JP5654936B2 - Transparent composite - Google Patents

Description

  The present invention relates to a transparent composite, a circuit board using the same, an electron wave shielding material, a building material, a window for a moving body, a base for display, and a base for solar cell.

  In recent years, in various fields including electronic materials and the like, glass has been replaced with transparent plastic in order to reduce thickness and weight. Further, in addition to the characteristics of such general transparent plastics, a transparent composite material composed of a transparent resin and a glass fiber substrate has been proposed as a material having high heat resistance and high dimensional stability against temperature and humidity. (See Patent Documents 1 and 2).

  When manufacturing such a transparent composite material, a high refractive index resin having a refractive index larger than that of glass fiber and a low refractive index resin having a refractive index smaller than that of glass fiber are mixed, and the refractive index is glass fiber. The resin composition is obtained by adjusting so as to approximate the refractive index. Then, a glass fiber base material is impregnated with the resin composition, dried and semi-cured to prepare a prepreg, and the prepreg is heated and pressed to produce a transparent composite material. An epoxy resin or the like is used as the high refractive index resin and the low refractive index resin.

  Thus, by combining the glass fiber of the substrate and the refractive index of the matrix fiber (resin composition), it can be used as a transparent composite material that suppresses light refraction in the transparent composite material and has excellent visibility. .

  And this transparent composite material attracts attention as a material applicable to various fields, such as a circuit board.

JP 2004-307851 A JP 2009-066931 A

  However, the transparent composite material comprising the transparent resin and the glass fiber base as described above has room for improvement in flame retardancy. That is, the conventional transparent composite material has a problem that its use is limited because it is easy to burn.

  The present invention has been made in view of the circumstances as described above, and an object thereof is to provide a transparent composite material excellent in flame retardancy.

The transparent composite according to the present invention comprises a glass fiber base material containing a tetrabromobisphenol A type epoxy resin and a polyfunctional epoxy resin having a structure represented by the following structural formula (I). The formed transparent resin is retained, and the tetrabromobisphenol A type epoxy resin has a content in the resin component in the resin composition of 20 to 65% by mass, and is at least V-1 or higher and VTM-1 or higher. Either one has flame retardancy.

  In the said invention, it is preferable to have a flame retardance of at least any one of V-0 or more and VTM-0 or more.

In the above invention, tetrabromobisphenol A type epoxy resins, the content of the resin component in the resin composition, and more preferably 30 to 58 wt%.

  In the above invention, the transparent resin preferably has a glass transition temperature measured by a dynamic viscoelasticity test (DMA) of 180 ° C. or higher.

  In the said invention, it is preferable that the said glass fiber is E glass fiber.

  In the said invention, it is preferable to have copper in at least any one of the surface and an inside. Moreover, it is preferable that the copper foil is laminated | stacked on the surface and the part by which the said copper foil was etched is smooth | blunted with the resin layer.

  The transparent circuit board, the transparent electron wave shielding material, the building material, the window material for moving bodies, the display substrate, and the solar cell substrate according to the present invention use the above transparent composite.

  According to the present invention, a transparent composite material that is transparent and has excellent flame retardancy can be obtained.

  Hereinafter, modes for carrying out the present invention will be described.

  In the transparent composite of this embodiment, a transparent resin is held on a glass fiber substrate. The transparent resin is formed of a resin composition containing a brominated bisphenol A type epoxy resin. The transparent composite has flame retardancy of at least one of V-1 or higher and VTM-1 or higher.

  The transparent composite is preferably formed by impregnating a glass composition with a resin composition and curing. The resin composition may be transparent in the state of the resin composition, but may be at least as long as it becomes transparent after curing. The resin composition is adjusted so that the refractive index approximates the refractive index of the glass fiber by mixing a high refractive index resin having a higher refractive index than the glass fiber and a low refractive index resin having a lower refractive index than the glass fiber. It is preferable that Thereby, excellent transparency can be obtained.

  In the present specification, the refractive index of the resin means the refractive index in the cured resin state (cured resin). That is, the refractive index of the resin and the resin composition is measured as a cured product. The refractive index is measured by a test according to ASTM D542.

