JP2012051379A - Transparent composite sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent composite sheet excelling in transparency and heat resistance with a small linear expansion coefficient and having small waviness so as not to degrade display quality, and to provide an electronic device.SOLUTION: The transparent composite sheet includes a core layer containing transparent resin and a fibrous filler, and a surface smoothing layer containing transparent resin. The transparent resin in the core layer and the transparent resin in the surface smoothing layer are obtained by curing a resin composition containing hydrogenated biphenyl type cycloaliphatic epoxy resin represented by a chemical formula (1).

Description

The present invention relates to a transparent composite sheet and an electronic device including the same.

In general, substrates for liquid crystal display elements and organic EL display elements (especially active matrix type)
Glass plates are widely used as color filter substrates, solar cell substrates, and the like. However, plastic materials have recently been examined 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.
As a resin used for a plastic substrate for a display element, for example, Patent Document 1 discloses a composition comprising an alicyclic epoxy resin, an acid anhydride curing agent, alcohol, and a curing catalyst, Patent Document 2
Is a resin composition comprising an alicyclic epoxy resin, an acid anhydride curing agent partially esterified with alcohol, and a curing catalyst. Patent Document 3 discloses an alicyclic epoxy resin and an acid anhydride curing having a carboxylic acid. A resin composition comprising an agent and a curing catalyst is shown.
However, the conventional glass substitute plastic materials disclosed in Patent Documents 1 to 3 have a larger coefficient of linear expansion than glass. Especially, when used for an active matrix display element substrate, there are problems such as warpage and disconnection of aluminum wiring in the manufacturing process. This is difficult to develop for these applications.

In order to solve such problems, Patent Document 4 discloses an alicyclic epoxy resin having an ester group, a bisphenol A type epoxy resin, an acid anhydride curing agent, and a transparent composite optical sheet comprising a catalyst and glass cloth, Document 5 includes an alicyclic epoxy resin having an ester group and an epoxy resin having a dicyclopentadiene skeleton, a transparent composite optical sheet comprising an acid anhydride curing agent and glass cloth, and Patent Document 6 includes a bisphenol A type epoxy resin, Bisphenol
A transparent substrate composed of an A novolak type epoxy resin, an acid anhydride curing agent and glass cloth is shown.
In the glass cloth composites shown in Patent Documents 4 to 6, the linear expansion coefficient is significantly lower than that of the plastic material shown in Patent Documents 1 to 3, but these glass cloth composites have undulations. If it is used as a substrate for a display element, the display quality deteriorates, which is inappropriate.

Such waviness is mainly due to the non-uniformity of strain in the sheet surface when the core layer is produced. Further, it is considered that the degree of undulation is further increased by coating the surface smooth resin layer on the core layer having the undulation resulting from the in-plane strain non-uniformity. This will be specifically described below.
First, the cause of the core layer swell will be described.
FIG. 3 is a top view schematically showing a fiber woven fabric. As shown in FIG. 3, the fiber woven fabric 8 includes a weft 9 and a warp 10. In a fiber woven fabric composed of wefts and warps, there are portions where wefts and warps overlap, wefts, warp single portions, and voids surrounded by wefts / warps. This non-uniformity of the weave density leads to non-uniformity of the resin amount per unit volume in the sheet.
In general, the resin shrinks in the process of curing, solidifying, and cooling from the curing temperature. If the shrinkage between the resin and the fibrous filler is equal, no interfacial stress occurs at room temperature. However, in general, the linear expansion coefficient is often different between the resin and the fiber, and stress is generated at the interface between the resin and the fibrous filler.
When the amount of the resin per unit volume of the core layer is uniform, the dimensional change rate per volume with respect to the temperature is uniform, so that the generated stress is uniform in the surface and no swell occurs. However, as described above, in the woven fabric, the amount of resin per unit volume in the sheet is often non-uniform, resulting in non-uniform stress. This stress non-uniformity is considered to be one of the main causes of waviness.

