TWI391463B - Water-proof double coated pressure sensitive adhesive tape - Google Patents

Description

Waterproof double-sided tape

The present invention relates to a waterproof double-sided tape having a foam base material as a core.

In the portable electronic devices such as electronic notebooks, mobile phones, PHS, cameras, and music players, the protection panel of the information display unit and the frame are attached, and the fixing of various components or modules has been Use double-sided tape. In order to ensure the superiority of the competition in the market, a variety of functions are required, one of which is to require the function of imparting water repellency.

As the tape used for fixing the parts of the electronic device, for example, it has been disclosed that the maximum value of the loss tangent (tan δ) is in the temperature range of -40 to -15 ° C, and the surface adhesion strength to a specific adherend is 19 N / The adhesive layer of cm ² or more is provided on both sides of the support body (see Patent Document 1). The double-sided adhesive sheet has an excellent adhesive force by having a specific adhesive layer, and has excellent impact resistance which is less likely to cause the part to fall off due to an impact when the object is dropped. However, if the protective panel is bonded to the frame body, in the joint between the rigid bodies, the double-sided adhesive sheet is difficult to be completely adhered to the joint surface with the adherend, and a slight gap may cause water immersion. Case.

As a double-sided tape excellent in adhesion, it has been disclosed that the temperature at which the maximum value of the loss tangent (tan δ) is expressed by the foam as a base material is -25 ° C or less, and the holding time of the holding test at 0 ° C is 24 A double-sided tape of an acrylic adhesive layer of an hour or more (see Patent Document 2). The double-sided tape is excellent in adhesion to the adherend, and the members can be suitably joined between the members when they are bonded to each other. However, in the case where the foam is used as a substrate, it is difficult to suppress the degree of a slight gap in the interface between the member and the adhesive layer, even if there is a gap or bulge in which a part can be immersed in water. , because the water intrusion path is enlarged, it is difficult to achieve waterproofness. In particular, in the case of a portable electronic device, it is required to have a narrow tape width and a thin tape thickness in accordance with the demand for a narrower margin of the screen in recent years and a thinner thickness. It is difficult to give sufficient water resistance.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2005-187513

Patent Document 2: Japanese Laid-Open Patent Publication No. 2005-281360

An object of the present invention is to provide a double-sided tape which exhibits good adhesion to an adherend even if the thickness of the tape is thin, and which is excellent in waterproof function.

Further, in addition to the above problems, a double-sided tape for waterproofing which is excellent in impact resistance and is suitable for use in a portable electronic device is provided.

As a result of intensive studies, the present inventors have found that by using a foam substrate having specific flexibility and strength as a substrate, even when a rigid body is bonded, a double-sided tape can be realized between the double-sided tape and the adherend. The excellent adhesion can effectively prevent the impregnation of water, thereby solving the above problems.

That is, the present invention provides a double-sided tape for waterproofing, which is a double-sided tape having a foam substrate and an adhesive layer, and the 25% compressive strength of the foam substrate is 40 ～. 160 kPa and tensile strength of 300 to 1500 N/cm ² .

The double-sided tape for waterproofing of the present invention exhibits appropriate adhesion to an adherend, and can effectively prevent water from entering from the close gap, and has an excellent waterproof function. Therefore, even in a portable electronic device in which the volume restriction in the casing is strict and it is difficult to provide another water sealing means, the waterproof function can be effectively imparted.

The double-sided tape for waterproofing of the present invention has a foam base material and an adhesive layer, and the foam base material has a 25% compressive strength of 40 to 160 kPa and a tensile strength of 300 to 1500 N/cm ² .

(foam substrate)

The foam base material used in the present invention is a foam base material having a 25% compression strength of 40 to 160 kPa, preferably 50 to 140 kPa, more preferably 60 to 130 kPa. By using a foam substrate having a 25% compressive strength in this range, it has excellent adhesion to an adherend, and is excellent even if it is suitable for adherends having a concave-convex shape or a rough surface. The adhesion. Further, since the foam base material having such a compressive strength has excessive cushioning properties, the pressure at the time of attachment concentrates on the joint portion, and it is easy to extrude the air existing at the joint interface, so that even in the joint between the rigid bodies, It does not produce excellent adhesion to the gap of the influent water.

The foamed structure of the foam substrate used in the present invention has a closed cell structure, and thus it is possible to effectively prevent water immersion from the cross section of the foam substrate, which is preferable. The shape of the bubble forming the closed cell structure is not particularly limited, but is independent of the shape of the foam in the flow direction or the width direction, or the average bubble diameter in the both directions is longer than the average bubble diameter of the foam in the thickness direction. The bubbles are preferred because of their moderate cushioning properties.

The average cell diameter in the thickness direction of the foam substrate is preferably from 1 to 100 μm, more preferably from 10 to 50 μm, and the average cell diameter in the flow direction and the width direction of the foam substrate is preferably from 1.2 to 700 μm, more preferably It is 10 to 500 μm, preferably 50 to 300 μm. By setting the average cell diameter to this range, even when the width of the double-sided tape is narrowed, the closed cells are easily formed, and the water immersion path from the cross section of the foam substrate can be appropriately cut off.

