TW201835266A - Adhesive tape which has an excellent stripping property after heating and has less adhesive residue to an adhered object - Google Patents

Abstract

The present invention provides an adhesive tape including heat-expandable microspheres, which has an excellent stripping property after heating and has less adhesive residue to an adhered object. The adhesive tape of the present invention includes a substrate and an adhesive layer configured on at least one surface of the substrate. The adhesive layer includes heat-expandable microspheres. In a thermo-mechanical analysis, when the adhesive tape is heated at a heating rate of 3 DEG C per minute, the deformation start point is set to point A, the point at which the amount of deformation of the adhesive tape becomes maximum after passing while the point A being expanded is set to point C, and the point at which the amount of deformation from the point A to the point C is half of the amount of deformation at the point C is set to point B, whereby the time from point A to point B is 45 to 200 seconds.

Description

Adhesive tape

The invention relates to an adhesive tape. More specifically, it relates to an adhesive tape that exhibits easy peelability in response to a thermal stimulus.

In the step of manufacturing electronic parts, as an adhesive tape used for the purpose of temporarily fixing a processed product, an adhesive tape that exhibits adhesiveness when temporarily fixed and easily peelable when it is not fixed is known. . As one of such adhesive tapes, an adhesive tape composed of thermally expandable microspheres in an adhesive layer has been studied (for example, Patent Document 1). The adhesive tape exhibits the required adhesive force at a relatively low temperature represented by normal temperature. On the other hand, by heating, the thermally expandable microspheres expand, and unevenness and adhesive force are generated on the surface of the adhesive layer. decline. Such an adhesive tape can also peel off the adherend only by the action of gravity. On the other hand, it is required for the easily peelable adhesive tape to reduce the residue of the paste when the adherend is peeled off, and the problem of reducing the residue of the paste is also the same with the use of an adhesive tape having thermally expandable microspheres. When this adhesive tape is applied to a fragile adherend, a small adherend, an adherend requiring cleanliness, etc., paste residue becomes a problem particularly. [Prior Art Document] [Patent Document] [Patent Document 1] Japanese Patent Laid-Open No. 2001-131507

[Problems to be Solved by the Invention] The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a heat-expandable microsphere which has excellent peelability after heating and has less paste residue on an adherend. Adhesive tape. [Technical means to solve the problem] The adhesive tape of the present invention includes a substrate and an adhesive layer disposed on at least one side of the substrate. The adhesive layer includes thermally expandable microspheres, and the adhesive tape is subjected to thermomechanical analysis. When heating at a heating rate of 3 ° C / min, the deformation starting point is set to point A, and the point where the expansion of the adhesive tape is maximized after the point A is set to point C is the point from point A to point C. Between points, when the point where the amount of deformation becomes half of the point C is set to point B, the time from point A to point B is 45 seconds to 200 seconds. In one embodiment, the time from the point B to the point C is 200 seconds or more. In one embodiment, the temperature at point B is 50 ° C to 250 ° C. In one embodiment, the thermally expandable microspheres include a shell made of 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 include a shell made of a resin and an organic solvent contained in the shell, and the glass transition temperature of the resin is 50 ° C to 250 ° C. In one embodiment, the thermally expandable microspheres include a shell made of a resin and an organic solvent contained in the shell, and the resin forming the shell includes a member selected from the group consisting of a structural unit derived from an isoacrylate and a methacrylonitrile derived. A group consisting of structural units derived from acrylonitrile, structural units derived from methyl (meth) acrylate, structural units derived from vinylidene chloride, and structural units derived from (meth) acrylic acid At least one of them. In one embodiment, the boiling point of the organic solvent is -50 ° C to 100 ° C. In one embodiment, the elastic modulus of the adhesive layer measured by the nanoindentation method is 0.1 MPa to 500 MPa. In one embodiment, the gel fraction of the adhesive constituting the adhesive layer is 30% to 99% by weight. [Effects of the Invention] According to the present invention, by appropriately controlling the deformation behavior during heating, it is possible to provide an adhesive tape that is excellent in peelability after heating and has less paste residue on the adherend to be peeled off.

A. The overall composition of the adhesive tape FIG. 1 is a schematic cross-sectional view of an adhesive tape according to an embodiment of the present invention. The adhesive tape 100 includes a base material 10 and an adhesive layer 20 disposed on at least one surface (one surface in the example of the figure) of the base material 10. The adhesive layer included in the adhesive tape of the present invention includes thermally expandable microspheres. The thermally expandable microspheres can expand at a specific temperature. The adhesive layer containing such heat-expandable microspheres expands the heat-expandable microspheres by heating, and generates unevenness on the adhesive surface (that is, the surface of the adhesive layer), so that the adhesive force decreases or disappears. When the adhesive tape of the present invention is used, for example, as a sheet for temporary fixing of a processed object when processing an electronic component (such as a ceramic capacitor), it exhibits the adhesiveness required for temporary fixing when the processed object is subjected to a specific processing. When the adhesive tape is peeled from the processed object after processing, the adhesive force is reduced or disappeared by heating, showing good peelability. In one embodiment, the thermally expandable microsphere includes a shell and an organic solvent contained in the shell, and the organic solvent contained in the shell expands due to 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 ° C./minute in a thermomechanical analysis, the time from the deformation start point to the time point when the deformation amount when the swelling and deformation becomes one and a half of the maximum deformation amount. It is 45 seconds to 200 seconds. In more detail, it demonstrates using FIG. FIG. 2 is a diagram showing an example of measurement results when the adhesive tape according to an embodiment of the present invention is subjected to thermomechanical analysis, and shows the relationship between the temperature and the amount of deformation (displacement) of the adhesive tape in the analysis. The adhesive tape is heated (heating rate: 3 ° C./minute), and when it reaches a specific temperature, the adhesive tape starts to deform (expand). This time point is the "deformation start point" described above. For convenience, let the deformation start point be A point. Moreover, the deformation of the adhesive tape mainly depends on the expansion and contraction of the thermally expandable microspheres contained in the adhesive layer. After passing the point A, if the heating is continued, the adhesive tape (substantially thermally expandable microspheres) continues to expand, and then begins to shrink. For example, in the case of using a thermally expandable microsphere including a shell and an organic solvent contained in the shell, the thermally expandable microspheres swell by the volatilization of the organic solvent before a specific temperature, and the time when the organic solvent is completely volatilized. Dots begin to shrink. The point where the contraction starts is the point where the amount of deformation of the adhesive tape becomes the largest. For convenience, this point is set to point C. Furthermore, the time from the point A to the point C, the amount of deformation becomes one and a half of the amount of deformation X (100 μm in the example of the figure) of the point C (the time when the amount of deformation during expansion and deformation becomes half of the maximum amount of deformation) Point (50 μm in the figure example) is set to point B. In the present invention, the time from point A to point B is 45 seconds to 200 seconds. The analysis conditions in the thermomechanical analysis are as follows. <Analysis conditions> Device name: Seiko Instruments Inc., trade name "TMA / SS150" Measurement mode: Expansion method with adhesive layer on the probe side Sample size: 5 mm square Probe: 1 mmProbe load: 0 