JP4701613B2 - 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 3 and Patent Document 4 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, an optical sheet comprising a transparent resin (a) and a glass filler (b), wherein the transparent resin (a) has an elastic modulus at 100 ° C. of 0.5 GPa or less, has excellent optical properties. The present inventors have found that the linear expansion coefficient is small and have completed the present invention.

That is, the present invention
(1) It consists of a transparent resin (a) and a glass filler b,
The difference between the refractive index of the transparent resin (a) and the refractive index of the glass filler (b) is 0.01 or less,
The glass transition temperature of the transparent resin (a) is 100 ° C. or less,
An optical sheet having an elastic modulus at 100 ° C. of 0.5 GPa or less and an Abbe number of 45 or more.
(2) The optical sheet according to (1), wherein the glass filler b is a glass fiber.
(3) The optical sheet according to any one of (1) to (2), wherein the transparent resin (a) is an acrylate resin crosslinked with a (meth) acrylate having two or more functional groups as a constituent component.
(4) The optical sheet according to any one of (1) to (3), wherein the transparent resin (a) is an epoxy resin cured with an epoxy resin having two or more functional groups as a constituent component.
(5) The optical sheet of any one of (1) to (4), wherein the glass filler b has a refractive index of 145 to 155.
(6) The optical sheet according to any one of (1) to (5), wherein a glass cloth is used as the glass filler b.
(7) The optical sheet according to any one of (1) to (6), wherein an average linear expansion coefficient at 30 to 150 ° C. is 40 ppm or less.
(8) The optical sheet according to any one of (1) to (7), wherein the thickness is 50 to 2000 μm.
(9) The optical sheet according to any one of (1) to (8), wherein the light transmittance at 550 nm is 80% or more.
(10) The optical sheet according to any one of (1) to (9), wherein the optical sheet is a display element plastic substrate or an active matrix display element substrate.

  As described above, the optical sheet of the present invention has a small coefficient of linear expansion, a high light transmittance in a wide wavelength range, and optical characteristics such as less light leakage between orthogonal polarizing plates (crossed Nicols). For example, it can be suitably used for a plastic substrate for liquid crystal display elements, a substrate for color filters, a plastic substrate for organic EL display elements, a solar cell substrate, and a touch panel.

Next, the present invention will be described in more detail.
The present invention is characterized by comprising a transparent resin (a) and a glass filler (b), and the elastic modulus of the transparent resin (a) at 100 ° C. is 0.5 GPa or less.
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 a transparent resin and a glass filler. 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 presume that this light leakage is derived from retardation occurring in the vicinity of the glass filler. Furthermore, it has been found that when a resin having an elastic modulus at 100 ° C. of 0.5 GPa or less is used, thermal stress is reduced and light leakage at crossed Nicols is reduced.

  The transparent resin (a) of the present invention is not particularly limited as long as it has an elastic modulus at 100 ° C. of 0.5 GPa or less and becomes transparent when combined with a glass filler. The elastic modulus of the transparent resin (a) of the present invention is 0.5 GPa or less, preferably 0.3 GPa or less, more preferably 0.2 GPa or less. When the elastic modulus at 100 ° C. is 0.5 GPa or more, distortion due to thermal stress is likely to occur when compounded with a glass filler, and light leakage at crossed Nicols is also likely to occur.

The transparent resin (a) of the present invention preferably has a glass transition temperature of 100 ° C. or lower in addition to an elastic modulus at 100 ° C. of 0.5 GPa or lower. More preferably, it is 80 degreeC, Most preferably, it is 60 degrees C or less. When the glass transition temperature exceeds 100 ° C., distortion due to thermal stress is likely to occur when compounded with a glass filler, and light leakage at crossed Nicols is also likely to occur.
The glass transition temperature referred to here is the maximum value of tan δ when measured using a viscoelasticity measuring device at a heating rate of 5 ° C./min and a frequency of 1 Hz.

  The difference between the refractive index of the transparent resin (a) and the refractive index of the glass filler (b) is preferably 0.01 or less and more preferably 0.005 or less in order to maintain excellent transparency. When the refractive index difference is larger than 0.01, 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 filler (b) 0.01 or less, (1) select a resin having a refractive index difference with the glass filler of 0.01 or less, (2) A method of adjusting the refractive index of the glass filler to match the refractive index of the resin, (3) a method of adjusting the refractive index of the resin to match the refractive index of the glass filler, and the like can be adopted.

