JP2013028776A - Transparent composite sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent composite sheet which has reduced optical anisotropy.SOLUTION: The transparent composite sheet includes: a cured product obtained by curing a curable composition; and a glass fiber buried into the cured product. The curable composition includes: first monomers forming a polymer having positive refractive index anisotropy; and second monomers forming a polymer having negative refractive index anisotropy. A difference between the refractive index of the cured product in a wavelength of 589 nm and the refractive index of the glass fiber in a wavelength of 589 nm is ≤0.01, and the in-plane phase difference in a wavelength of 550 nm of the transparent composite sheet in which the polymers are uniaxially oriented along the glass fiber is ≤5 nm.

Description

  The present invention relates to a transparent composite sheet having a cured product obtained by curing a curable composition and glass fibers embedded in the cured product.

  Glass substrates are widely used for display element substrates such as liquid crystal display elements or organic EL display elements, and solar cell substrates. The glass substrate has problems that it is easily broken, has low bendability, and cannot be reduced in weight. For this reason, in recent years, it has been studied to use a plastic substrate instead of a glass substrate.

  As an example of the plastic substrate, the following Patent Document 1 describes a plastic obtained by impregnating a glass cloth with a resin composition and drying to obtain a prepreg, and then thermally curing the prepreg while pressing. A substrate is disclosed.

  On the other hand, a plastic substrate used for a display element is required to have a small optical anisotropy. If the optical anisotropy is large, the display performance of the display element may be degraded.

  In a display element such as a liquid crystal display element using an optical shutter function of a polarizing plate and a liquid crystal drive, the display performance of the display element is affected by a change in the polarization state of transmitted light passing through a transparent substrate which is a plastic substrate. . When the optical anisotropy of the transparent substrate is large, the incident linearly polarized light that has passed through the polarizing plate becomes elliptically polarized light due to the optical anisotropy in the transparent substrate, and is transmitted through the output-side polarizing plate when the liquid crystal is driven. The switching performance between light transmission and non-transmission may deteriorate. In order to obtain a high-contrast display element, it is necessary to apply a transparent substrate having a small optical anisotropy.

  However, conventionally, a transparent substrate used in a display element has a problem that optical anisotropy occurs due to a stress generated at a contact interface between a glass fiber and a resin. Thermal stress caused by the difference in process temperature and thermal expansion coefficient during the production of transparent substrates is generated with a distribution in the transparent substrate due to the effect of compounding materials with different volumetric shrinkage and thermal expansion coefficient during curing. To do. There is a possibility that an optical anisotropy along the glass fiber and an optical anisotropy perpendicular to the glass fiber may appear due to the stress generated at the contact interface. For example, in the case of a transparent substrate using glass fibers and resin woven in length and width, a local optical difference between the direction along the glass fiber axis and the direction perpendicular to the direction along the glass fiber axis. Anisotropy develops. For this reason, a transmitted light pattern can be seen in a lattice pattern under a polarizing microscope in which the polarizer and the analyzer are crossed at 90 ° in the deflection axis (in a crossed Nicol state). In addition, since the optical anisotropy of the transparent substrate appears in a direction orthogonal to the direction along the fiber axis of the glass fiber, the lattice-shaped transmitted light pattern has the fiber axis of the glass fiber inclined by 45 ° from the polarizer. Brightest in condition. That is, in a display element using a transparent substrate, depending on the arrangement of the polarizing plate and the fiber axis of the glass fiber in the transparent substrate, there is a possibility that the contrast of the display element is lowered due to disturbance of the polarization state of transmitted light.

  So far, studies on improvement of optical anisotropy have been reported. For example, in Patent Document 2 below, reduction of birefringence in a composite sheet using glass fibers and a resin is examined by using a specific inorganic filler. Moreover, in the following patent document 3, suppression of the expression of the optical anisotropy in a composite sheet is examined by using resin whose volume hardening shrinkage rate is 5% or less. In the following Patent Document 4, suppression of expression of optical anisotropy in the composite sheet is examined by selecting a resin structure. Moreover, in the following patent document 5, reduction of the birefringence of the composite sheet is examined by using glass fibers laminated so that the axes are shifted.

JP 2004-151291 A Japanese Patent No. 4539113 JP 2005-240028 A JP 2007-108553 A JP 2005-297212 A

  However, in the conventional composite sheets as described in Patent Documents 1 to 5, it may be difficult to obtain a composite sheet having sufficiently small optical anisotropy. Moreover, it is difficult for the conventional composite sheet to increase transparency, decrease optical anisotropy, and further increase heat resistance.

  An object of the present invention is to provide a transparent composite sheet having small optical anisotropy.

  A limited object of the present invention is to provide a transparent composite sheet having high transparency, low optical anisotropy, and excellent heat resistance.

  According to a wide aspect of the present invention, the curable composition has a cured product obtained by curing the curable composition and glass fibers embedded in the cured product, and the curable composition has a positive refractive index anisotropy. There is provided a transparent composite sheet comprising a first monomer that forms a polymer having a second polymer and a second monomer that forms a polymer having negative refractive index anisotropy.

  On the specific situation with the transparent composite sheet which concerns on this invention, the difference of the refractive index of the said hardened | cured material in wavelength 589nm and the refractive index of the said glass fiber in wavelength 589nm is 0.01 or less.

  In another specific aspect of the transparent composite sheet according to the present invention, the in-plane retardation at a wavelength of 550 nm of the transparent composite sheet in which the polymer is uniaxially oriented along the glass fiber is 5 nm or less.

  The light transmittance at a wavelength of 550 nm of the transparent composite sheet according to the present invention is preferably 85% or more. It is preferable that the average linear expansion coefficient in 50-200 degreeC of the transparent composite sheet which concerns on this invention is 20 ppm / degrees C or less. The thickness of the transparent composite sheet according to the present invention is preferably 25 μm or more and 200 μm or less.

