Method for production of pressure-sensitive adhesive sheet

TECHNICAL FIELD

0001The present invention relates to a method for production of a pressure sensitive adhesive sheet capable of preventing or removing an air trapping or a blister.

BACKGROUND ART

0002When manually sticking a pressure sensitive adhesive sheet on an adherend, there has been a problem that an air trapping can be formed between the adherend and the adhesive face so that the pressure sensitive adhesive sheet is disfigured in some cases. This air trapping is likely to occur more often when the area of the pressure sensitive adhesive sheet is large.

0003In order to solve the problem in the appearance of the pressure sensitive adhesive sheet due to the air trapping, it has been performed that a pressure sensitive adhesive sheet is replaced by the other pressure sensitive adhesive sheet, a pressure sensitive adhesive sheet is removed and attached again, or a hole is formed using a needle in the expanded portion of the pressure sensitive adhesive sheet to deflate air in question. However, the following problems have often occurred. For example, when replacing the pressure sensitive adhesive sheet, it is not only troublesome, but also causes an increase in the cost. In addition, when attaching the pressure sensitive adhesive sheet again, the pressure sensitive adhesive sheet may be damaged, wrinkles may be generated on the surface, or the pressure sensitive adhesive properties may be deteriorated. On the other hand, the method to make a hole using a needle disfigures the pressure sensitive adhesive sheet.

0004In order to prevent an air trapping, there has been used a method to attach water onto the adherend or the adhesive face in advance of sticking. However, when large-size pressure sensitive adhesive sheets such as a glass shatterproof film for windows, a decorative film, a marking film or the like are stuck, much time and much effort are required. In addition, apparatus have been used to stick such sheets to prevent an air trapping rather than manual work. However, sticking by apparatus cannot always be applied depending on uses of the pressure sensitive adhesive sheet or portion and/or shape of the adherend.

0005In the meantime, resin materials such as an acrylic resin, an ABS resin, a polystyrene resin, a polycarbonate resin or the like generate gas either by heating or without heating. When a pressure sensitive adhesive sheet is stuck to the adherend made from such a resin material, the gas generated from the adherend causes a blister in the pressure sensitive adhesive sheet.

0006In order to solve the above problems, there has been proposed a pressure sensitive adhesive sheet where a plurality of independent small projections are placed in a disseminated dot state on an adhesive face of the pressure sensitive adhesive layer in Gazette of Japanese Utility Model Registration No. <patcit id="pcit0001" dnum="JP2503717B"><text>2503717</text></patcit> and Gazette of Japanese Utility Model Registration No.<patcit id="pcit0002" dnum="JP2587198B"><text> 2587198</text></patcit>. In this pressure sensitive adhesive sheet, the tip of the small projections of the pressure sensitive adhesive layer is closely contacted to the adherend and the flat base surface of the pressure sensitive adhesive layer is kept spacing from the adherend, therefore a gap leading to the outside between the flat base surface of the pressure sensitive adhesive layer and the adherend is formed. Consequently, by deflating air or gas from the gap to the outside, an air trapping or a blister can be prevented.

0007However, on the pressure sensitive adhesive sheet disclosed in the above gazettes, there have been problems that an adhesive strength is poor because only the tip of the small projections in the pressure sensitive adhesive layer is bonded to the adherend, and water, chemicals or the like can easily be infiltrated between the pressure sensitive adhesive layer and the adherend, thus lowering an adhesive strength moreover. Even though such an adhesive sheet is strongly pressed to the adherend, an adhesive strength is not strong enough due to the small projections of the pressure sensitive adhesive layer. Furthermore, in that cases, the gap leading to the outside is filled up, therefore a blister cannot be prevented, which is formed while gas is generated from the adherend.

0008<patcit id="pcit0003" dnum="US3085024A"><text>US 3,085,024</text></patcit> discloses a pressure-sensitive adhesive tape in which perforations, formed by passing a heated projection through the tape, are arranged to facilitate tearing.

0009<patcit id="pcit0004" dnum="US5810756A"><text>US 5,810,756</text></patcit> discloses a medical perforated adhesive tape formed by heated needles used to form protrusions with pierced openings.

0010<patcit id="pcit0005" dnum="US5275856A"><text>US 5,275,856</text></patcit> discloses an electrically conductive tape formed from a tape having a plurality of perforations that are filled with a plurality of electrically conductive particles.

0011<patcit id="pcit0006" dnum="JP4100235U"><text>JP 4 100 235 U1</text></patcit>, discloses a pressure sensitive adhesive sheet having through holes formed by a heated needle.

0012<patcit id="pcit0007" dnum="JP2107628A"><text>JP-A-2 107 628</text></patcit> discloses a pressure sensitive adhesive sheet having through holes formed by a cutting out process using a cutting blade.

DISCLOSURE OF THE INVENTION

0013The present invention was made in consideration with the above circumstances and has as an object to provide a method for production of a pressure sensitive adhesive sheet capable of preventing or removing an air trapping or a blister without disfiguring the pressure sensitive adhesive sheet and while securing a sufficient adhesive strength.

0014The present invention provides a method for production of pressure sensitive adhesive sheet (1), comprising the steps of: <ul id="ul0001" list-style="none" compact="compact"><li>preparing a pressure sensitive adhesive sheet comprising a base material (11), a pressure sensitive adhesive layer (12) and a process material or a removable protective sheet (3), laminated on the surface of the base material (11);</li><li>performing a hole-forming processing on the pressure sensitive adhesive sheet to form through holes (2) such that the hole diameter at the base material and the pressure sensitive adhesive layer is 0.1 to 300µm and the hole density is 30 to 50,000/100cm²;</li><li>characterised in that the hole-forming processing is a laser beam machining and is performed while the process material or removable protective sheet (3) is laminated on the surface of the base material (11); and</li><li>wherein a laser is directly radiated to the pressure sensitive adhesive layer.</li></ul>

0015According to the above aspect of the invention, pressure sensitive adhesive sheets can be produced, from which an air trapping or a blister can be prevented or removed by deflating air between the adherent and the adhesive face or gas generating from the adherent via the through holes.

0016In the above invention the hole-forming process is a laser beam machining.

