CN114316821B

CN114316821B - adhesive tape

Info

Publication number: CN114316821B
Application number: CN202111506159.7A
Authority: CN
Inventors: 川西道朗; 平山高正; 西尾昭德
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2017-02-28
Filing date: 2018-02-28
Publication date: 2023-12-12
Anticipated expiration: 2038-02-28
Also published as: TW201835266A; TWI751091B; TW202140718A; CN108504298B; TW202140709A; KR102412256B1; CN114316821A; CN108504298A; JP2018141086A; KR20180099506A; JP6908395B2; TWI732101B; TWI751092B

Abstract

The application provides an adhesive tape which contains thermally expandable microspheres, has excellent releasability after heating, and has less residual adhesive on an adherend. The adhesive tape of the present application is an adhesive tape comprising a substrate and an adhesive layer disposed on at least one surface of the substrate, wherein the adhesive layer contains thermally expandable microspheres, the adhesive tape is heated at a heating rate of 3 ℃/min in a thermo-mechanical analysis, the deformation starting point is set as point A, the point at which the deformation amount of the adhesive tape reaches the maximum after passing through the point A is set as point C, and the time from point A to point B is 45 seconds to 200 seconds when the point at which the deformation amount reaches half of the deformation amount at point C in the period from point A to point C is set as point B.

Description

Adhesive tape

The present application is a divisional application of application number 201810165873.6, the title of which is "adhesive tape" and having application date of 2018, 2 and 28.

Technical Field

The present application relates to an adhesive tape. More particularly, the present application relates to an adhesive tape that can exhibit easy peelability in response to thermal stimulus.

Background

In the process of manufacturing electronic parts, as an adhesive tape used for temporarily fixing a work, an adhesive tape that exhibits adhesion at the time of temporary fixing and easy peelability at the time of unnecessary fixing is known. As one of such pressure-sensitive adhesive tapes, a pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer and thermally expandable microspheres therein has been studied (for example, patent document 1). The pressure-sensitive adhesive tape exhibits a desired adhesive force at a relatively low temperature represented by normal temperature, and on the other hand, the heat-expandable microspheres expand by heating, thereby generating irregularities on the surface of the pressure-sensitive adhesive layer and deteriorating the adhesive force. In such an adhesive tape, the adherend can be peeled off by the action of gravity alone.

On the other hand, the easily releasable pressure-sensitive adhesive tape is required to reduce the residual adhesive at the time of releasing the adherend, and similarly, the pressure-sensitive adhesive tape using thermally expandable microspheres has a problem of reducing the residual adhesive. The adhesive tape is particularly problematic when applied to fragile adherends, minute adherends, adherends requiring cleanliness, and the like.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2001-131507

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide an adhesive tape containing thermally expandable microspheres, which has excellent releasability after heating and less residual adhesive on an adherend.

Solution for solving the problem

The adhesive tape of the present invention is an adhesive tape comprising a substrate and an adhesive layer disposed on at least one surface of the substrate, wherein the adhesive layer contains thermally expandable microspheres, the adhesive tape is heated at a heating rate of 3 ℃/min in a thermo-mechanical analysis, the deformation starting point is set as point A, the point at which the deformation amount of the adhesive tape reaches the maximum after passing through the point A is set as point C, and the time from point A to point B is 45 seconds to 200 seconds when the point at which the deformation amount reaches half of the deformation amount at point C in the period from point A to point C is set as point B.

In one embodiment, the time from the point B to the point C is 200 seconds or longer.

In one embodiment, the temperature at the point B is 50 to 250 ℃.

In one embodiment, the thermally expandable microspheres are composed of a shell formed of a resin and an organic solvent contained in the shell, and the thickness of the shell is 1 μm to 15 μm.

In one embodiment, the thermally expandable microspheres are composed of a shell formed of a resin having a glass transition temperature of 50 ℃ to 250 ℃ and an organic solvent contained in the shell.

In one embodiment, the heat-expandable microspheres are composed of a shell formed of a resin and an organic solvent contained in the shell, and the resin forming the shell contains at least one selected from the group consisting of a constituent unit derived from isobornyl acrylate, a constituent unit derived from methacrylonitrile, a constituent unit derived from acrylonitrile, a constituent unit derived from methyl (meth) acrylate, a constituent unit derived from vinylidene chloride, and a constituent unit derived from (meth) acrylic acid.

In one embodiment, the organic solvent has a boiling point of-50℃to 100 ℃.

In one embodiment, the adhesive layer has an elastic modulus of 0.1MPa to 500MPa obtained by nanoindentation.

In one embodiment, the adhesive constituting the adhesive layer has a gel fraction of 30 to 99% by weight.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, by appropriately controlling the deformation behavior upon heating, it is possible to provide an adhesive tape which is excellent in peelability after heating and is less in residual adhesive on the peeled adherend.

Drawings

Fig. 1 is a schematic cross-sectional view of an adhesive tape according to an embodiment of the present invention.

Fig. 2 is a diagram showing an example of measurement results when the pressure-sensitive adhesive tape according to an embodiment of the present invention is subjected to thermal mechanical analysis.

Description of the reference numerals

10. Adhesive layer

20. Substrate material

100. Adhesive tape

Detailed Description

A. Integral construction of adhesive tape

Fig. 1 is a schematic cross-sectional view of an adhesive tape according to an embodiment of the present invention. The pressure-sensitive adhesive tape 100 includes a substrate 10 and a pressure-sensitive adhesive layer 20 disposed on at least one surface (in the example shown in the figure, one surface) of the substrate 10.

The pressure-sensitive adhesive layer provided in the pressure-sensitive adhesive tape of the present invention contains thermally expandable microspheres. The thermally expandable microspheres are expandable at a prescribed temperature. The pressure-sensitive adhesive layer containing such thermally-expandable microspheres expands by heating, and thus irregularities are formed on the pressure-sensitive adhesive surface (i.e., the pressure-sensitive adhesive layer surface), thereby reducing or eliminating the adhesive force. When the pressure-sensitive adhesive tape of the present invention is used as a sheet for temporary fixation of a processed product in the processing of an electronic component (for example, a ceramic capacitor), the pressure-sensitive adhesive tape exhibits adhesion required for temporary fixation when a predetermined processing is performed on the processed product, and exhibits good peelability when the pressure-sensitive adhesive tape is peeled off from the processed product after the processing, the pressure-sensitive adhesive force is reduced or eliminated by heating. In one embodiment, the thermally expandable microspheres are composed of a shell and an organic solvent contained in the shell, and expansion occurs by volatilization of the organic solvent.

In the adhesive tape of the present invention, when the adhesive tape is heated at a heating rate of 3 ℃/min in the thermo-mechanical analysis, the time from the deformation start point to the time when the deformation amount upon expansion reaches half the maximum deformation amount is 45 seconds to 200 seconds. More specifically, the description will be given with reference to fig. 2. Fig. 2 is a diagram showing an example of measurement results when the pressure-sensitive adhesive tape according to an embodiment of the present invention is subjected to thermal mechanical analysis, and shows a relationship between temperature and deformation amount (displacement amount) of the pressure-sensitive adhesive tape in the analysis.

The adhesive tape was heated (heating rate: 3 ℃ C./min), and when the predetermined temperature was reached, the adhesive tape started to deform (expand). This time is the "deformation start point". For convenience, the deformation start point is set to point a. In addition, deformation of the adhesive tape is mainly dependent on expansion/contraction of the thermally expandable microspheres contained in the adhesive layer.

After passing the point a, if the heating is continued, the pressure-sensitive adhesive tape (substantially thermally expandable microspheres) continues to expand, and thereafter, starts to shrink. For example, when using a thermally expandable microsphere comprising a shell and an organic solvent contained in the shell, the thermally expandable microsphere expands by volatilization of the organic solvent up to a predetermined temperature, and starts to shrink at the point when all the organic solvent is volatilized. The point at which shrinkage begins is the point at which expansion and deformation of the adhesive tape reach the maximum. For convenience, this point is set to point C.

Further, the point at which the deformation amount reaches half of the deformation amount X (100 μm in the illustrated example) at the point C (the time at which the deformation amount at the time of expansion and deformation reaches half of the maximum deformation amount, 50 μm in the illustrated example) during the period from the point a to the point C is set as the point B.

In the present invention, the time from the point A to the point B is 45 seconds to 200 seconds.

In addition, the analysis conditions in the above-described thermo-mechanical analysis are as follows.

