JPH041341B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to transparent imageable sheets for use in mechanical copying machines. More particularly, the invention relates to a composite sheet structure comprising a transparent sheet and an opaque element adhered thereto. Such composite transparencies can be used in state-of-the-art reproduction machines that use optical sensing means to track the advancement of the imageable sheet through the feed mechanism. Modern copiers use sophisticated mechanisms that allow such sheets to be selected from stacks of imageable sheets, imaged and processed by the use of rollers, gears, belts, etc. The sheets can then be moved quickly and accurately through various points on the machine for depositing into receptacles that are then received by the machine operator. Such machines can produce a large number of copies in a relatively short period of time. To accomplish this task, sheets must be fed quickly and accurately through the machine. This type of copier can typically provide up to 120 copies per minute. Because rapid handling and processing of sheets can be achieved, sophisticated sensing mechanisms are installed in such machines to prevent damage to the machine in the event of wrinkle formation, tearing or other damage to the sheets. For example, these sensing mechanisms serve to shut down the machine in the event of a blockage, thereby preventing damage to the machine caused by such a blockage. Many sensing mechanisms use photodetectors to track the passage of the sheet through the machine. To operate such a sensing mechanism, the sheet must be opaque in certain areas to block the light beam used by the light sensing mechanism. Therefore, when transparent sheet material is used in such reproduction machines, the sheet material must be opaque in selected areas for the machine to operate properly. Some copiers require only a portion of the transparency to be opaque, in which case printing a dark line along the top or side edges of the transparency is sufficient. Other types of machines require more areas of the sheet to be made opaque, or key image areas of the sheet to be made opaque. It is clear that in this case it is not possible to use a transparent sheet with a discreet opaque line printed along one edge. To use a transparency in such a machine, a paper backing substantially the same size as the sheet is adhered to the transparency and removed therefrom after passage through the machine. Paper sheets are generally bonded together by thin lines of adhesive applied continuously or discontinuously near the common edge of the stacked sheets.
Glue it to the transparent sheet. Once the transparency has formed an image, the operator peels the paper sheet from the transparency and discards the paper sheet. The use of such conventional paper backing sheets has not provided satisfactory imageable multilayer structures. When the paper sheet is peeled away from the transparency, visible paper fibers remain in the adhesively bonded areas of the transparency. Discontinuous adhesive bonds, e.g. "interrupted"
The use of dashed adhesive lines somewhat reduces the amount of paper fibers remaining on the transparency after removing the paper sheet. However, such structured sheets create a more serious problem in that they have a greater tendency to clog in the reproduction machine's feed mechanism. The present invention is often used on "plain paper"
transparent imaging sheet manifold for use in copying machines such as electrophotographic machines called copiers
Or regarding "set". More particularly, the present invention provides a combination of a transparent polymer-based sheet that can be imaged in a copier; an opaque paper sheet; and an adhesive composition sandwiched between and bonding the paper sheet and the transparent sheet. An imageable multilayer sheet comprising: The adhesive composition is selected such that the adhesive's affinity for the surface of the paper sheet is greater than its affinity for other elements of the multilayer structure, ie, the transparent sheet or the adhesive itself. Furthermore, the adhesive is formulated such that the peel strength of the adhesive bond is less than the adhesive bond strength that would tear the paper fibers when separating the paper sheets. This careful balancing of adhesive forces allows the paper sheet to be made transparent without leaving any visible paper residue on the transparency, and preferably without leaving any substantial amount of adhesive residue on the transparency. It becomes possible to peel it off from the sheet. Preferably, the sheets of the multilayer structure of the present invention are joined by a continuous line of adhesive, such as a line of adhesive near a common edge. Many adhesives can be formulated to have the above properties. For example, natural rubber adhesives have been found to work well. It has also been discovered that certain synthetic polymer based adhesives have the necessary properties. For example, poly(vinyl acetate) polymers have been found to provide acceptable adhesives when modified by the addition of esters, particularly to modify the adhesive properties of poly(vinyl acetate). Furthermore, isooctyl acrylate/acrylimide copolymer in combination with a release agent coated on a transparent sheet has proven to be a suitable combination. The imageable multiple sheets according