WO2000016167A1

WO2000016167A1 - Multilayer adhesively bonded articles having an ink-containing surface bonded to a second surface

Info

Publication number: WO2000016167A1
Application number: PCT/US1999/020743
Authority: WO
Inventors: Eric D. Morrison; Minyu Li; Bao Tran; Marvin C. Trulsen; James P. Gardner, Jr.; James A. Baker
Original assignee: Imation Corp.
Priority date: 1998-09-11
Filing date: 1999-09-09
Publication date: 2000-03-23
Also published as: JP2002525656A; KR20010079785A

Abstract

Laminates that include at least one ink-bearing surface of a polymeric substrate adhesively bonded to a surface of a second polymeric substrate in which the peel strength between the substrates is at least 6 N/cm. The ink is an electrophotographic ink. In one aspect of the invention, the two substrates are different from each other. In another aspect of the invention, the peel strength reaches 6 N/cm within 1 hour minutes following lamination under prescribed conditions.

Description

MULTILAYER ADHESIVELY BONDED ARTICLES HAVING

AN INK-CONTAINING SURFACE BONDED TO A SECOND SURFACE

Background of the Invention This invention relates to multilayer laminates in which at least one of the layers includes an ink-bearing surface.

There has been an interest in printing images such as photographic images onto plastic substrates. It would be particularly desirable to use liquid toner-based electrophotographic printing for this purpose because this printing technique produces high quality images.

Once the image has been printed onto the surface of the plastic substrate, it is necessary to apply a protective film over the printed ink-bearing surface. The bond strength between the protective film and the printed surface must be sufficient to resist delamination under typical use conditions.

Summary of the Invention In a first aspect, the invention features an article that includes (a) a first polymeric substrate having a major surface; (b) a second polymeric substrate different from the first substrate having a major surface; and (c) an adhesive bonding the major surface of the first polymeric substrate to the major surface of the second polymeric substrate such that the peel strength between the polymeric substrates is at least 6 N/cm. At least one of the major surfaces is an ink-bearing surface. It is also possible for the major surfaces of both substrates to be ink- bearing surfaces. The two polymeric substrates are "different" in the sense that they are made from different base polymers.

The ink preferably is an electrophotographic ink. In some embodiments, the ink includes a polymer having a Tg no greater than about 30°C, while in other embodiments the ink includes a polymer having a Tg greater than about 30°C. One example of a suitable ink is derived from gel organosol-containing, liquid toner compositions described, e.g., in Baker et al., U.S. 5,652,282 and Baker et al., U.S. 5,698,616. These toners include (a) a carrier liquid (e.g., an aliphatic hydrocarbon carrier liquid having a Kauri-Butanol number less than 30) and (b) a (co)polymeric steric stabilizer having a molecular weight greater than or equal to 50,000 Daltons and a polydispersity less than 15 covalently bonded to a thermoplastic (co)polymeric core that is insoluble in the carrier liquid. The core preferably has a Tg no greater than about 30°C. The toner may further include a colorant and a charge director. Also suitable are non-gel organosol-containing liquid toner compositions described, for example, in Baker et al., U.S. 5,886,067. Another example of a suitable ink is derived from liquid toners described in Landa et al., U.S. 4,794,651; Landa et al., U.S. 4,842,974; Landa et al., U.S. 5,047,306; Landa et al., U.S. 5,047,307; Landa et al., U.S. 5,192,638; Landa et al., US. 5,208,130; Landa et al., U.S. 5,225,306; Landa et al., U.S. 5,264,313; Landa et al., U.S. 5,266,435; Landa et al., U.S. 5,286,593; Landa et al., U.S. 5,346,796; Landa et al., U.S. 5,407,771; and Landa, WO92/17823 published October 15, 1992 entitled "Polymer Blends."

The compositions are also useful with inks such as ink jet inks and lithographic inks. Any of these inks may be used alone or in combination with each other. For example, the ink-bearing surface may include electrophotographically printed areas featuring an electrophotographic ink and offset printed areas featuring a lithographic ink. Preferably, however, all the printed areas of the laminate are electrophotographically printed areas featuring an electrophotographic ink.

