JP7543026B2 - Dental hardenable composition - Google Patents

Description

The present invention relates to a dental hardenable composition. More specifically, the present invention relates to a dental hardenable composition that, particularly when modeled by stereolithography, is not unpleasant due to its low odor, is easy to model due to its low viscosity and excellent curing properties, and can give a three-dimensional object having excellent stress retention, toughness, water resistance, color tone, and color stability in the cured product. The dental hardenable composition of the present invention is particularly suitable for dental mouthpieces and denture base materials.

Many proposals have been made for a method of producing a three-dimensional object by 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 controlled conditions to harden it into a thin layer. This is known as optical three-dimensional modeling.

A typical method for optically manufacturing a three-dimensional object is liquid vat stereolithography, in which the 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 to form a cured layer, and then a layer of liquid photocurable resin composition is supplied on top of the cured layer, which is similarly irradiated with an ultraviolet laser to cure the composition in the same manner as above to form a continuous cured layer. This lamination process is repeated to produce a three-dimensional object of the final shape. This method has attracted much attention in recent years because it can easily and accurately manufacture the desired three-dimensional object in a relatively short time, even if the object has a fairly complex shape.

The uses of the three-dimensional objects obtained by stereolithography have expanded from mere concept models to test models, prototypes, etc., and as a result, there is an increasing demand for these three-dimensional objects to have excellent modeling precision. In addition to these characteristics, they are also required to have excellent properties suited to the purpose. In particular, in the field of dental materials, the application of stereolithography is expected to be applied to dental mouthpieces and denture bases, as the shapes of which vary from patient to patient and are complex.

Dental mouthpieces include orthodontic aligners, which are worn on the teeth to correct the alignment of teeth; dental splints, which are worn to correct jaw position; mouthpieces worn on the teeth while sleeping at night to treat sleep apnea syndrome; mouthpieces worn on the teeth to prevent tooth wear caused by teeth grinding; and mouthpieces worn in the mouth 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 these devices in orthodontics has rapidly expanded due to their aesthetic quality and the fact that they can be removed whenever desired. Sleep apnea syndrome is also a case that has attracted attention in the medical field, and their use as a treatment tool is rapidly increasing.

Denture base material is the material used on the gums when dentures are fitted due to tooth loss. In recent years, the demand for dentures has increased dramatically due to the increase in the elderly population.

These dental mouthpieces and denture base materials are commonly required to have a color tone that does not spoil the appearance, stress retention, toughness, and water resistance. In particular, these characteristics are more strongly required for orthodontic aligners and partial denture bases that do not contain metal clasps, commonly known as non-clasp dentures. More specifically, a major advantage of orthodontic aligners is that they can avoid the poor appearance of orthodontics using brackets and wires. Similarly, the significance of using non-clasp dentures is to avoid the poor appearance of metal clasps, and a color tone that does not spoil the appearance is related to the main purpose of using these materials and is extremely important. In addition, if the stress retention is lost, the mechanical load (hereinafter sometimes referred to as "orthodontic force") or shock absorption in orthodontic treatment will be lost, and the device will not function as a wearing device, and if the toughness is lost, the wearing comfort will be poor, and if it becomes easily broken, frequent remaking will be required. Furthermore, if water resistance is impaired, the mechanical properties will decrease, and the straightening power or shock absorption properties will be lost, or the material will become more fragile and unsuitable for practical use.

In addition, when making dental mouthpieces, denture base materials, and treatment devices for sleep apnea syndrome, it is usually necessary to take an impression of the oral cavity, but problems such as the discomfort of the impression and the need for skill in technical operations 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 to apply optical three-dimensional modeling to molding. Photocurable resin compositions are used in modeling, but generally, the more flexible and water-resistant a resin composition is, the more likely it is to use a monomer with low polarity, which reduces the curing property and tends to result in poor stress retention of the cured product. In particular, in optical three-dimensional modeling, the light irradiation time is extremely short and each layer is exposed to oxygen for modeling, so that curing is particularly likely to be insufficient, and it has been difficult to achieve both stress retention and toughness and water resistance. On the other hand, the more stress retention and strength a resin composition is, the more likely it is to use a monomer with high polarity, which reduces water resistance, and the more likely it is to discolor due to the presence of polar groups, which can easily damage the color tone. Furthermore, the resin composition needs to have a viscosity that allows it to be molded, but if a low molecular weight monomer is used to reduce the viscosity, the curing property is likely to decrease, and the vapor pressure is likely to increase, making it easy to emit an odor. On the other hand, many monomers that exhibit stress retention properties have high molecular weights and high viscosities, which causes problems such as reduced moldability. For this reason, it has been difficult to obtain a resin composition for three-dimensional modeling that is low in viscosity and low in odor, has a good color tone in the cured product, and has excellent properties such as stress retention, toughness, and water resistance.

In this context, for example, Patent Document 1 discloses a hardenable composition containing N-acryloylpiperidine and a urethane acrylate oligomer as a technique for obtaining a dental hardenable composition that has low viscosity and exhibits excellent mechanical properties and moisture resistance of the hardened product.

JP 2005-82691 A

The dental hardenable composition described in Patent Document 1 contains a compound having an amine structure that is prone to discoloration, but there is no mention of the color tone, nor of the stress retention.

The present invention aims to provide a dental hardenable composition that, particularly when modeled by stereolithography, is not unpleasant due to its low odor, is easy to model due to its low viscosity and excellent curing properties, and can give three-dimensional objects that are excellent in stress retention, toughness, water resistance, color tone, and color stability. The dental hardenable composition of the present invention can be particularly suitably used for dental mouthpieces and denture base materials.

（式中、Ｒ¹～Ｒ³は、それぞれ独立して、置換基を有していてもよい炭素数１～２０のアルキル基、置換基を有していてもよい炭素数１～２０のアルコキシ基、置換基を有していてもよい炭素数６～１２のアリール基又は水酸基を表し、Ｒ¹～Ｒ³の前記基（水酸基を除く）は、－Ｏ－、－Ｓ－、－ＮＨ－、－Ｎ（Ｒ⁴）－、－Ｏ（ＣＯ）－、及び－ＣＯ－からなる群から選ばれる少なくとも１種の結合基を含んでいてもよい。Ｒ⁴は炭素数１～６のアルキル基を表す。）

（式中、Ｒ¹⁰及びＲ¹¹は、それぞれ独立して、置換基を有していてもよい炭素数１～２０のアルキル基、置換基を有していてもよい炭素数１～２０のアルコキシ基、又は置換基を有していてもよい炭素数６～１２のアリール基を表し、Ｚ¹は置換基を有していてもよい炭素数１～２０のアルキレン基を表し、Ｚ²は炭素原子、酸素原子、窒素原子、硫黄原子、又はアリール基を表し、ｎは２～６の整数を表し、Ｒ¹⁰、Ｒ¹¹及びＺ¹の前記基は、－Ｏ－、－Ｓ－、－ＮＨ－、－Ｎ（Ｒ¹²）－、－Ｏ（ＣＯ）－、及び－ＣＯ－からなる群から選ばれる少なくとも１種の結合基を含んでいてもよい。Ｒ¹²は炭素数１～６のアルキル基を表す。）
［３］前記ヒンダードフェノール化合物（Ｃ）が、一般式［ＩＩＩ］で表される化合物を含有する、［１］又は［２］に記載の歯科用硬化性組成物；
［４］厚さが２．０ｍｍ±０．２ｍｍである硬化物の２４時間後の応力保持率が、５０％以上である、［１］～［３］のいずれかに記載の歯科用硬化性組成物；
［５］（メタ）アクリルアミド（Ａ）以外のα，β－不飽和二重結合基含有化合物（Ｄ）を含有する、［１］～［４］のいずれかに記載の歯科用硬化性組成物；
［６］前記（メタ）アクリルアミド（Ａ）以外のα，β－不飽和二重結合基含有化合物（Ｄ）が、常圧換算沸点が２５０℃以上である、［５］に記載の歯科用硬化性組成物；
［７］前記（メタ）アクリルアミド（Ａ）以外のα，β－不飽和二重結合基含有化合物（Ｄ）が、ウレタン化（メタ）アクリル化合物（Ｄ）－１を含有する、［５］又は［６］に記載の歯科用硬化性組成物；
［８］前記ウレタン化（メタ）アクリル化合物（Ｄ）－１が、１分子内に、ポリエステル、ポリカーボネート、ポリウレタン、及びポリエーテルからなる群より選ばれる少なくとも１種の構造、並びにウレタン結合を含有する（メタ）アクリレートである、［７］に記載の歯科用硬化性組成物；
［９］前記（メタ）アクリルアミド（Ａ）以外のα，β－不飽和二重結合基含有化合物（Ｄ）が、ウレタン結合を有しない（メタ）アクリル酸エステル化合物（Ｄ）－２を含有する、［５］～［７］のいずれかに記載の歯科用硬化性組成物；
［１０］ウレタン結合を有しない単官能性の（メタ）アクリル酸エステル化合物（Ｄ）－２－１を実質的に含有しない、［１］～［９］のいずれかに記載の歯科用硬化性組成物；
［１１］前記光重合開始剤（Ｂ）が、（ビス）アシルホスフィンオキシド類である、［１］～［１０］のいずれかに記載の歯科用硬化性組成物；
［１２］［１］～［１１］のいずれかに記載の歯科用硬化性組成物の硬化物からなる、歯科用マウスピース。
［１３］［１］～［１１］のいずれかに記載の歯科用硬化性組成物の硬化物からなる、義歯床材料；
［１４］［１］～［１１］のいずれかに記載の歯科用硬化性組成物の硬化物からなる、睡眠障害治療材料；
［１５］［１］～［１１］のいずれかに記載の歯科用硬化性組成物からなる、光造形用材料；
［１６］［１］～［１１］のいずれかに記載の歯科用硬化性組成物を用いて、光学的立体造形法によって立体造形物を製造する方法。 That is, the present invention includes the following inventions.
[1] An ink composition comprising: a (meth)acrylamide (A) having an alicyclic amino group (a); a photopolymerization initiator (B); and a hindered phenol compound (C);
the alicyclic amino group (a) has only one nitrogen atom as a heteroatom in a ring structure, and a (meth)acryloyl group is directly bonded to the nitrogen atom of the alicyclic amino group (a);
a dental curable composition, in which the content of the hindered phenol compound (C) is 0.1 to 200 parts by mass per 100 parts by mass of the photopolymerization initiator (B);
[2] The dental curable composition according to [1], wherein the hindered phenol compound (C) contains a compound represented by the following general formula [I] and/or a compound represented by the following general formula [III]:

(In the formula, R ¹ to R ³ each independently represent an alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or a hydroxyl group, and the groups (excluding the hydroxyl group) of R ¹ to R ³ may contain at least one bonding group selected from the group consisting of -O-, -S-, -NH-, -N(R ⁴ )-, -O(CO)-, and -CO-. R ⁴ represents an alkyl group having 1 to 6 carbon atoms.)

