AU748253B2 - Adhesive sheets and adhesive structures - Google Patents

Description

WO-00/22059 PCT/US99/23855 ADHESIVE SHEETS AND ADHESIVE STRUCTURES Field of the Invention The present invention relates to an improvement in an outdoor adhesive sheet suited particularly as a marking film for concrete or mortar, and an improvement in an adhesive structure comprising an adherend having an adherend surface made of concrete or mortar, and an adhesive sheet bonded onto the adherend surface of the adherend.

Background of the Invention When an adhesive sheet is used by applying onto an adherend wall of buildings, structures, etc.) made of a material such as mortar, concrete or the like arranged outside, the following problems occur. That is, since mortar or concrete is a water absorbing porous material, when the adhesive sheet is applied onto it, an outgas such as water vapor penetrated into the adherend from the outside oozed out onto the adhesive interface and, therefore, appearance defects are caused by expansion of the adhesive sheet.

Accordingly, when the adhesive sheet is applied onto the outdoor concrete adherend, the adherend surface is subjected to an undercoating treatment using a sealer or a primer to prevent the outgas from oozing put onto the adhesive interface from the adherend.

However, such an undercoating treatment requires much labor and time and, therefore, the applicability (workability) was lowered.

On the other hand, an adhesive sheet, which can make the above undercoating treatment unnecessary and can prevent the outgas from the adherend from retaining between the adherend and the adhesive layer of the adhesive sheet, is also used. An adhesive sheet comprising an adhesive layer having a concave-convex (irregular) structure on an adhesive surface is disclosed, for example, in Japanese Unexamined Patent Publication (Kokai) Nos. 6-287525, 8-113768 and 9-157606. These adhesive layers are formed by applying an adhesive of a mixture of elastic microspheres and an adhesive binder, and have a concave-convex structure on the adhesive surface. Such an irregular adhesive surface forms passages, which are surrounded with the concave portions and an adherend surface of an adherend and is in communication with the outside, when the adhesive sheet is applied onto the adherend. It is possible to let the outgas from the -1adherend escape to the outside through these passages and to prevent appearance defects caused by expansion.

Another example includes an adhesive-processed sheet disclosed in Japanese Utility Model No. 2503717. This sheet is obtained by imparting a concave-convex structure to the surface of the adhesive layer using a release paper on which an embossing treatment is provided, and the same effect as that in case of using the above elastic microparticles can be obtained.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 6-108605 discloses an adhesive sheet comprising an adhesive layer containing a rubber adhesive polymer, which is used at water section (environment and place always in contact with water) such as tile surface of bath room, although the adhesive sheet is not for outdooruse.

The above adhesive layer is superior in water-resistant adhesive strength and can maintain high adhesive strength for a long period of time even if it is used at water section. Since the outgas is not usually evolved from the tile surface, this publication does not describe 15 the prevention of expansion as described above.

.•oo.i SSummary of the Invention It has been found that expansion of an adhesive sheet caused by applying (bonding) onto a adherend surface having a comparative large area about 1 m 2 of the outdoor 20 concrete adherend is not sufficiently avoided by merely preventing the outgas from S•retaining between the adherend and adhesive sheet. Normally, such an expansion is caused by peeling at the interface between the substrate and the adhesive layer of the adhesive sheet and peeling at the interface between the adhesive layer of the adhesive sheet and the adherend surface.

SBy merely enhancing the water-resistant adhesive strength of the adhesive layer naving a concave-convex surface, peeling at the interface between the adhesive layer and the adherc:-id of can be effectively prevented but expansion caused by peeling at the interface between the substrate and the adhesive layer of(l) can not be prevented.

Accordingly, the present invention seeks to provide an adhesive sheet capable of effectively preventing expansion of the adhesive sheet caused by both and described above even if the adhesive sheet is applied onto the adherend surface having a comparatively large area about 1 m 2 or more) of the outdoor concrete adherend.

