Metallized multilayer film

Abstract: A metallized multilayer film comprising a first substrate layer, (10) a second substrate layer, (20) and a layer of metal (30). The first substrate layer comprises from 0 to about 40 parts by weight poly(vinylidine fluoride) and, correspondingly, from 100 to about 60 parts by weight poly(methyl methacrylate). The second substrate layer comprises from about 70 to 100 parts by weight poly(vinylidine fluoride) and, correspondingly, from about 30 to 0 parts by weight poly(methyl methacrylate).

Description: Field of the Invention This invention relates to metallized multilayer films and, more particularly, to metallized films having a substrate which includes poly(vinylidine fluoride) and poly(methyl methacrylate). Description of the Related Art Metallized films, that is, films comprising a polymeric substrate on which has been deposited a layer of metal, are often employed in, for example, the automotive, furniture, stationery, interior building material, and advertising industries so as to provide an aesthetic or decorative enhancement to manufactured articles. Such films, in order to be commercially useful as decorative and aesthetic enhancements, should possess several characteristics. For example, the substrate layer should be highly transparent so as not to detract from the reflective quality of the metal layer and the overall appearance of the article. The films should also exhibit good heat stability, especially when employed in the construction of outdoor signs, motor vehicles and other articles where high temperatures may be encountered. For example, the interior of a motor vehicle on a warm, sunny day in certain climates may experience temperatures in excess of 90°C. Flexibility is another desirable quality because flexible films are more readily applied to rough or uneven surfaces and multifaceted articles having a compound geometry. In still other applications, metallized multilayer films may be embellished with printed messages, decorative patterns, or complementary decorative transparent, colored layers. Metallized films, in order to be commercially useful, should readily accept printing and should be susceptible to the adhesion of further decorative layers thereto. Such films should also possess excellent adhesion between the metal and substrate layers. The films should be capable of being applied in an economical manner and retain a quality appearance without developing bubbles, wrinkles or swells. Once applied, the films should remain durable and exhibit good resistance to a wide variety of weathering and environmental conditions. Those metallized films which are presently known exhibit some, but not all, of these desirable features. Thus, while being useful in particular applications, the presently known films may not be broadly employed in a diverse myriad of circumstances. For example, metallized polyester films (as described in the Plastic Handbook published by Asakura Shoten), while being transparent and heat stable, have poor flexibility and exhibit, at best, only fair post-application durability. Various metallized polyester films are commercially available and have been for many years. Metallized acrylic films described in Plastic Material Course , Volume 12, Acrylic Resin, published by Nikkan Kogyo Shimbunsha, while being transparent and having good adhesion between the metal layer and the acrylic resin substrate, do not exhibit good heat stability or flexibility. Metallized films comprising a metal layer deposited on a single layer fluoropolymer substrate have fair heat stability and durability, as well as good adhesion between the metal layer and the fluoropolymer substrate. However, these films are not readily printable. Films of this type are illustrated in Japanese Patent Kokai No. 22973/72, Japanese Patent Kokai No. 71249/85, and Japanese Utility Model Kokai No. 87027/88. The performance characteristics of the presently known metallized films are summarized in Table I below. A double layer film believed to include a first layer having 80% poly(vinylidine fluoride) and 20% poly(methyl methacrylate) and a second layer having 20% poly(vinylidine fluoride) and 80% poly(methyl methacrylate) is commercially available in Japan from Denki Kagaku Kogyo K.K. as DENKA DX-Film. The film is stated to exhibit excellent weatherability and may be used as a protective cover for metal and plastic boards, as a protective cover for tent clothes, and as a protective or a decorative cover for various