0017When forming the through holes by a laser beam machining, since many of the through holes are tapered, the hole diameter of the through holes at the surface of the pressure sensitive adhesive sheet is smaller than at the back surface of the pressure sensitive adhesive sheet by performing a laser beam machining from the back surface side of the pressure sensitive adhesive sheet. Accordingly, the through holes at the surface of the pressure sensitive adhesive sheet are much less noticeable so that the appearance of the pressure sensitive adhesive sheet can be maintained in a good condition.

0018In the above invention a laser is directly radiated to the pressure sensitive adhesive layer. When a release material is laminated on the pressure sensitive adhesive layer, it is preferable that the release material laminated on the pressure sensitive adhesive layer is peeled from the pressure sensitive adhesive layer, a laser is directly radiated to the pressure sensitive adhesive layer, and then the release' material is laminated again on the pressure sensitive adhesive layer,

0019When the third layer such as a release material or the like is laminated on the pressure sensitive adhesive layer, if a laser is radiated to the pressure sensitive adhesive layer through the third layer, the dross to be formed on the third layer may enlarge the opening of the through holes in the pressure sensitive adhesive layer depending on the materials of the third layer. Therefore, the accuracy of the hole diameter or the hole density of the through holes to be formed on the pressure sensitive adhesive sheet is deteriorated. In addition, if the openings of the through holes enlarge as the above, then internal spaces of the through holes becomes large so that air in the through hole or water which entered the through hole may influence the surface of the pressure sensitive adhesive sheet in any way after the pressure sensitive adhesive sheet is stuck to the adherend.

0020According to the above invention, enlarging the opening of the through holes in the pressure sensitive adhesive layer due to the third layer is avoided, thus the through holes can be formed such that the accuracy of the hole diameter of the holes or the hole density is high and internal space is small. In addition, with interposing no third layer, the laser radiation time can be shortened or the laser output energy can be low. If the laser output energy is low, a heat has less effect on the pressure sensitive adhesive sheet. Therefore, the dross can be reduced and the through holes in a uniform shape can be formed.

0021In the above invention, the laser beam machining is performed while a process material or a removable protective sheet is laminated on the surface of the base material. Here, the process material refers to an assistant material to form any layer. For example, when forming a layer by a cast film process, a process material is used as a supporter of a resin solution for forming layer. In general, the process material is obtained by release processing on a paper or a resin film, which is peeled from the pressure sensitive adhesive sheet after the production of the pressure sensitive adhesive sheet or when the pressure sensitive adhesive sheet is used. On the other hand, the removable protective sheet refers to a protective sheet that can be peeled after a laser beam machining is performed. For example, a pressure sensitive adhesive protective sheet constituted by a base material and a removable pressure sensitive adhesive layer can be used.

0022When the through holes are formed by a laser beam machining, melt due to the heat, so-called dross, may be attached around the opening of the through holes in some cases. However, if a process material or a protective sheet is laminated on the surface of the base material, the dross is attached to the process material or the protective sheet rather than the base material. Thus, the appearance of the pressure sensitive adhesive sheet can be maintained in a better condition.

0023Note that, when the process material or the protective sheet is peeled from the base material prior to sticking the pressure sensitive adhesive sheet to the adherend, the holes formed by a laser beam machining need not to be passing through the process material or the protective sheet.

0024As described above, according to the present invention, a pressure sensitive adhesive sheet capable of preventing or removing an air trapping or a blister can be obtained without disfiguring the pressure sensitive adhesive sheet, while securing a sufficient adhesive strength.

BRIEF DESCRIPTION OF THE DRAWINGS

0025<ul id="ul0002" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> is a sectional view of a pressure sensitive adhesive sheet according to an embodiment of the present invention.</li><li><figref idref="f0001">Fig. 2</figref> is a partially enlarged sectional view of a pressure sensitive adhesive sheet according to an embodiment of the present invention.</li><li><figref idref="f0002">Fig. 3</figref> is a sectional view showing a production method of a pressure sensitive adhesive sheet not according to an embodiment of the present invention.</li><li><figref idref="f0003">Fig. 4</figref> is a sectional view showing another production method of a pressure sensitive adhesive sheet not according to an embodiment of the present invention.</li><li><figref idref="f0004">Fig. 5</figref> is a sectional view showing another production method of a pressure sensitive adhesive sheet not according to an embodiment of the present invention.</li><li><figref idref="f0005">Fig. 6</figref> is a partially enlarged sectional view of a pressure sensitive adhesive sheet according to an embodiment of the present invention.</li></ul>

BEST MODE FOR CARRYING OUT THE INVENTION

0026Embodiments of the present invention will be described as follows:

[Adhesive Sheet]

0027<figref idref="f0001">Fig. 1</figref> is a sectional view of a pressure sensitive adhesive sheet according to an embodiment of the present invention.

0028As shown in <figref idref="f0001">Fig. 1</figref>, a pressure sensitive adhesive sheet 1 according to the preferred embodiment of the present invention is prepared by laminating a base material 11, a pressure sensitive adhesive layer 12 and a release material 13. However, the release material 13 is peeled when the pressure sensitive adhesive sheet 1 is used.

0029In the pressure sensitive adhesive sheet 1, a plurality of through holes 2 are formed, which are passing through the base material 11, the pressure sensitive adhesive layer 12 and the release material 13 from the surface 1A of the pressure sensitive adhesive sheet 1 to the back surface 1B of the pressure sensitive adhesive sheet 1. When using the pressure sensitive adhesive sheet 1, air between the adherend and the adhesive face of the pressure sensitive adhesive layer 12 or gas generating from the adherend can be deflated to the outside of the surface 1A of the pressure sensitive adhesive sheet 1 via the through holes 2 so that an air trapping or a blister can be prevented or removed as described later.

0030The horizontal cross sectional shape of the through hole 2 is not particularly limited. However, the hole diameter of the through hole 2 at the base material 11 and the pressure sensitive adhesive layer 12 is 0.1 to 300 µm, and preferably 0.5 to 150 µm. If the hole diameter of the through hole 2 is less than 0.1 µm, it is difficult to deflate air or gas. If the hole diameter of the through hole 2 is more than 300 µm, the through hole 2 can be noticeable, thus the pressure sensitive adhesive sheet 1 is disfigured.

