JP4539113B2 - Plastic composite transparent sheet and display element using the same - Google Patents

Description

  The present invention relates to a plastic composite transparent sheet having a low birefringence, a small linear expansion coefficient, and a high transparency, and a display element using the same.

In general, glass plates are often used as substrates for liquid crystal display elements, color filter substrates, organic EL display element substrates, solar cell substrates, and the like. However, in recent years, many attempts have been made to use a plastic material instead of a glass plate because of problems such as being easily broken, not being bent, having a large specific gravity, and not suitable for weight reduction. For example, Patent Document 1 and Patent Document 2 disclose a cured product obtained by curing an epoxy resin composition containing an epoxy resin, an acid anhydride curing agent, and a curing catalyst, and a transparent liquid crystal display element made of a thermoplastic resin. A resin substrate is described.
However, since conventional plastic materials for glass replacement have a large coefficient of linear expansion, for example, when used for an active matrix display element substrate, problems such as warping and disconnection of aluminum wiring occur in the manufacturing process, which makes it difficult to apply. Met.
In addition, the plastic sheet used for the display element is required to have low birefringence. Plastic sheets are molded by many molding methods such as calendering, injection molding, compression molding, coating / impregnation, etc., but all molding methods generate thermal stress due to resin flow or cooling, resulting in plastic sheeting. Birefringence always occurs. The generation of birefringence is a problem for optical applications, and a product having a low photoelastic constant indicating the magnitude of birefringence is extremely required.
Furthermore, surface smoothness is required for plastic sheets used in display devices. In particular, when used in a display device, a semiconductor element may be directly written on a substrate and smoothness at the maximum surface roughness of 200 nm level is required. However, it is very difficult to create a smooth surface property. It was a problem.

JP-A-6-337408 JP-A-7-120740

  The present invention provides a plastic transparent composite sheet having a smooth surface, very little birefringence, low linear expansion coefficient and excellent transparency, and as a result, suitable for various optical applications, particularly various display element applications. In addition, an object of the present invention is to provide a display element using the same.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that the resin (a), particularly a curable resin such as a thermosetting resin or an ultraviolet curable resin, has an average particle diameter of 5 nm to 100 nm and an aspect ratio. A plastic composite transparent sheet comprising an inorganic filler (b) having a ratio of 2 or more and a fibrous inorganic filler (c) having an aspect ratio of 20 or more as essential components, the resin (a) and the inorganic filler (b ) And a plastic composite transparent sheet characterized in that the difference in refractive index between the inorganic filler (c) and the inorganic filler (c) is 0.03 or less, and has a low thermal expansion coefficient and low birefringence, The present inventors have found that a plastic composite transparent sheet excellent in smoothness and transparency can be obtained, and further found that a display element can be produced using the plastic composite transparent sheet, and have reached the present invention.

That is, the present invention
(1) 1,2-epoxy-4- (2-oxiranyl) cyclosoxane adduct of 2,2-bis (hydroxymethyl) -1-butanol (a) having an average particle diameter of 5 nm to 100 nm and an aspect ratio Is a plastic composite transparent sheet having an inorganic filler (b) of 2 to 20 and a fibrous inorganic filler (c) having an aspect ratio of 20 or more as essential components and a light transmittance of 60% or more at a wavelength of 550 nm. The inorganic filler (b) having an average particle diameter of 5 nm to 100 nm and an aspect ratio of 2 to 20 is 1,2-epoxy-4- (2,2-bis (hydroxymethyl) -1-butanol. 2-oxiranyl) 1 to 50% by weight relative to Shikurosekisan adduct (a), the 2,2-bis (hydroxymethyl) -1-butanol 1,2-epoxy And 4- (2-oxiranyl) Shikurosekisan adduct (a) an inorganic filler (b) the refractive index of a complex comprising a difference between the refractive index of the inorganic filler (c) is, is 0.03 or less Plastic composite transparent sheet.
(2) The plastic composite transparent sheet according to (1), wherein an average linear expansion coefficient at 30 to 150 ° C. is 25 ppm or less.
(3) The plastic composite transparent sheet according to (1) or (2), wherein the maximum surface roughness of the substrate surface is 200 nm or less.
(4) The plastic composite transparent sheet according to any one of (1) to (3), wherein the inorganic filler (b) is a metal oxide.

