JP5529786B2 - Flexible optical sheet - Google Patents

Description

  The present invention relates to a flexible optical sheet used for a key sheet (key top sheet, key mat sheet, etc.), a light guide sheet, a reflective sheet, an optical transparent adhesive tape base material, etc. for electrical / electronic devices or optical devices.

  With recent miniaturization and sophistication of optical and electronic devices, optical sheets such as light guide sheets or films (or light guide plates) are required to have various characteristics depending on the application. The light guide sheet used is required to have elasticity and flexibility to be bent by being pressed by a hand or the like. Furthermore, an illumination type key for using a terminal at night or in a dark place is adopted in a mobile device such as a mobile phone.

  For example, as shown in FIG. 1, an illumination key switch structure of a cellular phone that has been thinned in recent years has been developed to illuminate with an LED light source 6 or the like from the side portion of the operation surface. . In this switch structure, a click dome 4 that is a spring member made of metal or the like is formed on the flexible printed wiring board 5, and the light from the light source 6 is guided on the click dome 4. For this purpose, a light guide sheet 3 is formed. Further, an embossed key top sheet 1 and a key mat sheet 2 are laminated on the light guide sheet 3 as an operation panel (operation surface) of an illumination type key. By clicking, the key mat sheet 2 laminated on the back surface of the key top sheet 1 comes into contact with the light guide sheet 3 and the click dome 4 is pressed. That is, in this switch structure, the key top sheet 1, the key mat sheet 2, and the light guide sheet 3 need to be bent by clicking. Furthermore, since the light from the light source 6 is guided by the light guide sheet 3 and passes through the key mat sheet 2 and the key top sheet 1, these sheets are required to have transparency.

  As an optical sheet used for such applications, JP-A-8-112822 (Patent Document 1) discloses a thin-walled portion and a base portion made of drawn polyethylene terephthalate and a Shore D hardness of 40 degrees or more. There is disclosed a pushbutton switch cover member in which a key top portion made of a high hardness resin is integrated. This document describes that the high-hardness resin may be selected from general resins such as silicone, urethane, epoxy, acrylic, and PET.

  In JP-A-10-172379 (Patent Document 2), a film in which a display portion curved in the same shape is integrally formed on the upper surface side of a key top body made of a thermoplastic material molded by a mold. In the sheet-like key top of the push button switch thus formed, the film is a multilayer elastic film having two or more layers, and the display portion is printed on the key top body side of the multilayer elastic film to form the display portion printed layer. A sheet-like key top structure is disclosed. This document discloses a multilayer elastic film in which an elastic film composed of various thermoplastic elastomers and a base material composed of various hard thermoplastic resins are laminated. A key top sheet in which nylon is laminated on both sides of a thermoplastic elastomer film is described.

  However, in these sheets, it is difficult to satisfy both mechanical properties such as flexibility and toughness, transparency, durability (heat resistance, weather resistance, water resistance, etc.) and moldability. For example, with silicone resins and urethane resins that are widely used as key top sheets, sheets made of silicone resins have low moldability and transparency, and sheets made of urethane resins are heat and water resistant. , Hydrolysis resistance and moldability are not sufficient. Furthermore, since thermoplastic resins or elastomers are not sufficient in heat resistance and transparency and are molded by extrusion, it is difficult to produce a thin film or a film having a smooth surface.

  On the other hand, as a sheet composed of a thermosetting resin, Japanese Patent Application Laid-Open No. 2008-62217 (Patent Document 3) applies a radiation curable paint containing a radiation curable silicone compound on a substrate to form a coating film. A step of forming, a step of covering the surface of the coating film with a release substrate having a silicone-treated surface so that the silicone-treated surface is in contact with the coating film, and irradiating the coating film covered with the release substrate with radiation. There is disclosed a method for forming a cured coating film comprising a step of curing the film and a step of peeling the release substrate from the cured coating film. This document describes silicone-modified urethane (meth) acrylate as a radiation-curable silicone compound. Furthermore, the obtained cured film is used for articles that require contamination resistance, abrasion resistance, and transparency, such as wallpaper; furniture, bathrooms, kitchens, decorative sheets or makeup for home appliances (air conditioners, televisions, refrigerators, etc.). It is described that it is used as a protective film for a material; an interior material for automobiles; a protective layer for an optical disk; a display (liquid crystal display or the like). However, while the cured resin has high heat resistance and rigidity, thermal shrinkage easily occurs due to crosslinking. Moreover, when such a sheet | seat is applied to a keytop sheet | seat, it will be easy to tear when peeling a base material in a manufacturing process.

JP-A-8-112822 (Claim 1, paragraph [0012]) JP-A-10-172379 (claims 1 to 3, paragraph [0012], examples) JP 2008-62217 A (claims, paragraphs [0029] [0058])

  Accordingly, an object of the present invention is to provide an optical sheet having high transparency, high flexibility, and excellent toughness, moldability and processability, and a method for producing the same.

  Another object of the present invention is to provide an optical sheet having a low thermal shrinkage rate and excellent dimensional stability and a method for producing the same.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have a high transparency and a high flexibility when the optical sheet is composed of a cured product of a polymerizable composition containing a vinyl oligomer having a specific molecular weight. In addition, the present inventors have found that the toughness is improved because the entanglement between molecular chains increases, and that the moldability and workability are excellent, and the present invention has been completed.

  That is, the optical sheet of the present invention is composed or formed of a cured product of a polymerizable composition containing a vinyl oligomer having a number average molecular weight of 2000 to 50000. In the polymerizable component having an α, β-ethylenically unsaturated double bond in the polymerizable composition, the number average molecular weight (hereinafter simply referred to as “weighted average” per α, β-ethylenically unsaturated double bond) The “weighted average double bond equivalent” may be about 1000 to 10,000. The vinyl oligomer may be urethane (meth) acrylate [for example, aliphatic urethane (meth) acrylate]. The glass transition temperature of the vinyl oligomer [eg, urethane (meth) acrylate] may be about −80 ° C. to −30 ° C. The polymerizable composition may further contain at least one vinyl monomer selected from a monofunctional vinyl monomer, a bifunctional vinyl monomer, and a trifunctional vinyl monomer. The ratio (weight ratio) between the vinyl oligomer [eg, urethane (meth) acrylate] and the vinyl monomer is about the former / the latter = 90/10 to 10/90.

  The optical sheet of the present invention is composed or formed of a cured product of a polymerizable composition containing a bifunctional urethane (meth) acrylate having a number average molecular weight of 2000 to 50000, a trifunctional vinyl monomer, and a monofunctional vinyl monomer. May be. The bifunctional urethane (meth) acrylate may have a number average molecular weight per α, β-ethylenically unsaturated double bond (hereinafter sometimes simply referred to as “double bond equivalent”) of about 1000 to 20000. Good. In the polymerizable component having an α, β-ethylenically unsaturated double bond in the polymerization composition, the number average molecular weight in terms of weighted average per α, β-ethylenically unsaturated double bond is about 1000 to 10,000. There may be. The monofunctional vinyl monomer may contain at least one monofunctional (meth) acrylate selected from a heterocyclic (meth) acrylate containing a nitrogen atom as a heterocyclic atom and a bridged cyclic (meth) acrylate. Good.

