Field of the Invention This invention relates generally to the field of pressure sensitive adhesive envelopes.

Background of the Invention Standard envelopes generally have dry sealing adhesive located on the flap. Because the adhesive is in a dry, solid state, the adhesive must be moistened for it to bond to a substrate. Moistening can be accomplished in a number of ways, including the most common way of licking the flap. Licking an envelope flap, however, is not only distasteful, it is also unsanitary and likely to leave bacteria on the envelope. Sponges and other devices are often used to provide moisture to the flap. In either case, effort must be made to moisten the adhesive to seal the envelopes.

In recent years, due to advances in adhesive technology, pressure sensitive adhesives have been used in envelopes to permit them to be sealed without having to moisten the flap. Such adhesives are tacky to the touch, and typically adhere upon contact. Pressure sensitive adhesives, however, must be covered and protected. Otherwise, the adhesive will adhere to virtually anything it comes into contact with. Accordingly, pressure sensitive adhesive envelopes are typically protected by a release liner or tape. A disadvantage of having a separate release liner or tape to protect the adhesive is that it must be removed each time an envelope is used. Manual effort must be made to peel off each liner or tape and the liner or tape must be disposed of after each use. Release tapes and liners also detract from the appearance of the envelopes, generally require that the envelopes have a straight flap, rather than a diagonal flap, and cause the envelopes to be more expensive to manufacture.

Summary of the Invention The present inv ention represents a significant improvement over past pressure sensitive adhesive envelopes in that it comprises a plurality of pressure sensitive adhesive envelopes that are stacked together with the flaps open and extended, wherein pressure sensitive adhesive is applied to the front of each flap, and a release coating is applied to the back of each flap, such that when the envelopes are stacked together, they adhere to one another. The release coating on the back of each flap permits each envelope to have a substantially permanent adhesive thereon, while making it possible for the envelopes to be easily separated and released from each other when desired. Simply lifting an envelope from the stack separates an envelope from the stack and exposes the adhesive, such that the envelope can be sealed simply by closing the flap and applying pressure. No release liners

or tapes are required, because the adhesive of each envelope is covered and protected by the release coating of an adjacent envelope in the stack.

Each envelope of the present invention can be constructed like any conventional envelope with a pocket or pouch and a sealing flap. A separate release liner or tape is not required to protect the pressure sensitive adhesive because the adhesive is protected by the release coating of an adjacent envelope in the stack. That is, each of the envelopes are stacked together with the flaps open and extended, facing the same direction, so that the front "tacky" side of each envelope is positioned directly adjacent the release coating of an adjacent envelope in the stack. In this manner, the envelopes are removably adhered to one another. This alleviates the need to package the envelopes in boxes.

To use, each envelope can be released and separated merely by lifting, or otherwise removing, the envelopes from the stack. Once the contents are placed into the envelope, the envelope can be sealed simply by folding, closing and applying pressure to the flap. In the preferred embodiment, the pressure sensitive adhesive bonds substantially permanently to the non-release coated body portion of the envelope. The aggressiveness, or permanence, of the adhesive, however, can be varied so that the adhesive bonds immediately, gradually, or, in some cases, non-permanently. Indeed, adhesives which are initially repositionable, and then become permanent over time, can be used in the present invention for added convenience.

Each envelope in the stack can be lifted and sealed, one-by-one, in the above described manner, without having to moisten the flap, and without having to remove any release liners or tapes, although a release sheet is provided at the bottom of the stack to protect the adhesive of the bottom envelope.

Other advantages of the present invention will be apparant from the detailed description of the invention and the following drawings. Brief Description of the Drawings

FIGURE 1 represents a perspective view of a stack of envelopes;

FIGURE 2 is a schematic view showing how the envelopes are stacked;

FIGURE 3a is a front view of an envelope of the present invention;

FIGURE 3b is a back view of an envelope of the present invention; FIGURES 4a and 4b are drawings showing how the envelopes can be removed from the stack;

FIGURE 5 represents an alternative embodiment having a window;

FIGURE 5a shows the adhesive strip of an alternate embodiment;

FIGURE 5b shows the sealant material on the sealing flap;

FIGURE 6 represents a schematic diagram of a method of manufacture used to make the present invention;

FIGURES 7a and 7b represent an alternate embodiment; and FIGURES 8a and 8b represent an alternate embodiment.

