JP5845591B2 - Double-sided adhesive tape for bonding rigid bodies - Google Patents

Description

  The present invention relates to a double-sided pressure-sensitive adhesive tape. Specifically, the present invention relates to a double-sided pressure-sensitive adhesive sheet that does not float or peel off when the rigid bodies are bonded to each other and has excellent adhesion.

  Double-sided adhesive tapes are used for fixing parts in various industrial fields because of their good workability and workability. In particular, it is more advantageous than an adhesive when the component to be fixed has a complicated shape or when productivity in an automated line or a cell production method is required. Therefore, double-sided pressure-sensitive adhesive sheets are used for nameplates of portable electronic devices such as mobile phones, transparent panels of information display units, and various electronic components and modules.

  In portable electronic devices, it is assumed that the mobile electronic device will fall from a height of 1 to 2 meters, such as falling from the user's hand or falling from a desk or the like. There is a demand for durability that does not cause parts to drop off or damage the main body against the generated impact. On the other hand, double-sided pressure-sensitive adhesive sheets are used for fixing various rigid members such as electronic device casings and components, or components, but recently, the design and design of portable electronic devices Due to the limitation, it is difficult to secure the adhesion area of the double-sided PSA sheet. Especially in mobile phones, the size of the image display unit such as LCD (Liquid Crystal Display) and organic EL (Electro Luminescence) has been increased in order to improve visibility while the size of the main body has been reduced. The adhesion area for fixing a transparent transparent panel made of acrylic resin or polycarbonate resin that protects the image display unit to the casing of the mobile phone is small.

  By the way, in the double-sided pressure-sensitive adhesive sheet used for portable electronic devices, in addition to the above characteristics that can withstand impacts when dropped and prevent parts from falling off, some force is applied to the electronic devices when being carried or used, As a result, when the mobile electronic device is distorted and the distortion is transmitted to the components of the mobile electronic device, or when the protective seal affixed to the component fixed to the electronic device is peeled off, the force is relatively low. The adhesion strength (hereinafter referred to as “surface adhesion strength”) in the case where is added from the outside has also become important. In particular, as described above, at the present time when the adhesion area by the double-sided pressure-sensitive adhesive sheet is narrowing, improvement of the surface adhesion strength is also an important issue. In particular, touch panel-equipped mobile phones (smartphones) with superior operability, which have increased production and sales in recent years, have a touch panel module inserted between the transparent panel and the image display module. Since (Reflexible Print Circuit) flexible panel applies a repulsive force to the transparent panel, high surface adhesion strength is required.

As a double-sided pressure-sensitive adhesive sheet for fixing components of an electronic device, for example, (a) it is composed of one pressure-sensitive adhesive layer, and (b) the pressure-sensitive adhesive layer has a loss tangent in a temperature range of −40 to −15 ° C. A double-sided pressure-sensitive adhesive tape having a maximum value (M1) of (tan δ) and (c) an adhesive strength of the pressure-sensitive adhesive layer to acrylonitrile / butadiene / styrene copolymer resin of 19 N / cm ² or more It is disclosed (see Patent Document 1). The double-sided pressure-sensitive adhesive tape has excellent impact resistance, but when a relatively slow force as described above is applied from the outside when the rigid members are bonded together and fixed, the fixed rigid member In some cases, floating or peeling occurred.

JP 2005-187513 A

  The problem to be solved by the present invention is to provide a double-sided pressure-sensitive adhesive tape that has good impact resistance even when the rigid bodies are bonded to each other, and has high surface adhesive strength that prevents the fixed rigid member from floating or peeling off. There is to do.

  In the double-sided pressure-sensitive adhesive tape of the present invention, after the double-sided pressure-sensitive adhesive tape is attached to one rigid body member, another rigid body member is attached via the double-sided pressure-sensitive adhesive tape, and the two rigid body members are bonded together and fixed. By making the pressure-sensitive adhesive layer that is first attached to the rigid member a flexible pressure-sensitive adhesive layer that is more likely to be stretched than the pressure-sensitive adhesive layer that has a certain peel resistance that is later attached to the rigid member, the rigid bodies are preferably combined. Can be crimped. Further, even when a force is applied in the peeling direction, the peeling energy due to the extension of the pressure-sensitive adhesive layer at the time of peeling can be increased, and the peeling resistance performance as a double-sided pressure-sensitive adhesive tape can be optimized. Although the peeling resistance performance and impact absorption in the double-sided pressure-sensitive adhesive tape are contradictory properties, according to the double-sided pressure-sensitive adhesive tape of the present invention, a pressure-sensitive adhesive layer having a low tensile rupture strength and good impact resistance is used. On the other hand, by making each pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape as the above-mentioned pressure-sensitive adhesive layer, it is possible to improve the peel resistance without reducing the impact resistance, and it is also suitable for bonding rigid bodies that are difficult to adhere to each other. Impact resistance and high surface adhesion strength can be achieved.

  The double-sided pressure-sensitive adhesive tape for sticking rigid bodies of the present invention can realize suitable impact resistance and high surface adhesive strength even when sticking together rigid bodies that are difficult to adhere. For this reason, it can be used very effectively for fixing parts of small electronic terminals such as mobile phones, which are likely to cause drop impacts or pressure on members, for example, fixing a transparent panel and a casing of a small electronic terminal having an image display unit. . In particular, in a small electronic terminal having a touch panel such as a smartphone, the transparent panel is deformed by pressing the transparent panel of the image display unit, and a force in a direction in which the transparent panel is peeled off from the housing is likely to be generated. The double-sided adhesive tape for rigid body application can be suitably applied to such a touch panel type small electronic terminal.

