Adhesive electrostatic sheets

Electrostatic sheet coated with viscous substance

FIELD OF THE INVENTION The present invention relates to sheets that are electrostatically attached to a substrate. More specifically, it involves the combined application of static electricity and a sheet attached to the substrate with an adhesive.

BACKGROUND OF THE INVENTION Films are electrostatically charged, so they can be attached to substrates without the use of adhesives. Films with long-lasting dielectric polarization are called electrets.

U.S. Patent No. 5,258,214 discloses a plastic film wall sticker with a pre-printed image, which is then provided with an electrostatic charge so that the sticker is firmly covered on a surface.

U.S. Patent 5,207,581 discloses a writing device including an electret film. The electret film is a kind of flexible plastic film with electrostatic charge induced up. As a printing medium, a dry erasable marker can be used to write on it, and then it can be erased. This device has a roll of electret film.

US Patent 5,989,685 discloses an electret film composition suitable for printing on inkjet printers. In the second column of the patent, lines 37-39 describe "improved printed materials that combine the advantages of electrets." The advantages of electrets are stated in column 1, lines 53-57 as "it is expected to provide a display that can be attached to a surface without using fasteners or adhesives." The electrostatically charged sheet of the invention is pasted on a layer of paper backing, which avoids the problem of processing the sheet on the paper feeding mechanism of the printing press. These carrier backing papers are attached to the sheet with glued edges, see column 4, lines 24-52.

U.S. Patent 5,807,624 discloses an electrophotographic copy. This kind of better imaging copy "includes a layer of transparent polymer sheet, which can be imaged, under which there is a layer of opaque base film to cooperate with the above transparent sheet, the adhesion of the two layers is by means of static electricity and pressure sensitive adhesive. The combined effect of "see column 3, lines 55-60." This adhesive provides an additional protection against "crimping" or improves its feeding performance with the paper carried, see column 12, line 66-column 13, line 2.

US Patent 6,023,870 discloses a device for displaying and replacing image sheets on vending machines. The image sheets are electrostatically attached and can be removed on the back of the clean display panel. An alternative embodiment, see column 7, lines 38-50, is the use of topical adhesives or reusable adhesives (referred to as "tacky" adhesives) to achieve the function of being attachable and removable. The adhesive described in this patent is 3M's Post-it brand adhesive, and it is specifically pointed out that the sticky adhesive is 3M's SPRAY MOUNT brand adhesive, which is commercially available, and the adhesive applied by the user can be used in location shooting. The specification claims that the principles of the various embodiments can be used in combination. See column 8, lines 32-36, which gives an example of using a sticky adhesive to ensure that an image sheet product is fixed on the four corners, but the original It is fixed by electrostatic adhesion method.

SUMMARY OF THE INVENTION The present invention provides an image sheet including a film having a top surface and a bottom surface. The film is electrostatically charged, and an activated adhesive is pre-applied. The electrostatic charge is sufficient to support the sheet on a vertical clean insulating surface. The activatable adhesive can help the sheet adhere to the display substrate.

The detailed description of the presently preferred embodiment is as described above, and it is known that electrostatically charged sheets used on a variety of surfaces are known. The main advantage of these systems is that the sheet can be attached to the final substrate used without the need for adhesive. Therefore, in the prior art, avoiding the use of adhesives has been the primary goal.

It has been found that after a period of time, at least part of the charge in the charged sheet material will dissipate, so that the sheet material cannot be attached to the substrate used. This phenomenon occurs even more when the sheet has undergone certain printing steps, such as offset printing. See USP 5,904,985, column 2, lines 5-18. In order to provide sufficient electric charge so that the sheet can be fixed in the desired position, these sheets must be pre-charged before use.

The present invention provides a combined adhesion system that provides adhesion through both electrostatic charge and pre-applied activatable adhesive. The present invention provides a positionable sheet, the attachment between the sheet and the display substrate is easy to move, the position of the sheet can be determined by movement, and then the sheet and the substrate are adhered by a pre-applied activatable adhesive. Early image sheets made using charged sheets are easy to change positions or even fall off accidentally. Therefore, accidentally touching or blowing a gust of wind (for example, fan wind) when a passerby passes by may cause the image sheet to move or fall. The present invention uses static electricity to provide firm adhesion to the image sheet to be attached to the display substrate.