The adhesive is preferably selected from adhesive compositions which, when interposed between the major surfaces of the first and second polymeric substrates and laminated together between a pair of lamination rollers using a line speed of about 0.2-10 inch/sec, a temperature of about 65-150°C, and a nip pressure of about 15-110 lbs/in.² to bond the first and second polymeric substrates together, achieve a peel strength of at least 6 N/cm within a period of no greater than about 1 hour following lamination. A number of polymeric substrates may be used. In one preferred embodiment, the first polymeric substrate features a rigid core layer and the second polymeric substrate features a flexible overlay film. Preferably, at least one of the substrates is substantially transparent to permit viewing of the printed image on the ink-bearing substrate surface.

Examples of suitable polymeric substrates are selected from the group consisting of polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, polyesters, polyolefins, polycarbonates, and combinations thereof. Also suitable are microporous substrates such as that commercially available under the trade designation TESLIN films available from PPG, Inc. of Pittsburgh, PA. One preferred construction includes a polyvinyl chloride substrate adhesively bonded to a substantially transparent polyester overlay film.

The article may include more than two substrates. For example, the article may include a core substrate having a pair of opposed major surfaces, each of which is bonded to a separate overlay film. Such constructions are particularly useful for articles having printed images on two different surfaces.

In a second aspect, the invention features an article that includes: (a) a first polymeric substrate having a major surface; (b) a second polymeric substrate having a major surface; and (c) an adhesive bonding the major surface of the first polymeric substrate to the major surface of the second polymeric substrate such that the peel strength between the polymeric substrates is at least 6 N/cm, where the adhesive is selected from adhesive compositions which, when interposed between the major surfaces of the first and second polymeric substrates and laminated together between a pair of lamination rollers using a line speed of about 0.2-10 inch/sec, a temperature of about 65-150°C, and a nip pressure of about 15- 110 lbs/in.² to bond the first and second polymeric substrates together, achieve a peel strength of at least 6 N/cm within a period of no greater than about 1 hour following lamination. One, or both, of the major surfaces is an ink-bearing surface. The polymeric substrates may be the same as, or different from, each other. Useful polymeric substrates include those described above in connection with the first aspect of the invention. The article may also include more than two substrates. For example, the article may include a core substrate having a pair of opposed major surfaces, each of which is bonded to a separate overlay film. Such constructions are particularly useful for articles having printed images on two different surfaces.

In a third aspect, the invention features a lamination process for preparing the above-described articles in which the major surfaces of the first and second substrates are laminated together through the adhesive using a line speed of about 0.2-10 inch/sec, a temperature of about 65-150°C, and a nip pressure of about 15-110 lbs/in.² to achieve a peel strength between the first and second substrates of at least 6 N/cm within a period no greater than about 1 hour following lamination. The ink-bearing image is preferably formed according to an electrophotographic process that includes:

(i) charging the surface of an electrophotographic photoreceptor;

(ii) imagewise exposing the charged surface of the photoreceptor to radiation to dissipate charge in selected areas and thereby form a latent image on the photoreceptor surface;

(iii) contacting the latent image with a toner to form a toned image; and

(iv) transferring the toned image to the major surface of the first polymeric substrate.

The toner preferably is a liquid toner. Preferred liquid toners, in turn, include a film-forming polymer. In some embodiments, the film-forming polymer has a Tg no greater than about 30°C, while in other embodiments, the film-forming polymer has a Tg greater than 30°C. Following lamination, the article may be subjected to a number of operations, including slitting, cutting, hole punching and drilling, foil stamping, sewing and grommeting, foil stamping, perforation, folding, surface texturing, and the like. Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.

Detailed Description

The invention will now be described further by way of the following examples.

The black, positive-acting, film-forming, electrophotographic ink used in the examples was prepared at an organosol pigment ratio of 6 following the procedure described in Example 40 of U.S. 5,652,282 modified as follows.

