JP4613492B2 - Optical sheet - Google Patents

Description

  The present invention relates to an optical sheet having a small coefficient of linear expansion, excellent optical characteristics, and capable of replacing glass. The optical sheet of the present invention is preferable for a liquid crystal display element substrate, an organic EL display element substrate, a color filter substrate, a touch panel substrate, a solar cell substrate, and the like.

In general, glass plates are widely used as display element substrates (particularly active matrix type) for liquid crystal display elements and organic EL display elements, color filter substrates, solar cell substrates, and the like. However, in recent years, plastic materials have been studied as an alternative to glass plates because they are easily broken, cannot be bent, have a large specific gravity, and are not suitable for weight reduction.

For example, Patent Document 1 and Patent Document 2 describe a transparent resin substrate for a liquid crystal display element comprising a cured product obtained by curing an epoxy resin composition containing an epoxy resin, an acid anhydride curing agent, and a curing catalyst. ing. Patent Document 3 describes a liquid crystal display element using a transparent substrate obtained by curing and molding a composition containing a specific bis (meth) acrylate with active energy rays or the like.
However, these conventional plastic materials for glass substitutes have a larger coefficient of linear expansion than glass plates, and particularly when used for active matrix display element substrates, problems such as warping and disconnection of aluminum wiring occur in the manufacturing process. It is difficult to use. Therefore, there is a demand for a plastic material having a low linear expansion coefficient while satisfying the transparency, heat resistance, etc. required for a display element substrate, particularly an active matrix display element substrate.

  In order to reduce the coefficient of linear expansion, it is often performed to combine an inorganic filler such as glass fiber with a resin. However, the composite of these resins and inorganic fillers usually cannot provide a transparent composite material. This is mainly because the light transmitted through the resin is irregularly refracted because the refractive index of the inorganic filler is different from the refractive index of the resin.

  In order to solve such a problem, various studies have been made to make the refractive index of the resin and the glass fiber transparent. For example, Patent Document 4 and Patent Document 5 show that a transparent composite material can be obtained by reducing the difference in refractive index between a cyclic olefin resin and glass fiber. Non-Patent Document 1 shows that a transparent composite can be obtained using an epoxy resin and glass fibers having a refractive index close to that. However, when these materials are sandwiched between orthogonal polarizing plates (crossed Nicols) and irradiated with light, the polarization may be disturbed and light leakage may occur. For this reason, when these materials are used for a liquid crystal display element substrate or the like, the display quality may be deteriorated.

JP-A-6-337408 JP-A-7-120740 JP-A-10-90667 JP-A-6-256604 JP-A-6-305077 Abstracts of Symposium on Composite Materials, 22, 86 (1997)

An object of the present invention is to provide an optical sheet having a small linear expansion coefficient, excellent optical characteristics, and capable of replacing glass. The optical sheet of the present invention is suitably used for a liquid crystal display element substrate including an active matrix type, an organic EL display element substrate, a color filter substrate, a touch panel substrate, a solar cell substrate, and the like.

  The present inventors diligently studied to achieve the above problems. As a result, two or more layers of glass fibers formed by arranging and arranging glass fibers (b) close to or adjacent to each other in the same direction are laminated so that the axial directions of the glass fibers are perpendicular to each other, and transparent resin ( It has been found that the optical sheet embedded in a) is excellent in optical properties such as less light leakage in crossed Nicols and has a low linear expansion coefficient, thereby completing the present invention.

That is, the present invention
(1) Two or more layers of glass fibers formed by arranging and arranging the lath fibers (b) close to or adjacent to each other in the same direction are laminated so that the axial directions of the glass fibers are substantially orthogonal, and transparent resin (A) an optical sheet embedded in,
(2) When the substantially orthogonal glass fiber layers are distinguished in the vertical direction and the horizontal direction, the ratio of the total thickness of the glass fibers in the vertical direction and the total thickness in the horizontal direction is 0.67 to 1.5. (1) The optical sheet characterized by the above-mentioned.
(3) The optical sheet of (1) or (2), wherein the thickness of each layer of the glass fiber is 10 μm to 200 μm.
(4) The optical sheet of (1) to (3), wherein the difference between the refractive index of the transparent resin (a) and the refractive index of the glass fiber (b) is 0.01 or less.
(5) The optical sheet of (1) to (4), wherein the transparent resin (a) has an Abbe number of 45 or more,
(6) The optical sheet of (1) to (5), wherein the transparent resin (a) is an acrylate resin crosslinked with a (meth) acrylate having two or more functional groups as a constituent component,
(7) The optical sheet of (1) to (5), wherein the transparent resin (a) is an epoxy resin obtained by curing an epoxy resin having two or more functional groups as a constituent component,
(8) The optical sheet of (1) to (7), wherein the glass fiber (b) has a refractive index of 1.45 to 1.55,
(9) The optical sheet according to (1) to (8), wherein the average linear expansion coefficient at 30 to 150 ° C. is 40 ppm or less,
(10) The optical sheet of (1) to (9) having a total thickness of 50 to 2000 μm,
(11) The optical sheet according to (1) to (10), wherein the light transmittance at 550 nm is 80% or more,
(12) The optical sheet of (1) to (11), wherein the optical sheet is a plastic substrate for a display element or an active matrix display element substrate,
It is.