Detailed Description of the Invention As can be seen in Figure 1 , the present invention 2 comprises a plurality of envelopes 4 stacked together with sealing flaps 6 open and extended. The stack preferably comprises a multiple number of envelopes 4, each facing the same direction and aligned along edges 22 of the envelopes. As seen in Figure 2, the envelopes are stacked together with a front side 10 of each sealing flap 6 positioned adjacent and facing a back side 14 of a corresponding adjacent envelope in the stack.

As seen in Figures 3a and 3 b, pressure sensitive adhesive 8 is applied on the front side 10 of each sealing flap 6, and a release coating 12 is applied on the back side 14 of each sealing flap 6. When the envelopes 4 are stacked together, as described above, with the sealing flaps 6 open and extended, as shown in Figures 1 and 2, the envelopes adhere to each other by virtue of the pressure sensitive adhesive 8 being in direct contact with the release coating 12 of an adjacent envelope in the stack. Because the back side 14 of each sealing flap 6 is release coated 12, however, the envelopes can easily be released and separated from each other when needed, as shown in Figures 4a and 4b, simply by lifting each envelope from the stack. Lifting and separating the envelopes also automatically exposes the pressure sensitive adhesive 8 on the front side 10 of the sealing flaps 6. Once an envelope is lifted from the stack and the adhesive is exposed, the contents can be placed into the envelope, and the envelope can be sealed simply by folding and closing the flap. Because the pressure sensitive adhesive bonds on contact, just bringing the pressure sensitive adhesive 8 into contact with the non-treated envelope body portion 16. and applying pressure, seals the envelope. A release coated sheet 34 is provided at the bottom of the stack so that the adhesive on the bottom envelope is protected as well. Envelope Construction As with standard envelopes, each envelope of the present invention is preferably made from a single thin sheet of flexible material, such as paper. Although the term "paper" will be used throughout this discussion, it is understood that any suitable thin, flexible material can be used. In fact, any type of paper, including wove, recycled, bonded,

laid, cotton, paperboard and kraft, as well as other materials, such as plastic and vinyl, can be used. Although envelopes constructed from a single sheet of paper are preferred, it is intended that envelopes made from more than one sheet, or a combination of materials, as well as bags, are also within the contemplation of this invention. As is typical of most envelopes, the preferred envelopes 4 are formed in a generally rectangular outline shape 20, wherein a single sheet of paper is folded forward along a rectangular crease 22a, 22b and 22c. Three lower flaps 24, 26, 28 extend forward from the rectangular crease and are folded and secured together in overlapping fashion on the front side 16 to form a front wall 5. The front wall 5 is formed by the three flaps 24, 26, and 28, which can be secured with glue or any suitable adhesive, to form a pouch or pocket 18, as shown Figure 3 a. The sealing flap 6 extends from a back wall 21, wherein a line of weakness 30 is provided, which extends along the lower edge of the sealing flap 6 where it meets with the body of the envelope. The sealing flap 6, when desired, can be folded along the line of weakness 30 and serves to seal the envelope. As mentioned above, the envelopes of the present invention can be constructed in virtually any style, including diagonal, booklet (otherwise known as side-seam), and center seam, unlike previous pressure sensitive adhesive envelopes. Diagonal style envelopes are shown and discussed throughout, but it is intended that any style can be used. Each envelope 4 of the present invention can also be made in any size or shape, i.e., small, large, rectangular, square, etc. The Release Coating

The release coating 12, which is applied to the back side 14 of each flap, can be made from any of a plurality of commercially available materials. The preferred release coating is one containing what is colloquially known in the art as "silicon". Although any suitable release coating material can be used, it is nevertheless important that it have characteristics which are suitable for the type of paper being used, and compatible with the adhesive material, as will be discussed.

The surface of the paper upon which the release coating is applied is preferably relatively smooth, not rough, to make it easier for the coating to be applied, and to provide a smooth finished surface, resulting in better performance of the release coating. With certain grades of paper, it may be desirable that the surface be made smooth before applying the coating. This can be accomplished by machine finishing, or calendaring, or the like. Nevertheless, sufficiently smooth paper is available, which should make this unnecessary.

The paper should also not be too porous such that the release coating soaks into and through the paper, as will be discussed.