  The resin composition contains brominated bisphenol A type epoxy resin. Thereby, the flame retardance of the transparent composite increases. Brominated bisphenol A type epoxy resin functions as a high refractive index resin. Since the brominated bisphenol A type epoxy resin is a high refractive index resin, a low refractive index resin is contained, and the refractive index of the transparent resin is adjusted. Further, the brominated bisphenol A type epoxy resin may contain other high refractive index resins. It becomes possible to adjust the refractive index by using other resins together.

  The brominated bisphenol A type epoxy resin preferably contains a tetrabromobisphenol A type epoxy resin. Thereby, a flame retardance can be improved. In order to further increase the flame retardancy, the content of the tetrabromobisphenol A type epoxy resin in the resin component in the resin composition is preferably 20 to 65% by mass, and preferably 30 to 58% by mass. More preferred. The term “in the resin component” means a solvent or a component excluding the solvent.

  The resin composition preferably includes a polyfunctional epoxy resin having a structure represented by the following structural formula (I). The polyfunctional epoxy resin of the structural formula (I) is a resin that can function as a low refractive index resin. The compound constituting the polyfunctional epoxy resin of the structural formula (I) is a polyfunctional epoxy compound, is alicyclic, has high transparency, has a high glass transition temperature, and can improve the heat resistance of the cured product.

  (In the formula, R represents an organic group, and n and m independently represent an integer).

  In the structural formula (I), the organic group R may be arbitrary as long as it can constitute an alicyclic epoxy structure, and examples thereof include a linear or branched hydrocarbon group having 1 to 10 carbon atoms. It is done. In Structural Formula (I), m is not particularly limited, but is 1 to 5, for example. In Structural Formula (I), n is not particularly limited, but is preferably 1-50. The values of m and n are preferably set in a range that loses fluidity at normal temperature (25 ° C.) and becomes solid. Production of a transparent composite can be facilitated by being solid at room temperature.

  For example, the epoxy resin represented by the structural formula (I) preferably has a melting point of about 85 ° C., and the molecular weight is not particularly limited, but is preferably, for example, 2000 to 3000 in terms of weight average molecular weight.

  Examples of the polyfunctional epoxy resin having a structure represented by the structural formula (I) include 1,2-epoxy-4- (2-oxiranyl) cyclohexane to 2,2-bis (hydroxymethyl) -1-butanol. What is obtained by adding can be used.

  The resin used for adjusting the refractive index of the transparent resin will be further described together with the brominated bisphenol A type epoxy resin.

  As the high refractive index resin blended in the resin composition, a cyanate ester resin and an epoxy resin composed of a compound represented by the following structural formula (II) are preferably used. These may be used alone or in combination.

  Examples of cyanate ester resins include 2,2-bis (4-cyanatephenyl) propane, bis (3,5-dimethyl-4-cyanatephenyl) methane, 2,2-bis (4-cyanatephenyl) ethane, and the like. Or an aromatic cyanate ester compound can be used. These may be used alone or in combination of two or more.

  Cyanate ester resin generates a triazine ring or an oxazoline ring by causing a curing reaction together with the epoxy resin, increases the crosslink density of the epoxy resin, and forms a rigid structure to give the cured product a high glass transition temperature. Can do. In addition, since cyanate ester resin is solid at room temperature, it becomes easy to touch and dry when preparing a prepreg by impregnating a resin composition into a glass fiber substrate and drying, and handling of the prepreg Will be better.

  When the cyanate ester resin in the resin composition is blended, the blending amount is preferably 10 to 40% by mass with respect to the total amount of the high refractive index resin and the low refractive index resin. The amount of cyanate ester resin is within this range, so that the glass transition temperature can be sufficiently improved, and the solubility is insufficient and the cyanate ester resin precipitates from the varnish during the impregnation process and storage. It is possible to suppress this. From these viewpoints, the amount of the cyanate ester resin is more preferably 25 to 35% by mass.