< analysis conditions >

Device name: seiko Instruments trade name "TMA/SS150" manufactured by Inc "

Measurement mode: expansion method, setting the pressure-sensitive adhesive layer to the probe side

Sample size: 5mm square

And (3) probe:

probe load: 0N

Measuring temperature range: room temperature (25 ℃ +/-5 ℃) to 250 DEG C

Heating rate: 3 ℃/min

In the present invention, by setting the time from the point a to the point B to 45 seconds to 200 seconds, an adhesive tape with less residual adhesive at the time of peeling off an adherend can be obtained. It is considered that the pressure-sensitive adhesive layer deforms (expands) with the expansion of the thermally expandable microspheres from the point a to the point B, but the pressure-sensitive adhesive layer surface has no irregularities or is minute if formed, and almost the entire surface of the pressure-sensitive adhesive layer surface is pressed by the adherend. Such a state is considered to be a state in which the adhesive interacts with softening of the adhesive by heating to promote the adhesive residue on the adherend. In the present invention, the time in such a state (i.e., the time from the point a to the point B) is set to 200 seconds or less, whereby an adhesive tape with less residual adhesive can be obtained. On the other hand, when the time from the point a to the point B is less than 45 seconds, it means that the thermally expandable microspheres expand rapidly. In such a case, there is a possibility that the adhesive may splash or the like due to a rapid change in the thermally expandable microspheres.

The time from the point a to the point B is preferably 70 seconds to 180 seconds, more preferably 90 seconds to 170 seconds. When the content is within such a range, the above-described effects become remarkable.

The time from the point B to the point C is preferably 30 seconds or more, more preferably 60 seconds or more, still more preferably 180 seconds or more, and particularly preferably 200 seconds or more. In the stage of passing through the point B and approaching the point C, the thermally expandable microspheres expand further, and as a result, irregularities are formed on the surface of the pressure-sensitive adhesive layer, and the contact surface between the pressure-sensitive adhesive layer and the adherend gradually becomes smaller. As a result, the adhesive force of the adhesive tape is reduced or eliminated. On the other hand, when the thermally expandable microspheres start to shrink through point C, the contact surface between the adhesive layer and the adherend starts to increase, and the adhesive tape again exhibits adhesiveness. That is, the adhesive tape exhibits excellent releasability from the point B until the point C is reached. By setting the time in this state to be equal to or longer than the predetermined time as described above, the time taken for the step of peeling off the adherend can be sufficiently ensured when the adhesive tape is used in the step of manufacturing electronic components and the like. Further, too short a time from point B to point C means that the thermally expandable microspheres are rapidly deformed, and that the adhesive layer component (for example, adhesive) that cannot follow the rapid deformation of the thermally expandable microspheres is subject to chip separation, and the adhesive layer component separated from the chip may cause adhesive residue.

The upper limit of the time from the point B to the point C is, for example, 3600 seconds or less, preferably 1800 seconds or less, and more preferably 1000 seconds or less. Within this range, thermally expandable microspheres having an appropriate amount of the organic solvent contained therein can be used.

In the above-mentioned thermo-mechanical analysis, the temperature at the point A (also referred to as the point A temperature) is preferably 30℃to 200℃and more preferably 40℃to 180℃and particularly preferably 60℃to 180 ℃.

In the above-mentioned thermal mechanical analysis, the temperature at the point B (also referred to as the point B temperature) is preferably 50℃to 250℃and more preferably 70℃to 200℃and still more preferably 80℃to 150 ℃. By setting the temperature at the point B to 50 ℃ or higher, unwanted release performance of the pressure-sensitive adhesive tape (e.g., release performance in a condition of high outside air temperature such as summer) can be prevented. Further, when the B-site temperature exceeds 250 ℃, deterioration, ignition, and the like of the adhesive tape may occur during a period before releasability is exhibited.

In the above-mentioned thermo-mechanical analysis, the temperature at the C-point (also referred to as the C-point temperature) is preferably 90℃to 350℃and more preferably 100℃to 200 ℃.

The adhesive force of the adhesive tape of the present invention before foaming the thermally expandable microspheres is preferably 0.2N/20mm or more, more preferably 0.2N/20 to 20N/20mm, still more preferably 2N/20 to 10N/20mm, when the adhesive surface is adhered to a polyethylene terephthalate film (for example, 25 μm thick) at an ambient temperature of 25 ℃. In such a range, for example, an adhesive tape useful as a temporary fixing sheet used in the manufacture of electronic components can be obtained. The adhesive force in this specification means by following JISZ 0237:2000 (bonding conditions: 1 round trip of 2kg roller, peeling speed: 300mm/min, peeling angle 180 ℃).

The thickness of the pressure-sensitive adhesive tape of the present invention is preferably 30 μm to 500. Mu.m, more preferably 40 μm to 300. Mu.m.

B. Adhesive layer

The adhesive layer contains thermally expandable microspheres. In practice, the adhesive layer further comprises an adhesive.

B-1 thermally expansive microspheres

Any suitable thermally expandable microspheres may be used as long as they expand by heating to form irregularities on the surface of the pressure-sensitive adhesive layer. As the thermally expandable microspheres, for example, microspheres composed of a shell and a volatile substance (typically, an organic solvent) contained in the shell can be used.

Examples of the material forming the shell include resin, glass, and metal. Among them, a resin is preferable. When a resin is used, thermally expandable microspheres that are easily expandable by softening by heating can be obtained. Further, the shell formed of the resin is advantageous in that it has a density close to that of the adhesive agent, and therefore, it is easy to disperse with high uniformity in the adhesive agent layer.

As the resin forming the shell, for example, a resin having a constituent unit derived from a monomer capable of radical polymerization can be used. Examples of the monomer include nitrile monomers such as acrylonitrile, methacrylonitrile, α -chloroacrylonitrile, α -ethoxyacrylonitrile, and fumaric nitrile; carboxylic acid monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid; vinylidene chloride; vinyl acetate; (meth) acrylic esters such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, and beta-carboxyethyl acrylate; styrene monomers such as styrene, α -methylstyrene, chlorostyrene, etc.; acrylamide monomers such as acrylamide, substituted acrylamide, methacrylamide and substituted methacrylamide. The polymer composed of these monomers may be a homopolymer or a copolymer.

The resin forming the shell may be a crosslinked material. The free volume of the polymer can be controlled by crosslinking, whereby the diffusivity of the volatile substance contained in the polymer, the swelling property of the shell, and the like can be controlled. The crosslinked material may further contain a constituent unit derived from a monomer having 2 or more polymerizable double bonds in the molecule. In one embodiment, the above-described radically polymerizable monomer is used in combination with a monomer having 2 or more polymerizable double bonds in the molecule. Examples of the monomer having 2 or more polymerizable double bonds in the molecule include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; allyl methacrylate, 1,3, 5-triacryloylhexahydro-s-triazine (triacrylforma), triallyl isocyanate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1, 4-butane diol di (meth) acrylate, 1, 9-nonane diol di (meth) acrylate, 1, 10-decane diol di (meth) acrylate, PEG #200 di (meth) acrylate, PEG #400 di (meth) acrylate, PEG #600 di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 6-hexane diol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, glycerol di (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, neopentyl glycol acrylic acid, trimethylolpropane acrylate, 2-hydroxy-3-acryloxypropyl (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 2-butyl-2-ethyl-1, 3-propane diol di (meth) acrylate, polytetramethylene diol di (meth) acrylate, phenyl glycidyl ether acrylate hexamethylene diisocyanate urethane prepolymer, phenyl glycidyl ether acrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, and the like.

In one embodiment, the shell-forming resin comprises at least one selected from the group consisting of a constituent unit derived from isobornyl acrylate, a constituent unit derived from methacrylonitrile, a constituent unit derived from acrylonitrile, a constituent unit derived from methyl (meth) acrylate, a constituent unit derived from vinylidene chloride, and a constituent unit derived from (meth) acrylic acid. When a resin having these constituent units is used, a shell having low solubility in the organic solvent contained therein and being less likely to be permeated or infiltrated by the organic solvent before heating can be formed. Further, when the resin is used, thermally expandable microspheres having good deformability due to heating can be obtained. Further, if the above monomer is used, thermal properties of the shell can be easily controlled by crosslinking or the like.

In one embodiment, methacrylonitrile and/or acrylonitrile is preferably used from the viewpoint of an improved resistance to the organic solvent of the inner package. When these monomers are used, the total content of the structural units derived from methacrylonitrile and the structural units derived from acrylonitrile is preferably 10 to 99% by weight, more preferably 20 to 99% by weight, and particularly preferably 30 to 95% by weight, relative to 100% by weight of the resin forming the shell. When the amount is in this range, thermally expandable microspheres having excellent solvent resistance and a temperature at the B-site can be easily and appropriately set can be obtained.

