KR101142880B1 - Water-proof double coated pressure sensitive adhesive tape - Google Patents

Abstract

An object of this invention is to provide the double-sided adhesive tape which shows favorable adhesiveness with a to-be-adhered body even if it is thin tape thickness, and was excellent in waterproofing function.

In order to solve the said subject, in the double-sided adhesive tape which has a foam base material and an adhesive layer, by using 25-% compressive strength 40-160 kPa and tensile strength 300-1500 N / cm <^2> as a foam base material, Even when bonding rigid bodies together, the waterproof double-sided adhesive tape which has the outstanding adhesiveness between a double-sided adhesive tape and a to-be-adhered body, and prevents invasion of water can be achieved.

Double sided adhesive tape, foam base

Description

Waterproof double-coated adhesive tape {WATER-PROOF DOUBLE COATED PRESSURE SENSITIVE ADHESIVE TAPE}

TECHNICAL FIELD This invention relates to the waterproof double-sided adhesive tape centered on a foam base material.

BACKGROUND ART In portable electronic devices such as an electronic notebook, a mobile phone, a PHS, a camera, a music player, and the like, a double-sided adhesive tape is used for fixing various members and modules, including bonding of a protective panel and a case of an information display unit. In order to secure a competitive advantage in the market, various functions are required, and one of them is required to provide a waterproof function.

As an adhesive tape used for fixing parts of an electronic device, it has the maximum value of loss tangent (tan-delta) in the temperature range of -40--15 degreeC, for example, and the surface adhesive strength with respect to a specific to-be-adhered body is 19 N / cm. The double-sided adhesive sheet in which ^two or more adhesive layers were provided on both surfaces of the support body is disclosed (refer patent document 1). By having a specific adhesive layer, the said double-sided adhesive sheet has favorable adhesive force, and has the outstanding impact resistance that it is hard to produce the fall of a component by the impact at the time of the fall of an object. However, in the bonding between rigid bodies, as in the bonding between the protective panel and the case, the double-sided adhesive sheet hardly obtains perfect adhesion at the bonding surface with the adherend, so that a slight gap may cause immersion. .

A double-sided adhesive tape having excellent adhesiveness, which has a foam and a double-sided acrylic pressure-sensitive adhesive layer having a holding time in a holding test at -25 ° C or lower and 0 ° C at which the maximum value of loss tangent (tanδ) is -25 ° C or less. An adhesive tape is disclosed (refer patent document 2). The said double-sided adhesive tape is excellent in the adhesiveness to a to-be-adhered body, and can bond together between members suitably at the time of adhesion | attachment of members. However, it is difficult to suppress even a slight gap at the interface between the member and the adhesive layer only by using the foam as a base material, and if there is a gap or moxibustion where water can invade even a part of the interface, there is a possibility of intrusion of water therefrom. Because of the expansion, it was difficult to realize waterproofness. In particular, in the use of portable electronic devices, in the case where narrow tape width or thin tape thickness is required due to the narrowing of softening and the thinning of thin screens in recent years, sufficient waterproofing is provided. It was difficult.

[Patent Document 1] Japanese Patent Application Laid-Open No. 2005-187513

[Patent Document 2] Japanese Patent Application Laid-Open No. 2005-281360

The problem to be solved by this invention is providing the double-sided adhesive tape which shows the favorable adhesiveness with a to-be-adhered body even if it is thin tape thickness, and was excellent in waterproofing function.

Furthermore, in addition to the said subject, it is providing the waterproof double-sided adhesive tape which is excellent in impact resistance, and is suitable for a portable electronic device use.

As a result of earnest research, the inventors of the present invention use a foam base material having a specific flexibility and strength as a base material, thereby realizing excellent adhesion between the double-sided adhesive tape and the adherend even when bonding rigid bodies together, thereby effectively preventing water immersion. We found out what we could do and solved the said subject.

That is, this invention is a double-sided adhesive tape which has a foam base material and an adhesive layer, and provides the waterproof double-sided adhesive tape whose 25% compressive strength of the said foam base material is 40-160 kPa, and tensile strength is 300-1500 N / cm <^2> .

The waterproof double-sided adhesive tape of the present invention exhibits good adhesion with the adherend, can effectively prevent ingress of water from the adhesion gap, and has an excellent waterproof function. For this reason, thinning progresses, the volume limitation in a case is severe, and even if it is difficult to provide a separate water sealing means, it can effectively provide a waterproof function.

The waterproof double-sided adhesive tape of this invention is a double-sided adhesive tape which has a foam base material and an adhesive layer, 25-% compressive strength of the said foam base material is 40-160 kPa, and tensile strength is 300-1500 N / cm <^2> .

[Foam base material]

The foam base material used for this invention is a foam base material of 25% compressive strength 40-160 kPa, Preferably 50-140 kPa, More preferably, 60-130 kPa. By using the foam base material of 25% of compressive strength in this range, it has the outstanding adhesiveness with a to-be-adhered body, and also adheres suitably also to the to-be-adhered body which has an uneven shape or roughness, and has the outstanding adhesiveness. Moreover, since the foam base material of the said compressive strength has moderate cushioning property, since the pressure at the time of sticking concentrates on a junction part, and it is easy to extrude the air which exists in an adhesive interface, water invades even when joining rigid bodies. Excellent adhesion without creating a gap can be realized.