N Measurement temperature range: room temperature (25 ° C ± 5 ° C) to 250 ° C Heating rate: 3 ° C / min In the present invention, the time from point A to point B is set to 45 seconds to In 200 seconds, an adhesive tape with less paste residue when peeling the adherend can be obtained. It is considered that from point A to point B, with the expansion of the thermally expandable microspheres, the adhesive layer is deformed (expanded), but no unevenness is formed on the surface of the adhesive layer, or even if it is formed, the entire surface of the adhesive layer surface is almost In a state of being pressed against the adherend. It is considered that this state promotes the state where the paste remains on the adherend together with the softening of the adhesive caused by heating. In the present invention, by setting the time in such a state (that is, the time from point A to point B) to 200 seconds or less, an adhesive tape with less paste residue 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 are rapidly expanded. In such a case, there is a possibility that an undesirable situation such as flying up of an adherend may occur with the rapid change of the thermally expandable microspheres. The time from point A to point B is preferably 70 seconds to 180 seconds, and more preferably 90 seconds to 170 seconds. If it is such a range, the said effect will become remarkable. The time from point B to point C is preferably 30 seconds or more, more preferably 60 seconds or more, still more preferably 180 seconds or more, and even more preferably 200 seconds or more. At the stage close to point C after passing point B, the thermally expandable microspheres further expand, and as a result, unevenness is generated on the surface of the adhesive layer, and the contact surface between the adhesive layer and the adherend gradually decreases. As a result, the adhesive force of the adhesive tape decreases or disappears. On the other hand, if the thermally expandable microspheres begin to shrink after passing point C, the contact surface between the adhesive layer and the adherend starts to increase, and the adhesive tape exhibits adhesiveness again. That is, before the point B reaches the point C, the adhesive tape shows excellent peelability. By setting the time in this state to a specific time or more as described above, when the adhesive tape is used in a manufacturing step of an electronic component or the like, the time taken for the peeling step of the adherend can be sufficiently secured. In addition, when the time from point B to point C is too short, it means that the thermally expandable microspheres are rapidly deformed, and there is a small piece of the adhesive layer component (such as an adhesive) that cannot follow the rapid deformation of the thermally expandable microspheres. Separation, and the composition of the adhesive layer separated by the small pieces may cause the paste to remain. The upper limit of the time from point B to point C is, for example, 3600 seconds or less, preferably 1800 seconds or less, and more preferably 1000 seconds or less. Within this range, heat-expandable microspheres with an appropriate amount of organic solvent can be used. In the above thermomechanical analysis, the temperature at point A (also referred to as point A temperature) is preferably 30 ° C to 200 ° C, more preferably 40 ° C to 180 ° C, and even more preferably 60 ° C to 180 ° C. In the above thermomechanical analysis, the temperature at point B (also referred to as point B temperature) is preferably 50 ° C to 250 ° C, more preferably 70 ° C to 200 ° C, and even more preferably 80 ° C to 150 ° C. By setting the temperature at point B to 50 ° C or higher, it is possible to prevent unnecessary peeling performance of the adhesive tape (for example, peeling performance under conditions of high external temperature such as summer). When the temperature at the point B exceeds 250 ° C., there is a possibility that deterioration of the adhesive tape, fire, etc. may occur before the release property is exhibited. In the above thermomechanical analysis, the temperature at the C point (also referred to as the C point temperature) is preferably 90 ° C to 350 ° C, and more preferably 100 ° C to 200 ° C. At 25 ° C, the adhesive force when the adhesive surface of the adhesive tape of the present invention is laminated to a polyethylene terephthalate film (for example, 25 μm thick) before the thermally expandable microspheres are foamed is preferably 0.2 N / 20 mm or more, more preferably 0.2 N / 20 mm to 20 N / 20 mm, and still more preferably 2 N / 20 mm to 10 N / 20 mm. Within this range, for example, an adhesive tape useful as a sheet for temporary fixing used in the manufacture of electronic parts can be obtained. The adhesive force in this specification refers to an adhesive force measured by a method in accordance with JIS Z 0237: 2000 (adhesion conditions: 2 kg roller reciprocating once, peeling speed: 300 mm / min, and peeling angle 180 °). The thickness of the adhesive tape of the present invention is preferably 30 μm to 500 μm, and more preferably 40 μm to 300 μm.B. Adhesive layer The adhesive layer contains thermally expandable microspheres. Practically, the adhesive layer further includes an adhesive. B-1. Heat-expandable microspheres As the heat-expandable microspheres, any appropriate heat-expandable microspheres can be used as long as they are expandable by heating to such an extent that the surface of the adhesive layer is uneven. As the thermally expandable microsphere, for example, a microsphere including 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 these, resin is preferable. When a resin is used, heat-expandable microspheres that are easily softened and expanded by heating can be obtained. In addition, since the shell made of resin has a density close to that of the adhesive, it is also advantageous in terms of being easily dispersed in the adhesive layer with high uniformity. As the resin forming the shell, for example, a resin having a structural 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; acrylic acid, methacrylic acid, itaconic acid, Maleic acid monomers such as maleic acid, fumaric acid, citraconic acid; vinylidene chloride; vinyl acetate; methyl (meth) acrylate, ethyl (meth) acrylate, (meth) N-butyl acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, isoester (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, acrylic acid (meth) acrylates such as β-carboxyethyl esters; styrene monomers such as styrene, α-methylstyrene, and chlorostyrene; acrylamide, substituted acrylamide, methacrylamide, substituted methyl Ammonium monomers such as acrylamide. The polymer containing these monomers may be a homopolymer or a copolymer. The resin forming the shell may be a crosslinked body. By cross-linking, the repulsive free volume of the polymer can be adjusted, thereby controlling the diffusibility of the volatile substances contained therein, the expansion of the shell, and the like. The crosslinked body may further include a structural unit derived from a monomer having two or more polymerizable double bonds in a molecule. In one embodiment, the monomer capable of radical polymerization is used in combination with a monomer having two or more polymerizable double bonds in the molecule. Examples of the monomer having two or more polymerizable double bonds in the molecule include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; allyl methacrylate, tripropenyl formal, Triallyl isocyanate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,4-butanediol Di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol 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-hexanediol di (meth) acrylate, trihydroxy Methylpropane tri (meth) acrylate, EO modified trimethylolpropane tri (meth) acrylate, glycerol di (meth) acrylate, dimethylol-tricyclodecane bis (meth) Acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, neopentyl glycol acrylate, trimethylolpropane acrylate ester 2-hydroxy-3-propenyloxypropyl (meth) acrylate, neopentyl glycol di (meth) acrylate hydroxypivalate, di-trimethylolpropane tetra (meth) acrylate, 2 -Butyl-2-ethyl-1,3-propanediol di (meth) acrylate, polytetramethylene glycol 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 triacrylic acid Ester toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, and the like. In one embodiment, the shell-forming resin comprises a member selected from the group consisting of a structural unit derived from an isoacrylate, a structural unit derived from methacrylonitrile, a structural unit derived from acrylonitrile, At least one of a structural unit, a structural unit derived from vinylidene chloride, and a structural unit derived from (meth) acrylic acid. If a resin having these structural units is used, it can form a shell with low solubility in the organic solvent contained therein, and the organic solvent is difficult to penetrate or wet before being heated. In addition, when the resin is used, thermally expandable microspheres having good deformability due to heating can