In one embodiment, methyl (meth) acrylate is preferably used from the viewpoint of easiness of control of the shell hardness. When methyl (meth) acrylate is used, for example, the hardness of the shell can be easily controlled by crosslinking by electron beam crosslinking or the like in combination with a crosslinkable monomer (e.g., a monomer having 2 or more polymerizable double bonds in the molecule). When methyl (meth) acrylate is used, the content of the methyl (meth) acrylate is preferably less than 65% by weight, more preferably 1% by weight to 55% by weight, and particularly preferably 1% by weight to 50% by weight, relative to 100% by weight of the resin forming the shell.

In addition, vinylidene chloride is preferably used in imparting flexibility to the shell. The amount of vinylidene chloride to be used may be set to any suitable amount depending on the glass transition temperature of the desired resin.

The thickness of the shell is preferably 15 μm or less, more preferably 7 μm or less, further preferably 5 μm or less, particularly preferably 4 μm or less. In such a range, the time from the point a to the point B can be shortened, and it is easy to set the time from the point a to the point B to 200 seconds or less as described above. The lower limit of the thickness of the shell is preferably 1 μm or more, more preferably 2 μm or more. When the content is within this range, thermally expandable microspheres that are less likely to be broken by unexpected external force or the like can be produced. In addition, when the thickness of the shell is less than 1 μm, the physical properties of the shell change due to wetting (diffusion) of the organic solvent enclosed in the shell, and as a result, the time from point B to point C may be significantly shortened. That is, by setting the upper and lower limits of the thickness of the shell to the above ranges, the thermally expandable microspheres can be rapidly expanded in the initial stage of heating (points a to B), and the thermally expandable microspheres can be easily obtained which can maintain the expanded state for a long period of time in the subsequent heating (points B to C). Further, by setting the upper and lower limits of the thickness of the shell to the above ranges, the temperature unevenness at the time of foaming can be reduced.

The glass transition temperature (Tg) of the resin constituting the shell is preferably 50 to 250 ℃, more preferably 60 to 200 ℃, and even more preferably 80 to 150 ℃. When the temperature is within this range, thermally expandable microspheres that can be expanded appropriately can be obtained, and when the thermally expandable microspheres are used, an adhesive tape having a suitably set B-point temperature can be obtained easily. In the present specification, when the resin is a copolymer (copolymer), the glass transition temperature is obtained by the calculation formula of Fox. The calculation formula of Fox is represented by the following glass transition temperature Tg (. Degree. C.) of the copolymer and glass transition temperature Tg of a homopolymer (homopolymer) obtained by homopolymerizing each of the monomers constituting the copolymer _i Relational expression of (DEG C). In the following formula of Fox, tg (. Degree. C.) represents the glass transition temperature of the copolymer, W _i Represents the weight fraction, tg, of monomer i _i (. Degree.C.) represents the glass transition temperature of the homopolymer formed from monomer i.

1/(273+Tg)＝Σ(W _i /(273+Tg _i ))

Glass transition temperature as homopolymer formed from monomers, acrylonitrile homopolymer (AN): methyl methacrylate homopolymer (MMA) at 97 ℃ C: methacrylonitrile homopolymer (MAN) at 102 ℃): vinylidene chloride homopolymer at 120 ℃): isobornyl acrylate homopolymer at 75 ℃): 97 ℃. The glass transition temperatures of homopolymers other than these may be values described in "Polymer Handbook" (4 th edition, john Wiley & Sons, inc., 1999). In addition, in this document, when values of a plurality of Tg are described, a value of "constant" is used.

The absolute value of the difference between the glass transition temperature (Tg) of the resin forming the shell and the desired B-point temperature (|tg-B-point temperature|) is preferably 45 ℃ or less, more preferably 5 to 35 ℃. When a resin having such a glass transition temperature is used, it is easy to set the temperature at the point B to a desired temperature.

The volatile substances contained in the above-mentioned shell are typically organic solvents. Examples of the organic solvent include linear aliphatic hydrocarbons having 3 to 8 carbon atoms and fluorides thereof, branched aliphatic hydrocarbons having 3 to 8 carbon atoms and fluorides thereof, linear alicyclic hydrocarbons having 3 to 8 carbon atoms and fluorides thereof, ether compounds having a hydrocarbon group having 2 to 8 carbon atoms, and compounds in which 1 part of the hydrogen atoms of the hydrocarbon group is substituted with a fluorine atom. In one embodiment, as the organic solvent, hydrocarbons composed of only hydrogen atoms and carbon atoms such as propane, cyclopropane, butane, cyclobutane, isobutane, pentane, cyclopentane, neopentane, isopentane, hexane, cyclohexane, 2-methylpentane, 2-dimethylbutane, heptane, cycloheptane, octane, cyclooctane, methylheptanes, trimethylpentanes, and the like are used; c (C) ₃ F ₇ OCH ₃ 、C ₄ F ₉ OCH ₃ 、C ₄ F ₉ OC ₂ H ₅ And hydrofluoroethers, etc. These organic solvents may be used alone in 1 kind, or may be used in combination of 2 or more kinds. The organic solvent has advantages of low affinity with the resin and/or binder forming the shell, difficulty in dissolving the shell and/or binder, and difficulty in changing physical properties such as thermal properties. Hydrocarbons composed of only hydrogen atoms and carbon atoms are preferable from the viewpoint of industrial utilization.

In one embodiment, branched hydrocarbons (e.g., isobutane, isopentane, etc.) are used as hydrocarbons composed only of hydrogen atoms and carbon atoms. Branched hydrocarbons are less likely to be charged, and if the solvent is used, accidents such as ignition due to charging can be prevented.

The boiling point of the organic solvent is preferably-50℃to 100℃and more preferably-20℃to 100 ℃. When the amount is within this range, thermally expandable microspheres in which the shell can be expanded well without being broken can be obtained. In addition, if the boiling point of the organic solvent is too low, the operation for suppressing volatilization at the time of producing the thermally expanded microspheres may become complicated.

The absolute value (|bp-Tg|) of the difference between the boiling point (bp) of the organic solvent and the glass transition temperature (Tg) of the resin constituting the shell is preferably 0℃to 150℃and more preferably over 0℃and 150℃or less, and still more preferably 5℃to 125 ℃. When 2 or more organic solvents (mixed solvents) are used, it is preferable that the difference between the boiling point of the solvent having the largest weight ratio and the glass transition temperature (Tg) of the resin constituting the shell is within the above range. In such a range, the time from the point a to the point B and the time from the point B to the point C can be adjusted appropriately and easily. The boiling point (bp) of the organic solvent is preferably lower than the glass transition temperature (Tg) of the resin forming the shell. If an organic solvent having a boiling point higher than the glass transition temperature of the shell is used, the shell may be broken by the pressure generated when the organic solvent is heated, or the binder may be scattered, and the functions and effects expected in the present application may be impaired.

Further, the thermally expandable microspheres are often exposed to an environment in which the thermally expandable microspheres are crushed before being heated by a surrounding adhesive, an attaching operation, or the like. Therefore, it is preferable that the thermally expandable microspheres have vapor pressure so as not to be crushed even before heating.

The content of the organic solvent is preferably 5 to 35% by weight, more preferably 10 to 30% by weight, based on the weight of the thermally expandable microspheres before heating. When the amount is within this range, an adhesive tape in which the thermally expandable microspheres are dispersed in the adhesive layer with high uniformity can be obtained. When the content is less than 5% by weight, the heat-expandable microspheres may be likely to be unevenly present on the surface of the pressure-sensitive adhesive layer or excessively large irregularities may be generated on the surface of the pressure-sensitive adhesive layer after heating in the production of the pressure-sensitive adhesive layer because of low density and the like. When the content exceeds 35 wt%, the density is high and the adhesive layer is settled, and even if heated, sufficient irregularities cannot be formed on the surface of the adhesive layer, and the desired peelability may not be obtained, and the adhesive residue may be generated.

The average particle diameter (number basis) of the thermally expandable microspheres before foaming at an ambient temperature of 25℃is preferably 1 to 40. Mu.m, more preferably 5 to 40. Mu.m, still more preferably 10 to 40. Mu.m. When the content is within this range, thermally expandable microspheres having high dispersibility in the pressure-sensitive adhesive layer can be obtained. The pressure-sensitive adhesive layer containing the thermally expandable microspheres in a highly dispersed state has high uniformity of irregularities produced by heating, and can exhibit excellent releasability. The average particle diameter of the thermally expandable microspheres can be controlled, for example, by the conditions under which the thermally expandable microspheres are polymerized (details will be described later). In the present specification, the average particle diameter can be measured by observing the thermally expandable microspheres used or the thermally expandable microspheres taken out from the adhesive layer before heating using an optical microscope or an electron microscope. Further, the average particle diameter can be measured by a particle size distribution measurement method in a laser light scattering method. More specifically, the average particle diameter may be measured by dispersing the thermally expandable microspheres in a predetermined solvent (e.g., water) and then measuring the dispersion using a particle size distribution measuring apparatus (e.g., trade name "SALD-2000J" manufactured by shimadzu corporation).