Another aspect of the present invention is to provide a more perfect adhesion between the sheet and the display substrate through the combined action of electrostatic adhesion and the adhesion of the pre-applied activatable adhesive. Therefore, even if the conventional adhesive is used at only a few spots, the entire sheet can be closely attached to the display substrate. The advantage of this method is that swelling occurs in the areas where there is no adhesive, and there is no physical separation between the sheet and the display substrate. Due to the combined action of static charge and adhesive, the adhesion force of static charge does not require the strength to support the entire weight of the entire image sheet product during its service life. Similarly, the adhesive force of the pre-applied activatable adhesive does not need to be strong enough to support the weight of the entire image sheet during its service life, because static electricity can enhance its adhesion.

In addition, the present invention can provide a perfect adhesion method between the sheet and the display substrate without the need to coat the adhesive all over the sheet. When the adhesive-coated sheet is stuck on the display substrate, it is difficult to avoid wrinkles or air bubbles. Therefore, the image sheet made according to the present invention can be easily applied on the display substrate by a person with little skill, and then adjusted to achieve a better position and appearance, and then fixed on the position with an adhesive.

In this context, "display substrate" refers to a substrate on which the sheet of the present invention is finally placed to serve as an image product, such as a wall sticker or a media surface. The display substrate is different from the carrier substrate because the carrier substrate is only a vehicle that transports the fragile and fragile film to another destination. Earlier art films used adhesives to attach them to the carrier substrate, but after the carrier substrate reached the destination, before applying the electrostatic film to the display substrate, the adhesive was intended to be damaged or removed. Earlier technology emphasized the need to provide a sheet that can be attached to the final surface without the use of adhesives. The application of the sheet of the present invention to any particular display substrate may be temporary, and it may also be intended to apply the sheet to another display substrate. At this time, it is shown that the substrate is not only a carrier, and its adhesion ability will not be damaged before the sheet is used to exert its final function.

In this context, the "firmly" attachment of the sheet to the substrate means that the sheet will not slip off when lightly pressed on the sheet with one finger or a hand and smoothly pressed in a direction parallel to the surface of the display substrate.

In a preferred embodiment of the invention, the image sheet is imageable. In a preferred embodiment, the upper surface of the film is imageable. In another preferred embodiment, the upper surface of the film is coated with an imageable surface. In a further preferred embodiment, the sheet is a laminate including an image receiving layer on the upper surface of the film.

In another embodiment of the present invention, the image sheet is a pre-imaged wall sticker. This embodiment of the invention has great advantages because it can now be used to effectively replace traditional wall sticker. Through the combination of electrostatic charge and the adhesion of activatable adhesives, the application of wall adhesives now does not require the use of annoying liquid adhesives and pastes like traditional methods. In addition, the present invention can provide a dimensionally stable wall surface material, because the back surface does not need to be in contact with water or other liquids during the application process, which avoids the wall surface material swelling when wet and shrinking when dry. When applying this wall sticker, there can be enough time to position it, so that the image on the surface of the image sheet can match, and it will be finally attached only after the user determines the appropriate position. Therefore, a better activatable adhesive is an adhesive that can maximize the positioning ability of the image sheet before the final attachment. In addition, the activatable adhesive should preferably have strong adhesion to the display substrate, so that the expected adhesive strength can be maintained for at least 5 years or more in this better solution.

In some preferred embodiments of the present invention, the wall covering is provided in the form of a roll and is at least 20 feet (6.1 meters) long. It is especially preferable that the pattern printed on the edge of the wall sticker should be designed to match the opposite edge of another adjacent wall sticker to provide the aesthetic feeling of a complete pattern on its surface.

In another embodiment of the present invention, the image sheet has a writable surface, which can be written on after being applied to the display substrate. Preferably, the image sheet can be used, for example, a dry erasable marker pen can be used to write on it, and then it can be erased when needed. In this embodiment, the sheet has an easy-to-place writable surface, which can be used in place of or in addition to the writable surface of a traditional blackboard.

