Patent Application
20080038539
Organic particles can include materials that are roughly spherical in shape. These materials may be prepared by free radical polymerization or polycondensation polymerization to produce stable high polymer. These particles may have high thermal stability, high melting or no melting temperature and good wet-out in a polyester film matrix. Many such methods exist to prepare these organic particles in including, but not limited to, suspension polymerization, dispersion polymerization, emulsion polymerization, melt polymerization and solution polymerization. These particles may be reduced in size through grinding and classification in order to get them in the ranges desired.
In embodiments, the anti-iridescent layer is laminated at a film thickness of from about 0.07 μm to about 0.12 nm or from about 0.09 μm to about 0.11 μm. When the film thickness is selected at about 0.07 μm to about 0.12 nm, the node of the ripples is located in the center part of visible range (from about 380 to about 780 nm), which can minimize the amplitude of the ripples. If the film thickness is selected to be less than about 0.07 μm, the node shifts to a lower wave number range. If the film thickness is selected to be greater than about 0.12 nm, the node shifts to a higher wave number range. These lower or higher wave ranges may not minimize the amplitude of the ripples. For example,
In embodiments, the anti-iridescent coating materials may be selected from water soluble or dispersible polymers having an RI of from about 1.55 to about 1.62, which represents the mean value of the RI between a biaxially oriented polyester film (having an RI of from about 1.64 to about 1.68) and acrylic materials (having an RI of from about 1.48 to about 1.54). To achieve the desired RI, the coating materials may include aromatic and conjugated components such as styrene, melamine, polyester including a diphenyl or naphthyl structure, imide compounds, and the like, although not limited thereto. If the RI of the coating layer is out of the range of from about 1.55 to about 1.62, the node itself diminishes or disappears and may not be achieved regardless of the thickness of the film. If desired, additives such as cross-linkers, fillers, surfactants, among others, can also be added.
This invention will be better understood with reference to the following examples, which are intended to illustrate specific embodiments within the overall scope of the invention.
Test Methods:
Friction was measured with the use of a Testing Machine, Inc. slip tester (TMI-Model #32-06) using ASTM D1894-95. Polyester film samples were cut to specified sizes. One sheet of polyester was clamped, “A” surface up, onto an 18″ MD (machine direction)×6″ TD (transverse direction) glass plate. Another piece of polyester film was mounted using double-sided tape to a 2.5″×2.5″ 200 g sled, with the “B” surface down. The sled was placed on top of the glass plate and attached to the load sensing device. The sled was then dragged over the film on the glass plate at 6 in/min. The only contact during the testing was polyester film surface “A” rubbing against polyester film surface “B”. The measuring distance used to calculate the value of μs was 1″ and 4″ for μd.
Average surface roughness (Ra) was measured using a Kosaka Laboratory Limited Model #SE-30AK and #Ay-31. The average value of the data of 10 times measurements was taken as the surface roughness of the film according to the present invention. All measurements were run at 50,000× magnification and in the transverse direction of the film. The length of the measurement was 4 mm and the cut-off value was 0.08 mm.
Haze was measured using Suga Test Instruments Co. Model #HGM-2DP, using the methods of ASTM Standard D1003.
Total luminous transmission, herein referred to as TLT, was measured on a Suga Test Instruments Co. Model #HGM-2DP, using method described in ASTM Standard D1003.
Clarity was measured on a Byk Garner Hazeguard-Plus device, using methods described in ASTM Standard D1003.
Cloudiness was assessed by visual inspection as follows: single sheet samples of film were viewed at a distance of approximately 1 ft. in bright sunlight or under intense light at a slight glancing angle, typically less than 15 degrees. Cloudiness is the milkiness or translucence that appears from such a viewer angle. From this assessment a rating system was established for the film samples. A rating value of “poor” (Grade 10) indicates that the sample looks visibly cloudy to the viewer. The samples were then further ranked according to the perceived cloudiness.
Laminate layer and main layer thicknesses were determined based on a ratio of extruder outputs.
Average Particle Size Measurement:
Organic Particles
The particles were placed on the object stage of an electron microscope without overlapping them as far as possible, and observed at a magnification of 10,000 to 100,000 times using a scanning electron microscope or transmission electron microscope. In the case of a scanning electron microscope, on the surface of a sample, a platinum film of about 200 angstroms was vapor deposited using a sputtering apparatus beforehand. From the screen or photographed image, the areas of at least 200 particles were measured to calculate the equivalent diameters, and from the area equivalent diameters the volumes of the individual particles were calculated. Based on the volumes, the volume average particle diameter was calculated. Reference, for example, U.S. Pat. No. 5,912,074, which is totally incorporated by reference herein.
Inorganic Particles
A sample slurry was added to solvent (methanol) at a concentration of the slurry/solvent sufficient to show adequate light transmission. This solution was pipetted into the Honeywell Microtrac X100 machine. The average particle size and distribution was then measured via this machine.
Anti-Iridescent Appearance After Acrylic Coating.
The acryl based hard coat material (UVHC 8558® available from General Electric Corporation) was mixed with an equal amount of methyl ethyl ketone. The mixture was drawn down on the polyester film with a size #3 coating rod and dried in a 175° F. oven for 2 minutes. The film was subsequently cured with UV light of 300WPI for 15 seconds. The back side of the hard coated film was sprayed with flat black paint to eliminate interference from back side. Then, the surface of the hard coating was observed under fluorescent lamp.
Refractive Index and Thickness of the Anti-Iridescent Layer.