It is a conceptual sectional view showing an example of composition of an adhesive tape of the present invention. It is a conceptual sectional view showing one embodiment of the adhesive tape of the present invention. It is a conceptual diagram which shows the test piece for a surface adhesive strength and a drop impact test measurement. It is a conceptual diagram which shows the test piece for surface adhesive strength measurement which affixed the acrylic board 5 with the double-sided adhesive sheet 4 so that the center of the acrylic board 5 might correspond with the center of the hole of the ABS board 6. FIG. It is a perspective view which shows the square measuring stand 8 (The outer dimension of each surface is 80 mm in width, 60 mm in height, an inner dimension is 70 mm x 60 mm, and 5 mm in thickness made of aluminum) formed in 4 surfaces. It is the conceptual diagram which looked at the state when the test piece for surface adhesive strength measurement was installed in the measurement stand 8 from the measurement stand 8 side. It is a conceptual diagram which shows the measuring method of surface adhesive strength. It is a conceptual diagram which shows the test piece for a drop impact test. It is the conceptual diagram which looked at the state which put the ABS board 9 which stuck the acrylic board 5 on the U-shaped measurement stand 12 (made of aluminum of thickness 5mm) with the acrylic board down, from the bottom face side of the measurement stand 12. is there. It is a conceptual diagram which shows the measuring method of a drop impact test.

  The double-sided pressure-sensitive adhesive tape for bonding rigid bodies of the present invention is a double-sided pressure-sensitive adhesive tape used for bonding two rigid members, and after the double-sided pressure-sensitive adhesive tape is bonded to the rigid body member (1), It is a double-sided pressure-sensitive adhesive tape used for an application in which another rigid member (2) is attached and the rigid member (1) and the rigid member (2) are fixed. When applied to the application, the double-sided pressure-sensitive adhesive tape of the present invention has a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer on both sides of a base material, By using different pressure-sensitive adhesive layers, suitable impact resistance and high surface adhesive strength can be realized.

[Adhesive layer]
The pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape for bonding rigid bodies of the present invention includes a pressure-sensitive adhesive layer (1) (hereinafter referred to as a pre-adhesive pressure-sensitive adhesive layer (1)) that is previously bonded to the rigid member (1), When the other rigid member (2) is attached to the rigid member (1) to which the adhesive tape is attached, the adhesive layer (2) to which the rigid member (2) is attached (hereinafter referred to as the post-adhesive adhesive layer (2) )). In the present invention, the tensile strength obtained by a strength-strain curve at a strain amount of 500% of the post-adhesive pressure-sensitive adhesive layer (2) is 0.1 MPa or more, preferably 0.1 to 1.0 MPa, more preferably 0.1. By setting it to ˜0.5 MPa, the surface adhesion strength can be increased when the rigid bodies are bonded together. When floating and peeling of the rigid body fixed with the double-sided pressure-sensitive adhesive tape occurs, the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape extends about 0.5 to 1 mm, which corresponds to a strain amount of about 500%. Therefore, the adhesive layer of the double-sided pressure-sensitive adhesive tape is stretched by about 500% by setting the tensile strength obtained by the strength-strain curve of the strain amount 500% of the post-adhesive pressure-sensitive adhesive layer (2) to 0.1 MPa or more. Can withstand the force of the rigid body peeling off.

  In the present invention, the ratio of the tensile strength at 500% strain of the first adhesive layer (1) to the tensile strength at 500% strain of the post-adhesive adhesive layer (2) is 0.5-0. By setting it to 95, the surface adhesion strength when the rigid bodies are bonded together can be increased. By setting it as said range, the adhesive layer of both sides expand | extends equally, and the peeling energy by expansion | extension of the adhesive layer at the time of peeling can be enlarged. Therefore, it is possible to improve the surface adhesive strength while using a pressure-sensitive adhesive layer having good impact resistance in a rigid-bonded double-sided pressure-sensitive adhesive tape.

  Moreover, in this invention, in order to implement | achieve suitable impact resistance, it obtains with the intensity | strength-distortion curve of at least one adhesive layer of a front-attached adhesive layer (1) and a back-attached adhesive layer (2). The tensile strength at break is 1.10 MPa or less, preferably 0.59 to 1.10 MPa, more preferably 0.59 to 0.80 MPa. The tensile breaking strength represents the hardness when the pressure-sensitive adhesive layer is broken at high speed, and the pressure-sensitive adhesive layer having a high tensile breaking strength is hardened during high-speed deformation. Cannot absorb. On the other hand, the pressure-sensitive adhesive layer having a low tensile breaking strength does not become hard even during high-speed deformation, can absorb impact energy when dropped, and has excellent drop impact properties. Therefore, when the breaking strength measured by measuring the tensile strength of the pressure-sensitive adhesive layer is 1.10 MPa or less, a pressure-sensitive adhesive layer capable of absorbing impact energy is obtained, and suitable impact resistance can be imparted to the double-sided pressure-sensitive adhesive tape.

  The tensile strength at a strain of 500% and the tensile strength at break of each pressure-sensitive adhesive layer can be obtained by measuring the strength-strain curve of the pressure-sensitive adhesive layer. Specifically, the pressure-sensitive adhesive layer to be measured is superposed on about 400 μm, cut to a size of 10 mm × 20 mm to obtain a test piece, and the test piece is obtained using a Tensilon universal tensile testing machine (Orientec, RTA100). By pulling at a speed of 300 mm / min under a temperature and humidity condition of an environmental temperature of 23 ° C. and a humidity of 50% to obtain a strength-strain curve, the tensile strength at a strain of 500% and the tensile strength at break can be measured.