to the present invention have sufficient dimensional and structural stability so that they do not cause undue clogging in copying machines. Upon processing, the multiple sheets of the present invention can be easily separated without leaving visible paper fiber residues attached to the transparent sheets. The image receiving portion of the multilayer structure of the present invention is a transparent polymeric sheet. Representative examples of such polymeric sheets include poly(ethylene terephthalate) and polycarbonate sheets having a thickness of about 2 to 5 mils (50 to 200 micrometers). The image-receiving surfaces of these sheets can be treated with various surface treatments known per se to improve their imaging capabilities. Additionally, antistatic agents and friction reducing coatings may be used, as is well known in the art. Typical antistatic agents are quaternary ammonium salts, and finely divided urea formaldehyde granules can be used to form friction reducing coatings. As mentioned above, transparency sheets must be made opaque by some means to be useful in copying machines that use a light sensing mechanism to control the feed machine. This is accomplished by gluing a sheet of opaque paper to the underside (non-image receiving side) of the transparent sheet. Thus, the multiplex becomes opaque and the copier "sees" the opaque portion of the paper passing through it. After imaging, the multiplex is separated by peeling the paper sheet from the transparent sheet. Paper sheets useful in the multilayer structures of the present invention can be selected from a wide variety of paper materials. The paper should be opaque and should have sufficient dimensional stability, heat resistance, and wrinkle resistance during passage through a copier. The working characteristics of various copiers dictate the paper that should be used. For example, a copier with a relatively high fusing site temperature may use heavy weight paper, while a copier having a low fusing site temperature may perform better with low weight paper. Generally, 18 to 46 pounds (8 to 21 Kg)/ream [24" x 36" (70 x 91
cm) Paper in the weight range of 500 sheets of paper is just right. Machine glazed or calender rolled papers are preferred because there is less chance of paper tearing when the paper sheet is peeled from the transparency. Adhesives used in this invention must be formulated to have carefully balanced adhesion properties. On the other hand, the adhesive must firmly adhere the paper to the transparency so that the stacked sheets do not separate during handling and packaging or during imaging in a copier. On the other hand, the adhesive must be such that the paper sheet can be easily removed from the transparent sheet without leaving paper fibers attached to the transparent sheet. According to the invention, it has been found that the adhesive should have a bonding or cohesive strength to the transparent sheet that does not exceed the tear strength of the paper used. That is, as long as the adhesive bonding force can be coagulated or disintegrated at the adhesive-adhesive interface with a force that does not exceed this bonding force value, the paper fibers will not be torn from the surface of the paper and will not remain on the transparent sheet. For example, 30 pounds (13.6
g) Glazed paper and 3 mil (76 micrometer)
When measured with a 180 degree peel at 100 inches/minute (40 cm/minute) using polyester of approximately
An adhesive bond with a peel strength less than 1400 g/inch width (550 g/cm) is a satisfactory bond. If the adhesive bond strength is greater than this value, the paper fibers will tear from the paper when the sheets are separated. Preferably, the adhesive bond breaks down preferentially at the interface between the adhesive and the transparent sheet, leaving no adhesive residue on the transparent sheet. This is easily accomplished using certain adhesive materials, as will be seen below. Adhesives having the necessary adhesive properties can be formulated by those skilled in the adhesive art once the desired critical conditions have been established. Such formulation operations include the selection of adhesive materials that have the necessary physical properties and affinity for the surfaces to be bonded, and then, if necessary, the addition of polymers to "tweak" the balance of adhesion. Includes degeneration. Various polymers can be used as the base polymer for adhesive formulations. Rubber and poly(vinyl acetate) are two materials that are particularly useful in making water-based adhesives. Natural rubber latex is a particularly useful substrate for water-based adhesives because it is elastic, tough, and has good aging properties. Its tackiness can be easily adjusted by suitable formulation, and its aging properties can be improved by the addition of antioxidants and other known additives.
Useful compositions are 60% solids natural rubber latex
167 parts by weight, 8.0 parts of terpene tackifier resin, 0.2 parts of antioxidant, 0.7 parts of thermoplastic resin/ester substance
2.8 parts of plasticizer, 2.3 parts of 26 Baumé ammonia and 58 parts of water. Another type of adhesive that has been found to work satisfactorily is a modified poly(vinyl acetate) adhesive. The main components of this adhesive are approximately 46 to 51 parts by weight of poly(vinyl acetate) and 2 parts of diethylene glycol dibenzoate.
