JP7320685B1 - Urethane (meth)acrylate, energy beam-curable resin composition, optical film and display device - Google Patents

Abstract

A urethane (meth)acrylate that has excellent adhesion to acrylic substrates and can improve the hardness of coating films. A urethane (meth)acrylate according to an embodiment comprises (A) a difunctional polycaprolactone-based polyol, (B) a trifunctional or higher polyether polyol, (C) an alicyclic polyisocyanate, and (D ) with 2-hydroxyethyl (meth)acrylate, and has a number average molecular weight of 1,500 or more and 3,000 or less. [Selection figure] None

Description

TECHNICAL FIELD The present invention relates to a urethane (meth)acrylate, an energy ray-curable resin composition, an optical film and a display device using the same.

Energy ray-curable resin compositions that are cured by energy rays such as ultraviolet rays are used, for example, as coating agents, and urethane (meth)acrylate is known as a compounding component thereof. A urethane (meth)acrylate is a urethane compound having a (meth)acryloyl group, and is obtained by reacting a polyol, a polyisocyanate, and a hydroxy group-containing (meth)acrylate.

For example, Patent Document 1 discloses an energy ray-curable resin composition containing a urethane (meth)acrylate obtained by reacting a polycaprolactone-based polyol, a polyether polyol, a polyisocyanate, and a (meth)acrylate having a hydroxyl group. things are described. More specifically, polycaprolactone-based polyol, bisphenol A ethylene oxide adduct and trifunctional or higher polyether polyol as polyether polyol, isophorone diisocyanate and xylylene diisocyanate as polyisocyanate, and 2-hydroxyethyl acrylate are reacted. urethane (meth)acrylates obtained by

JP 2014-189651 A

Urethane (meth)acrylates are sometimes used for coating acrylic substrates, in which case adhesion to acrylic substrates is required. In addition, for example, in coating applications for optical films, hardness is required for the coating film, which is a cured film. It has been found that some of the urethane (meth)acrylates described in Patent Document 1 have excellent adhesion to acrylic substrates, but are inferior in hardness of coating films.

In view of the above points, an object of the embodiments of the present invention is to provide a urethane (meth)acrylate that has excellent adhesion to acrylic substrates and can improve the hardness of coating films.

The present invention includes embodiments shown below.
[1] (A) a bifunctional polycaprolactone-based polyol, (B) a trifunctional or higher polyether polyol, (C) an alicyclic polyisocyanate, and (D) 2-hydroxyethyl (meth)acrylate, A urethane (meth)acrylate having a number average molecular weight of 1,500 or more and 3,000 or less, obtained by the reaction.
[2] The urethane (meth) according to [1], wherein the ratio of the (A) bifunctional polycaprolactone-based polyol to 100 mol% of the total reaction raw materials constituting the urethane (meth)acrylate is 8 to 22 mol%. Acrylate.
[3] The urethane (meth)acrylate according to [1] or [2], wherein the (A) bifunctional polycaprolactone-based polyol has a hydroxyl value of 100 to 300 mgKOH/g.
[4] The urethane (meth)acrylate according to any one of [1] to [3], wherein the (B) polyether polyol having a functionality of 3 or more has a hydroxyl value of 190 to 1000 mgKOH/g.

[5] An energy ray-curable resin composition for coating an acrylic substrate, comprising the urethane (meth)acrylate according to any one of [1] to [4].
[6] The energy ray-curable resin composition for coating an acrylic substrate according to [5], which is used for producing an optical film.
[7] An optical film obtained by coating an acrylic substrate with the energy ray-curable resin composition according to [6].
[8] A display device comprising the optical film of [7].

The urethane (meth)acrylate according to the embodiment of the present invention is excellent in adhesion to acrylic substrates and can improve the hardness of the coating film.

As used herein, "(meth)acrylate" means either one or both of acrylate and methacrylate. The same applies to terms such as "(meth)acryloyl group".

[(A) Bifunctional polycaprolactone-based polyol]
A bifunctional polycaprolactone-based polyol is a polycaprolactone-based polyol having two hydroxy groups in the molecule, and includes those obtained by subjecting a diol to ring-opening reaction with a caprolactone compound. As the diol, one having a molecular weight of 150 or less, more preferably 100 or less is preferably used. Examples of caprolactone compounds include ε-caprolactone, 3-methyl-ε-caprolactone, 4-methyl-ε-caprolactone, 3,3,5-trimethyl-ε-caprolactone, and 3,5,5-trimethyl-ε-caprolactone. etc. In one embodiment, the bifunctional polycaprolactone-based polyol is preferably obtained by reacting a diol such as ethylene glycol, diethylene glycol or 1,4-butanediol with ε-caprolactone.

