JP7624253B2 - Transparent Sheet - Google Patents

Description

The present invention relates to a transparent sheet, specifically to a transparent sheet suitable for use in a smoke barrier, and a smoke barrier using the same.

The Building Standards Act and its Enforcement Order prescribe that smoke exhaust systems must be installed to prevent the flow of smoke, toxic gases, and other substances 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-blocking vertical walls and other smoke exhaust systems installed as smoke-blocking and smoke-blocking equipment.

Smoke barriers are usually attached to the ceilings of buildings to temporarily block the flow of smoke and toxic gases into corridors and upper floors in the event of a fire, thereby ensuring the time required for evacuation. For this reason, transparent plate glass and transparent resin composites of glass fibers and resin are used as smoke barriers to prevent them from obstructing the view or spoiling the aesthetic appearance. Transparent resin composites of glass fibers 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.

Patent Document 2 also discloses a non-flammable sheet having at least one glass fiber fabric and a photocurable resin impregnated into the glass fiber fabric, in which the difference in refractive index between the glass composition constituting the glass fibers in the glass fiber fabric and the photocurable resin is 0.02 or less, the ratio of the glass fiber fabric to the non-flammable sheet is 20 to 70% by weight, the ratio of the photocurable resin to the non-flammable sheet is 80 to 30% by weight, and the photocurable resin is a cured composition containing at least a brominated vinyl ester.

JP 2005-319746 A JP 2014-213489 A

The Building Standards Act requires that smoke barriers be made of noncombustible materials. Requirements for certification tests of noncombustible materials include that in a specified heat generation test, the total heat generation amount for 20 minutes after the start of heating is 8 MJ/m2 ^or less, and that the maximum heat generation rate during the 20 minutes after the start of heating does not exceed 200 kW/ ^m2 for 10 seconds or more. The total heat generation amount tends to be higher as the amount of resin (g/ ^m2 ) contained in the sheet increases.

For example, Patent Document 1 discloses a sheet with a resin amount of 300 g/ ^m2 as Example 2, but the total heat generation amount is 8.74 MJ/ ^m2 , which does not satisfy the requirements for the certification test of noncombustible materials.

On the other hand, in Patent Document 2, it is said that the problem of not being able to obtain non-combustible certification when the resin weight is 200 g/m ² or more is solved by using a photocurable resin obtained by curing a composition containing a brominated vinyl ester as the photocurable resin impregnated into the glass fiber fabric. As specific examples, Example 1 in which the resin weight is 380±10 g/m ² , Example 2 in which the resin weight is 260±7 g/m ² , and Example 3 in which the resin weight is 140±5 g/m ² are disclosed, and it is disclosed that the total heat generation amounts are 5.0 MJ/m ² , 3.0 MJ/m ² , and 2.0 MJ/m ^2, respectively. However, in this document, there is a problem that the range of the resin weight of 400 g/m ² or more is considered to be the range in which non-combustible certification is not obtained.

In addition, the inventors have found that, in the sheet of Patent Document 2, when the resin weight is increased from Example 3 to Example 2 and Example 1, the weight of the glass fiber fabric must be increased at the same time in order to reduce the total heat generation. In fact, in Patent Document 2, the glass fiber fabric weight is 50 g/m ² in Example 3, 100 g/m ² in Example 2, and 150 g/m ² in Example 1, and the glass fiber fabric weight is also increased with the increase in resin weight, and thus the total heat generation can be set to 8 MJ/m ² or less. The inventors have found that there is a problem that the haze of the obtained sheet increases with the increase in the glass fiber fabric weight, and the transparency of the sheet decreases. Therefore, the invention disclosed in Patent Document 2 still has a problem that, when the resin weight is increased, it is still insufficient to improve the transparency of the sheet and to reduce the total heat generation at the same time.

The present invention aims to solve the above problems and provide a transparent sheet that contains glass fiber fabric and resin, and a smoke barrier using the transparent sheet, which makes it possible to achieve both improved transparency and a low total heat generation when the resin weight is increased.

In order to solve the above problem, the present inventors have further studied the invention of Patent Document 2 in detail. In the invention disclosed in Patent Document 2, a brominated vinyl ester is impregnated into a glass fiber fabric to form a photocurable resin, and the difference in refractive index between the glass fiber fabric and the photocurable resin is reduced to achieve transparency. However, in the invention of Patent Document 2, in order to reduce the refractive index difference, the content of brominated vinyl ester in the photocurable resin is limited, and it is necessary to contain components other than brominated vinyl ester, and it has been found that when the resin weight is increased, it is still insufficient to improve the transparency of the sheet and to reduce the total heat generation. That is, in a resin having a halogen element as a substituent, such as brominated vinyl ester, the halogen element is a high refractive index substituent, so that the refractive index of the resin is considerably higher than that of the glass fiber fabric. And, in the invention of Patent Document 2, it has been found that in order to match the refractive index of the resin contained in the state of being impregnated into the glass fiber fabric with the refractive index of the glass fiber fabric, it is necessary to mix it with another component having a lower refractive index and a lower bromine concentration than the glass fiber fabric. In fact, in the examples of Patent Document 2, the brominated vinyl ester 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 inventors have found that the content of brominated vinyl ester in the sheet of Patent Document 2 is limited, the low heat generation characteristics of brominated vinyl ester cannot be fully utilized, and when the resin weight is increased, the weight of the glass fiber fabric must be increased at the same time, and it is still insufficient to improve the transparency of the sheet and reduce the total heat generation at the same time.

After further investigation, the inventors found that, since Patent Document 2 requires the use of brominated vinyl ester as the resin to be impregnated into the glass fiber fabric, it is necessary to dilute the concentration of bromine, which is a high refractive index substituent, to match the refractive index of the glass fiber fabric, and that the content of brominated vinyl ester is limited. The inventors then discovered that by laminating a resin composition layer that is not impregnated into the glass fiber fabric in addition to the resin composition layer that is impregnated into the glass fiber fabric, and using a resin that contains bromine atoms as a substituent, such as brominated vinyl ester, as the resin composition layer that is not impregnated into the glass fiber fabric, it is not necessary to dilute the resin that contains bromine atoms as a substituent with another resin, and it is possible to further utilize the low heat generation characteristics of the resin that contains bromine atoms as a substituent. That is, by using a resin with a low bromine concentration (including a resin that does not contain bromine, as described later) for the resin composition layer impregnated in the glass fiber fabric, the refractive index difference with the glass fiber fabric can be easily reduced, and by laminating a resin composition layer not impregnated in the glass fiber fabric separately from the resin composition layer impregnated in the glass fiber fabric and using a resin with a high bromine concentration as the resin composition layer not impregnated in the glass fiber fabric, the low heat generation characteristics of the resin with a high bromine concentration can be fully utilized, and it has been found that it is possible to more suitably achieve both improved transparency and a low total heat generation when the resin weight is increased. The present invention is an invention that was completed through further investigation based on these findings.

That is, the present invention provides the following aspects.
Item 1. A transparent sheet comprising a plain woven glass fiber fabric and a resin, the transparent sheet comprising, in a thickness direction of the transparent sheet, a first resin layer impregnated in the glass fiber fabric and a second resin layer not impregnated in the glass fiber fabric, the second resin layer having a higher bromine concentration than the first resin layer, and the transparent sheet having a total light transmittance of 85% or more and a haze of 10% or less.
Item 2. The transparent sheet according to item 1, wherein the total heat generation amount is 8 MJ/m2 or less in a heat generation test in which a surface of the sheet is irradiated with radiant heat of 50 kW/ ^m2 from a radiant electric heater, as measured according to "4.10.2 Heat Generation Test and Evaluation Method" in the "Fire Resistance Test and Evaluation Procedure Manual" (revised on March 1, ²⁰¹⁴⁾ of the General Incorporated Foundation Building Materials Testing Center.
Item 3. The transparent sheet according to item 1 or 2, wherein the first resin layer is laminated on each of both sides of the second resin layer.
Item 4. The transparent sheet according to any one of Items 1 to 3, wherein a total content of the resins contained in the first resin layer and the second resin layer is 200 g/ ^m2 or more.
Item 5. The transparent sheet according to any one of Items 1 to 4, wherein the total thickness of the first resin layer and the second resin layer is 180 μm or more.
Item 6. The transparent sheet according to any one of Items 1 to 5, wherein the second resin layer contains a brominated vinyl ester resin.
Item 7. The transparent sheet according to item 6, wherein the first resin layer contains tetrabromobisphenol A.

According to the transparent sheet of the present invention, the transparent sheet contains a plain woven glass fiber fabric and a resin, and in the thickness direction of the transparent sheet, a first resin layer impregnated in the glass fiber fabric and a second resin layer not impregnated in the glass fiber fabric are included, and the bromine concentration of the second resin layer is higher than that of the first resin layer. Since the total light transmittance of the transparent sheet is 85% or more and the haze is 10% or less, it is possible to achieve both improved transparency and low total heat generation when the resin weight is increased. Therefore, if the transparent sheet is used to make a smoke barrier wall, it is possible to make a thick smoke barrier wall with a large resin weight while having excellent transparency and low total heat generation.

FIG. 1 is a schematic cross-sectional view illustrating one embodiment of a transparent sheet of the present invention. FIG. 1 is a schematic cross-sectional view illustrating one embodiment of a transparent sheet of the present invention. FIG. 1 is a schematic cross-sectional view illustrating one embodiment of a transparent sheet of the present invention. FIG. 1 is a schematic cross-sectional view illustrating one embodiment of a transparent sheet of the present invention. FIG. 1 is a schematic cross-sectional view illustrating one embodiment of a transparent sheet of the present invention. FIG. 1 is a schematic cross-sectional view illustrating one embodiment of a transparent sheet of the present invention. This is a diagram showing an outline of the test equipment used when performing 4.10.2 Heat generation test and evaluation method in the "Fire resistance performance test and evaluation procedure manual" (revised on March 1, 2014) of the General Incorporated Foundation Building Materials Testing Center. This is a schematic diagram of the test holder and the press frame included in the test equipment used when performing the heat generation test and evaluation method described in 4.10.2 of the "Fire Resistance Test and Evaluation Procedure Manual" (revised on March 1, 2014) of the General Incorporated Foundation Construction Materials Testing Center. The unit of the values (dimensions) shown in Figure 8 is mm.

The transparent sheet of the present invention is a transparent sheet containing a plain weave glass fiber fabric and a resin, and is characterized in that it contains, in the thickness direction of the transparent sheet, a first resin layer that is impregnated in the glass fiber fabric and a second resin layer that is not impregnated in the glass fiber fabric, the second resin layer has a higher bromine concentration than the first resin layer, the transparent sheet has a total light transmittance of 85% or more, and a haze of 10% or less.

For example, as shown in Figures 1 to 6, the transparent sheet 1 of the present invention includes a glass fiber fabric 2, a first resin layer 3 that is impregnated in the glass fiber fabric 2, and a second resin layer 4 that is not impregnated in the glass fiber fabric 2, and the bromine concentration of the second resin layer 4 is higher than the bromine concentration of the first resin layer 3.

The transparent sheet 1 of the present invention may contain at least one glass fiber fabric 2, or may contain multiple glass fiber fabrics. As shown in Figs. 1 to 6, the first resin layer 3 fills the gaps between the glass fibers constituting the glass fiber fabric 2, and one surface side portion of the first resin layer 3 communicates with the other surface side portion through the gaps. As shown in Figs. 1, 3, 4, and 6, the transparent sheet 1 of the present invention may contain multiple first resin layers 3 that are impregnated into the glass fiber fabric 2. Although not shown in Figs. 1 to 6, multiple glass fiber fabrics 2 may be contained in one first resin layer 3.

In the transparent sheet 1 of the present invention, the second resin layer 4 that is not impregnated into the glass fibers may be one layer, as shown in Figures 1 and 4, or may be multiple layers, as shown in Figures 2, 3, 5, and 6. When the second resin layer 4 is multiple layers, it is preferably 2 to 5 layers, and more preferably 2 to 3 layers.

For example, the transparent sheet 1 in FIG. 1, FIG. 3, FIG. 4, and FIG. 6 has a laminated structure in which the first resin layer 3 is laminated on both sides of the second resin layer 4. The transparent sheet 1 in FIG. 2, FIG. 3, FIG. 5, and FIG. 6 has a laminated structure in which the second resin layer 4 is laminated on both sides of the first resin layer 3. Specific examples of the laminated structure of the first resin layer 3 and the second resin layer 4 in the transparent sheet 1 of the present invention include a laminated structure in which the first resin layer 3/second resin layer 4/first resin layer 3 are laminated in this order as shown in FIG. 1 and FIG. 4; a laminated structure in which the second resin layer 4/first resin layer 3/second resin layer 4 are laminated in this order as shown in FIG. 2 and FIG. 5; and a laminated structure in which the second resin layer 4/first resin layer 3/second resin layer 4/first resin layer 3/second resin layer 4 are laminated in this order as shown in FIG. 3 and FIG. 6.

The transparent sheet 1 of the present invention may have layers other than the first resin layer 3 and the second resin layer 4. For example, as shown in Figures 4 to 6, the transparent sheet 1 of the present invention may include a film layer 5. It is preferable that one film layer 5 is included on the outer side of each of the first resin layer 3 and the second resin layer 4. Although not shown, the transparent sheet 1 of the present invention may also have a cover layer that is peeled off when used as, for example, a smoke barrier. Each layer constituting the transparent sheet 1 of the present invention will be described in detail below.

