LIGHT SHIELDING AND ANTISTATIC SHEET AND

CONTAINER

Technical Field

[1] The present invention relates to a light shielding and antistatic sheet, and more particularly, to a sheet for preparing a container for transporting, packaging or protecting parts or products which need light shielding and antistaticity. Also, the present invention relates to a light shielding and antistatic container prepared using the sheet. Background Art

[2] In order to prevent damage caused by static electricity generated during transporting or handling of precision electronic parts, a carrier container prepared using antistatic sheet has been widely used. Recently, an antistatic polymer sheet with a conductive polymer on the surface has been developed and applied in various transparent permanent antistatic products. Such products solve the problems involved in the conventional carrier container formed of carbon black mixture that black impurities falling off from the carrier container cause malfunction of electronic parts, though the container has excellent antistaticity. Use of this carrier container formed of a polymer sheet with a transparent permanent antistatic layer thereon is gradually increased.

[3] However, the biggest problem in the carrier container formed of a polymer sheet with a transparent permanent antistatic layer using a conductive polymer is that the conventional inspection method should be changed or it is impossible to cut-off light when the light shielding is needed for an inspection. When the light is irradiated to the carrier container produced using the transparent antistatic polymer sheet, the light transmits the sheet and thus, it is not possible for a sensor or laser to detect whether or not the electronic parts exist in the cavity of the container. In order to solve this problem, there is a need for a novel packaging inspection method without using light or a light shielding permanent antistatic carrier container for transporting electronic parts which can block light transmission while maintaining other properties of the conventional transparent carrier container such as antistaticity.

[4] Here, in order to block the light transmission, black colored carbon black may be mixed into a polymer but there are several problems. Firstly, the black colored carbon black is basically black colored but has poor light shielding effect. Generally, though the light shielding is achieved by black color, the carbon black has poor light shielding effect and thus, a great amount of carbon black is needed for complete light shielding. However, if the carbon black content is too high upon mixing with a polymer, forming by heat and pressure of vacuum cannot be achieved. Even if forming can be performed

and a carrier container can be prepared, there are various defects such as the same defect as in the conventional container, such as falling off of black impurities from the container during transporting and handling, since the amount of carbon black mixed with the polymer is too high. These defects may be the biggest limit in the development of the light shielding carrier container. Disclosure of Invention Technical Problem

[5] In order to solve the foregoing problems, it is an object of the present invention to provide a permanent antistatic polymer sheet which has excellent light shielding effect and can readily produce a container by secondary forming such as vacuum forming without producing black impurities.

[6] Also, it is another object of the present invention to provide a light shielding and permanent antistatic container prepared from the sheet.

[7] Also, it is a still another object of the present invention to provide a light shielding and permanent antistatic container which has the same structure as the sheet and excellent light shielding effect without producing black impurities.

[8] Also, it is a further object of the present invention to provide a light shielding and antistatic polymer sheet for transporting electronic parts which can prevent examination error by controlling light transmission in the examination of various steps such as packaging and inspection and shows permanent antistatic effect, and a light shielding and antistatic container for transporting electronic parts prepared therefrom.

Technical Solution

[9] In order to achieve the foregoing objects, the present invention provides a sheet comprising at least one sheet layer comprising a polymer resin as a main component and a permanent antistatic layer at one side or both sides, in which the sheet layer, the antistatic layer, or the sheet layer and the antistatic layer is(are) subjected to a light shielding treatment, which is performed adding an inorganic filler inducing light scattering alone or combined with a dye, or separately adding the filler and dye, the layer(s) subjected to the light shielding treatment comprises the inorganic filler in an amount of 0.1 to 20 parts per hundred resin (pphr) and the dye in an amount of 0.05 to 10 pphr, and the antistatic layer has a thickness of 0.02 to 2 micrometers and has permanent antistatic effect and controllable light-shieldability.

[10] The container according to the present invention is directly prepared from the sheet according to the present invention by secondary forming such as vacuum forming or prepared to have the same structure as the sheet.

