JP5394661B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive sheet having release sheets attached to both sides of a pressure-sensitive adhesive layer.

  Conventionally, a double-sided pressure-sensitive adhesive sheet in which pressure-sensitive adhesive layers are provided on both surfaces of a core material has been used to bond two members. However, when high transparency is required or when the pressure-sensitive adhesive layer is thin, a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer without a core material is sandwiched between two release sheets is used.

  However, in the pressure-sensitive adhesive sheet having no core material in the pressure-sensitive adhesive layer, when the one release sheet is peeled off, the pressure-sensitive adhesive layer may float or peel off from the other release sheet due to the absence of the core material. Due to such a peeling failure, a defect occurs in the pressure-sensitive adhesive layer, or a minute bubble is formed between the pressure-sensitive adhesive layer and the adherend (adhesion interface) when bonded to the adherend. Occurs.

In order to solve such a problem, techniques such as increasing the difference in peel force between two release sheets (a heavy release sheet having a large peel force and a light release sheet having a small peel force) have been proposed ( Patent Documents 1 to 5).
JP 7-41736 A JP-A-11-209710 JP 11-353709 A JP 2000-90495 A JP 2003-201452 A

  However, merely increasing the peel force difference between the two release sheets may not be sufficient to eliminate the above problems. Also, when increasing the peel force difference between both release sheets, if the release force of the heavy release sheet is increased, the light release sheet is peeled off and the adhesive layer is applied to the adherend, and then the heavy release sheet is peeled off. In addition, the heavy release sheet may not be removed cleanly from the adherend, or the adherend may be damaged. On the other hand, when the release force of the light release sheet was made smaller, there were problems such as the light release sheet being peeled off from the adhesive layer before use. Thus, in order to increase the difference in peel force between the two release sheets, the setting of the peel force is limited, which is inconvenient for practical use.

  The present invention has been made in view of such a situation, and in a pressure-sensitive adhesive sheet without a core material in the pressure-sensitive adhesive layer, defects in the pressure-sensitive adhesive layer due to defective peeling of the release sheet and bubbles at the adhesive interface are generated. A pressure-sensitive adhesive sheet excellent in workability is provided.

  In order to achieve the above object, the present invention comprises a first release sheet, a second release sheet, and an adhesive layer sandwiched between the first release sheet and the second release sheet. In the pressure-sensitive adhesive sheet provided, the pressure-sensitive adhesive at the end of the pressure-sensitive adhesive layer covers the end surface of the first release sheet to form a cover, and the distance of the cover in the thickness direction of the pressure-sensitive adhesive sheet Provides a pressure-sensitive adhesive sheet characterized by being 0.01 to 5 μm (Invention 1).

  In this specification, “sheet” includes the concept of film, and “film” includes the concept of sheet.

  According to the above invention (Invention 1), since the covering portion adheres to the end face of the first release sheet with a predetermined force, the first release sheet and the pressure-sensitive adhesive layer are bonded to each other by the adhesive force of the covering portion. . Therefore, when the second release sheet is peeled off from the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer bonded to the first release sheet is not peeled off from the first release sheet, and the second release sheet can be peeled off without any problem. Thereby, generation | occurrence | production of the bubble of the defect of the adhesive layer resulting from the peeling defect of a 2nd peeling sheet and the adhesion interface of an adhesive layer and a to-be-adhered body is prevented.

  In the said invention (invention 1), it is preferable that the difference which pulled the peeling force of the said 2nd peeling sheet from the peeling force of the said 1st peeling sheet is 0-100 mN / 25mm (invention 2).

  In the above invention (Invention 1), the peel force of the first release sheet and the peel force of the second release sheet may be the same (Invention 3).

  In the pressure-sensitive adhesive sheet of the present invention, since the peeling failure of the release sheet is prevented, the workability is excellent, and defects in the pressure-sensitive adhesive layer due to the peeling failure of the release sheet and bubbles at the adhesive interface are not generated. Such an effect is particularly effective in a pressure-sensitive adhesive sheet in which there is no difference in peeling force between both release sheets.

Hereinafter, embodiments of the present invention will be described.
[Adhesive sheet]
FIG. 1 is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention.

