Abstract:
An index tab assembly may include a liner sheet with an adhesive releasing surface and an overlying plastic sheet with die cut partial fold tabs therein, and with a layer of pressure sensitive adhesive between the two sheets. The tabs include two printable areas of substantially equal size and a securing area extending from one of the printable areas. The securing area has a narrow strip area adjacent the printable area which is free from adhesive. In use, the tabs are removed from the liner, the two printable areas are folded together, and the resultant step or lip and the adhesive free area cooperate to facilitate accurate placement of the index tab.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to index tabs, and more particularly to self adhesive index tabs that can be attached by the user to the edge of sheets.  
         BACKGROUND OF THE INVENTION  
         [0002]    Many index tab constructions have been proposed heretofore, and some of the prior patents in this field include the following: U.S. Pat. No. 3,314,529; U.S. Pat. No. 3,473,827; U.S. Pat. No. 4,972,615; U.S. Pat. No. 5,662,976; U.S. Pat. No. 6,086,107; U.S. Pat. No. 6,013,154; U.S. Pat. No. 6,132,831; Great Britain Patent No. 2,006,683A; and Great Britain Patent No. 1,212,619.  
           [0003]    However, the tabs and tab sheets which have been proposed heretofore are subject to various problems. For example, when a polyester sheet is laminated to a paper liner, and is stored for a time prior to printing in a laser or ink jet printer, certain problems may arise. If the tabs on the polyester sheet have a free edge, they may fold outward and interfere with smooth rapid feeding of the sheets through the printer; and paper jams may occur. In addition, under high humidity conditions curling of the sheets may occur. Further, if the matrix of polyester around the tabs is removed, release material on the liner may engage the printer rollers and may cause feeding problems.  
           [0004]    In addition, with prior art tabs, it is often difficult to locate the tabs accurately on the edge of the sheet material to which the tab is to be fastened.  
         SUMMARY OF THE INVENTION  
         [0005]    In accordance with one illustrative embodiment of the invention, sheets of index tabs may include a liner sheet and an overlying plastic sheet, preferably of translucent polyester, with the index tabs being die cut through the plastic sheet. The liner sheet has a release surface, and a layer of pressure sensitive adhesive is located between the two sheets, except for certain non-adhesive strip areas. The sheets may be letter size, 8½×11 inches, or A-4 paper size, or have other dimensions.  
           [0006]    The index tabs have three areas, including first and second printable areas of approximately equal size, and a securing area extending from one of the printable areas. A score line is provided between the two printable areas to facilitate folding them over against each other, with two full thickness ties at the ends of the score line. A narrow strip area free of adhesive is located on the securing area next to the adjacent printable area.  
           [0007]    After the sheets are printed, preferably with the die cut tabs and the entire plastic sheet intact, a printed tab may be removed, and the two adhesive coated printable areas are folded together. This forms a lip or step immediately adjacent the adhesive free strip area. The index tab is then attached to the edge of sheet material, with the lip or step being placed against the edge of the sheet material, and with any needed slight adjustments being facilitated by the adhesive free area; and then the adhesive coated securing area is pressed onto the sheet to accurately secure the tab in position.  
           [0008]    Concerning other aspects or features of the invention, the tabs are preferably formed of translucent plastic material such as polyester.  
           [0009]    When the sheets are being printed, with indexing information, the full plastic sheet including the matrix around the die cut tabs is fed through the printer. Cuts may be provided in the plastic sheet from the edges of the plastic sheets to the die cut tabs and between the die cut tabs, to avoid curling of the two layer sheet assemblies, which might otherwise occur as a result of non-uniform moisture absorption.  
           [0010]    The plastic sheet material is preferably treated to receive a coating, normally a colored coating such as colored ink, to form a suitable background for printing indexing information on the tabs, using a laser ink jet printer or by any known printing method. The colored coating is preferable on the side of the plastic sheet to which the adhesive is applied, facing the liner, but may be on the outer surface of the plastic sheets.  
           [0011]    It is to be understood that the tabs per se could be sold individually rather than on letter size sheets, or in strip format, for examples.  
