Stereolithographic resin composition

Abstract

The present invention provides a stereolithographic resin composition which is excellent in modeling accuracy, strength, toughness, and water resistance of a modeled article, and has little eluate from a modeled article. The present invention relates to a stereolithographic resin composition that contains a polyfunctional (meth)acrylic polymerizable compound (A) and a photopolymerization initiator (B) containing four or more heteroatoms per molecule. The stereolithographic resin composition preferably also contains a monofunctional (meth)acrylic polymerizable compound (C). The polyfunctional (meth)acrylic polymerizable compound (A) preferably contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500.

Description

Resin composition for stereolithography

[0001] The present invention relates to a stereolithography resin composition. More specifically, the present invention can provide a stereolithography material that exhibits excellent modeling accuracy, strength, toughness, and water resistance, and is biologically safe due to minimal elution from the stereolithography material. The stereolithography resin composition is ideal for dental applications, particularly dental occlusal splints, denture base materials, and treatment devices for sleep apnea syndrome.

[0002] Many proposals have been made regarding so-called optical three-dimensional modeling methods, which involve repeating the process of supplying a required amount of controlled light energy to a liquid photocurable resin to harden it into a thin layer, supplying more liquid photocurable resin on top of it, and then irradiating it with light under control to harden the resulting thin layer.

[0003] A typical method for optically producing a three-dimensional object is liquid vat stereolithography, in which a liquid surface of a liquid photocurable resin composition placed in a container is selectively irradiated with a computer-controlled ultraviolet laser to obtain the desired pattern, curing the composition to a predetermined thickness and forming a cured layer. Next, a layer of liquid photocurable resin composition is supplied on top of the cured layer, and similarly irradiated with an ultraviolet laser to cure the composition in the same manner as above, forming successive cured layers. This lamination process is repeated to produce a three-dimensional object of the final shape. This method has attracted considerable attention in recent years because it can produce the desired three-dimensional object easily, in a relatively short time, and with high accuracy, even if the object has a fairly complex shape.

[0004] The applications of three-dimensional objects obtained by stereolithography have expanded from mere concept models to test models, prototypes, and final products. In particular, in the field of dental materials, applications of stereolithography are expected to be expanded for dental occlusal splints, denture base materials, and mouthpiece-type sleep disorder treatment materials such as devices to prevent teeth grinding and treat sleep apnea syndrome, as the shapes vary from patient to patient and are complex.

[0005] Dental occlusal splints are devices worn to correct the alignment of teeth and jaw position, such as orthodontic mouthpieces and aligners, devices worn on the teeth to prevent tooth wear due to teeth grinding, and mouthguards worn in the oral cavity to reduce trauma caused by large external forces applied to the teeth and jawbone during contact sports and to protect the stomatognathic system and brain. In recent years, the use of orthodontic devices has rapidly expanded due to their aesthetic appeal and the ability to be removed whenever desired.

[0006] Denture base materials are materials used in the gum area when wearing dentures due to tooth loss. In recent years, the demand for dentures has increased dramatically due to the increase in the elderly population.

[0007] A device for treating sleep apnea syndrome is an apparatus (oral appliance: OA) that is attached to the teeth while sleeping at night to treat obstructive sleep apnea syndrome (OSAS), and its use is rapidly increasing.

[0008] Dental occlusal splints, denture base materials, and OAs all require molding precision, strength, toughness, and water resistance. Poor molding precision results in poor fit, impairing comfort, and the intended functionality is not achieved. Poor strength also results in significant deflection and deformation during wear, resulting in a poor wearing experience. Impaired toughness also leads to problems such as increased breakage due to occlusal loads and deformation during wear, necessitating frequent remaking. Impaired water resistance also leads to problems such as a decline in mechanical properties during use, making the splint more susceptible to deformation and breakage during wear, making it unsuitable for practical use.

[0009] Furthermore, when producing dental occlusal splints, denture base materials, and treatment devices for sleep apnea syndrome, it is usually necessary to take an intraoral impression. However, issues such as the discomfort this creates and the need for skilled laboratory procedures have been pointed out. In recent years, with the development of digital technology, attempts have been made to apply optical intraoral scanning to take impressions, and optical 3D modeling to mold. Stereolithography resin compositions are used in modeling, but generally, the stronger a resin composition is, the more brittle it tends to be, making it difficult to achieve toughness, i.e., flexibility. Therefore, in addition to the difficulty of achieving both strength and toughness, modeling ability and water resistance are also required, making it extremely difficult to develop a product that satisfies all of the requirements for modeling accuracy, strength, toughness, and water resistance.

[0010] Against this background, Patent Documents 1 and 2, for example, disclose examples of techniques for obtaining cured products excellent in strength, toughness, and water resistance, which combine a specific multifunctional methacrylate and a monofunctional acrylate having multiple aromatic rings as polymerizable compounds, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide as a photopolymerization initiator as essential components.

[0011] JP 2020-158417 A International Publication No. 2021 / 162007

[0012] However, upon investigation by the present inventor, it was found that although the resin compositions for stereolithography described in Patent Documents 1 and 2 are somewhat excellent in terms of modeling accuracy, and strength, toughness, and water resistance of the cured product, there is no mention of leaching properties, such as the tendency for decomposition products of the photopolymerization initiator and unpolymerized materials to leach out.

[0013] The inventors have discovered that when attempting to impart toughness, i.e., flexibility, in addition to strength to a cured product of a stereolithography resin composition, the monomer would be changed, but the molecular structure of the monomer used to impart flexibility would become flexible, making it easier for moisture to penetrate, which not only reduces strength but also poses a major problem of leaching, in that decomposition products of the photopolymerization initiator and unpolymerized materials would be more likely to leach out.

[0014] In particular, materials for stereolithography require a large amount of photopolymerization initiator because the light irradiation time is extremely short compared to dental materials not designed for stereolithography. For example, dental filling materials and dental resin cements, which have been widely used as photocurable dental materials used in the direct method, i.e., by intraoral curing, are typically irradiated with light for approximately 10 to 30 seconds using a dental light irradiator. When used in the indirect method, i.e., when cured outside the oral cavity and then used intraoral, they are typically irradiated with light for 60 seconds to several minutes using a dental laboratory irradiator. On the other hand, stereolithography, such as liquid vat stereolithography, typically uses light irradiation times of several tenths of a second or several seconds. Accordingly, the total amount of photopolymerization initiator contained in dental filling materials and dental resin cements is approximately 0.1% to 0.5% by mass, and in stereolithography materials, it is 1% to 5% by mass. As described above, the irradiation time of the stereolithography material is about one-tenth of that of conventional dental materials, and the content of the photopolymerization initiator is about ten times that of conventional dental materials. Therefore, the problem of elution from the cured product is particularly large compared to conventional dental materials, and it has been particularly difficult to satisfy all of the requirements for shaping accuracy, strength, toughness, water resistance, and suppression of elution from the shaped product.

[0015] As described above, it has been found that solving the problem of elution from the cured product is particularly important for materials for stereolithography, since the light irradiation time is extremely short compared to dental materials not for stereolithography, and a large amount of photopolymerization initiator must be blended in. However, reducing the content of the photopolymerization initiator in order to reduce decomposition products of the photopolymerization initiator results in a decrease in performance such as strength, and the requirement that a large amount of photopolymerization initiator must be blended in due to the unique circumstance of the short light irradiation time in materials for stereolithography cannot be met, making it extremely difficult to satisfy all of the requirements for modeling accuracy, strength, toughness, water resistance, and suppression of elution from the modeled product.

[0016] Therefore, an object of the present invention is to provide a resin composition for stereolithography that is excellent in modeling accuracy, strength, toughness, and water resistance of the modeled object, and that produces little elution from the modeled object.

[0017] That is, the present invention encompasses the following inventions: [1] A stereolithography resin composition comprising a polyfunctional (meth)acrylic polymerizable compound (A) and a photopolymerization initiator (B) containing four or more heteroatoms in one molecule, wherein the content of the photopolymerization initiator (B) containing four or more heteroatoms in one molecule is 0.75 to 3.0 parts by mass per 100 parts by mass of the total amount of polymerizable compounds; [2] The stereolithography resin composition according to [1], further comprising a monofunctional (meth)acrylic polymerizable compound (C); [3] The stereolithography resin composition according to [1] or [2], wherein the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500; [4] The stereolithography resin composition according to any one of [1] to [3], wherein the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more; [5] The stereolithography resin composition according to any one of [1] to [4], wherein the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500, and a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more; [6] The stereolithography resin composition according to any one of [1] to [5], wherein the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I-1 having a molecular weight of less than 500 and / or a (meth)acrylic polymerizable compound (A)-II-1 having a molecular weight of 500 or more and containing a urethane bond; [7] The stereolithography resin composition according to any one of [1] to [6], wherein the molecular weight of the photopolymerization initiator (B) is 400 or more; [8] The stereolithography resin composition according to any one of [1] to [7], wherein the photopolymerization initiator (B) contains two or more carbonyl groups in one molecule; [9] The stereolithography resin composition according to any one of [1] to [8], wherein the photopolymerization initiator (B) contains bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide;

[10] A dental material comprising an object shaped from the stereolithography resin composition according to any one of [1] to [9];

[11] A denture base material comprising an object shaped from the stereolithography resin composition according to any one of [1] to [9];

[12] A dental occlusal splint consisting of an object molded from the stereolithography resin composition according to any one of [1] to [9];

[13] A sleep disorder treatment material consisting of an object molded from the stereolithography resin composition according to any one of [1] to [9];

[14] A method for producing a three-dimensional object by a stereolithography method using the stereolithography resin composition according to any one of [1] to [9];

[0018] According to the present invention, a stereolithography resin composition can be provided that exhibits excellent modeling accuracy, strength, toughness, and water resistance of the molded object, and produces little elution from the molded object. Therefore, the stereolithography resin composition of the present invention is suitable for use as a denture base material, a dental material such as a dental occlusal splint, and also as a material for use in a treatment device for sleep apnea syndrome.