Hereinafter, the present invention will be described in detail.
The resin (a) in the present invention indicates a plastic resin or a curable resin.
Plastic resins include polyethylene, polypropylene, polymethyl methacrylate, polycarbonate, polytetrafluoroethylene, polyvinyl chloride, polyvinylidene chloride, polyethersulfone, polyphenylene oxide, and the like, blends thereof, block or graft copolymers, etc. A resin that is not three-dimensionally cross-linked and melts by heating.

The curable resin refers to a thermosetting resin that is cured by heating, and a high energy beam curable resin that is cured by irradiation with a high energy beam such as an ultraviolet ray or an electron beam.
The thermosetting resin refers to a general resin that is three-dimensionally crosslinked and cured by heat, such as an epoxy resin, a phenol resin, a melamine resin, or a polyester resin. These may be used alone or in combination. An epoxy resin is most preferably used as the thermosetting resin, and for example, epoxy resins represented by chemical structural formulas (1) to (3) are particularly preferable. Moreover, when resin to use requires a hardening | curing agent and a hardening accelerator, it can also use it together. In this case, amine-based, particularly dicyandiamide and aromatic amine, tetramethylenehexamine, phenol novolac-based curing agent and acid anhydride-based curing agent are used as the curing agent. As the curing accelerator, an organic phosphorus-based organic accelerator such as triphenylphosphine, an imidazole-based nitrogen-based curing accelerator, or a photocationic catalyst or a thermal cation catalyst such as a dialkyl-4-hydroxyphenylsulfonium salt is preferably used.

  The high energy beam curable resin generally indicates a resin that is three-dimensionally crosslinked and cured by a high energy beam such as an ultraviolet ray or an electron beam, such as an acrylate resin or an epoxy acrylate resin. These may be used alone or in combination. At this time, it is desirable to blend a substance capable of generating radicals upon irradiation with high energy rays, such as an aryl alkyl ketone, or a substance capable of generating cations upon irradiation with high energy rays, such as an aryldiazonium salt, as a polymerization initiator. In addition, since an epoxy resin can also be made to react when using a cationic polymerization initiator, such a resin system can also be classified into a high energy ray curable resin.

  Naturally, the plastic composite transparent sheet for display elements is desirably transparent. The transparency of the transparent resin of the present invention (the resin single cured product before being formed into a plastic composite sheet) is such that the linear light transmittance at 550 nm is 60% or more when formed into a sheet having a thickness of 50 to 100 microns. More preferably, it indicates 85% or more, most preferably 90% or more. When used as a display element substrate, 85% or more is preferable. These resins may be used alone or in combination of two or more.

  The inorganic filler (b) used in the present invention is a nano-order particulate inorganic filler, and its aspect ratio is 2 to 20, and the average particle diameter is required to be 5 to 100 nm. . The aspect ratio of the inorganic filler can be measured by an image of a transmission electron microscope or a scanning electron microscope. It is possible to reduce the birefringence of the resin by dispersing the nano-sized inorganic filler (b) in the form of a rod or rugby ball with an aspect ratio of 2 to 20 or bent into a banana shape in the resin. It is. The principle is considered to be a phenomenon that the inherent birefringence of the resin is relaxed by the expression of the structural birefringence. Structural birefringence is a birefringence phenomenon that occurs when the system has inhomogeneities that are significantly smaller than the wavelength of the light. In particular, rod-like particles such as rods are oriented in one direction inside the matrix. When mixed in a state, it exhibits structural birefringence. According to the theoretical calculation by Winner, the refractive index of polarized light in the vertical direction is larger than that of the polarized light component parallel to the orientation direction of the rod-like particles (expression of negative birefringence).