[11] In another aspect of the present invention, a polymer resin for preparing a container is mixed with an inorganic filler to effectively improve the light shieldability by light

scattering alone or in combination with a dye for coloration and extruded to prepare a light shielding polymer sheet having a predetermined thickness. Then, permanent antistatic layers are formed on the both sides of the sheet to form a light shielding and antistatic sheet, which is used in preparation of a light shielding and antistatic container for transporting electronic parts.

[12] Now, the light shielding will be explained prior to describing the sheet according to the present invention. In the present invention, the light shielding means control of light transmission as needed as well as complete interception of light. That is, the light shielding of the container according to the present invention includes complete interception of light so that naked eyes can not see the contents in the container and partial interception of light while allowing a part of light needed for examination to transmit so that the container is sensed by a laser or a sensor and naked eyes can see the contents. Also, it includes interception of light with predetermined wavelength light (for example, red visible light) from light (for example visible lights and UV rays).

[13] According to the present invention, in order to provide light shielding effect for the conventional sheet having a sheet layer comprising a polymer resin as a main component and antistatic layers, the sheet layer and/or the antistatic layer is(are) subjected to light shielding treatment. The light shielding treatment can be diversely performed. Preferably, the sheet layer is prepared by mixing the polymer resin with an inorganic filler. Alternatively, the antistatic layer is formed by mixing a conductive polymer with an inorganic filler to provide the sheet with light shielding property. In addition, the treatment is performed using difference of refractive indices of polymer resins of the sheet layer with a two or more layer structure. The sheet according to the present invention may have a color in addition to the light shielding property. For this, the sheet layer and/or the antistatic layer is (are) prepared by adding the inorganic filler along with a dye for colorization.

[14] Examples of the inorganic filler which can be used in the present invention are diverse and most inorganic fillers can be used. This is because when impurities such as the an inorganic filler is added to the polymer resin, light is scattered on the particle surface and if the scattering of light is good enough, the light cannot transmit to the opposite side. Examples of the inorganic filler which can be usefully used in the present invention include calcium carbonate, clay, talc, mica, titanium oxide, zinc oxide and the like, which is used alone or in combination with at least one filler. The total inorganic filler content is preferably 0.1 to 20 parts per hundred resin (pphr). If the inorganic filler content is less than 0.1 pphr, the light shielding effect is insignificant. If the content exceeds 20 pphr, the extrusion is difficult or the extruded sheet cannot be vacuum formed, or, even when the sheet can be vacuum formed, it has

a brittleness increased.

[15] When the inorganic filler is added, the sheet has milky color or the color of the inorganic particle because of the light scattering by particles. If it is desired to have a sheet with a color, a dye with a desired color, for example, carbon black of black color, can be used in an amount of 0.05 to 10 pphr upon mixing of the inorganic filler, or can be added to the sheet layer and/or the antistatic layer to prepare the light shielding and antistatic sheet according to the present invention. Here, the color of the entire sheet varies according to the mixing ratio of the inorganic filler and the dye. For example, in case of black color, it is possible to control from milky color to black color. If the carbon black content is less than 0.05 pphr, the sheet shows nearly a gray color with little black color effect. If the content exceeds 10 pphr, the extrusion is hard or the extruded sheet can not be secondarily processed by vacuum forming, since the total filler content is too high.

[16] In order to maximize the light shielding effect by the inorganic filler, the particle sizes of the inorganic filler should be evenly distributed over the resin. For this, the inorganic filler has a small particle size, or the inorganic particles are surface-treated so the inorganic filler particles can be readily dispersed. Thus, the inorganic filler preferably has a particle size as small as possible. Generally, when the particle size is less than 5 micron or the inorganic filler particles are surface-treated with silane type or titanate type coupling agents or fatty stearic acid adjuvant, it is possible to efficiently provide the light shielding property with a small amount.

[17] Also, the inorganic filler used in the present invention can facilitate mixing upon polymer processing or improve the processibility. Therefore, it is possible to manufacture the sheet with improved processibility as well as light scattering.