The release coating can be applied to the paper by using any suitable method known in the industry, such as by roller, spray, or other conventional means, although the preferred method is by printing (stamping, stenciling, etc.), as will be discussed. The thickness of the coating need only be sufficient to provide the necessary coverage and release characteristics. Indeed, due to the cost of release coating materials, it is preferable that the coating be applied as thin as possible. The preferred range of thickness is typically between about .05 mil and 1 mil (.00127 mm to .0254 mm), although the actual thickness can vary depending on the type of paper and release coating being used, and the release characteristics desired. The release coating viscosity can affect the quality of the coating, and in particular, the extent to which the coating is absorbed into the paper, which is generally undesirable. To help prevent soaking and absorption, the viscosity of the release coating material is preferably such that, with respect to the paper being used, the coating material stays substantially on the surface of the paper, i.e., does not soak into and through the paper.

This not only improves the release characteristics of the coating, it also reduces the amount of release coating that must be used.

For these reasons, the proper viscosity of the release coating is determined, in large part, by the surface condition and porosity of the paper. For certain grades of paper, for instance, such as wove, the viscosity preferably ranges between 1,000 cps to 3,000 cps, while other types of paper, which are more porous, may require a relatively high viscosity release coating, or, in some cases, when the paper is less porous, a relatively low viscosity release coating. The viscosity level of the release coating that is selected can also be a function of how quickly the release coating can be cured, as will be discussed, insofar as quicker curing release coatings do not have to be as viscous to avoid soaking and absorption.

Proper curing of the release coating is also an important consideration in the application of the release coating to the envelopes. Once the release coating is applied, the coating material should be dried or cured, by any suitable means, such as by air, or air and heat combined, or ultra-violet (UV) light, or whatever means achieves the desired result. The release coating is preferably adequately cured such that when the adhesive is applied and removed, none of the release coating comes off onto the adhesive, and conversely, none of the adhesive remains on the release coating. In either case, the lack of proper cure can

cause the envelope adhesive to become ineffective, and lose its adhesive properties.

The preferred curing method, as will be discussed in more detail, is ultra-violet light, which cures the release coating more quickly than other curing methods. With ultra violet light curing, the release coating can generally be cured in an instant. For this purpose, an ultra-violet light curable release coating can be used. The virtually instant cure provided by ultra-violet light helps prevent the release coating from being undesirably absorbed into the paper. The pH balance of the paper, if necessary, should also be compatible with the release coating material to ensure proper cure.

The release coating material is preferably applied up to and along the edge 32 of the sealing flap 6, in a continuous strip, as shown in Figure 3b. The size of the application, or amount of coverage, however, need only be sufficient to cover and protect the pressure sensitive adhesive 8 material that is applied on the front of the sealing flap 6, as discussed. That is, when the envelopes are stacked together with the flaps extended, the release coating of each flap should be sufficient to cover the adhesive of an adjacent envelope in the stack, so that none of the adhesive sticks to the non- treated plain paper portion of the adjacent envelope. The release coating surface is preferably similar in shape and size to the adhesive coating surface although it is preferably slightly larger than the adhesive surface, although not necessarily so, to permit some margin for error in the alignment of the envelopes. As long as the release coating surface adequately covers and protects the corresponding adhesive area of an adjacent envelope, the envelopes will separate properly. The Pressure Sensitive Adhesive

The pressure sensitive adhesive 8 is applied in a manner which results in the adhesive 8 being positioned on the front side 10 of each flap 6 at the time the envelope is ready for use. This can be accomplished by applying the adhesive 8 directly onto the front side 10 of the flap 6, or, as discussed below, by appying the adhesive to the release coating, and then, superimposing the flaps so that the adhesive is relocated to the front side 10 when pulled from the stack.

Although it is preferable that the adhesive be applied directly to the front side 10, as will be discussed, application of the adhesive can be accomplished when stacking is desired by applying the adhesive directly onto the release coating itself after the release coating has dried or cured. Stacking the envelopes, as will be discussed, will bring the adhesive 8 into contact with the front side 10 of each adjacent envelope. Because the strength of the bond between the adhesive 8 and the release coating 12 will be much less than the bond between

the adhesive and the uncoated front side 10, when an envelope is eventually pulled from the stack, the adhesive 8 will remain on the uncoated surface of the front side 10 and be removed from the release coated back side 14. The adhesive will be relocated to the front side 10 and the release coating 12 will remain on the back side 14. The top and bottom envelope in each stack will, of course, have to be adapted so that there is no adhesive on the back side of the top envelope and that there is adhesive on the front side of the bottom envelope.