The gel organosol prepared according to the procedure of Example 22 of U.S. 5,652,282 was mixed using a Silverson mixer (Model L2R, Silverson Machines, Ltd.) operated at the lowest speed setting. After mixing for five minutes, 1912 g of the homogenized organosol at 16.14% (w/w) solids in NORPAR 12 were combined with 1031 g of NORPAR 12 (Exxon Chemical Co., Houston, TX), 51 g of MONARCH 120 carbon black (Cabot Corp., Billerica, MA), and 6.08 g of Zirconium HEX-CEM (OMG Chemical Company, Cleveland, OH) in a 4.0 liter polyethylene container. This mixture was then milled in ten vertical bead mills, each having a capacity of 0.5 liter (Model 6TSG-1/4, Aimex Co. Ltd., Tokyo, Japan) by placing 300 g of millbase and 390 g of 1.3 mm diameter Potters glass beads (Potters Industries, Inc., Parsippany, NJ) in each mill. Each mill was operated at 2,000 rpm for 1.5 hours without cooling water circulating through the cooling jacket of the milling chamber.

A portion of the 12% (w/w) solids toner concentrate thus formed was diluted to approximately 3% (w/w). This dilute toner sample exhibited the following properties, as determined using the test methods described in U.S.

5,652,282:

Number Mean Particle Size: 0.261 micron

Bulk Conductivity: 149 picoMhos/cm Percent Free Phase Conductivity: 5%

Dynamic Mobility: 0.0402 micron-cm/[volt-second]

This 3% toner was tested on the toner plating apparatus described in U.S. 5,652,282. The reflection optical density (ROD) was greater than 1.47 at plating voltages greater than 400 volts.

EXAMPLES

Example 1

An adhesive-coated polyester film was prepared by solution coating DesmocoU 8634 polyurethane resin solution (15 wt. % in methyl ethyl ketone, available from Bayer Chemical Co.) onto Mellinex 454 polyester film (0.92 mil, available from Dupont) at a wet coating coverage of approximately 375 g/square meter, followed by drying to give an adhesive-coated film. The dry thickness of the adhesive layer was 1.0 mil. The adhesive portion of the film was area printed using a liquid toner- based, black, positive-acting, film-forming, electrophotographic ink (prepared as described above) to a net optical density of 1.6. The net optical density is equal to the white light optical density minus the white light optical density of unprinted film, measured in reflectance mode with a Macbeth densitometer. The net optical density corresponded to an ink net optical density of 1.3 for a paper substrate printed under identical conditions.

After printing, the adhesive-coated film was laminated to a white polyvinyl chloride substrate. Lamination took place between two heated rollers (roll surface temperature = 135-138°C) at a rate of 0.4 inches/second to give a laminated, printed article. The article was cut into strips measuring one inch wide and the 180 degree peel force required to cause delamination was measured 15 minutes after the lamination step using an Instron Tester (Model 5542). The crosshead speed was 12 inches/minute. The peel force was determined to be 5.0 pounds/inch (= 8.8 N/cm). In a separate experiment, unprinted adhesive-coated polyester film was laminated to an identical white polyvinyl chloride substrate in an identical manner. The peel force was determined to be approximately 12 pounds/inch (21 N/cm), which resulted in tearing of the polyester film.

Example 2

The procedure of Example 1 was followed except that an adhesive coating solution, prepared by adding methyl ethyl ketone (201 g), Epon 1007F epoxy resin (143 g of a 20 wt. % solution in methyl ethyl ketone, available from Shell Chemical Co.), epoxy cyclohexylethyl trimethoxy silane (14.4 g, available from Aldrich Chemical Co.), and Vestanat T1890E isocyanate (215 g of a 20 wt. % solution in methyl ethyl ketone, available from Creanova) to 1428 g of a solution of DesmocoU 8634 polyurethane resin (15 wt. % in methyl ethyl ketone, available from Bayer Chemical Co.), was used. The resulting laminate had a peel strength of 4.5 pounds/inch (7.9 N/cm).

Example 3

An adhesive-coated polyester film was prepared by solution coating Airflex 7200 ethylene vinyl acetate copolymer dispersion (72 wt. % in water, available from Air Products Chemical Co.) onto Mellinex 454 polyester film (0.92 mil, available from Dupont) at a wet coating coverage of approximately 75 g/square meter, followed by drying to give an adhesive-coated film. The dry thickness of the adhesive layer was 2 mil.

The adhesive portion of the film was area printed using a liquid toner- based, black, positive-acting, film-forming, electrophotographic ink (prepared as described above) to a net optical density of 1.6 and then laminated to a white polyvinyl chloride substrate following the procedure described in Example 1. The peel strength, measured as described in Example 1, was determined to be 4.5 pounds/inch (7.9 N/cm).

