Urethane (meth)acrylate and its manufacturing method, active energy ray curable resin composition, cured product and laminate

Abstract

The present invention provides a urethane (meth)acrylate and a method for producing the same, which can provide an active energy ray curable resin composition that has excellent transparency, resilience, and heat resistance and yields a low-hardness coating film (cured product), an active energy ray curable resin composition containing the urethane (meth)acrylate, a cured product of the active energy ray curable resin composition, and a laminate comprising the cured product. [Solution] A urethane (meth)acrylate having a structure derived from linear polypropylene glycol of the following formula (I), and containing a urethane bond and a (meth)acryloyl group. [Formula 1] TIFF2026115431000015.tif24170 (In formula (I), n1 represents a number between 10 and 100.)

Description

[Technical Field]

[0001] This disclosure relates to urethane (meth)acrylate and methods for producing the same, active energy ray curable resin compositions, cured products and laminates. [Background technology]

[0002] Displays used in personal computers, car navigation systems, televisions, mobile phones, etc., project images using light from a backlight. These displays utilize transparent substrates such as glass substrates and plastic films. However, the amount of light emitted from the light source to the outside of the display can decrease due to light scattering and absorption by these substrates. If this decrease in light intensity is significant, the screen becomes darker, reducing visibility.

[0003] Methods to improve visibility include enhancing the light scattering prevention properties of the display surface layer and increasing the amount of light from the light source. One specific method involves replacing the air layer between transparent substrates such as glass or plastic substrates with a resin layer (a cured resin layer). By replacing the air layer with a resin layer, light scattering at the interface between the air and the transparent substrate can be prevented, thus preventing a decrease in the amount of light output from the light source to the outside of the display and improving visibility.

[0004] The resins used between layers of transparent substrates are required to have good adhesion to the substrate when cured (as a coating), excellent deformation resistance and transparency, and low coating hardness from the standpoint of flexibility. Furthermore, high heat resistance is required, specifically minimal change in shape and color at 95°C. Various urethane (meth)acrylates have been proposed to impart these properties to the cured product.

[0005] Patent document 1, etc., reports on urethane (meth)acrylate containing hydrogenated polyolefin polyol as a component, and active energy ray curable resin compositions containing the same. Using hydrogenated polyolefin polyol as a component of urethane (meth)acrylate is very effective from the viewpoint of preventing deterioration of the cured product due to oxidation. However, because such urethane (meth)acrylate is highly hydrophobic, it tends to have poor compatibility with other components that may be included in the composition, making it difficult to adjust the viscosity of the composition and impart desired properties (e.g., flexibility, heat resistance, etc.) to the cured product. In addition, hydrogenated polyolefin polyol is expensive and has high viscosity, making it difficult to manufacture urethane (meth)acrylate on a large scale, and it also has problems such as poor handling. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2010-265402 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The object of this disclosure is to provide a urethane (meth)acrylate and a method for producing the same that can give an active energy ray curable resin composition that has excellent transparency, resilience, and heat resistance and yields a low-hardness coating film (cured product), an active energy ray curable resin composition containing the urethane (meth)acrylate, a cured product of the active energy ray curable resin composition, and a laminate comprising the cured product. [Means for solving the problem]

[0008] This disclosure includes the following aspects: A urethane (meth)acrylate having a structure derived from the linear polypropylene glycol of the following formula (I), and containing a urethane bond and a (meth)acryloyl group. [ka] (In equation (I), n1 represents a number between 10 and 100.) [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a urethane (meth)acrylate and a method for producing the same, which can give an active energy ray curable resin composition that has excellent transparency, resilience and heat resistance and yields a coating film (cured product) with low hardness, an active energy ray curable resin composition containing the urethane (meth)acrylate, a cured product of the active energy ray curable resin composition, and a laminate comprising the cured product. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing one embodiment of the laminate in this disclosure. [Figure 2] This is a schematic diagram of the test specimens used to evaluate the resilience and coating hardness of the examples. [Figure 3] This is a schematic diagram of the test specimen used to evaluate the recovery properties and coating hardness of the examples. (a) in the figure is a top view of the test specimen, and (b) is a side view of the test specimen. [Modes for carrying out the invention]

[0011] Hereinafter, an embodiment of the present disclosure will be described in detail. However, the scope of the present disclosure is not limited to the embodiment described here, 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 features disclosed in this specification. When a plurality of upper limit values and lower limit values are described for a specific parameter, any upper limit value and lower limit value can be combined to form a suitable numerical range. The lower limit value and / or upper limit value of the numerical range described in the present disclosure are numerical values within that numerical range and may be replaced with the numerical values shown in the examples. The expression "X~Y" indicating a numerical range means "X or more and Y or less". When a specific description described for one embodiment also applies to other embodiments, the description may be omitted in other embodiments.

[0012] [Urethane (meth)acrylate] The first embodiment of the present disclosure relates to urethane (meth)acrylate. The urethane (meth)acrylate according to the first embodiment has a structure derived from linear polypropylene glycol of the following formula (I) and contains a urethane bond and a (meth)acryloyl group. [Chemical formula] (In formula (I), n1 represents a number from 10 to 100.)

[0013] The urethane (meth)acrylate according to the first embodiment, more specifically, has a structure derived from the linear polypropylene glycol of the above formula (I) (hereinafter, may also be referred to as "linear PPG"), and has one or more urethane bonds and one or more (meth)acryloyl groups. In formula (I), n1 can be any number from 10 to 100. From the viewpoint of easily setting the weight average molecular weight (Mw) of the urethane (meth)acrylate within a preferable range, n1 is preferably from 10 to 100, more preferably from 20 to 100, and even more preferably from 20 to 80. In a more preferable embodiment, n1 may be from 25 to 70 or may be from 30 to 50. Whether the structure of the above formula (I) is contained in the urethane (meth)acrylate can be confirmed by analysis using NMR or IR.

[0014] Formula (I) is a structure derived from a polyol. That is, in the first embodiment, a polyol containing a linear PPG skeleton is used as a raw material. As described above, the urethane (meth)acrylate has problems such as low heat resistance of the cured product, specifically, when the cured product is exposed to high temperature, its shape and hue are likely to change. To improve the heat resistance, it is effective to increase the crosslinking density, but increasing the crosslinking density impairs the appropriate flexibility as a coating film, so the heat resistance and flexibility are in an antagonistic relationship. The inventors of the present application have conducted intensive research and found that a urethane (meth)acrylate having a structure derived from the linear PPG of formula (I) can provide an active energy ray-curable resin composition having excellent transparency, recovery property, and heat resistance, and capable of obtaining a coating film (cured product) with low hardness, thus completing the present disclosure.

[0015] That is, the inventors of the present application have found that by having a repeating unit derived from 1,3-propanediol (trimethylene oxide) having a linear structure as in the above formula (I) in the structure, the intermolecular cohesive force is increased, and high heat resistance can be obtained without increasing the crosslinking density. As a result, it has been found that a coating film having both heat resistance and flexibility, which were in an antagonistic relationship, can be obtained, and the coating film has low hardness and high heat resistance. Furthermore, in the case of conventional polyether-based urethane (meth)acrylates, a coating hardness of A50 or higher is required to maintain the durability of the coating film under high temperature conditions of 95°C. On the other hand, the urethane (meth)acrylate according to the first embodiment can maintain heat resistance even at a lower coating hardness. Due to these characteristics, the urethane (meth)acrylate according to the first embodiment can be used, for example, as an adhesive for large displays.

[0016] In one embodiment, urethane (meth)acrylate can have the following structure. [ka] (In formula (IA), Y1 is -NHCOO-* or -NHCOO-(AO1) n2 -* represents Y2, and Y2 is *-CONH-, *-(AO2) n3 -CONH- represents the molecule, AO1 and AO2 represent alkylene oxides which may have substituents with 1 to 5 carbon atoms, n1 represents a number from 10 to 100, n2 and n3 represent a number from 1 to 100, and * represents the bond to the linear PPG skeleton.

[0017] In equation (IA), Y1 and / or Y2 are -NHCOO-(AO1) n2 -*, and / or, *-(AO2) n3 If it is -CONH-, then n2 and n3 are numbers from 1 to 100. In one embodiment, n2 and n3 may be from 1 to 80, from 1 to 50, from 1 to 10, or from 1 to 5.

[0018] In formula (IA), AO1 and AO2 represent alkylene oxides which may have substituents having 1 to 5 carbon atoms. Examples of such alkylene oxides include ethylene oxide (EO), propylene oxide (PO), butylene oxide (BO), and tetrahydrofuran (THF). In formula (IA), when n2 and n3 are 2 or more, (AO1) n2 , (AO2) n3represents a polyalkylene oxide chain. When n2 and / or n3 are 2 or more, AO1 and / or AO2 may contain one type of alkylene oxide or two or more types. For example, it may be a skeleton in which EO and PO are randomly polymerized.