be obtained. Furthermore, if the monomer is used, the thermal properties of the shell can be easily controlled by cross-linking and the like. In one embodiment, methacrylonitrile and / or acrylonitrile are preferably used from the viewpoint of improving the resistance to the organic solvent contained therein. When using these monomers, the total content ratio of the structural unit derived from methacrylonitrile and the structural unit derived from acrylonitrile is preferably 10% to 99% by weight relative to 100% by weight of the shell-forming resin. , More preferably 20% to 99% by weight, and particularly preferably 30% to 95% by weight. Within such a range, thermally expandable microspheres having excellent solvent resistance and easily setting the temperature at the point B can be obtained. In one embodiment, from the viewpoint of ease of controlling the hardness of the shell, it is preferable to use methyl (meth) acrylate. When methyl (meth) acrylate is used, it can be easily combined with a crosslinkable monomer (for example, the above-mentioned monomer having two or more polymerizable double bonds in the molecule) and easily crosslinked by electron beam crosslinking or the like. Ground controls the hardness of the shell. When methyl (meth) acrylate is used, the content ratio of the methyl (meth) acrylate is preferably less than 65% by weight, and more preferably 1% by weight to 55% by weight based on 100% by weight of the shell-forming resin. % By weight, particularly preferably 1 to 50% by weight. When imparting flexibility to the shell, vinylidene chloride is preferably used. The amount of vinylidene chloride used can be any appropriate amount depending on the glass transition temperature of the resin required. The thickness of the shell is preferably 15 μm or less, more preferably 7 μm or less, still more preferably 5 μm or less, and even more preferably 4 μm or less. With such a range, it is possible to shorten the time from the point A to the point B, 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, and more preferably 2 μm or more. Within this range, it is possible to produce thermally expandable microspheres that are not easily destroyed by an external force or the like. When the thickness of the shell is less than 1 μm, the physical properties of the shell are changed due to the wetting (diffusion) of the organic solvent contained in the shell. As a result, the time from point B to point C becomes significantly shorter. Fear. That is, by setting the upper and lower limits of the thickness of the shell to the above range, it is easy to obtain rapid expansion at the initial stage of heating (points A to B), and a long period of time during subsequent heating (points B to C). Thermally expandable microspheres that maintain an expanded state. Furthermore, by setting the upper and lower limits of the thickness of the shell to the above range, it is possible to reduce temperature unevenness during foaming. The glass transition temperature (Tg) of the resin constituting the shell is preferably 50 ° C to 250 ° C, more preferably 60 ° C to 200 ° C, and even more preferably 80 ° C to 150 ° C. Within such a range, appropriately expandable thermally expandable microspheres can be obtained, and if the thermally expandable microspheres are used, an adhesive tape with an appropriately set point B temperature can be easily obtained. In addition, in this specification, when resin is a copolymer, the said glass transition temperature is calculated | required by the calculation formula of Fox. The calculation formula of Fox is shown below, which is the glass transition temperature Tg (° C) of the copolymer and the glass transition temperature Tg of the homopolymer obtained by homopolymerizing the monomers constituting the copolymer._i (° C). Furthermore, in the following formula of Fox, Tg (° C) represents the glass transition temperature of the copolymer, W_i Represents the weight fraction of monomer i, Tg_i (° C) represents the glass transition temperature of the homopolymer formed from the monomer i. 1 / (273 ＋ Tg) = Σ (W_i / (273 ＋ Tg_i )) As the glass transition temperature of the homopolymer formed from monomers, acrylonitrile homopolymer (AN): 97 ° C, methyl methacrylate homopolymer (MMA): 102 ° C, methacrylonitrile homopolymer (MAN): 120 ° C, vinylidene chloride homopolymer: 75 ° C, isoacrylate homopolymer: 97 ° C. As the glass transition temperature of the other homopolymers, the values described in "Polymer Handbook" (4th edition, John Wiley & Sons, Inc, 1999) can be used. In addition, in this document, when a value of a plurality of Tg is described, a value of "conventional" is used. The absolute value (| Tg-B point temperature |) of the difference between the glass transition temperature (Tg) of the resin forming the shell and the required point B temperature is preferably 45 ° C or lower, more preferably 5 ° C to 35 ° C. When a resin having such a glass transition temperature is used, it becomes easy to set the temperature at point B to a desired temperature. The volatile substances contained in the shell are typically organic solvents. Examples of the organic solvent include linear aliphatic hydrocarbons having 3 to 8 carbon atoms and their fluorides, branched aliphatic hydrocarbons having 3 to 8 carbon atoms and their fluorides, and carbon number 3 A linear alicyclic hydrocarbon to 8 and its fluoride, an ether compound having a hydrocarbon group having 2 to 8 carbon atoms, or a compound in which a part of hydrogen atoms of the hydrocarbon group is replaced by a fluorine atom, and the like. In one embodiment, as the organic solvent, propane, cyclopropane, butane, cyclobutane, isobutane, pentane, cyclopentane, neopentane, isopentane, hexane, cyclohexane, 2 -Methylpentane, 2,2-dimethylbutane, heptane, cycloheptane, octane, cyclooctane, methylheptanes, trimethylpentane, etc. consist of only hydrogen and carbon atoms Composition of hydrocarbons; C₃ F₇ OCH₃ , C₄ F₉ OCH₃ , C₄ F₉ OC₂ H₅ And other hydrofluoroethers. These organic solvents may be used alone or in combination of two or more. The organic solvent has the advantages of low affinity with the shell-forming resin and / or adhesive, difficulty in dissolving the shell and / or adhesive, and difficulty in changing physical properties such as thermal properties. In addition, hydrocarbons composed of only hydrogen atoms and carbon atoms are preferred from the viewpoint of industrial use. In one embodiment, branched hydrocarbons (for example, isobutane, isopentane, etc.) are used as the hydrocarbons composed of only hydrogen atoms and carbon atoms. Branched hydrocarbons are not easy to be charged. If this solvent is used, accidents such as fire caused by charging can be prevented. The boiling point of the organic solvent is preferably -50 ° C to 100 ° C, and more preferably -20 ° C to 100 ° C. Within this range, it is possible to obtain thermally expandable microspheres in which the shell can expand well without breaking. Furthermore, when the boiling point of the organic solvent is too low, the operation for suppressing volatilization during the production of 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 ° C to 150 ° C, more preferably more than 0 ° C and 150 ° C or lower, more preferably 5 ° C to 125 ° C. When two or more organic solvents (mixed solvents) are used, 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 preferably in the above range. Within such a range, the time from point A to point B and the time from point B to 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 damaged due to the pressure generated when the organic solvent is heated, or the adhesive may be scattered, which may prevent the function or effect expected from the present invention. In addition, in many cases, the thermally expandable microspheres are exposed to an environment where an adhesive or a sticking operation existing around them will crush the thermally expandable microspheres before heating. Therefore, it is preferable to have a vapor pressure before heating so that the thermally expandable microspheres are not crushed. The content ratio of the organic solvent with respect to the weight of the thermally expandable microspheres before heating is preferably 5% to 35% by weight, and more preferably 10% to 30% by weight. 