However, it is not easy to select a combination in which the refractive index difference between the resin and the glass filler is 0.01 or less while satisfying various characteristics required for the display element substrate. It is preferable to adjust the refractive index difference to 0.01 or less. In the method of adjusting the refractive index of the glass filler to match the refractive index of the resin, a special glass filler 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 filler. preferable.

To match the refractive index of the resin to the refractive index of the glass filler, (1) a method of combining two or more resins having different refractive indexes, and (2) an additive having a refractive index larger or smaller than that of the resin is added. 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 the glass filler (b) and a resin having a lower refractive index than the glass filler (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 48 or more, in order to obtain excellent transparency by combining with the glass filler (b). The Abbe number (ν _d ) here indicates the wavelength dependency of the refractive index, that is, the degree of dispersion, and can be obtained by ν _d = (n _D −1) / (n _F −n _C ). . Here, n _C , n _D , and n _F are the C line (wavelength 656 nm) and D line (589 n) of the Brownhofer line, respectively.
m) and the refractive index with respect to F-line (486 nm). 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.

  As a transparent resin having an Abbe number of 45 or more and an elastic modulus at 100 ° C. of 0.5 GPa or less, an acrylate resin crosslinked with (meth) acrylate having a flexible chain and having two or more functional groups as a constituent component, Contains epoxy resin cured with epoxy resin containing flexible chain and having two or more functional groups, cycloolefin resin polymerized norbornene derivative or cyclohexanediene derivative having flexible chain in side chain, rubber and elastomer Examples thereof include a transparent thermosetting resin and a photocurable resin, and a transparent thermosetting resin and a photocurable resin containing a plasticizer. Among these, acrylate resins cross-linked with (meth) acrylate having two or more functional groups as constituents and epoxy resins having two or more functional groups because of excellent thermal stability and chemical resistance at high temperatures. An epoxy resin cured with as a constituent is preferred.

  As the (meth) acrylate having two or more functional groups having an elastic modulus at 100 ° C. of 0.5 GPa or less of the crosslinked resin and an Abbe number of 45 or more, hexanediol di (meth) acrylate, nonanediol Di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, caprolactone modified hydroxypivalate ester neopentyl glycol di (meth) acrylate, ethylene oxide modified neopentyl glycol di (meth) acrylate, propylene Examples include oxide-modified neopentyl glycol di (meth) acrylate and di (meth) acrylate of ethylene oxide-modified hydrogenated bisphenol A. Particularly, the glass transition temperature is low, the water absorption is low, and the reaction Propylene glycol diacrylate because of high, caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate, nonanediol diacrylate, and most preferably caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate. Examples of available products of caprolactone-modified hydroxypivalate ester neopentyl glycol diacrylate include Karayad HX-220 and HX-620 manufactured by Nippon Kayaku. By using these (meth) acrylates having two or more functional groups as a constituent component, a crosslinked material having an elastic modulus at 100 ° C. of 0.5 GPa or less, a glass transition temperature of 100 ° C. or less, and an Abbe number of 45 or more. An acrylate resin is obtained.

  These (meth) acrylates are preferably used in combination with other (meth) acrylates for the purpose of matching the refractive index with the glass filler. In addition, monofunctional (meth) acrylates can be used in combination as long as the required characteristics are not significantly impaired.

  As a method of crosslinking these (meth) acrylates, 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 these (meth) acrylates are cured by active energy rays such as ultraviolet rays, it is preferable to include a photopolymerization initiator that generates radicals in the resin 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 difficult to remove due to adhesion 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 two or more functional groups having an elastic modulus at 100 ° C. of the cured resin of 0.5 GPa or less and an Abbe number of 45 or more varies depending on the curing agent used, for example, an acid anhydride. In the case of a system hardening agent, polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, hexanediol diglycidyl ether and the like can be mentioned.