[0019] In one embodiment, Y1 and Y2 are -NHCOO-(AO1) n2 -*, *-(AO2) n3 When it is -CONH-, AO1 and AO2 are preferably linear alkylene oxides without substituents.

[0020] As shown in formula (IA) above, the urethane (meth)acrylate has a structure derived from the linear PPG of formula (I), and may further have a structure in which a urethane bond is directly bonded to the linear PPG-derived structure, or it may include a structure derived from linear PPG and a structure derived from alkylene oxide, and may include a structure in which a urethane bond is bonded to the alkylene oxide-derived structure. From the viewpoint of easily obtaining a coating film that achieves both high heat resistance and flexibility, a structure in formula (IA) in which Y1 is -NHCOO-* and Y2 is *-CONH- is preferred.

[0021] <(meth)acryloyl group concentration> In one embodiment, the (meth)acryloyl group concentration of the urethane (meth)acrylate is preferably 2200 g / mol or more, preferably 2600 g / mol or more, preferably 2200 g / mol or more and 6000 g / mol or less, more preferably 2600 g / mol or more and 6000 g / mol or less, even more preferably 3200 g / mol or more and 6000 g / mol or less, and even more preferably 4000 g / mol or more and 6000 g / mol or less. In a preferred embodiment, the (meth)acryloyl group concentration is 4500 g / mol or more and 6000 g / mol or less, and 5000 g / mol or more and 5500 g / mol or less. When the (meth)acryloyl group concentration is within the above range, the active energy ray curable resin composition containing urethane (meth)acrylate cures more easily, and initial adhesion to the substrate is improved. Furthermore, it becomes easier to obtain a coating film with low hardness and good heat resistance. The (meth)acryloyl group concentration can be calculated from the amount of monomer used when preparing the urethane (meth)acrylate. The method for calculating the (meth)acryloyl group concentration will be described later.

[0022] <Weight average molecular weight (Mw)> In one embodiment, the weight-average molecular weight (Mw) of the urethane (meth)acrylate is preferably 3,000 to 50,000, more preferably 5,000 to 40,000, even more preferably 10,000 to 30,000, and particularly preferably 13,000 to 16,000, from the viewpoint of flexibility. The "weight-average molecular weight" in this disclosure is a polystyrene equivalent value measured by GPC, and can be measured, for example, by the method described in the examples of this disclosure.

[0023] <Viscosity> In one embodiment, the viscosity of the urethane (meth)acrylate is preferably 50,000 mPa·s / 60°C or less, more preferably 30,000 mPa·s / 60°C or less, and even more preferably 20,000 mPa·s / 60°C, from the viewpoint of good handling. In one embodiment, the viscosity of the urethane (meth)acrylate may be 14,000 to 16,000 mPa·s / 60°C. The viscosity of the urethane (meth)acrylate (60°C) is the value measured at 60°C using an E-type viscometer (for example, TV-25 model manufactured by Toki Sangyo Co., Ltd.).

[0024] <Exterior> When used for interlayer filling between transparent substrates, the appearance of the urethane (meth)acrylate is preferably close to colorless. In one embodiment, the Hazen color number is preferably 100 or less. The Hazen color number can be measured in accordance with JIS K 0071-1. Specifically, the urethane (meth)acrylate is prepared as a uniform solution at a weight ratio of 6% using a mixed solvent of methylene chloride / methanol = 9 / 1 (volume ratio), and the Hazen color number can be determined by comparing the color of this solution with a standard colorimetric solution.

[0025] In one embodiment, from the viewpoint of producing a urethane (meth)acrylate with a low environmental impact, a biomass content of 30% or more is preferred. Furthermore, from the viewpoint of producing a urethane (meth)acrylate with an even lower environmental impact, the biomass content may be 50% or more, 70% or more, or even 100%. The biomass content of the urethane (meth)acrylate can be calculated from the biomass content of the raw materials used in the production of the urethane (meth)acrylate. A urethane (meth)acrylate with a biomass content of 30% or more can be easily achieved, for example, in the urethane (meth)acrylate production method described later, by replacing part or all of the polyol (A) (preferably polyol (a1)) with a biomass-derived component.

[0026] [Manufacturing method for urethane (meth)acrylate] Next, a method for producing urethane (meth)acrylate according to the first embodiment (second embodiment) will be described. The second embodiment relates to a method for producing urethane (meth)acrylate, comprising a urethane reaction of raw materials including a polyol (A) containing a polyol (a1) having a linear polypropylene glycol skeleton of the following formula (II), a polyisocyanate (B), and a hydroxyl group-containing (meth)acrylate (C). [ka] (In equation (II), n1 represents a number between 10 and 100.) The details of the manufacturing method according to the second embodiment will be described below.

[0027] <Polyol (A)> (Polyol (a1)) In the second manufacturing method, polyol (A) includes polyol (a1) having a linear PPG skeleton of formula (II). Polyol (a1) is a polyol component having a linear PPG skeleton of formula (II) and having two or more hydroxyl groups. Preferably, polyol (a1) has two hydroxyl groups. In formula (II), n1 can be any number between 10 and 100. From the viewpoint of easily setting the weight-average molecular weight (Mw) of the urethane (meth)acrylate within a preferred range, n1 is preferably between 10 and 100, more preferably between 20 and 100, and even more preferably between 20 and 80. In a more preferred embodiment, n1 may be between 25 and 70, or between 30 and 50.

[0028] Polyol (a1) may be a single type having the linear PPG skeleton of formula (II) above, or two or more types may be used in combination. In one embodiment, the weight-average molecular weight (Mw) of polyol (a1) is preferably 500 to 5000, more preferably 500 to 3000, even more preferably 1500 to 3000, even more preferably 1500 to 2500, and particularly preferably 1800 to 2200. By having the weight-average molecular weight (Mw) of polyol (a1) within the above range, the glass transition temperature Tg of the resulting urethane (meth)acrylate does not become too high, the decrease in flexibility is easily suppressed, the formation of by-products is easily suppressed, and the compatibility between the urethane (meth)acrylate and other components is also easily improved.

[0029] In one embodiment, the polyol (a1) is preferably a polyol having the structure of the following formula (IIA). [ka] (In formula (IIA), X1 is a hydroxyl group or HO-(AO1) n2 -*, X2 is hydrogen or *-(AO2) n3 -H, AO1 and AO2 represent alkylene oxides which may have substituents with 1 to 5 carbon atoms, n1 represents a number from 10 to 100, n2 and n3 represent numbers from 1 to 100, and * represents the bonding part with the linear PPG backbone.)

[0030] In formula (IIA), when X1 and / or X2 is HO-(AO1) n2 -*, and / or *-(AO2) n3 -H, n2 and n3 are numbers from 1 to 100. In one embodiment, n2 and n3 may be from 1 to 80, may be from 1 to 50, may be from 1 to 10, or may be from 1 to 5.)

[0031] In formula (IIA), examples of AO1 and AO2 are the same as those described in the above formula (IA), and the preferred embodiments are also the same.)

[0032] As described above, the polyol (a1) may be a linear PPG (the structure where X1 is a hydroxyl group and X2 is a hydrogen atom), or may be a polyol having a structure in which an alkylene oxide with 1 to 5 carbon atoms is added to the end of the linear PPG. From the viewpoint of easily obtaining a coating film with both high heat resistance and flexibility, the polyol (a1) is preferably a linear PPG, and more preferably a linear PPG with an Mw of 500 or more and 5000 or less.)

[0033] In one embodiment, from the viewpoint of obtaining a urethane (meth)acrylate with a low environmental impact, the polyol (a1) may be a polymer of biomass-derived 1,3-propanediol. Commercially available products may be used as such a polyol (a1), for example, products such as "ECOTRION (registered trademark) H2000" manufactured by SK Chemicals can be used.)

[0034] In one embodiment, the proportion of polyol (a1) in polyol (A) is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, and particularly preferably 100% by mass, with respect to the total mass of polyol (A), from the viewpoint of easily obtaining a coating film that achieves both high heat resistance and flexibility.

[0035] In one embodiment, the biomass content of polyol (A) is preferably 30% or more, more preferably 50% or more, even more preferably 70% or more, and particularly preferably 100%. A polyol (A) having such a biomass content is easily achieved when polyol (a1) contains the aforementioned polymer of biomass-derived 1,3-propanediol.