-2- As now claimed, in one aspect the present invention an adhesive sheet comprising a substrate and an adhesive layer, having a regularly arranged concave-convex structure on the adhesive surface of the adhesive layer placed on one principal surface of said substrate, wherein passages in communication with the outside are formed, when said adhesive sheet is bonded to an adherent, the passages being determined by said concave portions and said adherend characterized in that: said adhesive layer contains a rubber adhesive polymer and is fixed onto one principal surface of said substrate via a primer layer and said rubber adhesive polymer is adapted to retain the concave-convex structure.

oC oo CoC ooooo oooo o•i 2a- W0 00/22059 PCTIUS99/23855 Brief Description of the Drawings Fig. 1 is a cross-sectional view showing one preferred aspect of the adhesive sheet according to the present invention.

Fig. 2 is a cross-sectional view showing one further preferred aspect of the adhesive structure according to the present invention.

Detailed Description of Presently Preferred Embodiments To accomplish the above object, the present invention provides an adhesive sheet comprising a substrate and an adhesive layer having concave portions on an adhesive surface, placed on one principal surface of said substrate, Wherein passages in communication with the outside are formed, when said adhesive sheet is bonded to said adherend, the passages being determined by said concave portions and an adherend characterized in that: said adhesive layer contains a rubber adhesive polymer and is fixed onto one principal surface of said substrate via a primer layer.

Describing with reference to Fig. 1 and Fig. 2, an adhesive sheet 1 of the present invention comprises an adhesive layer 2 having concave portions 8 and a plurality of convex portions 7 whose contour was formed by the concave portions 8 thereof on the adhesive surface, thereby to form a plurality of passages, which are surrounded with the concave portions 8 and an adherend surface 9 and are in communication with the outside, when the adhesive sheet is bonded to an adherend 6 at the top surface of the concave portions 7. Consequently, the outgas from the adherend 6 can be effectively prevented from retaining between the adherend 6 and adhesive sheet 1 (outgas dissipation operation).

Since the adhesive layer 2 contains a rubber adhesive polymer, the water-resistant adhesive strength is effectively enhanced and peeling at the interface between the adhesive layer and the adherend of described above can be effectively prevented. Furthermore, since the above adhesive layer 2 is fixed onto one principal surface of a substrate 4 via a primer layer 3, expansion of the adhesive sheet 1 caused by peeling at the interface between the substrate and the adhesive layer of(1) described above can be effectively prevented.

Accordingly, according to a synergistic effect of them, expansion of the adhesive sheet 1 caused by both and described above can be effectively prevented even if the -3- -WO-00/2059 PCT/US99/23855 adhesive sheet is applied onto the adherend surface 9 having a comparatively large area about 1 m 2 or more) of the outdoor concrete adherend 6.

The adherend 6, to which the adhesive sheet 1 of the present invention is bonded, is not specifically limited. However, the adhesive sheet is particularly suited to form an adhesive structure 5 comprising an adherend 6 wall of buildings, structures, etc.) made of a material such as mortar, concrete or the like arranged outside. Because appearance defects caused by expansion of the adhesive sheet 1 can be effectively prevented even if the outgas such as water vapor penetrated into mortar or concrete oozes out onto the adhesive interface.

Accordingly, when the adhesive sheet I is applied onto such an adherend 6, it is not necessary to subject the adherend surface to an undercoating treatment using a sealer or a primer and the applicability (workability) can be improved.

Adhesive sheet According to one preferred aspect of the adhesive sheet of the present invention, the adhesive sheet comprises: A: a flexible base film as a substrate; and B: an adhesive layer having a concave-convex structure, which is closely bonded onto one principal surface of the base film via a primer layer and includes: a plurality of convex portions bonded to the adherend, and (ii) continuous groove-shaped concave portions which are formed between adjacent convex portions and is in communication with the outside, when the adherend and the convex portions are contacted, on the adhesive surface opposite the closely bonded surface.