Any suitable commercially available pressure sensitive adhesive can be used, including those containing acrylic or rubber. Pressure sensitive adhesive is one that is tacky at room temperature, and which tenaciously adheres to a variety of surfaces by mere contact and only slight pressure. Preferably, the tackiness of the adhesive will not change over time so that the adhesive will not lose its ability to bond with an applied substrate. It is also preferred that the strength of the adhesive will not change as a result of extreme changes in temperature and humidity, either before or after sealing. This is particularly important because envelopes are often subjected to extreme changes in temperature, such as when envelopes are stored in the cargo of an airplane. It is also preferable that the adhesive material have a low creep factor so as to minimize migration along a substrate and to prevent bleeding of the adhesive into the substrate material. Use of any suitable adhesive that now exists or will exist is within the contemplation of the present invention. The preferred adhesive also remains tacky indefinitely, or at least for a long duration. Unlike gum adhesives used in standard envelopes which are dry and require moistening, pressure sensitive adhesives remain tacky and do not dry or harden after being applied. Pressure sensitive adhesives have an inherent tackiness that adheres and bonds directly to the substrate surface. Pressure sensitive adhesives do not "anchor" into the substrate fibers for bonding strength as regular gum adhesives do after moistening and hardening. Instead, the adhesive must be inherently tacky, or sticky, and strong enough to adhere to the surface of the substrate, and itself provide adequate bonding strength. For these reasons, the paper used to make the envelopes 4 is preferably compatible with the pressure sensitive adhesive such that the proper level of adherence is provided. The adhesive can be applied by any conventional means, such as by roller, spray, stamping, stenciling, etc., that acheives the desired results. Preferably, the adhesive is applied evenly and in a manner sufficient to provide the necessary shear resistance as is known in the art. Application of the adhesive so as to eliminate streaking, excess build up

and bleeding between the substrates is also preferred.

While the thickness of the adhesive can vary, the thickness is preferably such that the maximum adhesive strength is provided with the minimum thickness. Although a thicker layer will generally provide a stronger bond, this is not necessarily true. In some cases, a thicker layer of adhesive will actually weaken the adhesion, because the thickness may lower shear resistance. The amount of adhesive to be used may also depend on the type of paper being used. A porous paper or one that has loose fibers may be easier to bond to and require less adhesive, while a paper with tight fibers may require more adhesive to provide the proper bonding strength. An acceptable thickness is typically in the range of between .5 to 1 mil (.0127 mm to .0254 mm), although the actual thickness can vary depending on the type of paper and adhesive being used, and the desired results.

In the preferred embodiment, the adhesive is one which provides a permanent bond within a certain time after the envelope is sealed. "Permanent" means that the adhesion is nearly as great or greater than the strength of the substrate material it is applied to such that removal of one surface from the other is difficult or impossible without damaging the substrate or causing "fiber tear". Preferably, the adhesive 8 can bond substantially permanently within about 1 to 30 minutes to the non-coated body portion 16 of the envelope once it is sealed, although a wide degree of adhesiveness and bonding strength, including immediate bonding, and non-permanent bonding, is within the scope of the present invention. For general mailing purposes, and to prevent the accidental or unauthorized opening of an envelope, the preferred adhesive is one which bonds permanently, such that it would cause damage or fiber tear to the paper, within approximately 1 to 10 minutes of application, although this time period can be more or less depending on the desired results. For other uses, where security is not a concern, such as in inner-office mailing, the adhesive can be less aggressive, and can, in some instances, be non-permanent, or repositionable, so that it can be removed and reused if desired.

For added convenience, an adhesive that is initially repositionable, and gradually becomes permanent, can be used. This type of adhesive is repositionable, with respect to a variety of substrates, during the first few seconds, i.e., 10 or more seconds, after application, before the bond becomes permanent, although this time period can be more or less depending on the desired results. Repositionability allows the adhesive to be removed from the body of the envelope, or any other substrate, or surface, during the first few moments after it is applied. It also allows the envelopes to be opened and resealed, during the first

few seconds, if desired.

Of course, not all of the above properties are required for the present invention to perform properly. For instance, in some instances, as discussed above, it may be desirable for the adhesive to be non-permanent and repositionable, and in other instances, it may be desireable to have an adhesive that bonds permanently immediately upon sealing. Any degree of aggressiveness of the adhesive is within the contemplation of the present invention, as determined by the type of adhesive and paper that is being used.

