WO2004023532A2 - Charge control members - Google Patents

Charge control members Download PDF

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Publication number
WO2004023532A2
WO2004023532A2 PCT/JP2003/011208 JP0311208W WO2004023532A2 WO 2004023532 A2 WO2004023532 A2 WO 2004023532A2 JP 0311208 W JP0311208 W JP 0311208W WO 2004023532 A2 WO2004023532 A2 WO 2004023532A2
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WO
WIPO (PCT)
Prior art keywords
polyamide
charge control
control member
member according
weight
Prior art date
Application number
PCT/JP2003/011208
Other languages
French (fr)
Other versions
WO2004023532A3 (en
Inventor
Naomitsu Nishihata
Masahito Tada
Yuuichi Komatsu
Original Assignee
Kureha Chemical Industry Company, Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kureha Chemical Industry Company, Limited filed Critical Kureha Chemical Industry Company, Limited
Priority to JP2004534137A priority Critical patent/JP4540478B2/en
Priority to AU2003263593A priority patent/AU2003263593A1/en
Publication of WO2004023532A2 publication Critical patent/WO2004023532A2/en
Publication of WO2004023532A3 publication Critical patent/WO2004023532A3/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
    • C08L51/003—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
    • C08L77/12—Polyester-amides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/673—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere using specially adapted carriers or holders; Fixing the workpieces on such carriers or holders

Definitions

  • the present invention relates generally to a charge control member, and more particularly to a charge control member that is useful for substrate cassettes for receiving and holding various thin-sheet substrates such as electronic component mount substrates .
  • the substrate cassette according to the invention is preferred for receiving and holding glass substrates such as those for liquid crystal displays, plasma displays, thermal heads, thin-film EL display devices, sensors, magneto-optical disks and solar cells in the electronics packaging art field in particular.
  • charge control member used herein is understood to mean a member that has a surface resistivity belonging to the moderately conductive region and an antistatic capability in itself, and can show a charge control function as well.
  • the charge control function is understood to mean a function that makes it possible to control the amount of electrification (the amount of static electricity or charges) of an article or product coming in contact with the surface of the charge control member.
  • the surface resistivity belonging to the moderately conductive region should be in the range of 1.0 X10 6 to 1.0X10 1 ⁇ /D.
  • the surface resistivity is given generally in ⁇ , and in some cases in ⁇ /D.
  • the surface resistivity is a numerical value found by dividing a potential inclination in the direction parallel with a current flowing along the surface of a test piece by a current per unit surface width. This numerical value is equal to a surface resistance between two electrodes defined by two opposite sides of a square whose sides are each 1 cm. This is the reason the surface resistivity is given in ⁇ /D in the prior art, and so in the disclosure set forth hereinafter.
  • thin-sheet substrates such as glass substrates, ceramic substrates, silicon substrates, composite substrates (e.g., resin/ceramic and resin/silicon combinations) , and metal- base, metal-cored substrates (with glass or polyimide insulating layers) .
  • Two or more of substrates with or without conductor patterns formed thereon or highly functional devices such as thin-film transistors incorporated therein are loaded in a single cassette for conveniences of delivery, storage and assembly operations in processes of fabrication of packaging substrates and electronic circuit components .
  • a substrate cassette must have a structure that enables substrates to be loaded or unloaded in a non- contact fashion and be received and held in an independent manner.
  • the substrate cassette is constructed of a boxy framework wherein grooved side plates are located on a pair of opposite sides of the framework. Each substrate is received and held between the corresponding grooves on the side plates.
  • each grooved side plate has a number of rib-like shelving pieces projecting from its thick back. Adjacent shelving pieces define a groove space for receiving and holding the substrate.
  • the substrate cassette having such a structure is disclosed in JP-A's 6-286812, 6-247483, 5-147680 and 9- 36219.
  • Fig. 1 is a front view of that embodiment.
  • This substrate cassette is built up of a bottom-side frame 1, an upper-side frame 2, side plates 3 and 3, rib-like shelving plates 4 and 4 provided on the respective side plates and receiver-side plates 5 and 5. Adjacent rib-like shelving plates define a groove in which a substrate A is to be received and held.
  • Fig. 2 is illustrative in perspective of the above substrate cassette that is made up of a boxy framework having a pair of sides, each provided with three grooved side plates 3 and 3. The number of grooved side plates may be optional depending on substrate size, etc.
  • the bottom- side frame 1 and upper-side frame 2 are each configured in a lattice form; however, other configuration may be used.
  • the substrate cassette having such a structure is generally formed of a polymer material, a metal material or a composite material (e.g., a metal insert or outsert member) comprising these materials. In most cases, however, that cassette is formed of a polymer material or a member with at least its surface being made up of a polymer material.
  • melt molding typically, injection molding
  • the substrate comes in contact with the respective members forming the substrate cassette such as grooved side plates.
  • the respective members forming the substrate cassette are each of chargeability or electric conductivity or when they are each formed of a material of the type that allows the substrate to be largely charged upon contact with or disengagement from each member, the substrate would undergo various adverse influences through the respective members. This problem is now explained more specifically with reference to a glass substrate with thin-film transistors mounted thereon.
  • the glass substrate having thin- film transistors mounted thereon is received and held in the substrate cassette and a member in contact with the glass substrate is an insulator having a very high surface resistivity
  • circuits on the glass substrate will be damaged by static electricity built upon the surface of the member or airborne dust will be electrostatically adsorbed onto the glass substrate.
  • the member in contact with the glass substrate has too low a surface resistivity, the glass substrate subjected to an electric shock or a leakage of current or being electrically charged will be suddenly discharged, causing a circuit breakdown.
  • the antistatic agent present on the surface of the member forming the substrate cassette comes off by reason of water washing, friction, etc., and so the antistatic effect vanishes prematurely.
  • the amount of the antistatic agent added may be increased to help migrate the antistatic agent to the surface of the member so that the antistatic effect is kept alive.
  • the antistatic agent bleeds out on the surface of the member, causing contamination of the substrate with dirt and dust adhering to it, and pollution of ambient environments by bleeding and scattering by volatilization of the antistatic agent.
  • JP-A 5-147680 discloses a substrate cassette obtained by melt molding of a resin composition in which metal fibers and a whisker form of electrically conductive material are incorporated into a resin component
  • JP-A 9-36219 teaches a substrate cassette using a member obtained by forming a resin composition in which electrically conductive materials such as metal fibers, metal particles, carbon fibers , carbon blacks and graphite are incorporated in a resin composition.
  • the electrical resistivity of the resin compositions comprising resin components and conductive fillers change drastically even with a slight change in the content of the conductive fillers, in part because of a large difference in conductivity between the conductive fillers and the resins. Fluctuations of surface resistivity become noticeable especially in the surface resistivity range of 10 6 to 10 14 ⁇ /D demanded for substrate cassettes.
  • the surface resistivity of products obtained by forming of the resin compositions varies largely from site to site. With the resin compositions containing resin components and electrically conductive fillers, it is thus very difficult to provide stable formation of members having a desired surface resistivity in the range of 10 6 to 10 14 ⁇ /D. Since the members, if somehow formed, have large surface resistivity variations from site to site, it is also difficult to produce substrate cassettes showing a consistent antistatic capability and surface resistivity regardless of site.
  • the glass substrate in the substrate cassette is controlled to within the range of 10 6 to 10 14 ⁇ /D, the glass substrate will be electrified by itself upon contact with or disengagement from the substrate cassette, resulting in a breakdown of circuits formed on the glass substrate, because the glass substrate is a sort of insulator.
  • One object of the invention is to provide a charge control member that is useful for substrate cassettes for receiving and holding various thin-sheet substrates such as electronic component mount substrates .
  • a particular object of the invention is to provide a substrate cassette that has a proper degree of surface resistivity and stabilized antistatic capability, so that when substrates such as glass substrates with circuits formed on them are received and held therein, the substrates are unlikely to undergo electrification which may otherwise cause a breakdown of the circuits.
  • a further object of the invention is to provide a charge control member having such improved properties for substrate cassettes, using a polymer material that has improved melt fluidity, moldability, dust-proof capability and mechanical properties and is little susceptible of migration of impurities onto the surface of a substrate.
  • a member wherein at least a part of the substantial body or surface layer thereof is formed of a polyamide resin composition comprising a specific polymer type antistatic agent is incorporated in a polyamide resin is so improved in terms of antistatic capability that the amount of electrification of an article in touch with that member can be controlled.
  • the substrate cassette can then be much more improved in terms of such properties as referred to above.