The adhesive layer of the adhesive sheet of the present invention contains a rubber adhesive polymer and, if necessary, a curing agent. The thickness of the adhesive layer is not specifically limited as far as the effect of the present invention is not adversely affected, but is normally from 30 to 200 ptm, and preferably from 35 to 150 pm. Since the adhesive layer of the adhesive sheet of the present invention contains the adhesive polymer as an adhesive component, it can be used in a manner similar to a normal adhesive sheet.

Even if bubbles are evolved between the adhesive surface and adherend surface by an WO 00/22059 PCT/US99/23855 action of the concave portions of the adhesive layer, it is possible to let air escape to the outside through the passages.

Rubber adhesive polymer The rubber adhesive polymer (hereinafter merely referred to as an "adhesive polymer", sometimes) is made of a rubber polymer and exhibits adhesion properties at a normal temperature (about 25 0 The rubber polymer includes, for example, polybutadiene, polyisoprene, nitrile-butadiene copolymer (NBR), styrene-butadiene copolymer (SBR), ethylene-propylene copolymer (EPDM), polychloroprene, fluorine rubber polymer, silicone polymer (including polysiloxane-urea block copolymer) or the like. The adhesive polymer is composed of one kind of these rubber polymers alone or a mixture of two or more kinds of them. Among them, a nitrile-butadiene copolymer, a styrene-butadiene copolymer or a mixture of them is preferred. Because the waterresistant adhesive strength is high and the shape of the concave portions of the adhesive layer is easily retained. Specific examples of such a rubber polymer include a butadiene rubber manufactured by Rikidain Co., Ltd. "(product No.) GR1035: mixture of NBR/SBR in a weight ratio of 75:25, solid content: about 33% by weight".

The molecular weight of the adhesive polymer may be within the range where a predetermined adhesive strength is exhibited, and is normally within the range from 10,000 to 100,000 in terms of weight-average molecular weight. As the adhesive polymer, both a solution type adhesive polymer (a polymer is contained by dissolving in a solvent) and an emulsion type adhesive polymer (a polymer is contained by disperse in a solvent) can be used and a mixture thereof can also be used. The adhesive polymer may also be crosslinked. In that case, a crosslinking agent containing an isocyanate compound, a melamine compound, a poly(meth)acrylate compound or the like is added.

The proportion of the rubber adhesive polymer is normally not less than 55% by weight, and preferably from 60 to 100% by weight, based on the whole adhesive layer.

When the content of the rubber adhesive polymer is too small, the water-resistant adhesive strength is lowered and there is a fear that peeling at the interface between the adhesive layer and adherend is not effectively prevented. Similar to a conventional known adhesive sheet, a tackifier can also be used, together with the adhesive polymer. As far as the effect of the present invention is not adversely affected, the adhesive polymer may be those W000/22059 PCTIUS99/23855 which are curable by heat or radiation. The adhesive polymer can be cured before and/or after bonding onto the adherend.

The adhesive layer preferably contains a curing agent, in addition to the rubber adhesive polymer. Consequently, the shape retention of the above concave-convex structure is substantially maintained even after applying onto the adherend. If the above concave-convex structure passages in communication with the outside) is lost in a predetermined time after the adhesive sheet was applied onto the adherend, the outgas dissipation effect is lowered.

As the curing agent of the adhesive layer, a mixture of a crosslinking polymer or a crosslinking agent and an adhesive polymer is preferably used. Consequently, the dimensional stability (shape retention of adhesive layer) to humidity can be enhanced.

The crosslinking polymer is a crosslinkable polymer, and a self-crosslinking polymer alone can be used, or a combination of a crosslinking polymer and a crosslinking agent for the crosslinking polymer can also be used. In case that the adhesive polymer is crosslinkable, a crosslinking agent for adhesive polymer can also be used as a curing agent. The proportion of the curing agent is normally not more than 30% by weight, preferably from 0.1 to 20% by weight, and more preferably from 0.5 to 15% by weight, based on the whole adhesive layer. When the amount of the curing agent is too small, there is a fear that the shape retention of the adhesive layer can not be substantially maintained. On the other hand, when the amount of the curing agent is too large, there is a fear that the adhesive strength is lowered.