The adhesive used in the image sheet of the present invention is a preformed activatable adhesive. Therefore, the structure of this image sheet makes it easy to apply to the display substrate, and there is no need to further assemble some parts on the display substrate. This structure has many advantages for the final applicator of the image sheet, which saves time, is easy to apply, and requires simple materials. The applicator of the image sheet of the present invention only needs to place the image sheet on the display substrate, position the image sheet according to the expected position and orientation, and then activate the adhesive.

The activatable adhesive can be any suitable adhesive system, which initially has little or no adhesion, but after activation it can provide the adhesion desired by the applicator. Examples of such activatable adhesives include repositionable pressure sensitive adhesives, positionable pressure sensitive adhesives, pressure sensitive adhesives with peelable liners, heat activatable adhesives, microencapsulated adhesives, and the like.

In one embodiment of the present invention, the activatable adhesive is a repositionable pressure sensitive adhesive. The "repeatable positioning" mentioned here refers to the property that it can be repeatedly attached and removed on the substrate without losing much adhesion. Preferably, the image sheet of the present invention uses a roller pressure of 2 kg on a 20-pound white high-quality copy paper, and after pasting and peeling for 5 times, the peeling adhesion loss does not exceed 75%. In a preferred embodiment of the present invention, when the film has been attached to the display substrate for a long period of time, it can be removed. Therefore, the adhesive used in the present invention preferably does not increase much adhesion over time.

The repositionable pressure-sensitive adhesive on the film preferably contains 60-100% (weight percentage) of pressure-sensitive microspheres. These microspheres are hollow, polymer, acrylate, and have a certain viscosity and are not meltable. , Insoluble, solvent-dispersible, flexible, at least 1 mm in diameter. It also contains 0-40% (weight percentage) non-spherical polyacrylic adhesive. Hollow microspheres can be made according to the method described in European Patent Application 371,635. The non-spherical polyacrylic adhesive may be a general pressure-sensitive adhesive. Examples of such adhesives include polymers produced from the following "soft" monomers (such as n-butyl acrylate, isobutyl acrylate, etc.), or from soft components (such as isobutylene, n-butyl acrylate, etc.) Copolymers composed of isooctyl acrylate, ethylhexyl acrylate, etc.) and polar monomers (such as acrylic acid, acrylonitrile, acrylamide, methacrylic acid, methyl methacrylate). Non-spherical polyacrylic adhesives are available on the market, such as Rohm and Haas Adhesive from RhoplexTM. The weight percentage of the non-spherical polyacrylic acid adhesive in the repositionable pressure-sensitive adhesive is preferably 10-35%. When the repositionable pressure-sensitive adhesive contains a non-spherical polyacrylic adhesive, the adhesion of the total adhesive to the sheet is improved, and there is little adhesive residue left on the substrate when the sheet is peeled off. Similarly, when the repositionable pressure-sensitive adhesive with adhesive microspheres also contains non-spherical polyacrylic acid adhesive, its shear adhesion performance is also very good, even on rough vertical surfaces. When these favorable adhesion characteristics are obtained, there is no strong adhesion between the sheet and the substrate, so that, for example, when the adhesive component on the sheet is removed from a painted wall, the paint on the wall will peel off.

There are known repositionable pressure-sensitive adhesives in which the microspheres are non-sticky. For this type of adhesive, please refer to the US Patent (USP4,735,837, patentee: Miyasaka) for the preparation of repositionable pressure-sensitive adhesives, which can be made by adding some components to conventional adhesive formulations to change its viscosity and flow properties. U.S. Patent (USP 4,599,265 patentee: Esmay) discloses an adhesive with strong adhesion, low tack, and releasability on various substrates. U.S. Patent (USP4,737,559, patentee: Kekkeb, etc.) describes a PSA formulation in which a small amount of free radical polymerizable photocrosslinking agent is added to control its viscosity flow and thus control the increase in adhesion. Big.