The foam structure of the foam base material used in the present invention is preferable because the foam structure of the foam base material can be effectively prevented from immersion from the cut surface of the foam base material. Although the bubble shape which forms an independent bubble structure is not specifically limited, Since the independent bubble of the shape where the average bubble diameter of a flow direction, the width direction, or both is longer than the average bubble diameter of the thickness direction of a foam has moderate cushioning property, it is preferable. Do.

The average bubble diameter in the thickness direction of the foam base material is preferably 1 to 100 μm, more preferably 10 to 50 μm, and the average bubble diameter in the flow direction and the width direction of the foam base material is preferably 1.2 to 700 μm, More preferably, it is 10-500 micrometers, More preferably, it is 50-300 micrometers. By making the average bubble diameter into the said range, even if the width | variety of a double-sided tape is narrowed, it is easy to form an independent bubble, and the submerged path | route from the foam substrate cross section can be interrupted suitably.

Although the ratio of an average bubble diameter is not specifically limited, The ratio (average bubble diameter / thickness direction in a flow direction) of the average bubble diameter in the flow direction of a foam base material with respect to the average bubble diameter in the thickness direction of a foam base material 1.2-15 are preferable, and, as for the average bubble diameter in ,, 3-8 are more preferable. Moreover, the ratio (average bubble diameter in the width direction / average bubble diameter in the width direction) of the average bubble diameter in the width direction of a foam base material with respect to the average bubble diameter in the thickness direction of a foam base material is 1.2. -15 is preferable, More preferably, it is 3-8. Moreover, it is further more preferable that it is the said ratio range in both a flow direction and a width direction. When the said ratio is 1.2 or more, it is easy to ensure the flexibility of the thickness direction, and followability improves. Moreover, if it is 15 times or less, the variation of the flexibility and tensile strength of the flow direction and width direction of a foam base material hardly arise.

In addition, as for the ratio of the average bubble diameter of a flow direction and a width direction, when making a flow direction 1, 0.25-4 times are preferable, More preferably, it is 0.33-3 times. If it is the said ratio range, the softness | flexibility of the flow direction and width direction of a foam base material, and the dispersion | variation in tensile strength will hardly arise.

The average bubble diameter of the width direction of a foam base material and a flow direction is measured with the following method. First, a foam base material is cut | disconnected in the width direction and the flow direction by 1 cm. Next, after expanding the cut surface center part of the cut | disconnected foam base material by 50 times with a scanning electron microscope (SEM), the width direction of a foam base material or the width direction of a foam base material so that the cut surface of a foam base material may be contained in a photograph over the full length of the base material thickness direction. Photograph the cross section in the flow direction. In the obtained photograph, all the bubble diameters which exist in the cut surface for 2 mm for the actual length before expansion of a flow direction or the width direction are measured, and an average bubble diameter is computed from the average value.

The average bubble diameter of the thickness direction of a foam base material is measured with the following method. First, the thickness of the foam base material photographed by SEM is measured. Next, SEM photographing is performed on the conditions similar to the average bubble diameter measurement of the flow direction of a foam base material. Next, in the obtained photograph, the number of bubbles of the thickness direction which exists in arbitrary places of a foam base material is visually counted, and the average bubble diameter of the thickness direction is computed from the following formula | equation.

Average bubble diameter (micrometer) in thickness direction = thickness (micrometer) of foam base material / number of bubbles

This is measured at three arbitrary places, and the average value is called the average bubble diameter in the thickness direction.

Since the foam structure of a foam base material adjusts compressive strength and tensile strength to the said range, and it is easy to realize the outstanding adhesiveness with a to-be-adhered body, it is preferable to make the foaming ratio 2 to 5 times, and to make 2.4 to 4 times. More preferred.

Moreover, 25% compressive strength superimposes the sample cut | disconnected by 50 mm square until it becomes about 10 mm in thickness. The sample is sandwiched by a plate with a larger area than the sample, the sample is compressed to about 2.5 mm (25% of the original thickness) at 23 mm, and stopped, and the strength after 20 seconds is measured.

The compressive strength and tensile strength of a foam base material can be suitably adjusted according to the raw material and foam structure of the base material to be used. Although the kind of foam base material used for this invention will not be restrict | limited especially if it has the said compressive strength and tensile strength, Polyolefin foam and poly which consist of polyethylene, a polypropylene, ethylene propylene copolymer polymer, ethylene-vinyl acetate copolymer polymer, etc. Rubber foams composed of urethane foams, acrylic rubbers, other elastomers, and the like can be used, and among these, polyolefin foams are preferable because they are easy to produce a thin foam substrate having excellent trackability to unevenness on the surface of the adherend, buffer absorption, and the like. Can be used.

Although the thickness of a foam base material may adjust suitably according to the aspect to be used, it is 50-1200 micrometers. In the case of fixing a part of an electronic device, especially a small and thin portable electronic device, since a thin tape thickness is required, it is preferable that the base material thickness is 50-250 micrometers, and it is preferable that it is 75-150 micrometers.

Further, the tensile strength of the foam substrate 300 ~ 1500N / cm ^2, preferably 500 ~ 1300N / cm ^2, and more preferably 700 ~ 1200N / cm ^2. Cutting elongation is 100 to 1000%, Preferably it is 300 to 700%. Even if the tensile strength or the cutting is a foamed base material of the above-mentioned range, even if the flexible base material is foamed, it is possible to suppress deterioration of workability of the double-sided adhesive tape, cracking, and deterioration of sticking workability.