In one embodiment, the content of the thermally expandable microspheres is expressed as an area ratio of the thermally expandable microspheres measured by cross section. When the cross-sectional area of the adhesive layer in the predetermined cross-section is a and the cross-sectional area of the thermally expandable microspheres in the cross-section is B, the ratio of the cross-sectional area B of the thermally expandable microspheres to the cross-sectional area a of the adhesive layer is preferably 3% to 75%, more preferably 3.5% to 70%. If the ratio of the cross-sectional area B is less than 3%, even if the thermally expandable microspheres are expanded by heating, the irregularities generated on the adhesive surface become insufficient, and the desired peelability may not be obtained. On the other hand, when the ratio of the cross-sectional area B exceeds 75%, the volume change of the adhesive layer becomes excessive, and there is a possibility that the substrate and the adhesive layer may float or peel off, and the content of the adhesive in the adhesive layer is low, and the desired adhesive force may not be obtained. The ratio of the cross-sectional area B of the thermally expandable microspheres can be obtained by appropriately processing an image obtained by observing the cross-section of the adhesive layer with an electron microscope (for example, a low vacuum scanning electron microscope under the trade name "S-3400N", manufactured by Hitachi High-Technologies Corporation). For example, the image may be output from paper, and the weight a of the paper in the adhesive layer portion (i.e., the entire adhesive layer including the thermally expandable microspheres) and the weight b of the paper after only cutting out the thermally expandable microspheres may be obtained by the formula b/a×100.

The content of the thermally expandable microspheres is preferably 5 to 95 wt%, more preferably 10 to 70 wt%, and even more preferably 10 to 50 wt% based on the weight of the adhesive layer. When the ratio is within this range, the ratio of the cross-sectional area B of the thermally expandable microspheres can be achieved. Further, by setting the content ratio of the thermally expandable microspheres to the above range and performing an operation such as stirring the composition for forming the adhesive layer before the application step so that the thermally expandable microspheres do not unevenly exist in the adhesive layer, the cross-sectional area B of the thermally expandable microspheres can be set to a preferable range. The content of the thermally expandable microspheres was determined by the following formula. The weight of the thermally expandable microspheres was determined by measuring the weight of the thermally expandable microspheres taken out of the adhesive layer.

The content ratio (wt%) of the thermally-expansive microspheres=weight of the thermally-expansive microspheres/weight of the adhesive layer×100

The thermally expandable microspheres may be produced by any suitable method. In one embodiment, the thermally expandable microspheres are obtained by a suspension polymerization method. Suspension polymerization is usually carried out by dispersing a monomer (shell-forming material) and an organic solvent in an aqueous dispersion medium containing a dispersing agent, and polymerizing the monomer in the presence of the organic solvent. In addition, a dispersion stabilizer for stabilizing dispersion may be used. Examples of the dispersion stabilizer in the aqueous dispersion medium include inorganic fine particles such as silica, magnesium hydroxide, calcium phosphate, and aluminum hydroxide. As the dispersion stabilizing auxiliary agent, for example, a condensation product of diethanolamine and an aliphatic dicarboxylic acid, polyvinylpyrrolidone, methylcellulose, polyethylene oxide, polyvinyl alcohol, various emulsifiers, and the like can be used.

The characteristics of the thermally expandable microspheres such as particle diameter and organic solvent content can be controlled by the polymerization conditions of the suspension polymerization, the types and amounts of the mixed components, and the like. For example, by reducing the amount of the dispersant to be added and by slowing down the stirring speed during polymerization, thermally expandable microspheres having a large particle diameter can be obtained. Further, if the amount of the monomer to be blended is increased or the stirring speed during polymerization is reduced, thermally expandable microspheres having a relatively thick shell thickness can be obtained.

B-2 adhesive

As the adhesive constituting the adhesive layer, any suitable adhesive may be used as long as the effects of the present invention can be obtained. Examples of the adhesive include acrylic adhesives, silicone adhesives, vinyl alkyl ether adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, fluorine adhesives, styrene-diene block copolymer adhesives, and active energy ray-curable adhesives. Among them, an acrylic adhesive, a rubber adhesive or a silicone adhesive is preferable, and an acrylic adhesive is more preferable.

The gel fraction of the adhesive is preferably 20 to 100 wt%, more preferably 30 to 99 wt%, and even more preferably 50 to 99 wt%. When the gel fraction is less than 20% by weight, even if the thermally expandable microspheres expand to generate projections and depressions on the surface of the adhesive layer, the adhesive layer may flow and the projections and depressions may disappear in a short period of time. In addition, since the polymer molecules are small in the exclusion volume and the organic solvent in the thermally expandable microspheres easily penetrates between the polymer molecules, the time from the point a to the point B may be long. On the other hand, if the gel fraction exceeds 99% by weight, the heat expansion of the thermally expandable microspheres is inhibited and sufficient projections and depressions are not generated, or even if projections and depressions are generated, the thermally expandable microspheres explode, and the shell of the thermally expandable microspheres and the surrounding adhesive layer may be scattered, thereby deteriorating the residual gel property. The gel fraction of the adhesive can be controlled by adjusting the composition of the base polymer constituting the adhesive, the kind or content of the crosslinking agent added to the adhesive, the kind or content of the tackifier, and the like. The method for determining the gel fraction is described later.

The base polymer contained in the above adhesive preferably has OH groups or COOH groups. When such a base polymer is used, a crosslinking agent can be used to adjust the gel fraction. In addition, the amount of OH groups or COOH groups that do not react with the crosslinking agent can adjust the aggregation of the base polymer due to intermolecular forces such as hydrogen bonds. This can control the uneven shape of the adhesive surface generated by the expansion of the thermally expandable microspheres and the shell permeability of the organic solvent contained in the thermally expandable microspheres.

The hydroxyl value of the base polymer having an OH group is preferably 0 to 50, more preferably 20 to 30. The acid value of the base polymer having COOH groups is preferably 10 to 100, more preferably 20 to 50. The hydroxyl value and acid value of the polymer in the adhesive layer can be measured by extracting the solvent-soluble component in the adhesive layer. Specifically, the solvent-soluble component can be extracted by the following method.

(i) The adhesive layer was put into a solvent to prepare a solution sample in which the solvent-soluble component in the adhesive layer was dissolved in the solvent.

As the solvent, chloroform (CHCl) may be used in consideration of polarity and the like ₃ ) Dichloromethane (CH) ₂ Cl ₂ ) Any one of 1 or a mixture of 2 or more solvents selected from Tetrahydrofuran (THF), acetone, dimethylsulfoxide (DMSO), N-Dimethylformamide (DMF), methanol, ethanol, toluene, water, and the like is contained in an arbitrary ratio.

Typically, about 30mL of the solvent is added to about 0.2g of the pressure-sensitive adhesive layer, and the mixture is stirred for about 30 minutes to 12 hours in a temperature range from room temperature to about the boiling point of the solvent used. If necessary, for example, in the case where the extraction efficiency of the component to be analyzed is low, a solution sample may be prepared by adding a solvent to the sample after the solution is collected, stirring the solution, and repeating the process of collecting the solution 1 or more times.

(ii) The solvent can be removed from the solution sample by evaporation or the like, and the solvent-soluble polymer can be removed.

In addition, the solvent-soluble polymer may contain a solvent-soluble component that is not a measurement target, such as a low molecular weight component of the unreacted crosslinking agent. In this case, the solvent-soluble polymer containing only the object to be measured is adjusted by a method (reprecipitation method) in which the above-mentioned solution sample is put into a solvent in which only the polymer component is insoluble, molecular weight fractionation (preparative liquid chromatography) by gel filtration chromatography using the above-mentioned solution sample, or the like.

(acrylic adhesive)

Examples of the acrylic pressure-sensitive adhesive include an acrylic pressure-sensitive adhesive comprising an acrylic polymer (homopolymer or copolymer) as a base polymer, wherein the base polymer is 1 or 2 or more of alkyl (meth) acrylates. Specific examples of the alkyl (meth) acrylate include (C1-20) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, and eicosyl (meth) acrylate. Among them, alkyl (meth) acrylates having a linear or branched alkyl group having 4 to 18 carbon atoms can be preferably used.