The hydroxyl value of the bifunctional polycaprolactone-based polyol is more preferably 100 to 300 mgKOH/g from the viewpoint of adhesion to the acrylic substrate and hardness of the coating film. The hydroxyl value of the bifunctional polycaprolactone-based polyol is more preferably 150-280 mgKOH/g, still more preferably 180-250 mgKOH/g, still more preferably 200-230 mgKOH/g.

As used herein, the hydroxyl value is measured according to JIS K1557-1:2007 A method.

[(B) Trifunctional or higher polyether polyol]
The trifunctional or higher polyether polyol is a polyether polyol having 3 or more hydroxy groups in the molecule, and includes a compound obtained by addition polymerization of alkylene oxide to a compound having 3 or more hydroxy groups.

The compound having 3 or more hydroxy groups is preferably an aliphatic compound having 3 or more hydroxy groups. mentioned.

As the alkylene oxide, for example, alkylene oxides having 2 to 4 carbon atoms such as ethylene oxide, propylene oxide and butylene oxide are preferably used.

The tri- or higher functional polyether polyol is preferably tri- to hexa-functional, more preferably tri- or tetra-functional, still more preferably tri-functional.

It is more preferable that the polyether polyol having a functionality of 3 or more has a hydroxyl value of 190 to 1000 mgKOH/g from the viewpoint of adhesion to the acrylic substrate and hardness of the coating film. The hydroxyl value of the trifunctional or higher polyether polyol is more preferably 300 to 800 mgKOH/g, still more preferably 400 to 700 mgKOH/g, still more preferably 430 to 600 mgKOH/g.

[(C) Alicyclic polyisocyanate]
Examples of alicyclic polyisocyanates include isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4′-diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1, 3-bis(isocyanatomethyl)cyclohexane and the like. Isocyanurate, adduct, burette, and the like of these alicyclic polyisocyanates may also be used. Any one of these alicyclic polyisocyanates may be used, or two or more thereof may be used in combination.

[(D) 2-hydroxyethyl (meth)acrylate]
2-Hydroxyethyl (meth)acrylate is a (meth)acrylate having a hydroxy group, and may be 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate, or both.

[Urethane (meth)acrylate]
The urethane (meth)acrylate according to the present embodiment is a urethane compound (also referred to as an oligomer) having a (meth)acryloyl group, and is obtained by reacting the above components (A) to (D). be. Therefore, the urethane (meth)acrylate has (A) a structure derived from a bifunctional polycaprolactone-based polyol, (B) a structure derived from a trifunctional or higher polyether polyol, and (C) a structure derived from an alicyclic polyisocyanate. and (D) a structure derived from 2-hydroxyethyl (meth)acrylate.

Specifically, the hydroxy groups of components (A), (B) and (D) react with the isocyanate groups of component (C) to form urethane bonds. Since the component (D) has one hydroxy group, the urethane (meth)acrylate has a (meth)acryloyl group derived from the component (D) at its terminal. Urethane (meth)acrylate may be composed only of a compound containing all of the structures derived from components (A) to (D) in one molecule, but the structure derived from component (A) and the structure derived from component (B) It may also contain compounds that do not contain Moreover, the number of each component contained in one molecule is not particularly limited. Therefore, urethane (meth)acrylate, which is a product obtained by reacting components (A) to (D), may be a mixture of compounds having not only a single structure but also a plurality of different structures. Further, for example, an excess component (D) that remains without reacting may be included. The structure of such urethane (meth)acrylate depends on reaction conditions such as the types and amounts of components (A) to (D).

The urethane (meth)acrylate is basically composed of only the above components (A) to (D) as reaction raw materials, but other polyols, polyisocyanates, and hydroxy Group-containing (meth)acrylates may be included as reactants.

In the urethane (meth)acrylate, the proportions of the components (A) to (D) are preferably as follows.