  The glass transition temperature of the cured product of the polymerizable composition may be about -80 ° C to 100 ° C. The cured product of the polymerizable composition may be a photocured product (in particular, a photocured product obtained by irradiating an electron beam and substantially free of a polymerization initiator). The elongation at break of the optical sheet of the present invention is about 100 to 300%. The tensile elastic modulus of the optical sheet of the present invention is about 1 to 150 MPa. The optical sheet of the present invention may have a haze of 5% or less and a total light transmittance of 90% or more. The optical sheet of the present invention is a kind selected from a key sheet (key top sheet, key mat sheet, etc.), a light guide sheet, a reflective sheet, and an optical transparent adhesive tape substrate (Optical Clear Adhesive (OCA) tape substrate). It can be suitably used as a sheet.

  In the present invention, a coating step of applying a polymerizable composition containing a vinyl-based oligomer [e.g., urethane (meth) acrylate] on a substrate, curing the applied polymerizable composition by irradiation with active energy rays The manufacturing method of the said optical sheet containing the hardening process to perform and the peeling process which peels the hardened | cured material of polymeric composition from the said base material is also contained.

  In the present specification, a vinyl oligomer having a polymerizable group and a vinyl monomer may be collectively referred to as a polymerizable component. Further, in the present specification, “number average molecular weight in weighted average per α, β-ethylenically unsaturated double bond” means the total amount of polymerizable components having α, β-ethylenically unsaturated double bonds. The double bond equivalent of the weighted average of For example, a polymerizable component having an α, β-ethylenically unsaturated double bond is an A component (having three ethylenically unsaturated double bonds in one molecule and a number average molecular weight is Ma), a B component ( 2 ethylenically unsaturated double bonds per molecule, number average molecular weight Mb), C component (one ethylenically unsaturated double bond per molecule, number average molecular weight Mc) In the polymerizable composition containing the A component as Wa parts by weight, the B component as Wb parts by weight, and the C component as Wc parts by weight, the number average as the weighted average per α, β-ethylenically unsaturated double bond The molecular weight can be calculated by the following formula (1).

  As the number average molecular weight of the low molecular weight polymerizable component, a value calculated from the chemical formula and the atomic weight can be adopted.

  In the present invention, since the optical sheet is composed of a cured product of a polymerizable composition containing a vinyl oligomer having a specific molecular weight [for example, urethane (meth) acrylate], it has high transparency and high flexibility. Also excellent in toughness, moldability and productivity. In the polymerizable component of the polymerizable composition, when the number average molecular weight in the weighted average per α, β-ethylenically unsaturated double bond is increased, the thermal shrinkage rate can be lowered and the dimensional stability can be improved. Moreover, in this invention, it is excellent also in durability, such as heat resistance and a weather resistance. The optical sheet of the present invention is suitable for a key top sheet and the like, and can be effectively prevented from being broken when it is peeled off from a substrate after printing in the key top sheet manufacturing process.

FIG. 1 is a schematic diagram showing a switch structure of a lighted key of a thin cellular phone.

[Optical sheet]
The optical sheet of the present invention is composed of a cured product of a polymerizable composition containing a vinyl oligomer having a specific molecular weight. In the present invention, since a vinyl oligomer having a specific molecular weight is contained, the toughness can be improved because the entanglement points between the molecular chains are increased, and even if the elastic limit is exceeded, it does not break easily. Furthermore, in the present invention, the crosslinking density can be reduced, the thermal shrinkage rate is small, and the dimensional stability can be improved.

(Vinyl oligomer)
Examples of vinyl oligomers include oligomers having a polymerizable group, such as urethane (meth) acrylate, polyester (meth) acrylate [for example, polyvalent carboxylic acid, polyol, (meth) acrylic acid and / or hydroxyalkyl (meth) acrylate. Polyester (meth) acrylates produced by the reaction with the like]; Epoxy (meth) acrylates [for example, epoxy compounds having a plurality of epoxy groups (polyhydric alcohol type, polyvalent carboxylic acid type, bisphenol A, F, S, etc. (Epoxy (meth) acrylates with ring-opening addition of (meth) acrylic acid to epoxy resins such as bisphenol type and novolac type)]; polyacryl (meth) acrylate [for example, (meth) acrylic monomers and glycidyl (meth) ) Copolymer with acrylate Polyacrylic (meth) acrylates with ring-opening addition of (meth) acrylic acid to epoxy groups]; polyether (meth) acrylates; polybutadiene-based (meth) acrylates; melamine (meth) acrylates; polyacetal (meth) acrylates, etc. it can. These vinyl oligomers can be used alone or in combination of two or more. Among these vinyl oligomers, an oligomer having a (meth) acryloyl group, for example, at least one (meth) acrylic oligomer selected from urethane (meth) acrylate, polyester (meth) acrylate and polyether (meth) acrylate In particular, urethane (meth) acrylate is preferable from the viewpoint of flexibility.

  Urethane (meth) acrylates are polyisocyanates [or urethane prepolymers having a free isocyanate group produced by reaction of polyisocyanates and polyols] and (meth) acrylates [for example, hydroxyalkyl (Meth) acrylate etc.] is made of urethane (meth) acrylate obtained by reacting.

  Polyisocyanates are not particularly limited as long as they have two or more isocyanate groups in the molecule. For example, aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, heterocyclic polyisocyanates, and polyisocyanates thereof. Examples include isocyanate derivatives. Of these, aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, polyisocyanate derivatives, and the like are often used.

Examples of the aliphatic polyisocyanate include diisocyanates [for example, C _2-16 alkanes such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate (TMDI). Diisocyanate, 2,6-diisocyanatomethylcaproate, lysine diisocyanate (LDI), etc.], polyisocyanates having 3 or more isocyanate groups in the molecule (for example, lysine ester triisocyanate, 1,3,6-hexamethylene) Triisocyanate, C _6-20 alkane triisocyanate such as 1,6,11-undecane triisocyanate methyloctane) and the like.

  Examples of the alicyclic polyisocyanate include diisocyanates (for example, 1,4-cyclohexane diisocyanate, isophorone diisocyanate (IPDI), 4,4′-methylenebis (cyclohexyl isocyanate), hydrogenated xylylene diisocyanate, hydrogenated bis (isocyanatophenyl). ) Methane, norbornane diisocyanate, etc.), polyisocyanates having 3 or more isocyanate groups in the molecule (for example, 1,3,5-trimethylisocyanatocyclohexane, 2- (3-isocyanatopropyl) -2,5-di (Isocyanatomethyl) -bicyclo [2.2.1] heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo [2.2.1] Triisocyanates such as heptane Over, such as theft), and the like.

  Examples of the aromatic polyisocyanate include diisocyanates (for example, phenylene diisocyanate, 1,5-naphthylene diisocyanate (NDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), diphenylmethane diisocyanate (MDI), and tolylene diene. Isocyanate (TDI), 4,4′-toluidine diisocyanate (TODI), 4,4′-diphenyl ether diisocyanate, 1,3-bis (isocyanatophenyl) propane, etc.), poly having three or more isocyanate groups in the molecule Isocyanates (eg, triisocyanates such as 1,3,5-triisocyanatomethylbenzene, triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 4,4′-diisocyanate) Enirumetan 2,2 ', like tetraisocyanates such as 5,5'-tetra isocyanate) and the like.

  Examples of the polyisocyanate derivatives include dimer, trimer, biuret, allophanate of polyisocyanate, and polyisocyanate having 2,4,6-oxadiazinetrione ring, which is a polymer of carbon dioxide and the above polyisocyanate monomer. Isocyanates, carbodiimides, uretdiones and the like.

