Urethane (METH) acrylate, method for producing same, curable composition, and cured coating film

Abstract

Provided is a urethane (meth) acrylate with which it is possible to form a cured coating film having high hardness, less susceptible to warping of a thin film, and more excellent repeated bending resistance. A urethane (meth) acrylate which is represented by formula (1) and which has a weight average molecular weight of 8000 to 100000. R1-[OC (= O) NH-R2] n (1) (In formula (1), R1 is an n-valent residue obtained by removing a hydroxyl group from a polyether polyol having n hydroxyl groups in one molecule, n R2 are each independently a residue obtained by removing an isocyanate group from a monoisocyanate having a (meth) acryloyloxy group, and n is 22-60. ).

Description

Technical Field

[0001] The present invention relates to a urethane (meth) acrylate suitable for a coating agent, a method for producing the same, a curable composition containing the urethane (meth) acrylate, and a cured coating film. Background Art

[0002] Regarding urethane (meth) acrylate, by using it as a monomer, functional polymers excellent in various properties such as flexibility, toughness, impact resistance, and adhesiveness can be obtained, and thus it is a highly versatile compound as a monomer. As an example of its use, utilization as a coating agent component for surface protection for preventing scratches, cracks, etc. on displays, touch panels, etc. of image display devices can be cited. Furthermore, research has also been conducted on application to coating agent components for surface protection of flexible displays, foldable devices, etc.

[0003] For example, Patent Document 1 describes that a flexible plastic film having an ultraviolet-curable coating layer containing a crosslinked polymer of a 7- to 20-functional urethane acrylate-based binder and a 3- to 6-functional acrylate-based binder has high hardness and excellent flexibility and bending durability.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-530631 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] The urethane acrylate-based binder described in Patent Document 1 is a polyfunctional urethane acrylate-based binder having 7 to 20 acryloyloxy groups in one molecule. However, although such a polyfunctional urethane acrylate-based binder can form a cured coating film (coating layer) having high hardness, there are the following problems: the film having the cured coating film formed thereon is likely to warp, and in addition, the cured coating film is likely to peel off from the film substrate due to repeated bending and stretching.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide a urethane (meth) acrylate capable of forming a cured coating film having high hardness, not easily causing warping of the film, and having more excellent resistance to repeated bending.

[0010] Means for Solving the Problems

[0011] The present invention is based on the following findings: a cured coating film obtained using a specified polyfunctional urethane (meth)acrylate has high hardness, a film formed with the cured coating film is less likely to warp, and has excellent resistance to repeated bending.

[0012] The present invention provides the following solutions.

[0013] [1] A urethane (meth)acrylate represented by the following formula (1) and having a weight average molecular weight of 8000 to 100,000,

[0014] R 1 -[OC(=O)NH-R 2 n (1)

[0015] In formula (1), R 1 is an n-valent residue obtained by removing hydroxyl groups from a polyether polyol having n hydroxyl groups in one molecule, and n Rs 2 are each independently a residue obtained by removing an isocyanate group from a mono isocyanate having a (meth)acryloyloxy group, and n is 22 to 60.

[0016] [2] The urethane (meth)acrylate according to [1], wherein the polyether polyol is a polymer obtained by adding an alkylene oxide to polyglycerol, and the alkylene oxide has 2 to 4 carbon atoms.

[0017] [3] The urethane (meth)acrylate according to [2], wherein, in a total of 100 mol% of the alkylene oxide, propylene oxide is 50 mol% or more.

[0018] [4] A method for producing a urethane (meth)acrylate, which is a method for producing the urethane (meth)acrylate according to any one of [1] to [3], wherein a urethanization reaction is carried out between the polyether polyol and the mono isocyanate having a (meth)acryloyloxy group, and the polyether polyol is obtained by subjecting polyglycerol having 22 to 60 hydroxyl groups in one molecule as an initiator to addition polymerization of 100 to 500 mol of an alkylene oxide having 2 to 4 carbon atoms in the presence of a catalyst.

[0019] [5] The method for producing a urethane (meth)acrylate according to [4], wherein, in a total of 100 mol% of the alkylene oxide, propylene oxide is 50 mol% or more.

[0020] [6] A curable composition containing the urethane (meth)acrylate according to any one of [1] to [3].

[0021] ​[7] The curable composition according to [6] further contains inorganic particles.

[0022] [8] The curable composition according to [7], wherein the surface of the inorganic particles is modified with a silane coupling agent.

[0023] [9] The curable composition according to any one of [6] to [8] further contains a polyfunctional (meth)acrylate other than urethane (meth)acrylate.

[0024]

[10] The curable composition according to [9], wherein the polyfunctional (meth)acrylate is a compound having a multi-branched structure and having a (meth)acryloyl group at the end of each branch.

[0025]

[11] The curable composition according to any one of [6] to

[10] is a coating agent.

[0026]

[12] A cured coating film which is a cured product of the curable composition according to any one of [6] to

[11] .

[0027] Effects of the Invention

[0028] According to the present invention, a urethane (meth)acrylate capable of forming a cured coating film having high hardness, less likely to cause warping of the thin film, and excellent in repeated bending resistance can be provided.

[0029] Therefore, the urethane (meth)acrylate of the present invention is useful, for example, in applications such as coating agents for surface protection of flexible displays, foldable devices, and the like. Detailed Embodiments

[0030] Hereinafter, definitions and meanings of terms and expressions in this specification are shown.