  The 300 degree / min 180 degree peeling adhesive strength of each adhesive layer of the first adhesive layer (1) and the rear adhesive layer (2) of the double-sided adhesive tape for rigid body bonding of the present invention is 15 N / 25 mm, respectively. The above is preferable, and 15 to 25 N / 25 mm is more preferable. By setting the adhesive strength of each pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape within the above range, good adhesiveness can be obtained in addition to the surface adhesive strength and the drop impact resistance.

  In addition, 180 degree | times peeling adhesive force of each adhesive layer can be calculated | required by the following procedure according to the test method of 180 degree | times peeling adhesive force of JIS-Z0237 (2000). A pressure-sensitive adhesive composition was applied on a PET release sheet having a thickness of 75 μm after the release treatment so that the thickness after drying was 52 μm, and dried at 85 ° C. for 3 minutes to form a pressure-sensitive adhesive layer in the form of a release sheet. create. The obtained pressure-sensitive adhesive layer is lined with a 25 μm-thick polyester film to prepare a 25-mm-wide pressure-sensitive adhesive tape sample, which is added to polycarbonate once and twice with a 2 kg roller under conditions of an environmental temperature of 23 ° C. and a humidity of 50% After pressing and allowing to stand for 1 hour, using a Tensilon universal tensile tester (Orientec, RTA100), it is pulled at a speed of 300 mm / min under the same temperature and humidity conditions, and then peeled off 180 degrees to measure the adhesive strength.

(Acrylic copolymer)
The above-mentioned pre-adhesive pressure-sensitive adhesive layer (1) and post-adhesive pressure-sensitive adhesive layer (2) are an acrylic copolymer comprising a (meth) acrylate having a C 4-8 alkyl group as a main monomer component, and a crosslinking agent. It is formed from the acrylic adhesive composition containing these. By using a (meth) acrylate having a C 4-8 alkyl group as a main monomer component as a monomer component constituting the acrylic copolymer, suitable adhesiveness can be easily obtained. In addition, by using the (meth) acrylate as the main monomer component, the relationship between the tensile strain amount and the tensile strength of the resulting pressure-sensitive adhesive layer shows a certain tendency, so by adjusting the amount and type of crosslinking agent to be added The tensile strength and tensile breaking strength can be easily adjusted. Examples of the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms include n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n -Octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. can be illustrated, These can be used individually or in combination of 2 or more types. Especially, it is preferable to make n-butyl acrylate into a main component, and it is preferable that the usage-amount is 70 mass% or more in the monomer component which comprises an acrylic copolymer, and it is more preferable that it is 80 mass% or more. This makes it easy to adjust the tensile strength at a strain of 500% to 0.1 MPa or more.

  Furthermore, it is preferable to add a vinyl monomer having a functional group such as a hydroxyl group, a carboxyl group or an amino group in the side chain in the range of 0.01 to 15% by mass. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, crotonic acid, fumaric acid , Carboxypropyl acrylate maleate, dimethylaminoethyl acrylamide, N-vinyl pyrrolidone, acrylonitrile, N-vinyl caprolactam, acrylamide, styrene, vinyl acetate, N-methylol acrylic amide, glycidyl methacrylate, etc. The above can be used in combination.

  The acrylic copolymer can be obtained by copolymerization by a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, an ultraviolet irradiation method, or an electron beam irradiation method.

  The mass average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC) of the acrylic copolymer is preferably 400,000 to 1,400,000, more preferably 500,000 to 1,000,000. When the average molecular weight is in the above range, the tensile strength and the tensile strength at break can be easily controlled within the target ranges.

(Crosslinking agent)
As a crosslinking agent used for this invention, an isocyanate type crosslinking agent, an epoxy-type crosslinking agent, a chelate type crosslinking agent etc. can be used, for example. In the present invention, by adjusting the type and amount of the cross-linking agent, the cross-linking structure of the pre-adhesive pressure-sensitive adhesive layer (1) and the post-adhesive pressure-sensitive adhesive layer (2) is adjusted, and the strength-distortion of these pressure-sensitive adhesive layers. The tensile strength and tensile breaking strength obtained by the curve can be adjusted. As the cross-linking agent, an isocyanate cross-linking agent can be preferably used. When an isocyanate cross-linking agent is used, the solid content of the cross-linking agent is 0.1 to 5 parts by mass with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive composition. It is preferable to mix | blend between. Thereby, it is easy to control the tensile strength and tensile rupture strength obtained from the strength-strain curve of the pressure-sensitive adhesive layer within a target range.

  The addition amount of the crosslinking agent in the pre-adhesive pressure-sensitive adhesive layer (1) is preferably adjusted so that the gel fraction of the pressure-sensitive adhesive layer is 40 to 55%. A more preferable gel fraction is 45 to 50%. By setting the gel fraction of the pre-adhesive pressure-sensitive adhesive layer (1) within the above range, it is easy to control the tensile strength and tensile breaking strength obtained from the strength-strain curve within the target ranges. Moreover, it is preferable to adjust so that the gel fraction of an adhesive layer may be 40 to 60% as an addition amount of the crosslinking agent of a back sticking adhesive layer (2). A more preferable gel fraction is 50 to 55%. By setting the gel fraction of the post-adhesive pressure-sensitive adhesive layer (2) within the above range, it is easy to control the tensile strength and the tensile strength at the target range. Moreover, by setting the ratio of the gel fraction of the pre-adhesive pressure-sensitive adhesive layer (1) to the gel fraction of the post-adhesive pressure-sensitive adhesive layer (2) in the range of 0.75 to 0.95, the post-adhesive pressure-sensitive adhesive layer ( Ratio of tensile strength obtained by strength-strain curve at 500% strain of pre-adhesive pressure-sensitive adhesive layer (1) to tensile strength obtained by strength-strain curve at 2% strain of 500% (1) / (2) It is easy to control the target range.