[Glass fiber fabric 2]
In the transparent sheet 1 of the present invention, the glass fiber fabric 2 is included in a state in which it is impregnated with the first resin layer 3 described later. In the transparent sheet 1 of the present invention, the glass fiber fabric 2 contributes to improving the fire resistance of the sheet. The refractive index of the glass fiber fabric 2 is set to be close to the refractive index of the first resin layer 3 described later, and this allows the transparent sheet 1 of the present invention to have a total light transmittance of 85% or more and a haze of 10% or less. In other words, the transparent sheet 1 of the present invention having a total light transmittance of 85% or more and a haze of 10% or less indicates that at least the refractive index of the glass fiber fabric 2 and the refractive index of the first resin layer 3 described later are sufficiently close (for example, the difference between the refractive index of the glass fiber fabric 2 and the refractive index of the first resin layer 3 is 0.02 or less).

In the transparent sheet 1 of the present invention, the glass fiber fabric 2 is composed of a plurality of glass fibers in a plain weave structure. In the glass fiber fabric 2, the plurality of glass fibers are intertwined with each other to form a single piece of cloth.

The glass material of the glass fibers constituting the glass fiber fabric 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.), alkali-resistant glass (AR glass), etc., and preferably alkali-free glass (E glass) which is highly versatile. The glass fibers constituting the glass fiber fabric 2 may be made of one type of glass material, or may be a combination of two or more types of glass fibers made of different glass materials. In addition, from the viewpoint of improving transparency, it is preferable to select a glass material that is close to the refractive index of the first resin layer 3 described later.

The count of the glass fibers constituting the glass fiber fabric 2 is not limited to any particular count, so long as it can form the glass fiber fabric 2. From the viewpoint of further improving transparency, the count of the glass fibers is preferably 20 tex or less, more preferably 3 to 6 tex, and even more preferably 3 to 5 tex. The count of the glass fibers may be one type alone, or two or more types may be combined. The tex count of the glass fibers corresponds to the number of grams per 1000 m.

The glass fibers constituting the glass fiber fabric 2 are preferably glass yarns in which multiple single fibers, which are long glass fibers, are twisted together. The number of single fibers in the glass yarn is preferably about 30 to 400, and more preferably about 40 to 120. The diameter of the single fiber in the glass yarn is preferably about 3.0 to 6.0 μm, and more preferably about 3.0 to 5.0 μm, from the viewpoint of further improving the transparency of the transparent sheet 1 while improving the non-combustibility of the transparent sheet 1. The count of the glass yarn is preferably 2 to 30 tex, more preferably 2 to 12 tex, and even more preferably 2 to 5 tex, from the viewpoint of further improving the transparency of the transparent sheet 1 while improving the non-combustibility of the transparent sheet 1.

In the transparent sheet 1, the ratio (mass %) of the total mass of the glass fiber fabric 2 in the transparent sheet 1 to the sum (g/m ² ) of the total mass (g/m ² ) of the glass fiber fabric 2 and the total mass (g/m ² , excluding the glass fiber fabric 2) of the first resin layer 3 described later is preferably 20 to 60 mass %, more preferably 30 to 60 mass %, from the viewpoint of further achieving both improved transparency and low total heat generation when the resin weight in the transparent sheet is increased. Moreover, the ratio (mass %) of the total mass (g/m ² ) of the glass fiber fabric 2 in the transparent sheet 1 to the total mass (g/m ² ) of the transparent sheet 1 excluding the cover layer that is peeled off when used as a hanging smoke barrier described later is preferably 5 to 50 mass %, more preferably 5 to 28 mass %, even more preferably 5 to 25 mass %, and particularly preferably 8 to 19 mass %, from the viewpoint of further achieving both improved transparency and low total heat generation. The mass (g/m ² ) per sheet of the glass fiber fabric 2 is preferably 10 to 120 (g/m ² ), more preferably 10 to 60 (g/m ² ), and even more preferably 20 to 40 (g/m ² ). From the viewpoint of further improving the transparency of the transparent sheet 1 while improving the flame retardancy of the transparent sheet 1, the total mass (g/m ² ) of the glass fiber fabric 2 in the transparent sheet 1 is preferably 10 to 120 (g/m ² ), more preferably 20 to 100 (g/m ² ), and particularly preferably 30 to 80 (g/m ² ).

The difference in refractive index between the glass fiber fabric 2 and the first resin layer 3 described below is preferably 0.02 or less, and more preferably 0.01 or less. The refractive index of the glass fiber fabric 2 is preferably about 1.50 to 1.58, and more preferably about 1.53 to 1.57.

The refractive index of the glass fiber fabric 2 is measured in accordance with JIS K 7142:2008 B method. Specifically, the glass fibers constituting the glass fiber fabric are crushed to an extent that the Becke lines can be observed when observed with an optical microscope at a magnification of 400 times. Then, a halogen lamp equipped with an interference filter for D-line is used as a light source, and the optical microscope is used to observe and measure the refractive index at a magnification of 400 times and a temperature of 23 ° C. The average value of three tests is taken as the refractive index value. The refractive index of the first resin layer 3 and the second resin layer 4 is measured in accordance with JIS K 7142:2008 B method. Specifically, the first resin layer 3 or the second resin layer 4 is crushed to an extent that the Becke lines can be observed when observed with an optical microscope at a magnification of 400 times. Then, using a halogen lamp equipped with a D-line interference filter as the light source, observations and measurements were made using an optical microscope at a magnification of 400 times and a temperature of 23°C, and the average value of three tests was taken as the refractive index value.

The difference in Abbe number between the glass fiber fabric 2 and the first 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 fabric 2 is preferably 30 to 80, more preferably 40 to 70, and even more preferably 50 to 65. The Abbe numbers of the first resin layer 3 and the glass fiber fabric 2 are each measured as follows.

(Abbe number of first resin layer 3)
A sheet not including the glass fiber fabric 2 is produced using the resin constituting the first resin layer 3, with a width of 8 mm, a length of 20 mm, and a thickness of 0.2±0.1 mm, and the refractive index at a wavelength of 589 nm is measured in accordance with JIS K 7142A using an Abbe refractometer manufactured by Atago Co., Ltd., NAR-2T, a contact liquid, diiodomethane, a light source, and sodium D line with a wavelength of 589 nm, at a measurement temperature of 23° C. Next, the dispersion value is measured and calculated using natural light as a light source, and the Abbe number is calculated according to the following formula (I).
Abbe number = (refractive index at wavelength 589 nm - 1) / dispersion value (I)

(Abbe number of glass fiber fabric 2)
A glass sheet having a width of 8 mm, a length of 20 mm, and a thickness of 5±1 mm is prepared using the glass material constituting the glass fiber, the surface is thoroughly polished, and the refractive index at a wavelength of 589 nm is measured in accordance with JIS K 7142A method using an Abbe refractometer NAR-2T manufactured by Atago Co., Ltd., diiodomethane as a contact liquid, and sodium D line having a wavelength of 589 nm as a light source at a measurement temperature of 23° C. Subsequently, the dispersion value is measured and calculated using natural light as a light source, and the Abbe number is calculated according to the above formula (I).

From the viewpoint of improving the flame retardancy of the transparent sheet 1 while further improving the transparency of the transparent sheet 1, the thickness of each piece of the glass fiber fabric 2 is, for example, about 10 to 100 μm, preferably about 10 to 55 μm, and more preferably about 10 to 35 μm. When the thickness of the glass fiber fabric 2 is 10 to 35 μm, it is particularly preferable that the glass fiber fabric 2 has a glass volume fraction of 38% or more as calculated by the following formula (II). A glass fiber fabric 2 having a thickness of 10 to 35 μm and a glass volume fraction of 38% or more can be obtained, for example, by subjecting the glass fiber fabric to an opening process.

Glass volume ratio (%) = (A / (B × C)) × 100 (II)
A: mass of glass fiber fabric (g/m ² )
B: Specific gravity of the glass material constituting the glass fiber fabric (g/m ³ )
C: Thickness of glass fiber fabric (m)

(First resin layer 3)
In the transparent sheet 1 of the present invention, the first resin layer 3 is impregnated into the glass fiber fabric 2 and is formed by curing or solidifying a resin composition containing a resin. As described later, the second resin layer 4 is included in the glass fiber fabric without being impregnated therein. Therefore, at least when the first resin layer 3 and the second resin layer 4 are in contact with each other, the glass fiber fabric 2 is not exposed on the surface of the first resin layer 3, and the glass fiber fabric 2 is included in the first resin layer 3. As described above, the first resin layer 3 is selected and set to be close to the refractive index of the glass fiber fabric 2, which can reduce light scattering on the glass fiber surface, and can be configured to have a total light transmittance of 85% or more and a haze of 10% or less, as described later.

The first resin layer 3 can be a cured resin layer or a thermoplastic resin layer. When it is a cured resin layer, it can be a cured product (a photocured resin composition or a thermoset resin composition) obtained by applying energy such as light or heat to a resin composition containing a curable resin to cure the resin composition. When it is a thermoplastic resin layer, it can be a cured product obtained by drying and solidifying the thermoplastic resin composition.

The transparent sheet 1 of the present invention requires that the bromine concentration of the second resin layer 4 described below is higher than that of the first resin layer 3. That is, the inventors have found that if the bromine concentration in the resin impregnated in the glass fiber fabric is high, the heat generation amount of the resin is low, while the refractive index of the resin is higher than that of the glass fiber fabric, and the transparency of the resulting sheet is easily impaired. Therefore, by using a resin with a lower bromine concentration for the first resin layer 3 impregnated in the glass fiber fabric, the refractive index difference with the glass fiber fabric 2 can be easily reduced, and by laminating the second resin layer 4 not impregnated in the glass fiber fabric 2 separately from the first resin layer 3 impregnated in the glass fiber fabric, and using a resin with a higher bromine concentration as the second resin layer 4 not impregnated in the glass fiber fabric 2, the low heat generation characteristic of the resin with a higher bromine concentration can be fully utilized, and it has been found that it is possible to improve transparency and reduce the total heat generation amount at the same time when the resin weight is increased.

From the viewpoint of further reducing the haze of the transparent sheet 1 of the present invention, the bromine concentration in the first resin layer 3 is, for example, 30% by mass or less, preferably 26% by mass or less, more preferably 20% by mass or less, and even more preferably 16.7% by mass or less. The lower limit of the bromine concentration in the first resin layer 3 is 0% by mass. In other words, the first resin layer 3 may not contain bromine.

In the present invention, the bromine concentration is measured by EDS analysis. Specifically, as shown in Figs. 1 to 6, a cut surface in the thickness direction of the transparent sheet 1 is used as the measurement surface, and a sample thickness (i.e., the length of the transparent sheet 1 in the vertical or horizontal direction) of 1 cm is used as the measurement sample. Using an apparatus manufactured by JEOL Ltd. under the trade name JSM-6390A, a measurement is made at one arbitrary point near the center of the thickness direction of the layer to be measured, and the value obtained is regarded as the bromine concentration of each layer.

In the transparent sheet 1 of the present invention, the difference between the bromine concentration (% by mass) of the first resin layer 3 and the bromine concentration (% by mass) of the second resin layer 4 described below (=bromine concentration of the second resin layer 4 - bromine concentration of the first resin layer 3) is, for example, 3% by mass or more, and from the viewpoint of achieving a better balance between improved transparency and a low total heat generation when the resin weight is increased, 5 to 50% by mass is preferred, 10 to 40% by mass is even more preferred, and 20 to 30% by mass is particularly preferred.

As the curable resin used to form the first resin layer 3, from the viewpoint of further improving the transparency of the transparent sheet 1, it is preferable that the first resin layer 3 and the above-mentioned glass fiber fabric 2 have a refractive index that is close to each other. As the curable resin, it is preferable that the curable resin composition is photocurable, and examples thereof include vinyl ester resin, urethane acrylate resin, fluorene acrylate resin, unsaturated polyester resin, curable acrylic resin, epoxy resin, etc. Among them, when the film layer 5 is provided, from the viewpoint of further improving the adhesion with the film layer 5, a curable acrylic resin is more preferable, and a resin composition containing acrylic syrup is particularly preferable. In the present invention, acrylic syrup refers to a polymerizable liquid mixture in which a (meth)acrylic acid ester polymer such as polymethyl methacrylate (PMMA) is dissolved in an acrylic monomer such as methyl methacrylate. Among the above acrylic syrups, acrylic syrups in which one or more acrylic ester polymers selected from the group consisting of polymethyl methacrylate, methyl methacrylate/methyl acrylate copolymer, and methyl methacrylate/normal butyl acrylate copolymer are dissolved in methyl methacrylate monomer are particularly preferred. In this way, when the first resin layer 3 is made of a cured resin composition containing acrylic syrup, the adhesion with the film layer 5 is further improved, and the transparency of the transparent sheet 1 is further improved, which is preferable.