In addition, the above-mentioned tensile strength measures the sample of 2 cm of line length and 1 cm of width using the Tensileron tensile tester under the measurement conditions of 300 mm / min of tensile velocity in the environment of 23 degreeC-50% RH. One is maximum strength.

Such a foam base material is obtained by supplying a polyolefin resin and a thermal decomposition foaming agent to an extruder to melt kneading and foaming, stretching and thinning the cross-linked foamable polyolefin resin sheet formed by extruding the sheet from an extruder into an electron beam, followed by foaming, stretching and thinning. Polyolefin resin foam is mentioned. Although a conventionally well-known thing can be used for polyolefin resin, It is preferable to contain 40 mass% or more of polyethylene-type resin obtained using the metallocene compound containing a tetravalent transition metal. In addition, after foaming the foam, the foam sheet may be sliced in the thickness direction, then stretched with a heat roll, and then surface treated.

In order to improve adhesiveness with an adhesive layer or another layer, the foam base material may be surface-treated, such as a corona treatment, a flame treatment, a plasma treatment, a hot air treatment, ozone-ultraviolet treatment, and application | coating of an antiadhesive treatment agent. In the surface treatment, a good wettability with the pressure-sensitive adhesive is obtained when the wetness index by the wetting reagent is 36 mN / m or more, preferably 40 mN / m.

[Adhesive Layer]

The adhesive composition which comprises the adhesive layer of the waterproof double-sided adhesive tape of this invention should just be able to form the adhesive layer which has the said characteristic, and the adhesive composition used for a normal double-sided adhesive tape can be used. As the said adhesive composition, the acrylic copolymer which consists of (meth) acrylate alone or the copolymer of (meth) acrylate and another monomer is made into a base polymer, and additives, such as tackifying resin and a crosslinking agent, are mix | blended with this as needed. An acrylic adhesive composition can be used preferably.

As (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, for example and monomers such as n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (meth) acrylate, and 2-ethylhexyl methacrylate. 1 type, or 2 or more types of is used. Especially, the C1-C8 (meth) acrylate of an alkyl group, especially n-butylacrylate is preferable because it is easy to ensure adhesiveness with a to-be-adhered body, and is excellent in cohesion force.

It is preferable that it is 80-98.5 mass% in the monomer component which comprises an acrylic copolymer, and, as for content of the (meth) acrylate in an acryl-type copolymer, it is more preferable that it is 90-98.5 mass%.

Moreover, the acryl-type copolymer used for this invention may copolymerize a high polar vinyl monomer, As a high polar vinyl monomer, the monomer which has a hydroxyl group, the monomer which has a carboxyl group, the monomer which has an amide group, etc. are mentioned.

As a monomer which has a hydroxyl group, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth Hydroxyl group-containing (meth) acrylates, such as) acrylate, can be used.

As a monomer which has a carboxyl group, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth) acrylic acid dimer, crotonic acid, etc. can be used, Especially, it is preferable to use acrylic acid as a copolymerization component.

Moreover, as a monomer which has an amide group, N-vinylpyrrolidone, N-vinyl caprolactam, acryloyl morpholine, acrylamide, N, N- dimethyl acrylamide, etc. are mentioned.

Examples of other high polar vinyl monomers include sulfonic acid group-containing monomers such as vinyl acetate, ethylene oxide-modified succinate acrylate, and 2-acrylamide-2-methylpropanesulfonic acid.

It is preferable that content of a high polar vinyl monomer is 1.5-20 mass% in the monomer component which comprises an acryl-type copolymer, It is more preferable that it is 1.5-10 mass%, It is further more preferable that it is 2-8 mass%. By containing in the said range, it is easy to adjust the cohesion force, holding force, and adhesiveness of an adhesive to the suitable range.

Moreover, when using an isocyanate type crosslinking agent as a crosslinking agent, as a vinyl monomer which has a functional group reacting with this, a hydroxyl-containing vinyl monomer is preferable, and 4-hydroxybutyl (meth) acrylate and 6-hydroxyhexyl (meth) Acrylate is particularly preferred. It is preferable that it is 0.01-1.0 mass% of the monomer component which comprises an acrylic copolymer, and, as for content of the hydroxyl-containing vinyl monomer reacting with an isocyanate type crosslinking agent, 0.03-0.3 mass% is especially preferable.

Although an acryl-type copolymer can be obtained by copolymerizing by well-known polymerization methods, such as solution polymerization method, block polymerization method, suspension polymerization method, and emulsion polymerization method, solution polymerization method and block polymerization method are preferable at the water resistance of an adhesive. The method of initiation of polymerization is also a method of initiation by heat using a peroxide-based, such as benzoyl peroxide or lauroyl peroxide, or an azo-based thermal polymerization initiator such as azobisisobutylnitrile, acetophenone, benzoin ether, or benzylke. The method of starting by ultraviolet irradiation or the method by electron beam irradiation can be arbitrarily selected using a photopolymerization initiator of a de-systemic, acylphosphine oxide-based, benzoin-based or benzophenone-based.

As for the molecular weight of the said acryl-type copolymer, the weight average molecular weight in standard polystyrene conversion measured by a gel permeation chromatograph (GPC) is 40-1,600,000, Preferably it is 60-1 million.

In the acrylic adhesive composition used for this invention, in order to improve adhesiveness with a to-be-adhered body, it is preferable to use tackifying resin. As tackifying resin, rosin type, polymeric rosin type, polymeric rosin ester type, rosin phenol type, stabilized rosin ester type, disproportionated rosin ester type, hydrogenated rosin ester type, terpene type, terpene phenol type, petroleum resin type, (meth) An acrylate resin etc. can be illustrated. When using for the emulsion type adhesive composition, it is preferable to use emulsion type tackifying resin.

