JP2010180328A - Light guide-forming composition and light guiding sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a light guide-forming composition suitable for forming a light guide having excellent transparency, moderate hardness, and moderate flexibility and suppressing stickiness; and a light guiding sheet formed using the composition. <P>SOLUTION: The light guide-forming composition comprises a prepolymer produced by reacting (A) a polyether polyol, (B) a polycarbonate diol, (C) an aliphatic and/or alicyclic polyisocyanate, and (D) a (meth)acrylate having a hydroxy group, wherein the prepolymer preferably comprises as the polyisocyanate (C), at least an alicyclic polyisocyanate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is formed using a composition for forming a light guide suitable for forming a light guide excellent in transparency, having appropriate hardness and flexibility, and having reduced stickiness, and the composition. The present invention relates to a light guide sheet. The light guide sheet of the present invention is used as a member constituting an illumination structure of an operation unit in an electronic device such as a mobile phone.

In recent years, as electronic devices such as mobile phones, electronic notebooks, electronic dictionaries, cameras, and the like have become smaller, it has become increasingly necessary to reduce the size and thickness of members. In addition, in the past, there have been devised measures to reduce the number of parts that required the same member by changing the design of the structure, etc., and at least maintain the performance while reducing the weight, reducing the thickness, saving power, etc. .
For example, in a mobile phone or the like, an illumination structure in which a key button emits light generally has a structure in which a plurality of light emitters (LEDs or the like) are arranged for a plurality of key buttons so that the luminance becomes equal. Designed to be stored inside. However, since a plurality of members (light emitters) are required, there is a problem that weight saving and power saving are not sufficient. Therefore, a structure including a thin light guide and a small number of light emitters arranged around the light guide and provided to transmit light from the end of the light guide to the entire interior is proposed. (See Patent Document 1). That is, the number of light emitters as light sources is reduced to further reduce weight, thickness, and power saving.

  As the material for forming the light guide, a polymer having excellent transparency or a composition containing the same is usually used. Acrylic polymers such as polymethyl methacrylate, polyesters such as silicone, polycarbonate, and polyethylene terephthalate And polyurethane are known (see Patent Documents 1 and 2, etc.).

JP-A-9-55143 JP 2007-291313 A

When a thin light guide as described above is used to give a light emitting function to a key button of an electronic device or the like, this light guide is used to maintain high luminance over a long period of time. It is required to have not only transparency (a decrease in translucency and coloring are not remarkable with time) but also appropriate hardness, flexibility, and non-adhesiveness for smooth normal pressing action. .
As described above, the composition for forming a light guide suitable for forming a light guide excellent in transparency, having appropriate hardness and flexibility, and having reduced stickiness, and formed using this composition There is also a need for a light guide sheet that is excellent in the transparency and light guide properties.

The present invention is as follows.
1. (A) A polyether polyol, (B) a polycarbonate diol, (C) an aliphatic and / or alicyclic polyisocyanate, and (D) a prepolymer obtained by reacting a (meth) acrylate having a hydroxyl group. A composition for forming a light guide.
2. 2. The composition for forming a light guide according to 1 above, wherein the polyether polyol (A) has a number average molecular weight of 1,000 to 2,800.
3. The composition for forming a light guide according to 1 or 2 above, wherein the polycarbonate diol (B) has a number average molecular weight of 300 to 1,500.
4). The composition for light guide formation in any one of said 1 thru | or 3 whose said polyisocyanate (C) is alicyclic polyisocyanate at least among alicyclic polyisocyanate and aliphatic polyisocyanate.
5). A light guide sheet obtained by irradiating an active energy ray on a coating formed using the composition for forming a light guide according to any one of 1 to 4 above and curing it.

According to the light guide forming composition of the present invention, the total light transmittance exceeds 85%, the A hardness is 71 to 95, the tensile strength is 6 to 40 MPa, and the tensile elongation is 60 to 130%. In addition, it is possible to form a light guide whose surface is not sticky, that is, non-adhesive.
When the number average molecular weight of the polyether polyol (A) is 1,000 to 2,800, a light guide having excellent transparency, moderate hardness and flexibility, and suppressing stickiness is obtained. It can form suitably.
When the polycarbonate diol (B) has a number average molecular weight of 300 to 1,500, it is excellent in transparency, excellent in balance between tensile strength and tensile elongation, has appropriate hardness and flexibility, and has stickiness. The suppressed light guide can be suitably formed.
When the polyisocyanate (C) is at least an alicyclic polyisocyanate among alicyclic polyisocyanates and aliphatic polyisocyanates, it is a lead that suppresses discoloration and fading and deterioration of transparency due to long-term use. A light body can be formed.

According to the light guide sheet of the present invention, since it is excellent in transparency, excellent light guide properties can be obtained even if light is incident from any surface portion including its end face. For example, when the inside of the sheet is guided in a dark place, excellent surface light emission and uniform brightness can be obtained.
In addition to transparency to maintain a uniform brightness over a long period of time (not that translucency is reduced and coloring is not noticeable over time), for example, a normal pressing action in an electronic device such as a mobile phone It has moderate flexibility (press feeling) and non-adhesiveness for smoothing, and further has repeated strain resistance and excellent durability. Therefore, the light guide sheet of the present invention is suitable as a member constituting an illumination structure of an operation unit in various electronic devices.

It is a schematic perspective view which shows the illumination structure which has arrange | positioned the light source for introducing light in the end surface of the light guide sheet. It is a schematic perspective view which shows the illumination structure which has arrange | positioned the mask part on the surface of the light guide sheet in FIG.

  The present invention will be described in detail below. In the present specification, “(meth) acrylate” means acrylate and methacrylate, and “(meth) acryloyl” means acryloyl and methacryloyl.

1. Composition for light guide formation The composition for light guide formation of the present invention comprises (A) polyether polyol (hereinafter referred to as “component (A)”), (B) polycarbonate diol (hereinafter referred to as “component (B)”. ) ”), (C) aliphatic and / or alicyclic polyisocyanate (hereinafter referred to as“ component (C) ”) and (D) (meth) acrylate having a hydroxyl group (hereinafter referred to as“ component ( D) "is a composition containing a prepolymer obtained by reaction.
As will be described later, the composition for forming a light guide according to the present invention can contain a photopolymerization initiator to form a photo-curable composition for forming a light guide.