0031Note that, if the hole diameter of the through hole 2 at the surface 1A of the pressure sensitive adhesive sheet 1 is 40 µm or less, the hole itself of the through hole 2 (internal space of the through hole 2) can be invisible to the naked eye. Therefore, in case it is particularly required that the hole itself of the through hole 2 is not invisible on the appearance of the pressure sensitive adhesive sheet 1, it is preferable that the upper limit of the hole diameter of the through hole 2 at the surface 1A of the pressure sensitive adhesive sheet 1 is 40 µm. In this case, when the base material 11 is transparent in particular, since the hole diameter at the internal of the base material 11 and the pressure sensitive adhesive layer 12 as well as at the surface 1A of the pressure sensitive adhesive sheet 1 can influence the visibility of the hole, it is preferable that the upper limit of the hole diameter of the through hole 2 at the internal of the base material 11 and the pressure sensitive adhesive layer 12 is particularly 60 µm.

0032The hole diameter of the through hole 2 can be uniform in a thickness direction of the pressure sensitive adhesive sheet 1 or can be changed in a thickness direction of the pressure sensitive adhesive sheet 1. When the hole diameter of the through hole 2 is changed in a thickness direction of the pressure sensitive adhesive sheet 1, it is preferable that the hole diameter of the through hole 2 gets gradually smaller from the back surface 1B to the surface 1A of the pressure sensitive adhesive sheet 1, as shown in <figref idref="f0001">Fig. 2</figref>. Since the hole diameter of the through hole 2 is changed like this, the through hole 2 on the surface 1A of the pressure sensitive adhesive sheet is much less noticeable. Therefore, the appearance of the pressure sensitive adhesive sheet 1 can be maintained in a good condition. However, in this case, the hole diameter of the through holes 2 in the base material 11 and the pressure sensitive adhesive layer 12 must be in the above range (0.1 to 300 µm).

0033The hole density of the through hole 2 is 30 to 50,000/100 cm², and preferably 100 to 10,000/100 cm². If the hole density of the through hole 2 is less than 30/100 cm², it is difficult to deflate air or gas. If the density is more than 50,000/100 cm², the mechanical strength of the pressure sensitive adhesive sheet 1 is deteriorated.

0034Through hole 2 is formed by a laser beam machining as set forth later. According to a laser beam machining, fine through holes having good air deflation properties can be easily formed with desired hole density.

0035As far as the through holes 2 can be formed in the base material 11, the materials of the base material 11 are not particularly limited. For example, as for the materials of the base material 11, resin film, metal film, metallized resin film, a paper, a laminate thereof or the like can be used. When the base material 11 is made from resin film, the base material 11 can be opaque or transparent, but generally, if the base material 11 is opaque, the through holes 2 are more difficult to be noticeable.

0036As for resin films, there can be used, for example, films, foaming films or laminated films thereof comprising polyolefin such as polyethylene, polypropylene or the like; polyester such as polyethylene terephthalate, polybutylene terephthalate or the like; polyvinyl chloride, polystyrene, polyurethane, polycarbonate, polyamide, polyimide, poly methyl methacrylate, polybutene, polybutadiene, poly methyl pentene, ethylene-vinyl acetate copolymer, ethylene (meth) acrylic copolymer, ethylene (meth) acrylate copolymer, ABS resin, ionomer resin or the like. As for resin films, commercial films can be used, and films formed by a cast film process using a process material can also be used. As for paper, woodfree paper, glassine paper, coated paper, laminated paper or the like can be used.

0037As far as the through holes 2 can be formed in the process material using a desired hole-forming processing method, the process materials are not particularly limited. For example, various kinds of paper or resin films such as polyethylene terephthalate, polypropylene, polyethylene or the like which has been subjected to release treating using silicone type, polyester type, acrylic type, alkyd type or urethane type release agents or synthetic resins can be used. A thickness of the process material is usually about 10 to 200 µm, and preferably about 25 to 150 µm.

0038A thickness of the base material 11 is usually about 1 to 500 µm, and preferably about 3 to 300 µm. The thickness can be appropriately changed according to uses of the pressure sensitive adhesive sheet 1.

0039Kinds of the pressure sensitive adhesive for the pressure sensitive adhesive layer 12 are not particularly limited as far as the through hole 2 as described above can be formed in the pressure sensitive adhesive layer 12. The pressure sensitive adhesive can be any of acrylic type, polyester type, polyurethane type, rubber type, silicone type or the like. In addition, the pressure sensitive adhesive can be any of emulsion type, solvent type or solvent-free type, and also can be either crosslinking type or non-crosslinking type. Furthermore, the pressure sensitive adhesive can be any of strong type adhesive which has high adhesive strength, weak type adhesive which has low adhesive strength, or removable type adhesive which can repeat adhere and release.

0040A thickness of the pressure sensitive adhesive layer 12 is usually about 1 to 300 µm, and preferably about 5 to 100 µm. The thickness can be appropriately changed according to uses of the pressure sensitive adhesive sheet 1.

0041As far as the through holes 2 can be formed in the release material 13, the materials of the release material 13 are not particularly limited. For example, resin films of polyethylene terephthalate, polypropylene, polyethylene or the like or foaming films thereof or paper such as glassine paper, coated paper, laminated paper or the like which has been subjected to release treating using silicone type, fluorine type or carbamate including long-chain alkyl group type release agents can be used.

0042A thickness of the release material 13 is usually about 10 to 250 µm, and preferably about 20 to 200 µm. A thickness of a release agent in the release material 13 is usually 0.05 to 5 µm, and preferably 0.1 to 3 µm.

[Production of Adhesive Sheet (1)]

0043An example not according to the invention of method for production of the pressure sensitive adhesive sheet 1 of the above embodiment will be explained in reference to <figref idref="f0002">Figs. 3(a) to (d)</figref>.

0044In this production method, the pressure sensitive adhesive layer 12 is first formed on the release surface of the release material 13 as shown in <figref idref="f0002">Figs. 3 (a) to (b)</figref>. To form the pressure sensitive adhesive layer 12, for example, a coating agent containing a pressure sensitive adhesive which constitutes the pressure sensitive adhesive layer 12 and, if desired, a solvent is prepared. The coating agent is then applied to the release surface of the release material 13 using a coating machine such as roll coater, knife coater, roll-knife coater, air-knife coater, die coater, bar coater, gravure coater, curtain coater or the like, and dried.