Next, the mechanism by which the surface smooth resin layer increases the undulation generated in the core layer will be described. The mechanism by which the surface smooth resin layer increases waviness can be considered to be due to the non-uniformity of in-plane stress as the main factor, similar to the core layer. That is, when a smooth surface resin layer is coated on a wavy core layer, the coating thickness is often non-uniform. This is because a coated portion having a large amount of resin per unit volume and a coated portion having a small amount of resin are produced, resulting in stress non-uniformity during molding.
When a flat core layer without waviness is evenly coated with a smooth surface resin layer and no waviness occurs, and when a smooth surface resin layer with a thickness distribution is intentionally coated with a flat core layer without waviness From the fact that waviness occurs, it is presumed that the non-uniformity of the resin amount per unit volume as described above, that is, the non-uniformity of in-plane stress is the main factor of the waviness.
However, when the composite structure has a sufficiently high rigidity with respect to the amount of stress variation caused by the unevenness of the resin amount per unit volume of the core layer and the coat layer, the occurrence of undulation is suppressed.

JP-A-6-337408 JP 2001-59015 A JP 2001-59014 A JP 2004-51960 A JP 2005-146258 A JP 2004-233851 A

An object of the present invention is to provide a transparent composite sheet and an electronic device that can be substituted for glass without reducing the display quality because the linear expansion coefficient is small, the transparency and heat resistance are excellent, and the swell is small. .

This invention is (1) the transparent composite sheet comprised from the core layer containing transparent resin and a fibrous filler, and the surface smoothing layer containing transparent resin, Comprising: Of the transparent resin of the said core layer, and the said surface smoothing layer A transparent composite sheet obtained by curing a resin composition containing a hydrogenated biphenyl-type alicyclic epoxy resin represented by the chemical formula (1),

(2) The transparent composite sheet according to (1), wherein the core layer has a thickness of 50 to 200 μm,
(3) The transparent composite sheet according to (1) or (2), wherein the fibrous filler of the core layer is a glass fiber cloth,
(4) The transparent composite sheet according to any one of (1) to (3), wherein the surface smoothing layer further contains an inorganic filler,
(5) The surface waviness characteristic value of the surface smoothing layer is 1.5 × 10 ⁻⁶ or less (1) to (4)
) Any one of the transparent composite sheets,
(6) The transparent composite sheet according to any one of (1) to (5), wherein the light transmittance at a wavelength of 400 nm is 80% or more,
(7) The transparent composite 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,

Since the transparent composite sheet of the present invention has small undulation and excellent flatness, it does not deteriorate the display quality, and the liquid crystal display element substrate including the active matrix type, organic EL display element substrate, color filter substrate, touch panel substrate, electronic It is suitably used for optical sheets such as paper substrates and solar cell substrates, transparent plates, optical lenses, optical elements, optical waveguides, LED sealing materials, and the like.

Hereinafter, the present invention will be described in detail.
The transparent composite sheet of the present invention is a transparent composite sheet composed of a core layer containing a transparent resin and a fibrous filler, and a surface smoothing layer containing a transparent resin, the transparent resin of the core layer and the surface smoothing The transparent resin of the chemical layer is obtained by curing a resin composition containing an alicyclic epoxy resin represented by the chemical formula (1).

FIG. 3 is a top view schematically showing a fiber woven fabric. As shown in FIG. 3, the fiber fabric 8 is composed of weft yarns 9 and warp yarns 10. In a fiber woven fabric composed of wefts and warps, there are portions where wefts and warps overlap, wefts, warp single portions, and voids surrounded by wefts / warps. This non-uniformity of the weave density leads to non-uniformity of the resin amount per unit volume in the sheet.
Since the composite of the resin and the fibrous filler combines materials having different coefficients of thermal linear expansion, thermal stress due to the process temperature at the time of sheet manufacture and the thermal expansion difference of the material is generated in the composite material.
If the generated thermal stress is uniform in the surface of the composite sheet, the composite sheet does not swell, but in the fiber woven fabric composed of the weft and the warp as described above, the portion where the weft and the warp overlap, There are wefts, single parts of warp, and voids surrounded by wefts and warps. Such non-uniformity in the weave density leads to non-uniformity in the amount of resin per unit volume in the sheet, and thus non-uniform stress. Bring sex. This non-uniform stress in the composite sheet surface is considered to be one of the main causes of waviness.