The ratio of the average cell diameter is not particularly limited, and the ratio of the average cell diameter in the flow direction of the foam substrate to the average cell diameter in the thickness direction of the foam substrate (average cell diameter/thickness direction in the flow direction) The average cell diameter) is preferably from 1.2 to 15, more preferably from 3 to 8. Further, the ratio of the average cell diameter in the width direction of the foam substrate to the average cell diameter in the thickness direction of the foam substrate (average cell diameter in the width direction/average cell diameter in the thickness direction) is preferably 1.2 to 15 More preferably 3 to 8. Further, it is preferable that the flow direction and the width direction are both the above ranges. When the ratio is 1.2 or more, it is easy to ensure the flexibility in the thickness direction, and thus the followability is improved. Further, when it is 15 times or less, the flexibility deviation or the tensile strength of the foam base material in the flow direction and the width direction is less likely to occur.

Further, the ratio of the average cell diameter in the flow direction and the width direction is preferably 0.25 to 4 times, more preferably 0.33 to 3 times, in the case where the flow direction is 1. When it is the above ratio range, the flexibility deviation of the foam base material in the flow direction and the width direction or the variation in tensile strength is less likely to occur.

The average bubble diameter in the width direction and the flow direction of the foam substrate was measured in the following manner. First, the foam substrate was cut 1 cm in both the width direction and the flow direction. Then, the central portion of the cut surface of the cut foam substrate was enlarged by 50 times using a scanning electron microscope (SEM), and then the cut surface of the foam base material was accommodated in the entire thickness direction of the substrate. In a full-length manner, a photograph is taken of a cross section in the width direction or the flow direction of the foam substrate. In the obtained photograph, all the bubble diameters existing in the cut surface having an actual length before expansion in the flow direction or the width direction of 2 mm were measured, and the average bubble diameter was calculated from the average value.

The average bubble diameter in the thickness direction of the foam substrate was measured in the following manner. First, the thickness of the foam substrate photographed by SEM was measured. Then, SEM photographing was performed under the same conditions as the measurement of the average bubble diameter in the flow direction of the foam substrate. Then, in the obtained photograph, the number of bubbles in the thickness direction existing in any one of the foam base materials was visually counted, and the average bubble diameter in the thickness direction was calculated by the following formula.

Average bubble diameter in the thickness direction (μm) = thickness of the foam substrate (μm) / number of bubbles

On the other hand, measurement was performed in any three places, and the average value was made into the average bubble diameter in the thickness direction.

The foamed structure of the foam base material has a compression strength or a tensile strength adjusted to the above range, and it is easy to achieve excellent adhesion to the adherend. Therefore, the foaming ratio is preferably 2 to 5 times, more preferably 2.4 to 4 times.

Further, regarding the 25% compressive strength, the sample cut into 50 mm squares was superimposed to a thickness of about 10 mm. The sample was sandwiched by a plate having a larger area than the sample, and the sample was compressed at a rate of 10 mm/min at 23 ° C for about 2.5 mm (25% of the original thickness), and the strength after 20 seconds passed was measured.

The compressive strength or tensile strength of the foam substrate can be appropriately adjusted depending on the raw material or foamed structure in which the substrate is used. The type of the foam base material used in the present invention is not particularly limited as long as it has the above-mentioned compressive strength and tensile strength, and copolymerization of polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-vinyl acetate can be used. A polyolefin-based foam composed of a material or the like, or a rubber-based foam composed of a polyurethane-based foam, an acrylic rubber, or another elastic material, etc., in order to easily produce a followability to the unevenness of the adherend A polyolefin-based foam can be preferably used as the thin foam substrate excellent in buffer absorption and the like.

The thickness of the foam substrate can be appropriately adjusted depending on the use, and is 50 to 1200 μm. In the case of fixing the parts of the electronic device, particularly in the case of a small, thin portable electronic device, the thickness of the substrate is preferably 50 to 250 μm, more preferably 75 to 150 μm, since a thin tape thickness is required.

Further, the tensile strength of the foam substrate is 300 ~ 1500N / cm ^2, preferably 500 ~ 1300N / cm ^2, more preferably 700 ~ 1200N / cm ^2. The elongation at break is from 100 to 1000%, preferably from 300 to 700%. By the tensile strength or the foam base material cut into the above range, it is possible to prevent the processability of the double-sided tape from being deteriorated or peeled off, and the workability of the attachment work is lowered even in the foamed soft base material.

The above tensile strength is the maximum measured by a TENSILON tensile tester in a sample having a length of 2 cm and a width of 1 cm in an environment of 23 ° C ‧50% RH at a tensile speed of 300 mm/min. strength.

The foam base material is a crosslinked polyolefin resin foam which is supplied to an extruder by a polyolefin resin and a thermally decomposable foaming agent. In the melt-kneading, the foamable polyolefin-based resin sheet which is formed by extruding into a sheet shape from an extruder is crosslinked by an electron beam, and then obtained by foaming, stretching, and thinning. The polyolefin-based resin may be a conventionally known one, and is preferably a material containing 40% by mass or more of a polyethylene-based resin obtained by using a metallocene containing a tetravalent transition metal. Further, after the foam is foamed, the foam may be sliced in the thickness direction, and then stretched by a hot roll and taped to produce.