In one embodiment, the acrylic polymer contains a constituent unit derived from a monomer having a glass transition temperature (Tg) of 80 ℃ or higher (preferably 90 ℃ or higher, more preferably 100 ℃ or higher) of a homopolymer. When such a polymer is used, an adhesive layer having a proper elastic modulus can be formed. Examples of the monomer include cyclohexyl methacrylate (Tg: 83 ℃ C.), dicyclopentanyl acrylate (Tg: 120 ℃ C.), dicyclopentanyl methacrylate (Tg: 175 ℃ C.), isobornyl acrylate (Tg: 94 ℃ C.), isobornyl methacrylate (Tg: 150 ℃ C.), t-butyl methacrylate (Tg: 118 ℃ C.), methyl methacrylate (Tg: 105 ℃ C.), trimethylolpropane triacrylate (Tg: 250 ℃ C.), styrene (Tg: 80 ℃ C.), acrylonitrile (Tg: 97 ℃ C.), and N-acryloylmorpholine (Tg: 145 ℃ C.). Among them, methyl methacrylate is preferable. The content of the constituent unit of the monomer having a glass transition temperature (Tg) of 80 ℃ or higher derived from the homopolymer is preferably 1 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the base polymer (acrylic polymer).

The acrylic polymer may contain a unit corresponding to another monomer copolymerizable with the alkyl (meth) acrylate, if necessary, for the purpose of modifying the cohesive force, heat resistance, crosslinking property, and the like. Examples of such monomers include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; anhydride monomers such as maleic anhydride and itaconic anhydride; hydroxy-containing monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxydecyl (meth) acrylate, hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl methacrylate; sulfonic acid group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloxynaphthalene sulfonic acid; (N-substituted) amide monomers such as (meth) acrylamide, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, and N-methylol propane (meth) acrylamide; aminoalkyl (meth) acrylate monomers such as aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate; alkoxyalkyl (meth) acrylate monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide and N-phenylmaleimide; an itaconimide monomer such as N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, N-2-ethylhexyl itaconimide, N-cyclohexyl itaconimide and N-month Gui Jiyi itaconimide; succinimide-based monomers such as N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, and N- (meth) acryloyl-8-oxyoctamethylene succinimide; vinyl monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methyl vinylpyrrolidone, vinyl pyridine, vinyl piperidone, vinyl pyrimidine, vinyl piperazine, vinyl pyrazine, vinyl pyrrole, vinyl imidazole, vinyl oxazole, vinyl morpholine, N-vinylcarboxylic acid amide, styrene, α -methylstyrene, N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate; glycol-based acrylate monomers such as polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate; acrylic acid ester monomers having a heterocycle, a halogen atom, a silicon atom, or the like, such as tetrahydrofurfuryl (meth) acrylate, fluoro (meth) acrylate, and silicone (meth) acrylate; multifunctional monomers such as hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate; olefin monomers such as isoprene, butadiene, and isobutylene; vinyl ether monomers such as vinyl ether, and the like. These monomers may be used alone or in combination of 2 or more.

(additive)

The above-mentioned adhesive may contain any suitable additive as required. Examples of the additives include crosslinking agents, tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, peeling regulators, softeners, surfactants, flame retardants, antioxidants, and the like.

As the thickener, any suitable thickener is used. As the tackifier, for example, a tackifier resin is used. Specific examples of the tackifying resin include rosin-based tackifying resins (for example, unmodified rosin, modified rosin, rosin phenol-based resin, rosin ester-based resin, and the like), terpene-based tackifying resins (for example, terpene-based resins, styrene-modified terpene-based resins, aromatic modified terpene-based resins, and hydrogenated terpene-based resins), hydrocarbon-based tackifying resins (for example, aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aromatic hydrocarbon resins (for example, styrene-based resins, xylene-based resins, and the like), aliphatic/aromatic petroleum resins, aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, coumarone indene-based resins, and the like), phenolic tackifying resins (for example, alkylphenol-based resins, xylene-formaldehyde-based resins, resol-type phenolic resins, novolac-type resins, and the like), ketone-based tackifying resins, polyamide-based tackifying resins, epoxy-based tackifying resins, and elastomeric-based tackifying resins, and the like.

The amount of the tackifier is preferably 5 to 100 parts by weight, more preferably 10 to 50 parts by weight, based on 100 parts by weight of the base polymer.

Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a melamine crosslinking agent, and a peroxide crosslinking agent, and urea crosslinking agent, a metal alkoxide crosslinking agent, a metal chelate crosslinking agent, a metal salt crosslinking agent, a carbodiimide crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, and an amine crosslinking agent. Among them, isocyanate-based crosslinking agents or epoxy-based crosslinking agents are preferable.

Specific examples of the isocyanate-based crosslinking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; aromatic isocyanates such as 2, 4-toluene diisocyanate, 4' -diphenylmethane diisocyanate and xylylene diisocyanate; isocyanate adducts such as trimethylolpropane/toluene diisocyanate trimer adduct (Nippon Polyurethane Industry co., ltd., trade name "Coronate l"), trimethylolpropane/hexamethylene diisocyanate trimer adduct (Nippon Polyurethane Industry co., ltd., trade name "cornonate HL"), isocyanurate of hexamethylene diisocyanate (Nippon Polyurethane Industry co., ltd., trade name "cornonate HX"), and the like. The content of the isocyanate-based crosslinking agent may be set to any suitable amount depending on the desired adhesive force, the elasticity of the adhesive layer, etc., and is typically 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, relative to 100 parts by weight of the base polymer.

Examples of the epoxy-based crosslinking agent include N, N, N ', N' -tetraglycidyl-meta-xylylenediamine, diglycidyl aniline, 1, 3-bis (N, N-glycidylaminomethyl) cyclohexane (MITSUBISHI GAS CHEMICAL COMPANY, manufactured by INC. Under the trade name "TETRADC"), 1, 6-hexanediol diglycidyl ether (manufactured by Kyowa chemical Co., ltd., "Epoligo 1600"), neopentyl glycol diglycidyl ether (manufactured by Kyowa chemical Co., ltd., "Epoligo 1500 NP"), ethylene glycol diglycidyl ether (manufactured by Kyowa chemical Co., ltd., "Epoligo 40E"), propylene glycol diglycidyl ether (manufactured by Kyowa chemical Co., ltd., "Epoligo 70P"), polyethylene glycol diglycidyl ether (manufactured by Japanese fat Co., ltd., "Epiol E-400"), polypropylene glycol diglycidyl ether (manufactured by Japanese COMPANY, trade name "P-200"), sorbitol polyglycidyl ether (62, trade name "DenaEX" 611-611 ", polyglycidyl ether (manufactured by Japanese fat-62, manufactured by Japanese fat-400), polyglycidyl ether (manufactured by Japanese fat-62, DEC-62), polyglycidyl diglycidyl ether (manufactured by Japanese fat-35), polyglycidyl ether (manufactured by Japanese fat-2, DEC-glycidyl ether, polyglycidyl ether (manufactured by De-512), triglycidyl-glycidyl ether (manufactured by DEC), bisphenol-S-diglycidyl ether, and epoxy resins having 2 or more epoxy groups in the molecule. The content of the epoxy-based crosslinking agent may be set to any suitable amount depending on the desired adhesive force, the elasticity of the adhesive layer, etc., and is typically 0.01 to 10 parts by weight, more preferably 0.03 to 5 parts by weight, relative to 100 parts by weight of the base polymer.

As the plasticizer, any suitable plasticizer may be used. Specific examples of the plasticizer include trimellitate plasticizers, pyromellitic acid plasticizers, polyester plasticizers, and adipic acid plasticizers. Among them, trimellitate plasticizers (e.g., tri (n-octyl) trimellitate, tri (2-ethylhexyl) trimellitate, etc.) or pyromellitic acid plasticizers (e.g., tetra (n-octyl) pyromellitic acid, tetra (2-ethylhexyl) pyromellitic acid, etc.) are preferable. The plasticizer may be used alone or in combination of 2 or more. The content of the plasticizer is preferably 1 to 20 parts by weight, more preferably 1 to 5 parts by weight, relative to 100 parts by weight of the base polymer.

B-3 Properties of the adhesive layer

The elastic modulus of the adhesive layer obtained by nanoindentation at 23℃is preferably 0.1 to 500MPa, more preferably 0.5 to 400MPa. In one embodiment, an adhesive layer having an elastic modulus of 0.8MPa to 50MPa is used. When the elastic modulus of the pressure-sensitive adhesive layer is less than 0.1MPa, the organic solvent that diffuses out of the thermally expandable microspheres during heating rapidly penetrates the pressure-sensitive adhesive layer, and therefore the time from point B to point C may be shortened. On the other hand, if the elastic modulus exceeds 500MPa, expansion of the thermally expandable microspheres may be inhibited, and the adhesive layer may be broken when the thermally expandable microspheres expand. The elastic modulus of the pressure-sensitive adhesive layer can be controlled by introducing a constituent unit derived from a monomer having a glass transition temperature (Tg) of 80 ℃ or higher, adjusting the degree of crosslinking, or the like. The elastic modulus obtained by the nanoindentation method was obtained from a load-indentation depth curve obtained by continuously measuring the load and indentation depth of the indenter when the indenter was pressed into the adhesive layer during loading and unloading, with a portion (a portion 1 μm or more from the shell surface of the thermally expanded microsphere) which was located at a distance of about 3 μm from the surface of the adhesive layer and where the thermally expanded microsphere was not present. In the present specification, the elastic modulus obtained by the nanoindentation method means that the measurement conditions are set to the load/unload speed: 1000nm/s, press depth: the elastic modulus obtained was measured at 800nm as described above.

