Transparent sheet

Abstract

To provide a transparent sheet comprising a glass fiber cloth and a cured resin layer with which the glass fiber cloth is impregnated, the transparent sheet exhibiting low heat generation.SOLUTION: A transparent sheet comprises a glass fiber cloth and a cured resin layer with which the glass fiber cloth is impregnated. The cured resin layer is formed of a cured material of a resin composition including (A) a brominated vinyl ester resin and (B) a fluorine-containing (meth)acrylate. The transparent sheet exhibits a total light transmittance of 80% or more and a haze of 30% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a transparent sheet comprising a transparent resin composite of glass fiber cloth and a cured resin. [Background technology]

[0002] The Building Standards Act and its Enforcement Order stipulate that smoke exhaust systems must be installed to prevent the flow of smoke, toxic gases, etc. that are generated in the event of a fire in a building, and to facilitate evacuation and firefighting activities. Therefore, office buildings, commercial facilities, and other buildings often have smoke exhaust systems and smoke barriers such as vertical smoke barriers installed.

[0003] Hanging smoke barriers are usually attached to the ceilings of buildings to temporarily block the flow of smoke, toxic gases, etc. into corridors or upper floors in the event of a fire, thereby ensuring the necessary time for evacuation. Therefore, to prevent the hanging smoke barriers from obstructing visibility or spoiling the aesthetics, transparent plate glass, transparent resin composites of glass fiber and resin, etc. are used for the hanging smoke barriers. Transparent resin composites of glass fiber and resin have the advantage of being less likely to break than transparent plate glass. For example, Patent Document 1 discloses a transparent non-combustible sheet containing a glass fiber fabric and a cured resin layer.

[0004] Patent Document 2 also discloses a non-flammable sheet having at least one glass fiber fabric and a photo-curable resin impregnated into the glass fiber fabric, wherein the difference in refractive index between the glass composition constituting the glass fibers in the glass fiber fabric and the photo-curable resin is 0.02 or less, the proportion of the glass fiber fabric to the non-flammable sheet is 20 to 70% by weight, the proportion of the photo-curable resin to the non-flammable sheet is 80 to 30% by weight, and the photo-curable resin is obtained by curing a composition containing at least a brominated vinyl ester. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-319746 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-213489 Summary of the Invention [Problem to be solved by the invention]

[0006] The Building Standards Act requires that smoke barriers be made of non-combustible materials. The requirements for certification testing of non-combustible materials include a total heat release of 8MJ / m2 for 20 minutes after the start of heating in a specified heat release test. 2 and the maximum heat generation rate is 200kw / m or less for 10 seconds or more within 20 minutes of starting heating. 2 The total calorific value mentioned above is the amount of resin contained in the sheet (g / m 2 ) tends to be higher the larger it is.

[0007] For example, in Patent Document 1, Example 2 shows a resin amount of 300 g / m 2 The total calorific value is 8.74MJ / m 2 This does not satisfy the requirements for the certification test for non-combustible materials.

[0008] On the other hand, in Patent Document 2, a photocurable resin obtained by curing a composition containing a brominated vinyl ester is used as the photocurable resin impregnated into a glass fiber fabric, and a resin weight of 200 g / m 2 This is said to solve the problem of not being able to obtain non-flammable certification if the resin weight is more than 380±10g / m. 2 Example 1: 260±7 g / m 2 and Example 2, in which the 2 Example 3 is disclosed, in which the total calorific value is 5.0 MJ / m 2 , 3.0MJ / m 2 , 2.0MJ / m 2 However, in the literature, the resin weight was 400 g / m 2The problem is that the above range is not certified as non-combustible.

[0009] Therefore, the present invention aims to solve the above problems and has as its main objective the provision of a transparent sheet that has low heat generation, comprising a glass fiber cloth and a cured resin layer impregnated into the glass fiber cloth. [Means for solving the problem]

[0010] The present inventors have conducted studies to solve the above problems and have found that the above problems can be solved by providing a transparent sheet comprising a glass fiber cloth and a cured resin layer impregnated in the glass fiber cloth, wherein the cured resin layer is formed from a cured product of a resin composition comprising (A) a brominated vinyl ester resin and (B) a fluorinated (meth)acrylate. The present invention was completed based on these findings and further studies.

[0011] That is, the present invention provides the following aspects of the invention. Item 1. A transparent sheet comprising a glass fiber cloth and a cured resin layer impregnated in the glass fiber cloth, wherein the cured resin layer is formed from a cured product of a resin composition comprising (A) a brominated vinyl ester resin and (B) a fluorinated (meth)acrylate, and wherein the transparent sheet has a total light transmittance of 80% or more and a haze of 30% or less. [Effects of the Invention]