[0031] “(Meth)acrylate” refers to a general term for acrylate and methacrylate. Similarly, “(meth)acryloyloxy” refers to a general term for acryloyloxy and methacryloyloxy, and “(meth)acrylic acid” refers to a general term for acrylic acid and methacrylic acid.

[0032] The numerical range represented by “to” means that the numerical values before and after “to” are the lower limit value and the upper limit value.

[0033] The weight average molecular weight (Mw) and the number average molecular weight (Mn) are polystyrene equivalent molecular weights determined by gel permeation chromatography (GPC) based on a standard curve prepared using a standard polystyrene sample. Specifically, they are determined according to the method described in the examples.

[0034] "Isocyanate index" is a value expressed as a percentage representing the number of moles of isocyanate groups of an isocyanate compound corresponding to each 1 mole of hydroxyl groups of a polyol.

[0035] [Urethane (meth)acrylate]

[0036] The urethane (meth)acrylate of the present invention is represented by the following formula (1) and has a weight average molecular weight of 8,000 to 100,000.

[0037] R 1 -[OC(=O)NH-R 2 n (1)

[0038] In formula (1), R 1 is an n-valent residue obtained by removing hydroxyl groups from a polyether polyol having n hydroxyl groups in one molecule, and n R 2 are each independently a residue obtained by removing isocyanate groups from a monoisocyanate having a (meth)acryloyloxy group, and n is 22 to 60.

[0039] The urethane (meth)acrylate of an embodiment of the present invention (hereinafter, referred to as this embodiment) has a skeleton derived from a polyether polyol having a higher molecular weight than before and has a urethane bond. Therefore, high hardness and good flexibility can be imparted to a cured coating film obtained by using it. Therefore, by using the urethane (meth)acrylate of the present invention, a cured coating film having high hardness, less likely to cause warping of the film, and more excellent repeated bending resistance can be formed.

[0040] (Polyether polyol)

[0041] In formula (1), R 1 is an n-valent residue obtained by removing hydroxyl groups from a polyether polyol having n hydroxyl groups in one molecule, and n is 22 to 60.

[0042] Based on such a urethane (meth)acrylate having a skeleton derived from a polyether polyol having 22 to 60 hydroxyl groups in one molecule, a crosslinked network is formed at a high density, and a cured product having high hardness can be easily obtained, and scratches are not easily generated on the surface of the cured product. In addition, when using such a urethane (meth)acrylate, even when a cured coating film is formed on a thin film substrate, warping of the thin film is not easily generated.

[0043] The number of hydroxyl groups in one molecule of the polyether polyol, that is, n is 22 to 60, preferably 22 to 54, more preferably 22 to 48, and further preferably 30 to 48.

[0044] When the polyether polyol is composed of a plurality of types, n is the average number of hydroxyl groups in one molecule calculated based on the content ratio of each polyether polyol.​

[0045] When n is 22 or more, the cured product obtained by using the urethane (meth)acrylate as described above is likely to have a high hardness, and in addition, warping of the film caused by the cured coating film is less likely to occur. From the viewpoint of practicality such as manufacturing and workability, n is 60 or less.

[0046] The polyether polyol is not particularly limited as long as it is a polyether polyol having 22 to 60 hydroxyl groups in one molecule, and a polymer obtained by adding an alkylene oxide to polyglycerol is particularly preferred and has a repeating unit derived from an alkylene oxide.

[0047] The average degree of polymerization of glycerol in the above polyglycerol is 20 to 58, and the number of hydroxyl groups in one molecule is 22 to 60. The polyglycerol may be linear, but from the viewpoint of high density of the above crosslinked network in the cured product based on the urethane (meth)acrylate, it is preferably branched, more preferably multi-branched, and particularly preferably a dendritic polymer.

[0048] Examples of commercially available products of the above polyglycerol include "PGL 20PW" (manufactured by Daicel Corporation; average degree of polymerization 20, number of hydroxyl groups in one molecule 22), "PGL X" (manufactured by Daicel Corporation; average degree of polymerization 40, number of hydroxyl groups in one molecule 42), etc.

[0049] The number of carbon atoms of the above alkylene oxide is preferably 2 to 4. Specifically, ethylene oxide, propylene oxide, and 1,4-epoxybutane (tetrahydrofuran) can be cited. The alkylene oxide may be a single type or two or more types. The alkylene oxide preferably contains propylene oxide.

[0050] From the viewpoints of high hardness and good softness of the cured product using the urethane (meth)acrylate, in 100 mol% in total of the alkylene oxide, propylene oxide is preferably 50 mol% or more, more preferably 70 to 100 mol%, further preferably 90 to 100 mol%, and still more preferably 100 mol%.

[0051] (monoisocyanate)

[0052] In formula (1), n Rs 2 are each independently a residue obtained by removing an isocyanate group from a monoisocyanate having a (meth)acryloyloxy group.

[0053] The monoisocyanate having a (meth)acryloyloxy group has 1 isocyanate group and 1 or more (meth)acryloyloxy groups in one molecule.

[0054] The monoisocyanate having a (meth)acryloyloxy group is preferably a compound in which one or more (meth)acryloyloxy groups are bonded to a hydrocarbon skeleton having an isocyanate group. The hydrocarbon skeleton is preferably an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, and may contain an etheric oxygen atom. The number of carbon atoms in the aliphatic hydrocarbon group or alicyclic hydrocarbon group is preferably 8 or less, more preferably 2 to 6, and further preferably 2 to 4.

