Active energy ray-curable composition, cured product thereof, and layered product

Abstract

Provided are: an active energy ray-curable composition which has a low viscosity, exhibits excellent transparency, and can yield a cured product having excellent flexibility and heat resistance; a cured product thereof; and a layered product.　The active energy ray-curable composition contains: a urethane (meth)acrylate (X) having a structural unit derived from farnesene; a (meth)acrylate (Y) other than the urethane (meth)acrylate (X); and a photopolymerization initiator (Z). The cured product is made of the active energy ray-curable composition. The layered product comprises: a layer containing at least one of the active energy ray-curable composition and the cured product; and two or more transparent base materials.

Description

Active energy ray-curable composition, cured product thereof, and laminate

[0001] The present invention relates to an active energy ray-curable composition, a cured product thereof, and a laminate.

[0002] In optical components such as displays for electronic devices, a transparent resin composition is filled between layers of a transparent substrate to improve visibility. Furthermore, liquid gaskets are filled into joints of automobile parts and the like to fill gaps between the parts, and transparent liquid gaskets are used from the viewpoints of visibility and appearance. For such resin compositions for optical components and liquid gaskets, resin materials that can form cured products that are not only transparent but also have excellent flexibility and good heat resistance are required.

[0003] Patent Document 1 proposes a curable composition containing a hydrogenated polybutadiene polyol-based urethane (meth)acrylate as a highly transparent resin material (for example, Patent Document 1, etc.), and Patent Document 2 proposes a curable composition containing a polypropylene glycol-based urethane (meth)acrylate.

[0004] Patent Document 1: JP 2010-265402 A, International Publication No. 2009 / 142237

[0005] Hydrogenated polybutadiene polyol-based urethane (meth)acrylates have high viscosity, and therefore require the addition of a large amount of monomer to adjust the viscosity. If the amount of monomer added is too large, the cohesive strength of the cured product weakens, resulting in a coating film with reduced flexibility. Therefore, it is difficult to obtain a curable composition with low viscosity while maintaining the flexibility of the coating film.

[0006] On the other hand, polypropylene glycol-based urethane (meth)acrylates have low viscosity, so they can be formulated in small amounts with less monomer, but they have the problem of low heat resistance of the cured product.

[0007] An object of the present disclosure is to provide an active energy ray-curable composition that has a low viscosity and that can give a cured product that is excellent in transparency, flexibility, and heat resistance, as well as a cured product thereof, and a laminate.

[0008] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by an active energy ray-curable composition containing a urethane (meth)acrylate (X) containing a structural unit derived from farnesene, a (meth)acrylate (Y) other than the urethane (meth)acrylate (X), and a photopolymerization initiator (Z).

[0009] According to the present disclosure, it is possible to provide an active energy ray-curable composition having a low viscosity, which can give a cured product having excellent transparency, flexibility, and heat resistance, a cured product thereof, and a laminate.

[0010] 1 is a schematic diagram showing a test piece for evaluating transparency in an example; FIG. 2 is a top view of a laminate 20 for evaluating heat resistance in an example; FIG. 3 is a side view of a laminate 20 for evaluating heat resistance in an example.

[0011] An embodiment of the present disclosure will be described in detail below. However, the scope of the present disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present disclosure. Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, when multiple upper and lower limit values ​​are described for a specific parameter, any of these upper and lower limit values ​​can be combined to form a suitable numerical range. Furthermore, the lower and / or upper limit values ​​of a numerical range described in this disclosure are numerical values ​​within that numerical range and may be replaced with numerical values ​​shown in the examples. The expression "1 to 10" indicating a numerical range means "1 or more and 10 or less." If a specific description described for one embodiment also applies to other embodiments, that description may be omitted in other embodiments.

[0012] The configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope of the gist of the present disclosure. The present disclosure is not limited to the embodiments.

[0013] Each feature disclosed herein may be combined with any other feature disclosed herein.

[0014] [Active Energy Ray-Curable Composition] A first embodiment of the present disclosure relates to an active energy ray-curable composition. The active energy ray-curable composition according to the first embodiment includes a urethane (meth)acrylate (X) containing a structural unit derived from farnesene, a (meth)acrylate (Y) other than the urethane (meth)acrylate (X), and a photopolymerization initiator (Z). The active energy ray-curable composition according to the first embodiment (hereinafter simply referred to as "curable composition") provides a cured product that has low viscosity yet is excellent in transparency, flexibility, and heat resistance.

[0015] The curable composition according to the first embodiment contains a urethane (meth)acrylate (X) (hereinafter sometimes referred to as "component (X)") containing a structural unit derived from farnesene. The urethane (meth)acrylate (X) containing a structural unit derived from farnesene has a small side chain molecular weight and weak intermolecular interactions, making it difficult to increase viscosity. Therefore, a low-viscosity curable composition can be obtained with a small amount of monomer blended. Even more surprisingly, a curable composition with low viscosity obtained by combining component (X) with a (meth)acrylate (Y) other than component (X) (hereinafter sometimes referred to as "component (Y)") can produce a cured product with excellent flexibility and heat resistance. Furthermore, the cured product obtained from such a curable composition containing component (X) and component (Y) also has good transparency.

[0016] <Urethane (meth)acrylate (X)> The curable composition according to the first embodiment contains the component (X). As described above, the component (X) is unlikely to increase in viscosity due to its structure. The component (X) may be used alone or in combination of two or more types.

[0017] Component (X) is a compound containing a structural unit derived from farnesene, one or more urethane bonds, and one or more acryloyl groups. In one embodiment, component (X) is preferably a compound containing a structural unit derived from farnesene, two or more urethane bonds, and one or less acryloyl groups.

[0018] (Physical Properties) Viscosity In one embodiment, from the viewpoint of achieving a low viscosity of the curable composition, the viscosity of the component (X) at 60°C is preferably 10 to 10,000 mPa·s, more preferably 100 to 8,000 mPa·s, even more preferably 500 to 5,000 mPa·s, and particularly preferably 1,000 to 4,000 mPa·s. The viscosity of the component (X) can be measured at 60°C using an E-type viscometer (for example, product name "TV-25 Model" manufactured by Toki Sangyo Co., Ltd.).

[0019] Weight-Average Molecular Weight (Mw) In one embodiment, the weight-average molecular weight (Mw) of the (X) component is preferably 5,000 to 30,000, more preferably 5,000 to 20,000, and even more preferably 8,000 to 18,000. An Mw of 5,000 or more tends to improve the flexibility of the cured product. Furthermore, fewer by-products are produced during the production of the (X) component, which tends to improve the appearance of the curable composition. Furthermore, an Mw of 30,000 or less tends to reduce the curability and shape change (melt) due to a decrease in crosslink density. The "weight-average molecular weight (Mw)" of the (X) component is a polystyrene-equivalent value measured by GPC, specifically, a value measured by the method described below. In one embodiment, the Mw of the (X) component may be greater than 12,000, greater than 12,000 but not greater than 30,000, or greater than 12,000 but not greater than 18,000. When the Mw of the component (X) exceeds 12,000, the appearance of the curable composition tends to be better, and the flexibility of the cured product tends to be better.

[0020] In one embodiment, the (X) component is preferably a reaction product of a polyol (A) containing a farnesene-derived structural unit, a polyisocyanate (B), and a (meth)acrylate (C) having a hydroxyl group. Alternatively, the (X) component may be a reaction product of a urethane prepolymer having an isocyanate group, which is a reaction product of the polyol (A) containing a farnesene-derived structural unit and the polyisocyanate (B), and a (meth)acrylate (C) having a hydroxyl group. Alternatively, the (X) component may be a reaction product of the polyol (A) containing a farnesene-derived structural unit, the polyisocyanate (B), the (meth)acrylate (C) having a hydroxyl group, and an alcohol (D) having one hydroxyl group.