[18] According to the present invention, in order to provide a desired color for the sheet, a compound showing the desired color is previously prepared and used by in a part diluting with the inorganic filler upon extrusion of the sheet to prepare a light shielding and antistatic sheet with the desired color. In case the sheet has a single layer structure, a dye is mixed with the inorganic filler to prepare the sheet of the single layer structure. However, in case of sheet having multi-layer structure such as the three-layer structure, the middle layer or the surface layer, or both the middle layer and the surface layer may have a color.

[19] The method for preparing the sheet according to the present invention, includes preparing the sheet having a single layer structure and preparing the sheet by multilayer extrusion with two or more layers, in which the inorganic filler and/or the dye may be added to prepare the sheet. In case of preparing the sheet with a single-layer structure, the polymer resin including the inorganic particles and/or the dye is prepared by extrusion. The single-layer sheet has a length increased of a predetermined amount

by heat upon the secondary processing such as vacuum forming. Therefore, since the whole layers expand at the same time, there may be a region where the light can transmit. Therefore, the single-layer sheet has a light shielding effect inferior to the multi-layer structure, for example, a sheet prepared by triple layer extrusion or co- extrusion.

[20] In case of three-layer structure, the raw material of the middle layer and the raw material of the surface layers can be the same or the raw material of the middle layer comprise a filler with excellent light shielding and the raw material of the surface layer contain a large amount of dye to provide color of the raw material (for example, carbon black for black color). The latter construction is more effective in the light shielding. Therefore, the number of layers in the sheet structure is selected according to the need of the container but the three-layer structure is preferable in terms of light shielding property. In the sheet having a three-layer structure, preferably the middle layer forms 50 to 97% of the total thickness and two outer layer, the upper layer and the lower layer, each form 1.5 to 25% of the total thickness.

[21] Also, alternatively, the method for preparing the light shielding sheet includes mixing two or more types of polymer resins. When a transparent amorphous polymer is mixed with another polymer having a different refractive index in a proper mixing ratio, the light transmission is reduced. Applying this principle, polymer compounds are mixed. Here, polymers having a refractive index of 1.4 to 1.7 are properly mixed. This method uses only polymers without an inorganic filler. Alternatively, in case of using an opaque polymer as a single layer, the light transmission is deteriorated and thus, the whole light is intercepted such that the naked eyes cannot figure out the light. Therefore, this method includes using an opaque polymer in the middle layer upon construction of the multi-layer structure and a transparent polymer in the outer layer, or using a transparent polymer in the middle layer and an opaque polymer in the outer layer. Alternatively, the method includes mixing a transparent amorphous polymer to a crystalline polymer considering light shielding effect and compatibility so that the mechanical properties are not considerably deteriorated. By using this method, it is possible to prepare a single layer or multi-layer light shielding sheet.

[22] The sheet prepared by the above-described methods has light shielding effect and thus, can prevent inspection error in the procedure of various steps. Also, if it is formed in the multi-layer structure and the container is translucency, it is possible to confirm if the container contains contents by observing the inside of the container

[23] The antistatic layer can have the light shielding effect by mixing an inorganic filler in a conductive polymer solution to form an antistatic layer. That is, in the preparation of the conductive polymer solution, titanium oxide, tin oxide, zinc oxide, calcium carbonate, or indium oxide can be added. Also, by using a conductive inorganic filler

such as doped tin oxide and doped indium tin oxide instead of the conductive polymer, it is possible to provide the light shielding effect and the antistatic effect at the same time. Further, in order for the antistatic layer to have a color, a die is mixed into the antistatic coating solution and thus, the resulting antistatic layer has a color along with the light shielding effect.