  • the substrate cassette of the invention can never be electrified by itself, because at least its site in contact with substrates is formed of the polyamide resin composition that contains the polymer type antistatic agent.
  • the polyamide resin composition used herein is improved in terms of melt fluidity, moldability, dust-proof capability and mechanical strength, and so a product molded or otherwise formed of it can never contaminate the surfaces of substrates.
  • the charge control member of the invention used for substrate cassettes, etc. ensures that articles such as substrates are protected against static electricity, and helps repel dust and dirt, thereby keeping a proper degree of cleanliness and preventing drastic discharge of those articles .
  • the substrate cassette of the invention it is possible to considerably reduce electrification of glass substrates that are insulators. Why this is achievable has yet to be clarified; however, a possible reason could be that the amount of electrification becomes relatively small upon friction between materials that take close positions in the electrification train. In other words, it could be believed that the electrification train of the polyamide resin that is a main component of the substrate cassette of the invention is relatively approximate to that of the glass substrate, and so when the glass substrate comes in contact with or disengages from the substrate cassette, the amount of electrification occurring at the glass substrate becomes small .
  • the present invention underlies those findings.
  • the present invention provides a charge control member, characterized in that at least a part of the substantial body or surface layer thereof is formed of a polyamide resin composition comprising: (A) 100 parts by weight of a polyamide resin, and
  • a polymer type antistatic agent selected from the group consisting of (Bl) a polyether ester amide, and (B2) a graft copolymer obtained by graft polymerization of an ethylenic unsaturated monomer onto a rubber-like backbone polymer having an alkylene oxide group.
  • a typical embodiment of the charge control member of the invention is a substrate cassette wherein at least a part thereof in touch with a substrate is formed of the polyamide composition. Taking full advantage of the properties, the charge control member of the invention is also useful for applications other than substrate cassette one .
  • Figs 1 and 2 are a front and a perspective view of one typical embodiment of the substrate cassette.
  • the polyamide resin used herein includes ring-opening polymers of cyclic lactams, polycondensation products of amiocarboxylic acids, and polycondensation products of dibasic acids and diamines .
  • Exemplary polyamide resins are aliphatic polyamide resins represented by polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12 and polyamide 46; aliphatic-aromatic polyamide resins represented by polyamide MXD6 (i.e., polymethaxylene adipamide) , polyamide 6T (i.e., polyhexamethylene terephthalamide) , polyamide 61 (i.e., polyhexamethylene isophthalamide) , polyamide 41 (i.e., polytetramethylene isophthalamide) , polyamide 6T/66 (i.e., hexamethylene- diamine/adipic acid/terephthalic acid copolymer) , polyamide 6
  • a polymer type antistatic agent selected from the group consisting of (Bl) a polyether ester amide and (B2) a graft copolymer with an ethylenic unsaturated monomer graft polymerized onto a rubber-like backbone polymer is used as the antistatic agent.
  • polyether ester amide used herein is understood to mean a polymer wherein a polyamide component having carboxyl groups at both terminals is ester bonded to a polyether component such as a polyoxyalkylene glycol .
  • the polyether component for instance, includes polyoxyalkylene glycols or combinations of polyoxyalkylene glycols and alkylene oxide adducts of bisphenols .
  • the polyamide component having carboxyl groups at both terminals for instance, includes ring-opening polymers of lactams , polycondensation products of aminocarboxylic acids and polycondesation products of dicarboxylic acids and diamines .
  • the polyether ester amide may be prepared by any of known methods.
  • an amide-forming monomer is allowed to react with a dicarboxylic acid to form a polyamide having carboxyl groups at both terminals.
  • an ethylene oxide adduct of bisphenols is added to the polyamide for the subsequent polymerization reaction at high temperature under reduced pressure.
  • a commercially available product represented by Pellestat NC6321 made by Sanyo Kasei Co., Ltd. and Hepax 4011 made by Atochem co . , Ltd. may be used.
  • a preferred rubber-like backbone polymer that forms the graft copolymer used herein is obtained by co- polymerization of 50 to 95% by weight of at least one monomer selected from the group consisting of conjugated dienes and acrylic acid esters and 5 to 50% by weight of at least one monomer having 4 to 500 alkylene oxide groups and ethylenic unsaturated bonds (hereinafter called the polyalkylene oxide monomer) , if required, with 0 to 50% by weight, preferably 0 to 40% by weight of at least one ethylenic unsaturated monomer that is copolymerizable with the above monomers .
  • the rubber-like backbone polymer is composed mainly of at least one monomer selected from the group consisting of conjugated dienes and acrylic acid esters.
  • conjugated dienes 1 , 3-butanediene , isoprene, chloroprene, 1 , 3-pentadiene or the like may beused
  • acrylic acid esters ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, nonyl acrylate or the like may be used.
  • the ethylenic unsaturated monomer to be graft polymerized onto the rubber-like backbone polymer includes alkyl esters of methacrylic acid represented by methyl methacrylate, butyl methacrylate and propyl methacrylate; vinyl aromatic compounds represented by styrene, 2-methylstyrene, 3-methylstyrene and ⁇ - methylstryrene; and other vinyl monomers such as vinyl acetate, vinyl chloride and acrylonitrile .
  • the graft copolymer may be obtained by graft polymerization of 10 to 50% by weight, preferably 15 to 45% by weight of the ethylenic unsaturated monomer in the presence of 50 to 90% by weight, preferably 55 to 85% by weight of the rubber-like backbone polymer.
  • graft polymerization is carried out by emulsion polymerization.
  • various fillers may be incorporated in the polyamide resin composition used herein for the purpose of improving its mechanical strength, heat resistance, etc.
  • the fillers usable herein, for instance, include fibrous reinforcing materials such as inorganic fibers represented by glass fibers, carbon fibers, asbestos fibers, silica fibers, alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers and potassium titanate fibers; metal fibrous materials represented by stainless, aluminum, titanium, steel and brass; and high- melting-point organic fibrous materials formed of polyamide resins, fluororesins, polyester resins, acrylic resins, and so on.
  • Particulate or powdery fillers are also usable for the filler, such as mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide, ferrite, clay, glass powders, zinc oxide, nickel carbonate, iron oxide, quartz powders, magnesium carbonate and barium sulfate .
  • non-conductive fillers To control the surface resistivity of charge control members such as substrate cassettes to within the desired range, it is preferable to use non-conductive fillers. To reinforce the substrate cassette and control its surface resistivity to within the preferred range, it is particularly desired to select glass fibers as the fibrous reinforcing material from these fillers .
  • fillers could be used alone or in combination of two or more.
  • Each filler could have been treated with a sizing agent or a surface treating agent.
  • a sizing agent or surface treating agent for instance, functionality compounds such as epoxy compounds, isocyanate compounds, silane compounds and titanate compounds could be used. These compounds could have been treated with the surface treating agent or sizing agent before used with the filler, or they could be added to the filler simultaneously with the preparation of the resin composition.
  • the polyamide resin composition used herein may additionally contain additives other than the above ones such as impact resistance modifiers like epoxy group- containing ⁇ -olefin copolymers , resin improvers like ethylene glycidyl methacrylate, lubricants like pentaerythritol tetrastearate, flame retardants , coloring agents like dyes and pigments.
  • a polyamide resin composition which comprises (A) 100 parts by weight of a polyamide resin, and (B) 4 to 95 parts by weight of at least one polymer type antistatic agent selected from the group consisting of (Bl) a polyether ester amide and (B2) a graft copolymer obtained by graft polymerization of an ethylenic unsaturated monomer onto a rubber-like backbone polymer having an alkylene oxide group.
  • the polymer type antistatic agent should be used in an amount of 4 to 95 parts by weight, preferably 5 to 90 parts by weight, and more preferably 6 to 80 parts by weight per 100 parts by weight of the polyamide resin.
  • the content of the polymer type antistatic agent When the content of the polymer type antistatic agent is too small, the antistatic capability of the composition becomes low, and when the content of the polymer type antistatic agent is too large, the mechanical strength of the composition drops with a decrease in its fluidity, and its injection moldability and extrusion moldability become insufficient as well.
  • the content of the graft copolymer in the polymer antistatic agent is too large, the moldability of the polyamide resin composition becomes low with an excessive decrease in its modulus of elasticity.
  • the polymer type antistatic agent is a polyether ester amide
  • a charge control member having a surface resistivity within the desired range can often be obtained even when the content of the polyether ester amide is 4 to 50 parts by weight, and preferably 5 to 45 parts by weight per 100 parts by weight of the polyamide resin.