  The transparent composite sheet according to the present invention has a cured product obtained by curing the curable composition and glass fibers embedded in the cured product, and the curable composition further has a positive refractive index anisotropic. A first monomer that forms a polymer having high refractive index and a second monomer that forms a polymer having negative refractive index anisotropy. By mixing at a ratio that cancels the refractive index anisotropy, the expression of optical anisotropy can be suppressed. The optical anisotropy of the transparent composite sheet according to the present invention can be reduced.

  Hereinafter, the present invention will be described in detail.

  The transparent composite sheet which concerns on this invention has the hardened | cured material which hardened the curable composition, and the glass fiber embedded in this hardened | cured material. The curable composition includes a first monomer that forms a polymer having positive refractive index anisotropy, and a second monomer that forms a polymer having negative refractive index anisotropy. including. The first and second monomers are curable compounds. A polymer obtained by curing the first monomer alone as a curable compound has positive refractive index anisotropy. A polymer obtained by curing the second monomer alone as a curable compound has negative refractive index anisotropy. By adjusting the mixing ratio of the two types of the first and second monomers to a ratio that cancels the refractive index anisotropy in the cured product, it is possible to suppress the expression of optical anisotropy. A transparent composite sheet having a very small optical anisotropy is suitably used for a liquid crystal display element. Moreover, since the transparent composite sheet which concerns on this invention is equipped with the said structure, it is highly transparent, its optical anisotropy is small, and also is excellent in heat resistance.

  The difference between the refractive index of the cured product obtained by curing the curable composition and the refractive index of the glass fiber is preferably 0.01 or less. The refractive index is a value at a wavelength of 589 nm. By satisfying such a refractive index difference, the transparency of the transparent composite sheet is further improved. For example, the haze value of the transparent composite sheet can be 10% or less, and can be 5% or less.

  The transparent composite sheet can be obtained by curing the curable composition by at least one of heating and irradiation with actinic rays. The transparent composite sheet can be obtained, for example, by impregnating glass fiber with a curable composition and then curing the curable composition.

  Hereinafter, first, the detail of each component contained in the transparent composite sheet which concerns on this invention is demonstrated.

[Curable compound]
The first and second monomers contained in the transparent composite sheet are curable compounds. A transparent resin is suitably used as the curable compound. The first monomer is not particularly limited as long as it is a monomer that forms a polymer having positive refractive index anisotropy. The second monomer is not particularly limited as long as it is a monomer that forms a polymer having negative refractive index anisotropy.

  Examples of the transparent resin include polyester resin, polyethylene resin, poly (meth) acrylic resin, polystyrene resin, polycarbonate resin, polyamide resin, polyacetal resin, polyphenylene sulfide resin, (meth) acrylic resin, epoxy resin, phenol resin, vinyl ester resin. , Polyimide resin, melamine resin, urea resin, silsesquioxane resin and the like.

  The transparent resin is preferably a liquid curable resin at room temperature (25 ° C.) before curing. The transparent resin is preferably at least one selected from the group consisting of (meth) acrylate compounds, epoxy compounds, silsesquioxane compounds, and compounds having a vinyl group.

  In order to use the transparent composite sheet according to the present invention as a plastic substrate, the transparent composite sheet is required to have high heat resistance. In order to increase the heat resistance of the transparent composite sheet, the first monomer preferably has two or more polymerizable functional groups, and more preferably has two or more unsaturated bonds. In order to increase the heat resistance of the transparent composite sheet, the second monomer preferably has two or more polymerizable functional groups, and more preferably has two or more unsaturated bonds.

  The compound having two or more polymerizable functional groups is not particularly limited, but a polyfunctional (meth) acrylate compound is preferable. In the present specification, the (meth) acrylate compound means an acrylate compound and a methacrylate compound. From the viewpoint of further improving the heat resistance of the transparent composite sheet, a methacrylate compound is preferable among the acrylate compound and the methacrylate compound. That is, from the viewpoint of further improving the heat resistance, the polymerizable functional group is preferably a methacryloyl group. The polyfunctional (meth) acrylate compound is not particularly limited. For example, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, neopentyl glycol, 3-methyl 1,5-pentanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 2-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, dimethylol-tricyclode Bifunctional monomers such as candi (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate and tritetramethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylol group Trifunctional monomers such as pantri (meth) acrylate, trimethylolethane tri (meth) acrylate and dipentaerythritol tri (meth) acrylate, as well as pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol Examples include tetra- or higher functional monomers such as penta (meth) acrylate and dipentaerythritol hexa (meth) acrylate. A polyfunctional epoxy (meth) acrylate compound is also preferably used, and a polyfunctional urethane (meth) acrylate compound is also preferably used. Furthermore, a modified product of polyfunctional (meth) acrylate can also be used. As for the said polyfunctional (meth) acrylate compound, only 1 type may be used and 2 or more types may be used together.

  The polyfunctional (meth) acrylic compound is more preferably a polyfunctional alicyclic (meth) acrylate or a (meth) acrylate having a polyfunctional triazine ring structure. The polyfunctional alicyclic (meth) acrylate is preferably norbornane dimethylol diacrylate or dicyclopentadienyl diacrylate. The (meth) acrylate having a polyfunctional triazine ring structure is preferably isocyanuric acid tris (2-acryloyloxyethyl) or ε-caprolactone-modified isocyanuric acid tris (2-acryloyloxyethyl).

  A polymer obtained by polymerizing a compound having two or more polymerizable functional groups often has positive refractive index anisotropy. A polymer obtained by polymerizing a compound having two or more polymerizable functional groups is suitably used as the first monomer. By blending the second monomer that forms a polymer having negative refractive index anisotropy with the first monomer that forms such a polymer having positive refractive index anisotropy, Thus, the expression of refractive index anisotropy can be effectively suppressed. When the first monomer and the second monomer are used, compared to the case where only the first monomer is used or the case where only the second monomer is used. Thus, the refractive index anisotropy can be reduced.