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 ratio is less than 5% by weight, for reasons such as low density, the thermally expanded microspheres tend to be biased on the surface of the adhesive layer during the production of the adhesive layer, and excessively generated on the surface of the adhesive layer after heating The risk of bumps. When the content ratio exceeds 35% by weight, there may be a high density and sedimentation in the adhesive layer, and even heating may not form sufficient unevenness on the surface of the adhesive layer, and may not obtain the required peelability. Also, There is a possibility that a paste residue may be generated. The average particle diameter (quantity basis) of the thermally expandable microspheres before foaming the thermally expandable microspheres at an ambient temperature of 25 ° C is preferably 1 μm to 40 μm, more preferably 5 μm to 40 μm, and further It is preferably 10 μm to 40 μm. Within this range, thermally expandable microspheres having high dispersibility in the adhesive layer can be obtained. The adhesive layer containing the heat-expandable microspheres in a state of high dispersibility has high uniformity of unevenness caused by heating, and can exhibit excellent peelability. The average particle diameter of the heat-expandable microspheres can be controlled, for example, by conditions under which the heat-expandable microspheres are polymerized (the details will be described later). In addition, in this specification, the average particle diameter can be measured by observing the thermally expandable microspheres used by an optical microscope or an electron microscope, or the thermally expandable microspheres taken out from the adhesive layer before heating. The average particle diameter can be measured by a particle size distribution measurement method in a laser scattering method. More specifically, the average particle diameter can be used to disperse the thermally expandable microspheres used in a specific solvent (for example, water), and then measure it using a particle size distribution measuring device (for example, Shimadzu Corporation's trade name "SALD-2000J"). . In one embodiment, the content ratio of the thermally expandable microspheres is expressed as the area ratio of the thermally expandable microspheres measured from a cross section. When the cross-sectional area of the adhesive layer in a specific 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 adhesive layer is The cross-sectional area A is preferably 3% to 75%, and more preferably 3.5% to 70%. When the ratio of the cross-sectional area B is less than 3%, even if the thermally expanded microspheres are expanded by heating, the unevenness on the surface of the adhesive is 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 may become too large, which may cause bulging and peeling between the substrate and the adhesive layer, and there may be a problem in the adhesive layer. There is a fear that the adhesive content is low and the required adhesion cannot be obtained. The ratio of the cross-sectional area B of the thermally expandable microspheres can be obtained, for example, by observing the cross-section of the adhesive layer with an electron microscope (for example, Hitachi High-Technologies Corporation, trade name "S-3400N Low Vacuum Scanning Electron Microscope"). The image is appropriately processed and obtained. For example, the image may be output on paper from the weight a of the adhesive layer portion (that is, the entire adhesive layer containing the thermally expandable microspheres) to the weight b of the paper after only the thermally expandable microsphere portions It is obtained by the formula of b / a × 100. The content ratio of the heat-expandable microspheres with respect to the weight of the adhesive layer is preferably 5 to 95% by weight, more preferably 10 to 70% by weight, and even more preferably 10 to 50% by weight. Within this range, the ratio of the cross-sectional area B of the thermally expandable microspheres as described above can be achieved. In addition, by setting the content ratio of the thermally expandable microspheres to the above range, and in order to prevent the thermally expandable microspheres from being unevenly distributed in the adhesive layer, operations such as stirring the composition for forming an adhesive layer before the coating step are performed. The cross-sectional area B of the thermally expandable microspheres can be set to a preferable range. The content ratio of the thermally expandable microspheres is determined by the following formula. The weight of the thermally expandable microspheres is determined by measuring the weight of the thermally expandable microspheres taken out of the adhesive layer. The content ratio of the thermally expandable microspheres (% by weight) = the weight of the thermally expandable microspheres / the weight of the adhesive layer × 100 The thermally expandable microspheres can be produced by any appropriate method. In one embodiment, the thermally expandable microspheres are obtained by a suspension polymerization method. Suspension polymerization is generally performed by dispersing a monomer (shell-forming material) and an organic solvent in an aqueous dispersion medium containing a dispersant, and polymerizing the monomer in the presence of an organic solvent. Also, a dispersion stabilizer that stabilizes dispersion can be used. Examples of the dispersion stabilizer in the aqueous dispersion medium include inorganic fine particles such as silicon dioxide, magnesium hydroxide, calcium phosphate, and aluminum hydroxide. As the dispersion stabilization aid, 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 the particle size and the content of the organic solvent, can be controlled by the above-mentioned polymerization conditions for suspension polymerization, the type of mixed components, and the amount of addition. For example, it is possible to obtain thermally expandable microspheres with a large particle diameter by operations such as reducing the amount of the dispersant added and slowing the stirring speed during polymerization. Moreover, if the compounding amount of a monomer is increased or the stirring speed at the time of polymerization is slowed, a thermally expandable microsphere with a thick shell can be obtained. B-2. Adhesive As the adhesive constituting the above-mentioned adhesive layer, any appropriate adhesive can be used as long as the effect of the present invention can be obtained. Examples of the adhesive include an acrylic adhesive, a polysiloxane adhesive, a vinyl alkyl ether adhesive, a polyester adhesive, a polyamide adhesive, and a urethane adhesive. , Fluorine-based adhesives, styrene-diene block copolymer-based adhesives, active energy ray hardening adhesives, and the like. Among them, an acrylic adhesive, a rubber adhesive or a silicone adhesive is preferred, and an acrylic adhesive is more preferred. The gel fraction of the adhesive is preferably 20% to 100% by weight, more preferably 30% to 99% by weight, and still more preferably 50% to 99% by weight. When the gel fraction is less than 20% by weight, even if the thermally expanded microspheres expand and cause unevenness on the surface of the adhesive layer, the adhesive layer may flow and the unevenness may disappear in a short time. In addition, because the polymer molecule has a small repulsive volume, the organic solvent in the thermally expandable microspheres easily permeates between the polymer molecular chains, so that the time from point A to point B may be longer. On the other hand, when the gel fraction exceeds 99% by weight, the thermal expansion of the heat-expandable microspheres is prevented without generating sufficient unevenness, or even when the unevenness is generated, the thermally expandable microspheres explode and cause thermal expansion Phenomenon such as scattering of the shell of the microspheres or the surrounding adhesive layer may worsen the residual property of the paste. The gel fraction of the adhesive can be controlled by adjusting the composition of the base polymer constituting the adhesive, the type or content of the cross-linking agent added to the adhesive, and the type or content of the adhesion-imparting agent. The measurement method of the gel fraction is described later. The base polymer contained in the above-mentioned adhesive preferably has an OH group or a COOH group. The reason is that if such a base polymer is used, the above-mentioned gel fraction can be adjusted using a crosslinking agent. In addition, by the amount of the OH group or the COOH group that does not react with the cross-linking agent, it is possible to adjust the agglutination property of the base polymer by an intermolecular force such as a hydrogen bond. This makes it possible to control the unevenness of the surface of the adhesive caused by the expansion of the thermally expandable microspheres and the permeability of the shell 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, and more preferably 20 to 30. The acid value of the base polymer having a COOH group is preferably 10 to 100, and more preferably 20 to 50. Moreover, the hydroxyl value and acid value of the polymer in the adhesive layer can be measured by extracting the solvent-soluble components in the adhesive layer. Specifically, the solvent-soluble component can be extracted by the following method. (i) Put the adhesive layer into a solvent, and prepare a solution sample in which a solvent-soluble component in the adhesive layer is dissolved in the solvent. As the solvent, considering polarity and the like, a member selected from chloroform (CHCl₃ ), Methylene chloride (CH₂ Cl₂ ), Tetrahydrofuran (THF), acetone, dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), methanol, ethanol, toluene, water, etc. The ratio includes two or more mixed