(In the formula, R ¹⁰ and R ¹¹ each independently represent an alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent; Z ¹ represents an alkylene group having 1 to 20 carbon atoms which may have a substituent; Z ² represents a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, or an aryl group; n represents an integer of 2 to 6; and the groups of R ¹⁰ , R ¹¹ , and Z ¹ may contain at least one bonding group selected from the group consisting of -O-, -S-, -NH-, -N(R ¹² )-, -O(CO)-, and -CO-. R ¹² represents an alkyl group having 1 to 6 carbon atoms.)
[3] The dental curable composition according to [1] or [2], wherein the hindered phenol compound (C) contains a compound represented by general formula [III]:
[4] The dental curable composition according to any one of [1] to [3], wherein the stress retention rate of a cured product having a thickness of 2.0 mm±0.2 mm after 24 hours is 50% or more;
[5] The dental curable composition according to any one of [1] to [4], which contains an α,β-unsaturated double bond group-containing compound (D) other than the (meth)acrylamide (A);
[6] The dental curable composition according to [5], wherein the α,β-unsaturated double bond group-containing compound (D) other than the (meth)acrylamide (A) has a boiling point converted to normal pressure of 250° C. or higher;
[7] The dental curable composition according to [5] or [6], wherein the α,β-unsaturated double bond group-containing compound (D) other than the (meth)acrylamide (A) contains a urethane-modified (meth)acrylic compound (D)-1;
[8] The dental curable composition according to [7], wherein the urethane-modified (meth)acrylic compound (D)-1 is a (meth)acrylate containing, in one molecule, at least one structure selected from the group consisting of polyester, polycarbonate, polyurethane, and polyether, and a urethane bond;
[9] The dental curable composition according to any one of [5] to [7], wherein the α,β-unsaturated double bond group-containing compound (D) other than the (meth)acrylamide (A) contains a (meth)acrylic acid ester compound (D)-2 having no urethane bond;
[10] The dental curable composition according to any one of [1] to [9], which is substantially free of a monofunctional (meth)acrylic acid ester compound (D)-2-1 having no urethane bond;
[11] The dental curable composition according to any one of [1] to [10], wherein the photopolymerization initiator (B) is a (bis)acylphosphine oxide;
[12] A dental mouthpiece comprising a cured product of the dental curable composition according to any one of [1] to [11].
[13] A denture base material comprising a cured product of the dental hardenable composition according to any one of [1] to [11];
[14] A sleep disorder treatment material comprising a hardened product of the dental hardenable composition according to any one of [1] to [11];
[15] A material for stereolithography, comprising the dental curable composition according to any one of [1] to [11];
[16] A method for producing a three-dimensional object by a stereolithography method using the dental curable composition according to any one of [1] to [11].

The dental hardenable composition of the present invention, particularly when modeled by photolithography, is not unpleasant due to its low odor, is easy to model due to its low viscosity and excellent hardening properties, and can give three-dimensional objects with excellent stress retention, toughness, water resistance, color tone and color stability. Therefore, it can be suitably used in applications where stress is continuously applied in the oral environment, such as various dental materials (particularly dental mouthpieces and denture base materials) or various sleep disorder treatment materials (particularly treatment devices for sleep apnea syndrome).

The dental curable composition of the present invention contains a (meth)acrylamide (A) in which a (meth)acryloyl group is directly bonded to the nitrogen atom of an alicyclic amino group (a) that does not contain a heteroatom other than one nitrogen atom in the ring structure, a photopolymerization initiator (B), and a hindered phenol compound (C). In this specification, the upper and lower limits of the numerical ranges (contents of each component, values calculated from each component, and each physical property, etc.) can be appropriately combined.

[(Meth)acrylamide (A) containing an alicyclic amino group (a)]
The dental curable composition of the present invention contains a (meth)acrylamide (A) (hereinafter may be simply referred to as "(meth)acrylamide (A)") containing an alicyclic amino group (a), in which the alicyclic amino group (a) has only one nitrogen atom in its ring structure as a heteroatom and a (meth)acryloyl group is directly bonded to the nitrogen atom of the alicyclic amino group (a). This improves the melting point (Tm) or glass transition temperature (Tg) of the three-dimensional object after light irradiation, thereby further improving the internal cohesive force, and makes it possible to form a three-dimensional object with good stress retention and toughness.

The alicyclic amino group (a) of the (meth)acrylamide (A) of the present invention must have only one nitrogen atom in the ring structure as a heteroatom, and the (meth)acryloyl group must be directly bonded to the nitrogen atom of the alicyclic amino group (a). By not containing any heteroatoms other than the one nitrogen atom in the ring structure, the water resistance of the cured product of the dental hardenable composition is excellent. In addition, by directly bonding the (meth)acryloyl group to the alicyclic amino group without an alkylene chain or the like, the rigidity of the molecular structure is increased, and the dielectric effect of the nitrogen atom with a fixed conformation increases the glass transition temperature of the cured product of the dental hardenable composition obtained, resulting in good stress retention and toughness of the cured product. Furthermore, generally, polymerizable monomers, except for those having active hydrogen such as hydroxyl groups or acidic groups, tend to have a strong odor when the molecular weight is about 250 or less. However, (meth)acrylamide (A) is presumed to have a stronger polarity due to the ring structure, so that even if it has a relatively low molecular weight, it has a small odor, and it is possible to select a low molecular weight to keep the viscosity of the dental hardenable composition low. In addition, since it has high hardening properties, it also has excellent moldability. In the present invention, "one nitrogen atom in a ring structure" means that one nitrogen atom itself is incorporated in the hydrocarbon chain forming the ring structure, and is distinguished from an atom as a substituent directly bonded to the ring skeleton. The number of carbon atoms in the hydrocarbon chain forming the ring structure of the alicyclic amino group (a) may be 3 or more, may be 4 to 8, and preferably 4 to 5.

The molecular weight of the (meth)acrylamide compound (A) is not particularly limited, but from the viewpoints of odor and viscosity, it is preferably 100 to 210, more preferably 110 to 180, and even more preferably 120 to 160.

In terms of the water resistance of the resulting cured product, it is preferable that the alicyclic amino group (a) in the present invention does not contain a substituent containing active hydrogen, such as a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amino group, or a nitro group, or a strongly polar group.

Examples of the alicyclic amino group (a) in the present invention include an aziridyl group, an azetidyl group, a pyrrolidyl group, a piperidyl group, and the like, with a pyrrolidyl group and a piperidyl group being preferred. The alicyclic amino group (a) may have a substituent. As described above, it is preferable that the substituent does not contain a substituent containing active hydrogen and a strong polar group, and therefore examples of the substituent include an alkyl group having 1 to 6 carbon atoms and a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom). Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an n-pentyl group, and the like. The alkyl group may be substituted with a halogen atom. When the alicyclic amino group (a) has a substituent, examples of the alicyclic amino group (a) include a 4-methylpiperidyl group, a 4-ethylpiperidyl group, a 4-t-butylpiperidyl group, a 2,5-dimethylpiperidyl group, a 3,5-dimethylpiperidyl group, a 4,4-dimethylpiperidyl group, a 2-fluoropiperidyl group, and a 2-chloropiperidyl group.

In the present invention, the (meth)acrylamide (A) is preferably a monofunctional (meth)acrylamide from the viewpoint of excellent toughness of the resulting cured product. In this specification, "monofunctional" means having one polymerizable group. In this specification, the term "(meth)acryloyl" is used to include both methacryloyl and acryloyl, and the same applies to similar terms such as "(meth)acrylic."

Examples of the (meth)acrylamide (A) of the present invention include N-(meth)acryloylpyrrolidine, N-(meth)acryloylpiperidine, N-(meth)acryloylazepane, N-(meth)acryloylazocane, N-(meth)acryloylazonane, N-(meth)acryloylazecane, N-(meth)acryloylazonine, N-(meth)acryloylmorphane, N-(meth)acryloylindoline, N-(meth)acryloyliso ...isoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth)acryloylisoindoline, N-(meth) Examples of such compounds include t) acryloyl-4-methylpiperidine, N-(meth)acryloyl-4-ethylpiperidine, N-(meth)acryloyl-4-t-butylpiperidine, N-(meth)acryloyl-2,5-dimethylpiperidine, N-(meth)acryloyl-3,5-dimethylpiperidine, N-(meth)acryloyl-4,4-dimethylpiperidine, N-(meth)acryloyl-2-fluoropiperidine, and N-(meth)acryloyl-2-chloropiperidine. These compounds may be used alone or in combination of two or more. Among these, from the viewpoint of providing a dental curable composition with low viscosity and excellent toughness of the cured product, N-(meth)acryloylpyrrolidine, N-(meth)acryloylpiperidine, N-(meth)acryloylazepane, N-(meth)acryloyl-4-methylpiperidine, N-(meth)acryloyl-4-ethylpiperidine, and N-(meth)acryloyl-4-t-butylpiperidine are preferred, with N-(meth)acryloylpyrrolidine and N-(meth)acryloylpiperidine being more preferred.

The content of (meth)acrylamide (A) in the dental curable composition of the present invention is preferably 1.0 to 90 parts by mass per 100 parts by mass of the total of (meth)acrylamide (A), the α,β-unsaturated double bond group-containing compound (D) other than (meth)acrylamide (A) described below, and other polymerizable monomers (hereinafter collectively referred to as "polymerizable compounds"). In terms of superior moldability, toughness and water resistance of the cured product, the content is more preferably 5.0 to 80 parts by mass, and even more preferably 10 to 70 parts by mass. In one preferred embodiment, in terms of superior toughness of the cured product in particular, the dental curable composition has a content of (meth)acrylamide (A) of 30 to 70 parts by mass per 100 parts by mass of the total of the polymerizable compounds.

[Photopolymerization initiator (B)]
The photopolymerization initiator (B) used in the present invention can be selected from polymerization initiators generally used in industry, and among them, polymerization initiators used for dental purposes are preferably used.

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

Among these photopolymerization initiators (B), it is preferable to use (bis)acylphosphine oxides. This makes it possible to obtain a dental curable composition that has excellent photocurability in the ultraviolet and visible light regions, exhibits sufficient photocurability using any light source, including lasers, halogen lamps, light-emitting diodes (LEDs), and xenon lamps, and produces a cured product that does not discolor.