  The first monomer forming the polymer having positive refractive index anisotropy has a (meth) acrylate compound having a triazine skeleton, a (meth) acrylate compound having a fluorene skeleton, or a dioxane skeleton. A (meth) acrylate compound is preferred. The first monomer may be a (meth) acrylate compound having a dicyclopentanyl skeleton or a (meth) acrylate compound having a fluorene skeleton, and a (meth) acrylate having a dicyclopentanyl skeleton. It may be a compound or a (meth) acrylate compound having a dioxane skeleton, or a (meth) acrylate compound having a fluorene skeleton or a (meth) acrylate compound having a dioxane skeleton. The first monomer may be a (meth) acrylate compound having a triazine skeleton, a (meth) acrylate compound having a fluorene skeleton, or a (meth) acrylate compound having a dioxane skeleton. May be.

  As the (meth) acrylate compound having a triazine skeleton, a (meth) acrylate compound having a triazine skeleton represented by the following formula (1) (hereinafter sometimes abbreviated as (meth) acrylate compound (1)) is preferable. Used for. The refractive index of the cured product of the (meth) acrylate compound (1) is 1.530 or more and 1.545 or less.

  In said formula (1), R1-R6 represents a hydrogen atom or a methyl group, respectively, and the sum total of n1, n2, and n3 represents 0.5-3 on average. The sum total of n1, n2 and n3 is an average, preferably 0.5-2.

  In addition, the average value of the sum total of n1, n2, and n3 is a value in the whole (meth) acrylate compound having a triazine skeleton represented by the formula (1) contained in the curable composition. That is, for example, as a compound represented by the above formula (1), a compound in which n1 = 1, n2 = 0 and n3 = 0 (n1 + n2 + n3 = 1), n1 = 1, n2 = 1 and n3 = 0 (n1 + n2 + n3) = 2) When the same number of compounds is included, the sum of n1, n2 and n3 is 1.5 on average.

  In display elements and solar cells, an inorganic material layer is often formed as a semiconductor layer or a conductive layer using an inorganic material. In the process of forming the inorganic material layer, the substrate is heated to about 180 to 300 ° C. The glass transition temperature of the cured product of the (meth) acrylate compound (1) is about 200 to 250 ° C. Therefore, by using the (meth) acrylate compound (1), the heat resistance of the cured product of the curable composition can be increased, and the glass transition temperature of the cured product can be 180 ° C. or higher. Moreover, the curable composition which gives the hardened | cured material which can endure the high temperature process which forms the inorganic material layer in a display element and a solar cell can be obtained by use of the said (meth) acrylate compound (1).

  Furthermore, a (meth) acrylate compound having a fluorene skeleton is also preferably used as the first monomer that forms the polymer having positive refractive index anisotropy. By using the (meth) acrylate compound having the fluorene skeleton, the transparency of the cured product is further enhanced.

  The (meth) acrylate compound having the fluorene skeleton is a (meth) acrylate compound having a fluorene skeleton represented by the following formula (2) (hereinafter sometimes abbreviated as (meth) acrylate compound (2)). It is preferable. By using the (meth) acrylate compound (2), the refractive index of the cured product of the curable composition can be easily controlled within a suitable range, and the transparency of the cured product can be further enhanced.

  In the above formula (2), R11 to R16 each represent a hydrogen atom or a methyl group, and m1 and m2 each represent 1 or 2.

  The glass transition temperature of the cured product of the (meth) acrylate compound having the fluorene skeleton is relatively high. The glass transition temperature of the cured product of the (meth) acrylate compound (2) is 250 to 300 ° C. Therefore, by using the (meth) acrylate compound having a fluorene skeleton, the glass transition temperature of the cured product of the curable composition can be further increased, and the heat resistance of the cured product can be further enhanced. In particular, by using the (meth) acrylate compound (2), the glass transition temperature of the cured product of the curable composition can be further increased, and the heat resistance of the cured product can be further enhanced.

  Furthermore, a (meth) acrylate compound having a dioxane skeleton is also suitably used as the first monomer that forms the polymer having positive refractive index anisotropy. The (meth) acrylate compound having a dioxane skeleton is preferably a compound having a dioxane skeleton represented by the following formula (3) (hereinafter sometimes abbreviated as (meth) acrylate compound (3)). By using the (meth) acrylate compound (3), the refractive index of the cured product of the curable composition can be easily controlled within a suitable range, and the transparency of the cured product can be further enhanced.

  In said formula (3), R11 and R12 represent a hydrogen atom or a methyl group, respectively.

  Therefore, the first monomer forming the polymer having positive refractive index anisotropy is preferably a compound having a bifunctional or higher unsaturated bond, and has two or more (meth) acryloyl groups. More preferably, it is a compound having Further, the compound having two or more (meth) acryloyl groups is preferably a (meth) acrylate compound having a triazine skeleton, a (meth) acrylate compound having a fluorene skeleton, or a (meth) acrylate compound having a dioxane skeleton. . The first monomer is preferably a (meth) acrylate compound having a triazine skeleton, a (meth) acrylate compound having a fluorene skeleton, or a (meth) acrylate compound having a dioxane skeleton.

  Examples of the second monomer that forms the polymer having negative refractive index anisotropy include styrene, alkyl-substituted styrenes, vinyl aromatics, substituted products of the vinyl aromatics, and (meth) acrylate compounds. And maleimide compounds. The second monomer is preferably a monomer having a vinyl group or a (meth) acryloyl group.