Next, the mechanism by which the surface smoothing layer increases the undulation generated in the core layer will be described.
The mechanism that increases the waviness of the surface smoothing layer can be considered to be due to the non-uniformity of in-plane stress, as in the core layer. That is, when the surface smoothing layer is coated on the wavy core layer, the in-plane coating thickness becomes non-uniform. As a result, a coated portion having a large amount of resin per unit volume and a coated portion having a small amount of resin are produced, resulting in stress nonuniformity during sheet production.
As a method of reducing the in-plane non-uniformity of the stress of the core layer, which is the main factor of such a composite sheet, improvement in the uniformity of the woven fabric's woven density, for example, a method of weaving, opening method, etc. It is conceivable to make the uniformity of the resin per unit volume as high as possible. However, in the case of a woven fabric, there is a limit to improving the uniformity of the woven density.
Even if the weave density is not uniform, the core layer waviness can be reduced, that is, the stress at the interface between the fiber and the resin matrix can be reduced by reducing the linear expansion of the matrix resin or by the glass transition of the matrix resin. Measures such as lowering the temperature, lowering the temperature at which the stress becomes zero as much as possible, reducing the temperature difference from room temperature, or lowering the elastic modulus can be considered. This is because the stress generated at the interface between the fiber and the matrix resin can be expressed by Equation (1).

In Equation (1), E is the elastic modulus of the matrix resin, and Tg is the glass transition temperature or substrate manufacturing temperature of the matrix resin, or the temperature at which the stress approaches zero without limit. αm means the linear expansion coefficient of the resin, and αf means the linear expansion coefficient of the fiber.

On the other hand, the method for reducing the stress generated at the interface between the core layer and the surface smoothing layer is the same as the method for reducing the stress at the interface between the resin and the fiber in the core layer, and the linear expansion of the surface smoothing layer resin is reduced. Alternatively, a method of lowering the glass transition temperature, lowering the temperature at which the stress becomes zero as much as possible, reducing the temperature difference from room temperature, or lowering the elastic modulus can be considered.

As a component of the transparent resin used for the core layer and the surface smoothing layer of the present invention, a known crosslinkable resin can be used, but a resin obtained by curing a resin composition containing an epoxy resin is preferable. Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, or hydrogenated products thereof, epoxy resin having a dicyclopentadiene skeleton, epoxy resin having a triglycidyl isocyanurate skeleton, cardo Examples thereof include an epoxy resin having a skeleton, an alicyclic polyfunctional epoxy resin, an alicyclic epoxy resin having a hydrogenated biphenyl skeleton, and an alicyclic epoxy resin having a hydrogenated bisphenol A skeleton. In addition, oxetane compounds such as 1,4-bis [(3-ethyl-3-oxetanylmethoxy) methyl] benzene, 2-ethyl-3-hydroxymethyloxetane, oxetanylsilsesquioxane, oxetanyl silicate, and vinyl ether compounds can also be used. .

Among these resins, alicyclic epoxy resins are preferable, and it is particularly preferable to include an alicyclic epoxy resin having a hydrogenated biphenyl structure and an alicyclic epoxy resin represented by the chemical formula (1). Because the curability at low temperature is excellent, the temperature difference between the temperature at which the interface stress between the fibrous filler and the resin or the interface layer between the core layer and the surface smoothing resin layer is zero and the room temperature is small, And since the linear expansion coefficient after hardening is low, it is because the stress of each interface can be made small.

In order to cure these resins or compounds, they can be cured using a cation catalyst or an anion catalyst when cured alone. On the other hand, it can be cured using various curing agents. For example, in the case of an epoxy resin, it can be cured using an acid anhydride or an aliphatic amine.

However, in order to reduce the stress at the interface as much as possible, a resin that can be cured using a cationic curing catalyst is preferred. This is because if the alicyclic epoxy resin is cured with a cationic curing catalyst, the resin material can be cured at a low temperature. This is because the temperature difference between and the stress becomes smaller.

On the other hand, when the epoxy resin is cured using a curing agent such as an acid anhydride, unlike the cationic polymerization system, it is difficult to cure at a low temperature, and the temperature between the temperature at which the stress becomes zero and the room temperature is unlimited. The difference becomes larger, and the linear expansion coefficient becomes larger than that of the cationic polymerization system, so that the stress becomes larger.

Moreover, when the epoxy resin is cured using the cationic curing catalyst, the heat resistance (eg, glass transition temperature) of the cured product is higher than that of a cured product cured using another curing agent (eg, acid anhydride). Because it becomes high. The reason why the heat resistance of the cured product using the cationic curing catalyst is higher than that using the other catalyst is that the crosslinking density of the cured product obtained by curing the epoxy resin using the cationic curing catalyst is different from the others. This is considered to be because it becomes higher than the cross-linking density of the cured product cured using the above curing agent (for example, acid anhydride).