  These polyisocyanates can be used alone or in combination of two or more. Among these polyisocyanates, aliphatic diisocyanates such as HDI, alicyclic diisocyanates such as IPDI and hydrogenated XDI, araliphatic diisocyanates such as XDI, and aromatic diisocyanates such as TDI, MDI and NDI may be used. Non-aromatic polyisocyanates such as non-aromatic polyisocyanates, for example, aliphatic diisocyanates such as HDI, alicyclic diisocyanates such as IPDI and hydrogenated XDI, or derivatives thereof when high weather resistance is required (Such as a trimer having an isocyanurate ring) may be used.

Examples of the polyols include aliphatic diol [alkanediol (ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene ether glycol, 1,3-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1, C _2-10 alkane diols such as 6-hexanediol), diethylene glycol, triethylene glycol, dipropylene glycol, etc.], cycloaliphatic diols (1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, etc.) s, hydrogenated bisphenol such as hydrogenated bisphenol a, or an C _2-4 alkylene oxide adduct thereof), aromatic aliphatic diols and aromatic diols (xylylene glycol, bis Phenol A, bisphenol S, bisphenol such as bisphenol F, or a diol such as these _{C 2-4} alkylene oxide adduct thereof), triols (glycerol, trimethylolethane, trimethylolpropane, 1,2,6 Hexanetriol, triethanolamine and the like), tetraols (such as pentaerythritol, sorbitan or derivatives thereof), hexaols (such as dipentaerythritol), and polymer polyols.

  The polymer polyols include polyester polyols, polyether polyols, polyether ester polyols, polycarbonate polyols, polyester amide polyols, polymer polyols such as acrylic polymer polyols, and the like.

  The polyester polyol may be, for example, a reaction product of a polycarboxylic acid (or its anhydride) and a polyol, or a reaction product obtained by ring-opening addition polymerization of a lactone with respect to an initiator.

Polycarboxylic acids include dicarboxylic acids [for example, aromatic dicarboxylic acids or anhydrides thereof (terephthalic acid, isophthalic acid, phthalic anhydride, etc.), alicyclic dicarboxylic acids or anhydrides thereof (tetrahydrophthalic anhydride, het anhydride, etc. , Hymic anhydride, etc.), aliphatic dicarboxylic acid or its anhydride (succinic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid and other C _4-20 alkanedicarboxylic acid, maleic anhydride, fumaric acid etc. Saturated dicarboxylic acid etc.)], polyvalent carboxylic acids (for example, trimellitic acid, trimellitic anhydride, pyromellitic anhydride, etc.) or alkyl esters of these carboxylic acids. Of these polycarboxylic acids, aliphatic dicarboxylic acids or anhydrides thereof (C _6-20 alkane dicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid) are preferable. These polycarboxylic acids can be used alone or in combination of two or more. Examples of the polyol include the aliphatic diol, the alicyclic diol, and the aromatic diol. These polyols can be used alone or in combination of two or more.

Examples of lactones include C such as γ-butyrolactone (GBL), γ-valerolactone, δ-valerolactone, β-methyl-δ-valerolactone, γ-caprolactone, and enanthlactone (7-hydroxyheptanoic acid lactone). _3-10 lactone etc. are mentioned. These lactones can be used alone or in combination of two or more. Of these lactones, C _4-8 lactones such as valerolactone and caprolactone are preferred.

Initiators for lactones include, for example, water, oxirane compounds (eg, C _2-6 alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, etc.) or copolymers [eg, polyethylene glycol (PEG) , Polypropylene glycol (PPG), polytetramethylene ether glycol (PTMG), etc.], low molecular weight polyols (ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexamethylene glycol, trimethylolpropane, glycerin, penta Erythritol, bisphenol A, etc.), compounds having an amino group (for example, ethylenediamine, hexamethylenediamine, hydrazine, xylylenediamine, isophoronediamine). Which diamine compounds, polyamine compounds such as diethylenetriamine, etc.). These initiators can be used alone or in combination of two or more.

Examples of the polyether polyol include a ring-opening polymer of the oxirane compound (for example, poly C _2-4 alkylene glycol such as polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.).

  Examples of the polyether ester polyol include a polyether which is a polymer of the dicarboxylic acid (aromatic dicarboxylic acid, alicyclic dicarboxylic acid, aliphatic dicarboxylic acid, etc.) or a dialkyl ester thereof and the polyether polyol. Examples include ester polyols.

  Examples of the polycarbonate polyol include glycols (alkane diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol; diethylene glycol, dipropylene glycol). (Poly) oxyalkylene glycols such as: 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A and other alicyclic diols; bisphenols such as bisphenol A, alkylene oxide adducts of bisphenols, etc. One or more glycols selected from aromatic diols) and carbonates (dimethyl carbonate, ethylene carbonate, diphenyl carbonate, etc.) or phosgene And the like polymers and the like.

  As the polyesteramide polyol, in the reaction of the polyester polyol (polymerization of dicarboxylic acid and diol, etc.), a terminal carboxyl group-containing polyester and a diamine (for example, an aliphatic group having an amino group such as ethylenediamine, propylenediamine, hexamethylenediamine, etc.) And polyester amide polyol having a diamine as a reaction component.

  As the acrylic polyol, a polymerizable monomer having a hydroxyl group (for example, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, etc.) and a hydroxyl group-free (meth) An acrylic polyol which is a polymer with an acrylic monomer (for example, (meth) acrylic acid or an ester thereof) may be used.

  These polyols can be used individually or in combination of 2 or more types. Of these polyols, polyester polyols, polyether polyols, polycarbonate polyols, and acrylic polyols are preferable from the viewpoints of flexibility and versatility. Of these, polyester polyols and polyether polyols are preferable from the viewpoint of flexibility and the like, and polyester polyols are particularly preferable from the viewpoint of excellent moisture absorption stability.

  Examples of the polyurethane prepolymer include a multimer of the polyisocyanates, a bullet-modified multimer of the polyisocyanates, an adduct of the polyisocyanates and the polyols, and an excess of the polyisocyanate with respect to the polyols. Examples thereof include polyurethane prepolymers obtained by reacting isocyanates. These prepolymers can be used alone or in combination of two or more.

  Preferred polyurethane prepolymers include, for example, multimers (trimers, pentamers, heptamers, etc.) of the polyisocyanates, burette multimers (burette-modified products) of the polyisocyanates, the polyisocyanates and polyols. Adducts with diols (triols such as glycerin and trimethylolpropane), polyurethane prepolymers of the diisocyanates and polyester polyols, polyurethane prepolymers of the diisocyanates and polyether polyols, especially the diisocyanates and polyether polyols or polyesters A polyurethane prepolymer with a polyol is preferred.

Examples of the (meth) acrylate having an active hydrogen atom include hydroxy C _2-6 alkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; 2-hydroxy-3- Hydroxyalkoxy C _2-6 alkyl (meth) acrylate such as methoxypropyl (meth) acrylate; hydroxyalkanedi (such as glycerin di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolethane di (meth) acrylate) Meth) acrylates; hydroxyglycans tri (meth) acrylates such as diglycerin tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol tri (meth) acrylate Dipentaerythritol tetra or penta (meth) acrylate can be exemplified.

  These urethane (meth) acrylates can be used alone or in combination of two or more. Of these urethane (meth) acrylates, bifunctional urethane (meth) acrylates are widely used, and aliphatic urethane (meth) acrylates are preferable from the viewpoint of improving the flexibility of the optical sheet.