1-1. Prepolymer and its manufacturing method The prepolymer contained in the composition for forming a light guide of the present invention is usually a component (A), a component (B), a component (C), a component (D), A compound having an unsaturated bond derived from component (D) and a urethane bond, obtained by reacting components (A) to (D) in the presence of this catalyst using a catalyst. And this prepolymer is a compound which may have a hydroxyl group derived from the said component (A), (B).
In addition, the said prepolymer does not contain the isocyanate group originating in the said component (C) substantially. Here, “substantially free” means that it contains no unreacted isocyanate groups (that is, it cannot be detected) or contains a trace amount of unreacted isocyanate groups. Specifically, it means that the amount is small enough not to adversely affect the deterioration of transparency due to long-term fading deterioration, fading, discoloration and the like. And the density | concentration of the isocyanate group in this prepolymer is an amount as small as 1% or less normally as a residual amount computed from the usage-amount of the said component (C).

In the prepolymer, the concentration of the unsaturated bond derived from the component (D) is not particularly limited.
The number average molecular weight of the prepolymer is preferably 500 to 4,000, more preferably 1,000 to 3,000, and still more preferably 1,500 to 2,500. When the number average molecular weight is within the above range, a light guide having appropriate hardness and flexibility and excellent durability against repeated compression can be obtained. The number average molecular weight can be measured by gel permeation chromatography (GPC).

1-1-1. Polyether polyol (A)
The component (A) is not particularly limited as long as it is a compound having two or more hydroxyl groups.
As the component (A), at least one compound selected from polyhydric alcohols, polyhydric phenols, and amine compounds having two or more hydroxyl groups, ethylene oxide, propylene oxide, 1,2-butylene oxide , 2,3-butylene oxide, 1,4-butylene oxide, and other compounds obtained by addition (block and / or random addition) of alkylene oxide can be used.

  Examples of the polyhydric alcohol include aliphatic diols such as ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, and neopentylglycol, cyclohexanediol, cyclohexane A dihydric alcohol having 2 to 20 carbon atoms such as an alicyclic diol such as cycloalkylene glycol such as dimethanol; an aliphatic triol such as alkanetriol such as glycerin, trimethylolpropane, trimethylolethane, and hexanetriol; 3-8 carbon trihydric alcohols; 4-8 carbon atoms having 5-20 carbon atoms, such as aliphatic polyols such as alkane polyols such as pentaerythritol, sorbitol, mannitol, sorbitan, diglycerin, dipentaerythritol, etc. Or higher polyhydric alcohol.

  Examples of the polyhydric phenol include monocyclic polyhydric phenols such as pyrogallol and hydroquinone; bisphenols such as bisphenol A, bisphenol F and bisphenol sulfone; and phenol and formaldehyde condensates (novolac).

Examples of the amine compound having two or more hydroxyl groups include alkanolamines such as diethanolamine, ethanolisopropanolamine, diisopropanolamine, ethanol-2-hydroxybutylamine, isopropanol-2-hydroxybutylamine, and triethanolamine.
In addition, when using an amine compound having two or more hydroxyl groups, a monoalkanolamine having 2 to 20 carbon atoms, such as monoethanolamine, isopropanolamine, aminoethylethanolamine, n-butylamine, C1-C20 monoamine compounds such as octylamine, ethylenediamine, propylenediamine, hexamethylenediamine and other diamine compounds, diethylenetriamine, triethylenetetramine and other polyalkylenes having 4 to 20 carbon atoms Aliphatic amine compounds such as polyamines; aromatic amine compounds having 6 to 20 carbon atoms such as aniline, phenylenediamine, tolylenediamine, xylylenediamine, diethyltoluenediamine, methylenedianiline, diphenyletherdiamine; Ronjiamin, cyclohexylene diamines, such as dicyclohexylmethane diamine, may be used in combination of other amine compounds of alicyclic amine compounds having 4 to 20 carbon atoms.

The average number of functional groups (average number of hydroxyl groups) of the component (A) is preferably 1.5 to 3.0, more preferably 1.8 to from the viewpoints of appropriate hardness, flexibility and non-adhesiveness. 2.2. If the average number of functional groups is too small, the hardness may be lowered and the stickiness may become remarkable. On the other hand, if the average number of functional groups is too large, the stickiness is suppressed, but the hardness becomes too high and becomes brittle, and the durability against repeated compression may be reduced.
The hydroxyl value of the component (A) is preferably 28 to 170 mgKOH / g, more preferably 38 to 90 mgKOH / g, from the viewpoint of transparency and a balance between appropriate hardness and non-adhesiveness. If the hydroxyl value is too small, the hardness may decrease and the stickiness may become significant. On the other hand, if the hydroxyl value is too large, a light-turbid light guide may be obtained, the hardness may be too high, and it may become brittle.
In addition, the number average molecular weight of the component (A) is preferably 1,000 to 2,800, more preferably 1,400 to 2, from the viewpoint of transparency and a balance between appropriate hardness and non-adhesiveness. 600. If this number average molecular weight is too small, a light-turbid light guide may be obtained, the hardness may be too high, and it may become brittle. On the other hand, if the number average molecular weight is too large, the hardness may be lowered and the stickiness may become remarkable.

  The said component (A) may be used independently and may be used in combination of 2 or more. In the present invention, the preferred component (A) is a compound obtained by adding propylene oxide and / or ethylene oxide to a polyhydric alcohol such as polypropylene glycol, polytetramethylene glycol, glycerin, dipropylene glycol and trimethylolpropane. is there.