The ratio of (A) the bifunctional polycaprolactone-based polyol to 100 mol % of the total reaction raw materials constituting the urethane (meth)acrylate is preferably 8 to 22 mol %. When the ratio of the component (A) is 8 mol % or more, the effect of improving the adhesion to the acrylic substrate can be enhanced. When the proportion of component (A) is 22 mol % or less, the effect of improving the hardness of the coating film can be enhanced. The proportion of component (A) is more preferably 9 to 20 mol %, still more preferably 10 to 19 mol %.

The ratio of the (B) trifunctional or higher polyether polyol to 100 mol % of the total reaction raw materials constituting the urethane (meth)acrylate is preferably 5 to 18 mol %, more preferably 6 to 15 mol %. and more preferably 7 to 13 mol %.

The ratio of (C) the alicyclic polyisocyanate to 100 mol% of the total reaction raw materials constituting the urethane (meth)acrylate is preferably 30 to 60 mol%, more preferably 35 to 55 mol%. , more preferably 40 to 50 mol %.

The ratio of the above (D) 2-hydroxypropyl (meth)acrylate to 100 mol% of the total reaction raw materials constituting the urethane (meth)acrylate is preferably 20 to 50 mol%, more preferably 25 to 45 mol. %, more preferably 27 to 40 mol %. When the component (D) is charged excessively as in Examples described later, the proportion of the component (D) includes the excess. In that case, the excess amount is preferably 15 mol % or less, more preferably 10 mol % or less of component (D). The amount of component (D) contained as an excess in the above product is preferably 5 mol % or less, more preferably 4 mol % or less, based on 100 mol % of the total reaction raw materials.

Although the molar ratio (A)/(B) of (A) a bifunctional polycaprolactone-based polyol and (B) a trifunctional or higher polyether polyol is not particularly limited, it is preferably 1/3 to 3/1, and more It is preferably 1/2 to 2/1, more preferably 2/3 to 3/2, still more preferably 3/4 to 4/3.

The molar ratio [(A) + (B)] / (C) of the sum of (A) a difunctional polycaprolactone-based polyol and (B) a trifunctional or higher polyether polyol and (C) an alicyclic polyisocyanate is particularly Although not limited, it is preferably 3/10 to 7/10, more preferably 4/10 to 6/10.

Although the molar ratio (C)/(D) of (C) alicyclic polyisocyanate and (D) 2-hydroxypropyl (meth)acrylate is not particularly limited, it is preferably 1.05 to 2.0, and more It is preferably 1.1 to 1.8, more preferably 1.2 to 1.5.

The molar ratio between the isocyanate group (NCO) of the polyisocyanate (specifically component (C)) and the hydroxy group (OH) of the polyol (specifically component (A) and component (B)) is not particularly limited. , NCO/OH may be 1.20 to 1.90, or 1.40 to 1.75. In addition, the isocyanate (NCO) of the polyisocyanate (specifically the (C) component) and the hydroxy groups of the polyol and the hydroxy-containing (meth)acrylate (specifically the (A) component, the (B) component and the (D) component) The molar ratio with (OH) is also not particularly limited, and NCO/OH may be 0.90 to 0.99 or 0.95 to 0.97.

The urethane (meth)acrylate has a number average molecular weight (Mn) of 1,500-3,000. When the number average molecular weight is 1500 or more, the adhesiveness to acrylic substrates can be improved. Further, when the number average molecular weight is 3000 or less, the hardness of the coating film can be improved. The number average molecular weight of the urethane (meth)acrylate is preferably 1800-2500, more preferably 2000-2300.

As used herein, the number average molecular weight (Mn) is a value measured by a GPC method (gel permeation chromatography) and calculated using a standard polystyrene calibration curve. Specifically, as conditions for GPC, column: "GPC KF-601 + GPC KF-602 + GPC KF-603 + GPC KF-604" manufactured by Showa Denko Co., Ltd., mobile phase: THF (tetrahydrofuran), mobile phase flow rate: 0.6 mL / min , column temperature: 40° C., sample injection volume: 10 μL, sample concentration: 0.2% by mass.

[Method for producing urethane (meth)acrylate]
The method for producing the urethane (meth)acrylate according to the present embodiment is not particularly limited, and it can be synthesized by a known method.