[24] The method for preparing the light shielding and antistatic sheet according to the present invention includes forming a conductive polymer layer as a transparent antistatic layer on the surface of one side or the surfaces of both sides of the light shielding polymer sheet prepared by the above-described method, forming a light shielding and antistatic layer on one side or both sides of a common sheet which is not subjected to light shielding treatment, or forming a light shielding and antistatic layer on one side or both sides of the light shielding polymer sheet prepared by the above- described method. In the three methods, the formation of the antistatic layer on the sheet is performed as follows. In forming of a conductive polymer layer as an antistatic layer on one side or both sides of the sheet, it is preferable to form a conductive polymer layer on both sides. The method for forming a conductive polymer layer as an antistatic layer on the sheet includes solution coating, direct polymerization such as liquid phase polymerization and vapor phase polymerization. The solution coating is a method for forming an antistatic layer on a surface by mixing a conductive polymer and an organic and inorganic binder, as effective components, and an additive of a thickening agent, an antioxidant or releasing enhancer and applying the mixture on the surface of the sheet, followed by drying.

[25] The conductive polymer which can be used in the antistatic layer of the sheet according to the present invention includes polyaniline, polypyrrole, polythiophene and modified conductive polymer thereof. Among them, poly

(3,4-ethylenedioxythiophene) which is environmentally friendly and can be dispersed in a relatively non-toxic solvent such as water and alcohol is preferable (Baytron, H. C. Satrck, German). The method for preparing the conductive polymer coating solution and the coating method are performed according to a known method, for example, Korean patent Registration No. 426792, "Coating composition for Electrostatic Dissipative and Electrostatic Dissipative Shielding and Moisture Barrier Bags dopped coating composition for Electrostatic Dissipative". The conductive polymers are transparent and thus, it is possible to readily control the light shieldability by mixing an inorganic filler and/or a dye.

[26] If it is difficult to coat the conductive polymer on the sheet due to the difference of the surface tension between the sheet and the conductive polymer coating solution, the surface of the polymer sheet is subjected to corona treatment to make the surface tension at least 35 dyne/unit area for wetting.

[27] Also, for antistatic effect, it is possible to directly form a conductive polymer layer on the polyester polymer sheet prepared by vapor phase polymerization or liquid phase polymerization (Korean Registered Patent No. 422321 and Korean Patent Application No. 2003-67853). According to this direct polymerization, a monomer for a conductive polymer, a dopant, and an oxidizing agent (or a reaction inhibitor as needed) are mixed together and applied on the surface of a base polymer and dried to form a conductive polymer layer, followed by washing to remove un-reacted residuals to form an antistatic layer on the surface of the base polymer, or an oxidizing agent and a monomer in the gas phase is deposited on the surface upon which a dopant are previously coated to form a conductive polymer, followed by washing to remove un- reacted residuals to form an antistatic layer.

[28] The sheet according to the present invention can be directly formed into a container which can carry parts or products by various methods including secondary forming such as vacuum forming. The antistatic sheet with light shielding property has a great advantage in preparation of the container by vacuum forming. Thus, considering stretching index as described in the reference patents, the vacuum forming is preferable in the production of the container in terms of readiness and cost.

[29] Also, in addition to the above-described methods, the containers according to the present invention can be prepared by forming a light shielding sheet into a container to have the same structure as the light shielding and antistatic sheet or forming an antistatic layer comprising a conductive polymer as an effective component on the formed container. Here, various methods such as solution coating, direct polymerization, and ion-beam treatment can be performed. The most effective method is the solution coating method, in which an antistatic coating solution comprising a conductive polymer as an effective component is previously prepared and applied on the surface of the part carrier container by spraying, electro deposition coating (plating) or dipping to form an antistatic layer on the surface of the parts carrier container. According to the curing method of the solution, thermal curing method or UV curing method can be used. Advantageously, the UV curing method can form an antistatic layer with excellent properties that it has a surface hardness of 1 H or more and cannot be removed by a common alcoholic solvent.

[30] In the sheet and container according to the present invention, after drying upon forming the antistatic layer comprising the conductive polymer as an effective component, the antistatic layer has a thickness of 0.02 to 2 micrometers. If the antistatic layer has a thickness of less than 0.02 micrometers, it is difficult to obtain uniform coating thickness since the thickness is too thin. Also, the formed film has poor solidity. If the thickness exceeds 2 micrometers, the antistatic effect does not increase any more in proportion to the increase of the thickness.