1-1-2. Polycarbonate diol (B)
Although this component (B) will not be specifically limited if it is a compound which has two hydroxyl groups, Usually, it is a compound which has a structure represented with the following general formula.
H— (O—R ¹ —OCO—) _n R ² —OH
[Wherein, R ¹ and R ² are the same or different from each other and are divalent hydrocarbon groups, and n is an integer of 1 or more. ]

  Examples of the component (B) include aliphatic polycarbonate diol, aromatic polycarbonate diol, alicyclic polycarbonate diol, aromatic / aliphatic copolymer polycarbonate diol, aliphatic / alicyclic copolymer polycarbonate diol, alicyclic / aromatic. Group-copolymerized polycarbonate diol, aromatic / aliphatic / alicyclic copolymerized polycarbonate diol, and the like. Of these, aliphatic polycarbonate diols are preferred.

  Aliphatic polycarbonate diols include ethylene glycol, propylene glycol, butanediol (1,4-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol), pentanediol (1,5-pentane). Diol, neopentyl glycol), hexanediol (1,6-hexanediol, 1,5-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol), heptanediol ( 1,7-heptanediol, 2,4-heptanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol), octanediol (1,8- Octanediol, 2-ethyl-1,3-hexanediol, 2-ethyl- , 6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol), nonanediol (1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl -1,3-propanediol), polycarbonate diol obtained by co-condensation of aliphatic diols such as decanediol, dodecanediol, eicosanediol and carbonates such as dimethyl carbonate, diethyl carbonate, diphenyl carbonate, etc. Can be mentioned. Among these, since a light guide having excellent transparency and reduced stickiness is obtained, one or more aliphatic diols having 4 to 9 carbon atoms are co-condensed with a carbonate. The polycarbonate diol obtained is preferred.

  Specific examples of the aliphatic polycarbonate diol include 1,4-butylene polycarbonate diol; 1,5-pentylene polycarbonate diol; 1,6-hexylene polycarbonate diol; 1,4-butanediol and 1,6-hexanediol. And a co-condensate of carbonate ester; 3-methyl-1,5-pentanediol and 1,6-hexanediol, and a co-condensate of carbonate ester; 2-methyl-1,8-octanediol and 1, Examples thereof include 9-nonanediol and a co-condensate of carbonate.

Examples of the aromatic polycarbonate diol include bisphenol A type polycarbonate diol and bisphenol F type polycarbonate diol.
Examples of the alicyclic polycarbonate diol include 1,4-di (methylene) cyclohexane polycarbonate diol, decahydronaphthalene polycarbonate diol, hydrogenated bisphenol A type polycarbonate diol, and the like.
Examples of the aromatic / aliphatic copolymer polycarbonate diol include polycarbonate diol obtained by co-condensation of bisphenol A and 1,6-hexylene glycol with a carbonate ester.
Examples of the aliphatic / alicyclic copolymer polycarbonate diol include polycarbonate diol obtained by co-condensation of 1,6-hexylene glycol and 1,4-cyclohexanedimethanol with a carbonate.
Examples of the alicyclic / aromatic copolymer polycarbonate diol include polycarbonate diol obtained by co-condensation of 1,4-cyclohexanedimethanol and bisphenol A with a carbonate ester.

The hydroxyl value of the component (B) is preferably 74 to 375 mgKOH / g, more preferably 85 to 280 mgKOH / g, from the viewpoints of transparency and a balance between appropriate hardness and non-adhesiveness. If this hydroxyl value is too small, a cloudy light guide may be obtained, and the hardness may decrease. On the other hand, if the hydroxyl value is too large, the hardness may be too high.
In addition, the number average molecular weight of the component (B) is preferably 300 to 1,500, more preferably 400 to 1,300, from the viewpoints of transparency and a balance between appropriate hardness and non-adhesiveness. If this number average molecular weight is too small, the hardness may be too high. On the other hand, when the number average molecular weight is too large, a light-turbid light guide is obtained, and the hardness may decrease.
The said component (B) can be used individually by 1 type or in combination of 2 or more types.

1-1-3. Polyisocyanate (C)
This component (C) is an aliphatic polyisocyanate and / or an alicyclic polyisocyanate, and is preferably a compound having two or more isocyanate groups. That is, the component (C) may be only aliphatic polyisocyanate, may be only alicyclic polyisocyanate, or may be a combination of both. Each polyisocyanate is preferably a compound having 50 or less carbon atoms.

Aliphatic isocyanates include methylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), 1,10-decamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 2,2,4- Examples include trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate (LDI), and lysine triisocyanate (LTI).
Examples of the alicyclic isocyanate include 1,4-cyclohexylene diisocyanate (CHDI), 4,4′-methylenebis (cyclohexylene isocyanate), 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate (IPDI), hydrogenated xylylene diisocyanate ( H ₆ XDI or hydrogenated XDI), dicyclohexylmethane diisocyanate (H ₁₂ MDI or hydrogenated MDI), and the like. Of these, dicyclohexylmethane diisocyanate is preferred.

The component (C) preferably contains an alicyclic isocyanate because it is excellent in transparency and a light guide body in which coloring such as yellowing is suppressed is obtained. In addition, you may use together this alicyclic isocyanate and aliphatic isocyanate, In that case, when the total of both is 100 mass%, the minimum of content of alicyclic isocyanate is 5 masses preferably. %, More preferably 10% by mass, still more preferably 15% by mass.
The said component (C) can be used individually by 1 type or in combination of 2 or more types.

1-1-4. (Meth) acrylate (D) having a hydroxyl group
This component (D) is a (meth) acrylate having at least one hydroxyl group and at least one (meth) acryloyl group.
The component (D) is preferably a mono (meth) acrylate having one hydroxyl group, such as an esterified product of (meth) acrylic acid and an aliphatic diol, alicyclic diol or aromatic diol. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4- Hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, poly (n = 2 to 10 as an average value) ethylene glycol mono (meth) acrylate, poly (average As value n = 2 to 10) propylene glycol mono (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate. Of these, 2-hydroxyethyl methacrylate is preferred. In addition, as said component (D), the (meth) acrylate which has a 2 or more hydroxyl group can also be used.
The said component (D) may be used independently and may be used in combination of 2 or more.