For example, a predetermined amount of (A) difunctional polycaprolactone-based polyol and (B) trifunctional or higher polyether polyol are added to an excess amount of (C) alicyclic polyisocyanate, and a predetermined amount of free isocyanate is added at 80 ° C. Polyurethane is obtained by reacting until Next, in the presence of a polymerization inhibitor such as hydroquinone monomethyl ether, (D) 2-hydroxypropyl (meth)acrylate is charged at 70 to 80°C, and heated and stirred at 70 to 80°C until free isocyanate disappears. , urethane (meth)acrylates can be synthesized. (D) The amount of 2-hydroxyethyl (meth)acrylate to be charged is set to be equal to or greater than the amount with which all free isocyanates can react. Therefore, excess (D) 2-hydroxyethyl (meth)acrylate may remain. In order to accelerate the reaction, a tin-based catalyst such as dibutyltin dilaurate may be added.

[Energy ray-curable resin composition]
The energy ray-curable resin composition according to this embodiment contains the urethane (meth)acrylate. The energy ray-curable resin composition may contain only the urethane (meth)acrylate as a monomer or oligomer that undergoes a polymerization reaction with energy rays, but it also contains other unsaturated group-containing compounds along with the urethane (meth)acrylate. It's okay.

As the other unsaturated group-containing compound, a (meth)acrylate compound and/or a (meth)acrylamide compound are preferably used.

(Meth)acrylate compounds include, for example, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, adamantyl (meth)acrylate, cyclohexyl (meth)acrylate, trimethylcyclohexyl (meth) acrylate, cyclohexylmethyl (meth)acrylate, cyclohexylethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, methyl methacrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate ) acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (Meth)acrylate, isodecyl (meth)acrylate and the like. Any one of these may be used, or two or more thereof may be used in combination.

Examples of (meth)acrylamide compounds include acryloylmorpholine, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, diacetone(meth)acrylamide and the like. . Any one of these may be used, or two or more thereof may be used in combination.

When the urethane (meth)acrylate and another unsaturated group-containing compound are used in combination, the proportion of the urethane (meth)acrylate in the total mass of these is not particularly limited, and may be, for example, 30% by mass or more, or 30 to 30% by mass. It may be 90% by mass, 40 to 80% by mass, or 50 to 80% by mass.

The energy ray-curable resin composition according to the present embodiment contains a polymerization initiator together with the urethane (meth)acrylate. Examples of the polymerization initiator include photopolymerization initiators and polymerization initiators by active energy rays such as ultraviolet rays.

Examples of photopolymerization initiators include aromatic ketones such as benzophenone, aromatic compounds such as anthracene and α-chloromethylnaphthalene, and sulfur compounds such as diphenyl sulfide and thiocarbamate.

Examples of polymerization initiators using active energy rays other than visible light such as ultraviolet rays include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexylphenyl ketone, 2,2-dimethoxy-1,2-diphenylethan-1-one, and xanthone. , fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, benzoin propyl ether, benzoin ethyl ether, benzyl Dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethylthioxanthone, 2-isopropyl Thioxanthone, 2-chlorothioxanthone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl) -butanone-1,4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)- 2,4,4-trimethylpentylphosphine oxide, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone) and the like.

Commercially available polymerization initiators using active energy rays include, for example, IGM Resins B.V. V. Product name: Omnirad 184, 369, 651, 500, 819, 907, 784, 2959, 1000, 1300, 1700, 1800, 1850 BASF Product name: Lucilin TPO, UCB Product name: Uvecryl P36, Fratelli Lamberti trade names: Ezacure KIP150, KIP100F, KT37, KT55, KTO46, TZT, KIP75LT manufactured by Nippon Kayaku Co., Ltd.;

The content of the polymerization initiator varies depending on its type and the like, but as a guideline, it is 1 to 8 parts by weight per 100 parts by weight of the total weight of the energy ray-curable component containing urethane (meth)acrylate.

Various additives and organic solvents can be added to the energy ray-curable resin composition, if necessary, in addition to the energy ray-curable component including the urethane (meth)acrylate and the polymerization initiator. Examples of additives include light stabilizers, ultraviolet absorbers, catalysts, leveling agents, defoaming agents, polymerization accelerators, antioxidants, flame retardants, infrared absorbers, antistatic agents, slip agents, plasticizers, dispersants agents and the like.

The energy ray source for curing the energy ray curable resin composition is not particularly limited, but examples include high pressure mercury lamps, electron beams, γ rays, carbon arc lamps, xenon lamps, metal halide lamps and the like. In the case of curing by heating, it can be cured by heating to a temperature range of 60 to 250.degree.