The anchoring force between the pressure-sensitive adhesive layer and the substrate is preferably 4N/20mm or more, more preferably 5N/20mm or more. When the amount is within this range, the adhesion between the base material and the pressure-sensitive adhesive layer is maintained even after the thermally expandable microspheres are expanded, and a pressure-sensitive adhesive tape with less residual adhesive can be obtained. The method of measuring the anchoring force will be described later.

The arithmetic mean height Sa of the pressure-sensitive adhesive layer before foaming the thermally expandable microspheres is preferably 500nm or less, more preferably 400nm or less, and still more preferably 300nm or less at an ambient temperature of 25 ℃. When the thickness is in this range, the pressure-sensitive adhesive tape can be obtained in which irregularities generated on the surface to which the adherend is attached can be reduced. The arithmetic mean height Sa may be in accordance with JIS B0601: 1994, measurement was performed by using a laser microscope (LEXT OLS-4000, manufactured by Olympus Corporation, image magnification 432, measurement area 640X 640 μm (sampling rate 0.625 μm)).

The arithmetic average height Sa of the adhesive layer when the adhesive tape of the present invention is heated to the point C is preferably 10 μm to 50. Mu.m, more preferably 3 μm to 30. Mu.m. When the amount is within this range, the adhesive force decreases or disappears after heating, and an adhesive tape that can easily release an adherend can be obtained. In addition, when the arithmetic average surface height Sa exceeds 50 μm, the foaming stress at the time of generation of the projections and depressions is excessively large, and although no external force is given, there is a possibility that blow-off or the like of the adherend occurs to adversely affect the subsequent recovery of the adherend. The "arithmetic average height Sa of the adhesive layer when the adhesive tape is heated to point C" is the arithmetic average height Sa of the adhesive layer of the adhesive tape (5 cm square) heated on a hot plate set to the temperature of point C for 60±5 seconds, and can be measured using the above-described laser microscope. In addition, the arithmetic average surface height Sa of the adhesive layer refers to the arithmetic average surface height Sa after heating in a state where no adherend is present.

The thickness of the pressure-sensitive adhesive layer is preferably 5 μm to 300. Mu.m, more preferably 15 μm to 250. Mu.m, still more preferably 30 μm to 100. Mu.m, particularly preferably 30 μm to 60. Mu.m.

B-4 other ingredients

The pressure-sensitive adhesive layer may further contain any suitable other component as long as the effects of the present invention are obtained. Examples of the other component include beads. Examples of the beads include glass beads and resin beads. By adding such beads to the pressure-sensitive adhesive layer, the elastic modulus of the pressure-sensitive adhesive layer can be increased, and a pressure-sensitive adhesive tape that can process a work with improved accuracy can be obtained. The beads have an average particle diameter of, for example, 0.01 μm to 50. Mu.m. The amount of the beads to be added is, for example, 10 to 200 parts by weight, preferably 20 to 100 parts by weight, based on 100 parts by weight of the adhesive layer.

C. Substrate material

Examples of the base material include a resin sheet, a nonwoven fabric, paper, a metal foil, a woven fabric, a rubber sheet, a foamed sheet, and a laminate thereof (particularly a laminate including a resin sheet). Examples of the resin constituting the resin sheet include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), polyamide (nylon), wholly aromatic polyamide (aramid), polyimide (PI), polyvinyl chloride (PVC), polyphenylene Sulfide (PPs), a fluororesin, and polyether ether ketone (PEEK). Examples of the nonwoven fabric include nonwoven fabrics made of heat-resistant natural fibers such as a nonwoven fabric containing manila hemp; and synthetic resin nonwoven fabrics such as polypropylene resin nonwoven fabrics, polyethylene resin nonwoven fabrics, and ester resin nonwoven fabrics. Examples of the metal foil include copper foil, stainless steel foil, and aluminum foil. Examples of the paper include japanese paper and kraft paper.

The thickness of the base material may be set to any suitable thickness depending on the desired strength, flexibility, purpose of use, and the like. The thickness of the base material is preferably 1000 μm or less, more preferably 1 μm to 1000 μm, still more preferably 1 μm to 500 μm, particularly preferably 3 μm to 300 μm, and most preferably 5 μm to 250 μm.

The substrate may be subjected to surface treatment. Examples of the surface treatment include corona treatment, chromic acid treatment, ozone exposure, flame exposure, high-voltage electric shock exposure, ionizing radiation treatment, and coating treatment with a primer.

Examples of the organic coating material include those described in plastic hard coating material II (CMC publication, (2004)). Preferably, urethane polymers are used, more preferably, polyacrylic urethanes, polyester urethanes or precursors thereof are used. This is because the application and coating on the substrate are easy and convenient, and various industrial choices are available at low cost. The urethane polymer is, for example, a polymer comprising a reaction mixture of an isocyanate monomer and an alcoholic hydroxyl group-containing monomer (e.g., a hydroxyl group-containing acrylic compound or a hydroxyl group-containing ester compound). The organic coating material may contain a chain extender such as polyamine, an antioxidant, an oxidation stabilizer, and the like as optional additives. The thickness of the organic coating layer is not particularly limited, and is preferably about 0.1 μm to 10 μm, more preferably about 0.1 μm to 5 μm, and still more preferably about 0.5 μm to 5 μm.

F. Method for producing adhesive tape

The adhesive tape of the present invention can be manufactured by any suitable method. Examples of the pressure-sensitive adhesive tape of the present invention include a method of directly applying a pressure-sensitive adhesive layer-forming composition comprising a pressure-sensitive adhesive and thermally expandable microspheres to a substrate, and a method of transferring a coating layer formed by applying a pressure-sensitive adhesive layer-forming composition to an arbitrary suitable substrate to a substrate. The adhesive layer-forming composition may contain any suitable solvent. Alternatively, after forming the adhesive coating layer from the adhesive-containing composition, the thermally expandable microspheres may be dispersed on the adhesive coating layer, and then the thermally expandable microspheres may be embedded in the coating layer using a laminator or the like to form an adhesive layer containing the thermally expandable microspheres.

The content of the thermally expandable microspheres in the pressure-sensitive adhesive layer-forming composition is preferably 5 to 95% by weight, more preferably 10 to 70% by weight, and even more preferably 10 to 50% by weight, based on the weight of the solid content of the pressure-sensitive adhesive layer-forming composition.

Any suitable coating method can be used as the coating method of each composition. For example, each layer may be formed by drying after coating. Examples of the coating method include coating methods using a multilayer coater (multicoter), a die coater, a gravure coater, an applicator, and the like. Examples of the drying method include natural drying and heat drying. The heating temperature at the time of heating and drying may be set to any suitable temperature according to the characteristics of the substance to be dried.

G. Use of the same

The adhesive tape of the present invention can be suitably used as a sheet for temporarily fixing an electronic component material at the time of manufacturing an electronic component. In one embodiment, the adhesive tape of the present invention can be used as a temporary fixing sheet when cutting electronic component materials. As the electronic component material, for example, a ceramic capacitor material is cited. If an electronic component material such as a ceramic capacitor material is temporarily fixed to the adhesive tape of the present invention, misalignment of the material can be prevented, and as a result, the material can be cut with excellent accuracy. Any suitable cutting method can be used as the cutting method in the cutting step.

Examples

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The evaluation method in the examples is as follows. In the following evaluation, an adhesive tape from which a separator was peeled was used. In the examples, unless specifically stated otherwise, "parts" and "%" are based on weight.

[ evaluation ]

(1) Determination of the hydroxyl number of the base Polymer of the adhesive

(pretreatment)

(i) 2g of the adhesive layer was added to 300ml of chloroform and refluxed for 1 day. From the obtained solution, impurities such as refuse are removed by filtration, and the filtrate is recovered.

(ii) The chloroform solution prepared in (i) above was dropped into methanol 10L over 1 hour, and the obtained precipitate was recovered.

(iii) The precipitate obtained by the operation of (ii) above was dissolved in 300ml of chloroform. This solution was dropped into 10L of methanol over 1 hour, and the obtained precipitate was recovered.

(iv) The precipitate obtained by the operation of (iii) above was dissolved again in 300ml of chloroform. This solution was dropped into 10L of methanol over 1 hour, and the obtained precipitate was recovered.