These epoxy resins are preferably used in combination of two or more kinds including other epoxy resins for the purpose of matching the refractive index with the glass filler. In addition, a monofunctional epoxy compound may be used in combination as long as required characteristics are not significantly impaired.
The epoxy resin (a) 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 (a) and the acid anhydride curing agent is such that the acid anhydride group in the acid anhydride curing agent is 0.5 to 1 with respect to 1 equivalent of the epoxy group in the epoxy resin (a). Is preferably set to 5 equivalents, more preferably 0.7 to 1.2 equivalents.
Cationic catalysts include organic acids such as acetic acid, benzoic acid, salicylic acid, paratoluenesulfonic acid, boron trifluoride amine complex, boron trifluoride ammonium salt, aromatic diazonium salt, aromatic sulfonium salt, aromatic iodonium. Examples thereof include a cationic curing catalyst containing a salt and an aluminum complex, and among these, a cationic curing catalyst containing an aluminum complex is preferable.

  Although the refractive index of the glass filler (b) used in the present invention is not particularly limited, it is preferably 1.45 to 1.55, more preferably 1.50 to 1.54. When the refractive index of the glass filler (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 filler include E glass, C glass, A glass, S glass, D glass, NE glass, T glass, and quartz glass. Among them, a refractive index can be easily controlled with a resin having an Abbe number of 45 or more. S glass, T glass, and NE glass, which are easily available, are preferred.

  Examples of the glass filler (b) used in the present invention include glass fiber cloths such as glass fiber, glass cloth and glass nonwoven fabric, glass beads, glass flakes, glass powder, and milled glass. Since it is high, glass fiber, glass cloth and glass nonwoven fabric are preferable, and glass cloth is most preferable.

  The blending amount of the glass filler (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, the closer the glass filler and the resin are, the better the transparency of the optical sheet. Therefore, it is preferable to treat the glass filler surface with a known surface treatment agent such as a silane coupling 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, in the composite composition of the present invention, a small amount of antioxidant, ultraviolet absorber, dye / pigment, etc., as long as necessary, properties such as transparency, solvent resistance, and heat resistance are not impaired. A filler such as an inorganic filler may be included.

  There is no limitation on the method for producing the optical sheet of the present invention. For example, when (meth) acrylate having two or more functional groups is used as a transparent resin, the resin and filler are directly mixed to obtain a necessary mold. Examples thereof include a method of cross-linking after casting, and a method of cross-linking after impregnating a glass cloth or glass nonwoven fabric with a resin.

  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 comprising the transparent resin (a) and the glass filler (b) 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 80% or more. Is more preferable, and 85% or more is more preferable. 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.

In the case of 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)
A NE glass-based glass cloth of 100 μm (Nittobo # 2116 type, refractive index 1.510) was baked to remove organic substances, and then treated with acryloyloxypropyltriethoxysilane (acrylic silane). To this glass cloth, 80 parts by weight of caprolactone-modified hydroxypivalate ester neopentyl glycol diacrylate (Nippon Kayaku Co., Ltd. KAYARAD HX-220, refractive index 1.493 after crosslinking), dicyclopentadienyl diacrylate ( M-203 manufactured by Toagosei Co., Ltd., 3 parts by weight of refractive index after crosslinking 1.527), 17 weights of bis [4- (acryloyloxyethoxy) phenyl] fluorene (prototype TO-2065) manufactured by Toagosei Co., Ltd. And impregnated with a resin (refractive index after cross-linking 1.510) of 0.5 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184 manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator, and defoamed did. The cloth impregnated with the resin was sandwiched between release-molded glass plates and cross-linked by irradiation with a total of about 2000 mJ / cm ² of UV light from both sides. Further in a vacuum oven at 100 ° C. for 2 hours, further 2
Heat treatment was performed at 50 ° C. for 3 hours to obtain a 0.1 mm transparent sheet.

