Title of Invention

A TRANSPARENT THERMOPLASTIC RESINOUS LAMINATE FILM & A PROCES OF PREPARING THE SAME

Abstract

Disclosed is a transparent thermoplastic resinous film of at least 10 generally parallel layers in which the contiguous adjacent layers are of diverse transparent thermoplastic resinous material differing in refractive index by at least about 0.03, the film containing a sufficient quantity of a transparent dye which is soluble in the thermoplastic resinous material of the layers in which it is located to enhance or modify the apparent color of at least one of the reflection and transmission colors of the film. PRICE; THIRTY RUPEES

Full Text

BACKGROUND OF THE INVENTION The present invention relates to multilayer coextruded light-reflecting films which have a narrow reflection band due to light interference. When the reflection band occurs within the range of visible wavelength, the film is iridescent. Similarly, when the reflection band falls outside the range of visible wavelength, the film is either ultraviolet or infrared reflecting. Such multilayer films and methods by which they can be produced are known in the art. They are described, for instance, in U.S. Patents 3,565,985, 3,759,657, 3,773,882 and 3,801,429 and other patents. The multilayer films are compossd ot a plurality of generally parallel layers of transparent thermoplastic resinous material in which the contiguous adjacent layers are of diverse resinous material whose index of refraction diffeers by at least about 0.03. The film contains at least 10 layers and more usually at least 3 5 layers and. preferably, at least about 70 layers. The individual layers of the film are very thin, usually in the range of about 30 to 500 nm, preferably about 50 — 4 00 mn, which causes constructive interference in light waves reflected from the many interfaces. Depending on the layer thickness and the refractive index of the polymers, one dominant wavelength band is reflected and the remaining light is transmitted through the film. The reflected wavelength is proportional to the sum of the optical thickness of a pair of layers. The quantity of the reflected light (reflectance) and the color intensity depend on the difference between the two refractive indices, on the ratio of optical thicknesses of the layers, on the number of layers and on the uniformity of the thickness. If the refractive indices are the same, there is no reflection at all from the interfaces between the layers. In multilayer iridescent films, the refractive indices of contiguous adjacent layers differ by at least 0.03 and preferably by at 1 east 0.06 or more. For first order reflections, reflectance is highest when the optical thicknesses of the layers are equal, although suitably high reflectances can be achieved when the ratio of the two optical thicknesses falls oetween 5:95 and 95:5. Distinct color reflections are obtained with as few as 10 iayr,:.-3. However, for maximun colur intensity it is desired to have been 35 a.nd 1,000C or even more layers. High color intensity is associated with a reflection haxid which is relatively narrow and which has high reflectance at its peak. It should be recognized that although the term "color intensity" has been used here for convenience, the same considerations apply to the invisible reflection in the ultraviolet and infrared ranges. The multilayer films can be made by a chill-roll casting technique using a conventional single manifold flat film die in combination with a feedblock which collects the melts from each of two or more extruders and arranges them into the desired layer pattern. Feedblocks are described for instance in U.S. Patent Nos. 3,565,985 and 3,773,882. The feedblocks can be used to form components (i.e. ABAB...); three components (e.g. ABCABCA... or ACBCACBC...); or more. The very narrow multilayer stream flows through a single manifold flat film die where the layers are simultaneously spread to the width of the die and thinned to the final die exit thickness. The number of layers and their thickness distribution can be changed in inserting a different feedblock module. Usually, the outermost layer or layers on each side of the sheet are thicker than the other layers. This thicker skin may consist of one of the components which makes up the optical core; may be a different polymer which is utilized to impart desirable mechanical, heat sealing, or other properties; or may be a combination of these. Some recent developments in the iridescent film are described in United States Patents Reissue 31,780; 4,937,134; and 5,039,? 18. U.S. Patent No. Reissue 31,730 describes using a thermoplastic terephthalate polyester or copolyester resin as the high refractive index ccsnponent of the system. Formation of elastomeric interference films are described in U.S. Patent 4,937,134 in which all of the resinous materials are certain therm.oplastic polyurethanes, polyester block amides or flexible copolyesters. U.S. Patent No. 5,083,318 discloses improved multilayer light-reflecting transparent thermoplastic resinous film of at least 10 generally parallel layers in which the contiguous adjacent layers are of diverse transparent thermoplastic resinous material differing in refractive index by at least about 0.03 and at least one of the resinous materials being an engineering thermoplastic elastomer resin. It has been desired to incorporate color into these iridescent films in order to add a new dimension to their appearance. Such colors can enhance or change the reflection or transmission colors of the iridescent film. In addition, while iridescent colors change with the viewing angle, the non-iridescent colors remain the sane and hence the colors that can be observed can and will change dramatically based on the combination of the iridescent and non-iridescent component. Unfortunately, incorporation of the non-iridescent color into the iridescent film has proven ro be elusive. in discussing colorants for plastics it is important to make a distinction between dyes and pigments. Under the prevailing