  The optical sheet of the present invention has a small coefficient of linear expansion, excellent transparency in a wide wavelength range, and less light leakage between orthogonal polarizing plates (crossed Nicols). For example, a plastic substrate for a liquid crystal display element, a color It can be suitably used for filter substrates, plastic substrates for organic EL display elements, solar cell substrates, and touch panels.

In the optical sheet of the present invention, two or more layers of glass fibers formed by laying glass fibers (b) close to or adjacent to each other in the same direction are laminated so that the axial directions of the glass fibers are orthogonal to each other. It is characterized by being embedded in the transparent resin (a).
When a glass substrate used as a liquid crystal display element substrate is sandwiched between orthogonal polarizing plates (crossed Nicols) and light is applied, the light is blocked and light leakage hardly occurs. However, light leakage may occur in a transparent composite sheet made of transparent resin and glass fiber. If light leaks through crossed Nicols, the display quality may deteriorate when used as a liquid crystal display element substrate. As a result of detailed analysis of the phenomenon of light leakage in crossed Nicols, the present inventors have presumed that this light leakage originates from retardation that occurs in the vicinity of the glass fiber. Furthermore, it has been found that this retardation can be canceled by making the glass fibers orthogonal to each other, and light leakage in crossed Nicols can be improved.

  The glass fiber layer formed by laying close to or adjacent to each other in the same direction of the present invention can be obtained, for example, by spreading glass fibers and rovings bundled together in one direction and spreading them into a sheet. In addition, the glass fiber axis direction being orthogonal means that a glass fiber layer aligned in another direction is laminated on a glass fiber layer aligned in the same direction so that the glass fiber axis direction is at an angle of 90 degrees. It means the state. It is preferable that the glass fiber layers orthogonal to each other have the same thickness so that the fibers in each direction are uniform, and two or more layers are alternately stacked in an orthogonal manner. Therefore, it is desirable that the glass fibers (b) are adjacent or at least close to each other. If glass fibers are arranged at intervals, a non-orthogonal portion is generated, and light leakage may occur at this portion. When the orthogonal glass fiber layers are distinguished in the vertical direction and the horizontal direction, the ratio of the total thickness of the glass fibers in the vertical direction and the total thickness in the horizontal direction is preferably 0.67 to 1.5, More preferably, it is 0.83-1.2, Most preferably, it is 0.91-1.1. If the ratio of the total thickness of the glass fibers in the vertical direction and the total thickness in the horizontal direction is less than 0.67 or exceeds 1.5, it is insufficient to cancel the retardation in the vicinity of the glass fibers, and light leakage may occur. There is. The thickness of the glass fiber layers arranged in the same direction is preferably 10 μm to 200 μm, more preferably 20 μm to 100 μm. When the thickness of the glass fiber layers arranged in the same direction is 10 μm or less, handling is difficult. Further, when the thickness is 200 μm or more, the retardation is increased, and it is difficult to prevent light leakage even if glass fibers are laminated perpendicularly.

  The transparent resin (a) of the present invention is not particularly limited as long as it has high transparency to visible light. Specifically, the light transmittance at a wavelength of 550 nm when the transparent resin (a) is a sheet having a thickness of 200 μm is preferably 80% or more, more preferably 85% or more, and most preferably 90% or more. . When the light transmittance at a wavelength of 550 nm is 80% or less, for example, when used for a liquid crystal display element substrate, the display performance is lowered, which is not preferable.