[0012] According to the transparent sheet of the present invention, the transparent sheet comprises a glass fiber cloth and a cured resin layer impregnated in the glass fiber cloth, wherein the cured resin layer is formed from a cured product of a resin composition comprising (A) a brominated vinyl ester resin and (B) a fluorinated (meth)acrylate, and the transparent sheet has a total light transmittance of 80% or more and a haze of 30% or less, and therefore has low heat buildup. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view illustrating one embodiment of a sheet of the present invention. [Figure 2] 1 is a cross-sectional view illustrating one embodiment of a sheet of the present invention. [Figure 3] This is a diagram showing an outline of the test equipment used when conducting "4.9.2 Heat generation test" in the "Fire resistance performance test and evaluation procedure manual" (revised version as of July 1, 2021) of the Japan Testing Center for Construction Materials. [Figure 4] This is a schematic diagram of the test holder and clamping frame included in the testing equipment used when conducting "4.9.2 Heat Generation Test" in the "Fire Resistance Testing and Evaluation Procedures Manual" (revised July 1, 2021) of the Japan Testing Center for Construction Materials. The values ​​(dimensions) shown in Figure 4 are in mm. DETAILED DESCRIPTION OF THE INVENTION

[0014] The transparent sheet of the present invention comprises a glass fiber cloth and a cured resin layer impregnated in the glass fiber cloth, wherein the cured resin layer is formed from a cured product of a resin composition comprising (A) a brominated vinyl ester resin and (B) a fluorinated (meth)acrylate, and the transparent sheet has a total light transmittance of 80% or more and a haze of 30% or less.

[0015] The transparent sheet 1 of the present invention may contain at least one glass fiber cloth 2, or may contain multiple glass fiber cloths 2. As shown in Figures 1 and 2, in the transparent sheet 1 of the present invention, the cured resin layer 3 fills the gaps between the glass fibers that make up the glass fiber cloth 2, and one surface side portion of the cured resin layer 3 communicates with the other surface side portion through the gaps. The transparent sheet 1 of the present invention may also contain multiple cured resin layers 3. One cured resin layer 3 may also contain multiple glass fiber cloths 2.

[0016] The transparent sheet 1 of the present invention may have layers other than the cured resin layer 3. For example, as shown in FIG. 2, the transparent sheet 1 of the present invention may include a thermoplastic resin layer 4. It is preferable that the thermoplastic resin layer 4 is included on the outer side of the cured resin layer 3. Furthermore, when the thermoplastic resin layer 4 is provided, another layer may be provided between the cured resin layer 3 and the thermoplastic resin layer 4, and such another layer may be, for example, an adhesive layer. Each layer constituting the transparent sheet 1 of the present invention will be described in detail below.

[0017] (glass fiber cloth 2) In the transparent sheet 1 of the present invention, the glass fiber cloth 2 is contained in a state in which it is impregnated with a cured resin layer 3 described below. In the transparent sheet 1 of the present invention, the glass fiber cloth 2 contributes to increasing the mechanical strength of the sheet. The refractive index of the glass fiber cloth 2 can be set to be similar to the refractive index of the cured resin layer 3 described below, thereby enabling the transparent sheet 1 of the present invention to have a total light transmittance of 80% or more and a haze of 30% or less, which are indicators of transparency, as described below. In other words, the total light transmittance of 80% or more and a haze of 30% or less, which are indicators of transparency possessed by the transparent sheet 1 of the present invention, at least indicates that the refractive index of the glass fiber cloth 2 and the refractive index of the cured resin layer 3 described below are sufficiently similar (for example, the difference between the refractive index of the glass fiber cloth 2 and the refractive index of the cured resin layer 3 is 0.02 or less).

[0018] In the transparent sheet 1 of the present invention, the glass fiber cloth 2 is composed of a plurality of glass fibers. In the glass fiber cloth 2, the plurality of glass fibers are entangled with each other to form a single piece of cloth. The glass fiber cloth 2 may be, for example, a glass fiber fabric (glass cloth) composed of a plurality of warp threads and a plurality of weft threads. The weave of the glass fiber fabric is not particularly limited, and examples thereof include plain weave, satin weave, twill weave, basket weave, and rib weave. The weave density of the glass fiber fabric is not particularly limited, and examples thereof include 20 to 100 threads / 25 mm or more for both the warp and weft, and preferably 20 to 80 threads / 25 mm or more.

[0019] The glass material of the glass fibers constituting the glass fiber cloth 2 is not particularly limited, and for example, known glass materials can be used. Examples of glass materials include alkali-free glass (E glass), acid-resistant alkali-containing glass (C glass), high-strength, high-elasticity glass (S glass, T glass, etc.), and alkali-resistant glass (AR glass), and preferably the versatile alkali-free glass (E glass). The glass fibers constituting the glass fiber cloth 2 may be made of one type of glass material or a combination of two or more types of glass fibers made of different glass materials. Furthermore, from the viewpoint of improving transparency, it is preferable to select a glass material whose refractive index is close to that of the cured resin layer 3 described below.

[0020] The glass fibers constituting the glass fiber cloth 2 are preferably glass yarns in which a plurality of filaments, which are long glass fibers, are twisted together. The number of filaments in the glass yarns may be 30 to 420. The diameter of the filaments in the glass yarns may be 3 to 10 μm. The count of the glass yarns may be, for example, 3 to 70 tex. The tex count of the glass fibers corresponds to the number of grams per 1000 m.

[0021] In the transparent sheet 1, the proportion (mass %) of the glass fiber cloth 2 relative to the total mass of the glass fiber cloth 2 and the cured resin layer 3 is 5 to 55 mass %, from the viewpoint of achieving both transparency and a lower total heat generation amount and heat generation rate in the heat generation test of the certification standard for non-combustible materials in the Building Standards Act. 2 ) is 10 to 250 (g / m 2 The thickness of the glass fiber cloth 2 is, for example, about 10 to 250 μm.