The above-mentioned urethane (meth)acrylate is preferably used for coating an acrylic base material because it has excellent adhesion to the acrylic base material. Therefore, the energy ray-curable resin composition is suitably used for coating acrylic substrates.

An acrylic base material means a base material containing a (meth)acrylic resin. The form of the acrylic base material is not particularly limited, and may be, for example, a film form, a sheet form, a plate form, or the like. Examples of the acrylic resin constituting the acrylic base material include (meth)acryl such as polymethyl (meth)acrylate, polyethyl (meth)acrylate, and methyl (meth)acrylate-butyl (meth)acrylate copolymer. acid esters.

In one embodiment, the urethane (meth)acrylate has a low haze and a low yellowness index (YI value), and is therefore preferably used for producing an optical film. Therefore, the energy ray-curable resin composition is preferably used for producing an optical film.

An optical film according to one embodiment is obtained by coating an acrylic substrate with the energy ray-curable resin composition. Therefore, the optical film includes an acrylic base material and a coating film made of the energy ray-curable resin composition provided on the acrylic base material. Since the energy ray-curable resin composition has excellent adhesion to acrylic substrates, a coating film made of the energy ray-curable resin composition can be formed without providing a primer layer.

In the optical film, the thickness of the coating made of the energy ray-curable resin composition is not particularly limited, and may be, for example, 2 to 10 μm or 4 to 8 μm.

In one embodiment, the optical film is preferably incorporated into a display device. That is, a display device according to one embodiment includes the optical film. Examples of display devices include liquid crystal displays, plasma displays, and organic EL displays.

The present invention will be described in more detail below based on Examples and Comparative Examples, but the present invention is not limited thereto.

<Raw materials used>
[Polyol]
· Polycaprolactone-based polyol PCL-205: Daicel Co., Ltd. "PLAXEL 205" (product name), bifunctional, hydroxyl value 213.3 mgKOH / g
・Polycaprolactone-based polyol PCL-303: Daicel Co., Ltd. “PLAXEL 303” (product name), trifunctional, hydroxyl value 541.3 mgKOH/g

· Bifunctional polyether polyol BPE-40: Bisphenol A ethylene oxide 4 mol adduct, "Newpol BPE-40" (product name) manufactured by Sanyo Chemical Industries, Ltd., hydroxyl value 276.0 mgKOH / g
- Trifunctional polyether polyol G-480: propylene oxide adduct of glycerin, "DK Polyol G-480" (product name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., hydroxyl value 480.9 mgKOH/g

[Polyisocyanate]
Polyisocyanate IPDI: isophorone diisocyanate, molecular weight 222.29
- Polyisocyanate XDI: xylylene diisocyanate, molecular weight 188.19
- Polyisocyanate TDI: tolylene diisocyanate, molecular weight 174.16

[Hydroxy group-containing (meth)acrylate]
2-hydroxyethyl acrylate: HEA, molecular weight 116.12
2-hydroxypropyl acrylate: HPA, molecular weight 130.14
・Hydroxy group-containing polyfunctional acrylate: pentaerythritol acrylate, "PET-3R" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., hydroxyl value 190 mgKOH / g

<Synthesis of urethane (meth)acrylate>
[Example 1]
Put 41.31 parts by mass of polyisocyanate IPDI in a flask, add 24.62 parts by mass of polycaprolactone-based polyol PCL-205 and 16.26 parts by mass of trifunctional polyether polyol G-480 while stirring, and add 80 parts by mass. C. and allowed to react until the desired free isocyanate content is reached. Next, after adding 0.05 parts by mass of hydroquinone monomethyl ether as a polymerization inhibitor, 17.80 parts by mass of 2-hydroxyethyl acrylate was added, and the residual isocyanate concentration was reduced to less than 0.1% by mass at 70 to 80 ° C. The reaction was carried out until the solution reached the temperature, and urethane acrylate (1) of Example 1 was produced.

[Examples 2-3 and Comparative Examples 1-9]
The types and amounts of polyol, polyisocyanate and hydroxy group-containing (meth) acrylate were changed as shown in Table 1 below, and the rest was the same as in Example 1, Examples 2 to 3. Urethane acrylates (2) to (3) of Comparative Examples 1 to 9 and urethane acrylates (C1) to (C9) of Comparative Examples 1 to 9 were produced.

In addition, in the formulations shown in Table 1, the numerical values written in square brackets below the parts by mass of each raw material represent the molar ratio of each raw material.