In a separate experiment, unprinted adhesive film was laminated to an identical white polyvinyl chloride substrate in an identical manner. The peel force was determined to be approximately 5.0 pounds/inch (8.8 N/cm).

Example 4

A laminated construction was prepared by laminating a sheet of Bynel E418 anhydride-modified ethylene vinyl acetate polymer adhesive (5.0 mil thick, available from Dupont Chemical Co.) between a white polyvinyl chloride substrate and the coated side of a sheet of coated polyester film (Mylar 50RL31, available from Dupont Chemical Co.). Lamination was accomplished following the procedure described in Example 1. The resulting laminate had a peel strength, measured as described in Example 1, of 6 pounds/inch (10.5 N/cm).

In a separate experiment, the adhesion of Bynel E418 to an electrophotographic ink was tested. A substrate was prepared by forming a primer layer and then a subbing layer on 4 mil thick polyvinylidene chloride primed polyester film (available from 3M Company). The primer layer was prepared by coating (to a wet thickness of 12.5 microns) an aqueous dispersion containing 250 ppm by weight colloidal vanadium oxide (added as a 1% dispersion in water, available from 3M Company), 2500 ppm by weight of hydrolyzed glycidoxypropyl trimethoxy silane (hydrolyzed in water at 5% concentration using 50 ppm HC1 as a catalyst 18 hours before addition to the primer layer coating solution), 500 ppm by weight Triton X-100 surfactant (available from Rohm and Haas), and 2.5 % by weight Eastek 2400 polymer (available as a 40% dispersion from Eastman Chemical Co.), followed by drying. The subbing layer was prepared by coating (to a wet thickness of 9 microns) the coating solution of Example 1. A. of U.S. Patent 5,204,219 onto the primer layer, followed by drying. The subbing layer of the resulting film was area printed using a liquid toner-based, black, positive-acting, film-forming, electrophotographic ink (prepared as described above) to an optical density of 1.2. The adhesion of Bynel E418 adhesive to the ink was determined by laminating a 5.0 mil thick sheet of the adhesive between the printed surface of the subbing layer of the polyester film and the coated side of Mylar 50RL31 film following the procedure described in Example 1.

The peel strength of the resulting laminate was measured according to the procedure described in Example 1. Separation between the Bynel E418 and the printed surface occurred at a peel force of 3.5 pounds/inch (6.1 N/cm). Separation of Bynel E418 adhesive from the Mylar 50RL31 film did not occur in the peel testing.

Example 5

The procedure of Example 4 was followed except that 2 mil thick Bynel 11E554 film (available from Dupont Chemical Co. and described as a modified ethylene vinyl acetate) was used in place of Bynel E418. Peeling of the adhesive from bare polyvinyl chloride resulted in a peel force of 5 pounds/inch (8.8 N/cm). Peeling of the adhesive from the electrophotographic ink resulted in a peel force of 6 pounds/inch (10 N/cm). Separation of Bynel 11E554 adhesive from the Mylar 50RL31 film did not occur in the peel testing.

Example 6

A coating solution was prepared by adding Irgacure 1700 photoinitiator (3 g, available from Ciba-Geigy), a 15 wt.% solution of a 2-isocyanato ethyl methacrylate-modified polyacrylic acid photopolymer in Dowanol PM (Dow Chemical Co.) (240 g, prepared as described in published PCT application no. PCT/US96/03542, and Sartomer SR 259 polyethylene glycol diacrylate (21.0 g of neat liquid, available from Sartomer, Inc.) to 104.5 g of Dowanol PM. The solution was then knife-coated onto polyethylene naphthalate film (available from Teijin Films, LTD) at a wet coating coverage of approximately 200 g/square meter and then dried for 3 minutes at 80°C to give a u.v. -curable adhesive-coated film. The dry thickness of the adhesive layer was 1.0 mil.

The adhesive portion of the film was area printed using a liquid toner- based, black, positive-acting, film-forming, electrophotographic ink (prepared as described above) to a net optical density of 1.6 and then laminated to a white polyvinyl chloride substrate following the procedure described in Example 1.