substrates. The DENKA DX-Film does not include a metal layer. U.S. Patent No. 4,068,034 (Segawa et al.) discloses a heat insulating laminate comprising a metal layer sandwiched between an outermost, transparent polyvinylidene fluoride layer, and an innermost heat insulating material such as paper, fabric, glass cloth, wood, plastic, foam plastic, or metal. Accordingly, there remains a need for a metallized film which is transparent, heat stable, flexible, readily printable, durable after being applied, and wherein the metal layer has good adhesion to the film substrate. SUMMARY OF THE INVENTION This invention relates to a metallized multilayer film comprising a first substrate layer, a second substrate layer on the first substrate layer, and a layer of metal on the second substrate layer. The first substrate layer comprises from 0 to 40 parts by weight poly(vinylidine fluoride) and, correspondingly, from 100 to 60 parts by weight poly(methyl methacrylate). The second substrate layer comprises from about 70 to 100 parts by weight poly(vinylidine fluoride) and, correspondingly, from 30 to 0 parts by weight poly(methyl methacrylate). The metal layer may be formed of chromium, nickel, aluminum, stainless steel, tin and alloys thereof and may be in the form of an interrupted pattern on the second substrate layer. The metallized multilayer film may further comprise a layer of an adhesive on the metal layer and a release liner on the adhesive layer. The first substrate layer may further include a printing ink deposited thereon or a layer of a colored resinous material. Metallized multilayer films according to the invention may be applied to the surface of an article so as to provide a decorative and aesthetic enhancement therefor. Metallized multilayer films according to the invention are flexible, durable, heat stable, readily printable, and exhibit good resistance to outdoor weathering. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood with reference to the following drawings wherein similar reference numerals identify analogous components throughout and in which: FIG. 1 is an enlarged cross-sectional view of a metallized multilayer film according to the invention; FIG. 2 is an enlarged cross-sectional view of a second embodiment of a metallized multilayer film according to the invention; and FIG. 3 is an enlarged cross-sectional view of a third embodiment of a metallized multilayer film according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to the drawings, FIG. 1 is an enlarged cross-sectional view of a metallized multilayer film 5 according to the invention. The film 5 comprises a multilayer composite substrate 8 (which, in turn, comprises a first substrate layer 10 and a second substrate layer 20 on the first substrate layer) and a metal layer 30 on the composite substrate 8. The first substrate layer 10 comprises either poly(methyl methacrylate) (PMMA) or a blend or poly(vinylidine fluoride)(PVDF) and PMMA. The PVDF and the PMMA comprising the first substrate layer 10 are combined in a ratio of from 0 to 40 parts by weight PVDF and, correspondingly, from 100 to 60 parts by weight PMMA. The second substrate layer 20 comprises either PVDF or a blend of PVDF and PMMA. In the second substrate layer 20, the PVDF and PMMA are combined in a ratio of from 70 parts to 100 parts by weight PVDF and, correspondingly, from 30 parts to 0 parts by weight PMMA. As used herein, poly(vinylidine fluoride) includes both homopolymers of vinylidine fluoride and copolymers comprising vinylidine fluoride and another monomer copolymerizable therewith. Examples of suitable comonomers include, for example, vinyl fluoride, tetrafluoroethylene, and chlorotrifluoroethylene. Similarly, poly(methyl methacrylate), as used herein, includes both methyl methacrylate homopolymers and copolymers comprising methyl methacrylate and another monomer copolymerizable therewith. Suitable comonomers, include, for example, butyl methacrylate and ethyl methacrylate. Furthermore, the first and second substrate layers 10 and 20, respectively, may include various antioxidants and UV stabilizers, so long as they are added in an amount that does not materially adversely affect the ultimate performance of the metallized multilayer film 5. A substrate based on PVDF, PMMA and blends thereof exhibits superior transparency as compared to substrates based exclusively on PVDF, polytetrafluoroethylene or polyvinyl chloride. The transparency of these various substrates was qualitatively