The thermoplastic resin used to form the first resin layer 3 is preferably one that can approximate the refractive index of the first resin layer 3 and the glass fiber fabric 2 from the viewpoint of further improving the transparency of the transparent sheet 1. Examples of preferred thermoplastic resins include polyvinyl chloride resins, saturated polyester resins, polyolefin resins, thermoplastic acrylic resins, polycarbonate resins, polyvinyl alcohol resins, ethylene vinyl acetate copolymers, polyamide resins, polyarylate resins, and the like. For example, when E-glass is used as the glass material of the glass fibers constituting the glass fiber fabric 2, polyvinyl chloride resins, saturated polyester resins, thermoplastic acrylic resins, and the like are preferred from the viewpoint of further approximating the refractive index of both. The thermoplastic resin may be used alone, or two or more types having different refractive indices may be used in combination for the purpose of approximating the refractive index of the glass fiber used. In the transparent sheet 1 of the present invention, when the first resin layer 3 is a thermoplastic resin composition layer, the first resin layer 3 is preferably one that is impregnated with a thermoplastic resin composition in a sol state or dissolved in a solvent and solidified (solidified by heating or solidified by drying).

The resin composition constituting the first resin layer 3 may contain phosphorus from the viewpoint that the maximum heat generation rate does not exceed 200 kW/m 2 for 10 seconds or more during the first 20 minutes of heating in a heat generation test in which radiant heat of 50 kW/m ² is irradiated from a radiant electric heater to the surface of the sheet, as measured according to "4.10.2 Heat Generation Test/Evaluation Method" in the "Fire Resistance Test/Evaluation Service Manual" (revised version on March ^1, 2014) of the General Incorporated Foundation Building Materials Testing Center, which will be described later. The form of phosphorus inclusion may be, for example, a resin composition made of a resin having a phosphorus atom introduced as a substituent among the above-mentioned resins, or a resin composition in which a known phosphorus-based flame retardant is added to the above-mentioned resin. Examples of the phosphorus-based flame retardant include those containing condensed phosphate ester compounds such as non-halogen condensed phosphate ester compounds and halogen-containing condensed phosphate ester compounds, and from the viewpoint of refractive index adjustment, it is more preferable to contain a non-halogen condensed phosphate ester compound. From the viewpoint of further suppressing bleeding out of the phosphate ester compound, it is more preferable to use a condensed phosphate ester compound having a molecular weight of 420 or more. Examples of non-halogen condensed phosphate ester compounds include 1,3-phenylene bis(diphenyl phosphate) [RDP, molecular weight 574.46], bisphenol A bis(diphenyl phosphate) [BDP, molecular weight 692.64], 1,3-phenylene bis(dixylenyl)phosphate [molecular weight 686.67], and bisphenol A bis((bisdimethylphenyl)phosphate) [molecular weight 804.86]. Examples of halogen-containing condensed phosphate ester compounds include 2,2-bis(chloromethyl)trimethylene bis(bis(2-chloroethyl)phosphate) [molecular weight 582.99]. These phosphate ester compounds may be used alone or in combination of two or more.

Furthermore, the resin composition constituting the first resin layer 3 preferably contains tetrabromobisphenol A, decabromodiphenyl ether or brominated vinyl ester, and more preferably contains tetrabromobisphenol A, from the viewpoint of ensuring that the maximum heat release rate does not exceed 200 kW/m2 for 10 seconds or more within 20 minutes from the start of heating in a heat release test in which radiant heat of 50 kW/ ^m2 is irradiated onto the surface of the sheet from a radiant electric heater, as measured in accordance with "4.10.2 Heat Release Test and Evaluation Method" in the "Fire Prevention and Evaluation Procedure Manual for Fire Resistance Performance Testing and Evaluation" (revised version on March ¹ , 2014) of the General Incorporated Foundation Building Materials Testing Center, which will be described later, and further reducing the occurrence of cracks and holes that penetrate to the back surface and are harmful in terms of fire prevention, within 20 minutes from the start of heating. Specifically, particularly when the glass fiber fabric 2 is lightweight, for example having a mass of 40 g/ ^m2 or less, if the first resin layer 3 impregnated in the glass fiber fabric 2 contains the above-mentioned phosphorus, the first resin layer may blister in the heat generation test, which may lead to the glass fiber fabric 2 becoming more easily deformed. On the other hand, if the first resin layer 3 contains tetrabromobisphenol A, decabromodiphenyl ether or brominated vinyl ester, the occurrence of the above-mentioned blister is suppressed, and cracks and holes penetrating to the back surface, which are harmful in terms of fire prevention, are even less likely to occur.

The resin composition constituting the first resin layer 3 may also contain inorganic flame retardants such as antimony trioxide and magnesium hydroxide.

In addition, the resin composition constituting the first resin layer 3 may further contain additives such as a curing accelerator, an ultraviolet absorber, a filler, and a photopolymerization initiator. Examples of ultraviolet absorbers include benzotriazole. Examples of fillers include calcium carbonate, silica, and talc. Examples of photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethane-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 the additives include 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. Among these, when a curable acrylic resin is used as the first resin layer 3, 1-hydroxy-cyclohexyl-phenyl-ketone is preferred from the viewpoint of improving transparency. These additives may be used alone or in combination of two or more types. When the first resin layer 3 contains an additive, the content thereof is preferably 0.1 to 5% by mass, more preferably 0.1 to 3% by mass.

In the transparent sheet 1 of the present invention, the total mass of the resin composition of the first resin layer 3 (mass excluding the glass fiber fabric 2) is, for example, 20 to 250 g/m ^2. From the viewpoint of further achieving both improved transparency and better non-combustibility when the resin weight is increased, 20 to 200 g/m ² is preferably exemplified, 20 to 120 g/m ² is more preferably exemplified, and 20 to 80 g/m ² is particularly preferably exemplified. In addition, the thickness per layer of the first resin layer 3 (thickness including the glass fiber fabric 2) is, for example, 20 to 150 μm. From the viewpoint of further achieving both improved transparency and better non-combustibility when the resin weight is increased, 20 to 100 μm is preferably exemplified, and 20 to 50 μm is more preferably exemplified.

In the transparent sheet 1 of the present invention, the refractive index of the first resin layer 3 is preferably about 1.50 to 1.58, and more preferably about 1.53 to 1.57.

(Second resin layer 4)
In the transparent sheet 1 of the present invention, the second resin layer 4 is contained in a state where it is not impregnated in the glass fiber fabric 2. As described above, the bromine concentration of the second resin layer 4 is higher than that of the first resin layer 3. In the transparent sheet 1 of the present invention, the first resin layer 3 contained in a state where it is impregnated in the glass fiber fabric 2 and the second resin layer 4 contained separately in a state where it is not impregnated in the glass fiber fabric 2 are laminated, and a resin having a relatively high bromine concentration is used as the second resin layer 4 contained in a state where it is not impregnated in the glass fiber fabric 2. As a result, the transparent sheet 1 of the present invention does not need to be made to approximate the refractive index of the glass fiber fabric 2 by, for example, diluting it with another resin having a low bromine concentration as in Patent Document 2, and the low heat generation characteristic of the resin having a high bromine concentration can be fully utilized.

The bromine concentration in the second resin layer 4 of the transparent sheet 1 of the present invention is, from the viewpoint of further suppressing the total heat generation while further increasing the resin weight, for example, 31% by mass or more, preferably 35% by mass. There is no particular upper limit, but examples include 60% by mass or less, or 55% by mass or less.

Methods for incorporating bromine into the second resin layer 4 include, for example, a method in which the resin constituting the second resin layer 4 is a resin containing bromine atoms as a substituent, and a method in which a flame retardant containing bromine atoms is added to a curable resin or a thermoplastic resin to form a resin composition.

The resin containing a bromine atom as a substituent may be a curable resin or a thermoplastic resin containing a bromine atom as a substituent. Examples of curable resins containing a bromine atom as a substituent include brominated epoxy resins, brominated vinyl ester resins, and brominated unsaturated polyester resins. Examples of thermoplastic resins containing a bromine atom as a substituent include brominated polycarbonate resins, brominated polyurethane resins, and brominated polyester resins.

Examples of the flame retardant containing bromine atoms include decabromodiphenyl, tetrabromobisphenol A (TBBA) and its derivatives, bis(pentabromophenyl)ethane, 1,2-bis(2,4,6-tribromophenoxy)ethane, brominated polystyrene, hexabromocyclododecane, hexabromobenzene, pentabromobenzyl acrylate, pentabromobenzyl acrylate, decabromodiphenyl oxide, octabromodiphenyl oxide, and tetrabromodiphenyl oxide. Examples of the resin that contains the flame retardant include a resin that contains a bromine atom as a substituent, and the curable resin or thermoplastic resin exemplified for the first resin layer 3.

In the transparent sheet 1 of the present invention, the total mass of the second resin layer 4 is, for example, 100 to 600 g/m ² , and preferably 180 to 500 g/m ^2. The thickness of each of the second resin layers 4 is, for example, 80 to 600 μm, and preferably 100 to 400 μm.

In the transparent sheet 1 of the present invention, the refractive index of the second resin layer 4 is not particularly limited, but may be, for example, 1.570 to 1.650, more preferably 1.572 to 1.620, and even more preferably 1.580 to 1.620. The difference between the refractive index of the glass fiber fabric 2 and the refractive index of the second resin layer 4 may be greater than 0.01, and may be greater than 0.02.

Furthermore, from the viewpoint of achieving a balance between improving the transparency of the transparent sheet 1 of the present invention and reducing the total heat generation, and further increasing the resin weight of the transparent sheet 1 to effectively increase the mechanical strength, the total content of the resin constituting the first resin layer 3 and the second resin layer 4 (the total of all the first resin layers 3 (excluding the mass of the glass fiber fabric 2) and the second resin layers 4 contained in the transparent sheet 1) is preferably 200 g/ ^m2 or more, more preferably 240 g/m2 or ^more , and even more preferably 270 g/m2 or ^more . The upper limit of the total content is, for example, 600 g/m2 ^or less.

From the same viewpoint, the total thickness of the first resin layer 3 and the second resin layer 4 (the total of all the first resin layers 3 and the second resin layers 4 included in the transparent sheet 1) is preferably 180 μm or more, more preferably 200 μm or more, and even more preferably 240 μm or more. The upper limit of the total thickness is, for example, 500 μm or less, or 450 μm or less.

(Film Layer 5)
In the transparent sheet 1 of the present invention, the film layer 5 is laminated on the first resin layer 3 or the second resin layer 4 as necessary, and serves to further improve the initial tear strength of the transparent sheet 1. It is preferable that one film layer 5 is included on the outer side of each of the first resin layer 3 and the second resin layer 4.

The material constituting the film layer 5 is not particularly limited. Examples include polyester resin, polycarbonate resin, polyolefin resin, fluororesin, acrylic resin, and polyamide resin. On the other hand, the film layer 5 preferably contains a thermoplastic resin other than polyvinyl chloride resin. Examples of thermoplastic resins other than polyvinyl chloride resin include those that can be made into a film even with a small amount of plasticizer, and a biaxially stretched film containing an amorphous thermoplastic resin other than polyvinyl chloride resin is preferable. Examples of thermoplastic resins other than polyvinyl chloride resin include polyester resin, polycarbonate resin, fluororesin, acrylic resin, and polyamide resin, and at least one of these may be included. The film layer 5 may also be one that does not contain polyvinyl chloride resin. From the viewpoint of further improving the initial tear strength of the transparent sheet 1, the film layer 5 has an Elmendorf tear propagation resistance of 1 N/mm or more in both the vertical and horizontal directions, preferably 3 to 20 N/mm, and more preferably 5 to 15 N/mm. Among them, from the viewpoint of further improving chemical resistance (including alkaline detergent resistance when used as a smokeproof hanging wall), initial tear strength, and transparency, it is preferable that the film layer 5 contains a polyester resin. Examples of the polyester resin include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). The Elmendorf tear propagation resistance means the tear propagation resistance (N/mm) obtained by measuring the tear strength (N) based on JIS K7128-2.1998 using an Elmendorf tearing machine manufactured by Toyo Seiki Seisakusho Co., Ltd. and dividing the measured value by the film thickness. The tear strength is the average of the test results of 20 samples in each of the vertical and horizontal directions. If the film layer 5 is made of a resin composition containing PVDF and an acrylic resin (PMMA, etc.), it will have excellent weather resistance and excellent adhesion to the first resin layer 3 and the second resin layer 4, making it suitable as a membrane material.

In the transparent sheet of the present invention, the film to be used as the film layer 5 is preferably excellent in transparency and smoothness. As the transparency of the film to be used as the film layer 5, for example, the total light transmittance (JIS K 7105:1981) is preferably 90% or more, and more preferably 91 to 98%. Also, for example, the haze (JIS K 7105:1981) is preferably 1.5% or less, and more preferably 0.3 to 1.0%.

(Antistatic layer containing metal or metal compound)
The transparent sheet 1 of the present invention can be provided with an antistatic layer containing a metal or a metal compound so as to become the outermost layer when used as, for example, a smoke barrier.