processing conditions, pigments are virtually insoluble in plastics, whereas dyes are soluble- Attempts to incorporate various pigments, both of a pearlescent and non-pearlescent nature, did not give rise to satisfactory results. It is now believed that the reason for these poor results was due to one or more of the following reasons: For the first order colors, v/hich are the brightest., the layers in rhs optical core of the film usually have a thickness of about 0.03 to 0,2 micron while the pigment particle size is usually in the range of dbout 0.3 micron. This means that the pigments are larger than the layers and their use disrupts the interfaces between the layers which in turn results in the loss of iridescence and light scattering. The use of pigments whose particle size is less than that of the layer thickness in the optical core has resulted in agglomeration and aggregation during processing of the film resulting in the formation of a color body whose particle size was greater than the optical core layer thicJcness. In those instances in which such aggregation did not occur, one of two equally undesirable results was encountered. Either the pigment concentration was inadequate to realize any significant effect or when the pigment was incorporated in a concentration sufficient to contribute significantly to the appearance of the final film, the characteristics of the resin had been changed to such an extent that a co-extruded film could not be made. An attempt to overcome this problem was made by incorporating the pigment in to the skin layer of the film which typically was in the range of 3 to 7 microns in thickness and comprised 20 to 25% of the total film thickness. Here also, up to a given pigment concentration, the contribution of the pigment was inadequate and was overpowered by the iridescent colors so the film appeared as if no pigment had been added and when this concentration was exceeded, the loading levels were found to be too high for the resins to be drawn down to be cast into film. It has now been discovered that the fcrsijaisg problem can be overcome if a transparent dye having certain characteristics is incorporated into the resinctjs material of the layers. SUMMARY OF THE INVENTION This invention relates to an improved colored multilayer light-reflecting film and more particularly to a transparent thermoplastic resinous film of at least 10 generally parallel layers in which the contiguous adjacent layers are of diverse transparent thermoplastic resinous material differing in refractive index by at least about 0.03, the film containing a sufficient quantity of a transparent dye which is soluble in the thermoplastic resinous material of the layers in which it is located to enhance or modify the apparent color of at least one of reflection and/or transmission colors of the film. Accordingly the present invention provides a transparent thermoplastic resinous laminate film of at least 10 very thin layers of substantially uniform thickness of about 30 to 500 nm, said layers being generally parallel and one surface of two of said layers constituting the outermost surfaes of the laminate fihn, the contiguous adjacent layers being of different transparent thermoplastic resinous materials, the contiguous adjacent layers differing in refractive index by at least about 0.03, and the film containing a predetermined quantity of a stable transparent dye which is soluble m the thermoplastic resinous material of the layers in which it is located to enhance or modify the apparent color of at least one of the reflection and transmission colors of the film. The present invention also relates to a process for preparing a transparent thermoplastic resinous laminate film as herein above described having at least 10 very thin layers of substantial uniform thickness, said layers being generally parallel and the contiguous adjacent layers being of different transparent thermoplastic resinous materials differing in refi:active index by at least about 0.03 by assembling the layers of the film such that the contiguous adjacent layers differ in reflective index by at least about 0.03, wherein the improvement comprises utilizing as at least one of the layers, a transparent thermoplastic resinous material containing a dissolved, stable transparent dye in an amount sufficient to enhance or modify the apparent color of at least one of the reflection and/or transmission colors of In accordance with the present invention, the iridescent film of the prior art is improved by incorporating certain dyes therein. The present invention is applicable to all of 10 the multilayer films which heretofore exist. Those films are composed of a plurality of generally parallel layers of transparent thermoplastic resinous material in which the contiguous adjacent layers are of diverse resinous materials whose index of refraction differs by at least 15 about 0.03 and preferably 0.06. These films contain at least 10 layers, or usually at least 35 layers, and preferably at least 70 layers. The individual layers of the film are very thin, usually in the range of about 30 to 500 nm, and preferably about 50 to 400 nm. 20 The multilayer films are usually made by a chill-roll casting technique in which melts of the thermoplastic resinous material from two or more extruders are collected by a feedblock which arranges them into a desired layered pattern. The very narrow 25 multilayer stream flows through a single manifold flat film die with the layers simultaneously spread to the width of the die and thinned to the final die exit thickness. The number of layers and their thickness distribution can be changed by using a different 3 0 feedblock module. Usually, the outermost layer or layers on each side of the sheet is thicker than the other layers so as to form a relatively thick skin. The resinous material used to form the skin may be one of the components which makes up the optical core, or a different polymer which is utilized to impart a desirable mechanical, heat sealing or other property, or a