JP2015145437A - Urethane resin for display buffer layer and resin composition for display buffer layer containing the urethane resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active energy ray-curable urethane resin for an OCR (optically clear resin), which achieves all of excellent fast curability, storage stability, and application suitability, and an active energy ray-curable resin composition containing the above urethane resin.SOLUTION: A urethane resin (E) for a display buffer layer is obtained by the reaction of the following components and has a number average molecular weight of 3000 to 120000. The components are: (A) a polyether diol having a number average molecular weight of 200 to 10000 and prepared by copolymerizing tetrahydrofuran (a1) and at least one compound (a2) selected from a group consisting of neopentyl glycol, tetrahydrofuran having a specific substituent, oxetane, and oxetane having a specific substituent; (B) a dicarboxylic acid having 2 to 20 carbon atoms; (C) an organic diisocyanate and/or a modified product thereof; and (D) a (meth)acrylate having 4 to 100 carbon atoms and an active hydrogen-containing group.

Description

  The present invention relates to an active energy ray-curable urethane resin that is cured by irradiation with an active energy ray and used as a buffer layer between an image display unit of an image display and a front plate, and an active energy ray curable containing the same. It relates to the resin composition.

  Currently, image display displays such as liquid crystal displays (LCDs) and plasma displays (PDPs) are indispensable for many electronic devices such as personal computers, televisions, tablet terminals, and mobile phones. The demand for a large number of constituent optical materials is also growing significantly. In recent years, the panel size has been increased, and further improvements in contrast, brightness, high heat resistance, high adhesion and high transparency are desired.

  In general, in order to further improve the contrast and brightness, it is proposed to fill the space between the image display unit and the front plate with a photosensitive resin {OCR: Optically Clear Resin} to form a buffer layer. (For example, Patent Document 1).

  In Patent Document 1, 2-hydroxyethyl methacrylate half esterified product of polyisoprene maleic anhydride adduct (UC-203: manufactured by Kuraray Co., Ltd.) is used as a resin for OCR. There is a problem in coexistence of sex. Specifically, the acrylate group is preferable to the methacrylate group from the viewpoint of the reaction rate, but the methacrylate group is used because the COOH group and the acrylate group present in the half-esterified product cause Michael addition and gelation occurs. I have to. However, since a methacrylate group is used, poor curing often occurs, resulting in a problem of yield reduction in the image display display manufacturing process. On the other hand, it has been proposed to achieve both fast curability and storage stability by using a urethane resin having an acrylate group (for example, Patent Document 2). However, a urethane resin generally exhibits thixotropic properties. For small displays, the coating suitability deteriorates.

JP 2009-186957 A JP 2007-182557 A

  An object of the present invention is to provide an active energy ray-curable urethane resin for OCR and an active energy ray-curable resin composition containing the same, which can achieve both excellent quick-curing property, storage stability, and coating suitability. It is to provide.

The inventors of the present invention have reached the present invention as a result of studies to achieve the above object. That is, the present invention is the following three inventions.
(I) Tetrahydrofuran (a1), neopentyl glycol, tetrahydrofuran having at least one substituent selected from a hydrocarbon group having 1 to 10 carbon atoms and an alkyl ether group, oxetane, and hydrocarbon having 1 to 10 carbon atoms A polyether diol having a number average molecular weight of 200 to 10,000 obtained by copolymerization with at least one compound (a2) selected from the group consisting of oxetane having at least one substituent selected from a group and an alkyl ether group (A), a dicarboxylic acid (B) having 2 to 20 carbon atoms, an organic diisocyanate and / or a modified product thereof (C), and a (meth) acrylate having an active hydrogen-containing group having 4 to 100 carbon atoms (D) ) Is reacted, and the display buffer having a number average molecular weight of 3000 to 120,000 Layer urethane resin (E).
(II) The resin composition for display buffer layers containing the urethane resin (E) for display buffer layers of the said (I), and a polymerization initiator (F).
(III) Image display unit and front plate of image display, wherein urethane resin (E) for display buffer layer of (I) or resin composition for display buffer layer of (II) is cured by active energy rays Buffer layer between.

The urethane resin for display buffer layer and the resin composition for display buffer layer of the present invention have the following effects.
(1) Expresses fast curability when cured by irradiation with active energy rays.
(2) Storage stability is good.
(3) The coating suitability is good.

  The urethane resin for display buffer layer of the present invention includes tetrahydrofuran (a1), neopentyl glycol, tetrahydrofuran having at least one substituent selected from a hydrocarbon group having 1 to 10 carbon atoms and an alkyl ether group, oxetane, and The number average molecular weight formed by copolymerization with at least one compound (a2) selected from the group consisting of oxetane having at least one substituent selected from a hydrocarbon group having 1 to 10 carbon atoms and an alkyl ether group Polyether diol (A) having 200 to 10,000, dicarboxylic acid (B) having 2 to 20 carbon atoms, organic diisocyanate and / or a modified product thereof (C), and active hydrogen-containing group having 4 to 100 carbon atoms The number average molecular weight obtained by reacting (meth) acrylate (D) having It is a ～120000 is a urethane resin (E).

  In the above and the following, when referring to both and / or “acrylate” and “methacrylate”, when referring to “(meth) acrylate” and “acryl” and / or “methacryl”, “(meth) acryl” May be described respectively.

  The polyether diol (A) used for the urethane resin for display buffer layer of the present invention is at least one substitution selected from tetrahydrofuran (a1), neopentyl glycol, a hydrocarbon group having 1 to 10 carbon atoms and an alkyl ether group. Copolymerized from at least one compound (a2) selected from the group consisting of tetrahydrofuran having a group, oxetane, and oxetane having at least one substituent selected from a hydrocarbon group having 1 to 10 carbon atoms and an alkyl ether group Is a polyether diol obtained by

The number average molecular weight of the polyether diol (A) is 200 to 10,000, preferably 1000 to 8,000.
The number average molecular weight in the present invention is measured under the following conditions.
Apparatus: Gel permeation chromatography Solvent: Tetrahydrofuran Reference substance: Polystyrene Sample concentration: 3mg / ml
Column stationary phase: PLgel MIXED-B
Column temperature: 40 ° C

Examples of the polyether diol (A) include tetrahydrofuran (a1), neopentyl glycol, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2,5-dimethoxytetrahydrofuran, 2-methyloxetane, 2 , 2-dimethyloxetane, 2-ethyloxetane, 2,2-diethyloxetane, 2-ethylhexyloxetane and 3-ethyl-3- (2-ethylhexyloxy) ethyloxetane Examples include coalescence.
Among these, preferred from the viewpoint of elongation at break, storage elastic modulus and coating suitability are tetrahydrofuran (a1) and at least one selected from neopentyl glycol, 3-methyltetrahydrofuran and 2,2-dimethyloxetane. More preferably, it is a copolymer of tetrahydrofuran and neopentyl glycol. (A) may be used individually by 1 type, respectively, and may use 2 or more types together.

  Examples of the dicarboxylic acid (B) having 2 to 20 carbon atoms used in the urethane resin for display buffer layer of the present invention include oxalic acid, malonic acid, dipropylmalonic acid, succinic acid, and 2,2-dimethylsuccinic acid, Glutaric acid, 2-methylglutaric acid, 2,2-dimethylglutaric acid, 2,4-dimethylglutaric acid, 3-methylglutaric acid, 3,3-dimethylglutaric acid, 3-ethyl-3-methylglutaric acid, adipine Acid, 3-methyladipic acid, pimelic acid, 2,2,6,6-tetramethylpimelic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, pentadecanedioic acid, tetradecanedioic acid, heptadecanedioic acid , Octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid, 1,4-cyclohexanedicarboxylic acid and terephthalic acid. Preferred from the viewpoint of elongation at break, storage elastic modulus and coating suitability are aliphatic dicarboxylic acids, more preferably dipropylmalonic acid, 2,2-dimethylsuccinic acid, glutaric acid, 2-methylglutaric acid, 2 2,2-dimethylglutaric acid, 2,4-dimethylglutaric acid, 3-methylglutaric acid, 3,3-dimethylglutaric acid, 3-ethyl-3-methylglutaric acid, 3-methyladipic acid, pimelic acid and 2, 2,6,6-tetramethylpimelic acid. (B) may be used individually by 1 type, respectively, and may use 2 or more types together.

