JP4511320B2 - Single-sided adhesive sheet and method for producing the same - Google Patents

Description

  The present invention relates to a single-sided adhesive sheet having adhesiveness (so-called tackiness) only on one side, and a method for producing the same.

  Conventionally, a heat conductive sheet formed by filling a base material made of rubber or resin with a heat conductive filler, an electromagnetic wave shield sheet formed by filling a similar base material with a conductive filler, and the like are known. These sheets may be used by being attached to an electronic component such as a CPU or a housing (hereinafter referred to as an electronic component) containing the electronic component.

  Sheets that are not sticky at all are attached to electronic parts using double-sided adhesive tape, etc., but in this case, it is necessary to attach double-sided adhesive tape, so workability of attaching to electronic parts etc. Is bad. Moreover, especially in a heat conductive sheet, a double-sided adhesive tape may act as a thermal resistance. On the other hand, a sheet having adhesiveness on the entire surface can be directly attached to an electronic component or the like, but the workability is still poor because it adheres to an operator's hand when attaching. In addition, such a sheet is difficult to be reattached after being attached once, and requires skill in the work.

  Therefore, in this type of sheet, it is desired that one surface has a so-called single-sided adhesiveness with a lower adhesive strength than the other surface. Such a single-sided adhesive sheet can be easily peeled off from the one surface side even when the other surface is attached to an electronic component or the like, so that the workability in attaching and detaching the sheet is improved. However, in order to manufacture such a sheet having single-sided adhesiveness, it is necessary to perform another process after the sheet is formed.

Accordingly, the applicant of the present application has proposed that a large amount of a curing retarder is kneaded into a silicone rubber together with a heat conductive filler and formed into a sheet shape, and then the sheet is cured with one side facing downward. By carrying out like this, a sheet | seat is shape | molded in the state which the heat conductive filler settled on the said one surface side, and the adhesive force of the said one surface falls compared with the opposite surface. Therefore, the sheet having the single-sided adhesive property as described above can be manufactured very easily (see, for example, Patent Document 1).
JP 2003-183500 A

  However, in this case, when a large amount of filler is filled, the filler is distributed also on the opposite side, and good single-sided adhesiveness cannot be obtained. Therefore, the present invention is a single-sided adhesive sheet in which a base material made of rubber or resin is filled with a filler, one side of which has a lower adhesive strength than the other side, and is easy to manufacture and is filled with a filler. The present invention was made for the purpose of providing a single-sided adhesive sheet that can provide good single-sided adhesiveness even when filled in a large amount, and a method for producing the same.

The present invention made to achieve the above object is a single-sided adhesive sheet in which a base material made of rubber or resin is filled with a filler, and one surface has a lower adhesive strength than the other surface, and has a thickness. Over the entire direction, a large particle size filler having a large specific gravity and a small particle size filler having a specific gravity and a particle size smaller than that of the large particle size filler are distributed . on the side, a filler of the small particle size is characterized in that it is uniformly distributed respectively to the other side.

  In the present invention configured as described above, a filler having a large particle size is distributed on one side of the sheet, and a filler having a small particle size is distributed unevenly on the other surface of the sheet. Since the filler having a large particle size has a higher effect of inhibiting the adhesiveness of the substrate than the filler having a small particle size, in the present invention, even if at least one filler is distributed over the entire substrate, the above-mentioned The adhesive strength of one surface can be made lower than the adhesive strength of the other surface. Also, since the filler with a large particle size has a large specific gravity and the filler with a small particle size has a small specific gravity, by causing precipitation or the like in an uncured base material, the fillers are unevenly distributed as described above. It is also easy. Therefore, the single-sided pressure-sensitive adhesive sheet of the present invention is easy to produce, and good single-sided adhesiveness can be obtained even when a large amount of filler is filled.

  In addition, even when the specific gravity of the large particle size filler is small and the specific gravity of the small particle size filler is large, it is possible to cause uneven distribution of the filler by precipitation or the like, but in this case, depending on the filling amount of the filler There is a possibility that the filler having a large particle size does not reach the vicinity of the surface of the sheet. In this case, both sides of the sheet have adhesiveness, and good single-sided adhesiveness cannot be obtained. On the other hand, in the present invention, the specific gravity of the large particle size filler is large and the specific gravity of the small particle size filler is small. In the vicinity of the surface, good single-sided adhesiveness is obtained.

  Further, in the present invention, when the particle size of the large particle size filler is not less than 5 times the particle size of the small particle size filler, the difference in adhesiveness between the one surface and the other surface is remarkable. Thus, better single-sided adhesiveness can be obtained.