compared by vapor coating a layer of alumium thereon with the results shown in Table II below. The PVDF and PMMA in the composite film structure were blended in an arbitrary ratio. The thickness of each sample film was about 50 µm (microns). Table II indicates that film substrates based on PVDF and PMMA exhibit superior transparency over other substrates. Metallized Film Substrate Material Transparency PVDF 0 - ▵ PVDF/PMMA 0 Polytetrafluoroethylene X Polyvinyl chloride X 0: High ▵: Medium X: Low The first and second substrate layers 10 and 20, respectively, are combined so as to form the composite substrate layer 8 using conventional techniques such as, for example, coextrusion at a temperature of 200-300°C or roll pressing at a temperature of 170-250°C and a pressure of 5-20 kilograms/square centimeter. Once the composite substrate layer 8 comprising the first and second substrate layers 10 and 20 has been formed, the metal layer 30 may be deposited thereon using well known techniques such as, for example, vacuum vapor deposition, sputtering, ion plating or the like. The metal layer 30 may be formed of materials such as chromium, nickel, aluminum, stainless steel, tin and alloys thereof. Preferably, the metal layer 30 is deposited on the substrate layer having the predominant amount of PVDF, i.e., the second substrate layer 20 herein. Referring now to FIG. 2, an enlarged cross-sectional view of a second embodiment of a metallized multilayer film 5 according to the invention, the film comprises a composite substrate 8 (which, in turn, comprises first and second substrate layers 10 and 20), and a metal layer 30, all as described more fully hereinabove. The film 5 further comprises an adhesive layer 40 and a release liner 50. Adhesive layer 40 may comprise any of a wide variety of conventionally known adhesive materials including, for example, acrylic, rubber, silicone resin and heat curable epoxy adhesives. Preferably, the adhesive layer 40 is applied to the surface of the metal layer 30 opposite the surface which engages the second substrate layer 20. Release liner 50 is applied to the exposed surface of the adhesive layer 40 and protects the adhesive layer until the film 5 is ready for use. In application, release liner 50 is removed thereby exposing adhesive layer 40. The film 5 is then placed on the surface (not shown separately in the drawings) to which the film is to be applied and pressure is applied to the film for a time sufficient to strongly adhere the same to the surface. A third embodiment of a metallized multilayer film 5 according to the invention is illustrated in the enlarged cross-sectional view of FIG. 3. The metallized multilayer film 5 is similar to that shown in FIG. 1 and comprises a composite substrate layer 8 (which, in turn, comprises first and second substrate layers 10 and 20 respectively), and a layer of metal 30, which metal layer has been applied to the second substrate layer in an interrupted arrangement so as to provide a decorative pattern. Though not shown separately in FIG. 3, the film 5 thereof may also include an adhesive layer and a release liner as described in conjunction with FIG. 2. In each of the embodiments of FIGS. 1 to 3, the first substrate layer 10 may further include a printing ink or a layer of a colored resinous material deposited thereon. Suitable printing inks include, for example, acrylic and polyvinyl chloride/acetate copolymer inks. Suitable resinous materials include, as examples, laminates which incorporate polyvinyl chloride or an acrylate resin. The following examples are offered to further illustrate the invention and are not to be construed as limiting the scope thereof. In the examples, all parts refer to parts by weight unless indicated otherwise. Examples 1-8 A series of metallized films comprising a layer of aluminum deposited on different substrates was prepared. The substrates comprised a single PVDF/PMMA layer, the examples varying in the relative proportions of PVDF and PMMA. The samples were then evaluated for their heat stability and their ability to adhere a printing ink. More particularly, approximately 10 cm x 10 cm sections of the sample materials were placed in an oven and maintained at an elevated temperature of either 70°C, 100°C or 120°C for one week. After the expiration of one week, the samples were qualitatively evaluated for the quality of the mirror-like appearance which the metal layer exhibited. The results are shown below in Table III. Ability to adhere a