0045Then, as shown in <figref idref="f0002">Fig. 3 (c)</figref>, the base material 11 is stuck with pressure onto the surface of the pressure sensitive adhesive layer 12 to obtain a laminate constituted by the base material 11, the pressure sensitive adhesive layer 12 and the release material 13. Further, as shown in <figref idref="f0002">Fig. 3(d)</figref>, the through holes 2 are formed on the obtained laminate. In this production method, the though holes 2 are formed by a laser beam machining. It is preferable to perform a laser beam machining from the side of the release material 13. When forming the through holes 2 by a laser beam machining, since the through holes 2 are tapered in many cases as shown in <figref idref="f0001">Fig. 2</figref>, the hole diameter of the through holes 2 at the side of the base material 11 is smaller than at the side of the release material 13 by performing a laser beam machining from the side of the release material 13. Accordingly, the through holes 2 at the surface of the pressure sensitive adhesive sheet 1 are much less noticeable so that the appearance of the pressure sensitive adhesive sheet 1 can be maintained in a good condition.

0046Kinds of lasers to be used for a laser beam machining are not particularly limited. As for lasers, for example, carbon dioxide (CO₂) laser, TEA-CO₂ laser, YAG laser, UV-YAG laser, excimer laser, semiconductor laser, YVO₄ laser, YLF laser or the like can be used.

0047Note that, the release material 13 is peeled from the pressure sensitive adhesive layer 12 when the pressure sensitive adhesive sheet 1 is used.

0048A removable protective sheet can be laminated on the surface of the base material 11 in any step prior to performing a laser beam machining in this production method. As for the protective sheets, for example, known pressure sensitive adhesive protective sheet constituted by a base material and a removable pressure sensitive adhesive layer or the like can be used.

0049When the through holes 2 are formed by a laser beam machining, melt due to the heat, so-called dross, may be attached around the opening of the through holes 2 in some cases. However, if the protective sheet is laminated on the surface of the base material 11, the dross is attached to the protective sheet rather than the base material 11. Thus, the appearance of the pressure sensitive adhesive sheet 1 can be maintained in a better condition. In addition, if a laser beam machining is performed from the side of the protective sheet, since the through holes 2 are formed in taper, the hole diameter of the through holes 2 at the surface of the base material 11 is smaller than when using no protective sheet.

0050The above protective sheet is peeled from the base material 11 usually after production of the pressure sensitive adhesive sheet 1 is completed or before sticking the pressure sensitive adhesive sheet 1. However, the protective sheet can be peeled after sticking the pressure sensitive adhesive sheet 1 on the adherend while the protective sheet is laminated on it. When the protective sheet is peeled after sticking the pressure sensitive adhesive sheet 1 on the adherend, the through hole 2 needs to be passing through the protective sheet as well as the pressure sensitive adhesive layer 12 and the base material 11. On the other hand, when the protective sheet is peeled prior to sticking the pressure sensitive adhesive sheet 1, the through holes 2 do not have to be necessarily passing through the protective sheet. That is, when a laser beam machining is performed from side of the release material 13, a laser can be radiated such that the holes passing through the release material 13, the pressure sensitive adhesive layer 12 and the base material 11 are formed to the middle of the protective sheet.

[Production of Adhesive Sheet (2)]

0051Another example not according to the invention of method for production of the pressure sensitive adhesive sheet 1 of the above embodiment will be explained in reference to <figref idref="f0003">Figs. 4(a) to (e)</figref>.

0052In this production method, the base material 11 is formed on the release surface of the process material 3 as shown in <figref idref="f0003">Figs. 4(a) to (b)</figref>. To form the base material 11, for example, a coating agent containing the resin which constitutes the base material 11 and, if desired, a solvent is prepared. The coating agent is then applied to the process material 3 using a coating machine such as roll coater, knife coater, roll-knife coater, air-knife coater, die coater, bar coater, gravure coater, curtain coater or the like, and dried.

0053On the other hand, as shown in <figref idref="f0003">Fig. 4(c)</figref>, the pressure sensitive adhesive layer 12 is formed on the release surface of the release material 13 using the same method as in forming the pressure sensitive adhesive layer of the production method (1) for the pressure sensitive adhesive sheet as described above.

0054Then, as shown in <figref idref="f0003">Fig. 4(d)</figref>, a laminate constituted by the process material 3 and the base material 11, and a laminate constituted by the pressure sensitive adhesive layer 12 and the release material 13 are bonded with pressure such that the base material 11 formed on the process material 3 and the pressure sensitive adhesive layer 12 formed on the release material 13 are closely contacted to obtain a laminate constituted by the process material 3, the base material 11, the pressure sensitive adhesive layer 12 and the release material 13.

0055As shown in <figref idref="f0003">Fig. 4 (e)</figref>, the through holes 2 are formed on the obtained laminate. In this production method, the through holes 2 are formed by a laser beam machining. It is preferable to perform this laser beam machining from the side of the release material 13 on the same reason as in the method (1) for production of the pressure sensitive adhesive sheet as described above. However, if a laser beam machining is performed from the side of the process material 3, since the through holes 2 are tapered, the hole diameter of the through holes 2 at the surface of the base material 11 is smaller than when the process material 3 is not used.

0056In addition, when the through holes 2 are formed by a laser beam machining, dross may be attached around the opening of the through holes 2 in some cases. However, since the process material 3 is laminated on the surface of the base material 11 in this production method, the dross is attached to the process material 3 rather than the base material 11. Thus, the appearance of the pressure sensitive adhesive sheet 1 can be maintained in a better condition.

0057Note that, the release material 13 is peeled from the pressure sensitive adhesive layer 12 when the pressure sensitive adhesive sheet 1 is used. On the other hand, the process material 3 is peeled from the base material 11 usually after production of the pressure sensitive adhesive sheet 1 is completed or before sticking the pressure sensitive adhesive sheet 1. However, the process material 3 can be peeled after sticking the pressure sensitive adhesive sheet 1 on the adherend while the process material 3 is laminated on it. When the process material 3 is peeled after sticking the pressure sensitive adhesive sheet 1 on the adherend, the through holes 2 need to be passing through the process material 3 as well as the pressure sensitive adhesive layer 12 and the base material 11. When the process material 3 is peeled prior to sticking the pressure sensitive adhesive sheet 1, the through holes 2 do not have to be necessarily passing through the process material 3. That is, when a laser beam machining is performed from the side of the release material 13, a laser can be radiated such that the holes passing through the release material 13, the pressure sensitive adhesive layer 12 and the base material 11 are formed to the middle of the process material 3.