  Urethane (meth) acrylate is a ratio of polyisocyanate and (meth) acrylate having an active hydrogen atom, which is generally equivalent to an isocyanate group and an active hydrogen atom (isocyanate group / active hydrogen atom = 0.8 / 1). To about 1.2 / 1). In addition, about the manufacturing method of these urethane (meth) acrylate, Unexamined-Japanese-Patent No. 2008-74891 etc. can be referred. The trifunctional or higher polyfunctional urethane (meth) acrylate may be a urethane (meth) acrylate obtained using polyols such as trimethylolpropane, pentaerythritol, dipentaerythritol and the like.

  The number of (meth) acryloyl groups in one molecule of vinyl oligomer [eg urethane (meth) acrylate] can be selected from the range of about 1 to 10, for example 2 to 8, preferably 2 to 6 More preferably, the number is about 2 to 4 (for example, 2 or 3).

  The number average molecular weight of the vinyl oligomer [e.g. urethane (meth) acrylate] can be selected from a range of about 2000 or more (e.g. 2000 to 50000) in terms of polystyrene in gel permeation chromatography (GPC), for example, 2500. -45,000 (for example, 3000-40000), preferably 3500-35000 (for example, 4000-30000), more preferably about 4500-25000 (for example, 4500-20000), and about 10,000 or more (for example, 15000-20000). It may be. If the molecular weight of the vinyl-based oligomer is too large, the crosslinking density is reduced and the heat resistance is lowered. On the other hand, if the molecular weight of the vinyl-based oligomer is too small, the entanglement of the molecules becomes small or the toughness decreases.

  Number average molecular weight per double α, β-ethylenically unsaturated double bond (double bond equivalent) of vinyl oligomer {eg urethane (meth) acrylate [eg bifunctional urethane (meth) acrylate]} (g / mol) ) Can be selected from a range of, for example, about 1000 or more (for example, 1000 to 20000), 1200 to 18000 (for example, 1400 to 16000), preferably 1500 to 15000 (for example, 1800 to 14000), more preferably 2000 to 2000 It is about 12000 (for example, 2200 to 10000), and may be about 5000 or more (for example, 6000 to 10000). If the double bond equivalent of the vinyl oligomer is increased, the weighted average double bond equivalent of the total amount of the polymerizable components can be increased, the crosslinking density can be reduced, and the entanglement by the molecular chain can be improved. Dimensional stability can be improved.

  The glass transition temperature (Tg) of the vinyl oligomer [eg, urethane (meth) acrylate] can be selected, for example, from a range of about −80 ° C. to 80 ° C. (eg, −80 ° C. to 60 ° C.). It may be about -30 ° C, preferably -70 ° C to 0 ° C, more preferably about -65 ° C to -20 ° C (eg, -60 ° C to -30 ° C), and about -80 ° C to -30 ° C. It may be. If the Tg of the vinyl oligomer is too large, the flexibility is lowered. Tg can be measured using a differential scanning thermometer.

(Vinyl monomer)
The polymerizable composition may further contain a vinyl monomer. As a vinyl-type monomer, as long as it is a compound (curing compound) mainly blended for controlling the softness (glass transition temperature) of the polymerizable composition and having an α, β-ethylenically unsaturated double bond, There is no particular limitation.

  Examples of vinyl monomers include monofunctional vinyl monomers [monofunctional (meth) acrylate (or mono (meth) acrylate), etc.], bifunctional vinyl monomers [bifunctional (meth) acrylate (or di (meth) acrylate), etc. ] A trifunctional or higher functional vinyl monomer [a trifunctional or higher functional polyfunctional (meth) acrylate (or poly (meth) acrylate), etc.].

Monofunctional vinyl monomers include, for example, (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl ( (Meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, C _1-24 alkyl (meth) acrylates such as stearyl (meth) acrylate; cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate; dicyclopentanyl (meth) acrylate, dicyclo Bridged cyclic (meth) acrylates such as pentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate; phenyl (meta ) Acrylate, aryl (meth) acrylates such as nonylphenyl (meth) acrylate; aralkyl (meth) acrylates such as benzyl (meth) acrylate; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate hydroxy _{C 2-10} alkyl (meth) acrylate or _{C 2-10} alkanediol mono (meth) acrylate and the like; trifluoroethyl (meth) acrylate, Tetorafuru Ropuropiru (meth) acrylate, fluoroalkyl C _1-10 alkyl (meth) acrylates such as hexafluoroisopropyl (meth) acrylate; alkoxyalkyl such as methoxyethyl (meth) acrylate (meth) acrylate; phenoxyethyl (meth) acrylate, phenoxypropyl Aryloxyalkyl (meth) acrylates such as (meth) acrylate; aryloxy (poly) alkoxyalkyl (meta) such as phenyl carbitol (meth) acrylate, nonylphenyl carbitol (meth) acrylate, nonylphenoxypolyethylene glycol (meth) acrylate ) Acrylate; polyalkylene glycol mono (meth) acrylate such as polyethylene glycol mono (meth) acrylate; 2-meth (Poly) alkylene glycol mono (meta) having substituents (alkyl group etc.) such as ciethyl (meth) acrylate, methyltriethylene glycol (meth) acrylate, ethyl carbitol (meth) acrylate, 2-ethylhexyl diethylene glycol (meth) acrylate ) Acrylate [eg linear or branched C _1-10 alkyl poly C _2-4 alkylene glycol (meth) acrylate etc.]; alkane polyol mono (meth) acrylate such as glycerin mono (meth) acrylate; 2-dimethyl (Meth) acrylates having amino groups such as aminoethyl (meth) acrylate, 2-diethylaminoethyl (meth) acrylate, 2-t-butylaminoethyl (meth) acrylate; glycidyl (meth) acrylate Piperidinyl (meth) acrylate, alkylpiperidinyl (meth) acrylate (such as pentamethylpiperidinyl (meth) acrylate), morpholino (meth) acrylate, tetrahydrofurfuryl (meth) acrylate and other heterocyclic (meta) ) Acrylates; N-vinyl heterocyclic compounds such as N-vinyl pyrrolidone, N-vinyl pyridine, N-vinyl caprolactam; N-vinyl acetamide, N-vinyl formamide and the like.

Examples of bifunctional vinyl monomers include allyl (meth) acrylate; ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,3-propanediol di (meth) acrylate, and 1,4-butanediol. Alkanediol di (meth) acrylates such as di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate; alkane polyol di (meth) such as glycerin di (meth) acrylate Acrylate: Diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polypropylene glycol Polyalkylene glycol di (meth) acrylates such as di (meth) acrylate; 2,2-bis (4- (meth) acryloxyethoxyphenyl) propane, 2,2-bis (4- (meth) acryloxydiethoxyphenyl) ) Di (meth) acrylates of C _2-4 alkylene oxide adducts of bisphenols (bisphenol A, S, etc.) such as propane and 2,2-bis (4- (meth) acryloxypolyethoxyphenyl) propane; Examples include di (meth) acrylates of acid-modified alkane polyols such as pentaerythritol; bridged di (meth) acrylates such as tricyclodecane dimethanol di (meth) acrylate.

Examples of the polyfunctional vinyl monomer include trimethylolpropane tri (meth) acrylate, glycerin tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, and tetramethylolmethane tetra (meth) acrylate. Alkane polyol (meth) acrylate such as dipentaerythritol penta (meth) acrylate and dipentaerythritol hexa (meth) acrylate; Tri (meth) of C _2-4 alkylene oxide adduct of alkane polyol such as trimethylolpropane and glycerin Examples include tri (meth) acrylate having a triazine ring such as acrylate; tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate. Yes.