[0036] (Polyol(a2)) In one embodiment, from the viewpoint of improving the appearance of the urethane (meth)acrylate (for example, controlling the Hazen unit color number to a lower range) and controlling flexibility (for example, controlling the coating hardness to a lower range, as described later), polyol (A) may include any polyol (a2) other than polyol (a1). Examples of polyol (a2) include polyalkylene glycol (excluding polyol (a1); for example, polyethylene glycol (PEG), polytetramethylene glycol (PTMG), polypropylene glycol (PPG) without a linear structure, etc.), polyolefin polyol, hydrogenated polyolefin polyol, polyester polyol, trimethylolpropane, pentaerythritol, glycerin, butylethylpropanediol, etc. Any of these polyols may be used alone or in combination of two or more. Furthermore, the Mw of polyalkylene glycol, polyolefin polyol, hydrogenated polyolefin polyol, and polyester polyol among the above polyol (a2) is not particularly limited, and any Mw can be used depending on the desired physical properties. Furthermore, the proportion of polyol (a2) in polyol (A) is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, even more preferably 0 to 10% by mass, and still more preferably 0 to 5% by mass.

[0037] <Polyisocyanate (B)> In the manufacturing method according to the second embodiment, polyisocyanate (B) is not particularly limited, and for example, aliphatic polyisocyanate, aromatic polyisocyanate, etc. can be used. Among these, aliphatic polyisocyanate is preferred from the viewpoint of recovery under high temperature conditions and heat resistance (change in hue). Polyisocyanate (B) may be used alone or two or more types may be used in combination.

[0038] Examples of aliphatic polyisocyanates include alicyclic polyisocyanates and linear or branched aliphatic polyisocyanates. Examples of alicyclic polyisocyanates include alicyclic diisocyanates such as isophorone diisocyanate, and alicyclic polyisocyanates obtained by hydrogenating aromatic polyisocyanates such as hydrogenated diphenylmethane diisocyanate (dicyclohexylmethane 4,4'-diisocyanate) and hydrogenated xylylene diisocyanate. Examples of linear or branched aliphatic polyisocyanates include linear aliphatic diisocyanates such as hexamethylene diisocyanate, and branched aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate. Among these, alicyclic diisocyanates such as isophorone diisocyanate are preferred from the viewpoint of improving the transparency of the cured product.

[0039] Examples of aromatic polyisocyanates include aromatic diisocyanates such as diphenylmethane diisocyanate, aromatic triisocyanates, and aromatic tetraisocyanates. Examples of diisocyanate compounds obtained by hydrogenating aromatic polyisocyanates include hydrogenated xylylene diisocyanate and hydrogenated diphenylmethane diisocyanate.

[0040] In one embodiment, the polyisocyanate (B) preferably comprises one or more selected from isophorone diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and methylenebis(4-cyclohexyl isocyanate).

[0041] <Hydroxyl group-containing (meth)acrylate (C)> In the manufacturing method according to the second embodiment, the hydroxyl group-containing (meth)acrylate (C) is a (meth)acrylate containing one or more hydroxyl groups and one or more (meth)acryloyl groups in its structure. From the viewpoint of the hardness of the cured product, for example, (meth)acrylates containing one (meth)acryloyl group and one hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate (2-hydroxyn-propyl (meth)acrylate), and 4-hydroxybutyl (meth)acrylate, and in which the alkylene group of the ester portion has 2 to 10 carbon atoms; and (meth)acrylates containing two or more (meth)acryloyl groups and one hydroxyl group, such as pentaerythritol triacrylate, are preferred. The hydroxyl group-containing (meth)acrylate (C) may be used alone or two or more types may be used in combination.

[0042] In one embodiment, from the viewpoint of easily adjusting the (meth)acryloyl group concentration to the aforementioned preferred range, the hydroxyl group-containing (meth)acrylate (C) is preferably a (meth)acrylate containing one (meth)acryloyl group and one hydroxyl group, with the alkylene group of the ester portion having 2 to 10 carbon atoms, and more preferably containing 2-hydroxyethyl (meth)acrylate.

[0043] (Alcohol (D) having at least one hydroxyl group) In one embodiment, the raw material for producing urethane (meth)acrylate preferably further contains an alcohol (D) having at least one hydroxyl group. Further inclusion of an alcohol (D) having at least one hydroxyl group in the raw material improves the reactivity of the raw material and further improves the yield of urethane (meth)acrylate. Alcohol (D) is not particularly limited as long as it has at least one hydroxyl group, but examples include monohydric alcohols with 2 to 20 carbon atoms, such as 1-butanol, 1-heptanol, 1-hexanol, n-octyl alcohol, 2-ethylhexanol, cyclohexanemethanol, caprylic alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol (cetanol), and stearyl alcohol. Among these, monohydric alcohols with 2 to 10 carbon atoms are preferred from the viewpoint of boiling point, price, and availability, and the inclusion of 2-ethylhexanol is more preferred. Alcohol (D) may be used alone or in combination of two or more types. Note that alcohol (D) having at least one hydroxyl group does not include hydroxyl group-containing (meth)acrylate (C) and polyol (A).

[0044] The manufacturing method according to the second embodiment involves urethane-forming a raw material comprising the aforementioned polyol (A), polyisocyanate (B), and hydroxyl group-containing (meth)acrylate (C), and optionally an alcohol (D) having at least one hydroxyl group. Hereinafter, polyols (A) may be simply referred to as "component (A)", polyisocyanates (B) as simply "component (B)", hydroxyl group-containing (meth)acrylates (C) as simply "component (C)", and alcohols (D) having at least one hydroxyl group as simply "component (D)".

[0045] The method for reacting components (A) to (C) (or components (A) to (D)) is not particularly limited, but it is preferable to first form a urethane prepolymer by reacting component (A) and component (B), and then produce urethane (meth)acrylate by reacting the urethane prepolymer with component (C). When reacting the urethane prepolymer with component (C), component (C) and component (D) may be added simultaneously.

[0046] The above manufacturing method, namely "a method in which component (A) and component (B) are reacted together, and then component (C) is reacted," is preferable to "a method in which components (A), (B), and (C) are mixed together and reacted" or "a method in which component (B) and component (C) are reacted together, and then component (A) is reacted" from the viewpoint of preventing an increase in the viscosity of the reactants, suppressing by-products, and improving the transparency and heat resistance of the cured product. Specifically, urethane (meth)acrylate obtained by the method of "mixing and reacting components (A), (B), and (C) all at once" tends to have high viscosity. Furthermore, because the reaction proceeds unevenly, partial gelation is likely. Additionally, urethane (meth)acrylate that does not contain component (A) in its structure (i.e., by-products) is generated, making it difficult to obtain a coating film that simultaneously possesses high heat resistance and flexibility. Moreover, because various urethane (meth)acrylates with different molecular weights and structures are easily generated, quality control tends to be difficult.

[0047] Furthermore, in the method of "reacting component (B) with component (C) and then reacting with component (A)," there is a tendency to produce urethane (meth)acrylate (i.e., a by-product) in which all the isocyanate groups of component (B) react with the hydroxyl groups of component (C). Since this by-product does not contain the skeleton of component (A), it tends to exhibit crystalline properties, which not only easily reduces transparency but can also cause gelation of the urethane (meth)acrylate. In addition, as mentioned above, it becomes difficult to obtain a coating film that is both highly heat resistant and flexible.

[0048] From the above viewpoint, it is preferable to adopt a method for producing urethane (meth)acrylate by first forming a urethane prepolymer by reacting component (A) and component (B), and then reacting the urethane prepolymer with component (C). This makes it possible to efficiently obtain a urethane prepolymer having the structure of formula (I) and a urethane bond by reacting component (B) with component (A) (i.e., polyol component (a1) having the structure of formula (II)). The following methods 1 to 3 can be used to form the urethane prepolymer. (Method 1) A method in which components (A) and (B) are mixed together and reacted. (Method 2) A method in which component (A) is added dropwise to component (B) while the reaction is carried out. (Method 3) A method in which component (B) is added dropwise to component (A) and the reaction is carried out.

[0049] In method 3, the urethane reaction is carried out by dropping component (B) into a large amount of component (A). The isocyanate groups on both sides of component (B) urethane react with 2 moles of hydroxyl groups in component (A), resulting in the formation of a by-product that is schematically represented as an ABA-type diol with hydroxyl groups at both ends. Furthermore, 2 moles of (B) react with this, resulting in the formation of a by-product that is schematically represented as a BABAB-type compound with isocyanate groups at both ends. Repeating this reaction may result in the formation of a large amount of a by-product with the following schematic structure. B - [AB]nAB (an integer greater than or equal to n = 1) When a large amount of such by-products are produced, the concentration of (meth)acryloyl groups in the urethane (meth)acrylate obtained by reacting the urethane prepolymer containing the by-products with component (C) (or component (C) and component (D)) decreases, and as a result, the crosslinking density of the cured product tends to decrease. Therefore, in order to obtain the target urethane isocyanate prepolymer in good yield, (Method 1) or (Method 2) is preferred.