combination of these. In accordance with the invention, a colorant is added to one or more of the resinous materials in an amount which is sufficient to result in an enhancement or in a change of at least one of the reflection colors of the film or one of the transmission colors of the film, or both, relative tc the same characteristic present when the colorant is not used. The colorant can be incorporated in all or less than all of the layers of the optical core and/or in all or less than all of the skin layers. The number of layers in which the colorant is incorporated and t.he concentration of the colorant in an individual layer is a function of the desired colon. effect. In order to be useful in the present invention, the colorant; must have three characteristics. First, it must be transparent in rhe sense that the iridescent characteristics of the film in the absence of the colorant are not substantially interfered with, i.e. the iridescent appearance of the film is not significantly changed. Second, the colorant must be soluble in the thermoplastic resinous material in which it is incorporated. That means that pigmentary colorants can not be used. Third, the colorant must be stable under the process conditions used to form the film. Stability refers not only to the color of the dye but also means the dye must be non-migratory and non-volatile at the temperatures encountered during formation of the film which typically range up to about 300°C, and usually about 200-260°C. Among the dyes which can be employed in the present invention, those that are soluble in aliphatic and aromatic compounds are of special interest. In general, azo dyes, anthraquinone dyes, pyrazolone derivatives and pyridone dyes are suitable for use in the present invention. There are a variety of fluorescent dyes which can also be incorporated into plastics for use in the present invention. While the foregoing dyes are among the preferred, it will be appreciated that other dyes can also be used as long as they have the three characteristics noted above. It will also be appreciated that a film may contain different dyes in the individual layers of the optical core since a dye which is soluble in the thermoplastic resinous material of one of the layers may lack one or more of the required characteristics when inccrporated into the resinoius material of the adjacent contiguous layer. Whether or not any particular dye satisfies me three necessary conditions can readily be determined by conducting a short test procedure combining the dye with the resinous material and observing the resulting characteristics. The manner in which the dye and the resinous thermoplastic material are combined does not form a part of the present invention and any convenient procedure can be employed. The properties of iridescent films are such that for a given reflection color the films have a unique transmission color. For example, a red reflection color has a blue transmission color, a green reflection color has a pink transmission color, a blue reflection color has a yellow transmission color, and so on. Incorporation of a transparent dye will either enhance and/or change the reflection and/or transmission colors. A red dye will enhance the reds in a red reflecting iridescent film and change the blue transmission color to purple or magenta depending on the concentration of the red dye. Similarly, a red dye will change the blue in a blue reflecting iridescent film to purple or magenta, and change the yellow transmission color to an orange. Similar changes will occur with different combinations of dyes and reflection or transmission colors of the iridescent films. Different colored dyes may be used la the different components of the iridescent films and the result will be similar to combining the dyes. Red dye used in one of the component, and a yellow dye used in another component, of the iridescent film will result in an effect similar to using an orange dye. The amount of dye that can be incorporated into 5 thermoplastic resinous material is only limited by the amount that can be solubiiized in the thermoplastic resinous material and can be processed at the prevailing processing conditions without migrating or volatilizing. The amount of dye that is incorporated into the thermoplastic resinous material depends on the effect desired. Very low concentrations of dye will result in an iridescent film with a light tint or a pastel color highlight. High concentrations of dyes will result in strong contributions of the dye to the final appearance of the iridescent film. In order to illustrate the present invention, various examples are set forth below and it will be appreciated that these examples are not intended to limit the invention. Unless otherwise stated, all temperatiures are in degree Centigrade and all parts and percentages are by weight throughout this specification and claims. Example 1 Polyethylene terephthalate thermoplastic polyester (PET) was fed to the feedblock from one extruder and polymethyl methacrylate (PMMA) from a second extruder to form a 115 layer optical core, and a second skin layer of polybutylene terephthalate was added to each surface by means of a third extruder to form a 0.75 mil (19 micron) thick iridescent film. The film was brightly iridescent and was prevailing red when seen by reflection at perperidicuidr incidence, and blue when seen by transmission at perpendicular incidence. The foregoing procedure was repeated except that a red pyridone dye was incorporated into the PMMA at a concentration of about 0.7%. This dye was transparent, soluble in the PMMA, and stable under the processing conditions (being non-migratory and non-volatile at the maximum temperature encountered during the processing of the film at about 260°c), The resulting film was brightly iridescent, the red reflection colors were enhanced by the red dye, the blue transmission colors changed to purple, and the film had a red hue. Example 2 A multilayer structure with the same polymers in the optical core as in Example l was