Especially, disproportionated rosin ester tackifying resin, polymerization rosin ester tackifying resin, rosin phenol tackifying resin, hydrogenated rosin ester tackifying resin, and (meth) acrylate type resin are preferable.

Although the softening point of tackifying resin is not specifically defined, it is 30-180 degreeC, Preferably it is 70 degreeC-140 degreeC. In addition, you may use 1 type, or 2 or more types of tackifying resin. By mix | blending tackifying resin with a high softening point, high adhesive performance can be expected.

It is preferable that content of tackifying resin with respect to 100 mass parts of acryl-type copolymers is 5-40 mass parts, and, as for the compounding ratio when using an acrylic copolymer and tackifying resin, it is preferable that it is 10-30 mass parts. By making ratio of both into the said range, adhesiveness with a to-be-adhered body becomes easy to be ensured.

In an acrylic adhesive composition, in order to raise the cohesion force of an adhesive layer, it is preferable to crosslink an adhesive. As such a crosslinking agent, an isocyanate type crosslinking agent, an epoxy type crosslinking agent, a metal chelate type crosslinking agent, an aziridine type crosslinking agent, etc. are mentioned. Especially, the crosslinking agent of the type which adds after completion | finish of superposition | polymerization and advances a crosslinking reaction is preferable, and isocyanate type crosslinking agent and epoxy type crosslinking agent which are rich in reactivity with a (meth) acrylic copolymer are preferable. Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, trimethylolpropane modified tolylene diisocyanate and the like. Particularly preferred are trifunctional polyisocyanate compounds. As a trifunctional isocyanate type compound, tolylene diisocyanate, these trimethylol propane adducts, triphenylmethane isocyanate, etc. are mentioned.

As an index of the degree of crosslinking, the value of the gel fraction for measuring the insoluble content after immersing the pressure-sensitive adhesive layer in toluene for 24 hours is used. The gel fraction is preferably 25 to 70 mass%. More preferably, both cohesion and adhesiveness are good in it being the range of 30-60 mass%, More preferably, it is the range of 35-55 mass%.

In addition, the measurement of a gel fraction is based on the following. The adhesive composition is coated on the release sheet so that the thickness after drying is 65 μm, dried at 100 ° C. for 5 minutes, and cut at 40 ° C. for 2 days at 50 mm angle to obtain a sample. Next, the weight (G1) before the toluene immersion of the sample was measured in advance, and the toluene insoluble fraction of the sample after immersion in the toluene solution at 23 ° C. for 24 hours was separated by filtration with a 300 mesh gold mesh, and 110 The weight (G2) of the residue after drying at 1 degreeC for 1 hour is measured, and a gel fraction is calculated | required by the following formula.

Gel fraction (mass%) = (G2 / G1) * 100

As additives, plasticizers, softeners, antioxidants, fillers such as glass or plastic fibers, balloons, beads, metal powders, colorants such as pigments and dyes, leveling agents, thickeners, water repellents, and antifoaming agents, as necessary. Known things, such as these, can be added arbitrarily to an adhesive composition.

As for the adhesive layer used for the waterproof double-sided adhesive tape of this invention, the peak value of loss tangent (tan-delta) in frequency 1Hz becomes like this. Preferably it is -30 degreeC-0 degreeC, More preferably, it is -20 degreeC --5 degreeC. . By making the peak value of the loss tangent of an adhesive layer into the said range, it becomes easy to provide favorable adhesiveness with a to-be-adhered body under normal temperature.

The loss tangent tan δ is obtained from the equation of tanb = G '' / G 'from the storage modulus G' and the loss modulus G '' obtained by the dynamic viscoelasticity measurement by temperature dispersion. From the dynamic viscoelasticity measurement by temperature dispersion, the peak value of the loss tangent tan δ at a certain frequency is obtained.

The dynamic viscoelastic properties can be adjusted by appropriately selecting the kind and proportion of monomers used in the copolymer constituting the pressure sensitive adhesive, the kind and amount of the polymerization initiator, the amount and amount of the crosslinking agent and the tackifying resin, the polymerization method and the like.

The dynamic viscoelastic properties of the pressure-sensitive adhesive layer described above are defined by the loss tangent of the dynamic viscoelastic spectrum, or the loss tangent and the storage elastic modulus at a specific frequency and a specific temperature, and the loss of the dynamic viscoelastic spectrum at the specific frequency. It defines by the temperature which shows the peak of a tangent, or the peak value of a loss tangent. In the measurement of the dynamic viscoelasticity, a test piece was sandwiched between parallel disks, which are measuring sections of the tester, using a viscoelastic tester (trade name: Ares 2KSTD), and the storage modulus from -50 ° C to 150 ° C at a frequency of 1 Hz. (G ') and loss modulus (G' ') are measured. The test piece forms an adhesive layer having a thickness of about 2 mm, and is sandwiched between parallel discs and measured.

Since the adhesiveness with a to-be-adhered body is easy to ensure the thickness of the adhesive layer used for this invention as a thin tape, it is preferable that it is 10-100 micrometers in thickness of a single side, and it is more preferable that it is 30-80 micrometers. .

[Double Sided Adhesive Tape for Waterproofing]

The double-sided tape of this invention shows favorable adhesiveness with a to-be-adhered body by using the said foam base material and an adhesive layer, can effectively prevent the intrusion of water from an adhesion gap, and has the outstanding waterproof function.