[0019] The present invention will be described in detail below using embodiments. In this specification, the upper and lower limits of numerical ranges (such as the content of each component, values ​​calculated from each component, and physical properties) can be combined as appropriate. For example, in this specification, the lower and upper limits of numerical ranges described in stages can be independently combined. For example, a description of the same item as "preferably 0.2 to 8.0 mass%, more preferably 0.5 to 5.0 mass%" can be combined with the "preferable lower limit (0.2 mass%)" and the "more preferable upper limit (5.0 mass%)" to yield "0.2 to 5.0 mass%" or 0.5 to 8.0 mass%. Furthermore, regarding a numerical range, for example, based on the description "more preferably 12 to 28 mass%, and even more preferably 12.5 to 25 mass%, " the upper limit can be specified without any particular upper limit, and only the lower limit can be specified as "12 mass% or more" or "12.5 mass% or more". Similarly, the lower limit can be specified without any particular lower limit, and only the upper limit can be specified as "28 mass% or less" or "25 mass% or less". Unless otherwise specified, when a numerical range is simply described as "30 to 70", it represents a range of 30 to 70. Furthermore, for example, when the numerical range is "25 mass% or more and 75 mass% or less", the boundary of the numerical range can be selected from any of "more than 25 mass%, "25 mass% or more", "75 mass% or less", and "less than 75 mass%". As above, for example, from the description "more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more" and the description "more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less" for the same item, the "more preferable lower limit (0.05 parts by mass or more)" and the "more preferable upper limit (10 parts by mass or less)" can be combined to form "0.05 parts by mass or more and 10 parts by mass or less." Also, as above, only the lower limit can be specified as "0.05 parts by mass or more" or "0.1 parts by mass or more," and similarly, only the upper limit can be specified as "15 parts by mass or less" or "10 parts by mass or less." The numerical ranges described above are merely examples of mass % and parts by mass, and the same applies to molecular weight, bending strength, bending modulus, etc.The present invention includes embodiments in which all or part of the embodiments described in this specification are combined in various ways within the scope of the technical idea of ​​the present invention, as long as the effects of the present invention are achieved.

[0020] In this specification, the term "polymerizable compound" refers to a polymerizable compound that is polymerized by the photopolymerization initiator (B) described below. In this specification, the term "(meth)acrylic" encompasses both "methacrylic" and "acrylic." The same applies to similar terms such as "(meth)acrylate," "(meth)acrylic acid ester," "(meth)acrylamide," and "(meth)acryloyloxy." In this specification, the term "(meth)acrylic polymerizable compound" encompasses both a polymerizable compound having a "(meth)acryloxy group" as a polymerizable group and a polymerizable compound having a "(meth)acrylamide group" as a polymerizable group. In this specification, the term "multifunctional" refers to a compound having more than one polymerizable group (e.g., a (meth)acrylic group). In this specification, the term "monofunctional" refers to a compound having one polymerizable group (e.g., a (meth)acrylic group). In this specification, the term "molecular weight" refers to a single value calculated from atomic weights when an oligomer or polymer structure is not contained, and refers to a weight average molecular weight when an oligomer or polymer structure is contained, unless otherwise specified, and means a weight average molecular weight calculated in terms of polystyrene obtained by gel permeation chromatography (GPC). In this specification, the term "heteroatom" contained in the photopolymerization initiator (B) refers to all atoms other than carbon atoms and hydrogen atoms.

[0021] The stereolithography resin composition of the present invention contains a polyfunctional (meth)acrylic polymerizable compound (A) and a photopolymerization initiator (B) containing four or more heteroatoms in one molecule.

[0022] [Polyfunctional (meth)acrylic polymerizable compound (A)] In the stereolithography resin composition of the present invention, the polyfunctional (meth)acrylic polymerizable compound (A) is used to impart curability to the stereolithography resin composition by combining it with a photopolymerization initiator (B), thereby imparting strength and toughness to the cured product. The polyfunctional (meth)acrylic polymerizable compound (A) preferably contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500 (also simply referred to as "polyfunctional (meth)acrylic polymerizable compound (A)-I") and / or a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more (also simply referred to as "polyfunctional (meth)acrylic polymerizable compound (A)-II"). The polyfunctional (meth)acrylic polymerizable compound (A)-I is used to impart particular strength to the cured product of the stereolithography resin composition. On the other hand, the polyfunctional (meth)acrylic polymerizable compound (A)-II is used to impart toughness to the cured product of the stereolithography resin composition. The polyfunctional (meth)acrylic polymerizable compound (A) may be used alone or in combination of two or more.

[0023] From the viewpoint of excellent water resistance, the polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500 preferably does not contain a polymer structure in one molecule, and more preferably is a methacrylate that does not contain a polymer structure in one molecule. When a polymer structure is not contained, the content per molecule of repeating units of polar functional groups such as ester groups, carbonate groups, urethane groups, ether groups, amide groups, imide groups, and arylate groups becomes small, and therefore water resistance tends to be excellent. Examples of polymer structures include polyester, polycarbonate, polyurethane, polyether, polyamide, polyimide, polyarylate, and polyacrylate.

[0024] The molecular weight of the polyfunctional (meth)acrylic polymerizable compound (A)-I must be less than 500, and from the viewpoint of strength and toughness, it is preferably 250 or more and 495 or less, and more preferably 300 or more and 490 or less.

[0025] Examples of the polyfunctional (meth)acrylic polymerizable compound (A)-I include a polyfunctional (meth)acrylic polymerizable compound (A)-I-1 containing a urethane bond (hereinafter also simply referred to as "polyfunctional (meth)acrylic polymerizable compound (A)-I-1") and a polyfunctional (meth)acrylic polymerizable compound (A)-I-2 not containing a urethane bond (hereinafter also simply referred to as "polyfunctional (meth)acrylic polymerizable compound (A)-I-2"). From the viewpoint of achieving better toughness in the cured product and of the urethane bond also functioning as a hydrogen-donating structure, thereby further improving curability and reducing leachable matter from the cured product, it is preferable to contain the polyfunctional (meth)acrylic polymerizable compound (A)-I-1, and it is more preferable that the polyfunctional (meth)acrylic polymerizable compound (A)-I-1 is a (meth)acrylate not containing a polymer structure in one molecule.

[0026] The polyfunctional (meth)acrylic polymerizable compound (A)-I-1 can be easily synthesized, for example, by addition reaction of a compound having an isocyanate group containing an alkylene skeleton or a phenylene skeleton with a (meth)acrylic compound having a hydroxyl group (—OH). Examples of the compound having an isocyanate group and the (meth)acrylic compound having a hydroxyl group (—OH) include the same compounds as those exemplified in the synthesis of the polyfunctional urethane-modified (meth)acrylic polymerizable compound (A)-II-1 described below. The addition reaction can be carried out using known methods and conditions, and is not particularly limited.

[0027] Examples of the polyfunctional (meth)acrylic polymerizable compound (A)-I-1 include hexamethylenebis(2-carbamoyloxyethyl)dimethacrylate, 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)dimethacrylate (commonly known as UDMA), 2,4-tolylenebis(2-carbamoyloxyethyl)di(meth)acrylate, bishydroxyethyl methacrylate-isophorone diurethane, and polyfunctional urethane-modified (meth)acrylate of 2,4-tolylenebis(2-carbamoyloxyethyl)dimethacrylate. These may be used alone or in combination of two or more. Among these, from the viewpoint of the strength and toughness of the shaped product, 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)dimethacrylate is preferred, 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)dimethacrylate and bishydroxyethyl methacrylate-isophorone diurethane are more preferred, and 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)dimethacrylate is even more preferred.

[0028] The content of the polyfunctional (meth)acrylic polymerizable compound (A)-I is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, even more preferably 25 to 70% by mass, and particularly preferably 30 to 60% by mass, based on 100% by mass of the total amount of the polymerizable compounds, in order to obtain a shaped product with superior strength and water resistance when combined with other components. The content of the polyfunctional (meth)acrylic polymerizable compound (A)-I can be appropriately selected from the above-mentioned ranges, and can be, for example, 25 to 55% by mass based on 100% by mass of the total amount of the polymerizable compounds. In another preferred embodiment, the content of the polyfunctional (meth)acrylic polymerizable compound (A)-I is preferably 20 to 90% by mass, more preferably 25 to 80% by mass, even more preferably 30 to 70% by mass, and particularly preferably 35 to 60% by mass, based on the total 100% by mass of the polyfunctional (meth)acrylic polymerizable compound (A), from the viewpoint of achieving superior strength of the molded object. In another preferred embodiment, the content of the polyfunctional (meth)acrylic polymerizable compound (A)-I is preferably 10 to 70% by mass, more preferably 20 to 65% by mass, even more preferably 20 to 60% by mass, and particularly preferably 30 to 55% by mass, based on the total 100% by mass of the stereolithography resin composition, from the viewpoint of achieving superior strength, toughness, and water resistance of the molded object when combined with other components. It is most preferably 35 to 50% by mass. In any embodiment herein, the content of the polyfunctional (meth)acrylic polymerizable compound (A)-I can be read as the content of the polyfunctional (meth)acrylic polymerizable compound (A)-I-1, since the amount of elution from the cured product can be further reduced.

[0029] In another preferred embodiment, the content of the polyfunctional (meth)acrylic polymerizable compound (A)-I-1 in the polyfunctional (meth)acrylic polymerizable compound (A)-I is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, and particularly preferably 80% by mass or more, based on the viewpoint of superior strength of the shaped object and the fact that the urethane bond also functions as a hydrogen donor structure, further improving curability and reducing elution from the cured product. Furthermore, in a preferred embodiment, the content of the polyfunctional (meth)acrylic polymerizable compound (A)-I-1 in the polyfunctional (meth)acrylic polymerizable compound (A)-I may be 100% by mass.

[0030] Examples of the polyfunctional (meth)acrylic polymerizable compound (A)-I include bifunctional (meth)acrylic polymerizable compounds and trifunctional or higher functional (meth)acrylic polymerizable compounds. From the viewpoint of toughness of the cured product, bifunctional (meth)acrylic polymerizable compounds are preferred.