Another way to provide repositionable pressure-sensitive adhesives by reducing the contact area of the adhesive is to deposit a discontinuous or patterned film on the backing. The world patent (WO85/04602, patentee: Newing et al.) describes an adhesive product, which is a pattern of discontinuous adhesive segments on at least a part of at least one side of a carrier or backing. These segments The coverage is about 10% to 30% of the total carrier surface. European patent (EP276,557, patentee: Fry) describes a repositionable pressure-sensitive sheet, on one surface of which is a discontinuous non-repetitive adhesive coating, forming many separate coatings Area, its coverage is about 10 to 85%. U.S. Patent (USP4,889,234, patentee: Sorenson et al.) discloses a label structure with a discontinuous adhesive pattern, and its adhesion varies with the following factors: the adhesive coverage on the label, the pattern formed by the adhesive , And the adhesive properties when the adhesive is fully covered. The European patent (application number: 279,579, patentee: Tanuma et al.) describes a pressure-sensitive film material in one of its embodiments, which includes a pressure-sensitive adhesive layer with "irregular sections" (that is, "...uneven pressure-sensitive adhesive layer) ...") A continuous adhesive layer. According to the aforementioned patent application, this uneven pressure-sensitive adhesive layer is a continuous adhesive layer formed by various pressing, molding and embossing methods.

A better aspect of the present invention provides a sheet in which a pressure-sensitive adhesive is coated on the bottom surface of the film in a certain pattern. The pattern applied is preferably a strip pattern so that no matter how the printer and the end user cut it, there will always be an adhesive on the image sheet. In a preferred embodiment, the coverage of the pressure sensitive adhesive is less than 10% of the bottom surface of the film.

It is preferable that the activatable adhesive is practically non-tacky at the beginning, so that the image sheet can easily slide from the initial placement position of the display substrate to the final position.

In a particularly preferred embodiment of the invention, the activatable adhesive is a positionable pressure sensitive adhesive. "Positionable" means that the pressure-sensitive adhesive can be placed on the surface of the substrate first, and then not moved to the correct position along the surface. At this time, the activatable adhesive will not first attach the adhesive product to the starting position. After it is placed in the final position, it is necessary to pressurize the image sheet to activate the adhesive. The adhesive can also be designed to increase the adhesion after being placed on the display substrate for a period of time.

In one embodiment, the positionable pressure sensitive adhesive may be provided by a dry application agent (e.g., particulate matter). The powdered substance or talc has been proven to be effective in preventing early adhesion (see U.S. Patent Nos. 4,376,151 and 4,556,595). These techniques make application easy, and easy to position and repeat positioning. These technologies may require continuous contact for 1 to 7 days after the adhesive is activated to form a strong adhesive connection between the adhesive and the display substrate.

In the application of pressure-sensitive adhesive, the discontinuous coating of non-sticky substances protruding on the relatively flat surface of the adhesive can also be used to prevent the pressure-sensitive adhesive layer from adhering in advance. When these adhesive films and tapes are lightly placed on the surface of the substrate, they do not have an adhesive effect and can be placed on the surface of the substrate, but can move freely on it. Such coatings include patterned polymer coatings, particulate matter and films (see U.S. Patent Nos. 3,554,835; 4,054,697; 4,151,319 and UK Patent 1,541,311).

Another type of positionable adhesive includes a number of randomly distributed hollow glass microspheres partially embedded in the adhesive layer to prevent the adhesive from contacting the substrate surface and early adhesion (see US Patent 3,331,279). EGTacTM brand adhesive film uses similar "non-fragile" hollow glass microspheres to be partially embedded on the surface of the adhesive (see USP 5,008,139). The Hi-S-CalTM brand pressure-sensitive adhesive film similarly uses solid glass microspheres to be partially embedded on the surface of the adhesive to prevent the adhesive from contacting and pre-adhering to the surface of the substrate. In either case, applying pressure on the sheet can cause the microspheres to break and/or be embedded in the adhesive layer, thereby allowing the adhesive body to contact the substrate, thereby rapidly forming a strong bond.