  The compound represented by the structural formula (II) is a trifunctional or higher polyfunctional epoxy compound. And by using this as a monomer and using an epoxy resin (polyfunctional epoxy resin) obtained by polymerization, it is possible to increase the heat resistance of the cured product with a high glass transition temperature while maintaining high transparency. Further, discoloration due to heat can be suppressed.

R ¹ in the structural formula (II) is hydrogen or an organic group. Although it does not specifically limit as an organic group, For example, hydrocarbon groups, such as lower alkyl groups, such as a methyl group and an ethyl group, other organic groups, etc. are mentioned.

R ² in the structural formula (II) is preferably a divalent organic group bonded to adjacent carbon atoms and oxygen atoms, and examples thereof include substituted or unsubstituted arylene such as a phenylene group. A group having a structure in which a group, a substituted or unsubstituted arylene group and a carbon atom or a carbon chain are bonded to each other. Examples of the carbon atom or carbon chain include an alkylene group such as a methylmethylene group and a dimethylmethylene group, and a carbonyl group.

As R ² , a group constituting glycidyloxyphenyl in which phenylene group is bonded to glycidyloxy group in Structural Formula (II) is preferably used. Further, from the viewpoint of suppressing discoloration of the transparent composite due to heat, a carbon atom or carbon chain interposed between arylene groups preferably does not contain a methylene group (—CH ₂ —).

Examples of the divalent organic group represented by R ² include the following structures (inside square brackets).

Examples of the substituent of R ³ to R ¹⁰ in the structural formula (II), is not particularly limited, for example, hydrogen, a hydrocarbon group such as a lower alkyl group, and other organic groups. Examples of the epoxy group-containing molecular chain of R ^{3 to} R ¹⁰ include the following structures (inside square brackets).

(In the formula, m represents a positive integer).

  The epoxy resin is preferably in a range that loses fluidity and becomes solid at room temperature (25 ° C.). Production of a transparent composite can be facilitated by being solid at room temperature. For example, the epoxy resin preferably has a melting point of about 85 ° C. Moreover, although the molecular weight of an epoxy resin is not specifically limited, For example, it is preferable that it is 2000-3000 in a weight average molecular weight.

  The compound of structural formula (II) is a trifunctional epoxy compound, has high transparency, has a high glass transition temperature, and can improve the heat resistance of the cured product.

  Examples of the epoxy resin based on the compound represented by the structural formula (II) include polyfunctional epoxy resins composed of the compounds represented by the following structural formulas (II-a), (II-b) and (II-c). Preferably used. In (II-b), n represents a positive integer.

  The refractive index of the brominated bisphenol A type epoxy resin, cyanate ester resin, epoxy resin by the compound represented by the structural formula (II), or a mixture thereof (high refractive index resin mixture) as the high refractive index resin is preferably 1.58 to 1.63. For example, when the refractive index of the glass fiber is 1.563 (E glass fiber), the high refractive index resin preferably has a refractive index of around 1.6, and n + 0.03 when the refractive index of the glass fiber is n. Those in the range of n + 0.06 are preferred. When the refractive index of the glass fiber is 1.528 (T glass fiber), the high refractive index resin preferably has a refractive index of around 1.55. When the refractive index of the glass fiber is n, n + 0.03 The thing of the range of -n + 0.08 is preferable.

  An epoxy resin can be used as the low refractive index resin having a refractive index smaller than that of the glass fiber.

  As the low refractive index resin, the epoxy resin of the structural formula (I) described above is preferable.

  Further, as the low refractive index resin, for example, a hydrogenated bisphenol type epoxy resin can be used in addition to the above. As the hydrogenated bisphenol type epoxy resin, for example, bisphenol A type, bisphenol F type, bisphenol S type and the like can be used. Preferably, a hydrogenated bisphenol type epoxy resin that is solid at room temperature is used. It is also possible to use a hydrogenated bisphenol-type epoxy resin that is liquid at room temperature, but in that case, it is sticky to the touch when preparing a prepreg by impregnating the resin composition into a glass fiber substrate and drying it. There is a possibility that it can be dried only to the state, and there is a possibility that the handleability of the prepreg is deteriorated.

