WO2008154231A2 - Antistatic film and article comprising the same - Google Patents

Antistatic film and article comprising the same Download PDF

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Publication number
WO2008154231A2
WO2008154231A2 PCT/US2008/065691 US2008065691W WO2008154231A2 WO 2008154231 A2 WO2008154231 A2 WO 2008154231A2 US 2008065691 W US2008065691 W US 2008065691W WO 2008154231 A2 WO2008154231 A2 WO 2008154231A2
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WO
WIPO (PCT)
Prior art keywords
layer
film
conductive
protective layer
antistatic film
Prior art date
Application number
PCT/US2008/065691
Other languages
French (fr)
Other versions
WO2008154231A3 (en
Inventor
Li Zhang Yang
Zhou Jin
Linlin Zhang
Wei Xiang Zhang
Original Assignee
3M Innovative Properties Company
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Filing date
Publication date
Application filed by 3M Innovative Properties Company filed Critical 3M Innovative Properties Company
Publication of WO2008154231A2 publication Critical patent/WO2008154231A2/en
Publication of WO2008154231A3 publication Critical patent/WO2008154231A3/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B65CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65DCONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D85/00Containers, packaging elements or packages, specially adapted for particular articles or materials
    • B65D85/30Containers, packaging elements or packages, specially adapted for particular articles or materials for articles particularly sensitive to damage by shock or pressure
    • B65D85/38Containers, packaging elements or packages, specially adapted for particular articles or materials for articles particularly sensitive to damage by shock or pressure for delicate optical, measuring, calculating or control apparatus
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04Coating
    • C08J7/042Coating with two or more layers, where at least one layer of a composition contains a polymer binder
    • C08J7/0423Coating with two or more layers, where at least one layer of a composition contains a polymer binder with at least one layer of inorganic material and at least one layer of a composition containing a polymer binder
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04Coating
    • C08J7/043Improving the adhesiveness of the coatings per se, e.g. forming primers
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04Coating
    • C08J7/044Forming conductive coatings; Forming coatings having anti-static properties
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04Coating
    • C08J7/046Forming abrasion-resistant coatings; Forming surface-hardening coatings
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08KUse of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00Use of inorganic substances as compounding ingredients
    • C08K3/02Elements
    • C08K3/04Carbon
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00Adhesives in the form of films or foils
    • C09J7/20Adhesives in the form of films or foils characterised by their carriers
    • C09J7/29Laminated material
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2400/00Characterised by the use of unspecified polymers
    • C08J2400/12Polymers characterised by physical features, e.g. anisotropy, viscosity or electrical conductivity
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08KUse of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00Use of inorganic substances as compounding ingredients
    • C08K3/01Use of inorganic substances as compounding ingredients characterized by their specific function
    • C08K3/017Antistatic agents
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08KUse of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00Use of inorganic substances as compounding ingredients
    • C08K3/02Elements
    • C08K3/04Carbon
    • C08K3/041Carbon nanotubes
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08KUse of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00Use of inorganic substances as compounding ingredients
    • C08K3/18Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20Oxides; Hydroxides
    • C08K3/22Oxides; Hydroxides of metals
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00Additional features of adhesives in the form of films or foils
    • C09J2301/20Additional features of adhesives in the form of films or foils characterized by the structural features of the adhesive itself
    • C09J2301/204Additional features of adhesives in the form of films or foils characterized by the structural features of the adhesive itself the adhesive coating being discontinuous
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00Additional features of adhesives in the form of films or foils
    • C09J2301/40Additional features of adhesives in the form of films or foils characterized by the presence of essential components
    • C09J2301/41Additional features of adhesives in the form of films or foils characterized by the presence of essential components additives as essential feature of the carrier layer
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2400/00Presence of inorganic and organic materials
    • C09J2400/10Presence of inorganic materials
    • C09J2400/16Metal
    • C09J2400/163Metal in the substrate

Definitions

  • the present invention relates to an antistatic film, particularly to a transparent and low contaminative antistatic film used in a cover tape for electronic component packaging.
  • the present invention also relates to an article comprising the film, for example, a cover tape and a system comprising the cover tape, a carrier tape and an optional tape package.
  • the component In the industry of electronic component packaging, the component is generally produced by one manufacturer and then sent to another manufacturer or user for further processing. Using semiconductor chips as an example, after being produced in a factory or a "superclean room,” the chip will be packed and transferred to another manufacturer or a user such as a PC wholesaler, who will then mount the chip on a PC board or other similar devices.
  • Electronic components include mainly, but are not limited to RAM chips, transistors, connectors, DIPS, capacitors, etc.
  • electronic components such as IC chips or capacitors are packed in a carrier tape then delivered to the users.
  • the carrier tape normally has pockets to receive the electronic components. After receiving the electronic component, the pocket will be sealed with a cover tape to form a tape package. During an assembling process, the cover tape of the tape package will be peeled off, and the electronic component will be taken out and surface-mounted onto a circuit substrate, for example.
  • a cover tape must be peeled off readily from a carrier type during the assembling process. If the peel force (also known as peel strength or hot sealing strength) is too low, the tape package could delaminate during transportation and storage. On the other hand, if the peel force is too strong or the variation of the peel force is too big, it will be hard to stably remove the cover tape and the enclosed IC unit might jump out of the pocket in this case too. Antistatic property is another key property because the static could damage the electronic units, and could cause difficulties in the process. Transparency of the cover tape is also important because the status of the electronic component may need to be checked through the cover tape. Finally, the cover tape should not contaminate the electronic component.
  • cover tapes There are generally two types of cover tapes. One is pressure sensitive adhesive (PSA), and the other is heat activated adhesive (HAA).