The United States Patent (USP3,314,838) describes a similar structure in which a thin layer of pressure-sensitive adhesive is coated on the top of the hollow microspheres protruding from the surface of the adhesive layer. After the pressure is applied, the microspheres are broken, and the adhesive body contacts the substrate, thereby forming a strong bond.

Other methods to prevent early adhesion include the formation of brittle and fragile plastic projections on the surface of the PSA (see U.S. Patent 3,301,741), or the formation of small aggregates of dispersed particles protruding from the surface of the adhesive (see U.S. Patent 5,141,790). ). For example, in US Patent No. 5,141,790, these particles are sticky adhesive microspheres, which can produce weak adhesion when applied with light pressure, and can produce strong adhesion when applied with higher pressure.

Adhesives with surface structure can also be used to form positionable pressure-sensitive adhesives. For example, it has been described that a relatively large area of embossing on the adhesive can permanently reduce the contact area between the pressure-sensitive adhesive and the substrate, thereby also reducing the adhesive strength of the pressure-sensitive adhesive (see European Patent EPO,279,579). A variety of surface structures including concave and convex "V"-shaped grooves, diamonds, cups, hemispheres, cones, volcanoes and other three-dimensional shapes, their top surface area is much smaller than the adhesive layer The bottom surface. Generally speaking, these surface structures can provide adhesive films, adhesive sheets and adhesive tapes, and their peel adhesion is lower than that of an adhesive layer with a smooth surface. In many cases, the adhesive film with a surface structure increases slowly as the contact time increases.

There is an adhesive sheet with a micro-structured adhesive surface. On the functional part of the adhesive surface, there are evenly distributed adhesive or composite adhesive "pins" protruding outward. The adhesive sheet is both positionable and repeatable when placed on the surface of the substrate (see US Patent No. 5,296,277). Applying pressure on this adhesive film immediately forms a strong bond between the adhesive sheet and the substrate. This type of adhesive requires a relatively expensive peelable liner with a consistent microstructure to protect and "bolt" it during storage and handling.

In WO91/06424, a positionable-repeatable pressure-sensitive adhesive is described. This adhesive is a mixture of the following components: adhesive resin, detackifying resin, detackifying particles and tackifying resin. The sheet product with such an adhesive layer exhibits low viscosity and is easy to position; the initial adhesive force when pressed in place is low, so that it is easy to repeat positioning. The adhesive sheet with such an adhesive layer can slide on the contact surface when it is in contact with the surface of the substrate, and has a moderate adhesive strength after being pressed. The sheet coated with this adhesive can still slide freely when it comes in contact with the surface after being removed. However, the increase in adhesion of this adhesive is relatively slow, which will prolong the installation time. For example, when a large image sheet is applied to the truck wall, there must be sufficient adhesion to ensure that the truck operates at normal driving speed. Does not fall off from time to time. In addition, the temperature range in which this adhesive sheet can be applied is very limited.

US Patent No. 5,795,636 describes a particularly good positionable pressure-sensitive adhesive, and its adhesive layer has the following characteristics: (1) It has micro-structured surface characteristics, so that the adhesive sheet has the characteristics of positionability and repeatability; (2) It has sufficient elasticity so that when this type of product is applied and then removed from the surface of the substrate, backing or releasable liner, it can mostly restore the size and shape of its microstructure surface characteristics.

In another embodiment, the bottom surface of the image sheet may have a non-uniform surface structure, the bottom surface of which has protrusions when initially contacting the display substrate, and valleys and depressions between these protrusions on the bottom surface. Coated with adhesive. After the image sheet is placed on the display substrate, the image sheet is pressed to press down the protruding part, and the adhesive in the depression can contact the display substrate, thereby attaching the image sheet to the display substrate on. U.S. Patent No. 5,965,235 describes such a structure in which the protrusions are randomly distributed. These protruding parts can also be regularly oriented, in the form of ridges or other geometric shapes, while the recessed parts are regular channels or grooves.