  The gel fraction is expressed as a percentage of the original mass by immersing the composition of the pressure-sensitive adhesive layer after curing in toluene, measuring the mass of the insoluble matter remaining after drying for 24 hours and drying it.

(Tackifying resin)
In the present invention, it is also preferable to add a tackifier resin in order to improve the adhesive strength of the adhesive layer. In addition, by adding these tackifying resins, it is possible to increase the tensile strength and tensile rupture strength, so depending on the acrylic copolymer used, by appropriately adding a tackifying resin, the tensile strength and The tensile breaking strength can be adjusted. Examples of the tackifying resin added to the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape of the present invention include rosin resins such as rosin and rosin ester compounds; terpene resins such as diterpene polymers and α-pinene-phenol copolymers. A petroleum resin such as an aliphatic (C5) or aromatic (C9); a styrene resin, a phenol resin, a xylene resin, and the like. In particular, in a pressure-sensitive adhesive composition using an acrylic copolymer containing n-butyl (meth) acrylate as a main monomer component, both the polymerized rosin pentaerythritol ester and the non-polymerized rosin pentaerythritol ester are used for achieving both impact resistance and surface adhesion hardness. It is preferable to use a mixture of glycerin ester of leveled rosin.

  As addition amount of tackifying resin, it is preferable to add 20-40 mass parts with respect to 100 mass parts of acrylic copolymers. In particular, the addition amount of the polymerized rosin pentaerythritol ester and the disproportionated rosin glycerin ester is most preferably 10 to 15 parts by mass. By adding a tackifying resin, the tensile strength and tensile breaking strength obtained from the strength-strain curve are increased, and the strength can be adjusted.

  In addition, to the pressure-sensitive adhesive composition used in the present invention, known and conventional additives such as a light stabilizer, an ultraviolet absorber, a plasticizer, a softener, a filler, a pigment, and a flame retardant are added as necessary. May be. Examples of the light stabilizer include a chain inhibitor, a hydroperoxide decomposing agent, a metal deactivator, and an ultraviolet absorber. By using such an additive, the above yellowing resistance can be improved.

[Base material]
As the base material used in the present invention, various resin film base materials generally used as a base material for double-sided pressure-sensitive adhesive tapes can be used. For example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, cellophane, diacetyl Cellulose, triacetyl cellulose, acetyl cellulose butyrate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polystyrene, polycarbonate, polymethylpentene, polysulfone, polyether ether ketone, polyether sulfone, poly Examples of the resin film include ether imide, polyimide, fluorine resin, nylon, and acrylic resin.

  When these resin films are used as a base material, surface unevenness treatment such as sandblasting or solvent treatment, corona discharge treatment, chromic acid treatment, flame for the purpose of improving adhesion with the adhesive layer Surface treatment such as surface oxidation treatment such as treatment, hot air treatment, ozone / ultraviolet irradiation treatment, etc. may be applied.

  The thickness of the substrate is preferably 3 μm to 100 μm, more preferably 5 μm to 50 μm, and still more preferably 10 μm to 30 μm. If the thickness of the base material is 100 μm or less, and further 50 μm or less, the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape expands, and the base material is easily deformed when peeled off. It can be prevented from progressing. Therefore, it becomes easy to prevent the bonded member from being completely peeled off. Moreover, by setting it as 3 micrometers or more, workability, such as a punching process required in the case of the component fixation use etc. of a small electronic terminal, can be made favorable.

[Double-sided adhesive tape for bonding rigid bodies]
The double-sided pressure-sensitive adhesive tape for bonding rigid bodies of the present invention is a double-sided pressure-sensitive adhesive tape used for bonding two rigid members, and after the double-sided pressure-sensitive adhesive tape is bonded to the rigid body member (1), The other rigid body member (2) is attached and used for fixing the rigid body member (1) and the rigid body member (2). And when applying to the said use, the double-sided adhesive tape of this invention uses the said pre-adhesive adhesive layer (1) and rigid member (2) as an adhesive layer of the side bonded previously with a rigid member (1). By having the post-adhesive pressure-sensitive adhesive layer (2) on each surface of the substrate as the pressure-sensitive adhesive layer on the side to be adhered, suitable impact resistance and high surface adhesion strength can be realized.

  When a rigid member is bonded to one side of the double-sided pressure-sensitive adhesive tape and another rigid body member is bonded to the other side of the double-sided pressure-sensitive adhesive tape, the rigid bodies are bonded to each other. Adhesion often becomes insufficient, and sufficient surface adhesion strength is often not obtained. This is presumably because the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape cannot be sufficiently pressurized when the rigid bodies are bonded to each other. If the adhesion between the adhesive layer and the rigid member is inadequate, the adhesive layer peels off from the rigid member before the peel energy due to the elongation of the adhesive is maximized, and the original adhesive layer has the surface adhesion It is considered that the strength cannot be fully exhibited. In the present invention, according to the above configuration, the adhesive layer on the side to which the rigid member is to be attached later can be sufficiently adhered to the rigid member, and the peeling energy due to the expansion of the adhesive layer at the time of peeling can be increased. The surface adhesive strength can be greatly increased without deteriorating the properties.