(Example 2)
NE glass powder having an average particle size of 3.2 μm (refractive index: 1.510, manufactured by Nittobo Co., Ltd.) was baked to remove organic substances, and then treated with acryloyloxypropyltriethoxysilane (acrylic silane). To 100 parts by weight of this glass powder, 80 parts by weight of caprolactone-modified hydroxypivalate ester neopentyl glycol diacrylate (KAYARAD HX-220 manufactured by Nippon Kayaku Co., Ltd., refractive index after crosslinking 1.493), dicyclopentadienyl di 3 parts by weight of acrylate (Toagosei Co., Ltd. M-203, refractive index 1.527 after crosslinking), bis [4- (acryloyloxyethoxy) phenyl] fluorene (Toagosei Co., Ltd. prototype TO-2065) 17 parts by weight of 1-hydroxy-cyclohexyl-ketone (Irgacure 184 manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator was melt-mixed with a resin (refractive index of cured resin 1.510). Dispersed and degassed. This was sandwiched between glass plates with an aluminum foil having a thickness of 80 μm as a spacer and cross-linked by irradiating UV light of about 2000 mJ / cm ^{2 in} total from both sides. 2 in a vacuum oven at 100 ° C
Heat treatment was further performed at 250 ° C. for 3 hours to obtain a 0.1 mm transparent sheet.

(Comparative Example 1)
A 100 μm E glass-based glass cloth (E10A (# 2117) refractive index 1.560 manufactured by Unitika cloth) was baked to remove organic substances, and then treated with acryloyloxypropyltriethoxysilane (acrylic silane). To this glass cloth, 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 impregnated with a resin comprising a part (refractive index after cross-linking: 1.560) and defoamed. The cloth impregnated with the resin was sandwiched between release-molded glass plates and cross-linked by irradiation with a total of about 2000 mJ / cm ² of UV light from both sides. In a vacuum oven
Heat treatment was performed at about 100 ° C. for 2 hours and further at about 250 ° C. for 3 hours to obtain a 0.1 mm transparent 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) Elastic modulus and glass transition temperature Using a DMS-210 type viscoelasticity measuring device manufactured by Seiko Electronics Co., Ltd., the temperature was increased from -30 ° C to 400 ° C at a rate of 5 ° C / minute, and the frequency at 100 ° C. The storage elastic modulus at 1 Hz was taken as the elastic modulus at 100 ° C. The maximum value of tan δ was defined as the glass transition temperature.
b) Light leakage between polarizing plates orthogonal to each other (crossed Nicols) The prepared optical sheet was observed with a polarizing microscope in crossed Nicols. The optical axis of the polarizing microscope was fixed, the sample was rotated, and the angle was set so that a part or the whole of the optical sheet became brightest. The image at that time was converted into black and white, and the sum of the gradations (0 to 255 gradations) of each pixel (number of pixels 640 × 480) was taken. The sum was less than 10 million, and the case above was ×.
c) Average coefficient of linear expansion Using a TMA / SS120C type thermal stress strain measuring device manufactured by Seiko Electronics Co., Ltd., the temperature was increased from 30 ° C. to 400 ° C. at a rate of 5 ° C. per minute in the presence of nitrogen. 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.
d) Light transmittance The light transmittance at 400 nm and 550 nm was measured with a spectrophotometer U3200 (manufactured by Hitachi, Ltd.).
e) 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 (10)

It consists of transparent resin (a) and glass filler b,
The difference between the refractive index of the transparent resin (a) and the refractive index of the glass filler (b) is 0.01 or less,
The glass transition temperature of the transparent resin (a) is 100 ° C. or less,
An optical sheet having an elastic modulus at 100 ° C. of 0.5 GPa or less and an Abbe number of 45 or more. The optical sheet according to claim 1, wherein the glass filler b is a glass fiber. The optical sheet according to any one of claims 1 to 2, wherein the transparent resin (a) is an acrylate resin crosslinked with a (meth) acrylate having two or more functional groups as a constituent component. The optical sheet according to any one of claims 1 to 3, wherein the transparent resin (a) is an epoxy resin cured by using 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 the glass filler b has a refractive index of 145 to 155. The optical sheet according to claim 1, wherein a glass cloth is used as the glass filler b. The optical sheet according to any one of claims 1 to 6, 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 7, having a thickness of 50 to 2000 µm. The optical sheet according to any one of claims 1 to 8, wherein a light transmittance at 550 nm is 80% or more. The optical sheet according to claim 1, wherein the optical sheet is a display element plastic substrate or an active matrix display element substrate.