  As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to this embodiment is sandwiched between a first release sheet 2, a second release sheet 3, and the first release sheet 2 and the second release sheet 3. The pressure-sensitive adhesive layer 4 is formed.

  As the first release sheet 2 and the second release sheet 3, conventionally known ones can be used. For example, the first release sheet 2 and the second release sheet 3 are peeled off from a resin film made of a resin such as polyester such as polyethylene terephthalate; polyolefin such as polypropylene or polyethylene. A material coated with a release agent (release treatment) can be used, such as paper coated with a release agent (peeling treatment), glassine paper, clay coated paper, laminated paper (mainly polyethylene laminated paper). Moreover, if the resin film itself has peelability, such as a resin film made of a polyolefin resin or the like, the resin film that has not been subjected to the peeling treatment can be used.

  When transparency is required for the pressure-sensitive adhesive sheet 1, or when smoothness is required for the pressure-sensitive adhesive layer 4, it is preferable to use a resin film or a resin film coated with a release agent.

  The release agent is usually coated on the entire surface of at least a portion of the resin film or paper (base material) in contact with the pressure-sensitive adhesive layer 4 to constitute a release agent layer. That is, when the first release sheet 2 is made of a base material coated with a release agent, the first release sheet 2 is formed on the entire surface of the base material and at least the portion of the base material that is in contact with the adhesive layer 4. And a release agent layer. The second release sheet 3 is the same, but is not limited to this.

  As the release agent, for example, silicone resin, fluororesin, long chain alkyl resin, polybutadiene or the like is used.

  The first release sheet 2 and the second release sheet 3 may be the same type or different types. Moreover, the peeling force of the 1st peeling sheet 2 and the peeling force of the 2nd peeling sheet 3 may be the same, and there may be a difference. According to the pressure-sensitive adhesive sheet 1 according to this embodiment, even if the peeling force of the first release sheet 2 and the second release sheet 3 is the same, the effect of preventing a peeling failure described later can be obtained. If there is a difference, a better peeling failure prevention effect can be obtained. In addition, peeling force is peeling force with respect to the adhesive layer of a peeling sheet, and the measuring method of peeling force is shown by the Example mentioned later.

  The peeling force of the first release sheet 2 is preferably 5 to 500 mN / 25 mm, and more preferably 50 to 500 mN / 25 mm. Moreover, it is preferable that the peeling force of the 2nd peeling sheet 3 is 5-500 mN / 25mm, and it is more preferable that it is 5-200 mN / 25mm. However, the peel force of the first release sheet 2 is preferably equal to or greater than the peel force of the second release sheet 3.

  The difference obtained by subtracting the peel force of the second release sheet 3 from the peel force of the first release sheet 2 (peeling force difference) is preferably 0 to 100 mN / 25 mm, and preferably 0 to 50 mN / 25 mm. More preferred. If the peel force difference is too large, workability may be hindered as in the conventional problem. In addition, in the adhesive sheet 1 which concerns on this embodiment, since the peeling defect prevention effect is exhibited even if the peeling force difference of both peeling sheets is small, specifically, a peeling force difference is 10 mN / 25 mm or less, peeling is demonstrated. The force difference may be 10 mN / 25 mm or less, and may be 8 mN / 25 mm or less.

  The thickness of the first release sheet 2 and the second release sheet 3 is preferably 1 to 150 μm, and more preferably 5 to 100 μm. What is necessary is just to set suitably the surface roughness (Ra) of the peeling surface of the 1st peeling sheet 2 and the 2nd peeling sheet 3 according to the smoothness which should be provided to the adhesive layer 4. FIG.

  The pressure-sensitive adhesive layer 4 is composed of a pressure-sensitive adhesive and does not have a core material. The type of pressure-sensitive adhesive is not particularly limited, and examples thereof include acrylic pressure-sensitive adhesives, polyester-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, silicone resin-based pressure-sensitive adhesives, and ethylene-vinyl acetate-based pressure-sensitive adhesives. It is done. This pressure-sensitive adhesive may be an adhesive, for example, an energy ray-curable adhesive. When the pressure-sensitive adhesive layer 4 is used for optical purposes, it is preferable to use an acrylic pressure-sensitive adhesive having excellent transparency and handleability.

  The thickness of the pressure-sensitive adhesive layer 4 is preferably 1 to 100 μm, and more preferably 3 to 80 μm.