[Comparative Example 10]
17.56 parts by mass of polyisocyanate IPDI and 14.87 parts by mass of polyisocyanate XDI are placed in a flask, and 41.86 parts by mass of polycaprolactone-based polyol PCL-205 and 16.06 parts by mass of bifunctional polyol are added while stirring. Add ether polyol BPE-40, add 0.05 parts by mass of hydroquinone monomethyl ether as a polymerization inhibitor, add 5.06 parts by mass of 2-hydroxyethyl acrylate, raise the temperature to 80 ° C., The reaction was allowed to reach the free isocyanate content. Next, 4.61 parts by mass of trifunctional polyether polyol G-480 was added, and the reaction was carried out at 70 to 80° C. until the residual isocyanate concentration was less than 0.1% by mass. ) was manufactured.

[Comparative Example 11]
The urethane of Comparative Example 11 was prepared in the same manner as in Comparative Example 10, except that the types and amounts of the polyol, polyisocyanate, and hydroxy group-containing (meth)acrylate were changed as shown in Table 1 below (parts by mass). Acrylate (C11) was prepared. Comparative Examples 10 and 11 are examples corresponding to Production Examples 1 and 2 of Patent Document 1 above.

The number average molecular weights of the urethane acrylates (1) to (3) and (C1) to (C11) obtained above were measured. Table 1 shows the results.

<Evaluation method>
3 parts by mass of a polymerization initiator ("Omnirad 184" manufactured by IGM Resins B.V.) was added to 100 parts by mass of each of the urethane acrylates (1) to (3) and (C1) to (C11) obtained above. , and uniformly stirred to prepare an energy ray-curable resin composition. The resulting energy ray-curable resin composition was applied to an untreated surface of an acrylic substrate (acrylic film, “Technolloy S000 (thickness: 75 μm)” manufactured by Sumitomo Chemical Co., Ltd.) so that the film thickness after drying was about 5 μm. After coating with a bar coater and drying at 80 ° C. for 1 minute, use a high pressure mercury lamp (80 W / cm x 1 lamp) under a nitrogen atmosphere to irradiate with ultraviolet rays at an integrated illuminance of 600 mJ / cm ² to cure the coating film. Adhesion to substrate, Martens hardness, total light transmittance, haze, and YI value of the resulting cured film were measured and evaluated. The measurement and evaluation methods are as follows.

[Substrate Adhesion]
A 2 mm cross-cut test was carried out according to JIS K5400-8.5:1990, and the residual ratio of the cured film to the acrylic substrate was calculated by the following formula.
Remaining rate (%) = 100 - (number of peeled squares)
Based on the calculated residual ratio, the substrate adhesion was evaluated according to the following criteria.
A: Residual rate is 90% or more B: Residual rate is 70% or more and less than 90% C: Residual rate is less than 70%

[Martens hardness]
The indentation hardness (load) of the cured film was determined using a microhardness tester (“ENT-1100a” by Elionix Co., Ltd., test load of 0.3 mN, triangular pyramid indenter, edge interval of 115 degrees). Martens hardness (HM) is obtained from the formula HM = F / As (h). is the divided value. A higher Martens hardness indicates a higher hardness of the coating film.

[Total light transmittance and haze]
Using Haze Meter NDH4000 (product name) manufactured by Nippon Denshoku Industries Co., Ltd., the total light transmittance and haze of the cured film were measured.

[YI value]
The YI value (initial) of the cured film was measured by a transmission method using a spectral color difference meter SD-6000 (product name) manufactured by Nippon Denshoku Industries Co., Ltd. Further, after the cured film obtained above was excessively irradiated with ultraviolet rays, the YI value (after excessive UV irradiation) was similarly measured by the transmission method using the spectrocolorimeter. The UV over-irradiation condition was set to an integrated illuminance of 2000 mJ/cm ² using a high-pressure mercury lamp (80 W/cm×1 lamp).

The results are shown in Table 1. In Comparative Examples 8 to 11 corresponding to Patent Document 1, the adhesiveness to the acrylic substrate was excellent, but the Martens hardness was low and the hardness of the cured film was poor. Moreover, the YI value, especially the YI value after excessive UV irradiation, was high, and the yellowness of the cured film was inferior.