As an embodiment of the waterproof double-sided adhesive tape of this invention, the structure which has an adhesive layer provided in the both surfaces of the said base material centering on a foam base material is made into a basic structure. The substrate and the pressure-sensitive adhesive layer may be directly laminated or may have other layers. What is necessary is just to select these aspects suitably according to a use use, and when providing dimensional stability and tensile strength to a tape, laminate layers, such as a polyester film, and light-shielding layer, when giving a light-shielding property to a tape, When securing the light reflection layer may be provided. When providing these other layers, a waterproof layer is used as the said other layer.

As a light shielding layer, what is formed with the ink containing coloring agents, such as a pigment, is used simply, and since the layer which consists of black ink is excellent in light-shielding property, it is used preferably. As the reflective layer, a layer formed of white ink can be used simply. As thickness of these layers, 2-20 micrometers is preferable, and 4-6 micrometers is especially preferable. By making thickness into the said range, the curl of the base material by hardening shrinkage of an ink hardly arises, and the processability of a tape becomes favorable.

The waterproof double-sided adhesive tape of this invention can be manufactured by a well-known conventional method. For example, after directly applying the acrylic pressure-sensitive adhesive composition to the foam base material or on the surface of another layer laminated on the foam base material, or applying the acrylic pressure-sensitive adhesive composition to the release sheet and drying it, the foam base material or The transfer method bonding to another layer surface is mentioned.

Although the thickness of the waterproof double-sided adhesive tape of this invention may be suitably adjusted according to the aspect to be used, it is 70-1400 micrometers. In the case of fixing a part of an electronic device, especially a small and thin portable electronic device, since a thin tape thickness is calculated | required, it is preferable that it is 100-300 micrometers, and it is especially preferable that it is 150 micrometers-250 micrometers. By setting the thickness of the tape, the tape thickness can be suitably applied to thin and small portable electronic devices, and a good waterproof function can be realized.

Waterproof double-sided pressure-sensitive adhesive tape of the present invention, to the surface adhesion strength of 1 measured by the measuring conditions, and preferably in the 100 ~ 200N / 4cm ^2, more preferably 120 ~ 180N / 4cm ^2.

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

1) At 23 ° C, two double-sided adhesive tapes having a width of 5 mm and a length of 4 cm are attached in parallel to a 5 cm square acrylic plate at a thickness of 2 mm.

2) Next, the acrylic plate with double-sided pressure-sensitive adhesive tape produced in 1) was made into a rectangular flat ABS plate having a thickness of 2 mm and a 10 × 15 cm in which a hole having a diameter of 1 cm was provided at the center, and the center of the acrylic plate and the ABS plate. It affixes so that this may match and pressurizes 1 round trip with a 2 kg roller, and it is left to stand at 23 degreeC for 1 hour, and it is set as a test piece.

3) Press the acrylic plate at 10 mm / min with the tensile tester which attached the stainless steel probe of diameter 8mm through the hole of ABS plate from the ABS side of a test piece, and measure the strength by which an acrylic plate peels.

Moreover, it is preferable that the surface adhesive strength 2 measured by the following measurement conditions of the waterproof double-sided adhesive tape of this invention is 250-600 mJ, and it is preferable that it is 350-600 mJ.

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

1) After cut | disconnecting a double-sided adhesive tape at a 2 cm square, it sticks to an acrylic plate of thickness 2mm and a 2 cm square.

2) The acryl plate with a double-sided adhesive tape coincides with the polyamide plate (40 mass% glass fiber addition) of thickness 2mm and 4cm with a hole of diameter 1cm in the center, and the center of the acryl plate matches the center of the polyamide plate. It adhere | attaches so that it may pressurize 1 round trip with a 2 kg roller, and it is left to stand at 23 degreeC for 24 hours, and it is set as a test piece.

3) The test piece is placed on a stainless steel pedestal of 4 cm square, 3 cm long and 5 mm thick with the polyamide side up.

4) A 100 mm-weight brass cone having a diameter of 5 mm and a protrusion of length 1 cm at the tip was continuously dropped (3 times per step) at 10 cm intervals to the specimen through the hole on the polyamide side. Measure the height when the tape is peeled or broken.

5) The falling energy mJ (= 9.8 x height (m) x 100 g) is calculated from the measurement result.

The waterproof double-sided adhesive tape of the present invention exhibits good adhesion with the adherend, can effectively prevent ingress of water from the adhesion gap, and has an excellent waterproof function. For this reason, thinning progresses, the volume limitation in a case is severe, and even if it is difficult to provide a separate water-sealing means, it can effectively provide a waterproof function. As a specific use aspect, for example, in portable electronic devices, such as an electronic notebook, a mobile telephone, a PHS, a camera, a music player, bonding of the protection panel and case of an information display part, bonding of cases, a case and a sheet-like ten key It can be suitably used for bonding an input device such as a ten key or a touch panel, bonding a case and a decorative sheet, fixing other members or modules, and the like.