The adhesive material is also preferably applied up to and along the edge 32 of the flaps 6. It can be applied continuously, or, in some cases, as shown in Figure 5a, the adhesive can be applied intermittently along the edge, with gaps 37 along the length of the strip. When the adhesive is placed along the edge of the the flaps 6 there may be a tendency of the adhesive to ooz or squeeze out from between the envelopes in the stack, which may cause the edges to be tacky to the touch. This can be avoided by applying the adhesive strip slightly inside 39 the edge 32 of the flaps, as shown in Figure 5a, so that the adhesive is close to, but not all the way to, the edge of the flap 6. On the other hand, adhesives are known in the art which have non-oozing and non-creeping properties so that placement of the adhesive up to and along the edge 32 is acceptable. Compatibility of Release Coating. Adhesive and Paper

The release coating 12, pressure sensitive adhesive 8 and paper are preferably compatible with one another. By compatible, it is generally meant that the adhesive and release coating materials are such that the adhesive can easily be removed from the release coated back side of the flap, while the adhesive tenaciously bonds to the non-coated surface of the body 16 of the envelope.

For instance, in the preferred envelope, only a slight amount of force should be required to remove the envelopes from the stack, or otherwise separate the interface between the adhesive and the release coating. The separation should easily occur with only a minimal amount of force applied at a 90 degree angle without any adhesive material being lifted and causing no damage to the substrate. Of course, if a non-permanent adhesive is used, such as for re-usable envelopes, no release coating may be needed at all for the adhesive to be removed. Although ease of removal is important, the release coating should nevertheless permit the adhesive to bond slightly so that the envelopes will stay together in the stack. It is important that the release coating permit some adhesion between the adhesive and an adjacent envelope, so that the envelopes will remain stacked together, to

avoid the need for boxes, and the like, to store the envelopes.

In addition, as discussed, the adhesive is preferably compatible with the release coating and paper, such that, once it is removed from the adjacent envelope in the stack, the adhesive bonds to the non-treated plain paper body portion of the envelope, which can be a permanent, or non-permanent bond. The preferred adhesive is also one which does not cause the paper to which it is applied to curl, that is, the tendency of the paper by itself or in the laminate to bend or wrap around itself. The release coating that is applied to the back side of the flap and cured helps to prevent the paper from curling, which is particularly important if the adhesive being applied has a high water or solvent content. The preferred adhesive should also not migrate or penetrate (bleed through) the substrate surface so as to change the appearance of the surface to which it is applied. The materials should also age in a manner which does not alter the basic properties of the materials including their appearance, viscosity and consistency. The adhesive should also be of a consistency which does not ooz or squeeze out from between the envelopes. The viscosity of the adhesive, as will be discussed, should also be appropriate for the given type of equipment being used.

The paper should also be compatible with the materials so that the release coating and adhesive materials can be applied and co-exist on opposite sides of the same sheet of paper. In particular, both the adhesive and release coating materials preferably -ire capable of being applied without either material being absorbed into and penetrating through to the other side. For instance, the paper that is selected should have sufficient fiber content and density such that the adhesive and release coating materials are not absorbed into the paper before they are dried or cured. On the other hand, the paper is preferably porous and loose enough to permit the pressure sensitive adhesive to bond properly to the paper. If the paper is too porous or not sufficiently smooth, or if the release coating or adhesive materials are too low in viscosity, or if the pH balance of the paper is not compatible with the chemical make-up of the release coating, it may be necessary to apply a sealant material 43 or primer, such as polyethylene, onto the paper before the release coating is applied, as shown in Figure 5b. The sealant or primer can be applied directly to the paper to help provide a better, smoother surface on which the release coating can be applied. The sealant or primer forms a relatively smooth barrier between the release coating and paper which helps prevent soaking and any adverse reactions therebetween. A UV curable, substantially colorless, sealant or primer is preferred and commercially available.

The above properties and characteristics are not intended to be limitations but rather preferred properties and characteristics. It should be emphasized that the present invention comprises the broad concept of stacking pressure sensitive adehsive envelopes. Not all of the above properties and characteristics are necessary for the present invention to provide the intended objectives. Method of Manufacture

The present invention can be manufactured in a variety of ways, from applying the adhesive and release coating by hand with a roller or brush, to systematically manufacturing the envelopes at high speeds on line with high speed equipment. Although any method that achieves the desired results is within the contemplation of the present invention, the particular methods described herein have been found to be desirable for a number of reasons, as will be explained.