The curing agent is not specifically limited provided that the shape retention of the adhesive layer can be substantially maintained. For example, a crosslinking polymer containing polyol, polyacrylate, polyurethane, polyolefin, epoxy resin or the like can be used. -Examples of crosslinking agents include polyisocyanate, melamine compound, dicyandiamide, polyamine or the like. For example, as the curing agent used in combination with a nitrile-butadiene copolymer, a styrene-butadiene copolymer or a mixture thereof, a mixture of polyol and polyisocyanate is preferred. This is one of the best combinations capable of effectively enhancing both the water-resistant adhesive strength and shape retention of the adhesive layer. To promote crosslinking of the polymer, energy such as heat, radiations or the like is preferably used. The polymer can also be crosslinked by directly reacting reaction points in the polymer molecule each other.

WO-00/22059 PCT/US99/23855 The adhesive layer can be cured before and/or after bonding onto the adherend. In the embodiment where curing of the adhesive layer is performed before bonding onto the adherend by using the adhesive sheet in the same manner as that in case of a conventional adhesive sheet, it is necessary to pay attention that adhesion properties of the adhesive layer are not lost. In such a case, the cured adhesive layer may be heated to exhibit adhesion properties.

The concave-convex structure including the concave portions (groove portions) of the adhesive surface is not specifically limited, provided that the effect of the present invention is not adversely affected. A preferred embodiment of the concave-convex structure is a horizontal cross section (cross section parallel to the adhesive surface) formed of convex portions having a shape such as polygon quadrilateral), circle, etc.

or a similar shape thereof and groove portions formed continuously to surround the periphery of the convex portions. As the shape of a vertical cross section of the convex portions (cross section vertical to the adhesive surface), quadrilateral such as trapezoid, rectangle, etc., semicircle or a similar shape thereof can be employed.

The height (depth of the concave portions or groove portions) of the convex portions is normally within the range from 5 to 200 pm, and preferably from 10 to 100 gm. When the height of the convex portions is too small, it may be difficult to remove bubbles trapped between the adhesive surface and adherend surface. On the other hand, when the height is too large, there is a fear that the appearance of the adhesive sheet after the completion of the application may be detrimentally affected. The maximum width (maximum dimension in horizontal direction) is within the range from 0.1 to 10 mm. On the other hand, the maximum width (maximum distance between adjacent convex portions) of the groove portions is normally within the range from 0.05 to 1 mm.

It is preferred that convex portions are regularly arranged. For example, the convex portions are arranged at nearly center of respective masses (generally square) of an in-line geometric pattern. In this case, the groove portion are formed along lines of squares and at least one groove portion (preferably a plurality of groove portions) has an opening so as to communicate with the outside in the outer peripheral end of the adhesive sheet applied onto the adherend. Alternatively, a plurality of groove portions can be arranged so that they intersect each other at an angle of about 60 degrees. Furthermore, a plurality of linear groove portions can be arranged in nearly parallel each other without WO 00/22059 PCT/US99/23855 intersecting each other. It is preferred that the respective dimensions of a plurality of convex portions and groove portions are almost the same.

To form concave-convex structure on the adhesive surface of the adhesive layer, fine particles can also be used. As such fine particles, for example, rubber particles, adhesive particles, glass beads and rigid plastic particles can be used. In this case, a coating solution is prepared by mixing the above fine particles with a matrix component containing an adhesive polymer and an adhesive layer of a coated film of the coating solution is used. The average volume diameter of the fine particles is normally within the range from 10 to 300 tm. The "average volume diameter" is a value determined by measuring 100 fine particles using an-image processing device due to an optical microscope and then applying the measured values to the following equation Average volume diameter E(di 4 9 ni) /(di 3 ni) where di denotes a diameter tm) having the i-th largest size of fine particle and ni denotes the number of fine particles having a diameter di.

The amount of the fine particles contained in the adhesive layer is normally from to 80 parts by weight, based on 100 parts by weight of the adhesive polymer. As the fine particles, solid or hollow spheres having one or more pores can be used.