Usually, in the plastic transparent composite sheet in the present invention, a strong stress is generated at the contact interface between the inorganic filler (c) and the resin (a), and the stress causes a strong birefringence from the resin component. Application as a transparent sheet for use becomes difficult. At this time, the molecular skeleton of the resin is oriented in the direction of tensile stress, so that the refractive index of polarized light parallel to the orientation direction of the resin is larger than that in the perpendicular direction (positive birefringence), but rod-like particles ( When the inorganic filler (b)) is mixed in the resin, structural birefringence (negative birefringence) occurs due to the orientation of the rod-like particles in the direction where the tensile stress is applied, so that the birefringence of the composite is reduced. It is considered that the photoelastic constant can be greatly reduced by greatly relaxing.
When the aspect ratio of the inorganic filler (b) is 2 or less, a decrease in photoelasticity due to the structural birefringence effect is less likely to occur, the birefringence of the plastic composite transparent sheet increases, and it cannot be used as a sheet for optical applications. Also, inorganic fillers (b) having an aspect ratio of 20 or more are currently difficult to obtain and possibly difficult to disperse well in the resin (a), so that the moldability of the plastic composite transparent sheet is extremely high. Expected to decline.
Because the particle diameter is significantly shorter than the wavelength of visible light, the inorganic filler (b) is less likely to cause scattering and diffraction phenomena regardless of the material, and as a result, Become invisible. Therefore, the light transmittance in the plastic composite transparent sheet is greatly improved. It is particularly important that the inorganic filler (b) blended with the resin (a) and cured (hereinafter referred to as a composite) is refracted depending on the type and amount of the inorganic filler. It becomes possible to control the optical characteristics represented by the rate and the Abbe number. The refractive index of this complex can be predicted by Maxwell-Garnet rule. Therefore, it is possible to obtain a composite having a desired refractive index and Abbe number by blending a predetermined amount of a powdery inorganic filler having a high refractive index with a resin having a low refractive index. (Of course, the refractive index may be controlled by blending a powdery inorganic filler having a low refractive index with a resin having a high refractive index). Therefore, the refractive index difference between the composite and the fibrous inorganic filler (c) can be brought close to zero, and the transparency of the plastic composite transparent sheet can be further improved. The difference in refractive index between the composite and the inorganic filler (c) is preferably 0.03 or less from the viewpoint of improving transparency. When the refractive index difference is more than that, the transparency of the plastic composite transparent sheet is lowered.
It does not specifically limit regarding the raw material of an inorganic filler (b). Examples include various metals, metal oxides, glass compositions, resin powders, and mixtures or hybrids thereof. However, in particular, various metal oxides that have high chemical stability and that can easily adjust nanoparticles by sol-gel method, such as silica, alumina, titania, zirconia, ceria, zinc oxide, cobalt oxide, iron oxide Etc. are preferably used.

  The inorganic filler (c) used in the present invention includes an inorganic filler having an aspect ratio of 20 or more, or a knitted fabric or a nonwoven fabric. Unlike the inorganic filler (b), the diameter of the inorganic filler is not particularly limited. Therefore, when applied to a plastic composite transparent sheet, it is important that the material is transparent in the visible light region. There is no particular limitation as long as it is an inorganic filler that meets these conditions, but for example, glass fiber, glass cloth, glass nonwoven fabric, glass beads, glass powder, milled glass because of its easy availability from the market and its high transparency. Among them, glass fiber, glass cloth, and glass nonwoven fabric are more preferable, and glass cloth is most preferable. Although it does not specifically limit regarding the diameter of a fibrous inorganic filler, It is more desirable for the softness | flexibility of a plastic composite transparent sheet to be 10 micrometers or less. Although the thickness of the cloth when the fibrous inorganic filler is made into a cloth state such as glass cloth or glass nonwoven fabric is not particularly limited, it is preferably 30 to 300 μm. Examples of the glass include E glass, C glass, A glass, S glass, D glass, NE glass, and T glass. Among them, E glass, S glass, T glass, and NE glass with few alkali metals are preferable.

  In the present invention, the amount of the inorganic filler (b) to be blended is not particularly limited with respect to the total weight of 100% by weight of the plastic composite transparent sheet, but preferably 1 to 50% by weight with respect to the resin (a). More desirably, 1 to 20% by weight, and further desirably 3 to 10% by weight. When the blending amount of the inorganic filler (b) is less than 1% by weight, the effect of reducing the photoelastic constant is insufficient, and when the blending amount is greater than 50% by weight, the inorganic filler (b) is a resin ( It cannot be uniformly dispersed in a) and becomes extremely brittle and is not practical. In addition, the compounding quantity of an inorganic filler (c) does not specifically limit.