[0022] The difference in refractive index between the glass fiber cloth 2 and the cured resin layer 3 described below is preferably 0.05 or less, more preferably 0.02 or less, and even more preferably 0.01 or less. The refractive index of the glass fiber cloth 2 is preferably about 1.45 to 1.65, and more preferably about 1.50 to 1.60.

[0023] The refractive index of the glass fiber cloth 2 is measured in accordance with the B method of JIS K 7142:2008. Specifically, the glass fibers constituting the glass fiber cloth 2 are immersed in methylene iodide (n D 23 1.747), butyl phthalate (n D 23 1.491) and dimethyl carbonate (n D 23 1.366), an Abbe refractometer NAR-2T manufactured by Atago Co., Ltd. was used as a light source, and sodium D line with a wavelength of 589 nm was used as a light source, and measurements were carried out at a temperature of 23°C, and the average value of five tests was taken as the refractive index value. The refractive index of the resin layer 3 was measured in accordance with the B method of JIS K 7142:2008. Specifically, the cured or solidified resin layer 3 was powdered, and the powder was immersed in methylene iodide (n D 23 1.747), butyl phthalate (n D 23 1.491) and dimethyl carbonate (n D 23 1.366), and a small measuring microscope STM5-311 (Olympus, observation magnification 400x) was used as the microscope, and measurements were taken at a temperature of 23°C using sodium D line with a wavelength of 589 nm as the light source, and the average value of 5 tests was taken as the refractive index value.

[0024] The difference in Abbe number between the glass fiber cloth 2 and the cured resin layer 3 is preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less. The Abbe number of the glass fiber cloth 2 is preferably 30 to 80, more preferably 40 to 70, and even more preferably 50 to 65. The Abbe numbers of the resin layer and the glass fiber cloth are measured as follows.

[0025] (Abbe number of resin layer) A sheet of the cured resin composition not containing glass fiber cloth was prepared under the same conditions and thickness as the case containing glass fiber cloth, and a test piece was cut to a width of 8 mm and a length of 20 mm. The surface was well polished, and the refractive index at a wavelength of 589 nm was measured in accordance with JIS K 7142A using an Abbe refractometer NAR-2T manufactured by Atago Co., Ltd., diiodomethane as the contact liquid, and sodium D line with a wavelength of 589 nm as the light source at a measurement temperature of 23° C. Next, the dispersion value was measured and calculated using natural light as the light source, and the Abbe number was calculated according to the following formula (I). Abbe number = (refractive index at wavelength 589 nm - 1) / dispersion value (I)

[0026] (Abbe number of glass fiber cloth) A glass sheet 8 mm wide, 20 mm long, and 5 mm thick was prepared using the glass material that constitutes the glass fiber, and the surface was thoroughly polished. The refractive index at a wavelength of 589 nm was measured in accordance with JIS K 7142A using an Abbe refractometer NAR-2T manufactured by Atago Co., Ltd., diiodomethane as the contact liquid, and sodium D line with a wavelength of 589 nm as the light source at a measurement temperature of 23° C. Next, the dispersion value was measured and calculated using natural light as the light source, and the Abbe number was calculated according to the above formula (I).

[0027] [Cured resin layer 3] The transparent sheet of the present invention is a transparent sheet comprising a cured resin layer impregnated in a glass fiber cloth, wherein the cured resin layer is formed from a cured product of a resin composition comprising (A) a brominated vinyl ester resin and (B) a fluorine-containing (meth)acrylate.

[0028] The present inventors have studied the invention of Patent Document 2 and found that the invention disclosed in Patent Document 2 involves impregnating a glass fiber fabric with a brominated vinyl ester resin to form a photocurable resin, thereby achieving transparency by reducing the difference in refractive index between the glass fiber fabric and the photocurable resin. However, the invention of Patent Document 2 limits the content of the brominated vinyl ester resin in the photocurable resin to reduce the refractive index difference, and requires the inclusion of components other than the brominated vinyl ester resin. Therefore, the inventors found that increasing the resin weight still results in insufficient compatibility between improved sheet transparency and low heat buildup. Furthermore, the inventors found that the invention of Patent Document 2 requires the resin impregnated in the glass fiber fabric to be mixed with another component having a lower refractive index and a lower bromine concentration than the glass fiber fabric in order to match its refractive index to that of the glass fiber fabric. Indeed, in the examples of Patent Document 2, the brominated vinyl ester resin is diluted with styrene, neopentyl glycol, or the like to adjust the refractive index to match that of the glass fiber fabric, but the bromine concentration is low. Therefore, the present inventors have found that the content of brominated vinyl ester resin in the sheet of Patent Document 2 is limited, the low heat generation property of brominated vinyl ester resin cannot be fully utilized, and when the weight of the resin is increased, the weight of the glass fiber fabric must also be increased at the same time, and therefore it is still insufficient to improve the transparency of the sheet while reducing the total heat generation.