In order to improve the adhesion to the adhesive layer or other layers, the foam substrate can be subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone, ultraviolet treatment, and easy application of a treatment agent. . The surface treatment can achieve excellent adhesion to the adhesive by setting the wetting index of the wetting agent to 36 mN/m or more, preferably 40 mN/m.

[Adhesive layer]

The adhesive composition constituting the adhesive layer of the double-sided tape for waterproofing of the present invention may be an adhesive composition for a double-sided tape as long as it forms an adhesive layer having the above characteristics. As the adhesive composition, an acrylic adhesive composition which is a copolymer of (meth) acrylate or (meth) acrylate and another monomer alone can be preferably used. The acrylic copolymer to be formed is used as a base polymer, and an additive such as a tackifier resin or a crosslinking agent is blended therein as needed.

Examples of the (meth) acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and uncle. Butyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isodecyl (meth) acrylate, cyclohexyl (meth) acrylate, 2- One or two or more of these may be used as the monomer such as ethylhexyl methacrylate. Among them, a (meth) acrylate having an alkyl group having 1 to 8 carbon atoms, particularly n-butyl acrylate, is preferred because it is easy to ensure adhesion to a adherend and has excellent cohesive strength.

The content of the (meth) acrylate in the acrylic copolymer is preferably from 80 to 98.5% by mass, more preferably from 90 to 98.5% by mass, based on the monomer component constituting the acrylic copolymer.

Further, the acrylic copolymer used in the present invention may be a copolymer of a highly polar vinyl monomer, and examples of the highly polar vinyl monomer include a monomer having a hydroxyl group, a monomer having a carboxyl group, and a fluorene. Amine-based monomers and the like.

As the monomer having a hydroxyl group, a hydroxyl group-containing (meth) acrylate such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate or 4-hydroxybutyl group can be used. Methyl) acrylate, 6-hydroxyhexyl (meth) acrylate, and the like.

As the monomer having a carboxyl group, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth)acrylic acid dimer, crotonic acid or the like can be used, and among them, acrylic acid is preferably used as a copolymerization component.

Further, examples of the monomer having a guanamine group include N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, N,N-dimethylpropenamide, and the like. .

Examples of the other highly polar vinyl monomer include a sulfonic acid group-containing monomer such as vinyl acetate, ethylene oxide modified succinic acid acrylate, or 2-acrylamide-2-methylpropane sulfonic acid.

The content of the highly polar vinyl monomer is preferably from 1.5 to 20% by mass, more preferably from 1.5 to 10% by mass, most preferably from 2 to 8% by mass, based on the monomer component constituting the acrylic copolymer. By containing a highly polar vinyl monomer in this range, it is easy to adjust the cohesive force, the holding force, and the adhesive force of the adhesive within an appropriate range.

When an isocyanate-based crosslinking agent is used as the crosslinking agent, the vinyl monomer having a functional group reactive therewith is preferably a vinyl monomer having a hydroxyl group, particularly preferably 4-hydroxybutyl (meth)acrylate. 6-hydroxyhexyl (meth) acrylate. The content of the hydroxyl group-containing vinyl monomer to be reacted with the isocyanate crosslinking agent is preferably 0.01 to 1.0% by mass, particularly preferably 0.03 to 0.3% by mass, based on the monomer component constituting the acrylic copolymer.

The acrylic copolymer can be obtained by copolymerization by a known polymerization method such as a solution polymerization method, a monolithic polymerization method, a suspension polymerization method, or an emulsion polymerization method, and the water resistance of the adhesive is preferably a solution polymerization method or a bulk polymerization method. . The starting method of the polymerization can be arbitrarily selected by using a heat of an azo-based thermal polymerization initiator such as a peroxide such as a benzoyl sulfhydryl group or a ruthenium laurate or a azobisisobutyronitrile. The initial method, or an initial method of ultraviolet irradiation using an acetophenone-based, benzoin ether-based, benzyl ketal-based, mercaptophosphine-based, benzoin-based, or benzophenone-based photopolymerization initiator Or the method of electron ray.

The molecular weight of the acrylic copolymer is a standard polystyrene-equivalent weight average molecular weight measured by a gel permeation chromatography (GPC) of 40 to 1.6 million, preferably 60 to 1,000,000.

In the acrylic pressure-sensitive adhesive composition used in the present invention, in order to improve the adhesion to the adherend, it is preferred to use a tackifier resin. Examples of the tackifier resin include rosin, polymerized rosin, polymerized rosin ester, rosin phenol, stabilized rosin ester, heterogeneous rosin ester, hydrogenated rosin ester, terpene, and terpene phenol. A petroleum resin system or a (meth) acrylate resin. When used in an emulsion type adhesive composition, it is preferred to use an emulsion type tackifying resin.

Among them, a non-homogeneous rosin ester-based tackifying resin, a polymerized rosin ester-based tackifying resin, a rosin-based tackifying resin, a hydrogenated rosin ester-based tackifying resin, and a (meth) acrylate-based resin are preferable.