[0055] Examples of the monoisocyanate having a (meth)acryloyloxy group include compounds having 1 (meth)acryloyloxy group in one molecule such as isocyanatomethyl (meth)acrylate, 2-isocyanatoethyl (meth)acrylate, and 1,1-bis(acryloxymethyl)ethyl isocyanate; compounds having 2 (meth)acryloyloxy groups in one molecule such as 1,1-bis((meth)acryloxymethyl)ethyl isocyanate and 1,1-bis((meth)acryloxymethyl)propyl isocyanate. As commercially available products, "KARENZ (registered trademark; the following description is omitted.) AOI" (2-isocyanatoethyl acrylate, purity ≥ 97% by mass), "KARENZ AOI-VM" (2-isocyanatoethyl acrylate, purity ≥ 96% by mass), "KARENZ MOI" (2-isocyanatoethyl methacrylate), "KARENZ BEI" (1,1-bis(acryloxymethyl)ethyl isocyanate), "KARENZ MOI-EG" (1,1-bis(acryloxymethyl)ethyl isocyanate) (all of the above are manufactured by Resonac Corporation).

[0056] (Weight-average molecular weight)

[0057] The weight-average molecular weight (Mw) of the urethane (meth)acrylate of the present embodiment is 8,000 to 100,000, preferably 8,300 or more, more preferably 8,500 or more, and preferably 80,000 or less, more preferably 40,000 or less.

[0058] When Mw is 8,000 or more, the urethane (meth)acrylate easily forms a cured coating film that is less likely to warp and has excellent resistance to repeated bending. From the practical viewpoints of manufacturing and operability, Mw is 100,000 or less.

[0059] It should be noted that from the same viewpoints, the number-average molecular weight (Mn) is preferably 4,000 to 80,000, more preferably 4,500 to 50,000, further preferably 5,000 to 20,000, and even more preferably 10,000 to 20,000.

[0060] [Manufacturing method]

[0061] The method for producing the urethane (meth)acrylate of the present embodiment is not particularly limited, and the production method of the present embodiment can be suitably used for production. In the production method of the present embodiment, a urethanization reaction is carried out between the polyether polyol and the aforementioned monoisocyanate. The polyether polyol is obtained by subjecting polyglycerol having 22 to 60 hydroxyl groups in one molecule as an initiator to addition polymerization of 100 to 500 moles of an alkylene oxide having 2 to 4 carbon atoms in the presence of a catalyst.

[0062] In the production method of the present embodiment, a polyether polyol is obtained by addition polymerizing an alkylene oxide to an initiator, and a urethanization reaction is carried out between the polyether polyol and a monoisocyanate having a (meth)acryloyloxy group to produce a urethane (meth)acrylate.

[0063] The polyglycerol of the initiator corresponds to the polyglycerol in the above-mentioned polyether polyol, and the alkylene oxide added and polymerized to the initiator corresponds to the alkylene oxide in the above-mentioned polyether polyol. In addition, the monoisocyanate also corresponds to the above-mentioned monoisocyanate having a (meth)acryloyloxy group. Therefore, the description of polyglycerol, alkylene oxide, and monoisocyanate in the production method of the present embodiment is omitted.

[0064] It should be noted that by 1 1H-NMR and 13 13C-NMR analysis, it can be confirmed that the compound produced by the production method of the present embodiment is the urethane (meth)acrylate represented by the formula (1).

[0065] In order to obtain the urethane (meth)acrylate having the above-mentioned Mw, the polyether polyol preferably has a polyoxyalkylene chain obtained by addition polymerizing 100 to 500 moles of an alkylene oxide per mole of the polyglycerol of the initiator.

[0066] The addition molar number of the alkylene oxide per 1 mole of the initiator is preferably 100 to 500 moles, more preferably 110 to 400 moles, and still more preferably 120 to 300 moles.

[0067] If the addition molar number of the alkylene oxide per 1 mole of the initiator is 100 moles or more, it is easy to obtain a urethane (meth)acrylate that can form a cured coating film that is not easily warped and has excellent resistance to repeated bending. From the viewpoint of practicality such as production and operability, the above-mentioned addition molar number is preferably 500 moles or less.

[0068] Regarding the alkylene oxide, as described above, from the viewpoints of the high hardness and good flexibility of the cured product using the urethane (meth)acrylate, in a total of 100 mol%, propylene oxide is preferably 50 mol% or more, more preferably 70 to 100 mol%, still more preferably 90 to 100 mol%, and even more preferably 100 mol%.

[0069] The step of obtaining a polyether polyol by addition polymerization of an alkylene oxide to polyglycerol as an initiator can be carried out using a known synthesis method, and a known catalyst can be used as the addition polymerization catalyst. As the catalyst, for example, basic catalysts such as potassium hydroxide, transition metal compound-porphyrin complex catalysts such as complexes obtained by reacting an organoaluminum compound with porphyrin, double metal cyanide complex catalysts such as zinc hexacyanocobaltate complex having tert-butanol as a ligand, and catalysts composed of phosphazene compounds can be mentioned. The catalysts can be used alone or in combination of two or more.

[0070] In the urethanization reaction of the polyether polyol and a monoisocyanate having a (meth)acryloyloxy group, the reaction product of the polyether polyol having n hydroxyl groups in one molecule derived from R in the formula (1) and the monoisocyanate derived from R, namely, the urethane (meth)acrylate can be obtained. 1 The reaction product of the polyether polyol having n hydroxyl groups in one molecule derived from R 2 and the monoisocyanate derived from R, namely, the urethane (meth)acrylate.

[0071] The urethanization reaction can be carried out using a known method. Usually, the polyether polyol and the monoisocyanate are mixed, and the reaction is carried out using a urethanization catalyst in an atmosphere of nitrogen or an inert gas.