[0029] Here, the present inventors focused on adding a fluorine-containing (meth)acrylate. Since fluorine-containing (meth)acrylates contain fluorine atoms, they were expected to reduce heat buildup, but their refractive index is approximately 1.3 to 1.4. Since the refractive index of brominated vinyl ester resins is approximately 1.6, they thought that using a combination of the two would make it easier to adjust the refractive index to approximately 1.53 to 1.57, the refractive index of glass fibers in general-purpose glass compositions, and ensure transparency. After extensive research, the present inventors discovered that the transparent sheet of the present invention can reduce heat buildup compared to the sheet of Patent Document 2.

[0030] Examples of the fluorine-containing (meth)acrylate include 2,2,2-trifluoroethyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, 2-(perfluorohexyl)ethyl methacrylate, and 2-(perfluorobutyl)ethyl methacrylate.

[0031] The resin composition forming the cured resin layer 3 may further contain additives such as a curing accelerator, a flame retardant, an ultraviolet absorber, a filler, and a photopolymerization initiator. Examples of flame retardants include aluminum hydroxide, magnesium hydroxide, trichloroethyl phosphate, triallyl phosphate, ammonium polyphosphate, and phosphoric acid ester. Examples of ultraviolet absorbers include benzotriazole. Examples of fillers include calcium carbonate, silica, and talc. Photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-methyl Examples of suitable methylbenzoyl compounds include 2-benzyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

[0032] In the present invention, in order to enhance the transparency of the sheet, it is desirable to set the refractive indexes of the glass fiber cloth 2 and the cured resin layer 3 to be similar to each other. From this perspective, the refractive index of the cured resin layer 3 is preferably about 1.45 to 1.65, and more preferably about 1.50 to 1.60. The mass ratio of the brominated vinyl ester resin to the fluorinated (meth)acrylate can be adjusted appropriately depending on the refractive index of the glass fiber used and the type of fluorinated (meth)acrylate, and is, for example, 1 to 10, preferably 2 to 8, and more preferably 3 to 5, as the (mass of brominated vinyl ester resin / mass of fluorinated (meth)acrylate) ratio.

[0033] In the transparent sheet 1 of the present invention, the mass of the cured resin layer 3 is, for example, 20 to 400 g / m 2 and 20 to 300 g / m 2 The thickness of the cured resin layer 3 is, for example, 20 to 500 μm, and more preferably 30 to 300 μm.

[0034] [Thermoplastic resin layer 4] In the transparent sheet 1 of the present invention, a thermoplastic resin layer 4 is laminated on the cured resin layer 3 as needed to improve the weather resistance, tear strength, folding endurance, etc. of the transparent sheet 1. It is preferable that one thermoplastic resin layer 4 is included on the outer side of the cured resin layer 3.

[0035] The material constituting the thermoplastic resin layer 4 is not particularly limited. Examples include polyester resins (including polyethylene terephthalate), polycarbonate resins, polyolefin resins, fluororesins, acrylic resins, polyamide resins, and polyvinyl chloride resins. Polyvinyl chloride resins are preferred from the viewpoint of achieving both flame retardancy and tear strength of the transparent sheet. Among polyvinyl chloride resins, those with a chlorine concentration of 40% by mass or more are preferred, more preferably 40 to 55% by mass, and even more preferably 45 to 55% by mass are preferred. This further reduces the heat buildup of the transparent sheet when the thermoplastic resin layer 4 is provided. Here, the chlorine concentration is a value measured using energy dispersive X-ray analysis (EDS analysis). Commercially available examples of such thermoplastic resin layers 4 include hard vinyl chloride sheets manufactured by Mataelon (registered trademark) product number CB-N-MO manufactured by Matanaga Chemical Co., Ltd. Furthermore, the thermoplastic resin layer 4 is preferably a film layer made of the above-mentioned resins.

[0036] The thickness of each thermoplastic resin layer 4 is, for example, 50 to 200 μm, and from the viewpoint of achieving both flame retardancy and folding resistance, is preferably 60 to 150 μm, and more preferably 80 to 140 μm. The mass of each thermoplastic resin layer 4 is, for example, 60 to 280 g / m 2 From the viewpoint of achieving both non-combustibility and folding resistance, 70 to 200 g / m 2 is preferable, and 95 to 190 g / m 2 are more preferred.

[0037] When the thermoplastic resin layer 4 is laminated, another layer, for example, an adhesive layer, may be provided between the cured resin layer 3 and the thermoplastic resin layer 4. When an adhesive layer is provided, the mass of each adhesive layer is 3 to 20 g / m 2 and 5 to 15 g / m 2 are preferred.

[0038] (Transparent Sheet 1 Characteristics) The transparent sheet of the present invention has a total light transmittance of 80% or more and a haze of 30% or less. In this specification, the total light transmittance of the transparent sheet 1 is a value measured in accordance with Japanese Industrial Standard JIS K 7361-1:1997, "Test method for total light transmittance of plastic transparent materials - Part 1: Single beam method." The haze of the transparent sheet 1 is a value measured in accordance with Japanese Industrial Standard JIS K7136 2000, "Determination of haze of plastic transparent materials." The transparent sheet of the present invention preferably has a total light transmittance of 85% or more, more preferably 90% or more. Furthermore, the haze of the transparent sheet of the present invention is preferably 20% or less, more preferably 10% or less.