Following lamination, the adhesive was cured by exposing the printed, laminated article to ultraviolet radiation in air (40 units exposure using a Burgess Controlux Exposure Unit, available from Burgess Industries, Minneapolis MN). The article was then cut into strips measuring one inch wide. Adhesive tape (No. 396 adhesive tape commercially available from 3M) was applied to the exposed polyethylene naphthalate surface of the article and the 180 degree peel force required to cause delamination of the polyethylene naphthalate film from the polyvinyl chloride substrate was measured followed the procedure described in Example 1. The peel force was determined to be in excess of 3.5 pounds/inch (6.1 N/cm).

In a separate experiment, unprinted adhesive film was laminated to an identical white polyvinyl chloride substrate in an identical manner, and the peel strength measured. The peel strength was sufficiently high to cause tearing of the polyethylene naphthalate film.

Example 7

An adhesive-coated polyethylene naphthalate film was prepared following the procedure of Example 6 except that Sartomer SR 610 polyethylene glycol diacrylate was used in place of Sartomer SR 259 polyethylene glycol diacrylate. The dry thickness of the adhesive layer was 1.0 mil. The film was then used to prepare a laminated article as described in Example 1, except that the temperature of the heated rollers used for lamination was 95-120°C. The resulting article had a peel strength in excess of 3.5 pounds/inch (6.1 N/cm). In a separate experiment, unprinted adhesive film was laminated to an identical white polyvinyl chloride substrate in an identical manner, and the peel strength measured. The peel strength was sufficiently high to cause tearing of the polyethylene naphthalate film.

Example 8

The procedure of Example 7 was followed except that the adhesive was coated onto a polyethylene terephthalate film (1 mil thick E2Q film available from Teijin Films, Ltd.). In addition, instead of Sartomer SR 610 polyethylene glycol diacrylate, Sartomer CN 966 A80, a urethane acrylate blended with tripropylene glycol diacrylate, was used. The 180 degree peel force required to cause delamination was determined to be in excess of 3.5 pounds/inch (6.1 N/cm).

In a separate experiment, unprinted adhesive film was laminated to an identical white polyvinyl chloride substrate in an identical manner, and the peel strength measured. The peel strength was sufficiently high to cause tearing of the polyethylene terephthalate film.

Example 9

The procedure of Example 4 was followed except that a polyester film coated with Bostik Nitel 3554 adhesive (an amorphous, thermoplastic, high molecular weight, linear, saturated, polyester resin) was used in place of Bynel E418. The adhesive-coated film was prepared by solution coating a 40% solids solution of Bostik Nitel 3554 polyester adhesive onto Mellinex 454 polyester film (0.92 mil, available from DuPont) at a wet coating coverage of approximately 125 g/square meter, followed by drying to give an adhesive-coated film. The dry thickness of the adhesive layer was 2.0 mil. Lamination to a white polyvinyl chloride substrate yielded an article having a peel strength greater than 10 pounds/inch (18 Ν/cm). In a separate experiment, the adhesion of Bostik Nitel 3554 to an electrophotographic ink was tested following the procedure of Example 4. Peeling of the adhesive-coated polyester film from the electrophotographic ink resulted in a peel force of 4 pounds/inch (7.1 Ν/cm).

Example 10

The procedure of Example 4 was followed except that a polyester film coated with a mixture of DesmocoU 8634 semi-crystalline polyurethane resin solution (Bayer Chemical Co.) and Bostik Nitel 3554 amorphous polyester resin was used in place of Bynel E418. The adhesive-coated film was prepared by solution coating a solution containing a mixture of 7.5% solids DesmocoU 8634 and 7.5% solids Bostik Nitel 3554 40% onto Mellinex 454 polyester film (0.92 mil, available from DuPont) at a wet coating coverage of approximately 170 g/square meter, followed by drying to give an adhesive-coated film. The dry thickness of the adhesive layer was 1.0 mil. Lamination to a white polyvinyl chloride substrate yielded an article having a peel strength greater than 10 pounds/inch (18 Ν/cm). In a separate experiment, the adhesion of the DesmocoU 8634 Bostik Nitel 3554 mixture to an electrophotographic ink was tested following the procedure of Example 4. Peeling of the adhesive-coated polyester film from the electrophotographic ink resulted in a peel force of 4 pounds/inch (7.1 Ν/cm).