[0072] As the urethanization catalyst, for example, organotin compounds such as dibutyltin(IV) dilaurate, dioctyltin(IV) dilaurate, dibutyltin(IV) dioctanoate, tin(II) 2-ethylhexanoate; iron compounds such as iron(III) acetylacetonate, iron(III) chloride; lead compounds such as lead(II) 2-ethylhexanoate; bismuth compounds such as bismuth(III) 2-ethylhexanoate; tertiary amines such as triethylamine, triethylenediamine can be mentioned. Among these, organotin compounds, lead(II) 2-ethylhexanoate, and bismuth(III) 2-ethylhexanoate are preferred. The urethanization catalyst can be used alone or in combination of two or more.

[0073] The amount of the urethanization catalyst is preferably 0.001 to 1 part by mass, more preferably 0.002 to 0.5 part by mass, still more preferably 0.005 to 0.1 part by mass, based on a total of 100 parts by mass of the polyether polyol and the monoisocyanate as the reaction product.

[0074] The reaction temperature of the carbamation reaction is preferably 20 to 100 °C, more preferably 30 to 90 °C, and further preferably 40 to 80 °C.

[0075] [Curable composition]

[0076] The curable composition of the present invention contains the urethane (meth) acrylate of the present embodiment described above.

[0077] The curable composition preferably contains a polymerization initiator and other components as needed.

[0078] From the viewpoint of obtaining a cured product with excellent toughness, the content of the urethane (meth) acrylate in the curable composition is preferably 30% by mass or more, more preferably 40% by mass or more and less than 100% by mass.

[0079] Each compounding component in the curable composition is preferably uniformly mixed. For example, a known mixing device such as a magnetic stirrer, a rotation-revolution type stirring and defoaming mixer, a homogenizer, a planetary mixer, a three-roll mill, a bead mill, etc. can be used for mixing. Each compounding component can be mixed simultaneously or by sequential addition.

[0080] (Polymerization initiator)

[0081] The polymerization initiator is preferably a radical polymerization initiator, which can be a photoinitiator or a thermal polymerization initiator, and known initiators can be used.

[0082] From the viewpoint of ease of controlling the polymerization reaction, the photoinitiator is preferably one that can be used by irradiation with ultraviolet light having a wavelength of 380 nm or less, and the thermal polymerization initiator is preferably one that can be used by heating in the range of 50 to 120 °C.

[0083] As the photopolymerization initiator, for example, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl acetophenone, diethoxy acetophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methyl propanone, 1-(4-dodecylphenyl)-2-hydroxy-2-methyl propanone, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl) ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin phenyl ether, benzil dimethyl ketal, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone-4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, methyl benzoylformate, benzil, camphorquinone can be cited. The photopolymerization initiator can be used alone as one kind, or two or more kinds can be used in combination.

[0084] As the thermal polymerization initiator, for example, azo compounds; organic peroxides such as hydrogen peroxide, dialkyl peroxides, peroxy esters, diacyl peroxides, diperoxy carbonates, peroxoketals, and ketone peroxides can be cited. Specifically, azobisisobutyronitrile, benzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, tert-butyl peroxybenzoate, tert-butyl peroxide, cumene hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-dibutylperoxyhexane, 2,4-dichlorobenzoyl peroxide, 1,4-bis(2-tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, methyl ethyl ketone peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate can be cited. The thermal polymerization initiator can be used alone as one kind, or two or more kinds can be used in combination.

[0085] From the viewpoint of an appropriate polymerization rate, the content of the polymerization initiator in the curable composition is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 10 parts by mass, and still more preferably 0.1 to 7 parts by mass with respect to 100 parts by mass of the urethane (meth)acrylate.

[0086] In the case of obtaining a cured product by irradiating a curable composition with light, the light source can be appropriately set according to the light absorption ability of the photopolymerization initiator incorporated. For example, an ultraviolet light-emitting diode (LED), a low-pressure mercury lamp, a high-pressure mercury lamp, a mercury-xenon lamp, a metal halide lamp, a tungsten lamp, an arc lamp, an excimer lamp, an excimer laser, a semiconductor laser, a YAG laser, a laser system combining a laser and a nonlinear optical crystal, a high-frequency induction ultraviolet generating device can be used as the light source. The cumulative light quantity is, for example, 0.01 to 50 J / cm 2 or so.

[0087] From the viewpoint of further stabilizing the physical properties of the cured product, after light irradiation, a heat treatment can also be further carried out. Usually, the heating temperature is about 40 to 200°C, and the heating time is about 1 minute to 15 hours. In addition, when left standing at room temperature (about 15 to 25°C) for about 1 to 48 hours, the physical properties of the cured product can also be stabilized.

[0088] In the case of obtaining a cured product by subjecting the curable composition to a heat treatment, usually, the heating temperature is about 40 to 250°C, and the heating time is about 5 minutes to 24 hours. Preferably, when the heating temperature is high, the heating time is shortened, and when the heating temperature is low, the heating time is extended.

[0089] (Other components)

[0090] According to good operability and its use, in addition to the urethane (meth)acrylate and the polymerization initiator, the curable composition may further contain other components. Examples of other components include inorganic particles, other monomer components other than the urethane (meth)acrylate of the present embodiment, catalysts, pigments, colorants such as dyes, silane coupling agents, tackifying resins, antioxidants, light stabilizers, metal deactivators, rust inhibitors, anti-aging agents, moisture absorbers, hydrolysis inhibitors, defoaming agents, filler materials. In addition, an organic solvent may also be contained. These other components in the curable composition can be incorporated in amounts within a range that does not impair the effects of the present invention.