The softening point of the tackifying resin is not particularly specified, and is 30 to 180 ° C, preferably 70 to 140 ° C. In addition, one or two or more kinds of tackifying resins may be used. Higher adhesion properties can be expected by blending a tackifying resin having a high softening point.

The blending ratio of the acrylic copolymer and the tackifying resin is preferably 5 to 40 parts by weight, more preferably 10 to 30 parts by weight, based on 100 parts by weight of the acrylic copolymer. By making the ratio of the two to be in this range, it is easy to ensure adhesion to the adherend.

In the acrylic pressure-sensitive adhesive composition, in order to increase the cohesive force of the pressure-sensitive adhesive layer, it is preferred to crosslink the adhesive. Examples of such a crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a metal chelate crosslinking agent, and an aziridine crosslinking agent. Among them, a crosslinking agent of a type which is added after the completion of the polymerization to carry out the crosslinking reaction is more preferably an isocyanate crosslinking agent which is rich in reactivity with the (meth)acrylic copolymer and an epoxy crosslinking. Agent. Examples of the isocyanate crosslinking agent include tolylene diisocyanate, naphthalene 1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, and trishydroxymethyl modification. Toluene diisocyanate or the like. Particularly preferred is a trifunctional polyisocyanate compound. Examples of the trifunctional isocyanate compound include tolylene diisocyanate, a trimethylolpropane adduct thereof, and triphenylmethane isocyanate.

As an index of the degree of crosslinking, the value of the gel fraction of the insoluble matter after the adhesion of the adhesive layer to the toluene for 24 hours was measured. The gel fraction is preferably from 25 to 70% by mass. If it is more preferably 30 to 60% by mass, and most preferably 35 to 55% by mass, the cohesiveness and the adhesion are excellent.

In addition, the measurement of the gel fraction was performed as follows. The adhesive composition was applied on the release sheet so that the thickness after drying was 65 μm, dried at 100 ° C for 5 minutes, and the material aged at 40 ° C for two days was cut into 50 mm squares as a sample. Then, the weight (G1) before the toluene immersion of the above sample was measured in advance, and the toluene-insoluble matter of the sample which was immersed in the toluene solution at 23 ° C for 24 hours was separated by filtration through a metal mesh of 300 mesh, and the measurement was performed. The weight (G2) of the residue after drying at 110 ° C for 1 hour was determined according to the following formula.

Gel fraction (% by mass) = (G2/G1) × 100

As an additive, if necessary, a plasticizer, a softener, an antioxidant, a glass or a plastic fiber, a filler such as a microsphere, a microbead, a metal powder, a coloring agent such as a pigment, a dye, or the like may be added to the adhesive composition. A known additive such as a leveling agent, a tackifier, a hydrophobic agent, or an antifoaming agent.

In the adhesive layer used in the double-sided tape for waterproofing of the present invention, the peak of the loss tangent (tan δ) at a frequency of 1 Hz is preferably -30 ° C to 0 ° C, more preferably -20 ° C to -5 ° C. By setting the peak of the loss tangent of the adhesive layer to this range, it is easy to impart excellent adhesion to the adherend at normal temperature.

The loss tangent (tan δ) is a storage elastic modulus (G') and a loss elastic modulus (G" obtained by measurement of dynamic viscoelasticity caused by temperature dispersion, and the equation tan δ = G" / G' Find out. The measurement of the dynamic viscoelasticity caused by temperature dispersion can obtain the peak value of the loss tangent (tan δ) at a certain frequency.

The dynamic viscoelastic property can be selected by appropriately selecting the kind and ratio of the monomer used in the copolymer constituting the adhesive, the kind of the polymerization initiator and the amount thereof, the kind of the crosslinking agent or the tackifying resin, and The amount of use, the polymerization method, and the like are adjusted.

The dynamic viscoelastic property of the above adhesive layer is defined by the loss angle tangent of the dynamic viscoelastic spectrum at a specific frequency and a specific temperature, or the loss tangent and the storage elastic modulus, and further, by displaying the dynamic viscoelasticity in a specific frequency. The peak of the loss tangent of the spectrum, or the peak of the loss tangent, is specified. In the measurement of dynamic viscoelasticity, a viscoelasticity tester (manufactured by Rehometric Co., Ltd., trade name: ARES 2KSTD) was used, and the test piece was sandwiched between parallel disks as a measuring portion of the test machine, and measured at a frequency of 1 Hz. Storage elastic modulus (G') and loss elastic modulus (G") at 50 ° C to 150 ° C. The test piece was formed into an adhesive layer having a thickness of about 2 mm and sandwiched between parallel disks for measurement.

The thickness of the adhesive layer used in the present invention is such that it is easy to ensure adhesion to the adherend even when a thin adhesive tape is formed, and the thickness of one side is preferably from 10 to 100 μm, more preferably from 30 to 80 μm.

[Waterproof double-sided tape]

The double-sided tape of the present invention exhibits an appropriate adhesion to the adherend by using the above-mentioned foam base material and the adhesive layer, and can effectively prevent the intrusion of water from the adhesion gap, and has excellent waterproof function. .