  Specific examples of the alkyl-substituted styrenes include p-methylstyrene, m-methylstyrene, o-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3 , 5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene and the like. Examples of the vinyl aromatics and substituted vinyl aromatics include 1,1-diphenylethylene, N-vinylcarbazole, 2-vinylcarbazole, 4-vinylphenol, 4-vinylbiphenyl, methylcarboxyphenyl methacrylamide, (1-acetylindazol-3-ylcarbonyloxy) ethylene, phthalimidoethylene, 4- (1-hydroxy-1-methylpropyl) styrene, 2-hydroxymethylstyrene, 2-dimethylaminocarbonylstyrene, 2-phenylaminocarbonylstyrene 3- (4-biphenylyl) styrene, 4- (4-biphenylyl) styrene, 2,6-dichlorostyrene, perfluorostyrene, 2,4-diisopropylstyrene, 2,5-diisopropylstyrene, 2,4,6 -Trimethi Styrene, alpha-methyl styrene, 1-vinylnaphthalene and 2-vinylnaphthalene, and the like. Examples of the (meth) acrylate compound include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, and cyclohexyl (meth) acrylate. , Dicyclopentenyloxyethyl (meth) acrylate, dicyclopentenyloxy (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, naphthyl (meth) acrylate, N, N-dimethylacrylamide and N- (meth) Examples include acryloylmorpholine. Examples of the maleimide compound include N-phenylmaleimide and N-cyclohexylmaleimide.

  The transparent composite sheet according to the present invention is obtained by embedding glass fibers in a curable composition and curing the curable composition. In the transparent composite sheet according to the present invention, higher transparency is exhibited by bringing the refractive indexes of the cured product of the curable composition and the glass fiber closer to each other.

  In general, in order to obtain sufficient transparency applicable to a display element substrate or the like, a refractive index difference between a cured product of a curable composition serving as a matrix and glass fibers embedded in the cured product is 0.01. The following is desirable. In reality, it is difficult to completely match the refractive index of the cured product of the curable composition serving as the matrix and the refractive index of the glass fiber over the entire visible light range. In the present invention, light scattering can be minimized by appropriately designing the refractive index of the cured product of the curable composition serving as a matrix for the glass fiber.

  In the present invention, T glass or E glass can be used as the glass fiber. The refractive index of T glass at a wavelength of 589 nm is about 1.524. When T glass is used, the refractive index of the cured product of the curable composition at a wavelength of 589 nm is 1.515 or more and 1.535 or less, thereby having a cured product of the curable composition and glass fibers. Light scattering of the composite sheet, that is, haze value can be minimized. The refractive index of E glass at a wavelength of 589 nm is about 1.558. When using E glass, the refractive index of the hardened | cured material of a curable composition in wavelength 589nm shall be 1.548 or more and 1.568 or less, and it has the hardened | cured material and glass fiber of a curable composition. Light scattering of the composite sheet, that is, haze value can be minimized.

  In the transparent composite sheet according to the present invention, a first monomer that forms a polymer having positive refractive index anisotropy and a second monomer that forms a polymer having negative refractive index anisotropy Is used as appropriate, or the refractive index adjusting agent is used together with the first and second monomers, and the type and amount of the refractive index adjusting agent are appropriately adjusted to cure at a wavelength of 589 nm. The refractive index of the cured product of the adhesive composition can be adjusted. When the refractive index difference between the refractive index of the cured product and the glass fiber is 0.05 or less, the transparency of the transparent composite sheet can be increased, and the haze value of the transparent composite sheet can be further reduced.

  Examples of the method for curing the curable composition according to the present invention include a method for curing by heating and a method for curing by actinic rays. You may use together hardening by heating, and hardening by actinic light. From the viewpoint of shortening the reaction time and completing the curing reaction, it is preferable to cure the curable composition by heating after curing the curable composition with actinic rays.

  The active light is preferably ultraviolet light. Examples of the light source for irradiating the ultraviolet light include a metal halide lamp and a high-pressure mercury lamp. When the curable composition is cured by heating, an oven and a heater are used. In order to suppress coloring due to oxidation and deterioration of the curable compound, when the curable composition is cured by heating, it may be heated at 150 to 300 ° C. for 1 to 24 hours in a nitrogen atmosphere or in a vacuum state. preferable.

  In order to cure the curable composition by heating, the curable composition preferably contains a thermal polymerization initiator. The thermal polymerization initiator is preferably a radical polymerization initiator. Examples of the radical polymerization initiator include peroxide radical polymerization initiators, azo radical polymerization initiators, and redox radical polymerization initiators. Thermal polymerization initiators other than these may be used. As for the said thermal-polymerization initiator, only 1 type may be used and 2 or more types may be used together.

  Examples of the azo radical polymerization initiator include azobisisobutyronitrile, azobiscyclohexanecarbonitrile, and azobisdimethylvaleronitrile.

  Examples of the peroxide radical polymerization initiator include a diacyl radical polymerization initiator, a peroxyester radical polymerization initiator, a dialkyl radical polymerization initiator, a carbonate radical polymerization initiator, and a ketone peroxide radical polymerization start. Agents and the like.

  Examples of the diacyl radical polymerization initiator include lauroyl peroxide and benzoyl peroxide. Examples of the peroxyester radical polymerization initiator include t-butyl peroxybenzoate, t-butyl peroxyacetate, t-butyl peroxypivalate, and t-butyl peroxy-2-ethylhexanoate. . Examples of the dialkyl radical polymerization initiator include dicumyl peroxide and di-t-butyl peroxide. Examples of the percarbonate-based radical polymerization initiator include diisopropyl peroxydicarbonate. Examples of the ketone peroxide radical polymerization initiator include methyl ethyl ketone peroxide.

  The redox radical polymerization initiator includes, for example, a peroxide and a reducing agent or a metal-containing compound. Specific examples of the redox radical polymerization initiator include a mixture of benzoyl peroxide and organic amines, a mixture of the peroxyester radical polymerization initiator and a reducing agent such as mercaptans, and methyl ethyl ketone peroxide and organic. Examples thereof include a mixture with a cobalt salt.