  Here, as shown in FIG. 1, the adhesive at the end of the adhesive layer 4 covers the end face of the first release sheet 2. This covered portion is referred to as a covered portion 41. Since the end surface of the first release sheet 2 does not have releasability, the covered portion 41 adheres to the end surface of the first release sheet 2 with a predetermined force. Therefore, the first release sheet 2 and the pressure-sensitive adhesive layer 4 are bonded to each other by the adhesive force of the covering portion 41. Accordingly, when the second release sheet 3 is peeled off from the pressure-sensitive adhesive layer 4, the pressure-sensitive adhesive layer 4 bonded to the first release sheet 2 is not peeled off from the first release sheet 2, and the second release sheet 3 without any problems. Can be peeled off.

  The height h (the distance in the thickness direction of the pressure-sensitive adhesive sheet 1) of the covering portion 41 is 0.01 to 5 μm, preferably 0.1 to 3 μm. If the height h of the covering portion 41 is too low, the adhesive force of the covering portion 41 to the end face of the first release sheet 2 is insufficient, and the above-described peeling failure prevention effect cannot be obtained. On the other hand, if the height h of the covering portion 41 is too high, it is difficult to peel off the first release sheet 2 when the first release sheet 2 is peeled off in the next step, or all or part of the pressure-sensitive adhesive layer 4. May adhere to the first release sheet 2 and the adhesive layer 4 may be deformed. Further, in an optical application in which a precise dimension of the pressure-sensitive adhesive layer 4 is required, for example, a display or an optical disk, the cover portion 41 may be preferably small so as not to reduce the dimensional accuracy of the pressure-sensitive adhesive layer 4. In that case, the height h of the covered portion 41 is preferably 0.01 to 1 μm.

  The width w of the covering portion 41 (distance in the planar direction of the pressure-sensitive adhesive sheet 1) is preferably 0.001 to 4 μm, and more preferably 0.01 to 1 μm. If the width w of the cover portion 41 is too small, the bonding force with the end face of the first release sheet 2 may be insufficient, and the above-described peeling failure prevention effect may not be obtained, and the width w of the cover portion 41 is too large. Then, the covering portion 41 becomes unnecessarily large, and the dimensional accuracy of the pressure-sensitive adhesive layer 4 is lowered.

  When the pressure-sensitive adhesive sheet 1 is a rectangular sheet, the covered portion 41 may exist on four sides of the pressure-sensitive adhesive sheet 1, may exist on two opposite sides, or may be on any one side. May be present. When the pressure-sensitive adhesive sheet 1 is obtained by cutting a long sheet, the covering portion 41 is usually present on two sides generated by cutting. When the covering part 41 exists on one side, the covering part 41 is preferably located on the side corresponding to the start of peeling of the second release sheet 3 when the second release sheet 3 is peeled off. The pressure-sensitive adhesive sheet 1 may have an arbitrary shape, and the position, length, and the like of the cover portion 41 are not limited as long as the effect of preventing the peeling failure by the cover portion 41 is obtained.

[Manufacture of adhesive sheet]
Next, an example of the manufacturing method of the adhesive sheet 1 will be described.
In this production method, first, the pressure-sensitive adhesive layer 4 is formed on the release surface of the first release sheet 2 (or the second release sheet 3). In order to form the pressure-sensitive adhesive layer 4, a coating agent containing the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 4 and, if desired, a solvent is prepared, and a roll coater, knife coater, roll knife coater, air knife coater, die coater is prepared. What is necessary is just to apply | coat and dry to the peeling surface of the 1st peeling sheet 2 (or 2nd peeling sheet 3) with coating machines, such as a bar coater, a gravure coater, and a curtain coater.

  And the peeling surface of the 2nd peeling sheet 3 (or 1st peeling sheet 2) is bonded to the surface of the formed adhesive layer 4, and they are crimped | bonded, The 1st peeling sheet 2 and 2nd It is set as the laminated body which consists of the peeling sheet 3 and the adhesive layer 4 pinched | interposed between them.