           [0012]    Other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description and from the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 represents a two sheet assembly showing index tabs mounted on a liner or backing sheet, and illustrating the principles of the invention;  
         [0014]    [0014]FIG. 2 is an enlarged showing of one of the index tabs along with a portion of the sheet assembly of FIG. 1;  
         [0015]    [0015]FIG. 3 is a cross sectional view taken along lines  3 - 3  of FIG. 2;  
         [0016]    [0016]FIG. 4 is a cross sectional view taken along lines  4 - 4  of FIG. 2;  
         [0017]    [0017]FIG. 5 is a fragmentary view of a sheet with an index tab attached thereto; and  
         [0018]    [0018]FIG. 6 illustrates the method of securing an index tab to the edge of a sheet, with arrangements to ensure accurate and convenient location of the tab, illustrating one aspect of the principles of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    Referring more particularly to the drawings, FIG. 1 shows a two layer assembly  12  which includes a liner sheet  14  to which a large number of index tabs  16  are secured. At the location designated  14 - 1  and  14 - 2  the index tabs have been removed, and accordingly, the underlying liner or support sheet  14  may be seen in the showing of FIG. 1. Each of the index tabs such as the index tab  16 - 1  includes a first printable area  18 , a second printable area  20 , and a securing area  22 . The printable areas  18  and  20  are provided with a coating or treatment on the exposed surface to make the areas more ink or toner receptive. The underlying liner  14  is provided with a release surface; and a layer of adhesive is provided between the index tab layer, which may be plastic sheet material such as polyester (which may have an opaque coating thereon), and the underlying substrate or liner  14 .  
         [0020]    Reference is now made to index tab  16 - 2  which has index information printing on the two printable areas, and which is in the process of being removed from the backing sheet  14 .  
         [0021]    Referring now to the index tab  16 - 3  it may be noted that it has a score line  24  between the two printable areas so that, upon removal, the two printable areas may be folded together and the index tab may be therefore read from two directions. A score line in this location is also present in the other index tabs on the sheet.  
         [0022]    Referring now to FIG. 2 of the drawings, an enlarged showing of one of the index tabs  16 - 4 , is presented. In FIG. 2, the two printable areas  18  and  20  may be noted, along with the securing area  22  which is to be adhesively secured to the edge of a sheet where the index tab is to be located.  
         [0023]    For convenience, reference will now be made to FIGS. 3 and 4 of the drawings which are cross sectional views taken along lines  3 - 3 , and  4 - 4 , respectively, of FIG. 2. In each case, the index tab  16 - 4  is shown mounted on the liner  14  which has a slick upper surface  32  which may be provided through the use of a release layer such as a silicone on the surface  32  or by the use of machine grade siliconized paper. A layer of adhesive, preferably pressure sensitive adhesive,  34  is located between the liner  14  and the plastic sheet material  36  of the index tab, in order to hold the two portions  18  and  20  together, when folded, and to hold the securing portion or area  22  to the sheet where the index tab is finally mounted. Other adhesives, such as permanent pressure sensitive adhesive, or water activated adhesives, may be used.  
         [0024]    As shown in FIG. 3, the index tab  16 - 4  is provided with a score line  38  to facilitate folding the two printable areas  18  and  20  together. The cross sectional view of FIG. 4 is taken along the score line and shows the score line  38 , with two ties  40  and  42  at the ends of the score line to help avoid accidental ripping of the index tab along the score line as the index tab is being removed from the underlying liner sheet  14 .  
         [0025]    Concerning one other minor matter, it may be noted that a broad substantially opaque area, layer  44  is provided on the two printable areas  18  and  20  of the index tab between the plastic sheet material  36  and the liner  14 . This opaque layer provides an opaque background for the index information printing on the two printable areas  18  and  20 . The layer  44  is preferably located as shown in FIGS. 3 and 4, but may be on the outer exposed surface of the printable areas.  
         [0026]    Incidentally, in order for convenience of disclosure, the thicknesses of the various layers as shown in FIGS. 3, 4, and  6  are somewhat exaggerated, and the actual layers would be somewhat thinner. More specifically, the liner  14  would normally be about two to four thousandths of an inch thick and the plastic layer  36  would be of similar thickness. More generally, various thicknesses of the liner and the plastic layer may be used, but it is desirable that the entire sheet assembly of FIG. 1 be not more than about 0.012 or 0.015 of an inch thick for convenience in feeding through a laser or an ink jet printer.  
         [0027]    Referring now to FIG. 5 of the drawings, the reference numeral  52  refers to the corner of a sheet to which the index tab  16  is secured. Visible in FIG. 5 is the printed surface  20  and the securing area  22  which holds the index tab  16  to the sheet  52 .  
         [0028]    [0028]FIG. 6 shows the application of an index tab  16  to a sheet  52 . Visible in FIG. 6 is the securing area  22  and the adhesive  34  which is on the underside of the securing area  22 . The two printable areas  18  and  20  have been folded over against one another to provide a shoulder or a lip  54  which can engage the outer edge of the sheet  52  to assist in the location of the index tab precisely on the edge of the sheet  52 .  
         [0029]    In addition, as shown in FIGS. 3 and 6, there is a narrow strip area  56  which is free of adhesive and which also serves to assist in the proper location of the tab  16  on the edge of the sheet  52  as shown in FIG. 6. This adhesive free area  56  avoids premature contact of the adhesive  34  with the edge of the sheet  52 , and thus facilitates accurate location of the index tab  16 .  