Among the (bis)acylphosphine oxides, examples of the acylphosphine oxides include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylmethoxyphenylphosphine oxide, 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide, 2,3,5,6-tetramethylbenzoyldiphenylphosphine oxide, benzoyldi(2,6-dimethylphenyl)phosphonate, 2,4,6-trimethylbenzoylphenylphosphine oxide sodium salt, 2,4,6-trimethylbenzoylphenylphosphine oxide potassium salt, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide ammonium salt. 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, and bis(2,5,6-trimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide. Further examples include compounds described in JP-A-2000-159621.

Among these (bis)acylphosphine oxides, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylmethoxyphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2,4,6-trimethylbenzoylphenylphosphine oxide sodium salt are particularly preferred.

Examples of α-diketones include diacetyl, benzil, camphorquinone, 2,3-pentadione, 2,3-octadione, 9,10-phenanthrenequinone, 4,4'-oxybenzil, and acenaphthenequinone. Examples of germanium compounds include monoacylgermanium compounds such as benzoyltrimethylgermanium(IV); and diacylgermanium compounds such as dibenzoyldiethylgermanium or bis(4-methoxybenzoyl)-diethylgermanium.

From the viewpoint of the curability, color tone, and color tone stability of the dental curable composition obtained, the content of the photopolymerization initiator (B) in the dental curable composition of the present invention is preferably 0.1 to 10 parts by mass per 100 parts by mass of the total amount of (meth)acrylamide (A), the α,β-unsaturated double bond group-containing compound (D) described later, and other polymerizable monomers. If the content of the photopolymerization initiator (B) is less than 0.1 parts by mass, the polymerization may not proceed sufficiently, and a molded product or a cured product may not be obtained. The content of the photopolymerization initiator (B) is more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more, per 100 parts by mass of the total amount. On the other hand, if the content of the photopolymerization initiator (B) exceeds 10 parts by mass, the light transmittance of the photopolymerization initiator itself decreases, the polymerization may not proceed sufficiently, and a molded product or a cured product may not be obtained. In addition, the discoloration of the cured product may become significant. The content of the photopolymerization initiator (B) is more preferably 7.5 parts by mass or less, and even more preferably 5.0 parts by mass or less, per 100 parts by mass of the total amount.

Hindered phenol compound (C)
The dental curable composition of the present invention contains a hindered phenol compound (C). The hindered phenol compound (C) is used in the dental curable composition of the present invention to suppress coloration of the cured product of the dental curable composition and discoloration after storage. In addition, by blending the hindered phenol compound (C) with the photopolymerization initiator (B) in a specific ratio, when combined with (meth)acrylamide (A), the cured product has excellent stress retention, water resistance, and toughness.

Generally, phenolic compounds are blended as polymerization inhibitors or antioxidants to ensure the storage stability of resin compositions, and are prone to yellowing or browning by oxidation. On the other hand, in the present invention, a hindered phenolic compound (C) is used to suppress coloring and discoloration after storage caused by irradiation with active energy rays such as a very strong ultraviolet laser emitted by a stereolithography device, which is different from the general purpose of use and has a completely different behavior regarding color tone. In addition, among phenolic compounds, it is necessary to use a hindered phenolic compound because it has little curing inhibition and is excellent in suppressing coloring and discoloration of the cured product. Furthermore, only when the hindered phenolic compound (C) is blended in a specific ratio with respect to the photopolymerization initiator (B), the dental curable composition of the present invention can produce a molded product or a cured product, and the coloring and discoloration after storage of the cured product are suppressed. Furthermore, it has been found that in the combination of the (meth)acrylamide compound (A), a specific amount of the photopolymerization initiator (B), and the hindered phenolic compound (C) of the present invention, the cured product is less likely to break due to deformation, and its toughness is further improved. This is presumably due to the high strength-producing effect of the (meth)acrylamide compound and the change in polymerization behavior caused by the hindered phenol compound (C), which results in a good balance between strength and flexibility.

（式中、Ｒ¹～Ｒ³は、それぞれ独立して、置換基を有していてもよい炭素数１～２０のアルキル基、置換基を有していてもよい炭素数１～２０のアルコキシ基、置換基を有していてもよい炭素数６～１２のアリール基又は水酸基を表し、Ｒ¹～Ｒ³の前記基（水酸基を除く）は、－Ｏ－、－Ｓ－、－ＮＨ－、－Ｎ（Ｒ⁴）－、－Ｏ（ＣＯ）－、及び－ＣＯ－からなる群から選ばれる少なくとも１種の結合基を含んでいてもよい。Ｒ⁴は炭素数１～６のアルキル基を表す。）

（式中、Ｒ⁵～Ｒ⁸は、それぞれ独立して、置換基を有していてもよい炭素数１～２０のアルキル基、置換基を有していてもよい炭素数１～２０のアルコキシ基、置換基を有していてもよい炭素数６～１２のアリール基又は水酸基を表し、Ｘは置換基を有していてもよい炭素数１～２０のアルキレン基を表し、Ｙはビニルオキシ基、又は（メタ）アクリロイルオキシ基を表し、Ｒ⁵～Ｒ⁸及びＸの前記基（水酸基を除く）は、－Ｏ－、－Ｓ－、－ＮＨ－、－Ｎ（Ｒ⁹）－、－Ｏ（ＣＯ）－、及び－ＣＯ－からなる群から選ばれる少なくとも１種の結合基を含んでいてもよい。Ｒ⁹は炭素数１～６のアルキル基を表す。）

（式中、Ｒ¹⁰及びＲ¹¹は、それぞれ独立して、置換基を有していてもよい炭素数１～２０のアルキル基、置換基を有していてもよい炭素数１～２０のアルコキシ基、又は置換基を有していてもよい炭素数６～１２のアリール基を表し、Ｚ¹は置換基を有していてもよい炭素数１～２０のアルキレン基を表し、Ｚ²は炭素原子、酸素原子、窒素原子、硫黄原子、又はアリール基を表し、ｎは２～６の整数を表し、Ｒ¹⁰、Ｒ¹¹及びＺ¹の前記基は、－Ｏ－、－Ｓ－、－ＮＨ－、－Ｎ（Ｒ¹²）－、－Ｏ（ＣＯ）－、及び－ＣＯ－からなる群から選ばれる少なくとも１種の結合基を含んでいてもよい。Ｒ¹²は炭素数１～６のアルキル基を表す。） Examples of the hindered phenol compound (C) include a compound represented by the following general formula [I], a compound represented by the following general formula [II], a compound represented by the following general formula [III], and the like. Of these, the compound represented by the following general formula [I] and the compound represented by the following general formula [III] are preferred.

(In the formula, R ¹ to R ³ each independently represent an alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or a hydroxyl group, and the groups (excluding the hydroxyl group) of R ¹ to R ³ may contain at least one bonding group selected from the group consisting of -O-, -S-, -NH-, -N(R ⁴ )-, -O(CO)-, and -CO-. R ⁴ represents an alkyl group having 1 to 6 carbon atoms.)

(In the formula, R ⁵ to R ⁸ each independently represent an alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, or a hydroxyl group; X represents an alkylene group having 1 to 20 carbon atoms which may have a substituent; Y represents a vinyloxy group or a (meth)acryloyloxy group; and the groups (excluding the hydroxyl group) of R ⁵ to R ⁸ and X may contain at least one bonding group selected from the group consisting of -O-, -S-, -NH-, -N(R ⁹ )-, -O(CO)-, and -CO-. R ⁹ represents an alkyl group having 1 to 6 carbon atoms.)

(In the formula, R ¹⁰ and R ¹¹ each independently represent an alkyl group having 1 to 20 carbon atoms which may have a substituent, an alkoxy group having 1 to 20 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent; Z ¹ represents an alkylene group having 1 to 20 carbon atoms which may have a substituent; Z ² represents a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, or an aryl group; n represents an integer of 2 to 6; and the groups of R ¹⁰ , R ¹¹ , and Z ¹ may contain at least one bonding group selected from the group consisting of -O-, -S-, -NH-, -N(R ¹² )-, -O(CO)-, and -CO-. R ¹² represents an alkyl group having 1 to 6 carbon atoms.)

The alkyl group having 1 to 20 carbon atoms represented by R ¹ to R ³ and R ⁵ to R ⁸ may be linear or branched. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a 2-methylpropyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a neopentyl group, a 1-ethylpropyl group, a 1,1-dimethylpropyl group, an n-hexyl group, a 1-methylpentyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1,1-dimethylbutyl group, an n-heptyl group, a 2-methylhexyl group, an n-octyl group, an isooctyl group, a tert-octyl group, an n-nonyl group, an n-decyl group, a 1-methylnonyl group, an n-undecyl group, and an n-dodecyl group. The alkyl groups of R ¹ to R ³ and R ⁵ to R ⁸ may be unsubstituted. The number of carbon atoms of the alkyl groups of R ¹ to R ³ and R ⁵ to R ⁸ is preferably 1 to 10, and more preferably 1 to 6, from the viewpoint of excellent inhibition effect of coloring and discoloration. The alkoxy groups of R ¹ to R ³ and R ⁵ to R ⁸ having 1 to 20 carbon atoms may be linear or branched. Examples of the alkoxy groups include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentyloxy, isopentyloxy, and n-hexyloxy. The alkoxy groups of R ¹ to R ³ and R ⁵ to R ⁸ may be unsubstituted. The number of carbon atoms of the alkoxy groups of R ¹ to R ⁷ is preferably 1 to 10, and more preferably 1 to 6, from the viewpoint of excellent inhibition effect of coloring and discoloration. Examples of the aryl group having 6 to 12 carbon atoms for R ¹ to R ³ and R ⁵ to R ⁸ include a phenyl group, a benzyl group, and a naphthyl group. The number of carbon atoms of the aryl group is preferably 6 to 10. Examples of the substituents of the alkyl group, alkoxy group, and aryl group for R ¹ to R ³ and R ⁵ to R ⁸ include a linear or branched alkyl group having 1 to 10 carbon atoms, a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), and a carboxy group. Examples of the alkyl group for R ⁴ and R ⁹ include those of R ¹ to R ³ and R ⁵ to R ⁸ described above, which have an alkyl group having 1 to 6 carbon atoms. The alkylene group having 1 to 20 carbon atoms of X may be linear or branched, and examples thereof include a methylene group, a methylmethylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, a 1-methylbutylene group, an n-pentylene group, a 1,1-dimethylpropylene group, an n-hexylene group, an n-heptylene group, an n-octylene group, an n-nonylene group, and an n-decylene group. The number of carbon atoms of the alkylene group of X is preferably 1 to 10, and from the viewpoint of excellent suppression effect of coloring and discoloration, 1 to 6 is more preferable, and 1 to 4 is even more preferable. Y is preferably a (meth)acryloyloxy group, and more preferably an acryloyloxy group. In addition, in one preferred embodiment, there is provided a dental hardenable composition in which the hindered phenol compound (C) contains a compound represented by general formula [I], and the groups R ¹ to R ³ do not contain the bonding groups -O-, -S-, -NH-, -N(R ⁴ )-, -O(CO)-, and -CO-.