[0021] (Polyol (A)) The polyol (A) is a polyol containing structural units derived from farnesene. In the present disclosure, "polyol" refers to a compound having two or more hydroxyl groups in its structure. Preferred examples of the polyol (A) include diols containing structural units derived from α-farnesene and / or β-farnesene. From the viewpoint of ease of production, it is preferable that the polyol (A) contains structural units derived from β-farnesene. Note that α-farnesene and β-farnesene may be used in combination.

[0022] The polyol (A) may contain structural units (other structural units) other than the structural units derived from farnesene. Examples of the other structural units include structural units derived from conjugated dienes having 12 or less carbon atoms. In a preferred embodiment, the polyol (A) may be a polyol containing structural units derived from farnesene and structural units derived from conjugated dienes having 12 or less carbon atoms.

[0023] The conjugated diene having 12 or less carbon atoms is not particularly limited, and examples thereof include butadiene, isoprene, 2,3-dimethyl-butadiene, 2-phenyl-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, myrcene, chloroprene, etc. These conjugated dienes may be used alone or in combination of two or more.

[0024] In one embodiment, the polyol (A) is preferably a diol represented by the following formula (I) or a diol obtained by reducing (hydrogenating) the diol, and more preferably a diol represented by the following formula (I).

[0025]

[0026] In the above formula (I), m and n each independently represent an integer of 1 to 7.

[0027] The polyol (A) represented by the formula (I) is preferably a polyfarnesene glycol. As the polyfarnesene glycol, a commercially available product may be used, for example, "KRASOL (registered trademark) F3000" manufactured by Cray Valley.

[0028] In one embodiment, the weight-average molecular weight (Mw) of the polyol (A) is preferably 1,000 to 4,000, more preferably 1,000 to 3,000. When the Mw of the polyol (A) is 1,000 to 4,000, the Tg of the (X) component is not too high, and the flexibility of the cured product is likely to be good. Furthermore, the amount of by-products in the (X) component tends to be small. Furthermore, the compatibility of the (X) component with other components, including the (Y) component, is unlikely to deteriorate. The "weight-average molecular weight (Mw)" of the polyol (A) is a value measured in polystyrene equivalent terms by GPC, specifically, a value measured by the method described below. In one embodiment, the Mw of the polyol (A) may be less than 2,000, or may be 1,000 or more but less than 2,000. When the Mw of the polyol (A) is less than 2,000, a lower viscosity (X) component is likely to be obtained, and viscosity adjustment of the curable composition is likely to be easier.

[0029] (Other Polyols) In one embodiment, the component (X) may contain a polyol other than the polyol (A) as a raw material. Examples of other polyols include polyolefin polyols, hydrogenated polyolefin polyols, polyester polyols, trimethylolpropane, pentaerythritol, glycerin, and modified compounds thereof. From the viewpoint of easily obtaining a component (X) with a lower viscosity, it is preferable to contain only the polyol (A).

[0030] (Polyisocyanate (B)) In the present disclosure, "polyisocyanate" refers to a compound having two or more isocyanate groups within its structure. The polyisocyanate (B) is not particularly limited, and for example, at least one diisocyanate selected from the group consisting of an alicyclic diisocyanate, a branched aliphatic diisocyanate, and a diisocyanate compound obtained by hydrogenating an aromatic diisocyanate is preferred. The alicyclic diisocyanate is not particularly limited, but examples thereof include isophorone diisocyanate. The branched aliphatic diisocyanate is not particularly limited, but examples thereof include 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, etc. The diisocyanate compound obtained by hydrogenating the aromatic isocyanates is not particularly limited, but examples thereof include hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, etc.

[0031] ((Meth)acrylate (C) Having a Hydroxy Group) The (meth)acrylate (C) having a hydroxyl group (hereinafter sometimes referred to as "(meth)acrylate (C)") is not particularly limited as long as it is a compound having one or more hydroxyl groups and one or more acryloyl groups. In one embodiment, a (meth)acrylate of an aliphatic alcohol is preferred, and from the viewpoint of good compatibility with the polyol (A), a monofunctional (meth)acrylate of an aliphatic alcohol having one hydroxyl group and one acryloyl group is particularly preferred. Preferred examples of such a (meth)acrylate (C) include, for example, 2-hydroxyethyl (meth)acrylate, 3-hydroxy-n-propyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. One type of (meth)acrylate (C) having a hydroxyl group may be used alone, or two or more types may be used in combination.

[0032] (Alcohol (D) Having One Hydroxyl Group) In one embodiment, the component (X) may contain, as a raw material, an alcohol (D) having one hydroxyl group (hereinafter sometimes referred to as "alcohol (D)"). By including the alcohol (D) as a raw material, it becomes easier to adjust the acryloyl group concentration of the component (X), as described below. Examples of such alcohols (D) include aliphatic or alicyclic primary alcohols having 3 or more carbon atoms, and their molecular weights are preferably 70 to 400. Alcohols (D) having 3 or more carbon atoms or a molecular weight of 70 or more are preferred because they are less likely to volatilize during the synthesis of the component (X). Furthermore, if the molecular weight is 400 or less, the reactivity with the polyisocyanate (B) is less likely to decrease, and the production time is not too long. Furthermore, if the alcohol is an aliphatic or alicyclic alcohol, the hue of the component (X) will not be too high, and weather resistance is also likely to be good. Specific examples include 1-butanol, 1-heptanol, 1-hexanol, normal octyl alcohol, 2-ethylhexyl alcohol, cyclohexanemethanol, capryl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol (cetanol), stearyl alcohol, and mixtures thereof. Among these, 2-ethylhexyl alcohol is preferred from the viewpoints of boiling point, cost, and availability. The alcohol (D) may be used alone or in combination of two or more.

[0033] <Method for producing urethane (meth)acrylate (X)> The method for producing the (X) component includes reacting a polyol (A), a polyisocyanate (B), and a (meth)acrylate (C) (urethanization reaction). The reaction method is not particularly limited. In one embodiment, however, a preferred method involves reacting the polyol (A) with the polyisocyanate (B) to prepare a urethane isocyanate prepolymer (step (1)), and then reacting the urethane isocyanate prepolymer with a (meth)acrylate (C) (step (2)) to obtain the (X) component. When reacting the urethane isocyanate prepolymer with the (meth)acrylate (C), the (meth)acrylate (C) and an alcohol (D) may be used in combination.

[0034] (Step (1)) Step (1) is more likely to prevent an increase in viscosity, improve the appearance of the component (X), suppress the production of by-products, and improve the transparency and heat resistance of the cured product, as compared to conventional production methods such as "a method of mixing polyol (A), polyisocyanate (B), and (meth)acrylate (C), or (A) to (C) and alcohol (D) all at once and reacting them" or "a method of reacting polyisocyanate (B), (meth)acrylate (C), and alcohol (D) to form a urethane isocyanate prepolymer containing an isocyanate group, and then reacting the prepolymer with polyol (A)."

[0035] Specifically, when a curable composition is produced by a method in which polyol (A), polyisocyanate (B), and (meth)acrylate (C), or (A) to (C) and alcohol (D) are mixed together and reacted, the resulting component (X) tends to have a high viscosity. As a result, a large amount of monomer must be added to adjust the viscosity of the curable composition. Furthermore, stirring becomes difficult or the reaction proceeds unevenly, increasing the probability of partial gelation. Furthermore, the amount of by-products of compounds that do not have polyol (A) in their skeletons tends to increase, resulting in reduced transparency and flexibility. Furthermore, the tendency for various compounds to be generated irregularly makes it difficult to control the quality of curable compositions containing component (X).

