KR20210037872A - Polycarbonate resin composite having good transparency, flame retardancy, thermal and mechanical properties, method of manufacturing flame retarded polycarbonate sheet using the resin composition - Google Patents

Abstract

The present invention relates to a polycarbonate resin composition having excellent transparency, flame resistance, heat resistance, and mechanical properties, and a flame resistant polycarbonate sheet using the same. Particularly, the present invention relates to a polycarbonate resin composition including a polycarbonate resin, a phosphorus-based flame retardant and a sulfonate-based flame retardant at a specific content, and a method for manufacturing a flame resistant polycarbonate sheet showing excellent transparency, flame resistance, heat resistance and mechanical properties. According to the present invention, a halogen-based flame retardant containing bromine or chlorine is not used, and a phosphoric acid-based flame retardant and sulfonate-based flame retardant are combined suitably at a low content. In this manner, it is possible to obtain a resin composition for a flame resistant polycarbonate molded article and a flame resistant sheet, which maintains transparency and has excellent thermal and mechanical properties.

Description

Polycarbonate resin composition with excellent transparency, flame retardancy, thermal and mechanical properties, and manufacturing method of polycarbonate flame retardant sheet using the same {POLYCARBONATE RESIN COMPOSITE HAVING GOOD TRANSPARENCY, FLAME RETARDANCY, THERMAL AND MECHANICAL PROPERTIES, METHOD OF MANUFACTURING FLAME RETARDED SPOLYCARBON }

The present invention relates to a polycarbonate resin composition having excellent transparency, flame retardancy, heat resistance, and mechanical properties, and a polycarbonate flame retardant sheet using the same, and more particularly, to a polycarbonate resin containing a phosphorus-based flame retardant and a sulfonate-based flame retardant in a specific content. It relates to a carbonate resin composition and a method of producing a polycarbonate flame-retardant sheet exhibiting excellent transparency, flame retardancy, heat resistance and mechanical properties.

Polycarbonate is the only general-purpose engineering plastic that has transparency and is a thermoplastic resin that has excellent properties such as impact resistance, heat resistance, and compatibility. It is widely used in various fields such as, and food containers.

Sheets made of polycarbonate resin are widely used not only as materials such as clean room transparent walls such as semiconductors and display factories, indoor windows of airplanes, and LED lighting covers, but also as architectural exterior materials such as arcades and signboards. PC sheet has lightness, light weight, self-extinguishing property, and high heat deflection temperature due to high impact resistance and transparency, so it is increasingly used as a building material, and the market size is gradually expanding. The safety of Korea is gradually being emphasized. However, polycarbonate resin has poor scratch resistance with a pencil hardness of 2B or less, and its flame retardancy is an international standard, UL94 (underwriters laboratory) V2 grade, and has excellent scratch resistance, excellent flame resistance, transparency, and excellent thermal and mechanical properties. Interest in high-functional PC resin and its application products is increasing.

Polycarbonate resins have self-extinguishing properties, but the thinner the thickness, the less flame retardant properties, so bromine-based flame retardants were used to increase the flame-retardant properties.However, the use of halogen-based flame retardants is strictly regulated due to the recent regulations on environmentally hazardous substances. Accordingly, research for non-halogen flame retardant is being actively conducted. In particular, in the case of polycarbonate resin, phosphorus-based, silicone-based, and inorganic non-halogen flame retardants that do not decompose at the processing temperature and have excellent compatibility with PC are applied, but transparent products or other mechanical and thermal properties deteriorate. As such, there is a limit to being used in various polycarbonate resin products. Currently, the definition of halogen-free products is according to IEC 61349-2-21 international standard and IPC 4101B; 1) 900 ppm maximun chlorine, 2) 900 ppm maximum bromine, 3) 1500 ppm maximum total halogen, defined as the total amount of bromine (Br) and chlorine (Cl), which are highly hazardous.