(Preparation of Adhesive Solution A)

96.4 parts by mass of butyl acrylate, 3.5 parts by mass of acrylic acid, 0.1 parts by mass of 2-hydroxyethyl acrylate, and 2,2 as polymerization initiators in a reaction vessel equipped with a stirrer, a reflux cooler, a thermometer, a dropping funnel and a nitrogen gas inlet. 0.1 mass part of "-azobisisobutyronitrile was melt | dissolved in the solvent which consists of 100 mass parts of ethyl acetate, and superposed | polymerized at 70 degreeC for 12 hours, and the weight average molecular weight obtained the acrylic copolymer of 800,000 (polystyrene conversion). Next, with respect to 100 mass parts of acrylic copolymers, 10 mass parts of Pencel D135 (pentaerythritol ester of a polymerized rosin) by Arakawa Chemical Co., Ltd., and 10 mass parts of superester A100 (glycerin ester of disproportionated rosin) by Arakawa Chemical Co., Ltd. were made. Addition and ethyl acetate were added and mixed uniformly, and the adhesive solution A of 40% of non volatile matter was obtained.

(Preparation of Adhesive Solution B)

44.9 parts by mass of butyl acrylate, 50 parts by mass of 2-ethylhexyl acrylate, 2 parts by mass of acrylic acid, and 3 parts by mass of vinyl acetate, in a reaction vessel equipped with a stirrer, a reflux cooler, a thermometer, a dropping funnel and a nitrogen gas inlet. 0.1 mass part of 4-hydroxybutyl acrylate and 0.1 mass part of 2,2'- azobisisobutyronitrile as a polymerization initiator are melt | dissolved in the solvent which consists of 100 mass parts of ethyl acetate, and they superpose | polymerize at 70 degreeC for 12 hours, and weight The average molecular weight obtained the acrylic copolymer of 700,000 (polystyrene conversion). Next, 10 mass parts of Pencel D135 (pentaerythritol ester of a polymerized rosin) by Arakawa Chemical Co., Ltd. was added with respect to 100 mass parts of acryl-type copolymers, ethyl acetate was added, it mixed uniformly, and the adhesive solution B of 45% of non volatile matters was mixed. Got it.

Example 1

(Production of Double-sided Adhesive Tape)

The PET film of 75 micrometers in thickness which carried out peeling process after adding 1.1 mass parts of "Coronate L-45" (isocyanate type crosslinking agent, 45% of solid content) by the Japan Polyurethane Company, and stirring for 15 minutes with respect to 100 mass parts of said adhesive solutions A It coated on it so that thickness after drying might be 50 micrometers, and it dried at 80 degreeC for 3 minutes, and formed the adhesive layer.

Next, the above-mentioned pressure-sensitive adhesive on both sides of the black polyolefin-based foam (thickness: 100 µm, foaming ratio 3 times, 25% compressive strength: 70 kPa, tensile strength: 1010 N / cm ² ) with the wetness index of 60 mN / m by corona treatment. The layers were bonded one by one and then laminated with a roll of linear pressure 5 kg / cm. Thereafter, the mixture was aged at 40 ° C. for 48 hours to obtain a double-sided adhesive tape having a thickness of 200 μm.

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

The double-sided adhesive tape was obtained by the same method as Example 1 except having used the foam base material of Tables 1-3 instead of the black polyolefin foam.

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 solution B was used instead of the pressure-sensitive adhesive solution A.

[Comparative Example 3]

90 mass parts of 2-ethylhexyl acrylate, 10 mass parts of acrylic acid, and 0.2 mass parts of "Tarocure 1173" by Chiba-Specialty-Chemical Co., Ltd. were mixed with the stainless reaction container provided with the stirrer, the reflux cooler, the thermometer, and the nitrogen gas inlet. Then, the ultraviolet-ray was irradiated with the fluorescent chemical lamp and the acrylic syrup of 5 mass% of polymerization rates was obtained. 0.3 mass parts of polypropylene glycol diacrylates ("APG700" by Shin-Nakamura Chemical Co., Ltd.), 0.1 mass part of "Lucirine TPO" by BASF Corporation, and glass microballoons (made by Fuji-Silicon Co., Ltd.) with respect to 100 mass parts of this acrylic syrup. H-40 ", density 0.4g / cm <^3> , average particle diameter: 50 micrometers), 8.55 mass parts was added, it mixed uniformly, and it vacuum-defoamed, and prepared the active energy ray curable composition.

After coating this composition so that the thickness after UV hardening might be set to 200 micrometers on the PET film of thickness 75 micrometers which carried out the peeling process, and after bonding the PET film of thickness 75 micrometers which peeled, it bonded a fluorescent chemical lamp (wavelength 300-400 nm, 350 nm). Center), ultraviolet-ray was irradiated for 6 minutes from both sides by the irradiation intensity of 0.32 mW / cm <^2> on one side, and the double-sided adhesive tape of thickness 200micrometer was obtained.

[Comparative Example 4]

90 mass parts of isooctyl acrylates, 10 mass parts of acrylic acid, and 0.2 mass parts of "irgacure 651" by Chiba-Specialty-Chemicals were mixed with the stainless steel reaction container provided with the stirrer, the reflux cooler, the thermometer, and the nitrogen gas inlet. Then, the ultraviolet-ray was irradiated with the fluorescent chemical lamp and the acrylic syrup of 5 mass% of polymerization rates was obtained. 0.3 mass part of 1, 6- hexanediol diacrylate, 0.1 mass part of "irgacure 651" made from Chiba-Specialty-Chemical Company, glass microballoons ("H- made by Fuji-Silician company) with respect to 100 mass parts of this acrylic syrup 40 ", density 0.4g / cm <^3> , average particle diameter 50micrometer) 8.55 mass part, 0.2 mass part of fluorine-type surfactants (" TG-656 "by Daikin Kogyo Co., Ltd.) are added, it mixes uniformly, and it vacuum-defoases. This mixture was supplied to a vibratory stirring mixer, and nitrogen was mixed and dispersed at about 15 volume% to obtain a coating liquid containing fine bubbles having an average diameter of 400 µm or less.