[0031] Examples of the polyfunctional (meth)acrylic polymerizable compound (A)-I-2 include 2,2-bis((meth)acryloyloxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypropoxyphenyl)propane, 2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxyisopropoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane (average number of moles of ethoxy groups added: 2.6), 1,4-bis(2-(meth)acryloyloxyethyl)pyromellitate, glycerol di(meth)acrylate, ethylene glycol di(meth)acrylate, 1,4-bis(2-(meth)acryloyloxyethyl)pyromellitate ... ) acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 2-ethyl-1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,2-bis(3-methacryloyloxy-2-hydroxypropoxy)ethane, tricyclodecane dimethanol di(meth)acrylate, and the like.

[0032] Examples of trifunctional or higher functional polymerizable compounds include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolmethane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate.

[0033] The polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more (hereinafter also referred to simply as "polyfunctional (meth)acrylic polymerizable compound (A)-II") is used in the stereolithography resin composition of the present invention to impart toughness to the cured product.

[0034] The polyfunctional (meth)acrylic polymerizable compound (A)-II is classified into polyfunctional (meth)acrylic polymerizable compounds containing an oligomer or polymer structure and polyfunctional (meth)acrylic polymerizable compounds not containing an oligomer or polymer structure. From the viewpoint of achieving excellent strength and toughness of a shaped product when combined with other components, it is preferable to contain a polyfunctional (meth)acrylic polymerizable compound containing an oligomer or polymer structure. Furthermore, examples of the polyfunctional (meth)acrylic polymerizable compound (A)-II include a polyfunctional (meth)acrylic polymerizable compound (A)-II-1 containing a urethane bond (hereinafter also simply referred to as "polyfunctional (meth)acrylic polymerizable compound (A)-II-1") and a polyfunctional (meth)acrylic polymerizable compound (A)-II-2 containing no urethane bond. From the viewpoint of excellent toughness of the cured product and the fact that the urethane bond also functions as a hydrogen-donor structure, further improving curability and reducing leachable matter from the cured product, it is preferable to contain the polyfunctional (meth)acrylic polymerizable compound (A)-II-1, and it is more preferable to contain a polyfunctional urethanated (meth)acrylic polymerizable compound (A)-II-1 containing an oligomer or polymer structure. In a preferred embodiment, a stereolithography resin composition containing the polyfunctional (meth)acrylic polymerizable compound (A)-I-1 and / or the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 can be used, from the viewpoint of achieving superior toughness of the cured product and of enabling the urethane bond to also function as a hydrogen-donating structure, thereby further improving curability and reducing elution from the cured product. In a particularly preferred embodiment, a stereolithography resin composition containing the polyfunctional (meth)acrylic polymerizable compound (A)-I-1 and the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 can be used, from the viewpoint of achieving superior strength and water resistance of the cured product, suppressing elution from the cured product, and achieving superior toughness of the cured product.

[0035] When the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 contains an oligomer or polymer structure, the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 containing an oligomer or polymer structure can be easily synthesized by addition reaction of a polyol having a polymer skeleton such as a polymer structure of polyester, polycarbonate, polyurethane, polyether, polydiene, hydrogenated polydiene, etc., with a compound having an isocyanate group (-NCO), and a (meth)acrylic compound having a hydroxyl group (-OH). Alternatively, the polyfunctional (meth)acrylic compound can be easily synthesized by ring-opening addition reaction of a lactone or alkylene oxide with a (meth)acrylic compound having a hydroxyl group, followed by addition reaction of the resulting compound having a hydroxyl group at one end with a compound having an isocyanate group.

[0036] When the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 contains an oligomer or polymer structure, the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 containing an oligomer or polymer structure is preferably a (meth)acrylate containing, in one molecule, at least one structure selected from the group consisting of polyester, polycarbonate, polyurethane, polyether, polyconjugated diene, and hydrogenated polyconjugated diene.

[0037] In the above structure, examples of the polyester include copolymers of dicarboxylic acids (e.g., aromatic dicarboxylic acids such as phthalic acid and isophthalic acid; unsaturated aliphatic dicarboxylic acids such as maleic acid) and aliphatic diols having 2 to 18 carbon atoms, copolymers of dicarboxylic acids (e.g., saturated aliphatic dicarboxylic acids such as adipic acid and sebacic acid) and aliphatic diols having 2 to 18 carbon atoms, β-propiolactone polymers, γ-butyrolactone polymers, δ-valerolactone polymers, ε-caprolactone polymers, and copolymers thereof, and preferred are copolymers of dicarboxylic acids (preferably aromatic dicarboxylic acids, unsaturated aliphatic dicarboxylic acids) and aliphatic diols having 2 to 12 carbon atoms, and copolymers of dicarboxylic acids (preferably saturated aliphatic dicarboxylic acids) and aliphatic glycols having 2 to 12 carbon atoms. Examples of polycarbonates include polycarbonates derived from aliphatic diols having 2 to 18 carbon atoms, polycarbonates derived from bisphenol A, and polycarbonates derived from aliphatic diols having 2 to 18 carbon atoms and bisphenol A, with polycarbonates derived from aliphatic diols having 2 to 12 carbon atoms, polycarbonates derived from bisphenol A, and polycarbonates derived from aliphatic diols having 2 to 12 carbon atoms and bisphenol A being preferred. Examples of polyurethanes include polymers of aliphatic diols having 2 to 18 carbon atoms and diisocyanates having 1 to 18 carbon atoms, with polymers of aliphatic diols having 2 to 12 carbon atoms and diisocyanates having 1 to 12 carbon atoms being preferred. Examples of polyethers include polyethylene glycol, polypropylene glycol, polybutylene glycol, and poly(1-methylbutylene glycol). Examples of polyconjugated dienes and hydrogenated polyconjugated dienes include 1,4-polybutadiene, 1,2-polybutadiene, polyisoprene, poly(butadiene-isoprene), poly(butadiene-styrene), poly(isoprene-styrene), polyfarnesene, and hydrogenated products thereof. Among these, polyester structures are preferred because of their excellent toughness and water resistance.

[0038] In view of superior toughness and water resistance, the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 is preferably a (meth)acrylate containing, in one molecule, at least one polyol moiety selected from the group consisting of polyesters, polycarbonates, polyurethanes, polyethers, polyconjugated dienes, and hydrogenated polyconjugated dienes, each having a structure derived from a branched aliphatic chain diol unit having 4 to 18 carbon atoms. Examples of the polyester include copolymers having a structure derived from a branched aliphatic chain diol unit having 4 to 18 carbon atoms and a structure derived from an unbranched aliphatic chain dicarboxylic acid and / or aromatic dicarboxylic acid unit having 4 to 18 carbon atoms. Examples of the polycarbonate include copolymers having a structure derived from a branched aliphatic chain diol unit having 4 to 18 carbon atoms and a structure derived from an unbranched aliphatic chain diol unit having 4 to 18 carbon atoms. Examples of the polyurethane include a polycondensate of a structure derived from a branched aliphatic chain diol unit having 4 to 18 carbon atoms and a diisocyanate compound. Examples of the polyether include a polyether having a structure derived from a branched aliphatic chain diol unit having 4 to 18 carbon atoms, and a polyether having a structure derived from a non-branched aliphatic chain diol unit having 4 to 18 carbon atoms. Examples of the polyconjugated diene include a homopolymer or copolymer of a conjugated diene polymerizable compound. Examples of the conjugated diene polymerizable compound include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Examples of the hydrogenated polyconjugated diene include hydrogenated polybutadiene, hydrogenated polyisoprene, and hydrogenated polyisobutylene.Among these, in terms of excellent toughness and water resistance, it is preferable that the polymer skeleton contains at least one structure selected from the group consisting of polyesters, polycarbonates, polyethers, and hydrogenated polyconjugated dienes, it is more preferable that the polymer skeleton contains at least one structure selected from the group consisting of polyesters and polycarbonates, and it is even more preferable that the polymer skeleton contains at least one structure selected from the group consisting of polyesters.

[0039] Examples of diols constituting the aliphatic chain diol unit having 4 to 18 carbon atoms and a branched structure include 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,3-butanediol, 2-methyl-1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1,8-octanediol, 2-methyl-1,9-nonanediol, 2,8-dimethyl-1,9-nonanediol, 2-methyl-1,10-decanediol, 2,9-dimethyl-1,10-decanediol, 2-methyl-1,1 Examples of the diol include 1-undecanediol, 2,10-dimethyl-1,11-undecanediol, 2-methyl-1,12-dodecanediol, 2,11-dimethyl-1,12-dodecanediol, 2-methyl-1,13-tridecanediol, 2,12-dimethyl-1,13-tridecanediol, 2-methyl-1,14-tetradecanediol, 2,13-dimethyl-1,14-tetradecanediol, 2-methyl-1,15-pentadecanediol, 2,14-dimethyl-1,15-pentadecanediol, 2-methyl-1,16-hexadecanediol, and 2,15-dimethyl-1,16-hexadecanediol. Among these, from the viewpoint of achieving excellent curability and low viscosity in the stereolithography resin composition, it is preferable to use an aliphatic diol having 5 to 12 carbon atoms and having a methyl group as a side chain, such as 2-methyl-1,4-butanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1,8-octanediol, 2-methyl-1,9-nonanediol, or 2,8-dimethyl-1,9-nonanediol, as the polyol; 2-methyl-1,4-butanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, or 2,7-dimethyl-1,8-octanediol are more preferable, and 3-methyl-1,5-pentanediol or 2-methyl-1,8-octanediol are even more preferable.

[0040] Examples of compounds having an isocyanate group include hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMHMDI), tricyclodecane diisocyanate (TCDDI), and adamantane diisocyanate (ADI).

[0041] Examples of the (meth)acrylic compound having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, glycerin mono(meth)acrylate, and 2-hydroxy-3-acryloyloxypropyl (meth)acrylate. hydroxy(meth)acrylate compounds such as dipentaerythritol, 2,2-bis[4-(2-hydroxy-3-(meth)acryloyloxypropoxy)phenyl]propane, 1,2-bis[3-(meth)acryloyloxy-2-hydroxypropoxy]ethane, pentaerythritol tri(meth)acrylate, and dipentaerythritol tri- or tetra(meth)acrylate; and hydroxy(meth)acrylamide compounds such as N-hydroxyethyl(meth)acrylamide and N,N-bis(2-hydroxyethyl)(meth)acrylamide. When the desired polyfunctional (meth)acrylic polymerizable compound (A)-II-1 is a (meth)acrylate compound, it can be produced by selecting a hydroxy(meth)acrylate compound.