Examples of the cationic curing catalyst include those that release a substance that initiates cationic polymerization by heating (for example, an onium salt cationic curing catalyst or an aluminum chelate cationic curing catalyst), and substances that initiate cationic polymerization by active energy rays. (For example, an onium salt-based cationic curing catalyst). Among these,
Thermal cationic curing catalysts are preferred. Thereby, the hardened | cured material which is more excellent in heat resistance can be obtained.

Examples of the thermal cationic curing catalyst include aromatic sulfonium salts, aromatic iodonium salts, ammonium salts, aluminum chelates, and boron trifluoride amine complexes. Specifically, SI-60L and SI-80 manufactured by Sanshin Chemical Industry as aromatic sulfonium salts are used.
L, SI-100L, hexafluoroantimonate salts such as SP-66 and SP-77 manufactured by Asahi Denka Kogyo, and examples of aluminum chelates include ethyl acetoacetate aluminum diisopropylate and aluminum tris (ethyl acetoacetate). Examples of the boron trifluoride amine complex include boron trifluoride monoethylamine complex, boron trifluoride imidazole complex, and boron trifluoride piperidine complex.
Examples of the photocationic curing catalyst include SP170 manufactured by Asahi Denka Kogyo.

Although the content of the cationic catalyst is not particularly limited, for example, when using an epoxy resin represented by the chemical formula (1), 0.1 to 5 parts by weight is preferable with respect to 100 parts by weight of the epoxy resin, 0.5-3 weight part is especially preferable. If the content is less than the lower limit, the curability may be reduced, and if the content exceeds the upper limit, the transparent composite may become brittle.
In the case of photocuring, a sensitizer, an acid proliferating agent and the like can be used together to accelerate the curing reaction as necessary.

In the transparent resin used for the core layer, when the fibrous filler used has a diameter of 100 nm or less, there is no problem because light scattering at the interface is small, but when it exceeds 100 nm, the refractive index of the fibrous filler and the resin is controlled. In order to improve transparency, a refractive index adjusting component can be added. When the refractive index of the main component resin is higher than the refractive index of the fibrous filler used, the refractive index adjusting component can be added with a component lower than the refractive index of the fibrous filler. When the refractive index is lower than the fibrous filler used, a component higher than the refractive index of the fibrous filler can be added.

When the refractive index of the resin is higher than the refractive index of the fibrous filler, it is not particularly limited as a low refractive index component that can be added as a refractive index adjusting component, for example, low refractive index resin, low refractive inorganic and Organic fine particles etc. are mentioned. When an organic component is added as a low refractive resin component, it preferably has a functional group that undergoes a crosslinking reaction with the matrix resin. This is because the linear expansion coefficient of the cured product increases, the difference between the linear expansion coefficients of the fiber and the resin matrix increases, and the stress increases.

Specifically, an alicyclic epoxy monomer having a silsesqui skeleton, an oxetane monomer having a silsesqui skeleton, an oligomer having a silicate structure (manufactured by Konishi Chemical: PSQ resin,
Toa Gosei: Oxetanylsilsesquioxane, oxetanyl silicate), β- (3,4
And a coupling agent such as epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycidoxypropyltriethoxysilane.

Examples of the inorganic fine particles include nanoparticles and glass beads, and particles having an average dispersed particle diameter of 100 nm or less are preferable. This is because the scattering of the transparent composite sheet increases when the particle diameter exceeds the upper limit.
Specific examples include silica fine particles having a silicate structure, titanium oxide fine particles, zirconia oxide fine particles, and alumina fine particles. These particles can be appropriately used for adjusting the refractive index.

For example, when the refractive index of the resin as the main component is higher than the refractive index of the fibrous filler, silica fine particles having a refractive index lower than that of the fibrous filler or fine particles having a silicate structure are preferable. Thereby, high transparency can be obtained without deteriorating the physical properties of the cured product such as heat resistance and linear expansion coefficient.
Further, when silica fine particles are used, among the same silica fine particles, silica fine particles subjected to surface treatment are more preferable. This is because active hydrogen (silanol group) that promotes cationic polymerization exists on the surface of the fine particles, and when there is no surface treatment, the curing reaction proceeds and the storage stability is low.