In the antistatic layer containing a metal or a metal compound, the metal element contained therein may be, for example, Ag, Ni, Cu, Sn, Sb, Al, In, Ti, etc., and may be a metal element having a standard electrode potential of less than 0 eV when the metal is a simple substance. The metal compound may be, for example, a metal oxide (antimony pentoxide, tin oxide, zinc oxide, indium oxide, antimony-doped indium oxide, tin-doped indium oxide, silver oxide, etc.). The antistatic layer may also be free of fine particles made of barium sulfate, calcium carbonate, aluminum oxide, magnesium silicate, glass, etc. Examples of the form in which the metal or metal compound is contained include a metal or metal compound thin film formed by vapor deposition, sputtering, plating, etc., or a layer in which metal or metal compound fine particles are dispersed in a fixed resin. Examples of the shape of the metal or metal compound fine particles include granular, flake, and needle (fibrous). The average particle diameter of the metal or metal compound fine particles is, for example, an average particle diameter determined by the BET method (specific surface area diameter calculated as the average particle diameter by a conventional method from the specific surface area ( ^m2 /g) measured by a nitrogen gas adsorption method) of 100 nm or less, which is less than the wavelength of visible light, preferably 1 to 100 nm, so that the transparency of the transparent sheet 1 can be more easily maintained.

When the antistatic layer containing a metal or metal compound contains metal or metal compound fine particles, it is preferable to include a fixing resin that fixes the metal or metal compound fine particles to the substrate. That is, it is preferable that the antistatic layer is a layer containing a fixing resin and metal or metal compound fine particles dispersed in the fixing resin. Examples of the fixing resin include polyurethane resin, polyester resin, acrylic resin, polyether resin, cellulose resin, polyvinyl alcohol resin, epoxy resin, polyvinylpyrrolidone, polystyrene resin, polyethylene glycol, pentaerythritol, etc., and particularly preferably polyurethane resin, polyester resin, and acrylic resin. Examples of the acrylic resin include modified acrylic resin (urethane modified, polyester modified, polycarbonate modified, fluorine modified, etc.). The mass of the antistatic layer is, for example, 0.1 to 10 g/m ² per layer, preferably 0.1 to 5 g/m ² , more preferably 0.1 to 3 g/m ² , and particularly preferably 0.1 to 1 g/m ² . The thickness of the antistatic layer is, for example, 0.01 to 3 μm per layer, preferably 0.05 to 1 μm. The mass ratio of the fixing resin to the metal or metal compound fine particles in the antistatic layer (mass of fixing resin (g/m ² ): mass of metal or metal compound fine particles (g/m ² )) is preferably 10:1 to 1:1, more preferably 8:1 to 2:1, and particularly preferably 4:1 to 2:1. When an antistatic layer containing a metal or metal compound is provided, the surface smoothness is, for example, a surface roughness Ra of 1 to 200 nm. The ratio of the mass (g/m ² ) of the metal and metal compound fine particles to the total mass (g/m ² ) of the antistatic layer is, for example, 50 to 10 mass%, preferably 30 to 20 mass%.

(Removable cover layer that is peeled off when used)
The transparent sheet 1 of the present invention may further have a peelable cover layer laminated thereon, as necessary, on the outside of the first resin layer 3, the second resin layer 4, or the film layer 5 (when the antistatic layer 6 is provided on the outside of the first resin layer 3, the second resin layer 4, or the film layer 5, the antistatic layer 6 may further be laminated on the outside of the antistatic layer 6). The peelable cover layer may be suitably provided on the outermost surface of the transparent sheet 1 of the present invention. This makes it easier to prevent, for example, when the transparent sheet 1 of the present invention is used as a hanging smoke barrier, from causing scratches or the like on the transparent sheet 1 during construction, which would reduce transparency and aesthetics.

As the peelable cover layer to be peeled off during use, for example, a polyethylene film, a polytetrafluoroethylene film, a polypropylene film, a polyester film, etc. can be used. Among them, if a light-transmitting protective film is used as the peelable cover layer to be peeled off during use, for example, when the resin composition forming the first resin layer 3 or the second resin layer 4 is a photocurable curable resin composition, it is preferable in that it is easy to prevent the surface of the layer that will be the outermost layer during use from being scratched or the like, which would reduce transparency and aesthetics, even in the process of curing the curable resin composition. The light transmittance is not particularly limited as long as it transmits light that cures the photocurable resin, but examples include those that transmit light with a wavelength of 100 to 400 nm and those that transmit light with a wavelength of 250 to 400 nm. As the light transmittance of the cover layer, for example, the average transmittance between measurement wavelengths of 250 to 400 nm measured with a UV transmittance meter (manufactured by Shimadzu Corporation under the product name UV3150) is preferably 40% or more, more preferably 50% or more, and particularly preferably 60% or more.

The peelable cover layer that is peeled off during use is, for example, a smoke barrier, and is peeled off during use, so there are no particular restrictions on transparency and smoothness. For example, from the viewpoint of cost, the total light transmittance may be about 80 to 95% (JIS K 7105:1981), and the haze may be about 2 to 10% (JIS K 7105:1981).

(Physical Properties of Transparent Sheet 1)
The transparent sheet 1 of the present invention has a total light transmittance (if a peelable cover layer that is peeled off during use is included, the total light transmittance after peeling off the cover layer) of 85% or more, and a haze (if a peelable cover layer that is peeled off during use is included, the haze after peeling off the cover layer) of 10% or less. As described above, the total light transmittance of the transparent sheet 1 of the present invention is 85% or more and the haze is 10% or less, which indicates that at least the refractive index of the glass fiber fabric 2 and the refractive index of the first resin layer 3 are sufficiently close (for example, the difference between the refractive index of the glass fiber fabric 2 and the refractive index of the first resin layer 3 is 0.02 or less). The total light transmittance is preferably 90% or more. The haze is preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. The total light transmittance of the transparent sheet 1 is a value obtained by measuring in accordance with JIS K7361-1 1997, and the haze is a value obtained by measuring in accordance with JIS K 7136:2000.

The thickness of the transparent sheet 1 of the present invention is, for example, the thickness of the transparent sheet 1 after peeling off the peelable cover layer peeled off during use (i.e., the thickness excluding the peelable cover layer peeled off during use) of 200 to 700 μm, preferably 250 to 600 μm. In addition, the mass of the transparent sheet 1 of the present invention is, for example, the mass of the transparent sheet 1 after peeling off the peelable cover layer peeled off during use (i.e., the mass excluding the peelable cover layer peeled off during use) of 200 to 800 g/m ² , preferably 400 to 750 g/m ^2. In addition, the total mass of the resin in the transparent sheet 1 after peeling off the peelable cover layer peeled off during use (for example, when the transparent sheet 1 has the laminated structure of FIG. 4, the total of the resin masses of the first resin layer 3, the second resin layer 4, and the film layer 5) is, for example, 300 to 700 g/m ² , preferably 390 to 700 g/m ² , more preferably 450 to 650 g/m ² .

The transparent sheet 1 of the present invention, after peeling off the peelable cover layer that is peeled off during use, preferably has a total heat generation amount of 8 MJ/m2 or less in a heat generation test in which radiant heat of 50 kW/ ^m2 is irradiated onto the surface of the sheet from a radiant electric heater, as measured according to "4.10.2 Heat Generation Test and Evaluation Method" in the "Fire Resistance Performance Test and Evaluation Procedure Manual" (revised version March 1, 2014) of the General Incorporated Foundation Building Materials Testing Center. Furthermore, the transparent sheet 1 of the present invention, after peeling off the peelable cover layer that is peeled off during use, preferably has a maximum heat generation rate of ^not more than 200 kW/ ^m2 after the start of heating in the heat generation test.

In the present invention, the total heat generation amount (MJ/m2) and the time (S) at which the maximum heat generation rate after the start of heating exceeds 200 kW/ ^m2 in a heat generation test in which radiant heat of 50 kW/ ^m2 is irradiated onto the surface of a sheet from a radiant electric heater are measured according to "4.10.2 Heat Generation Test and Evaluation Method" in the "Fire Resistance Test and Evaluation Procedure Manual" (revised on March 1, 2014) of the General Incorporated ^Foundation Construction Materials Testing Center, are specifically measured according to the test specimen, test equipment, and test conditions described below.

[Test specimen]
(1) The number of test specimens (sheets) shall be three.
(2) The shape and dimensions of the test specimen shall be a square with each side measuring 99 mm ± 1 mm.
[Test Equipment]
(1) A schematic diagram of the test equipment used is shown in Figure 7. The test equipment is composed of a cone-shaped radiant electric heater, an ignition plug, a radiant heat shield, a test specimen holder, a gas concentration analyzer, an exhaust system capable of measuring gas flow rate, a heat flow meter, etc.
(2) The radiant electric heater must be capable of stably and uniformly irradiating 50 kW/ ^m2 of radiant heat onto the surface of the test specimen.
(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 pressing frame included in the test equipment is shown in Figure 8. The specimen holder is a square with outer dimensions of 106 mm ± 1 mm on each side, a depth of 25 mm ± 1 mm, and a thickness of 2.15 mm ± 0.25 mm, made of stainless steel, with a square opening with sides of 94.0 mm ± 0.5 mm in the center at the top. The pressing frame is a square with inner dimensions of 111 mm ± 1 mm on each side, and made of stainless steel with a depth of 54 mm ± 1 mm.
(5) The exhaust system is equipped with a centrifugal exhaust fan, hood, vent, exhaust duct, orifice plate flow meter, etc. that function effectively at the test temperature. The distance between the lower end of the hood and the surface of the test specimen is 210 mm ± 50 mm, and the exhaust device of the exhaust system in this state is to have a flow rate converted to standard temperature and standard pressure of 0.024 m ³ /s or more. For the measurement of the exhaust flow rate, an orifice with an inner diameter of 57 mm ± 3 mm is provided between the hood and the duct. For the purpose of exhaust gas sampling, a ring sampler with 12 holes with a diameter of 2.2 mm ± 0.1 mm is attached at a position 685 mm ± 15 mm from the hood so that the holes face in the opposite direction to the flow. In addition, the temperature of the exhaust gas is measured at the center of the exhaust duct at a position 100 mm ± 5 mm upstream from the orifice. The orifice is installed at a position that does not affect the measurement of the flow rate.
(6) The gas analyzer shall be capable of continuously and accurately measuring the concentrations of oxygen, carbon monoxide, and carbon dioxide in the exhaust gas.
(7) The ignition plug shall be capable of receiving power from a 10 kV transformer or induction coil system, etc. The distance between the spark electrodes shall be 3 mm ± 0.5 mm, and the electrodes shall be positioned, in principle, 13 mm ± 2 mm on the central axis of the test specimen.
(8) The heat flow meter used shall be a Schmidt-Boulder type capable of measuring up to 100 kW/ ^m2 ±10 kW/ ^m2 . The heat sensing part of the heat flow meter shall be circular with a diameter of 12.5 mm, and the surface emissivity shall be 0.95 ±0.05.
[Test conditions]
(1) The test time shall be 20 minutes from the time when radiant heat is applied to the surface of the test specimen and an electric spark is generated at the same time. However, the measurement may be terminated when the combustion clearly does not continue.
(2) The sides and back of the specimen shall be wrapped in aluminum foil having a thickness of 0.025 mm or more and 0.04 mm or less, placed in a frame, and the back side shall be filled with inorganic fiber (nominal thickness 13 mm, density 65 kg/ ^m3 ) before being pressed into the specimen holder.
(3) During the test, radiant heat of 50 kW/ ^m2 is irradiated onto the surface of the test specimen from a radiant electric heater.
(4) Adjust the exhaust gas flow rate to 0.024 ^m3/s ± 0.002 ^m3 /s.
(5) Until the start of the test, a radiant heat shield is used to protect the test specimen from radiant heat.
(6) Before moving the radiant heat shield, set the spark plug in the designated position.
[measurement]
(1) Measure the concentrations of oxygen, carbon monoxide, and carbon dioxide at intervals of no more than 5 seconds.
(2) Using the method described below, calculate the heat generation rate per unit area (kW/ ^m2 ), and further calculate the total heat generation amount per unit area (MJ/ ^m2 ) by accumulating the heat generation rate from the start to the end of heating.

The heat release rate (q) is calculated according to the following formula:

Where:
V ₂₉₈ = C(Δp·Te) ^1/2 /350 (: duct flow rate at 25°C)
E=17.2×10 ³ kJ/m ^3
X0O2 : Average value of oxygen concentration by baseline measurement for 1 minute _X02 : Actual measured value of oxygen concentration _Heat generation rate (q") per unit area is
q" = q/As
Where:
As: initial exposed area of the specimen (0.0088 m ² ).
C (orifice coefficient) is calculated from the oxygen concentration (X _O2 ) and differential pressure (Δp) when methane is burned at a flow rate equivalent to a heat release rate of q _b = 5 kW ± 0.5 kW in this measurement under a specified exhaust flow rate, using the following formula.
C=q _{b /} (△hc/ro×1.10) (Te/△p) ^1/2 (1.105-1.5X _O2 )/(0.2095-X _O2 )
Where:
q _b : Heat release rate of methane supplied Δhc/ro: 12.54×10 ³ kJ/kg in the case of methane
Te: Gas temperature in the exhaust duct (measured near the two-way pitot tube)

(Method for producing transparent sheet 1 of the present invention)
The method for producing the transparent sheet 1 of the present invention is not particularly limited, but may include, for example, a first step of preparing an intermediate body containing a glass fiber fabric 2 in an impregnated state with a first resin layer 3, and a second step of laminating a second resin layer 4 on the intermediate body. An example of the laminate structure shown in FIG. 1 will be described below.