Examples of the alkyl group, alkoxy group, and aryl group of R ¹⁰ and R ¹¹ are the same as those of R ¹ to R ³ and R ⁵ to R ^8. R ¹⁰ and R ¹¹ are preferably alkyl groups, and from the viewpoint of excellent suppression effect of coloring and discoloration, branched alkyl groups are more preferable, and branched alkyl groups having 3 to 6 carbon atoms are even more preferable. Examples of the alkyl group of R ¹² are the same as those of R ⁴ and R ^9. Examples of the alkylene group of Z ¹ are the same as those of X. Z ² represents a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, or an aryl group, and preferably a carbon atom, a sulfur atom, or an aryl group. Examples of the aryl group of Z ² are the same as those of R ¹ to R ³ and R ⁵ to R ⁸ , and preferably a phenyl group, more preferably a substituted phenyl group, and even more preferably a substituted phenyl group substituted with an alkyl group having 1 to 3 carbon atoms. n represents an integer of 2 to 6, and preferably an integer of 2 to 4. n is appropriately selected according to the number of bonds of Z ² . Another preferred embodiment includes a dental curable composition, in which the hindered phenol compound (C) comprises a compound represented by general formula [III], and the alkylene group of Z ¹ comprises at least one bonding group selected from the group consisting of -O-, -S-, -NH-, -N(R ¹² )-, -O(CO)-, and -CO-. Among these, a hindered phenol compound in which the alkylene group of Z ¹ comprises at least one bonding group selected from the group consisting of -O-, -O(CO)-, and -CO- is preferred, and a hindered phenol compound in which Z ¹ is an alkylene group having 1 to 6 carbon atoms and the alkylene group comprises at least one bonding group selected from the group consisting of -O-, -O(CO)-, and -CO- is more preferred.

Examples of hindered phenol compounds (C) include 3,5-di-t-butyl-4-hydroxytoluene, 3,5-di-t-butyl-4-hydroxyanisole, 2,6-di-t-butyl-4-hydroxytoluene, 2,6-di-t-butyl-4-hydroxyanisole, 4-t-butylpyrocatechol, pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], thiodiethylene Examples of suitable tert-butyl esters include ethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, N,N'-hexane-1,6-diylbis(3-(3,5-di-t-butyl-4-hydroxyphenylpropionamide)), octyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate (IRGANOX 1135), 3,3',3",5,5',5"-hexa-t-butyl-α,α',α"-(mesitylene-2,4,6-triyl)tri-p-cresol, and 4,6-bis(octylthiomethyl)-o-cresol. Among these, 3,5-di-t-butyl-4-hydroxytoluene is preferably used because it has a small curing inhibition effect and a strong discoloration suppression effect.

The content of the hindered phenol compound (C) in the dental curable composition of the present invention is preferably 2.0 to 200 parts by mass, more preferably 2.5 to 100 parts by mass, even more preferably 5.0 to 50 parts by mass, particularly preferably 8.0 to 40 parts by mass, and most preferably 10 to 30 parts by mass, relative to 100 parts by mass of the photopolymerization initiator (B). By making the content of the hindered phenol compound (C) 2.0 to 200 parts by mass, the curability, stress retention of the cured product, toughness, water resistance, color tone, and color tone stability are well maintained. When the content of the hindered phenol compound (C) is 2.0 parts by mass or more relative to 100 parts by mass of the photopolymerization initiator (B), yellowing of the molded product of the dental curable composition is easily suppressed, and the color tone and color tone stability tend to be excellent. On the other hand, when the content of the photopolymerization initiator (B) is 200 parts by mass or less per 100 parts by mass, the degree of polymerization becomes sufficiently large when the dental curable composition is molded, and the mechanical strength of the molded product tends to improve. In particular, when using the liquid tank stereolithography method, the occurrence of falling off, modeling interruptions, etc. due to insufficient curing can be suppressed, and the moldability is excellent.

[α,β-Unsaturated Double Bond Group-Containing Compound (D) Other Than (Meth)acrylamide (A)]
The dental curable composition of the present invention preferably contains an α,β-unsaturated double bond group-containing compound (D) other than the (meth)acrylamide (A) (hereinafter, may be simply referred to as "α,β-unsaturated double bond group-containing compound (D)"). The α,β-unsaturated double bond group-containing compound (D) is used in the dental curable composition of the present invention to adjust the flexural modulus of the cured product of the dental curable composition. Furthermore, by containing the α,β-unsaturated double bond group-containing compound (D), the dental curable composition of the present invention has better toughness and water resistance of the cured product.

In this specification, the α,β-unsaturated double bond group means a polymerizable group such as a (meth)acryloyl group, a vinyl group, or a styrene group. The α,β-unsaturated double bond group-containing compound (D) in the present invention preferably has a boiling point converted to normal pressure of 250°C or higher, in order to suppress the odor of the dental hardenable composition. By having a normal pressure boiling point of 250°C or higher, it is possible to suppress an increase in vapor pressure, suppress the generation of odor, and make it difficult to feel an unpleasant odor. The normal pressure boiling point of the α,β-unsaturated double bond group-containing compound (D) is preferably 275°C or higher, and more preferably 300°C or higher. Note that the normal pressure boiling point in this invention is a measured value obtained by normal pressure distillation, and for compounds whose normal pressure boiling point cannot be observed, the normal pressure boiling point converted from the reduced pressure boiling point measured by reduced pressure distillation using a boiling point conversion table (Science of Petroleum, Vol.II. p.1281(1938)) is used. Examples of the α,β-unsaturated double bond group-containing compound (D) include a urethane-modified (meth)acrylic compound (D)-1 and a (meth)acrylic acid ester compound (D)-2 that does not have a urethane bond, and these preferably have a boiling point converted to normal pressure of 250°C or higher. From the viewpoint of excellent toughness of the resulting cured product, the α,β-unsaturated double bond group-containing compound (D) preferably contains a urethane-modified (meth)acrylic compound (D)-1.

The urethane-modified (meth)acrylic compound (D)-1 is not particularly limited as long as it is a (meth)acrylic compound containing a urethane bond. Examples of the urethane-modified (meth)acrylic compound (D)-1 include urethane-modified (meth)acrylic compounds that do not have a polymer skeleton, such as 2,2,4-trimethylhexamethylene bis(2-carbamoyloxyethyl) dimethacrylate (commonly known as "UDMA") and N,N'-(2,2,4-trimethylhexamethylene) bis[2-(aminocarboxy)propane-1,3-diol] tetra(meth)acrylate. In addition, examples of the urethane-modified (meth)acrylic compound (D)-1 include urethane-modified (meth)acrylic compounds that have a polymer skeleton. The urethane-modified (meth)acrylic compound that has a polymer skeleton can be easily synthesized by addition reaction of a polyol containing a polymer skeleton described later, a compound having an isocyanate group (-NCO), and a (meth)acrylic compound having a hydroxyl group (-OH). In addition, the urethane-modified (meth)acrylic compound (D)-1 can be easily synthesized by subjecting a (meth)acrylic compound having a hydroxyl group to a ring-opening addition reaction with a lactone or an alkylene oxide, and then subjecting the resulting compound having a hydroxyl group at one end to an addition reaction with a compound having an isocyanate group. The urethane-modified (meth)acrylic compound (D)-1 may be used alone or in combination of two or more types.

The urethane-modified (meth)acrylic compound (D)-1 is preferably a (meth)acrylate that contains, within one molecule, at least one structure (polymer backbone) selected from the group consisting of polyester, polycarbonate, polyurethane, and polyether, as well as a urethane bond, and more preferably a (meth)acrylate that contains, within one molecule, at least one polyol portion selected from the group consisting of polyester, polycarbonate, polyurethane, polyether, polyconjugated diene, and hydrogenated polyconjugated diene, which has a structure derived from an aliphatic diol having 4 to 18 carbon atoms and a branched structure, as well as a urethane bond. In the above structure, examples of polyesters include copolymers of aromatic dicarboxylic acids such as phthalic acid (e.g., isophthalic acid, terephthalic acid) or unsaturated aliphatic dicarboxylic acids such as maleic acid and aliphatic diols having 2 to 18 carbon atoms, copolymers of saturated aliphatic dicarboxylic acids such as adipic acid and sebacic acid and aliphatic diols having 2 to 18 carbon atoms, polymers of β-propiolactone, polymers of γ-butyrolactone, polymers of δ-valerolactone, polymers of ε-caprolactone, and copolymers thereof, and copolymers of aromatic dicarboxylic acids or unsaturated aliphatic dicarboxylic acids and aliphatic diols having 2 to 12 carbon atoms, and copolymers of saturated aliphatic dicarboxylic acids and aliphatic diols having 2 to 12 carbon atoms are preferred. With regard to polyesters, the aliphatic diols having 2 to 18 carbon atoms may have a branched structure. Examples of branched structures include alkyl groups having 1 to 10 carbon atoms, preferably alkyl groups having 1 to 6 carbon atoms, more preferably alkyl groups having 1 to 4 carbon atoms, and even more preferably alkyl groups having 1 to 3 carbon atoms. Examples of the polycarbonate include polycarbonates derived from an aliphatic diol having 2 to 18 carbon atoms, polycarbonates derived from bisphenol A, and polycarbonates derived from an aliphatic diol having 2 to 18 carbon atoms and bisphenol A, and are preferably polycarbonates derived from an aliphatic diol having 2 to 12 carbon atoms, polycarbonates derived from bisphenol A, and polycarbonates derived from an aliphatic diol having 2 to 12 carbon atoms and bisphenol A. Regarding the polycarbonate, the aliphatic diol having 2 to 18 carbon atoms may have a branched structure. Examples of the branched structure include the same as the aliphatic diol of the polyester. Examples of the polyurethane include copolymers of an aliphatic diol having 2 to 18 carbon atoms and a diisocyanate having 1 to 18 carbon atoms, and are preferably copolymers of an aliphatic diol having 2 to 12 carbon atoms and a diisocyanate having 1 to 12 carbon atoms. Regarding polyurethane, the aliphatic diol having 2 to 18 carbon atoms may have a branched structure. Examples of the branched structure include the same as the aliphatic diol of polycarbonate. Examples of polyether include polyethylene glycol, polypropylene glycol, polybutylene glycol, poly(1-methylbutylene glycol), and the like. Among these, the polyester structure is preferred in terms of excellent toughness. Furthermore, in terms of excellent water resistance and toughness, the polyester structure preferably contains a polyol portion having a structure derived from an aliphatic diol having 4 to 18 carbon atoms and a branched structure, and a phthalate ester (e.g., isophthalate ester, terephthalate ester) or a sebacic acid ester, and in terms of excellent water resistance and modeling, it is more preferred that the polyester structure contains a polyol portion having a structure derived from an aliphatic diol having 4 to 12 carbon atoms and a branched structure, and a sebacic acid ester, and it is even more preferred that the polyester structure contains a polyol portion having a structure derived from an aliphatic diol having 5 to 12 carbon atoms and a branched structure, and an isophthalate ester or a sebacic acid ester. The polyol having the polymer skeleton described above can be used to produce the urethane-modified (meth)acrylic compound (D)-1.