[0042] The addition reaction between a compound having an isocyanate group and a (meth)acrylic compound having a hydroxyl group can be carried out using known methods and conditions, and is not particularly limited.

[0043] Examples of the polyfunctional urethane-modified (meth)acrylic polymerizable compound (A)-II-1 that does not contain a polymer structure include dipentaerythritol penta(meth)acrylate hexamethylene diisocyanate urethane prepolymer.

[0044] The molecular weight of the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 must be 500 or more, preferably 600 or more, more preferably 700 or more, and from the viewpoint of strength and toughness, even more preferably 750 or more, and particularly preferably 1000 or more. The molecular weight of the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 is preferably 6000 or less, more preferably 5500 or less, and from the viewpoint of strength and toughness, even more preferably 5000 or less, and particularly preferably 3000 or less. That is, from the viewpoint of strength and toughness, the molecular weight of the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 is preferably 750 to 5000, and more preferably 1000 to 3000.

[0045] Examples of the polyfunctional (meth)acrylic polymerizable compound (A)-II include bifunctional (meth)acrylic polymerizable compounds and trifunctional or higher functional (meth)acrylic polymerizable compounds.

[0046] In a preferred embodiment, the content of the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, even more preferably 15 to 60% by mass, and particularly preferably 20 to 50% by mass, based on 100% by mass of the total amount of the polymerizable compounds, from the viewpoint that when combined with other components, the shaped object will have better strength, toughness, and water resistance, and that the urethane bond also functions as a hydrogen-donating structure, further improving curability and reducing elution from the cured object. In another preferred embodiment, the content of the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 is preferably 10 to 75% by mass, more preferably 15 to 70% by mass, even more preferably 20 to 65% by mass, and particularly preferably 25 to 60% by mass, based on 100% by mass of the total amount of the polyfunctional (meth)acrylic polymerizable compound (A), from the viewpoints that when the compound is combined with other components, the strength, toughness, and water resistance of a shaped object will be superior, and that the urethane bond also functions as a hydrogen-donor structure, further improving curability and reducing elution from the cured product. In another preferred embodiment, the content of the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 is preferably 1 to 70% by mass, more preferably 5 to 60% by mass, even more preferably 10 to 50% by mass, and particularly preferably 20 to 40% by mass, based on 100% by mass of the total amount of the stereolithography resin composition, from the viewpoints that when combined with other components, the strength, toughness, and water resistance of the shaped object will be superior, and that the urethane bond also functions as a hydrogen-donating structure, further improving the curability and reducing the amount of elution from the cured product.

[0047] The content of the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, and particularly preferably 80% by mass or more, based on the viewpoint that when combined with other components, the strength, toughness, and water resistance of the cured product are superior, and the urethane bond also functions as a hydrogen donor structure, further improving curability and reducing elution from the cured product. Furthermore, the content of the polyfunctional (meth)acrylic polymerizable compound (A)-II-1 in the polyfunctional (meth)acrylic polymerizable compound (A)-II may be 100% by mass.

[0048] Examples of the polyfunctional (meth)acrylic polymerizable compound (A)-II-2 that does not contain a urethane bond include bifunctional (meth)acrylic polymerizable compounds and trifunctional or higher functional (meth)acrylic polymerizable compounds.

[0049] Examples of the polyfunctional (meth)acrylic polymerizable compound (A)-II-2 not containing a urethane bond include 2,2-bis(4-(meth)acryloyloxydiethoxyphenyl)propane, 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (commonly known as "Bis-GMA"), 2,2-bis(4-(meth)acryloyloxytetraethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypentaethoxyphenyl)propane, and 2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane. , 2-(4-(meth)acryloyloxydipropoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane (for example, an average number of moles of ethoxy groups added: 4 or more), polyethylene glycol di(meth)acrylate, and other bifunctional (meth)acrylic polymerizable compounds; and trifunctional or higher functional (meth)acrylic polymerizable compounds such as dipentaerythritol penta(meth)acrylate and 1,7-di(meth)acryloyloxy-2,2,6,6-tetra(meth)acryloyloxymethyl-4-oxaheptane. Examples of the polyfunctional (meth)acrylic polymerizable compound (A)-II-2 that does not contain a urethane bond are preferably polymerizable compounds that do not have a hydroxyl group, as they have better water resistance.

[0050] The content of the polyfunctional (meth)acrylic polymerizable compound (A)-II in the stereolithography resin composition of the present invention is preferably 1 to 80% by mass, more preferably 5 to 70% by mass, even more preferably 10 to 60% by mass, and particularly preferably 20 to 50% by mass, based on 100% by mass of the total amount of polymerizable compounds, in order to achieve superior strength, toughness, and water resistance of the cured product when combined with other components. The content of the polyfunctional (meth)acrylic polymerizable compound (A)-II can be appropriately selected from the above-mentioned ranges, and can be, for example, 15 to 45% by mass based on 100% by mass of the total amount of polymerizable compounds. One type of polyfunctional (meth)acrylic polymerizable compound (A)-II may be used alone, or two or more types may be used in combination. Furthermore, the content of the polyfunctional (meth)acrylic polymerizable compound (A)-II in the stereolithography resin composition of the present invention is preferably 10 to 60 mass%, more preferably 15 to 65 mass%, even more preferably 20 to 50 mass%, particularly preferably 25 to 45 mass%, and most preferably 25 to 40 mass%, based on the total amount (100 mass%) of the stereolithography resin composition, from the viewpoint that the strength, toughness, and water resistance of the cured product when combined with other components are superior.

[0051] In the stereolithography resin composition of the present invention, the ratio of the content of the polyfunctional (meth)acrylic polymerizable compound (A)-I to the content of the polyfunctional (meth)acrylic polymerizable compound (A)-II ((A)-I:(A)-II) is preferably 5:95 to 95:5, more preferably 10:90 to 90:10, and even more preferably 20:80 to 80:20, in terms of achieving superior strength, toughness, and water resistance of the cured product. In a preferred embodiment, the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500 and a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more, and the mass ratio of the content of the polyfunctional (meth)acrylic polymerizable compound (A)-I to the content of the polyfunctional (meth)acrylic polymerizable compound (A)-II is (A)-I:(A)-II = 51:49 to 95:5, from the viewpoint of achieving superior strength, toughness, and water resistance of the cured product. The mass ratio of (A)-I:(A)-II is more preferably 52:48 to 90:10, and even more preferably 55:45 to 80:20. In the preferred embodiment, the content of the monofunctional (meth)acrylic polymerizable compound (C) in the stereolithography resin composition is 7 to 40 mass % relative to 100 mass % of the total amount of the polymerizable compounds.

[0052] The content of the polyfunctional (meth)acrylic polymerizable compound (A) in the stereolithography resin composition of the present invention is preferably 10 to 95% by mass, based on 100% by mass of the total amount of polymerizable compounds. From the viewpoint of superior strength, toughness, and water resistance of the molded object when combined with other components, it is more preferably 20 to 92% by mass, even more preferably 30 to 90% by mass, and particularly preferably 40 to 85% by mass. Furthermore, the content of the polyfunctional (meth)acrylic polymerizable compound (A) in the stereolithography resin composition of the present invention is preferably 10 to 96% by mass, based on 100% by mass of the total amount of the stereolithography resin composition, based on superior strength, toughness, and water resistance of the molded object when combined with other components, it is more preferably 20 to 94% by mass, even more preferably 30 to 92% by mass, particularly preferably 40 to 90% by mass, and most preferably 50 to 90% by mass.

[0053] [Photopolymerization initiator (B) containing four or more heteroatoms in one molecule] The photopolymerization initiator (B) containing four or more heteroatoms in one molecule used in the present invention (sometimes simply referred to as "photopolymerization initiator (B)") is used in the stereolithography resin composition of the present invention to impart curability to the stereolithography resin composition by combining it with a polyfunctional (meth)acrylic polymerizable compound (A) and, preferably, a monofunctional (meth)acrylic polymerizable compound (C) as needed, thereby imparting low leachability to the cured product.

[0054] It is important that the photopolymerization initiator (B) of the present invention contains four or more heteroatoms per molecule. The inclusion of four or more heteroatoms per molecule increases the absorption coefficient and the number of cleavage sites, resulting in the generation of more active polymerization-initiating species per molecule. This improves initiator efficiency (meaning the proportion of the photopolymerization initiator that actually functions as an initiator), enabling polymerization initiation with a low light exposure. Furthermore, it is believed that the active polymerization-initiating species cleaved by light exposure favor the polymerization initiation reaction over the concurrent hydrogen abstraction reaction. Residues of the photopolymerization initiator generated by the hydrogen abstraction reaction become free low-molecular-weight compounds, causing an increase in elution. On the other hand, in the case of a polymerization initiation reaction, the photopolymerization initiator is incorporated into the cured product as a photopolymerization initiator residue, preventing elution. For these reasons, when the photopolymerization initiator (B) of the present invention is combined with the polyfunctional (meth)acrylic polymerizable compound (A), it improves the curability of the stereolithography resin composition and improves the mechanical properties of the cured product, thereby achieving excellent modeling precision, strength, toughness, and water resistance, and making it possible to suppress elution from the modeled product (cured product).

[0055] The heteroatoms contained in the photopolymerization initiator (B) of the present invention are all atoms other than carbon and hydrogen atoms, and from the viewpoint of having a strong effect of extending the life of the polymerization initiation active species generated from the photopolymerization initiator and improving initiator efficiency, it is preferable to contain a nitrogen atom, an oxygen atom, a fluorine atom, a phosphorus atom, a sulfur atom, an iron atom, or a titanium atom, and it is more preferable to contain at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, a phosphorus atom, and a sulfur atom, and further from the viewpoint of being less likely to absorb light in the visible light range and less likely to impair color tone, it is even more preferable to contain at least one atom selected from the group consisting of an oxygen atom and a phosphorus atom. The type of heteroatom contained in the photopolymerization initiator (B) may be only one type, or may be two or more types.