  As the organic diisocyanate (C) used for the urethane resin for display buffer layer of the present invention, a compound having 4 to 50 carbon atoms is preferred, and aliphatic diisocyanate (C1) and alicyclic diisocyanate (C2) having 4 to 50 carbon atoms. ) And modified products thereof (urethane group, carbodiimide group, allophanate group, urea group, biuret group, isocyanurate group and oxazolidone group-containing modified product) (C3) and the like. Examples of the aliphatic diisocyanate (C1) include 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and lysine diisocyanate, and alicyclic diisocyanate (C2). ), For example, isophorone diisocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-bis (isocyanate methyl) cyclohexane, 1,4-bis (isocyanate methyl) Cyclohexane, 4,4′-dicyclohexylmethane diisocyanate, norbornane diisocyanate, etc., and modified products of (C1) or (C2) (urethane group, carbodiimi Group, allophanate group, urea group, biuret group, isocyanurate group and oxazolidone group-containing modified product (C3), for example, biuret-modified 1,6-hexamethylene diisocyanate, isocyanurate-modified 1,6-hexamethylene diisocyanate, isocyanate Examples thereof include nurate-modified isophorone diisocyanate. Among these, the aliphatic diisocyanate having 4 to 30 carbon atoms (C1) is more preferable from the viewpoint of elongation at break and storage elastic modulus, and 2,2,4-trimethylhexamethylene diisocyanate is more preferable. (C) may be used individually by 1 type, respectively, and may use 2 or more types together.

As the (meth) acrylate (D) having an active hydrogen-containing group having 4 to 100 carbon atoms (as a compound) used in the urethane resin for display buffer layer of the present invention, a compound having 5 to 100 carbon atoms is used. Preferably, examples of the active hydrogen-containing group of the (meth) acrylate (D) having an active hydrogen group include a hydroxyl group and an amino group.
Examples of the (meth) acrylate (D1) having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxy-1-adamantyl (meth) acrylate, 2-hydroxybutyl ( (Meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, glycidyl ether of alkyl alcohol having 1 to 24 carbon atoms (alkyl alcohol) and (meth) acrylic acid react Epoxy acrylates, 2-hydroxyethyl acrylamide, 2-acryloxy-2-hydroxyethyl terephthalate, 2-acryloxy-2-hydroxypropyl terephthalate, and their (meth) acrylates and ( Data) obtained by adding an alkylene oxide of 2 to 100 carbon atoms in the acrylic acid (meth) acrylate.
Examples of the (meth) acrylate (D2) having an amino group include tetramethylpiperidinyl (meth) acrylate.
Of these, (meth) acrylate (D1) having a hydroxyl group having 5 to 50 carbon atoms, more preferably 2-hydroxyethyl (meth) acrylate, is more preferable from the viewpoint of elongation at break and storage modulus. It is. (D) may be used individually by 1 type, respectively, and may use 2 or more types together.

  The urethane resin (E) for display buffer layer of the present invention is prepared by, for example, producing a polyester resin having a terminal hydroxyl group obtained by reacting the polyether diol (A) and the dicarboxylic acid (B), and then reacting the organic diisocyanate (C). It can manufacture by making the prepolymer made to make it react, and also (meth) acrylate (D) which has an active hydrogen containing group, and a manufacturing method is not limited. If necessary, a catalyst such as an esterification catalyst and a urethanization catalyst may be used.

  The number average molecular weight of the urethane resin (E) is preferably 3000 to 120,000, more preferably 4000 to 50000.

  The resin composition for display buffer layer of the present invention contains the urethane resin (E) for display buffer layer and a polymerization initiator (F). When (F) is contained, the curability by an active energy ray becomes better.

The urethane resin (E) for display buffer layer used in the resin composition for display buffer layer of the present invention is preferably 1 to 4 based on the weight of the resin composition for display buffer layer from the viewpoint of elongation at break and storage elastic modulus. 90% by weight, more preferably 2 to 80% by weight.
Moreover, content of (E) with respect to the total weight of a urethane resin (E) and a polymerization initiator (F) becomes like this. Preferably it is 70-99.9 weight%, Preferably it is 80-99.5 weight%.

The urethane group concentration of (E) is preferably 0.004 mmol / g to 0.30 mmol / g, more preferably 0.005 mmol / g to 0.20 mmol / g, and still more preferably from the viewpoint of a thixotropic index. 0.008 mmol / g to 0.15 mmol / g. Furthermore, from the viewpoint of storage stability, the water content of (E) is preferably 0.10% by weight or less, more preferably 0.05% by weight or less.
In addition, the urethane group density | concentration in this invention is the value computed by the following formula from the elemental analysis value of (E).
[When (Meth) acrylate (D) having an active hydrogen group is (Meth) acrylate (D1) having a hydroxyl group]
Urethane group concentration [mmol / g] = (mmol number of ammonia molecules generated when sodium hydroxide was added to 1 g of sample and heated)
[When (meth) acrylate (D) having an active hydrogen group is (meth) acrylate (D2) having an amino group]
Urethane group concentration [mmol / g] = (mmol number of ammonia molecules generated when sodium hydroxide was added to 1 g of sample and heated) * {C = O stretch (1690 cm ⁻¹ ) peak area / urethane group by IR measurement / (C = O stretching (1690 cm ⁻¹ ) peak area of urethane group by IR measurement + C═O stretching (1650 cm ⁻¹ ) peak area of amide group by IR measurement)}

  Examples of the polymerization initiator (F) used in the display buffer layer resin composition of the present invention include a polymerization initiator (F1) having an acylphosphine oxide skeleton, a polymerization initiator (F2) having an α-aminoacetophenone skeleton, Polymerization initiator (F3) having a benzyl ketal skeleton, polymerization initiator (F4) having an α-hydroxyacetophenone skeleton, polymerization initiator (F5) having a benzoin skeleton, polymerization initiator (F6) having an oxime ester skeleton, titanocene Examples thereof include a polymerization initiator (F7) having a skeleton and other radical initiators (F8). (F) may be used individually by 1 type, and may use 2 or more types together.

  Examples of the polymerization initiator (F1) having an acylphosphine oxide skeleton include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide [manufactured by BASF (Lucirin TPO)] and bis (2,4,6-trimethylbenzoyl). -Phenylphosphine oxide [manufactured by BASF (Irgacure 819)].

  Examples of the polymerization initiator (F2) having an α-aminoacetophenone skeleton include 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one [manufactured by BASF (Irgacure 907)], 2 -Benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone [manufactured by BASF (Irgacure 369)] and 1,2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1 -[4- (4-morpholinyl) phenyl] -1-butanone [manufactured by BASF (Irgacure 379)].

  Examples of the polymerization initiator (F3) having a benzyl ketal skeleton include 2,2-dimethoxy-1,2-diphenylethane-1-one [manufactured by BASF (Irgacure 651)].

  Examples of the polymerization initiator (F4) having an α-hydroxyacetophenone skeleton include 1-hydroxy-cyclohexyl-phenyl-ketone [manufactured by BASF (Irgacure 184)], 2-hydroxy-2-methyl-1-phenyl-propane- 1-one [manufactured by BASF (Darocur 1173)], 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one [manufactured by BASF (Irgacure 2959) )] And 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one [manufactured by BASF (Irgacure 127)] Is mentioned.

  Examples of the polymerization initiator (F5) having a benzoin skeleton include benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether.

  As the polymerization initiator (F6) having an oxime ester skeleton, for example, 1,2-octanedione-1- (4- [phenylthio) -2- (O-benzoyloxime)] [manufactured by BASF (Irgacure OXE 01)] And ethanone-1- (9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl] -1- (O-acetyloxime) [manufactured by BASF (Irgacure OXE 02)].

  As the polymerization initiator (F7) having a titanocene skeleton, for example, bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl)- Phenyl) titanium [manufactured by BASF (Irgacure 784)].

  Examples of the other polymerization initiator (F8) include 2,3-dimethyl-2,3-diphenylbutane.

  Among the polymerization initiators (F), the polymerization initiator (F1) having an acylphosphine oxide skeleton and the polymerization initiator (F4) having an α-hydroxyacetophenone skeleton are preferable from the viewpoint of fast curability.

  The content of the polymerization initiator (F) in the display buffer layer resin composition of the present invention is preferably 0.05 to 30 based on the weight of the display buffer layer resin composition from the viewpoint of fast curing. % By weight, more preferably 0.1 to 10% by weight.

  The display buffer layer resin composition of the present invention may contain an acid generator (G) as necessary. Examples of the acid generator (G) include an active energy ray acid generator (G1) that generates an acid by active energy rays and a thermal acid generator (G2) that generates an acid by heat. (G) may be used individually by 1 type, and may use 2 or more types together.

  Examples of the active energy ray acid generator (G1) that generates an acid by active energy rays include a sulfonium salt (G11) and an iodonium salt (G12).

  Examples of the sulfonium salt (G11) include triphenylsulfonium tetrafluoroborate, triphenylsulfonium bromide, tri-p-tolylsulfonium hexafluorophosphate, triphenylsulfonium trifluoromethanesulfonate [manufactured by Wako Pure Chemical Industries, Ltd. WPAG-281H], tri-p-tolylsulfonium trifluoromethanesulfonate, [p- (phenylmercapto) phenyl] diphenylsulfonium hexafluorophosphate ["CPI-100P" and [p- (phenylmercapto) phenyl manufactured by San Apro Co., Ltd.] ] Diphenylsulfonium [tri (perfluoroethyl)] trifluorophosphate and the like.