[Production of Adhesive Sheet (3)]

0058Another example not according to the invention of method for production of the pressure sensitive adhesive sheet 1 of the above embodiment will be explained in reference to <figref idref="f0004">Figs. 5(a) to (f)</figref>.

0059In this production method, as shown in <figref idref="f0004">Figs. 5(a) to (c)</figref>, a laminate constituted by the base material 11, the pressure sensitive adhesive layer 12 and the release material 13 is produced in the same method as the production method (1) of the pressure sensitive adhesive sheet as described above.

0060As shown in <figref idref="f0004">Fig. 5(d)</figref>, the release material 13 is peeled from the pressure sensitive adhesive layer 12 and then a laser is directly radiating to the pressure sensitive adhesive layer 12 from the side of the pressure sensitive adhesive layer 12 as shown in <figref idref="f0004">Fig. 5 (e)</figref>. After that, the release material 13 is stuck again to the pressure sensitive adhesive layer 12 as shown in <figref idref="f0004">Fig. 5(f)</figref>.

0061When radiating a laser from the side of the release material 13 while the release material 13 is laminated on the pressure sensitive adhesive layer 12, as shown in <figref idref="f0005">Fig. 6(a)</figref>, the opening of the through hole 2 of the pressure sensitive adhesive layer 12 is enlarged due to the dross in some cases that is formed around the opening of the through hole 2 in the release material 13 depending on the material of the release material 13. In this case, the accuracy of the hole diameter or the hole density of the through holes 2 formed on the pressure sensitive adhesive sheet 1 is deteriorated. In addition, if the opening of the through hole 2 of the pressure sensitive adhesive layer 12 is enlarged, then internal space of the through hole 2 becomes large so that air in the through hole 2 or water which entered the through hole 2 or the like may influence the surface of the pressure sensitive adhesive sheet 1 in any way after sticking the pressure sensitive adhesive sheet 1 to the adherend. This kind of problem is likely to occur when the release material 13 is made from resin such as polyethylene terephthalate, polypropylene or the like.

0062According to this production method, once the release material 13 is peeled and a laser is directly radiated to the adhesive later 12, the opening of the through hole 2 of the pressure sensitive adhesive layer 12 is not enlarged as shown in <figref idref="f0005">Fig. 6(b)</figref>, thus resulting in high accuracy of the hole diameter or the hole density and small internal space of the through hole 2. In addition, when radiating a laser to the pressure sensitive adhesive layer 12, without interposing the release material 13, the laser radiation time can be shortened or the laser output energy can be low. If the laser output energy is low, a heat has less effect on the pressure sensitive adhesive layer 12 and the base material 11, thus dross or the like can be reduced and uniformly shaped through holes 2 can be formed.

0063Note that, in the production methods (1) to (3) above, the pressure sensitive adhesive layer 12 is formed on the release material 13 and the pressure sensitive adhesive layer 12 thus formed and the base material 11 are stuck together. However, the present invention is not limited thereto. For example, the pressure sensitive adhesive layer 12 can be formed directly on the base material 11 and the pressure sensitive adhesive layer 12 thus formed and the release material 13 can be stuck together.

[Uses of Adhesive Sheet]

0064When sticking the pressure sensitive adhesive sheet 1 on an adherend, the release material 13 is peeled from the pressure sensitive adhesive layer 12, the pressure sensitive adhesive sheet 1 is pressed onto the adherend such that an adhesive face of the exposed pressure sensitive adhesive layer 12 is closely contacted to the adherend. At this time, since air between the adherend and the adhesive face of the pressure sensitive adhesive layer 12 is deflated to the outside of the surface 1A of the pressure sensitive adhesive sheet 1 via the through hole 2 formed in the pressure sensitive adhesive sheet 1, air can hardly be caught between the adherend and the adhesive face, and an air trapping can be prevented. Even if air is caught and an air trapping is formed, by pressing again the air trapping part or the vicinity of the air trapping part (including the air trapping part), air is deflated to the outside of the surface 1A of the pressure sensitive adhesive sheet via the through hole 2 and the air trapping can be eliminated. Such an air trapping can be eliminated even after a long time since the pressure sensitive adhesive sheet 1 is stuck.

0065In addition, even when gas is generated from the adherend after sticking the pressure sensitive adhesive sheet 1 to the adherend, gas is deflated to the outside of the surface 1A of the pressure sensitive adhesive sheet 1 via the through hole 2 formed on the pressure sensitive adhesive sheet 1. Therefore a blister on the pressure sensitive adhesive sheet 1 can be prevented.

0066An air trapping or a blister can be prevented or removed from the pressure sensitive adhesive sheet 1 as described above. The through hole 2 formed on the pressure sensitive adhesive sheet 1 is extremely fine, therefore, the pressure sensitive adhesive sheet is not disfigured and the adhesive strength is not lowered despite of the presence of the through holes 2.

[Other embodiments]

0067In the pressure sensitive adhesive sheet 1 of the above embodiment, the through holes 2 are passing through the release material 13. However, the present invention is not limited thereto. For example, the through holes 2 can be passing through only the base material 11 and the pressure sensitive adhesive layer 12. In addition, the pressure sensitive adhesive sheet 1 of the above embodiment has the release material 13, but the present invention is not limited thereto. For example, the release material 13 can be absent. In these cases, the material of the release material 13 does not need to be the one in which the through holes 2 can be formed. Further, the size, shape or the like of the pressure sensitive adhesive sheet 1 of the above embodiment are not particularly limited.

0068For example, the pressure sensitive adhesive sheet 1 may be a tape shaped one (pressure sensitive adhesive tape) constituted by the base material 11 and the pressure sensitive adhesive layer 12 only, which can be wound into a roll. In this case, the pressure sensitive adhesive layer 12 is overlapped on the surface (the face on which the pressure sensitive adhesive layer 12 is not laminated) of the base material 11. Therefore, it is preferable that the surface of the base material 11 has a release property such that the pressure sensitive adhesive layer 12 overlapped on the surface of the base material 11 can be smoothly peeled from the surface of the base material 11 when the pressure sensitive adhesive tape is pulled out from the roll.

