Substrate film for adhesive sheet and adhesive sheet using...

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Reexamination Certificate

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C428S143000, C428S149000, C428S402000

Reexamination Certificate

active

06372339

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate film for an adhesive sheet and to an adhesive sheet using the same. More specifically, the invention relates to a substrate film for an adhesive sheet, that is used as a support (substrate) of, for example, a pressure-sensitive adhesive sheet for skin adhesion, and to an adhesive sheet.
2. Description of the Related Art
As a support (substrate) of an adhesive sheet applied to a curved, movable or bending surface, such as a skin, an elastomer film such as a polyurethane film having high rubber-like elasticity, or a flexible vinyl chloride film having an increased flexibility by using a plasticizer has been used for the reason that such a film follows up to a skin satisfactorily.
However, the flexible vinyl chloride film has had the problems that it follows up to the elongation and contraction of a skin insufficient yet, and after it is applied a stretch feeling or a skin irritation during adhering tends to develop, and further, since its flexibility is insufficient, there is the problem that edge portions of the film are liable to peel during its application. In addition, there has been the problems that the phenomenon of migration of a plasticizer in the film into an adhesive tends to occur, so that a film having a sufficiently stable quality is not obtained.
The elastomer film has the defect that stress when receiving small deformation is relatively small as compared with stress when receiving large deformation, thus showing a rubber elasticity, and as a result, a so-called stiffness of a film is weak, a support twists, or wrinkles tend to occur. Consequently, the elastomer film also has the defect that the processability of the film while it is being produced is poor, and the operation of applying the film is difficult since adhesive surface portions stick each other when applying a pressure-sensitive adhesive sheet to a skin.
This problem can be solved by temporarily adhering and supporting the adhesive sheet on a separate film or sheet having a sufficient stiffness before its supply and use. However, the elastomer film still has the problems that its production step or adhering work is complicated, cost of a film or an adhesive sheet increases, and wastes are generated.
Further, the elastomer film generally has a large surface abrasion resistance. Therefore, when it is used as a substrate for a pressure-sensitive adhesive sheet for skin adhesion, the problem has been pointed out that a difference between the slipperiness of skin surface and the slipperiness of the elastomer film is big, so that uncomfortable feeling when it is applied to the skin increases, and the pressure-sensitive adhesive sheet is liable to peel off by rubbing with cloths, etc.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described problems.
Accordingly, one object of the present invention is to provide a substrate film suitable for an adhesive sheet which sufficiently satisfies the processability in producing an adhesive sheet and adhering property even without a temporary adhering support, and also has a sufficient flexibility in adhering and skin follow-up property.
Another object of the present invention is to provide an adhesive sheet having improved adhesion to a skin by using the above film as a substrate.
As a result of extensive investigations, it has been found that the objects of the present invention can be attained by inclusion of a specified modifier in an elastomer resin having a flexibility.
The specified modifier used in the present invention includes a hydrophilic polymer having a tensile modulus of elasticity higher than that of the elastomer resin, and inorganic fine particles having an average particle diameter of 15 &mgr;m or less.
In other words, the objects of the present invention can be attained by using a mixture of the elastomer resin and a polymer which is higher in elasticity than the elastomer resin and has a water absorption ability.
Further, by blending a specified amount of inorganic fine particles such as zeolite with the elastomer resin, not only the objects of the present invention are attained and but also there can be provided a film having a break strength decreased to a level such that the film can easily be cut with hands, while maintaining sufficient barrier property required as a support of a pressure-sensitive adhesive sheet for skin adhesion.
A substrate film for an adhesive sheet of the present invention is characterized in that the film contains an elastomer resin, and at least one of a hydrophilic polymer having a tensile modulus of elasticity higher than that of the elastomer resin and inorganic fine particles having an average particle size of 15 &mgr;m or less.
Here, the elastomer resin may be a thermoplastic block polymer.
Further, the elastomer resin may be at least a member selected from the group consisting of polyester polyurethane, polyether polyamide, polyether polyurethane, and polyether polyester.
The hydrophilic polymer may be polyvinyl pyrrolidone.
Preferably, the hydrophilic polymer may be contained in a weight proportion of hydrophilic polymer:elastomer resin=2:98 to 40:60.
The film may have a water absorption of preferably 5 to 200%.
The tensile modulus of elasticity of the film in a saturated water absorption state may be 50% or less of a tensile modulus of elasticity in a dry state.
The inorganic fine particles may be dispersed in an amount of preferably 8 to 100 parts by weight per 100 parts by weight of the elastomer resin.
The inorganic fine particles may be zeolite or amorphous silica.
The film may have a tensile strength of preferably 12 to 28 MPa.
An adhesive sheet of the present invention, characterized in that an adhesive layer is formed on at least one surface of the substrate film for an adhesive sheet as the above.
Here, the sheet may be used for skin adhesion.
Other objects and advantages of the present invention will become apparent from the detailed description to follow taken in conjunction with the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
In order to achieve the objects of the present invention, the substrate film for an adhesive sheet of the present invention is a film which comprises an elastomer resin as a base which has been modified.
That is, the substrate film for an adhesive sheet according to a first embodiment of the present invention is a film which comprises an elastomer and a hydrophilic polymer higher in elasticity than the elastomer and having water absorption as a blend, the film being formed in a state that the hydrophilic polymer is molten or dispersed in the elastomer resin.
When such a modified elastomer film is adhered to a skin, the hydrophilic polymer absorbs the moisture perspired from a skin or moisture in environment, so that the film exhibits a plasticity. As a result, when the film is formed as a pressure-sensitive adhesion sheet and adhered to a skin, the tensile modulus of elasticity of the substrate film for an adhesive sheet decreases, which improves the flexibility and skin follow-up property of the adhesive sheet.
On the other hand, during the production of the adhesive sheet, the hydrophilic polymer does not sufficiently absorb water, and it is therefore believed that the hydrophilic polymer can show a tensile modulus of elasticity substantially equal to, or rather larger than that of the elastomer resin alone. As a result, the mechanical strength of the film can sufficiently be maintained, and a film having more excellent processability and further higher flexibility than the conventional one can be obtained.
The substrate film for an adhesive sheet according to a second embodiment of the present invention is a modified elastomer film, i.e., a non-porous elastomer film which comprises an elastomer resin and inorganic fine particles having an average particle size of 15 &mgr;m or less dispersed therein in an amount of 8 to 100 parts by weight of per 100 parts by weight of the elastomer resin.
By the above-described modification, th

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