As the Abbe number of the mixture of the resin (a) of the present invention and the inorganic filler (b) is closer to that of the inorganic filler (c), it is desirable to maintain excellent transparency. This is because, in order to maintain transparency in any wavelength range in the plastic transparent composite sheet, it is necessary to match the wavelength dependence of the refractive index of the composite and the fibrous inorganic filler as much as possible. In this patent, the Abbe number is not limited, but the difference between the Abbe number of the composite containing the resin (a) and the inorganic filler (b) and the Abbe number of the inorganic filler (c) is 10 or less. desirable.

  In the present invention, the closer the inorganic filler and the resin are, the better the transparency of the plastic composite transparent sheet of the present invention. Therefore, the surfaces of the inorganic filler (b) and the inorganic filler (c) are treated with silane. It is preferable to treat with a known surface treating agent such as a coupling agent. Examples of the silane coupling agent include an epoxy silane coupling agent, a titanate coupling agent, an aminosilane coupling agent, and a silicone oil type coupling agent. These may be used alone or in combination. Good.

  The molding method of the plastic composite transparent sheet in the present invention is not limited. For example, a method of dispersing the resin (a) and the inorganic filler (b) in a solvent and impregnating the resin (a) and the inorganic filler (b) in the inorganic filler (c) and then thermally curing the resin component can be given as an example. There is no problem even if the surface is smoothed by applying a smoothing coating to the surface after the sheet is produced by the above or other methods.

  The maximum surface roughness (PV value) of the plastic composite transparent sheet in the present invention is desirably 500 nm or less, more preferably 200 nm or less, and most preferably 50 nm or less. When the PV value in the plastic transparent composite sheet is coarser than this, the light transmittance is reduced or uneven due to irregular reflection on the surface, which is not suitable for optical applications. Specifically, when applied to a display element, a problem of display failure may occur.

  The plastic transparent composite sheet according to the present invention is made of 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, a touch panel, an optical element, an optical waveguide, and an LED sealing. When used as a transparent sheet such as a material, the light transmittance at a wavelength of 550 nm is preferably 60% or more, more preferably 85% or more when formed on a substrate having a thickness of 50 to 100 μm. When the light transmittance at a wavelength of 550 nm is 60% or less, the efficiency of using light is lowered, which is not preferable for applications where light efficiency is important.

  The plastic composite transparent sheet of the present invention is made of 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, a touch panel, an optical element, an optical waveguide, and an LED sealing. When used as a material or the like, the average linear expansion coefficient at 30 to 150 ° C. is preferably 25 ppm or less. For example, when this plastic composite transparent 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.

  The transparent composite sheet of the present invention may be provided with a single layer or multiple layers on both sides or one side in order to improve smoothness or improve various functions. The material to be coated preferably has transparency, heat resistance, and chemical resistance. For example, a curable resin such as polyfunctional acrylate or epoxy resin, an inorganic material such as silicon oxide, silicon nitride, or ITO film. Examples thereof include a film and a thermoplastic resin such as polyvinylidene fluoride and polyvinylidene chloride, but are not particularly limited. As thickness of resin to coat, 0.1-50 micrometers is preferred and 0.5-30 micrometers is more preferred. The refractive index of the resin to be coated is not particularly limited.

In the transparent composite sheet of the present invention, if necessary, a small amount of antioxidant, ultraviolet absorber, dye / pigment, and the like, as long as the properties such as transparency, solvent resistance and heat resistance are not impaired. It may contain a filler such as an inorganic filler.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Powdered inorganic filler (1): Nanosilica prototype (1) (banana shape with an average particle size of 20 nm, aspect ratio = 4, methyl ethyl ketone sol, 10 wt% blended)
Powdered inorganic filler (2): Alumina prototype (rod shape with an average particle diameter of 35 nm, aspect ratio = 3, methyl ethyl ketone sol, 10 wt% blended)
Powdered inorganic filler (3): Nanosilica prototype (2) (average particle size 30 nm, spherical shape (aspect ratio = 1.0), methyl ethyl ketone sol, 10 wt%)
Note that the powdery inorganic fillers (1) and (2) correspond to the inorganic filler (b), and the powdery inorganic filler (3) does not correspond to the fine particle size filler. is there.