These vinyl monomers can be used alone or in combination of two or more. Of these vinyl monomers, at least one monomer selected from monofunctional vinyl monomers, bifunctional vinyl monomers, and trifunctional vinyl monomers is preferred. As the bifunctional vinyl-based monomer, for example, (poly) C _2-6 alkylene glycol di (meth) acrylate is widely used, and from the viewpoint of flexibility, poly C _2-6 alkylene glycol di (meth) acrylate is used. Poly C _3-4 alkylene glycol di (meth) acrylate such as polypropylene glycol di (meth) acrylate is preferred from the viewpoint of low skin irritation in addition to flexibility. The average number of repeating oxy C _3-4 alkylene units can be selected from a range of about 1.2 to 30 mol per molecule, for example, 1.5 to 20 mol, preferably 2 to 15 mol, more preferably 3 About 10 mol (for example, 5-9 mol) may be sufficient.

  The number average molecular weight [for example, (meth) acryloyl group equivalent] per α, β-ethylenically unsaturated double bond of the vinyl monomer is, for example, 10 to 500, preferably 50 to 400, and more preferably 100 to 300. It may be a degree.

  A typical polymerizable composition includes a bifunctional urethane (meth) acrylate, a monofunctional vinyl monomer [monofunctional (meth) acrylate, etc.], and a trifunctional vinyl monomer [trifunctional (meth)] as polymerizable components. Acrylate etc.].

The monofunctional vinyl-based monomer is a heterocyclic (meth) acrylate containing a nitrogen atom (N) as a heterocyclic atom [for example, 5-6 members such as (meth) acryloylmorpholine, etc. from the viewpoint of Tg adjustment of a cured product. N-containing heterocyclic (meth) acrylates and the like] and bridged cyclic (meth) acrylates [eg C _6-10 bridged cyclic (meth) acrylates such as isobornyl (meth) acrylate, etc.] It preferably contains a kind of monofunctional (meth) acrylate. The monofunctional vinyl monomer further includes a (meth) acrylate having an aliphatic skeleton, such as an alkyl (poly) alkylene glycol, from the viewpoints of adjusting the viscosity of the polymerizable composition, adjusting the Tg of the cured product, and imparting flexibility. (Meth) acrylate [for example, linear or branched C _1-10 alkyl (poly) C _2-4 alkylene glycol (meth) acrylate such as 2-ethylhexyldiethylene glycol (meth) acrylate] may be included. In the alkyl (poly) alkylene glycol (meth) acrylate, the average added mole number of alkylene oxide (C _2-4 alkylene oxide and the like) is, for example, 1 to 10 moles, preferably 1 to 5 moles, more preferably 1 to 5 moles. About 3 mol may be sufficient.

The trifunctional vinyl monomer is preferably a tri (meth) acrylate of an alkylene oxide (for example, C _2-4 alkylene oxide) adduct of an alkane polyol such as trimethylolpropane or glycerin. In this tri (meth) acrylate, the average added mole number of alkylene oxide (for example, C _2-4 alkylene oxide) is, for example, 1 to 10 mol, preferably 1 to 5 mol, more preferably 1 to 3 mol (for example, 1 or 2 mol).

  The ratio (weight ratio) between the vinyl oligomer [eg, urethane (meth) acrylate] and the vinyl monomer is the former / the latter = 100/0/1/99 depending on the desired softness (glass transition temperature) and the like. For example, the former / the latter = 90/10 to 10/90 (for example, 85/15 to 15/85), preferably 80/20 to 20/80 (for example, 75/25 to 25 / 75), more preferably about 70/30 to 30/70 (for example, 65/35 to 35/65).

For 100 parts by weight of vinyl oligomer {eg, urethane (meth) acrylate [eg, bifunctional urethane (meth) acrylate]},
The proportion of the monofunctional vinyl monomer is, for example, 1 to 200 parts by weight, preferably 5 to 180 parts by weight, more preferably about 10 to 150 parts by weight,
When the monofunctional vinyl-based monomer includes a heterocyclic (meth) acrylate containing a nitrogen atom as a heterocyclic atom, the proportion thereof is, for example, 10 to 200 parts by weight, preferably 50 to 150 parts by weight, and more preferably 80. ~ 120 parts by weight,
When the monofunctional vinyl-based monomer includes a bridged cyclic (meth) acrylate, the ratio is, for example, 1 to 100 parts by weight, preferably 5 to 80 parts by weight, more preferably about 10 to 50 parts by weight. ,
When the monofunctional vinyl-based monomer includes (meth) acrylate having an aliphatic skeleton, the ratio is, for example, 1 to 100 parts by weight, preferably 5 to 80 parts by weight, and more preferably about 10 to 50 parts by weight. Yes,
The proportion of the trifunctional vinyl monomer may be, for example, 1 to 100 parts by weight, preferably 5 to 80 parts by weight, and more preferably about 10 to 50 parts by weight.

  In the polymerization composition, each molecule of the polymerizable component having an α, β-ethylenically unsaturated double bond is mutually overlapped by a π electron cloud of a carbon-carbon double bond, and interacts by van der Waals force. It is exerting. When this polymerizable composition is cured (crosslinked), a covalent bond is formed between the molecules, so that the intermolecular distance is reduced and volume shrinkage occurs. In order to suppress this volume shrinkage, it is advantageous to reduce the number of α, β-ethylenically unsaturated double bonds and increase the molecular weight of the polymerizable component.

  In the polymerization composition having an α, β-ethylenically unsaturated double bond in the polymerizable composition, the number average molecular weight in the weighted average per α, β-ethylenically unsaturated double bond [eg, weighted average (meta)] The acryloyl group equivalent] (g / mol) is, for example, about 1000 or more (for example, 1000 to 10,000), preferably about 1100 to 8000 (for example, 1200 to 6000), and more preferably about 1300 to 5000 (for example, 1500 to 4500). It may be. If the number average molecular weight in the weighted average per α, β-ethylenically unsaturated double bond is too small, the thermal shrinkage rate increases and the dimensional stability decreases, and if it is too large, the crosslinking density decreases and the heat resistance increases. Solvent resistance (ink adhesion, etc.) and mechanical strength are reduced.

(Polymerization initiator)
The polymerizable composition may contain a polymerization initiator. The polymerization initiator may be a thermal polymerization initiator (thermal radical generator such as a peroxide such as benzoyl peroxide) or a photopolymerization initiator (photo radical generator). A preferred polymerization initiator is a photopolymerization initiator. Examples of the photopolymerization initiator include benzoins (benzoin alkyl ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether), phenyl ketones [for example, acetophenones (for example, acetophenone, 2-hydroxy 2-methyl-1-phenylpropan-1-one, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, etc.), 2-hydroxy-2 -Alkyl phenyl ketones such as methylpropiophenone; cycloalkyl phenyl ketones such as 1-hydroxycyclohexyl phenyl ketone], aminoacetophenones {2-methyl-1- [4- (methylthio) phene Lu] -2-morpholinoaminopropanone-1, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1}, anthraquinones (anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone) , 2-t-butylanthraquinone, 1-chloroanthraquinone, etc.), thioxanthones (2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone, etc.), ketals (acetophenone) Dimethyl ketal, benzyl dimethyl ketal, etc.), benzophenones (benzophenone, etc.), xanthones, phosphine oxides (eg 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc.) It can be shown. These photopolymerization initiators can be used alone or in combination of two or more.