  From the viewpoint of further increasing the toughness of the cured product, a peroxide radical polymerization initiator is preferred. The amount of the thermal polymerization initiator used is not particularly limited. The content of the thermal polymerization initiator is preferably 0.05 parts by weight or more and preferably 5 parts by weight or less with respect to 100 parts by weight of the curable compound in the curable composition.

  In order to cure the curable composition by irradiation with actinic rays, the curable composition preferably contains a photopolymerization initiator. Examples of the photopolymerization initiator include a photo radical polymerization initiator and a photo cationic polymerization initiator. The photopolymerization initiator is preferably a radical photopolymerization initiator. As for a photoinitiator, only 1 type may be used and 2 or more types may be used together.

  The photo radical polymerization initiator is not particularly limited, and examples thereof include benzophenone, N, N′-tetraethyl-4,4′-diaminobenzophenone, 4-methoxy-4′-dimethylaminobenzophenone, and 2,2-diethoxyacetophenone. , Benzoin, benzoin methyl ether, benzoin propyl ether, benzoin isobutyl ether, benzyldimethyl ketal, α-hydroxyisobutylphenone, thioxanthone, 2-chlorothioxanthone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio ) Phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2,6-dimethylbenzoyldiphenylphosphine Xoxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, t-butylanthraquinone, 1-chloroanthraquinone, 2,3-dichloroanthraquinone, 3-chloro-2-methylanthraquinone, 2-ethylanthraquinone, 1,4-naphthoquinone 9,10-phenanthraquinone, 1,2-benzoanthraquinone, 1,4-dimethylanthraquinone, 2-phenylanthraquinone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2-mercapto Examples include benzothiazole, 2-mercaptobenzoxazole, and 4- (p-methoxyphenyl) -2,6-di- (trichloromethyl) -s-triazine. As for the said radical photopolymerization initiator, only 1 type may be used and 2 or more types may be used together.

  It does not specifically limit as said photocationic polymerization initiator, For example, a sulfonium salt, an iodonium salt, a metallocene compound, a benzoin tosylate etc. are mentioned. As for the said photocationic polymerization initiator, only 1 type may be used and 2 or more types may be used together.

  Commercially available products of the above cationic photopolymerization initiator include Cyracure UVI-6970, Cyracure UVI-6974, and Cyracure UVI-6990 (all manufactured by Union Carbide), Irgacure 264 (Ciba Japan), and CIT-1682 ( Nippon Soda Co., Ltd.).

  The content of the photopolymerization initiator is preferably 0.01 parts by weight or more and preferably 10 parts by weight or less with respect to 100 parts by weight of the curable compound in the curable composition. A curable composition can fully be hardened as content of the said photoinitiator is more than the said minimum. When the content of the polymerization initiator is less than or equal to the above upper limit, polymerization does not proceed rapidly, and problems such as increased birefringence, coloring, and cracking during curing are less likely to occur.

  When the photopolymerization initiator is a photoradical polymerization initiator, the content of the photoradical polymerization initiator is preferably 0.01% by weight with respect to 100 parts by weight of the curable compound in the curable composition. Part or more, more preferably 0.1 part by weight or more, preferably 2 parts by weight or less, more preferably 1 part by weight or less.

  When the photopolymerization initiator is a photocationic polymerization initiator, the content of the photocationic polymerization initiator is preferably 1 part by weight or more with respect to 100 parts by weight of the curable compound in the curable composition. , Preferably 10 parts by weight or less, more preferably 5 parts by weight or less.

  The said curable composition may contain the solvent as needed by the objective etc. which adjust a viscosity. The solvent is preferably a solvent that does not react with the components in the curable composition. A volatile solvent is preferred because it needs to be removed by heating in an oven or hot plate and reduced pressure in a vacuum chamber before the curing reaction of the curable composition.

  The curable composition includes a weathering agent, an antioxidant, a heat stabilizer, an antistatic agent, a whitening agent, a colorant, a conductive agent, a release agent, a surface treatment agent, a viscosity modifier, etc. May be included.

[Glass fiber and transparent composite sheet]
The transparent composite sheet which concerns on this invention has the hardened | cured material which hardened the said curable composition, and the glass fiber embedded in this hardened | cured material.

  After making the curable composition concerning this invention into a sheet form, a transparent composite sheet can be obtained by bridge | crosslinking and hardening a curable composition by irradiation of irradiation of actinic light.

  Examples of the glass fiber include chopped strands of glass fiber, woven fabric of glass fiber, and nonwoven fabric of glass fiber. The glass fiber is preferably a glass fiber woven fabric.

  As the glass fiber woven fabric, for example, a yarn obtained by twisting about 100 to 800 long fibers (filaments) having a circular or oval cross section and a longest cross sectional diameter of about 3 to 10 μm is used as a warp. And obtained by weaving these yarns so as to cross each other. Examples of the weaving method include plain weave, twill weave and satin weave.

  The thickness of the glass fiber is the thickest part and is usually 10 to 500 μm. The thickness of the glass fiber is the thickest part, and is preferably 15 to 350 μm.

  The glass fiber is preferably E glass or T glass. Regarding the fiber diameter, fiber bundle diameter, basis weight as a glass cloth, weaving density, thickness, and the like, the E glass and T glass have various standard products. From the viewpoints of performance, cost, and availability, E glass is preferably used. Moreover, T glass is used suitably from a viewpoint of making the thermal dimensional stability of the transparent composite sheet obtained favorable. T glass has a small coefficient of thermal expansion.

  The tensile elastic modulus of the glass fiber is preferably 5 GPa or more, more preferably 10 GPa or more, preferably 500 GPa or less, more preferably 200 GPa or less. The intensity | strength of a transparent composite sheet becomes it high that the said tensile elasticity modulus is more than the said minimum.