The first step will be described taking the case where the resin constituting the first resin layer 3 is a curable resin as an example. In the first step, first, prepare a glass fiber fabric 2 and an uncured curable resin composition to be the first resin layer 3. The uncured curable resin composition is applied to a process film (e.g., a PET film, etc.), and the glass fiber fabric 2 is placed on the applied uncured curable resin composition, and the glass fiber fabric 2 is impregnated with the uncured curable resin composition. Next, another process film (e.g., a PET film, etc.) is placed on the uncured curable resin composition impregnated in the glass fiber fabric 2, and pressure is applied from above the process film B with a roller to adjust the mass of the first resin layer 3. Then, the uncured curable resin composition to be the first resin layer 3 is irradiated with light using a black light fluorescent lamp through the process PET film B to cure the curable resin composition and form the first resin layer 3, and then one of the process films (process film A for convenience in this example) is peeled off to obtain an intermediate having a laminated structure of the process film B/the first resin layer 3 impregnated in the glass fiber fabric 2. Two intermediates are prepared. At this time, if the transparent sheet 1 is to include a film layer 5, the film layer 5 can be used instead of the process film B included in the intermediate. In addition, if the transparent sheet 1 is to include, for example, a film layer 5 and a peelable cover layer that is peeled off when used, the film layer 5 and the peelable cover layer that is peeled off when used are laminated in advance to form a laminated film, and the laminated film can be used in place of the process film B included in the intermediate so that the cover layer is on the surface side.

The second step will be described by taking the case where the resin constituting the second resin layer 4 is a curable resin. In the second step, an uncured curable resin to be the second resin layer 4 is prepared, and the uncured curable resin is applied to the first resin layer 3 side of the intermediate obtained in the first step. Next, the other intermediate obtained is placed on the uncured curable resin to be the second resin layer 4 so that the first resin layer 3 side is the uncured curable resin to be the second resin layer 4 side, and pressure is applied from above the other intermediate with a roller to adjust the mass of the second resin layer 4. After that, the uncured curable resin composition to be the second resin layer 4 is irradiated with light using a black light fluorescent lamp through the other intermediate to cure the curable resin composition, and the second resin layer 4 is formed and laminated. Then, by peeling off the process film B on both surfaces of the second resin layer 4, the transparent sheet 1 of the present invention can be obtained, which has a laminated structure of the first resin layer 3 impregnated in the glass fiber fabric 2, the second resin layer 4 not impregnated in the glass fiber fabric 2, and the first resin layer 3 impregnated in the glass fiber fabric 2. In addition, when the film layer 5 is included or when a cover layer that can be peeled off during use is included, the uncured curable resin composition that is to be the second resin layer 4 is cured to form the second resin layer 4, and then the film layer 5 and the cover layer that can be peeled off during use are not peeled off to form the transparent sheet 1.

(Uses of the transparent sheet 1 of the present invention)
The transparent sheet 1 of the present invention can be used as a hanging smokeproof wall that is hung down from the ceiling of a building. The hanging smokeproof wall can be a known one that uses a transparent sheet 1 made of glass fiber fabric and resin. For example, a hanging smokeproof wall can be used that includes a mounting rail arranged on the ceiling surface of a building, a transparent sheet 1 that is hung with its upper end held by the mounting rail, and a pair of end mullions arranged on both sides of the transparent sheet 1, and the transparent sheet 1 and the end mullions are joined so as to be separable. The hanging smokeproof wall can also be used as a hanging smokeproof wall in which the transparent sheet 1 is stretched between two pairs of mullions, for example, a hanging smokeproof wall that does not have a mesh on the lower side of the transparent sheet 1 when hung down from a ceiling. In addition, when the transparency is increased, it can be used as a substitute for glass, so it can be used in other applications where glass is used, such as partitions, partitions, smokeproof sheets, and smokeproof curtains (for example, those used in factories, etc.).

The present invention will be described in detail below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

The resin composition constituting the first resin layer 3 to be impregnated into the above-mentioned glass fiber fabric 2 was a mixture of acrylic syrup (manufactured by Ryoko Corporation under the trade name of "Acrysirup XD8005" (refractive index 1.550)), a non-halogen condensed phosphate ester compound RDP (manufactured by ADEKA Corporation under the trade name of "ADEKA STAB PFR"), and a photopolymerization initiator (manufactured by IGM under the trade name of Omnirad 184) in the compositions shown in Table 1 in Examples 1 to 6. The mass ratio (acrylic syrup:non-halogen condensed phosphate ester compound:photopolymerization initiator)=70:30:3 in Examples 7 to 10 was a mixture of acrylic syrup (manufactured by Ryoko Corporation under the trade name of "XY1087" (refractive index 1.520), "XY1088" (refractive index 1.540), tetrabromobisphenol A (TBBA, manufactured by Tosoh Corporation under the trade name of "Framecut 120G"), and a photopolymerization initiator (manufactured by IGM under the trade name of Omnirad 184). A mixture of brominated vinyl ester resin (manufactured by Japan U-PICA Corporation under the trade name Neopol 8197) and photopolymerization initiator (manufactured by IGM under the trade name Omnirad 184) (mass ratio (acrylic syrup XY1087:acrylic syrup XY1088:TBBA:photopolymerization initiator) = 34:42:24:3) was used as the resin composition constituting the second resin layer 4, which is contained in a state in which it is not impregnated into the glass fiber fabric 2, so as to have the composition shown in Table 1 was used. The amount of the photopolymerization initiator was 3 parts by mass per 100 parts by mass of the brominated vinyl ester resin. As the film layer 5, two types of commercially available biaxially stretched polyester films manufactured by Toyobo Co., Ltd. (trade name "Cosmoshine (registered trademark) A4300", thickness 38 μm, mass 53 g/m ² , total light transmittance (JIS K 7105:1981) 93%, haze (JIS K 7105:1981) 0.9%), (product name "Cosmoshine (registered trademark) A4300", thickness 50 μm, mass 70 g/m ² , total light transmittance (JIS K 7105:1981) 93%, haze (JIS K 7105:1981) 0.9%), and a commercially available film containing PVDF and acrylic resin (a sheet obtained by bonding a sheet A, which is an alloy of PVDF and PMMA and has a PVDF content of 80 mass% and a PMMA content of 20 mass%, and a sheet B, which has a PVDF content of 20 mass% and a PMMA content of 80 mass%, (manufactured by Denka Company Ltd., product name "Denka DX Film DX-14S50", thickness 50 μm, mass 68 g/m ² , total light transmittance (JIS K As the peelable cover layer to be peeled off during use, a polypropylene film (thickness 40 μm, mass 36 g/m ² ) coated on one side with an acrylic acid ester adhesive that peelably adheres to the film layer 5, and a PET film (thickness 50 μm, total light transmittance 93%, haze 4% (JIS K 7105:1981)) were used. The PET film was also used as a process film, which will be described later.

Example 1
(Preparation of fiberglass fabric)
The warp and weft yarns were made of Unitika Glass Fiber Co., Ltd.'s trade name "ECC1200 1/0 1.0Z" (average filament diameter 4.5 μm, average number of filaments 100, twist number 1.0Z, yarn count 4.2 tex), and woven with an air jet loom to obtain a plain weave glass fiber fabric with a warp density of 90/25 mm and a weft density of 90/25 mm. Next, the spinning sizing agent and weaving sizing agent attached to the obtained glass fiber fabric were removed by heating at 400°C for 30 hours. Thereafter, the surface treatment agent, a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Corporation) was adjusted to a concentration of 15 g/L, and the fabric was squeezed with a padder roll, followed by drying and curing at 120°C for 1 minute. The glass fiber fabric was then subjected to a width-widening treatment once using a water flow process at a pressure of 1.5 MPa while setting the tension of the glass fiber fabric to 100 N/m in the warp direction, to obtain a glass fiber fabric 2. The obtained glass fiber fabric had a warp density of 90 threads/25 mm, a weft density of 90 threads/25 mm, a thickness of 27 μm, a mass of 30 g/m ² , and a refractive index of 1.561.

(Lamination of Antistatic Layer to Film Layer 5)
An antistatic layer was laminated on one side of Cosmoshine (registered trademark) A4300 (thickness 38 μm) as the film layer 5. The antistatic layer was provided by coating and drying an antistatic agent prepared by mixing and dispersing tin oxide fine particles (average particle diameter 20 nm) in a polyester resin as an adhesive resin such that the mass ratio of the adhesive resin to the tin oxide fine particles (adhesive resin:tin oxide fine particles) was 75:25 on one side of Cosmoshine (registered trademark) A4300 (thickness 38 μm) as the film layer 5. The mass and thickness of the provided antistatic layer were 0.5 g/m ² and 0.4 μm, respectively.

(Lamination of a peelable protective film to be peeled off during use onto film layer 5 (antistatic layer side))
The aforementioned COSMOSHINE (registered trademark) A4300 having an antistatic layer on one side thereof as film layer 5 was laminated with a polypropylene film having an acrylic ester adhesive applied to one side thereof as a peelable cover layer to be peeled off when used, on the antistatic layer, with the adhesive facing the antistatic layer, and dried to obtain a laminate X having a laminate structure of COSMOSHINE (registered trademark) A4300 having a peelable protective film to be peeled off when used/acrylic ester adhesive/antistatic layer/film layer 5. Two sheets of the laminate X were prepared.

(Formation of the first resin layer 3, and lamination of the laminate A including the film layer 5 onto the first resin layer 3)
A curable resin composition made of the acrylic syrup shown in Table 1 was applied to the Cosmoshine (registered trademark) A4300 surface side (i.e., the surface opposite to the peelable cover layer to be peeled off during use) of one sheet of the obtained laminate X as the first resin layer 3. Next, the obtained glass fiber fabric 2 was placed on the curable resin composition to be the first resin layer 3, and left to stand for 1 minute to impregnate the gaps in the glass fiber fabric 2 with the curable resin composition made of the acrylic syrup. Next, the PET film used as the process film described above was placed on the curable resin composition made of the acrylic syrup, and pressure was applied from above the PET film with a roller so that the mass of the first resin layer 3 was 30 g/ ^m2 . Then, the curable resin composition made of acrylic syrup, which is the first resin layer 3, was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (Toshiba Corporation, product name FL15BLB) through the process PET film to cure the curable resin composition and form the first resin layer 3, and then the laminated process PET film was peeled off to obtain a laminate Y having a laminated structure of a peelable cover layer that is peeled off when used/an acrylic acid ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 impregnated in a glass fiber fabric 2. In the obtained laminate Y, the first resin layer 3 (cured product of the resin composition) made of acrylic syrup was impregnated into the gaps between the glass fibers of the glass fiber fabric 2 without exposing the glass fibers. Two sheets of the laminate Y were prepared.

(Lamination of the second resin layer 4 included in the glass fiber fabric 2 without being impregnated therein)
A brominated vinyl ester resin composition shown in Table 1 was applied to the side of the first resin layer 3 contained in a state impregnated in the glass fiber fabric 2 of one sheet of the obtained laminate Y as the second resin layer 4 contained in a state not impregnated in the glass fiber fabric 2. Next, the other one of the obtained laminates Y was placed on top of the brominated vinyl ester resin composition so that the first resin layer 3 side of the laminate Y faced the brominated vinyl ester resin composition side, and pressure was applied from above the other laminate Y with a roller so that the mass of the second resin layer 4 made of the brominated vinyl ester resin composition was 183 g/ ^m2 . Thereafter, the brominated vinyl ester resin composition serving as the second resin layer 4 was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (manufactured by Toshiba Corporation, product name FL15BLB) through the other laminate Y to harden the brominated vinyl ester resin composition to form the second resin layer 4, thereby forming a transparent sheet 1 of the present invention having a laminate structure of a peelable cover layer that is peeled off when used/an acrylic ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a second resin layer 4 that is not impregnated in the glass fiber fabric 2/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a film layer 5 (Cosmoshine (registered trademark) A4300)/an antistatic layer/an acrylic ester-based adhesive that is peelable together with the cover layer/a peelable cover layer that is peeled off when used. The bromine concentration, total light transmittance, haze, total heat generation, and time exceeding 200 kW of the transparent sheet described below were evaluated by peeling off the peelable cover layer that is peeled off when using the transparent sheet 1 obtained above and the acrylic ester-based adhesive that is peelable together with the cover layer.

Example 2
The same procedure as in Example 1 was carried out except that in lamination of the second resin layer 4 contained in a state in which it is not impregnated in the glass fiber fabric 2 in Example 1, pressure was applied from above the other laminate Y with a roller so that the mass of the second resin layer 4 made of a brominated vinyl ester resin composition became 233 g/ ^m2 , thereby obtaining a transparent sheet 1 of the present invention having a laminate structure of a peelable cover layer that is peeled off when used/an acrylic acid ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 contained in a state in which it is impregnated in the glass fiber fabric 2/a second resin layer 4 contained in a state in which it is not impregnated in the glass fiber fabric 2/a first resin layer 3 contained in a state in which it is impregnated in the glass fiber fabric 2/a film layer 5 (Cosmoshine (registered trademark) A4300)/an antistatic layer/an acrylic acid ester-based adhesive that is peelable together with the cover layer/a peelable cover layer that is peeled off when used. The bromine concentration, total light transmittance, haze, total heat generation, and time exceeding 200 kW of the transparent sheet described below were evaluated by peeling off the peelable cover layer that is peeled off when using the transparent sheet 1 obtained above and the acrylic ester-based adhesive that is peelable together with the cover layer.