  The refractive index of the low refractive index resin is preferably 1.47 to 1.53. That is, the low refractive index resin preferably has a refractive index of around 1.5. For example, when the refractive index of the glass fiber is 1.563 (E glass fiber), the refractive index of the glass fiber is n−. The thing of the range of 0.04-n-0.08 is preferable. When the refractive index of the glass fiber is 1.528 (T glass fiber), the low refractive index resin is in the range of n-0.01 to n-0.03, where n is the refractive index of the glass fiber. Those are preferred.

  The ratio of the content of the high refractive index resin and the low refractive index resin is a mass ratio, and the ratio of high refractive index resin: low refractive index resin is preferably in the range of 5:95 to 70:30. By blending the respective resins with a content ratio in this range, the refractive index can be adjusted more easily.

  A curing initiator (curing agent) can be blended in the resin composition. As the curing initiator, for example, an organic metal salt can be used. Examples of the organic metal salt include salts of organic acids such as octanoic acid, stearic acid, acetyl acetate, naphthenic acid, and salicylic acid with metals such as Zn, Cu, and Fe. These may be used alone or in combination of two or more. Of these, zinc octoate is preferable. By using zinc octoate as the curing initiator, the glass transition temperature of the cured resin can be increased. The amount of the organic metal salt such as zinc octoate in the resin composition is preferably in the range of 0.01 to 0.1 PHR.

  In addition, in this specification, PHR is a unit of mass ratio (mass%) with respect to the total mass of high refractive index resin and low refractive index resin.

  A cationic curing agent can also be used as the curing initiator. By using a cationic curing agent, the transparency of the cured resin can be increased. Examples of the cationic curing agent include aromatic sulfonium salts, aromatic iodonium salts, aromatic ammonium salts, aluminum chelates, and boron trifluoride amine complexes. The blending amount of the cationic curing agent in the resin composition is preferably in the range of 0.2 to 3.0 PHR.

  Further, as a curing initiator, a curing catalyst such as a tertiary amine such as triethylamine or triethanolamine, or an imidazole compound such as 2-ethyl-4-imidazole, 4-methylimidazole or 2-ethyl-4-methylimidazole should be used. You can also. The blending amount of these curing catalysts in the resin composition is preferably in the range of 0.5 to 5.0 PHR.

  The transparent resin constituting the transparent composite preferably has a glass transition temperature (Tg) measured by a dynamic viscoelasticity test (DMA) of 180 ° C. or higher. That is, the resin composition is prepared such that the glass transition temperature (Tg) of the cured product (cured resin) is preferably 180 ° C. or higher, more preferably 200 ° C. or higher, and further preferably 220 ° C. or higher. Due to the high glass transition temperature after curing, the heat resistance of the transparent composite can be increased. The upper limit of the glass transition temperature is not particularly limited, but about 280 ° C. is practically the upper limit. The glass transition temperature is measured according to JIS C6481 DMA method.

  The resin composition can be prepared by blending the high refractive index resin, the low refractive index resin, and a curing initiator as necessary. This resin composition can be prepared as a varnish by diluting with a solvent as necessary. Examples of the solvent include benzene, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, acetone, methanol, ethanol, isopropyl alcohol, 2-butanol, ethyl acetate, butyl acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, diacetone. Alcohol, N, N′-dimethylacetamide and the like can be mentioned.

  As the glass fiber constituting the glass fiber base material, E glass fiber is preferably used from the viewpoint of enhancing the impact resistance of the transparent composite, inexpensive and stable supply quality, and the like. The E glass fiber is also called an alkali-free glass fiber, and is a glass fiber that is widely used as a glass fiber for resin reinforcement. T glass fibers can also be used. T glass has better mechanical and thermal properties than general-purpose E glass.

  As the glass fiber substrate, a glass fiber woven fabric or non-woven fabric can be used. For example, T glass cloth formed of T glass fiber or E glass cloth formed of E glass fiber can be used.

  Moreover, it is preferable to surface-treat glass fiber with the silane coupling agent normally used as a glass fiber processing agent in order to improve impact resistance.