4 parts by weight, 2 to 3.5 parts dipropylene glycol dibenzoate and 44 parts by weight water. These adhesives are particularly desirable because they also tend to be substantially removed from the transparent polyester sheet when the paper sheet is peeled from the polyester sheet. Many other adhesives can also be used in combination with release agents or other surface modified coatings. For example, isooctyl acrylate/isooctyl acrylate in organic solvent
Acrylic imide copolymers can be used in combination with low-adhesion surface treatments such as poly(octadecyl isocyanate)-based urethanes. Ethylene/vinyl acetate copolymer hot melt adhesives can also be formulated to provide the necessary adhesive. In addition to the adhesives described above, a unique class of adhesive materials based on the use of inherently sticky, elastomeric copolymer microspheres can be used in the present invention. These sticky microspheres provide a pressure sensitive adhesive with a low degree of adhesion that allows easy separation of the adhered objects. Microspheres of this type are described in US Pat. Nos. 3,691,140 and 4,166,152, which are incorporated herein by reference. These sticky microspheres can be adhered or fixed to multilayer paper sheets by primers, adhesives, or binders (see, e.g., U.S. Pat. No. 3,857,731), and can be used to form imageable sheet multilayer structures according to the present invention. It can produce low tack paper sheets that can be used in manufacturing. Multilayer structures made using these microsphere-coated paper sheets can be imaged and then separated without leaving visible paper fibers or adhesive residue on the transparent sheet. The maximum bond strength that can be created in an adhesive can be determined by testing papers used in multiplex structures with adhesives having different bond strengths. A 180 degree peel test using various adhesives can measure the amount of paper fiber removed. 30 pounds (13.6
Kg) This figure is 100 in/min (40 cm/min) at room temperature when using mechanically polished bond paper.
was found to be approximately 1400 g/inch width (550 g/cm). Various adhesives are applied to transparent substrates (e.g., plain or release agent-coated polyester) selected with a peel value that is less than or equal to the previously determined tear strength value.
Can be formulated to fail to cohere or adhere to. The imageable multilayer sheets of the present invention are formed by conventional molding by extrusion applying a continuous bead of adhesive along one edge of a paper sheet or transparency, then stacking the sheets and allowing the adhesive to dry. Can be manufactured using product forming equipment. Water-based adhesives are preferred from a cost and pollution standpoint. Additionally, organic solvent-based systems pose a potential ignition hazard due to the significant static electricity generated in some molding equipment. The imageable multiple sheets of the present invention can be successfully used in copiers that utilize photodetecting devices. The multilayer structure of the present invention is opaque and can be processed in a copier substantially like a sheet of paper without undue clogging. After processing, the multiplex can be separated by peeling the paper sheet from the transparency without leaving any visible paper residue on the transparency. The invention will be further illustrated using the following example. Example 1 A 56% solids poly(vinyl acetate) aqueous emulsion (adhesive
S6920 available from HBFuller Co.) whose solids are 76% poly(vinyl acetate) and diethylene glycol dibenzoate and dipropylene.
56% solids aqueous emulsion that is 20% 55:45 weight ratio blend with glycol dibenzoate (available from HBFuller Co. as adhesive PA3473)
Manufactured by blending with. adhesive PA3473
Glue from 10% by weight and adhesive S6920 90%
Adhesives are made over various formulation ranges up to 90% by weight PA3473 and 10% adhesive S6920. The peel strengths of these adhesive formulations and the individual peel strengths of each adhesive were determined using 30 lb (13.6 Kg) mechanically glazed bond paper (Thilmany Paper Company).
sheets bonded to 3 mil (76 micrometer) polyester. 1 inch (2.5cm)
The pieces are peeled (room temperature) by peeling 180 degrees at 100 inches/minute (40 cm/minute) and the average peel force is measured in grams. The results are shown in Table 1. The multilayer sheet is made by bonding 35 pound mechanically polished bond paper to 3 mil (76 micrometer) polyester with an adhesive containing 60 parts by weight of adhesive PA3473 and 40 parts by weight of adhesive S6920. Place a continuous 1/8 inch (0.3 cm) bead of glue onto the paper sheet.
8.5 inches x 11 inches (22 x 28 cm) long one
Apply along the edges and stack the polyester sheets together to form a multilayer structure. Once dry, the sheet can be imaged in a copier and peeled off without leaving any visible paper or adhesive residue on the polyester sheet. Continuously feeding these multiplex structures into a Sharp 810 copier did not cause any clogging of the machine when the test was stopped while feeding the 1200 sequential number multiplex structures.
A comparative multiplex construction with discontinuous adhesive lines, when similarly fed through the same copier, experienced three machine clogging during the production of 60 copies. Example 2 A natural latex rubber adhesive for imageable multi-sheet bonding was applied to 60% solids natural rubber latex 167.