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).

Examples of (meth)acrylic compounds 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. , 2,2-bis[4-[3-(meth)acryloyloxy-2-hydroxypropoxy]phenyl]propane, 1,2-bis[3-(meth)acryloyloxy-2-hydroxypropoxy]ethane, pentaerythritol tri(meth)acrylate, dipentaerythritol tri- or tetra(meth)acrylate, and other hydroxy(meth)acrylamide compounds; N-hydroxyethyl(meth)acrylamide, N,N-bis(2-hydroxyethyl)(meth)acrylamide, and other hydroxy(meth)acrylamide compounds.

Examples of the aliphatic diols having 4 to 18 carbon atoms and having 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, and 2-methyl-1,11-undecanediol. Examples of the dimethyl-1,15-pentadecanediol include 2,14-dimethyl-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 the dental hardenable composition having excellent hardening properties and low viscosity, it is preferable to use an aliphatic diol having 5 to 12 carbon atoms and 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 component, more preferably 2-methyl-1,4-butanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, or 2,7-dimethyl-1,8-octanediol, and even more preferably 3-methyl-1,5-pentanediol or 2-methyl-1,8-octanediol.

The addition reaction between a compound having an isocyanate group and a (meth)acrylic compound having a hydroxyl group can be carried out according to a known method, and there are no particular limitations.

The resulting urethane-modified (meth)acrylic compound (D)-1 may be any combination of a polyol having at least one structure selected from the group consisting of polyester, polycarbonate, polyurethane, polyether, and polyconjugated diene, a compound having an isocyanate group, and a (meth)acrylic compound having a hydroxyl group.

From the viewpoints of viscosity and strength, the weight average molecular weight (Mw) of the urethane-modified (meth)acrylic compound (D)-1 is preferably 300 to 10,000, more preferably 500 to 5,000, even more preferably 750 to 4,000, and particularly preferably 1,000 to 3,000. In the present invention, the weight average molecular weight (Mw) refers to the weight average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC).

The content of the urethane-modified (meth)acrylic compound (D)-1 in the dental curable composition of the present invention is preferably 10 to 90 parts by mass per 100 parts by mass of the total amount of (meth)acrylamide (A), the α,β-unsaturated double bond group-containing compound (D), and other polymerizable monomers, and from the viewpoint of superior curability and toughness of the cured product, is more preferably 20 to 80 parts by mass, and even more preferably 30 to 70 parts by mass.

In the dental hardenable composition of the present invention, the α,β-unsaturated double bond group-containing compound (D) may contain a (meth)acrylic acid ester compound (D)-2 that does not have a urethane bond in order to adjust the toughness of the resulting cured product. Examples of the (meth)acrylic acid ester compound (D)-2 that does not have a urethane bond include a monofunctional (meth)acrylic acid ester compound (D)-2-1 that does not have a urethane bond and a polyfunctional (meth)acrylic acid ester compound (D)-2-2 that does not have a urethane bond. Among these, a monofunctional (meth)acrylic acid ester compound (D)-2-1 that does not have a urethane bond (hereinafter, sometimes simply referred to as "monofunctional (meth)acrylic acid ester compound (D)-2-1") that does not have a urethane bond is preferably used in view of the excellent toughness of the resulting cured product.

Examples of the monofunctional (meth)acrylic acid ester compound (D)-2-1 include, for example, o-phenylphenol (meth)acrylate, m-phenylphenol (meth)acrylate, p-phenylphenol (meth)acrylate, methoxylated-o-phenylphenol (meth)acrylate, methoxylated-m-phenylphenol (meth)acrylate, methoxylated-p-phenylphenol (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. acrylate, propoxylated p-phenylphenol (meth)acrylate, butoxylated o-phenylphenol (meth)acrylate, butoxylated m-phenylphenol (meth)acrylate, butoxylated p-phenylphenol (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, 3-(o-phenoxyphenyl)propyl (meth)acrylate, 3-(m-phenoxyphenyl)propyl (meth)acrylate Monofunctional (meth)acrylic acids having at least one aromatic ring, such as 3-(p-phenoxyphenyl)propyl (meth)acrylate, 4-(o-phenoxyphenyl)butyl (meth)acrylate, 4-(m-phenoxyphenyl)butyl (meth)acrylate, 4-(p-phenoxyphenyl)butyl (meth)acrylate, 5-(o-phenoxyphenyl)pentyl (meth)acrylate, 5-(m-phenoxyphenyl)pentyl (meth)acrylate, 5-(p-phenoxyphenyl)pentyl (meth)acrylate, 6-(o-phenoxyphenyl)hexyl (meth)acrylate, 6-(m-phenoxyphenyl)hexyl (meth)acrylate, and 6-(p-phenoxyphenyl)hexyl (meth)acrylate. Ester compounds: aliphatic monofunctional (meth)acrylic acid ester compounds such as undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, palmitoleic (meth)acrylate, heptadecyl (meth)acrylate, oleyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, glycerol mono(meth)acrylate, and erythritol mono(meth)acrylate. These may be used alone or in combination of two or more. Among these, from the viewpoints of excellent hardenability of the dental hardenable composition and toughness of the hardened product, monofunctional (meth)acrylic acid ester compounds having at least one aromatic ring are preferred. From the viewpoints of high hydrophobicity and higher water resistance, o-phenoxybenzyl acrylate, m-phenoxybenzyl acrylate, p-phenoxybenzyl acrylate, 2-(o-phenoxyphenyl)ethyl acrylate, 2-(m-phenoxyphenyl)ethyl acrylate, 2-(p-phenoxyphenyl)ethyl acrylate, ethoxylated-o-phenylphenol (meth)acrylate, ethoxylated-m-phenylphenol (meth)acrylate, Monofunctional (meth)acrylic acid ester compounds having two aromatic rings, such as ethoxylated-p-phenylphenol (meth)acrylate, are more preferred, with o-phenoxybenzyl acrylate, m-phenoxybenzyl acrylate, p-phenoxybenzyl acrylate, and ethoxylated-o-phenylphenol (meth)acrylate being even more preferred, with o-phenoxybenzyl acrylate, m-phenoxybenzyl acrylate, and ethoxylated-o-phenylphenol (meth)acrylate being particularly preferred, and m-phenoxybenzyl acrylate and ethoxylated-o-phenylphenol (meth)acrylate being the most preferred.

The content of the monofunctional (meth)acrylic acid ester compound (D)-2-1 having no urethane bond in the dental hardenable composition of the present invention is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 10 to 30 parts by mass, per 100 parts by mass of the total amount of the polymerizable compounds, in terms of superior hardenability, toughness and water resistance of the hardened product.

Examples of the (meth)acrylic acid ester compound (D)-2-2 that does not have a polyfunctional urethane bond (hereinafter, sometimes simply referred to as "polyfunctional (meth)acrylic acid ester compound (D)-2-2") include aromatic compound-based bifunctional (meth)acrylic acid ester compounds, aliphatic compound-based bifunctional (meth)acrylic acid ester compounds, and trifunctional or higher (meth)acrylic acid ester compounds.

Examples of aromatic bifunctional (meth)acrylic acid ester compounds include 2,2-bis((meth)acryloyloxyphenyl)propane, 2,2-bis[4-(3-acryloyloxy)-2-hydroxypropoxyphenyl]propane, 2,2-bis[4-(3-methacryloyloxy)-2-hydroxypropoxyphenyl]propane (commonly known as "Bis-GMA"), 2,2-bis(4-(meth)acryloyloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypolyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxytetraethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypentaethoxyphenyl)propane, ) propane, 2,2-bis(4-(meth)acryloyloxydipropoxyphenyl)propane, 2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxyethoxyphenyl)propane, 2-(4-(meth)acryloyloxydiethoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane, 2-(4-(meth)acryloyloxydipropoxyphenyl)-2-(4-(meth)acryloyloxytriethoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxypropoxyphenyl)propane, 2,2-bis(4-(meth)acryloyloxyisopropoxyphenyl)propane, 1,4-bis(2-(meth)acryloyloxyethyl)pyromellitate, etc.

Examples of aliphatic bifunctional (meth)acrylic acid ester compounds include glycerol di(meth)acrylate, ethylene glycol di(meth)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.

Examples of trifunctional or higher (meth)acrylic acid ester compounds include trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolmethane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, 1,7-diacryloyloxy-2,2,6,6-tetra(meth)acryloyloxymethyl-4-oxaheptane, etc.

When the (meth)acrylic acid ester compound (D)-2 contains a polyfunctional (meth)acrylic acid ester compound (D)-2-2 and a monofunctional (meth)acrylic acid ester compound (D)-2-1, the content of the monofunctional (meth)acrylic acid ester compound (D)-2-1 is preferably 10 to 100 parts by mass, more preferably 30 to 100 parts by mass, and even more preferably 50 to 100 parts by mass, per 100 parts by mass of the total amount of the (meth)acrylic acid ester compound (D)-2.

The content of the α,β-unsaturated double bond group-containing compound (D) in the dental hardenable composition of the present invention is preferably 1 to 50 parts by mass per 100 parts by mass of the total amount of the polymerizable compounds, and from the viewpoint of superior hardenability, toughness and water resistance of the hardened product, it is more preferably 2.5 to 40 parts by mass, and even more preferably 5.0 to 30 parts by mass.