  • the polymer type antistatic agent is a graft copolymer obtained by the graft polymerization of an ethylenic unsaturated monomer onto a rubber-like backbone polymer having alkylene oxide groups
  • it should preferably be used in an amount of preferably 45 to 95 parts by weight, and more preferably 50 to 90 parts by weight per 100 parts by weight of the polyamide resin so that a charge control member having a surface resistivity within the desired range can be obtained.
  • the fibrous reinforcing material such as glass fibers
  • any reinforcing effect is not obtained at all, and at too high a content, it is likely that the antistatic capability of the composition may drop with a decrease in the surface smoothness of the member.
  • the polyamide resin composition of the invention may be prepared with facilities and processes generally used for synthetic resin compositions.
  • the respective starting components are pre-mixed together in a mixer such as a Henschel mixer, a tumbler or the like.
  • the pre-mixture is mixed optionally with the filler such as glass fibers and other additives.
  • the mixture is kneaded through a single- or twin-screw extruder, and then subjected to melt extrusion from a die into a forming pellet.
  • a part of all the components may be used to make a master batch, which is then mixed with the rest.
  • a part of the raw materials used may be pulverized to a uniform particle diameter, and then mixed with the rest for melt extrusion.
  • CHARGE CONTROL MEMBER For the charge control member of the invention, its substantial body or its surface layer formed of the polyamide resin composition should have a surface resistivity within the range of preferably 1.0X10 6 to 1.0* 10 14 ⁇ /D, more preferably 1.0X10 7 to 1.0X10 14 ⁇ /D, and even more preferably 1.0X10 9 to 1.0X10 14 ⁇ /D.
  • the upper limit to the surface resistivity should preferably be 0.5 10 14 ⁇ /D.
  • the charge control member for instance in the form of a substrate cassette, is susceptible of sudden discharge when the substrate cassette comes in touch with a substrate.
  • this surface resistivity is too high, the charge control member such as a substrate cassette is likely to be charged and so it is difficult to protect the article such as a substrate against static electricity and repel dust, thereby keeping a proper degree of cleanliness.
  • Too high a surface resistivity also causes the antistatic capability of the charge control member to drop, restricting its use in fields where antistatic capabilities are in need.
  • too high a surface resistivity renders it difficult to control the quantity of electrification of other article in touch with the charge control member.
  • the charge control member of the invention should preferably have a charge control function such that, after a glass substrate is brought in frictional contact with the surface of the substantial body or surface layer formed of the polyamide resin composition at a temperature of 23°C and a relative humidity of 50%, the surface potential of the glass substrate becomes preferably 150 V or lower, more preferably 100 V or lower, and even more preferably 80 V or lower, as measured by a surface potentiometer.
  • the charge control member of the invention should also have a static decay time from 5,000 V to 50 V of preferably 5 seconds or less, more preferably 3 seconds or less, and even more preferably 2 seconds or less, as measured according to MIL-B-81705C using a static decay meter .
  • the charge control member of the invention is preferably a substrate cassette.
  • at least the part of the substrate cassette in contact with a substrate is formed of the polyamide resin composition.
  • the structure of the substrate cassette of the invention should preferably be built up of a boxy framework that has a structure wherein grooved side plates are provided on a pair of opposite sides of the framework.
  • a boxy framework that has a structure wherein grooved side plates are provided on a pair of opposite sides of the framework.
  • one specific embodiment of that substrate cassette has such a structure as shown in Figs. 1 and 2.
  • a typical substrate cassette is built up of a bottom- side frame 1, an upper-side frame 2, side plates 3 and 3, rib-like shelving plates 4 and 4 provided on the respective side plates and receiver-side plates 5 and 5.
  • a number of rib-like shelving plates extend from the thick portion of each side plate at a given pitch and in a parallel fashion. Adjacent rib-like shelving plates define a groove in which a substrate A is received and held. The configuration and size of each grooved side plate could be variously varied if desired.
  • These members are made usually by means of injection molding, and then assembled into a boxy framework. Each member could be either formed of a thermoplastic resin composition in its entirety or a metal insert or outsert member .
  • all the members could be formed of the polyamide resin composition. If necessary, however, only the member in touch with the substrate could be formed of the polyamide resin composition.
  • the member in contact with the substrate for instance, could be the grooved side plates 3, 3 , and the receiver frames 5 , 5.
  • the side plate body and the rib-like shelving plates could be integrally formed of the polyamide resin composition, or alternatively they could be separately formed and then assembled into a single integral piece.
  • the side plate body could have its skeletal frame formed of a metal with the polyamide resin composition combined with around the same by insert or outsert molding.
  • the number of the receiver frames 5 , 5 could be one or two or more.
  • Each receiver frame could be in a flat form or provided with rib-like shelving plates as in the case of the grooved side plate. It is here understood that the structure of the substrate cassette according to the invention could include, in addition to the above ones, what is widely used as substrate cassettes for receiving and holding various thin- sheet forms of substrates such as electronic component mount substrates .
  • the substrate cassette of the invention can be used to receive and hold thin-sheet substrates such as glass substrates, ceramic substrates, silicon substrates, composite substrates (e.g., resin/ceramic substrates and resin/silicon substrates) , and metal-based, metal-cored substrates (with insulating layers of glasses, polyimides or the like) .
  • substrates for instance, are used as substrates in the electronics packaging technologies such as liquid crystal display glass substrates, plasma display glass substrates, thermal head glass substrates, LSI packaging ceramic substrates, and hybrid IC ceramic substrates .
  • the substrate cassette of the invention because of being capable of considerably reducing the amount of electrification of glass substrates, are best suited to receive and hold glass substrates such as liquid crystal display glass substrates, plasma display glass substrates, thermal head glass substrates, thin-film EL display device glass substrates, sensor glass substrates, magneto-optical disk glass substrates, and solar cell glass substrates.
  • glass substrates such as liquid crystal display glass substrates, plasma display glass substrates, thermal head glass substrates, thin-film EL display device glass substrates, sensor glass substrates, magneto-optical disk glass substrates, and solar cell glass substrates.
  • the charge control member of the invention may also be useful as such various members as listed below.
  • Automotive components Electronic housings gas tank caps, fuel filters, fuel line connectors, fuel line clips, fuel reservoirs or tanks, instrument bezels, door handles, fuel lines, and interiors .
  • Samples having a surface resistivity of 1.0X10 6 ⁇ /D or greater were measured at an applied voltage of 100 V using a constant voltage device (Model 300-1A made by Kikusui Co., Ltd.) , an ammeter (Model 616 made by Keithley Co. Ltd.) and a sample cell (Model 1608A made by Yokogawa Hewlett-Packard, Ltd.) in compliance with JIS K-6911, and samples having a surface resistivity of less than 1.0X10 6 ⁇ /D were measured using Loresta HP made by Mitsubishi Chemical Co. in compliance with JIS K-7194.
  • the obtained latex was removed, and 200 parts by weight of a 0.7% by weight aqueous solution of hydrochloric acid were added thereto for precipitation of the graft copolymer.
  • Water washing and dehydration gave a powdery graft copolymer having a water content of 43% by weight.
  • the copolymer was dried a hot-air temperature of 100°C in an airborne flash dryer to obtain a white powdery graft copolymer in a 97% yield.
  • Ninety-nine (99) parts by weight of the obtained graft copolymer and 1 part by weight of an anionic surface active agent were dry blended together in a Henschel mixer to prepare a polymer type antistatic agent.
  • Examples 1-6 and Comparative Examples 1-6 The components shown in Table 1 were uniformly dry blended together in a Henschel mixer, and then melt extruded through a 45 mm ⁇ twin-screw extruder (PCM-45 made by Ikegai Iron Works Co., Ltd.) to obtain a pellet, which was in turn dried and fed through an injection molding machine (IS-75 made by Toshiba Machine Co., Ltd.) to prepare a flat sheet whose physical properties were to be measured. The results are summed up in Table 1.
  • PCM-45 twin-screw extruder
  • Polyamide 46 Stanyl TS300 made by DSM JSR Enplar Co., Ltd.
  • Polyphthalamide Polyamide 6T/6I/66 made by Amoco Co., Ltd. and available in the trade name of Amodel .
  • Carbon Fibers PAN-series carbon fibers "Bethfight HTA 3000" made by Toho Rayon Co., Ltd.