Example 3
The same procedure as in Example 1 was carried out except that in lamination of the second resin layer 4 contained in a state in which it was not impregnated in the glass fiber fabric 2, pressure was applied from above the other laminate Y with a roller so that the mass of the second resin layer 4 made of a brominated vinyl ester resin composition became 322 g/ ^m2 , thereby obtaining a transparent sheet 1 of the present invention having a laminate structure of a peelable cover layer that is peeled off when used/an acrylic acid ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 contained in a state in which it is impregnated in the glass fiber fabric 2/a second resin layer 4 contained in a state in which it is not impregnated in the glass fiber fabric 2/a first resin layer 3 contained in a state in which it is impregnated in the glass fiber fabric 2/a film layer 5 (Cosmoshine (registered trademark) A4300)/an antistatic layer/an acrylic acid ester-based adhesive that is peelable together with the cover layer/a peelable cover layer that is peeled off when used. The bromine concentration, total light transmittance, haze, total heat generation, and time exceeding 200 kW of the transparent sheet described below were evaluated by peeling off the peelable cover layer that is peeled off when using the transparent sheet 1 obtained above and the acrylic ester-based adhesive that is peelable together with the cover layer.

Example 4
The same procedure as in Example 1 was carried out except that in lamination of the second resin layer 4 contained in a state in which it was not impregnated in the glass fiber fabric 2, pressure was applied from above the other laminate Y with a roller so that the mass of the second resin layer 4 made of the brominated vinyl ester resin composition became 476 g/ ^m2 , thereby obtaining a transparent sheet 1 of the present invention having a laminate structure of a peelable cover layer that is peeled off when used/an acrylic acid ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 contained in a state in which it is impregnated in the glass fiber fabric 2/a second resin layer 4 contained in a state in which it is not impregnated in the glass fiber fabric 2/a first resin layer 3 contained in a state in which it is impregnated in the glass fiber fabric 2/a film layer 5 (Cosmoshine (registered trademark) A4300)/an antistatic layer/an acrylic acid ester-based adhesive that is peelable together with the cover layer/a peelable cover layer that is peeled off when used. The bromine concentration, total light transmittance, haze, total heat generation, and time exceeding 200 kW of the transparent sheet described below were evaluated by peeling off the peelable cover layer that is peeled off when using the transparent sheet 1 obtained above and the acrylic ester-based adhesive that is peelable together with the cover layer.

Example 5
(Preparation of fiberglass fabric)
The warp and weft yarns were made of Unitika Glass Fiber Co., Ltd.'s trade name "ECE225 1/0 1.0Z" (average filament diameter 7.0 μm, average number of filaments 200, twist number 1.0Z, yarn count 22.5 tex), and woven with an air jet loom to obtain a plain weave glass fiber fabric with a warp density of 60/25 mm and a weft density of 57/25 mm. Next, the spinning bundling agent and weaving bundling agent attached to the obtained glass fiber fabric were removed by heating at 400 ° C. for 30 hours. Thereafter, the surface treatment agent, silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Corporation) was adjusted to a concentration of 15 g/L, squeezed with a padder roll, and then dried and cured at 120 ° C. for 1 minute to obtain a glass fiber fabric 2. The obtained glass fiber fabric had a warp density of 60 threads/25 mm, a weft density of 57 threads/25 mm, a thickness of 90 μm, a mass of 105 g/m ² , and a refractive index of 1.561.

(Formation of the first resin layer 3 and lamination of the film layer 5 onto the first resin layer 3)
A curable resin composition made of the acrylic syrup shown in Table 1 was applied to the PET film used as the process film described above to form the first resin layer 3. Next, the glass fiber fabric 2 obtained above was placed on the curable resin composition made of the first resin layer 3, and left to stand for 1 minute to impregnate the curable resin composition made of the acrylic syrup into the gaps in the glass fiber fabric 2. Next, another PET film used as the process film described above was placed on the curable resin composition made of the acrylic syrup, and pressure was applied from above the PET film with a roller so that the mass of the first resin layer 3 was 105 g/ ^m2 . Thereafter, the curable resin composition made of acrylic syrup to be the first resin layer 3 was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (product name FL15BLB, manufactured by Toshiba Corporation) through the process PET film to cure the curable resin composition and form the first resin layer 3, and then one of the laminated PET films to be used as the process film was peeled off to obtain a laminate Z having a laminated structure of the PET film to be used as the process film/the first resin layer 3 contained in an impregnated state in the glass fiber fabric 2. In the obtained laminate Z, the first resin layer 3 made of acrylic syrup (cured product of the resin composition) was impregnated into the gaps between the glass fibers of the glass fiber fabric 2 without exposing the glass fibers. Two sheets of the laminate Z were prepared.

(Lamination of the second resin layer 4 included in the glass fiber fabric 2 without being impregnated therein)
A brominated vinyl ester resin composition shown in Table 1 was applied to the first resin layer 3 side of one of the obtained laminates Z, which was contained in a state of being impregnated in the glass fiber fabric 2, as the second resin layer 4, which was contained in a state of not being impregnated in the glass fiber fabric 2. Next, the other of the obtained laminates Z was placed on top of the brominated vinyl ester resin composition, so that the first resin layer 3 side of the laminate Z faced the brominated vinyl ester resin composition side, and pressure was applied from above the other laminate Z with a roller so that the mass of the second resin layer 4 made of the brominated vinyl ester resin composition became 184 g/ ^m2 . Thereafter, the brominated vinyl ester resin composition serving as the second resin layer 4 was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/ ^cm2 ) using a black light fluorescent lamp (manufactured by Toshiba Corporation, product name FL15BLB) through the other laminate Z to harden the brominated vinyl ester resin composition to form the second resin layer 4, and the PET films serving as process films on both sides were peeled off to obtain a laminate consisting of the first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/the second resin layer 4 contained in a state not impregnated in the glass fiber fabric 2/the first resin layer 3 contained in a state impregnated in the glass fiber fabric 2. The obtained laminate was sandwiched between two sheets containing the above-mentioned PVDF and acrylic resin, which serve as film layers 5, so that the surfaces of both sheets that were to be bonded to the laminate were the sheet B side (i.e., the acrylic resin-rich surfaces), and pressed in a heating press under conditions of a temperature of 160°C, a press pressure of 10 kgf/ ^cm2 , and a time of 5 minutes to bond the laminate to the sheets containing PVDF and acrylic resin, thereby obtaining a transparent sheet 1 of the present invention having a laminated structure of film layer 5 (sheet containing PVDF and acrylic resin)/first resin layer 3 contained in a state impregnated in glass fiber fabric 2/second resin layer 4 contained in a state not impregnated in glass fiber fabric 2/first resin layer 3 contained in a state impregnated in glass fiber fabric 2/film layer 5 (sheet containing PVDF and acrylic resin). The bromine concentration, total light transmittance, haze, total heat generation, and 200 kW excess time of the transparent sheet, which will be described later, were evaluated using the above-obtained transparent sheet.

Example 6
(Preparation of fiberglass fabric)
The warp and weft yarns were made of Unitika Glass Fiber Co., Ltd.'s product name "ECBC2250 1/0 0.5Z" (average filament diameter 4.0 μm, average number of filaments 66, twist number 0.5Z, yarn count 2.3 tex), and woven with an air jet loom to obtain a plain weave glass fiber fabric with a warp density of 95/25 mm and a weft density of 95/25 mm. Next, the spinning bundling agent and weaving bundling agent attached to the obtained glass fiber fabric were removed by heating at 400 ° C. for 30 hours. Thereafter, the surface treatment agent, silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Corporation) was adjusted to a concentration of 15 g/L, squeezed with a padder roll, and then dried and cured at 120 ° C. for 1 minute to obtain a glass fiber fabric 2. The obtained glass fiber fabric had a warp density of 95 threads/25 mm, a weft density of 95 threads/25 mm, a thickness of 15 μm, a mass of 17 g/m ² , and a refractive index of 1.561.

(Lamination of Antistatic Layer to Film Layer 5)
An antistatic layer was laminated on one side of Cosmoshine (registered trademark) A4300 (thickness 50 μm) serving as the film layer 5. The antistatic layer was provided by coating and drying an antistatic agent prepared by mixing and dispersing tin oxide fine particles (average particle diameter 20 nm) in a polyester resin as a fixing resin such that the mass ratio of the fixing resin to the tin oxide fine particles (fixing resin:tin oxide fine particles) was 75:25 on one side of Cosmoshine (registered trademark) A4300 (thickness 50 μm) serving as the film layer 5. The mass and thickness of the provided antistatic layer were 0.5 g/m ² and 0.4 μm, respectively.

(Lamination of a peelable protective film to be peeled off during use onto film layer 5 (antistatic layer side))
The aforementioned COSMOSHINE (registered trademark) A4300 having an antistatic layer on one side thereof as film layer 5 was laminated with a polypropylene film having an acrylic ester adhesive applied to one side thereof as a peelable cover layer to be peeled off when used, on the antistatic layer, with the adhesive facing the antistatic layer, and dried to obtain a laminate X having a laminate structure of COSMOSHINE (registered trademark) A4300 having a peelable protective film to be peeled off when used/acrylic ester adhesive/antistatic layer/film layer 5. Two sheets of the laminate X were prepared.

(Formation of the first resin layer 3, and lamination of the laminate A including the film layer 5 onto the first resin layer 3)
A curable resin composition made of the acrylic syrup shown in Table 1 was applied to the Cosmoshine (registered trademark) A4300 surface side (i.e., the surface opposite to the peelable cover layer to be peeled off during use) of one sheet of the obtained laminate X as the first resin layer 3. Next, the obtained glass fiber fabric 2 was placed on the curable resin composition to be the first resin layer 3, and left to stand for 1 minute to impregnate the gaps in the glass fiber fabric 2 with the curable resin composition made of the acrylic syrup. Next, the PET film used as the process film described above was placed on the curable resin composition made of the acrylic syrup, and pressure was applied from above the PET film with a roller so that the mass of the first resin layer 3 was 25 g/ ^m2 . Then, the curable resin composition made of acrylic syrup, which is the first resin layer 3, was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (Toshiba Corporation, product name FL15BLB) through the process PET film to cure the curable resin composition and form the first resin layer 3, and then the laminated process PET film was peeled off to obtain a laminate Y having a laminated structure of a peelable cover layer that is peeled off when used/an acrylic acid ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 impregnated in a glass fiber fabric 2. In the obtained laminate Y, the first resin layer 3 (cured product of the resin composition) made of acrylic syrup was impregnated into the gaps between the glass fibers of the glass fiber fabric 2 without exposing the glass fibers. Two sheets of the laminate Y were prepared.

(Lamination of the second resin layer 4 included in the glass fiber fabric 2 without being impregnated therein)
A brominated vinyl ester resin composition shown in Table 1 was applied to the side of the first resin layer 3 contained in a state impregnated in the glass fiber fabric 2 of one sheet of the obtained laminate Y as the second resin layer 4 contained in a state not impregnated in the glass fiber fabric 2. Next, the other one of the obtained laminates Y was placed on top of the brominated vinyl ester resin composition so that the first resin layer 3 side of the laminate Y faced the brominated vinyl ester resin composition side, and pressure was applied from above the other laminate Y with a roller so that the mass of the second resin layer 4 made of the brominated vinyl ester resin composition was 387 g/ ^m2 . Thereafter, the brominated vinyl ester resin composition serving as the second resin layer 4 was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (manufactured by Toshiba Corporation, product name FL15BLB) through the other laminate Y to harden the brominated vinyl ester resin composition to form the second resin layer 4, thereby forming a transparent sheet 1 of the present invention having a laminate structure of a peelable cover layer that is peeled off when used/an acrylic ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a second resin layer 4 that is not impregnated in the glass fiber fabric 2/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a film layer 5 (Cosmoshine (registered trademark) A4300)/an antistatic layer/an acrylic ester-based adhesive that is peelable together with the cover layer/a peelable cover layer that is peeled off when used. The bromine concentration, total light transmittance, haze, total heat generation, and time exceeding 200 kW of the transparent sheet described below were evaluated by peeling off the peelable cover layer that is peeled off when using the transparent sheet 1 obtained above and the acrylic ester-based adhesive that is peelable together with the cover layer.