Another preferred embodiment (X-1) is a dental hardenable composition that is substantially free of monofunctional (meth)acrylic acid ester compound (D)-2-1. "Substantially free of monofunctional (meth)acrylic acid ester compound (D)-2-1" means that the content of monofunctional (meth)acrylic acid ester compound (D)-2-1 is less than 1.0 part by mass, preferably less than 0.5 parts by mass, more preferably less than 0.1 parts by mass, and even more preferably less than 0.01 parts by mass, per 100 parts by mass of the total amount of polymerizable monomers. Another preferred embodiment (X-2) is a dental hardenable composition that is substantially free of monofunctional (meth)acrylic acid ester compound (D)-2-1a (hereinafter sometimes simply referred to as "(meth)acrylic acid ester compound (D)-2-1a") that has a boiling point of 280°C or higher at normal pressure, has a carbocyclic group, and does not have a nitrogen-containing heterocyclic group and a urethane bond. "Substantially free of (meth)acrylic acid ester compound (D)-2-1a" means, as in embodiment (X-1), that the content of the monofunctional (meth)acrylic acid ester compound (D)-2-1a is less than 1.0 part by mass, preferably less than 0.5 part by mass, more preferably less than 0.1 part by mass, and even more preferably less than 0.01 part by mass, per 100 parts by mass of the total amount of polymerizable monomers. Note that the normal pressure boiling point in the present invention is a value measured by normal pressure distillation, and for compounds whose normal pressure boiling point cannot be observed, the normal pressure boiling point converted from the reduced pressure boiling point measured by reduced pressure distillation using a boiling point conversion table (Science of Petroleum, Vol.II. p.1281(1938)) is used. Examples of carbocyclic groups include monocyclic aromatic groups (phenyl groups), aromatic condensed bicyclic groups (naphthyl groups, etc.), and polycyclic aromatic groups such as condensed tricyclic carbocyclic groups (anthryl groups, etc.); and aliphatic ring groups (cyclopentyl groups, decahydronaphthalenyl groups, etc.).

The dental curable composition of the present invention contains the above-mentioned (meth)acrylamide (A), photopolymerization initiator (B), and hindered phenol compound (C), and the content of the hindered phenol compound (C) is not particularly limited except that it is 0.1 to 200 parts by mass per 100 parts by mass of the photopolymerization initiator (B), and can be produced according to a known method.

The dental hardenable composition of the present invention may contain polymerizable monomers other than (meth)acrylamide (A) and the α,β-unsaturated double bond group-containing compound (D), but may be substantially composed of only (meth)acrylamide (A), or may be substantially composed of only (meth)acrylamide (A) and the α,β-unsaturated double bond group-containing compound (D). The polymerizable monomer being substantially composed of only alicyclic (meth)acrylamide (A) and the α,β-unsaturated double bond group-containing compound (D) means that the content of other polymerizable monomers other than (meth)acrylamide (A) and the α,β-unsaturated double bond group-containing compound (D) is less than 10.0 parts by mass, preferably less than 5.0 parts by mass, more preferably less than 1.0 parts by mass, even more preferably less than 0.1 parts by mass, and particularly preferably less than 0.01 parts by mass, based on 100 parts by mass of the total amount of polymerizable monomers contained in the dental hardenable composition.

The dental hardenable composition of the present invention may contain a polymerization accelerator for the purpose of improving photocurability, within the scope of the present invention. Examples of the polymerization accelerator include amine compounds such as 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, 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 from the viewpoint of imparting excellent hardening properties to the dental hardenable composition.

The dental hardenable composition of the present invention may contain a chemical polymerization initiator, mainly for the purpose of improving the hardening property of the post cure, within the scope of the present invention. Organic peroxides and azo compounds are preferably used. The organic peroxides and azo compounds used as the chemical polymerization initiator are not particularly limited, and known ones can be used. Representative organic peroxides include ketone peroxides, hydroperoxides, diacyl peroxides, dialkyl peroxides, peroxyketals, peroxyesters, and peroxydicarbonates. The chemical polymerization initiator may be used alone or in combination of two or more kinds.

Examples of ketone peroxides include methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, methylcyclohexanone peroxide, and cyclohexanone peroxide.

Examples of hydroperoxides include 2,5-dimethylhexane-2,5-dihydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, and 1,1,3,3-tetramethylbutyl hydroperoxide.

Examples of diacyl peroxides include acetyl peroxide, isobutyryl peroxide, benzoyl peroxide, decanoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, 2,4-dichlorobenzoyl peroxide, and lauroyl peroxide.

Examples of dialkyl peroxides include di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,3-bis(t-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne.

Examples of peroxyketals include 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)butane, 2,2-bis(t-butylperoxy)octane, and 4,4-bis(t-butylperoxy)valeric acid n-butyl ester.

Examples of peroxyesters include α-cumyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, 2,2,4-trimethylpentyl peroxy-2-ethylhexanoate, t-amyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, di-t-butyl peroxyisophthalate, di-t-butyl peroxyhexahydroterephthalate, t-butyl peroxy-3,3,5-trimethylhexanoate, t-butyl peroxyacetate, t-butyl peroxybenzoate, and t-butyl peroxymaleate.

Examples of peroxydicarbonates include di-3-methoxyperoxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, di(2-ethoxyethyl)peroxydicarbonate, and diallylperoxydicarbonate.

The dental hardenable composition of the present invention may further contain a filler in order to adjust the paste properties or to modify the surface properties or strength of the hardened product of the dental hardenable 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.

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. From the viewpoint of the handleability and mechanical strength of the obtained dental curable composition, the average particle size of the organic filler is preferably 0.001 to 50 μm, more preferably 0.001 to 10 μm, and even more preferably 0.001 to 1.0 μm.

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 or spherical fillers, etc. may be appropriately selected and used. From the viewpoint of the handleability and mechanical strength of the resulting dental curable composition, the average particle size of the inorganic filler is preferably 0.001 to 50 μm, more preferably 0.001 to 10 μm, and even more preferably 0.001 to 1.0 μm.

The inorganic filler may be surface-treated with a known surface treatment agent such as a silane coupling agent before use, if necessary, in order to adjust the fluidity of the dental hardenable composition. Examples of the surface treatment agent include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrichlorosilane, vinyltri(β-methoxyethoxy)silane, γ-methacryloyloxypropyltrimethoxysilane, 8-methacryloyloxyoctyltrimethoxysilane, 11-methacryloyloxyundecyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-aminopropyltriethoxysilane.

The organic-inorganic composite filler used in the present invention is obtained by adding a monomer component to the inorganic filler described above in advance, forming a paste, polymerizing it, and pulverizing it. As the organic-inorganic composite filler, for example, TMPT filler (trimethylolpropane trimethacrylate and silica filler mixed, polymerized, and pulverized) can be used. The shape of the organic-inorganic composite filler is not particularly limited, and the particle size of the filler can be appropriately selected and used. From the viewpoint of the handleability and mechanical strength of the obtained dental hardenable composition, the average particle size of the organic-inorganic composite filler is preferably 0.001 to 50 μm, more preferably 0.001 to 10 μm, and even more preferably 0.001 to 1.0 μm.

In this specification, the average particle size of the filler refers to the average primary particle size, which can be determined by the laser diffraction scattering method or by observing the particles with an electron microscope. Specifically, the laser diffraction scattering method is convenient for measuring the particle size of particles of 0.1 μm or more, while the electron microscope observation is convenient for measuring the particle size of ultrafine particles of less than 0.1 μm. 0.1 μm is a value measured by the laser diffraction scattering method.

Specifically, the laser diffraction scattering method can be performed, for example, by using a laser diffraction particle size distribution analyzer (SALD-2300: manufactured by Shimadzu Corporation) and measuring on a volume basis using a 0.2% aqueous solution of sodium hexametaphosphate as the dispersion medium.

Specific examples of electron microscope observations include taking a photograph of the particles with an electron microscope (S-4000 model, manufactured by Hitachi, Ltd.) and measuring the particle diameters of the particles (200 or more) observed within a unit field of view of the photograph using image analysis particle size distribution measurement software (Mac-View (manufactured by Mountec Co., Ltd.)). In this case, the particle diameter is found as the arithmetic mean value of the longest and shortest lengths of the particles, and the average primary particle diameter is calculated from the number of particles and their particle diameters.

A polymer can be added to the dental hardenable composition of the present invention for the purpose of improving flexibility, flowability, 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, or hydrogenated products thereof. These polymers may be used alone or in combination of two or more types.

The dental curable composition of the present invention may contain a softener as 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. There are no particular restrictions on the content of the softener as long as it does not impair the purpose of the present invention, but it is usually 200 parts by mass or less, and preferably 100 parts by mass or less, per 100 parts by mass of the total amount of (meth)acrylamide (A) and the α,β-unsaturated double bond group-containing compound (D).

In addition, the dental curable composition of the present invention may contain a known stabilizer for the purpose of suppressing deterioration of the cured product or adjusting the photocurability. Examples of such stabilizers include ultraviolet absorbers, polymerization inhibitors, and antioxidants (however, the above stabilizers exclude the hindered phenol compound (C)). The stabilizers may be used alone or in combination of two or more. In one embodiment, the dental curable composition does not contain an ultraviolet absorber, a polymerization inhibitor, or an antioxidant other than the hindered phenol compound (C).

In addition, known additives can be blended into the dental hardenable composition of the present invention for the purpose of adjusting the color tone or paste properties. Examples of such additives include pigments, dyes, organic solvents, thickeners, etc. One type of additive may be used alone, or two or more types may be used in combination.

When the dental hardenable composition of the present invention is modeled by stereolithography (particularly suspended liquid tank stereolithography), it is easy to model due to its low odor and excellent hardening properties, and can produce a model with excellent color tone and color tone stability, stress retention, toughness, and water resistance. It can also be applied to inkjet stereolithography. Therefore, the dental hardenable composition of the present invention and its hardened product can be applied to applications (e.g., intraoral applications) in which such advantages can be utilized, and is particularly suitable for dental materials and medical materials such as dental mouthpieces (orthodontic aligners, oral appliances (OA), night guards, dental splints) and denture base materials. As a medical material, it is particularly suitable for treatment devices for sleep apnea syndrome. Furthermore, the dental hardenable composition of the present invention can be suitably used as a mouthguard, a protective device against external forces in sports, in addition to dental treatment applications such as dental mouthpieces and denture base materials. In addition, the dental curable composition of the present invention is preferably used as a curable composition for liquid vat stereolithography, since it is easier to obtain effects such as excellent color tone and color tone stability, toughness, water resistance, and moldability. The shape of the cured product using the dental curable composition of the present invention can be changed depending on each application. In addition, the dental curable composition of the present invention can be adjusted in type and content of each component ((meth)acrylamide (A), photopolymerization initiator (B), hindered phenol compound (C), α,β-unsaturated double bond group-containing compound (D), and various other components (polymerization accelerator, filler, polymer, softener, stabilizer, additive, etc.)) for each application such as a dental mouthpiece and denture base material, as necessary.