The difference between the refractive index of the transparent resin (a) and the refractive index of the glass fiber (b) is preferably 0.01 or less and more preferably 0.005 or less in order to maintain excellent transparency. Refractive index difference is 0.0
When it is larger than 1, the transparency of the obtained optical sheet tends to be inferior.

In order to make the refractive index difference between the transparent resin (a) and the glass fiber (b) 0.01 or less, (1) a resin having a refractive index difference with the glass fiber of 0.01 or less is selected. (2) A method of adjusting the refractive index of the glass fiber by adjusting the refractive index of the glass fiber, (3) a method of adjusting the refractive index of the resin and adjusting the refractive index of the glass fiber, etc. can be adopted.

However, it is not easy to select a combination in which the difference in refractive index between a single resin and glass fiber is 0.01 or less while satisfying various characteristics required for a display element substrate. The refractive index difference is preferably adjusted to 0.01 or less by adjusting the refractive index. In the method of adjusting the refractive index of the glass fiber to match the refractive index of the resin, a special glass fiber is used. From the viewpoint of cost, there is a method of adjusting the refractive index of the resin to match the refractive index of the glass fiber. preferable.

To match the refractive index of the resin to the refractive index of the glass fiber, (1) a method of combining two or more resins having different refractive indexes, (2) adding an additive having a refractive index larger or smaller than that of the resin The method of adjustment etc. are mentioned. Among these, a method of adjusting the refractive index by combining a resin having a higher refractive index than that of the glass fiber (b) and a resin having a lower refractive index than that of the glass fiber (b) is preferable. According to this method, it is relatively easy to match the refractive index of the resin with the refractive index of a general-purpose glass filler such as E glass, S glass, or NE glass.

  The transparent resin (a) of the present invention preferably has an Abbe number of 45 or more, more preferably 50 or more, in order to obtain excellent transparency by compounding with the glass fiber (b). The Abbe number (υd) here indicates the wavelength dependence of the refractive index, that is, the degree of dispersion, and can be obtained by υd = (nD−1) / (nF−nC). Here, nC, nD, and nF are refractive indices with respect to the C-line (wavelength 656 nm), D-line (589 nm), and F-line (486 nm) of the Brownhofer line, respectively. The refractive index of a material having a small Abbe number varies greatly depending on the wavelength. Since a general glass filler has an Abbe number of 50 or more, when combined with a transparent resin having an Abbe number of 45 or less, even if the refractive index is adjusted at a wavelength of 589 nm, the refractive index is shifted at a wavelength of 400 nm or less, for example. Therefore, the light transmittance of 400 nm or less tends to decrease. If a transparent resin having an Abbe number of 45 or more is used, the refractive index can be matched with a general glass filler in a wide wavelength range, and an excellent light transmittance can be realized even at a wavelength of 400 nm or less, for example.

  Examples of transparent resins having an Abbe number of 45 or more include thermoplastic acrylic resins such as PMMA, crosslinked acrylate resins having (meth) acrylate having two or more functional groups, and two or more epoxy groups. Cured epoxy resin comprising epoxy resin, cycloolefin resin polymerized with norbornene derivative or cyclohexanediene derivative, olefin-maleimide alternating copolymer, olefin resin such as poly-4-methylpentene-1, CR-39 And thermosetting resins for optical lenses. Among these, since it has excellent heat resistance and chemical resistance, a cross-linked acrylate resin having two or more functional groups (meth) acrylate as a constituent component and an epoxy resin having two or more functional groups as constituent components A cured epoxy resin is preferred.

  Examples of the (meth) acrylate having two or more functional groups with an Abbe number of 45 or more of the crosslinked resin include di (meth) of an acetal compound of alicyclic (meth) acrylate, hydroxypivalaldehyde and trimethylolpropane. Cyclic ether type di (meth) acrylate such as acrylate, hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, hydrogenated bisphenol A ethylene Examples include di (meth) acrylates of oxide adducts, etc., but because of their high heat resistance, cycloaliphatic (meth) acrylates represented by formulas (1) and (2), hydroxypival represented by formula (3) Aldehyde and trimethylolpropa Preferred cyclic ether type di (meth) acrylates such as di (meth) acrylate of the acetal compound.

  These (meth) acrylates may be used alone as long as the refractive index matches that of the glass fiber, but for the purpose of adjusting the refractive index, it is preferable to use two or more kinds in combination with other (meth) acrylates. In addition, for the purpose of imparting flexibility, monofunctional (meth) acrylates can be used in combination as long as the required characteristics are not extremely impaired.