(Examples and Comparative Examples)
80 parts by weight of an alicyclic epoxy resin (EHPE3150 manufactured by Daicel Chemical Industries), 20 parts by weight of a bisphenol S type epoxy resin (Epiclon EXA1514 manufactured by Dainippon Ink and Chemicals), methylhexahydrophthalic anhydride (Rikacid MH-700 manufactured by Shin Nippon Chemical Co., Ltd.) ) 75 parts by weight, tetraphenylphosphonium bromide (TPP-PB manufactured by Hokuko Chemical Co., Ltd.) at a ratio of 0.5 part by weight, 100 parts by weight of uncrosslinked resin, 30 parts by weight of 1,3 dioxolane were mixed to obtain a varnish. . To this varnish, powdery inorganic fillers (1) to (3) were added and mixed in the proportions shown in Table 1 to obtain varnishes. Using the obtained varnish, it was molded by the following molding method. The varnish was impregnated into an NE glass-based glass cloth having a thickness of 80 μm, dried at 140 ° C. for 3 minutes and then sandwiched between release-molded glass plates, and pressed at a pressure of 30 kg / cm ² using a vacuum press machine at 200 ° C. And cured for 2 hours to obtain a plastic composite transparent sheet.

About the plastic composite transparent sheet produced as mentioned above, various characteristics were measured by the evaluation method shown below.
(1) Surface roughness (PV value)
The maximum surface roughness (PV value) of the transparent composite sheet was measured using an interferometer manufactured by ZYGO.
(2) 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. for 1 minute in a nitrogen atmosphere for 20 minutes. It hold | maintained and measured and calculated | required the value at the time of 30 to 150 degreeC. The load was 5 g and the measurement was performed in the tensile mode. For the measurement, an independently designed quartz tension chuck (material: quartz, coefficient of linear expansion 0.5 ppm) was used.
(3) Light transmittance The light transmittance at 550 nm was measured with a spectrophotometer U3200 (manufactured by Hitachi, Ltd.).
(Four)
Evaluation of birefringence Micropolar birefringence was determined by observing the sample under a crossed Nicol using a polarizing microscope.
The results are shown in Table 1.

  The plastic transparent composite sheet of the present invention can be used for many optical applications, and is not particularly limited to the application. For example, transparent substrates for liquid crystal displays, organic EL display element substrates, color filter substrates, touch panels, solar cell substrates and other optical sheets, transparent plates, optical lenses, optical elements, optical waveguides, light guide plates, transparent sealing materials for LEDs It can be suitably used for bulletproof glass, BGA substrates, electronic paper, optical recording devices, etc., but in particular, display elements such as substrates for various liquid crystal display elements, color filters, organic EL substrates, electronic paper, etc. Is more desirable.

Claims (4)

1,2-epoxy-4- (2-oxiranyl) cyclosexane adduct of 2,2-bis (hydroxymethyl) -1-butanol (a) having an average particle diameter of 5 nm to 100 nm and an aspect ratio of 2 An inorganic filler (b) of 20 and a fibrous inorganic filler (c) having an aspect ratio of 20 or more as essential components, and a plastic composite transparent sheet having a light transmittance of 60% or more at a wavelength of 550 nm,
1,2-epoxy-4- (2-) in which the average particle diameter is 5 nm to 100 nm and the inorganic filler (b) having an aspect ratio of 2 to 20 is 2,2-bis (hydroxymethyl) -1-butanol. 1 to 50% by weight based on the oxiranyl) cyclosexane adduct (a),
The refractive index of a complex comprising 1,2-epoxy-4- (2-oxiranyl) cyclosoxane adduct of 2,2-bis (hydroxymethyl) -1-butanol (a) and an inorganic filler (b); A plastic composite transparent sheet in which the difference in refractive index of the inorganic filler (c) is 0.03 or less.   The plastic composite transparent sheet according to claim 1, wherein an average linear expansion coefficient at 30 to 150 ° C is 25 ppm or less.   The plastic composite transparent sheet according to claim 1 or 2, wherein the maximum surface roughness of the substrate surface is 200 nm or less.   The plastic composite transparent sheet according to any one of claims 1 to 3, wherein the inorganic filler (b) is a metal oxide.