  The refractive index of the glass fiber is 1.563 for the E glass fiber and 1.528 for the T glass fiber, but is not particularly limited, and is, for example, in the range of 1.45 to 1.65. Can do. When the refractive index of the glass fiber is within this range, a transparent composite having excellent visibility can be obtained.

  And in producing a transparent composite, it is preferable to first prepare a prepreg by impregnating a glass fiber base material with a varnish of a resin composition, heating and drying. At this time, it is preferable that the high refractive index resin and the low refractive index resin are uniformly dispersed in the prepreg. The drying conditions are not particularly limited, but a drying temperature of 100 to 160 ° C. and a drying time of 1 to 10 minutes are preferable.

  Next, one or a plurality of the prepregs are stacked and heated and pressed to cure the resin composition to obtain a transparent composite. The conditions for the heat and pressure molding are not particularly limited, but a temperature of 150 to 200 ° C., a pressure of 1 to 4 MPa, and a time of 10 to 120 minutes are preferable.

  The glass fiber substrate used for the transparent composite may be a single sheet or a plurality of sheets. For example, in order to obtain high transparency, a plurality of thin ones can be used in a stacked manner. Specifically, a glass fiber substrate having a thickness of 50 μm or less can be used, and two or more of them can be used in an overlapping manner. Although the thickness of a glass fiber base material is not specifically limited, About 10 micrometers is a practical minimum. The number of glass fiber substrates is not particularly limited, but about 20 is the practical upper limit. When producing a transparent composite using a plurality of glass fiber substrates in this way, each glass fiber substrate is impregnated with a resin composition and dried to produce a prepreg, and a plurality of the prepregs are stacked and heated. A transparent composite can be obtained by pressure molding. Alternatively, the resin composition may be impregnated and dried in a state where a plurality of glass fiber base materials are stacked, and a prepreg may be produced, and the prepreg may be heated and pressed to obtain a transparent composite.

  In the transparent composite, the content of the glass fiber substrate is preferably in the range of 25 to 65% by mass. If it is this range, while being able to obtain high impact resistance with the reinforcement effect by glass fiber, sufficient transparency can be obtained. It is preferable that the content ratio of the glass fiber base in the transparent composite does not exceed this range so that there is no risk of surface irregularities becoming large or transparency being lowered. Moreover, it is preferable that the content rate of a glass fiber base material does not fall below this range so that the thermal expansion coefficient of a transparent composite may not become large. From such a viewpoint, the content of the glass fiber substrate is more preferably in the range of 35 to 60% by mass.

  The flame retardancy of the transparent composite satisfies at least one of V-1 or higher and VTM-1 or higher. Both criteria may be met. By having such flame retardancy, a transparent composite having excellent flame retardancy can be obtained. From that viewpoint, it is more preferable that the transparent composite has flame retardancy of at least one of V-0 or more and VTM-0 or more. Both criteria may be met. Flame retardancy is measured according to JISK6911.

  In the transparent composite thus obtained, the high refractive index resin and the low refractive index resin in the transparent resin composition are polymerized to form a resin matrix containing a brominated bisphenol A resin. Therefore, it becomes a transparent composite excellent in flame retardancy.

  The white light transmittance of the transparent composite can be, for example, 88% or more. In addition, the transparent composite can be provided with conductivity by forming a conductive film such as an ITO film on the surface or by providing copper wiring, and is suitable for an electronic circuit board, an electromagnetic shielding material, and the like. is there.

  Further, the above transparent composite has high dimensional stability, and particularly has a low coefficient of thermal expansion (CTE) in the plane direction (XY direction). For example, the thermal expansion coefficient in the plane direction at 50 to 150 ° C. can be set to 30 ppm / ° C. or less.

  Moreover, it is preferable that the surface of a transparent composite body is smooth, for example, surface roughness (Rz) can be 1 micrometer or less. According to the resin composition as described above, the surface of the transparent composite can be easily smoothed.

  The transparency of the transparent composite can be confirmed by visual observation. For example, using a haze meter such as a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd., the haze value of the transparent composite conforms to JISK7136. It can also be confirmed by measuring.