  • PSA pressure sensitive adhesive
  • HAA heat activated adhesive
  • conductive properties may be obtained by adding a conductive agent in the heat activated adhesive or on the surface of the adhesive layer.
  • the conductive agent is inorganic conductive filler, which is added to the adhesive layer to achieve conductive properties along the XY directions.
  • a large amount of fillers (30% or more in general) needs to be added due to the Percolation theory.
  • the antistatic property can be obtained by using conductive polymers such as polypyrrole, polyaniline and so on, or by adding antistatic agents such as quaternary ammonium salts, aliphatic sulfonate salts and so on.
  • conductive polymers such as polypyrrole, polyaniline and so on
  • antistatic agents such as quaternary ammonium salts, aliphatic sulfonate salts and so on.
  • An exemplary method is disclosed in U.S. Patent No. 5,064,064.
  • Another approach to achieve conductive properties, as reported in U.S. Patent No. 6,027,802 is by evaporation or sputtering a metal on a base film. The film can have good static dissipative properties, but without a protective top coat the metal will be easily peeled off from the base film. These peeled metal flakes would be a big threat for the IC units.
  • U.S. Patent No. 5,441,809 reports a transparent static dissipative cover tape, which is composed of a biaxially oriented base film, a vacuum deposited metal conductive layer, and a heat sealing adhesive layer, wherein antiblock microspheres and conductive fillers have been added into the heat sealing adhesive layer.
  • the invention solves the problem of humidity sensitivity and provides good protection for the metal layer.
  • the transparency of the cover tape is poor due to the large amount of the conductive fillers, making it difficult to monitor the electronic components through the tape.
  • the heat sensitive adhesive layer therein may contaminate the electronic components.
  • present invention provides an antistatic film, especially an antistatic film suitable for a cover tape which comprising: a base film; a conductive layer on the top of one surface of the base film to provide conductivity; and a protective layer on the top of the conductive layer to protect the conductive layer, wherein the protective layer contains a film-forming polymer and particles for inhibiting the decrease of surface conductivity due to the protective coating layer. At least some of the particles have a particle diameter larger than the thickness of the protective layer.
  • Another aspect of the present invention is to provide an article comprising the antistatic film according to the present invention.
  • the examples of the articles include, but not limited to, a cover tape, a system comprising a cover tape, a carrier tape and an optional tape package.
  • Figure 1 is a cross-section view of an antistatic film of the present invention.
  • Figure 2 is a cross-section view of a cover tape according to one embodiment of the present invention.
  • Figure 3 is a cross-section view of a cover tape according to another embodiment of the present invention.
  • FIG 4 is a perspective view of an article according to an embodiment of the present invention (a carrier tape/cover tape system) used for electronic component packaging, illustrating the cover tape being detached from the system.
  • a particle used for inhibiting the decrease of surface conductivity of the film means any particle capable of reducing the decrease in the surface resistivity caused by the protective layer.
  • Such particle can be inorganic or organic, conductive or nonconductive, metallic or nonmetallic.
  • the present invention provides an antistatic film which may be transparent, may have a low haziness, and can be either conductive or static dissipative.
  • the film can be used to produce a cover tape. Furthermore, it can be made into packaging bags for static dissipation applications.
  • the film of the present invention comprises a base film, a conductive layer, and a protective layer.
  • the base film can be produced with any materials, as long as the material is relatively transparent and has superior mechanical strength. Suitable material includes, but is not limited to polypropylene, polyethylene, polycarbonate, celluloid, nylon, etc. Most preferably, the material is a plastic film which can be easily torn off, such as Biaxially Oriented Polypropylene (BOPP). Although not preferred, polyesters can also be used in the present invention. There is no limitation on the thickness of the base film. The transparent base film is preferred to produce cover tape.
  • the conductive layer is disposed on one surface of the base film (the other surface of the film is optionally coated with a releasing agent).
  • the conductive layer is made of materials with conductive property, which can be a metal layer or a metal oxide layer. Metals often used for this purpose include nickel chrome alloy, aluminum, etc., and metal oxides often used for this purpose include indium-tin oxide, doped tin oxide, magnesium oxide, etc.
  • the layer can be formed by ways of evaporation, sputtering, or coating.
  • the conductive layer can also be formed of a conductive polymer (such as poly (3,4-ethylenedioxythiophene) poly(styrene sulfonate) available under the trade designation CLEVIOS P (formerly BAYTRON P) from H.C. Starck, Inc., Newton, MA) or a polymer material filled with conductive particles such as carbon black, carbon nanotube, metal powders, metal oxides, etc.
  • a conductive polymer such as poly (3,4-ethylenedioxythiophene) poly(styrene sulfonate) available under the trade designation CLEVIOS P (formerly BAYTRON P) from H.C. Starck, Inc., Newton, MA) or a polymer material filled with conductive particles such as carbon black, carbon nanotube, metal powders, metal oxides, etc.
  • the surface conductivity of the layer is preferably 1 x 10 10 Q/ square or less, more preferably IxIO 7 Q/ square, and most preferably IxIO 5 Q/
  • the protective layer is disposed on the surface of the conductive layer opposite to the base film so as to provide mechanical protection to the conductive layer which is easily scratched off.
  • the protective layer should not reduce the conductivity of the overall structure of the film too significantly, so that the film will still maintain the desired antistatic properties. Accordingly, the protective layer should contain particles used for inhibiting the decrease of surface conductivity of the film (simply referred to as "particle" herein).