On the other hand, urethane having a number average molecular weight in the range of 1500 to 3000 obtained by reacting a bifunctional polycaprolactone-based polyol, a trifunctional polyether polyol, an alicyclic polyisocyanate and 2-hydroxyethyl (meth)acrylate In Examples 1 to 3, which are (meth)acrylates, the adhesion to the acrylic substrate is excellent, and the Martens hardness is higher than in Comparative Examples 8 to 11, and the hardness of the cured film is improved. rice field. In addition, the total light transmittance was high, the haze and YI values were low, and the film had excellent properties for use as an optical film.

Comparative Example 1 using a trifunctional polycaprolactone-based polyol as the polyol and Comparative Example 2 using 2-hydroxypropyl acrylate as the hydroxy group-containing (meth)acrylate were inferior in adhesion to the acrylic substrate. In Comparative Example 3, in which an aromatic polyisocyanate was used as the polyisocyanate, the adhesiveness to the acrylic substrate was poor, the hardness of the cured film was low, and the YI value after UV irradiation was high. In Comparative Example 4, in which trimethylolpropane was used as the polyol used in combination with the bifunctional polycaprolactone-based polyol, the adhesion to the acrylic substrate was poor. In Comparative Example 5, in which the number average molecular weight is too large, the hardness of the cured film is low.

<Combination use of urethane (meth)acrylate and (meth)acrylate monomer>
[Example 4]
70 parts by mass of the urethane acrylate (1) of Example 1 and 30 parts by mass of acryloylmorpholine ("ACMO" (product name) manufactured by KJ Chemicals Co., Ltd.) were mixed, and a polymerization initiator (manufactured by IGM Resins BV " Omnirad 184”) was added and stirred uniformly to prepare an energy ray-curable resin composition. Using the obtained energy ray-curable resin composition, a cured film was prepared in the same manner as in Example 1, and the obtained cured film was evaluated for substrate adhesion, Martens hardness, total light transmittance, haze, and YI. values were measured and evaluated.

[Examples 5 and 6]
Instead of the urethane acrylate (1), the urethane acrylate (2) of Example 2 was used in Example 5, the urethane acrylate (3) of Example 3 was used in Example 6, and the rest was the same as in Example 4. An energy ray-curable resin composition was prepared, and the resulting cured film was measured and evaluated for substrate adhesion, Martens hardness, total light transmittance, haze, and YI value.

The results are as shown in Table 2. Even when the urethane acrylates (1) to (3) of Examples 1 to 3 were used in combination with other (meth)acrylate monomers, the substrate adhesion to the acrylic substrate was excellent. , the Martens hardness was high, and the hardness of the cured film was improved. In addition, the total light transmittance was high, the haze and YI values were low, and the film had excellent properties for use as an optical film.

It should be noted that the various numerical ranges described in the specification can be arbitrarily combined with their upper and lower limits, and all combinations thereof are described in this specification as preferred numerical ranges. Further, the description of the numerical range "X to Y" means X or more and Y or less.

Although several embodiments of the invention have been described above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments, their omissions, replacements, modifications, etc., are included in the invention described in the scope of claims and equivalents thereof, as well as being included in the scope and gist of the invention.

Claims (5)

An energy ray-curable resin composition for coating an acrylic substrate, which is used for producing an optical film,
(A) a bifunctional polycaprolactone-based polyol, (B) a trifunctional or higher polyether polyol, (C) an alicyclic polyisocyanate, and (D) 2-hydroxyethyl (meth)acrylate are reacted. The obtained urethane (meth)acrylate having a number average molecular weight of 1500 or more and 3000 or less ,
The ratio of the (A) difunctional polycaprolactone-based polyol to 100 mol% of the total reaction raw materials constituting the urethane (meth)acrylate is 8 to 22 mol%, and the (B) trifunctional or higher polyether polyol the proportion is 5 to 18 mol%,
An energy ray-curable resin composition for coating acrylic substrates. 2. The energy ray -curable resin composition for acrylic base coating according to claim 1, wherein (A) the difunctional polycaprolactone-based polyol has a hydroxyl value of 100 to 300 mgKOH/g. 2. The energy ray-curable resin composition for acrylic base coating according to claim 1, wherein the (B) tri- or higher functional polyether polyol has a hydroxyl value of 190 to 1000 mgKOH/g. An optical film obtained by coating an acrylic substrate with the energy ray-curable resin composition according to any one of claims 1 to 3 . A display device comprising the optical film according to claim 4 .