prepared except that the optical core had 229 layers and the two outer skin layers added by means of a third extruder were polyethylene terephthalate (PET)i The resulting film was 1.40 mils (35.5 microns) in thickness and had more intense iridescent colors than the film in Example 1 number of layers in the optical core. The addition of the red dye resulted in the red reflection colors to be enhanced, and changed the blue transmission colors to purple. Examples 7-30 All the above six examples were repeated with different film thickness to obtain the following reflection colors at perpendicular incidence: blue/violet, blue/green, red/green and red/yellow. Examples 31-60 Examples 1 to 2 4 were repeated with a blue anthraquinone dye at: a concentration of about 0.4% Examples 61-90 Examples 1 to 24 were repeated with a combination of a green anthraquinone dye and a yellow pyrazolone dye at a concentration of 0.15%. Examples 91-92 Examples 1 and 2 were run with a yellow pyrazolone dye at a concentration of 0.6% with an iridescent film which was red and yellow when seen by reflection at perpendicular incidence. I f r Example 93 Example 2 was run with a black chrome complex dye at a concentration 6% with an iridescent film which was red and yellow when seen by reflection at 5 perpendicular incidence. Various changes and modifications can be made in the present invention without departing from the spirit and scope thereof. The above examples show films made with combinations of PBT, PET and PMMA, and with the 10 dye incorporated into one of the components. The dyes can be incorporated into any thermoplastic resinous material that can be used to make cia iridescent film as long as the three necessary conditions for the use of the dyes are satisfied. The dyes can also be incorporated 15 into more than one component of the iridescent film and it is possible for all components in the iridescent film to contain dyes. It will also be appreciated that while the in^intion has been described with reference to the cast, fiat film type of film production, iridescent filBS 20 can also be made by the tubular (blown film) process. Accordingly, the various embodiments disclosed hersin were for the purpose of illustration only and were not intended to limit the invention. WE CLAIM: 1. A transparent thermoplastic resinous laminate film of at least 10 very thin layers of substantially uniform thickness of about 30 to 500 nm, said layers being generally parallel and one surface of two of said layers constituting the outermost surfaces of the laminate film, the contiguous adjacent layers being of different transparent thermoplastic resinous materials, the contiguous adjacent layers differing in refractive index by at least about 0.03, at least one of said outer most layers has a thickness greater than the thickness of said inner layer and the film containing a predetermined quantity of a stable transparent dye which is soluble in the thermoplastic resinous material of the at least one layer in which it is located to enhance or modify the apparent color of at least one of the reflection and transmission colors of the film. 2. The transparent thermoplastic laminate film of claim 1 wherein the outermost surfaces of laminate film have a skin laminated thereto, said skin being a layer of transparent thermoplastic resinous material of substantially uniform thickness and each skin being at least 5% of the total thickness of the film and skins. 3. The transparent thermoplastic resinous laminate film of claim 2, wherein the skin comprises polyethylene terephthalate or polybutylene terephthalate. 4. The transparent thermoplastic resinous laminate film of claim 1, wherein said adjacent resinous material has a refractive index which is lower by at least about 0.06. 5. The transparent thermoplastic resinous laminate film of claim 1, wherein one of the thermoplastic resinous materials is polyethylene terephthalate or polymethyl methacrylate. 6. The transparent thermoplastic resinous laminate film of claim 1, wherein the dye is present in each of the different thermoplastic resinous materials. 7. The transparent thermoplastic resinous laminate film of claim 1, wherein the dye is present in less than all of the different transparent thermoplastic resinous materials. 8. A process for preparing a transparent thermoplastic resinous laminate film claimed in any one of the preceding claims having at least 10 very thin layers of substantial uniform thickness, said layers being generally parallel and the contiguous adjacent layers being of different transparent thermoplastic resinous materials differing in refractive index by at least about 0.03 by assembling the layers of the film such that the contiguous adjacent layers differ in refractive index by at least about 0.03, at least one of said outermost layers has a thickness greater than the thickness of said inner layer, the improvement comprises utilizing as at least one of the layers, a transparent thermoplastic resinous material containing a dissolved, stable transparent dye in an amount sufficient to enhance or modify the apparent color of at least one of the reflection and/or transmission colors of the laminate film. 9. The process of claim 8, wherein all of the different transparent thermoplastic resinous materials contain the dissolved transparent dye. 10. The process of claim 8, wherein less than all of the transparoit thermoplastic resinous material contain the dissolved transparent dye. 11. A transparent thermoplastic resinous laminate film, substantially as herein described and exemplified. 12. A process of preparing a transparent thermoplastic resinous laminate film, substantially as herein described and exemplified.

Documents:

494-mas-95 abstract.pdf

494-mas-95 assignment.pdf

494-mas-95 claims.pdf

494-mas-95 correspondence-others.pdf

494-mas-95 correspondence-po.pdf

494-mas-95 description (complete).pdf

494-mas-95 form-1.pdf

494-mas-95 form-10.pdf

494-mas-95 form-13.pdf

494-mas-95 form-26.pdf

494-mas-95 form-4.pdf

494-mas-95 others document.pdf