Korean Patent No. 10-1134015 discloses a polycarbonate resin composition having excellent transparency, flame retardancy and scratch resistance, but it is 2 mm thick using bromine or chlorine molecules by using a phosphate ester compound and a halogen-substituted polycarbonate oligomer as a flame retardant. It is a technology that achieves flame retardancy V0 in. Korean Patent No. 10-1138797 discloses a resin composition for a transparent flame retardant film having excellent flame retardancy and light transmittance using a phosphoric acid ester compound, a phosphazene compound, and a silicone compound, and a method of manufacturing a polycarbonate transparent flame retardant film using the same. There is no mention of the thickness, thermal and mechanical properties of the film. Korean Patent No. 10-1402579 discloses a molded article having good flame retardant properties while maintaining transparency in linear and branched polycarbonate resins containing a specific amount of a sulfonate-based flame retardant modified with lactones. It does not contain high functional properties such as antistatic properties.

Korean Patent Registration No. 10-1134015 Korean Patent Registration No. 10-1138797 Korean Patent Registration No. 10-1402579

As a result of making diligent efforts to solve the above problems, the present invention has excellent flame retardancy by mixing a phosphoric acid-based and sulfonate-based flame retardant in an appropriate amount, and has excellent thermal and mechanical properties of the polycarbonate resin itself. It is an object of the present invention to provide a resin composition capable of holding as it is.

Another object of the present invention is to provide a method of manufacturing a flame-retardant sheet using the resin composition and a transparent film that can exhibit excellent scratch resistance and antistatic properties by forming a coating layer on the surface of the flame-retardant sheet substrate.

The present invention,

It provides a polycarbonate resin composition comprising 0.1 to 20 parts by weight of a phosphoric acid-based flame retardant and 0.01 to 10 parts by weight of a sulfonate-based flame retardant based on 100 parts by weight of the polycarbonate resin.

The polycarbonate resin may have a weight average molecular weight of 15,000 to 50,000.

The phosphoric acid-based flame retardant may be one or a mixture of two or more selected from a compound represented by the following formula (1), a compound represented by the following formula (2), and a compound represented by the following formula (3).

[Formula 1]

[Formula 2]

In Formula 2, R is a C1 to C10 alkyl group or a C6 to C20 aryl group, n is 1 to 10, and m is an integer of 50 to 700.

[Formula 3]

The sulfonate-based flame retardant may be a compound represented by the following formula (4), a compound represented by the following formula (5), or a mixture thereof.

[Formula 4]

[Formula 5]

The polycarbonate resin composition may include one or two or more additives selected from an ultraviolet absorber, a heat stabilizer, a dispersant, an antioxidant, a lubricant, and a colorant.

On the other hand, the present invention,

Preparing a resin composition by adding 0.1 to 20 parts by weight of a phosphoric acid-based flame retardant and 0.01 to 10 parts by weight of a sulfonate-based flame retardant based on 100 parts by weight of a polycarbonate resin;

Melt-extruding the resin composition to obtain an extruded product; And

It provides a method for producing a transparent flame-retardant sheet comprising the step of cooling the extrudate to obtain a transparent flame-retardant sheet.

The transparent flame-retardant sheet has a light transmittance of 85% or more, a haze of 2% or less, and a flame retardancy of a 1.5 mm thick specimen measured by the UL-94 method is V0 or more.

Meanwhile, the present invention,

A substrate made of the prepared transparent flame-retardant sheet; A hardness enhancing coating layer formed on the surface of the substrate; And it provides a transparent film comprising a conductive coating layer formed on the surface of the hardness improvement coating layer.

The transparent film has a pencil hardness of 3H or more, and a surface reduction rate of 10 ⁶ Ω/sq or less.

According to the present invention, without using a halogen-based flame retardant containing bromine or chlorine, a low content of phosphoric acid-based and sulfonate-based flame retardants are appropriately mixed to maintain transparency, and a polycarbonate flame-retardant molded article and flame-retardant sheet having excellent thermal and mechanical properties. It is possible to prepare a resin composition for use.

In addition, additives such as light safety agents, lubricants, and antioxidants can be added appropriately for the use of the final product without deteriorating the flame retardant performance, and a highly functional polycarbonate flame-retardant sheet with excellent scratch resistance and antistatic properties by hard coating with a functional material. It is possible to manufacture.

1 is a spectrum showing an NMR measurement analysis peak of fluoroglucinol diffi (Ph-DP) synthesized among phosphoric acid-based flame retardants used in an embodiment of the present invention.
2 is a flow chart schematically showing a method of manufacturing a polycarbonate flame-retardant sheet according to an embodiment of the present invention.
3 is a cross-sectional view of a polycarbonate flame retardant film hard coated with a functional material according to an embodiment of the present invention.