  As a method of crosslinking (meth) acrylate having two or more functional groups, there are a method of curing with active energy rays, a method of thermal polymerization by applying heat, and the like, and these can be used in combination. In particular, for the purpose of completing the reaction, reducing the linear expansion coefficient, etc., it is preferable to use a heat treatment at a higher temperature in combination with the step of curing with active energy rays and / or thermal polymerization by applying heat. The active energy ray used is preferably ultraviolet rays. Examples of the lamp that generates ultraviolet rays include a metal halide type and a high-pressure mercury lamp.

  When the composite composition is cured by active energy rays such as ultraviolet rays, it is preferable to contain a photopolymerization initiator that generates radicals in the composite composition. Examples of the photopolymerization initiator used in this case include benzophenone, benzoin methyl ether, benzoin propyl ether, diethoxyacetophenone, 1-hydroxy-cyclohexyl-phenyl ketone, 2,6-dimethylbenzoyldiphenylphosphine oxide, 2,4,6. -Trimethylbenzoyldiphenylphosphine oxide. Two or more of these photopolymerization initiators may be used in combination.

  The content of the photopolymerization initiator in the resin may be an appropriate amount to be cured, and 0.01 to 2 parts by weight with respect to a total of 100 parts by weight of (meth) acrylate having two or more functional groups. It is preferably 0.02 to 1 part by weight, more preferably 0.1 to 0.5 part by weight. When the amount of the photopolymerization initiator added is too large, the polymerization proceeds rapidly, and problems such as increased birefringence, coloring, and cracks during curing occur. On the other hand, if the amount is too small, the composition cannot be sufficiently cured, and problems such as being unable to adhere to the mold after crosslinking occur.

  When heat treatment is performed at a high temperature after curing by active energy rays and / or crosslinking by thermal polymerization, it is preferable to include a heat treatment step at 250 ° C. to 300 ° C. for 1 to 24 hours in a nitrogen atmosphere or in a vacuum state.

  The epoxy resin having an Abbe number of 45 or more after curing varies depending on the curing agent used. For example, in the case of an acid anhydride curing agent, the alicyclic epoxy represented by the formulas (4) to (9) Resins and triglycidyl isocyanurate represented by the formula (10) can be exemplified as preferable examples. Among them, it is more preferable to use an alicyclic epoxy resin represented by the general formula (7) and a triglycidyl isocyanurate represented by the general formula (10) because of excellent heat resistance.

These epoxy resins may be used alone as long as the refractive index can be combined with the glass fiber, but it is preferable to use two or more types in combination with other epoxy resins for the purpose of adjusting the refractive index. Further, for the purpose of imparting flexibility, a monofunctional epoxy compound may be used in combination as long as required characteristics are not significantly impaired.
The epoxy resin used in the present invention is used after being cured by heating or irradiation with active energy rays in the presence of a curing agent or a polymerization initiator. The curing agent to be used is not particularly limited, but an acid anhydride curing agent or a cationic curing catalyst is preferable because an excellent transparent cured product is easily obtained.

  Acid anhydride curing agents include phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyl nadic anhydride, nadic anhydride, glutaric anhydride, methyl Examples include hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methyl hydrogenated nadic acid anhydride, hydrogenated nadic acid anhydride, etc. Among them, methyl hexahydrophthalic anhydride and methyl hydrogenated nadic acid anhydride are excellent in transparency. Is preferred.

  When using an acid anhydride curing agent, it is preferable to use a curing accelerator in combination. Examples of the curing accelerator include 1,8-diaza-bicyclo (5,4,0) undecene-7, tertiary amines such as triethylenediamine, 2-ethyl-4-methylimidazole and 1-benzyl-2-phenyl. Examples include imidazoles such as imidazole, phosphorus compounds such as triphenylphosphine and tetraphenylphosphonium tetraphenylborate, quaternary ammonium salts, organometallic salts, and derivatives thereof. Among these, phosphorus is excellent because of its excellent transparency. Compounds and imidazoles such as 1-benzyl-2-phenylimidazole are preferred. These curing accelerators may be used alone or in combination of two or more.

  The mixing ratio of the epoxy resin and the acid anhydride curing agent is such that the acid anhydride group in the acid anhydride curing agent is 0.5 to 1.5 equivalents relative to 1 equivalent of the epoxy group in the epoxy resin (a). Is preferably set to 0.7 to 1.2 equivalents.