[0091] For inorganic particles, particularly in the case of using the urethane (meth)acrylate of the present embodiment to form a cured coating film, it is effective in improving the hardness of a coating film with a thickness of 10 μm or more and less than about 1 mm.

[0092] Examples of inorganic particles include silica particles, alumina particles, titanium dioxide particles, zinc oxide particles. The inorganic particles can be used singly or in combination of two or more.

[0093] In addition, from the viewpoint of obtaining a cured coating film with high hardness by virtue of good dispersibility in the cured coating film, etc., it is preferable to use in combination inorganic particles having two or more kinds of average particle diameters. For example, when the thickness of the produced cured coating film is about 5 to 15 μm, it is preferable to use in combination inorganic particles having an average particle diameter of 10 nm or more and less than 35 nm and inorganic particles having an average particle diameter of 35 nm or more and less than 100 nm.

[0094] From the viewpoint of making the compatibility (wettability) with the urethane (meth)acrylate of the present embodiment good and obtaining a cured coating film with high hardness and excellent resistance to repeated bending, the inorganic particles are preferably surface-modified with a silane coupling agent.

[0095] Examples of the silane coupling agent include a (meth)acryloyl group-containing silane compound, a vinyl group-containing silane compound, an epoxy group-containing silane compound, and a mercapto group-containing silane compound. The silane coupling agent can be used alone or in combination of two or more. Among these, from the viewpoint of affinity with the urethane (meth)acrylate, a (meth)acryloyl group-containing silane compound ((meth)acrylate silane coupling agent) is preferable.

[0096] From the viewpoint of uniform dispersibility in the curable composition, the inorganic particles can be those pre-dispersed in an organic solvent (medium), for example, an organosol.

[0097] The content of the inorganic particles in the curable composition is set within a range that does not hinder the effects of the present invention. Relative to 100 parts by mass of the urethane (meth)acrylate of the present embodiment, it is preferably 50 parts by mass or less, more preferably 5 to 50 parts by mass, and further preferably 10 to 40 parts by mass.

[0098] Other monomer components are compounds that can copolymerize with the urethane (meth)acrylate, and examples thereof include urethane (meth)acrylates other than the urethane (meth)acrylate of the present embodiment, (meth)acrylic acid alkyl esters, hydroxy group-containing (meth)acrylates, alkoxy group-containing (meth)acrylates, amino group-containing (meth)acrylates, and other (meth)acrylates. The other monomer components can be used alone or in combination of two or more.

[0099] Regarding the (meth)acrylate used in combination with the urethane (meth)acrylate of the present embodiment, from the viewpoint of obtaining a cured product having high hardness and good flexibility through compatibility with the urethane (meth)acrylate of the present embodiment and a high-density crosslinked network, a polyfunctional (meth)acrylate having 3 to 20 (meth)acryloxy groups in one molecule is preferred. Specifically, trimethylolpropane tri(meth)acrylate, trimethylolpropane ethoxylated tri(meth)acrylate, glycerol propoxylated tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate can be mentioned.

[0100] In addition, the aforementioned polyfunctional (meth)acrylate used in combination with the urethane (meth)acrylate of the present embodiment is preferably a compound having a multi-branched structure and having a (meth)acryloyl group at the end of each branch, more preferably at least one of a hyperbranched polymer and a dendrimer, and further preferably a dendrimer. A dendrimer is a polymer having relatively high regularity and symmetrically forming dendritic branches in a manner of spreading outward from the center. A hyperbranched polymer is a polymer forming dendritic branches with relatively low regularity. Compared with linear polymers, both have low viscosity and excellent solvent solubility.

[0101] As the dendrimer, for example, polymers represented by the following formulas (1) to (8) can be mentioned, but are not limited to these, and a compound having a dendrimer structure and having a (meth)acryloxy group at the end of each branch is sufficient.

[0102]

[0103] In formulas (1) to (8), R 1 represents a hydrogen atom or a methyl group, and R 2 represents a hydrocarbon group having 1 to 4 carbon atoms.

[0104] As the (meth)acrylate having a dendrimer structure, for example, "SIRIUS-501" (manufactured by Osaka Organic Chemical Industry Co., Ltd.; Mw about 13000 to 14000); "MIRAMER (registered trademark; the following description is omitted.) SP1106" (manufactured by Miwon Specialty Chemical Co., Ltd.; Mw about 1000 to 1100, and the average number of (meth)acryloyl groups per molecule is 18); "CN2301", "CN2302" (the average number of (meth)acryloyl groups per molecule is 16), "CN2304" (the average number of (meth)acryloyl groups per molecule is 18) (the above are manufactured by Sartomer Company) and other commercially available products can be used. These can be used alone or in combination of two or more.

[0105] The content of other monomer components in the curable composition is set within a range that does not hinder the effects of the present invention. With respect to a total of 100 parts by mass of the urethane (meth) acrylate and other monomer components of the present embodiment, it is preferably 50 parts by mass or less, more preferably 10 to 50 parts by mass, and still more preferably 10 to 40 parts by mass.

[0106] The organic solvent also functions as a dispersion medium for the compounding components in the curable composition, which is used to make each compounding component form a uniformly dissolved or dispersed state and has appropriate fluidity and coatability.