The laminate was also peeled at 90 degrees, resulting in smooth peel at a peel force of 2.5 pounds/inch (4.4 Ν/cm), compared to a zipper-like peel observed for a laminate construction featuring only the DesmocoU 8634 adhesive. The adhesive-coated film had a solid, non-tacky surface, compared to a tacky surface observed for adhesive compositions containing Bostik 3554 alone.

Example 11

The procedure of Example 4 was followed except that a polyester film coated with a two-layer adhesive composition was used in place of Bynel E418. The adhesive-coated film was prepared by first solution coating a 6.5% solids aqueous dispersion of Airflex 7200 ethylene- vinyl acetate copolymer dispersion (Air Products Chemical Co.) onto Mellinex 454 polyester film (0.92 mil, available from DuPont) at a wet coating coverage of approximately 40 g square meter, followed by drying to give an adhesive-coated film having a dry thickness of 1.0 mil. Next, a second adhesive layer was added by solution coating a 15% solids solution of DesmocoU 8634 on top of the Airflex 7200 layer at a wet coating coverage of 85 g/square meter, followed by drying to yield a layer having a dry thickness of 0.5 mil. The total thickness of the resulting two-layer adhesive was 1.5 mil. Lamination to a white polyvinyl chloride substrate yielded an article having a peel strength of 7 pounds/inch (11 N/cm).

In a separate experiment, the adhesion of the two-layer adhesive to an electrophotographic ink was tested following the procedure of Example 4 except that the net optical density of the area-printed adhesive film was 1.6. Peeling of the adhesive-coated polyester film from the electrophotographic ink resulted in a peel force of 4.8 pounds/inch (8.5 N/cm).

The laminate was also peeled at 90 degrees, resulting in smooth peel at a peel force of 6.7 pounds/inch (4.4 N/cm), compared to a zipper-like peel observed for a laminate construction featuring only the DesmocoU 8634 adhesive. The adhesive-coated film had a solid, non-tacky surface, compared to a tacky surface observed for adhesive compositions containing Bostik 3554 alone.

Example 12

The procedure of Example 1 was followed except that DesmocoU 530 polyester-based polyurethane was used in place of DesmocoU 8634 and the thickness of the polyester film was 3 mils. In addition, the lamination speed was

0.5 inch/second. The resulting article exhibited a peel force, measured as described in Example 1, of 4.0 pounds/inch (7.0 N/cm).

In a separate experiment, unprinted adhesive-coated polyester film was laminated to an identical white polyvinyl chloride substrate in an identical manner. The resulting article was stored for two weeks at 60°C and 100% relative humidity, after which the peel strength was measured and determined to be less than 3 pounds/inch (5.3 N/cm).

Example 13 The procedure of Example 12 was followed except that the adhesive was prepared by combining 15 parts DesmocoU 530, 85 parts methyl ethyl ketone, 3 parts Nestanat T1890E isocyanate, and 1 part epoxycyclohexylethyl trimethoxy silane. The resulting article exhibited a peel force, measured as described in Example 1, of 4.0 pounds/inch (7.0 Ν/cm). The failure mode is between the adhesive and the ink.

In a separate experiment, unprinted adhesive-coated polyester film was laminated to an identical white polyvinyl chloride substrate in an identical manner. The resulting article was stored for two weeks at 60°C and 100% relative humidity, after which the peel strength was measured and determined to be 10 pounds/inch (17.6 Ν/cm).

Example 14

The procedure of Example 12 was followed except that the adhesive was prepared by combining 15 parts DesmocoU 530, 85 parts methyl ethyl ketone, 3 parts Nestanat T1890E isocyanate, 1 part epoxycyclohexylethyl trimethoxy silane, and 2 parts Epon 1007F epoxy resin. The resulting article exhibited a peel force, measured as described in Example 1, of 4.0 pounds/inch (7.0 Ν/cm). The failure mode is ink splitting.

In a separate experiment, unprinted adhesive-coated polyester film was laminated to an identical white polyvinyl chloride substrate in an identical manner.