[0036] Furthermore, in the case of "a method of reacting polyisocyanate (B) with (meth)acrylate (C) and alcohol (D) to form a urethane isocyanate prepolymer containing an isocyanate group, and then reacting the prepolymer with polyol (A)," a compound in which all of the isocyanate groups of polyisocyanate (B) have reacted with (meth)acrylate (C) or alcohol (D) is likely to be produced as a by-product. This by-product exhibits crystallinity because it does not contain a polyol (A) skeleton, and as a result, transparency is likely to decrease and the possibility of gelation is also increased.

[0037] From the above viewpoints, a method is preferred in which polyol (A) and polyisocyanate (B) are reacted to form a urethane isocyanate prepolymer, and then the urethane isocyanate prepolymer is reacted with (meth)acrylate (C). That is, methods that can be employed in step (1) further include the following methods 1 to 3. [Method 1] A method in which polyol (A) and polyisocyanate (B) are mixed together and reacted. [Method 2] A method in which polyol (A) is reacted while being added dropwise to polyisocyanate (B). [Method 3] A method in which polyisocyanate (B) is reacted while being added dropwise to polyol (A).

[0038] In the case of [Method 3], polyisocyanate (B) is added dropwise to a large amount of polyol (A) while reacting the polyisocyanate (B). The isocyanate groups on both sides of the polyisocyanate (B) react with the hydroxyl groups of two moles of polyol (A) to form a urethane, which is schematically represented as an A-B-A type diol with hydroxyl groups at both ends. Furthermore, when two moles of polyisocyanate (B) react with this diol, a compound with isocyanate groups at both ends, schematically represented as a B-A-B-A-B type compound, is also likely to be produced as a by-product. Repeating a similar reaction may result in a large amount of a compound with the following structure, schematically represented as B-[A-B]n-A-B (n = an integer of 1 or greater). If a urethane prepolymer containing a large amount of such a by-product is reacted with a (meth)acrylate (C) and an alcohol (D), the acrylic density of the resulting component (X) will be low, making it difficult to obtain a sufficient crosslinking density in the cured product. Therefore, from the viewpoint of easily obtaining a cured product having excellent flexibility and heat resistance, it is preferable to synthesize the urethane isocyanate prepolymer by [Method 1] or [Method 2].

[0039] A preferred method for producing a urethane isocyanate prepolymer by [Method 1] is as follows. First, polyol (A) is charged into a reactor and stirred until homogeneous, and then polyisocyanate (B) is further charged and homogenized. When preparing an (X) component with a relatively large Mw, for example, (meth)acrylate (Y) may be added as a diluent to polyol (A), and the polyol (A) and (Y) components may be stirred until homogeneous, followed by charging polyisocyanate (B). This allows the viscosity of the reaction liquid to be kept low. Subsequently, a method is preferred in which the temperature is raised as necessary while stirring, and then a urethanization catalyst is added to initiate urethanization. After the urethanization catalyst is added, the temperature may be raised as necessary.

[0040] If the urethane-forming catalyst is initially added before the polyol (A) and the polyisocyanate (B) become uniform, the urethane-forming reaction will proceed in a non-uniform state between the polyol (A) and the polyisocyanate (B) at the stage of charging the polyisocyanate (B), which may result in changes in the molecular weight and viscosity of the resulting urethane prepolymer and in the reaction being terminated with unreacted polyisocyanate (B) remaining in the system. In such cases, the (meth)acrylate (C) and alcohol (D) used later will react with the remaining polyisocyanate (B), which is likely to produce by-products and tend to result in a low transmittance of the resulting cured product.

[0041] In one embodiment, the content of the by-products as described above in component (X) is preferably less than 7 wt %, based on the total weight of component (X). If the content of by-products is less than 7 wt %, the transparency of the cured product tends to be good.

[0042] [Method 1] is preferable in that when the polyol (A) having a high viscosity or the polyisocyanate (B) is a solid, these raw materials can be charged directly into the reactor, and that the component (X) can be produced in one pot.

[0043] A preferred method for producing a urethane isocyanate prepolymer by [Method 2] is as follows: A reactor is charged with polyisocyanate (B), a urethanization catalyst, and, if necessary, a portion of the (meth)acrylate (Y), and the mixture is stirred until homogeneous. While stirring, the temperature is raised as necessary, and a homogeneous mixture of polyol (A) and (meth)acrylate (Y) is added dropwise to cause reaction. [Method 2] is a method suitable for cases where polyol (A) has a high viscosity. By preparing a homogeneous mixture of polyol (A) and (meth)acrylate (Y) to obtain a low-viscosity mixture and adding this mixture dropwise to polyisocyanate (B), the by-products described in [Method 3] are less likely to be produced.

[0044] In either method, it is preferable to carry out the reaction in step (1) until all hydroxyl groups are urethane-converted. The end point of the reaction can be confirmed by measuring the isocyanate group concentration (hereinafter also referred to as "NCO group concentration") in the reaction solution, and checking whether the isocyanate group concentration is equal to or less than the isocyanate group concentration (theoretical NCO concentration) when all hydroxyl groups charged into the system are urethane-converted, or whether the isocyanate group concentration no longer changes.

[0045] In one embodiment, the molar ratio of the isocyanate groups of the polyisocyanate (B) to 1 mole of the hydroxyl groups of the polyol (A) is preferably 1.1 to 2.0 moles, more preferably 1.1 to 1.6 moles.

[0046] In one embodiment, step (1) is preferably carried out in the presence of a polymerization inhibitor. Preferred examples of polymerization inhibitors include dibutylhydroxytoluene, hydroquinone, hydroquinone monomethyl ether, and phenothiazine. These may be used alone or in combination of two or more. The amount of these polymerization inhibitors added is preferably 1 to 10,000 ppm (by weight) relative to the resulting component (X), more preferably 100 to 1,000 ppm, and even more preferably 400 to 1,000 ppm. When the amount of polymerization inhibitor added is within the above range, a sufficient polymerization inhibitor effect is easily obtained and the physical properties of the component (X) are less likely to be adversely affected.

[0047] (Step (2)) The urethane isocyanate prepolymer obtained in step (1) above is reacted with a (meth)acrylate (C) (in one embodiment, a (meth)acrylate (C) and an alcohol (D)) to obtain the component (X). If a large amount of unreacted isocyanate groups remain in the reaction solution, problems such as gelation or poor curing of the coating film may occur. To avoid these problems, it is preferable that step (2) be carried out so that the number of moles of hydroxyl groups in the (meth)acrylate (C) is in excess relative to the number of moles of isocyanate groups in the urethane isocyanate prepolymer, and that the reaction be continued until the concentration of residual isocyanate groups in the reaction solution reaches 0.05% by weight or less. In the reaction, the number of moles of hydroxyl groups in the (meth)acrylate (C) per mole of isocyanate groups in the urethane isocyanate prepolymer is preferably 1.005 to 1.1 moles, more preferably 1.01 to 1.05. In one embodiment, the molar ratio of polyisocyanate (B) to (meth)acrylate (C) ((B):(C)) may be from 3.00:2.00 to 3.00:2.09.

[0048] For the same purpose, the production of component (X) is preferably carried out in an atmosphere of a molecular oxygen-containing gas, the oxygen concentration being appropriately selected taking safety into consideration.

[0049] In one embodiment, a catalyst (urethanation catalyst) may be used to obtain a sufficient reaction rate. Examples of catalysts that can be used include dibutyltin dilaurate, tin octoate, tin chloride, bismuth(III) neodecanoate, bismuth(III) 2-ethylhexanoate, zinc neodecanoate, and zinc octoate, with dibutyltin dilaurate being preferred from the viewpoint of reaction rate. The amount of these catalysts added is typically preferably 1 to 3,000 ppm (by weight), and more preferably 50 to 1,000 ppm, relative to the resulting component (X). When the amount of catalyst added is within the above range, a sufficient reaction rate is likely to be obtained and the physical properties of component (X) are unlikely to be adversely affected.