The area of contact between the adhesive layer (convex portions) and the adherend is not specifically limited as far as the effect of the effect of the present invention is not adversely affected. However, when the contact area is defined by using the proportion of the contact area at the time of measuring by applying the adhesive sheet onto the flat adherend, the contact area is normally from 50 to 99%, preferably from 70 to 97%, and particularly from 80 to 95%. When the contact area is too small, the adhesive strength is lowered. On the other hand, when the contact area is too large, there is a fear that the outgas dissipation effect is lowered and there is a fear that peeling at the interface between the adhesive layer and adherend can not be prevented.

The measurement of the above contact area is specifically performed in the following manner. First, the surface of a flat glass plate such as slide glass and an adhesive surface of an adhesive layer of an adhesive sheet are closely contacted, and then pressed by moving it back and forth once between rollers of 2 kg to form a sample for measurement. In case of pressing, the width of the adhesive sheet is adjusted to 2 cm so that the linear pressure becomes 1 kg/cm and the rolling direction of rollers is a W000/22059 PCTIUS99/23855 longitudinal direction. Observing through a polarizing plate with casting white light on the side of the glass plate on which no sheet is applied, the region where the convex portions are contacted with the glass surface appears to be blackish, whereas, the noncontact region appears to be whitish. Such a observed state is photographed and the area of the contact area and that of the whole field of view to be observed (corresponding to apparent contact area) are measured, and then a ratio of both area; (area of the contact area/whole field of view to be observed) is represented by percentage and the resulting value is taken as a "contact area". Such an operation can be performed by using a normal optical microscope with a polaroid camera. In this case, the area of the field of view to be observed is normally 1 cm 2 The surface roughness Ra of the glass plate to be used is not more than 0.1 pm.

The substrate is not specifically limited, but there can be used those having flexibility, which have been used as a base film of a conventional adhesive sheet. For example, paper, metallic film and plastic film can be used. As the plastic, synthetic polymers such as polyvinyl chloride, polyester (PET), polyurethane, polyacrylate, fluorine polymer and the like can be used. The substrate may be capable of transmitting visible light and ultraviolet rays, or may be colored or decorated by printing. To impart an appearance with metallic luster, the substrate may be provided with a metallic deposit.

Furthermore, to impart an optical function to the adhesive sheet, for example, a polarizing film, a dielectric reflective film, a retroreflective film, a prism film, a fluorescent film, a film-shaped electroluminescence device or the like can also be used as the substrate.

The substrate may be composed of two or more different layers. For example, the substrate can include a base layer arranged at the adhesive layer side and a stain-resistant film layer arranged at the outermost layer side. As the base layer, there can be used a material having good adhesion properties to the adhesive layer polyvinyl chloride, polymethyl methacrylate, etc.). As the stain-resistant film, there can be used a film containing a fluorine polymer polyvinylidene fluoride, etc.) and a film supporting a photocatalyst layer.

The thickness of the substrate is normally from 10 to 500 tm. A primer layer is provided on the surface at the side where the adhesive layer of the substrate is formed, as described hereinafter.

-9- WO-00/22059 PCT/US99/23855 As the primer layer, a coated film containing a polymer having affinity to both of the substrate and the adhesive layer can be used. For example, when the substrate contains PVC (polyvinyl chloride), the coated film preferably contains an acrylic polymer. In this case, as the adhesive polymer, a nitrile-butadiene copolymer, a styrene-butadiene copolymer or a mixture thereof is preferred. In addition to them, a vinyl chloride copolymer vinyl chloride-vinyl acetate copolymer, etc.), polyurethane and polyester can also be used.

Specific examples of the material of the primer layer include Polyment NK350 (trade name, modified acrylic polymer) manufactured by Nippon Shokubai Co., Ltd., VYHH (trade name, vinyl chloride-vinyl acetate copolymer) manufactured by Union Carbide Co. and Acryloid B82 (trade name, acrylic polymer) manufactured by R&H (Roam Haas) Co.