As an embodiment of the double-sided tape for waterproofing of the present invention, a structure in which a foam base material is a center core and an adhesive layer is provided on both surfaces of the base material is used as a basic configuration. The substrate and the adhesive layer may be laminated directly or may have other layers. These methods can be appropriately selected depending on the intended use, and when further imparting dimensional stability or tensile strength to the tape, a laminate layer such as a polyester film can be provided, and a light shielding layer can be provided when imparting light shielding properties to the tape, and when light reflection is ensured A light reflecting layer can be provided. When these other layers are provided, a water-repellent layer is used as the other layer.

As the light-shielding layer, a substance formed of an ink containing a coloring agent such as a pigment is easily used, and a layer composed of a black ink is preferably used because it is excellent in light-shielding property. As the reflective layer, a layer formed of a white ink can be conveniently used. The thickness of these layers is preferably 2 to 20 μm, more preferably 4 to 6 μm. When the thickness is within this range, curling of the substrate due to hardening shrinkage of the ink is less likely to occur, and the workability of the tape is good.

The double-sided tape for waterproofing of the present invention can be produced by a conventionally known method. For example, a direct printing method in which an acrylic pressure-sensitive adhesive composition is applied and dried on a surface of another layer laminated directly on a foam substrate or on a foam base, or a release sheet may be mentioned. A transfer method in which an acrylic pressure-sensitive adhesive composition is applied and dried, and then bonded to a surface of a foam substrate or other layer.

The thickness of the double-sided tape for waterproofing of the present invention can be appropriately adjusted depending on the mode of use, and is 70 to 1400 μm. In the case of fixing parts of electronic equipment, particularly in the case of small-sized and thin portable electronic devices, it is preferably 100 to 300 μm, particularly preferably 150 μm to 250 μm, since a thin tape thickness is required. By making the thickness of the tape to this thickness, it is also suitable for a thin type ‧ small portable electronic device, and an excellent waterproof function can be achieved.

The double-sided tape for waterproofing of the present invention has an after-surface strength of 1 measured by the following measurement conditions, preferably 100 to 200 N/4 cm ² , more preferably 120 to 180 N/4 cm ² .

The measurement conditions of the above surface strength 1 are as follows.

1) Two sheets of double-sided tape with a width of 5 mm and a length of 4 cm were adhered in parallel on an acrylic plate having a thickness of 2 mm and a thickness of 5 cm at 23 ° C.

2) Then, a rectangular smooth ABS plate having a diameter of 1 cm, a thickness of 2 mm, and a size of 10 × 15 cm was provided in the center portion, and an acrylic plate with a double-sided tape made of 1) was adhered to make an acrylic plate. The center of the ABS plate was pressed in the same manner as the center of the ABS plate, and then placed at 23 ° C for 1 hour as a test piece.

3) The acrylic plate was pressed from the ABS side of the test piece through the hole of the ABS plate, and the strength of the acrylic plate peeling was measured by a tensile tester equipped with a stainless steel probe having a diameter of 8 mm at a condition of 10 mm/min.

Further, the double-sided tape for waterproofing of the present invention has a surface bonding strength 2 measured by the following measurement conditions, preferably from 250 to 600 mJ, more preferably from 350 to 600 mJ.

The measurement conditions of the above surface strength 2 are as follows.

1) Cut the double-sided tape into 2cm squares and stick it on the acrylic plate with a thickness of 2mm and 2cm.

2) Adhere the acrylic plate with double-sided tape to the polyamine plate (adding 40% by mass of glass fiber) with a diameter of 1 cm at the center and a thickness of 2 mm and 4 cm to make the center of the acrylic plate The center of the polyamide plate was uniform, and it was pressurized once with a 2 kg roller, and then left at 23 ° C for 24 hours as a test piece.

3) The test piece was placed on the stainless steel base of 4 cm in shape, 3 cm in length, and 5 mm in thickness with the polyamine side facing up.

4) A 100 g-weight brass cone having a projection of 5 mm in diameter and 1 cm in length at the tip of the polyacetamide was continuously dropped from a height of 10 cm at intervals of 10 cm (three times per stage), and measurement was confirmed. The height at which the tape was peeled off or destroyed on the test piece.

5) The drop energy mJ (= 9.8 × height (m) × 100 g) was calculated from the measurement results.

The double-sided tape for waterproofing of the present invention exhibits an appropriate adhesion to an adherend, and can effectively prevent the intrusion of water from the gap, and has an excellent waterproof function. Therefore, even in the case of the thinning, the volume limitation in the casing is strict, and it is difficult to provide a water-tight member of the water-sealing member in other ways, and the waterproof function can be effectively imparted. As a specific use mode, for example, an electronic electronic device such as an electronic organizer, a mobile phone, a PHS, a camera, or a music player can be applied to the bonding of the protective panel and the frame of the information display portion, and the sticker between the frames. The bonding of the assembly, the frame, the tablet digital key or the input device such as the touch panel, the bonding of the frame and the decorative sheet, and the fixing of various other members or modules.