1-1-5. Other Raw Materials for Production In forming the prepolymer, other polyol components other than the components (A) and (B) may be used.
Other polyol components include (1) polyhydric alcohol, (2) polyhydric phenol, (3) alkanolamine having two or more hydroxyl groups, (4) polyether ester polyol, (5) polyester polyol, (6 ) Polycarbonate polyol, (7) Polydiene polyol, (8) Acrylic polyol, (9) Silicone polyol, (10) Natural oil-based polyol such as castor oil, (11) Selected from (1) to (10) above Examples thereof include polymer polyols obtained by polymerizing vinyl monomers in the presence of at least one compound (raw material polyol).

  Polyether ester polyols include polyalkylene polyols such as polyethylene glycol, polypropylene glycol, and propylene oxide adducts of glycerin, polycarboxylic acid anhydrides such as succinic anhydride, adipic anhydride, and phthalic anhydride, and ethylene oxide and propylene oxide. And compounds obtained by reacting a compound having a cyclic ether group such as

Polyester polyols include polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyneopentyl adipate diol, polyethylene-butylene adipate diol, polyneopentyl-hexamethylene adipate diol, poly-3-methylpentane adipate diol, polyethylene Terephthalate diol, polybutylene terephthalate diol, polyhexamethylene terephthalate diol, polyneopentyl terephthalate diol, polyethylene-butylene terephthalate diol, polyneopentyl-hexamethylene terephthalate diol, poly-3-methylpentane terephthalate diol, polyethylene isophthalate diol, polybutylene Isophthale Tojioru, polyhexamethylene isophthalate diol, polyneopentyl Louis softer rate diol, polyethylene - butylene isophthalate diol, polyneopentyl - hexamethylene isophthalate diol, poly 3-methylpentane isophthalate diol,
Terephthalic acid, isophthalic acid, 1,5-naphthalic acid, 2,6-naphthalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decamethylene dicarboxylic acid, dodecamethylene dicarboxylic acid Polycarboxylic acids such as dicarboxylic acids such as
Reaction with polyols such as ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, cyclohexanediol, glycerin And a condensed polyester polyol obtained by ring-opening polymerization of ε-caprolactam; and the like.

  The polycarbonate polyol is a compound having three or more hydroxyl groups, and examples thereof include polyhexamethylene carbonate polyol and polycyclohexanedimethylene carbonate polyol.

As the polymer polyol, a compound (graft polymer) obtained by polymerizing a vinyl monomer using a polymerization initiator in the presence of a raw material polyol such as the above-described polyether polyol or polyester polyol may be used. it can. In this reaction, a chain transfer agent can also be used.
As the vinyl monomer, an aromatic vinyl compound, an unsaturated nitrile compound, a (meth) acrylic acid ester compound, or the like can be used. These may be used alone or in combination of two or more.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, vinyl toluene, vinyl naphthalene, and hydroxystyrene.
Examples of the unsaturated nitrile compound include acrylonitrile and methacrylonitrile.
As (meth) acrylic acid ester compounds, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, amyl (meth) acrylate, (meth) acrylic acid (Meth) acrylic acid alkyl esters such as hexyl, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate And the like, and the like.
Other vinyl compounds include unsaturated acids such as (meth) acrylic acid; unsaturated amide compounds such as (meth) acrylamide; amino group-containing unsaturated compounds such as diaminoethyl methacrylate and morpholinoethyl methacrylate; vinylidene chloride Halogen-containing vinyl compounds such as perfluorooctylethyl methacrylate, perfluorooctylethyl acrylate; divinylbenzene, ethylene di (meth) acrylate, polyalkylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta ( (Meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol di (meth) acrylate, Trimethylolpropane di (meth) acrylate, polyfunctional vinyl compounds such as trimethylolpropane tri (meth) acrylate.

Examples of the polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), and the like. Azo compounds; organic peroxides such as dibenzoyl peroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, and persuccinic acid; inorganic peroxides such as persulfate and perborate.
Examples of the chain transfer agent include mercaptan compounds such as dodecanethiol, ethanethiol, octanethiol, and toluenethiol; halogenated hydrocarbons such as carbon tetrachloride, carbon tetrabromide, and chloroform.

1-1-6. Production method of prepolymer When producing the prepolymer, the total number of hydroxyl groups of the components (A), (B) and (D), or the components (A), (B), (D) and as required The total number of isocyanate groups of the component (C) is preferably 0.90 to 1.15 times, more preferably 0.95, in terms of molar ratio with respect to the total number of hydroxyl groups of other polyol components used accordingly. It is used at a ratio of ˜1.10 times. By using a raw material component in the above preferred range, a prepolymer having a low residual ratio of isocyanate groups can be obtained.
The proportions of the components (A) and (B) used are preferably 40 to 95% by mass and 5 to 60% by mass, more preferably 50 to 85%, respectively, when the total of both is 100% by mass. They are mass% and 15-50 mass%, More preferably, they are 60-80 mass% and 20-40 mass%. When these proportions are in the above range, a light guide having excellent transparency and reduced stickiness can be obtained.
The amount of the component (D) used is the sum of the number of moles of the components (A) and (B), or the components (A) and (B) and other polyol components used as necessary. It is preferably 1.0 to 4.0 times, more preferably 1.5 to 3.0 times, and still more preferably 1.8 to 2.5 times the total number of moles. When the usage-amount of the said component (D) exists in the said range, the obtained light guide shall be provided with fixed and uniform hardness and non-adhesiveness in the surface irrespective of the position. Moreover, the stable manufacture of the light guide having the performance intended by the present invention can also be achieved.

  When other polyol components are used in combination in the formation of the prepolymer, the amount used is preferably 0.1 to 50 parts by mass when the total of the components (A) and (B) is 100 parts by mass. More preferably, it is 1-20 mass parts. If the amount of the other polyol component used is too large, the transparency is not sufficient, the stickiness becomes remarkable, and the discoloration resistance may be lowered.

  As described above, the prepolymer is formed in the presence of a catalyst. The catalyst is not particularly limited as long as it is a catalyst used in the reaction of the hydroxyl groups of the components (A), (B) and (D) and the isocyanate group of the component (C), that is, the urethanization reaction. .