[0050] Method 1 is industrially superior in that, when component (A) is highly viscous or component (B) is solid, these components (A) and (B) can be directly charged into the reactor, and urethane (meth)acrylate can be produced in a single pot. In Method 1, component (A) (including monofunctional (meth)acrylate if necessary) is charged into the reactor and stirred until homogeneous, then component (B) is charged and homogeneous is achieved. This keeps the viscosity of the reaction solution low. Subsequently, it is desirable to start the urethane formation by adding the urethane catalyst after stirring and raising the temperature as necessary. The temperature may also be raised as necessary after adding the urethane catalyst. If the urethane catalyst is added from the beginning before components (A) and (B) become homogeneous, the urethane formation reaction will proceed with components (A) and (B) in a non-uniform state at the stage of charging component (B), which may change the molecular weight and viscosity of the resulting urethane prepolymer, and the reaction may terminate with unreacted component (B) remaining in the system. In such cases, byproducts are generated when only component (C) (or components (C) and (D)) used later react with the remaining component (B), which tends to reduce transparency. In one embodiment, the content of the above-mentioned by-products is preferably less than 7% by mass of the total mass of the urethane (meth)acrylate, which is the reaction product of the target components (A) to (C) (or components (A) to (D)). If the content of the by-products is less than 7% by mass, the transparency is less likely to decrease. The "monofunctional (meth)acrylate" described in the section on the manufacturing method according to the second embodiment can be the same as the monofunctional (meth)acrylate exemplified in the "reactive diluent" section described later.

[0051] In Method 2, component (B), the urethane catalyst, and, if necessary, a portion of the monofunctional (meth)acrylate are charged into the reactor and stirred until homogeneous. While stirring, the temperature is increased as needed, and the reaction is carried out by adding a homogeneous mixture of component (A) and monofunctional (meth)acrylate dropwise. Although Method 2 requires the extra step of separately preparing a homogeneous mixture of component (A) and monofunctional (meth)acrylate and adding it dropwise to the reactor, it is preferred because it produces the fewest by-products as described in Method 3. In either method, when synthesizing a urethane prepolymer by the reaction of component (A) and component (B), it is preferable to continue the reaction until all hydroxyl groups are converted to urethane. The endpoint of the reaction can be confirmed by measuring the concentration of isocyanate groups in the reaction solution and determining when the concentration falls below the concentration of isocyanate groups when all hydroxyl groups introduced into the system have been converted to urethane, or when the concentration of isocyanate groups no longer changes.

[0052] It is preferable to use components (A) and (B) in the raw materials such that the molar ratio of component (A) to component (B) is preferably 1.1 to 2.0 moles, more preferably 1.1 to 1.8 moles, and even more preferably 1.1 to 1.6 moles of isocyanate groups of component (B) for every 1 mole of hydroxyl groups of component (A). Furthermore, when synthesizing the target urethane (meth)acrylate by reacting the urethane prepolymer with component (C), 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 to react in such a way that the number of moles of hydroxyl groups of component (C) is in excess of the number of moles of isocyanate groups of the urethane prepolymer, and to continue the reaction until the concentration of residual isocyanate groups in the reaction solution is 0.1% by mass or less. In one preferred embodiment, the reaction is continued until the residual isocyanate groups are 0.05% by mass or less. The residual isocyanate group concentration can be measured by gas chromatography, titration, or the like. In this reaction, the number of moles of hydroxyl groups of component (C) per 1.0 mole of isocyanate groups of the urethane prepolymer can preferably be 1.005 to 1.1 moles, and more preferably 1.01 to 1.05 moles.

[0053] In one embodiment, it is preferable to adjust the amount of component (C) so that the concentration of (meth)acryloyl groups in the final urethane (meth)acrylate is 2600 mol / g or more. The amount of component (C) can be calculated based on the following formula. (Meth)acryloyl group concentration (g / mol) = [(Total amount (g) excluding non-reactive components such as diluent monomers, diluent solvents, and catalysts) × (Molecular weight of hydroxyl group-containing (meth)acrylate (C))] ÷ (Weight (g) of hydroxyl group-containing (meth)acrylate (C)) The molecular weight of the hydroxyl group-containing (meth)acrylate (C) refers to the molecular weight of 1 mole on an atomic basis. The (meth)acryloyl group concentration may be adjusted by the amount of component (C) added, or by modifying some of the (meth)acryloyl groups with alkoxy groups, etc.

[0054] (Catalysts, additives) The above reaction is preferably carried out in the presence of polymerization inhibitors such as dibutylhydroxytoluene, hydroquinone, hydroquinone monomethyl ether, and phenothiazine, in order to prevent polymerization. The amount of these polymerization inhibitors added is preferably 1 to 10,000 ppm (by weight) relative to the urethane (meth)acrylate produced, more preferably 100 to 1,000 ppm, and even more preferably 400 to 1,000 ppm. By adding polymerization inhibitors within the above range relative to the urethane (meth)acrylate, a sufficient polymerization inhibition effect is easily obtained, and adverse effects on the physical properties of the product are less likely to occur. For the same purpose, this reaction is preferably carried out in a molecular oxygen-containing gas atmosphere. The oxygen concentration is appropriately selected considering safety.

[0055] The above reaction may be carried out using a catalyst to obtain a sufficient reaction rate. Suitable catalysts include dibutyltin dilaurate, tin octoate, tin chloride, bismuth(III) neodecanoate, bismuth(III) 2-ethylhexanoate, zinc neodecanoate, zinc octoate, DBU (diazabicycloundecene), DBN (1,5-diazabicyclononene), etc. Of these, dibutyltin dilaurate is preferred in terms of reaction rate. The amount of these catalysts added is usually 1 to 3000 ppm (by weight), preferably 50 to 1000 ppm, relative to the urethane (meth)acrylate produced. By adding catalyst within this range, a sufficient reaction rate can be easily obtained, and adverse effects on the physical properties of the product, such as a decrease in lightfastness, are less likely to occur.

[0056] (solvent) The above reaction can be carried out in the presence of a known volatile organic solvent. The volatile organic solvent can be removed by distillation under reduced pressure after the synthesis of the urethane (meth)acrylate. A volatile organic solvent refers to an organic solvent whose boiling point does not exceed 200°C. However, if the active energy ray curable resin composition is used for curing in a sealed state, it is preferable not to use any volatile organic solvents from the production of the urethane (meth)acrylate to the production of the active energy ray curable composition described later.

[0057] (Reaction temperature) The reaction temperature during the urethane formation reaction is preferably 130°C or lower, and more preferably between 40°C and 130°C. A reaction temperature within this range makes it easier to obtain a sufficient reaction rate and reduces the likelihood of gel formation due to crosslinking of double bonds by radical polymerization.

[0058] [Active energy ray curable resin composition] A third embodiment of this disclosure relates to an active energy ray curable resin composition comprising a urethane (meth)acrylate according to the first embodiment and a photopolymerization initiator. The active energy ray curable resin composition according to the third embodiment, by comprising the urethane (meth)acrylate according to the first embodiment, provides a coating film (cured product) with excellent transparency, resilience, and heat resistance, and low hardness. The active energy ray curable resin composition according to the third embodiment may further contain a volatile organic solvent and / or a reactive diluent.

[0059] <Photopolymerization initiator> In the active energy ray curable resin composition according to the third embodiment, the photopolymerization initiator is not particularly limited, but known photoradical polymerization initiators and photocationic polymerization initiators can be used, for example, 1-hydroxycyclohexylphenyl 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-morpholinopropan-1, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether Examples include benzoin-n-butyl ether, benzoin phenyl ether, benzyl dimethyl ketal, benzophenone, benzoyl benzoic acid, methyl benzoyl benzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylic benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3'-dimethyl-4-methoxybenzophenone, thioxanthone, 2-chlorthioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, methylphenyl glyoxylate, benzyl, camphorquinone, etc. The photopolymerization initiator may be used alone or in combination of two or more types.

[0060] The amount of photopolymerization initiator added is not particularly limited, but for example, 1 to 20 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the resin content of the active energy ray curable resin composition. When the amount of photopolymerization initiator added is within the above range, curing defects are less likely to occur, and odors derived from the photopolymerization initiator are less likely to remain in the cured product. Note that "resin content" refers to the curable resin contained in the active energy ray curable resin composition, and includes the above-mentioned urethane (meth)acrylate and the monofunctional (meth)acrylate described later. Photopolymerization initiators and volatile organic solvents do not fall under the category of "resin content".

[0061] The active energy ray curable resin composition according to the third embodiment may contain a volatile organic solvent, a monofunctional (meth)acrylate as a reactive diluent, and various additives, to the extent that the effects of the present disclosure are not impaired.

[0062] The amount of the above-mentioned volatile organic solvent is not particularly limited, but is preferably 100 parts by mass or less, and more preferably 50 parts by mass or less, relative to 100 parts by mass of the above-mentioned urethane (meth)acrylate contained in the active energy ray curable resin composition.