  • the use of the resin compositions (Examples 1-6) wherein specific amounts of the polymer type antistatic agent are added to the polyamide resin ensures extruded products having a surface resistivity in the range of 1.0X10 6 ⁇ /D to 1.0X 10 14 ⁇ /D, preferably 1.0X10 9 ⁇ /D to 1.0X10 14 ⁇ /D with a static decay time of 2 seconds or less and ensuring that upon frictional contact with a glass substrate, the surface potential of the glass substrate can be kept at an extremely low level. Those extruded products are unlikely to adsorb airborne dust and dirt.
  • these polyamide resin compositions are preferred as a material for forming substrate cassettes.
  • the substrate cassette of the invention is unlikely to break down circuits on glass substrates with thin-film transistors incorporated in them.
  • the product obtained by extrusion molding of the polyamide resin composition containing no polymer type antistatic agent (Comparative Example 1) has a high surface resistivity and a static decay time of as long as 60 seconds or more, failing to exert the antistatic function well .
  • the surface potential of the glass substrate rises to 1,200 V.
  • this comparative product cannot meet the performance demanded for the resin material for the substrate cassette.
  • the product obtained by extrusion molding of the polyamide resin composition with carbon fibers filled in the polyamide resin (Comparative Example 2) has a surface resistivity of lower than 10 5 ⁇ /D, and when a glass substrate comes into contact with that product, the glass substrate already subjected to an electric shock, a current leakage or electrification is susceptible to drastic discharge, resulting in a breakdown of circuits on it. Upon frictional contact with the glass substrate, the product causes its surface resistivity to rise to as high as 240 V. Thus, this comparative product cannot meet the performance demanded for the resin material for the substrate cassette.
  • the products obtained by extrusion molding of the resin compositions containing polycarbonate, polyethylene terephthalate, polybutylene terephthalate or polyphenylene sulfide and the polymer type antistatic agent have a surface resistivity in the range of 10 9 ⁇ /D to 10 14 ⁇ /D and a static decay time of 1 second or less; however, upon contact with glass substrates, they cannot keep the surface resistivity at a low level. Thus, the products cannot meet the performance demanded for the resin material for the substrate cassette.
  • the charge control member of the invention is useful for substrate cassettes for receiving and holding various thin-sheet substrates such as electronic component mount substrates.
  • the present invention can provide a substrate cassette that has a proper degree of surface resistivity and stable antistatic capability, so that when a substrate such as a glass substrate with circuits formed on it is received and held therein, the circuits are protected against any breakdown due to electrification of the substrate.
  • the substrate cassette having such improved properties can be provided using a polymer material that has improved melt fluidity, moldability, dust-proof capability and mechanical properties yet reduces bleeding of impurities onto the surface of a substrate as much as possible.
  • the charge control member of the invention is applicable to not only substrate cassettes but also various fields where antistatic capability and charge controllability are in need as already described.

Abstract

The invention provides a charge control member, wherein at least a part of a substantial body or surface layer thereof is formed of a polyamide resin composition comprising 100 parts by weight of a polyamide resin, and 4 to 95 parts by weight of at least one polymer type antistatic agent selected from the group consisting of a polyether ester amide, and a graft copolymer obtained by graft polymerization of an ethylenic unsaturated monomer onto a rubber-like backbone polymer having an alkylene oxide group.

Description

DESCRIPTION
CHARGE CONTROL MEMBERS
TECHNICAL FIELD
The present invention relates generally to a charge control member, and more particularly to a charge control member that is useful for substrate cassettes for receiving and holding various thin-sheet substrates such as electronic component mount substrates .
The substrate cassette according to the invention is preferred for receiving and holding glass substrates such as those for liquid crystal displays, plasma displays, thermal heads, thin-film EL display devices, sensors, magneto-optical disks and solar cells in the electronics packaging art field in particular.
The term "charge control member" used herein is understood to mean a member that has a surface resistivity belonging to the moderately conductive region and an antistatic capability in itself, and can show a charge control function as well. The charge control function is understood to mean a function that makes it possible to control the amount of electrification (the amount of static electricity or charges) of an article or product coming in contact with the surface of the charge control member.
Preferably, the surface resistivity belonging to the moderately conductive region should be in the range of 1.0 X106 to 1.0X101 Ω/D. The surface resistivity is given generally in Ω, and in some cases in Ω/D. In other words, the surface resistivity is a numerical value found by dividing a potential inclination in the direction parallel with a current flowing along the surface of a test piece by a current per unit surface width. This numerical value is equal to a surface resistance between two electrodes defined by two opposite sides of a square whose sides are each 1 cm. This is the reason the surface resistivity is given in Ω/D in the prior art, and so in the disclosure set forth hereinafter.
BACKGROUND ART
In the electronics packaging art field, film technologies and micro-connection technologies are put to full use to mount semiconductors, functional components, circuit components, etc. on an interconnecting substrate where they are interconnected together. Then, the interconnected board is assembled together with other component (s) to form a desired electronic circuit. For the substrates, for instance, there have been used thin-sheet substrates such as glass substrates, ceramic substrates, silicon substrates, composite substrates (e.g., resin/ceramic and resin/silicon combinations) , and metal- base, metal-cored substrates (with glass or polyimide insulating layers) .
Two or more of substrates with or without conductor patterns formed thereon or highly functional devices such as thin-film transistors incorporated therein (e.g., glass substrates for liquid crystal displays) are loaded in a single cassette for conveniences of delivery, storage and assembly operations in processes of fabrication of packaging substrates and electronic circuit components .
Typically, a substrate cassette must have a structure that enables substrates to be loaded or unloaded in a non- contact fashion and be received and held in an independent manner. Generally, the substrate cassette is constructed of a boxy framework wherein grooved side plates are located on a pair of opposite sides of the framework. Each substrate is received and held between the corresponding grooves on the side plates. Commonly, each grooved side plate has a number of rib-like shelving pieces projecting from its thick back. Adjacent shelving pieces define a groove space for receiving and holding the substrate. The substrate cassette having such a structure, for instance, is disclosed in JP-A's 6-286812, 6-247483, 5-147680 and 9- 36219.
One specific embodiment of the substrate cassette is now explained with reference to Figs. 1 and 2. Fig. 1 is a front view of that embodiment. This substrate cassette is built up of a bottom-side frame 1, an upper-side frame 2, side plates 3 and 3, rib-like shelving plates 4 and 4 provided on the respective side plates and receiver-side plates 5 and 5. Adjacent rib-like shelving plates define a groove in which a substrate A is to be received and held. Fig. 2 is illustrative in perspective of the above substrate cassette that is made up of a boxy framework having a pair of sides, each provided with three grooved side plates 3 and 3. The number of grooved side plates may be optional depending on substrate size, etc. The bottom- side frame 1 and upper-side frame 2 are each configured in a lattice form; however, other configuration may be used. The substrate cassette having such a structure is generally formed of a polymer material, a metal material or a composite material (e.g., a metal insert or outsert member) comprising these materials. In most cases, however, that cassette is formed of a polymer material or a member with at least its surface being made up of a polymer material. Generally, when the above members are each formed of a polymer material, they are formed by melt molding (typically, injection molding), and then assembled into a boxy framework.
With a substrate received and held in the substrate cassette of such a structure, the substrate comes in contact with the respective members forming the substrate cassette such as grooved side plates. When the respective members forming the substrate cassette are each of chargeability or electric conductivity or when they are each formed of a material of the type that allows the substrate to be largely charged upon contact with or disengagement from each member, the substrate would undergo various adverse influences through the respective members. This problem is now explained more specifically with reference to a glass substrate with thin-film transistors mounted thereon. Where the glass substrate having thin- film transistors mounted thereon is received and held in the substrate cassette and a member in contact with the glass substrate is an insulator having a very high surface resistivity, circuits on the glass substrate will be damaged by static electricity built upon the surface of the member or airborne dust will be electrostatically adsorbed onto the glass substrate. Conversely, when the member in contact with the glass substrate has too low a surface resistivity, the glass substrate subjected to an electric shock or a leakage of current or being electrically charged will be suddenly discharged, causing a circuit breakdown.
As an approach to a solution to the above problem, it is known to control the surface resistivity of the member in contact with the substrate cassette to within a proper value range. Referring more specifically to this approach, a resin composition comprising an antistatic agent or a filler of low electrical resistance blended with various polymer materials is used to form a member that is a part of the substrate cassette. If the surface resistivity of the member is controlled to within the range of 106 to 1014 Ω/D in this way, the above problem can then be solved. With the approach involving the formation of the member using an antistatic agent-containing resin composition, however, the antistatic effect over a long period of time is not expectable. The antistatic agent present on the surface of the member forming the substrate cassette comes off by reason of water washing, friction, etc., and so the antistatic effect vanishes prematurely. The amount of the antistatic agent added may be increased to help migrate the antistatic agent to the surface of the member so that the antistatic effect is kept alive.