  Examples of the iodonium salt (G12) include iodonium (4-methylphenyl) {4- (2-methylpropyl) phenyl} -hexafluorophosphate [manufactured by BASF (IRGACURE 250)], iodonium [bis (4-t- Butylphenyl)] hexafluorophosphate, iodonium [bis (4-t-butylphenyl)] trifluoro [tris (perfluoroethyl)] phosphate, iodonium [bis (4-methoxyphenyl)] trifluoro [tris (perfluoroethyl) )] Phosphate, iodonium [bis (4-methoxyphenyl)] [tetrakis (perfulphenyl)] borate, and a compound represented by the following chemical formula (1).

  Among these, an iodonium salt (G12) is preferable from the viewpoint of fast curability, and a compound represented by the chemical formula (3) is more preferable.

  Examples of the thermal acid generator (G2) that generates an acid by heat include a sulfonium salt (G21), an iodonium salt (G22), a benzothiazonium salt (G23), an ammonium salt (G24), and a phosphonium salt (G25). And onium salts. However, the compounds mentioned in (G1) are excluded.

  Examples of the sulfonium salt (G21) include (4-hydroxyphenyl) dimethylsulfonium bis (trifluoromethanesulfonyl) imide, (4-hydroxyphenyl) (2-methylbenzyl) methylsulfonium bis (trifluoromethanesulfonyl) imide, (4 -Hydroxyphenyl) benzylmethylsulfonium bis (trifluoromethanesulfonyl) imide, (4-hydroxyphenyl) dimethylsulfonium hexafluorophosphate, (4-hydroxyphenyl) (2-methylbenzyl) methylsulfonium hexafluorophosphate, (4-hydroxyphenyl) ) Benzylmethylsulfonium hexafluorophosphate, (4-hydroxyphenyl) (4-methylbenzyl) methylsulfonium hexafur Orophosphate, (4-hydroxyphenyl) dimethylsulfonium trifluoromethanesulfonate, (4-hydroxyphenyl) (2-methylbenzyl) methylsulfonium trifluoromethanesulfonate, (4-hydroxyphenyl) benzylmethylsulfonium trifluoromethanesulfonate, ( 4-hydroxyphenyl) (4-methylbenzyl) methylsulfonium trifluoromethanesulfonate, (4-acetophenyl) dimethylsulfonium hexafluoroantimonate, (4-benzyloxycarbonyloxyphenyl) dimethylsulfonium hexafluoroantimonate, (4- Benzoyloxyphenyl) dimethylsulfonium hexafluoroantimonate, (4-acetoxyphenyl) dimethyls Examples include rufonium hexafluoroarsenate and (4-benzoyloxyphenyl) dimethylsulfonium hexafluoroarsenate.

  Examples of the iodonium salt (G22) include diphenyliodonium bis (trifluoromethanesulfonyl) imide and (p-nitrophenyl) phenyliodonium hexafluorophosphate.

  Examples of the benzothiazonium salt (G23) include 3-benzylbenzothiazonium hexafluoroantimonate, 3- (4-methoxybenzyl) benzothiazonium hexafluoroantimonate, 2-methylsulfanyl-3-benzyl. Benzothiazonium hexafluoroantimonate, 5-chloro-3-benzylbenzothiazonium hexafluoroantimonate; 3-benzylbenzothiazonium hexafluorophosphate; 3-benzylbenzothiazonium tetrafluoroborate .

  Examples of the ammonium salt (G24) include tetramethylammonium butyltris (2,6-difluorophenyl) borate, tetramethylammonium hexyltris (p-chlorophenyl) borate, tetramethylammonium hexyltris (3-trifluoromethylphenyl) Examples include borate, benzyldimethylphenylammonium butyltris (2,6-difluorophenyl) borate, benzyldimethylphenylammonium hexyltris (p-chlorophenyl) borate, and benzyldimethylphenylammonium hexyltris (3-trifluoromethylphenyl) borate. .

  Examples of the phosphonium salt (G25) include (4-methylphenyl) diphenylphosphonium triflate.

  The content of the acid generator (G) in the display buffer layer resin composition of the present invention is preferably 0 to 30% by weight, based on the weight of the display buffer layer resin composition, from the viewpoint of fast curing. More preferably, it is 0.05 to 25% by weight, and particularly preferably 0.1 to 20% by weight.

  The display buffer layer resin composition of the present invention may contain a thermal radical initiator (H) if necessary. Examples of the thermal radical initiator (H) include an organic peroxide polymerization initiator (H1) and an azo compound polymerization initiator (H2). (H) may be used alone or in combination of two or more.

  Examples of the organic peroxide polymerization initiator (H1) include benzoyl peroxide, t-butyl peroxyacetate, 2,2-di- (t-butylperoxy) butane, t-butyl peroxybenzoate, and n-butyl. 4,4-di- (t-butylperoxy) valerate, di- (2-t-butylperoxyisopropyl) benzene, dicumyl peroxide, di-t-hexyl peroxide, 2,5, -dimethyl-2 , 5, -di (t-butylperoxy) hexane, t-butylcumyl peroxide, di-t-butyl peroxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, 1,1,3,3 -Tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-butylhydride Peroxide and t- butyl trimethylsilyl peroxide.

  Examples of the azo compound polymerization initiator (H2) include azobisisobutyronitrile, 1-[(1-cyano-1-methylethyl) azo] formamide, 2,2′-azobis (N-butyl-2-methyl). Propionamide), 2,2'-azobis (N-cyclohexyl-2-methylpropionamide) and 2,2'-azobis (2,4,4-trimethylpentane).

  The content of the polymerization initiator (H) in the display buffer layer resin composition of the present invention is preferably 0 to 20% by weight based on the weight of the display buffer layer resin composition from the viewpoint of thermosetting. More preferably, it is 0.05 to 10% by weight.

  The display buffer layer resin composition of the present invention can contain a radically polymerizable compound (I) as necessary, and examples of the radically polymerizable compound (I) include (meth) acrylamide compounds having 3 to 35 carbon atoms ( I1), C4-C35 (meth) acrylate compound (I2), C6-C35 aromatic vinyl compound (I3), C3-C35 vinyl ether compound (I4), and other radical polymerizable compounds (I5). (I) may be used individually by 1 type, and may use 2 or more types together.

  Examples of the (meth) acrylamide compound (I1) having 3 to 35 carbon atoms include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N- n-butyl (meth) acrylamide, Nt-butyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) ) Other than (meth) acryloylmorpholine such as acrylamide and N, N-diethyl (meth) acrylamide.

Examples of the (meth) acrylate compound (I2) having 4 to 35 carbon atoms include the following monofunctional to hexafunctional (meth) acrylates.
The “monofunctional to hexafunctional (meth) acrylate” means a (meth) acrylate having 1 to 6 (meth) acryloyl groups, and the same description method is used hereinafter.
Examples of the monofunctional (meth) acrylate include ethyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, tert-octyl (meth) acrylate, isoamyl (meth) acrylate, and decyl (meth) acrylate. , Isodecyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, 4-n-butylcyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, Benzyl (meth) acrylate, 2-ethylhexyl diglycol (meth) acrylate, butoxyethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 4-bromobutyl ( ) Acrylate, cyanoethyl (meth) acrylate, butoxymethyl (meth) acrylate, methoxypropylene mono (meth) acrylate, 3-methoxybutyl (meth) acrylate, alkoxymethyl (meth) acrylate, 2-ethylhexyl carbitol (meth) ) Acrylate, alkoxyethyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) acrylate, 2- (2-butoxyethoxy) ethyl (meth) acrylate, 2,2,2-tetrafluoroethyl (meth) Acrylate, 1H, 1H, 2H, 2H-perfluorodecyl (meth) acrylate, 4-butylphenyl (meth) acrylate, phenyl (meth) acrylate, 2,4,5-tetramethylphenyl (meth) acrylate, 4-chloro Enyl (meth) acrylate, phenoxymethyl (meth) acrylate, phenoxyethyl (meth) acrylate, glycidyl (meth) acrylate, glycidyloxybutyl (meth) acrylate, glycidyloxyethyl (meth) acrylate, glycidyloxypropyl (meth) ) Acrylate, tetrahydrofurfuryl (meth) acrylate, hydroxyalkyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl ( (Meth) acrylate, 4-hydroxybutyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropylene (Meth) acrylate, diethylaminopropyl (meth) acrylate, trimethoxysilylpropyl (meth) acrylate, trimethoxysilylpropyl (meth) acrylate, trimethylsilylpropyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, polyethylene oxide Monomethyl ether (meth) acrylate, oligoethylene oxide monomethyl ether (meth) acrylate, polyethylene oxide (meth) acrylate, oligoethylene oxide (meth) acrylate, oligoethylene oxide monoalkyl ether (meth) acrylate, polyethylene oxide monoalkyl ether (meta ) Acrylate, dipropylene glycol (meth) acrylate, polypropylene Xoxide monoalkyl ether (meth) acrylate, oligopropylene oxide monoalkyl ether (meth) acrylate, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyhexahydrophthalic acid, butoxydiethylene glycol (meth) acrylate, trifluoroethyl (Meth) acrylate, perfluorooctylethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, ethylene oxide (hereinafter referred to as EO) modified phenol (meth) acrylate, EO modified cresol (meth) acrylate , EO-modified nonylphenol (meth) acrylate, propylene oxide (hereinafter referred to as PO) modified nonylphenol (meth) acrylate and EO-modified-2-ethylhexyl (Meth) which does not have vinyl ether groups and / or allyl ether groups, such as acrylate.