After coating this coating liquid so that the thickness after UV hardening might be set to 200 micrometers on the PET film of thickness 75 micrometers which carried out the peeling process, and bonding the PET film of thickness 75 micrometers which carried out the peeling process, a fluorescent chemical lamp (wavelength 300-400 nm, 350 nm center), the ultraviolet-ray was irradiated for 6 minutes from both sides by 0.32 mW / cm < ² > of irradiation intensity on one side, and the double-sided adhesive tape of thickness 200micrometer was obtained.

The following evaluation was performed about the double-sided adhesive tape obtained by the foam base material used by the said Example and the comparative example, the said Example, and the comparative example. The obtained results are shown in Tables 1-3.

[Average bubble diameter in flow direction and width direction of foam base material]

The foam base material was cut in the width direction and the flow direction in 1 cm, and the cut surface center part of the cut foam base material was enlarged 50 times with a scanning electron microscope (SEM) (made by Hitachi Seisakusho, S-2380N), and then The cross section of the width direction or the flow direction of the foam base material was photographed so that a cut surface may be contained in a photograph over the full length of the base material thickness direction. In the obtained photograph, all the bubble diameters which existed in the cut surface for 2 mm for the actual length before expansion of a flow direction or the width direction were measured, and the average bubble diameter was computed from the average value.

[Average bubble diameter in thickness direction of foam base material]

The thickness of the foam base material photographed by SEM was measured, and SEM photographing was performed on the conditions similar to the average bubble diameter measurement of the flow direction of a foam base material. In the obtained photograph, the number of bubbles of the thickness direction which exists in arbitrary places of a foam base material was visually counted, and the average bubble diameter of the thickness direction was computed from the following formula | equation.

Average bubble diameter (micrometer) in thickness direction = thickness (micrometer) of foam base material / number of bubbles

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

[Double sided adhesive tape thickness]

After peeling a peeling film from a double-sided adhesive tape, it measured with the dial thickness gauge G type made by Ozaki Seisakusho.

Tensile Strength of Double-Sided Adhesive Tape

The strength at the time of cut | disconnecting the double-sided adhesive sheet (peeling film peeled off) processed to the test piece of 2 cm (flow direction of a polyolefin foam) and 1 cm of width | variety at the tensile velocity of 300 mm / min was measured.

[Adhesion strength 1]

1) A 2 mm thick, 5 cm square acrylic plate (Mitsubishi Rayon Co., Ltd. acrylate MR200 "trade name", color: transparent) is attached in parallel with two double-sided adhesive tapes of 5 mm in width and 4 cm in length. .

2) Next, an acrylic plate with a double-sided adhesive tape produced in 1) was made in a rectangular ABS plate (Takyron Corporation, color: natural, no wrinkles) having a thickness of 2 mm and a 10 × 15 cm with a hole of 1 cm in diameter at the center. After affixing so that the center of an acryl board and the center of an ABS board may correspond, it pressurizes 1 round trip with a 2 kg roller, it is left to stand at 23 degreeC for 1 hour, and it is set as a test piece.

3) The acrylic plate was pressed at 10 mm / min with the tensile tester which attached the stainless steel probe of diameter 8mm from the ABS side of the test piece through the hole of the ABS board, and the strength which peeled off the acrylic plate was measured.

[Adhesion strength 2]

1) After cut | disconnecting a double-sided adhesive tape at a 2 cm square, it sticks to an acrylic plate of thickness 2mm and a 2 cm square.

2) The acrylic plate with a double-sided adhesive tape is an acrylic plate on a polyamide plate (with Mitsui Chemical Co., Ltd. Lenny "trade name", 40wt% glass fiber addition) of thickness 2mm, 4cm with a hole of 1cm in diameter in the center. It is affixed so that the center of a metal and the center of a polyamide plate may correspond, and it pressurizes 1 round trip with a 2 kg roller, and it is left to stand at 23 degreeC for 24 hours, and is used as a test piece.

3) The test piece is placed on a stainless steel pedestal of 4 cm square, 3 cm long and 5 mm thick with the polyamide side up.

4) A 100 mm-weight brass cone having a diameter of 5 mm and a protrusion of length 1 cm at the tip was continuously dropped (3 times per step) at 10 cm intervals to the specimen through the hole on the polyamide side. Measure the height when the tape is peeled or broken.

5) Drop energy mJ (= 9 * 8 * height (m) * 100g) was computed from the measurement result.

[Waterproof Test 1]

1) A double-sided adhesive tape was produced with a liquid-shaped sample having an outer shape of 65 mm x 45 mm and a width of 2 mm, and affixed to an acrylic plate having a thickness of 2 mm and an outer shape of 65 mm x 45 mm, and then a thickness of 2 mm and an outer shape of 65 mm x 45 mm. It affixes on an ABS board, pressurizes 1 round trip with a 2 kg roller, and is left to stand at 23 degreeC for 24 hours to make a test piece.

2) After immersing the test piece in a 5 mass% surfactant solution (produced by diluting P & G Co., Ltd.) with tap water for 10 minutes at 10 ° C., the test piece was taken out and left for 10 minutes. The immersion in the liquid smoke when immersed was evaluated.