The terms or words used in the present specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

The present invention provides a polycarbonate resin composition comprising 0.1 to 20 parts by weight of a phosphoric acid-based flame retardant and 0.01 to 10 parts by weight of a sulfonate-based flame retardant based on 100 parts by weight of a polycarbonate resin.

Polycarbonate resin

The polycarbonate resin may be a generally distributed linear polycarbonate resin. The linear polycarbonate resin is a polymer obtained by a phosgene method in which various dihydroxy diaryl compounds and phosgene are reacted, or a transesterification method in which a dihydroxy diaryl compound and a carbonate ester such as diphenyl carbonate are reacted. Each manufacturing method and a method of using it in a resin composition are already well known to those of ordinary skill in the art to which the present invention pertains.

It is preferable that the polycarbonate resin has a weight average molecular weight of 15,000 to 50,000 (g/mol). When the weight average molecular weight of the polycarbonate resin is less than 15,000 (g/mol), it is not easy to manufacture a sheet or the like because the pressure does not rise sufficiently during extrusion, and when it exceeds 50,000 (g/mol), effective training is difficult. I can.

Phosphoric acid flame retardant

The phosphoric acid-based flame retardant may include 0.1 to 20 parts by weight, preferably 1 to 15 parts by weight, and more preferably 2 to 10 parts by weight based on 100 parts by weight of the polycarbonate resin.

When the content of the phosphoric acid-based flame retardant is less than the limited range, the flame retardant effect is insignificant, and when the content of the phosphoric acid-based flame retardant exceeds the limited range, the increase in haze increases, thereby reducing transparency.

The phosphoric acid-based flame retardant may be one or a mixture of two or more selected from a compound represented by the following formula (1), a compound represented by the following formula (2), and a compound represented by the following formula (3).

[Formula 1]

[Formula 2]

In Formula 2, R is a C1 to C10 alkyl group or a C6 to C20 aryl group, n is 1 to 10, and m is an integer of 50 to 700.

[Formula 3]

It is preferable to use the compound of Formula 3 as the phosphoric acid-based flame retardant, and the method of synthesizing the same consists of two steps as follows.

[Scheme 1]

In the first step, phenol (phenol) and phosphoryl trichloride (phosphoryl trichloride) as starting materials are mixed with tetrahydrofuran (THF), and then slowly added dropwise to obtain diphenyl phosphorochoridate, which is an intermediate. In the second step, THF is mixed with biphenyl and triethylamine in diphenyl phosphorochoridate, which is an intermediate, and then slowly added dropwise, followed by stirring at about 60°C. After washing with THF to remove triethylamine, distillation and concentration, and drying in a vacuum oven at about 60° C., the fluoroglucinol dipi (Ph-DP) compound of Formula 3 can be obtained. The NMR spectrum of the compound is shown in FIG. 1.

Sulfonate flame retardant

In addition, the sulfonate-based flame retardant may be included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the polycarbonate resin, preferably 0.02 to 5 parts by weight, and more preferably 0.1 to 1 part by weight.

If the content of the sulfonate-based flame retardant is less than the limited range, the flame-retardant effect is insignificant, and if the content of the sulfonate-based flame retardant is less than the limited range, the increased range of the haze increases, thereby reducing transparency, and deteriorating thermal and mechanical properties.

The sulfonate-based flame retardant may be a compound represented by the following formula (4), a compound represented by the following formula (5), or a mixture thereof.

[Formula 4]

[Formula 5]

Additive (D)

The polycarbonate resin composition according to the present invention may use various additives within a range that does not impair the effects of the present invention. Specifically, one or two or more additives selected from an ultraviolet absorber, a heat stabilizer, a dispersant, an antioxidant, a lubricant, and a colorant may be included.

The additive may be included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the polycarbonate resin, but is not limited thereto.

On the other hand, the present invention,

Preparing a resin composition by adding 0.1 to 20 parts by weight of a phosphoric acid-based flame retardant and 0.01 to 10 parts by weight of a sulfonate-based flame retardant based on 100 parts by weight of a polycarbonate resin;

Melt-extruding the resin composition to obtain an extruded product; And

It provides a method for producing a transparent flame-retardant sheet comprising the step of cooling the extrudate to obtain a transparent flame-retardant sheet.