The resulting article was stored for two weeks at 60°C and 100% relative humidity, after which the peel strength was measured and determined to be 10 pounds/inch (17.6 Ν/cm). Example 15

The procedure of Example 3 was followed except that the polyester film was coated with a mixture of DesmocoU 8634 polyurethane resin solution (Bayer Chemical Co.) and Airflex 7200 ethylene-vinyl acetate copolymer dispersion (Air Products Chemical Co.). The adhesive-coated film was prepared by solution coating a mixture of one part 15 wt.% DesmocoU 8634 and one part 15 wt.%) ethylene-vinyl acetate copolymer in methyl ethyl ketone (prepared by mixing 625 g of Airflex 7200 dispersion with 2375 g of methyl ethyl ketone) onto Mellinex 454 polyester film (0.92 mil, available from DuPont) at a wet coating coverage of approximately 170 g/square meter, followed by drying to give an adhesive-coated film. The dry thickness of the adhesive layer was 1.0 mil. The adhesive-coated film had a dry, non-tacky, feel.

The adhesive portion of the film was area printed using a liquid toner- based, black, positive-acting, film-forming, electrophotographic ink (prepared as described above) to a net optical density of 1.6 and then laminated to a white polyvinyl chloride substrate following the procedure described in Example 1. The peel strength, measured as described in Example 1 with the exception that the measurement was made 5 minutes after lamination, was determined to be 4.6 pounds/inch (8.1 N/cm). A second sample, identical to the first sample, was placed in a

Thermotron environmental chamber following lamination for a period of 14 days. The chamber was maintained at 60°C and 95% relative humidity. At the end of the 14 day period, the sample was removed and stored in a desiccator at room temperature for another 14 days. Its peel strength was then measured as described in Example 1 and determined to be 5.8 pounds/inch (10.2 N/cm).

In a separate experiment, unprinted adhesive-coated polyester film was laminated to an identical white polyvinyl chloride substrate in an identical manner. The peel force, measured 5 minutes following lamination, was determined to be 8.6 pounds/inch (15 N/cm). Two additional laminated samples were subjected to high humidity and heat (60°C/95% relative humidity) for 14 days, as described above. The peel strength of one of the samples was measured 5 minutes following removal from the Thermotron chamber and determined to be 5.4 pounds/inch (9.5 N/cm). The other sample was placed in a desiccator at room temperature for 14 days. Following removal from the desiccator, its peel strength was measured and determined to be 5.1 pounds/inch (9.0 N/cm).

In yet another experiment, the unprinted adhesive-coated film was held at 40°C for a period of one week. It was then laminated to an identical white polyvinyl chloride substrate in an identical manner. The peel strength, measured 5 minutes after lamination, was determined to be 10.6 pounds/inch (19 N/cm).

Example 16

The procedure of Example 15 was followed except that the adhesive coating solution was prepared by combining one part of the 15 wt.% ethylene-vinyl acetate solution with two parts of a 15 wt.% solution of Q-Thane Q A3781 polyurethane resin (available from K.J. Quinn and Co. of Seabrook, NH).

The adhesive-coated film was area-printed and laminated to a white polyvinyl chloride substrate, as described in Example 15. The peel strength of the laminate, measured 5 minutes after lamination, was determined to be 5.6 pounds/inch (9.9 N/cm). The peel strength of an identical laminate, measured after a 14 day exposure to high humidity and heat (60°C and 95% relative humidity), followed by a 14 day desiccation at room temperature, was 8.1 pounds/inch (14.3 N/cm).

The peel strength of a laminate prepared by laminating an unprinted adhesive-coated film and an identical white polyvinyl chloride substrate, as described in Example 15, was determined to be 5.6 pounds/inch (9.9 N/cm). Two additional laminated samples were subjected to high humidity and heat (60°C/95% relative humidity) for 14 days, as described above. The 180 degree peel force of one of the samples was measured 5 minutes following removal from the Thermotron chamber and determined to be 5.3 pounds/inch (9.5 N/cm). The other sample was placed in a desiccator at room temperature for 14 days. Following removal from the desiccator, its peel strength was measured and determined to be 8.5 pounds/inch (15 N/cm).

In another experiment, the unprinted adhesive-coated film was held at 40°C for a period of one week. It was then laminated to an identical white 5 polyvinyl chloride substrate in an identical manner. The peel strength, measured 5 minutes after lamination, was determined to be 7.5 pounds/inch (13.2 N/cm).