In the preferred method of manufacture, as schematically shown in Figure 6, a sheet or web of paper 40 is processed on-line, and is moved at high speeds through various stations, ultimately forming envelopes 4 in stacks 41. While the order of the steps in the preferred method is not necessarily critical, the curing steps follow immediately after the application steps, as will be discussed.

In the first step 42, in the preferred method of manufacture, the release coating material is applied to a sheet or web of paper 40, in patterns which correspond to the location of the release coating on the back side of each envelope flap 6. This first step can be accomplished by any conventional method, such as a roller, or a printing technique (off¬ set or flexo-graph). Printing is the preferred method because a variety of patterns can be applied, much the same way as ink is printed onto paper. UV curable release coating materials are also preferable, as discussed, so that the coating can be cured quickly. The release coating 12 is preferably applied up to and along the edge 32 of the envelope sealing flap 6 to minimize the amount of release coating material that will be wasted when the paper is cut. The release coating should nevertheless be applied in a manner that would ensure proper coverage, such as applying the release coating so that it extends over the anticipated edge 32 by about 1/8". This should account for the possibility of error in both cutting and applying the release coating. Of course, the actual margin of error should be based upon the accuracy of the equipment being used. With more accurate equipment, less margin for error may be necessary.

In the preferred method, when the release coating is applied to the sheet or web of

paper 40, the release coating is applied before the paper is cut into blanks. In an alternate method, however, the blanks 48 can be cut from sheets of paper or a web prior to applying the release coating, and the release coating can be applied up to and along the edge 32 of the blanks corresponding to the sealing flap 6. Custom printing of addresses, logos and/or other information can also be provided if desired virtually-at any stage in the process, such as either before or after the release coating is applied, or before or after the blanks are cut.

In the next step 44, the release coating is cured by an appropriate conventional method. The release coating can be dried or cured by air, air and heat combined, a conventional heater/blower, or ultra-violet light, whichever method achieves the desired results. Ultra-violet light curing is generally preferred, although not required, because ultra¬ violet light curing is generally faster than other methods. The faster curing time of ultra¬ violet light is ideal for use in equipment where the web moves at high speeds. A UV lamp(s) 45 is preferably positioned so that the release coating is cured immediately after the release coating is applied. The UV lamp 45 also must be powerful enough to provide sufficient cure at the rate of speed the web moves. If more UV wattage is needed, for instance, additional lamps can be positioned in place along the web. A protective housing is commonly provided with the lamp to shield the ultra-violet rays. Ventilation is also recommended to provide proper air circulation in the vacinity of the lamp to keep the lamp cool. Inerting systems may also be required depending on the type of release coating used. In an alternate method, the sealant material or primer 43, such as a UV curable sealant, can be applied to the paper and cured before the release coating is applied. In such case, an additional application station, such as a print station 42, and a curing station 44, to apply and cure the sealant before the release coating is required.

In the next step 46, the sheet or web of paper is cut to form blanks 48, which are preferably cut by conventional means, such as die-cutting. On a web, accurate cutting can be accomplished by registering the paper properly, or by keeping the web taught, and cutting the blanks as close to the printing station as possible. In a related step 50, each blank 48 is scored with lines of weakness 30, 22a, 22b, 22c, preferably in a conventional manner, to permit easier folding of the envelopes. The next step 52 involves applying the pressure sensitive adhesive 8 to the blanks in a pattern that corresponds to the location of the adhesive coating 8 on the front side of each sealing flap 6. Any conventional method, as is known in the art, can be used, but preferably, the same method used to apply regular gum adhesive, i.e., a roller, or stencil, is

used. Overlapping the blanks and using a roller to apply the adhesive along the edge of the blanks is suitable in cases where the adhesive is intended to extend all the way to the edge of the sealing flap. The adhesive material, when applied in this fashion, should have flow and viscosity characteristics that are similar to standard gum adhesive to allow for easy application. Stenciling, on the other hand, is suitable in cases where the adhesive extends close to but not all the way to the edge.