[0050] The production of component (X) can be carried out in the presence of a known volatile organic solvent. After the production of component (X), the volatile organic solvent can be distilled off under reduced pressure. Alternatively, the volatile organic solvent remaining in the active energy ray-curable composition can be applied to a transparent substrate and then removed by drying. The volatile organic solvent refers to an organic solvent having a boiling point not exceeding 200°C.

[0051] In one embodiment, when the curable composition is applied to a field in which curing is performed in a sealed environment, it is preferable that substantially no volatile organic solvents be used from the time of producing the component (X) to the time of preparing the final curable composition. That is, when the curable composition is applied to such a field, the proportion of the volatile organic solvent contained in the curable composition according to the first embodiment is preferably 0.5 wt % or less, and more preferably 0.1 wt % or less, relative to the total weight of the curable composition.

[0052] In one embodiment, the reaction temperature in step (1) and / or step (2) is preferably 130° C. or lower, more preferably 40 to 130° C. When the reaction temperature is within the above range, it is easy to suppress the generation of gelled matter while maintaining a practically sufficient reaction rate.

[0053] Step (2) is preferably carried out until the concentration of residual isocyanate groups reaches 0.1% by weight or less. The concentration of residual isocyanate groups can be analyzed by gas chromatography, titration, or the like.

[0054] In one embodiment, the acryloyl group concentration in component (X), calculated by the following formula (3), is preferably 0.10 mol / kg or more and less than 1.0 mol / kg, and more preferably 0.2 mol / kg or more and less than 0.60 mol / kg: Acryloyl group concentration (mol / kg) = weight (g) of (meth)acrylate (C) × number of (meth)acryloyl groups in (meth)acrylate (C) molecule ÷ molecular weight of (meth)acrylate (C) × 1000 ÷ weight (g) of component (X) (3) Here, with regard to the number of acryloyl groups in (meth)acrylate (C), for example, in the case of 2-hydroxyethyl acrylate, the number of acryloyl groups is 1, and in the case of pentaerythritol triacrylate, the number of acryloyl groups is 3.

[0055] If the acryloyl group concentration is 0.10 mol / kg or more, the composition is easily cured sufficiently upon irradiation with active energy rays, and the cohesive strength is not easily reduced, and the initial adhesion to the substrate is not easily reduced. Furthermore, if the concentration is less than 1.0 mol / kg, the heat resistance of the resulting cured product is not easily reduced. In the present disclosure, "excellent heat resistance" includes the absence of problems such as an increase in coating film hardness, a decrease in adhesion to the substrate, and curing shrinkage, which causes changes in the shape of the coating film, when the cured product is stored at 95°C for 1,000 hours. In other words, from the perspective of improving the heat resistance of the resulting cured product, it is effective to keep the acryloyl group concentration in component (X) low and reduce curing shrinkage. However, this will result in a decrease in coating film hardness, and adhesion to the substrate is likely to be reduced. In one embodiment, from the viewpoint of preventing a decrease in coating film hardness while keeping the acryloyl group concentration of component (X) low (preferably less than 1.0 mol / kg), the aforementioned alcohol (D) may be reacted with component (X) to alkoxylate some of the terminal acryloyl groups of component (X).

[0056] <(Meth)acrylate (Y)> The curable composition according to the first embodiment contains a (meth)acrylate (Y) other than the component (X). The component (Y) is selected from the viewpoint of adjusting the viscosity of the curable composition and various physical properties of the cured product. In one embodiment, from the viewpoint of easily adjusting the viscosity, improving the appearance of the curable composition, suppressing by-products, and improving the transparency and heat resistance of the cured product, it is preferable that the component (Y) contains a monofunctional (meth)acrylate.

[0057] As the monofunctional (meth)acrylate, from the viewpoint of ease of adjusting the viscosity and various physical properties of the cured product, methyl (meth)acrylate, ethyl (meth)acrylate, glycerin mono(meth)acrylate, glycidyl (meth)acrylate, dicyclopentenyl (meth)acrylate, n-butyl (meth)acrylate, β-carboxyethyl (meth)acrylate, isobornyl (meth)acrylate, octyl / decyl (meth)acrylate (a mixture of octyl (meth)acrylate and decyl (meth)acrylate), Examples of the acrylates include acrylates of the formula (I), n-octyl (meth)acrylate, isooctyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-stearyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and β-carboxyethyl acrylate. These may be used alone or in combination of two or more. Among these, from the viewpoints of high dilution efficiency and ease of viscosity adjustment of the curable composition, aliphatic (meth)acrylates in which the alkyl group has 1 to 15 carbon atoms are preferred, n-octyl (meth)acrylate and octyl / decyl (meth)acrylate are more preferred, and n-octyl acrylate (NOA) is even more preferred. Furthermore, from the viewpoint of easily improving the toughness and stretchability of the cured product, an alicyclic (meth)acrylate is preferred, isobornyl (meth)acrylate is more preferred, and isobornyl acrylate (IBOA) is even more preferred. In one embodiment, the component (Y) may contain one or more selected from n-octyl acrylate (NOA), isobornyl acrylate (IBOA), and octyl / decyl (meth)acrylate.

[0058] The curable composition according to the first embodiment can achieve low viscosity with at least the amount of component (Y). In one embodiment, the viscosity of the curable composition at 25°C may be 600 mPa·s or less. Furthermore, the content of component (Y) in the curable composition at this time is preferably 90 wt% or less, based on the total weight of the curable composition. In one embodiment, the proportion of component (Y) relative to the total weight of the curable composition may be 60 wt% or less, or may be 55 wt% or less. Furthermore, in one embodiment, when component (Y) includes at least one selected from NOA and IBOA, the proportion of component (Y) relative to the total weight of the curable composition having the aforementioned viscosity may be 20 to 55 wt%, or may be 25 to 55 wt%.

[0059] <Photopolymerization initiator (Z)> The curable composition according to the first embodiment contains a photopolymerization initiator (Z) (hereinafter, also referred to as "component (Z)"). As the component (Z), a known photoradical polymerization initiator or photocationic polymerization initiator can be used depending on the type of active energy ray and the component (X). Examples of the component (Z) include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, diethoxyacetophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl)ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin phenyl ether, and benzoin. Examples of the component (Z) include methyl dimethyl ketal, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3'-dimethyl-4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, methylphenyl glyoxylate, benzil, camphorquinone, etc. These components (Z) may be used alone or in combination of two or more.

[0060] The content of the component (Z) is not particularly limited. In one embodiment, the content is preferably 1 to 20 parts by weight, and more preferably 1 to 5 parts by weight, per 100 parts by weight of the total of the components (X) and (Y). When the content of the component (Z) is within the above range, poor curing is unlikely to occur, and a curable composition with little odor originating from the component (Z) is likely to be obtained.

[0061] <Additives> The curable composition according to the first embodiment may contain various additives as needed. Examples of such additives include organic and / or inorganic fillers, dyes and pigments, leveling agents, UV absorbers, light stabilizers, antifoaming agents, dispersants, and thixotropy-imparting agents. The content of these additives is not particularly limited, but may be, for example, 0 to 10 parts by weight, or 0.05 to 5 parts by weight, relative to 100 parts by weight of the curable composition.

[0062] As described above, the curable composition according to the first embodiment has low viscosity and can give a cured product having excellent transparency, heat resistance, and flexibility. In one embodiment, the cured product obtained by curing the curable composition under the following conditions preferably has a transmittance of 95% or more at a wavelength of 400 nm. (UV irradiation conditions) Irradiation intensity: 120 W / cm Irradiation distance: 10 cm Conveyor speed: 5 m / min Number of irradiations: 2

[0063] <Method for Producing Curable Composition> The curable composition according to the first embodiment can be produced by mixing the components (X) to (Z) described above with the additives described above. Known or conventional means, such as various mixers such as dissolvers and homogenizers, kneaders, rolls, bead mills, and planetary stirrers, can be used for mixing. The mixing conditions, such as the temperature and rotation speed, are not particularly limited and can be set appropriately. In one embodiment, the method for producing the curable composition may include blending the component (Y) with the component (X) to obtain a viscosity adjuster liquid, and blending the component (Z) with the viscosity adjuster liquid to obtain the curable composition.