solvents. Typically, about 30 g of a solvent is added to about 0.2 g of the adhesive layer, and the mixture is stirred at a temperature ranging from room temperature to the boiling point of the solvent used for about 30 minutes to about 12 hours. If necessary, for example, when the extraction efficiency of the analysis target component is low, etc., the same amount of solvent can be added to the sample after the above solution is dispensed and the solution is stirred, and the dispensed solution can be stirred. This operation is performed once or repeatedly to prepare a solution sample. (ii) The solvent-soluble polymer can be extracted by removing the solvent from the solution sample by a method such as evaporation. In addition, the solvent-soluble polymer may include a solvent-soluble component that is not an object of measurement, such as a low-molecular-weight component of an unreacted crosslinking agent. At this time, the molecular weight is distinguished by separating the above-mentioned solution sample into a solvent in which only the polymer component is insoluble (reprecipitation method) or by gel filtration chromatography using the above-mentioned solution sample (separating the liquid phase layer) (Analytical method), etc., to adjust the solvent-soluble polymer composed only of the measurement target. (Acrylic Adhesive) Examples of the acrylic adhesive include acrylic polymers (homopolymers or copolymers) using one or two or more kinds of (meth) acrylic acid alkyl esters as monomer components. Acrylic adhesives and the like as base polymers. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and (methyl) Base) butyl acrylate, isobutyl (meth) acrylate, second butyl (meth) acrylate, third butyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate , Heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, (meth) Isononyl acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, decyl (meth) acrylate Trialkyl ester, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, cetyl (meth) acrylate, heptadecyl (meth) acrylate, ( C1-20 alkyl (meth) acrylates, such as octadecyl (meth) acrylate, undecyl (meth) acrylate, and eicosyl (meth) acrylate. Among them, an alkyl (meth) acrylate having a linear or branched alkyl group having 4 to 18 carbon atoms can be preferably used. In one embodiment, the acrylic polymer includes a structural unit of a monomer derived from a homopolymer having a glass transition temperature (Tg) of 80 ° C or higher (preferably 90 ° C or higher, and more preferably 100 ° C or higher). When such a polymer is used, an adhesive layer having a moderate elastic modulus can be formed. Examples of the monomer include cyclohexyl methacrylate (Tg: 83 ° C), dicyclopentyl acrylate (Tg: 120 ° C), dicyclopentyl methacrylate (Tg: 175 ° C), and isoacrylate. (Tg: 94 ° C), isomethacrylate (Tg: 150 ° C), third butyl methacrylate (Tg: 118 ° C), methyl methacrylate (Tg: 105 ° C), trimethylolpropane Triacrylate (Tg:> 250 ° C), styrene (Tg: 80 ° C), acrylonitrile (Tg: 97 ° C), N-acrylfluorenylmorpholine (Tg: 145 ° C), and the like. Among them, methyl methacrylate is preferred. The content ratio of the structural unit of the monomer derived from the homopolymer having a glass transition temperature (Tg) of 80 ° C or higher is preferably 1 to 20 parts by weight relative to 100 parts by weight of the base polymer (acrylic polymer). More preferably, it is 1 to 10 parts by weight. The acrylic polymer may contain units corresponding to other monomers capable of copolymerizing with the (meth) acrylic acid alkyl ester as needed for the purpose of improving the cohesive force, heat resistance, and crosslinkability. Examples of such monomers include carboxyl-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; cis Anhydride monomers such as butadiene anhydride, itaconic anhydride; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxyhexyl (meth) acrylate, ( Hydroxyoctyl methacrylate, hydroxydecyl (meth) acrylate, hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl methacrylate and other hydroxyl-containing monomers; styrene sulfonic acid , Allylsulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate, (meth) Sulfonic acid group-containing monomers such as propylene naphthalenesulfonic acid; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, (N-substituted) fluorene-based monomers such as N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamine; aminoethyl (meth) acrylate, (formyl) ) N, N-dimethylaminoethyl acrylate (Aminoalkyl (meth) acrylate-based monomers, such as tert-butylaminoethyl (meth) acrylate); methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate Iso (meth) acrylic alkoxyalkyl ester-based monomers; N-cyclohexylcis-butenedifluoreneimide, N-isopropylcisbutenedifluoreneimide, N-laurylcisbutenedifluorene Immine, N-phenyl maleimide diimide and other maleimide monomers; N-methyl Ikonimide, N-ethyl Ikonimide, N-butyl Ikonimide, N-octyl Ikonimide, N-2-ethylhexyl Ikonimide, N-cyclohexyl Ikonimide, N-Lauryl Ikonimide, etc. Kanganimide monomers; N- (meth) acrylfluorenyloxymethylene succinimide, N- (meth) acrylfluorenyl-6-oxyhexamethylenesuccinimide, N -(Meth) acrylfluorenyl-8-oxyoctamethylene succinimide and other succinimide-based monomers; vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methyl vinyl Pyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpyridine, vinylpyridine, vinylpyrrole Vinyl monomers such as vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarboxamide, styrene, α-methylstyrene, and N-vinylcaprolactam; acrylonitrile , Cyanoacrylate monomers such as methacrylonitrile; epoxy-containing acrylic monomers such as glycidyl (meth) acrylate; polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate Diol-based acrylate monomers such as esters, methoxyethylene glycol (meth) acrylate, and methacrylate polypropylene glycol (meth) acrylate; tetrahydrofurfuryl (meth) acrylate, fluorine (methyl) ) Acrylates such as acrylates and polysiloxanes (meth) acrylates with heterocyclic rings, halogen atoms, silicon atoms, etc .; 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 Ester, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, propylene Polyfunctional urethane monomers; isoprene, butadiene, isobutylene and other olefinic monomers; vinyl ether vinyl ether-based monomers. These monomers can be used alone or in combination of two or more kinds. (Additive) The adhesive may include any appropriate additive as necessary. Examples of the additive include a crosslinking agent, an adhesion-imparting agent, a plasticizer, a pigment, a dye, a filler, an anti-aging agent, a conductive material, an antistatic agent, an ultraviolet absorber, a light stabilizer, a peeling adjuster, and a softening agent Agents, surfactants, flame retardants, antioxidants, etc. As the adhesion imparting agent, any appropriate adhesion imparting agent can be used. As the adhesion-imparting agent, for example, an adhesion-imparting resin is used. Specific examples of the adhesion-imparting resin include rosin-based adhesion-imparting resins (for example, unmodified rosin, modified rosin, rosin-phenol resin, rosin ester resin, etc.), and terpene-based adhesion-imparting resins (for example, terpene-based resins). Terpene-based resins, styrene-modified terpene-based resins, aromatic-modified terpene-based resins, hydrogenated terpene-based resins, hydrocarbon-based adhesion-imparting resins (e.g., aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbons) Resins, aromatic hydrocarbon resins (such as styrene resins, xylene resins, etc.), aliphatic / aromatic petroleum resins, aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, Coumarone indene resin, etc.), phenol-based adhesion-imparting resins (e.g., alkylphenol-based resins, xylene-formaldehyde-based resins, soluble phenol resins, novolacs, etc.), ketone-based adhesion-imparting resins, polyamine-based adhesion-imparting agents Resins, epoxy-based adhesion-imparting resins, and elastic-system adhesion-imparting resins. The added amount of the adhesion-imparting agent is preferably 5 to 100 parts by weight, and more preferably 10 to 50 parts by weight based on 100 parts by weight of the base polymer. Examples of the crosslinking agent include, in addition to isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, and peroxide-based crosslinking agents, urea-based crosslinking agents and metal alkoxide-based crosslinking agents. Crosslinking agent, metal chelate crosslinking agent, metal salt crosslinking agent, carbodiimide crosslinking agent, oxazoline crosslinking agent, aziridine crosslinking agent, amine crosslinking agent Wait. Among these, an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent is preferred. Specific examples of the isocyanate-based crosslinking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; cyclopentyl diisocyanate, cyclohexyl diisocyanate, isophorone Cycloaliphatic isocyanates such as diisocyanate; aromatic isocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; trimethylolpropane / methylenebenzene Diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry, trade