  The proportion of the polymerization initiator is 0.1 to 20 parts by weight, preferably 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight (particularly 3 to 8 parts by weight) with respect to 100 parts by weight of the polymerizable component. Part) degree.

  In addition, you may combine a photoinitiator with a photosensitizer. Examples of the photosensitizer include conventional components such as tertiary amines [for example, trialkylamine, trialkanolamine (such as triethanolamine), ethyl N, N-dimethylaminobenzoate, N, N-dimethyl. Dialkylaminobenzoic acid alkyl esters such as amyl aminobenzoic acid, bis (dialkylamino) benzophenones such as 4,4-bis (dimethylamino) benzophenone (Michler's ketone), 4,4′-diethylaminobenzophenone], triphenylphosphine, etc. Examples include phosphines, toluidines such as N, N-dimethyltoluidine, anthracene such as 9,10-dimethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, and 2-ethyl-9,10-diethoxyanthracene. It is done. The photosensitizers may be used alone or in combination of two or more.

  The ratio of the photosensitizer is, for example, about 0.1 to 100 parts by weight, preferably 0.5 to 80 parts by weight, and more preferably about 1 to 50 parts by weight with respect to 100 parts by weight of the photopolymerization initiator. There may be.

  It is preferable that the polymerization initiator (particularly the photopolymerization initiator and photosensitizer) is not substantially contained when the polymerizable composition is cured by irradiation with an electron beam. When it does not contain a polymerization initiator, weather resistance, in particular, difficult yellowing for long-term use is improved.

  In addition to the polymerization initiator, the polymerizable composition is a conventional additive such as an antioxidant, a stabilizer such as a heat stabilizer, a plasticizer, and an antistatic agent, as long as flexibility and transparency are not impaired. Further, it may contain a flame retardant, an ultraviolet absorber and the like.

  Furthermore, the polymerizable composition may be an organic solvent such as ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), ethers (dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic. Hydrocarbons (such as cyclohexane), aromatic hydrocarbons (such as benzene), halogenated carbons (such as dichloromethane and dichloroethane), esters (such as methyl acetate and ethyl acetate), water, alcohols (ethanol, isopropanol, butanol) , Cyclohexanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), cellosolve acetates, amides (dimethylformamide, dimethylacetamide, etc.) and the like.

(Characteristics and manufacturing method of optical sheet)
The optical sheet of the present invention includes a coating step of applying the polymerizable composition on a substrate, a curing step of irradiating the applied polymerizable composition with active energy rays and curing, and curing of the polymerizable composition. It is manufactured through a peeling process for peeling an object from the substrate.

  In the coating step, the substrate is not particularly limited as long as the surface of the cured product can be formed smoothly, and a sheet having a smooth surface and high peelability, such as a plastic sheet (for example, polyethylene terephthalate or polyethylene naphthalate). Polyester sheet such as polyethylene, polypropylene sheet such as polyethylene, polypropylene, styrene sheet such as polystyrene, polyamide sheet such as polyamide 6 and polyamide 66, polycarbonate sheet such as bisphenol A polycarbonate), release paper (for example, silicone) It may be paper treated with a release agent such as a compound or the plastic sheet). Among these base materials, polyester-based sheets such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin-based sheets such as polyethylene and polypropylene are widely used because the surface smoothness of the optical sheet can be easily improved. .

  As a coating method of the polymerizable composition, conventional methods such as roll coater, air knife coater, blade coater, rod coater, reverse coater, bar coater, comma coater, dip squeeze coater, die coater, gravure coater, microgravure coater Examples include coater, silk screen coater method, dip method, spray method, spinner method and the like. Of these methods, the bar coater method and the gravure coater method are widely used.

  When the polymerizable composition contains an organic solvent, it may be dried as necessary after coating. Drying may be performed at a temperature of about 50 to 150 ° C., preferably 60 to 140 ° C., and more preferably about 70 to 130 ° C., for example.

  In the curing step, the polymerizable composition may be cured by heating depending on the type of the polymerization initiator, but it can usually be cured by irradiation with active energy rays. As active energy rays, heat and / or light energy rays can be used, and it is particularly useful to use light energy rays. As light energy rays, radiation (gamma rays, X-rays, etc.), ultraviolet rays, visible rays, electron beams (EB), etc. can be used, and usually ultraviolet rays and electron beams are often used. In particular, when producing a sheet that can be polymerized without using a polymerization initiator and has high weather resistance, it may be irradiated with an electron beam.

As the light source, for example, in the case of ultraviolet rays, a Deep UV lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a halogen lamp, a laser light source (light source such as a helium-cadmium laser or an excimer laser) may be used. it can. The amount of irradiation light (irradiation energy) varies depending on the thickness of the coating film, but may be, for example, about 50 to 10,000 mJ / cm ² , preferably 70 to 7000 mJ / cm ² , and more preferably about 100 to 5000 mJ / cm ² .

  In the case of an electron beam, a method of irradiating an electron beam with an exposure source such as an electron beam irradiation apparatus can be used. The irradiation amount (dose) varies depending on the thickness of the coating film, but is, for example, about 1 to 200 kGy (gray), preferably 5 to 150 kGy, and more preferably 10 to 100 kGy (particularly 20 to 80 kGy). The acceleration voltage is, for example, about 10 to 1000 kV, preferably about 50 to 500 kV, and more preferably about 100 to 300 kV.

  In addition, you may perform irradiation of an active energy ray (especially electron beam) in inert gas (for example, nitrogen gas, argon gas, helium gas, etc.) atmosphere if necessary.

  In the peeling step, the cured product of the polymerizable composition is peeled from the substrate, but a cured product having a smooth surface can be easily obtained by using a sheet having a smooth surface as the substrate. In this invention, since it is excellent in toughness, it can prevent effectively that an optical sheet tears when peeling from a base material.

  The glass transition temperature (Tg) of the cured product (optical sheet) of the obtained polymerizable composition is, for example, -80 ° C to 100 ° C, preferably -50 ° C to 80 ° C, more preferably -20 ° C to 70 ° C. It may be about 20 ° C to 100 ° C (for example, 40 ° C to 80 ° C). In addition, when the glass transition temperature is in the vicinity of 20 ° C., that is, in the vicinity of the temperature to be used, the flexibility becomes softer in the use temperature range and the film becomes tough and firm.

  The tensile elastic modulus of the optical sheet is, for example, about 1 to 150 MPa, preferably 5 to 120 MPa, more preferably about 10 to 100 MPa (for example, 10 to 50 MPa) in accordance with JIS K7161.

  The elongation at break of the optical sheet can be selected from the range of, for example, about 50 to 500% (for example, 55 to 450%) in accordance with JIS K7161, 60 to 400%, preferably 65 to 350%, Preferably, it may be about 70 to 300% (for example, 100 to 300%).

  The optical sheet has high transparency, and the total light transmittance measured according to JIS K7361-1 is, for example, 80% or more (for example, 80 to 100%), preferably 85% or more (for example, 85-99%), more preferably 90% or more (for example, 90-98%). The haze measured according to JIS K7361-1 is, for example, 5% or less (for example, 0.1 to 5%), preferably 3% or less (for example, 0.2 to 3%), and more preferably 2. It is about 5% or less (for example, 0.5 to 2.5%).