(Surface adhesive strength)
The surface adhesive strength of the double-sided pressure-sensitive adhesive tape for bonding rigid bodies of the present invention is preferably 45 N or more as measured by the following method. By making the surface adhesive strength or higher, it is possible to suitably fix the rigid bodies, even when the transparent panel is deformed, especially when the housing of the small electronic terminal having the image display unit and the transparent panel are fixed. Dropping from the housing is less likely to occur.

The surface adhesive strength of the double-sided pressure-sensitive adhesive tape of the double-sided pressure-sensitive adhesive tape for rigid body bonding of the present invention is measured by the following (i) to (iii).
(I) On a square polycarbonate plate 5 having a thickness of 2 mm and a side length of 50 mm at 23 ° C., the two-sided adhesive sheet 4 having a width of 2 mm and a length of 40 mm is spaced by 40 mm. And opened in parallel (FIG. 3).
(Ii) Next, the polycarbonate plate 5 with the double-sided pressure-sensitive adhesive sheet 4 prepared in (i) is formed on the polycarbonate plate 6 having a thickness of 2 mm, a length of 150 mm, and a width of 100 mm. The post-adhesive pressure-sensitive adhesive surface was affixed so that the center of the polycarbonate plate 5 coincided with the center of the hole in the polycarbonate plate 6, and a 2 kg roller was reciprocated once to pressurize, and then allowed to stand at 23 ° C. for 1 hour. (Fig. 4)
(Iii) A square measuring table 8 formed of four surfaces (the outer dimensions of each surface are 80 mm wide, 60 mm high, the inner dimensions are 70 mm × 60 mm, and 5 mm thick aluminum (FIG. 5)). Prepared. A tensile tester (a stainless steel probe 7 having a diameter of 8 mm is attached from the side of the polycarbonate plate 6 through the hole by placing the polycarbonate plate 6 on which the polycarbonate plate 5 prepared in (ii) is attached (FIG. 6). The polycarbonate plate 5 was pressed by A & D Tensilon RTA-100 (compression mode), and the strength (N / cm ² ) at which the polycarbonate plate 5 was peeled was measured. The speed at which the probe 7 pushes the polycarbonate plate 5 was 1 mm / min (FIG. 7). The polycarbonate plate 6 was placed so that the center of the measurement table 8 and the center of the hole of the polycarbonate plate 6 coincided with each other (the distance between the long side of the polycarbonate plate 6 and the outer surface of the measurement table 8 was 10 mm, and the polycarbonate plate 6 was short. The distance between the side and the outer surface of the measuring table 8 is 35 mm).

  The thickness of the double-sided pressure-sensitive adhesive tape of the present invention may be adjusted as appropriate according to the mode of use, but when used for a portable or small electronic terminal, it is preferably 200 μm or less, and 150 μm or less. More preferably. By setting the thickness, it is possible to contribute to thinning of a product to be applied, and the advantages of impact resistance and surface adhesion strength are particularly suitable.

(Peeling sheet)
In the double-sided pressure-sensitive adhesive tape of the present invention, a release sheet can be provided on the pressure-sensitive adhesive layer as necessary. As this release sheet, paper such as kraft paper, glassine paper and high-quality paper, paper coated with synthetic resin such as polyvinyl alcohol or clay on one or both sides of the paper, or polyethylene resin or the like on one side of the paper Alternatively, a paper laminated on both surfaces, or a plastic film such as polyethylene terephthalate, polyethylene naphthalate, and polypropylene coated with a release agent such as a fluorine resin or a silicone resin on one surface or both surfaces can be used. The thickness of the release sheet is not particularly limited, but is generally in the range of 20 to 300 μm.

(Manufacturing method of double-sided adhesive tape)
An adhesive layer can be formed on a base film by the method generally used for application | coating of a double-sided adhesive tape. The composition of the pressure-sensitive adhesive layer is applied directly to the base film and dried, or once applied onto the separator, dried and then bonded to the base film.

[Rigid body member]
As the rigid body member fixed by the double-sided adhesive tape for rigid body bonding of the present invention, a variety of rigid members used as a transparent panel of an image display section of an LCD module or the like, as well as a housing and parts of a small electronic terminal are used. it can. For example, resins such as polystyrene, ABS, acrylic, polycarbonate, polyamide polyester, polypropylene, polyurethane, and phenol resin used for small electronic terminals having an image display unit such as a mobile phone, metals such as stainless steel, aluminum, galvanized steel sheet, There is a rigid member made of glass or the like. In particular, ABS, acrylic, and polycarbonate are preferable as the casing of the small electronic terminal, and acrylic, polycarbonate, and glass are preferable as the transparent panel of the image display unit from the viewpoint of adhesion to the double-sided adhesive tape.

  Moreover, when fixing two rigid body members with the double-sided adhesive tape for rigid body bonding of this invention, the rigid body member (1) and the post-adhesive pressure-sensitive adhesive layer (2 As for the rigid member (2) to be attached, any two members may be used in an appropriate order. For example, the double-sided adhesive tape for sticking a rigid body of the present invention is particularly preferably used for fixing a housing of an electronic terminal and a transparent panel used for an image display unit of the electronic terminal. Even if the transparent panel is used as a rigid member (1), the transparent panel is used as the rigid member (2) and fixed with double-sided adhesive tape, You may fix with an adhesive tape.

  The present invention will be specifically described below with reference to examples. In addition, the part displayed in the following examples represents a mass part.