         [0030]    Concerning one other minor matter, the sheet assembly  12  of FIG. 1 is provided with die cuts through the upper plastic sheet material, as indicated at the reference numerals  62  which appear in FIGS. 1 and 2. These cuts  62  which extend to the die cuts forming the tabs, allow the plastic sheet material to expand with the liner as the liner absorbs ambient moisture, and thus avoid curling or warping of the sheet assemblies. It may also be noted that similar cuts  64  extend between adjacent tabs  16 . The cuts  62  and  64  area preferably aligned parallel with the grain of the paper liner.  
         [0031]    It may also be noted that the tabs  16  may be different colors, for convenience in providing special indexing arrangements desired by customers for certain specific purposes. Additionally, in FIG. 1, it may be noted that the sheet is overprinted in the printable areas of the index tabs, leaving a residual coating around the areas  14 - 1  and  14 - 2  of FIG. 1, where tabs have been removed. This overprinting assures full coverage of the printable coating on the printable areas  18  and  20  of the tabs.  
         [0032]    In the preparation of the assembly of FIG. 1, the translucent polyester sheet material may be initially printed over the entire printable areas with colored ink, and then with white opaque ink for opacity, and subsequently with an adhesive layer in the areas described above. The sheet material is then combined with the layer of liner material, and thereafter the tabs are die cut and scored. Incidentally, the outer exposed surface of the polyester material may be specially treated or coated to enhance receptivity to printing by laser or ink jet printers, and/or for writing by pencil or pen, as detailed hereinbelow. It is also noted that the overall ink coating for opacity and color may be on the top exposed side of the polyester material or preferably on the underside as described hereinabove.  
         [0033]    Concerning other aspects of the preferred embodiments of the invention, the liner is preferably made of machine finished grade siliconized paper, although it could be calendared paper coated with a thin layer of silicone. The adhesive is preferably a rubber based hot melt adhesive, and is removable or repositionable adhesive. Other adhesives may be used, including acrylic pressure sensitive adhesives for one example. Concerning the thickness of the adhesive coating, it is preferably about one mil thick, but may be from about 0.0005 to 0.0015 inch in thickness. Regarding the background broad area coating on the underside of the printable areas, this may be accomplished using what is known as flexo-ink, or water based ink for flexographic printing processes. Other coatings may be employed to provide an opaque background for the letter or number printing to be applied to the printable areas of the tabs. The total thickness of the tab sheet assemblies in one preferred embodiment was about 8 mils, but somewhat greater or lesser thicknesses could be used, with a thickness more than about 12 or 15 thousandths of an inch being undesirable as being too thick for easy feeding through laser or ink jet printers. With regard to the ink receptive quality of the plastic sheet material various methods are known to make the surface ink receptive and these may involve treatment such as by high voltage, for example, or coating with an ink receptive coating. Polyester plastic sheet material pre-treated to be ink receptive is available from Mitsubishi, of Greer, S.C., as Hostaphan® 4IJL film. A coating which may be employed for the upper surface for receiving laser or ink jet printing or writing, is disclosed in U.S. patent application Ser. No. 09/726,196, filed Nov. 29, 2000, and comprises a mixture of polyvinyl pyrrolidone, silica, and a chromium complex capable of crosslinking polyvinyl pyrrolidone.  
         [0034]    It is further noted with respect to FIG. 1 of the drawings that the adhesive between the upper plastic sheet and the liner  14  is preferably spaced back from the edges of the sheet, by a few thousandths of an inch, leaving a very narrow adhesive free zone around all four edges of the sheet. This will avoid possible contamination of printers which might otherwise occur as a result of adhesive oozing out from the two layer assembly under applied heat and pressure which may occur during printing.  
         [0035]    It is to be understood that the foregoing detailed description and the accompanying drawings relate to one preferred embodiment of the invention. Various changes and modifications may be made without departing from the spirit and scope of the invention. Thus, by way of example and not of limitation, instead of being rectangular, the tabs may have other shapes. In addition, the two sheet materials as identified above, are preferred, but other sheet materials may be employed, including specifically a high strength paper for the tabbed materials. It may also be noted that the lip may be formed by a partially folded over tab area, or by a supplemental layer overlying a printable portion of the said tab. Regarding the score line, it may be in the form of a partial die cut part way through the plastic sheet material, or in the form of a line of perforations, for examples. Concerning the substantial opacity of the printable areas of the tabs, the sheet plastic may be substantially opaque; and if opaque colored ink is used, the additional opaque white ink may not be needed. Also, if the opaque layer is on the exposed surface of the tab, it would be preferable to apply the white ink first, and then a layer of colored ink. With regard to adhesives, while repositionable pressure sensitive adhesive is preferred, other adhesives may be used, including permanent pressure sensitive adhesives, or water activated adhesives, for examples. Accordingly, the present invention is not limited to the precise constructions shown in the drawings and described in detail hereinabove.