8 parts of terpene resin (Piccolyte S115), 2.8 parts of plasticizer (Plastinox2246), 0.65 parts of thermoplastic resin/ester material (Polypale Wood Rosin), 0.16 parts of antioxidant (Santovar A antioxidant),
Made from 2.3 parts of 26 Baume ammonia and 58 parts of water. When manufactured, the adhesive had a viscosity of less than 100 cps. To control the fluidity of this viscosity to the molding equipment, hydroxy, ethyl cellulose (Union Carbide, QP52000-H) or sodium polyacrylate (Diamond
By adding Shamrock, Modicol VD), approx.
Increase to 5000cps. The peel strength of this adhesive was tested as in Example 1 and the results are shown in Table 1. The multilayer sheet is made by bonding 35 pound (15.9 Kg) machine gloss paper (Thilmay) to 3 mil (76 micrometer) polyester as in Example 1. This multiple sheet could be imaged in a copier and the paper sheet could be peeled off from the polyester without leaving any paper residue on the polyester sheet. Example 3 A multilayer structure according to the invention is made using a polyester sheet treated with polyoctadecyl isocyanate-based urethane along one edge on its surface. This surface treatment results in a low adhesion surface treatment. An acrylic isocyanate/acrylimide copolymer in an organic solvent is applied to a sheet of bond paper. After drying at room temperature, the sheets are properly stacked together to form an imageable sheet multiple. This sheet can be imaged in a copier and then the paper sheet can be peeled from the polyester sheet without leaving any visible paper residue.

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Claims (1)

Claims: 1. (a) a transparent polymeric sheet capable of being imaged in a copier; (b) a sheet of opaque paper underlying and properly mated with the transparent sheet; and (c) a sheet of paper and a transparent sheet. an adhesive composition sandwiched between and bonding the sheets, the adhesive composition having a peel strength of the adhesive bond less than the tear strength of the paper; 2. the adhesive forms a continuous bond line having a length substantially equal to the length or width of the paper sheet;
An image-formable multiple sheet according to claim 1. 3. The imageable multilayer sheet of claim 1, wherein the adhesive comprises an organic polymeric adhesive. 4 The organic polymer adhesive is poly(vinyl acetate),
Claim 3 selected from the group consisting of natural rubber, isooctyl acrylate/acrylic imide copolymer and ethylene/vinyl acetate copolymer.
The image-forming multilayer sheet described in 2. 5 The adhesive is about 46 to 51 parts by weight of poly(vinyl acetate) and 2 to 5 parts by weight of diethylene glycol dibenzoate.
4 parts by weight of dipropylene glycol dibenzoate, 2 to 3.5 parts by weight of dipropylene glycol dibenzoate, and sufficient water to form an emulsion. 6 Adhesive is 60% by weight solid natural rubber latex, approximately 167 parts by weight, terpene tackifying resin, 8 parts by weight,
4. The imageable multilayer sheet of claim 3, comprising 2.8 parts by weight of plasticizer, 2.3 parts by weight of ammonia, and sufficient water to form an emulsion. 7 (a) a transparent polyester sheet capable of being imaged in a copier; (b) a sheet of opaque bond paper below the transparent sheet and properly mated; and (c) between the paper sheet and the transparent sheet. sandwiched between them, joining them along a thin continuous bond line near the shared edges of the sheets, the peel strength of whose adhesive bond is less than the tear strength of the paper, thus converting the paper sheet into a polyester sheet. An imageable multilayer sheet comprising: an organic polymer based adhesive composition which can be removed from the film without leaving any appreciable paper residue thereon; 8. The imageable multilayer sheet of claim 7, wherein the adhesive bond has a peel strength of less than about 550 g/linear cm. 9. Adhesive composition: 60% by weight solid natural rubber latex, approximately 167 parts by weight, terpene adhesion-imparting resin 8
8. An imageable multilayer sheet according to claim 7, comprising parts by weight of plasticizer, 2.8 parts by weight of plasticizer, 2.3 parts by weight of ammonia, and sufficient water to form an emulsion. 10 The adhesive is about 46 to 51 parts by weight of poly(vinyl acetate), diethylene glycol dibenzoate 2
8. The imageable multilayer sheet of claim 7, comprising -4 parts by weight, 2 to 3.5 parts by weight dipropylene glycol dibenzoate, and sufficient water to form an emulsion.