  Cationic curing catalysts include acetic acid, benzoic acid, salicylic acid, paratoluenesulfonic acid and other organic acids, boron trifluoride amine complexes, boron trifluoride ammonium salt, aromatic diazonium salt, aromatic sulfonium salt, aromatic Examples thereof include cationic catalysts containing iodonium salts and aluminum complexes. Among these, cationic catalysts containing aluminum complexes are preferred.

  The refractive index of the glass fiber (b) used in the present invention is not particularly limited, but is preferably 1.45 to 1.55, and more preferably 1.50 to 1.54. When the refractive index of the glass fiber (b) is 1.55 or more, it is difficult to select a resin having the same refractive index and an Abbe number of 45 or more. Disadvantageous. In particular, in the range of 1.50 to 1.54, a general glass filler can be applied, and a resin having the same refractive index and an Abbe number of 45 or more can be easily selected.

  Examples of the glass include E glass, C glass, A glass, S glass, D glass, NE glass, T glass, and quartz glass. Among them, the refractive index control is easy with a resin having an Abbe number of 45 or more. S glass, T glass, and NE glass, which are easily available, are preferred.

  The blending amount of the glass fiber (b) is preferably 1 to 90% by weight, more preferably 10 to 80% by weight, and still more preferably 30 to 70% by weight.

In the optical sheet of the present invention, as the glass fiber and the resin are in close contact with each other, the transparency of the composite composition such as a plastic substrate for a display element is improved. It is preferable to treat with a treating agent. Specifically, the acrylic resin is preferably treated with a silane compound having an acrylic group, and the epoxy resin is preferably treated with a silane compound having an epoxy group.

  In addition, the optical sheet of the present invention may contain a small amount of antioxidant, ultraviolet absorber, dye / pigment, and other inorganic fillers within the range that does not impair the properties such as transparency, solvent resistance and heat resistance. Or the like.

  There is no limitation on the molding method of the optical sheet of the present invention, for example, a method of laminating glass fiber layers arranged in one direction, and then impregnating the resin to crosslink, a glass fiber pre-adhered with the resin in one direction. Various methods such as a method of cross-linking after side-by-side lamination are possible.

  When the optical sheet of the present invention is used for applications such as a liquid crystal display element plastic substrate, a color filter substrate, an organic EL display element plastic substrate, a solar cell substrate, and a touch panel, the thickness of the substrate is preferably 50 to 2000 μm. More preferably, it is 50-1000 micrometers. When the thickness of the substrate is within this range, the flatness is excellent, and the weight of the substrate can be reduced as compared with the glass substrate.

  Moreover, when using this optical sheet for the said optical use, it is preferable that the average linear expansion coefficient in 30-150 degreeC is 40 ppm or less, More preferably, it is 30 ppm or less, Most preferably, it is 20 ppm or less. For example, when this optical sheet is used for an active matrix display element substrate, if this upper limit is exceeded, problems such as warpage and disconnection of aluminum wiring may occur in the manufacturing process.

  When the optical sheet of the present invention is used as a substrate for a display element such as a plastic substrate for a liquid crystal display element, the light transmittance at a wavelength of 550 nm is preferably 80% or more, more preferably 85% or more. If the light transmittance is lower than this, the light utilization efficiency is lowered, which is not preferable for applications where light efficiency is important.

  When the optical sheet of the present invention is used as a plastic substrate for a display element, a resin coating layer may be provided on both sides in order to improve smoothness. Such a resin preferably has excellent transparency, heat resistance, and chemical resistance. Specifically, polyfunctional acrylates, epoxy resins, and the like are preferable. The thickness of the coat layer is preferably from 0.1 to 50 μm, more preferably from 0.5 to 30 μm.

  The plastic substrate for display element of the present invention may be provided with a gas barrier layer against water vapor or oxygen and a transparent electrode layer as necessary.

  The present invention will be described more specifically with reference to examples and comparative examples below, but the present invention is not limited thereto.