  Examples of the bifunctional (meth) acrylate include 1,4-butanedi (meth) acrylate, 1,6-hexanedi (meth) acrylate, polypropylene di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, neopentyl di (meth) acrylate, neopentyl glycol di (meth) acrylate, 2,4-dimethyl-1,5-pentanediol di (meth) acrylate, butylethylpropanediol di (Meth) acrylate, ethoxylated cyclohexanemethanol di (meth) acrylate, polyethylene glycol di (meth) acrylate, oligoethylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, 2-ethyl-2- Cyl-butanediol di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, EO-modified bisphenol A di (meth) acrylate, bisphenol F polyethoxydi (meth) acrylate, polypropylene glycol di (meth) acrylate, oligopropylene Glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 2-ethyl-2-butyl-propanediol di (meth) acrylate, 1,9-nonane (meth) acrylate, propoxylated ethoxylated bisphenol A di (meth) acrylate, tricyclodecane di (meth) acrylate, etc. are mentioned.

  Examples of the trifunctional (meth) acrylate include trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, trimethylolpropane alkylene oxide-modified tri (meth) acrylate, and pentaerythritol tri (meth) acrylate. , Dipentaerythritol tri (meth) acrylate, trimethylolpropane tri ((meth) acryloyloxypropyl) ether, isocyanuric acid alkylene oxide modified tri (meth) acrylate, propionate dipentaerythritol tri (meth) acrylate, tri ( (Meth) acryloyloxyethyl) isocyanurate, hydroxypivalaldehyde-modified dimethylolpropane tri (meth) acrylate, sorbitol tri (meth) a Relate, tri (meth) having 2 to 4 alkylene oxide 30-mole adduct of carbon atoms of the pentaerythritol acrylate, ethoxylated glycerin tri (meth) acrylate.

  Examples of tetrafunctional (meth) acrylates include pentaerythritol tetra (meth) acrylate, sorbitol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, and dipentaerythritol propionate. Examples include tetra (meth) acrylates and tetra (meth) acrylates of 1 to 30 mol adducts of alkylene oxides having 2 to 4 carbon atoms of pentaerythritol and pentaerythritol.

  Examples of pentafunctional (meth) acrylates include sorbitol penta (meth) acrylate and dipentaerythritol penta (meth) acrylate.

  Examples of hexafunctional (meth) acrylates include dipentaerythritol hexa (meth) acrylate, sorbitol hexa (meth) acrylate, phosphazene alkylene oxide-modified hexa (meth) acrylate, and caprolactone-modified dipentaerythritol hexa (meth) acrylate. Is mentioned.

  Examples of the aromatic vinyl compound (I3) having 6 to 35 carbon atoms include vinyl thiophene, vinyl furan, vinyl pyridine, styrene, methyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloromethyl styrene, methoxy styrene, and acetoxy styrene. , Chlorostyrene, dichlorostyrene, bromostyrene, vinyl benzoic acid methyl ester, 3-methylstyrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-propylstyrene, 3-butyl Styrene, 4-butylstyrene, 3-hexylstyrene, 4-hexylstyrene, 3-octylstyrene, 4-octylstyrene, 3- (2-ethylhexyl) styrene, 4- (2-ethylhexyl) styrene, allyl styrene Emissions, isopropenyl styrene, butenylstyrene, octenyl styrene, 4-t-butoxycarbonyl styrene, 4-methoxystyrene and 4-t-butoxystyrene, and the like.

As a C3-C35 vinyl ether compound (I4), the following monofunctional or polyfunctional vinyl ether is mentioned, for example.
The “monofunctional vinyl ether” means a vinyl ether compound having one vinyl group, and the “polyfunctional vinyl ether” means two or more vinyl groups.
Examples of the monofunctional vinyl ether include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, 4-methyl Cyclohexylmethyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether , Tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxy Examples include ethyl vinyl ether, phenyl ethyl vinyl ether, and phenoxy polyethylene glycol vinyl ether.

  Examples of the polyfunctional vinyl ether include ethylene glycol divinyl ether, diethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, bisphenol F alkylene oxide divinyl ether. Divinyl ethers such as: trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl Ether, EO-added trimethylolpropane trivinyl ether, PO-added trimethylolpropane trivinyl ether, EO-added ditrimethylolpropane tetravinyl ether, PO-added ditrimethylolpropane tetravinyl ether, EO-added pentaerythritol tetravinyl ether, PO-added pentaerythritol tetravinyl ether, EO addition Examples thereof include dipentaerythritol hexavinyl ether and PO-added dipentaerythritol hexavinyl ether.

  Other radical polymerizable compounds (I5) include, for example, acrylonitrile, aliphatic vinyl ester compounds (such as vinyl acetate, vinyl propionate and vinyl versatate), aliphatic allyl ester compounds (such as allyl acetate), and halogen-containing single quantities. Other than aromatic ester compounds such as isomers (vinylidene chloride, vinyl chloride, etc.) and olefin compounds (ethylene, propylene, etc.).

  Among these, from the viewpoint of fast curability, (meth) acrylamide compound (I1) having 3 to 35 carbon atoms, (meth) acrylate compound (I2) having 4 to 35 carbon atoms, and 6 to 35 carbon atoms are preferable. The aromatic vinyl compound (I3) and the vinyl ether compound (I4) having 3 to 35 carbon atoms, more preferably the (meth) acrylamide compound (I1) having 3 to 35 carbon atoms and the (meth) having 4 to 35 carbon atoms. Acrylate compound (I2).

  The content of the radical polymerizable compound (I) in the resin composition for a display buffer layer according to the present invention is preferably 0 to 80 weight based on the weight of the resin composition for a display buffer layer from the viewpoint of fast curing. %, More preferably 1 to 50% by weight.

  The resin composition for a display buffer layer of the present invention can contain a solvent, a sensitizer, an adhesion-imparting agent (such as a silane coupling agent), a leveling agent, a polymerization inhibitor, and the like as necessary.

Examples of the solvent include glycol ether (ethylene glycol monoalkyl ether and propylene glycol monoalkyl ether), ketone (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), ester (ethyl acetate, butyl acetate, ethylene glycol alkyl ether acetate). And propylene glycol alkyl ether acetate), aromatic hydrocarbons (toluene, xylene, mesitylene, limonene, etc.), alcohols (methanol, ethanol, normal propanol, isopropanol, butanol, geraniol, linalool, citronellol, etc.) and ethers (tetrahydrofuran and 1 , 8-cineole, etc.). These may be used alone or in combination of two or more.
The content of the solvent is preferably 0 to 96% by weight, more preferably 3 to 95% by weight, and particularly preferably 5 to 90% by weight based on the weight of the display buffer layer resin composition.

  Examples of the sensitizer include ketocoumarin, fluorene, thioxanthone, anthraquinone, naphthiazoline, biacetyl, benzyl and derivatives thereof, perylene, and substituted anthracene. The content of the sensitizer is preferably 0 to 20% by weight, more preferably 1 to 15% by weight, and particularly preferably 5 to 10% by weight based on the weight of the resin composition for display buffer layer.

  Examples of the adhesion-imparting agent include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, vinyltriethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, urea Examples thereof include propyltriethoxysilane, tris (acetylacetonate) aluminum and acetylacetate aluminum diisopropylate, terpene resin, and hydrogenated terpene resin. The content of the adhesion-imparting agent is preferably 0 to 50% by weight, more preferably 1 to 40% by weight, and particularly preferably 5 to 25% by weight, based on the weight of the display buffer layer resin composition.