However, the antistatic agent bleeds out on the surface of the member, causing contamination of the substrate with dirt and dust adhering to it, and pollution of ambient environments by bleeding and scattering by volatilization of the antistatic agent.
Substrate cassettes formed using resin compositions containing fillers of low electrical resistance, too, have been put forward in the art. For instance, JP-A 5-147680 discloses a substrate cassette obtained by melt molding of a resin composition in which metal fibers and a whisker form of electrically conductive material are incorporated into a resin component, and JP-A 9-36219 teaches a substrate cassette using a member obtained by forming a resin composition in which electrically conductive materials such as metal fibers, metal particles, carbon fibers , carbon blacks and graphite are incorporated in a resin composition. With these conductive fillers, however, the electrical resistivity of the resin compositions comprising resin components and conductive fillers change drastically even with a slight change in the content of the conductive fillers, in part because of a large difference in conductivity between the conductive fillers and the resins. Fluctuations of surface resistivity become noticeable especially in the surface resistivity range of 106 to 1014 Ω/D demanded for substrate cassettes. In addition, the surface resistivity of products obtained by forming of the resin compositions varies largely from site to site. With the resin compositions containing resin components and electrically conductive fillers, it is thus very difficult to provide stable formation of members having a desired surface resistivity in the range of 106 to 1014 Ω/D. Since the members, if somehow formed, have large surface resistivity variations from site to site, it is also difficult to produce substrate cassettes showing a consistent antistatic capability and surface resistivity regardless of site.
Furthermore, even though the surface resistivity of the member in touch with the substrate, for instance, a glass substrate in the substrate cassette is controlled to within the range of 106 to 1014 Ω/D, the glass substrate will be electrified by itself upon contact with or disengagement from the substrate cassette, resulting in a breakdown of circuits formed on the glass substrate, because the glass substrate is a sort of insulator.
DISCLOSUE OF THE INVENTION
One object of the invention is to provide a charge control member that is useful for substrate cassettes for receiving and holding various thin-sheet substrates such as electronic component mount substrates .
A particular object of the invention is to provide a substrate cassette that has a proper degree of surface resistivity and stabilized antistatic capability, so that when substrates such as glass substrates with circuits formed on them are received and held therein, the substrates are unlikely to undergo electrification which may otherwise cause a breakdown of the circuits.
A further object of the invention is to provide a charge control member having such improved properties for substrate cassettes, using a polymer material that has improved melt fluidity, moldability, dust-proof capability and mechanical properties and is little susceptible of migration of impurities onto the surface of a substrate.
As a result of intensive studies made for the purpose of attaining the above objects, the inventors have now found that a member wherein at least a part of the substantial body or surface layer thereof is formed of a polyamide resin composition comprising a specific polymer type antistatic agent is incorporated in a polyamide resin is so improved in terms of antistatic capability that the amount of electrification of an article in touch with that member can be controlled.
Especially if at least a part of the substrate cassette in contact with substrates is formed of the polyamide resin composition, the substrate cassette can then be much more improved in terms of such properties as referred to above. The substrate cassette of the invention can never be electrified by itself, because at least its site in contact with substrates is formed of the polyamide resin composition that contains the polymer type antistatic agent.
The polyamide resin composition used herein is improved in terms of melt fluidity, moldability, dust-proof capability and mechanical strength, and so a product molded or otherwise formed of it can never contaminate the surfaces of substrates. Thus, the charge control member of the invention used for substrate cassettes, etc. ensures that articles such as substrates are protected against static electricity, and helps repel dust and dirt, thereby keeping a proper degree of cleanliness and preventing drastic discharge of those articles .
With the substrate cassette of the invention, it is possible to considerably reduce electrification of glass substrates that are insulators. Why this is achievable has yet to be clarified; however, a possible reason could be that the amount of electrification becomes relatively small upon friction between materials that take close positions in the electrification train. In other words, it could be believed that the electrification train of the polyamide resin that is a main component of the substrate cassette of the invention is relatively approximate to that of the glass substrate, and so when the glass substrate comes in contact with or disengages from the substrate cassette, the amount of electrification occurring at the glass substrate becomes small . The present invention underlies those findings.
Thus, the present invention provides a charge control member, characterized in that at least a part of the substantial body or surface layer thereof is formed of a polyamide resin composition comprising: (A) 100 parts by weight of a polyamide resin, and
(B) 4 to 95 parts by weight of at least one polymer type antistatic agent selected from the group consisting of (Bl) a polyether ester amide, and (B2) a graft copolymer obtained by graft polymerization of an ethylenic unsaturated monomer onto a rubber-like backbone polymer having an alkylene oxide group.
A typical embodiment of the charge control member of the invention is a substrate cassette wherein at least a part thereof in touch with a substrate is formed of the polyamide composition. Taking full advantage of the properties, the charge control member of the invention is also useful for applications other than substrate cassette one .
BRIEF EXPLANATION OF THE DRAWINGS
Figs 1 and 2 are a front and a perspective view of one typical embodiment of the substrate cassette.
BEST MODE FOR CARRYING OUT THE INVENTION
1. POLYAMIDE RESINS
The polyamide resin used herein, for instance, includes ring-opening polymers of cyclic lactams, polycondensation products of amiocarboxylic acids, and polycondensation products of dibasic acids and diamines . Exemplary polyamide resins are aliphatic polyamide resins represented by polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12 and polyamide 46; aliphatic-aromatic polyamide resins represented by polyamide MXD6 (i.e., polymethaxylene adipamide) , polyamide 6T (i.e., polyhexamethylene terephthalamide) , polyamide 61 (i.e., polyhexamethylene isophthalamide) , polyamide 41 (i.e., polytetramethylene isophthalamide) , polyamide 6T/66 (i.e., hexamethylene- diamine/adipic acid/terephthalic acid copolymer) , polyamide 6T/6I (i.e., hexamethylenediamine/isophthalic acid/ terephthalic acid copolymer), polyamide 6T/6I/66 (i.e., hexamethylenediamine/adipic acid/isophthalic acid/ terephthalic acid copolymer), polyamide 6T/M-5T (i.e., hexamethylenediamine/methylpentanedia ine/terephthalic acid copolymer) and polyamide 6T/6 (i.e., caprolactam/ hexamethylenediamine/terephthalic acid copolymer) ; and mixtures of two or more such polyamides .
2. POLYMER TYPE ANTISTATIC AGENT
In the invention, a polymer type antistatic agent selected from the group consisting of (Bl) a polyether ester amide and (B2) a graft copolymer with an ethylenic unsaturated monomer graft polymerized onto a rubber-like backbone polymer is used as the antistatic agent. (1) Polyether Ester Amide
The term "polyether ester amide" used herein is understood to mean a polymer wherein a polyamide component having carboxyl groups at both terminals is ester bonded to a polyether component such as a polyoxyalkylene glycol . The polyether component, for instance, includes polyoxyalkylene glycols or combinations of polyoxyalkylene glycols and alkylene oxide adducts of bisphenols . The polyamide component having carboxyl groups at both terminals, for instance, includes ring-opening polymers of lactams , polycondensation products of aminocarboxylic acids and polycondesation products of dicarboxylic acids and diamines .
No particular limitation is placed on how to prepare the polyether ester amide; it may be prepared by any of known methods. In one typical method, an amide-forming monomer is allowed to react with a dicarboxylic acid to form a polyamide having carboxyl groups at both terminals. Then, an ethylene oxide adduct of bisphenols is added to the polyamide for the subsequent polymerization reaction at high temperature under reduced pressure. For the polyether ester amide, a commercially available product represented by Pellestat NC6321 made by Sanyo Kasei Co., Ltd. and Hepax 4011 made by Atochem co . , Ltd. may be used. (2) Graft Copolymer of Rubber-Like Backbone Polymer
A preferred rubber-like backbone polymer that forms the graft copolymer used herein is obtained by co- polymerization of 50 to 95% by weight of at least one monomer selected from the group consisting of conjugated dienes and acrylic acid esters and 5 to 50% by weight of at least one monomer having 4 to 500 alkylene oxide groups and ethylenic unsaturated bonds (hereinafter called the polyalkylene oxide monomer) , if required, with 0 to 50% by weight, preferably 0 to 40% by weight of at least one ethylenic unsaturated monomer that is copolymerizable with the above monomers .