The primer layer can be formed by coating on the surface of the substrate using a normal coating means. The thickness of the primer layer is not specifically limited as far as the effect of the present invention is not adversely affected, but is normally from 0.1 to rim, and preferably from 0.2 to 20 .m.

Method of producing adhesive sheet The adhesive sheet of the present invention may be produced, for example, in the following manner. First, a liner having a structure corresponding to a negative of a concave-convex structure which is intended to be formed on an adhesive surface, on one surface is prepared. A coating solution containing an adhesive polymer and a curing agent to be optionally added is coated on the surface having a negative structure of the liner and then solidified drying, curing, etc.) to form an adhesive layer. Consequently, it is possible to form an adhesive layer having a concave-convex structure, which corresponds to a positive structure following the surface of a structure corresponding to the above negative of the above liner.

Then, the surface (nearly flat, normally), which is not contacted with the liner of the above adhesive layer, is contacted with the surface of the substrate which a primer layer has been applied. The substrate and adhesive layer are sufficiently bonded, for example, by using a pressing means such as roller to obtain an adhesive sheet with a liner.

Optionally, at the time of use of the adhesive sheet, the liner is removed and the adhesive WO 00/22059 PCT/US99/23855 sheet is applied onto the adherend in the same manner as that in case of a conventional adhesive sheet.

The adhesive sheet can also be produced by another method. First, a liner, an adhesive layer a primer layer and a base film (substrate) are laminated in this order to prepare a laminate comprising these four layers. Then, an emboss tool is pressed from the liner side of this laminate and the laminate is processed so that the adhesive layer (adhesive surface) has predetermined a concave-convex structure. The above liner is made of at least a material capable of causing plastic deformation by embossing resin film, etc.). Furthermore, fine particles are mixed with an adhesive polymer and an adhesive layer having a convex portions formed from the fine particles can also be used.

Now, specific production examples of the adhesive sheet of the present invention now will be described.

First, a coating solution for forming an adhesive layer is prepared. This coating solution is normally prepared by mixing an adhesive polymer, a curing agent, a solvent and, if necessary, various additives using a mixing device such as homomixer, planetary mixer or the like, and then uniformly dissolving or dispersing the respective materials.

The coating solution prepared in such a manner is coated on the liner and then dried to prepare an adhesive layer. As the coating means, for example, a known means such as knife coater, roll coater, die coater, bar coater or the like can be used. Drying is normally performed at a temperature within the range from 60 to 180 0 C. The drying time is normally from several tens seconds to several minutes.

As the solvent, for example, water or an organic solvent can be used. It is also possible to add an auxiliary solvent which is partially compatible with water. Examples of the useful auxiliary solvent include alkylene glycol monoalkyl ether ester such as 3methyl-3-methoxybutyl acetate or the like.

As far as the effect of the present invention is not adversely affected, conventional known additives can be added to the coating solution for adhesive layer. Examples thereof include viscosity adjustors, defoamers, leveling agents, ultraviolet absorbers, antioxidants, pigments, a fungicide, inorganic particles such as glass beads, and elastic microspheres.

The liner is normally formed from a paper, a plastic film, or a film obtained by laminating them. The liner having the above negative structure is formed, for example, by pressing a pressing tool having a positive shape to the flat surface of a film, thereby to -11- WO 00/22059 PCT/US99/23855 transfer the concave-convex structure corresponding to the negative shape to the film surface. In case of pressing, the above tool can also be heated. The above positive shape normally has the same shape and same dimension as those of the concave-convex structure to be formed on the adhesive surface. A liner having a concave-convex structure corresponding to the negative shape can also be obtained by casting a flowable material containing a plastic in a mold having a positive shape, solidifying the material on the mold, and removing the mold. The concave-convex structure surface of the liner can also be subjected to a releasing treatment such as silicone treatment. When the above plastic is polyolefin, the releasing treatment can also be omitted.

The adhesive sheet is normally formed by coating the above coating solution on the concave-convex structure surface of the above liner, drying the coating solution to form an adhesive layer with a liner, and laminating the adhesive layer with a base film (substrate). At this time, the adhesive layer with a liner and the base film with a primer are laminated so that the adhesive layer and the primer surface of the base film are closely bonded.