(Adjustment of acrylic pressure-sensitive adhesive composition A)
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 91.1 parts of n-butyl acrylate, 4.9 parts of vinyl acetate, 3.9 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate, Then, 0.2 part of 2,2′-azobisisobutylnitrile as a polymerization initiator is dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer having a mass average molecular weight of 500,000. Combined (1) was obtained. 12 parts of disproportionated rosin ester resin “Superester A100” manufactured by Arakawa Chemical Industries Co., Ltd. and polymerized rosin ester resin “Pencel D135” 12 manufactured by Arakawa Chemical Industries Co., Ltd. are added to 100 parts of the solid content of the acrylic copolymer (1). Part and 6 parts of petroleum resin “FTR6100” manufactured by Mitsui Petrochemical Industry Co., Ltd. were diluted with toluene to obtain an acrylic pressure-sensitive adhesive composition A having a solid content of 50%.

(Adjustment of acrylic pressure-sensitive adhesive composition B)
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 93.4 parts of n-butyl acrylate, 3 parts of vinyl acetate, 2.5 parts of acrylic acid, 1.0 part of N-vinylpyrrolidone, 4-hydroxy- 0.1 part of butyl acrylate and 0.2 part of 2,2′-azobisisobutylnitrile as a polymerization initiator are dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to mass average molecular weight 700,000 acrylic copolymers (2) were obtained. 10 parts of a polymerized rosin ester resin “Pentalin CJ” manufactured by Rika Finetech Co., Ltd., 15 parts of a terpene phenol resin “YS Polystar T130” manufactured by Yashara Chemical Co., Ltd., in 100 parts of the solid content of the acrylic copolymer (2), and 6 parts of petroleum resin “FTR6100” manufactured by Mitsui Petrochemical Co., Ltd. was blended and diluted with toluene to obtain an acrylic pressure-sensitive adhesive composition B having a solid content of 45%.

(Adjustment of acrylic pressure-sensitive adhesive composition C)
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 80.0 parts of n-butyl acrylate, 3.0 parts of vinyl acetate, 17.0 parts of 2-hydroxy-ethyl acrylate, and 2, as a polymerization initiator 0.2 part of 2′-azobisisobutylnitrile was dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization was carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer (3) having a mass average molecular weight of 500,000. . 12 parts of disproportionated rosin ester resin “Superester A100” manufactured by Arakawa Chemical Industries, Ltd., 100 parts of the acrylic copolymer (3), and a polymerized rosin ester resin “Pencel D135” manufactured by Arakawa Chemical Industries, Ltd. 12 And 6 parts of petroleum resin “FTR6100” manufactured by Mitsui Petrochemical Co., Ltd. were mixed and diluted with toluene to obtain an acrylic pressure-sensitive adhesive composition C having a solid content of 50%.

(Adjustment of acrylic pressure-sensitive adhesive composition D)
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 97.8 parts of n-butyl acrylate, 2.0 parts of acrylic acid, 0.2 part of 2-hydroxy-ethyl acrylate, and 2, as a polymerization initiator 0.2 part of 2′-azobisisobutylnitrile was dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization was carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer (4) having a mass average molecular weight of 1050,000. . 10 parts of hydrogenated rosin ester “KE656” manufactured by Arakawa Chemical Industries, 5 parts of polymerized rosin ester resin “Pencel D135” manufactured by Arakawa Chemical Industries, Ltd., and 100 parts by solid content of the acrylic copolymer (4) 30 parts of petroleum resin “FTR6100” manufactured by Petrochemical Industry Co., Ltd. was blended and diluted with toluene to obtain an acrylic pressure-sensitive adhesive composition D having a solid content of 40%.

(Example 1)
(Production of adhesive tape)
The acrylic adhesive composition A was blended with 0.9 parts of “Coronate L-45” (isocyanate-based cross-linking agent, solid content 40%) manufactured by Nippon Polyurethane Industry Co., Ltd., sufficiently stirred, and then subjected to mold release treatment. Coating was performed on a 75 μm PET film so that the thickness after drying was 52 μm, and drying was performed at 85 ° C. for 3 minutes to obtain a pressure-sensitive adhesive layer (a) to be a pre-adhesive pressure-sensitive adhesive layer. Next, a post-adhesive pressure-sensitive adhesive layer having a thickness of 52 μm was formed in the same manner as the adhesive layer (a) except that 1,24 parts were added instead of 0.9 part of “Coronate L-45”. An adhesive layer (b) was obtained. The obtained pressure-sensitive adhesive layer (a) was used as a pre-adhesive pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer (b) was used as a post-adhesive pressure-sensitive adhesive layer, and each pressure-sensitive adhesive layer was formed on both sides of a PET film “SG-16” made by Unitika. After bonding to each, it was cured at 40 ° C. for 2 days to obtain a double-sided adhesive tape.

(Example 2)
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (c) in which 1.6 parts of “Coronate L-45” was added to the acrylic pressure-sensitive adhesive composition A was used as the post-adhesive pressure-sensitive adhesive layer. Obtained.

(Example 3)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (b) was used as the pre-adhesive pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer (c) was used as the post-adhesive pressure-sensitive adhesive.

Example 4
The pressure-sensitive adhesive layer (b) is used as the pre-adhesive pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer (d) in which 1.3 parts of “Coronate L-45” is blended with the acrylic pressure-sensitive adhesive composition B is used as the post-adhesive pressure-sensitive adhesive layer. Except for this, a double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1.

(Example 5)
The pressure-sensitive adhesive layer (e) in which 2.1 parts of “Coronate L-45” was blended with the acrylic pressure-sensitive adhesive composition C as the pre-adhesive pressure-sensitive adhesive layer was used, and the acrylic pressure-sensitive adhesive composition C was “ A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (f) containing 2.6 parts of Coronate L-45 was used.