  The thickness of the transparent composite sheet according to the present invention is not particularly limited. The thickness of the transparent composite sheet according to the present invention is preferably 20 μm or more, more preferably 25 μm or more, preferably 1000 μm or less, more preferably 500 μm or less, and particularly preferably 200 μm or less. When the thickness of the transparent composite sheet is not less than the above lower limit, sufficient strength and rigidity can be maintained as a display device substrate. When the thickness of the transparent composite sheet is less than or equal to the above upper limit, volume shrinkage when the curable composition is cured is reduced, a phase difference due to residual stress is less likely to occur, and display contrast is less likely to be reduced. Further, when the thickness of the transparent composite sheet is not more than the above upper limit, the transparent composite sheet is hardly warped, and the thickness of the transparent composite sheet becomes uniform.

  Since it can use suitably for the use of a display element and a solar cell, the thickness of the transparent composite sheet which concerns on this invention becomes like this. More preferably, it is 25 micrometers or more, More preferably, it is 200 micrometers or less. Even when the thickness of the transparent composite sheet is not less than the above lower limit and not more than the above upper limit, the heat resistance can be sufficiently enhanced. The “thickness” indicates an average thickness.

  Regarding glass fibers such as glass cloth and glass nonwoven fabric, only one sheet may be used, or a plurality of sheets may be used in an overlapping manner.

  When the thickness of the transparent composite sheet exceeds 1000 μm, the transparent composite sheet according to the present invention may be cured after being divided into a plurality of sheets and laminated. Furthermore, a sheet laminate may be obtained by repeating sheeting and curing.

  The light transmittance at 550 nm of the transparent composite sheet according to the present invention is preferably 80% or more, more preferably 85% or more, and further preferably 90% or more. When the light transmittance is not less than the above lower limit, for example, when an image display device is obtained using a transparent composite sheet as a substrate for a liquid crystal display device or an organic EL display device substrate, a clear image with high display quality is obtained. It is done. The light transmittance can be determined by measuring the total light transmittance at a wavelength of 550 nm using a commercially available spectrophotometer.

  The haze value of the transparent composite sheet according to the present invention is preferably 10% or less, more preferably 5% or less, and particularly preferably 4% or less. The haze value is measured based on JIS K7136. A commercially available haze maker is used as the measuring device. Examples of the measuring device include “Fully Automatic Haze Meter TC-HIIIDPK” manufactured by Tokyo Denshoku Co., Ltd.

  From the viewpoint of enhancing the dimensional stability of the transparent composite sheet, the average linear expansion coefficient at 50 to 200 ° C. of the transparent composite sheet according to the present invention is preferably 20 ppm / ° C. or less.

  A surface smoothing layer, a hard coat layer, or a gas barrier layer may be laminated on the transparent composite sheet according to the present invention.

  The in-plane retardation at a wavelength of 550 nm of the transparent composite sheet in which the cured product is uniaxially oriented along the glass fiber is preferably 5 nm or less. It is preferable that the in-plane retardation at a wavelength of 550 nm of the transparent composite sheet obtained by pulling out the warp of the glass fiber, impregnating the glass fiber in which only the weft is present with the curable composition, and curing is 5 nm or less. By using such a transparent composite sheet, a decrease in display performance of the display element can be suppressed.

  When forming the surface smoothing layer or hard coat layer, for example, a known surface smoothing agent or hard coat agent is applied onto the transparent composite sheet, and dried to remove the solvent as necessary. To do. Next, the surface smoothing agent or hard coat agent is cured by heating or irradiation with actinic rays.

  A method for applying a surface smoothing agent or a hard coating agent on the transparent composite sheet is not particularly limited, and examples thereof include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, an extrusion method, and a curtain. Conventionally known methods such as a coating method and a spray coating method can be employed.

The gas barrier layer is not particularly limited, and for example, a metal such as aluminum, a silicon compound such as SiO ₂ and SiN, a transparent material such as magnesium oxide, aluminum oxide, and zinc oxide can be used. Among them, the gas barrier properties, because excellent adhesion and transparency to the substrate layer, it is preferable to use a silicon compound such as SiO ₂ and SiN.

  The method for forming the gas barrier layer is not particularly limited, and examples thereof include dry methods such as a vapor deposition method and a sputtering method, and wet methods such as a sol-gel method. Among these, the sputtering method is particularly preferable from the viewpoint of forming a dense gas barrier layer having excellent gas barrier properties and good adhesion to a substrate.

  The transparent composite sheet which concerns on this invention is used suitably for the plastic substrate for liquid crystal display elements, the plastic substrate for organic EL display elements, a solar cell substrate, a touch panel, etc.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited only to the following examples.

Example 1
4-acryloylmorpholine (manufactured by Tokyo Chemical Industry Co., Ltd.), which is a material exhibiting negative refractive index anisotropy, in 60 parts by weight of tris (2-acryloyloxyethyl) isocyanurate (“A-9300” manufactured by Shin-Nakamura Chemical Co., Ltd.) 40 parts by weight and 0.2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (“Irgacure 907” manufactured by Ciba Japan Co., Ltd.) 0.2 which is a photopolymerization initiator The curable composition was prepared by adding the weight part and stirring while heating to 100 ° C., and mixing and dissolving.

  As a glass fiber, a glass cloth (manufactured by Nittobo Co., Ltd.) corresponding to IPC # 2013, which is a T glass fiber, was prepared. This glass cloth was immersed in a curable composition heated to 70 ° C., and the glass cloth was impregnated with the curable composition while being irradiated with ultrasonic waves. Then, the glass cloth impregnated with the curable composition was pulled up and placed on the release-treated glass plate. The glass cloth impregnated with the curable composition on the glass plate is covered with a PET film having a thickness of 100 μm (“Cosmo Shine A4100” manufactured by Toyobo Co., Ltd.) and passed through a laminator whose temperature is adjusted to 50 ° C. The thickness was made uniform.

Next, the curable composition was cured by irradiating with 2000 mJ / cm ² (365 nm) of ultraviolet light from the PET film side with a high-pressure mercury lamp.