[0056] Furthermore, the photopolymerization initiator (B) of the present invention preferably has a molecular weight of 400 or more, from the viewpoint of achieving excellent modeling accuracy, strength, toughness, and water resistance when combined with the polyfunctional (meth)acrylic polymerizable compound (A), and suppressing elution from the cured product. Having a molecular weight of 400 or more, i.e., a larger molecule, reduces mobility within the cured product, making it possible to suppress elution from the cured product of the stereolithography resin composition of the present invention. A preferred embodiment includes a stereolithography resin composition in which the heteroatom contained in the photopolymerization initiator (B) is at least one selected from the group consisting of an oxygen atom and a phosphorus atom, and the molecular weight of the photopolymerization initiator (B) is 400 or more.

[0057] Furthermore, the photopolymerization initiator (B) of the present invention preferably contains two or more carbonyl groups per molecule, from the viewpoint of improving the curability of the stereolithography resin composition and improving the mechanical properties of the cured product, thereby achieving excellent modeling accuracy, strength, toughness, and water resistance, and further suppressing elution from the cured product. Having two or more carbonyl groups per molecule increases the number of cleavage points and the number of active species for polymerization initiation generated from one molecule, thereby further improving initiator efficiency. When combined with a polyfunctional (meth)acrylic polymerizable compound (A) in a stereolithography resin composition, polymerization initiation is possible even with a low light exposure dose. This allows the cured product of the stereolithography resin composition of the present invention to have a high polymerization rate, excellent mechanical properties, and a dense structure, thereby suppressing elution from the cured product. A preferred embodiment of the present invention is a stereolithography resin composition in which the photopolymerization initiator (B) contains two or more carbonyl groups per molecule and has a molecular weight of 400 or more. Another preferred embodiment is a resin composition for stereolithography, in which the heteroatoms of the photopolymerization initiator (B) are oxygen atoms and phosphorus atoms, the photopolymerization initiator (B) contains two or more carbonyl groups in one molecule, and has a molecular weight of 400 or more.

[0058] Examples of the photopolymerization initiator (B) include (bis)acylphosphine oxides, thioxanthones or quaternary ammonium salts of thioxanthones, ketals, α-diketones, coumarins, anthraquinones, benzoin alkyl ether compounds, α-aminoketone compounds, etc. One type of photopolymerization initiator (B) may be used alone, or two or more types may be used in combination.

[0059] Among these photopolymerization initiators (B), it is preferable to use at least one selected from the group consisting of bisacylphosphine oxides and oxime esters, and bisacylphosphine oxides are more preferable, thereby obtaining a stereolithography resin composition that has excellent photocurability in the ultraviolet and visible light regions and exhibits sufficient photocurability using any of a laser, a halogen lamp, a light-emitting diode (LED), and a xenon lamp as a light source.

[0060] Examples of bisacylphosphine oxides include bis(2,6-dichlorobenzoyl)phenylphosphine oxide, bis(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,5,6-trimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide, and ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate. Further examples include compounds described in JP-A No. 2000-159621. Among these, bis(2,6-dichlorobenzoyl)phenylphosphine oxide, bis(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate are preferred, bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide are more preferred, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is even more preferred, from the viewpoint that elution from the cured product is easily suppressed by acting integrally with the polyfunctional (meth)acrylic polymerizable compound (A) in the stereolithography resin composition.

[0061] Examples of the oxime ester compounds used as the photopolymerization initiator include 1,2-octanedione 1-[4-(phenylthio)phenyl]-2-(o-benzoyloxime) (also known as 1-[4-(phenylthio)phenyl]octane-1,2-dione-2-(o-benzoyloxime)), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(o-acetyloxime) (also known as Irgacure OXE-02), and the like.

[0062] From the viewpoint of modeling accuracy, it is important that the content of the photopolymerization initiator (B) in the stereolithography resin composition of the present invention is 0.75 to 3.0 parts by mass per 100 parts by mass of the total amount of polymerizable compounds. If the content of the photopolymerization initiator (B) is less than 0.75 parts by mass, the irradiated light will be more likely to penetrate the resin composition, which may reduce modeling accuracy and prevent the production of a model with the desired shape. On the other hand, if the content of the photopolymerization initiator (B) exceeds 3.0 parts by mass, the light will be blocked more strongly, weakening the bonds between layers and potentially resulting in modeling defects. The content of the photopolymerization initiator (B) is, relative to the total amount of 100 parts by mass, more preferably 0.8 parts by mass or more, even more preferably 0.9 parts by mass or more, and particularly preferably 1.0 parts by mass or more, from the viewpoint that when combined with the polyfunctional (meth)acrylic polymerizable compound (A) (and, if necessary, with the monofunctional (meth)acrylic polymerizable compound (C)), it acts as a unified unit, excellent in molding accuracy, strength, toughness, and water resistance, and can reduce elution from the cured product. The content of the photopolymerization initiator (B) is, relative to the total amount of 100 parts by mass, more preferably 2.5 parts by mass or less, even more preferably 2.0 parts by mass or less, and particularly preferably 1.5 parts by mass or less, from the viewpoint that when combined with the polyfunctional (meth)acrylic polymerizable compound (A) (and, if necessary, with the monofunctional (meth)acrylic polymerizable compound (C)), it acts as a unified unit, excellent in molding accuracy, strength, toughness, and water resistance, and can reduce elution from the cured product.

[0063] The stereolithography resin composition of the present invention is not particularly limited as long as it contains the above-mentioned polyfunctional (meth)acrylic polymerizable compound (A) and photopolymerization initiator (B), and may contain, for example, other components. The method for producing the stereolithography resin composition of the present invention is not particularly limited, and the stereolithography resin composition of the present invention can be produced in accordance with known methods for producing stereolithography resin compositions.

[0064] [Monofunctional (meth)acrylic polymerizable compound (C)] The stereolithography resin composition of the present invention preferably further contains a monofunctional (meth)acrylic polymerizable compound (C) that acts integrally when combined with the polyfunctional (meth)acrylic polymerizable compound (A) to improve modeling properties by reducing viscosity, improve toughness, and improve water resistance. The monofunctional (meth)acrylic polymerizable compound (C) may be used alone or in combination of two or more. A preferred embodiment includes a stereolithography resin composition in which the monofunctional (meth)acrylic polymerizable compound (C) is a monofunctional acrylic polymerizable compound.

[0065] Examples of the monofunctional (meth)acrylic polymerizable compound (C) include o-phenylphenyl (meth)acrylate, m-phenylphenyl (meth)acrylate, p-phenylphenyl (meth)acrylate, ethoxylated o-phenylphenol (meth)acrylate, ethoxylated m-phenylphenol (meth)acrylate, ethoxylated p-phenylphenol (meth)acrylate, propoxylated o-phenylphenol (meth)acrylate, propoxylated m-phenylphenol (meth)acrylate, propoxylated p-phenylphenol (meth)acrylate, butoxylated o-phenylphenol (meth)acrylate, butoxylated m-phenylphenol (meth)acrylate, butoxylated p-phenylphenol (meth)acrylate, diphenylmethyl (meth)acrylate, 4-(1-methyl-1-phenylethyl) (meth)acrylate, triphenylmethyl (meth)acrylate, o-phenylphenol ... phenoxyphenyl (meth)acrylate, m-phenoxyphenyl (meth)acrylate, p-phenoxyphenyl (meth)acrylate, o-phenoxybenzyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate, p-phenoxybenzyl (meth)acrylate, 2-(o-phenoxyphenyl)ethyl (meth)acrylate, 2-(m-phenoxyphenyl)ethyl (meth)acrylate, 2-(p-phenoxyphenyl)ethyl (meth)acrylate (meth)acrylic acid ester compounds containing two or more aromatic rings, such as acrylate, 3-(o-phenoxyphenyl)propyl (meth)acrylate, 3-(m-phenoxyphenyl)propyl (meth)acrylate, 3-(p-phenoxyphenyl)propyl (meth)acrylate, 9-(meth)acryloyloxyfluorene, 9-(meth)acryloyloxymethylfluorene, N-(meth)acryloylcarbazole, and N-(meth)acryloylmethylcarbazole;(Meth)acrylic acid ester compounds containing one aromatic ring, such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxybutyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, 4-methylphenyl (meth)acrylate, 4-n-butylphenyl (meth)acrylate, 4-t-butylphenyl (meth)acrylate, 4-nonylphenyl (meth)acrylate, o-2-propenylphenyl (meth)acrylate, benzhydrol (meth)acrylate, and cumylphenol (meth)acrylate; cyclic trimethylolpropane formal (meth)acrylate, isobornyl (meth)acrylate, 2-(1-adamantyl)propyl (meth)acrylate, (meth)acrylic acid ester compounds containing one aromatic ring, such as methylphenyl (meth)acrylate, ... Alicyclic (meth)acrylic acid ester compounds such as 2-methyladamantyl-2-yl acrylate, 2-ethyladamantyl-2-yl (meth)acrylate, 2-n-propyladamantyl-2-yl (meth)acrylate, 2-isopropyladamantyl-2-yl (meth)acrylate, 1-(adamantan-1-yl)-1-methylethyl (meth)acrylate, 1-(adamantan-1-yl)-1-ethylethyl (meth)acrylate, 1-(adamantan-1-yl)-1-methylpropyl (meth)acrylate, and 1-(adamantan-1-yl)-1-ethylpropyl (meth)acrylate; nitrogen atom-containing cyclic (meth)acrylic acid ester compounds such as pentamethylpiperidinyl (meth)acrylate, tetramethylpiperidinyl (meth)acrylate, and 4-(pyrimidin-2-yl)piperazin-1-yl (meth)acrylate;Examples of the cyclic (meth)acrylamide compounds include N-(meth)acryloylmorpholine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylpiperidine, N-(meth)acryloyl-2-methylpiperidine, and N-(meth)acryloyl-2,2,6,6-tetramethylpiperidine. Among these, (meth)acrylic acid ester compounds and alicyclic (meth)acrylic acid ester compounds containing two or more aromatic rings are preferred, and from the viewpoint of providing a stereolithography resin composition with low viscosity and excellent shaping properties and a shaped product with excellent water resistance, (meth)acrylic acid ester compounds containing two or more aromatic rings are more preferred, and examples thereof include ethoxylated-o-phenylphenol (meth)acrylate, ethoxylated-m-phenylphenol (meth)acrylate, ethoxylated-p-phenylphenol (meth)acrylate, o-phenoxybenzyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate, p-phenoxybenzyl (meth)acrylate, 2-(o-phenoxyphenyl)ethyl (meth)acrylate, 2-(m-phenoxybenzyl)ethyl (meth)acrylate, and 2-(o-phenoxyphenyl)ethyl (meth)acrylate. More preferred are 2-(p-phenoxyphenyl)ethyl (meth)acrylate, 2-(p-phenoxyphenyl)ethyl (meth)acrylate, and even more preferred are ethoxylated o-phenylphenol (meth)acrylate, ethoxylated m-phenylphenol (meth)acrylate, ethoxylated p-phenylphenol (meth)acrylate, o-phenoxybenzyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate, and p-phenoxybenzyl (meth)acrylate, and even more preferred are ethoxylated o-phenylphenol (meth)acrylate, o-phenoxybenzyl (meth)acrylate, and m-phenoxybenzyl (meth)acrylate, and most preferred is m-phenoxybenzyl (meth)acrylate;