(v) The precipitate obtained in (iv) was measured by GPC, and it was confirmed that no low molecular weight component having a weight average molecular weight of 2000 or less was contained, and the precipitate (base polymer) was used as a sample for measuring a hydroxyl value.

(v') when the precipitate contains a low molecular weight compound having a weight average molecular weight of 2000 or less, the operation (iv) is repeated until the low molecular weight compound is not contained.

The GPC measurement was performed under the following conditions using a trade name "HLC-8120GPC" manufactured by TOSOH CORPORATION and polystyrene as a molecular weight standard.

< conditions for measuring GPC >

Sample concentration: 0.2 wt% (tetrahydrofuran solution)

Sample injection amount: 10 μl of

Eluent: tetrahydrofuran (THF)

Flow (flow rate): 0.6mL/min

Column temperature (measurement temperature): 40 DEG C

Column: trade name "TSKgelSuperHM-H/H4000/H3000/H2000" (manufactured by TOSOHCORPORATION)

Detector: differential Refractometer (RI)

Standard polystyrene: TOSOH CORPORATION Tsk gel standard polystyrene F-288, tsk gel standard polystyrene F-40, tsk gel standard polystyrene F-4, tsk gel standard polystyrene A-5000, tsk gel standard polystyrene A-500

(determination of hydroxyl value)

The hydroxyl value was evaluated in accordance with JIS K0070-1992 (acetylation method). About 25g of acetic anhydride was taken, pyridine was added thereto, and the total amount was set to 100mL, and the mixture was stirred well to prepare an acetylation reagent.

About 2g of the base polymer to be sampled was accurately weighed in a flat-bottomed flask, 5mL of an acetylating reagent and 10mL of pyridine were added, and an air condenser was installed. After heating at 100℃for 70 minutes, cooling was performed, 35mL of toluene (tetrahydrofuran in the case where the binder was insoluble in toluene) was added as a solvent from the upper part of the condenser, and after stirring, 1mL of water was added and stirred, and acetic anhydride was decomposed. To allow the decomposition to proceed completely, the mixture was heated again for 10 minutes and cooled.

The condenser was rinsed with 5mL of ethanol and removed, and 50mL of pyridine was added as a solvent and stirred. To this solution, 25mL of 0.5mol/L potassium hydroxide ethanol solution was added using a full-volume pipette, and potential difference titration was performed with 0.5mol/L potassium hydroxide ethanol solution, and the hydroxyl value was calculated from the following formula.

Hydroxyl value (mgKOH/g) = (B-C) ×f 28.05/S+D

B: amount of 0.5mol/L Potassium hydroxide ethanol solution (mL) used in the blank test

C: amount of 0.5mol/L Potassium hydroxide ethanol solution (mL) used in the sample

f: factor of 0.5mol/L potassium hydroxide ethanol solution

S: sample collection amount (g)

D: acid value

(2) Gel fraction determination of adhesive

About 0.1g of the adhesive (weight of the sample) of the adhesive layer was sampled and precisely weighed, and the sample was wrapped with a mesh sheet (trade name "NTF-1122", manufactured by Nito electric Co., ltd.) and immersed in about 50ml of toluene at room temperature for 1 week. Thereafter, the solvent-insoluble component (the content of the net sheet) was taken out of toluene, dried at 70℃for about 2 hours, and the dried solvent-insoluble component (the weight after impregnation and drying) was weighed, and the gel fraction (weight%) was calculated from the following formula (a). In comparative example 4, ultraviolet rays were irradiated at 500mJ/cm before the measurement ² And the adhesive is uv cured. For irradiation with ultraviolet light, "UM810" manufactured by niton corporation is used.

Gel fraction (% by weight) = [ (weight after impregnation/drying)/(weight of sample) ]. Times.100 (a)

(3) Thermo-mechanical analysis of adhesive tapes

The adhesive tape was cut into pieces of 5mm by 5mm to obtain a measurement sample. The measurement sample is brought into contact with the probe side of the measurement device and mounted on the measurement device. Then, the temperature was heated from room temperature at a predetermined heating rate to obtain a temperature-displacement (length) curve.

Based on the temperature-displacement curve, the time from the deformation start point (point a) to the time (point B) at which the deformation amount at the time of expansion reaches half the maximum deformation amount, the time from point B to the point (point C) at which the deformation amount of the adhesive tape reaches the maximum, the temperature at point a, the temperature at point B, and the temperature at point C are obtained.

< analysis conditions >

Device name: seiko Instruments trade name "TMA/SS150" manufactured by Inc "

Sample size: 5mm square

And (3) probe:

probe load: 0N

Measuring temperature range: room temperature (25 ℃ +/-5 ℃) to 250 DEG C

Heating rate: 3 ℃/min

(4) Arithmetic mean height Sa of adhesive layer at C point

The adhesive tape was cut into pieces of 5 cm. Times.5 cm to obtain a measurement sample. The measurement sample was heated on a hot plate set to the temperature of point C for 60.+ -. 5 seconds. After heating, the arithmetic mean height Sa of the adhesive layer was measured using a laser microscope (LEXT OLS-4000, manufactured by Olympus Corporation, image magnification 432, measurement area 640X 640 μm (sampling rate 0.625 μm)).

(5) Elastic modulus of adhesive layer obtained by nanoindentation method

The adhesive tape was cut in the thickness direction by a microtome, and the elastic modulus was measured on the cut surface by a nanoindenter.

More specifically, the surface of the cut surface of the portion (adhesive 1 μm or more from the shell surface of the thermally expandable microspheres) which is located at a distance of about 3 μm from the surface of the adhesive layer and where the thermally expandable microspheres are not present was set as the object of measurement.

The elastic modulus (average of 10 measurements) was obtained by performing numerical processing on a displacement-load hysteresis curve obtained by pressing a probe (indenter) into a measurement object by software (triboscan) attached to the measurement device.

The nanoindenter device and measurement conditions are as follows.

< apparatus and measurement conditions >

The device comprises: a nano indentation instrument; triboindinder manufactured by Hysicron Inc

The measuring method comprises the following steps: single press-in method

Measuring temperature: 23 DEG C

Press-in speed: about 1000nm/sec

Depth of press-in: about 800nm

And (3) probe: diamond Berkovich type (triangular cone type)

(6) Substrate-adhesive layer anchoring force

The pressure-sensitive adhesive layer side of the pressure-sensitive adhesive tape described in the examples was bonded to the pressure-sensitive adhesive surface of a pressure-sensitive adhesive tape (No. 315, manufactured by Nito electric Co., ltd.) by a hand press roll. Next, a double-sided tape (No. 5000N, manufactured by Nito electric Co., ltd.) was attached to the base material side of the pressure-sensitive adhesive tape described in the examples, and a 10mm X70 mm long sheet was produced. Thereafter, a SUS plate having a thickness of 2mm was attached to the other surface of the double-sided tape to prepare a test body.

The adhesive tape of the test piece obtained was peeled at 180℃and torn off at 50 mm/mm.

As a result, the release force was measured only when the adhesive tape was released, that is, when the anchor breaking did not occur, and the adhesive layer was set to be acceptable (good in the table) when the adhesive tape was torn off together with the adhesive tape and when the anchor breaking occurred.

Further, since the adhesive force when the adhesive tape is directly attached to the SUS plate was 5N/10mm, the above-mentioned test-qualified product can be said to have an anchor force of 5N/10mm or more.

(7) Evaluation of residual glue 1 (relationship between time of point A. Fwdarw. Point B and residual glue)

The adhesive tape was attached to the entire surface of a 4-inch silicon mirror wafer (bare wafer, tape orientation flat) by hand press roll, and left at room temperature for 1 hour.

The wafers bonded with the adhesive tapes (the wafers having the surface of the hot plate in contact with the surface of the wafer to which the adhesive tapes were not bonded) were set on the hot plates set to the B-point temperatures of the respective adhesive tapes ± 5 ℃ and heated for 10 sec ± 1 sec.

After the wafer with the adhesive tape is taken out from the hot plate, the wafer with the adhesive tape is arranged so that the adhesive tape is naturally peeled (the wafer is turned upside down with the adhesive tape face), and the adhesive tape is removedA belt. In addition, when the adhesive tape does not naturally fall down and is not removed from the wafer, the adhesive tape is nipped and removed with tweezers in this state. In comparative example 4, ultraviolet rays were irradiated at 500mJ/cm before this operation ² And the adhesive is uv cured. For irradiation with ultraviolet light, "UM810" manufactured by niton corporation was used.

The number of residual adhesives (substantially dot-like (granular) or amorphous images not seen on a new wafer before the adhesive tape was attached) on the wafer surface was counted by observing the inside of the plane of 1×1mm in the center of the mirror surface after the adhesive tape was removed with an Optical microscope (Olympus Optical co., ltd. Manufactured by ltd. At 5 magnification of objective lens, eyepiece 10 magnification).