The refractive index of the fibrous filler used in the present invention is not particularly limited as long as the diameter is 100 nm or less because scattering at the interface between the fibrous filler and the matrix resin is small. 1 diameter
When it exceeds 00 nm, 1.4 to 1.6 is preferable to suppress scattering, and particularly 1.5 to 1 is preferable.
. 55 is preferred. This is because it is particularly preferable that the refractive index is in the above-mentioned range since a transparent resin close to the Abbe number of the fiber material can be selected. Further, the closer the Abbe number of the transparent resin and the Abbe number of the glass, the higher the refractive index in a wide wavelength region, and the higher light transmittance can be obtained in a wide range.

Examples of the fibrous filler used in the present invention include nanofibers, fiber cloths such as glass fiber cloths and nonwoven fabrics. Among them, glass cloths and glass nonwoven fabrics are preferable because they have a high effect of reducing the linear expansion coefficient. Is preferred.

The types of glass include E glass, C glass, A glass, S glass, T glass, D glass, NE glass, quartz, low dielectric constant glass, and high dielectric constant glass, among which ionic impurities such as alkali metals E glass, S glass, and T glass NE glass, which are easy to obtain with little, are preferable.

The blending amount of the fibrous filler is preferably 1 to 90% by weight, more preferably 10 to 80% by weight, and still more preferably 30 to 70% by weight with respect to the core layer.
If the amount of fibrous filler in the core layer is large, the uniformity of the resin amount per unit volume in the core layer surface is improved, and the uniformity of stress is improved.

The transparent resin used for the surface smoothing layer of the present invention is particularly preferably an alicyclic epoxy resin having a hydrogenated biphenyl structure that is cured at a low temperature and has a small linear expansion coefficient as described above. In order to further reduce, it is preferable to add an inorganic filler within a range that does not impair the transparency.

Examples of the inorganic filler to be added include nanoparticles, nanofibers, glass beads and the like, and particles having an average dispersed particle diameter of 100 nm or less are preferable. This is because when the particle diameter is larger than this, scattering at the interface increases when the refractive index of the particles and the resin is different.

The thickness of the surface smoothing layer is preferably from 0.1 to 30 μm, more preferably from 0.5 to 30 μm, still more preferably from 1 to 10 μm.

The core layer and the surface smoothing layer of the transparent composite sheet of the present invention may be used together with an oligomer or a monomer of a thermoplastic resin or a thermosetting resin as long as the characteristics are not impaired. When these oligomers and monomers are used, it is necessary to adjust the composition ratio so that the overall refractive index matches the refractive index of the glass filler. In addition, the composite composition of the present invention contains a small amount of an antioxidant, an ultraviolet absorber, a dye / pigment, etc., as necessary, as long as the properties such as transparency, solvent resistance, and heat resistance are not impaired. May be.

There is no limitation on the production method of the core layer of the transparent composite sheet of the present invention, for example, a method in which an uncured resin composition and a glass filler are directly mixed, cast into a necessary one, and then cross-linked into a sheet, A method in which an uncured resin composition is dissolved in a solvent and a glass filler is dispersed and cast, and then crosslinked to form a sheet. An uncured resin composition or a varnish in which a resin composition is dissolved in a solvent is used as a glass cloth or Examples thereof include a method of impregnating a glass nonwoven fabric and then crosslinking to form a sheet.

The method for forming the surface smoothing layer of the present invention is not particularly limited, and examples thereof include gravure coating, kiss coating, spin coating, bar coating, dip coating, and a smooth surface transfer coating method.
The waviness characteristic value of the surface of the surface smoothing layer is measured by the method described later, but is preferably 1.5 × 10 ⁻⁶ or less, and more preferably 1.0 × 10 ⁻⁶ or less. When the waviness characteristic value exceeds the upper limit value, it becomes difficult to maintain the uniformity of the cell gap, and the display quality may be deteriorated.

When the transparent composite sheet of the present invention is used for optical applications such as a liquid crystal display element plastic substrate, a color filter substrate, an organic EL display element plastic substrate, an electronic paper substrate, a solar cell substrate, a touch panel, etc. The thickness is preferably 50 to 200 μm, more preferably 50 to 100 μm. This is because if the thickness of the core layer exceeds the upper limit, the rigidity of the core layer is so high that there is a low possibility of waviness even if there is non-uniformity in the texture of a normal fiber cloth. .