(Example 6)
The pressure-sensitive adhesive layer (f) is used as the pre-adhesive pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer (g) in which 3.1 parts of “Coronate L-45” is blended with the acrylic pressure-sensitive adhesive composition C is used as the post-adhesive pressure-sensitive adhesive layer. Except for this, a double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1.

(Example 7)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive layer (e) was used as the pre-adhesive pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer (g) was used as the post-adhesive pressure-sensitive adhesive.

(Example 8)
A pressure-sensitive adhesive layer (h) in which 1.2 parts of “Coronate L-45” was blended into the acrylic pressure-sensitive adhesive composition D as the pre-adhesive pressure-sensitive adhesive layer was used. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (i) containing 1.8 parts of Coronate L-45 was used.

Example 9
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layers (b) and (c) were bonded to both surfaces of a 6 μm PET film “Lumirror 6CF53” manufactured by Toray DuPont.

(Example 10)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that coating was performed so that the thickness of the pressure-sensitive adhesive layers (b) and (c) was 92 μm.

(Comparative Example 1)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (a) was used on both sides.

(Comparative Example 2)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (b) was used on both sides.

(Comparative Example 3)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (c) was used on both sides.

(Comparative Example 4)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (d) was used on both sides.

(Comparative Example 5)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (b) was used as the pre-adhesive pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer (a) was used as the post-adhesive pressure-sensitive adhesive layer.

(Comparative Example 6)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (c) was used as the pre-adhesive pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer (a) was used as the post-adhesive pressure-sensitive adhesive layer.

(Comparative Example 7)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (c) was used as the pre-adhesive pressure-sensitive adhesive layer.

(Comparative Example 8)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (c) was used as the pre-adhesive pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer (d) was used as the post-adhesive pressure-sensitive adhesive layer.

(Comparative Example 9)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer (f) was used as the pre-adhesive pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer (e) was used as the post-adhesive pressure-sensitive adhesive layer.

  About the adhesive solution and double-sided adhesive tape which were created in Examples 1-3 and Comparative Examples 1-6, it tested by the method shown below and the evaluation result was shown in Table 1 and Table 2.

(Adhesive strength measurement)
The adhesive strength of each pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape was determined according to the following procedure according to the JIS-Z0237 (2000) 180-degree peeling adhesive strength test method.
The pressure-sensitive adhesive composition used for each pressure-sensitive adhesive layer was applied onto a PET release sheet having a thickness of 75 μm after the release treatment so that the thickness after drying was 52 μm, and dried at 85 ° C. for 3 minutes. Each pressure-sensitive adhesive layer was prepared in the form of a release sheet. The obtained pressure-sensitive adhesive layer was lined with a 25 μm-thick polyester film to obtain a 25 mm-wide pressure-sensitive adhesive tape sample. A polycarbonate plate is used as the adherend, and the pressure-sensitive adhesive tape sample obtained is pressure-applied once with a 2 kg roller under the conditions of an environmental temperature of 23 ° C. and a humidity of 50%, and left for 1 hour. Using a machine (Orientec, RTA100), the film was pulled at a speed of 300 mm / min under the same temperature and humidity conditions, and then peeled off by 180 degrees to measure the adhesive force S25.

(Tensile strength measurement)
Each cured adhesive layer was laminated to about 400 μm to obtain a test piece. Using a Tensilon universal tensile tester (Orientec, RTA100), the test piece was pulled at a speed of 300 mm / min under an ambient temperature of 23 ° C. and a humidity of 50%, and the elongation of each adhesive layer was 500%. The tensile strength at break and the tensile break strength at break were measured.

(Surface adhesion strength measurement)
(I) On a square polycarbonate plate 5 having a thickness of 2 mm and a side length of 50 mm at 23 ° C., the two-sided adhesive sheet 4 having a width of 2 mm and a length of 40 mm is spaced by 40 mm. And opened in parallel (FIG. 3).
(Ii) Next, the polycarbonate plate 5 with the double-sided pressure-sensitive adhesive sheet 4 prepared in (i) is formed on the polycarbonate plate 6 having a thickness of 2 mm, a length of 150 mm, and a width of 100 mm. The post-adhesive pressure-sensitive adhesive surface was affixed so that the center of the polycarbonate plate 5 coincided with the center of the hole in the polycarbonate plate 6, and a 2 kg roller was reciprocated once to pressurize, and then allowed to stand at 23 ° C. for 1 hour. (Fig. 4)
(Iii) A square measuring table 8 formed of four surfaces (the outer dimensions of each surface are 80 mm wide, 60 mm high, the inner dimensions are 70 mm × 60 mm, and 5 mm thick aluminum (FIG. 5)). Prepared. A tensile tester (a stainless steel probe 7 having a diameter of 8 mm is attached from the side of the polycarbonate plate 6 through the hole by placing the polycarbonate plate 6 on which the polycarbonate plate 5 prepared in (ii) is attached (FIG. 6). The polycarbonate plate 5 was pressed by A & D Tensilon RTA-100 (compression mode), and the strength (N / cm ² ) at which the polycarbonate plate 5 was peeled was measured. The speed at which the probe 7 pushes the polycarbonate plate 5 was 1 mm / min (FIG. 7). The polycarbonate plate 6 was placed so that the center of the measurement table 8 and the center of the hole of the polycarbonate plate 6 coincided with each other (the distance between the long side of the polycarbonate plate 6 and the outer surface of the measurement table 8 was 10 mm, and the polycarbonate plate 6 was short. The distance between the side and the outer surface of the measuring table 8 is 35 mm).