  The single-sided pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as the large particle size filler having a large specific gravity and the small particle size filler having a small specific gravity are distributed as described above. However, after the above fillers are kneaded into the uncured base material and formed into a sheet shape, the base material is cured with the one side facing downward. Thus, the manufacture becomes easier. That is, when producing a single-sided adhesive sheet in this way, while the substrate is cured with one side facing downward, the large-diameter filler is lowered by the specific gravity difference (that is, the one side (Surface side) is unevenly distributed, and the filler having a small particle size is unevenly distributed upward (that is, the other surface side). Therefore, in this case, the production can be further facilitated and the production cost of the single-sided adhesive sheet can be further reduced.

  Furthermore, in this case, if the specific gravity difference between the small particle size filler and the large particle size filler is 0.5 or more, the uneven distribution of filler due to the specific gravity difference becomes more remarkable, and better single-sided adhesion Sex is obtained.

  Moreover, as a base material which comprises the single-sided adhesive sheet of this invention, various rubber | gum or resin can be used if it has a certain amount of adhesiveness, The said base material is an acrylic elastomer. In this case, the following additional effects are produced.

  Acrylic elastomers have advantages such as higher tear strength, less elongation after molding, and better shape stability than silicone rubber. For this reason, when an acrylic elastomer is used as the base material, the so-called repair property is improved such that the pasted one can be peeled off and pasted again.

  As each filler, various fillers such as a heat conductive filler, a heat insulating filler, a conductive filler, an insulating filler, a magnetic filler, a vibration damping filler, and an insect repellent filler can be used. Further, the shape is not limited to particles and powders, and fibrous fillers such as carbon fibers and structures such as microcapsules containing air can also be used as fillers.

  However, when each of the above fillers is a heat conductive filler, and the thermal conductivity of the small particle size filler is superior to the thermal conductivity of the large particle size filler, the following additional effects Occurs.

  In this case, the thermal conductivity in the vicinity of the adhesive side surface (the other surface) of the single-sided adhesive sheet is extremely excellent, and the thermal conductivity in the vicinity of the one surface is improved by the large-diameter thermal conductive filler. But not as much as the other side. For this reason, if the single-sided adhesive sheet configured in this way is attached to an electronic component or the like, the heat generated by the electronic component or the like can be quickly absorbed through the other surface, and the absorbed heat Can be dissipated relatively slowly through the one surface.

  Such a single-sided pressure-sensitive adhesive sheet has a very remarkable effect when applied to a device such as a cellular phone that is held and used by a person. That is, if the single-sided adhesive sheet has a good thermal conductivity as a whole, the heat generated by the electronic component or the like is immediately transmitted to the part that is touched by the hand, and the part becomes hot. For this reason, there is a possibility that the user may feel uncomfortable, but in the above case, the heat is gently transmitted from one surface to the user so that there is little discomfort.

  Moreover, when the said large particle size filler is an electroconductive filler and the said small particle size filler is an insulating filler, the surface (the said other surface) which has adhesiveness becomes insulation. For this reason, even if this single-sided adhesive sheet is directly affixed to the surface of an electronic component without providing an insulating layer, a conductive filler is disposed at a position insulated from the electronic component, and enters and exits the electronic component. Electromagnetic waves can be shielded.

  On the other hand, the method for producing a single-sided pressure-sensitive adhesive sheet of the present invention comprises at least two kinds of a non-cured base material made of rubber or resin and a small particle size filler having a small specific gravity and a large particle size filler having a large specific gravity. After the filler is kneaded and formed into a sheet shape, the substrate is cured with one surface facing downward.

  When producing a single-sided pressure-sensitive adhesive sheet by such a production method, due to the difference in specific gravity between the large particle size filler and the small particle size filler while the substrate is cured with one side facing downward. The large particle size fillers are distributed downward and the small particle size fillers are distributed upward. Therefore, according to the manufacturing method of this invention, the single-sided adhesive sheet of said each invention can be manufactured easily.

  Next, an embodiment of the present invention will be described. In this Embodiment, the single-sided adhesive sheet was manufactured with the following manufacturing methods. First, the acrylic resin was filled with the heat conductive filler by mixing the uncured acrylic resin (corresponding to the base material) shown in Table 1, a heat conductive filler with a small particle size, and a heat conductive filler with a large particle size. .