(Example 1)
Roving (refractive index: 1.530) made of S glass fiber was baked to remove organic substances, and then treated with acryloyloxypropyltriethoxysilane (acrylic silane). The rovings were arranged in one direction so as to form a uniform sheet with a thickness of 50 μm, and the rovings were arranged side by side so as to form a uniform sheet with a thickness of 50 μm. In this laminated glass fiber, 92 parts by weight of dicyclopentadienyl diacrylate (M-203 manufactured by Toagosei Co., Ltd., refractive index 1.527 after crosslinking) and bis [4- (acryloyloxyethoxy) phenyl] sulfide ( Toagosei Co., Ltd. Prototype TO-2066, 8 parts by weight of refractive index after crosslinking (1.606), 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184 manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator It was impregnated with 5 parts by weight of a resin (refractive index after crosslinking of 1.533) and defoamed. The laminated glass fiber impregnated with this resin was sandwiched between release-treated glass plates, and crosslinked by irradiation with UV light of about 10 J / cm 2 from both sides. Furthermore, it heated at 250 degreeC in the vacuum oven for 3 hours, and obtained the 0.1-mm optical sheet.

(Example 2)
Roving (refractive index: 1.530) made of S glass fiber was baked to remove organic substances, and then treated with γ-glycidoxypropyltrimethoxysilane (epoxysilane). The rovings were arranged in one direction so as to form a uniform sheet with a thickness of 50 μm, and the rovings were arranged side by side so as to form a uniform sheet with a thickness of 50 μm. To this laminated glass fiber, 90 parts by weight of triglycidyl isocyanurate (TEPIC manufactured by Nissan Chemical Industries), bisphenol S type epoxy resin (Epicron EXA manufactured by Dainippon Ink & Chemicals, Inc.)
1514) 10 parts by weight, 153 parts by weight of methyl hydrogenated nadic anhydride (manufactured by Shin Nippon Chemical Co., Ltd., HNA-100), and 1.4 parts by weight of tetraphenylphosphonium bromide (TPP-PB, manufactured by Hokuko Chemical Co., Ltd.) at 110 ° C. The melt-mixed resin was impregnated and degassed. The laminated glass fiber impregnated with this resin was sandwiched between release-treated glass plates and heated in an oven at 100 ° C. for 2 hours + 200 ° C. for 2 hours to obtain an optical sheet having a thickness of 0.1 mm.

(Comparative Example 1)
A glass chop (refractive index: 1.560) made of E glass fiber was baked to remove organic substances, and then this glass chop was treated with acryloyloxypropyltriethoxysilane (acrylic silane). To this glass chop, 58 parts by weight of dicyclopentadienyl diacrylate (M-203 manufactured by Toagosei Co., Ltd., refractive index 1.527 after crosslinking) and bis [4- (acryloyloxyethoxy) phenyl] sulfide (Toago) Synthetic Co., Ltd. Prototype TO-2066, 42 parts by weight of refractive index after crosslinking (1.606), 0.5 weight of 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184 manufactured by Ciba Specialty Chemical) as a photopolymerization initiator And filled with resin (refractive index after cross-linking: 1.533). The resin filled with this glass chop was sandwiched between release-molded glass plates and cured by irradiating with UV light of about 10 J / cm 2 from both sides. Furthermore, it heated at 250 degreeC in the vacuum oven for 3 hours, and obtained the 0.1-mm optical sheet.

(Comparative Example 2)
A glass chop (refractive index: 1.530) made of E glass fiber was baked to remove organic substances, and then treated with γ-glycidoxypropyltrimethoxysilane (epoxysilane). This glass chop was triglycidyl isocyanurate (manufactured by Nissan Chemical Industries, Ltd.
PIC) 20 parts by weight, bisphenol S type epoxy resin (Epiclon EXA1514 manufactured by Dainippon Ink and Chemicals) 80 parts by weight, methyl hydrogenated nadic acid anhydride (Shin Nippon Rika Rikacide HNA-100) 75 parts by weight, and tetraphenylphosphonium bromide 1.4 parts by weight (TPP-PB manufactured by Hokuko Chemical Co., Ltd.) was filled in a resin melt-mixed at 110 ° C. and defoamed. The resin filled with this glass chop was sandwiched between release-molded glass plates and heated in an oven at 100 ° C. for 2 hours + 200 ° C. for 2 hours to obtain an optical sheet having a thickness of 0.1 mm.
(Comparative Example 3)
Roving (refractive index: 1.530) made of S glass fiber was baked to remove organic substances, and then treated with acryloyloxypropyltriethoxysilane (acrylic silane). The rovings were arranged in one direction so as to form a uniform sheet having a thickness of 100 μm, and the rovings were arranged side by side so as to form a uniform sheet having a thickness of 50 μm. In this laminated glass fiber, 92 parts by weight of dicyclopentadienyl diacrylate (M-203 manufactured by Toagosei Co., Ltd., refractive index 1.527 after crosslinking) and bis [4- (acryloyloxyethoxy) phenyl] sulfide ( Toagosei Co., Ltd. prototype TO-2066, refractive index 1.6 after crosslinking
06) A resin (refractive index after crosslinking of 1.533) comprising 8 parts by weight, 0.5 part by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184 manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator. Impregnated and degassed. The laminated glass fiber impregnated with this resin was sandwiched between release-treated glass plates, and crosslinked by irradiation with UV light of about 10 J / cm 2 from both sides. Furthermore, it heated at 250 degreeC in the vacuum oven for 3 hours, and obtained the 0.15 mm optical sheet.