Example 17

The procedure of Example 15 was followed except that the adhesive o coating solution was prepared by combining one part of the 15 wt.% ethylene-vinyl acetate solution, two parts of the 15 wt.% solution of the Q-Thane QA3781 polyurethane resin, and one part of a 15 wt.% amorphous polyester resin (Nitel B3554 from Bostik Co. of Middleton, MA).

The adhesive-coated film was area-printed and laminated to a white 5 polyvinyl chloride substrate, as described in Example 15. The peel strength of the laminate, measured 5 minutes after lamination, was determined to be 5.9 pounds/inch (10.4 Ν/cm). The peel strength of an identical laminate, measured after a 14 day exposure to high humidity and heat (60°C and 95% relative humidity), followed by a 14 day desiccation at room temperature, was 7.8 o pounds/inch (13.8 Ν/cm) .

The peel strength of a laminate prepared by laminating an unprinted adhesive-coated film and an identical white polyvinyl chloride substrate, as described in Example 15, was determined to be 6.6 pounds/inch (11.6 Ν/cm). Two additional laminated samples were subjected to high humidity and heat (60°C/95% 5 relative humidity) for 14 days, as described above. The 180 degree peel force of one of the samples was measured 5 minutes following removal from the Thermotron chamber and determined to be 5.8 pounds/inch (10.2 Ν/cm). The other sample was placed in a desiccator at room temperature for 14 days. Following removal from the desiccator, its peel strength was measured and 0 determined to be 6.8 pounds/inch (12 Ν/cm). In another experiment, the unprinted adhesive-coated film was held at 40°C for a period of one week. It was then laminated to an identical white polyvinyl chloride substrate in an identical manner. The peel strength, measured 5 minutes after lamination, was determined to be 5.4 pounds/inch (9.5 N/cm). Other embodiments are within the following claims.

Claims

What is claimed is:

1. An article comprising:

(a) a first polymeric substrate having a major surface;

(b) a second polymeric substrate different from said first substrate having a major surface, wherein one of said major surfaces comprises an ink-bearing image; and

(c) an adhesive bonding said major surface of said first polymeric substrate to said major surface of said second polymeric substrate such that the peel strength between said polymeric substrates is at least 6 N/cm.

2. An article according to claim 1 wherein said first polymeric substrate comprises a rigid core layer and said second polymeric substrate comprises a flexible overlay film.

3. An article according to claims 1-2 wherein one of said polymeric substrates is substantially transparent.

4. An article according to claims 1-3 wherein said polymeric substrates are selected from the group consisting of polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, polyesters, polyolefins, polycarbonates, and combinations thereof.

5. An article according to claims 1-4 wherein said first polymeric substrate comprises polyvinyl chloride and said second polymeric substrate comprises a polyester.

6. An article according to claims 1-5 wherein one of said polymeric substrates comprises a microporous film.

7. An article according to claims 1-6 wherein said adhesive is selected from adhesive compositions which, when interposed between said major surfaces of said first and second polymeric substrates and laminated together between a pair of lamination rollers using a line speed of about 0.2-10 inch/sec, a temperature of about 65-150┬░C, and a nip pressure of about 15-110 lbs/in.² to bond said first and second polymeric substrates together, achieve said peel strength of at least 6 N/cm within a period of no greater than about 1 hour following lamination.

8. A process for preparing an article comprising:

(a) combining a first polymeric substrate having a major surface and a second polymeric substrate having a major surface with an adhesive such that said adhesive is intermediate said major surfaces of said polymeric substrates, wherein one of said major surfaces comprises an ink-bearing image; and

(b) laminating said major surfaces of said first and second substrates together through said adhesive using a line speed of about 0.2-10 inch/sec, a temperature of about 65-150┬░C, and a nip pressure of about 15-110 lbs/in.² to achieve a peel strength between said first and second substrates of at least 6 N/cm within a period no greater than about 1 hour following lamination.

9. A process according to claim 8 comprising forming said ink- bearing image according to an electrophotographic imaging process comprising: (a) charging the surface of an electrophotographic photoreceptor;

(b) imagewise exposing the charged surface of said photoreceptor to radiation to dissipate charge in selected areas and thereby form a latent image on said photoreceptor surface;

(c) contacting said latent image with a liquid toner to form a toned image; and (d) transferring said toned image to said major surface of said first polymeric substrate.

10. A process according to claim 9 wherein said toner comprises a liquid toner comprising a film-forming polymer.