name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry, product ("Coronate HL"), isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry, trade name "Coronate HX"), and the like. The content of the isocyanate-based crosslinking agent can be set to any appropriate amount according to the required adhesive force, the elasticity of the adhesive layer, etc., and it is typically 0.1 to 20 parts by weight relative to 100 parts by weight of the base polymer, and more It is preferably 0.5 parts by weight to 10 parts by weight. Examples of the epoxy-based crosslinking agent include N, N, N ', N'-tetraglycidyl metaxylylenediamine, diglycidylaniline, and 1,3-bis (N, N-glycidyl). Aminoaminomethyl) cyclohexane (manufactured by MITSUBISHI GAS Chemical Co., Ltd., trade name "TETRAD C"), 1,6-hexanediol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 1600") , Neopentyl glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 1500NP"), ethylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 40E"), propylene glycol diethylene glycol Glycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd. under the trade name "Epolight 70P"), polyethylene glycol diglycidyl ether (manufactured by Nihon Oil Co., Ltd. under the trade name "Epiol E-400"), polypropylene glycol diglycidyl ether ( Manufactured by Nippon Oil and Fat Company, trade name "Epiol P-200"), sorbitol polyglycidyl ether (manufactured by Nagase ChemteX company, trade name "Denacol EX-611"), glycerin polyglycidyl ether (manufactured by Nagase ChemteX company, product "Denacol EX-314"), pentaerythritol polyglycidyl ether, polyglycerol Polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name "Denacol EX-512"), sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, phthalate Diglycidyl formate, tris (2-hydroxyethyl) isocyanurate triglycidyl ester, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, with two or more rings in the molecule Oxygen-based epoxy resins. The content of the epoxy-based crosslinking agent can be set to any appropriate amount according to the required adhesive force, the elasticity of the adhesive layer, etc., and is typically 0.01 to 10 parts by weight relative to 100 parts by weight of the base polymer. More preferably, it is 0.03 parts by weight to 5 parts by weight. As the plasticizer, any appropriate plasticizer can be used. Specific examples of the plasticizer include, for example, trimellitate-based plasticizers, pyromellitic ester-based plasticizers, polyester-based plasticizers, and adipic acid-based plasticizers. Among them, trimellitate-based plasticizers (such as tri-n-octyl trimellitate, tris (2-ethylhexyl) trimellitate, etc.) or pyromellitic acid-based plasticizers are preferred (For example, tetra-n-octyl pyromellitic acid, tetra (2-ethylhexyl) pyromellitic acid, etc.). The plasticizer can be used alone or in combination of two or more. The content of the plasticizer is preferably 1 to 20 parts by weight, and more preferably 1 to 5 parts by weight based on 100 parts by weight of the base polymer. B-3. Characteristics of the adhesive layer The elastic modulus of the above adhesive layer at 23 ° C measured by the nanoindentation method is preferably 0.1 MPa to 500 MPa, and more preferably 0.5 MPa to 400 MPa. In one embodiment, an adhesive layer having an elastic modulus of 0.8 MPa to 50 MPa is used. In the case where the elastic modulus of the adhesive layer is less than 0.1 MPa, the organic solvent that diffuses out of the heat-expandable microspheres during heating quickly passes through the adhesive layer, thereby shortening the time from point B to point C. On the other hand, when the elastic modulus exceeds 500 MPa, the expansion of the thermally expandable microspheres may be hindered, and the adhesive layer may be damaged when the thermally expandable microspheres expand. The elastic modulus of the adhesive layer can be controlled by introducing a structural unit of a monomer derived from a homopolymer having a glass transition temperature (Tg) of 80 ° C or higher, and adjusting the degree of crosslinking. In addition, the elastic modulus measured by the nanoindentation method is a part that is 3 μm away from the surface of the adhesive layer and there is no thermally expandable microsphere (a part more than 1 μm from the surface of the shell of the thermally expandable microsphere) as the elastic modulus. The measurement object continuously measures the load load and the depth of indentation of the indenter when the indenter is pressed into the adhesive layer at the time of loading and the load is removed, and is obtained from the obtained load-indentation depth curve. In this specification, the elastic modulus measured by the nanoindentation method refers to the elasticity measured as described above by setting the measurement conditions to a load / unload speed: 1000 nm / s and an indentation depth: 800 nm. Modulus. The gripping force between the adhesive layer and the substrate is preferably 4 N / 20 mm or more, and more preferably 5 N / 20 mm or more. If it is this range, the adhesive tape which maintains the adhesive force between a base material and an adhesive bond layer and has few paste residues can be obtained even after expansion of a heat-expandable microsphere. The measuring method of the gripping force is described later. At an ambient temperature of 25 ° C., the arithmetic mean height Sa of the adhesive layer before the thermally expandable microspheres are foamed is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. If it is this range, the adhesive tape which can reduce the unevenness | corrugation which generate | occur | produces on the bonding surface of an adherend can be obtained. The arithmetic mean height Sa can be measured in accordance with JIS B 0601: 1994 using a laser microscope (LEXT OLS-4000 manufactured by Olympus, an image magnification of 432 times, a measurement area of 640 × 640 μm (sampling rate of 0.625 μm)). The arithmetic mean height Sa of the above adhesive layer when the adhesive tape of the present invention is heated to reach point C is preferably 10 μm to 50 μm, and more preferably 3 μm to 30 μm. Within this range, an adhesive tape can be obtained in which the adhesive force decreases or disappears after heating, and the adherend can be easily peeled off. In addition, when the arithmetic average surface height Sa exceeds 50 μm, the foaming stress when the unevenness is generated may be too large, and even if no external force is applied, the adherend is blown away, which causes a failure in the subsequent adherend recovery. Risk of influence. `` The arithmetic mean height of the adhesive layer Sa when the adhesive tape is heated to reach point C '' is the adhesive layer of the adhesive tape (5 cm square) heated on the hot plate set to the temperature of point C for 60 ± 5 seconds The arithmetic mean height Sa can be measured using the above-mentioned laser microscope. Here, the arithmetic mean surface height Sa of the adhesive layer refers to the arithmetic mean surface height Sa after being heated without being adhered. The thickness of the adhesive layer is preferably 5 μm to 300 μm, more preferably 15 μm to 250 μm, still more preferably 30 μm to 100 μm, and even more preferably 30 μm to 60 μm. B-4. Other components The adhesive layer may further contain any appropriate other components as long as the effect of the present invention can be obtained. Examples of other components include beads. Examples of the beads include glass beads and resin beads. If such beads are added to the adhesive layer, the elastic modulus of the adhesive layer can be increased, and an adhesive tape capable of processing the object with better accuracy can be obtained. The average particle diameter of the beads is, for example, 0.01 μm to 50 μm. The added amount of the beads is, for example, 10 to 200 parts by weight, and preferably 20 to 100 parts by weight, based on 100 parts by weight of the adhesive layer.C. Substrate Examples of the substrate include a resin sheet, a non-woven fabric, paper, a metal foil, a woven fabric, a rubber sheet, a foamed sheet, a laminated body (particularly a laminated body including a resin sheet), and the like. Examples of the resin constituting the resin sheet include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polyethylene (PE). ), Polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), polyamide (nylon), fully aromatic polyamide (aramid), polyimide (PI), Polyvinyl chloride (PVC), polyphenylene sulfide (PPS), fluorine-based resin, polyetheretherketone (PEEK), etc. Examples of non-woven fabrics include non-woven fabrics made of natural fibers having heat resistance such as non-woven fabrics made of Manila hemp; synthetic resin non-woven fabrics such as polypropylene resin non-woven fabric, polyethylene resin non-woven fabric, and ester-based resin non-woven fabric. 