The base film with a primer can be obtained by preparing a coating solution containing a polymer for primer, and coating the coating solution on one principal surface of the base film to form a primer layer. Preparation and coating of the coating solution for primer are performed according to the same manner as that in case of the above adhesive layer.

An adhesive surface having a concave-convex structure can also be formed by pressure-bonding the above concave-convex liner on the adhesive layer having a nearly flat adhesive surface, which is formed by coating a coating solution for adhesive layer on the primer surface of the base film with a primer.

Examples Example 1 First, a vinyl chloride film having a thickness of 100 gm was prepared as a base film (substrate). This base film was made from a vinyl chloride homopolymer solution by a casting method. On one principal surface of this base film, a coating solution for a primer was coated by using a gravure roll coater and then dried at 65C for about 1 minute to form a base film with a primer. This coating solution was prepared by diluting the -12- WO 00/22059 PCT/US99/23855 above NK350 (trade name) to 15% by weight in terms of concentration of a nonvolatile matter.

On the other hand, an adhesive layer with a liner was made.

The concave-convex structure of the liner used in this example had a structure wherein a plurality of protrusions corresponding to the groove portion to be formed on the adhesive surface are continuously arranged along lines of squares so that they intersect each other.

The height of the protrusion was 1.7 gm and the maximum distance between adjacent protrusions (distance between bottom surfaces of the protrusions) was 1.2 mRm.

The shape of the vertical cross section of the concave portion surrounded by the protrusions was generally trapezoid, whereas, the shape of the vertical cross section of the convex portion of the adhesive layer was generally trapezoid.

The coating solution for adhesive layer was formed by mixing 100 parts by weight of an adhesive polymer (GR1 035 (trade name), supra) and 4 parts by weight of a curing agent "Sunpasuta HD739D" (trade name, polyol/isocyanate curing agent) manufactured by Rikidain Co. This coating solution was coated on the concave-convex structure surface of the above liner, dried at 65°C for 3 minutes and then dried at 95 0 C for 3 minutes to form an adhesive layer. The thickness of the adhesive layer (to the height of the convexs) after drying was about 50 gm.

Finally, the primer surface of the base film with a primer obtained as described above was contacted with the surface of the adhesive layer of the liner with an adhesive layer, and then the adhesive layer and primer layer are closely bonded by using rollers to form an adhesive sheet of this example. A continuous groove portion was formed on the adhesive surface of the adhesive layer, and the contact area measured by the following method was about 92%. Furthermore, the adhesive layer had suitable tack similar to the adhesive layer of a normal adhesive sheet.

Contact area A flat surface of a slide glass of 76 mm (length) x 26 mm (width) x 1 mm (thickness) (MICRO SLIDE GLASS, White Edge, No. 1, manufactured byMatsunami Glass Industry Co.) and an adhesive surface of an adhesive sheet (2 cm in width x 5 cm in length) whose liner was removed were closely contacted, and then pressed by moving it -13- WO-00/22059 PCT/US99/23855 back and forth once between rollers of about 4.5 cm in width and 2 kg in weight in the longitudinal direction to form a sample. The sample was measured according to the above method. Ra of the flat surface of this slide glass was about 0.001 .tm.

The adhesive sheet of this example was evaluated in the following manner.

Dry adhesive strength and water-resistant adhesive strength An adhesive sheet cut into a piece of 150 mm x 25 mm was applied onto a mortar plate manufactured by Nippon Test Panel Co. (150 x 70 mm x 10 mm) under the conditions of 20'C x 65% RH, and the peel strength after allowing to stand under the same conditions for 48 hours was measured. The peel rate was 300 mm/min. and the peel angle was 180'. The dry adhesive strength of the adhesive sheet of this example to the mortar plate was about 2.6 kgf/inch.