  Examples of the leveling agent include fluorine-based leveling agents (perfluoroalkylethylene oxide adducts, etc.) and silicone-based leveling agents (amino polyether-modified silicone, methoxy-modified silicone, polyether-modified silicone, etc.). The content of the leveling agent is preferably 2% by weight or less, more preferably 0.05 to 1% by weight, particularly preferably 0 based on the weight of the resin composition for display buffer layer, from the viewpoint of the effect of addition and transparency. .1 to 0.5% by weight.

  Examples of the polymerization inhibitor include hydroquinone and methyl ether hydroquinone. The content of the polymerization inhibitor is preferably 0 to 1% by weight, more preferably 0 to 0.1% by weight, based on the weight of the display buffer layer resin composition.

  The resin composition for a display buffer layer of the present invention further comprises inorganic fine particles, a dispersant, an antifoaming agent, a thixotropic agent, a slip agent, a flame retardant, an antistatic agent, an antioxidant, a plastic, depending on the purpose of use. An agent (such as polybutadiene) and an ultraviolet absorber can be contained.

  The resin composition for a display buffer layer of the present invention comprises a urethane resin (E) for a display buffer layer having a number average molecular weight of 3000 to 120,000, a polymerization initiator (F), and an acid generator (G) and a thermal radical as necessary. It can be obtained by mixing and stirring the initiator (H), other radically polymerizable compound (I), solvent and other components with a disperser or the like. The mixing and stirring temperature is usually 10 ° C to 40 ° C, preferably 20 ° C to 30 ° C.

Examples of the method of applying the urethane resin for display buffer layer and the resin composition for display buffer layer of the present invention to the substrate include known coating methods such as spin coating, roll coating and spray coating, and lithographic printing, carton printing, and metal printing. In addition, known printing methods such as offset printing, screen printing, and gravure printing can be applied. In addition, ink-jet coating that continuously discharges fine droplets can also be applied.
A coating film thickness is 0.5-300 micrometers normally as a film thickness after hardening drying. The upper limit is preferably 250 μm from the viewpoints of drying properties and curability, and the lower limit is preferably 1 μm from the viewpoints of wear resistance, solvent resistance, and contamination resistance.

  When the urethane resin for display buffer layer and the resin composition for display buffer layer of the present invention are diluted with a solvent, it is preferably dried after coating. Examples of the drying method include hot air drying (such as a dryer). The drying temperature is usually 10 to 200 ° C, the upper limit is preferably 150 ° C from the viewpoint of the smoothness and appearance of the coating film, and the lower limit is preferably 30 ° C from the viewpoint of the drying speed.

  As an energy source when curing the urethane resin for display buffer layer and the resin composition for display buffer layer of the present invention by irradiation with actinic rays, in addition to a commonly used high-pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, High power metal halide lamps and the like (the latest trend of UV / EB curing technology, edited by Radtech Institute, CM Publishing, page 138, 2006) can be used. Moreover, the irradiation apparatus using an LED light source can also be used conveniently. Heating may be performed for the purpose of diffusing the acid generated from the photoacid generator during and / or after irradiation with actinic rays. The heating temperature is usually 30 ° C to 200 ° C, preferably 35 ° C to 150 ° C, more preferably 40 ° C to 120 ° C.

As an energy source for curing the urethane resin for display buffer layer and the resin composition for display buffer layer of the present invention by electron beam irradiation, a commonly used electron beam irradiation device can be used.
The irradiation amount (Mrad) of electron beam is usually 0.5 to 20, curable urethane resin for display buffer layer and resin composition for display buffer layer and flexibility of cured product, damage to cured film and substrate. From the viewpoint of avoidance, it is preferably 1-15.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to these. Hereinafter, unless otherwise specified, parts are parts by weight.

Production Example 1
[Synthesis of copolymer of tetrahydrofuran and 3,3-dimethyloxetane (A-3)]
A pressure-resistant reaction vessel equipped with a stirrer, a condenser, a thermometer, and a dropping pump was charged with 90 parts of 1,4-butanediol (molecular weight 90.12) and 3 parts of a 25% aqueous solution of tetramethylammonium hydroxide. It dehydrated under reduced pressure (2 kPa) at ° C. Next, 12 parts of a 25% toluene solution of triisobutylaluminum was added, and 1510 parts of tetrahydrofuran (molecular weight 72.11) and 3,3-dimethyloxetane (molecular weight 86.13) (manufactured by Alfa Aesar) at 70 ° C. with stirring. After 200 parts of the mixed solution was continuously introduced over 4 hours, the mixture was aged at the same temperature for 4 hours. After adding 30 parts of water, 5 parts of Kyoward 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) as an adsorbent was mixed and stirred for 30 minutes, and then filtered off. Subsequently, the volatile component was distilled off under reduced pressure (3 kPa) at 130 ° C. for 2 hours to obtain 1800 parts of the intended (A-3) (colorless liquid). The number average molecular weight was 1800.

Production Example 2
[Synthesis of copolymer of tetrahydrofuran and 2,5-dimethyltetrahydrofuran (A-6)]
Except for changing tetrahydrofuran from 1510 parts to 182 parts and 200 parts of 3,3-dimethyloxetane to 28 parts of 2,5-dimethyltetrahydrofuran (molecular weight 100.16) (manufactured by Tokyo Chemical Industry), the same as in Production Example 1. 300 parts of the intended (A-6) (colorless liquid) were obtained. The number average molecular weight was 300.

Production Example 3
[Synthesis of copolymer of tetrahydrofuran and 3-ethyl-3- (2-ethylhexyloxy) ethyloxetane (A-7)]
From 1510 parts to 5850 parts of tetrahydrofuran, 200 parts of 3,3-dimethyloxetane were added to 3-ethyl-3- (2-ethylhexyloxy) ethyloxetane (molecular weight 228.4) (“OXT-212 (EHOX) manufactured by Toagosei Co., Ltd.) ) Except for changing to 2060 parts, 8000 parts of the intended (A-7) (colorless viscous liquid) were obtained in the same manner as in Production Example 1. The number average molecular weight was 8,000.

Production Example 4
[Synthesis of Acid Generator (G2-1) {Compound Represented by Chemical Formula (1)}]

  In a flask equipped with a stirrer, a condenser, a thermometer, and a dropping pump, 6.5 parts of toluene, 8.1 parts of isopropylbenzene, 5.35 parts of potassium iodide, and 20 parts of acetic anhydride are dissolved in 70 parts of acetic acid. Then, a mixed solution of 12 parts of concentrated sulfuric acid and 15 parts of acetic acid was added dropwise over 1 hour while maintaining the temperature at 10 ± 2 ° C. It heated up to 25 degreeC and stirred for 24 hours. Thereafter, 50 parts of diethyl ether was added to the reaction solution, washed with water three times, and diethyl ether was distilled off under reduced pressure. An aqueous solution in which 118 parts of potassium {trifluoro [tris (perfluoroethyl)] phosphate} was dissolved in 100 parts of water was added to the residue, followed by stirring at 25 ° C. for 20 hours. Thereafter, 500 parts of ethyl acetate was added to the reaction solution, washed three times with water, and the organic solvent was distilled off under reduced pressure to obtain 5.0 parts of the desired acid generator (G2-1) (pale yellow solid). It was.

Comparative Production Example 1: Example in which the number average molecular weight of (A) is less than 200 [Synthesis of copolymer of tetrahydrofuran and 3,3-dimethyloxetane (A′-3)]
11 parts for comparison (A′-3) (colorless liquid) were prepared in the same manner as in Production Example 1 except that tetrahydrofuran was changed from 1510 parts to 90 parts and 3,3-dimethyloxetane was changed from 200 parts to 10 parts. Obtained. The number average molecular weight was 190.

Comparative production example 2: Example in which the number average molecular weight of (A) is larger than 10,000 [Synthesis of copolymer of tetrahydrofuran and 3,3-dimethyloxetane (A′-4)]
(A′-4) (colorless high viscosity liquid) for comparison in the same manner as in Production Example 1, except that tetrahydrofuran is changed from 1510 parts to 10515 parts and 3,3-dimethyloxetane is changed from 200 parts to 1395 parts. 12000 parts were obtained. The number average molecular weight was 12000.

Comparative Production Example 3: Example in which monomer copolymerized with tetrahydrofuran (a1) is other than compound (a2) [Synthesis of copolymer of tetrahydrofuran and propylene oxide (A′-5)]
Comparative (A′-5) (colorless) in the same manner as in Production Example 1, except that tetrahydrofuran is changed from 1510 parts to 2670 parts and 200 parts of 3,3-dimethyloxetane are changed to 240 parts of propylene oxide (molecular weight 58). (Viscous liquid) 3000 parts were obtained. The number average molecular weight was 3000.