Polycarbonate transparent flame retardant sheet manufacturing method

2 is a flow chart schematically showing a method of manufacturing a transparent flame-retardant sheet according to an embodiment of the present invention.

Referring to FIG. 2, a method of manufacturing a transparent flame-retardant sheet according to the present invention includes a resin composition manufacturing step (S110), a melt extrusion step (S120), and a cooling step (S130).

In the resin composition manufacturing step (S110), a resin composition including 100 parts by weight of a polycarbonate resin, 0.1 to 20 parts by weight of a phosphoric acid-based flame retardant, and 0.01 to 10 parts by weight of a sulfonate-based flame retardant is prepared. In this case, the resin composition may include 0.01 to 10 parts by weight of other additives.

The resin composition is preferably blended using a twin screw extruder having excellent kneading performance of various flame retardants and additives. In the twin-screw extruder, the ratio (L/D) of the screw length (L) to the diameter (D) is preferably 20 to 50, and more preferably 30 to 40. The larger the L/D is, the more homogeneous dispersion can be performed, but if it is 50 or more, decomposition of the resin due to deterioration is likely to occur. It may be desirable to introduce 1 to 3 kneading disc segments in the screw to improve training performance.

In the melt extrusion step (S120), the resin composition may be melt-extruded in a sheet form using an extruder. At this time, it is preferable to use a single screw extruder so that the resin composition does not deteriorate excessively. In addition, it is preferable that a T-die is attached to the extruder used for manufacturing the sheet form so that the resin melt can be discharged in the form of a sheet. The T-die is preferably capable of adjusting the spacing of the die so that the thickness of the final sheet can be adjusted to a desired level, and the spacing of the die can be adjusted manually or automatically.

In the cooling step (S130), the melt-extruded extrudate is cooled and solidified. At this time, it is preferable to cool using a cooling roll, and when the resin is overheated, the resin melt extrudate is naturally discharged to the cooling roll to form a sheet while passing through several cooling rolls, and the resin melts between two cooling rolls. A polishing method in which the extrudate is discharged and the two cooling rolls apply pressure to the melt to cool the sheet may be applied. The cooling roll may be a mirror-treated or embossed or regular pattern-etched roll depending on the purpose.

The transparent flame-retardant sheet obtained by the above manufacturing method has a light transmittance of 85% or more, a haze of 2% or less, and a flame retardancy of a 1.5 mm-thick specimen measured by the UL-94 method is V0 or more.

Polycarbonate transparent film coated with functional materials

3 is a schematic cross-sectional view of a transparent film coated with a functional material according to an embodiment of the present invention.

3, a polycarbonate transparent film coated with a functional material is a hardness-enhancing coating layer 300 for scratch resistance on the polycarbonate transparent flame-retardant sheet substrate 200, and for preventing static electricity on the surface of the improved coating layer 300. It includes a conductive coating layer 400.

For example, a six-functional urethane acrylate oligomer binder may be applied to one surface of the polycarbonate transparent flame-retardant sheet substrate 200, and then cured to form a hard coating layer 300 for improving scratch resistance. In addition, in order to prevent static electricity on the surface of the hardness enhancing coating layer 300, a conductive coating layer (Poly(3,4-ethylenedioxythiophene, PEDOT): Polystylenesulfonic acid (PSS)) is applied and then cured to prevent static electricity. 400).

The polycarbonate transparent film may have a pencil hardness of 3H or more and a surface resistivity of 10 ⁶ Ω/sq or less.

Hereinafter, examples and experimental examples will be described in detail in order to describe the present invention in detail. However, the embodiments and experimental examples according to the present invention may be modified in various other forms, and the examples and experimental examples described below in which the scope of the present invention is more detailed to those of ordinary skill in the art. It is provided for thorough explanation.

Examples 1 to 13: Preparation of transparent flame-retardant sheet

A resin composition for preparing a polycarbonate transparent flame-retardant sheet was prepared by blending the raw materials in the composition ratios shown in Tables 1 and 2 below.