  Furthermore, the above-mentioned transparent composite can be provided with a hard coat layer on at least one surface thereof to form a transparent composite with a hard coat layer. The hard coat layer may be provided on both sides. As the hard coat layer, a structure known as a hard coat layer such as a plastic film can be applied. The hard coat layer is preferably transparent. For example, a hard coat layer having a smooth surface can be obtained by forming an epoxy resin layer of several μm on the surface of the transparent composite by a laminate transfer method. Specifically, first, an epoxy resin having a large molecular weight dissolved in a solvent is applied to a PET film or the like as a carrier film. Next, this film is laminated on the surface of the transparent composite by a vacuum laminator. Thereafter, the epoxy resin is cured by ultraviolet irradiation or heat treatment, and finally the carrier film is removed to form a smooth hard coat layer on the surface of the transparent composite, thereby obtaining a transparent hard coat film. By forming the hard coat layer, surface smoothness and impact resistance can be improved.

The transparent composite may be provided with a gas barrier layer on at least one side thereof. The gas barrier layer may be provided on both sides. For example, a gas barrier layer having a smooth surface can be formed by forming a thin film of SiO ₂ or SiON _{X on} the surface of the transparent composite as described above by sputtering or by laminating these inorganic thin film and organic thin film. Can be formed. By forming the gas barrier layer, the gas barrier property can be enhanced.

  Further, the transparent composite may have copper on at least one of the surface and the inside. In that case, application to a circuit board or an electromagnetic wave shielding material is possible, and flame retardancy can be imparted to these materials. In order for the transparent composite to have copper, a copper foil may be superimposed on the surface, or a copper layer (copper film) may be formed on the surface by a method such as sputtering. In order to have copper inside, for example, when a plurality of prepregs are overlapped, the copper foil can be overlapped inside, but the present invention is not limited to this. Moreover, you may have copper on both the surface and the inside.

  In addition, the transparent composite may be one in which a copper foil is laminated on the surface, and a portion where the copper foil is etched is smoothed with a resin layer. In that case, a circuit board having flame retardancy and high transparency can be obtained. For example, the surface smoothness (Rz) can be 1 μm or less. Such a transparent composite is obtained by removing the copper by etching after the copper foil is superimposed on the surface of the transparent composite as described above. The surface of the transparent resin (resin layer) from which copper has been removed is a smoothened surface obtained by curing the resin composition.

  The transparent composite can be used in various applications, but is particularly preferably used for a transparent circuit board, a transparent electron wave shield material, a building material, a window for a moving body, a display substrate, and a solar cell substrate. In the case of a transparent circuit board, there is an advantage that a circuit board excellent in flame retardancy, transparency, heat resistance and dimensional stability can be provided. In the case of a transparent electron wave shielding material, there is an advantage that an electromagnetic wave shielding material excellent in flame retardancy, transparency, heat resistance and dimensional stability can be provided. In the case of building materials, there is an advantage that a building material excellent in flame retardancy, transparency and strength can be provided. Examples of building materials include window materials. In the case of the window material for moving bodies, there is an advantage that a window material for movement excellent in flame retardancy and transparency can be provided. The moving body window material is, for example, a vehicle window material. In the case of a display substrate, there is an advantage that a display substrate excellent in flame retardancy, transparency, heat resistance and dimensional stability can be provided. In the case of a solar cell substrate, there is an advantage that a solar cell substrate excellent in flame retardancy, transparency, heat resistance and dimensional stability can be provided. For these materials, the transparent composite can be used as it is or after being appropriately processed.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to these Examples at all.

  The followings were used as the blending components of Examples and Comparative Examples.

[High refractive index resin]
Tetrabromobisphenol A type epoxy resin (TBBA), DIC Corporation Epicron 153, refractive index 1.59
・ Techmore VG3101, manufactured by Printec Co., Ltd., trifunctional epoxy resin having a molecular structure represented by the above formula (II-a), refractive index of 1.59
[Low refractive index resin]
EHPE3150, manufactured by Daicel Chemical Industries, Ltd., 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol, represented by the above formula (I) Epoxy resin, epoxy equivalent 185, molecular weight 2234, refractive index 1.51
2021P, manufactured by Daicel Chemical Industries, Ltd., 3,4-epoxycyclohexenylmethyl-3, '4'-epoxycyclohexenecarboxylate resin, refractive index 1.51
[Curing initiator]
SI150L, manufactured by Sanshin Chemical Co., Ltd., cationic curing initiator Toluene and methyl ethyl ketone were used as solvents.