[0063] The monofunctional (meth)acrylate used as a reactive diluent is not particularly limited and includes, for example, 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, 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, cyclihexyl (meth)acrylate, other alkyl (meth)acrylates, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. Among these, n-octyl (meth)acrylate, isobornyl (meth)acrylate, and octyl / decyl (meth)acrylate are preferred, with n-octyl (meth)acrylate being particularly preferred. Monofunctional (meth)acrylates may be used alone or in combination of two or more types. Note that monofunctional (meth)acrylates do not contain component (C).

[0064] The amount of the monofunctional (meth)acrylate blended is not particularly limited, but is preferably 0 to 100 parts by mass, and more preferably 0 to 20 parts by mass, relative to 100 parts by mass of the urethane (meth)acrylate contained in the active energy ray curable resin composition.

[0065] Examples of additives include fillers, dyes and pigments, leveling agents, ultraviolet absorbers, light stabilizers, defoamers, dispersants, and thixotropy-imparting agents. The amount of these additives is not particularly limited, but is preferably, for example, 0 to 10 parts by mass, and more preferably 0.05 to 6 parts by mass, per 100 parts by mass of the total resin content of the active energy ray curable resin composition.

[0066] (Method for producing an active energy ray-curable resin composition) The active energy ray curable resin composition according to the third embodiment can be produced by mixing the urethane (meth)acrylate according to the first embodiment with a photopolymerization initiator and, if necessary, a reactive diluent, a volatile organic solvent, an additive, etc. Known or conventional means of mixing can be used, such as various mixers including dissolvers and homogenizers, kneaders, rolls, bead mills, and self-rotating agitators. The conditions during mixing, such as temperature and rotation speed, are not particularly limited and can be set as appropriate.

[0067] The active energy ray curable resin composition according to the third embodiment has excellent transparency, resilience, and heat resistance, and yields a low-hardness coating film (cured product), making it suitable for interlayer filling. In one embodiment, the active energy ray curable resin composition according to the third embodiment can be suitably used as an adhesive for interlayer filling.

[0068] [Cured product] A fourth embodiment of this disclosure relates to a cured product of an active energy ray curable resin composition according to a third embodiment. The cured product according to the fourth embodiment has excellent transparency, resilience, and heat resistance, and is low hardness. A cured product can be obtained by curing the active energy ray curable resin composition according to the third embodiment by irradiation with active energy rays. In one embodiment, the form of the cured product according to the fourth embodiment is preferably a sheet (film-like or sheet-like shape, cured coating).

[0069] The cured product according to the fourth embodiment can be obtained as a cured coating film by, for example, applying the active energy ray curable resin composition according to the third embodiment to an object such as a substrate, and then curing it by irradiating it with active energy rays such as ultraviolet light or electron beams. Known or conventional methods can be used for application, such as coating methods and casting methods. Examples of light sources used for ultraviolet irradiation include high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, xenon lamps, and metal halide lamps. The irradiation time for ultraviolet light varies depending on the type of light source, the distance between the light source and the coated surface, and other conditions, but is at most several tens of seconds, and usually only a few seconds. After ultraviolet irradiation, further heat curing may be performed as needed. When performing electron beam irradiation, it is preferable to use an electron beam with an energy in the range of 50 to 1000 keV, for example, and to irradiate with an irradiation dose of 2 to 5 Mrad. Typically, an irradiation source with a lamp output of about 80 to 300 W / cm is used. Furthermore, the thickness of the cured coating film is typically around 10 to 1000 μm, preferably around 30 to 500 μm.

[0070] Examples of objects to which the active energy ray-curable resin composition according to the third embodiment is applied (objects to be coated) include plastic articles such as polyethylene terephthalate (PET), polycarbonate, polymethacrylate, and polyvinyl chloride resin; articles on which metal vapor deposition has been applied to the plastic surface; and various articles such as glass, wood, metal plates, and paper. The coated surface may be treated with a release agent. The shape of the object (object to be coated) is not particularly limited, but it is preferably in the form of a sheet (flat).

[0071] In one embodiment, the coating hardness of the cured product according to the fourth embodiment, as measured using a Type A hardness tester in accordance with JIS K6253, is preferably A50 or less, more preferably A40 or less, and even more preferably A30 or less. Since the cured product according to the fourth embodiment is a cured product containing urethane (meth)acrylate according to the first embodiment, it has excellent heat resistance even with low coating hardness.

[0072] The cured product according to the fourth embodiment has excellent transparency, resilience, and heat resistance, and low hardness, making it particularly suitable for use as a substrate in the electronics field, an optical substrate such as an optical component or display substrate, or a substrate for adhesive sheets. Furthermore, the active energy ray curable resin composition according to the third embodiment can also be used, for example, to form a cured coating film on the surface of an article, specifically as a coating agent (for coating applications), a paint (for paint applications), or an adhesive (for adhesive applications).

[0073] [Laminated structure] A fifth embodiment of the present disclosure relates to a laminate comprising a layer of cured material according to the fourth embodiment between a first transparent substrate selected from glass and plastic substrates and a second transparent substrate selected from glass and plastic substrates.

[0074] <Transparent base material> In the laminate according to the fifth embodiment, the first and second transparent substrates are selected from glass or plastic substrates. Existing transparent materials can be used as the plastic substrates, and are not particularly limited, but examples 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; and polycarbonate resins.

[0075] (Method for coating, injecting, and curing onto a transparent substrate) When applying the active energy ray-curable resin composition according to the third embodiment to a transparent substrate, the application method is not particularly limited, and methods such as spraying, airless spraying, air spraying, roll coating, bar coating, and gravure printing can be used. Among these, the roll coating method is most preferred from the viewpoint of aesthetics, cost, and workability. The application may be carried out in the manufacturing process of the plastic substrate, etc., using the so-called in-line coating method, or it may be carried out in a separate process on an already manufactured transparent substrate, using the so-called offline coating method. From the viewpoint of production efficiency, the offline coating method is preferred. Furthermore, when injecting, it is desirable to use a cartridge to prevent the generation of air bubbles. In the laminate according to the fifth embodiment, the thickness of the cured layer is preferably 30 to 1000 μm, and more preferably 50 to 400 μm. When the thickness of the cured layer is within the above range, the uniformity of the film thickness is easily improved, and the cured layer tends to have suitable flexibility.

[0076] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of this disclosure are disclosed below. [1] A urethane (meth)acrylate having a structure derived from a linear polypropylene glycol of the following formula (I), and containing a urethane bond and a (meth)acryloyl group. [ka] (In equation (I), n1 represents a number between 10 and 100.) [2] The urethane (meth)acrylate according to [1], wherein the (meth)acryloyl group concentration is 2600 g / mol or more. [3] The urethane (meth)acrylate according to [1] or [2], wherein the (meth)acryloyl group concentration is 3200 g / mol or more and 6000 g / mol or less. A method for producing urethane (meth)acrylate according to any one of [4], [1] to [3], A method for producing urethane (meth)acrylate, comprising urethane-forming a raw material containing a polyol (A) having a linear polypropylene glycol skeleton of formula (II) below, a polyisocyanate (B), and a hydroxyl group-containing (meth)acrylate (C). [ka] (In equation (II), n1 represents a number between 10 and 100.) [5] The method for producing urethane (meth)acrylate according to [4], wherein the ratio of polyol (a1) to the total mass of polyol (A) is 70 to 100% by mass. [6] A method for producing urethane (meth)acrylate according to [4] or [5], wherein the polyol (a1) has the structure of the following formula (IIA). [ka] (In formula (IIA), X1 is a hydroxyl group or HO-(AO1) n2 -* represents hydrogen, or *-(AO2) n3 -H represents H, AO1 and AO2 represent alkylene oxides which may have substituents with 1 to 5 carbon atoms, n1 represents a number from 10 to 100, n2 and n3 represent a number from 1 to 100, and * represents a bond to the linear polypropylene glycol skeleton. [7] A method for producing urethane (meth)acrylate according to any one of [4] to [6], wherein the weight-average molecular weight (Mw) of the polyol (a1) is 500 or more and 5000 or less. [8] A method for producing urethane (meth)acrylate according to any one of [4] to [7], wherein the raw material further comprises an alcohol (D) having at least one hydroxyl group. [9] A method for producing urethane (meth)acrylate according to [4] to [8], wherein the biomass content of the polyol (A) is 30% or more. An active energy ray curable resin composition comprising a urethane (meth)acrylate described in any of [1] to [3] and a photopolymerization initiator.

[11] The active energy ray curable resin composition described in

[10] for interlayer filling. A cured product of the active energy ray curable resin composition described in

[12]

[10] or

[11] .

[13] The cured product described in

[12] , wherein the coating hardness is A50 or less.