Comparative Production Example 4: Example where (A) does not contain tetrahydrofuran (a1) [Synthesis of 3,3-dimethyloxetane homopolymer (A′-6)]
3000 parts for comparison (A′-6) (colorless viscous liquid) in the same manner as in Production Example 1 except that 1510 parts of tetrahydrofuran are not used and 3,3-dimethyloxetane is changed from 200 parts to 2910 parts. Got. The number average molecular weight was 3000.

Comparative Production Example 5: Example in which (B) has more than 20 carbon atoms [Synthesis of polybutadiene dicarboxylic acid (B′-1)]
A flask equipped with a stirrer, a condenser, a thermometer, and a dropping pump was charged with 100 parts of polybutadiene diol (“NISSO-PB G-1000 (number average molecular weight 1000: carbon number 70)” manufactured by Nippon Soda) and heated to 80 ° C. While maintaining the temperature at 80 ± 10 ° C., 20 parts of 30% hydrogen peroxide water was added dropwise over 5 hours, followed by stirring for 24 hours. Thereafter, it was washed with water three times to obtain 102 parts of the target acid generator (B′-1) (colorless viscous liquid).

Comparative Production Example 6: Example in which carbon number of (D) is larger than 100 A flask equipped with a stirrer, a condenser, a thermometer, and a Dean-Stark tube for dehydration, 10 parts of acrylic acid, polyethylene glycol having hydroxyl groups at both ends (manufactured by Sanyo Chemical) 230 parts of “PEG4500” weight average molecular weight 4500: 102 carbon atoms), 300 parts of toluene, 5 parts of sulfuric acid and 1 part of hydroquinone were charged, heated to 110 ° C., and reacted for 12 hours.
10 parts of triethylamine was added to neutralize the reaction catalyst, and then the reaction solvent and excess triethylamine were distilled off to obtain 240 parts of (D′-1) (white solid) for comparison. The number average molecular weight was 4600.

Examples 1-16, Comparative Examples 2-14
[Synthesis and evaluation of basic physical properties of urethane resin (E) for display buffer layer]
In a flask equipped with a stirrer, a condenser, a thermometer and an air compressor, 0.03 part of an esterification catalyst (“Neostan U-600” manufactured by Nitto Kasei), and (A) of the number of blending parts shown in Tables 1 and 2 and (B) was added all at once and stirred for 24 hours while maintaining the temperature at 230 ± 5 ° C. The temperature was lowered to 100 ° C., 1000 parts of ethyl methyl ketone and (C) of the blending parts shown in Tables 1 and 2 were added all at once, and the mixture was stirred for 24 hours while maintaining the temperature at 100 ± 5 ° C. The temperature was lowered to 70 ° C., the air compressor was started, and aeration into the solution in the flask was started. Then, (D) in the number of blending parts shown in Tables 1 and 2 was added all at once, and the temperature was adjusted to 70 ± 5. The mixture was stirred for 10 hours while maintaining the temperature. The target display buffer layer urethane resins (E-1) to (E-16) by distilling off the organic solvent under reduced pressure at 40 ° C., and the comparative display buffer layer urethane resins (E′-2) to (E'-14) was obtained.

Examples 17 to 32, Comparative Examples 15 to 28: Evaluation of physical properties before curing of (E) and (E ′) Urethane resins (E-1) to (E-16) of the present invention and a comparative urethane resin (E Table 3 shows the results of performance evaluation of “-1) to (E′-14) by the following method.

[Performance evaluation method of resin before curing]
(1) Number average molecular weight Apparatus: Gel permeation chromatography Solvent: Tetrahydrofuran Reference substance: Polystyrene Sample concentration: 3 mg / ml
Column stationary phase: PLgel MIXED-B
Column temperature: 40 ° C

(2) Urethane group concentration 1 g of sodium hydroxide is added to 1 g of each of (E) and (E ′), and measured using an elemental analyzer [“TruSpec Micro CHNS” manufactured by LECO]. The urethane group concentration was calculated.
[(E-1) to (E-14), (E-16) and (E'-1) to (E'-14)]
Urethane group concentration [mmol / g] = (mmol number of ammonia molecules generated when sodium hydroxide was added to 1 g of sample and heated)
[(E-15)]
Urethane group concentration [mmol / g] = (mmol number of ammonia molecules generated when sodium hydroxide was added to 1 g of sample and heated) * {C = O stretch (1690 cm ⁻¹ ) peak area / urethane group by IR measurement / (C = O stretching (1690 cm ⁻¹ ) peak area of urethane group by IR measurement + C═O stretching (1650 cm ⁻¹ ) peak area of amide group by IR measurement)}
In addition, [Hitachi High-Tech "Fourier transform infrared spectrometer Nicolet iS50 FT-IR"] was used for IR measurement.

(3) Viscosity Based on JIS-K7117, the viscosity at 38 ° C. was measured using a B-type viscometer. A preferable area | region from a viewpoint of coating appropriateness is 100-3000 Pa * s, More preferably, it is 150-2000 Pa * s.

(4) Thixotropic Index Viscosity at a shear rate of 0.01 s- ^{1 to} 10 s- ¹ was measured at 38 ° C using a rheometer [TA Instruments "AR-2000"]. An index was calculated.
Thixotropic index =
{(Viscosity at a shear rate of 10 s- ¹ )-(Viscosity at a shear rate of 0.01 s- ¹ )}
/ (Viscosity of shear rate 10s- ¹ )
From the viewpoint of proper coating, the preferred region is ± 1.0 or less, more preferably ± 0.5 or less.

(5) Water resistance Each (E) and (E ′) was immersed in water at 30 ° C. for 24 hours, and judged according to the following criteria. ○ Judgment: Change in number average molecular weight is less than 10% x Judgment: Change in number average molecular weight is 10% or more.

(6) Total light transmittance Based on JIS-K7136, it measured using the total light transmittance measuring apparatus ["haze-garddual" made by BYK gardner]. A preferable region from the viewpoint of transparency is 91% or more, and more preferably 92% or more.

(7) Storage stability It stored at 100 degreeC in the airtight container substituted by nitrogen atmosphere, and judged that it gelatinized when the viscosity became 8000 Pa.s (38 degreeC).

The following were used for (A), (B), (C), (D), (A ′), (B ′), (C ′), and (D ′) described in Tables 1 and 2.
Tetrahydrofuran and neopentyl glycol copolymer (Mn = 1800) (A-1): “PTX-G 1800” manufactured by Asahi Kasei Fibers
Tetrahydrofuran and neopentyl glycol copolymer (Mn = 1000) (A-2): “PTX-G 1000” manufactured by Asahi Kasei Fibers
Tetrahydrofuran and 3,3-dimethyloxetane copolymer (Mn = 1800) (A-3): Compound of Production Example 1 Tetrahydrofuran and 3-methyltetrahydrofuran copolymer (Mn = 3000) (A-4): Hodogaya Chemical "PTG-L 3000"
Copolymer of tetrahydrofuran and 3-methyltetrahydrofuran (Mn = 1000) (A-5): “PTG-L 1000” manufactured by Hodogaya Chemical
Copolymer of tetrahydrofuran and 2,5-dimethyltetrahydrofuran (A-6): Compound of Production Example 2 Copolymer of tetrahydrofuran and 3-ethyl-3- (2-ethylhexyloxy) ethyloxetane (A-7): Compound of Production Example 3

  Dicarboxylic acid (B): All made by Tokyo Chemical Industry

2,2,4-trimethylhexamethylene diisocyanate (C1-1): “TMDI” manufactured by Evonik
1,6-hexamethylene diisocyanate (C1-2): “Desmodur H” manufactured by Sumitomo Bayer Urethane
Isophorone diisocyanate (C2-1): "Desmodur I" made by Sumitomo Bayer Urethane
1,3-bis (isocyanatomethyl) cyclohexane (C2-2): “Takenate 600” manufactured by Mitsui Chemicals
4,4′-dicyclohexylmethane diisocyanate (C2-3): “Desmodur W” manufactured by Sumitomo Bayer Urethane
Norbornane diisocyanate (C2-4): “NBDI” manufactured by Mitsui Chemicals Fine
Biuret-modified 1,6-hexamethylene diisocyanate (C3-1): “Duranate 24A-100” manufactured by Asahi Kasei
Isocyanurate-modified-1,6-hexamethylene diisocyanate (C3-2): “Duranate TPA-100” manufactured by Asahi Kasei
Isocyanurate-modified isophorone diisocyanate (C3-3): “VESTANAT 1890/100” manufactured by Evonik Degussa Japan