  In the blending amounts (parts by mass) shown in Table 1, a high refractive index resin and a low refractive index resin are blended, a curing initiator is blended, and 50 parts by mass of toluene and 50 parts by mass of methyl ethyl ketone are added thereto as solvents The resin composition varnish was prepared by stirring and dissolving at a temperature of 70 ° C.

  Next, the glass fiber base material was impregnated with the varnish of the resin composition and heated at 150 ° C. for 5 minutes to remove the solvent and to semi-cur the resin to prepare a prepreg.

  As the glass fiber substrate, E glass cloth (Asahi Kasei Electronics Co., Ltd., product number “1035”, refractive index 1.563, thickness 25 μm) was used.

  Then, two sheets of this prepreg were stacked, set in a press machine, and heated and pressed under conditions of 170 ° C., 2 MPa, and 15 minutes to obtain a transparent composite having a thickness of about 70 μm.

  The following measurements and evaluations were performed on the transparent composites of Examples and Comparative Examples thus obtained.

[transparency]
Using a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd., the transparency (total light transmittance) of the transparent composite was measured in accordance with JISK7136.

[Glass-transition temperature]
The resin component was scraped off from the prepared prepreg and subjected to direct pressure molding under the same conditions as the molding conditions of the transparent composite to obtain a resin plate (cured product of resin composition) having a thickness of 2 mm. Using this resin plate as a test sample, the glass transition temperature was measured in accordance with JIS C6481 DMA method.

[Refractive index of cured resin]
A resin plate was prepared as a test sample in the same manner as the glass transition temperature, the test sample was polished, and the refractive index was measured with an Atago Co. refractive index measuring device in accordance with ASTM D542.

[Flame retardance]
Flame retardancy was measured according to the method of JIS K6911.

[result]
The evaluation results are shown in Table 1. From Table 1, it was confirmed that the transparent composite of each Example is excellent in flame retardancy and transparency. In addition, the transparent composite of each Example also showed the flame retardance more than VTM-0.

Claims (13)

A transparent resin formed of a resin composition containing a tetrabromobisphenol A type epoxy resin and a polyfunctional epoxy resin having a structure represented by the following structural formula (I) is held on a glass fiber substrate,
The tetrabromobisphenol A type epoxy resin has a content in the resin component in the resin composition of 20 to 65% by mass,
A transparent composite having flame retardancy of at least one of V-1 or higher and VTM-1 or higher.

  The transparent composite according to claim 1, which has flame retardancy of at least one of V-0 or higher and VTM-0 or higher. The said tetrabromobisphenol A type epoxy resin is a transparent composite body of Claim 1 or 2 whose content in the resin component in the said resin composition is 30-58 mass%. The transparent composite according to any one of claims 1 to 3 , wherein the transparent resin has a glass transition temperature measured by a dynamic viscoelasticity test (DMA) of 180 ° C or higher. The transparent composite body according to any one of claims 1 to 4 , wherein the glass fiber is an E glass fiber. The transparent composite according to any one of claims 1 to 5 , comprising copper on at least one of the surface and the inside. The transparent composite body of any one of Claims 1-6 by which the copper foil is laminated | stacked on the surface and the part by which the said copper foil was etched is smooth | blunted with the resin layer. Using the transparent composite according to any one of claims 1 to 7 transparent circuit board. Either using the transparent composite according to item 1, the transparent electromagnetic wave shielding material according to claim 1-7. Using the transparent composite according to any one of claims 1 to 7 building materials. Using the transparent composite according to any one of claims 1 to 7 moving object window material. Using the transparent composite according to any one of claims 1 to 7 display substrate. Using the transparent composite according to any one of claims 1 to 7 solar cell substrate.