The rubber-like backbone polymer is composed mainly of at least one monomer selected from the group consisting of conjugated dienes and acrylic acid esters. For the conjugated dienes, 1 , 3-butanediene , isoprene, chloroprene, 1 , 3-pentadiene or the like may beused, and for the acrylic acid esters, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, nonyl acrylate or the like may be used.
The ethylenic unsaturated monomer to be graft polymerized onto the rubber-like backbone polymer, for instance, includes alkyl esters of methacrylic acid represented by methyl methacrylate, butyl methacrylate and propyl methacrylate; vinyl aromatic compounds represented by styrene, 2-methylstyrene, 3-methylstyrene and α- methylstryrene; and other vinyl monomers such as vinyl acetate, vinyl chloride and acrylonitrile .
The graft copolymer may be obtained by graft polymerization of 10 to 50% by weight, preferably 15 to 45% by weight of the ethylenic unsaturated monomer in the presence of 50 to 90% by weight, preferably 55 to 85% by weight of the rubber-like backbone polymer. Usually but not exclusively, graft polymerization is carried out by emulsion polymerization.
3. FILLER If desired, various fillers may be incorporated in the polyamide resin composition used herein for the purpose of improving its mechanical strength, heat resistance, etc. The fillers usable herein, for instance, include fibrous reinforcing materials such as inorganic fibers represented by glass fibers, carbon fibers, asbestos fibers, silica fibers, alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers and potassium titanate fibers; metal fibrous materials represented by stainless, aluminum, titanium, steel and brass; and high- melting-point organic fibrous materials formed of polyamide resins, fluororesins, polyester resins, acrylic resins, and so on.
Particulate or powdery fillers are also usable for the filler, such as mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide, ferrite, clay, glass powders, zinc oxide, nickel carbonate, iron oxide, quartz powders, magnesium carbonate and barium sulfate .
To control the surface resistivity of charge control members such as substrate cassettes to within the desired range, it is preferable to use non-conductive fillers. To reinforce the substrate cassette and control its surface resistivity to within the preferred range, it is particularly desired to select glass fibers as the fibrous reinforcing material from these fillers .
These fillers could be used alone or in combination of two or more. Each filler could have been treated with a sizing agent or a surface treating agent. For the sizing agent or surface treating agent, for instance, functionality compounds such as epoxy compounds, isocyanate compounds, silane compounds and titanate compounds could be used. These compounds could have been treated with the surface treating agent or sizing agent before used with the filler, or they could be added to the filler simultaneously with the preparation of the resin composition.
4. OTHER ADDITIVES
The polyamide resin composition used herein may additionally contain additives other than the above ones such as impact resistance modifiers like epoxy group- containing α-olefin copolymers , resin improvers like ethylene glycidyl methacrylate, lubricants like pentaerythritol tetrastearate, flame retardants , coloring agents like dyes and pigments.
5. POLYAMIDE RESIN COMPOSITION
In the invention, a polyamide resin composition is used, which comprises (A) 100 parts by weight of a polyamide resin, and (B) 4 to 95 parts by weight of at least one polymer type antistatic agent selected from the group consisting of (Bl) a polyether ester amide and (B2) a graft copolymer obtained by graft polymerization of an ethylenic unsaturated monomer onto a rubber-like backbone polymer having an alkylene oxide group.
When the content of the polyamide resin is too small, the mechanical strength and fluidity of the composition become low and the injection moldability and extrusion moldability of the composition become insufficient. When the content of the polyamide resin is too large, the antistatic capability of the composition becomes low. Thus, the polymer type antistatic agent should be used in an amount of 4 to 95 parts by weight, preferably 5 to 90 parts by weight, and more preferably 6 to 80 parts by weight per 100 parts by weight of the polyamide resin.
When the content of the polymer type antistatic agent is too small, the antistatic capability of the composition becomes low, and when the content of the polymer type antistatic agent is too large, the mechanical strength of the composition drops with a decrease in its fluidity, and its injection moldability and extrusion moldability become insufficient as well. When the content of the graft copolymer in the polymer antistatic agent is too large, the moldability of the polyamide resin composition becomes low with an excessive decrease in its modulus of elasticity. Where the polymer type antistatic agent is a polyether ester amide, a charge control member having a surface resistivity within the desired range can often be obtained even when the content of the polyether ester amide is 4 to 50 parts by weight, and preferably 5 to 45 parts by weight per 100 parts by weight of the polyamide resin. Where the polymer type antistatic agent is a graft copolymer obtained by the graft polymerization of an ethylenic unsaturated monomer onto a rubber-like backbone polymer having alkylene oxide groups, it should preferably be used in an amount of preferably 45 to 95 parts by weight, and more preferably 50 to 90 parts by weight per 100 parts by weight of the polyamide resin so that a charge control member having a surface resistivity within the desired range can be obtained.
Where the fibrous reinforcing material such as glass fibers is used, it should be used in an amount of preferably up to 80 parts by weight, more preferably 5 to 70 parts by weight, and most preferably 10 to 60 parts by weight per 100 parts by weight of the polyamide resin. At too low a content of the fibrous reinforcing material, any reinforcing effect is not obtained at all, and at too high a content, it is likely that the antistatic capability of the composition may drop with a decrease in the surface smoothness of the member.
The polyamide resin composition of the invention may be prepared with facilities and processes generally used for synthetic resin compositions. For instance, the respective starting components are pre-mixed together in a mixer such as a Henschel mixer, a tumbler or the like. Then, the pre-mixture is mixed optionally with the filler such as glass fibers and other additives. The mixture is kneaded through a single- or twin-screw extruder, and then subjected to melt extrusion from a die into a forming pellet. Alternatively, a part of all the components may be used to make a master batch, which is then mixed with the rest. Still alternatively, a part of the raw materials used may be pulverized to a uniform particle diameter, and then mixed with the rest for melt extrusion.
6. CHARGE CONTROL MEMBER For the charge control member of the invention, its substantial body or its surface layer formed of the polyamide resin composition should have a surface resistivity within the range of preferably 1.0X106 to 1.0* 1014 Ω/D, more preferably 1.0X107 to 1.0X1014 Ω/D, and even more preferably 1.0X109 to 1.0X1014 Ω/D. The upper limit to the surface resistivity should preferably be 0.5 1014 Ω/D.
At too low a surface resistivity, the charge control member, for instance in the form of a substrate cassette, is susceptible of sudden discharge when the substrate cassette comes in touch with a substrate. When this surface resistivity is too high, the charge control member such as a substrate cassette is likely to be charged and so it is difficult to protect the article such as a substrate against static electricity and repel dust, thereby keeping a proper degree of cleanliness. Too high a surface resistivity also causes the antistatic capability of the charge control member to drop, restricting its use in fields where antistatic capabilities are in need. In addition, too high a surface resistivity renders it difficult to control the quantity of electrification of other article in touch with the charge control member. The charge control member of the invention should preferably have a charge control function such that, after a glass substrate is brought in frictional contact with the surface of the substantial body or surface layer formed of the polyamide resin composition at a temperature of 23°C and a relative humidity of 50%, the surface potential of the glass substrate becomes preferably 150 V or lower, more preferably 100 V or lower, and even more preferably 80 V or lower, as measured by a surface potentiometer.
The charge control member of the invention should also have a static decay time from 5,000 V to 50 V of preferably 5 seconds or less, more preferably 3 seconds or less, and even more preferably 2 seconds or less, as measured according to MIL-B-81705C using a static decay meter .
The charge control member of the invention is preferably a substrate cassette. Preferably in this case, at least the part of the substrate cassette in contact with a substrate is formed of the polyamide resin composition.
No specific limitation is imposed on the structure of the substrate cassette of the invention; however, it should preferably be built up of a boxy framework that has a structure wherein grooved side plates are provided on a pair of opposite sides of the framework. As already described, one specific embodiment of that substrate cassette has such a structure as shown in Figs. 1 and 2.
A typical substrate cassette is built up of a bottom- side frame 1, an upper-side frame 2, side plates 3 and 3, rib-like shelving plates 4 and 4 provided on the respective side plates and receiver-side plates 5 and 5. A number of rib-like shelving plates extend from the thick portion of each side plate at a given pitch and in a parallel fashion. Adjacent rib-like shelving plates define a groove in which a substrate A is received and held. The configuration and size of each grooved side plate could be variously varied if desired. These members are made usually by means of injection molding, and then assembled into a boxy framework. Each member could be either formed of a thermoplastic resin composition in its entirety or a metal insert or outsert member . In the substrate cassette of such a structure, all the members could be formed of the polyamide resin composition. If necessary, however, only the member in touch with the substrate could be formed of the polyamide resin composition. The member in contact with the substrate, for instance, could be the grooved side plates 3, 3 , and the receiver frames 5 , 5. For each grooved plate 3 , the side plate body and the rib-like shelving plates could be integrally formed of the polyamide resin composition, or alternatively they could be separately formed and then assembled into a single integral piece.