2-Hydroxyethyl acrylate (D1-1): “BHEA” manufactured by Nippon Shokubai
2-Hydroxypropyl acrylate (D1-2): Nippon Shokubai "HPA"
4-hydroxybutyl acrylate (D1-3): “4HBA” manufactured by Osaka Organic Chemical Industry
2-Hydroxyethylacrylamide (D1-4): “HEAA” manufactured by Kojin
2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid (D1-5): “Light acrylate HOA-MPE” manufactured by Kyoeisha Chemical Co., Ltd.
Hydroxyl-terminated decaethylene glycol acrylate (D1-6): NOF "Blemmer AE-400" (10 carbon atoms)
2-Hydroxyethyl methacrylate (D1-7): “HEMA” manufactured by Nippon Shokubai
Glycerin dimethacrylate (D1-8): “Blemmer GMR-H” (11 carbon atoms) manufactured by NOF
Hydroxyl-terminated tridecapropylene glycol methacrylate (D1-9): NOF "Blenmer PP-800" (43 carbon atoms)
Hydroxyl terminal (decaethylene glycol / pentapropylene glycol) methacrylate (D1-10): NOF “Blenmer 55PET-800” (44 carbon atoms)
Tetramethylpiperidinyl methacrylate (D2-1): Hitachi Chemical “Fancryl FA-712HM”

Reaction product of polypropylene maleic anhydride adduct and 2-hydroxyethyl methacrylate (E′-1): “UC-203 (number average molecular weight 35,000)” manufactured by Kuraray
Polytetramethylene glycol (A'-2): "PTMG-3000" manufactured by Mitsubishi Chemical
Tetrahydrofuran and 3,3-dimethyloxetane copolymer (Mn = 190) (A′-3): compound of Comparative Production Example 1 Tetrahydrofuran and 3,3-dimethyloxetane copolymer (Mn = 12000) (A ′ -4): Compound of Comparative Production Example 2 Tetrahydrofuran and propylene oxide copolymer (A′-5): Compound of Comparative Production Example 3 3,3-dimethyloxetane homopolymer (A′-6): Comparative production Compound of Example 4 Polybutadienedicarboxylic acid (B′-1): Compound of Comparative Production Example 5, 1,3,5-pentanetricarboxylic acid (B′-2): 4,4 ′, 4 ″ -methylidyne manufactured by Tokyo Chemical Industry Tris (isocyanate benzene) (C′-1): hydroxyl group-terminated polyethylene glycol methacrylate (D′-1) manufactured by BCO Sciences: Compound of Comparative Production Example 6 Suritoruji / triacrylate (D'-2): Kyoeisha Chemical Co., Ltd. "Light Acrylate PE3A"

In Comparative Example 1, since COOH groups remain, gelation occurs in a storage stability test. In Comparative Example 2, since (A) obtained by monopolymerization of tetrahydrofuran is solid at 38 ° C., (E) is also solid and cannot be applied. In Comparative Example 3, when the number average molecular weight of (A) is less than 200, the viscosity is too low, there is a problem with liquid dripping, and the urethane group concentration is also high, so there is a problem with the thixotropic index. On the other hand, in Comparative Example 4, even when the number average molecular weight of (A) is less than 200, it can be adjusted to an appropriate viscosity if devised, but there is a problem in hydrolysis resistance because the ester group concentration increases. In Comparative Example 5, when the number average molecular weight of (A) is larger than 10,000, (E) becomes a solid and cannot be applied. In Comparative Example 6, when (A) does not contain (a2), the interaction between the polymer chains becomes strong, the viscosity becomes very high, and coating cannot be performed. On the other hand, in Comparative Example 7, when (A) does not contain tetrahydrofuran (a1), the interaction between the polymer chains is too weak, and there is a problem with dripping. In Comparative Examples 8 to 10, when a compound having more than two functional groups is used as (B) or (C), it cannot be applied because it becomes gelled or solid. In Comparative Example 11, when the carbon number of (D) is larger than 100, the viscosity becomes very high and coating is impossible. In Comparative Example 12, when a compound having more than two functional groups is used as (D), there is a problem in storage stability. In Comparative Example 13, when the number average molecular weight of (E) is less than 3000, there is a problem in dripping because the viscosity is very low. In Comparative Example 14, when the number average molecular weight of (E) is larger than 120,000, there is a problem in dripping because the viscosity is very low. Moreover, in Comparative Examples 2-14, the total light transmittance is low.
In contrast to the above comparative examples, it can be seen that the urethane resin (E) for display buffer layer of the present invention has good viscosity, thixotropic index, water resistance, transparency, and storage stability.

Examples 33 to 48, Comparative Examples 29 to 42: Evaluation of physical properties after curing of (E) and (E ′) Urethane resins (E-1) to (E-16) for display buffer layer of the present invention and for comparison Display buffer layer urethane resins (E'-1) to (E'-14) 95 parts each and Irgacure 184 (E4-1) (BASF) 5 parts are mixed together, and mixed and stirred uniformly with a disperser. The display buffer layer resin compositions (Q-1) to (Q-16) and comparative display buffer layer resin compositions (Q′-1) to (Q′-14) of the present invention were obtained. In addition, about (E) whose property is solid, it heated up to 60 degreeC and mix | blended in the melted state.

[Evaluation of curing speed]
(Q-1) to (Q-16) and (Q′-1) to (Q′-14) were subjected to surface treatment and a PET (polyethylene terephthalate) film having a thickness of 100 μm [Cosmo Shine manufactured by Toyobo Co., Ltd. A4300] was applied using an applicator so as to have a film thickness of 20 μm, and was exposed using a belt conveyor type UV irradiation apparatus (Egraphics Corporation “ECS-151U”). Unsaturation bond at 1600 cm- ¹ before and after exposure with a transmission IR ("FT / IR-460Plus" manufactured by Nihon Bunko Co., Ltd.) with an exposure dose of 365 nm and shaking with 100, 300, 500 and 1000 mJ / cm ² From the disappearance degree of the reaction rate, the reaction rate (%) was calculated by the following formula.
Calculation formula of reaction rate (%) = 100 × (absorbance before exposure−absorbance after exposure) / absorbance before exposure

[Performance evaluation of cured resin]
Each of the resin compositions for display buffer layers obtained in Examples 33 to 48 and Comparative Examples 29 to 42 was subjected to a release treatment on the surface, and a 100 μm thick PET (polyethylene terephthalate) film ["PET-38C manufactured by Lintec". ]] Was applied using an applicator so as to have a film thickness of 200 μm, and was exposed using a belt conveyor type UV irradiation apparatus (“Egraphics Co., Ltd.“ ECS-151U ”). The exposure amount was 1000 mJ / cm ² at 365 nm. In addition, about (E) whose property is solid, it heated to 60 and applied in the state melted. After the exposure, the cured coating film was peeled off from the releasable treated PET film to obtain a test piece for evaluation.
Table 4 shows the results of performance evaluation of the cured coating film by the following method.

[Performance evaluation method for cured film]
(1) Elongation at break Each test piece was measured with a tensile tester (Orientec “Tensilon”) at a temperature of 25 ° C., a load of 5 kgf, and a pulling speed of 5 mm / min. From the viewpoint of substrate followability, it is preferably 500% or more.
(2) Storage elastic modulus About each test piece, the storage elastic modulus (Pa) (25 degreeC) was measured with the measurement frequency of 1 Hz using the viscoelasticity measuring apparatus ("DMS6100" by Seiko Instruments). From the viewpoint of impact resistance, the pressure is preferably 10 ⁴ to 10 ⁷ Pa.
(3) Total light transmittance Based on JIS-K7136, it measured with the total light transmittance measuring apparatus ["haze-garddual" made by BYK gardner]. A preferable region from the viewpoint of transparency is 91% or more, and more preferably 92% or more.
(4) Curing Shrinkage The specific gravity of the resin liquid before curing and the solid after curing was measured with an electronic hydrometer (SD-120L manufactured by MIRAGE).

  From the comparison of Examples 33 to 36, the elongation at break and cure shrinkage are the best values when the molecular weight is around 10,000. Moreover, it turns out from a comparative example that there exists a subject in breaking elongation, storage elastic modulus, transparency, and cure shrinkage other than the resin composition for display buffer layers of this invention.

Example 49: Evaluation as OCR (E-3) 30 parts, dicyclopentenyloxyethyl methacrylate [Hitachi Chemical "FA-512M"] (I2-1) 15 parts, 2-hydroxybutyl methacrylate [manufactured by Kyoeisha Chemical Co., Ltd.] Light ester HOB "] (I2-2) 5 parts, hydrogenated terpene resin [Yasuhara Chemical" Clearon P85 "] 10 parts, polybutadiene [Evonik" PolyOil 110 "] 33 parts, Lucirin TPO (F1-1 as a polymerization initiator) ) 2 parts [made by BASF], 5 parts Irgacure 184 (F4-1) (made by BASF), 0.1 part Irganox 1010 [made by BASF] and 0.1 part Irganox 1520L (made by BAFS) Mix in a lump, and mix and stir uniformly with a disperser. To give a layer resin composition (Q-17).