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 substrate can be set to any appropriate thickness depending on the required strength or flexibility, the purpose of use, and the like. The thickness of the substrate is preferably 1000 μm or less, more preferably 1 μm to 1000 μm, still more preferably 1 μm to 500 μm, even more preferably 3 μm to 300 μm, and most preferably 5 μm to 250 μm. The substrate may be subjected to a surface treatment. Examples of the surface treatment include corona treatment, chromic acid treatment, ozone exposure, flame exposure, high-voltage electric shock exposure, free radiation treatment, and coating treatment using a primer. Examples of the organic coating material include those described in Plastic Hard Coating Material II (CMC Publication, (2004)). It is preferable to use a urethane-based polymer, and it is more preferable to use a polyacrylate urethane, a polyester urethane, or a precursor thereof. The reason for this is that the application and application to the substrate are simple, and a variety of types can be industrially selected and can be obtained inexpensively. The urethane-based polymer is, for example, a polymer containing a reaction mixture of an isocyanate monomer and an alcoholic hydroxyl-containing monomer (for example, a hydroxyl-containing acrylic compound or a hydroxyl-containing ester compound). The organic coating material may contain a chain extender such as a polyamine, an anti-aging agent, and an oxidation stabilizer as optional additives. The thickness of the organic coating layer is not particularly limited, and is preferably about 0.1 μm to 10 μm, preferably about 0.1 μm to 5 μm, and more preferably about 0.5 μm to 5 μm.F. Method for manufacturing adhesive tape The adhesive tape of the present invention can be produced by any appropriate method. Examples of the adhesive tape of the present invention include a method of directly applying a composition for forming an adhesive layer containing an adhesive and thermally expandable microspheres on a substrate, or applying the composition for forming an adhesive layer on any appropriate substrate. A method for transferring the formed coating layer onto a substrate. The composition for forming an adhesive layer may contain any appropriate solvent. Alternatively, after the adhesive coating layer is formed from the composition containing the adhesive, the thermally expandable microspheres may be sprinkled on the adhesive coating layer, and then the thermally expandable microspheres may be applied using a laminator or the like. It is embedded in this coating layer to form an adhesive layer containing thermally expandable microspheres. The content ratio of the thermally expandable microspheres in the composition for forming an adhesive layer is preferably 5 to 95% by weight, and more preferably 10 to 70% by weight based on the weight of the solid component of the composition for forming the adhesive layer. %, More preferably 10 to 50% by weight. As a coating method of each of the above-mentioned compositions, any appropriate coating method can be adopted. For example, each layer can be formed by drying after coating. As a coating method, the coating method using a multicoter, a die coater, a gravure coater, an applicator, etc. is mentioned, for example. Examples of the drying method include natural drying and heat drying. In the case of heating and drying, the heating temperature can be set to any appropriate temperature according to the characteristics of the substance to be dried.G. use The adhesive tape of the present invention can be well used as a sheet for temporarily fixing electronic component materials when manufacturing electronic components. In one embodiment, the adhesive tape of the present invention can be used as a temporary fixing sheet when cutting an electronic component material. Examples of the electronic component material include ceramic capacitor materials. If the electronic component material such as a ceramic capacitor material is temporarily fixed to the adhesive tape of the present invention, the material can be prevented from being displaced, and as a result, the material can be cut with excellent accuracy. As the cutting method in the cutting step, any appropriate cutting method can be adopted. [Examples] Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited by these examples. The evaluation methods in the examples are as follows. In addition, in the following evaluation, the adhesive tape which peeled the release film was used. In the examples, "parts" and "%" are based on weight unless otherwise specifically described. [Evaluation] (1) Determination of the hydroxyl value of the base polymer of the adhesive (pretreatment) (i) 2 g of the adhesive of the adhesive layer was added to 300 ml of chloroform and refluxed for 1 day. From the obtained solution, impurities such as dirt are removed by filtration, and the filtrate is recovered. (ii) The chloroform solution prepared in the above (i) was added dropwise to 10 L of methanol over 1 hour, and the obtained precipitate was recovered. (iii) The precipitate obtained by the above-mentioned operation (ii) was dissolved in 300 ml of chloroform. This solution was added dropwise to 10 L of methanol over 1 hour, and the obtained precipitate was recovered. (iv) The precipitate obtained by the above-mentioned operation (iii) was dissolved again in 300 ml of chloroform. This solution was added dropwise to 10 L of methanol over 1 hour, and the obtained precipitate was recovered. (v) The precipitate obtained in (iv) was measured by GPC (Gel Permeation Chromatography), and no low molecular weight component having a weight average molecular weight of 2,000 or less was confirmed. The precipitate (base polymer) As a sample for measuring the hydroxyl value. (v ') When a low-molecular weight compound having a weight average molecular weight of 2,000 or less is included in the precipitate, the above-mentioned 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, using polystyrene as a standard substance for molecular weight. <GPC measurement conditions> ･ Sample concentration: 0.2% by weight (tetrahydrofuran solution) ･ Sample injection amount: 10 μl ･ Dissolving solution: tetrahydrofuran (THF) ･ Flow rate (flow rate): 0.6 mL / min ･ Column temperature (measurement temperature) : 40 ℃ ･ column: trade name "TSKgelSuperHM-H / H4000 / H3000 / H2000" (manufactured by TOSOH Corporation) 股份有限公司 detector: differential refractometer (RI) (standard polystyrene: Tsk gel standard manufactured by TOSOH company 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 (the hydroxyl value of Measurement) The hydroxyl value was evaluated in accordance with JIS K 0070-1992 (acetylation method). About 25 g of acetic anhydride was added, and pyridine was added, and the total amount was set to 100 mL, and the mixture was sufficiently stirred to prepare an acetylation reagent. Approximately 2 g of the base polymer collected as a sample was accurately weighed and placed in a flat-bottomed flask. 5 mL of acetylation reagent and 10 mL of pyridine were added, and an air condenser was installed. After heating at 100 ° C for 70 minutes, it was left to cool, and 35 mL of toluene (tetrahydrofuran when the adhesive was poorly soluble in toluene) was added from the upper part of the condensation tube as a solvent, and after stirring, 1 mL of water was added and stirred to decompose ethyl acetate. Acid anhydride. In order to complete the decomposition, it was heated again for 10 minutes and left to cool. Rinse the condenser tube with 5 mL of ethanol and remove it. Add 50 mL of pyridine as a solvent and stir. 25 mL of a 0.5 mol / L potassium hydroxide ethanol solution was added to the solution using a full pipette, and a 0.5 mol / L potassium hydroxide ethanol solution was used for potentiometric titration, and the hydroxyl value was calculated from the following formula. Hydroxyl value (mgKOH / g) = (B-C) × f × 28.05 / S + D B: 0.5 mol / L potassium hydroxide ethanol solution used in the blank test (mL) C: 0.5 mol / L used in the sample L amount of potassium hydroxide ethanol solution (mL) f: factor of 0.5 mol / L potassium hydroxide ethanol solution S: sample collection amount (g) D: acid value (2) gel fraction determination of adhesive About 0.1 g of the adhesive (weight of the sample) of the adhesive layer was accurately weighed, and the sample was wrapped with a mesh sheet (trade name "NTF-1122", manufactured by Nitto Denko Corporation), and then the weight was about 50 g. Soak in ml of toluene at room temperature for 1 week. After that, the solvent-insoluble component (the content of the mesh sheet) was taken out from toluene, and dried at 70 ° C for about 2 hours. The solvent-insoluble component (the weight after impregnation and drying) after the drying was weighed, and the following formula was used. (a) Calculate the gel fraction (% by weight). In addition, in Example 7, before this measurement, 10 mJ / cm was irradiated with ultraviolet rays.² The adhesive is UV-cured. In Comparative Example 4, before the measurement, 500 mJ / cm of ultraviolet light was irradiated.