[0107] Examples of the organic solvent include alcohols such as methanol, ethanol, isopropyl alcohol, and butanol; alkoxy alcohols such as 2-methoxyethanol, 2-ethoxyethanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and cyclohexanone; glycol monoethers such as propylene glycol monopropyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, and diethylene glycol-2-ethylhexyl ether; and aromatic solvents such as benzene, toluene, and xylene. The organic solvent can be used alone or in combination of two or more.

[0108] The content of the organic solvent in the curable composition is set within a range that does not hinder the effects of the present invention. From the viewpoints of appropriate fluidity and coatability of the curable composition, etc., it is preferably 50 parts by mass or less, more preferably 10 to 50 parts by mass, and still more preferably 10 to 40 parts by mass.

[0109] The curable composition containing the urethane (meth) acrylate of the present embodiment is suitable for uses such as coating agents for various substrates, especially coating agents for surface protection for preventing scratches, cracks, etc. of displays, touch panels, etc. of image display devices. In particular, the cured product of the curable composition can form a cured coating film with high hardness, less likely to cause warping of the thin film, and more excellent resistance to repeated bending, and thus is suitable for coating agents for surface protection of flexible displays, foldable devices, etc.

[0110] [Cured coating film]

[0111] The cured coating film of the present embodiment is a cured product of the curable composition containing the urethane (meth) acrylate of the above present embodiment. By coating a coating agent based on the curable composition of the present embodiment on a thin film substrate and curing it, a thin film formed with a cured coating film can be obtained. The cured coating film of the present embodiment has high hardness, is less likely to cause warping of the thin film, and has excellent resistance to repeated bending.

[0112] For example, known methods such as bar coating, knife coating, roll coating, scraping coating, die coating, microgravure coating, comma coating, slot die coating, die lip coating, and casting coating can be used for the coating method of the coating agent.

[0113] From the viewpoint of obtaining a cured coating film with high hardness, less prone to warping of the film, and excellent resistance to repeated bending, the thickness of the cured coating film is preferably 3 μm or more, more preferably 3 - 20 μm, and further preferably 3 - 15 μm.

[0114] The cured coating film according to the present embodiment can exhibit these characteristics in the above-mentioned uses, and thus can suitably provide coated products having the cured coating film, particularly articles such as flexible displays and foldable devices having a surface formed with the cured coating film.

[0115] Examples

[0116] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples, and various modifications can be made without departing from the gist of the present invention.

[0117] [Synthesis of polyether polyol]

[0118] According to the following synthesis examples, polyether polyols were synthesized. The details of the polyglycerols used in the synthesis examples are shown below.

[0119] [Polyglycerol]

[0120] ·PGL10PSW: Polyglycerol - 10; "PGL 10PSW", Daicel Corporation; average degree of polymerization 10, number of hydroxyl groups in one molecule 12

[0121] ·PGL20PW: Polyglycerol - 20; "PGL 20PW", Daicel Corporation; average degree of polymerization 20, number of hydroxyl groups in one molecule 22

[0122] ·PGLX: Polyglycerol - 40; "PGL X", Daicel Corporation; average degree of polymerization 40, number of hydroxyl groups in one molecule 42

[0123] [Synthesis Example 1]

[0124] In a pressure-resistant reactor equipped with a stirrer and a nitrogen inlet tube, 100 g of PGL20PW as an initiator and 2.0 g of potassium hydroxide were charged, and dehydration was carried out in advance for 3 hours under the conditions of 120 °C and 5 mmHg or less. Propylene oxide (PO) 567 g was charged at a constant rate over 12 hours under a nitrogen atmosphere at 120 °C. After confirming that the internal pressure of the pressure-resistant reactor stopped decreasing, a polymer (polyether polyol (P1): PGL(22)-PO(150) addition polymer) with 150 moles of PO added to polyglycerol was obtained.

[0125] [Synthesis Example 2]

[0126] Using PGLX as an initiator, the same procedure as in Synthesis Example 1 was carried out to obtain a polymer (polyether polyol (P2): PGL(42)-PO(200) addition polymer) with 200 moles of PO added to polyglycerol.

[0127] [Synthesis Example 3]

[0128] Using PGL10PSW as an initiator, the same procedure as in Synthesis Example 1 was carried out to obtain a polymer (polyether polyol (P3): PGL(12)-PO(100) addition polymer) with 100 moles of PO added to polyglycerol.

[0129] [Manufacture of urethane (meth)acrylate]

[0130] Using each polyether polyol obtained in the above synthesis examples, urethane (meth)acrylate was manufactured through the following production examples. Details of various compounds used in the production examples and methods for measuring various physical properties are shown below.

[0131] [Compounds used]

[0132] ·AOI: 2-acryloyloxyethyl isocyanate; "KARENZ AOI" (purity ≥ 97% by mass), manufactured by Resonac Corporation

[0133] ·AOI-VM: 2-acryloyloxyethyl isocyanate; "KARENZ AOI-VM" (purity ≥ 96% by mass), manufactured by Resonac Corporation

[0134] ·MOI: 2-methacryloyloxyethyl isocyanate; "KARENZ MOI", manufactured by Resonac Corporation

[0135] ·MOI-EG: 2-(2-methacryloyloxyethyloxy)ethyl isocyanate; "KARENZ MOI-EG", manufactured by Resonac Corporation

[0136] ·BEI: 1,1-bis(acryloxymethyl)ethyl isocyanate; manufactured by "KARENZ BEI", Resonac Corporation

[0137] ·PGL20PW: polyglycerol-20; "PGL 20PW", Daicel Corporation; average degree of polymerization 20, number of hydroxyl groups per molecule 22

[0138] ·PUCAT25: bismuth(III) 2-ethylhexanoate; "PUCAT (registered trademark) 25", manufactured by Nippon Chemical Industry Co., Ltd.; urethanization catalyst

[0139] 〔Measurement method〕

[0140] (Water content)

[0141] The water content of the polyether polyol is measured by the Karl Fischer coulometric titration method under the following measurement conditions.