  • the thickness of the protective layer is preferably not higher than 12 ⁇ m, more preferably not higher than 10 ⁇ m, further more preferably not higher than 5 ⁇ m (e.g., 0.1-5 ⁇ m), even more preferably not higher than 2 ⁇ m, and most preferably, 0.3-1 ⁇ m.
  • the particles used for inhibiting the decrease of surface conductivity of the film are in the form of fine powder, and there is no particular limitation on the shape and structure of the particles. They can be fine powder, laminar, branches, filaments, fine powder is preferred for this application.
  • the particle used for inhibiting the decrease of surface conductivity of the film is selected from metal particles, carbon black, carbon nanotube, conductive or semi-conductive polymer particles, polymer particles coated with conductive or semi-conductive material, metal oxides (such as titanium dioxide, zinc oxide and the like) particles, and the various mixtures thereof.
  • the diameter of at least some of the particles used for inhibiting the decrease of surface conductivity of the film is larger than the thickness of the protective layer so as to make it easy to form a conductive pathway along the Z direction from the metal layer to the protective layer (i.e., the direction perpendicular to the surface of the cover tape).
  • the particles can also function as antiblock particles (as shown in figure 3).
  • the protective layer further contains a film-forming polymer.
  • the polymer which can be polyurethanes, epoxy polymers, acrylic polymers, etc.
  • the D50 diameter of the particles used for inhibiting the decrease of surface conductivity of the film added in the protective layer is recommended as 50 ⁇ m or less, preferably 0.1-15 ⁇ m; and most preferably 0.5-10 ⁇ m.
  • the percentage by weight of the particles used for inhibiting the decrease of surface conductivity of the film is recommended as 30% or less, preferably 0.1-5%, and most preferably 0.3-2%. The reason for that is: Generally, the addition of a relatively low amount of fillers will result in a better film transparency and lower haziness.
  • a certain amount (more than 0.0001%, and preferably, 0.001% of the protective film weight) of the particles used for inhibiting the decrease of surface conductivity of the film have a diameter larger than the thickness of the protective layer which can provide conductivity along the Z direction and thus confer static dissipative or conductive property to the cover tape.
  • the transparent and low contaminative antistatic film according to the present invention has a preferred surface resistance of 1 x 10 4 - IxIO 12 Q/ square. When a higher requirement for conductivity applies, the surface resistance of the film should be less than IxIO 7 Q/ square.
  • antiblock particles can also be added into the protective layer.
  • the antiblock particles and the particles used for inhibiting the decrease of surface conductivity of the film can be the same or different.
  • Substances which can be used for this purpose include, but are not limited to, silicon dioxide, titanium dioxide, carbon black, metal powders, and polymer microspheres, etc.
  • the diameter of the antiblock particles is preferably in the range of 0-15 ⁇ m, and the percentage by weight of the particles preferably accounts for 0-5% of the protective layer.
  • the surface resistivity of a sample is measured by using a CS-5 grinding wheel after being rubbed a certain number of cycles. The sample is considered as failing at the certain cycle when the surface resistivity is higher than IxIO 13 Q/ square.
  • Test apparatus Trek 152 resistance meter Manufacturer: TREK, INC.
  • the surface resistivity is measured according to ESD S 11.11 standard test method under normal temperature and normal humidity: Adjust the test voltage to an appropriate value (10V or 100V), A 152P-CR-CE-EX probe is applied continuously on the surface of the film, and a surface resistivity value will be shown on the LCD screen of the meter.
  • the unit measure of surface resistivity is ⁇ / square.
  • the samples are placed into an aging chamber with a temperature of 52°C and a humidity of 95% RH. After aging for one, two, three and four weeks, the surface resistivity is tested.
  • the particle diameter of silicon dioxide is D50 particle diameter (D50 particle diameter is also called as "median particle diameter” and often used for representing the particle diameter of powder), and the data is provided by the supplier.
  • the particle diameters of silicon dioxide and carbon black are average particle diameter, which are determined by a scraper fineness gauge. Materials:
  • Titanium dioxide from PPG Coating (Tianjin) Ltd., Tianjin, China; and Silicon dioxide, from Degussa (China) Investment Ltd., Shanghai, China.
  • a BOPP film with a thickness of 50 ⁇ m has a light transmittance of about 70% and a surface resistivity of l ⁇ 10 3 ⁇ / square - IxIO 4 ⁇ / square.
  • a polyurethane layer with a thickness of 0.3 to 1.5 ⁇ m was coated to the metal-plated side.
  • the polyurethane layer contains 0.3% to 3% particles used for inhibiting the decrease of surface conductivity of the film.
  • FIG. 1 is a cross-section view of a transparent and low contaminative antistatic film 1 of the present invention.
  • Base film 2 is a Biaxially Oriented BOPP film (which can also be polypropylene, polyethylene, polycarbonate, celluloid, nylon, polyester, etc.).
  • Conductive layer 3 is disposed on one surface of base film 2.
  • the conductive layer 3 is a metal layer (which can also be a metal oxide layer), which is made by vapor coating or sputtering process.
  • Protective layer 4 is disposed on the other surface of conductive layer 3 opposite to the base film to provide mechanical protection for the conductive layer 3.
  • Protective layer 4 contains particles 5 used for inhibiting the decrease of surface conductivity of the film and used for providing conductivity along the Z direction.
  • This film is highly transparent, low contaminative, wear resistant, and permanently antistatic.
  • Example 2 Figure 2 is a cross-section view of cover tape 6 according to one embodiment of the present invention.
  • Cover tape 6 comprises base film 2, conductive layer 3, protective layer 4, release coating layer 7, and strip shaped adhesive layer 8.