  Examples of the catalyst include amine compounds and organometallic compounds. These can be used alone or in combination of two or more.

Examples of amine compounds include monoamine compounds, diamine compounds, triamine compounds, polyamine compounds, cyclic amine compounds, alcohol amine compounds, ether amine compounds, and the like. These may be used alone or in combination of two or more.
The amine compound may be a compound having reactivity with a compound having an isocyanate group such as the component (C), or may be a compound having no reactivity. Moreover, you may use combining these.

As the compound having reactivity with an isocyanate group, a compound having an —OH group and / or an —NH group can be used. Examples of the reactive amine compound having an —OH group include N, N-dimethylaminohexanol, N, N-dimethylaminoethoxyethoxyethanol, N, N-dimethylaminoethoxyethanol, diethanolamine, and triethanolamine. Examples of the reactive amine compound having an —NH group include N, N, N ″, N ″ -tetramethyldiethylenetriamine.
It is preferable to use a compound having reactivity with the isocyanate group because there is no outgas from the obtained light guide.

  Examples of the compound having no reactivity with the isocyanate group include triethylamine and N, N-dimethylcyclohexylamine.

  Examples of organometallic compounds include organotin compounds, organobismuth compounds, organolead compounds, and organozinc compounds. These may be used alone or in combination of two or more.

Organic tin compounds include dibutyltin diacetate, dibutyltin dilaurate, dibutyltin mercaptide, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin dilaurate, dioctyltin mercaptide, dioctyltin thiocarboxylate, dibutyltin dioctate, dibutyltin biscarboxylate Examples include isooctyl thioglycolate, tin octylate, tin 2-ethylhexanoate, stannous oleate, and the like.
Examples of the organic bismuth compound include bismuth acetate, bismuth naphthenate, dibutyl bismuth diacetate, dibutyl bismuth dilaurate, and dioctyl bismuth dilaurate.
Examples of the organic lead compound include lead acetate, lead octenoate, lead naphthenate, dibutyl lead diacetate, dibutyl lead dilaurate, and dioctyl lead dilaurate.
Examples of the organic zinc compound include zinc naphthenate, zinc decanoate, zinc 4-cyclohexylbutyrate, zinc neodecanoate, zinc isobutyrate, zinc benzoate, zinc p-toluenesulfonate, zinc (II) bis-2,2,6. , 6-tetramethyl-3,5-heptanedionate and the like.

  The amount of the catalyst used for forming the prepolymer is preferably 0.001 to 5.0 parts by mass when the total of the components (A), (B) and (D) is 100 parts by mass. More preferably, it is 0.005-2.0 mass part, More preferably, it is 0.01-1.0 mass part. When the usage-amount of a catalyst exists in the said range, a number average molecular weight, a viscosity, and a hue are suitable, and the prepolymer which gives the light guide which has the outstanding performance in this invention can be obtained.

As a method for producing the prepolymer, for example, the components (A), (B) and (D) are stirred with a stirring blade, a shaker, a rotary stirrer, etc., and then the component (C) is added, In the same manner as described above, a catalyst is added to the resulting mixture while stirring, and the components (A) to (D) are reacted at 40 ° C. to 120 ° C. (one-shot method), a sequential method, or the like. .
An example of the sequential method is shown below.
(A) First, after reacting the total amount of component (A), the total amount of component (B), and component (C) to obtain a prepolymer (P1) having an isocyanate group at the terminal, this prepolymer A method of reacting (P1) and component (D).
(B) First, the total amount of component (A) is reacted with component (C) to obtain a prepolymer (P1) having an isocyanate group at the end, and then this prepolymer (P1) and component (B ) And component (D).
(C) First, after the total amount of the component (B) and the component (C) are reacted to obtain a prepolymer (P1) having an isocyanate group at the terminal, the prepolymer (P1) and the component (A ) And component (D).
(D) First, a part of the component (A), a part of the component (B), and the component (C) are reacted to obtain a prepolymer (P1) having an isocyanate group at the terminal, A method of reacting the prepolymer (P1), the remainder of the component (A), the remainder of the component (B), and the component (D).
(E) First, a part of component (A) and a part of component (C) are reacted, and a part of component (B) and the rest of component (C) are reacted. A method of reacting these compounds (U1) and (U2) with component (D) after obtaining two monool urethane isocyanate compounds (U1) and (U2).
In addition, when using another polyol component, it can use together with any one or both of the components (A) and (B) in the said aspect (a)-(e).

When the component (D) is used when the prepolymer is produced, a polymerization inhibitor is added in advance to the reaction system in order to prevent gelation due to polymerization based on the unsaturated bond derived from the component (D). Or may be used simultaneously with component (D).
As polymerization inhibitors, phenol compounds such as hydroquinone, methyl hydroquinone, ethyl hydroquinone, tert-butyl hydroquinone, hydroquinone methyl ether, hydroquinone ethyl ether, di-tert-butyl-p-cresol, catechol, tert-butyl catechol; phenothiazine, And nitrogen-containing compounds such as diphenylamine.

  The prepolymer production time depends on the type of raw material components, the production method (one-shot method, sequential method), reaction temperature, etc., but is usually 20 minutes to 9 hours.

  After production of the prepolymer, it is preferable that the content of the free component (C) is not more than a predetermined amount in the reaction product, as described above. The presence or absence can be confirmed by the method described in JIS K1603-1 “Plastic-polyurethane raw material aromatic isocyanate test method”, the infrared absorption spectrum method, or the like.

1-2. Other component The composition for light guide formation of this invention may contain another component according to the objective, a use, etc.
As other components, photopolymerization initiator, thermal polymerization initiator, polymerization inhibitor, antioxidant, light stabilizer, photosensitizer, lubricant, anti-aging agent, antistatic agent, antifoaming agent, flame retardant, Examples thereof include an organic solvent, a compound having a polymerizable unsaturated bond and excluding the prepolymer.