Moreover, when this transparent composite sheet is used as an optical application, the average linear expansion coefficient at 30 ° C. to 150 ° C. is preferably 40 ppm or less, more preferably 30 ppm or less,
Most preferably, it is 20 ppm or less. For example, when this composite composition is used for an active matrix display element substrate, if this upper limit is exceeded, problems such as warping and disconnection of aluminum wiring may occur in the manufacturing process.

When the transparent composite sheet of the present invention is used as a display plastic substrate, the wavelength is 400 nm.
The light transmittance in is required to be 80% or more, more preferably 85% or more, and still more preferably 88% or more. If the light transmittance at a wavelength of 400 nm is less than the lower limit, the display performance is not sufficient.

Further, when the transparent composite composition of the present invention is used as a display plastic substrate, the glass transition temperature is preferably 200 ° C. or higher, more preferably 250 ° C. or higher. If the glass transition temperature is lower than the lower limit, the substrate may be deformed due to insufficient strength and elastic modulus of the substrate at a high temperature in a high temperature process.

EXAMPLES Hereinafter, although the content of this invention is demonstrated in detail by an Example, this invention is not limited to the following examples, unless the summary is exceeded.

Example 1
NE glass-based glass cloth (thickness 90 μm, refractive index 1.510, manufactured by Nittobo) 70 parts by weight of hydrogenated biphenyl type alicyclic epoxy resin (manufactured by Daicel Chemical Industries, E-BP), oxetanyl silicate (manufactured by Toa Gosei) , OXT-191) impregnated with a resin composition in which 30 parts by weight and 1 part by weight of an aromatic sulfonium-based thermal cation catalyst (SI-100L manufactured by Sanshin Chemical) were impregnated and defoamed. The glass cloth was sandwiched between copper foils, heated at 80 ° C. for 2 hours, and further heated at 250 ° C. for 2 hours to obtain a core layer of a transparent composite sheet having a thickness of 0.1 mm.
On both sides of the obtained core layer, 100 parts by weight of E-BP and a photocationic polymerization catalyst (SP manufactured by Asahi Denka)
170) After applying a resin composition consisting of 3 parts by weight, UV light was irradiated and 2 in a nitrogen atmosphere.
Heating was further performed at 50 ° C. for 2 hours to form a surface smoothing layer having a thickness of 4 μm.

(Example 2)
NE glass-based glass cloth (thickness 90 μm, refractive index 1.510, manufactured by Nittobo), hydrogenated biphenyl type alicyclic epoxy resin (Daicel Chemical Industrial Co., Ltd., E-BP) 100 parts by weight, Nano-Lishica MEK dispersion sol (Konishi) Chemical, PMSQ nanoparticles, average particle size 20nm, solid content 20wt
%) 60 parts by weight were mixed to volatilize the solvent, and then impregnated with a resin composition mixed with 1 part by weight of an aromatic sulfonium-based thermal cation catalyst (SI-100L manufactured by Sanshin Chemical Co., Ltd.) and degassed. This glass cloth is sandwiched between copper foils and heated at 80 ° C. for 2 hours, and further heated at 250 ° C. for 2 hours to obtain a thickness of 0,
A core layer of a 1 mm transparent composite sheet was obtained.
On both sides of the obtained core layer, 100 parts by weight of E-BP and a photocationic polymerization catalyst (SP manufactured by Asahi Denka)
170) After applying a resin composition consisting of 3 parts by weight, UV light was irradiated and heated at 250 ° C. for 2 hours under a nitrogen atmosphere to form a surface smoothing layer having a thickness of 4 μm.

(Example 3)
T glass-based glass cloth (thickness 90 μm, refractive index 1.523, manufactured by Nittobo), hydrogenated biphenyl type alicyclic epoxy resin (Daicel Chemical Industrial, E-BP) 100 parts by weight, aromatic sulfonium-based thermal cation A resin composition mixed with 1 part by weight of a catalyst (SI-100L manufactured by Sanshin Chemical Co., Ltd.) was impregnated and defoamed. The glass cloth was sandwiched between copper foils and heated at 80 ° C. for 2 hours, and then 250
It was further heated at 0 ° C. for 2 hours to obtain a core layer of a transparent composite sheet having a thickness of 0.1 mm.
On both sides of the obtained core layer, 100 parts by weight of E-BP and a photocationic polymerization catalyst (SP manufactured by Asahi Denka)
170) After applying a resin composition consisting of 3 parts by weight, UV light was irradiated and 2 in a nitrogen atmosphere.
Heating was further performed at 50 ° C. for 2 hours to form a surface smoothing layer having a thickness of 4 μm.