[14] A laminate comprising a layer of the cured material described in

[12] or

[13] between a first transparent substrate selected from glass or plastic substrates and a second transparent substrate selected from glass or plastic substrates. Each configuration and its combination in each embodiment is an example, and additions, omissions, substitutions, and other modifications can be made as appropriate without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments. [Examples]

[0077] The present disclosure will be further illustrated by the following examples, but these examples will not limit the interpretation of the present disclosure.

[0078] The following describes examples of urethane (meth)acrylate synthesis, comparative synthesis, methods for measuring weight-average molecular weight, viscosity, and Hazen color number. Unless otherwise specified, the concentration expressed as "ppm" or "mass%" refers to the concentration relative to the entire urethane (meth)acrylate obtained.

[0079] The polyol (A), polyisocyanate (B), hydroxyl group-containing (meth)acrylate (C), and alcohol (D) having at least one hydroxyl group used in the synthesis example and comparative synthesis example are as follows:

[0080] <Polyol (A)> (Polyol (a1)) H2000: Linear polypropylene glycol, manufactured by SK Chemicals, "ECOTRION H2000" (having the structure of formula (IIA), with X1 being a hydroxyl group and X2 being a hydrogen atom, Mw: 2009, hydroxyl value: 55.85 mg KOH / g). (Any polyol) PA2000: Polypropylene glycol, manufactured by Sanyo Chemical Industries, Ltd., "Sannix (registered trademark) PA2000" (Mw: 1975, hydroxyl value: 56.8 mg KOH / g, ratio of primary hydroxyl groups at terminal hydroxyl groups is 20 mol% or more (excluding ethylene oxide adducts of polypropylene glycol)). • PP2000: Polypropylene glycol, manufactured by Sanyo Chemical Industries, Ltd., "Sannix PP2000" (Mw: 2029, hydroxyl value: 55.3 mgKOH / g). • PP4000: Polypropylene glycol, manufactured by Sanyo Chemical Industries, Ltd., "Sannix PP4000" (Mw: 4156, hydroxyl value: 27.0 mgKOH / g). • PTMG1000: Polytetramethylene ether glycol, manufactured by Mitsubishi Chemical Corporation, "PTMG1000" (Mw: 1012, hydroxyl value: 110.8 mgKOH / g).

[0081] <Polyisocyanate (B)> IPDI: Isophorone diisocyanate, manufactured by Evonik Corporation, "VESTANAT® IPDI" (Mw:222). • HDI: Hexamethylene diisocyanate, manufactured by Tosoh Corporation, "HDI" (Mw: 168). • TMHDI: 2,2,4-trimethylhexamethylene diisocyanate, manufactured by Evonik Corporation, "TMDI" (Mw:210). • Hydrogenated MDI: Methylenebis(4-cyclohexyl isocyanate), manufactured by Evonik Corporation, "DESMODUR® W" (Mw:262).

[0082] <Hydroxyl group-containing (meth)acrylate (C)> • HEA: 2-hydroxyethyl acrylate (molecular weight: 116), manufactured by Nippon Shokubai Co., Ltd.

[0083] <Alcohols (D) having at least one hydroxyl group> • 2-EH: 2-ethylhexyl alcohol (molecular weight: 130), manufactured by Sankyo Chemical Co., Ltd.

[0084] In each synthesis example and comparative synthesis example, the (meth)acryloyl group concentration and the measured isocyanate group concentration were calculated using the following formula. (Measurement of (meth)acryloyl group concentration) (Meth)acryloyl group concentration (g / mol) = [(Total amount (g) excluding non-reactive components such as diluent monomers, diluent solvents, and catalysts) × (Molecular weight of hydroxyl group-containing (meth)acrylate (C))] ÷ (Weight (g) of hydroxyl group-containing (meth)acrylate (C)) Note that the total amount (g) refers to the weight (g) of the urethane (meth)acrylate produced.

[0085] The method for measuring the actual isocyanate group concentration and the method for calculating the theoretical endpoint isocyanate group concentration are as follows. (Measurement of actual isocyanate group concentration) The isocyanate group concentration was measured as follows. The measurement was performed in a 100 mL glass flask under stirring with a stirrer. • Measurement of blank values 15 mL of dibutylamine THF solution (0.1 N) was added to 15 mL of THF, and then 3 drops of bromophenol blue (1% methanol diluted solution) were added to color the solution blue. The solution was then titrated with HCl aqueous solution of normality 0.1 N. The volume of HCl aqueous solution titrated at the point when the color change was observed was defined as Vb (mL). • Measurement of actual isocyanate group concentration The sample was weighed in grams (Ws) and dissolved in 15 mL of THF. 15 mL of dibutylamine THF solution (0.1 N) was then added. After confirming that the solution was dissolved, 3 drops of bromophenol blue (1% methanol dilution) were added to color the solution blue. The solution was then titrated with HCl aqueous solution of 0.1 N normality. The volume of HCl aqueous solution titrated at the point of color change was defined as Vs (mL). The measured isocyanate group concentration was calculated using the following formula. Measured isocyanate group concentration (mass%) = (Vb - Vs) × 1.005 × 0.42 ÷ Ws (Method for calculating the theoretical endpoint isocyanate group concentration) Theoretical endpoint isocyanate group concentration = 42 × 2 × 100 ÷ (Mw × moles of polyol (A) + Mw × moles of polyisocyanate (B))

[0086] (Synthesis of urethane (meth)acrylate according to the first embodiment) <Synthesis Example 1> H2000, IPDI, HEA, and 2-EH were reacted in a molar ratio of 1.000:1.457:0.462:0.451. The actual amounts used and the reaction conditions are described below. The concentration of (meth)acryloyl groups in the urethane (meth)acrylate was 5273 g / mol.

[0087] A separable flask equipped with a thermometer and a stirrer was filled with H2000 (369.8 g, 0.184 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and after homogenizing the system, IPDI (59.4 g, 0.268 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. The completion of the reaction was confirmed when the measured isocyanate group concentration in the reaction solution became less than or equal to the residual isocyanate group concentration when all the hydroxyl groups used in the reaction have been urethane-converted (hereinafter referred to as the "theoretical endpoint isocyanate group concentration"). In Synthesis Example 1, the completion of the reaction was confirmed by the fact that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (1.64% by mass). The next step was then carried out. After confirming the completion of the reaction, 2-EH (10.9 g, 0.083 mol) was added, followed by HEA (9.9 g, 0.085 mol). After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Synthesis Example 1. The urethane (meth)acrylate of Synthesis Example 1 contains polyol (a1) as a raw material, and therefore contains a structure derived from the linear PPG of formula (I), a urethane bond, and a (meth)acryloyl group. The same applies to Synthesis Examples 2 to 4.

[0088] <Synthesis Example 2> H2000, HDI, HEA, and 2-EH were reacted in a molar ratio of 1.000:1.458:0.463:0.453. The actual amounts used and the reaction conditions are described below. The (meth)acryloyl group concentration of the urethane (meth)acrylate was formulated at 5104 g / mol. A separable flask equipped with a thermometer and a stirrer was packed with H2000 (382.1 g, 0.190 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and after homogenizing the system, HDI (46.5 g, 0.277 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. To confirm that the reaction was complete, the theoretical endpoint isocyanate group concentration was calculated as in Synthesis Example 1. In Synthesis Example 2, after confirming that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (1.69 mass%), the next step was taken. After confirming the completion of the reaction, 2-EH (11.2 g, 0.086 mol) was added, followed by HEA (10.2 g, 0.088 mol). After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Synthesis Example 2.

[0089] <Synthesis Example 3> H2000, TMHDI, HEA, and 2-EH were reacted in a molar ratio of 1.000:1.459:0.459:0.454. The actual amounts used and reaction conditions are described below. The (meth)acryloyl group concentration of the urethane (meth)acrylate was formulated at 5235 g / mol. A separable flask equipped with a thermometer and a stirrer was packed with H2000 (372.4 g, 0.185 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C and the system was homogenized, after which TMHDI (56.6 g, 0.270 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. To confirm that the reaction was complete, the theoretical endpoint isocyanate group concentration was calculated as in Synthesis Example 1. In Synthesis Example 3, after confirming that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (1.65 mass%), the next step was taken. After confirming the completion of the reaction, 2-EH (10.9 g, 0.084 mol) was added, followed by HEA (9.9 g, 0.085 mol). After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Synthesis Example 3.

[0090] <Synthesis Example 4> H2000, hydrogenated MDI, HEA, and 2-EH were reacted in a molar ratio of 1.000:1.450:0.467:0.456. The actual amounts used and reaction conditions are described below. The (meth)acryloyl group concentration of the urethane (meth)acrylate was formulated at 5399 g / mol. A separable flask equipped with a thermometer and a stirrer was packed with H2000 (361.2 g, 0.180 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and after homogenizing the system, hydrogenated MDI (68.5 g, 0.261 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. To confirm that the reaction was complete, the theoretical endpoint isocyanate group concentration was calculated as in Synthesis Example 1. In Synthesis Example 4, after confirming that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (1.60 mass%), the next step was taken. After confirming the completion of the reaction, 2-EH (10.6 g, 0.082 mol) was added, followed by HEA (9.7 g, 0.084 mol). After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Synthesis Example 4.