  Examples of the photopolymerization initiator include acetophenone compounds, benzoin compounds, benzophenone compounds, thioxanthone compounds, ketone compounds, imidazole compounds, acylphosphine oxide compounds, carbazole compounds, and the like. These can be used alone or in combination of two or more.

  Examples of acetophenone compounds include 2-hydroxy-2-methylpropiophenone, 2,2-dimethoxy-2-phenylacetophenone, 4-phenoxydichloroacetophenone, 4-tert-butyl-dichloroacetophenone, 4-tert-butyl-trichloro. Acetophenone, diethoxyacetophenone, 2-hydroxy-2-phenyl-1-phenylpropan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4- Isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) -phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenylketone, 2-methyl- 1- [4- (Methylthio) fe Le], etc. -2-morpholinopropan -1, and the like.

  Examples of the benzoin compounds include benzoin, benzoin methyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and benzyl methyl ketal.

  Examples of benzophenone compounds include benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4′-methyldiphenyl sulfide, and 3,3′-dimethyl-4-methoxy. Examples include benzophenone, 4,4′-dimethylaminobenzophenone, 4,4′-diethylaminobenzophenone, 3,3 ′, 4,4′-tetra (tert-butylperoxycarbonyl) benzophenone.

  Examples of thioxanthone compounds include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, isopropylthioxanthone, 1-chloro-4-propoxythioxanthone. 2,4-dichlorothioxanthone and the like.

  Examples of the ketone compounds include α-acyloxime ester, methylphenylglyoxylate, benzyl, 9,10-phenanthrenequinone, camphorquinone, dibenzosuberone, 2-ethylanthraquinone, 4 ′, 4 ”-diethylisophthalo. Examples include phenone.

  Examples of the imidazole compound include 2,2'-bis (2-chlorophenyl) -4,4 ', 5,5'-tetraphenyl-1,2'-imidazole.

Examples of the acylphosphine oxide compound include 2,4,6-trimethylbenzoyldiphenylphosphine oxide.
Others, triphenylphosphonium hexafluoroantimonate, triphenylphosphonium hexafluorophosphate, p- (phenylthio) phenyldiphenylsulfonium hexafluoroantimonate, 4-chlorophenyldiphenylsulfonium hexafluorophosphate, (2,4-cyclopentadien-1-yl ) Lewis acid onium salts such as [(1-methylethyl) benzene] -iron-hexafluorophosphate can be used.

  The content of the photopolymerization initiator in the composition for forming a light guide according to the present invention is preferably 0.001 to 5.0 parts by mass, more preferably 0.001 parts by mass when the prepolymer is 100 parts by mass. It is 01-3.0 mass parts, More preferably, it is 0.05-2.0 mass parts. When the content of the photopolymerization initiator is in the above range, the curing reaction can be efficiently advanced.

Moreover, although a polymerization inhibitor can be used during manufacture of a prepolymer as mentioned above, it can also be added after manufacture.
The content of the polymerization inhibitor in the light guide forming composition of the present invention is preferably 400 ppm by mass or less, more preferably 200 ppm by mass or less, and even more preferably 50 ppm by mass or less with respect to the prepolymer. is there. When the content of the polymerization inhibitor is within the above range, the prepolymer can be prevented from being altered.

  Examples of the organic solvent include aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; ester compounds such as ethyl acetate and butyl acetate; ether ester compounds such as methoxybutyl acetate; diethyl ether, tetrahydrofuran, ethylene glycol monoethyl ether, and ethylene glycol Ether compounds such as monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether; ketone compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone, di-n-butyl ketone, cyclohexanone; methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, sec-butyl alcohol, tert-butyl alcohol, 2-ethylhexyl alcohol Alcohol compounds such as benzyl alcohol; dimethylformamide, dimethylacetamide, amide compounds such as N- methylpyrrolidone; sulfoxides compounds such as dimethyl sulfoxide; water and the like. These can be used alone or in combination of two or more.

The composition for forming a light guide of the present invention contains a photopolymerization initiator, and is applied to a substrate, injected into a mold, etc., dried as necessary, and then irradiated with active energy rays. Thus, a cured product (light guide) excellent in transparency and suppressed in stickiness can be formed.
Active energy rays include ultraviolet rays, electron beams, X-rays, infrared rays and visible rays. Among these, from the viewpoints of curability and resin deterioration prevention, ultraviolet rays and electron beams are preferable, and ultraviolet rays are particularly preferable. As a light source for ultraviolet rays, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a metal halide lamp, a microwave excitation mercury lamp, or the like can be used.

Regarding the transparency of the light guide obtained as described above, the total light transmittance is preferably more than 85% when a light guide having a thickness of 2 mm is measured according to JIS K7361-1. Preferably it is 88% or more, More preferably, it is 90% or more.
Moreover, when A hardness of the said light guide is measured according to JISK6253, Preferably it is 71-95, More preferably, it is 78-94, More preferably, it is 80-93.
In addition, when a finger pressure or the like is obtained on the surface of the light guide so as to obtain a pressing feeling (feel the formation of a recess), the restoration from the recess to the original state (smooth surface) is quick, Appropriate flexibility and resistance to repeated strains. And stickiness is suppressed and it has non-adhesiveness.

2. Light Guide Sheet The light guide sheet of the present invention is characterized in that the coating formed using the light guide body forming composition of the present invention is irradiated with an active energy ray and cured. This light guide composition is usually a composition containing a photopolymerization initiator.
The light guide sheet of the present invention may be a cured sheet (single-layer sheet) formed using a light guide forming composition, or a thin-walled base material using a light guide forming composition. It may be a laminated sheet formed on the surface, and further, a laminated structure having a structure in which a cured layer formed by using a composition for forming a light guide is sandwiched from both sides by a two-leaf thin-walled substrate. It may be a mold sheet.

  When the light guide sheet of the present invention is all of the above embodiments, the thickness of the cured product formed using the composition for forming a light guide is preferably 50 μm to 1.0 mm, more preferably 100 μm. ˜500 μm.