Example 4
NE glass-based glass cloth (thickness 90 μm, refractive index 1.510, manufactured by Nittobo) 70 parts by weight of hydrogenated biphenyl type alicyclic epoxy resin (Daicel Chemical Industrial Co., Ltd., E-BP), oxetanyl silicate (manufactured by Toa Gosei) , OXT-191) impregnated with a resin composition in which 30 parts by weight and 1 part by weight of an aromatic sulfonium-based thermal cation catalyst (SI-100L manufactured by Sanshin Chemical) were impregnated and defoamed. The glass cloth was sandwiched between copper foils, heated at 80 ° C. for 2 hours, and further heated at 250 ° C. for 2 hours to obtain a core layer of a transparent composite sheet having a thickness of 0.1 mm.
100 parts by weight of E-BP and 200 parts by weight of nano-risica sol (manufactured by Fuso Chemical, Quatron, average particle size 40 nm, solid content 25 wt%) were mixed on both sides of the obtained core layer, and the solvent was evaporated. (SP 170 manufactured by Asahi Denka Co., Ltd.) After applying a resin composition consisting of 3 parts by weight, UV light was irradiated and heated at 250 ° C. for 2 hours under a nitrogen atmosphere to form a surface smoothing layer having a thickness of 4 μm.

(Comparative Example 1)
NE glass-based glass cloth (thickness 90 μm, refractive index 1.510, manufactured by Nittobo), polyfunctional alicyclic epoxy resin (Daicel Chemical Industrial Co., EHPE-3150) 80 parts by weight, bisphenol S type epoxy resin (Dainippon) 20 parts by weight, manufactured by Ink Chemical Co., EXA-1514), 77 parts by weight of methylhexahydrophthalic anhydride (manufactured by Nippon Nippon Chemical Co., Ltd., MH-700G), 1-benzyl
A resin composition mixed with 1 part by weight of -2-phenylimidazole (manufactured by Shikoku Kasei) was impregnated and defoamed. The glass cloth was sandwiched between copper foils, heated at 80 ° C. for 2 hours, and further heated at 200 ° C. for 2 hours to obtain a core layer of a transparent composite sheet having a thickness of 0.1 mm.
On both sides of the obtained core layer, 100 parts by weight of E-BP and a photocationic polymerization catalyst (SP manufactured by Asahi Denka)
170) After applying a resin consisting of 3 parts by weight, UV light was irradiated and 250 ° C. under a nitrogen atmosphere.
Was further heated for 2 hours to form a surface smoothing layer having a thickness of 4 μm.

(Comparative Example 2)
NE glass-based glass cloth (thickness 90 μm, refractive index 1.510, manufactured by Nittobo) 70 parts by weight of hydrogenated biphenyl type alicyclic epoxy resin (Daicel Chemical Industrial Co., Ltd., E-BP), oxetanyl silicate (manufactured by Toa Gosei) , OXT-191) impregnated with a resin composition in which 30 parts by weight and 1 part by weight of an aromatic sulfonium-based thermal cation catalyst (SI-100L manufactured by Sanshin Chemical) were impregnated and defoamed. The glass cloth was sandwiched between copper foils, heated at 80 ° C. for 2 hours, and further heated at 250 ° C. for 2 hours to obtain a core layer of a transparent composite sheet having a thickness of 0.1 mm.
Acrylic resin (manufactured by Toagosei Co., Ltd .: M-315) 50 parts by weight on both sides of the obtained core layer, R-60
4 (Nippon Kayaku Co., Ltd., R-604) 50 parts by weight and a photo radical generator (Ciba Specialty Chemicals, Irgacure 907) 3 parts by weight was applied, and then irradiated with UV light. A surface smoothing layer having a thickness of 4 μm was formed by heating at 250 ° C. for 2 hours under an atmosphere.

Table 1 shows the composition of the transparent composite sheets of Examples and Comparative Examples and the evaluation results of the properties.
The evaluation method is as follows.