(Evaluation methods)
About the optical sheet produced in the said Example and the comparative example, various characteristics were measured with the following evaluation method.

a) Light leakage between orthogonal polarizing plates (crossed nicols) The optical sheet thus prepared was observed with a polarizing microscope in crossed nicols. The sample was rotated while the optical axis of the polarizing microscope was fixed and the intensity of the light source was kept constant, and the sample was set at an angle at which part or all of the optical sheet became brightest. An observation portion of 2.4 mm × 1.8 mm was converted into an image (number of pixels: 640 × 480) and captured on a PC, which was converted into a black and white image with each pixel having a gradation of 0 to 255. The sum total of the gradations of each pixel in this black and white image was calculated.
b) Average coefficient of linear expansion Using a TMA / SS120C type thermal stress strain measuring device manufactured by Seiko Electronics Co., Ltd., increasing the temperature from 30 ° C. to 400 ° C. at a rate of 5 ° C. in the presence of nitrogen by 20 ° C. After holding for 5 minutes, the temperature was cooled to 0 ° C. at a rate of 5 ° C. per minute and held for 5 minutes. Thereafter, the temperature was increased again at a rate of 5 ° C. per minute, and the value at 30 ° C. to 150 ° C. was measured and determined. The load was 5 g and the measurement was performed in the tensile mode.
c) Light transmittance The light transmittance at 400 nm and 550 nm was measured with a spectrophotometer U3200 (manufactured by Hitachi, Ltd.).
d) Refractive index, Abbe number The refractive index of wavelength 589nm was measured at 25 degreeC using the Abbe refractometer DR-M2 by an Atago company. Further, the Abbe number was determined by measuring the refractive indexes at wavelengths of 656 nm and 486 nm.
The evaluation results are shown in Table 1.

Claims (9)

A glass fiber layer formed by laying and arranging glass fibers (b) close to or adjacent to each other in the same direction,
The axial direction of the glass fiber is substantially orthogonal,
In addition, when the layers of the glass fibers that are substantially orthogonal to each other are distinguished in the vertical direction and the horizontal direction, the ratio of the total thickness of the glass fibers in the vertical direction to the total thickness in the horizontal direction is 0.67 to 1.5. As more than one layer is laminated
Embedded in the transparent resin (a) having an Abbe number of 45 or more and a refractive index of 1.45 to 1.55 ,
And the difference between the refractive index of the said transparent resin (a) and the refractive index of glass fiber (b) is 0.01 or less, The optical sheet characterized by the above-mentioned.   The optical sheet according to claim 1, wherein the thickness of each layer of the glass fiber is 10 μm to 200 μm. The optical sheet according to claim 1 or 2 , wherein the transparent resin (a) is an acrylate resin that is cross-linked with a (meth) acrylate having two or more functional groups as a constituent component. The optical sheet according to claim 1 or 2 , wherein the transparent resin (a) is an epoxy resin cured with an epoxy resin having two or more functional groups as a constituent component. The optical sheet according to any one of claims 1 to 4 , wherein an average linear expansion coefficient at 30 to 150 ° C is 40 ppm or less. The optical sheet according to any one of claims 1 to 5 , wherein the total thickness is 50 to 2000 µm. The optical sheet according to any one of claims 1 to 6 , wherein the light transmittance at 550 nm is 80% or more. The plastic substrate for display elements produced using the optical sheet of any one of Claims 1 thru | or 7 . Substrates for active matrix display devices manufactured using the optical sheet according to any one of claims 1 to 7.