Hereinafter, the manufacturing method of a 1 layer type sheet | seat is demonstrated.
The composition for forming a light guide according to the present invention is applied onto a substrate having a smooth surface, and after the coating film is dried as necessary, the dry coating film is irradiated with active energy rays to form a one-layer sheet. Obtainable.
The base material for coating is polypropylene resin, polyethylene resin, ethylene / vinyl acetate copolymer, polyisobutylene, polybutadiene, polystyrene resin, polycarbonate resin, polymethylpentene resin, ionomer resin, ABS resin, acrylic resin, polyvinyl alcohol. Further, a sheet-like body, a plate-like body, a block-like body or the like containing a polyamide resin, a polyacetal resin, a polyester resin or the like can be used.
The coating method of the composition is not particularly limited, and is an applicator, bar coater, wire bar coater, roll coater, curtain flow coater, gravure coater, roll coater (size press roll coater, gate roll coater, etc.), air knife coater, spin coater. A blade coater or the like can be used.
In addition, the irradiation of active energy rays may be performed directly on the dried coating, or may be performed in a state where a film or the like that transmits active energy rays is disposed on the surface thereof. The irradiation energy (integrated light amount) is appropriately selected depending on the composition of the composition, the thickness of the dry film, etc., but is usually about 200 to 2,200 mJ / cm ² .

  The thickness of the light guide sheet of the present invention is usually 30 μm to 2.0 mm, preferably 50 μm to 1.0 mm, more preferably 100 μm to 500 μm.

Since the light guide sheet of the present invention obtained by using the composition for forming a light guide of the present invention has the properties as described above, it is suitable for electronic devices such as mobile phones, electronic notebooks, electronic dictionaries, and cameras. It can use as a translucent member etc. for arrangement | positioning.
For example, in the electronic device as described above, when a light emitting function is given to a plurality of key buttons or the like (operation unit) displaying or not displaying numbers, characters, symbols, illustrations, etc. on the front side, the brightness of the key buttons In order to equalize the light, a large number of light emitters are not disposed inside the device, but a light guide sheet (translucent member) is disposed on the lower side inside all the key buttons to guide the light. Light can be introduced from the end face of the light sheet (translucent member) by a smaller number of light emitters, and the key button can be illuminated from the surface of the light guide sheet (translucent member).
The illumination structure of this aspect is illustrated by FIG. That is, the illumination structure includes a light guide sheet 1 and a light source 2 (such as an LED) that is disposed on the end surface of the light guide sheet 1 and emits light toward the inside of the light guide sheet 1. By adopting such an illumination structure, it is possible to reduce the weight and power consumption of the electronic device and further reduce the size (thinner).

In order to further increase the brightness of the key button, a method of forming a fluorescent part on the surface of the light guide sheet 1 at a position corresponding to the key button (not shown), the key button on the surface of the light guide sheet 1 There is a method of disposing or printing the mask portion 5 on a portion not corresponding to (see FIG. 2).
The light guide sheet of the present invention is excellent in printability such as screen printing, and is excellent in image visibility even when the contact of a key button or the like is repeated.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.

1. Prepolymer production raw materials The prepolymer production raw materials used in the following Examples and Comparative Examples are shown.
1-1. Ingredient (A)
1-1-1. Polyether polyol (A1)
The number of functional groups is 2, the hydroxyl value is 56.1 mgKOH / g, and the number average molecular weight is 2,000.
1-1-2. Polyether polyol (A2)
The number of functional groups is 2, the hydroxyl value is 280.5 mgKOH / g, and the number average molecular weight is 400.
1-1-3. Polyether polyol (A3)
The number of functional groups is 2, the hydroxyl value is 37.4 mgKOH / g, and the number average molecular weight is 3,000.

1-2. Ingredient (B)
1-2-1. Polycarbonate diol (B1)
A polycarbonate polyol obtained by subjecting 3-methyl-1,5-pentanediol and 1,6-hexanediol in a molar ratio of 90:10 to diethyl carbonate and a condensation reaction was used. The number of functional groups is 2, the hydroxyl value is 224.4 mgKOH / g, and the number average molecular weight is 500.
1-2-2. Polycarbonate diol (B2)
A polycarbonate polyol obtained by condensation reaction of 2-methyl-1,8-octanediol and 1,9-nonanediol in a molar ratio of 85:15 and diethyl carbonate was used. The number of functional groups is 2, the hydroxyl value is 112.2 mgKOH / g, and the number average molecular weight is 1,000.
1-2-3. Polycarbonate diol (B3)
A polycarbonate polyol obtained by subjecting 3-methyl-1,5-pentanediol and 1,6-hexanediol in a molar ratio of 90:10 to diethyl carbonate and a condensation reaction was used. The number of functional groups is 2, the hydroxyl value is 65.1 mgKOH / g, and the number average molecular weight is 2,000.

1-3. Ingredient (C)
1-3-1. Polyisocyanate (C1)
Dicyclohexylmethane diisocyanate was used.
1-3-2. Polyisocyanate (C2)
Hexamethylene diisocyanate was used.
1-3-3. Polyisocyanate (C3)
Toluene diisocyanate was used.

1-4. Ingredient (D)
2-Hydroxyethyl methacrylate (HEMA) was used.

1-5. Catalyst Dibutyltin dilaurate was used.

2. Production and Evaluation of Light Guide Forming Composition Using the above-described raw materials for producing a prepolymer, a prepolymer was synthesized, and a photoinitiator was added to produce a composition for forming a light guide. Then, the cured film was produced by irradiating the film formed using the light guide forming composition with ultraviolet rays. Various evaluations were performed on the cured product.