Example 7
(Preparation of fiberglass fabric)
The warp and weft yarns were made of Unitika Glass Fiber Co., Ltd.'s trade name "ECC1200 1/0 1.0Z" (average filament diameter 4.5 μm, average number of filaments 100, twist number 1.0Z, yarn count 4.2 tex), and woven with an air jet loom to obtain a plain weave glass fiber fabric with a warp density of 90/25 mm and a weft density of 90/25 mm. Next, the spinning sizing agent and weaving sizing agent attached to the obtained glass fiber fabric were removed by heating at 400°C for 30 hours. Thereafter, the surface treatment agent, a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Corporation) was adjusted to a concentration of 15 g/L, and the fabric was squeezed with a padder roll, followed by drying and curing at 120°C for 1 minute. The glass fiber fabric was then subjected to a width-widening treatment once using a water flow process at a pressure of 1.5 MPa while setting the tension of the glass fiber fabric to 100 N/m in the warp direction, to obtain a glass fiber fabric 2. The obtained glass fiber fabric had a warp density of 90 threads/25 mm, a weft density of 90 threads/25 mm, a thickness of 27 μm, a mass of 30 g/m ² , and a refractive index of 1.561.

(Lamination of Antistatic Layer to Film Layer 5)
An antistatic layer was laminated on one side of Cosmoshine (registered trademark) A4300 (thickness 50 μm) serving as the film layer 5. The antistatic layer was provided by coating and drying an antistatic agent prepared by mixing and dispersing tin oxide fine particles (average particle diameter 20 nm) in a polyester resin as a fixing resin such that the mass ratio of the fixing resin to the tin oxide fine particles (fixing resin:tin oxide fine particles) was 75:25 on one side of Cosmoshine (registered trademark) A4300 (thickness 50 μm) serving as the film layer 5. The mass and thickness of the provided antistatic layer were 0.5 g/m ² and 0.4 μm, respectively.

(Lamination of a peelable protective film to be peeled off during use onto film layer 5 (antistatic layer side))
The aforementioned COSMOSHINE (registered trademark) A4300 having an antistatic layer on one side thereof as film layer 5 was laminated with a polypropylene film having an acrylic ester adhesive applied to one side thereof as a peelable cover layer to be peeled off when used, on the antistatic layer, with the adhesive facing the antistatic layer, and dried to obtain a laminate X having a laminate structure of COSMOSHINE (registered trademark) A4300 having a peelable protective film to be peeled off when used/acrylic ester adhesive/antistatic layer/film layer 5. Two sheets of the laminate X were prepared.

(Formation of the first resin layer 3, and lamination of the laminate A including the film layer 5 onto the first resin layer 3)
A curable resin composition made of the acrylic syrup shown in Table 1 was applied to the Cosmoshine (registered trademark) A4300 surface side (i.e., the surface opposite to the peelable cover layer to be peeled off during use) of one sheet of the obtained laminate X as the first resin layer 3. Next, the obtained glass fiber fabric 2 was placed on the curable resin composition to be the first resin layer 3, and left to stand for 1 minute to impregnate the gaps in the glass fiber fabric 2 with the curable resin composition made of the acrylic syrup. Next, the PET film used as the process film described above was placed on the curable resin composition made of the acrylic syrup, and pressure was applied from above the PET film with a roller so that the mass of the first resin layer 3 was 25 g/ ^m2 . Then, the curable resin composition made of acrylic syrup, which is the first resin layer 3, was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (Toshiba Corporation, product name FL15BLB) through the process PET film to cure the curable resin composition and form the first resin layer 3, and then the laminated process PET film was peeled off to obtain a laminate Y having a laminated structure of a peelable cover layer that is peeled off when used/an acrylic acid ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 impregnated in a glass fiber fabric 2. In the obtained laminate Y, the first resin layer 3 (cured product of the resin composition) made of acrylic syrup was impregnated into the gaps between the glass fibers of the glass fiber fabric 2 without exposing the glass fibers. Two sheets of the laminate Y were prepared.

(Lamination of the second resin layer 4 included in the glass fiber fabric 2 without being impregnated therein)
A brominated vinyl ester resin composition shown in Table 1 was applied to the side of the first resin layer 3 contained in a state impregnated in the glass fiber fabric 2 of one sheet of the obtained laminate Y as the second resin layer 4 contained in a state not impregnated in the glass fiber fabric 2. Next, the other one of the obtained laminates Y was placed on top of the brominated vinyl ester resin composition so that the first resin layer 3 side of the laminate Y faced the brominated vinyl ester resin composition side, and pressure was applied from above the other laminate Y with a roller so that the mass of the second resin layer 4 made of the brominated vinyl ester resin composition was 149 g/ ^m2 . Thereafter, the brominated vinyl ester resin composition serving as the second resin layer 4 was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (manufactured by Toshiba Corporation, product name FL15BLB) through the other laminate Y to harden the brominated vinyl ester resin composition to form the second resin layer 4, thereby forming a transparent sheet 1 of the present invention having a laminate structure of a peelable cover layer that is peeled off when used/an acrylic ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a second resin layer 4 that is not impregnated in the glass fiber fabric 2/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a film layer 5 (Cosmoshine (registered trademark) A4300)/an antistatic layer/an acrylic ester-based adhesive that is peelable together with the cover layer/a peelable cover layer that is peeled off when used. The bromine concentration, total light transmittance, haze, total heat generation, and time exceeding 200 kW of the transparent sheet described below were evaluated by peeling off the peelable cover layer that is peeled off when using the transparent sheet 1 obtained above and the acrylic ester-based adhesive that is peelable together with the cover layer.

Example 8
(Preparation of fiberglass fabric)
The warp and weft yarns were made of Unitika Glass Fiber Co., Ltd.'s trade name "ECC1200 1/0 1.0Z" (average filament diameter 4.5 μm, average number of filaments 100, twist number 1.0Z, yarn count 4.2 tex), and woven with an air jet loom to obtain a plain weave glass fiber fabric with a warp density of 90/25 mm and a weft density of 90/25 mm. Next, the spinning sizing agent and weaving sizing agent attached to the obtained glass fiber fabric were removed by heating at 400°C for 30 hours. Thereafter, the surface treatment agent, a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Corporation) was adjusted to a concentration of 15 g/L, and the fabric was squeezed with a padder roll, followed by drying and curing at 120°C for 1 minute. The glass fiber fabric was then subjected to a width-widening treatment once using a water flow process at a pressure of 1.5 MPa while setting the tension of the glass fiber fabric to 100 N/m in the warp direction, to obtain a glass fiber fabric 2. The obtained glass fiber fabric had a warp density of 90 threads/25 mm, a weft density of 90 threads/25 mm, a thickness of 27 μm, a mass of 30 g/m ² , and a refractive index of 1.561.

(Lamination of Antistatic Layer to Film Layer 5)
An antistatic layer was laminated on one side of Cosmoshine (registered trademark) A4300 (thickness 50 μm) serving as the film layer 5. The antistatic layer was provided by coating and drying an antistatic agent prepared by mixing and dispersing tin oxide fine particles (average particle diameter 20 nm) in a polyester resin as a fixing resin such that the mass ratio of the fixing resin to the tin oxide fine particles (fixing resin:tin oxide fine particles) was 75:25 on one side of Cosmoshine (registered trademark) A4300 (thickness 50 μm) serving as the film layer 5. The mass and thickness of the provided antistatic layer were 0.5 g/m ² and 0.4 μm, respectively.

(Lamination of a peelable protective film to be peeled off during use onto film layer 5 (antistatic layer side))
The aforementioned COSMOSHINE (registered trademark) A4300 having an antistatic layer on one side thereof as film layer 5 was laminated with a polypropylene film having an acrylic ester adhesive applied to one side thereof as a peelable cover layer to be peeled off when used, on the antistatic layer, with the adhesive facing the antistatic layer, and dried to obtain a laminate X having a laminate structure of COSMOSHINE (registered trademark) A4300 having a peelable protective film to be peeled off when used/acrylic ester adhesive/antistatic layer/film layer 5. Two sheets of the laminate X were prepared.

(Formation of the first resin layer 3, and lamination of the laminate A including the film layer 5 onto the first resin layer 3)
A curable resin composition made of the acrylic syrup shown in Table 1 was applied to the Cosmoshine (registered trademark) A4300 surface side (i.e., the surface opposite to the peelable cover layer to be peeled off during use) of one sheet of the obtained laminate X as the first resin layer 3. Next, the obtained glass fiber fabric 2 was placed on the curable resin composition to be the first resin layer 3, and left to stand for 1 minute to impregnate the gaps in the glass fiber fabric 2 with the curable resin composition made of the acrylic syrup. Next, the PET film used as the process film described above was placed on the curable resin composition made of the acrylic syrup, and pressure was applied from above the PET film with a roller so that the mass of the first resin layer 3 was 25 g/ ^m2 . Then, the curable resin composition made of acrylic syrup, which is the first resin layer 3, was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (Toshiba Corporation, product name FL15BLB) through the process PET film to cure the curable resin composition and form the first resin layer 3, and then the laminated process PET film was peeled off to obtain a laminate Y having a laminated structure of a peelable cover layer that is peeled off when used/an acrylic acid ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 impregnated in a glass fiber fabric 2. In the obtained laminate Y, the first resin layer 3 (cured product of the resin composition) made of acrylic syrup was impregnated into the gaps between the glass fibers of the glass fiber fabric 2 without exposing the glass fibers. Two sheets of the laminate Y were prepared.

(Lamination of the second resin layer 4 included in the glass fiber fabric 2 without being impregnated therein)
A brominated vinyl ester resin composition shown in Table 1 was applied to the side of the first resin layer 3 contained in a state impregnated in the glass fiber fabric 2 of one sheet of the obtained laminate Y as the second resin layer 4 contained in a state not impregnated in the glass fiber fabric 2. Next, the other one of the obtained laminates Y was placed on top of the brominated vinyl ester resin composition so that the first resin layer 3 side of the laminate Y faced the brominated vinyl ester resin composition side, and pressure was applied from above the other laminate Y with a roller so that the mass of the second resin layer 4 made of the brominated vinyl ester resin composition was 189 g/ ^m2 . Thereafter, the brominated vinyl ester resin composition serving as the second resin layer 4 was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (manufactured by Toshiba Corporation, product name FL15BLB) through the other laminate Y to harden the brominated vinyl ester resin composition to form the second resin layer 4, thereby forming a transparent sheet 1 of the present invention having a laminate structure of a peelable cover layer that is peeled off when used/an acrylic ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a second resin layer 4 that is not impregnated in the glass fiber fabric 2/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a film layer 5 (Cosmoshine (registered trademark) A4300)/an antistatic layer/an acrylic ester-based adhesive that is peelable together with the cover layer/a peelable cover layer that is peeled off when used. The bromine concentration, total light transmittance, haze, total heat generation, and time exceeding 200 kW of the transparent sheet described below were evaluated by peeling off the peelable cover layer that is peeled off when using the transparent sheet 1 obtained above and the acrylic ester-based adhesive that is peelable together with the cover layer.

<Example 9>
(Preparation of fiberglass fabric)
The warp and weft yarns were made of Unitika Glass Fiber Co., Ltd.'s trade name "ECC1200 1/0 1.0Z" (average filament diameter 4.5 μm, average number of filaments 100, twist number 1.0Z, yarn count 4.2 tex), and woven with an air jet loom to obtain a plain weave glass fiber fabric with a warp density of 90/25 mm and a weft density of 90/25 mm. Next, the spinning sizing agent and weaving sizing agent attached to the obtained glass fiber fabric were removed by heating at 400°C for 30 hours. Thereafter, the surface treatment agent, a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Corporation) was adjusted to a concentration of 15 g/L, and the fabric was squeezed with a padder roll, followed by drying and curing at 120°C for 1 minute. The glass fiber fabric was then subjected to a width-widening treatment once using a water flow process at a pressure of 1.5 MPa while setting the tension of the glass fiber fabric to 100 N/m in the warp direction, to obtain a glass fiber fabric 2. The obtained glass fiber fabric had a warp density of 90 threads/25 mm, a weft density of 90 threads/25 mm, a thickness of 27 μm, a mass of 30 g/m ² , and a refractive index of 1.561.

(Lamination of Antistatic Layer to Film Layer 5)
An antistatic layer was laminated on one side of Cosmoshine (registered trademark) A4300 (thickness 50 μm) serving as the film layer 5. The antistatic layer was provided by coating and drying an antistatic agent prepared by mixing and dispersing tin oxide fine particles (average particle diameter 20 nm) in a polyester resin as a fixing resin such that the mass ratio of the fixing resin to the tin oxide fine particles (fixing resin:tin oxide fine particles) was 75:25 on one side of Cosmoshine (registered trademark) A4300 (thickness 50 μm) serving as the film layer 5. The mass and thickness of the provided antistatic layer were 0.5 g/m ² and 0.4 μm, respectively.

(Lamination of a peelable protective film to be peeled off during use onto film layer 5 (antistatic layer side))
The aforementioned COSMOSHINE (registered trademark) A4300 having an antistatic layer on one side thereof as film layer 5 was laminated with a polypropylene film having an acrylic ester adhesive applied to one side thereof as a peelable cover layer to be peeled off when used, on the antistatic layer, with the adhesive facing the antistatic layer, and dried to obtain a laminate X having a laminate structure of COSMOSHINE (registered trademark) A4300 having a peelable protective film to be peeled off when used/acrylic ester adhesive/antistatic layer/film layer 5. Two sheets of the laminate X were prepared.