[0066] The content of the monofunctional (meth)acrylic polymerizable compound (C) in the stereolithography resin composition of the present invention is preferably 1.0 to 60% by mass, based on 100% by mass of the total amount of polymerizable compounds. From the viewpoints of superior modeling accuracy, toughness, and water resistance of the cured product, it is more preferably 2.5 to 50% by mass, even more preferably 5 to 45% by mass, and particularly preferably 7 to 40% by mass. In a preferred embodiment, the content of the monofunctional (meth)acrylic polymerizable compound (C) is preferably 1.0 to 60% by mass, more preferably 2.5 to 50% by mass, even more preferably 5 to 45% by mass, and particularly preferably 7 to 40% by mass, based on 100% by mass of the total amount of the stereolithography resin composition, based on the viewpoints of superior strength, toughness, and water resistance of the modeled product when combined with other components.

[0067] The stereolithography resin composition of the present invention may contain other polymerizable compounds (hereinafter also referred to simply as "other polymerizable compounds") other than the polyfunctional (meth)acrylic polymerizable compound (A) and the monofunctional (meth)acrylic polymerizable compound (C). In a preferred embodiment, the stereolithography resin composition includes a polymerizable compound consisting essentially of the polyfunctional (meth)acrylic polymerizable compound (A) and the monofunctional (meth)acrylic polymerizable compound (C). The phrase "the polymerizable compound consisting essentially of the polyfunctional (meth)acrylic polymerizable compound (A) and the monofunctional (meth)acrylic polymerizable compound (C)" refers to the content of the other polymerizable compounds other than the polyfunctional (meth)acrylic polymerizable compound (A) and the monofunctional (meth)acrylic polymerizable compound (C) in the total amount (100% by mass) of the stereolithography resin composition, preferably less than 10% by mass, more preferably less than 5% by mass, even more preferably less than 1% by mass, and particularly preferably less than 0.1% by mass. Examples of other polymerizable compounds include (meth)acrylamide oligomers (e.g., those having a weight average molecular weight of 1,000 or less, or those having a weight average molecular weight of 1,000 or more). In a preferred embodiment, it is preferable that the composition is substantially free of (meth)acrylamide oligomers (e.g., those having a molecular weight of 1,000 or less, or those having a molecular weight of 1,000 or more). "Substantially free of (meth)acrylamide oligomers" means that the content of (meth)acrylamide oligomers is less than 5% by mass, preferably less than 1% by mass, more preferably less than 0.1% by mass, and even more preferably less than 0.01% by mass, based on 100% by mass of the total amount of the stereolithography resin composition. The term "substantially free of other polymerizable compounds" has the same meaning as "substantially free of (meth)acrylamide oligomers" with respect to the content of other polymerizable compounds.

[0068] A preferred embodiment of the present invention is a stereolithography resin composition in which the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500, and the molecular weight of the photopolymerization initiator (B) is 400 or greater. Another preferred embodiment of the present invention is a stereolithography resin composition in which the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500, and the photopolymerization initiator (B) contains two or more carbonyl groups per molecule. Another preferred embodiment of the present invention is a stereolithography resin composition in which the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or greater, and the molecular weight of the photopolymerization initiator (B) is 400 or greater. Another preferred embodiment includes a stereolithography resin composition in which the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more, and the photopolymerization initiator (B) contains two or more carbonyl groups in one molecule. Another preferred embodiment includes a stereolithography resin composition in which the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500 and a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more, and the molecular weight of the photopolymerization initiator (B) is 400 or more. Another preferred embodiment is a stereolithography resin composition in which the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500 and a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more, and the photopolymerization initiator (B) contains two or more carbonyl groups in one molecule.Another preferred embodiment is a stereolithography resin composition in which the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500 and a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more, the photopolymerization initiator (B) has a molecular weight of 400 or more, and the photopolymerization initiator (B) contains two or more carbonyl groups in one molecule. Another preferred embodiment is a stereolithography resin composition in which the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500 and a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more, the photopolymerization initiator (B) contains two or more carbonyl groups in one molecule, and the heteroatoms in the photopolymerization initiator (B) are oxygen atoms and phosphorus atoms. Another preferred embodiment is a stereolithography resin composition in which the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500, the photopolymerization initiator (B) contains two or more carbonyl groups in one molecule, the content of the polyfunctional (meth)acrylic polymerizable compound (A) is 40 to 90 mass% based on 100 mass% of the total amount of the stereolithography resin composition, and the content of the polyfunctional (meth)acrylic polymerizable compound (A)-I is 35 to 50 mass% based on 100 mass% of the total amount of the stereolithography resin composition. Another preferred embodiment is a stereolithography resin composition in which the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500 and a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more, the photopolymerization initiator (B) contains two or more carbonyl groups in one molecule, and the heteroatoms of the photopolymerization initiator (B) are oxygen atoms and phosphorus atoms, the content of the polyfunctional (meth)acrylic polymerizable compound (A) is 40 to 90% by mass, based on a total 100% by mass of the stereolithography resin composition, and the content of the polyfunctional (meth)acrylic polymerizable compound (A)-I is 35 to 50% by mass, based on a total 100% by mass of the stereolithography resin composition.In any of the preferred embodiments described above, the type and content of each component can be appropriately changed based on the description in this specification.

[0069] The stereolithography resin composition of the present invention may contain a polymerization accelerator to improve photocurability, provided that the invention is not impaired by the spirit of the invention. The polymerization accelerator is not particularly limited, but considering that the stereolithography resin composition of the present invention is used in intraoral applications, polymerization accelerators used in dental applications can be suitably used. Preferred examples of known polymerization accelerators used in dental applications include amines. Examples of amines include aliphatic amines and aromatic amines. One type of polymerization accelerator may be used alone, or two or more types may be used in combination. Examples of aromatic amines include ethyl 4-(N,N-dimethylamino)benzoate, methyl 4-(N,N-dimethylamino)benzoate, n-butoxyethyl 4-(N,N-dimethylamino)benzoate, 2-(methacryloyloxy)ethyl 4-(N,N-dimethylamino)benzoate, 4-(N,N-dimethylamino)benzophenone, and butyl 4-(N,N-dimethylamino)benzoate. Among these, from the viewpoint of imparting excellent curability to the stereolithography resin composition, at least one selected from the group consisting of ethyl 4-(N,N-dimethylamino)benzoate, n-butoxyethyl 4-(N,N-dimethylamino)benzoate, and 4-(N,N-dimethylamino)benzophenone is preferably used.

[0070] The stereolithography resin composition of the present invention may further contain a filler in order to adjust the paste properties or to increase the mechanical strength of an object molded from the stereolithography resin composition. Examples of the filler include organic fillers, inorganic fillers, and organic-inorganic composite fillers. One type of filler may be used alone, or two or more types may be used in combination.

[0071] Examples of organic filler materials include polymethyl methacrylate, polyethyl methacrylate, methyl methacrylate-ethyl methacrylate copolymer, cross-linked polymethyl methacrylate, cross-linked polyethyl methacrylate, polyester, polyamide, polycarbonate, polyphenylene ether, polyoxymethylene, polyvinyl chloride, polystyrene, polyethylene, polypropylene, chloroprene rubber, nitrile rubber, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, acrylonitrile-styrene copolymer, and acrylonitrile-styrene-butadiene copolymer. These may be used alone or in combination of two or more. The shape of the organic filler is not particularly limited, and the particle size of the filler can be appropriately selected and used.

[0072] Examples of inorganic filler materials include quartz, silica, alumina, silica-titania, silica-titania-barium oxide, silica-zirconia, silica-alumina, lanthanum glass, borosilicate glass, soda glass, barium glass, strontium glass, glass ceramic, aluminosilicate glass, barium boroaluminosilicate glass, strontium boroaluminosilicate glass, fluoroaluminosilicate glass, calcium fluoroaluminosilicate glass, strontium fluoroaluminosilicate glass, barium fluoroaluminosilicate glass, and strontium calcium fluoroaluminosilicate glass. These may also be used alone or in combination of two or more. The shape of the inorganic filler is not particularly limited, and irregular fillers, spherical fillers, etc. may be appropriately selected and used. The content of the inorganic filler is not particularly limited as long as it does not impair the spirit of the present invention, but because of concerns about embrittlement of dental materials such as denture base materials and dental occlusal splints; and materials for treating sleep disorders, the content is usually 50 parts by mass or less, preferably 25 parts by mass or less, and more preferably 10 parts by mass or less, relative to 100 parts by mass of the total amount of the polymerizable compounds. Furthermore, the content of the filler (e.g., inorganic filler) is preferably 10% by mass or less, more preferably less than 5% by mass, and even more preferably less than 1% by mass, relative to 100% by mass of the total amount of the stereolithography resin composition.