[0064] <Applications of Curable Composition> The curable composition according to the first embodiment is characterized by a low viscosity at least when the amount of component (Y) is high. Furthermore, the curable composition can produce a cured product having excellent transparency, flexibility, and heat resistance. Such a curable composition can be suitably used, for example, as a curable composition for optical components or liquid gaskets. Naturally, the applications of the curable composition are not limited to these optical components and liquid gaskets.

[0065] [Cured Product] A second embodiment of the present disclosure is a cured product of the curable composition according to the first embodiment. The curable composition according to the first embodiment can be cured by irradiation with active energy rays. The cured product according to the second embodiment includes both a product obtained by irradiating the above-mentioned curable composition with active energy rays described below to promote the curing reaction, and a product obtained by irradiating the curable composition with active energy rays to completely cure it. In addition, a "semi-cured product" in which the curable composition has been cured to the extent that it no longer has fluidity is also included in the cured product of this embodiment.

[0066] The cured product according to the second embodiment can be obtained as a cured coating film, for example, by applying the curable composition according to the first embodiment to an object such as a substrate, and then irradiating the applied curable composition with active energy rays.

[0067] The method for applying the curable composition is not particularly limited, and conventionally known methods can be used, such as spraying, airless spraying, air spraying, roll coating, bar coating, and gravure coating. Among these, roll coating is most preferably used from the viewpoints of aesthetics, cost, workability, and the like. The application of the curable composition may be a so-called in-line coating method, in which the application is carried out during the production process of a plastic film or the like, or a so-called offline coating method, in which the application is carried out in a separate process on an already manufactured substrate. From the viewpoint of production efficiency, the offline coating method is preferred.

[0068] <Active energy rays> Examples of active energy rays include ultraviolet rays and electron beams. Light sources used for ultraviolet irradiation include, for example, high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, xenon lamps, and metal halide lamps. The irradiation time varies depending on the type of light source, the distance between the light source and the coating surface, and other conditions, but is at most several tens of seconds, and is usually several seconds. Typically, an irradiation source with a lamp output of approximately 80 to 300 W / cm is used. In the case of electron beam irradiation, it is preferable to use electron beams with an energy range of 50 to 1000 KeV, with an irradiation dose of 2 to 5 Mrad. After irradiation with active energy rays, heating may be performed as needed to promote curing.

[0069] The thickness of the cured coating film is not particularly limited and can be adjusted as desired depending on the application, for example, within the range of 0.5 to 1,000 μm, preferably 2 to 500 μm.

[0070] The object (subject to be coated) onto which the curable composition is applied is not particularly limited, and examples thereof include various articles such as plastic articles, articles on which metal has been vapor-deposited onto the plastic surface of the above-mentioned articles, glass, wood, metal plates, and paper. The coated surface may be subjected to a release treatment. When the curable composition according to the first embodiment is used for optical components, particularly as an interlayer filler for a transparent substrate (a curable composition for interlayer filling), it is preferable to apply the composition to a transparent substrate. Details of the transparent substrate will be described later.

[0071] [Laminate] A third embodiment of the present disclosure is a laminate comprising a layer containing one or more selected from the curable composition according to the first embodiment and the cured product according to the second embodiment. In one embodiment, the laminate may comprise a layer containing one or more selected from the curable composition according to the first embodiment and the cured product according to the second embodiment, and two or more transparent substrates. Furthermore, a layer containing one or more selected from the curable composition according to the first embodiment and the cured product according to the second embodiment may be provided between the two or more transparent substrates.

[0072] <Transparent Substrate> When the laminate includes a transparent substrate, the transparent substrate may be a glass substrate such as a transparent glass plate, or a plastic substrate such as a transparent plastic film.

[0073] The plastic substrate can be any existing transparent material and is not particularly limited, but examples thereof include polyolefin resins such as polyethylene, ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, acrylic resins, polycarbonate resins, etc. Among these, polycarbonate resins and acrylic resins are particularly preferably used.

[0074] <Method for producing laminate> An example of a method for producing a laminate according to the third embodiment is a method comprising applying the curable composition according to the first embodiment onto one or more substrates. In one embodiment, the method may comprise irradiating the curable composition with active energy rays after applying the curable composition. Furthermore, when the transparent substrate described above is used as the substrate, the method may comprise irradiating the curable composition with active energy rays from the transparent substrate side. As the method for applying the curable composition and the active energy rays, those described in the section on cured products can be preferably used.

[0075] In one embodiment, the method for producing a laminate according to the third embodiment may include injecting the curable composition according to the first embodiment between two or more transparent substrates. The method may also include irradiating the curable composition according to the first embodiment with active energy rays from the transparent substrate side after the injection. In this case, it is preferable to use a cartridge in order to prevent the generation of bubbles.

[0076] In the laminate, the thickness of the layer containing one or more selected from the curable composition according to the first embodiment and the cured product according to the second embodiment is preferably 30 to 300 μm, more preferably 50 to 200 μm. If the layer thickness is within the above range, the cost is not too high and the layer thickness tends to be uniform. In addition, flexibility tends to be good.

[0077] The present invention will be described in more detail below based on synthesis examples and working examples, but the present invention is not limited to these examples in any way.

[0078] Synthesis examples and comparative synthesis examples are described below. The concentration notations "ppm" and "wt%" refer to concentrations relative to the (theoretically) obtained urethane (meth)acrylate (X) unless otherwise specified. Furthermore, methods for measuring the isocyanate group concentration, viscosity, and weight-average molecular weight are described.

[0079] (Measurement of Isocyanate Group Concentration) The isocyanate group concentration was measured as follows. The measurement was performed in a 100 mL glass flask while stirring with a stirrer. - Measurement of Blank Value: 15 mL of a 0.1 N dibutylamine THF solution was added to 15 mL of THF, and three drops of bromophenol blue (1% methanol diluted solution) were added to color the solution blue. The solution was then titrated with a 0.1 N HCl aqueous solution. The titration volume of the HCl aqueous solution at the point when a color change was observed was recorded as Vb (mL). - Measurement of Actual Isocyanate Group Concentration: Ws (g) of the sample was weighed and dissolved in 15 mL of THF, and 15 mL of a 0.1 N dibutylamine THF solution was added. After confirming that the solution had been dissolved, three drops of 1% bromophenol blue (1% methanol diluted solution) were added to color the solution blue. The solution was then titrated with a 0.1 N HCl aqueous solution. The titration volume of the HCl aqueous solution at the time when discoloration was observed was defined as Vs (mL). The isocyanate group concentration in the sample was calculated using the following formula: Isocyanate group concentration (wt%) = (Vb - Vs) × 1.005 × 0.42 ÷ Ws

[0080] (Viscosity Measurement Method) Urethane (meth)acrylate (X) The viscosity of the urethane (meth)acrylate (X) was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TV-25 Model") at 60°C. Curable Composition The viscosity of the curable composition was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TV-25 Model") at 25°C.

