Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2002-02-21
2004-03-23
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S215000, C428S323000, C428S328000, C428S329000, C428S330000, C428S331000, C428S336000, C428S480000, C428S483000
Reexamination Certificate
active
06709740
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to thermoplastic polyester film, particularly to ultralow haze polyethyleneterephthalate film having a wide variety of applications.
BACKGROUND
Polyethyleneterephthalate films are used for a host of converting, printing, coating and metallizing applications. The thermal stability, dimensional stability, chemical resistance and relative high surface energy of polyethyleneterephthalate films are beneficial for typical enduse applications. For instance, polyethyleneterephthalate films are often used as coating bases for magnetic tape, thermal transfer ribbon, packaging materials, thermal lamination and many other web converted products.
Low film haze is often a key requirement for a range of applications of polyethyleneterephthalate films, herein sometimes referred to as “polyester films”. Labels, solar control films and other optical applications require films with very low film haze in order to satisfy enduser expectations. Films with high haze typically limit the enduser acceptance of such products. However, many solutions to film haze requirements render the polyester films difficult to handle and process. Clear polyester films are typically produced by coating or surface treating a plain almost particle free film base. This method produces clear film, but due to the surface treatment the film's chemical resistance and scratch resistance may be compromised rendering it unsuitable for specific applications.
Found within the art are many examples of low haze, easy handling polyester films. However, these prior art materials do not meet the requirements of ultra low haze, herein defined as about 0.6% haze. Such low haze numbers are required for highest performance in the optical requirements described above. Furthermore, traditional solutions to low haze polyester film formulations render the film handling properties extremely poor, often leading to converter yield losses and a host of other commercial issues. Therefore, there is a need for an ultra low haze polyester film with improved handling characteristics.
DESCRIPTION OF THE PRIOR ART
U.S. Pat. No. 6,180,209 describes a biaxially oriented polyester film containing inorganic and organic particle fillers. The particle size distribution of the particles are particularly specified within tight ranges. Our invention advantageously creates a co-extruded film structure with aluminum oxide particles and organic fillers of minimum sizes without the requirements for specific particle size distributions. Such particle size distributions are practically difficult to achieve.
U.S. Pat. No. 5,096,773 describes a biaxially oriented polyester film containing from 0.05 to 3 wt. % of primary aluminum oxide particles of about 5 to 40 nm in size. Furthermore, these primary particles are specified to aggregate to an average particle size of from 50 to 400 nm. Furthermore, this patent teaches the requirement of an F-5 value (force required for 5% extension) in either the machine or transverse direction of not less than about 12.0 kg/mm
2
. Our invention differs sharply from this prior art in that we achieve a co-extruded structure, and the minimum sizes of aluminum oxide and organic fillers required to produce a high clarity, easy handling film.
U.S. Pat. No. 5,023,291 describes a polyester composition of >80 mol % of ethylene terephthalate units or 2,6-napthalenedicarboxylate units having 40-80 equivalents/10{circumflex over ( )}6 g of terminal carboxyl groups. Further specified are the requirements of from 0.01 to 5% of aluminum oxide particles of 0.005 to 5 &mgr;m particle diameter, and also having a melt resistivity of 6E10{circumflex over ( )}6 to 5E10{circumflex over ( )}9 ohm-cm. Our invention uses low particle size aluminum oxide fillers in conjunction with organic particle fillers in a co-extruded film structure without particle requirements of melt resistivity.
U.S. Pat. No. 4,820,583 describes a metallized, composite polyester film with specific requirements for surface roughness. Our invention differentiates in that we have discovered specific particle type, concentration and layer thickness ranges that produce an ultra clear and easy handling polyester film.
U.S. Pat. No. 5,718,971 describes the formulation of a low haze polyester film prepared from alumina particles treated with a silane coupling agent. Our invention differentiates from this patent in avoiding the necessity of using treated alumina particles in order to obtain sufficient polymer wetting.
U.S. Pat. No. 5,475,046 describes the use of alumina particles of specific sizes added to a reactor blend to produce PET chip. This chip, when extruded, cast into sheets and biaxially oriented produces films of haze <2.0% and &mgr;s/&mgr;d of <0.7/0.6. Our invention sharply distinguishes from this patent in that we utilize much smaller particles and achieve the advantage of lower friction as well.
U.S. Pat. No. 4,828,918 describes a co-extruded film structure with low haze and low surface roughness required for the production of easy handling ultraclear films. Our invention covers the discovery of specific requirements for particle size, concentration and layer thickness necessary to produce easy handling, ultraclear polyester films.
U.S. Pat. No. 4,092,289 describes a monolayer PET film comprising particles of a mixture of pyrogenic alumina and pyrogenic silica. Our invention has specific requirements for particle size, concentration and co-extruded layer thickness necessary to produce easy handling, ultraclear polyester films.
SUMMARY OF THE INVENTION
This invention relates to an ultralow haze thermoplastic polyester film prepared by co-extrusion of a blend of polyethyleneterephthalate with inorganic and organic fillers in at least one skin layer on a substantially particle free polyethyleneterephthalate core layer, wherein the inorganic fillers are selected from the group consisting of aluminum oxide particles, silicon dioxide, zirconium oxide, titanium dioxide, tin oxide, calcium carbonate, barium sulfate, calcium phosphate, zeolite, hydroxy apatite, aluminum silicate and mixtures thereof, of average particle size of about 0.035 &mgr;m to about 0.3 &mgr;m, and wherein particles of the organic filler have a particle size of less than or equal to about 0.8 &mgr;m and are present in an amount less than about 0.04% by weight, based on the weight of the polyethyleneterephthalate, the skin layer being less than about 3 &mgr;m in thickness.
This invention also relates to a solar control film comprising an ultralow haze thermoplastic polyester film prepared by co-extrusion of a blend of polyethylene-terephthalate with inorganic and organic fillers in at least one skin layer on a substantially particle-free polyethyleneterephthalate core layer, wherein said inorganic fillers are selected from the group consisting of aluminum oxide particles, silicon dioxide, zirconium oxide, titanium dioxide, tin oxide, calcium carbonate, barium sulfate, calcium phosphate, zeolite, hydroxy apatite, aluminum silicate and mixtures thereof of average particle size about 0.035 &mgr;m to about 0.3 &mgr;m, and wherein particles of the organic filler have a particle size of less than or equal to about 0.8 &mgr;m and are present in an amount less than about 0.04% by weight, based on the weight of the polyethyleneterephthalate, the skin layer being less than about 3 &mgr;m in thickness.
Further, this invention relates to a label film including a polystyrene acrylate coating laminated with an ultralow haze thermoplastic polyester film prepared by co-extrusion of a layer of a blend of polyethyleneterephthalate with inorganic fillers including aluminum oxide particles of average particle size of between about 0.035 &mgr;m and about 0.3 &mgr;m, and said inorganic particles including one or more polymers having an average particle sizes of less than about 0.8 &mgr;m and are present in an amount less than about 0.04% by weight, based on the weight of the polyethyleneterephthalate, said co-extruded layer being less than about 3 &mgr;m thickness.
DETAILED DES
Butera Paul
Fritz William
Furuya Hiroshi
Nishigaki Yasuo
Sargeant Steven J.
Chen Vivian
Piper Rudnick LLP
Toray Plastics (America) Inc.
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