  Further, the cured sheet was peeled off from the PET film and the glass plate, and heat-treated in an oven at 200 ° C. for 1 hour to obtain a transparent composite sheet. The thickness of the obtained transparent composite sheet was 85 μm.

(Example 2)
30 parts by weight of tris (2-acryloyloxyethyl) isocyanurate (“A-9300” manufactured by Shin-Nakamura Chemical Co., Ltd.) and ε-caprolactone-modified tris (2-acryloyloxyethyl) isocyanurate (“A-manufactured by Shin-Nakamura Chemical Co., Ltd.) 9300-1CL "), 30 parts by weight, 40 parts by weight of 4-acryloylmorpholine (manufactured by Tokyo Chemical Industry Co., Ltd.), which is a material exhibiting negative refractive index anisotropy, and 2-methyl-1- [4- (methylthio) Phenyl] -2-Morifolinopropan-1-one (“Irgacure 907” manufactured by Ciba Japan Co., Ltd.) is added in an amount of 0.2 parts by weight, stirred while heating to 100 ° C., mixed and dissolved, and cured. A sex composition was prepared.

  Using the obtained curable composition, a transparent composite sheet was obtained under the same operations and conditions as in Example 1. The thickness of the obtained transparent composite sheet was 80 μm.

(Example 3)
25 parts by weight of tris (2-acryloyloxyethyl) isocyanurate (“A-9300” manufactured by Shin-Nakamura Chemical Co., Ltd.) corresponds to dioxane glycol diacrylate (a (meth) acrylate compound represented by the above formula (3)). 18 parts by weight of Shin-Nakamura Chemical Co., Ltd. “A-DOG”, 57 parts by weight of 4-acryloylmorpholine (manufactured by Tokyo Chemical Industry Co., Ltd.) which is a material exhibiting negative refractive index anisotropy, and a photopolymerization initiator 0.2 parts by weight of 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (“Irgacure 907” manufactured by Ciba Japan) was added and heated to 70 ° C. The mixture was mixed and dissolved while stirring to prepare a curable composition.

  Using the obtained curable composition, a transparent composite sheet was obtained under the same operations and conditions as in Example 1. The thickness of the obtained transparent composite sheet was 80 μm.

Example 4
Isocyanuric acid tris (2-methacryloyloxyethyl) (synthetic prototype) 27 parts by weight, dioxane glycol dimethacrylate (synthetic prototype corresponding to the (meth) acrylate compound represented by the above formula (3)) 26 parts by weight And 47 parts by weight of 4-acryloylmorpholine (manufactured by Tokyo Chemical Industry Co., Ltd.) which is a material exhibiting negative refractive index anisotropy, and 2-methyl-1- [4- (methylthio) phenyl] which is a photopolymerization initiator -2- morpholinopropan-1-one ("Irgacure 907" manufactured by Ciba Japan Co., Ltd.) 0.2 part by weight, stirred while heating to 70 ° C, mixed and dissolved, curable composition A product was prepared.

  Using the obtained curable composition, a transparent composite sheet was obtained under the same operations and conditions as in Example 1. The thickness of the obtained transparent composite sheet was 85 μm.

(Example 5)
60 parts by weight of tris (2-acryloyloxyethyl) isocyanurate (“A-9300” manufactured by Shin-Nakamura Chemical Co., Ltd.) and 40 parts by weight of styrene (manufactured by Tokyo Chemical Industry Co., Ltd.), which is a material exhibiting negative refractive index anisotropy And 0.2 parts by weight of 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (“Irgacure 907” manufactured by Ciba Japan) as a photopolymerization initiator, Was added while stirring at 100 ° C., and mixed and dissolved to prepare a curable composition.

  Using the obtained curable composition, the same operation and conditions as in Example 1 except that a glass cloth corresponding to IPC # 2013 which is E glass fiber (manufactured by Nittobo Co., Ltd.) was used as the glass fiber. A transparent composite sheet was obtained. The thickness of the obtained transparent composite sheet was 80 μm.

(Example 6)
Isocyanuric acid tris (2-acryloyloxyethyl) (“A-9300” manufactured by Shin-Nakamura Chemical Co., Ltd.), 33 parts by weight, 9,9′-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene (Shin-Nakamura Chemical) "A-BPEF") 27 parts by weight, 4-acryloylmorpholine (Tokyo Chemical Industry Co., Ltd.) 40 parts by weight, which is a material exhibiting negative refractive index anisotropy, and 2-methyl photoinitiator Add 0.2 parts by weight of -1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (“Irgacure 907” manufactured by Ciba Japan) and stir while heating to 100 ° C. Then, they were mixed and dissolved to prepare a curable composition.

  Using the obtained curable composition, a transparent composite sheet was obtained under the same operations and conditions as in Example 5. The thickness of the obtained transparent composite sheet was 85 μm.

(Comparative Example 1)
Isocyanuric acid tris (2-acryloyloxyethyl) (“A-9300” manufactured by Shin-Nakamura Chemical Co., Ltd.) 50 parts by weight, ε-caprolactone modified tris (2-acryloyloxyethyl) isocyanuric acid (“N-Nakamura Chemical Co., Ltd.“ A- 9300-1CL ") and 50 parts by weight of 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (" Irgacure 907 "manufactured by Ciba Japan). The mixture was dissolved while being heated to 100 ° C., and mixed and dissolved to prepare a curable composition.

  Using the obtained curable composition, a transparent composite sheet was obtained under the same operations and conditions as in Example 1. The thickness of the obtained transparent composite sheet was 80 μm.

(Comparative Example 2)
Isocyanuric acid tris (2-acryloyloxyethyl) (“A-9300” manufactured by Shin-Nakamura Chemical Co., Ltd.) 10 parts by weight, ε-caprolactone-modified isocyanuric acid tris (2-acryloyloxyethyl) (manufactured by Shin-Nakamura Chemical Co., Ltd., “A- 9300-1CL "), 85 parts by weight, 5,9'-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene (" A-BPEF "manufactured by Shin-Nakamura Chemical Co., Ltd.), and 2-methyl- Add 0.2 part by weight of 1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (“Irgacure 907” manufactured by Ciba Japan) and stir while heating to 100 ° C. Were mixed and dissolved to prepare a curable composition.