Example

(Modulation of Adhesive Solution A)

In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen gas inlet, 96.4 parts by weight of butyl acrylate, 3.5 parts by weight of acrylic acid, and 0.1 parts by weight of 2-hydroxyethyl acrylate were used as polymerization. 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a starting agent was dissolved in a solvent consisting of 100 parts by weight of ethyl acetate, and polymerized at 70 ° C for 12 hours to obtain a weight average molecular weight of 800,000 (polystyrene conversion) An acrylic copolymer. Then, 10 parts by weight of PENSEL D135 (pentaerythritol ester of polymerized rosin) manufactured by Arakawa Chemical Co., Ltd. and Super Ester A100 manufactured by Arakawa Chemical Co., Ltd. (non-homogeneous rosin glycerin) were added to 100 parts by weight of the acrylic copolymer. 10 parts by weight of the ester, and ethyl acetate was added thereto to uniformly mix to obtain an adhesive solution A having a nonvolatile content of 40%.

(Modulation of Adhesive Solution B)

In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel, and a nitrogen inlet, 44.9 parts by weight of butyl acrylate, 50 parts by weight of 2-ethylhexyl acrylate, 2 parts by weight of acrylic acid, and vinyl acetate 3 were used. 1 part by weight, 0.1 part by weight of 4-hydroxybutyl acrylate, and 0.1 part by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator are dissolved in a solvent consisting of 100 parts by weight of ethyl acetate to 70 The mixture was polymerized at ° C for 12 hours to obtain an acrylic copolymer having a weight average molecular weight of 700,000 (in terms of polystyrene). Then, 10 parts by weight of PENSEL D135 (pentaerythritol ester of polymerized rosin) manufactured by Arakawa Chemical Co., Ltd. was added to 100 parts by weight of the acrylic copolymer, and ethyl acetate was added thereto to uniformly mix to obtain an adhesive solution having a nonvolatile content of 45%. B.

[Example 1]

(modulation of double-sided tape)

1.1 parts by weight of "Coronet L-45" (isocyanate-based crosslinking agent, solid content: 45%) manufactured by Nippon Polyurethane Co., Ltd. was added to 100 parts by weight of the above-mentioned adhesive solution A, and after stirring for 15 minutes, the thickness after drying was The film was applied to a peel-treated PET film having a thickness of 75 μm in a manner of 50 μm, and dried at 80 ° C for 3 minutes to form an adhesive layer.

Next, in a black polyolefin-based foam (thickness: 100 μm, expansion ratio of 3 times, 25% compressive strength: 70 kPa, tensile strength: 1010 N/cm ² , surface soak index of 60 mN/m by corona treatment) On both sides of the film, after laminating one piece of the above-mentioned adhesive layer, lamination was carried out by a roll having a linear pressure of 5 kg/cm. Then, it was aged at 40 ° C for 48 hours to obtain a double-sided tape having a thickness of 200 μm.

[Examples 2 to 8, Comparative Examples 1, 2]

A double-sided tape was obtained in the same manner as in Example 1 except that the foam base material described in Tables 1 to 3 was used instead of the black polyolefin foam.

[Embodiment 9]

A double-sided tape was obtained in the same manner as in Example 1 except that the adhesive solution B was used instead of the adhesive solution A.

[Comparative Example 3]

In a stainless steel reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet, 90 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of acrylic acid, and "Darocure 1173" 0.2 weight manufactured by Ciba Specialty Chemicals Co., Ltd. were mixed. Then, ultraviolet rays were irradiated with a fluorescent chemical lamp to obtain an acrylic resin slurry having a polymerization rate of 5% by mass. 0.3 parts by weight of polypropylene glycol diacrylate ("APG700" manufactured by Shin-Nakamura Chemical Co., Ltd.), 0.1 part by weight of "Lucirin TPO" manufactured by BASF Corporation, and glass microspheres (Fuji Silysia Co., Ltd.) were added to 100 parts by weight of the acrylic resin syrup. The produced "H-40", having a density of 0.4 g/cm ³ and an average particle diameter of 50 μm) of 8.55 parts by weight, was uniformly mixed, and subjected to vacuum defoaming to prepare an active energy ray-curable composition.

The composition was applied to a peel-treated PET film having a thickness of 75 μm so as to have a thickness of 200 μm after being cured by ultraviolet rays, and a PET film having a thickness of 75 μm which was subjected to release treatment was attached, and then a fluorescent chemical lamp (wavelength 300) was used. ~400 nm, center of 350 nm), the irradiation intensity on one side was 0.32 mW/cm ² , and ultraviolet rays were irradiated from both sides for 6 minutes to obtain a double-sided tape having a thickness of 200 μm.

[Comparative Example 4]

In a stainless steel reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet, 90 parts by weight of isooctyl acrylate, 10 parts by weight of acrylic acid, and 0.2 parts by weight of "Irgacure 651" manufactured by Ciba Specialty Chemicals Co., Ltd. were mixed, and then The ultraviolet ray was irradiated with a fluorescent chemical lamp to obtain an acrylic resin syrup having a polymerization rate of 5% by mass. 0.3 parts by weight of 1,6-hexanediol diacrylate, 0.1 parts by weight of "Irgacure 651" manufactured by Ciba Specialty Chemicals Co., Ltd., and glass microspheres ("H manufactured by Fuji Silysia Co., Ltd.") were added to 100 parts by weight of the acrylic resin syrup. -40", density 0.4 g/cm ³ , average particle diameter 50 μm) 8.55 parts by weight, 0.2 parts by weight of a fluorine-based surfactant ("TG-656" manufactured by Daikin Industries Co., Ltd.), and uniformly mixed to carry out vacuum defoaming . The mixture was supplied to a vibrating stirring mixer, and nitrogen gas was mixed and dispersed at about 15% by volume to obtain a coating liquid containing fine bubbles having an average diameter of 400 μm or less.