printing ink was determined by applying an acrylic ink (SCOTCHCAL 3903 brand screen ink, commercially available from the Minnesota Mining and Manufacturing Co., St. Paul, Minnesota) and a polyvinyl chloride/acetate copolymer ink (SCOTCHCAL 3920 brand screen ink, commercially available from the Minnesota Mining and Manufacturing Co., St. Paul, Minnesota) and evaluating for peel adhesion. The inks were screen printed onto the substrate materials through a 53 µm (270 mesh) screen, dried at 65°C for two hours, and then allowed to cool at room temperature for about one hour. The ink layer was then cut through (without harming the underlying substrate) to form a grid or lattice pattern. A strip of SCOTCH 610 brand cellophane tape (commercially available from the Minnesota Mining and Manufacturing Co., St. Paul, Minnesota) was applied over the ink layer and firmly pressed thereto. The tape was then peeled from the film in a single continuous motion. If the ink remained on the substrate in good condition, the substrate was considered as having good adhesion to the printing ink. The results are shown below in Table III. Table III shows that substrates comprising PVDF and PMMA in the range of about 70 parts to 100 parts by weight PVDF and, correspondingly, from about 30 parts to 0 parts by weight PMMA exhibit good heat stability, even at temperatures of about 120°C. On the other hand, substrates comprising PVDF and PMMA in a ratio of 0 parts to about 40 parts PVDF and, correspondingly, from 100 parts to about 60 parts by weight PMMA exhibit good adhesion to acrylic and polyvinyl chloride/acetate copolymer printing inks. The substrate layer in which the PVDF predominates contributes to the heat stability of the overall article. On the other hand, the substrate layer in which the PMMA predominates demonstrates good adhesion to printing inks. By combining first and second substrate layers having the PVDF and PMMA ratios described hereinabove, the advantageous qualities of each layer may be realized. The outermost substrate layer (i.e. the first substrate layer 10 herein) comprises PVDF and PMMA in a ratio of about 0 parts to about 40 parts PVDF and, correspondingly, from 100 parts to about 60 parts PMMA. The innermost substrate layer (i.e. the second substrate layer 20 on which the metal layer may be deposited) preferably comprises PVDF and PMMA in a ratio of from about 70 parts to 100 parts PVDF and, correspondingly, from about 30 parts to 0 parts PMMA.

Claims: A metallized multilayer film (5) suitable for use for aesthetic or decorative enhancement, comprising a composite substrate and a layer of metal (30) on said composite substrate, said composite substrate comprising a first substrate layer (10) and a second substrate layer (20) on said first substrate layer (10), wherein said first substrate layer (10) comprises from 0 to 40 parts by weight poly(vinylidene fluoride) and, correspondingly, from 100 to 60 parts by weight poly(methyl methacrylate), and further wherein said second substrate layer comprises from 70 to 100 parts by weight poly(vinylidene fluoride) and, correspondingly, from 30 to 0 parts by weight poly(methyl methacrylate). A metallized multilayer film (5) according to claim 1 wherein said layer of metal (30) is on said second substrate layer (20). A metallised multilayer film (5) according to any preceding claim wherein said metal is selected from chromium, nickel, aluminium, stainless steel, tin and alloys thereof. A metallized multilayer film (5) according to any preceding claim wherein said layer of metal (30) forms an interrupted pattern on said second substrate layer. A metallized multilayer film (5) according to any preceding claim further comprising a layer of an adhesive (40) on said layer of metal (30). A metallized multilayer film (5) according to claim 5 further comprising a release liner (50) on said layer of adhesive (40). A metallized multilayer film (5) according to claim 1 further comprising a printing ink deposited on said first substrate layer (10). A metallized multilayer film (5) according to claim 1 further comprising a layer of a coloured resinous material on said first substrate layer (10). An article, said article having a surface which bears a metallized multilayer film according to claim 5 thereon.

Inventors: SUZUKI KOHJI, SUZUKI, KOHJI, Suzuki, Kohji, c/o Yamagata 3M Limited
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1991
Main classification: B32B27
IPC codes: B32B15, H05K1, B32B27, B44C1, C08L33, C08L27