  • Base film 2 is a Biaxially Oriented BOPP film with a thickness of 50 ⁇ m.
  • Conductive layer 3 is a metal layer, which is disposed on one surface of base film 2.
  • Protective layer 4 is disposed on the other surface of conductive layer 3 opposite to the base film to provide mechanical protection for the conductive layer 3.
  • Protective layer 4 is a polyurethane coating layer, which contains particles 5 used for inhibiting the decrease of surface conductivity of the film and used to provide conductivity along the Z direction.
  • Protective layer 4 further contains antiblock fillers 9. Antiblock fillers 9 and particles 5 can be the same (see figure 3) or different (see figure 2).
  • Strip shaped adhesive layer 8 is coated at the outside of protective layer 4 opposite to conductive layer 3, wherein the adhesive can be either pressure sensitive adhesives (PSA) or heat activated adhesives (HAA).
  • PSA pressure sensitive adhesives
  • HAA heat activated adhesives
  • the other surface of base film 2 opposite to conductive layer 3 is coated with release coating 7.
  • Tear enabling features 10 and 11 are parallel to the direction of strip shaped adhesive 8. When taking out a component, the operator can remove cover tape 6 by tearing apart the middle part of the tape between tear enabling features 10 and 11.
  • Cover tape 6 of the present invention can be applied in carrier tape /cover tape system 14 used for electronic component packaging.
  • Figure 4 is a perspective view of carrier tape/cover tape system 14 containing carrier tape 15 and cover tape 6.
  • Carrier tape 15 has a pair of opposed elongate lip portions 16, and one or more pockets 17.
  • Components 18, such as electronic components, can be placed in the pockets 17.
  • cover tape 6 can be adhered to elongate lip portions 16 in order to cover the pockets 17.
  • components 18 are contained between carrier tape 15 and cover tape 6.
  • the central portion 13 of cover tape 6 needs to be removed from carrier tape/cover tape system 14.
  • central portion 13 of cover tape 6 (between two tear enabling features 12) was separated from the system 14. Outer portions 19 of cover tape 6 remain adhered to carrier tape 15 after the central portion 13 was torn away. The central portion 13 can be wound into a roll for discard or recycling.
  • the coated film was placed in a 100 0 C oven 15 minutes for sufficient crosslinking of the polyurethane.
  • the dry thickness of the polyurethane coating was in the range of 0.9 - 1.0 ⁇ m, the surface resistivity of the coated film was in the range of 1 x 10 6 - 1 x 10 8 ⁇ / square.
  • the antistatic film and its articles of the present invention have many advantages.
  • the antistatic property of this kind of cover tape will not decrease even under low humidity environments.
  • the protective layer is abrasive resistant, therefore it can provide superior protection for the conductive layer.
  • the conductive layer is protected by the coating layer of the cover tape and the conductive pathway provided by the conductive particles is within the protective coating layer, while the adhesive layer is disposed on the two sides of the cover tape, rather than the center part thereof, thus, no matter whether a pressure sensitive or a heat sensitive adhesive layer is used, the cover tape will not cause contamination to the electronic components.
  • the protective layer according to the present invention can be made very thin, the particle diameter of the filled particles is small and the particle content is low.
  • the film has high light transmittance (the light transmittance can be more than 40%, usually more than 60%.
  • the haze can be less than 30%, and usually less than 10%). Therefore, the cover tape made with the film of the present invention possesses superior overall properties.
  • the cover tape not only meets the optical and electrical requirements, but also has the advantages of insensitive to humidity, stable for peeling force, free of contamination and quality controllable.

Abstract

An antistatic film and an article comprising the same. The film comprising: a base film; a conductive layer disposed on one surface of the base film; a protective layer disposed on the surface of the conductive layer opposite to the base film to protect the conductive layer, wherein the protective layer contains a particle used for inhibiting the decrease of surface conductivity of the film and a film-forming polymer, wherein at least a part of the particle has a particle diameter larger than the thickness of the protective layer.

Description

ANTISTATIC FILM AND ARTICLE COMPRISING THE SAME
TECHNICAL FIELD
The present invention relates to an antistatic film, particularly to a transparent and low contaminative antistatic film used in a cover tape for electronic component packaging. The present invention also relates to an article comprising the film, for example, a cover tape and a system comprising the cover tape, a carrier tape and an optional tape package.
BACKGROUND
In the industry of electronic component packaging, the component is generally produced by one manufacturer and then sent to another manufacturer or user for further processing. Using semiconductor chips as an example, after being produced in a factory or a "superclean room," the chip will be packed and transferred to another manufacturer or a user such as a PC wholesaler, who will then mount the chip on a PC board or other similar devices. Electronic components include mainly, but are not limited to RAM chips, transistors, connectors, DIPS, capacitors, etc. In recent years, electronic components such as IC chips or capacitors are packed in a carrier tape then delivered to the users. The carrier tape normally has pockets to receive the electronic components. After receiving the electronic component, the pocket will be sealed with a cover tape to form a tape package. During an assembling process, the cover tape of the tape package will be peeled off, and the electronic component will be taken out and surface-mounted onto a circuit substrate, for example.
A cover tape must be peeled off readily from a carrier type during the assembling process. If the peel force (also known as peel strength or hot sealing strength) is too low, the tape package could delaminate during transportation and storage. On the other hand, if the peel force is too strong or the variation of the peel force is too big, it will be hard to stably remove the cover tape and the enclosed IC unit might jump out of the pocket in this case too. Antistatic property is another key property because the static could damage the electronic units, and could cause difficulties in the process. Transparency of the cover tape is also important because the status of the electronic component may need to be checked through the cover tape. Finally, the cover tape should not contaminate the electronic component.