[0039] The transparent sheet 1 of the present invention has a property of being resistant to heat generation because the cured resin layer 3 is formed from a cured product of a resin composition containing (A) a brominated vinyl ester resin and (B) a fluorine-containing (meth)acrylate. As an index of this property of the sheet 1 of the present invention, a heat generation rate of 50 kW / m 2 In a heat generation test in which radiant heat is irradiated, the total heat generation amount for 20 minutes after the start of heating is, for example, 8MJ / m 2 Less than or equal to 7MJ / m 2 The following can be mentioned. In addition, other indexes of the properties possessed by the sheet 1 of the present invention include a thermal conductivity of 50 kW / m 2 In a heat generation test in which radiant heat is irradiated, the heat generation rate is 200 kW / m for 10 seconds or more continuously for 20 minutes after heating starts. 2 Preferably, the heat generation rate should not exceed 200 kW / m for 8 seconds or more for 20 minutes after the start of heating. 2 The main points are that it does not exceed 50kW / m 2 The total heat generation amount and heat generation rate per unit area in the heat generation test in which radiant heat is irradiated are values ​​calculated in accordance with "4.9.2 Heat Generation Test" in the "Fire Prevention and Evaluation Procedures Manual" (revised July 1, 2021) of the Japan Testing Center for Building Materials (General Incorporated Foundation).

[0040] The mass of the transparent sheet 1 of the present invention is not particularly limited, but is, for example, 100 to 800 g / m 2 , preferably 200 to 600 g / m2 The thickness of the transparent sheet 1 of the present invention is, for example, 80 to 600 μm, and preferably 150 to 500 μm.

[0041] (Use of transparent sheet 1) The transparent sheet 1 of the present invention can be suitably used as a material for constituting smoke-proof hanging walls, smoke-proof sheets, partition walls, smoke-proof curtains, touch panels, solar panels (back sheets, etc.), or as a membrane material used for roofing materials, lighting tents, etc.

[0042] (Method of manufacturing transparent sheet 1) The transparent sheet 1 of the present invention can be manufactured by the following method. First, the glass fiber cloth 2 and the uncured cured resin composition that will form the cured resin layer 3 are prepared. The cured resin composition is applied to a transparent casting film, and the glass fiber cloth 2 is placed on top of the cured resin composition to impregnate the glass fibers with the cured resin composition. Another casting film is then placed on the glass fiber cloth 2, and pressure is applied to the surfaces of the two casting films to further impregnate the glass fiber cloth 2 with the cured resin composition. The cured resin composition is cured by heating or light irradiation, and the two casting films are then peeled off to obtain the transparent sheet 1 of the present invention. If a thermoplastic resin layer 4 is to be provided, a film to serve as the thermoplastic resin layer 4 is used instead of the two casting films, and cured. By not peeling off the film afterwards, a transparent sheet 1 having a laminate structure of thermoplastic resin layer 4 / cured resin layer 3 impregnated in the glass fiber cloth 2 / thermoplastic resin layer 4 can be obtained. [Example]

[0043] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0044] 1. Measurement and evaluation methods 1-1. Average diameter (μm) and number of single fibers of glass yarn Two pieces of glass fiber cloth were cut into 30 cm squares, one for observing the warp yarns and the other for observing the weft yarns, and each was embedded in epoxy resin (product name "3091", manufactured by Marumoto Struers K.K.) and cured. Next, the glass cloth embedded in the epoxy resin was polished to an extent that the cross section of the single fibers constituting the warp or weft yarns could be observed, and the average single fiber diameter (μm) and the number of single fibers (number of fibers) of the glass yarn were measured by observing them at a magnification of 500 times using a scanning electron microscope (SEM) (product name "JSM-6390A", manufactured by JEOL Ltd.). (1) Average single fiber diameter of long glass fibers (μm) Twenty warp and weft yarns were randomly selected, and the cross sections of all the single fibers contained in each of the 20 glass yarns were observed, the diameters were measured, and the average value was calculated to obtain the average single fiber diameter of the warp and weft yarns. (2) Number of single fibers (pieces) Twenty warp and weft yarns were randomly selected, and the total number of single fibers contained in each of the 20 glass yarns was measured and the average value was calculated to determine the number of single fibers in the warp and weft yarns.

[0045] 1-2.Glass yarn count The count of the glass yarn was measured according to the method specified in "7.1 Count" of the Japanese Industrial Standard JIS R 3420 2013 "General Test Methods for Glass Fibers." Specifically, 500 m of glass yarn was first taken from the winding machine and used as a test piece. The test piece was placed flat in a muffle furnace and baked at 625°C for 25 minutes, then allowed to cool in a desiccator, and the mass of the test piece was measured. The count was calculated according to the following formula: (formula) t=(m / 500)×1000 t: count m: mass of test piece (g)

[0046] 1-3.Glass fiber cloth 2 weave density (threads / 25mm) The weave density of the glass fiber cloth 2 was measured for the warp and weft threads according to the method specified in "7.9 Density (Weave Density)" of the Japanese Industrial Standard JIS R 3420:2013 "General Test Methods for Glass Fibers." Specifically, the measurement targets were positions 50 mm or more away from the edges and selvages of the glass fiber cloth 2, with measurement intervals set to 10 mm or more and 200 mm or less, and the total number of threads within the set measurement interval was counted. This was counted as one measurement, and the measurement was then moved to another position that did not include the previously measured thread, and the total number of threads within the measurement interval was counted two more times in the same manner. For each of the three measurements, the number of threads per 25 mm was calculated using the following formula, and the average of the three measurements was calculated. (formula) Mi=(ni / ai)×25 Mi: Number of threads per 25mm ni: Number of measured yarns ai: the exact distance at which the measurement was taken (mm)