The coating liquid was applied to a peel-treated PET film having a thickness of 75 μm so as to have a thickness of 200 μm after being cured by ultraviolet rays, and a PET film having a thickness of 75 μm which was peeled off was attached, and then a fluorescent chemical lamp (wavelength) was used. 300 to 400 nm, center of 350 nm), with a single-side irradiation intensity of 0.32 mW/cm ² , and ultraviolet rays were irradiated from both sides for 6 minutes to obtain a double-sided tape having a thickness of 200 μm.

The foam base material used in the above examples and comparative examples, and the double-sided tape obtained in the above examples and comparative examples were evaluated as follows. The results obtained are shown in Tables 1-3.

[Flower direction of the foam substrate and average bubble diameter in the width direction]

The foam substrate was cut into 1 cm in both the width direction and the flow direction, and the central portion of the cut surface of the cut foam substrate was enlarged by a scanning electron microscope (SEM) (manufactured by Hitachi, Ltd., S-2380N). The cross section of the foam base material in the width direction or the flow direction is photographed so that the photograph can accommodate the entire length of the cut surface of the foam base material in the thickness direction of the entire substrate. The obtained photograph was measured for all the bubble diameters present in the cut surface having an actual length of 2 mm before the enlargement in the flow direction or the width direction, and the average bubble diameter was calculated from the average value.

[Average bubble diameter in the thickness direction of the foam substrate]

The thickness of the foam base material photographed by SEM was measured, and SEM photographing was performed under the same conditions as the measurement of the average bubble diameter in the flow direction of the foam base material. In the obtained photograph, the number of bubbles in the thickness direction existing in any place of the foam base material was visually counted, and the average bubble diameter in the thickness direction was calculated by the following formula.

Average bubble diameter in the thickness direction (μm) = thickness of the foam substrate (μm) / number of bubbles

It was measured at any three places, and the average value was made into the average bubble diameter in the thickness direction.

[double-sided tape thickness]

The peeling film was peeled off from the double-sided tape, and the measurement was performed using a Dial-thickness-gauge G type manufactured by Ozaki Seisakusho Co., Ltd.

[Tensile strength of double-sided tape]

The double-sided adhesive sheet (the peeling film was peeled off) which was processed into a test piece having a line spacing of 2 cm (flow direction of the polyolefin-based foam) and a width of 1 cm was cut at a tensile speed of 300 mm/min, and the measurement was performed at this time. Strength of.

[face after strength 1]

1) Two sheets of double-sided tape having a width of 5 mm and a length of 4 cm were attached in parallel to an acrylic plate (Mitsubishi Riyang Acrylite MR200 "trade name" having a thickness of 2 mm and 5 cm square at 23 ° C in a hue: transparent).

2) Next, a rectangular ABS plate (manufactured by TAKIRON Co., Ltd., hue: natural color, no wrinkles) having a thickness of 1 cm and a hole having a diameter of 1 cm toward the center portion, and the center of the acrylic plate coincides with the center of the ABS plate. In the manner, an acrylic plate with a double-sided tape produced by 1) was attached, and it was pressed once with a 2 kg roller, and then left at 23 ° C for 1 hour to serve as a test piece.

3) The acrylic plate was pressed from the ABS side of the test piece through the hole of the ABS plate, and the strength of the peeled acrylic plate was measured by a tensile tester equipped with a stainless steel probe having a diameter of 8 mm at a condition of 10 mm/min.

[face after strength 2]

1) After cutting the double-sided tape into 2 cm square, it was attached to an acrylic plate having a thickness of 2 mm and 2 cm square.

2) Polyamine plate (Titsui Chemical Co., Ltd.), having a diameter of 1 cm and a hole of 1 cm in the center, having a diameter of 1 cm, is added to the center of the acrylic plate. An acrylic plate with a double-sided tape was attached to the center of the amine plate in the same manner, and the mixture was pressurized once with a 2 kg roller, and then left at 23 ° C for 24 hours to serve as a test piece.

3) The test piece was placed on a stainless steel base having a shape of 4 cm square, a length of 3 cm, and a thickness of 5 mm with the polyamine side facing upward.

4) Passing through the hole on the polyamine side, a 100 g-weight brass cone having a protrusion having a diameter of 5 mm and a length of 1 cm at the tip end is continuously dropped on the acrylic plate at a height of 10 cm at intervals of 10 cm (one stage three times), and the measurement is possible. The height at which the tape was peeled off or broken on the test piece was confirmed.

5) The drop energy mJ (= 9.8 × height (m) × 100 g) was calculated from the measurement results.

[Water resistance test 1]

1) A double-sided tape is made into a frame-shaped sample having a shape of 65 mm × 45 mm and a width of 2 mm, attached to an acrylic plate having a thickness of 2 mm and a shape of 65 mm × 45 mm, and then attached to an ABS plate having a thickness of 2 mm and a shape of 65 mm × 45 mm. After pressurizing one time with a 2 kg roller, it was left at 23 ° C for 24 hours to serve as a test piece.