[0081] (Weight-average molecular weight (Mw)) The weight-average molecular weight was determined by GPC (gel permeation gas chromatography) under the following measurement conditions using standard polystyrene as the standard. Equipment used: High-speed GPC device (manufactured by Tosoh Corporation, product name "HLC-8220GPC") Pump: DP-8020 Detector: RI-8020 Column types: Super HZM-M, Super HZ4000, Super HZ3000, Super HZ2000 Solvent: Tetrahydrofuran Phase flow rate: 1 mL / min Column internal pressure: 5.0 MPa Column temperature: 40°C Sample injection amount: 10 μL Sample concentration: 0.2 mg / mL

[0082] <Materials> The materials used in the examples and comparative examples are as follows. Polyols (A) (A1): Polyfarnesene glycol (manufactured by Cray Valley, product name "KRASOL F3000" (Mw: 1488, hydroxyl value: 0.672 mmol / g, non-volatile content: 99.91%). Polyols (A'): (A'1): Polypropylene glycol (manufactured by Sanyo Chemical Industries, Ltd., product name "SANNICS (registered trademark) PT2001", Mw: 1964, hydroxyl value: 57.1 mg KOH / g). (A'2): Polyester polyol (manufactured by Mitsui Chemicals, Inc., product name "Takelac (registered trademark) U2710", Mw: 988, hydroxyl value: 113.5 mg KOH / g). (A'3): Hydrogenated polybutadiene glycol (manufactured by Nippon Soda Co., Ltd., product name "NISSO PB GI3000" (Mw: 3965, hydroxyl value: 28.3 mgKOH / g). The Mw of the polyol (A) and polyol (A') is a value calculated from the hydroxyl value using the following formula (4) or (5): Mw = 56.1 ÷ hydroxyl value (mgKOH / g) × 2,000 (4) Mw = 2,000 ÷ hydroxyl value (mmol / g) (5)

[0083] Polyisocyanates (B) (B1): Isophorone diisocyanate (IPDI) (manufactured by Evonik Corporation, product name "VESTANAT (registered trademark) IPDI", Mw: 222). (B2): Hexamethylene diisocyanate (HDI) (manufactured by Tosoh Corporation, product name "HDI", Mw: 168). (B3): 2,2,4-trimethylhexamethylene diisocyanate (TMHDI) (manufactured by Evonik Corporation, product name "TMDI", Mw: 210). (B4): Diphenylmethane diisocyanate (MDI) (manufactured by Tosoh Corporation, product name "MDI", Mw: 250). (B5): Methylenebis(4-cyclohexylisocyanate) (hydrogenated MDI) (manufactured by Evonik Co., Ltd., product name "DESMODUR (registered trademark) W", Mw: 262). (B6): Toluene diisocyanate (TDI) (manufactured by Tosoh Corporation, product name "TDI", Mw: 174).

[0084] (Meth)acrylate (C) having a hydroxyl group (C1): 2-hydroxyethyl acrylate (manufactured by Nippon Shokubai Co., Ltd., product name "HEA"). Alcohol (D) having one hydroxyl group (D1): 2-ethylhexyl alcohol (manufactured by Sankyo Chemical Co., Ltd., product name "2-ethylhexanol"). (Meth)acrylate (Y) (Y1): n-octyl acrylate (NOA) (manufactured by Osaka Organic Chemical Co., Ltd., product name "NOAA"). (Y2): isobornyl acrylate (IBOA) (manufactured by Daicel Allnex Co., Ltd., product name "IBOA-B"). Photopolymerization initiator (Z): 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM, product name "Omnirad (registered trademark) 184").

[0085] <Synthesis of Urethane (Meth)acrylate (X)> (Synthesis Example 1 / (X-1)) Polyol (A1), polyisocyanate (B1), and (meth)acrylate (C1) were reacted in a molar ratio of 2.0:3.0:2.02. The actual amounts charged and reaction conditions are described below. A separable flask equipped with a thermometer and a stirrer was charged with 303.0 g of polyol (A1) (polyfarnesene glycol) and 800 ppm of dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and the system was homogenized. Then, 34 g of polyisocyanate (B1) (IPDI) was added. Thereafter, 300 ppm of a urethane catalyst (dibutyltin dilaurate (DBTDL)) was added, and the internal temperature was set to 70°C to prepare a urethane isocyanate prepolymer. The completion of the reaction was confirmed when the isocyanate group concentration in the reaction solution was equal to or less than the theoretical NCO concentration (this was also the case in other synthesis examples). In this example, after confirming that the isocyanate group concentration in the reaction solution was equal to or less than the theoretical end-point isocyanate group concentration (1.27 wt%), the next step was carried out. The theoretical NCO concentration (prepolymer) was calculated using the following formula (6): Theoretical NCO concentration = 42 × 2 × 100 ÷ (Mw of polyol × 2 + Mw of isocyanate × 3) (6) After confirming the isocyanate group concentration in the reaction solution, 12.4 g of (meth)acrylate (C1) was added to the reaction solution all at once. After aging for 2 hours, it was confirmed that the isocyanate group concentration was less than 0.05 wt%, and then the reaction was terminated to obtain urethane (meth)acrylate (X-1). The acryloyl group concentration of the obtained urethane (meth)acrylate (X-1) was 1,918 g / mol (0.52 mol / kg).

[0086] (Synthesis Example 2 / (X-2)) Urethane (meth)acrylate (X-2) was obtained by the same synthesis procedure as in Synthesis Example 1, except that polyol (A1), polyisocyanate (B2), and (meth)acrylate (C1) were reacted in a molar ratio of 2.0:3.0:2.02. The acryloyl group concentration of the obtained urethane (meth)acrylate (X-2) was 1,838 g / mol (0.54 mol / kg).

[0087] (Synthesis Example 3 / (X-3)) Urethane (meth)acrylate (X-3) was obtained by the same synthesis procedure as in Synthesis Example 1, except that polyol (A1), polyisocyanate (B3), and (meth)acrylate (C1) were reacted in a molar ratio of 2.0:3.0:2.02. The acryloyl group concentration of the obtained urethane (meth)acrylate (X-3) was 1,901 g / mol (0.53 mol / kg).

[0088] (Synthesis Example 4 / (X-4)) Urethane (meth)acrylate (X-4) was obtained by the same synthesis procedure as in Synthesis Example 1, except that polyol (A1), polyisocyanate (B4), and (meth)acrylate (C1) were reacted in a molar ratio of 2.0:3.0:2.02. The acryloyl group concentration of the obtained urethane (meth)acrylate (X-4) was 1,950 g / mol (0.51 mol / kg).

[0089] (Synthesis Example 5 / (X-5)) Urethane (meth)acrylate (X-5) was obtained by the same synthesis procedure as in Synthesis Example 1, except that polyol (A1), polyisocyanate (B5), and (meth)acrylate (C1) were reacted in a molar ratio of 2.0:3.0:2.02. The acryloyl group concentration of the obtained urethane (meth)acrylate (X-5) was 1,978 g / mol (0.51 mol / kg).

[0090] (Synthesis Example 6 / (X-6)) Urethane (meth)acrylate (X-6) was obtained by the same synthesis procedure as in Synthesis Example 1, except that polyol (A1), polyisocyanate (B6), and (meth)acrylate (C1) were reacted in a molar ratio of 2.0:3.0:2.02. The acryloyl group concentration of the obtained urethane (meth)acrylate (X-6) was 1,847 g / mol (0.54 mol / kg).

[0091] (Synthesis Example 7 / (X-7)) Polyol (A1), polyisocyanate (B1), (meth)acrylate (C1), and alcohol (D1) were reacted in a molar ratio of 2.0:3.0:1.80:0.20. The actual charged amounts and reaction conditions are described below. A separable flask equipped with a thermometer and a stirrer was charged with 404.1 g of polyol (A1) (polyfarnesene glycol) and 800 ppm of dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and the system was homogenized. Then, 34 g of polyisocyanate (B1) (IPDI) was added. Thereafter, 300 ppm of a urethane catalyst (dibutyltin dilaurate (DBTDL)) was added, and the internal temperature was set to 70°C to prepare a urethane isocyanate prepolymer. Completion of the reaction was confirmed when the isocyanate group concentration in the reaction solution was equal to or less than the theoretical NCO concentration (this was also the case in other synthesis examples). In this example, after confirming that the isocyanate group concentration in the reaction solution was equal to or less than the theoretical end-point isocyanate group concentration (0.98 wt%), the next step was carried out. The theoretical NCO concentration (prepolymer) was calculated using the above formula (6). After confirming the isocyanate group concentration in the reaction solution, 10.6 g of (meth)acrylate (C1) and 1.3 g of alcohol (D1) were added to the reaction solution all at once. After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05 wt%, yielding urethane (meth)acrylate (X-7). The acryloyl group concentration of the resulting urethane (meth)acrylate (X-7) was 2,052 g / mol (0.49 mol / kg).

