiated with 100 mW/ ^cm2 ultraviolet light (wavelength 365 nm) for 30 seconds, and the appearance of the resulting photoirradiated object (2 cm x 2 cm x thickness 3 mm) was visually inspected and evaluated. The evaluation criteria were as follows. The results are shown in Table 1.
○: The light irradiated material did not flow, i.e., it hardened. ×: The light irradiated material was a liquid or viscous liquid and had flowability.

(3) Evaluation of Supportability The photocurable composition was irradiated with 100 mW/ ^cm2 ultraviolet light (wavelength 365 nm) for 3 minutes to obtain a cured product (2 cm x 2 cm x thickness 3 mm). The hardness was measured 0 seconds after the start of measurement using a Type E Durometer (manufactured by Kobunshi Keiki Co., Ltd.) and evaluated. The evaluation criteria were as follows. The results are shown in Table 1.
〇: Over 85 △: Between 65 and 85 ×: Less than 65

(4) Evaluation of Transparency The haze of a piece of the cured product (6 cm x 3 cm x 2 mm) obtained by irradiating the photocurable composition with 100 mW/ ^cm2 ultraviolet light (wavelength 365 nm) for 3 minutes was measured using a turbidity meter (Nippon Denshoku Industries Co., Ltd., Haze Meter NDH7000). The evaluation criteria are as follows. The results are shown in Table 1.
○: Haze is less than 5% △: Haze is 5% to 50% ×: Haze is more than 50%

(5) Evaluation of Water Solubility A piece of cured material (2 cm x 2 cm x 3 mm thick) obtained by irradiating a photocurable composition with 100 mW/ ^cm2 ultraviolet light (wavelength 365 nm) for 3 minutes was placed on a wire net and kept in 50 mL of water at 25°C, and the time until the cured material piece was completely dissolved was measured. The evaluation criteria were as follows. The results are shown in Table 1.
○: Less than 3 hours ×: More than 3 hours

Details of each component listed in Table 1 are as follows.
AM-90G: Methoxypolyethylene glycol acrylate (average number of repeating oxyethylene groups: about 9), manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester AM-90G"
AM-130G: Methoxypolyethylene glycol acrylate (average number of repeating oxyethylene groups: about 13), manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester AM-130G"
AM-230G: Methoxypolyethylene glycol acrylate (average number of repeating oxyethylene groups: about 23), manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester AM-230G"
M-90G: Methoxypolyethylene glycol methacrylate (average number of repeating oxyethylene groups: about 9), manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester M-90G"
M-130G: Methoxypolyethyleneglycol methacrylate (average number of repeating oxyethylene groups: about 13), manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester M-130G"
M-230G: Methoxypolyethyleneglycol methacrylate (average number of repeating oxyethylene groups: about 23), manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester M-230G"
Viscoat #MTG: Methoxytriethyleneglycol acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd., product name "Viscoat #MTG"
Polyethylene glycol 400: Fujifilm Wako Pure Chemical Industries, Ltd., product name "Polyethylene glycol 400"
Polypropylene glycol (diol type, Mn = 400): manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name "Polypropylene glycol, diol type, 400"
Omnirad 2959 (trade name): 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-methylpropanone (acetophenone-type photopolymerization initiator), manufactured by IGM Resins B.V.

The photocurable resin composition of the example containing a polymerizable monomer (A) having an oxyalkylene group and a water-soluble polymerizable monomer (B) other than the polymerizable monomer (A) had excellent curing properties as shown in Table 1, and a cured product (support material) with improved supportability, transparency, and solubility in water was obtained.

Claims (13)

A photocurable composition for a support material formed by an inkjet 3D printer, comprising a polymerizable monomer (A) having an oxyalkylene group and a water-soluble polymerizable monomer (B) other than the polymerizable monomer (A). The photocurable composition according to claim 1, wherein the polymerizable monomer (B) is an ionic monomer having an ionic group. The photocurable composition according to claim 2, wherein the ionic monomer includes an ionic monomer having a polyvalent metal ion that pairs with the ionic group. The photocurable composition according to claim 3, wherein the content of the ionic monomer having a polyvalent metal ion is 50% by mass or more in 100% by mass of the polymerizable monomer (B). The photocurable composition according to claim 1, wherein the total content of the polymerizable monomer (A) and the polymerizable monomer (B) is less than 50% by mass in 100% by mass of the photocurable composition. The photocurable composition according to claim 1 , wherein the polymerizable monomer (A) is a monomer represented by the following formula (1):
Z-(R ^a -O) _n -R ^b ...(1)
[In formula (1), Z represents an ethylenically unsaturated bond-containing group, R ^a represents an alkylene group, R ^b represents a hydrogen atom or a hydrocarbon group which may have a substituent, and n represents an integer of 1 or more. When n is an integer of 2 or more, the multiple R ^a 's may be the same or different.] In the formula (1),
Z is a group represented by CH ₂ ═C(R ¹ )-C(═O)-O-* or CH ₂ ═C(R ¹ )-(CH ₂ ) _m -O-* (R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent, m represents an integer of 0 to 6, and * represents a bond),
R ^a represents an alkylene group having 1 to 4 carbon atoms;
R ^b represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms;
The photocurable composition according to claim 6, wherein n is an integer of 1 to 100. The photocurable composition according to claim 1, further comprising a photopolymerization initiator. 2. The photocurable composition according to claim 1, wherein when a piece of the cured product (2 cm × 2 cm × 3 mm) obtained by irradiating the piece with light at 100 mW/ ^cm2 for 3 minutes is added to 50 mL of water at 25°C and allowed to stand for 3 hours, 50 mass% or more of the cured product piece dissolves. A method for producing a support material, comprising irradiating the photocurable composition according to any one of claims 1 to 9 with light. a step of forming a photo-modeled object precursor, the step of forming a supporting material layer by irradiating the photocurable composition according to any one of claims 1 to 9 with light, and the step of forming a model material layer by repeating the step of forming a supporting material layer multiple times and/or the step of forming a model material layer multiple times;
and removing the supporting material composed of the supporting material layer from the optically shaped object precursor. 　Use of the photocurable composition according to any one of claims 1 to 9 for forming a support material using an inkjet 3D printer. A photocurable composition (I) according to any one of claims 1 to 9,
a photocurable composition (II) different from the photocurable composition (I),
A method of using the photocurable composition (I) by ejecting it from different ejection heads in an inkjet 3D printer.