[0142] <Measurement conditions>

[0143] ·Machine used: "Karl Fischer moisture analyzer CA-310", manufactured by NITTOSEIKO CO., LTD.

[0144] ·Sample injection volume: 0.5 mL

[0145] (Weight-average molecular weight and number-average molecular weight)

[0146] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the urethane (meth)acrylate are measured by gel permeation chromatography (GPC) under the following measurement conditions.

[0147] <Measurement conditions>

[0148] ·Machine used: "HLC-8320GPC", manufactured by Tosoh Corporation

[0149] ·Columns used: The following 2 types of columns are connected in series

[0150] "TSKgel (registered trademark) SuperHZ2500", manufactured by Tosoh Corporation, 2 pieces

[0151] "TSKgel (registered trademark) SuperHZ4000", manufactured by Tosoh Corporation, 2 pieces

[0152] ·Column temperature: 40 °C

[0153] ·Detector: differential refractive index (RI) detector

[0154] ·Eluent: tetrahydrofuran

[0155] · Flow rate: 0.8 mL / minute

[0156] · Sample concentration: 0.5 mass%

[0157] · Sample injection volume: 100 μL

[0158] · Standard sample: Polystyrene

[0159] 〔Production Example 1〕

[0160] 161 g (80 mass parts) of polyether polyol (P1) was put into a reaction vessel equipped with a thermometer, a stirrer, and a nitrogen inlet, and heated to 130 °C with stirring under a nitrogen atmosphere for 3 hours for dehydration. After the water content became less than 150 mass ppm, it was cooled to 40 °C. Then, 40 g (20 mass parts) of AOI (isocyanate index 100) and 0.02 g (0.01 mass part) of PUCAT25 were added, and the reaction was carried out at 70 °C for 3 hours to produce urethane acrylate (U1).

[0161] 〔Production Examples 2 - 7〕

[0162] Urethane (meth) acrylates (U2) - (U7) were synthesized in the same manner as in Production Example 1 with the compounding compositions described in Production Examples 2 - 7 of Table 1.

[0163] 〔Production Example 8〕

[0164] In Production Example 1, 150 g (75 mass parts) of PGL20PW (polyether polyol (P4)) was used instead of polyether polyol (P1), and the addition amount of AOI was set to 50 g (25 mass parts). Otherwise, it was carried out in the same manner as in Production Example 1 to obtain urethane acrylate (U8).

[0165] [Table 1]

[0166]

[0167] [Production of Curable Composition]

[0168] According to the following examples, curable compositions of each urethane (meth) acrylate were produced. The details of the raw materials used in the following examples are shown below.

[0169] 〔Raw Materials Used〕

[0170] · U1 - U8: Each urethane (meth) acrylate produced through Production Examples 1 - 8

[0171] ·U9: 6-functional polyglycerol acrylate "SYntech SA TE-6", manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.; ethylene oxide 25 mol addition polymer

[0172] ·U10: A mixture of 4.0 g of 9-functional urethane acrylate "MIRAMER MU9800" (manufactured by Miwon Specialty Chemical Co., Ltd.) and 3.0 g of 10-functional urethane acrylate "MIRAMER MU9500" (manufactured by Miwon Specialty Chemical Co., Ltd.)

[0173] ·D1: Dendritic polymer type polyfunctional acrylate "SIRIUS-501", manufactured by Osaka Organic Chemical Industry Co., Ltd.; solid content 50 mass%

[0174] ·TMPTA: Trimethylolpropane triacrylate; manufactured by Tokyo Chemical Industry Co., Ltd.

[0175] ·SP1106: 18-functional dendritic polymer type polyfunctional acrylate "MIRAMER SP1106", manufactured by Miwon Specialty Chemical Co., Ltd.

[0176] ·Silica sol (S1): "MEK-AC-2140Z", manufactured by Nissan Chemical Industries, Ltd.; average particle size 12 nm, methyl ethyl ketone dispersed silica sol, solid content 40 mass%, silica particles surface-modified with methacrylate silane coupling agent

[0177] ·Silica sol (S2): "MEK-AC-4130Y", manufactured by Nissan Chemical Industries, Ltd., average particle size 45 nm, methyl ethyl ketone dispersed silica sol, solid content 30 mass%, silica particles surface-modified with methacrylate silane coupling agent

[0178] ·Omnirad184: 1-Hydroxycyclohexyl phenyl ketone; "Omnirad (registered trademark) 184", manufactured by IGM Resins B.V.; photoinitiator

[0179] ·MEK: Methyl ethyl ketone; organic solvent

[0180] ·Film substrate: Polyimide film "Kapton (registered trademark) 200EN", manufactured by DU PONT-TORAY CO., LTD.; thickness 50 μm

[0181] 〔Examples 1 to 4 and 6 to 11〕

[0182] Using a magnetic stirrer, 7.0 g of U1-U9 or D1, 3.0 g of TMPTA, 3.0 g of colloidal silica (S1), 2.5 g of colloidal silica (S2), 0.1 g of Omnirad 184, and 1.5 g of MEK were mixed for 1 hour to prepare each curable composition.