0069As the base material 11, for example, (1) resin films as mentioned above of which surface has been subjected to release treating using silicone type, fluorine type or carbamate including long-chain alkyl group type release agent, (2) materials which has a release property itself, for example, films made from polyolefin resin such as polyethylene, polypropylene or the like and (3) laminated films which are obtained by laminating the above material having a release property and a material having a low release property, for example, polyethylene terephthalate or the like can be used. Note that, in the above case of (2), it is preferable that a treatment to advance the adhesive strength with the pressure sensitive adhesive layer 12 such as corona discharge treatment, flame treatment, ultraviolet-light irradiation treatment, primer treatment, solvent treatment or the like is performed on the back surface (the face on which the pressure sensitive adhesive layer 12 is laminated) of the base material 11.

0070The above pressure sensitive adhesive tape can be produced, for example, by the following production method. <ol id="ol0001" compact="compact"><li>(1) A pressure sensitive adhesive agent is coated on the surface of the base material 11. The laminate is wound into a roll, at the same time, the pressure sensitive adhesive agent is transferred from the surface of the base material 11 to the back surface of the base material 11. Then, the laminate constituted by the base material 11 and the pressure sensitive adhesive layer 12 laminated on the back surface of the base material 11 is pulled out from the roll. A laser is radiated to the laminate from the side of the pressure sensitive adhesive layer 12 to form through holes 2. After that, the laminate is wound into a roll again.</li><li>(2) A pressure sensitive adhesive agent is coated on the back surface of the base material 11 and dried to form the pressure sensitive adhesive layer 12. Then a laser is radiated to the laminate from the side of the pressure sensitive adhesive layer 12 to form through holes 2, and the laminate is wound into a roll again.</li><li>(3) A pressure sensitive adhesive agent is coated on the release surface of the release material 3. The release material 3 and the base material 11 are wound into a roll while they are stuck together such that the pressure sensitive adhesive agent is closely contacted to the back surface of the base material 11. After that, while peeling the release material 3 from the pressure sensitive adhesive layer 12, the laminate constituted by the base material 11 and the pressure sensitive adhesive layer 12 are pulled out from the roll. A laser is radiated to the laminate from the side of the pressure sensitive adhesive layer 12 to form through holes 2. Then, the above laminate is wound into a roll without sticking the release material 3.</li></ol>

0071In the any production method as described above, since through holes 2 are formed in the laminate constituted by the base material 11 and the pressure sensitive adhesive layer 12, air is hardly caught when the laminate is wound into a roll. So that a roll which does not have air trappings is easily formed.

[EXAMPLES] (all not according to the invention)

0072The present invention will be described more specifically below using examples and the like. However, the scope of the present invention is not limited to or by these examples and the like.

[Example 1]

007325 parts by weight of ethyl acetate was added to 100 parts by weight of acrylic type pressure sensitive adhesive agent (Coponyl N-2147 manufactured by Nippon Synthetic Chemical Industry Co., Ltd., solid content: 35 weight %), and then 1 part by weight of an isocynate type crosslinking agent (Colonate L manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to them. The mixture was sufficiently agitated to obtain a coating agent of a pressure sensitive adhesive agent.

0074A release material (FPM-11 manufactured by Lintec Corporation, thickness : 175 µm) was produced by laminating a polyethylene on both faces of a woodfree paper and coating a silicone type release agent on one face. The coating agent of the pressure sensitive adhesive agent was coated with a knife coater on the release surface of the release material so as to reach a thickness of 30µm following drying, and the coating agent of the pressure sensitive adhesive agent was dried for one minute at 90°C to form a pressure sensitive adhesive layer. An opaque black base material (thickness : 100 µm) of polyvinyl chloride was stuck with pressure on the pressure sensitive adhesive layer thus formed to obtain a laminate of a 3-layers structure.

0075A UV-YAG laser was radiated to the obtained laminate from the side of the release material so that through holes having a hole diameter of 15 to 35 µm at the surface of the base material were formed with a hole density of 1,156/100 cm², thus a pressure sensitive adhesive sheet was produced.

[Example 2]

0076A pressure sensitive adhesive sheet was produced in a similar manner to the Example 1, except that the hole diameter of the through holes at the surface of the base material was 40 to 50 µm and the hole density was 4,900/100 cm².

[Example 3]

0077A laminate of a 3-layers structure was obtained in a similar manner to the Example 1, except that as for a base material, a transparent polyethylene terephthalate film (Lumirror T60 manufactured by Toray Inc., thickness: 50 µm) was used instead of polyvinyl chloride and as for a release material, a polyethylene terephthalate film coated with a silicone type release agent on one side (PET7511 manufactured by Lintec Corporation, thickness: 75 µm) was used.

0078An Excimer laser was radiated to the obtained laminate from the side of the release material so that through holes having a hole diameter of 0.5 to 10 µm at the surface of the base material and a hole diameter of 20 to 30 µm at the adhesive face (the hole diameter at the adhesive face is the maximum diameter in the base material and the pressure sensitive adhesive layer) were formed with a hole density of 10,000/100 cm², thus a pressure sensitive adhesive sheet was produced.

[Example 4]

0079A pressure sensitive adhesive sheet was produced in a similar manner to the Example 1, except that a laser was radiated from the side of the base material and the hole diameter of the through holes at the surface of the base material was about 60 µm.

[Example 5]

0080A pressure sensitive adhesive sheet was produced in a similar manner to the Example 1, except that a laser was radiated from the side of a base material using a CO₂ laser for a laser beam machining and the hole diameter of the through holes at the surface of the base material was about 100 µm.

[Example 6]

0081A pressure sensitive adhesive sheet was produced in a similar manner to the Example 1, except that the hole diameter of the through holes at the surface of the base material was 140 to 150 µm and the hole density was 100/100 cm².

[Example 7]

0082A pressure sensitive adhesive sheet was produced in a similar manner to the Example 1, except that a CO₂ laser was used for a laser beam machining, the laser was radiated from the side of the base material, the hole diameter of the through holes at the surface of the base material was about 250 µm and the hole density was 49/100 cm².