Example 50: Evaluation as OCR Resin composition for display buffer layer of the present invention (Q-18) in the same manner as in Example 49 except that 0.5 part of acid generator (G2-1) was newly added. Got.

Comparative Example 43: Evaluation as OCR A comparative display buffer layer resin composition (Q′-15) was prepared in the same manner as in Example 64 except that (E-3) was changed to (E′-1). Obtained.

[Evaluation of curing speed]
Each resin composition for display buffer layer obtained in Examples 49 and 50 and Comparative Example 43 was applied to a 100 μm thick PET (polyethylene terephthalate) film [Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.]. The film was applied to a film thickness of 20 μm and exposed using a belt conveyor type UV irradiation apparatus (“EICS-151U”, iGraphics Co., Ltd.). Unsaturation bond at 1600 cm ⁻¹ before and after exposure with a transmission IR (“FT / IR-460 Plus” manufactured by Nihon Bunko Co., Ltd.) with an exposure dose of 365 nm and shaking with 100, 300, 500 and 1000 mJ / cm ² From the disappearance degree of the reaction rate, the reaction rate (%) was calculated by the following formula.
Calculation formula of reaction rate (%) = 100 × (absorbance before exposure−absorbance after exposure) / absorbance before exposure

[Performance evaluation of cured resin]
Table 5 shows the results of the performance evaluation of the cured resins of Examples 49 and 50 and Comparative Example 43 and the evaluation of the following shielding part curability in the same manner as in Examples 33 to 48 and Comparative Examples 29 to 42. Show.

[Evaluation of curability of shielding part]
Each resin composition for display buffer layer obtained in Examples 49 and 50 and Comparative Example 43 was applied to a 100 μm thick PET (polyethylene terephthalate) film [Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.]. The film is applied to a film thickness of 20 μm, placed on the coated film coated with a black polycarbonate plate, and using a belt conveyor type UV irradiation device (“Egraphics Co., Ltd.“ ECS-151U ”). Then, exposure was performed. The exposure amount was 1000 mJ / cm ² at 365 nm.
After the exposure, the black polycarbonate plate is removed, and transmission IR (“FT / IR-460Plus” manufactured by Nihon Bunko Co., Ltd.) is used at 1600 cm ⁻¹ at each point 2 cm from the exposed / exposed part to the shielding part. From the disappearance degree of the unsaturated bond, the reaction rate (%) was calculated by the following formula.
Calculation formula of reaction rate (%) = 100 × (absorbance before exposure−absorbance after exposure) / absorbance before exposure

  The urethane resin for display buffer layer and the resin composition for display buffer layer containing the same of the present invention, even when it is a composition for OCR, fast curing, elongation at break, transparency of storage elastic modulus, low curing shrinkage and It is possible to satisfy all of the shielding part curability.

  The urethane resin for display buffer layer and the resin composition for display buffer layer containing the same of the present invention are suitable for coating before curing (viscosity, thixotropic index), high transparency of cured film after curing, and storage stability. Since it is excellent in substrate followability (elongation at break), low curing shrinkage and shielding part curability, it is useful as a buffer layer between the image display unit of the image display and the front plate.

Claims (13)

  Tetrahydrofuran (a1), neopentyl glycol, tetrahydrofuran having at least one substituent selected from a hydrocarbon group having 1 to 10 carbon atoms and an alkyl ether group, oxetane, and a hydrocarbon group having 1 to 10 carbon atoms and an alkyl A polyether diol (A) having a number average molecular weight of 200 to 10,000 obtained by copolymerization with at least one compound (a2) selected from the group consisting of oxetane having at least one substituent selected from ether groups , A dicarboxylic acid (B) having 2 to 20 carbon atoms, an organic diisocyanate and / or a modified product thereof (C), and a (meth) acrylate (D) having an active hydrogen-containing group having 4 to 100 carbon atoms. Display buffer layer window having a number average molecular weight of 3000 to 120,000. Tan resin (E).   The polyether diol (A) is tetrahydrofuran (a1), neopentyl glycol, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2,5-dimethoxytetrahydrofuran, 2-methyloxetane, 2,2 -Coordination with at least one compound selected from the group consisting of dimethyloxetane, 2-ethyloxetane, 2,2-diethyloxetane, 2-ethylhexyloxetane and 3-ethyl-3- (2-ethylhexyloxy) ethyloxetane. The urethane resin for a display buffer layer according to claim 1, which is a polymer.   The dicarboxylic acid (B) having 2 to 20 carbon atoms is oxalic acid, malonic acid, dipropylmalonic acid, succinic acid, 2,2-dimethylsuccinic acid, glutaric acid, 2-methylglutaric acid, 2,2- Dimethyl glutaric acid, 2,4-dimethyl glutaric acid, 3-methyl glutaric acid, 3,3-dimethyl glutaric acid, 3-ethyl-3-methyl glutaric acid, adipic acid, 3-methyl adipic acid, pimelic acid, 2, 2,6,6-tetramethylpimelic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, pentadecanedioic acid, tetradecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid, The display buffer layer according to claim 1 or 2, which is at least one selected from the group consisting of 1,4-cyclohexanedicarboxylic acid and terephthalic acid. Urethane resin.   The organic diisocyanate and / or its modified product (C) is an aliphatic diisocyanate (C1) having 4 to 50 carbon atoms, an alicyclic diisocyanate (C2) having 4 to 50 carbon atoms and a modified product thereof (urethane group, carbodiimide group). The urethane resin for a display buffer layer according to any one of claims 1 to 3, which is at least one selected from the group consisting of (C3), an allophanate group, a urea group, a biuret group, an isocyanurate group and an oxazolidone group-containing modified product). .   The aliphatic diisocyanate (C1) is at least one selected from the group consisting of 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and lysine diisocyanate, Cyclic diisocyanate (C2) is isophorone diisocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-bis (isocyanate methyl) cyclohexane, 1,4-bis ( Isocyanate methyl) cyclohexane, 4,4′-dicyclohexylmethane diisocyanate, and norbornane diisocyanate, and the modified product (C3) is bisulfur. Tsu DOO modified 1,6-hexamethylene diisocyanate, isocyanurate-modified 1,6-hexamethylene diisocyanate and at least one kind of claim 4, wherein the display buffer layer urethane resin selected from the group consisting of isocyanurate-modified isophorone diisocyanate.   The (meth) acrylate (D) having an active hydrogen-containing group having 4 to 100 carbon atoms is a (meth) acrylate (D1) having a hydroxyl group and / or a (meth) acrylate (D2) having an amino group. The urethane resin for display buffer layers according to claim 1.   (Meth) acrylate (D1) having a hydroxyl group is 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxy-1-adamantyl (meth) acrylate, 2-hydroxybutyl (meth) Acrylate, 4-hydroxybutyl (meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, epoxy acrylate in which glycidyl ether of alkyl alcohol having 1 to 24 carbon atoms and (meth) acrylic acid are reacted, 2-hydroxy Ethyl acrylamide, 2-acryloxy-2-hydroxyethyl terephthalate, 2-acryloxy-2-hydroxypropyl terephthalate, and these (meth) acrylates and (meth) acrylic acids have 2 to 100 carbon atoms 7. The (meth) acrylate (D2) having at least one selected from the group consisting of (meth) acrylates to which ruxylene oxide is added and having an amino group is tetramethylpiperidinyl (meth) acrylate. Urethane resin for display buffer layer.   The resin composition for display buffer layers containing the urethane resin (E) for display buffer layers in any one of Claims 1-7, and a polymerization initiator (F).   Polymerization initiator (F) is acylphosphine oxide derivative polymerization initiator (F1), α-aminoacetophenone derivative polymerization initiator (F2), benzyl ketal derivative polymerization initiator (F3), α-hydroxyacetophenone derivative. At least one radical polymerization initiation selected from the group consisting of a polymerization initiator (F4), a benzoin derivative polymerization initiator (F5), an oxime ester derivative polymerization initiator (F6) and a titanocene derivative polymerization initiator (F7). The resin composition for a display buffer layer according to claim 8, which is an agent.   The display buffer layer according to claim 8 or 9, wherein the content of the urethane resin (E) for the display buffer layer is 1 to 90% by weight, and the content of the polymerization initiator (F) is 0.05 to 30% by weight. Resin composition.   The resin composition for a display buffer layer according to any one of claims 8 to 10, further comprising an acid generator (G) that generates an acid by active energy rays.   The resin composition for a display buffer layer according to claim 11, wherein the acid generator (G) that generates an acid by active energy rays is a sulfonium salt and / or an iodonium salt.   The urethane resin for display buffer layers according to any one of claims 1 to 7 or the resin composition for display buffer layers according to any one of claims 8 to 12 that is cured by active energy rays. A buffer layer between the unit and the front plate.