[31] Types of the polymer which can be used in the sheet and the container according to the present invention does not include polymers having excellent light shielding property of the resin itself, since the present invention relates to improvement and control of light shieldability. Thus, polymers having at least 30% of light transmission at 550 nm can be applied. For example, it can be used in improvement of the light shieldability and antistaticity of the polymer sheet formed of one selected from transparent polymer such as amorphous polyester (A-PET), polyester copolymer (PETG), polycarbonate, polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), cyclic poly olefin (Alton) and the like or semi-transmparent polymer such as polyimide, polyether sulfone, polyphenylene oxide, polyetherimide and the like, or a blend thereof or copolymer thereof, as an effective component,

[32] Also, in using the light scattering and crystalline property, various polymers whose refractive index and transmission rate can be controlled can be selected and used without any limitation.

[33] Also, the sheet can be formed into a container itself and can be used as a part of other container, such as a side, and thus can be diversely used for light shielding and antistaticity of electronic parts.

Advantageous Effects

[34] The light shielding and antistatic sheet can readily produce a light shielding and antistatic container for electronic parts by secondary processing such as vacuum forming using a polymer with excellent transparency. [35] The light shielding and antistatic sheet and the container according to the present invention can prevent inspection error caused by light transmission upon examination of electronic parts, and can control light shieldability so that a naked eye inspection of the parts is available. Also, the light shielding and antistatic sheet and the container according to the present invention can prevent electronic parts sensitive to light from the damage by light during storage and transporting.

Brief Description of the Drawings [36] Figure 1 is a cross-sectional view showing the structure of the single-layer extruded light shielding and antistatic sheet according to an embodiment of the present invention. [37] Figure 2 is a cross-sectional view showing the structure of the single-layer extruded light shielding and antistatic sheet according to another embodiment of the present invention. [38] Figure 3 is a cross-sectional view showing the structure of the triple extruded light shielding and antistatic sheet according to an embodiment of the present invention. [39] Figure 4 is a cross-sectional view showing the structure of the triple extruded light

shielding and antistatic sheet according to another embodiment of the present invention.

[40] Figure 5 is a cross-sectional view showing the structure of the triple extruded light shielding and antistatic sheet according to a further embodiment of the present invention. Mode for the Invention

[41] Now, the structure of the sheet (and the container having the same structure) according to the present invention will be described in detail with reference to the drawings.

[42]

[43] Figure 1 is a cross-sectional view showing the structure of the single-layer extruded light shielding and antistatic sheet 1 according to an embodiment of the present invention. Referring to Figure 1, the sheet 1 has a structure including a sheet layer 40 comprising a polymer as a main component, an inorganic filler 20 and a dye 30, and antistatic layers 10 at both sides of the sheet layer 40.

[44] Figure 2 is a cross-sectional view showing the structure of the single-layer extruded light shielding and antistatic sheet 2 according to another embodiment of the present invention. Referring to Figure 2, the sheet 2 has a structure including a sheet layer 40 comprising a polymer as a main component and a dye 30, and antistatic layers 10 comprising an inorganic filler 20 at both sides of the sheet layer 40.

[45] Figure 3 is a cross-sectional view showing the structure of the triple extruded light shielding and antistatic sheet 3 according to an embodiment of the present invention. Referring to Figure 3, the sheet 3 has a three-layer structure including a middle layer 42 comprising a polymer as a main component and two outer layers 41 at both sides thereof. The middle layer 42 comprises both an inorganic filler 20 and a dye 30 while the outer layers 41 comprise a dye 30.

[46] Figure 4 is a cross-sectional view showing the structure of the triple extruded light shielding and antistatic sheet according to another embodiment of the present invention. Referring to Figure 4, the sheet 4 has a three-layer structure including a middle layer 42 and two outer layers 41 at both sides thereof. The outer layers 41 comprise an inorganic filler 20 and the middle layer 42 comprises a dye 30.