(Formation of the first resin layer 3, and lamination of the laminate A including the film layer 5 onto the first resin layer 3)
A curable resin composition made of the acrylic syrup shown in Table 1 was applied to the Cosmoshine (registered trademark) A4300 surface side (i.e., the surface opposite to the peelable cover layer to be peeled off during use) of one sheet of the obtained laminate X as the first resin layer 3. Next, the obtained glass fiber fabric 2 was placed on the curable resin composition to be the first resin layer 3, and left to stand for 1 minute to impregnate the gaps in the glass fiber fabric 2 with the curable resin composition made of the acrylic syrup. Next, the PET film used as the process film described above was placed on the curable resin composition made of the acrylic syrup, and pressure was applied from above the PET film with a roller so that the mass of the first resin layer 3 was 25 g/ ^m2 . Then, the curable resin composition made of acrylic syrup, which is the first resin layer 3, was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (Toshiba Corporation, product name FL15BLB) through the process PET film to cure the curable resin composition and form the first resin layer 3, and then the laminated process PET film was peeled off to obtain a laminate Y having a laminated structure of a peelable cover layer that is peeled off when used/an acrylic acid ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 impregnated in a glass fiber fabric 2. In the obtained laminate Y, the first resin layer 3 (cured product of the resin composition) made of acrylic syrup was impregnated into the gaps between the glass fibers of the glass fiber fabric 2 without exposing the glass fibers. Two sheets of the laminate Y were prepared.

(Lamination of the second resin layer 4 included in the glass fiber fabric 2 without being impregnated therein)
A brominated vinyl ester resin composition shown in Table 1 was applied to the first resin layer 3 side of one sheet of the obtained laminate Y, which was contained in a state of being impregnated in the glass fiber fabric 2, as the second resin layer 4, which was contained in a state of not being impregnated in the glass fiber fabric 2. Next, the other one of the obtained laminates Y was placed on top of the brominated vinyl ester resin composition, so that the first resin layer 3 side of the laminate Y faced the brominated vinyl ester resin composition side, and pressure was applied from above the other laminate Y with a roller so that the mass of the second resin layer 4 made of the brominated vinyl ester resin composition was 229 g/ ^m2 . Thereafter, the brominated vinyl ester resin composition serving as the second resin layer 4 was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (manufactured by Toshiba Corporation, product name FL15BLB) through the other laminate Y to harden the brominated vinyl ester resin composition to form the second resin layer 4, thereby forming a transparent sheet 1 of the present invention having a laminate structure of a peelable cover layer that is peeled off when used/an acrylic ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a second resin layer 4 that is not impregnated in the glass fiber fabric 2/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a film layer 5 (Cosmoshine (registered trademark) A4300)/an antistatic layer/an acrylic ester-based adhesive that is peelable together with the cover layer/a peelable cover layer that is peeled off when used. The bromine concentration, total light transmittance, haze, total heat generation, and time exceeding 200 kW of the transparent sheet described below were evaluated by peeling off the peelable cover layer that is peeled off when using the transparent sheet 1 obtained above and the acrylic ester-based adhesive that is peelable together with the cover layer.

Example 10
(Preparation of fiberglass fabric)
The warp and weft yarns were made of Unitika Glass Fiber Co., Ltd.'s trade name "ECC1200 1/0 1.0Z" (average filament diameter 4.5 μm, average number of filaments 100, twist number 1.0Z, yarn count 4.2 tex), and woven with an air jet loom to obtain a plain weave glass fiber fabric with a warp density of 90/25 mm and a weft density of 90/25 mm. Next, the spinning sizing agent and weaving sizing agent attached to the obtained glass fiber fabric were removed by heating at 400°C for 30 hours. Thereafter, the surface treatment agent, a silane coupling agent (S-350: N-vinylbenzyl-aminoethyl-γ-aminopropyltrimethoxysilane (hydrochloride) Chisso Corporation) was adjusted to a concentration of 15 g/L, and the fabric was squeezed with a padder roll, followed by drying and curing at 120°C for 1 minute. The glass fiber fabric was then subjected to a width-widening treatment once using a water flow process at a pressure of 1.5 MPa while setting the tension of the glass fiber fabric to 100 N/m in the warp direction, to obtain a glass fiber fabric 2. The obtained glass fiber fabric had a warp density of 90 threads/25 mm, a weft density of 90 threads/25 mm, a thickness of 27 μm, a mass of 30 g/m ² , and a refractive index of 1.561.

(Lamination of Antistatic Layer to Film Layer 5)
An antistatic layer was laminated on one side of Cosmoshine (registered trademark) A4300 (thickness 50 μm) serving as the film layer 5. The antistatic layer was provided by coating and drying an antistatic agent prepared by mixing and dispersing tin oxide fine particles (average particle diameter 20 nm) in a polyester resin as a fixing resin such that the mass ratio of the fixing resin to the tin oxide fine particles (fixing resin:tin oxide fine particles) was 75:25 on one side of Cosmoshine (registered trademark) A4300 (thickness 50 μm) serving as the film layer 5. The mass and thickness of the provided antistatic layer were 0.5 g/m ² and 0.4 μm, respectively.

(Lamination of a peelable protective film to be peeled off during use onto film layer 5 (antistatic layer side))
The aforementioned COSMOSHINE (registered trademark) A4300 having an antistatic layer on one side thereof as film layer 5 was laminated with a polypropylene film having an acrylic ester adhesive applied to one side thereof as a peelable cover layer to be peeled off when used, on the antistatic layer, with the adhesive facing the antistatic layer, and dried to obtain a laminate X having a laminate structure of COSMOSHINE (registered trademark) A4300 having a peelable protective film to be peeled off when used/acrylic ester adhesive/antistatic layer/film layer 5. Two sheets of the laminate X were prepared.

(Formation of the first resin layer 3, and lamination of the laminate A including the film layer 5 onto the first resin layer 3)
A curable resin composition made of the acrylic syrup shown in Table 1 was applied to the Cosmoshine (registered trademark) A4300 surface side (i.e., the surface opposite to the peelable cover layer to be peeled off during use) of one sheet of the obtained laminate X as the first resin layer 3. Next, the obtained glass fiber fabric 2 was placed on the curable resin composition to be the first resin layer 3, and left to stand for 1 minute to impregnate the gaps in the glass fiber fabric 2 with the curable resin composition made of the acrylic syrup. Next, the PET film used as the process film described above was placed on the curable resin composition made of the acrylic syrup, and pressure was applied from above the PET film with a roller so that the mass of the first resin layer 3 was 25 g/ ^m2 . Then, the curable resin composition made of acrylic syrup, which is the first resin layer 3, was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (Toshiba Corporation, product name FL15BLB) through the process PET film to cure the curable resin composition and form the first resin layer 3, and then the laminated process PET film was peeled off to obtain a laminate Y having a laminated structure of a peelable cover layer that is peeled off when used/an acrylic acid ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 impregnated in a glass fiber fabric 2. In the obtained laminate Y, the first resin layer 3 (cured product of the resin composition) made of acrylic syrup was impregnated into the gaps between the glass fibers of the glass fiber fabric 2 without exposing the glass fibers. Two sheets of the laminate Y were prepared.

(Lamination of the second resin layer 4 included in the glass fiber fabric 2 without being impregnated therein)
A brominated vinyl ester resin composition shown in Table 1 was applied to the first resin layer 3 side of one sheet of the obtained laminate Y, the second resin layer 4 being contained in a state of not being impregnated in the glass fiber fabric 2. Next, the other one of the obtained laminates Y was placed on top of the brominated vinyl ester resin composition, so that the first resin layer 3 side of the laminate Y faced the brominated vinyl ester resin composition side, and pressure was applied from above the other laminate Y with a roller so that the mass of the second resin layer 4 made of the brominated vinyl ester resin composition was 269 g/ ^m2 . Thereafter, the brominated vinyl ester resin composition serving as the second resin layer 4 was irradiated with light (light irradiation conditions: cumulative light amount 200 mJ/cm ² ) using a black light fluorescent lamp (manufactured by Toshiba Corporation, product name FL15BLB) through the other laminate Y to harden the brominated vinyl ester resin composition to form the second resin layer 4, thereby forming a transparent sheet 1 of the present invention having a laminate structure of a peelable cover layer that is peeled off when used/an acrylic ester-based adhesive that is peelable together with the cover layer/an antistatic layer/a film layer 5 (Cosmoshine (registered trademark) A4300)/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a second resin layer 4 that is not impregnated in the glass fiber fabric 2/a first resin layer 3 contained in a state impregnated in the glass fiber fabric 2/a film layer 5 (Cosmoshine (registered trademark) A4300)/an antistatic layer/an acrylic ester-based adhesive that is peelable together with the cover layer/a peelable cover layer that is peeled off when used. The bromine concentration, total light transmittance, haze, total heat generation, and time exceeding 200 kW of the transparent sheet described below were evaluated by peeling off the peelable cover layer that is peeled off when using the transparent sheet 1 obtained above and the acrylic ester-based adhesive that is peelable together with the cover layer.

In the examples, the weave density of the glass fiber fabric was measured and calculated in accordance with JIS R 3420 2013 7.9. The thickness of the glass fiber fabric was measured and calculated in accordance with JIS R 3420 2013 7.10.1A. The mass of the glass fiber fabric was measured and calculated in accordance with JIS R 3420 2013 7.2. The refractive indices of the glass fiber fabric 2, the first resin layer 3, and the second resin layer 4 were measured and calculated by the above-mentioned method. The Abbe numbers of the glass fiber fabric 2 and the first resin layer 3 were measured and calculated by the above-mentioned method. The following evaluations were performed after the transparent sheet 1 was produced and left indoors for one week.

Bromine concentration was measured and calculated using the method described above.

The total light transmittance and haze of the transparent sheet 1 after peeling off the peelable cover layer that is peeled off during use, and the total heat generation amount (MJ/m2) and the time (S) at which the heat generation rate exceeds 200kW/m2 in a heat generation test in which radiant heat of 50kW/m2 is irradiated from a radiant electric heater to the surface of the ^sheet , measured according to "4.10.2 Heat Generation Test and Evaluation Method" in the "Fire Resistance Test and Evaluation Procedure ^Manual " (revised version on March 1, ²⁰¹⁴ ) of the General Incorporated Foundation Building Materials Testing Center, were measured and calculated according to the above-mentioned method. In addition, the presence or absence of through holes was judged for the sheet 20 minutes after the start of heating according to the above-mentioned "4.10.2 Heat Generation Test and Evaluation Method".

The evaluation results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, the transparent sheets of Examples 1 to 10 are transparent sheets containing a plain woven glass fiber fabric and a resin, and include, in the thickness direction of the transparent sheet, a first resin layer impregnated in the glass fiber fabric and a second resin layer not impregnated in the glass fiber fabric, and the second resin layer has a higher bromine concentration than the first resin layer, and the transparent sheet has a total light transmittance of 85% or more and a haze of 10% or less. Therefore, when the resin weight is increased, it is possible to achieve both improved transparency and low total heat generation.

Among them, the transparent sheets of Examples 7 to 10 contained tetrabromobisphenol A, decabromodiphenyl ether or brominated vinyl ester in the first resin layer, and therefore, compared to Examples 1 to 6 in which the first resin layer contained phosphorus, in a heat generation test in which radiant heat of 50 kW/m2 was irradiated from a radiant electric heater to the surface of the sheet, measured in accordance with "4.10.2 Heat Generation Test and Evaluation Method" in the "Fire Resistance Performance Test and Evaluation Procedure Manual" (revised version on March 1, 2014) of the General Incorporated Foundation Building Materials Testing Center, the first ^resin layer was less likely to blister, and cracks and holes that are harmful in terms of fire prevention and extend through to the back surface due to the blister were less likely to occur for 20 minutes after the start of heating.

Reference Signs List 1: Transparent sheet 2: Glass fiber fabric 3: First resin layer 4: Second resin layer 5: Film layer

Claims (7)

A transparent sheet comprising a plain woven glass fiber fabric and a resin,
A first resin layer is included in the glass fiber fabric in a thickness direction of the transparent sheet, and a second resin layer is included in the glass fiber fabric without being impregnated therein,
The second resin layer includes a curable resin containing a bromine atom as a substituent, or a curable resin containing a flame retardant containing a bromine atom,
the second resin layer has a higher bromine concentration than the first resin layer;
The transparent sheet has a total light transmittance of 85% or more and a haze of 10% or less.
Transparent sheet. 2. The transparent sheet according to claim 1, wherein the total heat generation amount is 8 MJ/m2 or less in a heat generation test in which a surface of the sheet is irradiated with radiant heat of 50 kW/ ^m2 from a radiant electric heater, the heat generation test being measured according to "4.10.2 Heat Generation Test and Evaluation Method" in the "Fire Resistance Test and Evaluation Procedure Manual" (revised version as of March ¹ , 2014) of the General Incorporated Foundation Building Materials Testing Center. The transparent sheet according to claim 1 or 2, in which the first resin layer is laminated on both sides of the second resin layer. The transparent sheet according to any one of claims 1 to 3, wherein a total content of the resin contained in the first resin layer and the second resin layer is 200 g/m2 or ^more . The transparent sheet according to any one of claims 1 to 4, wherein the total thickness of the first resin layer and the second resin layer is 180 μm or more. The transparent sheet according to any one of claims 1 to 5, wherein the second resin layer contains a brominated vinyl ester resin. The transparent sheet according to claim 6, wherein the first resin layer contains tetrabromobisphenol A.