  Using the obtained curable composition, a transparent composite sheet was obtained under the same operations and conditions as in Example 1. The thickness of the obtained transparent composite sheet was 80 μm.

(Comparative Example 3)
Isocyanuric acid tris (2-acryloyloxyethyl) (“A-9300” manufactured by Shin-Nakamura Chemical Co., Ltd.) in 73 parts by weight, 9,9′-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene (Shin-Nakamura Chemical) "A-BPEF" manufactured by KK) and 27 parts by weight of 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one ("Irgacure 907" manufactured by Ciba Japan) .2 parts by weight was added and stirred while heating to 100 ° C., and mixed and dissolved to prepare a curable composition.

  Using the obtained curable composition, a transparent composite sheet was obtained under the same operations and conditions as in Example 3. The thickness of the obtained transparent composite sheet was 85 μm.

(Evaluation)
a) Refractive index Two glass plates subjected to release treatment were prepared. The two glass plates are spaced by 100 μm, the curable composition obtained is sandwiched between the glass plates, and irradiated with 2000 mJ / cm ² (365 nm) of UV light with a high-pressure mercury lamp. The product was crosslinked and cured. Thereafter, the cured product was peeled off from the glass plate and subjected to heat treatment in an oven at 200 ° C. for 1 hour to prepare a test piece (cured product). The refractive index nD (sodium D line (589 nm), 25 ° C.) of the test piece was measured using an Abbe refractometer (“NAR-1T” manufactured by Atago Co., Ltd.). For the refractive index of the glass fiber, the manufacturer (Nittobo) nominal value was adopted.

b) Retardation in orientation state The warp yarn of the glass fiber was pulled out to produce a portion where only the weft yarn was present. The glass fiber containing only the weft yarn was impregnated with the curable composition to obtain a transparent composite sheet cured under the conditions of Examples and Comparative Examples. Since the polymer (polymer of the first and second monomers) is oriented along the fiber of the yarn, the portion where only the weft is present can be in a state close to uniaxial orientation. The in-plane retardation R0 in this state was measured and evaluated using a retardation film / optical material inspection apparatus (“RETS-1200RF” manufactured by Otsuka Electronics Co., Ltd.). In the measurement, the sample was heated at 230 ° C. for 30 minutes, and the phase difference after heating was evaluated.

c) Retardation at the time of glass cloth impregnation The transparent composite sheet which impregnated the glass cloth with the curable composition and was hardened on each condition of an Example and a comparative example was obtained. The in-plane retardation R0 and the thickness direction retardation Rth in this state were measured and evaluated using a phase difference measuring device (“KOBRA-WR” manufactured by Oji Scientific Instruments). In the measurement, the sample was heated at 230 ° C. for 30 minutes, and the phase difference before and after heating was evaluated.

d) Linear expansion coefficient After heating the transparent composite sheet obtained at a rate of 10 ° C./min from 30 ° C. to 300 ° C. using a thermal stress strain measuring device (“TMA / EXSTAR 6000 type” manufactured by Seiko Electronics Co., Ltd.) And cooled to 30 ° C. at a rate of 20 ° C./min. Thereafter, the average linear expansion coefficient at 50 ° C. to 200 ° C. when the temperature of the transparent composite sheet was increased from 30 ° C. to 300 ° C. at a rate of 10 ° C./min was obtained.

e) Glass transition temperature Using a dynamic viscoelasticity measuring device ("DVA-200" manufactured by IT Measurement & Control Co., Ltd.), the temperature of the transparent composite sheet obtained from 30 ° C to 300 ° C was increased at a rate of 10 ° C / min. Then, it was cooled to 30 ° C. at a rate of 20 ° C./min. Thereafter, the temperature of the transparent composite sheet obtained at a rate of 10 ° C./min up to 300 ° C. was raised again, and measurement in the tensile mode was performed. The peak temperature of tan δ was defined as the glass transition temperature. This glass transition temperature corresponds to the glass transition temperature of a cured product obtained by curing the curable composition.

f) Light transmittance The light transmittance at 550 nm of the obtained transparent composite sheet was measured using a spectrophotometer (“UV-310PC” manufactured by Shimadzu Corporation). When the light transmittance is 85% or more, the transparency is excellent.

g) Haze value The haze value of the obtained transparent composite sheet was measured using a haze meter ("Fully automatic haze meter TC-HIIIDPK" manufactured by Tokyo Denshoku Co., Ltd.). When the haze value is 5% or less, the transparency is excellent.

  The evaluation results are shown in Table 1 below.

Claims (6)

A cured product obtained by curing the curable composition, and glass fibers embedded in the cured product,
The curable composition comprises a first monomer that forms a polymer having positive refractive index anisotropy, and a second monomer that forms a polymer having negative refractive index anisotropy A transparent composite sheet.   The transparent composite sheet according to claim 1, wherein a difference between a refractive index of the cured product at a wavelength of 589 nm and a refractive index of the glass fiber at a wavelength of 589 nm is 0.01 or less.   The transparent composite sheet according to claim 1 or 2, wherein an in-plane retardation at a wavelength of 550 nm of the transparent composite sheet in which the polymer is uniaxially oriented along the glass fiber is 5 nm or less.   The transparent composite sheet of any one of Claims 1-3 whose light transmittance in wavelength 550nm is 85% or more.   The transparent composite sheet of any one of Claims 1-4 whose average linear expansion coefficient in 50-200 degreeC is 20 ppm / degrees C or less.   The transparent composite sheet of any one of Claims 1-5 whose thickness is 25 micrometers or more and 200 micrometers or less.