[47] Figure 5 is a cross-sectional view showing the structure of the triple extruded light shielding and antistatic sheet according to a further embodiment of the present invention. Referring to Figure 5, the sheet 5 has a three-layer structure including a middle layer 42 comprising a polymer as a main component and two outer layers 41 at both sides thereof. The middle layer 42 comprises both an inorganic filler 20 and a dye 30 and the outer layers 41 do not comprise an inorganic filler nor dye.

[48]

[49] Now, the present invention will be described in detail using the following examples.

However, the present invention is not limited thereto.

[50] Evaluation of light shieldability: The present invention relates to improvement of the light shielding property of a product secondarily processed by vacuum forming, rather than improvement of light shielding property of the sheet itself. Therefore, it is hard to precisely evaluate the light shieldability by the visible light transmission measurement which is commonly used in the art. Accordingly, in the present invention, it is determined as good light shieldability that a carrier container which has been previously prepared by vacuum forming is placed at 5 cm from an observer and the light placed behind the container is not clearly shown. This evaluation method is commonly performed in the electronic part packaging industry and a very convenient and useful method.

[51]

[52] <Example 1>

[53] 100 pphr of an amorphous polyester resin was mixed with 5 pphr of calcium carbonate having an average particle size of 2.0 micrometers and 2 pphr of carbon black having an average particle size of 0.05 micrometers using a twin-screw extruder to prepare an amorphous polyester/calcium carbonate/carbon black compound. The resulting compound resin was extruded into a single-layered amorphous polyester sheet having a thickness of 0.9 mm which was then formed into a tray for transporting electronic parts by vacuum forming.

[54] Thus, a tray for transporting electronic parts could be prepared using the sheet prepared by the above described method by vacuum forming. Upon examination of the flat part and the expanded part of the tray, the flat part completely shielded light and the expanded part showed satisfactory light shieldability as the light of opposite side is glimmered.

[55] <Example 2>

[56] An amorphous polyester resin was mixed with 5.0 pphr of titanium oxide having an average particle size of 2.0 micrometers and 1.0 pphr of carbon black. Then, the resulting resin mixture as a middle layer and a mixture of an amorphous polyester resin with 3 pphr of carbon black as outer layers at both side were extruded to a thickness of 0.9 mm using a triple extruder. Here, the thickness ratio of the surface layers and the middle layer was 10:80:10.

[57] The sheet prepared by the above-described triple extrusion was formed into a tray by vacuum forming. The sheet had good formability. The flat surface of the tray showed complete light shielding effect and the expanded part showed such good light shielding effect that the light behind the tray was not clear, though not as complete as

the flat surface.

[58] <Example 3>

[59] An amorphous polyester resin was mixed with 5.0 pphr of titanium oxide having an average particle size of 2.0 micrometers and 3.0 pphr of carbon black. Then, the resulting resin mixture as a middle layer and an amorphous polyester resin without any additive as outer layers at both sides were extruded to a thickness of 0.9 mm using a triple extruder. Here, the thickness ratio of the surface layers and the middle layer was 10:80:10.

[60] The sheet prepared by the above-described triple extrusion was formed into a tray by vacuum forming. The sheet had good formability. The flat surface of the tray showed complete light shielding effect and the expanded part showed such good light shielding effect that the light behind the tray was not clear, though not as complete as the flat surface.

[61] <Example 4>

[62] This example was for evaluation of the surface resistance and light shieldability of structure which comprised the amorphous polyester sheet prepared in Example 1 and an antistatic layer comprising a conductive polymer as an effective component, applied on the sheet. The antistatic coating solution comprising a conductive polymer as an effective component was prepared as follows. 4 g of poly(3,4-ethylenedioxythiophene) aqueous dispersion, 9 g of a urethane -based binder having a molecular weight of 10,000, 0.01 g of a zonyl additive (DuPont), 0.2 g of ethylene glycol and 0.2 g of l-methyl2-pyrrolidinone were mixed with 25 g of a solvent mixture of ethyl alcohol, and isopropyl alcohol (1:1) to prepare a conductive coating solution. This solution was coated on the surface of the amorphous polyester sheet prepared in Example 1 to a thickness of 0.5 micrometers and dried at 8O ⁰ C for 2 minutes to prepare an antistatic sheet, which was then formed into a tray for transporting electronic parts by vacuum forming.