There are generally two types of cover tapes. One is pressure sensitive adhesive (PSA), and the other is heat activated adhesive (HAA). For HAA cover tape, conductive properties may be obtained by adding a conductive agent in the heat activated adhesive or on the surface of the adhesive layer. One example for the conductive agent is inorganic conductive filler, which is added to the adhesive layer to achieve conductive properties along the XY directions. However, in order to obtain this conductive property, a large amount of fillers (30% or more in general) needs to be added due to the Percolation theory.
This will greatly reduce the light transmittance of the tape. An exemplary method is disclosed in U.S. Patent No. 5,208,103.
For pressure sensitive cover tape, the antistatic property can be obtained by using conductive polymers such as polypyrrole, polyaniline and so on, or by adding antistatic agents such as quaternary ammonium salts, aliphatic sulfonate salts and so on. However, the antistatic property of this kind of cover tape is sensitive to humidity of the environment and can easily contaminate electronic components. An exemplary method is disclosed in U.S. Patent No. 5,064,064. Another approach to achieve conductive properties, as reported in U.S. Patent No. 6,027,802, is by evaporation or sputtering a metal on a base film. The film can have good static dissipative properties, but without a protective top coat the metal will be easily peeled off from the base film. These peeled metal flakes would be a big threat for the IC units.
U.S. Patent No. 5,441,809 reports a transparent static dissipative cover tape, which is composed of a biaxially oriented base film, a vacuum deposited metal conductive layer, and a heat sealing adhesive layer, wherein antiblock microspheres and conductive fillers have been added into the heat sealing adhesive layer. The invention solves the problem of humidity sensitivity and provides good protection for the metal layer. However, the transparency of the cover tape is poor due to the large amount of the conductive fillers, making it difficult to monitor the electronic components through the tape. Moreover, the heat sensitive adhesive layer therein may contaminate the electronic components.
Therefore, present invention provides an antistatic film, especially an antistatic film suitable for a cover tape which comprising: a base film; a conductive layer on the top of one surface of the base film to provide conductivity; and a protective layer on the top of the conductive layer to protect the conductive layer, wherein the protective layer contains a film-forming polymer and particles for inhibiting the decrease of surface conductivity due to the protective coating layer. At least some of the particles have a particle diameter larger than the thickness of the protective layer. Another aspect of the present invention is to provide an article comprising the antistatic film according to the present invention. The examples of the articles include, but not limited to, a cover tape, a system comprising a cover tape, a carrier tape and an optional tape package.
The above general description is not used to describe each embodiment of the invention. Exemplary embodiments of the invention will be discussed in detail with reference to the following drawings and accompanying specification.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross-section view of an antistatic film of the present invention.
Figure 2 is a cross-section view of a cover tape according to one embodiment of the present invention. Figure 3 is a cross-section view of a cover tape according to another embodiment of the present invention.
Figure 4 is a perspective view of an article according to an embodiment of the present invention (a carrier tape/cover tape system) used for electronic component packaging, illustrating the cover tape being detached from the system. Although some preferred embodiments of the present invention have been described here, other unspecified embodiments are intended to be covered within the scope of this invention. In all cases, these figures are merely illustrative and are not intended to limit the invention. Further modification of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention. It should be understood that the figures are drawn not in proportion, and the same reference sign represents similar parts throughout the specification.
DETAILED DESCRIPTION
Unless stated otherwise, the term "a particle used for inhibiting the decrease of surface conductivity of the film" means any particle capable of reducing the decrease in the surface resistivity caused by the protective layer. Such particle can be inorganic or organic, conductive or nonconductive, metallic or nonmetallic.
The present invention provides an antistatic film which may be transparent, may have a low haziness, and can be either conductive or static dissipative. The film can be used to produce a cover tape. Furthermore, it can be made into packaging bags for static dissipation applications.
The film of the present invention comprises a base film, a conductive layer, and a protective layer.
The base film can be produced with any materials, as long as the material is relatively transparent and has superior mechanical strength. Suitable material includes, but is not limited to polypropylene, polyethylene, polycarbonate, celluloid, nylon, etc. Most preferably, the material is a plastic film which can be easily torn off, such as Biaxially Oriented Polypropylene (BOPP). Although not preferred, polyesters can also be used in the present invention. There is no limitation on the thickness of the base film. The transparent base film is preferred to produce cover tape.
The conductive layer is disposed on one surface of the base film (the other surface of the film is optionally coated with a releasing agent). The conductive layer is made of materials with conductive property, which can be a metal layer or a metal oxide layer. Metals often used for this purpose include nickel chrome alloy, aluminum, etc., and metal oxides often used for this purpose include indium-tin oxide, doped tin oxide, magnesium oxide, etc. The layer can be formed by ways of evaporation, sputtering, or coating. The conductive layer can also be formed of a conductive polymer (such as poly (3,4-ethylenedioxythiophene) poly(styrene sulfonate) available under the trade designation CLEVIOS P (formerly BAYTRON P) from H.C. Starck, Inc., Newton, MA) or a polymer material filled with conductive particles such as carbon black, carbon nanotube, metal powders, metal oxides, etc. The surface conductivity of the layer is preferably 1 x 1010 Q/ square or less, more preferably IxIO7 Q/ square, and most preferably IxIO5 Q/ square.