[0092] Comparative Synthesis Example 1 (X'-1) Polyol (A'1), polyisocyanate (B1), and (meth)acrylate (C1) were reacted in a molar ratio of 2.0:3.0:2.10. The actual amounts charged and reaction conditions are described below. A separable flask equipped with a thermometer and a stirrer was charged with 307.8 g of polyol (A'1), 67.5 g of polyisocyanate (B1), and 800 ppm of dibutylhydroxytoluene (BHT). The mixture was stirred for 1 hour to homogenize the system, and then 300 ppm of a urethane catalyst (DBTDL) was added. After confirming that the internal temperature had risen, the temperature was raised to 70°C and the mixture was aged for 3 hours to prepare a urethane isocyanate prepolymer. After confirming that the isocyanate group concentration in the reaction solution was equal to or less than the theoretical value (2.27 wt%), 24.7 g of (meth)acrylate (C1) was added. The mixture was further aged for 2 hours to obtain urethane (meth)acrylate (X'-1). The acryloyl group concentration of the obtained urethane (meth)acrylate (X'-1) was 2,303 g / mol (0.43 mol / kg).

[0093] Comparative Synthesis Example 2 / X'-2 Polyol (A'2), polyisocyanate (B1), and (meth)acrylate (C1) were reacted in a molar ratio of 2.0:3.0:2.10. The actual amounts charged and reaction conditions are described below. 269.1 g of polyol (A'2), 22.6 g of polyisocyanate (B1), and 129 g of (meth)acrylate (Y1) as a diluent monomer were charged into a separable flask equipped with a thermometer and a stirrer. Furthermore, 800 ppm of dibutylhydroxytoluene (BHT) relative to the reaction components excluding the (meth)acrylate (Y1) was added. The internal temperature was raised to 50°C, and the mixture was stirred for 1 hour to homogenize the system. After that, a urethane catalyst (DBTDL) (300 ppm relative to the reaction components excluding the (meth)acrylate (Y1)) was added. After confirming that the internal temperature had risen, the temperature was raised to 70°C and the mixture was aged for 2 hours to prepare a urethane isocyanate prepolymer. After confirming that the isocyanate group concentration in the reaction solution was equal to or less than the theoretical value (0.68 wt%), 8.3 g of (meth)acrylate (C1) was added. The mixture was aged for another 2 hours to obtain urethane (meth)acrylate (X'-2). The proportion of (meth)acrylate (Y1) in urethane (meth)acrylate (X'-2) was 30 wt% ((X'-2) / (Y1)=70 / 30). The acryloyl group concentration of the obtained urethane (meth)acrylate (X'-2) was 1,374 g / mol (0.73 mol / kg).

[0094] Comparative Synthesis Example 3 / X'-3 Polyol (A'2), polyisocyanate (B1), and (meth)acrylate (C1) were reacted in a molar ratio of 2.0:3.0:2.10. The actual amounts charged and reaction conditions are described below. 269.1 g of polyol (A'2), 22.6 g of polyisocyanate (B1), and 129 g of (meth)acrylate (Y2) as a diluent monomer were charged into a separable flask equipped with a thermometer and a stirrer. Furthermore, 800 ppm of dibutylhydroxytoluene (BHT) relative to the reaction components excluding (meth)acrylate (Y2) was added. The internal temperature was raised to 50°C, and the mixture was stirred for 1 hour to homogenize the system. After that, a urethane catalyst (DBTDL) (300 ppm relative to the reaction components excluding (meth)acrylate (Y2)) was added. After confirming that the internal temperature had risen, the temperature was raised to 70°C and the mixture was aged for 2 hours. After confirming that the isocyanate group concentration in the reaction solution was equal to or less than the theoretical value (0.68 wt%), 8.3 g of (meth)acrylate (C1) was added. The mixture was aged for another 2 hours to obtain urethane (meth)acrylate (X'-3). The proportion of (meth)acrylate (Y2) in urethane (meth)acrylate (X'-3) was 30 wt% ((X'-3) / (Y2)=70 / 30). The acryloyl group concentration of the obtained urethane (meth)acrylate (X'-3) was 1,374 g / mol (0.73 mol / kg).

[0095] Comparative Synthesis Example 4 / X'-4 Polyol (A'3), polyisocyanate (B1), and (meth)acrylate (C1) were reacted in a molar ratio of 2.0:3.0:2.10. The actual amounts charged and reaction conditions are described below. A separable flask equipped with a thermometer and a stirrer was charged with 103.9 g of polyisocyanate (B1), 800 ppm of dibutylhydroxytoluene (BHT) relative to the reaction components, and a urethane catalyst (DBTDL) (300 ppm relative to the reaction components). The internal temperature was raised to 50°C, and 308.2 g of polyol (A'3) was added dropwise over 4 hours. During this time, the reaction was carried out while gradually heating with cooling water so that the internal temperature did not exceed 80°C. After the dropwise addition of polyol (A'3) was completed, the mixture was aged for 2 hours. After confirming that the isocyanate group concentration in the reaction solution was equal to or less than the theoretical value (3.18 wt%), 38 g of (meth)acrylate (C1) was added. The mixture was further aged for 4 hours to obtain urethane (meth)acrylate (X'-4). The acryloyl group concentration of the obtained urethane (meth)acrylate (X'-4) was 4,209 g / mol (0.24 mol / kg).

[0096] The viscosity (60°C) and Mw of the urethane (meth)acrylate obtained in each Synthesis Example and Comparative Synthesis Example were measured by the methods described above. A summary of each example is shown in Table 1.

[0097]

[0098] [Examples 1 to 8 and Comparative Examples 1 to 7] A (meth)acrylate (Y) was blended as a viscosity-adjusting monomer with the urethane (meth)acrylate (X) obtained in each Synthesis Example and Comparative Synthesis Example until the viscosity of the curable composition at 25°C was 600 mPa·s or less. Then, 3 wt% of a photopolymerization initiator (Z) was blended with the total weight of the resulting mixture to obtain a curable composition for each Example. Tables 2 and 3 show the blending ratios of the (X) component and the (Y) component. The viscosity of the curable composition obtained in each Example was measured using the method described above. The appearance of the curable composition obtained in each Example, and the transparency, heat resistance, and flexibility of the cured product were evaluated under the following conditions. The results are shown in Tables 2 and 3.

[0099] <Evaluation of Appearance of Curable Composition> The curable composition obtained in each example was stored at -30°C for 1 hour, and the presence or absence of turbidity or coloration due to crystallization or the like was evaluated visually according to the following evaluation criteria. (Evaluation criteria: Appearance) Pass: Neither turbidity nor coloration was observed visually. Fail: Turbidity and / or coloration was observed visually.

[0100] <Evaluation of Transparency of Cured Product> As shown in FIG. 1 , a square frame (inner dimensions: 1.0 × 40 × 10 mm) was made of silicone rubber 12 on a microglass 11 (dimensions: 1.0 × 76 × 26 mm), and 1.0 g of curable composition 13 was dropped into the frame. The sample was then heated to 70°C, and once the surface became smooth, it was irradiated with ultraviolet light under the following conditions to cure the composition, yielding a test piece of the cured product. (Ultraviolet Irradiation Conditions) Irradiation Intensity: 120 W / cm Irradiation Distance: 10 cm Conveyor Speed: 5 m / min Number of Irradiations: 2 Next, using a spectrophotometer (manufactured by Shimadzu Corporation, product name "UV-VISIBLE SPECTROPHOTO METER"), transmittance was measured using only the microglass as a reference, and the results were evaluated according to the following evaluation criteria. (Evaluation Criteria: Transparency) Pass: Transmittance at 400 nm was 95% or higher. Fail: The transmittance at 400 nm was less than 95%.