Example 1
In a reactor equipped with a stirring blade, 485.13 g of polyether polyol (A1), 121.28 g of polycarbonate polyol (B1), and 126.27 g of component (D) 2-hydroxyethyl methacrylate were added and stirred at room temperature for 30 minutes. did. Thereafter, 267.32 g of polyisocyanate (C1) was added while stirring the mixture, and the mixture was further stirred for 30 minutes.
Next, 0.03 g of dibutyltin dilaurate catalyst was added, and the temperature was gradually raised over 30 minutes until the internal temperature reached 85 ° C. And it stirred, maintaining internal temperature at 80 to 90 degreeC. After 4 hours, the amount of residual NCO in the reaction solution was measured by NCO titration according to JIS K1603. After confirming that it was 0.5% or less, the reaction was terminated, and prepolymer (P1) was removed. Obtained. When the viscosity of this prepolymer (P1) was measured with a B-type viscometer “DV-1 +” (model name) manufactured by BROOKFIELD (rotor type No. 4), it was 14,430 mPa · s (see Table 1). ).
Thereafter, the reaction solution is allowed to cool, and it is confirmed that the internal temperature is 40 ° C. or less, and 5.0 g of a photopolymerization initiator (2-hydroxy-2-methylpropiophenone) is added and stirred for 2 hours. And the composition for light guide formation containing the prepolymer (P1) and a photoinitiator was obtained.

For the test having the shape and size according to the evaluation contents (light transmittance, hue, stickiness, A hardness, tensile strength, tensile elongation and tear strength) using the obtained light guide forming composition A cured product was prepared and evaluated for physical properties. The results are shown in Table 1.
In addition, as a hardened | cured material, the preparation methods of a cured sheet are as follows, for example.
About 50 g of a light guide forming composition heated with stirring at 90 ° C. for 24 hours was fixed to a vacuum table of a single plate knife coater “SNC-300” (model name) manufactured by Yasui Seiki Co., Ltd. On a PET film (F1). Thereafter, a PET film (F2) having a thickness of 75 μm was placed on the composition, and the two films were fixed in a state of sandwiching the composition.
Next, the composition was stretched from above the PET film (F2) with a knife coater, so that the composition had a uniform thickness between the two films. And it was moved from the coater to the glass plate promptly with the composition sandwiched therebetween.
Then, with the PET film remaining, UV irradiation was performed using a UV irradiation machine “Grandage ECS-401GX” (trade name) manufactured by iGraphics, Inc. under the condition of an integrated light amount of 1,800 mJ / cm ² to obtain a cured sheet It was.

(1) Light transmittance Measurement was performed according to JIS K7361-1 using a cured sheet having a thickness of 2 mm as a test piece. The measurement apparatus is an ultraviolet-visible spectrophotometer “V-650” (model name) manufactured by JASCO Corporation, and the measurement wavelength is 380 to 780 nm.
(2) Hue Measured according to CIE 1976.
(3) Stickiness At room temperature, a cured sheet of 100 mm × 100 mm × 0.2 mm is placed on a white PET film (thickness 50 μm) manufactured by Toray Industries, and using only a spring, the surface of the cured sheet is After applying a load 2N for 5 seconds and subsequently applying a load 3N for 5 seconds, the load was released and the time until the cured cured sheet and white PET film were peeled was measured. The judgment criteria are as follows.
○: Within 0 to 30 seconds Δ: Over 30 seconds and within 60 seconds ×: Over 60 seconds (4) A hardness Measured according to JIS K6253.
(5) Tensile strength and tensile elongation Measured according to JIS K6251 (Dumbell No. 3).
(7) Tear strength Measured according to JIS K6252 (angle type without cut).

Examples 2-12 and Comparative Examples 1-4
Prepolymers (P2) to (P16) were produced in the same manner as in Example 1 except that the components (A) to (D) were used in the ratios shown in Tables 1, 2 and 3, and then the introduction A composition for forming a light body was prepared. And hardened | cured material (cured sheet) was produced like Example 1 and various evaluation was performed. The results are shown in Table 1, Table 2 and Table 3.

As is clear from Table 1, Table 2, and Table 3, Comparative Examples 1 to 3 are examples containing a prepolymer produced without using the component (B), and in the obtained cured sheet, light transmission Although the rate was high, the stickiness was high. Moreover, the comparative example 4 is an example using aromatic polyisocyanate, and the obtained cured sheet was colored slightly yellow. This yellow color increased in concentration over time.
On the other hand, Examples 1-12 are the examples using the composition for light guide formation containing the prepolymer concerning this invention, and the transmittance | permeability exceeds 85% and A hardness is 71-93. Could be formed. Among them, in Examples 1 and 2, the stickiness is remarkably suppressed, the A hardness is in the range of 80 to 93, the light transmittance is 90 to 92%, and the balance between hardness and transparency is achieved. It was excellent.

  A cured product having a thickness of 50 mm was formed using each of the compositions for forming light guides of Examples 3 and 4 and Comparative Example 1, and a durability test (temperature 85 ° C., humidity 85% RH, 1 , 000 hours) before and after the light transmittance was measured, the maintenance rate [(transmittance after test / transmittance before test) × 100] was 94%, 89% and 42%, respectively. .

  A cured product (light guide) obtained using the composition for forming a light guide according to the present invention has transparency, moderate hardness and flexibility, is suppressed in stickiness, and has excellent light resistance. Since it is excellent in shape stability, it is suitable as a translucent member. And as a desired shape such as a sheet, it can be used for lighting structures such as operation sections in electronic devices such as mobile phones, electronic notebooks, electronic dictionaries, cameras, etc., members constituting TVs, displays, personal computers, other household appliances, etc. Can do.

1: Light guide sheet 11: Exposed portion of light guide sheet 2: Light source 5: Mask portion

Claims (5)

  (A) A polyether polyol, (B) a polycarbonate diol, (C) an aliphatic and / or alicyclic polyisocyanate, and (D) a prepolymer obtained by reacting a (meth) acrylate having a hydroxyl group. A composition for forming a light guide.   The composition for forming a light guide according to claim 1, wherein the polyether polyol (A) has a number average molecular weight of 1,000 to 2,800.   The composition for forming a light guide according to claim 1 or 2, wherein the polycarbonate diol (B) has a number average molecular weight of 300 to 1,500.   The composition for forming a light guide according to any one of claims 1 to 3, wherein the polyisocyanate (C) is at least an alicyclic polyisocyanate among an alicyclic polyisocyanate and an aliphatic polyisocyanate.   A light guide sheet obtained by irradiating an active energy ray on a coating film formed using the composition for forming a light guide body according to claim 1.

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