At this time, the compound of Formula 1 is resorcinol bis (diphenyl phosphate) (RDP, SM Tech), and the compound of Formula 2 is a phosphate ester polymer having a weight average molecular weight of about 40,000 to 100,000 (g/mol) (Nofia HM1100, FRX Polymer), as the compound of Chemical Formula 3, fluoroglucinol diffi (Ph-DP, self-synthesized) was used.

Next, each pellet was prepared by melt-kneading extrusion at a resin temperature of 280°C and a screw rotation speed of 300 rpm using a twin screw extruder having a diameter of 45 mm and L/D = 40. After drying the prepared pellets at 120° C. for 4 hours, the extruder cylinder was discharged through a T-die at a temperature of 250° C. using a single screw extruder having a diameter of 45 mm and L/D = 36 to obtain an extrudate. . The extrudate was cooled by a polishing method of cooling while applying pressure between two rolls to prepare a transparent flame-retardant sheet having a thickness of 1.5 mm.

Example 14: Preparation of hard-coated transparent film

After applying a 6-functional urethane acrylate oligomer binder having a solid content of 45% on the surface of the prepared transparent flame-retardant sheet, coated with a #24 Mayer bar, dried in a dryer at 80°C, UV cured with a high pressure mercury lamp A hardness-enhancing coating layer having a thickness of about 15 μm was formed. After applying PEDOT:PSS having a solid content of 4.5% on the surface of the hardness enhancing coating layer, coating #6 Mayer bar, drying in a dryer at 80°C, UV curing with a high pressure mercury lamp to form a conductive coating layer having a thickness of about 0.5 μm to form a hard A coated transparent film was obtained.

Experimental example

(1) Flame retardant grade

When a methane gas flame was applied in a vertical direction to the injection-molded specimen according to the UL 94 V measurement standard, the degree of combustion was observed by time and evaluated.

(2) transmittance and haze

According to ASTM D1003, transmittance and scattering rate corresponding to total light transmittance were used, and values were measured at a reference wavelength (λ=550 nm) after measurement in a wavelength range of 380 to 780 nm.

(3) Tensile strength

According to ISO 527-2/1A, a temperature of 23±2° C., a relative humidity of 50%, and a cross head were measured at a test speed of 50 mm/min.

(4) Load deformation temperature

According to ISO 75, the temperature of the specimen was measured when the deformation of the specimen reached 0.25 mm while raising the temperature of the surrounding fluid at a rate of 2°C/min under a pressure of 1.80 MPa.

(5) adhesion

According to ASTM D3359, a checkerboard-shaped flaw was made on the specimen with a cutter, and then a 3M tape was well adhered to the specimen and removed several times with a constant force to measure the degree of adhesion between the coating layer and the substrate.

(6) Pencil hardness

The hardness was measured when a pencil was scratched at an angle of 45° on the coated surface according to ASTM D3363.

(7) Surface resistivity

In accordance with ASTM D991, a direct current power source was connected to measure the resistance on the surface.

Example Comparative example One 2 3 4 5 6 One 2 3 4 5 Suzy PC 94.1 94.1 94.1 94.1 94.1 94.1 95.1 95.1 95.1 99.5 99.5 Antioxidant Biphenyl diylbisphosphonite 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 UV absorber Benzotriazole 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Phosphorus flame retardant Formula 1 5 5 5 Formula 2 5 5 5 Formula 3 5 5 5 Sulfonate flame retardant Formula 4 0.5 0.5 0.5 0.5 Formula 5 0.5 0.5 0.5 0.5 Total (%) 100 100 100 100 100 100 100 100 100 100 100 Properties Haze% 3.1 13 3.8 2.1 12 3.2 1.3 9.8 2.2 1.8 1.0 UL 94 @1.5mm V2 V2 V1 V2 V2 V0 V2 V2 V2 V2 V2