The dental curable composition of the present invention can be used in a variety of applications by taking advantage of its properties, particularly the fact that when cured with light, it produces molded or three-dimensional objects that have a small volumetric shrinkage rate, excellent molding accuracy, and excellent toughness and water resistance of the cured product, as well as other cured products. For example, it can be used in the manufacture of three-dimensional objects by optical three-dimensional modeling methods, the manufacture of various molded products such as film-like objects or molded objects by casting methods or casting, and in coating and vacuum molding dies.

Among these, the dental curable composition of the present invention is suitable for use in the optical three-dimensional modeling method described above, and in this case, it is possible to smoothly produce a three-dimensional object that has excellent modeling precision, toughness, and water resistance while maintaining a small volumetric shrinkage rate during photocuring.

Another embodiment of the present invention is a method for producing a three-dimensional object by optical three-dimensional modeling using any of the dental hardenable compositions described above.

When performing optical 3D modeling (particularly suspended liquid tank stereolithography) using the dental hardenable composition of the present invention, any of the conventionally known optical 3D modeling methods and devices (e.g., a stereolithography machine such as DIGITALWAX (registered trademark) 020D manufactured by DWS) can be used. The optical 3D modeling method and device are not particularly limited, but from the viewpoint of the viscosity of the dental hardenable composition, the dental hardenable composition of the present invention is particularly suitable for a suspended optical 3D modeling device (suspended liquid tank stereolithography device). Among them, in the present invention, it is preferable to use active energy rays as the light energy for curing the dental hardenable composition. "Active energy rays" means energy rays that can cure a polymerizable composition, such as ultraviolet rays, visible rays, electron rays, X-rays, radiation, high frequency waves, etc. For example, the active energy rays may be ultraviolet rays having a wavelength of 300 to 420 nm. Examples of light sources for active energy rays include lasers such as Ar lasers and He-Cd lasers; and lighting such as LEDs, halogen lamps, xenon lamps, metal halide lamps, mercury lamps, fluorescent lamps, and organic ELs, with lasers and LEDs being particularly preferred. Examples of irradiation methods for active energy rays include laser methods (SLA methods) such as galvano laser methods and flatbed laser methods, projector methods (DLP methods), and liquid crystal display methods (LCD methods).

As described above, when performing optical three-dimensional modeling using the dental hardenable composition of the present invention, any of the conventionally known methods and conventionally known optical modeling system devices can be used without any particular limitations. A representative example of an optical three-dimensional modeling method preferably used in the present invention is a method in which a step of selectively irradiating the dental hardenable composition with an active energy ray to form a hardened layer having a desired pattern, and a step of supplying an unhardened liquid dental hardenable composition and irradiating it with an active energy ray in the same manner to form a new hardened layer continuous with the hardened layer, and laminating them, are repeated to finally obtain the desired three-dimensional object. The three-dimensional object obtained by this method may be used as it is, or in some cases, it may be used after further post-curing by light irradiation or heat to further improve its mechanical properties or shape stability.

The flexural modulus of the cured product of the dental hardenable composition of the present invention is preferably in the range of 0.4 to 3.0 GPa, more preferably in the range of 0.6 to 2.5 GPa, and even more preferably in the range of 0.8 to 2.0 GPa. When the flexural modulus of the cured product is 2.0 GPa or less, the product has a flexible property, and when made into a mouthpiece, it has good conformity to the teeth, so that it is comfortable to wear, and it is less likely to fall off due to bruxism during sleep at night. The flexural strength of the cured product of the dental hardenable composition of the present invention is preferably 30 MPa or more, more preferably 40 MPa or more, and even more preferably 50 MPa or more. The method for measuring the flexural modulus and flexural strength of the cured product is as described in the Examples below.

The stress retention of the cured product of the dental hardenable composition of the present invention is preferably a stress retention rate after 24 hours relative to the initial stress of the cured product of 50% or more, more preferably 55% or more, and even more preferably 60% or more, since this provides excellent shock absorption in intraoral applications such as dental mouthpieces and denture base materials, and excellent orthodontic force, particularly when used in orthodontic aligners. The method for measuring the stress retention rate of the cured product is as described in the Examples below.

The structure, shape, size, etc. of the three-dimensional object obtained by the optical three-dimensional modeling method are not particularly limited and can be determined according to each application. Representative application fields 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; direct molds for prototype metal molds, etc. 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, mother molds, etc., or models for processing.

The dental curable composition of the present invention has a low odor and exhibits excellent toughness, water resistance, color tone, and color stability in the cured product, and can be used not only for dental material applications obtained by optical three-dimensional modeling, but also for general photocurable dental material applications such as dental composite resins, dental cements, and dental adhesives.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples, and many modifications can be made by those with ordinary skill in the art within the scope of the technical concept of the present invention.

The components used in the dental hardenable compositions according to the examples and comparative examples are explained below together with their abbreviations.

[(Meth)acrylamide (A)]
PRAA: N-acryloylpyrrolidine (Merch KGaA, molecular weight 125)
PPAA: N-acryloylpiperidine (Merch KGaA, molecular weight 139)

[Photopolymerization initiator (B)]
TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide BAPO: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide

[Hindered phenol compound (C)]
BHT: 3,5-di-t-butyl-4-hydroxytoluene PETBHPP: pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]

[α,β-unsaturated double bond group-containing compound (D)]
[Urethanized (meth)acrylic compound (D)-1]
The urethane-modified (meth)acrylic compounds (D)-1-1 and (D)-1-2 produced in Synthesis Examples 1 and 2 described below were used.

[Monofunctional (meth)acrylic acid ester compound (D)-2-1]
POBA: m-phenoxybenzyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd., boiling point at normal pressure of 300°C or higher)

[Polyfunctional (meth)acrylic acid ester compound (D)-2-2]
TCDDMA: Tricyclodecane dimethanol dimethacrylate (manufactured by Kyoeisha Chemical Co., Ltd., boiling point at normal pressure of 300° C. or higher)

Synthesis Example 1: Production of urethane-modified (meth)acrylic compound (D)-1-1
(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 controller, a thermometer, and a condenser, and the mixture was heated to 70° C. with stirring.
(2) On the other hand, 2500 g of polyester polyol ("Kuraray Polyol (registered trademark) P-2030" manufactured by Kuraray Co., Ltd.; polyol composed of isophthalic 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 this dropping funnel was dropped into the flask in (1) above. Note that while stirring the solution in the flask in (1) above, the solution was dropped at a constant rate over 4 hours while maintaining the internal temperature of the flask at 65 to 75°C. After completion of the dropping, the mixture was stirred at the same temperature for 2 hours to react.
(3) Next, a liquid prepared by uniformly dissolving 150 g of 2-hydroxyethyl acrylate and 0.4 g of hydroquinone monomethyl ether in a separate dropping funnel was dropped at a constant rate over 2 hours while maintaining the internal temperature of the flask at 55 to 65° C., and then the reaction was allowed to proceed for 4 hours while maintaining the temperature of the solution in the flask at 70 to 80° C., thereby obtaining a urethane-type (meth)acrylic compound (D)-1-1. The weight average molecular weight Mw of the urethane-type (meth)acrylic compound (D)-1-1 as determined by GPC analysis was 2700, and the boiling point converted to normal pressure was 300° C. or higher.

Synthesis Example 2: Production of urethane-modified (meth)acrylic compound (D)-1-2
(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 controller, a thermometer, and a condenser, and the mixture was heated to 70° C. with stirring.
(2) On the other hand, 2500 g of polyester polyol ("Kuraray Polyol (registered trademark) P-2050" manufactured by Kuraray Co., Ltd.; 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 this dropping funnel was dropped into the flask in (1) above. Note that while stirring the solution in the flask in (1) above, the solution was dropped at a constant rate over 4 hours while maintaining the internal temperature of the flask at 65 to 75°C. After completion of the dropping, the mixture was stirred at the same temperature for 2 hours to react.
(3) Next, a liquid prepared by uniformly dissolving 150 g of 2-hydroxyethyl acrylate and 0.4 g of hydroquinone monomethyl ether in a separate dropping funnel was dropped at a constant rate over 2 hours while maintaining the internal temperature of the flask at 55 to 65° C., and then the reaction was allowed to proceed for 4 hours while maintaining the temperature of the solution in the flask at 70 to 80° C., thereby obtaining a urethane-type (meth)acrylic compound (D)-1-2. The weight average molecular weight Mw of the urethane-type (meth)acrylic compound (D)-1-2 as determined by GPC analysis was 2600, and the boiling point converted to normal pressure was 300° C. or higher.

[Examples 1 to 7 and Comparative Examples 1 to 8]
The components shown in Tables 1 and 2 were mixed at room temperature (20° C.±15° C., JIS (Japanese Industrial Standards) Z 8703:1983) in the amounts shown in Tables 1 and 2 to prepare pastes as dental curable compositions according to Examples 1 to 7 and Comparative Examples 1 to 8.

<Odor>
The dental curable compositions according to each Example and Comparative Example were evaluated for odor by 10 panelists (n=1). Among the 10 panelists, those who felt an unpleasant odor by less than 2 people were rated as "○", those who felt an unpleasant odor by 2 or more people but less than 5 people were rated as "△", and those who felt an unpleasant odor by 5 or more people were rated as "×". "○" was judged to be acceptable for odor.

<Formability>
For each of the dental curable compositions according to the Examples and Comparative Examples, a test piece having a thickness of 3.3 mm, a width of 10.0 mm, and a length of 64 mm was molded using a stereolithography machine (DIGITALWAX (registered trademark) 020D manufactured by DWS Corporation) (n=5). When a rectangular parallelepiped with the exact dimensions could be molded, it was marked as "OK" (printable), and when a three-dimensional object could not be obtained even once, it was marked as "X" (not printable). The molded test pieces were used to carry out the evaluation described below.