[0101] <Evaluation of Heat Resistance of Cured Product> A laminate 20 as shown in FIGS. 2 and 3 was prepared, and its heat resistance was evaluated. FIG. 2 is a top view of the laminate 20 as viewed from directly above, and FIG. 3 is a side view of the laminate 20. First, 0.50 g (±0.01 g) of the curable composition was accurately weighed and dropped onto the center of a glass plate 21 (1 mm thick, 5 cm square). Another glass plate 21 of the same shape was placed over the glass plate 21, and the curable composition was spread in a circle (4 cm diameter), to obtain a laminate 20 in which the glass plate 21 / curable composition 13 / glass plate 21 were laminated in this order. Then, ultraviolet light was irradiated from one side of the glass plate 21 using a high-pressure mercury lamp (manufactured by Eye Graphics Co., Ltd.) under the following conditions to cure the curable composition 13. (Ultraviolet light irradiation conditions) Irradiation intensity: 120 W / cm Irradiation distance: 10 cm Conveyor speed: 5 m / min Number of irradiations: 8 times (4 times on each side) Next, the cured laminate 20 was stored in a small environmental tester (manufactured by Espec Corporation, product name "SH-641") at a temperature of 95°C for 1000 hours. The shape of the laminate 20 after storage was evaluated according to the following evaluation criteria. (Evaluation criteria: heat resistance) Pass: There was no change in the shape of the laminate 20 after storage. Fail: The shape of the laminate 20 after storage had changed (wrinkles had occurred in the cured product and / or the glass plates had become misaligned).

[0102] <Evaluation of Flexibility of Cured Product> A square silicone rubber frame (inner dimensions: 7 × 40 × 40 mm) was created on a glass plate, and the curable composition was poured into the frame to fill the void volume. The curable composition was preheated and poured slowly to minimize the generation of air bubbles. If air bubbles were present in the curable composition, it was stored in an oven at 80°C until the bubbles were removed. The sample was heated to 80°C, and once the surface was smooth, it was irradiated with ultraviolet light under the following conditions for curing. (UV Irradiation Conditions) Irradiation Intensity: 120 W / cm Irradiation Distance: 10 cm Conveyor Speed: 3.5 m / min Number of Irradiations: 5 After curing, the cured product was removed from the silicone rubber, turned upside down, and further irradiated with ultraviolet light under the same conditions as above. This resulted in the preparation of a test piece of the cured product approximately 7 mm thick. Thereafter, hardness measurements were carried out in accordance with JIS K 6253 using an automatic constant pressure loader (manufactured by Teclock Corporation, product name "GS-610"). A Type A hardness tester was used. The load was 500 g and the load drop rate was 9 mm / s. After the load was removed, the mark left by the indenter in contact was observed and evaluated according to the following evaluation criteria. (Evaluation criteria: flexibility) Pass: No damage such as cracks was observed at the contact point with the indenter, or there was a crack or other damage at the contact point with the indenter, but it recovered within 24 hours. Fail: There was a crack or other damage at the contact point with the indenter, and it did not recover within 24 hours.

[0103]

[0104]

[0105] As shown in Table 2, the curable compositions of Examples 1 to 8, which fulfilled the configuration of the first embodiment, were able to produce low-viscosity curable compositions with a small amount of monomer (component (Y)) and also had good appearance. Furthermore, the cured products obtained from these curable compositions also had excellent transparency, heat resistance, and flexibility. On the other hand, as shown in Table 3, the curable compositions of Comparative Examples 1 to 4, which contained a urethane (meth)acrylate not containing a structural unit derived from farnesene, were able to produce low-viscosity curable compositions with a relatively small amount of monomer (component (Y)), and the appearance was good, but the heat resistance or flexibility of the cured products was poor. Furthermore, the curable compositions of Comparative Examples 5 and 6 exhibited cloudiness and phase separation over time, making it impossible to measure the viscosity of the curable compositions or evaluate the cured products. Note that, as shown in Table 3, in Comparative Examples 5 and 6, when the amount of component (Y) was less than 30 wt %, the appearance was good, but the viscosity of the curable compositions was so high that neither viscosity measurement nor cured product evaluation was possible. Furthermore, the curable composition of Comparative Example 7, which contained only the urethane (meth)acrylate (X-1) and the photopolymerization initiator (Z), had a very high viscosity (25°C) and was difficult to handle. From the above results, it was found that the curable composition according to the first embodiment is an active energy ray-curable composition having a low viscosity, and can give a cured product that is excellent in transparency, flexibility, and heat resistance.

[0106] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure are described below. [1] An active energy ray-curable composition comprising: a urethane (meth)acrylate (X) containing a structural unit derived from farnesene; a (meth)acrylate (Y) other than the urethane (meth)acrylate (X); and a photopolymerization initiator (Z). [2] The active energy ray-curable composition according to [1], wherein the urethane (meth)acrylate (X) is a reaction product of a polyol (A) containing a structural unit derived from farnesene, a polyisocyanate (B), and a (meth)acrylate (C) having a hydroxyl group. [3] The active energy ray-curable composition according to [1] or [2], wherein the urethane (meth)acrylate (X) has a weight average molecular weight (Mw) of 5,000 to 30,000. [4] The active energy ray-curable composition according to any one of [1] to [3], wherein the urethane (meth)acrylate (X) is a reaction product of a polyol (A) containing a structural unit derived from farnesene, a polyisocyanate (B), and a (meth)acrylate (C) having a hydroxyl group, and the polyol (A) contains a diol represented by the following formula (I): (In formula (I), m and n each independently represent an integer of 1 to 7.) [5] A cured product of the active energy ray-curable composition according to any one of [1] to [4]. [6] A laminate comprising one or more layers selected from the active energy ray-curable composition according to any one of [1] to [4] and the cured product according to [5].

[0107] The curable composition according to the first embodiment is characterized by a low viscosity even when the amount of component (Y) is at least. Furthermore, the curable composition can produce a cured product having excellent transparency, flexibility, and heat resistance. Such a curable composition can be suitably used, for example, as a curable composition for optical components or liquid gaskets.

[0108] 11: Microglass 12: Silicone rubber 13: Active energy ray-curable composition 20: Laminate 21: Glass plate

Claims

1. An active energy ray-curable composition comprising: a urethane (meth)acrylate (X) containing a structural unit derived from farnesene; a (meth)acrylate (Y) other than the urethane (meth)acrylate (X); and a photopolymerization initiator (Z).

2. The active energy ray-curable composition according to claim 1, wherein the urethane (meth)acrylate (X) is a reaction product of a polyol (A) containing a structural unit derived from farnesene, a polyisocyanate (B), and a (meth)acrylate having a hydroxyl group (C).

3. The active energy ray-curable composition according to claim 1 or 2, wherein the urethane (meth)acrylate (X) has a weight average molecular weight (Mw) of 5,000 to 30,000.

4. The active energy ray curable composition according to claim 1 or 2, wherein the urethane (meth)acrylate (X) is a reaction product of a polyol (A) containing a structural unit derived from farnesene, a polyisocyanate (B), and a (meth)acrylate (C) having a hydroxyl group, and the polyol (A) contains a diol represented by the following formula (I): (In formula (I), m and n each independently represent an integer of 1 to 7.) 5. A cured product of the active energy ray-curable composition according to claim 1.

6. A laminate comprising one or more layers selected from the active energy ray-curable composition according to claim 1 and the cured product according to claim 5.

Images