The adhesive can then be dried in the next step 54, preferably in a conventional manner, such as by heat and/or blower, although the adhesive does not necessarily have to be dried. Drying pressure sensitive adhesive means to remove the water or solvent from the adhesive, leaving behind only the solids. With many water based adhesives, the moisture will evaporate on its own, even after the envelopes are stacked, and therefore, no separate drying process is needed. However, because water based adhesives take longer to dry than solvent based adhesives, a tunnel 54 with heat and/or air blowers can be used if desired. In the next step 56, the envelopes are folded and the lower flaps glued together to form the front wall. It should be understood that the adhesive 8 can be applied before, during or after the envelopes are folded. If the adhesive 8 is applied during the folding step, the same pressure sensitive adhesive material used on the sealing flap can be used to glue the lower flaps together. Applying the adhesive 8 after the envelopes are folded is preferred because it reduces the possibility of the adhesive sticking to the folding equipment. If, however, the pressure sensitive adhesive is applied before the envelopes are folded, care must be taken to prevent the adhesive from making contact with and sticking to the equipment after it is applied to the paper.

Conventional envelope folding equipment have rollers and/or cylinders that rotate to convey or otherwise transfer the envelope blanks 48 through the folding equipment. One way to prevent the adhesive from making contact with and sticking to the rollers and/or cylinders is to place gaps 37 in the adhesive 8, as discussed, and then make the rollers and/or cylinders relatively narrow, so that they rotate between the gaps, so as to avoid contact with the adhesive. The rollers and/or cylinders can also be adjusted to apply pressure to the sides of each blank to avoid contact with the adhesive. Conveyor systems that manipulate the blanks by air, suction, or other pneumatic method, or make contact with other areas of the blanks, can also be used.

Folding cylinders are also typically used to compress the envelope blanks after the blanks are folded. During this process, to prevent the adhesive from making contact with

and sticking to the cylinder, a portion of each cylinder can be sectioned or cut-out. That is, the portion that would otherwise come into contact with the adhesive can be sectioned or cut-out so that as the cylinder rotates it avoids contact with the adhesive. The sectioned cylinder is also synchronized with the movement of the blanks so that the sectioned portion lines up with the adhesive during each rotation. The synchronization and timing of the cyliners to the blanks can also be made adjustable so that different size envelopes can be processed with the same equipment. A silicon coating can also be applied to the rollers and/or cylinders, or other equipment, to help prevent sticking.

Once the envelopes 4 are completed, the release sheets 34 are inserted 58 at the bottom of each stack, and the envelopes are mechancially sorted, stacked 60 and pressed 62, with the sealing flaps 6 open and extended, and facing substantially the same direction. A pressing mechanism is preferably provided which handles each individual stack and applies pressure to the sealing flap 6 portion. When envelopes are delivered at high speeds, a conveyor system, such as a moving belt, rotating platform, etc., can be provided to help sort the stacks away from each other as they are delivered.

The envelopes are preferably aligned along the edges 22, 32 to form a neat stack 41. Alignment of the envelopes can be accomplished by manipulating the envelopes as they are delivered. The edge 32 of the sealing flaps, for instance, can be shaped, or grooves provided, and then each envelope can be manipulated and aligned, either mechanically, pnuematically, or ultra-sonically, etc., against a template that has substantially the same shape as the edge, to facilitate alignment of the envelopes during stacking. Two opposed, tapered edges, or a single groove, can, for instance, be provided along the edge, to help center and align the envelopes. The shape of the edge, or grooves, can be part of the design of the flap. That portion can also be discarded by die-cutting if desired. Stacks that are slanted, or off-set, or fanned, or imperfect in some other way, are also within the contemplation of the present invention. The sealing flaps 6 in each stack can also be folded over collectively, so that the stack is no larger than the body 20 of the envelopes.

In an alternate method, to ensure that the edges 32 of the envelope sealing flaps in the stacks are aligned and straight, the sealing flaps of each stack can be individually die-cut 64 close to the edge 32 in the conventional manner, after the stacks are formed. In such case, the sealing flaps 6 should be made slightly larger at first so that the edge can be cut and discarded without affecting the overall size of the envelopes.