[Example 8]

0083A pressure sensitive adhesive sheet was produced in a similar manner to the Example 1, except that a release material was peeled, then a laser was radiated from the side of the adhesive face, and the hole diameter of the through holes at the surface of the base material was about 50 µm.

[Example 9]

0084A laminate of a 3-layers structure was obtained in a similar manner to the Example 1, except that as for a base material, a transparent polyethylene terephthalate film (Lumirror T60 manufactured by Toray Inc., thickness: 50 µm) was used instead of polyvinyl chloride.

0085A CO₂ laser was radiated to the obtained laminate from the side of the base material to form through holes having a hole diameter of about 70 µm at the surface of the base material and a hole diameter of about 80 µm at the adhesive face (the hole diameter at the adhesive face is the maximum diameter in the base material and the pressure sensitive adhesive layer) with a hole density of 1,156/100 cm², thus a pressure sensitive adhesive sheet was produced.

[Example 10]

0086100 parts by weight of a vinyl chloride resin, 2.5 parts by weight of an ultraviolet light absorber (benzotriazole type), 25 parts by weight of a polyester type plasticizer (Adekasizer PN260 manufactured by Asahi Denka Co., Ltd.), 10 parts by weight of a phthalate type plasticizer (DOP manufactured by Chisso Corporation), 20 parts by weight of a colorant (VTSK9311 black manufactured by Dainichiseika Color &amp; Chemicals Mfg. Co., Ltd.), 3 parts by weight of a heat stabilizer (Ba/Zn type), 25 parts by weight of a solvent (butylcellosolve) and 25 parts by weight of a solvent (Supersol #1500 manufactured by Godo Solvents Co.) were mixed to obtain a coating agent of a base material.

0087As a process material, a polyethylene terephthalate film having one face release treated (U4Z-50 manufactured by Teijin DuPont Films Japan Limited, thickness: 50 µm) was prepared. The coating agent of the base material was coated on the release surface of the process material with a knife coater, so as to reach a thickness of 100µm following drying, and the coating agent of the base material was dried for one minute at 140 °C and further for two minutes at 190°C to form an opaque black base material.

0088On the other hand, a pressure sensitive adhesive layer was formed on the release material in a similar manner to the Example 1 and a laminate of a 4-layers structure was obtained by bonding with pressure the pressure sensitive adhesive layer and the base material formed on the above process material to be closely contacted together.

0089A CO₂ laser was radiated to the obtained laminate from the side of the process material to form through holes having a hole diameter of about 65 µm at the surface of the base material with a hole density of 1,156/100 cm², thus a pressure sensitive adhesive sheet was produced.

[Example 11]

0090A pressure sensitive adhesive sheet was produced in a similar manner to the Example 10, except that a UV-YAG laser was used for a laser beam machining, the laser was radiated from the side of the release material, and the hole diameter of the through holes at the surface of the base material was 20 to 40 µm.

[Example 12]

0091A laminate of a 3-layers structure was produced in a similar manner to the Example 1. Then, a CO₂ laser was radiated to the laminate from the side of the release material to form through holes having a hole diameter of 40 to 50 µm at the surface of the base material and a hole diameter of 120 to 150 µm at the adhesive face with a hole density of 2,500/100 cm² to obtain a pressure sensitive adhesive sheet.

[Example 13]

0092A laminate of a 3-layers structure was produced in a similar manner to the Example 1. Then, the release material was peeled from the pressure sensitive adhesive layer, and a CO₂ laser was radiated to the laminate from the side of the pressure sensitive adhesive layer to form through holes having a hole diameter of 40 µm at the surface of the base material and a hole diameter of about 80 µm at the adhesive face with a hole density of 2,500/100 cm². And the release material was stuck with pressure to the pressure sensitive adhesive layer again to obtain a pressure sensitive adhesive sheet.

[Example 14]

0093A laminate of a 3-layers structure was produced in a similar manner to the Example 1. Then, a pressure sensitive adhesive protective sheet constituted by a base material and a removable pressure sensitive adhesive layer (HT25SCBA manufactured by Panac Co., Ltd., thickness: 28 µm) was stuck to the surface of the base material of the laminate.

0094The release material was peeled from the pressure sensitive adhesive layer of the laminate, then a CO₂ laser was radiated to the laminate from the side of the pressure sensitive adhesive layer to form through holes having a hole diameter of 35 µm at the surface of the base material with a hole density of 2,500/100 cm². And the release material was stuck with pressure to the pressure sensitive adhesive layer again and the pressure sensitive adhesive protective sheet was peeled from the base material, thus a pressure sensitive adhesive sheet was produced.

[Example 15]

0095As a base material, a transparent polyethylene terephthalate film on which one face was release treated with a silicone type release agent (Cerapeel BK(T) manufactured by Toyo Metallizing Co., Ltd., thickness: 38 µm) was prepared. The coating agent of the pressure sensitive adhesive agent obtained in the Example 1 was coated with a knife coater on the release surface of the base material, so as to reach a thickness of 30µm following drying, and the coating agent of the pressure sensitive adhesive agent was dried for one minute at 90 °C. Thus a laminate tape (A) of a 2-layers structure constituted by the base material and the pressure sensitive adhesive layer laminated on the release surface of the base material was obtained.

0096Next, the above laminate tape (A) was wound into a roll, at the same time, the pressure sensitive adhesive agent was transferred from the release surface of the base material to the non-release surface of the base material to obtain a laminate tape (B) of a 2-layers structure constituted by the base material and the pressure sensitive adhesive layer laminated on the non-release surface of the base material.

0097The obtained laminate tape (B) was pulled out from the roll, and a laser was radiated to the laminate tape (B) from the side of the pressure sensitive adhesive layer to form through holes having a hole diameter of about 50 µm at the surface of the base material and a hole diameter of about 95 µm at the adhesive face (the hole diameter at the adhesive face is the maximum diameter) with a hole density of 2,500/100 cm².

0098Then the laminate tape (B) in which through holes were formed was wound into a roll again, thus a pressure sensitive adhesive tape (pressure sensitive adhesive sheet) was produced.