On the other hand, the adhesive sheet applied onto the mortar plate in the same manner as described above was cured at room temperature for 24 hours, immersed in water at 40 0 C for 7 days, and then allowed to stand under the conditions of20'C x RH for 1 hour. The adhesive strength (water-resistant adhesive strength) measured in the same manner as that described above was about 1.1 kgf/inch.

Expansion resistance test The adhesive sheet having a planar dimension of 1 m x I m was applied onto the mortar plate under the conditions of20'C x 65% RH, cured at room temperature for 24 hours, and then immersed in water at 40 0 C for 7 days. It was observed whether expansion occurred or not. As a result, in case of the adhesive sheet of this example, the proportion of expansion is not more than 5% based on the whole area.

Example 2 In the same manner as that described in Example 1, except that a solution (concentration of nonvolatile matter: 25% by weight) prepared by dissolving a mixture of the above VYHH (trade name) and Acryloid B82 (trade name) in a weight ratio of4:1 in methyl ethyl ketone was used as the Coating solution for primer and the drying condition was changed to 65°C x about 1 minute and 120'C x about 1 minute, an adhesive sheet of -14- W000/22059 PCT/US99/23855 this example was made. The contact area of the adhesive layer measured in the same manner as that described in Example 1 was about 91%.

The dry adhesive strength measured in the same manner as that described in Example 1 was about 2.3 kgf/inch, and the water-resistant adhesive strength was about 0.9 kgf/inch. As a result of the expansion resistance test, expansion was hardly observed (the proportion of expansion is not more than 5% based on the whole area).

Comparative Example 1 In the same manner as that described in Example 1, except for changing the liner to KGM1 1S (trade name) manufactured by Rintek Co., an adhesive sheet of this example was formed. The adhesive surface of the adhesive layer was flat and the contact area was generally 100%.

The dry adhesive strength measured in the same manner as that described in Example 1 was about 3.2 kgf/inch, and the water-resistant adhesive strength was about 0.9 kgf/inch. As a result of the expansion resistance test, expansion caused by peeling at the interface between the base film and adhesive layer was effectively prevented, however, expansion caused by pop-off of the adhesive layer from the mortar plate was observed over almost the whole surface of the sheet.

Comparative Example 2 In the same manner as that described in Example 2, except for changing the liner to KGM 1 IS (trade name) manufactured by Rintek Co., an adhesive sheet of this example was formed. The adhesive surface of the adhesive layer was flat and the contact area was generally 100%.

The dry adhesive strength measured in the same manner as that described in Example 1 was about 2.4 kgf/inch, and the water-resistant adhesive strength was about 0.7 kgf/inch. As a result of the expansion resistance test, expansion caused by peeling at the interface between the base film and adhesive layer was effectively prevented, however, expansion caused by pop-off of the adhesive layer from the mortar plate was observed over almost the whole surface of the sheet.

WO 00/22059 PCT/US99/23855 Comparative Example 3 In the same manner as that described in Example 1, except for using no primer layer, an adhesive sheet of this example was formed.

The dry adhesive strength measured in the same manner as that described in Example I was about 1.9 kgf/inch, and the water-resistant adhesive strength was about 0.9 kgf/inch. As a result of the expansion resistance test, the proportion of expansion was about 30% based on the whole area in the adhesive sheet of this example. About 70% of expansion was caused by peeling at the interface between the base film and adhesive layer.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general acknowledge in Australia.

eoeeo -16-

Claims (3)

1. 2. The adhesive sheet of claim 1, said adhesive sheet expanding no more than about 5% when tested by applying to a mortar plate and curing it at room S. temperature for 24 hours and then immersing it in water at 400C for seven days.
2. 3. Use of an adhesive sheet according to claim 1 as an outdoor adhesive sheet on a water absorbing porous adherend material.
3. 4. The use according to claim 3 wherein the water absorbing material is selected from concrete or mortar. -17- Doe ,o,13-1 I/04A)1 18 An adhesive sheet substantially as herein described with reference to the accompanying drawings. DATE D this I1 lh~ day of April 2001 MINNESOTA MINING AND MANUFACTURING COMPANY By Its Patent Attorneys DAVIES COLLISON CAVE