The back side surface of the anti-iridescent coated film was sprayed with flat black paint to eliminate the interference from back side. The 5° absolute spectral reflectance (from about 380 to about 780 nm) of the anti-iridescent coated polyester film was measured. Refractive index and thickness were estimated by comparing this measured spectral reflectance and theoretical spectral reflectance which is represented by the following formula
R
λ=1−4n12ns/{n12(1+ns)2+(1−n12)(ns2−n12)sin2(2πn1d1/λ)}
wherein
The unagglomerated alumina particles having a -type crystal form and having an average primary particle diameter of 20 nm, a Mohs' hardness of 7.5 are dispersed substantially uniformly in ethylene glycol by a media dispersion method using glass beads having a particle diameter of 50 μm (rotational speed: 3000 rpm, dispersion time: 4 hours), and the ethylene glycol including the alumina particles was polymerized with dimethylterephthalate to make pellets of polyethylene terephthalate. The content of alumina particles in the polyester was 1.5 wt. %. See U.S. Pat. No. 5,284,699, which is totally incorporated by reference herein. During polymerization the alumina particles agglomerated into particles with an average particle size 0.1 μm. The average particle size was found to be approximately 0.1 μm, with a range of about 0.035 μm to about 0.3 μm. This particle type is herein defined as “particle (A)” and this pellet type is herein defined as “pellet (A).”
Polyethyleneterephthalate chips having an intrinsic viscosity of 0.62 were melted using a vent type 2-screw extruder, and a water slurry of the polymer particles prepared above (styrene/bisphenol A diglycidyl ether dimethacrylate copolymer particles) was added, to obtain a polyethylene terephthalate containing organic polymer particles. See U.S. Pat. No. 5,912,074, which is totally incorporated by reference herein. The content of particle (B) in the polyester pellet (B) was 1.0% with an average particle size of 0.8 μm.
Polyethyleneterephthalate chips having an intrinsic viscosity of 0.62 were melted using a vent type 2-screw extruder, and a water slurry of the polymer particles prepared above (styrene/bisphenol A diglycidyl ether dimethacrylate copolymer particles) was added, to obtain a polyethyleneterephthalate containing organic polymer particles. (See U.S. Pat. No. 5,912,074.) The content of particle (C) in the polyester pellet (C) was 1.0% with an average particle size of 0.5 μm.
Next, 49.2 parts by weight of pellets (A), 0.7 parts by weight of pellets (B), 0.9 parts by weight of pellets (C), and 49.2 parts by weight of pellets (D) which did not substantially include any particles, were mixed. The mixed pellets were extruded using a vent-type two-screw extruder and filtered using high accuracy filters. This melt stream (I) was fed through a rectangular joining zone where it was laminated to a melt stream of polyester (II), which contained substantially no particles. The laminate produced a three layer co-extruded I/II/I structure. The resulting melt curtain was quenched on a casting drum, and then biaxially oriented via subsequent stretching steps on a roller train and chain driven transverse stretcher. The biaxially oriented film had a total thickness of 23 μm. Both laminate layers (I) were 1.4 μm in thickness.
The resulting film had an exceptionally low haze value of 0.5% and excellent handling and cloudiness properties as shown in Table 1. However, the iridescence was detected strongly after the acrylic layer was coated.
Film as described in Comparative Example 1 was coated with a surface coating containing co-polyester having naphthalic acid as a component before transverse stretching. The mixtures were applied at a thickness of about 0.1 μm dry thickness after the tentering operation. The film was found to have low haze, excellent handling characteristics and subsequently, was determined to have low irridescence when topcoated with an acrylic based hard coating formulation.
Other surface coatings may also provide the functional benefit of anti-iridescence. It is thought that combination of coating thickness and refractive index are necessary to deliver the desired properties.
An ant iridescent coating consisting of a blend of polyvinylalcohol-co-vinylamine grafted with phthalamide at about a ratio of 5-15% mol ratio of the phthalamide was coated on to the ultra low haze surface. Subsequent processing with an acrylic type hardcoating produced a film with the desired anti-iridescence properties.
Ultra-low haze and easy handling in polyester film are desirable attributes. Such attributes are useful for use in optically clear products such as solar control films, safety films, labels, graphics and other film uses. However, previous solutions to these issues were either deficient in clarity, film handling properties, or more often both.
In our experience, film handling properties are directly related to the friction properties of the film. A high coefficient of friction tends to lead to difficult converting of the film due to difficulties in unwinding the film and in subsequent re-winding of the film due to the possibility of increased static and the requirements for higher load tensions to pull the film through the typical roller train used in converting processes. High coefficients of friction can also lead to end user roll formation issues such as pimples and high edges. For easy converting of the film it is desired to create a static coefficient of friction of less than or equal to about 0.55 together with a dynamic coefficient of friction of less than or equal to about 0.45.
Previous films disclosed, for example, how to manage iridescence, but without providing the characteristic of easy handling. These films required a thickness of greater than from about 50 μm. If the film thickness was selected at less than about 50 μm, the film was too flexible to be easily wound.
The present disclosure provides, in embodiments, films having the desired management of iridescent properties (that is, anti-iridescent) at thickness of less than 50 μm while also providing in combination desired handing characteristics such as ease of winding.
It will be appreciated that various of the above-discussed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
This application discloses several numerical ranges. The numerical ranges disclosed inherently support any range or value within the disclosed numerical ranges even though a precise range limitation is not stated verbatim in the specification because this invention can be practiced throughout the disclosed numerical ranges.
The above description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the preferred embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Thus, this invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. Finally, the entire disclosure of the patents and publications referred in this application are hereby incorporated herein by reference.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/836,428, filed Aug. 8, 2006.
| Number | Date | Country | |
|---|---|---|---|
| 60836428 | Aug 2006 | US |