  As a method for mixing the acrylic resin and each heat conductive filler, various methods such as extrusion, two rolls, Banbury mixer and the like can be applied in addition to a method of kneading using a machine such as a vacuum defoaming mixer. Of these, kneading using a mixer is desirable in terms of improving workability.

  Subsequently, the acrylic resin kneaded with the heat conductive filler was formed into a sheet shape. As this forming method, various methods such as a method of forming using a machine such as a coater, calendar roll, extrusion, press, etc. can be applied. In this embodiment, a roll is used as follows. Molded by a molding machine.

  FIG. 2 is an explanatory diagram schematically showing the configuration of this type of molding machine 51. As shown in FIG. 2, in this molding machine 51, the PET film 91 wound and held above the apparatus is conveyed through rolls 53 and 55, and the PET film 93 wound and held below the apparatus is rolled. It is conveyed via 57,59. The roll 55 and the roll 59 are arranged to face each other with a gap corresponding to the thickness of the single-sided adhesive sheet, and on one side of the PET film 93 conveyed between them from a material injection port 63 provided in the material tank 61. An adhesive sheet material 95 (a mixture of the acrylic resin and each heat conductive filler) is supplied.

  Then, the material 95 is formed into a sheet by being sandwiched between the rolls 55 and 59 via the PET films 91 and 93. Subsequently, the material 95 includes a first zone 71 for drying the material, a second zone 73 for vulcanization, a third zone 75 for vulcanization, and a fourth zone 77 for vulcanization. It is conveyed through. During this time, the material 95 is conveyed substantially horizontally with one surface (the surface on which the PET film 93 is stuck) facing downward.

  In the present embodiment, the path length from passing through the rolls 55 and 59 to vulcanization is appropriately set, and during that time, one surface of the material 95 is directed downward. The heat conductive filler precipitates as follows before it is cured by vulcanization. That is, a large particle size filler having a large specific gravity is precipitated on the one surface side, and a small particle size filler having a small specific gravity is deposited thereon.

  As a result, as shown in FIG. 1, the obtained single-sided pressure-sensitive adhesive sheet 1 contains the filler 5 having a small particle diameter in the acrylic resin 3 as a base material on the other side (the upper side in FIG. 1). ) Sidely distributed, and the filler 7 having a large particle size is distributed to the one surface (the lower surface in FIG. 1) side. Then, since the large-diameter filler 7 has a higher effect of inhibiting the adhesiveness of the substrate than the small-diameter filler 5, the one surface has a lower adhesive force than the other surface, Single-sided adhesiveness (so-called single-sided tackiness) is imparted to the adhesive sheet 1.

  Thus, when the single-sided adhesive sheet 1 has a single-sided tack property, the workability | operativity in the attachment or detachment operation | work of the single-sided adhesive sheet 1 can be improved as follows. First, when the single-sided adhesive sheet 1 is attached to an electronic component or the like, the adhesiveness can be applied without using a double-sided adhesive tape or the like, and the adhesiveness can be applied to one side (the other side). Therefore, the single-sided adhesive sheet 1 can be prevented from sticking to the operator's hand. Therefore, the workability of such a pasting operation is improved. Moreover, when peeling the single-sided adhesive sheet 1, it can be easily peeled off from the one surface side. Furthermore, the acrylic resin has higher tear strength, less elongation after molding, and better shape stability than silicone rubber and the like. For this reason, the single-sided adhesive sheet 1 is excellent in so-called repair property that it can be peeled off and pasted once.

  Also, when the one side adhesive sheet 1 is disposed between the electronic component or the like and the heat sink by attaching the one surface to the electronic component or the like or the heat sink, and then the electronic component or the like is peeled off from the heat sink. The single-sided adhesive sheet 1 can be surely adhered to a desired side of the electronic component or the heat sink. Furthermore, although PET films 91 and 93 are adhered to both sides of the single-sided adhesive sheet 1, it can always be peeled off from the PET film 93 during use.

  Furthermore, in the single-sided adhesive sheet 1, any of the fillers 5 and 7 as thermoelectric fillers is distributed over the entire thickness direction, and any of the fillers 5 and 7 has good thermal conductivity. Therefore, the single-sided adhesive sheet 1 as a whole has extremely good thermal conductivity. In the present embodiment, the single-sided adhesive sheet 1 having such excellent thermal conductivity and single-sided adhesiveness could be manufactured by a simple manufacturing process as described above.

  In the above embodiment, the fillers 5 and 7 having substantially the same good thermal conductivity were used. However, as shown in the following Table 2, a small particle size is used as the large particle size filler 7. When using a material having a thermal conductivity lower than that of the filler 5, the following effects are produced.