In the preferred embodiment, the envelopes are stacked with the adhesive 8 of each

envelope flap 6 facing the same direction, i.e., down, with a bottom release sheet 34 at the bottom of the stack, so that the adhesive on each envelope only becomes exposed when the envelope is removed from the stack. A stiff board or border, made of cardboard, or other suitable material, can be provided to protect the structure of the stack, or to cover the potentially tacky edge of the flaps, or to house the stack and dispense the envelopes. Any number of envelopes can be stacked together in each stack, but preferably between 2 to 50 to permit proper stacking, with a preferred range of between 2 to 25. In each stack, the bodies of the envelopes are typically thicker than the sealing flaps. This is because the body has a front wall 5 with three overlapping flaps 24, 26, 28 folded and glued together, as well as a back wall 21, while the sealing flap 6 is a single sheet.

Although the relative differences in thickness with respect to one envelope is insignificant, when a plurality of envelopes are stacked, this difference can become substantial. The greater the number of envelopes in the stack, the greater will be the difference in thickness. Although the present invention compensates slightly for this difference in thickness by virtue of the additional thickness of the adhesive and release coating materials, that difference is not enough to offset the total thickness of the overlapping lower flaps, including the paper and adhesive. Accordingly, the envelopes of the present invention are preferably stacked in numbers not exceeding 50. Use of the Invention In use, one merely removes an envelope by lifting or otherwise pulling the top envelope away from the stack. With one's fingers, one merely takes hold of the envelope and lifts upward, as shown in Figure 4b. The upward motion easily separates the sealing flap of that envelope from the envelope immediately below. Because of the release coating surface 12 on the back side 14 of the flap 6 of the envelope immediately below, the adhesive of the envelope being pulled is easily separated from the stack. Once the envelope is separated, the adhesive is automatically exposed so that the envelope can be sealed without having to remove a release liner or tape. The contents can be placed inside the envelope, and then, the sealing flap 6 can be folded along the line of weakness 30. The adhesive can be brought into contact with the body of the envelope 16, and the envelope can be sealed simply by applying slight pressure to the back of the sealing flap. Because the body of the envelope is not treated with the release coating, the adhesive adheres to the plain paper body portion of the envelope, to bond substantially permanently if desired. The present invention makes it easy to seal a large quantity of envelopes, such as when sealing

and mailing invitations, cards, announcements, promotional materials, invoices, statements, etc.

Alternate Embodiments

Alternate embodiments include different types and styles of envelopes, as discussed above. The envelopes can also come in different colors ~ either the entire stack can be a particular color, or each envelope in the stack can be a different color, or some combination, such as a rainbow of colors. The sealing flaps can also be cut-out in unique shapes, which can be done when the blanks are cut, or when die-cutting each stack. In stack form, the shape of the sealing flap can be used as a possible trademark or other identifying symbol. The adhesive and/or release coating surfaces can also present a unique idea, logo, pattern or design. The envelopes can also come with a cut-out window as shown in Figure 5.

In other embodiments, as shown in Figures 7a, 7b, 8a and 8b, sheets of paper 70 and 102, respectively, can be stacked together in a manner which will allow them to be separated and formed into envelopes by the user. In the embodiment shown in Figures 7a and 7b, each sheet of paper 70 has an adhesive portion 72, 82, and a release coating 74, 84, which are applied on opposite sides of the sealing flap 75 of the sheet 70 on areas corresponding along the edge 78 which allows each sheet to be folded and sealed by the user. The adhesive portion 72, 82 is applied to an area corresponding along the edge of the front side 76, and the release coating 74, 84 is applied to an area corresponding along the edge of the back side 80. A line of weakness 86 can be formed in the center or any other appropriate location so that the sheets can easily be folded. As in the preferred embodiment, each sheet can be separated from the stack 90, and then folded along the line of weakness 86, and then pressure applied to form each envelope. In the embodiment shown in Figures 8a and 8b, the sheet of paper 102 has thereon a sealing flap 93 and two additional side flaps 94 extending therefrom. An adhesive portion 98 is applied to the front side 91 of the sealing flap 93, and adhesive portion 99 is applied to the front side 95 of each of the side flaps 94. A release coating 100 is applied to the back side 101 of the sealing flap 93, and release coating 103 is applied to the back side 105 of each side flap 94. In this fashion, the sheets 102 are adhered together in a stack 97 but can be easily separated from the stack and each other when desired. Lines of weakness 96a, 96b, 96c, 96d are provided to allow the flaps 93, 94 to be easily folded and sealed to form envelopes 104. A release sheet is used at the bottom of each stack in both embodiments.