(A) Evaluation of Waviness Increment rate (S ₂ -S ₁ ) / S _{1 with} respect to the measurement area of the measured substrate surface area (S ₂ ) by scanning the surface of the substrate in a predetermined measurement area (S ₁ ) with a laser displacement meter. Was calculated as a swell characteristic value, and the swell characteristic value was determined according to the following criteria.
Good ○: Waviness characteristic value 1.5 × 10 ⁻⁶ or less Poor x: Waviness characteristic value A value exceeding 1.5 × 10 ⁻⁶ Details of the measuring method are as follows. FIG. 1A shows a surface shape measuring apparatus. The measuring device is fixed laser displacement meter 3 (manufactured by Keyence Corporation; LT-9030M) and XY auto stage 2 (
Coms). The substrate 1 is placed on the auto stage, and the measurement range is 4 [ _XL ×
Y _L ] is set. By scanning the laser displacement meter by moving the auto stage X direction, to measure the height of the substrate surface measured pitch X _P. By performing this scan every pitch Y _P, obtained X _P, the substrate surface shape data in the _Y P _(FIG. 1-b) intervals. 50mm the _{X L} and _{Y L} is in this measurement was set to _{X P} and _{Y P} to 0.5mm performed measurement.
FIG. 2A shows the substrate surface 5 measured in a predetermined range. In order to calculate the surface area of the measured substrate shape, the area of an element constituted by four adjacent measurement points is obtained. An enlarged view of the local portion 6 of the measurement surface is shown in FIG. In consists element 7 at four points adjacent sets a reference point 7a, X _P height difference point 7b and the reference point of the side Z _X 7b of the vector (X P relative to the reference point by calculating _{the, 0,} Z _X), obtained vector of 7c relative to the reference point _(0, Y _P, a _{Z Y)} by calculating the height difference _{Z Y} point 7c and the reference point of the _{Y P} side. The area of the plane formed by these two vectors is approximated to the area of the element 7, and the area is obtained by obtaining the size of the outer product. The surface area (S ₂ ) of the measured substrate is obtained by calculating the area for each element constituting the measurement surface by the same method and calculating the sum of these areas. As the measured surface shape is flatter, the surface area obtained becomes closer to the measured area X _L × Y _L , so the measured area (S ₁ ) is subtracted from the calculated surface area (S ₂ ), and the surface area increases due to unevenness. Calculate the amount. A value normalized by dividing the surface area increase (S ₂ -S ₁ ) by the measurement area (S ₁ ) was defined as the swell characteristic value.

(B) Average linear expansion coefficient Using a TMA / SS6000 type thermal stress strain measuring device manufactured by SEIKO ELECTRONICS CO., LTD., The temperature is raised at a rate of 5 ° C. per minute in a nitrogen atmosphere, the load is 5 g, and the tensile mode is measured. And
The average linear expansion coefficient in a predetermined temperature range was calculated.

(C) Heat resistance tan δ at 1 Hz using a DNS210 type dynamic viscoelasticity measuring device manufactured by SEIKO ELECTRONICS CO., LTD.
Was the glass transition temperature (Tg).

(D) Light transmittance The light transmittance at 400 nm was measured with a spectrophotometer U3200 (manufactured by Shimadzu Corporation).

The transparent composite sheet of the present invention includes, for example, a transparent plate, an optical lens, a liquid crystal display element plastic substrate, a color filter substrate, an organic EL display element plastic substrate, a solar cell substrate,
It can be suitably used for touch panels, light guide plates, optical elements, optical waveguides, LED sealing materials and the like.

Schematic diagram of surface shape measuring device (Fig.1-a) and measurement pitch (Fig.1-b) Measured substrate surface (Fig. 2-a) and enlarged view of local area (Fig. 2-b) Top view schematically showing fiber woven fabric

DESCRIPTION OF SYMBOLS 1 Substrate 2 XY auto stage 3 Laser displacement meter 4 Measurement range 5 Measured substrate surface 6 Local portion 7 of measurement surface Element 8 composed of four adjacent points 8 Woven fabric 9 Weft 10 Warp

Claims (1)

A transparent composite sheet comprising a core layer containing a transparent resin and a fibrous filler, and a surface smoothing layer containing a transparent resin, wherein the transparent resin of the core layer and the transparent resin of the surface smoothing layer are represented by the chemical formula (1 A transparent composite sheet obtained by curing a resin composition containing a hydrogenated biphenyl-type alicyclic epoxy resin.