[0091] <Comparative Synthesis Example 1> PA2000, IPDI, and HEA were reacted in a molar ratio of 1.000:1.447:0.915. The actual amounts used and the reaction conditions are described below. The (meth)acryloyl group concentration of the urethane (meth)acrylate was formulated at 2619 g / mol. A separable flask equipped with a thermometer and a stirrer was packed with PA2000 (369.6 g, 0.188 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and after homogenizing the system, IPDI (60.4 g, 0.272 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. To confirm that the reaction was complete, the theoretical endpoint isocyanate group concentration was calculated as in Synthesis Example 1. In Comparative Synthesis Example 1, after confirming that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (1.66 mass%), the next step was taken. After confirming the completion of the reaction, HEA (19.9 g, 0.172 mol) was added. After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Comparative Synthesis Example 1. The urethane (meth)acrylate of Comparative Synthesis Example 1 does not have a structure derived from the linear PPG of formula (I) because it contains a polyol without a linear PPG skeleton as a raw material. The same applies to Comparative Synthesis Examples 2 to 7.

[0092] <Comparative Synthesis Example 2> PA2000, IPDI, HEA, and 2-EH were reacted in a molar ratio of 1.000:1.455:0.829:0.091. The actual amounts used and reaction conditions are described below. The (meth)acryloyl group concentration of the urethane (meth)acrylate was formulated at 2908 g / mol. A separable flask equipped with a thermometer and a stirrer was packed with PA2000 (369.4 g, 0.187 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and after homogenizing the system, IPDI (60.4 g, 0.272 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. To confirm that the reaction was complete, the theoretical endpoint isocyanate group concentration was calculated as in Synthesis Example 1. In Comparative Synthesis Example 2, after confirming that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (1.66 mass%), the next step was taken. After confirming the completion of the reaction, 2-EH (2.2 g, 0.017 mol) was added, followed by HEA (18.0 g, 0.155 mol). After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Comparative Synthesis Example 2.

[0093] <Comparative Synthesis Example 3> PA2000, IPDI, HEA, and 2-EH were reacted in a molar ratio of 1.000:1.455:0.551:0.364. The actual amounts charged and reaction conditions are described below. The (meth)acryloyl group concentration of the urethane (meth)acrylate was formulated at 4345 g / mol. A separable flask equipped with a thermometer and a stirrer was packed with PA2000 (368.9 g, 0.187 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and after homogenizing the system, IPDI (60.3 g, 0.272 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. To confirm that the reaction was complete, the theoretical endpoint isocyanate group concentration was calculated as in Synthesis Example 1. In Comparative Synthesis Example 3, after confirming that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (1.66 mass%), the next step was taken. After confirming the completion of the reaction, 2-EH (8.8 g, 0.068 mol) was added, followed by HEA (12.0 g, 0.103 mol). After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Comparative Synthesis Example 3.

[0094] <Comparative Synthesis Example 4> PA2000, IPDI, and HEA were reacted in a molar ratio of 1.000:1.219:0.449. The actual amounts used and the reaction conditions are described below. The (meth)acryloyl group concentration of the urethane (meth)acrylate was formulated at 5120 g / mol. A separable flask equipped with a thermometer and a stirrer was packed with PA2000 (386.7 g, 0.196 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and after homogenizing the system, IPDI (53.1 g, 0.239 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. To confirm that the reaction was complete, the theoretical endpoint isocyanate group concentration was calculated as in Synthesis Example 1. In Comparative Synthesis Example 4, after confirming that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (0.83 mass%), the next step was taken. After confirming the completion of the reaction, HEA (10.2 g, 0.088 mol) was added. After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Comparative Synthesis Example 4.

[0095] <Comparative Synthesis Example 5> PP2000, IPDI, and HEA were reacted in a molar ratio of 1.000:1.253:0.505. The actual amounts used and reaction conditions are described below. The oligomer was formulated with a (meth)acryloyl group concentration of 4683 g / mol. A separable flask equipped with a thermometer and a stirrer was packed with PP2000 (386.1 g, 0.190 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and after homogenizing the system, IPDI (52.8 g, 0.238 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. To confirm that the reaction was complete, the theoretical endpoint isocyanate group concentration was calculated as in Synthesis Example 1. In Comparative Synthesis Example 5, after confirming that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (0.91 mass%), the next step was taken. After confirming the completion of the reaction, HEA (11.1 g, 0.096 mol) was added. After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Comparative Synthesis Example 5.

[0096] <Comparative Synthesis Example 6> PP4000, IPDI, and HEA were reacted in a molar ratio of 1.000:1.333:0.677. The actual amounts used and reaction conditions are described below. The oligomer was formulated with a (meth)acryloyl group concentration of 6728 g / mol. A separable flask equipped with a thermometer and a stirrer was packed with PP4000 (412.8 g, 0.099 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and after homogenizing the system, IPDI (29.4 g, 0.132 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. To confirm that the reaction was complete, the theoretical endpoint isocyanate group concentration was calculated as in Synthesis Example 1. In Comparative Synthesis Example 6, after confirming that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (0.63 mass%), the next step was taken. After confirming the completion of the reaction, HEA (7.8 g, 0.067 mol) was added. After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Comparative Synthesis Example 6.

[0097] <Comparative Synthesis Example 7> PTMG1000, IPDI, and HEA were reacted in a molar ratio of 1.000:1.500:1.010. The actual amounts used and reaction conditions are described below. The oligomer was formulated with a (meth)acryloyl group concentration of 1448 g / mol. A separable flask equipped with a thermometer and a stirrer was packed with PTMG1000 (311.5 g, 0.308 mol) and 800 ppm dibutylhydroxytoluene (BHT). The internal temperature was raised to 50°C, and after homogenizing the system, IPDI (102.5 g, 0.462 mol) was added. Subsequently, 100 ppm dibutyltin dilaurate (DBTDL) was added, and the internal temperature was set to 70°C. To confirm that the reaction was complete, the theoretical endpoint isocyanate group concentration was calculated as in Synthesis Example 1. In Comparative Synthesis Example 7, after confirming that the measured isocyanate group concentration was less than or equal to the theoretical endpoint isocyanate group concentration (3.12 mass%), the next step was taken. After confirming the completion of the reaction, HEA (36.1 g, 0.311 mol) was added. After aging for 2 hours, the reaction was terminated after confirming that the isocyanate group concentration was less than 0.05%, yielding the urethane (meth)acrylate of Comparative Synthesis Example 7.

[0098] (Measurement of weight-average molecular weight) The weight-average molecular weight of each urethane (meth)acrylate was determined by GPC (gel permeation gas chromatography) under the following measurement conditions, with standard polystyrene as the reference. Equipment used: TOSOH HLC-8220GPC Pump: DP-8020 Detector: RI-8020 Column types: Super HZM-M, Super HZ4000, Super HZ3000, Super HZ2000 Solvent: Tetrahydrofuran Phase flow rate: 1mL / min Column pressure: 5.0 MPa Column temperature: 40℃ Sample injection volume: 10 μL Sample concentration: 0.2 mg / mL

[0099] (Viscosity measurement) The viscosity of each urethane (meth)acrylate was measured using an E-type viscometer (TV-25 model, manufactured by Toki Sangyo Co., Ltd.) at a temperature of 60°C.

[0100] (Measurement of Hazen unit color count) In accordance with JIS K 0071-1, the number of Hazen unit colors was measured as follows. Each urethane (meth)acrylate used for color determination was prepared as a uniform 6% solution by weight using a mixed solvent of methylene chloride / methanol = 9 / 1 (volume ratio), and the color of this solution was compared with a standard colorimetric solution. The results are shown in Table 1.

[0101] [Table 1]

[0102] <Examples 1-4 and Comparative Examples 1-11> For each synthesis example and comparative synthesis example, urethane (meth)acrylates were obtained, and active energy ray-curable resin compositions were prepared under the following conditions. The obtained active energy ray-curable resin compositions were evaluated for transparency, recovery, coating hardness, and heat resistance under the conditions shown below. The results are shown in Tables 2 and 3.

[0103] (Preparation of active energy ray-curable resin composition) Using a 30 mL brown bottle, each active energy ray curable resin composition was prepared by blending 100 parts by mass of each urethane (meth)acrylate with 42 parts by mass of ethyl acetate (manufactured by Daicel Corporation, "AE") as a volatile organic solvent, the amount of alkylphenone-based photopolymerization initiator (manufactured by IGM, "Omnirad 184") shown in Tables 2 and 3 as a photopolymerization initiator, and the type and amount of monofunctional (meth)acrylate shown in Tables 2 and 3, so that the total volume was approximately 20 g.