The side plate body could have its skeletal frame formed of a metal with the polyamide resin composition combined with around the same by insert or outsert molding. The number of the receiver frames 5 , 5 could be one or two or more. Each receiver frame could be in a flat form or provided with rib-like shelving plates as in the case of the grooved side plate. It is here understood that the structure of the substrate cassette according to the invention could include, in addition to the above ones, what is widely used as substrate cassettes for receiving and holding various thin- sheet forms of substrates such as electronic component mount substrates .
The substrate cassette of the invention can be used to receive and hold thin-sheet substrates such as glass substrates, ceramic substrates, silicon substrates, composite substrates (e.g., resin/ceramic substrates and resin/silicon substrates) , and metal-based, metal-cored substrates (with insulating layers of glasses, polyimides or the like) . These substrates, for instance, are used as substrates in the electronics packaging technologies such as liquid crystal display glass substrates, plasma display glass substrates, thermal head glass substrates, LSI packaging ceramic substrates, and hybrid IC ceramic substrates .
The substrate cassette of the invention, because of being capable of considerably reducing the amount of electrification of glass substrates, are best suited to receive and hold glass substrates such as liquid crystal display glass substrates, plasma display glass substrates, thermal head glass substrates, thin-film EL display device glass substrates, sensor glass substrates, magneto-optical disk glass substrates, and solar cell glass substrates. Besides the substrate cassette, the charge control member of the invention may also be useful as such various members as listed below. (1) Electronics/Electrical Tote bins, wafer boats, wafer carriers, wafer cassettes, IC chip trays, IC chip carriers, IC shipping tubes, IC cards, tape and reel packing, equipment cases, storage trays, storage bins, transport enclosures, magnetic card readers, computer housings, modem housings, monitor housings, CR-ROM housings, DVD housings, printer housings, connectors , HD carriers , MR head carriers and trays , GMR head carriers and trays , HSA carriers and trays , HGA carriers and trays, VCMs in HDDs (materials for voice coil motors) , and liquid crystal panel carriers. (2) Business Machines/Computers
Printed circuit board cassettes, grounding bushings, paper tractors, font cartridges, ink ribbon canisters, guide pins, trays, rollers, gears, sprockets, belts, electronic enclosures, charging rolls, transfer rolls, developing rolls, static charge eliminating rolls, charging belts, transfer belts, developing belts, static charge eliminating belts , other parts in image forming apparatus of electrophotographic systems, paper and paper money carrying parts, and paper feed rails. (3) Teletronics
Portable telephone parts, pagers, and cellular phone parts . (4) Chemical and Other Processing
Tote bins, boxes, trays, wear-resistant, static- dissipative machine parts, equipment cases, pallets, enclosures for electronics controls , medical devices , test equipment, wire and power cable sheathing materials, wire supporters, electromagnetic wave absorbers, floor coverings, carpets, insect proofing sheets, wall plates, shoe soles, tapes, brushes, fan blades, flat heaters, and polyswitches.
(5) Automotive components Electronic housings, gas tank caps, fuel filters, fuel line connectors, fuel line clips, fuel reservoirs or tanks, instrument bezels, door handles, fuel lines, and interiors .
EXAMPLES
More specifically but not exclusively, the present invention is now explained with reference to examples and comparative examples. Physical properties were measured as mentioned below.
(1) Surface Resistivity
Samples having a surface resistivity of 1.0X106 Ω/D or greater were measured at an applied voltage of 100 V using a constant voltage device (Model 300-1A made by Kikusui Co., Ltd.) , an ammeter (Model 616 made by Keithley Co. Ltd.) and a sample cell (Model 1608A made by Yokogawa Hewlett-Packard, Ltd.) in compliance with JIS K-6911, and samples having a surface resistivity of less than 1.0X106 Ω/D were measured using Loresta HP made by Mitsubishi Chemical Co. in compliance with JIS K-7194. (2) Amount of Electrification of Glass Substrate The surface potential of a glass substrate after contact with a sample was measured at a temperature of 23°C and a relative humidity of 50%, using a surface potentiometer (Model 344 made by Trek Japan K.K.). , (3) Static Decay Time A static decay time from 5,000 V to 50 V was measured using STATIC DECAY METER-406C made by ETS Co. in compliance with MIL-B-81705C.
Synthesis Example 1 Example of Synthesis of Graft Copolymer Twenty-three (23) parts by weight of 1 , 3-butadiene,
30 parts by weight of butyl acrylate, 12 parts by weight of methoxy polyethylene glycol methacrylate, 0.016 part by weight of diisopropylbenzene hydroperoxide, 0.006 part by weight of formaldehyde sodium sulfoxylate, 0.0015 part by weight of iron (III) ethylenediaminetetraacetate, 0.2 part by weight of sodium pyrophosphate, 2.0 parts by weight of potassium oleate and 200 parts by weight of deionized water were charged in a pressure-resistant reactor having a stirrer, a thermometer and a pressure gauge, in which they were then stirred at 60°C for 10 hours. After polymerization, a rubber-like backbone polymer latex having an average particle diameter of 80 nm was obtained in a 99% yield .
Thirty-five (35) parts by weight of methyl methacrylate as an ethylenic unsaturated monomer mixture, 0.3 part by weight of n-octylmercaptan, 0.018 part by weight of diisopropylbenzene hydroperoxide, 0.007 part by weight of formaldehyde sodium sulfoxylate, 1.0 part by weight of potassium oleate and 50 parts by weight of deionized water were added to the rubber-like backbone polymer latex having 65 parts by weight of solid matter, substituted by nitrogen, and then stirred at 60°C for 10 hours for graft copolymerization. The obtained latex was removed, and 200 parts by weight of a 0.7% by weight aqueous solution of hydrochloric acid were added thereto for precipitation of the graft copolymer. Water washing and dehydration gave a powdery graft copolymer having a water content of 43% by weight. The copolymer was dried a hot-air temperature of 100°C in an airborne flash dryer to obtain a white powdery graft copolymer in a 97% yield. Ninety-nine (99) parts by weight of the obtained graft copolymer and 1 part by weight of an anionic surface active agent were dry blended together in a Henschel mixer to prepare a polymer type antistatic agent.
Examples 1-6 and Comparative Examples 1-6 The components shown in Table 1 were uniformly dry blended together in a Henschel mixer, and then melt extruded through a 45 mmφ twin-screw extruder (PCM-45 made by Ikegai Iron Works Co., Ltd.) to obtain a pellet, which was in turn dried and fed through an injection molding machine (IS-75 made by Toshiba Machine Co., Ltd.) to prepare a flat sheet whose physical properties were to be measured. The results are summed up in Table 1.
Figure imgf000029_0001
Notes :
(1) Polyamide 46: Stanyl TS300 made by DSM JSR Enplar Co., Ltd.
(2) Polyphthalamide: Polyamide 6T/6I/66 made by Amoco Co., Ltd. and available in the trade name of Amodel .
(3) Polycarbonate: Yupiron S-2000 made by Mitsubishi Gas Chemical Company, Inc.
(4) Polyethylene Terephthalate : SA 135 made by Mitsui Chemical Industries, Ltd. (5) Polybutylene Terephthalate: Julanecks 2002 made by Polyplastics Co., Ltd.
(6) Polyphenylene Sulfide: Fortlon KPS W-214 made by Kureha Chemical Industry Co., Ltd.
(7) Polyether Ester Amide: Pelestat NC6321 made by Sanyo Chemical Industries, Ltd.
(8) Glass Fibers: FT 689 made by Asahi Fiber Glass Co., Ltd.
(9) Carbon Fibers: PAN-series carbon fibers "Bethfight HTA 3000" made by Toho Rayon Co., Ltd.
As can be seen from the results of Table 1, the use of the resin compositions (Examples 1-6) wherein specific amounts of the polymer type antistatic agent are added to the polyamide resin ensures extruded products having a surface resistivity in the range of 1.0X106 Ω/D to 1.0X 1014 Ω/D, preferably 1.0X109 Ω/D to 1.0X1014 Ω/D with a static decay time of 2 seconds or less and ensuring that upon frictional contact with a glass substrate, the surface potential of the glass substrate can be kept at an extremely low level. Those extruded products are unlikely to adsorb airborne dust and dirt.