[0047] 1-4. Thickness of glass fiber cloth 2 (μm) The thickness of the glass fiber cloth 2 was measured in accordance with Method A specified in "7.10.1 Cloth Thickness" of the Japanese Industrial Standard JIS R3420:2013 "General Test Methods for Glass Fibers." Specifically, using a micrometer, the spindle was gently rotated to lightly contact the measurement surface parallel to it, and the thickness of the glass fiber cloth 2 was measured by reading the scale after the ratchet made three clicks. The thickness of the glass fiber cloth 2 was measured at the intersection of the warp and weft threads.

[0048] 1-5. Refractive index of the glass fiber cloth 2 and the cured resin layer 3 The refractive indices of the glass fiber cloth 2 and the cured resin layer 3 were measured in accordance with "Method B" specified in Japanese Industrial Standard JIS K 7142:2008, "Plastics - Determination of Refractive Index." Specifically, the glass fibers constituting the glass fiber cloth 2 and the cured resin layer 3 were first crushed to an extent that Becke lines could be observed when observed under an optical microscope at 400x magnification, and used as measurement samples. Separately, multiple immersion solutions with refractive indices differing by 0.002 were prepared. A small amount of the immersion solution was placed on a glass slide, and several grains of the measurement sample were placed in the immersion solution on the glass slide, followed by a cover glass. A halogen lamp equipped with a D-line interference filter was used as the light source. The measurement sample was focused on using an optical microscope at 400x magnification, and then the microscope stage and objective lens were moved slightly away from the focus. By this procedure, if the refractive index of the measurement sample does not match that of the immersion liquid, the Becke lines (i.e., the bright halo visible around or inside the powder) will shift to the higher refractive index, and if the refractive index of the measurement sample matches that of the immersion liquid, the Becke lines will not appear. The refractive index was measured by repeating the measurement until the refractive index of the measurement sample matches that of the immersion liquid or falls between two adjacent refractive indices in the series of immersion liquids. The refractive index was measured three times at a temperature of 23°C, and the average of the three measurements was taken as the refractive index.

[0049] 1-6. Mass of glass fiber cloth 2 (g / m 2 ) The mass of the glass fiber cloth 2 was measured in accordance with the method specified in "7.2 Mass (mass) of cloths and mats" of the Japanese Industrial Standard JIS R 3420:2013 "General test methods for glass fibers." Specifically, a 100 cm2 area was measured from a point 50 mm or more away from the edge of the glass fiber cloth 2. 2 A square test piece was taken and dried at 105°C for 1 hour, after which the mass of the test piece was measured and calculated as 1m according to the following formula: 2 The mass per unit was calculated. (formula) ρA=(ms / 100)×10 4 ρA:1m 2 Mass per unit (g / m2 ) ms: mass of test piece (g)

[0050] 1-7. Total light transmittance (%) and haze (%) The total light transmittance of the transparent sheet 1 was measured in accordance with Japanese Industrial Standard JIS K 7361-1:1997 "Test method for total light transmittance of plastic transparent materials - Part 1: Single beam method." The haze of the transparent sheet 1 was measured in accordance with Japanese Industrial Standard JIS K 7136:2000 "Determination of haze of plastic transparent materials."

[0051] 1-8. Total heat generation in heat generation test (MJ / m 2 ), and a heat generation rate per unit area of ​​200 kW / m 2 Exceeded duration (seconds) Transparent sheet 1: 50kW / m 2 The total heat generation amount in the heat generation test in which radiant heat is irradiated is 200kW / m and the heat generation rate per unit area is 200kW / m 2 The overload duration was measured in accordance with "4.9.2 Heat Generation Test" in the "Fire Resistance Performance Testing and Evaluation Procedure Manual" (revised July 1, 2021) of the Japan Testing Center for Construction Materials. The specific method is as follows:

[0052] [Test specimen] (1) The number of test specimens (sheet 1) shall be three. (2) The shape and dimensions of the test specimen shall be a square with each side measuring 99 mm ± 1 mm. (3) Before the test, the test specimen is cured at a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5% until it reaches a constant mass. [Test equipment] (1) A schematic diagram of the test equipment used is shown in Figure 3. The test equipment consists of a conical radiant electric heater, a spark plug, a radiant heat shield, a test specimen holder, a gas sampling device, an exhaust system capable of measuring gas flow rate, and a heat flow meter. (2) Radiant electric heater: 50 kW / m 2 The radiant heat must be able to be irradiated uniformly and stably onto the surface of the test piece. (3) The radiant heat shield must be capable of protecting the test specimen from radiant heat before the test begins. (4) A schematic diagram of the test holder and clamping frame included in the test equipment is shown in Figure 4. The specimen holder shall be made of stainless steel and be a square with outer dimensions of 106 mm ± 1 mm on each side, 25 mm ± 1 mm in depth, and 2.4 mm ± 0.15 mm in thickness. The clamping frame shall be made of stainless steel and be a square with inner dimensions of 111 mm ± 1 mm on each side, 54 mm ± 1 mm in height, and 1.9 mm ± 0.1 mm in thickness, with a square opening at the top measuring 94.0 mm ± 0.5 mm on each side. (5) The exhaust system shall be equipped with a centrifugal exhaust fan, hood, fan intake and exhaust ducts, an orifice plate flow meter, etc. that function effectively at the test temperature. The distance between the bottom end of the hood and the surface of the test specimen shall be 210 mm ± 50 mm, and the exhaust device of the exhaust system in this state shall have a flow rate of 0.024 m / s when converted to standard temperature and standard pressure. 3 The exhaust gas flow rate shall be at least 1 / s. To measure the exhaust gas flow rate, an orifice plate with an inner diameter of 57 mm ± 3 mm and a thickness of 1.6 mm ± 0.3 mm shall be installed in the exhaust duct at a position at least 350 mm ± 15 mm downstream from the fan. For exhaust gas sampling, a ring sampler with 12 holes, each 2.2 mm ± 0.1 mm in diameter, shall be installed 685 mm ± 15 mm from the hood, with the holes facing in the opposite direction to the flow. The exhaust gas temperature shall be measured at the center of the exhaust duct, 100 mm ± 5 mm upstream from the orifice plate. (6) The gas sampling device shall be capable of continuously and accurately measuring the concentrations of oxygen, carbon monoxide, and carbon dioxide in the exhaust gas. (7) The spark plug shall be capable of receiving power from a 10kV transformer or induction coil system, etc. The distance between the electrodes of the spark plug shall be 3mm ± 0.5mm, and the electrodes shall be positioned 13mm ± 2mm above the central axis of the test specimen, in principle. (8) The heat flow meter is 100kW / m 2 ±10kW / m 2The heat flow meter is a Schmidt-Boelter type that can measure up to 12.5 mm in diameter. The heat sensing part of the heat flow meter is circular and has a surface emissivity of 0.95±0.05.

[0053] [Test conditions] (1) The test time shall be 20 minutes from the time when radiant heat is irradiated onto the surface of the test specimen and an electric spark is simultaneously generated. (2) The test specimen is wrapped on the sides and back with aluminum foil of 0.025 mm or more and 0.04 mm or less in thickness, placed in a press frame, and then coated with inorganic fiber (nominal density 64 to 128 kg / m) on the back side. 3 ) and then pressed into the specimen holder. (3) During the test, a radiant electric heater was applied to the surface of the test specimen at 50 kW / m 2 It emits radiant heat. (4) Exhaust gas flow rate: 0.024 m 3 Adjust to / s. (5) Until the test begins, the test specimen is protected from radiant heat by a radiant heat shield. (6) Before moving the radiation heat shield, set the spark plug in place.

[0054] [measurement] (1) Measure the oxygen concentration at intervals of no more than 5 seconds. (2) The heat generation rate per unit area (kW / m 2 ) and the heat generation rate per unit area is calculated as 200 kW / m 2 The duration of the superheat state is calculated as "heat generation rate per unit area 200 kW / m 2 Furthermore, the total heat generation rate per unit area (MJ / m) was calculated by trapezoidal integration of the heat generation rate per unit area with respect to time. 2 Here, trapezoidal integration is performed by dividing the integration interval equally over the measurement interval, with negative heat release rates set to 0, and integrating only positive heat release rates.

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[0055] 2. Transparent sheet manufacturing [Example 1] (Preparation of fiberglass cloth 2) Glass yarns (trade name "ECG75 1 / 0 0.7Z", manufactured by Unitika Glass Fiber Co., Ltd.; average single fiber diameter 9 μm, single fiber count 400, twist count 0.7Z, count 67.5 tex) were used as warp and weft yarns. These were woven on an air jet loom to obtain a plain weave glass fiber fabric with a warp density of 44 / 25 mm and a weft density of 32 / 25 mm. The spinning and weaving sizing agents adhering to the resulting glass fiber fabric were then removed by heating at 400°C for 30 hours. The glass fiber fabric was then treated with a surface treatment agent containing a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride), manufactured by Chisso Corporation) adjusted to a concentration of 15 g / L, squeezed with a padder roll, and then dried at 120°C for 1 minute for curing. The glass fiber fabric was then subjected to a water jet processing at a pressure of 1.5 MPa, with the warp tension of the fabric set to 100 N / m, and a width-widening treatment was carried out once to obtain a glass fiber fabric 2 (glass fiber fabric). The obtained glass fiber fabric 2 had a warp density of 44 threads / 25 mm, a weft density of 32 threads / 25 mm, a thickness of 180 μm, and a mass of 210 g / m 2 The refractive index was 1.561. The average single fiber diameter and the number of single fibers of the glass yarn were measured using the glass fiber cloth 2.

[0056] (Preparation of curable resin solution used to form resin layer 3) As the curable resin solution to be used to form the resin layer 3, a brominated vinyl ester resin (product name "Neopol 8197", manufactured by Japan U-Pica Co., Ltd.), a fluorine-containing (meth)acrylate (product name "Light Ester M-3F", manufactured by Kyoeisha Chemical Co., Ltd., trifluoroethyl methacrylate), and a photopolymerization initiator (product name "Omnirad 184", manufactured by IGM) were prepared and mixed in the mass ratio shown in Table 1 to prepare the curable resin solution.