[0073] Polymers can be added to the stereolithography resin composition of the present invention to improve flexibility, fluidity, etc., within the scope of the present invention. For example, natural rubber, synthetic polyisoprene rubber, liquid polyisoprene rubber and its hydrogenated products, polybutadiene rubber, liquid polybutadiene rubber and its hydrogenated products, styrene-butadiene rubber, chloroprene rubber, ethylene-propylene rubber, acrylic rubber, isoprene-isobutylene rubber, acrylonitrile-butadiene rubber, or styrene-based elastomers can be added. Specific examples of other polymers that can be added include polystyrene-polyisoprene-polystyrene block copolymers, polystyrene-polybutadiene-polystyrene block copolymers, poly(α-methylstyrene)-polybutadiene-poly(α-methylstyrene) block copolymers, poly(p-methylstyrene)-polybutadiene-poly(p-methylstyrene) block copolymers, and hydrogenated products thereof.

[0074] The stereolithography resin composition of the present invention may contain a softener, if necessary. Examples of softeners include petroleum-based softeners such as paraffinic, naphthenic, and aromatic process oils, and vegetable oil-based softeners such as paraffin, peanut oil, and rosin. These softeners may be used alone or in combination of two or more. The content of the softener is not particularly limited as long as it does not impair the spirit of the present invention, but is usually 200 parts by mass or less, preferably 100 parts by mass or less, per 100 parts by mass of the total amount of polymerizable compounds.

[0075] The stereolithography resin composition of the present invention may contain a known stabilizer to inhibit deterioration or adjust photocurability. Examples of the stabilizer include polymerization inhibitors, ultraviolet absorbers, and antioxidants. One stabilizer may be used alone, or two or more stabilizers may be used in combination.

[0076] Examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, dibutylhydroquinone, dibutylhydroquinone monomethyl ether, 4-t-butylcatechol, 2-t-butyl-4,6-dimethylphenol, 2,6-di-t-butylphenol, and 3,5-di-t-butyl-4-hydroxytoluene. The content of the polymerization inhibitor is preferably 0.001 to 5.0 parts by mass per 100 parts by mass of the total amount of the polymerizable compounds.

[0077] The stereolithography resin composition of the present invention may contain known additives for adjusting the color tone or paste properties. Examples of such additives include pigments, dyes, organic solvents, and thickeners. One type of additive may be used alone, or two or more types may be used in combination.

[0078] The stereolithography resin composition of the present invention not only has excellent shaping properties, but also exhibits excellent strength, toughness, and water resistance in shaped objects, and produces little eluate. Therefore, the stereolithography resin composition of the present invention can be used in applications that utilize these advantages, such as intraoral applications. Examples of intraoral applications include denture base materials, dental materials such as dental occlusal splints, and materials for treating sleep disorders (particularly, devices for treating sleep apnea syndrome). The stereolithography resin composition of the present invention is particularly suitable for denture base materials, dental occlusal splints, and devices for treating sleep apnea syndrome.

[0079] The shape of an object molded using the stereolithography resin composition of the present invention can be changed depending on the intended use. Furthermore, the type and content of each component (the polyfunctional (meth)acrylic polymerizable compound (A), the photopolymerization initiator (B), and optionally the monofunctional (meth)acrylic polymerizable compound (C), and various optional components (such as a polymerization accelerator, a filler, a polymer, a softener, a stabilizer, and an additive)) of the stereolithography resin composition of the present invention can be adjusted as needed for each intended use, such as a denture base material, a dental occlusal splint, or a treatment device for sleep apnea syndrome.

[0080] The stereolithography resin composition of the present invention can be used in a variety of applications by taking advantage of its properties, particularly the property that when cured with light, molded articles or three-dimensional objects, as well as other objects, can be obtained that have a small volumetric shrinkage rate and excellent dimensional accuracy, and that furthermore have excellent strength, toughness, and water resistance. For example, it can be used in the production of three-dimensional objects by optical stereolithography, the production of various molded articles such as film-like objects or molded objects by casting or casting, and in coating and vacuum forming molds.

[0081] Among these, the resin composition for photopolymerization of the present invention is suitable for use in the above-mentioned optical three-dimensional modeling method, and in this case, it is possible to smoothly produce three-dimensional objects that have excellent dimensional accuracy, toughness, and mechanical properties while maintaining a small volume shrinkage rate during photocuring.

[0082] Another embodiment of the present invention is a method for producing a three-dimensional object by a stereolithography method using any of the stereolithography resin compositions described above. The stereolithography method is not particularly limited, and a liquid vat photopolymerization method such as a laser-type stereolithography apparatus (SLA) or a digital light processing (DLP)-type SLA can be used. Examples of SLA include low force stereolithography (LFS).

[0083] When performing stereolithography using the stereolithography resin composition of the present invention, any of the known stereolithography methods and devices (e.g., a stereolithography machine such as the DIGITALWAX (registered trademark) 028J-Plus manufactured by DWS) can be used. Among these, in the present invention, it is preferable to use active energy rays as the light energy for curing the resin. "Active energy rays" refers to energy rays capable of curing the stereolithography resin composition, such as ultraviolet rays, electron beams, X-rays, radiation, and high frequency waves. For example, the active energy rays may be ultraviolet rays having a wavelength of 300 to 400 nm. Examples of light sources for active energy rays include lasers such as Ar lasers and He-Cd lasers; and lighting such as halogen lamps, xenon lamps, metal halide lamps, LEDs, mercury lamps, and fluorescent lamps, with lasers being particularly preferred. When a laser is used as a light source, it is possible to increase the energy level and shorten the modeling time, and further, by utilizing the excellent focusing properties of the laser beam, it is possible to obtain a three-dimensional object with high modeling accuracy.

[0084] As described above, when performing stereolithography using the stereolithography resin composition of the present invention, any of known methods and known stereolithography systems can be employed, and there are no particular limitations. However, a representative example of a stereolithography method preferably used in the present invention is a method that involves selectively irradiating a stereolithography resin composition with an active energy ray to form a cured layer having a desired pattern, followed by a lamination step of supplying an uncured liquid stereolithography resin composition to the cured layer and similarly irradiating it with an active energy ray to form a new cured layer continuous with the cured layer, thereby finally obtaining the desired three-dimensional object. The three-dimensional object thus obtained can be used as is, or, in some cases, can be post-cured by light irradiation or heat to further improve its mechanical properties or shape stability before use.

[0085] The structure, shape, size, etc. of a three-dimensional object obtained by the optical three-dimensional modeling method are not particularly limited and can be determined depending on the respective applications. Typical applications of the optical three-dimensional modeling method of the present invention include the production of models for verifying the appearance design during the design process, models for checking the functionality of parts, resin molds for producing casting molds, base models for producing metal molds, and direct molds for prototype molds. More specifically, examples include the production of models for precision parts, electrical and electronic parts, furniture, architectural structures, automotive parts, various containers, castings, metal molds, master molds, etc., or models for processing. In particular, the excellent strength and toughness of the objects produced by the stereolithography resin composition can be utilized to extremely effectively apply to applications such as cushioning materials with complex shapes in structures (e.g., architectural structures), vacuum molding molds, etc.

[0086] From the viewpoint of the wearing comfort and usability of a denture base material or a dental occlusal splint, the flexural modulus of a cured product of the stereolithography resin composition of the present invention is preferably in the range of 200 to 3000 MPa, more preferably in the range of 400 to 2500 MPa, and even more preferably in the range of 600 to 2000 MPa. The flexural strength of a cured product of the stereolithography resin composition of the present invention is preferably 15 to 120 MPa, more preferably 20 to 100 MPa, and even more preferably 25 to 90 MPa. The methods for measuring the flexural modulus and flexural strength are as described in the Examples below.

[0087] Next, the present invention will be explained in more detail by way of examples, but the present invention is not limited to these examples in any way, and many modifications can be made by a person having ordinary skill in the art within the scope of the technical idea of ​​the present invention.

[0088] Each component used in the stereolithography resin composition according to the examples and comparative examples will be explained below together with its abbreviation.

[0089] [Polyfunctional (meth)acrylic polymerizable compound (A)-I-1] UDMA: 2,2,4-trimethylhexamethylenebis(2-carbamoyloxyethyl)dimethacrylate (manufactured by Kyoeisha Chemical Co., Ltd., molecular weight: 471) [Polyfunctional (meth)acrylic polymerizable compound (A)-I-2) not containing a urethane bond] D2.6E: 2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane (average number of moles of ethoxy groups added: 2.6, "BPE-100" manufactured by Shin-Nakamura Chemical Co., Ltd., molecular weight: approximately 478)

[0090] [Polyfunctional (meth)acrylic polymerizable compound (A)-II-1] <Synthesis Example 1> [Production of polyfunctional urethanized (meth)acrylic polymerizable compound UA1] (1) 250 g of isophorone diisocyanate and 0.15 g of di-n-butyltin dilaurate were added to a 5 L four-neck flask equipped with a stirrer, a temperature regulator, a thermometer, and a condenser, and the mixture was heated with stirring to 70° C. (2) Meanwhile, 2500 g of polyester polyol ("Kuraray Polyol (registered trademark) P-2050" manufactured by Kuraray Co., Ltd.; a polyol composed of sebacic acid and 3-methyl-1,5-pentanediol, weight average molecular weight Mw: 2000) was added to a dropping funnel equipped with a side tube, and the liquid in the dropping funnel was added dropwise to the flask (1) above. The solution in the flask (1) was added dropwise at a constant rate over 4 hours while stirring, while maintaining the internal temperature of the flask at 65-75°C. After the addition was completed, the mixture was stirred at the same temperature for 2 hours to allow the reaction to proceed. (3) Next, a solution prepared by uniformly dissolving 150 g of 2-hydroxyethyl acrylate and 0.4 g of hydroquinone monomethyl ether in a separate dropping funnel was added dropwise at a constant rate over 2 hours to the flask (2) while maintaining the internal temperature of the flask at 55-65°C. The reaction was then continued for 4 hours while maintaining the temperature of the solution in the flask at 70-80°C, yielding a urethane-modified (meth)acrylic polymerizable compound UA1. GPC analysis revealed that the weight-average molecular weight Mw of the polyfunctional urethane-modified (meth)acrylic polymerizable compound UA1 was 2600. The weight-average molecular weight Mw of the compound synthesized above refers to the weight-average molecular weight in terms of polystyrene, determined by gel permeation chromatography (GPC).