  Further, by forming a pressure-sensitive adhesive layer on the release surface of the first release sheet 2, forming a pressure-sensitive adhesive layer on the release surface of the second release sheet 3, bonding the pressure-sensitive adhesive layers together, and press-bonding, You may obtain the laminated body which consists of the 1st peeling sheet 2, the 2nd peeling sheet 3, and the adhesive layer 4 pinched | interposed between them.

  Next, with respect to the obtained laminated body, a cutting blade is inserted from the 2nd peeling sheet 3 side, and a laminated body is cut. At this time, the end portion of the pressure-sensitive adhesive layer 4 adheres to the cutting blade due to its adhesiveness, is pulled toward the first release sheet 2, and covers the end surface of the first release sheet 2.

  In order to set the height h of the covering portion 41 to 0.01 to 5 μm, the shape of the cutting blade, the blade insertion speed, the blade insertion pressure, etc. are appropriately set according to the material and thickness of each layer of the laminate. That's fine. As the cutting blade, for example, a cutting blade such as a punching cutter can be used.

  The pressure-sensitive adhesive sheet 1 can be obtained by cutting into an arbitrary shape from a sheet-like laminate, and can also be obtained by cutting at an arbitrary length from a long laminate. The covering portion 41 is formed on the side generated by cutting in this way.

[Use of adhesive sheet]
When using the pressure-sensitive adhesive sheet 1, first, the second release sheet 3 is peeled off from the pressure-sensitive adhesive layer 4. At this time, since the covering portion 41 is adhered to the end face of the first release sheet 2, the pressure-sensitive adhesive layer 4 is not peeled off from the first release sheet 2, and the second release sheet 3 can be peeled off without any problems. .

  Next, after sticking a 1st to-be-adhered body to the adhesive surface of the exposed adhesive layer 4, the 1st peeling sheet 2 is peeled from the adhesive layer 4. FIG. Then, the second adherend is attached to the exposed adhesive surface of the adhesive layer 4.

  By preventing the peeling failure of the second release sheet 3 as described above, defects in the pressure-sensitive adhesive layer 4 and generation of bubbles at the boundary surface (adhesive interface) between the pressure-sensitive adhesive layer 4 and the adherend are generated. Is prevented.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

  Here, the peeling force of the peeling sheet in the Example and comparative example which are mentioned later was measured as follows. The pressure-sensitive adhesive layer formed on the release sheet was fixed to a tester (Orientec, Tensilon), and the force when the release sheet was peeled off at 300 mm / min in the 180 ° direction was measured. 25 mm).

[Example 1]
As the first release sheet and the second release sheet, a polyethylene terephthalate film (thickness: 38 μm) having one surface peeled with a silicone resin-based release agent was prepared. The peeling force for the adhesive described later was 100 mN / 25 mm for the first release sheet and 80 mN / 25 mm for the second release sheet.

  An acrylic pressure-sensitive adhesive (96% by weight of butyl acrylate and 4% by weight of acrylic acid and 100 parts by weight of an acrylic copolymer having a weight-average molecular weight of 500,000% is added to trimethylolpropane tolylene diene. The coating agent (mixture obtained by mixing 2 parts by weight of isocyanate) was applied with a knife coater so that the thickness after drying was 30 μm, and dried at 90 ° C. for 1 minute. The pressure-sensitive adhesive layer thus formed was bonded to the release treatment surface of the second release sheet 3, and they were pressure-bonded to be sandwiched between the first release sheet and the second release sheet. A laminate comprising an adhesive layer was obtained.

  Next, a cutting blade was inserted into the laminated body from the second release sheet side using a single-blade punching and cutting machine and cut into 100 mm × 250 mm, which was used as an adhesive sheet.

[Example 2]
As the first release sheet, a polyethylene terephthalate film (thickness: 38 μm) having a release force of 60 mN / 25 mm with respect to the above-mentioned pressure-sensitive adhesive and peeled with a silicone resin-based release agent is used for the second release. As in the case of Example 1, except that a polyethylene terephthalate film (thickness: 38 μm) on which one side was peeled off with a silicone resin-based release agent having a peeling force of 50 mN / 25 mm with respect to the above-mentioned adhesive was used as a sheet. An adhesive sheet was prepared.

Example 3
As the first release sheet and the second release sheet, a polyethylene terephthalate film (thickness: 38 μm) having a release force of 60 mN / 25 mm with respect to the above-mentioned pressure-sensitive adhesive and having one side released with a silicone resin-based release agent is used. A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that.