[0104] (Transparency assessment) A rectangular frame (internal dimensions: 1 mm (thickness) x 40 mm x 10 mm) was created on a microglass (dimensions: 1 mm (thickness) x 76 mm x 26 mm) using silicone rubber, and 1.0 g of each active energy ray-curable resin composition was dropped into the frame. After heating to 70°C until the surface was smooth, the surface was irradiated with ultraviolet light under the following conditions to cure each active energy ray-curable resin composition, and the test specimens shown in Figure 2 were prepared. (Ultraviolet irradiation conditions) Irradiation intensity: 120W / cm Irradiation distance: 10cm Conveyor speed: 5m / min Number of treatments: 2 Using a spectrophotometer (Shimadzu Corporation, "UV-VISIBLE SPECTROPHOTO METER"), the transmittance of each test specimen was measured relative to the transmittance of only the reference microglass specimen, and evaluated according to the following criteria. • Evaluation 1: The transmittance at 400nm was 95% or higher. • Evaluation 2: The transmittance at 400nm was less than 95%. In other words, a rating of 1 means that a coating with higher transparency was obtained than a rating of 2.

[0105] (Evaluation of resilience and coating hardness) (Preparation of test specimens) A square frame (internal dimensions: 7mm x 40mm x 40mm) was created on a glass plate using silicone rubber, and each active energy ray-curable resin composition was dropped into the frame until it filled the void. To suppress the generation of air bubbles, each active energy ray-curable resin composition was preheated and slowly dropped. If air bubbles were visually observed, the mixture was stored in an 80°C oven until the bubbles disappeared. After heating each active energy ray-curable resin composition to 80°C and smoothing the surface, it was cured by ultraviolet irradiation under the following conditions. Irradiation intensity: 120W / cm Irradiation distance: 10cm Conveyor speed: 3.5 m / min Number of treatments: 5

[0106] After curing, the cured resin was removed from the silicone rubber, turned inside out, and exposed to ultraviolet light under the same conditions as above to prepare a test specimen with a thickness of approximately 7 mm. For each test specimen, an automatic constant-pressure load tester (Teclock Co., Ltd., "GS-610") was used, and in accordance with JIS K6253, a Type A hardness tester was used to apply a load of 500g at a load descent rate of 9mm / s. The coating hardness (A hardness) of each test specimen was measured and evaluated according to the following criteria. • Evaluation 1: The coating hardness was A50 or lower. • Evaluation 2: The coating hardness was above A50. In other words, evaluation 1 means that a coating with lower hardness was obtained than evaluation 2.

[0107] Regarding recovery, after unloading, the marks left by the indenter were visually observed and evaluated according to the following criteria. • Rating 1: No damage such as cracks was found. Indentations that recovered within 24 hours of unloading were not considered damage such as cracks and were therefore rated "1". • Rating 2: Damage such as cracks was observed. In other words, a rating of 1 meant that the recovery was superior to a rating of 2.

[0108] (Evaluation of heat resistance) (Preparation of test specimens (glass laminates) for heat resistance evaluation) The glass laminate for heat resistance evaluation shown in Figure 3 was prepared as follows. First, 0.50 g (±0.01 g) of each active energy ray-curable resin composition was accurately weighed and placed in the center of a glass plate (1 mm thick, 5 cm square). A glass substrate of the same shape was then placed on top, and the resin layer was spread in a circular shape (4 cm in diameter) to obtain the glass laminate for heat resistance evaluation. Subsequently, ultraviolet irradiation was performed from one glass surface of the glass laminate using a high-pressure mercury lamp (manufactured by I-Graphics Co., Ltd.) under the following conditions to obtain the glass laminate for heat resistance evaluation. (Ultraviolet irradiation conditions) Irradiation intensity: 120W / cm Irradiation distance: 10cm Conveyor speed: 5m / min Number of treatments: 8 (4 on each side) (Storage under heat-resistant conditions) Using a small environmental testing chamber (ESPEC Corporation, "SH-641"), the test specimens were stored for 1000 hours at a temperature of 95°C. (Measurement of shape) After storage under heat-resistant conditions, the samples were visually inspected and evaluated according to the following criteria. • Rating 1: There was no change in shape. • Evaluation 2: Some kind of shape change was observed, such as the formation of wrinkles or displacement of the glass plate. In other words, a rating of 1 meant that the heat resistance was superior to that of a rating of 2. The results of each of the above evaluations are shown in Tables 2 and 3.

[0109] [Table 2]

[0110] [Table 3]

[0111] As shown in Tables 2 and 3, the active energy ray curable resin compositions using urethane (meth)acrylate in the examples all received a rating of "1" for transparency, recovery, coating hardness, and heat resistance. In other words, the active energy ray curable resin compositions using urethane (meth)acrylate in the examples exhibited excellent transparency, recovery, and heat resistance, and produced a low-hardness coating (cured product). On the other hand, the active energy ray curable resin compositions using urethane (meth)acrylate in the comparative examples received a rating of "2" for at least one of the following: transparency, recovery, coating hardness, and heat resistance, and did not possess all the desirable properties. As described above, it has been confirmed that the urethane (meth)acrylate according to the first embodiment provides an active energy ray curable resin composition that has excellent transparency, resilience, and heat resistance, and yields a low-hardness coating film (cured product). A laminate having a cured product layer of the active energy ray curable resin composition according to the third embodiment between transparent substrates selected from glass or plastic substrates has properties suitable for use as a display substrate. [Industrial applicability]

[0112] The urethane (meth)acrylate according to the first embodiment provides an active energy ray curable resin composition that exhibits excellent transparency, resilience, and heat resistance, and yields a low-hardness coating film (cured product). Therefore, it can be suitably used as an interlayer filler for display substrates and has industrial applicability. [Explanation of Symbols]

[0113] 1. Laminate 2 Transparent base material 3. Layer of the cured product of the active energy ray curable resin composition 4 Test specimens 5 Microglass 6th slot 7. Cured product of an active energy ray curable resin composition 8 Glass plate

Claims

1. A urethane (meth)acrylate having a structure derived from the linear polypropylene glycol of the following formula (I), and containing a urethane bond and a (meth)acryloyl group. 【Chemistry 1】 (In equation (I), n1 represents a number between 10 and 100.)

2. The urethane (meth)acrylate according to claim 1, wherein the (meth)acryloyl group concentration is 2200 g / mol or more.

3. The urethane (meth)acrylate according to claim 1 or 2, wherein the (meth)acryloyl group concentration is 3200 g / mol or more and 6000 g / mol or less.

4. A method for producing urethane (meth)acrylate according to claim 1 or 2, A method for producing urethane (meth)acrylate, comprising urethaneizing a raw material containing a polyol (A) having a linear polypropylene glycol skeleton of formula (II) below, a polyisocyanate (B), and a hydroxyl group-containing (meth)acrylate (C). 【Chemistry 2】 (In equation (II), n1 represents a number between 10 and 100.)

5. The method for producing urethane (meth)acrylate according to claim 4, wherein the ratio of polyol (a1) to the total mass of polyol (A) is 70 to 100% by mass.

6. The method for producing urethane (meth)acrylate according to claim 4, wherein the polyol (a1) has the structure of the following formula (IIA). 【Transformation 3】 (In formula (IIA), X １ is a hydroxyl group, or HO-(AO １ ) ｎ２ - represents *, X ２ is hydrogen, or *-(AO ２ ) ｎ３ -H represents AO １ , AO ２ (wherein represents an alkylene oxide which may have substituents having 1 to 5 carbon atoms, n1 represents a number from 10 to 100, n2 and n3 represent a number from 1 to 100, and * represents a bond to the linear polypropylene glycol skeleton.)

7. The method for producing urethane (meth)acrylate according to claim 4, wherein the weight-average molecular weight (Mw) of the polyol (a1) is 500 or more and 5000 or less.

8. The method for producing urethane (meth)acrylate according to claim 4, wherein the raw material further comprises an alcohol (D) having at least one hydroxyl group.

9. The method for producing urethane (meth)acrylate according to claim 4, wherein the biomass content of the polyol (A) is 30% or more.

10. An active energy ray curable resin composition comprising a urethane (meth)acrylate according to claim 1 or 2 and a photopolymerization initiator.

11. The active energy ray curable resin composition according to claim 10, for interlayer filling.

12. A cured product of the active energy ray curable resin composition according to claim 10.

13. The cured product according to claim 12, wherein the coating hardness is A50 or less.

14. A laminate comprising a layer of the cured material according to claim 12 between a first transparent substrate selected from glass or a plastic substrate and a second transparent substrate selected from glass or a plastic substrate.

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