  The optical sheet has a small heat shrinkage, and when heated at 80 ° C. for 30 minutes (for example, drying conditions in a general key sheet manufacturing process), the heat shrinkage is, for example, 0.001 to 0.5%. The content is preferably about 0.005 to 0.4%, more preferably about 0.1 to 0.3% (for example, 0.05 to 0.2%). Thus, when the thermal contraction rate of the optical sheet is small, for example, in the key sheet manufacturing process in which the pitch between the keys is narrow, it is possible to prevent the keys from being fused by heat treatment in the drying step after printing. The heat shrinkage rate can be measured by the method described in the examples.

  The thickness of the optical sheet can be selected according to the application, for example, can be selected from a range of about 1 to 500 μm, for example, 3 to 300 μm, preferably 5 to 200 μm, more preferably 10 to 100 μm (particularly 20 to 100 μm). It is.

  The optical sheet of the present invention may be subjected to surface treatment. In addition to surface coating for imparting various properties such as heat resistance, the surface treatment includes printing treatment (printing treatment using heat or active energy rays such as screen printing and spray printing). Furthermore, the optical sheet of the present invention may be secondarily formed by punching or cutting, or may be laminated with another plastic sheet (via an adhesive layer as necessary).

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, the tension test of the obtained optical sheet, the total light transmittance, the measuring method of thermal contraction rate, and the content of each component are as follows.

(Tensile test)
The obtained sheet was punched into a No. 7 dumbbell shape, and in accordance with JIS K7161, in a test environment with a temperature of 25 ° C. and a humidity of 50% RH, a tensile / compression tester (Orientec Co., Ltd., Tensilon UCT-5T) Was used to obtain a stress-strain curve measured under a tensile speed of 20 mm / min. From the obtained stress-strain curve, the elastic modulus and elongation at break were determined.

(Total light transmittance)
About the obtained sheet | seat, based on JISK7361-1, the total light transmittance (TT) was measured using the haze meter (Nippon Denshoku Industries Co., Ltd. make, NDH-5000W).

(Heat shrinkage)
About the obtained sheet | seat, it cuts out to 12 cm square, and marks 10 cm each in the MD and TD directions, and describes three places. First, the distance between marked lines before heating was read with a digital scale (manufactured by Sony Magnescale Co., Ltd., LF-100). Further, the sheet was heated at 80 ° C. for 30 minutes, the distance between marked lines after heating was read in the same manner, and the contraction length was divided by the length before heating to calculate the heat shrinkage rate.

Heat shrinkage rate = (length before heating−length after heating) / length before heating × 100 (%)
(Content of each component)
KRM7735 (Daicel Cytec Co., Ltd., aliphatic urethane acrylate, bifunctional, number average molecular weight 5000, acryloyl group equivalent 2500)
PU2300T (manufactured by Bigen Specialty Chemical Co., Ltd., aliphatic urethane acrylate, bifunctional, number average molecular weight 16000, acryloyl group equivalent 8000)
EB230 (manufactured by Daicel Cytec Co., Ltd., “EBECRYL-230”, aliphatic urethane acrylate, bifunctional, number average molecular weight 5000, acryloyl group equivalent 2500, Tg: −55 ° C.)
EB270 (manufactured by Daicel Cytec Co., Ltd., “EBECRYL-270”, aliphatic urethane acrylate, bifunctional, number average molecular weight 1500, acryloyl group equivalent 750, Tg: −27 ° C.)
OTA480 (Daicel Cytec Co., Ltd., glycerin propoxytriacrylate, trifunctional, molecular weight 428, acryloyl group equivalent 143)
M-120 (manufactured by Toagosei Co., Ltd., 2-ethylhexyl ethylene oxide modified acrylate, ethylene oxide addition mol number: about 2 mol, monofunctional, molecular weight 260, acryloyl group equivalent 260, Tg: -65 ° C)
ACMO (manufactured by Kojin Co., Ltd., N-acryloylmorpholine, monofunctional, molecular weight 141, acryloyl group equivalent 141)
IBOA (manufactured by Daicel Cytec Co., Ltd., isobornyl acrylate, monofunctional, molecular weight 210, acryloyl group equivalent 210, Tg: 94 ° C.).

Example 1
60 parts by weight of urethane acrylate (KRM7735), 5 parts by weight of acrylic monomer (OTA480), 10 parts by weight of acrylic monomer (M-120), 25 parts by weight of acrylic monomer (ACMO), photopolymerization initiator (manufactured by Ciba Japan Co., Ltd.) 2 parts by weight of “Irgacure 184” were weighed and mixed in a light-shielding bottle. This solution was heated to 60 ° C. and cast on a base film (release PET film, T-789, manufactured by Daicel Value Coating Co., Ltd., thickness 50 μm) using wire bar # 55, and then nitrogen. A cured product having a thickness of 76 μm is irradiated with ultraviolet rays at an output of 4 kW and a conveying speed of 4 m / min using an ultraviolet irradiation device (“ECS-4011GX”, high-pressure mercury lamp) manufactured by Eye Graphics Co., Ltd. in an atmosphere. Got. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

Example 2
60 parts by weight of urethane acrylate (KRM7735), 5 parts by weight of acrylic monomer (OTA480), 10 parts by weight of acrylic monomer (M-120), and 25 parts by weight of acrylic monomer (ACMO) were weighed and mixed in a light shielding bottle. This solution was heated to 60 ° C. and cast on a base film (T-789) using a wire bar # 55, and then an electron beam irradiation apparatus (manufactured by NHV Corporation, “ EBC300-60 ") was irradiated with an electron beam under the conditions of an acceleration voltage of 200 kV and a dose of 100 kGy to obtain a cured product having a thickness of 75 μm. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

Example 3
50 parts by weight of urethane acrylate (PU2300T), 10 parts by weight of acrylic monomer (OTA480), 40 parts by weight of acrylic monomer (ACMO), and 2 parts by weight of photopolymerization initiator (Irgacure 184) were weighed and mixed in a light-shielding bottle. This solution was heated to 60 ° C. and cast on a base film (T-789) using a wire bar # 55, and then a lamp was used in a nitrogen atmosphere using an ultraviolet irradiation device (ECS-4011GX). Output: UV was irradiated at 4 kW and a conveyance speed of 4 m / min to obtain a cured product having a thickness of 72 μm. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

Example 4
50 parts by weight of urethane acrylate (PU2300T), 10 parts by weight of acrylic monomer (OTA480), and 40 parts by weight of acrylic monomer (ACMO) were weighed and mixed in a light shielding bottle. After heating this solution to 60 degreeC and casting on a base film (T-789) using wire bar # 55, in nitrogen atmosphere, using an electron beam irradiation apparatus (EBC300-60), An electron beam was irradiated under conditions of an acceleration voltage of 200 kV and a dose of 100 kGy to obtain a cured product having a thickness of 70 μm. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

Example 5
50 parts by weight of urethane acrylate (EB230), 25 parts by weight of acrylic monomer (OTA480), 25 parts by weight of acrylic monomer (IBOA) and 2 parts by weight of photopolymerization initiator (Irgacure 184) were weighed and mixed in a light-shielding bottle. This solution was heated to 60 ° C. and cast on a base film (T-789) using a wire bar # 55, and then a lamp was used in a nitrogen atmosphere using an ultraviolet irradiation device (ECS-4011GX). Output: UV was irradiated at 4 kW and a conveyance speed of 4 m / min to obtain a cured product having a thickness of 76 μm. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