Thus, these polyamide resin compositions are preferred as a material for forming substrate cassettes. The substrate cassette of the invention is unlikely to break down circuits on glass substrates with thin-film transistors incorporated in them.
On the other hand, the product obtained by extrusion molding of the polyamide resin composition containing no polymer type antistatic agent (Comparative Example 1) has a high surface resistivity and a static decay time of as long as 60 seconds or more, failing to exert the antistatic function well . To add to this , when the extruded product comes in frictional contact with a glass substrate, the surface potential of the glass substrate rises to 1,200 V. Thus, this comparative product cannot meet the performance demanded for the resin material for the substrate cassette. The product obtained by extrusion molding of the polyamide resin composition with carbon fibers filled in the polyamide resin (Comparative Example 2) has a surface resistivity of lower than 105 Ω/D, and when a glass substrate comes into contact with that product, the glass substrate already subjected to an electric shock, a current leakage or electrification is susceptible to drastic discharge, resulting in a breakdown of circuits on it. Upon frictional contact with the glass substrate, the product causes its surface resistivity to rise to as high as 240 V. Thus, this comparative product cannot meet the performance demanded for the resin material for the substrate cassette. The products obtained by extrusion molding of the resin compositions containing polycarbonate, polyethylene terephthalate, polybutylene terephthalate or polyphenylene sulfide and the polymer type antistatic agent (Comparative Examples 3-6) have a surface resistivity in the range of 109 Ω/D to 1014 Ω/D and a static decay time of 1 second or less; however, upon contact with glass substrates, they cannot keep the surface resistivity at a low level. Thus, the products cannot meet the performance demanded for the resin material for the substrate cassette.
INDUSTRIAL APPLICABILITY
The charge control member of the invention, for instance, is useful for substrate cassettes for receiving and holding various thin-sheet substrates such as electronic component mount substrates. The present invention can provide a substrate cassette that has a proper degree of surface resistivity and stable antistatic capability, so that when a substrate such as a glass substrate with circuits formed on it is received and held therein, the circuits are protected against any breakdown due to electrification of the substrate. According to the present invention, the substrate cassette having such improved properties can be provided using a polymer material that has improved melt fluidity, moldability, dust-proof capability and mechanical properties yet reduces bleeding of impurities onto the surface of a substrate as much as possible. According to the present invention, it is further possible to protect a substrate from static electricity and repel dust and dirt, thereby keeping a proper degree of cleanliness and preventing drastic discharge of the substrate. The charge control member of the invention is applicable to not only substrate cassettes but also various fields where antistatic capability and charge controllability are in need as already described.

Claims

1. A charge control member, wherein at least a part of a substantial body or surface layer thereof is formed of a polyamide resin composition comprising:
(A) .100 parts by weight of a polyamide resin, and
(B) 4 to 95 parts by weight of at least one polymer type antistatic agent selected from the group consisting of (Bl) a polyether ester amide, and (B2) a graft copolymer obtained by graft polymerization of an ethylenic unsaturated monomer onto a rubber-like backbone polymer having an alkylene oxide group.
2. The charge control member according to claim 1, wherein the substantial body or surface layer formed of the polyamide resin composition has a surface resistivity ranging from 1.0X106 Ω/D to 1.0X1014 Ω/D.
3. The charge control member according to claim 1 , wherein the polyamide resin (A) is an aliphatic polyamide resin, an aliphatic-aromatic polyamide resin or a mixture thereof .
4. The charge control member according to claim 3 , wherein the aliphatic polyamide resin is polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12 or polyamide 46.
5. The charge control member according to claim 3 , wherein the aliphatic-aromatic polyamide resin is polyamide MXD6 (polymethaxylene adipamide) , polyamide 6T
(polyhexamethylene terephthalamide) , polyamide 61 (polyhexamethylene isophthalamide) , polyamide 41
(polytetramethylene isophthalamide) , polyamide 6T/66 (hexamethylenediamine/adipic acid/terephthalic acid copolymer) , polyamide 6T/6I (hexamethylenediamine/ isophthalic acid/terephthalic acid copolymer) , polyamide 6T/6I/66 (hexamethylenediamine/adipic acid/isophthalic acid/terephthalic acid copolymer) , polyamide 6T/M-5T (hexamethylenediamine/methylpentanediamine/terephthalic acid copolymer) or polyamide 6T/6 (caprolactam/ hexamethylenediamine/terephthalic acid copolymer) .
6. The charge control member according to claim 1 , wherein the polyether ester amide (Bl) is a polymer wherein a polyamide component having carboxyl groups at both terminals and a polyether component are bonded together via an ester bond.
7. The charge control member according to claim 6, wherein the polyamide component having carboxyl groups at both terminals is a ring-opening polymer of a lacta , a polycondensation product of an aminocarboxylic acid or a polycondensation product of a dicarboxylic acid and a diamine .
8. The charge control member according to claim 6, wherein the polyether component is a polyoxyalkylene glycol or a combination of a polyoxyalkylene glycol with an alkylene oxide adduct of bisphenols .
9. The charge control member according to claim 1, wherein the graft copolymer (B2) is a graft copolymer obtained by graft polymerization of 10 to 50% by weight of an ethylenic unsaturated monomer in the presence of 50 to 90% by weight of a rubber-like backbone polymer.
10. The charge control member according to claim 9, wherein the rubber-like backbone polymer is a copolymer of 50 to 95% by weight of at least one monomer selected from the group consisting of a conjugated diene and an acrylc acid ester, 5 to 50% by weight of at least one polyalkylene oxide monomer having 4 to 500 alkylene oxide groups and an ethylenic unsaturated bond, and 0 to 50% by weight of at least one ethylenic unsaturated monomer copolymerizable with said both monomers.
11. The charge control member according to claim 9, wherein the ethylenic unsaturated monomer includes an alkyl ester of methacrylic acid, a vinyl aromatic compound, other vinyl monomer or a mixture thereof.
12. The charge control member according to claim 1, wherein the polyamide resin composition further comprises up to 80 parts by weight of a fibrous reinforcing material (C) per 100 parts by weight of the polyamide resin (A) .
13. The charge control member according to claim 12 , wherein the fibrous reinforcing material (C) is a glass fiber.
14. The charge control member according to claim 1, which has a charge control function such that after a glass substrate is brought into frictional contact with a surface of the substantial body or surface layer formed of the polyamide resin composition, a surface potential of the glass substrate becomes 150 V or lower as measured at a temperature of 23°C and a relative humidity of 50% using a surface potentiometer.
15. The charge control member according to claim 1, which has a static decay time from 5,000 V to 50 V of 5 seconds or less as measured in compliance with MIL-B-81705C using a static decay meter.
16. The charge control member according to claim 1, which is used for a substrate cassette.
17. The charge control member according to claim 16, wherein at least a part of the substrate cassette in contact with a substrate is formed of the polyamide resin composition.
18. The charge control member according to claim 17, wherein the substrate cassette is a glass substrate cassette .
PCT/JP2003/011208 2002-09-02 2003-09-02 Charge control members WO2004023532A2 (en)

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JP2006324640A (en) * 2005-04-21 2006-11-30 Kureha Corp Cassette for substrates
JP2006342345A (en) * 2005-05-13 2006-12-21 Kureha Corp Antistatic resin composition
WO2015078046A1 (en) * 2013-11-27 2015-06-04 深圳市华星光电技术有限公司 Substrate cassette

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KR101353157B1 (en) * 2010-12-28 2014-01-22 도쿄엘렉트론가부시키가이샤 Electrostatic chuck
KR101802863B1 (en) * 2016-12-06 2017-11-29 양락주 Mask cassette
CN108001843A (en) * 2017-12-06 2018-05-08 宣城杰爱新材料科技有限公司 A kind of composite mortar thermal insulation board dispenser

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JP2006324640A (en) * 2005-04-21 2006-11-30 Kureha Corp Cassette for substrates
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JP2005537378A (en) 2005-12-08
TWI291439B (en) 2007-12-21
KR100716701B1 (en) 2007-05-14
WO2004023532A3 (en) 2004-10-21
KR20050042796A (en) 2005-05-10
CN1679139A (en) 2005-10-05
JP4540478B2 (en) 2010-09-08
AU2003263593A1 (en) 2004-03-29
TW200407252A (en) 2004-05-16
CN100380577C (en) 2008-04-09

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