2) After immersing the test piece in a 5 mass% surfactant solution (made by tapping diluted Joy made by P&G company) at 23 ° C for 10 minutes, the test piece was taken out, and the step of placing for 30 cycles was carried out for 10 minutes, and then It was evaluated whether or not water immersion into the frame when immersed in the solution again.

○: no water immersion ×: water immersion

[Water resistance test 2]

1) A double-sided tape is made into a frame-shaped sample having a shape of 65 mm × 45 mm and a width of 2 mm, attached to an acrylic plate having a thickness of 2 mm and a shape of 65 mm × 45 mm, and then attached to a rectangular ABS having a thickness of 2 mm and a shape of 150 mm × 100 mm. The center of the board (Figure 1). After pressurizing one time with a 2 kg roller, it was left at 23 ° C for 24 hours to serve as a test piece.

2) On the base of the DuPont impact tester (manufactured by Tester Industries Co., Ltd.), a length of 150 mm, a width of 100 mm, and a height of 45 mm are provided. A glyph measuring table (manufactured by aluminum having a thickness of 5 mm) was placed thereon with a test piece and an acrylic plate side down (Fig. 2). A stainless steel core having a diameter of 25 mm and a mass of 300 g was dropped from the height of 50 cm from the side of the ABS plate, and five impacts were applied to the central portion of the ABS plate at intervals of 10 seconds (Fig. 3). When the impact was applied and the acrylic plate fell off, the test was terminated.

3) The test piece to which the impact was applied was immersed for 10 minutes at 5 ° C in a 5 mass% surfactant solution (manufactured by tapping a powder manufactured by P&G Co., Ltd.), and the test piece was taken out and placed in a 30-cycle stand for 10 minutes. In the step, then, it was evaluated whether or not water immersion into the frame when immersed in the solution again.

◎: no water immersion, no change in appearance of the foam; ○: no water immersion, but slight cracks were observed in a part of the foam layer; ×: water immersion was observed, or the acrylic plate was detached during the impact stage.

As shown in the above Examples 1 to 9, the double-sided tape for waterproofing of the present invention has excellent adhesion and water repellency to an adherend. On the other hand, the double-sided tape of Comparative Example 1 had a low surface strength 2, and the foaming property was not able to withstand the water repellency test 2 due to cracking of the foam at the time of the drop impact. Further, the double-sided tapes of Comparative Examples 2 to 4 were found to have water immersion in the water repellency test 1, and water repellency could not be achieved. Further, in the double-sided tapes of Comparative Examples 3 to 4, the tape was peeled off even when the water repellency test 2 was dropped.

1. . . double-sided tape

2. . . Acrylic board

3. . . ABS board

4. . . The place where the core is pressed

5. . . Falling impact

6. . . Glyph measuring platform

FIG. 1 is a conceptual diagram showing a test piece for the water repellency test 2.

2 is a view showing the test piece for the water repellency test 2 fixed to the state in which the acrylic plate is downloaded as viewed from the bottom surface side of the measurement table 6. A conceptual diagram of the state of the font measuring table 6 (thickness 5 mm aluminum).

Fig. 3 is a conceptual diagram showing an operation of giving a drop impact.

Claims (8)

A double-sided tape for waterproofing, which is a double-sided tape having a foam base material and an adhesive layer, wherein the foam base material has a 25% compressive strength of 50 to 160 kPa and a tensile strength of 300 to 1500 N. /cm ² . The double-sided tape for waterproofing according to the first aspect of the invention, wherein the foam substrate has an average cell diameter in the thickness direction of 1 to 100 μm, and an average cell diameter in the flow direction and the width direction is 1.2 to 700 μm. The double-sided tape for waterproofing according to the first or second aspect of the invention, wherein the ratio of the average cell diameter in the flow direction of the foam substrate to the average cell diameter in the thickness direction is 1.2 to 15. The double-sided tape for waterproofing according to the first or second aspect of the invention, wherein the ratio of the average cell diameter in the width direction of the foam substrate to the average cell diameter in the thickness direction is 1.2 to 15. The double-sided tape for waterproofing according to claim 1 or 2, wherein the foam base material is a polyolefin-based foam base material. The double-sided tape for waterproofing according to claim 1 or 2, wherein the foaming substrate has a foaming ratio of 2 to 5 times. The double-sided tape for waterproofing according to claim 1 or 2, wherein the adhesive layer contains an acrylic copolymer and a tackifying resin, and the content of the tackifying resin relative to 100 parts by mass of the acrylic copolymer is 5 to 40. The viscous resin is selected from the group consisting of rosin, polymerized rosin, polymerized rosin ester, rosin phenol, stabilized rosin ester, heterogeneous rosin ester, hydrogenated rosin ester, terpene, hydrazine. Enphenol-based, petroleum resin, and (methyl) One or more resins selected from the group consisting of acrylate resins. The double-sided tape for waterproofing according to claim 1 or 2, wherein the adhesive layer has a gel fraction of 25 to 70%.