<Stress retention>
For the cured product of the dental curable composition according to each Example and Comparative Example, a sheet-like cured product having a length of 60 mm, a width of 20 mm, and a thickness of 1.0 mm was prepared using a stereolithography machine (DIGITALWAX (registered trademark) 020D manufactured by DWS). The molded product obtained by curing was washed with ethanol to remove unpolymerized polymerizable monomers, and then further polymerized using a photoirradiator (Otoflash (registered trademark) G171 manufactured by EnvisionTEC). The molded product was punched with a punching blade of dumbbell-shaped No. 8 (thickness of parallel part: 2.0 mm, maximum thickness of parallel part: 2.5 mm) described in JIS K 6251:2010 (vulcanized rubber and thermoplastic rubber - Determination of tensile properties) to prepare a tensile test piece (n=5). The obtained test piece was used to evaluate the stress retention. Specifically, using a universal testing machine (Shimadzu Corporation, EZ Test EZ-SX 500N), the specimen was pulled 0.5 mm at a crosshead speed of 20 mm/min with a jig distance of 10 mm, and then held for 24 hours, and the stress (tensile stress at a given elongation) decay behavior was observed and calculated using the following formula. The average values are shown in Tables 1 and 2. The initial stress means the measured value immediately after pulling 0.5 mm. In this test, the stress after 24 hours is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more of the initial stress.
Stress retention rate (%) = stress after 24 hours / initial stress x 100

<Toughness (flexural modulus, flexural strength, break displacement)>
For the cured product of the dental curable composition according to each Example and Comparative Example, a test piece having a length of 64.0 mm, a width of 10.0 mm, and a thickness of 3.3 mm as described in JIS T 6501:2012 (acrylic resin for denture base) was prepared using a stereolithography machine (DIGITALWAX (registered trademark) 020D manufactured by DWS). The obtained molded product was washed with ethanol to remove unpolymerized polymerizable monomers, and then further polymerized using a light irradiation machine (Otoflash (registered trademark) G171 manufactured by EnvisionTEC) to obtain a cured product. The obtained cured product was stored in air for 1 day, and then evaluated by a bending strength test, which was taken as the initial value. That is, a bending strength test was performed at a crosshead speed of 5 mm/min using a universal testing machine (Autograph AG-I 100 kN manufactured by Shimadzu Corporation) (n=5). The average values of the measurement results are shown in Tables 1 and 2. The flexural modulus of the test piece is preferably in the range of 0.4 to 3.0 GPa, more preferably in the range of 0.6 to 2.5 GPa, and even more preferably in the range of 0.8 to 2.0 GPa. The flexural strength (three-point flexural strength) is preferably 30 MPa or more, more preferably 40 MPa or more, and even more preferably 50 MPa or more. As for the displacement at break, it is preferable that the specimen does not break. If the specimen does not break until the end or breaks at a displacement of 20 mm or more, the flexibility is good (○), if the specimen breaks at a displacement of more than 10 mm but less than 20 mm, the flexibility is medium (△), and if the specimen breaks at a displacement of 10 mm or less, the flexibility is poor (×). As for the toughness, if the evaluation of the displacement at break is "△" or "○", the flexural modulus is in the range of 0.4 to 3.0 GPa, and the flexural strength is 30 MPa or more, the specimen is considered to have passed the test.

<Water resistance>
The cured products of the dental curable compositions according to each Example and Comparative Example, which were prepared in the same manner as the cured products prepared in the toughness measurement, were immersed in water at 37°C for 168 hours, and the flexural strength was measured in the same manner as in the above flexural strength test (n=5). The measurement result of the flexural strength in the above toughness was taken as the initial flexural strength, and the change rate (decrease rate) of the flexural strength after 168 hours of immersion in water at 37°C relative to the initial flexural strength was calculated using the following formula. The average value of the calculated values is shown in Tables 1 and 2. If the decrease rate is 10% or less, the water resistance is excellent, and if it is 7% or less, the water resistance is even better. The flexural strength after 168 hours of immersion in water at 37°C is shown in Tables 1 and 2 as "flexural strength after immersion".
Rate of change (decrease) in bending strength (%)=[initial bending strength (MPa)−bending strength after 168 hours of immersion in water at 37° C. (MPa)]/initial bending strength (MPa)]×100

<Color Tone and Color Tone Stability>
For each dental curable composition of each Example and Comparative Example, a disk-shaped object having a diameter of 15.0 mm and a thickness of 1.0 mm was produced using the same stereolithography machine as above. The obtained object was washed with ethanol to remove unpolymerized polymerizable monomers, and then polymerized by a light irradiation machine (Otoflash (registered trademark) G171 manufactured by EnvisionTEC) to obtain a cured product. The obtained cured product was polished with silicon carbide paper No. 1000, and then polished with a dental lapping film (manufactured by 3M), and then the yellowness b ^* value and the yellowness Δb ^* value were measured using a spectrophotometer (manufactured by Konica Minolta, Inc., SPECTROPHOTOMETER CM-3610A, JIS Z 8722: 2009, condition c, D65 light source), and the average value was obtained (n = 5). The average values are shown in Tables 1 and 2. The yellowing index Δb* value is defined by the following formula.
Δb*=b ^* _(7d) -b ^* _(0d)
(In the formula, b ^* _(7d) represents the average value of the yellowness b ^* value in the L*a*b* color system of JIS Z 8781-4:2013 measured 7 days after shaping and secondary polymerization, and b ^* _(0d) represents the average value of the yellowness b ^* value in the L*a*b* color system measured immediately after shaping and secondary polymerization.)
When the yellowness b ^* value is 10.0 or less, a dental prosthesis is likely to be visually recognized as colorless when manufactured. When the yellowness Δb ^* value is 5.0 or less, a dental prosthesis is likely to be visually recognized as not yellowing when manufactured.

As shown in Tables 1 and 2, the dental curable compositions in Examples 1 to 7 had low odor and excellent moldability, and the cured products had excellent stress retention, toughness, water resistance, color tone, and color tone stability. In particular, the dental curable composition of Comparative Example 1, which did not contain acrylamide (A) and hindered phenol compound (C), did not produce molded products with the correct dimensions. The stress retention, toughness, and water resistance of the cured products were superior to the dental curable compositions of Comparative Examples 2 and 3, which contained acrylamide that does not fall under (meth)acrylamide (A). The color tone and color tone stability of the cured products were superior to the dental curable compositions of Comparative Examples 4 to 8, which did not contain the hindered phenol compound (C) in the appropriate content and blending ratio. In Comparative Example 6, which contained too much hindered phenol compound (C), the stress retention, toughness, and water resistance of the cured products were also inferior.

The dental curable composition of the present invention has low viscosity and is easy to mold when molded by photolithography, and has excellent stress retention, toughness, water resistance, color tone and color stability, so it can be suitably used in applications where stress is continuously applied in the oral environment, such as various dental materials (particularly dental mouthpieces and denture base materials) or various sleep disorder treatment materials (particularly treatment devices for sleep apnea syndrome). In addition, since it has low odor and excellent toughness, water resistance, color tone and color stability, it can also be used for photocurable dental material applications such as dental composite resins, dental cements, and dental adhesives.

Claims (14)

The composition contains a (meth)acrylamide (A) containing an alicyclic amino group (a), a photopolymerization initiator (B), and a hindered phenol compound (C),
the alicyclic amino group (a) has only one nitrogen atom as a heteroatom in a ring structure, and a (meth)acryloyl group is directly bonded to the nitrogen atom of the alicyclic amino group (a);
the number of carbon atoms in the hydrocarbon chain forming the ring structure of the alicyclic amino group (a) is 4 to 5,
the photopolymerization initiator (B) contains a (bis)acylphosphine oxide,
The hindered phenol compound (C) contains a compound represented by the following general formula [I] and/or a compound represented by the following general formula [III]:
The dental curable composition comprises a hindered phenol compound (C) in an amount of 0.1 to 200 parts by mass relative to 100 parts by mass of the photopolymerization initiator (B).

(In the formula, R ¹ to R ³ each independently represent an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkoxy group having 1 to 6 carbon atoms which may have a substituent, an aryl group having 6 to 10 carbon atoms which may have a substituent, or a hydroxyl group, and the groups (excluding the hydroxyl group) of R ¹ to R ³ may contain at least one bonding group selected from the group consisting of -O-, -S-, -NH-, -N(R ⁴ )-, -O(CO)-, and -CO-. R ⁴ represents an alkyl group having 1 to 6 carbon atoms.)

(In the formula, R ¹⁰ and R ¹¹ each independently represent an alkyl group having 1 to 6 carbon atoms which may have a substituent, an alkoxy group having 1 to 6 carbon atoms which may have a substituent, or an aryl group having 6 to 10 carbon atoms which may have a substituent; Z ¹ represents an alkylene group having 1 to 6 carbon atoms which may have a substituent; Z ² represents a carbon atom , a sulfur atom, or an aryl group; n represents an integer of 2 to 4 ; and the groups of R ¹⁰ , R ¹¹ , and Z ¹ may contain at least one bonding group selected from the group consisting of -O-, -S-, -NH-, -N(R ¹² )-, -O(CO)-, and -CO-. R ¹² represents an alkyl group having 1 to 6 carbon atoms.) The dental hardenable composition according to claim 1 , wherein the hindered phenol compound (C) contains a compound represented by general formula [III]. 3. The dental hardenable composition according to claim 1 , wherein a cured product having a thickness of 2.0 mm±0.2 mm has a stress retention rate of 50% or more after 24 hours. 4. The dental curable composition according to claim 1 , further comprising (D) an α,β-unsaturated double bond group-containing compound other than the (meth)acrylamide (A). 5. The dental curable composition according to claim 4 , wherein the α,β-unsaturated double bond group-containing compound (D) other than the (meth)acrylamide (A) has a boiling point converted to normal pressure of 250° C. or higher. The dental curable composition according to claim 4 or 5 , wherein the α,β-unsaturated double bond group-containing compound (D) other than the (meth)acrylamide (A) contains a urethanized (meth)acrylic compound (D)-1. The dental curable composition according to claim 6, wherein the urethane-modified (meth)acrylic compound (D)-1 is a (meth)acrylate containing, in one molecule, at least one structure selected from the group consisting of polyester, polycarbonate, polyurethane, and polyether , and a urethane bond. The dental curable composition according to any one of claims 4 to 6, wherein the α,β-unsaturated double bond group-containing compound (D) other than the (meth)acrylamide (A) contains a (meth)acrylic acid ester compound (D) -2 having no urethane bond. 9. The dental hardenable composition according to any one of claims 1 to 8 , which is substantially free of a monofunctional (meth)acrylic acid ester compound (D)-2-1 having no urethane bond. A dental mouthpiece comprising a cured product of the dental hardenable composition according to any one of claims 1 to 9 . A denture base material comprising a cured product of the dental hardenable composition according to any one of claims 1 to 9 . A material for treating a sleep disorder, comprising a hardened product of the dental hardenable composition according to any one of claims 1 to 9 . A material for stereolithography, comprising the dental curable composition according to any one of claims 1 to 9 . A method for producing a three-dimensional object by optical three-dimensional modeling using the dental curable composition according to any one of claims 1 to 9 .