Example 6
60 parts by weight of urethane acrylate (EB230), 20 parts by weight of acrylic monomer (OTA480), 20 parts by weight of acrylic monomer (IBOA) and 2 parts by weight of photopolymerization initiator (Irgacure 184) were weighed and mixed in a light-shielding bottle. This solution was heated to 60 ° C. and cast on a base film (T-789) using a wire bar # 55, and then a lamp was used in a nitrogen atmosphere using an ultraviolet irradiation device (ECS-4011GX). Output: UV was irradiated at 4 kW and a conveyance speed of 4 m / min to obtain a cured product having a thickness of 78 μm. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

Example 7
80 parts by weight of urethane acrylate (EB230), 10 parts by weight of acrylic monomer (OTA480), 10 parts by weight of acrylic monomer (IBOA), and 2 parts by weight of photopolymerization initiator (Irgacure 184) were weighed and mixed in a light-shielding bottle. This solution was heated to 60 ° C. and cast on a base film (T-789) using a wire bar # 55, and then a lamp was used in a nitrogen atmosphere using an ultraviolet irradiation device (ECS-4011GX). Output: UV was irradiated at 4 kW and a conveyance speed of 4 m / min to obtain a cured product having a thickness of 78 μm. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

Comparative Example 1
50 parts by weight of urethane acrylate (EB270), 25 parts by weight of acrylic monomer (OTA480), 25 parts by weight of acrylic monomer (IBOA) and 2 parts by weight of photopolymerization initiator (Irgacure 184) were weighed and mixed in a light-shielding bottle. This solution was heated to 60 ° C. and cast on a base film (T-789) using a wire bar # 55, and then a lamp was used in a nitrogen atmosphere using an ultraviolet irradiation device (ECS-4011GX). Output: UV was irradiated at 4 kW and a conveyance speed of 4 m / min to obtain a cured product having a thickness of 76 μm. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

Comparative Example 2
60 parts by weight of urethane acrylate (EB270), 20 parts by weight of acrylic monomer (OTA480), 20 parts by weight of acrylic monomer (IBOA) and 2 parts by weight of photopolymerization initiator (Irgacure 184) were weighed and mixed in a light-shielding bottle. This solution was heated to 60 ° C. and cast on a base film (T-789) using a wire bar # 55, and then a lamp was used in a nitrogen atmosphere using an ultraviolet irradiation device (ECS-4011GX). Output: UV was irradiated at 4 kW and a conveyance speed of 4 m / min to obtain a cured product having a thickness of 78 μm. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

Comparative Example 3
80 parts by weight of urethane acrylate (EB270), 10 parts by weight of acrylic monomer (OTA480), 10 parts by weight of acrylic monomer (IBOA) and 2 parts by weight of photopolymerization initiator (Irgacure 184) were weighed and mixed in a light-shielding bottle. This solution was heated to 60 ° C. and cast on a base film (T-789) using a wire bar # 55, and then a lamp was used in a nitrogen atmosphere using an ultraviolet irradiation device (ECS-4011GX). Output: UV was irradiated at 4 kW and a conveyance speed of 4 m / min to obtain a cured product having a thickness of 78 μm. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

Comparative Example 4
30 parts by weight of urethane acrylate (EB230), 35 parts by weight of acrylic monomer (OTA480), 35 parts by weight of acrylic monomer (IBOA), and 2 parts by weight of a photopolymerization initiator (Irgacure 184) were weighed and mixed in a light-shielding bottle. This solution was heated to 60 ° C. and cast on a base film (T-789) using a wire bar # 55, and then a lamp was used in a nitrogen atmosphere using an ultraviolet irradiation device (ECS-4011GX). Output: UV was irradiated at 4 kW and a conveyance speed of 4 m / min to obtain a cured product having a thickness of 68 μm. The obtained cured product was peeled from the substrate film to obtain an optical sheet.

  Table 1 shows the evaluation results of the optical sheets obtained in the examples and comparative examples.

  As is clear from Table 1, in the examples, the thermal shrinkage is small, the elasticity is appropriate, and the elongation at break is large compared to the comparative example.

  The optical sheet of the present invention can be used as an optical sheet used in various electric / electronic devices or optical devices such as portable devices, home appliances, and control devices. Specifically, push button switches (or operation panels) for applications requiring high transparency and flexibility, such as mobile phones, gaming devices, mobile devices, car navigation systems, watches, calculators, televisions, personal computers, etc. ), A sheet-like member such as a membrane switch, a sensor switch or a touch panel, and an optical adhesive tape substrate (for example, an OCA tape substrate). Such a sheet-like member includes a key top sheet, a key mat sheet, a light guide plate, a reflection plate, a retardation plate, a polarizing plate, a viewing angle expansion plate, a diffusion plate, an alignment film, and a luminance for constituting a switch or an operation panel. An improvement board etc. may be sufficient. Among these, a light guide sheet or a reflective sheet used for an operation panel of a mobile phone, a game machine, a mobile device, a touch panel, etc., for example, a back surface of a key top sheet by clicking on the back side of a key top sheet of a mobile phone. And a sheet for guiding or reflecting light from a light source such as an LED light source to the key top surface (operation surface).

DESCRIPTION OF SYMBOLS 1 ... Key top sheet 2 ... Key mat sheet 3 ... Light guide sheet 4 ... Click dome 5 ... Flexible printed wiring board 6 ... Light source

Claims (10)

An optical sheet composed of a cured product of a polymerizable composition containing a vinyl oligomer having a number average molecular weight of 2000 to 50000, wherein the vinyl oligomer has a glass transition temperature of -80 ° C to -30 ° C, and is polymerizable. In the polymerizable component having an α, β-ethylenically unsaturated double bond in the composition, the number average molecular weight in a weighted average per α, β-ethylenically unsaturated double bond is 1000 to 10,000. Sheet . Vinyl optical sheet oligomers claim 1 Symbol placement is a urethane (meth) acrylate. The optical sheet according to claim 1 or 2, wherein the vinyl oligomer is an aliphatic urethane (meth) acrylate. The optical sheet according to any one of claims 1 to 3 , wherein the polymerizable composition further comprises at least one vinyl monomer selected from a monofunctional vinyl monomer, a bifunctional vinyl monomer, and a trifunctional vinyl monomer. . The optical sheet according to claim 4 , wherein a ratio (weight ratio) of the vinyl-based oligomer and the vinyl-based monomer is the former / the latter = 90/10 to 10/90. An optical sheet composed of a cured product of a polymerizable composition containing a bifunctional urethane (meth) acrylate having a number average molecular weight of 2000 to 50000, a trifunctional vinyl monomer, and a monofunctional vinyl monomer,
The number average molecular weight per α, β-ethylenically unsaturated double bond of the bifunctional urethane (meth) acrylate is 1000-20000,
In the polymerizable component having an α, β-ethylenically unsaturated double bond in the polymerization composition, the number average molecular weight in a weighted average per α, β-ethylenically unsaturated double bond is 1000 to 10,000. Optical sheet. Monofunctional vinyl monomer is according to claim 6, further comprising at least one monofunctional (meth) acrylate selected from heterocyclic (meth) acrylate and bridged cyclic (meth) acrylate containing a nitrogen atom as a hetero ring atom Optical sheet. The optical sheet according to any one of claims 1 to 7 , wherein the cured product of the polymerizable composition is a photocured product obtained by irradiating an electron beam and substantially does not contain a polymerization initiator. The optical sheet according to any one of claims 1 to 8 , which has an elongation at break of 100 to 300%. Key sheet, the light guide sheet, an optical sheet according to any one of claims 1 to 9, which is one selected from the reflective sheet and the optical transparent adhesive tape base material.

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