Example Comparative example Sheet Surface coating 7 8 9 10 11 12 13 14 6 Suzy PC 94.2 94.5 95.4 95.05 97.5 98.5 98.5 98.5 99.6 Antioxidant Biphenyl diylbisphosphonite 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 UV absorber Benzotriazole 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Phosphorus flame retardant Formula 3 5 5 4 4 2 One One One Sulfonate flame retardant Formula 5 0.4 0.1 0.2 0.05 0.1 0.1 0.1 0.1 Total (%) 100 100 100 100 100 100 100 100 100 Properties Haze (%) 3.0 2.8 2.9 2.8 1.9 1.7 1.7 1.6 0.7 Transmittance (%) 84.2 83.2 83.1 86.3 89.2 89.1 89.1 89.5 89.98 Tensile strength (MPa) 62 61.5 63 65 68.5 67.5 67.5 69.5 67.5 Load deformation temperature (℃) 121 124.5 128 128 129 132 132 140 139 UL 94 @1.5mm V0 V0 V0 V0 V0 V0 V0 V0 V2 Adherence - - - - - - - 5B - Pencil hardness - - - - - - F 4H - Surface resistivity (Ω/sq) - - - - - - 6.2×10 ¹⁶ 5.7×10 ⁴ -

According to the evaluation of physical properties in Tables 1 and 2, it was confirmed that a resin composition having UL94-V0 characteristics can be prepared according to the type of flame retardant used.

It is judged that the prepared sheet exhibits flame-retardant properties because the phosphoric acid-based flame retardant forms char during combustion, and the sulfonate-based flame retardant promotes crosslinking during the polycarbonate decomposition process.

In particular, in the case of the flame-retardant sheets of Examples 11 and 12, a haze of 2% or less, a transmittance of 89% or more, and UL94-V0 flame-retardant properties were exhibited.The properties of the phosphoric acid-based flame retardant and the sulfonate-based flame retardant exhibited synergistic effect even at a thin thickness. It was demonstrated that it was possible to manufacture a polycarbonate flame-retardant sheet having excellent thermal and mechanical properties while being transparent.

In addition, it was confirmed that it was possible to manufacture a polycarbonate flame-retardant film having excellent adhesion, a pencil hardness of 4H, and a surface resistivity of 5.7×10 ^{4 Ω/sq by the surface coating of the functional material according to Example 14.} .

200: transparent flame-retardant sheet base material
300: hardness improvement coating layer
400: conductive coating layer

Claims (9)

Based on 100 parts by weight of polycarbonate resin,
A polycarbonate resin composition comprising 0.1 to 20 parts by weight of a phosphoric acid-based flame retardant and 0.01 to 10 parts by weight of a sulfonate-based flame retardant.
The method of claim 1,
The polycarbonate resin is a polycarbonate resin composition, characterized in that the weight average molecular weight is 15,000 ~ 50,000
The method of claim 1,
The phosphoric acid-based flame retardant is a polycarbonate resin composition, characterized in that one or a mixture of two or more selected from a compound represented by the following formula (1), a compound represented by the following formula (2), and a compound represented by the following formula (3).
[Formula 1]

[Formula 2]

In Formula 2, R is a C1 to C10 alkyl group or a C6 to C20 aryl group, n is 1 to 10, and m is an integer of 50 to 700.
[Formula 3]

The method of claim 1,
The sulfonate-based flame retardant is a compound represented by the following formula (4), a compound represented by the following formula (5), or a mixture thereof.
[Formula 4]

[Formula 5]

The method of claim 1,
A polycarbonate resin composition comprising one or two or more additives selected from an ultraviolet absorber, a heat stabilizer, a dispersant, an antioxidant, a lubricant and a colorant.
Preparing a resin composition by adding 0.1 to 20 parts by weight of a phosphoric acid-based flame retardant and 0.01 to 10 parts by weight of a sulfonate-based flame retardant based on 100 parts by weight of a polycarbonate resin;
Melt-extruding the resin composition to obtain an extruded product; And
A method for producing a transparent flame-retardant sheet, comprising the step of cooling the extrudate to obtain a transparent flame-retardant sheet.
The method of claim 6,
The transparent flame-retardant sheet has a light transmittance of 85% or more, a haze of 2% or less, and a flame retardancy of a 1.5 mm-thick specimen measured by UL-94 method is V0 or more.
A substrate made of a transparent flame-retardant sheet manufactured by the manufacturing method of claim 6;
A hardness enhancing coating layer formed on the surface of the substrate; And
A transparent film comprising a conductive coating layer formed on the surface of the hardness enhancing coating layer.
The transparent film according to claim 8, wherein the transparent film has a pencil hardness of 3H or more and a surface reduction rate of 10 ⁶ Ω/sq or less.

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