The activatable adhesive can also be activated by receiving energy, such as heat or radiation (including microwave, ultraviolet, visible light, etc.). A particularly good embodiment is to use a heat-activatable adhesive, which essentially provides a hot-melt adhesive on the bottom surface of the image sheet. The heat-activatable adhesive is preferably heat-activated by a hand-held heating device similar to a hair dryer for drying hair.

In another embodiment of the invention, the activatable adhesive is microencapsulated. In this embodiment, the activatable adhesive is encapsulated in the microcapsules until released. Therefore, after this kind of sheet is applied to the display substrate, only after the microcapsules are triggered to release the activatable adhesive, can the pressure-sensitive adhesive be activated to form additional adhesion. The microcapsules can release the pressure-sensitive adhesive in any way, usually by rupturing the microcapsules to release the adhesive. In a better application method, the sheet is placed on the display substrate and then positioned. At this time, the film only has a slight adhesion effect due to static electricity. When placed in the correct position of the display substrate, the user applies pressure to the film at the position where the microcapsules are located, thereby crushing the microcapsules to release the adhesive.

The adhesive can use any suitable technology in the field of microencapsulation for microcapsule encapsulation, such as interface encapsulation, complexation coacervation, etc. The adhesive to be encapsulated can be a pressure sensitive adhesive, or it can be cured after being released from the microcapsule The adhesive can be cured either by contact with air or by reacting with another reactant on the surface of the sheet or substrate, or separately encapsulated in a microcapsule.

In another embodiment, the activatable adhesive is a pressure-sensitive adhesive that uses a peelable liner to prevent early adhesion. The adhesive protected by the peelable liner can be activated after the peelable liner is removed. This solution preferably uses a stretchable peelable structure to provide a structure that makes it easy to remove the liner without damaging the display substrate, and preferably without damaging the image sheet.

The use of stretch-peelable tape makes a bonding system that can be used to attach to any surface and can be removed cleanly without damaging the surface. Therefore, even very strong adhesives can be used to stretch the peelable tape, so that the image sheet can be attached to particularly difficult to stick rough surfaces (such as colored bricks) without falling off the display substrate . Even if a strong adhesive is used, such products can be safely removed without damaging the display substrate (for example, paint peeling off the paint surface), because of the stretch-peelable structure of the pressure-sensitive adhesive.

When the activatable adhesive is a stretch-peelable structure, it is made into a double-sided pressure-sensitive adhesive ("DSPSA") with pressure-sensitive adhesive on both sides of the stretchable backing. This type of adhesive product is usually called a stretch-releasable tape. This tape works as follows: after the tape is adhered on one or both sides, the backing is stretched, and the adhesive is also stretched and separated cleanly from the attached one or two substrates. When the backing of the tape is stretched at an angle of preferably no more than 35 degrees to the surface of the substrate, this removal process usually proceeds from one end of the tape to the other. That is, when the tape is stretched from one end, it detaches from the stretched end toward the distal direction.

A particularly good embodiment for stretching the peelable structure is to use an adhesive tape with a plastic backing. In other words, when the backing is stretched, it undergoes permanent deformation, and the elastic recovery is quite small. Such belts include the following structures: a film layer, a foam material layer, and a laminate layer composed of a film and/or foam material.

The unapproved U.S. Patent Application Serial No. 08/308,937 (WO95/06691) jointly owned with the assignee of the present invention discloses some stretch-releasable tapes. The structures of these tapes are: film, foam, and film and/ Or laminated layers of foam materials. In addition, this type of tape contains conventional pressure-sensitive adhesives.

The United States patent (USP5,409,189, patentee: Luhmann) describes another type of stretchable peelable tape, the tape backing used is an elastic material. In contrast to the above-mentioned plastic materials, elastic materials refer to materials that can be stretched without much plastic deformation, and have high elastic recovery after being stretched and peeled off in place. Like the plastic tape mentioned above, the elastic tape can also be single-sided or double-sided, and the stretching of the backing will cause the adhesive to stretch and the resulting detachment of one or both surfaces of the adhesive. The detachment process follows the tape The stretching is carried out from the end of the stretching toward the distal direction.