In the table, the number of residual gums was set to 0 to 500, 500 to 1000 were good, 1000 to 5000 were Δ, and 5000 or more were x.

(8) Evaluation of residual glue 2 (relationship between time of B point and C point and residual glue)

The wafer to which the adhesive tape was bonded was set on a hot plate set to a B temperature of ±5 ℃ for each adhesive tape (set so that the surface of the hot plate was in contact with the surface of the wafer to which the adhesive tape was not bonded), and heated for 210±10 seconds.

After the wafer with the adhesive tape is taken out from the hot plate, the wafer with the adhesive tape is arranged so that the adhesive tape is naturally peeled (the wafer is turned over with the adhesive tape surface on the ground side), and the adhesive tape is removed. In addition, when the adhesive tape does not naturally fall and is not removed from the wafer, the adhesive tape is nipped and removed with tweezers in this state. In comparative example 4, ultraviolet rays were irradiated at 500mJ/cm before this operation ² And the adhesive is uv cured. For irradiation with ultraviolet light, "UM810" manufactured by niton corporation was used.

The number of residual adhesives (substantially dot-like (granular) or amorphous images not seen on a new wafer before the adhesive tape was attached) on the wafer surface was counted by observing the inside of the 1×1mm plane of the center of the mirror surface after the adhesive tape was removed with an Optical microscope (Olympus Optical co., ltd. Objective lens 5 magnification, eyepiece lens 10 magnification).

Production example 1 production of thermally expandable microspheres A

150g of sodium chloride, 70g of colloidal silica (trade name "SNOWTEX" manufactured by Nissan chemical Co., ltd.) having 20% by weight of silica as an active ingredient, 1g of polyvinylpyrrolidone, and 0.5g of a condensate of diethanolamine and adipic acid were added to 600g of distilled water, and the pH of the resultant mixture was adjusted to 2.8 to 3.2 to obtain an aqueous solution.

To the above aqueous solution, 80g of acrylonitrile, 40g of methyl methacrylate and 130g of vinylidene chloride were added as an oil-based additive for a shell-forming material. Further, 1g of ethylene glycol dimethacrylate as a crosslinking agent was added to obtain a reaction solution.

The above reaction solution was charged into a pressure-resistant reaction vessel equipped with a homomixer (trade name "TKhomomixer", manufactured by Special chemical industry Co., ltd.), and 70g of isobutane (boiling point: -11.7 ℃ C.) which was an organic solvent intended to be enclosed in a shell and 5g of an initiator (diisopropyloxy dicarbonate) were further charged into the pressure-resistant reaction vessel.

The homomixer was rotated under predetermined initial stirring conditions (stirring speed: 6000rpm, stirring time: 2 minutes) to stir the mixture, and then the mixture was heated to 60℃with stirring at 80rpm to perform a reaction for 24 hours. The solid component obtained by filtering the reaction solution after the reaction was left to stand at room temperature under a nitrogen stream for 1 week to obtain thermally expandable microspheres.

The obtained thermally expandable microspheres were measured with the trade name "SALD-2000J" manufactured by Shimadzu corporation, and the average particle diameter was 12.5. Mu.m. The solvent in the thermally expandable microspheres was isobutane and contained 13 wt% based on the weight of the thermally expandable microspheres, as determined by X-ray CT (X-ray 520versa (measurement conditions: tube voltage: 60KV tube current: 83. Mu.A, pixel size: 0.20 μm/pixel)). The thickness of the shell of the thermally expandable microspheres was 2.8. Mu.m, as measured by the X-ray CT method described above.

Production examples 2 to 6 and 8 to 11 thermally expandable microspheres B to F, H to K

Thermally expandable microspheres B to F, H to K were produced in the same manner as in production example 1, except that the blending amount of colloidal silica at the time of preparation of the aqueous solution, the blending amount of the oil-based additive (acrylonitrile, methacrylonitrile, isobornyl methacrylate, methyl methacrylate, vinylidene chloride), the organic solvent (isobutane, isopentane (boiling point: 27.7 ℃), petroleum ether, isooctane (boiling point: 99 ℃) intended to be enclosed in the shell, and the initial stirring conditions at the time of polymerization were set as described in table 1. The average particle diameter, the amount of the organic solvent contained, and the thickness of the shell of the thermally expandable microspheres were measured in the same manner as in production example 1. The results are shown in table 1.

TABLE 1

Example 1

An adhesive layer-forming composition was prepared by mixing 100 parts by weight of an acrylic copolymer (ethyl acrylate (EA), methyl Methacrylate (MMA), 2-ethylhexyl acrylate (2 EHA), a copolymer of 2-hydroxyethyl acrylate (HEA), an EA constituent unit, an MMA constituent unit, an HEA constituent unit=60:5:30:5 (weight ratio), a weight average molecular weight of 350000, a hydroxyl value of 24), 20 parts by weight of a tackifier (YASUHARA CHEMICAL co., ltd., trade name "YS POLYSTAR S145"), 3 parts by weight of an isocyanate-based crosslinking agent (TOSOH CORPORATION, trade name "Coronate L"), 30 parts by weight of thermally expandable microspheres a, and 210 parts by weight of toluene. The weight average molecular weight of the acrylic copolymer was measured by the method described in the above evaluation (1).

The adhesive tape (adhesive layer (thickness: 30 μm)/substrate) was obtained by coating the above adhesive layer-forming composition on a PET film (thickness: 50 μm) as a substrate and drying. In addition, the gel fraction of the adhesive was 85%.

The obtained adhesive tape was subjected to the above evaluations (3) to (8). The results are shown in table 2.

Examples 2 to 5 and comparative examples 1 to 4

An adhesive tape was obtained in the same manner as in example 1, except that the composition of the acrylic copolymer and the composition of the adhesive layer-forming composition were set to the compositions shown in table 2. The obtained adhesive tape was subjected to the above evaluations (3) to (8). The results are shown in table 2. In Table 2, "crosslinking agent TETRADC" is an epoxy crosslinking agent (trade name "TETRAD C") manufactured by MITSUBISHI GAS CHEMICAL COMPANY, INC, "DPHA" is dipentaerythritol hexaacrylate (manufactured by Santa Clara Industrial chemistry Co., ltd.), and "IRGACURE184" is a photoinitiator (trade name "IRGACURE 184") manufactured by BASF Japan Ltd.

TABLE 2

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Claims

1. An adhesive tape comprising a substrate and an adhesive layer disposed on at least one surface of the substrate,

the adhesive layer comprises thermally expandable microspheres,

the thermally expandable microspheres are composed of a shell formed of a resin and an organic solvent contained in the shell, the shell having a thickness of 1 μm to 15 μm,

When the adhesive tape is heated at a heating rate of 3 ℃/min in a thermo-mechanical analysis, the deformation start point is set as point A, the point at which the deformation amount of the adhesive tape reaches the maximum after passing through the point A is set as point C, and the point at which the deformation amount reaches half the deformation amount at point C from point A to point C is set as point B,

the time from the point A to the point B is 45-200 seconds,

the absolute value of the difference between the glass transition temperature (Tg) and the B-point temperature of the resin forming the shell, i.e., the |Tg-B-point temperature|, is 45 ℃ or lower.

2. The adhesive tape according to claim 1, wherein a time from the point B to the point C is 200 seconds or more.

3. The adhesive tape according to claim 1, wherein the temperature at the point B is 50 to 250 ℃.

4. The adhesive tape according to claim 1, wherein the resin has a glass transition temperature of 50 to 250 ℃.

5. The adhesive tape according to claim 1, wherein the resin forming the case contains at least one selected from the group consisting of a constituent unit derived from isobornyl (meth) acrylate, a constituent unit derived from methacrylonitrile, a constituent unit derived from acrylonitrile, a constituent unit derived from methyl (meth) acrylate, a constituent unit derived from vinylidene chloride, and a constituent unit derived from (meth) acrylic acid.

6. The adhesive tape according to claim 1, wherein the organic solvent has a boiling point of-50 ℃ to 100 ℃.

7. The adhesive tape according to claim 1, wherein the adhesive layer has an elastic modulus of 0.1MPa to 500MPa obtained by nanoindentation.

8. The adhesive tape according to claim 1, wherein the adhesive constituting the adhesive layer has a gel fraction of 30 to 99% by weight.

9. The adhesive tape according to claim 1, wherein an absolute value of a difference between a boiling point (bp) of the organic solvent and a glass transition temperature (Tg) of a resin constituting the case is 0 ℃ to 150 ℃.

10. The adhesive tape of claim 1, wherein the adhesive layer comprises an acrylic adhesive, a rubber adhesive, or a silicone adhesive.

11. The adhesive tape according to claim 1, wherein the adhesive layer has a thickness of 5 μm to 300 μm.