The protective layer is disposed on the surface of the conductive layer opposite to the base film so as to provide mechanical protection to the conductive layer which is easily scratched off. The protective layer should not reduce the conductivity of the overall structure of the film too significantly, so that the film will still maintain the desired antistatic properties. Accordingly, the protective layer should contain particles used for inhibiting the decrease of surface conductivity of the film (simply referred to as "particle" herein). The thickness of the protective layer is preferably not higher than 12 μm, more preferably not higher than 10 μm, further more preferably not higher than 5μm (e.g., 0.1-5 μm), even more preferably not higher than 2 μm, and most preferably, 0.3-1 μm. The particles used for inhibiting the decrease of surface conductivity of the film are in the form of fine powder, and there is no particular limitation on the shape and structure of the particles. They can be fine powder, laminar, branches, filaments, fine powder is preferred for this application. The particle used for inhibiting the decrease of surface conductivity of the film is selected from metal particles, carbon black, carbon nanotube, conductive or semi-conductive polymer particles, polymer particles coated with conductive or semi-conductive material, metal oxides (such as titanium dioxide, zinc oxide and the like) particles, and the various mixtures thereof. Preferably, the diameter of at least some of the particles used for inhibiting the decrease of surface conductivity of the film is larger than the thickness of the protective layer so as to make it easy to form a conductive pathway along the Z direction from the metal layer to the protective layer (i.e., the direction perpendicular to the surface of the cover tape). Meanwhile, the particles can also function as antiblock particles (as shown in figure 3). The protective layer further contains a film-forming polymer. There is no particular limitation on the types and contents of the polymer, which can be polyurethanes, epoxy polymers, acrylic polymers, etc.
The D50 diameter of the particles used for inhibiting the decrease of surface conductivity of the film added in the protective layer is recommended as 50 μm or less, preferably 0.1-15 μm; and most preferably 0.5-10 μm. The percentage by weight of the particles used for inhibiting the decrease of surface conductivity of the film is recommended as 30% or less, preferably 0.1-5%, and most preferably 0.3-2%. The reason for that is: Generally, the addition of a relatively low amount of fillers will result in a better film transparency and lower haziness. Preferably, a certain amount (more than 0.0001%, and preferably, 0.001% of the protective film weight) of the particles used for inhibiting the decrease of surface conductivity of the film have a diameter larger than the thickness of the protective layer which can provide conductivity along the Z direction and thus confer static dissipative or conductive property to the cover tape.
There is no particular limitation on the contents of the particles used for inhibiting the decrease of surface conductivity of the film and the film- forming polymers in the protection layer, as long as the combination can provide conductivity along the Z direction and therefore confer the thin film static dissipative or conductive property.
The transparent and low contaminative antistatic film according to the present invention has a preferred surface resistance of 1 x 104 - IxIO12 Q/ square. When a higher requirement for conductivity applies, the surface resistance of the film should be less than IxIO7 Q/ square.
In addition to particles used for inhibiting the decrease of surface conductivity of the film, antiblock particles can also be added into the protective layer. The antiblock particles and the particles used for inhibiting the decrease of surface conductivity of the film can be the same or different. Substances which can be used for this purpose include, but are not limited to, silicon dioxide, titanium dioxide, carbon black, metal powders, and polymer microspheres, etc. The diameter of the antiblock particles is preferably in the range of 0-15 μm, and the percentage by weight of the particles preferably accounts for 0-5% of the protective layer.
The invention will be illustrated in detail with reference to the drawings and preferred embodiments.
Test methods:
1. Abrasive test: Test apparatus: Taber Abraser 5130
Manufacturer: Taber Industries
The surface resistivity of a sample is measured by using a CS-5 grinding wheel after being rubbed a certain number of cycles. The sample is considered as failing at the certain cycle when the surface resistivity is higher than IxIO13 Q/ square. 2. Surface resistivity test:
Test apparatus: Trek 152 resistance meter Manufacturer: TREK, INC.
The surface resistivity is measured according to ESD S 11.11 standard test method under normal temperature and normal humidity: Adjust the test voltage to an appropriate value (10V or 100V), A 152P-CR-CE-EX probe is applied continuously on the surface of the film, and a surface resistivity value will be shown on the LCD screen of the meter. The unit measure of surface resistivity is Ω/ square.
3. Film thickness control:
The thickness of the coating layer is measured by weight gain method. Cut off a piece of film with a fixed size (area S), weigh it (Wo), then coat it with a coating and weigh it again (Wi). The thickness (T) of the coating layer was measured with the following equation by the weight gain (ΔW= Wi- Wo), the sample area (S) and the average density of the coating layer (D):
(W1-W0)
T= D*S 4. Aging test:
The samples are placed into an aging chamber with a temperature of 52°C and a humidity of 95% RH. After aging for one, two, three and four weeks, the surface resistivity is tested.
Note: Unless otherwise specified, all concentrations in the present invention refer to mass percentage concentrations. The particle diameter of silicon dioxide is D50 particle diameter (D50 particle diameter is also called as "median particle diameter" and often used for representing the particle diameter of powder), and the data is provided by the supplier. The particle diameters of silicon dioxide and carbon black are average particle diameter, which are determined by a scraper fineness gauge. Materials:
Two-component polyurethane, from Bayer Material Science & Technology Trade (Shanghai) Ltd., Shanghai, China;
Carbon black, from Nippon Coating (China) Ltd., Shanghai, China;
Titanium dioxide, from PPG Coating (Tianjin) Ltd., Tianjin, China; and Silicon dioxide, from Degussa (China) Investment Ltd., Shanghai, China.
Preparation example :
After metallization treatment, A BOPP film with a thickness of 50 μm has a light transmittance of about 70% and a surface resistivity of lχ103 Ω/ square - IxIO4 Ω/ square. A polyurethane layer with a thickness of 0.3 to 1.5 μm was coated to the metal-plated side. The polyurethane layer contains 0.3% to 3% particles used for inhibiting the decrease of surface conductivity of the film.