The said test was done with respect to the double-sided adhesive tape of an Example and a comparative example, and the following evaluation criteria evaluated.
○: Surface adhesion strength is 45N or more ×: Surface adhesion strength is less than 45N

(Drop impact test)
(I) At 23 ° C., a polycarbonate sheet 5 having a thickness of 2 mm, a length of 50 mm, and a width of 50 mm is parallel to the front adhesive layer of two double-sided pressure-sensitive adhesive sheets 4 having a width of 2 mm and a length of 40 mm with an interval of 40 mm. (Fig. 3).
(Ii) After sticking the polycarbonate plate 5 with the double-sided pressure-sensitive adhesive sheet 4 prepared in (i) on the ABS plate 9 not drilled with a thickness of 2 mm, a length of 150 mm, and a width of 100 mm, a 2 kg roller 1 reciprocating pressurization, Let stand at 23 ° C. for 1 hour (FIG. 8).
(Iii) A U-shaped measuring table 12 (aluminum having a thickness of 5 mm) having a length of 150 mm, a width of 100 mm, and a height of 45 mm is placed on the base of a DuPont impact tester (manufactured by Tester Sangyo Co., Ltd., not shown). The ABS plate 9 (FIG. 8) on which the polycarbonate plate 5 of (ii) was pasted was placed thereon with the polycarbonate plate down (FIG. 9). A stainless steel strike core 10 (tip diameter 12.7 mm) having a diameter of 25 mm and a mass of 300 g is dropped from a position of 500 mm height from the ABS plate 9 side, and an impact is applied to the central portion 10 of the ABS plate 9. The number of times until the polycarbonate plate 5 affixed to the side opposite to the surface where the polycarbonate plate 5 was removed from the ABS plate 9 was counted (FIG. 10).

The said test was done with respect to the double-sided adhesive tape of an Example and a comparative example, and the following evaluation criteria evaluated.
○: No peeling even after three impacts.
X: It peeled within 3 times.

  As shown in Tables 1 and 2 above, the double-sided pressure-sensitive adhesive tapes for rigid body application of Examples 1 to 10 of the present invention had suitable impact resistance and excellent surface adhesive strength. On the other hand, although the double-sided pressure-sensitive adhesive tapes of Comparative Examples 1, 2, 5-7, and 9 had suitable impact resistance, the surface adhesive strength was not sufficient. The double-sided pressure-sensitive adhesive tapes of Comparative Examples 3, 4, and 8 were inferior in impact resistance although they were excellent in surface adhesion strength.

DESCRIPTION OF SYMBOLS 1 Adhesive layer 2 Support body 3 Release sheet 4 Double-sided adhesive sheet 5 PC board 6 PC board (perforated)
7 Probe 8 Measuring table 9 ABS plate (no hole)
10 Location to hit the striker 11 Dropper impact striker 12 U-shaped measuring table

Claims (4)

Double-sided pressure-sensitive adhesive tape for bonding rigid bodies used when fixing another rigid body member (2) to the other surface of the double-sided pressure-sensitive adhesive tape (1) to which one side of the double-sided pressure-sensitive adhesive tape has been attached. Because
The rigid body is fixed between the casing member of the electronic terminal having the image display unit and the transparent panel, and when the rigid member (1) is the casing member, the rigid member (2) is the transparent panel. Yes, when the rigid member (1) is the transparent panel, the rigid member (2) is the housing member,
The double-sided pressure-sensitive adhesive tape has a pressure-sensitive adhesive layer (1) to be bonded to the rigid member (1) on one surface of the substrate, and a pressure-sensitive adhesive to bond the other rigid member (2) to the other surface of the substrate. Having a layer (2),
The acrylic system containing the acrylic copolymer which the said monomer layer (1) and adhesive layer (2) have as a main monomer component the (meth) acrylate which has a C4-C8 alkyl group, and a crosslinking agent It consists of an adhesive composition,
The tensile strength obtained by the strength-strain curve at a strain amount of 500% of the pressure-sensitive adhesive layer (2) attached to the other rigid member (2) is 0.1 MPa or more,
The ratio (1) / (2) of the tensile strength obtained by the strength-strain curve at the strain amount of 500% of the pressure-sensitive adhesive layer (1) to the tensile strength at the strain amount of 500% of the pressure-sensitive adhesive layer (2) is 0. .5 to 0.95,
A double-sided adhesive for laminating a rigid body, having a tensile breaking strength of 1.10 MPa or less obtained from a strength-strain curve of at least one of the pressure-sensitive adhesive layer (1) and the pressure-sensitive adhesive layer (2) tape.   The pressure-sensitive adhesive layer (1) has a gel fraction of 40 to 55%, the pressure-sensitive adhesive layer (2) has a gel fraction of 45 to 60%, and a pressure-sensitive adhesive layer with respect to the gel fraction of the pressure-sensitive adhesive layer (2). The ratio of the gel fraction of (1) is 0.75 to 0.95, The double-sided pressure-sensitive adhesive tape for laminating a rigid body according to claim 1.   The double-sided pressure-sensitive adhesive tape for laminating a rigid body according to claim 1 or 2, wherein the acrylic copolymer contains 70% by mass or more of n-butyl acrylate in a monomer component forming the acrylic copolymer.   The total thickness is 200 micrometers or less, and the thickness of the said base material is 100 micrometers or less, The double-sided adhesive tape for rigid body bonding in any one of Claims 1-3.

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