[Comparative Example 1]
In Example 3, a pressure-sensitive adhesive sheet was produced in the same manner as in Example 3 except that a double-edged cutter equipped with upper and lower cutting blades was used and the cutting blades were inserted from both sides of the first release sheet and the second release sheet. .

[Comparative Example 2]
In Example 1, a pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that a cutting blade was inserted from the second release sheet side and cut using a single-blade punching and cutting machine having a slightly rounded blade edge.

[Test example]
(1) Measurement of the height of the covering portion The end surface of the pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples was observed with a digital microscope (magnification 20 times), and the covering portion of the pressure-sensitive adhesive layer on the end surface of the first release sheet The height of the (covered part) was measured. The results are shown in Table 1.

(2) Evaluation of peelability The second release sheet was peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the peelability at that time was evaluated. The adhesive layer did not peel off from the first release sheet, and A was obtained by peeling off the second release sheet without any problems, and B was the adhesive layer floated or peeled off from the first release sheet. The results are shown in Table 1.

(3) Evaluation of pressure-sensitive adhesive layer The second release sheet was peeled off from the pressure-sensitive adhesive sheet, and a polyethylene terephthalate film (thickness: 100 μm) that was not subjected to a treatment such as a release treatment was attached to the pressure-sensitive adhesive surface of the exposed pressure-sensitive adhesive layer. After that, the first release sheet is peeled off from the adhesive layer, and another polyethylene terephthalate film (thickness: 100 μm) that has not been subjected to a treatment such as a release treatment is applied to the adhesive surface of the exposed adhesive layer. A laminate was obtained. At this time, the pressure-sensitive adhesive layer of the obtained laminate had no defects (including deformation) and had no bubbles at the adhesive interface, and A had defects or bubbles. The results are shown in Table 1.

  As can be seen from Table 1, the pressure-sensitive adhesive sheets obtained in the examples did not cause defective peeling when the second release sheet was peeled off, and there were no defects in the pressure-sensitive adhesive layer or bubbles at the adhesive interface. The pressure-sensitive adhesive sheet obtained in Comparative Example 1 had a peeling failure when the second release sheet was peeled off, and the pressure-sensitive adhesive sheet obtained in Comparative Example 2 was a pressure-sensitive adhesive when peeled off the first release sheet. A part of the layer was attached to the first release sheet, and a defect occurred in the adhesive layer.

  The pressure-sensitive adhesive sheet of the present invention is useful as a pressure-sensitive adhesive sheet in the field where the pressure-sensitive adhesive layer does not have a core material and there are no defects in the pressure-sensitive adhesive layer or air bubbles at the adhesive interface. It is useful as a pressure-sensitive adhesive sheet in a field where the difference between them cannot be increased.

It is sectional drawing of the adhesive sheet which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Adhesive sheet 2 ... 1st release sheet 3 ... 2nd release sheet 4 ... Adhesive layer 41 ... Cover part h ... Cover part height (distance of the thickness direction of an adhesive sheet)
w: Width of cover (distance in the plane direction of the adhesive sheet)

Claims (2)

A first release sheet;
A second release sheet;
In an adhesive sheet comprising an adhesive layer sandwiched between the first release sheet and the second release sheet,
The pressure-sensitive adhesive at the end of the pressure-sensitive adhesive layer covers the end surface of the first release sheet to form a covered portion,
Thickness direction of the distance of the pressure-sensitive adhesive sheet of the overlays part, Ri 0.01~5μm der,
The pressure-sensitive adhesive sheet , wherein a difference obtained by subtracting the peeling force of the second release sheet from the peeling force of the first release sheet is 0 to 100 mN / 25 mm . A first release sheet;
A second release sheet;
In an adhesive sheet comprising an adhesive layer sandwiched between the first release sheet and the second release sheet,
The pressure-sensitive adhesive at the end of the pressure-sensitive adhesive layer covers the end surface of the first release sheet to form a covered portion,
The distance in the thickness direction of the pressure-sensitive adhesive sheet of the covering portion is 0.01 to 5 μm,
The peeling force of the first release sheet and the peeling force of the second release sheet are the same.
A pressure-sensitive adhesive sheet.

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