[Example 16]

0099A laminate of a 3-layers structure was produced in a similar manner to the Example 9. Then, the release material was peeled from the pressure sensitive adhesive layer, and a CO₂ laser was radiated to the laminate from the side of the pressure sensitive adhesive layer to form through holes having a hole diameter of about 35 µm at the surface of the base material and a hole diameter of about 85 µm at the adhesive face (the hole diameter at the adhesive face is the maximum diameter) with a hole density of 2,500/100 cm². And the release material was stuck with pressure to the pressure sensitive adhesive layer again to obtain a pressure sensitive adhesive sheet.

[Comparative Example 1]

0100A laminate of a 3-layers structure was produced in a similar manner to the Example 1. Without forming any through holes, a pressure sensitive adhesive sheet was produced.

[Comparative Example 2]

0101A pressure sensitive adhesive sheet was produced in a similar manner to the Example 1, except that the hole density of the through holes was 4/100 cm².

[Comparative Example 3]

0102A pressure sensitive adhesive sheet was produced in a similar manner to the Example 1, except that a laser was radiated from the side of the base material and the hole diameter of the through holes was about 500 µm.

[Comparative Example 4]

0103A pressure sensitive adhesive sheet was produced in a similar manner to the Example 2, except that as for a base material, a transparent polyethylene terephthalate film (Lumirror T60 manufactured by Toray Inc., thickness: 50 µm) was used instead of polyvinyl chloride, the hole diameter of the through holes at the adhesive face was about 130 to 140 µm and the hole density of the through holes was 102,400/100 cm².

[Experiment Example]

0104A test of eliminating air trapping and a test of tensile strength were performed on the obtained pressure sensitive adhesive sheet in Examples 1 to 16 and Comparative Examples 1 to 4 as follows. Moreover, it was visually judged whether the surfaces of the pressure sensitive adhesive sheets were disfigured or not because of existence of through holes, and an examination of hole visibility was performed as follows.

0105Test of eliminating air trapping: The pressure sensitive adhesive sheet cut into 50 mm x 50 mm was stuck to a melamine coated plate such that an air trapping in a circular shape having a hole diameter of 15 mm was formed, then the pressure sensitive adhesive sheet was pressed with a squeegee. As a result, o is indicated when the air trapping was eliminated, Δ is indicated when the air trapping was reduced, and × is indicated when the air trapping remained.

0106Test of tensile strength: A pressure sensitive adhesive sheet was cut into 10 mm in width and 150 mm in length, and the release material was peeled. The pressure sensitive adhesive sheet (tape) was placed to a tensile strength tester (Tensilon manufactured by Orientec Co., Ltd.) in a clamping distance of 100 mm and was applied a tensile strength of 200 mm/min. o is indicated when the pressure sensitive adhesive sheet was not ruptured within 10 seconds, and × is indicated when the pressure sensitive adhesive sheet was ruptured within 10 seconds.

0107Examination of hole visibility: A pressure sensitive adhesive sheet (if a release material was laminated, a pressure sensitive adhesive sheet from which the release material was peeled) was stuck to a white melamine coated plate. It was examined whether the hole itself of the through hole (internal space of the through hole) was visible or not to the naked eye at the surface of the pressure sensitive adhesive sheet depend on the hole diameter under room fluorescent lighting. Note that, the distance from the eyes to the pressure sensitive adhesive sheet was about 30cm, and the angle of vision was variously changed. o is indicated when the internal spaces of the through holes were invisible, Δ is indicated when the internal spaces of the through holes were partly invisible and partly visible, and × is indicated when the internal spaces of the through holes were visible.

0108The results of each experiment are shown in Table 1. <tables id="tabl0001" num="0001"><table frame="all"><title>[Table 1]</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="39mm" /><colspec colnum="2" colname="col2" colwidth="37mm" /><colspec colnum="3" colname="col3" colwidth="27mm" /><colspec colnum="4" colname="col4" colwidth="23mm" /><colspec colnum="5" colname="col5" colwidth="23mm" /><thead><row><entry valign="top" /><entry align="center" valign="top">Eliminating air trapping</entry><entry align="center" valign="top">Tensile strength</entry><entry align="center" valign="top">Appearance</entry><entry align="center" valign="top">Hole visibility</entry></row></thead><tbody><row><entry>Example 1</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry></row><row><entry>Example 2</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">Δ</entry></row><row><entry>Example 3</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry></row><row><entry>Example 4</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">×</entry></row><row><entry>Example 5</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">×</entry></row><row><entry>Example 6</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">×</entry></row><row><entry>Example 7</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">×</entry></row><row><entry>Example 8</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">×</entry></row><row><entry>Example 9</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">×</entry></row><row><entry>Example 10</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">×</entry></row><row><entry>Example 11</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry></row><row><entry valign="middle">Example 12</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">Δ</entry></row><row><entry valign="middle">Example 13</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">Δ</entry></row><row><entry valign="middle">Example 14</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry></row><row><entry valign="middle">Example 15</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">×</entry></row><row><entry valign="middle">Example 16</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">Δ</entry></row><row><entry valign="middle">Comparative Example 1</entry><entry align="center" valign="middle">×</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">-</entry></row><row><entry valign="middle">Comparative Example 2</entry><entry align="center" valign="middle">×∼Δ</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry></row><row><entry valign="middle">Comparative Example 3</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">×</entry><entry align="center" valign="middle">×</entry></row><row><entry valign="middle">Comparative Example 4</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">×</entry><entry align="center" valign="middle">o</entry><entry align="center" valign="middle">Δ∼×</entry></row></tbody></tgroup></table></tables>

0109It is clear that the pressure sensitive adhesive sheet obtained in Examples 1 to 16 can easily eliminate an air trapping and has a sufficient strength and its appearance is in a good condition from Table 1. Moreover, the hole itself of the through hole is invisible at the surface of the pressure sensitive adhesive sheet obtained in Examples 1, 3, 11 and 14 in particular.

INDUSTRIAL APPLICABILITY

0110A pressure sensitive adhesive sheet obtainable according to the present invention and a pressure sensitive adhesive sheet produced by the production method of the present invention can be preferably used when an air trapping or a blister is likely to be formed in general, for example, when the area of a pressure sensitive adhesive sheet is large, when gas is generated from the adherend or the like.