[0183] 〔Example 5〕

[0184] In Example 1, U5 was used instead of U1, and SP1106 was used instead of TMPTA. Otherwise, the procedure was the same as in Example 1 to prepare a curable composition.

[0185] [Production of cured coating film]

[0186] Each curable composition prepared in Examples 1-10 was coated on a film substrate using a bar coater and dried at 100 °C for 3 minutes. Then, the curable composition on the film substrate was cured using a UV conveyor belt (ultraviolet cumulative irradiation dose: 2 J / cm 2 ) to produce a cured coating film.

[0187] For each produced cured coating film, the following items were evaluated. Table 2 shows the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of each urethane (meth)acrylate and the evaluation results. Note that in Table 2, D1 is a dendritic polymer type polyfunctional acrylate.

[0188] Examples 1-5 are examples, and Examples 6-11 are comparative examples.

[0189] 〔Thickness〕

[0190] The thickness of the cured coating film was measured using a dial thickness gauge (“PEACOCK G-6C”, manufactured by Ozaki Manufacturing Co., Ltd.).

[0191] 〔State〕

[0192] The state (shape) of the film on which the cured coating film was formed was evaluated by visual observation. The following shows the evaluation criteria for the results shown in Table 2.

[0193] A: Maintained a flat state.

[0194] B: Warping occurred.

[0195] 〔Pencil hardness〕

[0196] According to JIS K 5600-5-4:1999, a pencil was pressed against the coated surface of the cured coating film with a load of 750 g and an angle of 45°. After repeating the process of moving forward and backward 5 cm three times, the coated surface was visually inspected and judged.

[0197] If the pencil hardness is 4H or higher, it can be said that the hardness is high enough.

[0198] [Scratch Test]

[0199] Press steel wool (#0000) by hand onto the coated surface of the cured coating film, rub back and forth 10 times, and then visually inspect the resulting scratch state and evaluate it. The evaluation criteria for the results shown in Table 2 are shown below.

[0200] A: No scratches were generated.

[0201] B: Some scratches were confirmed.

[0202] C: Scratches were generated in all parts where the steel wool was rubbed.

[0203] [Repeated Bending Test]

[0204] Fix both ends in the length direction of a 140 mm × 40 mm specimen cut from a polyimide film formed with a cured coating film to the clamping part of a flat body unloaded U-shaped elongation testing machine (“DLDMLH-FS”, manufactured by YUASA SYSTEM Co., Ltd.) with double-sided tape.

[0205] Bend it into a U shape (bending R radius 1.5 mm) with the coated surface side of the specimen's cured coating film on the inside (coated surface inside), and conduct a test of repeating 100,000 times of bending and stretching at a speed of 50 times per minute. For the case where the coated surface side of the specimen's cured coating film becomes the outside of the U shape (coated surface outside), conduct the repeated bending and stretching test in the same way.

[0206] Visually inspect the state of the coated surface of the cured coating film of the specimen after the test and evaluate it. The evaluation criteria for the results shown in Table 2 are shown below.

[0207] A: No change.

[0208] B: Scratches were generated.

[0209] C: The coating film peeled off.

[0210] [Table 2]

[0211]

[0212] As can be seen from Table 2, the cured coating film of the curable composition containing the urethane (meth)acrylate (Examples 1 to 5) of the present invention maintains a flat state without bending, has high hardness, is not easily scratched, and has excellent resistance to repeated bending.

Claims

1. A urethane (meth)acrylate represented by the following formula (1) and having a weight-average molecular weight of 8,000 to 100,000, R 1 -[OC(=O)NH-R 2 n (1)​ In formula (1), R 1 is an n-valent residue obtained by removing hydroxyl groups from a polyether polyol having n hydroxyl groups in one molecule, and the n Rs 2 are each independently a residue obtained by removing an isocyanate group from a monoisocyanate having a (meth)acryloyloxy group, and n is from 22 to 60.

2. The urethane (meth)acrylate according to claim 1, wherein, The polyether polyol is a polymer obtained by adding an alkylene oxide to polyglycerol, and the alkylene oxide has 2 to 4 carbon atoms.

3. The urethane (meth) acrylate according to claim 2, wherein, In a total of 100 mol% of the alkylene oxide, propylene oxide is 50 mol% or more.

4. A method for manufacturing a urethane (meth) acrylate, which is the method for manufacturing a urethane (meth) acrylate according to claim 1 or 2, wherein, The urethanization reaction is carried out between the polyether polyol and the monoisocyanate having a (meth)acryloyloxy group. The polyether polyol is obtained by addition polymerization of 100 to 500 mol of an alkylene oxide having 2 to 4 carbon atoms in the presence of a catalyst using polyglycerol having 22 to 60 hydroxyl groups in one molecule as an initiator.

5. The production method of the urethane (meth) acrylate according to claim 4, wherein, In a total of 100 mol% of the alkylene oxide, propylene oxide is 50 mol% or more.

6. A curable composition comprising the urethane (meth)acrylate according to claim 1.

7. The curable composition according to claim 6, further comprising inorganic particles.

8. The curable composition according to claim 7, wherein, The inorganic particles are surface-modified with a silane coupling agent.

9. The curable composition according to claim 6 or 7, further comprising a polyfunctional (meth)acrylate other than the urethane (meth)acrylate.

10. The curable composition according to claim 9, wherein, The polyfunctional (meth)acrylate is a compound having a multi-branched structure and having a (meth)acryloyl group at the end of each branch.

11. The curable composition according to claim 6 or 7, which is a coating agent.

12. A cured coating film which is a cured product of the curable composition according to claim 6 or 7.

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