Stock material or miscellaneous articles – Layer or component removable to expose adhesive
Reexamination Certificate
2000-05-23
2003-10-07
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
C428S040200, C428S143000, C428S147000, C428S158000, C428S159000, C428S192000, C428S215000, C428S317300, C428S343000, C428S354000, C428S356000, C428S402000
Reexamination Certificate
active
06630218
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improvement of an adhesive sheet which has a specific uneven structure oh its adhesive surface, and can be adhered to an adherent without trapping unnecessary air between the adhesive surface and the surface of the adherent.
BACKGROUND OF THE INVENTION
Adhesive sheets are known, which can be bonded or adhered to adherents without trapping unnecessary air between the adhesive surface and the surface of the adherent.
An example of such an adhesive sheet (including an adhesive film) comprises a substrate film and an adhesive layer which is in contact with at least one of the main surfaces of the substrate film, and which has an regularly patterned uneven structure comprising (i) a plurality of projections which will be in contact with an adherent and (ii) grooves which are formed between adjacent projections and will communicate outside when the projections are in contact with the adherent.
This type of the adhesive sheet can allow the trapped air bubbles to escape outside when the adhesive sheet is in contact with an adherent. Thus, the adhesive sheet can be successfully adhered to the adherent without trapping air between the adhesive surface of the sheet and the surface of the adherent.
Such adhesive sheets comprising adhesive layers having such an uneven structure described above are disclosed in, for example, Japanese Patent Publication JP-U (utility model)-3-67043-A.
A conventional method for producing an adhesive sheet will be briefly explained.
First, a liner, an adhesive layer and a substrate film are laminated in this order to provide a laminate comprising these three layers.
Next, an embossing tool is pressed on the liner side of the laminate, and the laminate is processed so that a specific uneven structure is formed on the adhesive layer (adhesive surface). Therefore, the liner is made of a material which can be plastically deformed by above embossing, such as a resin film.
The substrate film of the usual adhesive sheet is also plastically deformed by above embossing, since it comprises a resin film. Thus, embossing marks remain on the main surface of the substrate film on which no adhesive layer is formed, and the appearance of the adhesive sheet deteriorates.
It is also known that a negative structure corresponding to a structure, which will be formed on the surface of an adhesive surface is formed on the surface of a liner. A liquid containing an adhesive polymer is applied on the structural surface of the liner and solidified to form a laminate consisting of the liner and solidified adhesive layer, and then a resin substrate film is laminated on the surface of the adhesive layer to form an adhesive sheet (see, for example, U.S. Pat. No. 5,650,215 (Mazurek et al.)). In this method, the liner and adhesive layer are laminated so that the positive structure on the adhesive surface and the negative structure of the liner are in contact with each other. In this case, no embossing marks remain on the main surface.
However, none of the above prior art teach that the adhesive layers of the adhesive sheets having the uneven structure contain elastic microspheres.
SUMMARY OF THE INVENTION
As described above, the adhesive sheets are known, which have no embossing marks on the main surface of the substrate film which is not in contact with the adhesive layer, and which can effectively prevent the deterioration of appearance.
However, with such an adhesive sheet, the uneven structure of the adhesive layer (i.e., adhesive surface) remains after the adhesion of the adhesive sheet to the adherent, and thus the shape of the uneven structure appears on the surface of the substrate film. Therefore, it is difficult to prevent the deterioration of the appearance of the adhesive sheet after the adhesion to the adherent. In particular, with the flexible substrate film, depressions are formed in areas of the substrate film corresponding to the depressed portions of the adhesive layer, when the adhesive sheet are adhered to the adherent, and such depressed portions remain for a relatively long time after the completion of the adhesion.
Thus, an aspect of the present invention provides an adhesive sheet which can maintain a specific uneven structure just after adhesion to an adherent so that bubbles can effectively escape even when the bubbles are trapped, and thereafter, the uneven structure deforms so that deterioration of the appearance can be prevented after adhesion.
The present invention provides an adhesive sheet comprising
(a) a flexible substrate film;
(b) an adhesive layer which is in contact with at least one of the main surfaces of said flexible substrate sheet, and which has an uneven structure comprising (i) a plurality of projections which will be in contact with an adherent and (ii) grooves which are formed between adjacent projections and will communicate outside when said plurality of projections are in contact with the adherent; and
(c) a liner which has, on at least one of its surfaces, a negative structure corresponding to said uneven structure of the adhesive layer, and is laminated on said adhesive layer so that said negative structure and said uneven structure on the surface of the adhesive layer are in contact with each other.
Preferably, in one embodiment, the adhesive layer comprises a crosslinked polymer, and maintains said uneven structure having an initial contact area just after the adhesive sheet is adhered to the adherent. Said uneven structure deforms to form an increased contact area of at least 92% after 48 hours at 25° C. from the adhesion of the sheet to the adherent. In a second embodiment, said adhesive layer comprises a matrix component containing an adhesive polymer and elastic microspheres, which are dispersed in said matrix component. The elastic microspheres have an average diameter of 10 to 100 &mgr;m as described below.
Further embodiments are disclosed below.
EMBODIMENTS OF THE INVENTION
Adhesive Sheet of One Embodiment
The adhesive sheet of the first embodiment according to the present invention has the following characteristics:
(a) the adhesive layer contains a crosslinked polymer, and
(b) the adhesive sheet maintains-an uneven structure just after a liner is peeled off and the adhesive sheet is adhered to the adherent. The uneven structure deforms and thus a contact area increases to at least 92% after 48 hours at 25° C. from the adhesion of the sheet to the adherent.
The above characteristic (b) is easily achieved due to the shape memory of the adhesive layer containing the crosslinked polymer. That is, such a characteristic is obtained by allowing the adhesive layer to memorize a flat shape having no uneven structure as the first shape, and then shaping the adhesive sheet to impart the specific uneven structure as the second shape to the adhesive layer. The easy and effective method for forming such an adhesive sheet will be explained below. In this case, the above liner, that is, the liner which has, on at least one of its surfaces, the negative structure corresponding to the uneven structure of the adhesive layer, and is laminated on the adhesive layer so that the negative structure and the uneven structure on the surface of the adhesive layer are in contact with each other, functions as a negative mold for imparting the above second shape (positive shape), and also as a protective film for maintaining the second shape of the adhesive layer during storage (before use).
The adhesive layer contains an adhesive polymer, and has tackiness at room temperature (about 25° C.). The crosslinked polymer may be the above adhesive polymer which has been crosslinked, or a separately added non-adhesive crosslinked polymer.
The polymer is usually crosslinked with a crosslinking agent. The amounts of the components are suitably selected in a range in which the adhesion force of the adhesive layer is not lower than a specified level, and the uneven structure deforms within a specific period of time so that the contact area increases to 92% or larger. For example, the adhesive layer may be for
3M Innovative Properties Company
Egan Brian P.
Peters Carolyn V.
Pyon Harold
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