[0091] UA2: N,N'-(2,2,4-trimethylhexamethylene)bis[2-(aminocarboxy)propane-1,3-diol]tetramethacrylate (manufactured by Kyoeisha Chemical Co., Ltd., molecular weight: 673)

[0092] [Polyfunctional (meth)acrylic polymerizable compound (A)-II-2) not containing a urethane bond] Bis-GMA: 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (manufactured by Shin-Nakamura Chemical Co., Ltd., molecular weight: 513)

[0093] [Photopolymerization initiator (B)] BAPO: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide ("Omnirad 819" manufactured by IGM Resins B.V. (NL), number of heteroatoms: 4, molecular weight: 418) OX1: 1,2-octanedione 1-[4-(phenylthio)phenyl]-2-(o-benzoyloxime) ("Irgacure OXE-01" manufactured by BASF Japan Ltd., number of heteroatoms: 5, molecular weight: 445) TEO: ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (manufactured by Tokyo Chemical Industry Co., Ltd., number of heteroatoms: 4, molecular weight: 316) [Photopolymerization initiators other than photopolymerization initiator (B)] TPO: diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (number of heteroatoms: 3, molecular weight: 348) TMO: (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide ("Sinocure 2425" manufactured by SINOCURE Chemical Group, number of heteroatoms: 3, molecular weight: 376)

[0094] [Monofunctional (meth)acrylic polymerizable compound (C)] POBA: m-phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd.) CTMPFA: cyclic trimethylolpropane formal acrylate (manufactured by SARTOMER) IBA: isobornyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd.)

[0095] [Polymerization inhibitor] BHT: 3,5-di-t-butyl-4-hydroxytoluene

[0096] [Examples 1 to 13 and Comparative Examples 1 to 7] The components were mixed at room temperature (20°C ± 15°C, JIS (Japanese Industrial Standards) Z 8703:1983) in the amounts (parts by mass) shown in Tables 1 and 2 to prepare pastes as stereolithography resin compositions according to Examples 1 to 13 and Comparative Examples 1 to 7.

[0097] <Modeling Accuracy> Using the compositions listed in Tables 1 and 2 of each Example and Comparative Example, a single 10.0 mm cube was produced using a stereolithography machine (DIGITALWAX (registered trademark) 028J-Plus, manufactured by DWS) at a pitch of 50 μm and with a light irradiation time of 0.6 seconds per layer. The resulting model was washed with methanol to remove any unpolymerized monomer, and then its dimensions (unit: mm) were measured in the x, y, and z axes using a micrometer. The arithmetic mean values ​​in the three directions were calculated, and the modeling error was calculated using the following formula. When the modeling error is 5.0% or less using this method, the modeling accuracy is excellent, and when aligners, denture bases, etc. are modeled, they are likely to have excellent compatibility. The results are shown in Tables 1 and 2. Modeling Error (%) = |(Measured Dimensions) - 10.0| × 100

[0098] <Strength (Flexural Modulus, Flexural Strength), Toughness (Displacement at Break)> The resulting stereolithography resin composition was used to form test pieces (length 64.0 mm, width 10.0 mm, thickness 3.3 mm) with dimensions specified in JIS T 6501:2012 (Acrylic Resins for Denture Bases) at a pitch of 100 μm using a stereolithography machine (DIGITALWAX® 020D manufactured by DWS) with a light irradiation time of 1.3 seconds per layer. These test pieces were used as objects molded from the stereolithography resin composition and subjected to bending tests. After storing the objects molded from the stereolithography resin compositions of each Example and Comparative Example in air for one day, the strength (flexural modulus, flexural strength) and toughness (displacement at break) were measured. Measurements were performed using a universal testing machine (Shimadzu Corporation, Autograph AG-I 100kN) at a crosshead speed of 5mm / min (n=5). The arithmetic mean values ​​of the measured values ​​are shown in Tables 1 and 2. From the viewpoint of wearing comfort and usability as a denture base material or dental occlusal splint, the flexural modulus is preferably in the range of 200 to 3000 MPa, more preferably in the range of 400 to 2500 MPa, and even more preferably in the range of 600 to 2000 MPa. The flexural strength is preferably in the range of 15 to 120 MPa, more preferably in the range of 20 to 100 MPa, and even more preferably in the range of 25 to 90 MPa. Regarding the fracture displacement, it is preferable that no fracture occurs, and the toughness is rated as excellent "S", if the fracture occurs at a displacement of 15 mm or more, the toughness is rated as good "A", if the fracture occurs at a displacement of 10 mm or more, the toughness is rated as fair "B", and if the fracture occurs at a displacement of less than 10 mm, the toughness is rated as poor "C", and "S", "A", and "B" were rated as passing.

[0099] <Water Resistance> Test pieces (length 64.0 mm, width 10.0 mm, thickness 3.3 mm) were molded from the resulting stereolithography resin composition using the same method as in the bending test described above. A bending test was conducted to measure water resistance using these test pieces as objects molded from the stereolithography resin composition. Objects molded from the stereolithography resin compositions of each Example and Comparative Example were immersed in water at 37°C for 168 hours, and then their bending strengths were measured in the same manner as in the bending strength test described above (n=5). The arithmetic mean values ​​of the measured values ​​are shown in Tables 1 and 2. When the bending strength measurement result for the toughness described above is taken as the initial bending strength, a change (decrease) in bending strength shown below of 10% or less indicates excellent water resistance. In Tables 1 and 2, the bending strength after immersion in water at 37°C for 168 hours is referred to as the "bending strength after immersion." Rate of change (decrease) in bending strength (%) = [{initial bending strength (MPa) - bending strength after immersion in water at 37°C for 168 hours (MPa)} / initial bending strength (MPa)] × 100

[0100] <Elution> The resulting stereolithography resin composition was used to form disks with a diameter of 15 mm and a thickness of 1.0 mm using a stereolithography machine (DIGITALWAX® 020D manufactured by DWS) at a pitch of 50 μm, with an average light irradiation time of 0.5 seconds per layer. One of the resulting disks was immersed in 2.0 mL of ethanol in a 10 mL glass bottle at 50° C. for 72 hours. The disk was then removed, the ethanol was distilled off, and the mass of the extract was measured (n=1). A leaching amount of 1.0 mg or less was considered to be low. The results are shown in Tables 1 and 2.

[0101]

[0102]

[0103] As shown in Tables 1 and 2, the stereolithography resin compositions of Examples 1 to 13 had excellent modeling accuracy, and the modeled objects had excellent strength, toughness, and water resistance, and the amount of elution was small. In particular, the modeling accuracy of the stereolithography resin compositions of Examples 1 to 13 was superior to that of the resin compositions of Comparative Examples 6 and 7. Furthermore, the water resistance of the objects modeled using the stereolithography resin compositions of Examples 1 to 13 was superior to that of the resin compositions of Comparative Examples 6 and 7. Furthermore, the elution from the objects modeled using the stereolithography resin compositions of Examples 1 to 13 was superior to that of the objects modeled using the resin compositions of Comparative Examples 1 to 5.

[0104] Comparisons between Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 4 and Comparative Example 3, and Example 13 and Comparative Example 4 confirmed that when the stereolithography resin composition contains a combination of components that does not contain the photopolymerization initiator (B), the amount of elution from the cured product increases. Furthermore, comparisons between Example 1 and Comparative Examples 6 and 7 confirmed that sufficient modeling precision and water resistance cannot be obtained when the photopolymerization initiator (B) is not in the range of 0.75 to 3.0 parts by mass per 100 parts by mass of the total amount of polymerizable compounds.

[0105] The stereolithography resin composition of the present invention has excellent modeling accuracy, strength, toughness, and water resistance of the molded object, and produces little elution from the molded object, making it suitable for intraoral applications such as various dental materials (particularly denture base materials and dental occlusal splints) and various sleep disorder treatment materials (particularly treatment devices for sleep apnea syndrome).

Claims

1. A resin composition for stereolithography comprising a polyfunctional (meth)acrylic polymerizable compound (A) and a photopolymerization initiator (B) containing four or more heteroatoms in one molecule, wherein the content of the photopolymerization initiator (B) containing four or more heteroatoms in one molecule is 0.75 to 3.0 parts by mass per 100 parts by mass of the total amount of the polymerizable compounds.

2. The stereolithography resin composition according to claim 1, further comprising a monofunctional (meth)acrylic polymerizable compound (C).

3. The optical molding resin composition according to claim 1 or 2, wherein the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500.

4. The stereolithography resin composition according to claim 1 or 2, wherein the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more.

5. The stereolithography resin composition according to claim 1 or 2, wherein the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I having a molecular weight of less than 500, and a polyfunctional (meth)acrylic polymerizable compound (A)-II having a molecular weight of 500 or more.

6. The stereolithography resin composition according to claim 1 or 2, wherein the polyfunctional (meth)acrylic polymerizable compound (A) contains a polyfunctional (meth)acrylic polymerizable compound (A)-I-1 having a molecular weight of less than 500 and containing a urethane bond, and / or a (meth)acrylic polymerizable compound (A)-II-1 having a molecular weight of 500 or more and containing a urethane bond.

7. The stereolithography resin composition according to claim 1 or 2, wherein the molecular weight of the photopolymerization initiator (B) is 400 or more.

8. The stereolithography resin composition according to claim 1 or 2, wherein the photopolymerization initiator (B) contains two or more carbonyl groups in one molecule.

9. The stereolithography resin composition according to claim 1 or 2, wherein the photopolymerization initiator (B) contains bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

10. A dental material comprising an object molded from the stereolithography resin composition according to claim 1 or 2.

11. A denture base material comprising an object molded from the stereolithography resin composition according to claim 1 or 2.

12. A dental occlusal splint comprising an object molded from the stereolithography resin composition according to claim 1 or 2.

13. A material for treating sleep disorders, comprising a molded object made from the resin composition for stereolithography according to claim 1 or 2.

14. A method for producing a three-dimensional object by optical three-dimensional modeling using the resin composition for stereolithography according to claim 1 or 2.