A preferred embodiment of the stretch-releasable adhesive tape that can be used in the present invention is described in detail in U.S. Patent No. 6,001,471. Other preferred embodiments are described in detail in U.S. Patent Nos. 5,672,402; 5,516,581; 4,024,312; 6,162,534 and German Patent No. 3331016C2. In addition, it may include a tearable layer, which is described in detail in WO99/31193 (US Patent Application Serial No. 08/989,507, filed 1997, 12, 12).

Commercially available stretch release tapes include COMMAND produced by Minnesota Mining and Manufacturing Company, St. Paul, MN, and POWER-STRIPS produced by Beiersdorf, Hamburg, Germany. These products are now made into discontinuous strips, with a non-sticky tearing head at one end of the strip, so that it can be easily stretched when removed. The adhesive surface of this tape is protected by another peelable liner.

Alternatively, the DSPSA side to be applied to the image sheet can be selected from some pressure-sensitive adhesives. Preferably, the side of the DSPSA to be applied to the image sheet is also easily removed from the image sheet without damaging the sheet. "Removable" means that the adhesive can be removed from the substrate without damaging the substrate. Even better, the adhesive can be removed from USGypsum 3/8 (9.5mm) gypsum board. The gypsum board is first painted with Sherwin Williams ProMarTM 200 inner latex primer, and then coated with Sherwin Williams ClassicTM 99 inner latex wall paint. Layer. The painted wallboard is used for the test after a minimum of 48 hours of aging at room temperature about 22°C. Even better, the adhesive can be removed from 20 pounds of white high-quality copy paper without tearing the paper .

In a better specific embodiment of the present invention, there is a repositionable pressure sensitive adhesive as defined above on the display substrate surface of DSPSA.

The image sheet of the present invention can have various shapes, preferably rectangular or square, and the activatable adhesive is applied to one of the four corners of the film.

The film is charged by passing it through an electrostatic field. This electrostatic field can be generated by any known charge generator, such as a corona charger, a friction charger, a conductive high-voltage drum-type charge generator or a contact charger, an electrostatic charge generator, etc. The sample can be charged with a DC charge, or with a DC charge followed by an AC charge, in order to form a sufficient degree of charge adhesion between the two surfaces. It is better to pass the film through an electrostatic field in a molten or semi-melted state, and cool it down before the charge dissipates, so as to "lock up" the charge and produce an electret with electrostatic properties that lasts for a long time. The film must be sufficiently charged to support the film to adhere to the vertical clean insulator surface. To check the ability of the image sheet to support itself, the charged film can be applied to the USGypsum 3/8 (9.5mm) gypsum board. The gypsum board is first painted with Sherwin Williams ProMarTM 200 inner latex primer, and then with Sherwin Williams ClassicTM 99 The latex wall paint is coated with a single-layer outer coating. The painted wall panels are tested after being aged for at least 48 hours at room temperature about 22°C. The image sheet is considered to be resistant to activatable adhesives at a temperature of 22°C When acting, it can support itself on the vertical surface as described above and will not fall off for at least 5 minutes.

Preferably, the material of the film is a polymer, selected from the following components: polypropylene, polyethylene, polyester, polyamide, polyimide, polyurethane, polyethylene acrylate, polyvinyl chloride, polymethyl Ethylene acrylate, thermoplastic rubber, polypropylene oxide, polystyrene, polystyrene-polydiene block copolymer, ionic thermoplastic elastomer, polyether, polyester amide, polyether ester amide, siloxane, Ethylene-vinyl acetate, polymethyl methacrylate (PMMA), polyvinyl chloride (PVDC), acetate copolymer, polybutene, fluoroelastomer, silane rubber, polycaprolactone, elastomer insert Block copolymers and their blends and combinations.

In a preferred embodiment, the image sheet of the present invention is imageable. In a specific embodiment, the electrostatically charged film should be selected from the image printed on it that is chemically acceptable for preservation. Alternatively, the electrostatically charged film can be processed by well-known chemical or physical methods in order to improve its ability to accept and preserve images. In another specific embodiment, the image sheet is provided as a laminated sheet, with an image receiving layer laminated on the film. Any suitable technique can be used for lamination, such as adhesion method, co-extrusion method and the like. The film can be electrostatically charged before or after processing or laminating to provide an image-receiving image sheet.