  In this case, the thermal conductivity in the vicinity of the adhesive side surface (the other surface) of the single-sided adhesive sheet 1 is extremely excellent, and the thermal conductivity in the vicinity of the one surface is improved to some extent by the filler 7. Not as much as the other side of the thing. For this reason, if the single-sided adhesive sheet 1 configured in this way is attached to an electronic component or the like, the heat generated by the electronic component or the like can be quickly absorbed through the other surface and absorbed. Heat can be radiated relatively slowly through the one surface.

  Such a single-sided adhesive sheet 1 has a very remarkable effect when applied to a device such as a mobile phone, a PDA, etc. that a person uses by hand. That is, if the single-sided adhesive sheet 1 has a good thermal conductivity as a whole, the heat generated by the electronic components and the like is immediately transmitted to the part that is touched by the hand, and the part becomes hot. For this reason, there is a possibility that the user may feel uncomfortable, but in the above case, the heat is gently transmitted from one surface to the user so that there is little discomfort.

  As the fillers 5 and 7, various fillers such as a heat insulating filler, a conductive filler, an insulating filler, a magnetic filler, a vibration damping filler, and a vibration damping filler can be used in addition to the heat conductive filler. Further, the shape is not limited to particles and powders, and fibrous fillers such as carbon fibers and structures such as microcapsules containing air can also be used as fillers.

  As shown in Table 3, when the filler 7 having a large particle size is a conductive filler and the filler 5 having a small particle size is an insulating filler, the surface having the stickiness (the other surface) is It becomes insulating. Therefore, in the single-sided adhesive sheet 1 manufactured in this way, the following effects are produced.

  When the other surface of the single-sided adhesive sheet 1 manufactured in this way is attached to an electronic component or the like, the single-sided adhesive sheet 1 is conductive even if it is attached directly to the surface of the electronic component without providing an insulating layer. The filler 7 is not in direct contact with the electronic component. For this reason, the layer of the conductive filler 7 can be disposed at a position insulated from the electronic component, and electromagnetic waves entering and exiting the electronic component can be well shielded.

  Furthermore, the present invention is not limited to the above embodiments, and can be implemented in various forms without departing from the gist of the present invention. For example, as the base material constituting the single-sided adhesive sheet of the present invention, various rubbers or resins can be used as long as they have a certain degree of adhesiveness. Moreover, you may shape | mold the single-sided adhesive sheet of this invention by methods, such as a press.

It is the schematic showing the structure of the single-sided adhesive sheet to which this invention was applied. It is the schematic showing the structure of the molding machine using a roll.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Single-sided adhesive sheet 3 ... Acrylic resin 5 ... Small particle size filler 7 ... Large particle size filler 51 ... Molding machine 53, 55, 57, 59 ... Roll 91, 93 ... PET film 95 ... Material

Claims (8)

Filler is filled in a base material made of rubber or resin, and one side is a single-sided adhesive sheet having a lower adhesive strength than the other side,
Over the entire thickness direction, a large particle size filler having a large specific gravity and a small particle size filler having a specific gravity and a particle size smaller than the large particle size filler are distributed,
Single-sided adhesive sheet, wherein the filler of the large diameter on one side of the filler of the small particle diameter is uniformly distributed respectively to the other side.
The single-sided pressure-sensitive adhesive sheet according to claim 1, wherein the particle size of the large particle size filler is at least 5 times the particle size of the small particle size filler. The said base material is hardened | cured in the state which orient | assigned one surface to the downward direction, after kneading each said filler to the said uncured said base material and shape | molding in the sheet form, The said base material is characterized by the above-mentioned. Single-sided adhesive sheet. The single-sided adhesive sheet according to claim 3, wherein the specific gravity difference between the small particle size filler and the large particle size filler is 0.5 or more. The single-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the substrate is an acrylic elastomer. Each of the above fillers is a heat conductive filler, and the thermal conductivity of the small particle size filler is superior to the thermal conductivity of the large particle size filler. The single-sided adhesive sheet according to any one of the above. The single-sided adhesive sheet according to any one of claims 1 to 6, wherein the large particle size filler is a conductive filler, and the small particle size filler is an insulating filler. An uncured base material made of rubber or resin is kneaded with at least two kinds of fillers consisting of a filler with a small particle size with a small specific gravity and a filler with a large particle size with a large specific gravity. A method for producing a single-sided pressure-sensitive adhesive sheet, wherein the substrate is cured with the surface facing downward.

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