EXAMPLES
Example 1
Figure 1 is a cross-section view of a transparent and low contaminative antistatic film 1 of the present invention. Base film 2 is a Biaxially Oriented BOPP film (which can also be polypropylene, polyethylene, polycarbonate, celluloid, nylon, polyester, etc.). Conductive layer 3 is disposed on one surface of base film 2. The conductive layer 3 is a metal layer (which can also be a metal oxide layer), which is made by vapor coating or sputtering process. Protective layer 4 is disposed on the other surface of conductive layer 3 opposite to the base film to provide mechanical protection for the conductive layer 3. Protective layer 4 contains particles 5 used for inhibiting the decrease of surface conductivity of the film and used for providing conductivity along the Z direction. This film is highly transparent, low contaminative, wear resistant, and permanently antistatic.
Example 2 Figure 2 is a cross-section view of cover tape 6 according to one embodiment of the present invention.
Cover tape 6 comprises base film 2, conductive layer 3, protective layer 4, release coating layer 7, and strip shaped adhesive layer 8. Base film 2 is a Biaxially Oriented BOPP film with a thickness of 50 μm. Conductive layer 3 is a metal layer, which is disposed on one surface of base film 2. Protective layer 4 is disposed on the other surface of conductive layer 3 opposite to the base film to provide mechanical protection for the conductive layer 3. Protective layer 4 is a polyurethane coating layer, which contains particles 5 used for inhibiting the decrease of surface conductivity of the film and used to provide conductivity along the Z direction. Protective layer 4 further contains antiblock fillers 9. Antiblock fillers 9 and particles 5 can be the same (see figure 3) or different (see figure 2). Strip shaped adhesive layer 8 is coated at the outside of protective layer 4 opposite to conductive layer 3, wherein the adhesive can be either pressure sensitive adhesives (PSA) or heat activated adhesives (HAA). The other surface of base film 2 opposite to conductive layer 3 is coated with release coating 7. Tear enabling features 10 and 11 are parallel to the direction of strip shaped adhesive 8. When taking out a component, the operator can remove cover tape 6 by tearing apart the middle part of the tape between tear enabling features 10 and 11.
Example 3 :
Cover tape 6 of the present invention can be applied in carrier tape /cover tape system 14 used for electronic component packaging. Figure 4 is a perspective view of carrier tape/cover tape system 14 containing carrier tape 15 and cover tape 6. Carrier tape 15 has a pair of opposed elongate lip portions 16, and one or more pockets 17. Components 18, such as electronic components, can be placed in the pockets 17. After the components 18 have been placed in the pockets 17 of carrier tape 15, cover tape 6 can be adhered to elongate lip portions 16 in order to cover the pockets 17. Thus, components 18 are contained between carrier tape 15 and cover tape 6. In order to expose and remove the components 18, the central portion 13 of cover tape 6 needs to be removed from carrier tape/cover tape system 14. As shown in figure 4, central portion 13 of cover tape 6 (between two tear enabling features 12) was separated from the system 14. Outer portions 19 of cover tape 6 remain adhered to carrier tape 15 after the central portion 13 was torn away. The central portion 13 can be wound into a roll for discard or recycling.
Example 4 :
0.3% SiO2 with 0-5 μm average particle diameters was added into 50% polyurethane solution and sufficiently stirred. The uniform solution was coated to the Aluminum (Al) vapor coated BOPP film which has surface resistivity of 1 x 106 Ω/ square.
The coated film was placed in a 1000C oven 15 minutes for sufficient crosslinking of the polyurethane. The dry thickness of the polyurethane coating was in the range of 0.9 - 1.0 μm, the surface resistivity of the coated film was in the range of 1 x 106 - 1 x 108 Ω/ square.
After one month aging in the aging chamber with the temperature of 52°C and 95% RH, the surface resistivity was reduced to 1 x 109 - 1 x 1012 Ω/ square. The abrasive tests were passed for 300 cycles.
Example 5 :
0.6% SiO2 with 0-6 μm average particle diameters and 0.3% carbon black with 0-5 μm average particle diameters were added into 50% polyurethane solution and sufficiently stirred. The uniform solution was coated to the Al vapor coated BOPP film which has surface resistivity of 1 x 106 Ω/ square. The coated film was allowed to pass through a six-meter long oven under 1000C with a speed of 10 meters/minute for sufficient crosslinking of the polyurethane. The dry thickness of the polyurethane coating layer was in the range of 1.0 and 1.2 μm, and the surface resistivity of the coated film was in the range of 1 x 107 - IxIO9 Q/ square. After one month aging in the aging chamber with the temperature of 52°C and 95% RH, the surface resistivity was reduced to 1 x 107 - 1 x 1010 Ω/ square. The abrasive tests were passed for 300 cycles.
Example 6 :
0.6% SiO2 with 0-6 μm average particle diameters was added into 50% polyurethane solution and sufficiently stirred. The uniform solution was coated to the Al vapor coated BOPP film which has surface resistivity of 1 χ 106 Ω/ square. The coated film was allowed to pass through a six-meter long oven under 1000C with a speed of 10 meters/minute for sufficient crosslinking of the polyurethane. The dry thickness of the polyurethane coating layer was in the range of 1.0 and 1.2 μm, and the surface resistivity of the film was in the range of 1 χ 107 - 1 x 1010 Ω/ square. After one month aging in the aging chamber with the temperature of 52°C and 95% RH, the surface resistivity was reduced to 1 χ 107 - 1 χ 1011 Ω/ square. The abrasive tests were passed 300 cycles.