○: no immersion

×: Inundation

[Waterproof Test 2]

1) A double-sided adhesive tape was produced with a liquid-shaped sample having an outer shape of 65 mm x 45 mm and a width of 2 mm, and affixed to an acrylic plate having a thickness of 2 mm and an outer shape of 65 mm x 45 mm, and then a rectangular ABS plate having a thickness of 2 mm and an outer shape of 150 mm x 100 mm. It affixes to a center part (FIG. 1). After pressurizing 1 round trip with a 2kg roller, it was left at 23 ° C for 24 hours to prepare a test piece.

2) On the pedestal of the DuPont Impact Tester (manufactured by Tester Sangyo Co., Ltd.), a '-' measuring bench (5 mm thick aluminum) measuring 150 mm in length, 100 mm in width and 45 mm in height is placed thereon. The plate side was raised downward (FIG. 2). A stainless steel core having a diameter of 25 mm and a mass of 300 g is dropped from a height of 50 cm from the ABS plate side, and an impact is applied five times at intervals of 10 seconds to the center portion of the ABS plate (FIG. 3). Moreover, when impact was added and an acrylic plate fell out, the test was complete there.

3) After immersing the impacted test piece in a 5 mass% surfactant solution (produced by diluting P & G Co., Ltd. with tap water) at 23 ° C. for 10 minutes, the test piece was taken out and left for 10 minutes, and then subjected to 30 cycles. Again, the presence or absence of immersion in the liquid lead when immersed in the solution was evaluated.

◎: No immersion, no change in appearance of foam

(Circle): There is no immersion, but a micro thermal image is recognized in a part of foam layer.

X: The acrylic plate fell out at the stage of the flooding or dropping impact

Table 1

[Table 2]

[Table 3]

Like the said Examples 1-9, it was clear that the waterproof double-sided adhesive tape of this invention has the outstanding adhesiveness and waterproofness with a to-be-adhered body. On the other hand, the double-sided adhesive tape of Comparative Example 1 had a low surface adhesive strength 2 and was unable to withstand the waterproof test 2 due to the tearing of the foam during drop impact. In addition, the double-sided adhesive tapes of Comparative Examples 2 to 4 were immersed in the waterproof test 1, and the waterproof properties could not be realized. In addition, in the double-sided adhesive tape of Comparative Examples 3-4, even if the dropping impact of the waterproof test 2 occurred, the tape fell off.

1 is a conceptual diagram showing a test piece for waterproof test 2. FIG.

2 is a bottom surface of the measuring table 6, in which a test piece for waterproof test 2 is fixed to a 'c' shaped measuring table 6 (made of aluminum having a thickness of 5 mm) in a state where an acrylic plate is placed downward. Conceptual view from the side.

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

[Description of the code]

One… Double-sided adhesive tape, 2... Acrylic plate, 3... ABS plate, 4... A place of intense feeling, 5... 6 cores for drop impacts; '-' Measuring platform

Claims (10)

A double-sided adhesive tape having a foam base material and a pressure-sensitive adhesive layer, which is used for fixing parts of portable electronic devices, has a thickness of 70 to 300 µm, and flows to an average bubble diameter in the thickness direction of the foam base material. The ratio of the average bubble diameter of the direction is 1.2-15, the ratio of the average bubble diameter of the width direction with respect to the average bubble diameter in the thickness direction of the said foam base material is 1.2-15, and the foaming ratio of the said foam base material is 2-5 times And a 25% compressive strength of 50 to 160 kPa and a tensile strength of 300 to 1500 N / cm ² of the foam base material. The method of claim 1, The waterproof double-sided adhesive tape whose average bubble diameter in the thickness direction of the said foam base material is 1-100 micrometers, and the average bubble diameter of a flow direction and the width direction is 1.2-700 micrometers. delete delete The method according to claim 1 or 2, Waterproofing double-sided adhesive tape, wherein the foam base material is a polyolefin foam base material. delete The method according to claim 1 or 2, The said adhesive layer contains an acrylic copolymer and tackifying resin, and the waterproof double-sided adhesive tape whose content of tackifying resin with respect to 100 mass parts of acrylic copolymers is 5-40 mass parts. The method according to claim 1 or 2, The fixing of the parts of the portable electronic device is performed by bonding the protective panel and the case of the information display unit of the portable electronic device, bonding the cases, bonding the case and the ten key on the sheet, bonding the case and the touch panel input device, or the case and Waterproof double-sided adhesive tape which is the bonding of the decorative sheet. A method of fixing between components of a portable electronic terminal to impart a waterproof function to a fixing portion, wherein the fixing between the components is performed at 25% compressive strength of 50 to 160 kPa, tensile strength of 300 to 1500 N / cm ² , in the thickness direction. The ratio of the average bubble diameter of the flow direction with respect to an average bubble diameter is 1.2-15, The ratio of the average bubble diameter of the width direction with respect to the average bubble diameter in a thickness direction is 1.2-15, The polyolefin type whose foaming ratio is 2-5 times. It has a pressure-sensitive adhesive layer on both sides of the foam base material of, and is bonded and fixed with a double-sided adhesive tape having a thickness of 70 ~ 300㎛, the method for providing a waterproof function to a portable electronic terminal. 10. The method of claim 9, The fixing between the components of the portable electronic terminal may include bonding of the protective panel and the case of the information display unit of the portable electronic terminal, bonding of the cases, bonding of the case and the ten key on the sheet, bonding of the case and the touch panel input device, or the case. And a waterproofing function for a portable electronic terminal, which is a bonding of a decorative sheet.

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