[0057] (Preparation of Thermoplastic Resin Sheet to be Used as Thermoplastic Resin Layer 4) A soft vinyl chloride film containing 73% vinyl chloride resin by mass was prepared. The film had a thickness of 120 μm and a mass of 156 g / m 2 Two sheets of the film were prepared.

[0058] (Manufacturing of transparent sheet 1) The prepared curable resin solution for the cured resin layer 3 was applied to one side of one of the thermoplastic resin films that would become the thermoplastic resin layer 4. Next, the prepared glass fiber cloth 2 was placed on the curable resin solution and left to stand for 1 minute, so that the curable resin solution was impregnated into the gaps in the glass fiber cloth 2. Next, another thermoplastic resin film that would become the thermoplastic resin layer 4 was placed on the curable resin solution, and a roller was used from above to roll the resin layer 3 until the mass of the resin layer 3 became 200 g / m. 2 Thereafter, the curable resin solution that passes through the thermoplastic resin film and becomes the cured resin layer 3 is irradiated with light using a black light fluorescent lamp (product name FL15BLB, manufactured by Toshiba Corporation) (light irradiation conditions: cumulative light amount 200 mJ / cm 2 ) to cure the curable resin solution, forming a cured resin layer 3, and obtaining a transparent sheet 1 of the present invention having a laminated structure of thermoplastic resin layer 4 / cured resin layer 3 contained in a state of being impregnated in glass fiber cloth 2 / thermoplastic resin layer 4. In the obtained transparent sheet, the gaps between the glass fibers of the glass fiber cloth were impregnated with cured resin layer 3 (a cured product of the curable resin), and cured resin layers 3 were formed on both sides of the glass fiber cloth layer.

[0059] [Comparative Example 1] (Preparation of fiberglass cloth 2) The same glass fiber cloth 2 as in Example 1 was prepared.

[0060] (Preparation of curable resin solution used to form resin layer 3) As the curable resin solution used to form the cured resin layer 3, brominated vinyl ester resin (trade name "Neopol 8197", manufactured by Japan U-Pica Co., Ltd.), bisphenol A type vinyl ester resin (trade name "Neopol 8114", manufactured by Japan U-Pica Co., Ltd.), neopentyl glycol diacrylate (trade name "NK Ester A-NPG", manufactured by Shin-Nakamura Chemical Co., Ltd.), and photopolymerization initiator (trade name "Omnirad 184", manufactured by IGM) were prepared and mixed to the mass ratio shown in Table 1 to prepare a curable resin solution.

[0061] (Preparation of Thermoplastic Resin Sheet to be Used as Thermoplastic Resin Layer 4) A soft vinyl chloride film containing 73% vinyl chloride resin by mass was prepared. The film had a thickness of 120 μm and a mass of 156 g / m 2 Two sheets of the film were prepared.

[0062] (Manufacturing of transparent sheet 1) The prepared curable resin solution for the cured resin layer 3 was applied to one side of one of the thermoplastic resin films that would become the thermoplastic resin layer 4. Next, the prepared glass fiber cloth 2 was placed on the curable resin solution and left to stand for 1 minute, so that the curable resin solution was impregnated into the gaps in the glass fiber cloth 2. Next, another thermoplastic resin film that would become the thermoplastic resin layer 4 was placed on the curable resin solution, and a roller was used from above to roll the resin layer 3 until the mass of the resin layer 3 became 200 g / m. 2 Thereafter, the curable resin solution that passes through the thermoplastic resin film and becomes the cured resin layer 3 is irradiated with light using a black light fluorescent lamp (product name FL15BLB, manufactured by Toshiba Corporation) (light irradiation conditions: cumulative light amount 200 mJ / cm 2) to cure the curable resin solution, forming a cured resin layer 3, and obtaining a comparative transparent sheet 1 having a laminated structure of thermoplastic resin layer 4 / cured resin layer 3 contained in a state of being impregnated in glass fiber cloth 2 / thermoplastic resin layer 4. In the obtained transparent sheet, the gaps between the glass fibers of the glass fiber cloth were impregnated with cured resin layer 3 (cured product of the curable resin), and cured resin layers 3 were formed on both sides of the glass fiber cloth layer.

[0063] 3.Results The results are shown in Table 1.

[0064] [Table 1]

[0065] The results showed that the transparent sheet of Example 1 was a transparent sheet comprising a glass fiber cloth and a cured resin layer impregnated in the glass fiber cloth, wherein the cured resin layer was formed from a cured product of a resin composition comprising (A) a brominated vinyl ester resin and (B) a fluorinated (meth)acrylate, and the transparent sheet had a total light transmittance of 80% or more and a haze of 30% or less, and therefore had lower heat buildup than the sheet of Comparative Example 1.

Claims

[Claim 1] A transparent sheet comprising a glass fiber cloth and a cured resin layer impregnated in the glass fiber cloth, the cured resin layer is formed from a cured product of a resin composition containing (A) a brominated vinyl ester resin and (B) a fluorinated (meth)acrylate, The transparent sheet has a total light transmittance of 80% or more and a haze of 30% or less.

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