Example 7 :
2% carbon black with 5-10 μm average particle diameters was added into 50% polyurethane solution and sufficiently stirred. The uniform solution was coated to the Al vapor coated BOPP film which has surface resistivity of 1 χ 106 Ω/ square. The coated film was allowed to pass through a six-meter long oven under 1000C with a speed of 10 meters/minute for sufficient crosslinking of the polyurethane. The dry thickness of the polyurethane coating layer was in the range of 1.0 and 1.2 μm, and the surface resistivity of the film was in the range of 1 χ 107 - 1 x 109 Ω/ square. After one month aging in the aging chamber with the temperature of 52°C and 95% RH, the surface resistivity was reduced to 1 χ 107 - 1 χ 1010 Ω/ square. The abrasive tests were passed for 500 cycles.
Example 8 :
2% SiO2 with 0-6 μm average particle diameters and 0.6% carbon black with 0-5 μm average particle diameters were added into 50% polyurethane solution and sufficiently stirred. The uniform solution was coated to the Al vapor coated BOPP film which has surface resistivity of 1 χ 106 Ω/ square. The coated film was allowed to pass through a six-meter long oven under 1000C with a speed of 10 meters/minute for sufficient crosslinking of the polyurethane. The dry thickness of the polyurethane coating layer was in the range of 0.9 and 1.2 μm, and the surface resistivity of the film was in the range of 1 x 107 - 1 x 109 Ω/ square. After one month aging in the aging chamber with the temperature of 52°C and 95% RH, the surface resistivity was reduced to 1 x 107 - 1 x 1010 Ω/ square. The abrasive tests were passed for 300 cycles.
As described above, the antistatic film and its articles of the present invention, such as cover tape, have many advantages. For instance, the antistatic property of this kind of cover tape will not decrease even under low humidity environments. The protective layer is abrasive resistant, therefore it can provide superior protection for the conductive layer. Especially, the conductive layer is protected by the coating layer of the cover tape and the conductive pathway provided by the conductive particles is within the protective coating layer, while the adhesive layer is disposed on the two sides of the cover tape, rather than the center part thereof, thus, no matter whether a pressure sensitive or a heat sensitive adhesive layer is used, the cover tape will not cause contamination to the electronic components. In addition, the protective layer according to the present invention can be made very thin, the particle diameter of the filled particles is small and the particle content is low. Accordingly, the film has high light transmittance (the light transmittance can be more than 40%, usually more than 60%. The haze can be less than 30%, and usually less than 10%). Therefore, the cover tape made with the film of the present invention possesses superior overall properties. The cover tape not only meets the optical and electrical requirements, but also has the advantages of insensitive to humidity, stable for peeling force, free of contamination and quality controllable.
Although some preferred embodiments and examples of the present invention have been described herein, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims

What is claimed is:
1. An antistatic film, comprising: a base film; and a conductive layer, which is disposed on one surface of the base film to provide electrical conductivity; and a protective layer, which is disposed on the surface of the conductive layer opposite to the base film to protect the conductive layer, wherein the protective layer contains a film-forming polymer and a sort of particle used for inhibiting the decrease of surface conductivity of the film, wherein at least some of the particles have a particle diameter larger than the thickness of the protective layer.
2. The antistatic film according to claim 1, wherein the surface resistivity of the film is in the range of 1 x 104 Ω/ square to 1 x 1011 Ω/ square.
3. The antistatic film according to claim 1, wherein the thickness of the protective layer is no larger than 12 μm.
4. The antistatic film according to claim 1, wherein the part of the particles having a particle diameter larger than the thickness of the protective comprises 0.0001 wt% or more of the protective layer.
5. The antistatic film according to claim 1, wherein the particle is selected from the group consisting of metal particles, carbon black, carbon nano-tube, conductive or semi-conductive polymer particles, polymer particles coated with conductive or semi-conductive materials, metal oxide particles, and the mixtures thereof.
6. The antistatic film according to claim 1, wherein the content of the particle used for inhibiting the decrease of surface conductivity of the film is 30wt% or less based on the total weight of the protective layer.
7. The antistatic film according to claim 1, wherein the protective layer further comprises an antiblock particle.
8. The antistatic film according to claim 1, wherein the conductive layer is selected from the group consisting of a metal layer, a metal oxide layer, and a conductive polymer layer.
9. The antistatic film according to claim 1, wherein the conductive layer is a layer of polymer material filled with particles selected from a group consisting of carbon black, carbon nanotube, metal powders, metal oxides and the mixtures thereof.
10. The antistatic film according to claim 1, wherein the surface resistivity of the conductive layer is 1 x 1010 Ω/ square or less.
11. The antistatic film according to claim 1 , wherein the film- forming polymer is selected from a group consisting of polyurethane, epoxy resin, acrylic resin and mixtures thereof.
12. The antistatic film according to claim 1, wherein the diameter of the particle used for inhibiting the decrease of surface conductivity of the film is 50μm or less.
13. An article comprising the antistatic film according to claim 1.
14. The article according to claim 13, wherein the article is a cover tape.
15. The article according to claim 14, further comprising: an adhesive layer adjacent to the longitudinal edges of the surface of the protective layer opposite to the conductive layer; tear enabling features on the side of protective layer of the cover tape and parallel to the longitudinal edges; and an adhesive release coating layer on the surface of the base film opposite to the conductive layer.
16. The article according to claim 15, further comprising a carrier tape.
PCT/US2008/065691 2007-06-06 2008-06-03 Antistatic film and article comprising the same WO2008154231A2 (en)

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