[63] The amorphous polyester sheet with the conductive coating solution coated was examined for its surface resistance by a known method. The coated sheet had a surface resistance of 10 ohm/square and an after vacuum forming surface resistance of 10 ohm/square. For the light shielding, the flat surface showed complete light shielding effect and the expanded part showed such good light shielding effect that the light behind the tray was not clear, like the result of Example 1.

[64] <Example 5>

[65] Except for using the amorphous polyester sheet having the three-layer structure of

Example 2, the procedure was the same as described in Example 4.

[66] The amorphous polyester sheet had a surface resistance of 10 ohm/square and the tray after forming had a surface resistance of 10 ohm/square. The flat surface and the

expanded part showed good light shieldability.

[67] <Example 6>

[68] Except for using the amorphous polyester sheet having the three-layer structure of

Example 3, the procedure was the same as described in Example 4.

[69] The amorphous polyester sheet had a surface resistance of 10 ohm/square and the tray after forming had a surface resistance of 10 ⁷ ohm/square. Also, the flat surface and the expanded part showed good light shieldability.

[70] <Example 7>

[71] An light shielding and antistatic amorphous polyester sheet was prepared by forming an antistatic layer comprising polypyrrole as a effective component on the surface of the triple extruded sheet prepared in the Example 2. The preparation of the antistatic coating solution comprising a polypyrrole as an effective component and the formation of the antistatic layer were performed as follows. 5 g of polypyrrole doped with iron chloride, 5 g of a mixture solution (Tg: 12 ⁰ C) of self curable polyol and isocianate (6:1), 10 g of toluene, and 10 g of chloroform were mixed to prepare a conductive coating solution, which was then applied on the surface of the sheet prepared in Example 2 and dried at 8O ⁰ C for 2 minutes to form an antistatic layer having a thickness of 1.0 micron

[72] The amorphous polyester sheet with the conductive coating solution coated was examined for its surface resistance by a known method. The coated sheet had a surface resistance of 10 ohm/square and the tray formed by vacuum forming had a good surface resistance of 10 ohm/square. Also, the flat surface and the expanded part showed good light shieldability.

[73] <Example 8>

[74] A conductive polymer was directly polymerized on the surface of the three-layer extruded sheet prepared in Example 2 to form an antistatic layer. 5 pphr of ferric toluene sulfonate as an oxidizing agent and a dopant was dissolved in n-butanol, coated on the sheet of Example 2 and dried at 8O ⁰ C for about 1 minute. The sheet coated with the oxidizing agent and dopant was passed through a closed chamber saturated with vapour of a mixture of 3,4-ethylenedioxythiopene monomer and ethanol at a speed of 2 m/min, followed by washing with ethanol to remove reaction residues to form an antistatic layer.

[75] The resulting sheet had a surface resistance of 10 ohm/square and the tray formed by vacuum forming had a good surface resistance of 10 ohm/square. Also, the flat surface and the expanded part showed good light shieldability.

[76] <Example 9>

[77] An amorphous polyester resin was mixed with 5.0 pphr of titanium oxide having a particle size of 2.0 micrometers and 3.0 pphr of carbon black. Then, the resulting resin

mixture as a middle layer and an amorphous polyester resin without any additive as outer layers at both sides were extruded to a thickness of 0.9 mm using a three-layer extruder. Here, the thickness ratio of the surface layers and the middle layer was 10:80:10.