Preferably, this imageable image sheet can adopt one or more imaging methods, such as electric recording, screen printing, thermal mass transfer, inkjet (including spraying with water-soluble ink, oil-soluble ink or UV-curable ink), offset printing, dye sublimation or other printing processes.

In addition to the above-mentioned usable layers, a multilayer sheet of the present invention may include other usable layers, such as an anti-abrasion layer and/or an anti-scribble contamination layer.

Alternatively, the bottom surface of the image sheet may have a surface structure such that when the image sheet is applied on the display substrate, fluid (including air) can escape. Preferably, the surface topography of the bottom surface should be such that when the film is applied to the display substrate, people with ordinary vision can see from a place 2 meters away from the image sheet that no air bubbles are trapped in it. More preferably, the surface structure is in the form of microgrooves or grooves, and its distribution pattern can effectively reduce or eliminate visible air bubbles entrained between the image sheet and the display substrate. Preferably, the microgrooves can have any suitable cross-sectional shape, such as a circle, a square, a triangle, or a trapezoid. The size of the microgrooves depends on the thickness of the image sheet, and the preferable range is: the width is less than 0.1 mm, and the depth is less than 25 mm. Even better, the arrangement of these microgrooves should make the electrostatic adhesion of the image sheet unaffected. The area of the bottom surface of the image sheet in contact with the display substrate is at least 35%. In addition, the surface structure of the bottom surface of the image sheet should be better designed so that when the sheet is attached to the display substrate, it has no effect on the appearance of the image. Even better, when the sheet is attached to the display substrate, people with normal vision can see from a place 2 meters away from the image sheet and cannot feel the existence of the sheet surface structure. Examples of these surface structures are described in detail in U.S. Patent Application Serial No. 9/098,961, which was filed on June 18, 1998 (WO99/65999).

Any of the above-mentioned layers, whether available or required, may contain at least one optional additive. Optional additives can be selected from: pigments, colorants, fillers, ultraviolet absorbers, anti-sticking agents, flame retardants, plasticizers, light stabilizers, heat stabilizers, slip agents, antistatic agents, free radicals Scavengers and carrier resins, all of which are familiar to those skilled in the art. These additives are best selected so as not to interfere with the co-extrusion process, image sensitivity, structural integrity of any layer, or combination of multilayer composites.

The present invention also provides a method for applying an image sheet on a display substrate, including:

The bottom surface of the film is applied to the desired position of the display substrate, and the sheet is temporarily attached to the substrate through the electrostatic charge of the film.

The sheet is oriented on the display substrate; the sheet is firmly attached to the display substrate by an activatable adhesive.

A better specific embodiment of the method: the active adhesive is a pressure-sensitive adhesive with a peelable liner to prevent premature adhesion, and after the sheet is oriented on the display substrate, the peelable liner is removed.

Another better specific embodiment of the method: the activatable adhesive is microencapsulated, and after the sheet is oriented on the display substrate, the adhesive is released from the encapsulated microcapsules.

Another better specific embodiment of the method: the activatable adhesive is a positioning pressure-sensitive adhesive activated by pressure. After the sheet is oriented on the display substrate, pressure is applied to the film on the part with the adhesive to make the adhesive Activation plays a role of adhesion.

Another better specific embodiment of the method: the activatable adhesive is a pressure-sensitive adhesive that can be positioned repeatedly. After the sheet is oriented on the display substrate, additional pressure is applied to the adhesive to ensure that the adhesive and the display substrate are very close. Good contact.

Another better embodiment of the method: the activatable adhesive is a pressure-sensitive adhesive with a peelable liner to prevent its premature adhesion. After the sheet is oriented on the display substrate, the peelable liner is removed Pad to activate the adhesive. The method further includes the step of removing the sheet from the display substrate, stretching the backing of the stretch adhesive at an angle of not more than 35° to leave the surface of the display substrate, thereby removing the adhesive without damaging the display substrate.