[78] 4g of poly (3,4-ethylenedioxythiophene) aqueous dispersion, 9 g of urethane binder having a molecular weight of 10,000, 0.01 g of a zonyl additive (DuPont), 0.2 g of ethylene glycol, 0.2 g of l-methyl2-pyrrolidinone, and 0.05 g of titanium oxide having a particle size of 1 micrometer were mixed with 25 g of a solvent mixture of ethyl alcohol and isopropyl alcohol (1:1). The resulting solution was coated on the surface of the sheet to a thickness of 1.0 micrometer and dried at 8O ⁰ C for 2 minutes to prepare an antistatic sheet, which was then formed into a tray for transporting electronic parts by vacuum forming.

[79] The resulting tray had a good surface resistance of 10 ohm/square and showed good light shieldability.

[80] <Example 10>

[81] An amorphous polyester/carbon black mixture of the amorphous polyester resin with 2 pphr of carbon black having an average particle size of 0.05 micrometers was extruded using a twin screw extruder to prepare a sheet having a thickness of 0.9 mm.

[82] 5 g of a doped tin oxide dispersion, 10 g of urethane acrylate dispersion having a molecular weight of 50,000, 0.2 g of ethylene glycol, and 0.2 g of l-methyl2-pyrrolidinone was mixed in 25 g of a solvent mixture of ethyl alcohol and isopropyl alcohol (1:1) to form an antistatic coating solution. The resulting solution was coated on the resulting sheet to a thickness of 1 micrometer after drying at 8O ⁰ C for 2 minutes and then formed into an antistatic carrier container by vacuum forming.

[83] The resulting tray had a good surface resistance of 10 ⁷ ohm/square and showed good light shieldability.

[84] <Example l l>

[85] In this example, a carrier container for electronic part packaging was prepared using the three-layer prepared in Example 2 and made to have antistatic property. 10 g of poly (3,4-ethylenedioxythiophene) aqueous dispersion of a conductive polymer, 1Og of hard coating UV-curable oligomer mixture, 3.5 g of a monomer, 1.5 g of an initiator, and 30 g of a mixture of isopropyl alcohol and ethylene glycol monoethylether (1:1) were mixed together. The carrier container vacuum formed from the sheet prepared in Example 2 was dipped in the resulting solution to form a coating layer, dried in an oven at 6O ⁰ C for 1 minute and UV-cured by applying an energy of 500 mJ/cm under nitrogen purging condition.

[86] The resulting tray had a good surface resistance of 10 ohm/square and showed uniform antistatic effect, and the flat surface and the expanded part showed good light

shielding effect. Also, after rubbing with isopropyl alcohol, the tray did not showed change in surface resistance.

[87] <Example 12>

[88] An amorphous polyester/carbon black mixture of the amorphous polyester resin with 2 pphr of carbon black having an average particle size of 0.05 micrometers was extruded using a twin screw extruder to prepare a sheet having a thickness of 0.9 mm. The resulting sheet was then vacuum formed to prepare a carrier container.

[89] 10 g of poly (3,4-ethylenedioxythiophene) aqueous dispersion of a conductive polymer, 10 g of hard coating UV curable oligomer mixture, 3.5 g of a monomer, 1.5 g of an initiator, 30 g of a mixture of isopropyl alcohol and ethylene glycol mo- noethylether (1:1) and 0.05 g of titanium oxide having a average particle size of 1 micron were mixed together. The vacuum formed carrier container was dipped in the resulting solution to form a coating layer having a thickness of 2 micrometers, dried in an oven at 6O ⁰ C for 2 minutes and UV cured by applying an energy of 500 mJ/cm under nitrogen purging condition.

[90] The resulting tray had a good surface resistance of 10 ohm/square and showed uniform antistatic effect, and the flat surface and the expanded part showed good light shieldability. Also, after rubbing with isopropyl alcohol, the tray did not showed change in surface resistance. Industrial Applicability

[91] According to the present invention, it is possible to prepare various light shielding and antistatic sheets and a container using the sheets. Also, the sheet according to the present invention can be formed into a container itself or used as a part of other container such as one side. Thus, the sheet according to the present invention can be diversely used for light shielding and antistatic effect of electronic parts.