² The adhesive is UV-cured. Ultraviolet irradiation was performed using "UM810" manufactured by Nitto Seiki Co., Ltd. Gel fraction (% by weight) = [(weight after dipping and drying) / (weight of sample)] × 100 (a) (3) Thermo-mechanical analysis of the adhesive tape Cut the adhesive tape to 5 mm × 5 mm to obtain a measurement sample. The measurement sample is brought into contact with the probe side of the measurement device, and is mounted on the measurement device. Then, heating was performed at a specific heating rate from room temperature to obtain a temperature-displacement (length) curve. Based on the temperature-displacement curve, the time from when the deformation start point (point A) reaches expansion and the time when the amount of deformation becomes half of the maximum deformation point (point B), and the amount of deformation from point B to the adhesive tape Time to reach the maximum point (point C), temperature at point A, temperature at point B, and temperature at point C. <Analysis conditions> Device name: Seiko Instruments Inc., trade name "TMA / SS150" Measurement mode: Expansion method with adhesive layer on the probe side Sample size: 5 mm square Probe: 1 mmProbe load: 0 N Measurement temperature range: room temperature (25 ° C ± 5 ° C) to 250 ° C Heating rate: 3 ° C / min (4) The arithmetic mean height Sa of the adhesive layer when point C is reached Cut the adhesive tape It was cut into 5 cm × 5 cm to obtain a measurement sample. The measurement sample was heated on a hot plate set to a 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 times, measurement area 640 × 640 μm (sampling rate 0.625 μm)). (5) The elastic modulus of the adhesive layer measured by the nanoindentation method The adhesive tape was cut in the thickness direction by a microtome, and the elastic modulus of the cut surface was measured by a nanoindenter. More specifically, the surface of the cut surface at a location of about 3 μm from the surface of the adhesive layer and where no thermally expandable microspheres are present (adhesive at least 1 μm from the surface of the shell of the thermally expandable microspheres) is used as a measurement object. The elastic modulus (average of 10 measurements) was obtained by numerically processing the displacement-load hysteresis curve obtained by pressing the probe (indenter) against the measurement object using software (triboscan) attached to the measurement device. . The nanoindenter device and measurement conditions are as follows. <Apparatus and measurement conditions> Apparatus: Nano indenter; Triboindenter manufactured by Hysitron Inc. Measurement method: Single indentation method Measurement temperature: 23 ° C Indentation speed: about 1000 nm / sec Indentation depth: about 800 nm Probe : Diamond, Berkovich type (triangular pyramid type) (6) Substrate-adhesive layer gripping force Adhesive tape is attached to the adhesive layer side of the adhesive tape described in the examples with a hand roller (manufactured by Nitto Denko Corporation) , No.315). Next, a double-sided adhesive tape (manufactured by Nitto Denko Corporation, No. 5000N) was bonded to the base material side of the adhesive tape described in the examples to make a short strip of 10 mm × 70 mm. Then, a 2 mm thick SUS board was bonded to the other side of the double-sided tape to prepare a test body. The obtained adhesive tape of the test body was peeled off at 180 ° at 50 mm / mm and then torn off. As a result, when only the peeling of the adhesive tape, that is, when the anchoring failure did not occur, it was set to pass (0 in the table), and when the adhesive layer was torn off with the adhesive tape, the anchoring failure occurred. In this case, the peel force at this time is measured. Furthermore, since the adhesive force when the adhesive tape is directly attached to the SUS board is 5 N / 10 mm, the qualified product in the above test can be said to have a gripping force of 5 N / 10 mm or more. (7) Paste Residue Evaluation 1 (Relationship between the time from point A to point B and paste residue) The entire mirror surface of a 4-inch silicon mirror wafer (bare wafer, with orientation plane) was bonded by hand pressing. The adhesive tape was left at room temperature for 1 hour. The wafer with the above-mentioned adhesive tape is set on a heating plate set with a temperature of point B of each adhesive tape of ± 5 ° C (the surface of the heating plate is in contact with the wafer surface without the adhesive tape), and the heating is performed. 10 seconds ± 1 second. After the wafer with the adhesive tape is taken out from the hot plate, the wafer with the adhesive tape is disposed in such a manner that the tape is naturally peeled off (the surface of the adhesive tape is on the lower side and the wafer is turned over) to remove the adhesive tape. Furthermore, when the adhesive tape does not drop naturally and is not removed from the wafer, the adhesive tape is sandwiched between the adhesive tape and removed in this state. In Example 7, before the peeling operation, ultraviolet rays were irradiated at 10 mJ / cm.² The adhesive is UV-cured. In Comparative Example 4, before this operation, 500 mJ / cm of ultraviolet light was irradiated² The adhesive is UV-cured. Ultraviolet irradiation was performed using "UM810" manufactured by Nitto Seiki Co., Ltd. Use an optical microscope (manufactured by Olympus Optical, 5x objective lens, 10x eyepiece) to observe the 1 × 1 mm center of the mirror surface after removing the adhesive tape, and count the residue of the paste on the wafer surface (not attached) The number of roughly spotted (grainy or irregularly shaped images) observed on the new wafer before the adhesive tape. In the table, the number of remaining pastes is 0 to 500, ◎, 500 to 1,000, 0, 0, 1000 to 5,000, and 5,000 or more. (8) Paste Residual Evaluation 2 (Relationship between time from point B to point C and paste residue) The entire mirror surface of a 4-inch silicon mirror wafer (bare wafer, with orientation plane) was bonded by hand pressing The adhesive tape was left at room temperature for 1 hour. The wafer with the above-mentioned adhesive tape is set on a heating plate set with a B temperature ± 5 ° C of each adhesive tape (the heating plate plate surface is in contact with the wafer surface without the adhesive tape), and the heating is 210 ± 10 seconds. After the wafer with the adhesive tape is taken out from the hot plate, the wafer with the adhesive tape is disposed in such a way that the tape is naturally peeled off (the surface of the adhesive tape is on the ground side and the wafer is turned over) to remove the adhesive tape. Furthermore, when the adhesive tape does not drop naturally and is not removed from the wafer, the adhesive tape is sandwiched between the adhesive tape and removed in this state. In Example 7, before the peeling operation, ultraviolet rays were irradiated at 10 mJ / cm.² The adhesive is UV-cured. In Comparative Example 4, before this operation, 500 mJ / cm of ultraviolet light was irradiated² The adhesive is UV-cured. Ultraviolet irradiation was performed using "UM810" manufactured by Nitto Seiki Co., Ltd. Use an optical microscope (manufactured by Olympus Optical, 5x objective lens, 10x eyepiece) to observe the 1 × 1 mm center of the mirror surface after removing the adhesive tape, and count the residue of the paste on the wafer surface (not attached) The number of roughly spotted (grainy or irregularly shaped images) observed on the new wafer before the adhesive tape. In the table, the number of remaining pastes is 0 to 500, ◎, 500 to 1,000, 0, 0, 1000 to 5,000, and 5,000 or more. [Manufacturing example 1] Production of thermally expandable microspheres A 150 g of sodium chloride and 20 g of colloidal silicon dioxide (manufactured by Nissan Chemical Co., Ltd., trade name "SNOWTEX") 70 g, After adding 1 g of polyvinyl pyrrolidone and 0.5 g of a condensate of diethanolamine and adipic acid to 600 g of distilled water, the pH value of the obtained mixture was adjusted to 2.8 to 3.2 to obtain an aqueous solution. To the above-mentioned aqueous solution, 80 g of acrylonitrile, 40 g of methyl methacrylate, and 130 g of vinylidene chloride were added as an oil-based additive for the shell material. Furthermore, 1 g of ethylene glycol dimethacrylate as a crosslinking agent was added to obtain a reaction solution. The above reaction solution was added to a pressure-resistant reaction vessel equipped with a homomixer (produced by Seki Chemical Co., Ltd. under the trade name "TK Homomixer"), and isobutane (boiling point) as an organic solvent intended to be enclosed in the shell was further added. : -11.7 ° C) 70 g and a starter (diisopropoxy dicarbonate) 5 g were added to a pressure-resistant reaction container. After the homomixer was rotated under specific initial stirring conditions (stirring speed: 6000 rpm, stirring time: 2 minutes) to stir the mixture, the mixture was heated to 60 ° C while stirring at 80 rpm to perform a reaction for 24 hours. The solid component obtained by filtering the reaction solution after the reaction was left at room temperature for one week under a nitrogen gas flow to obtain a thermally expandable microsphere. The obtained thermally expandable microspheres were measured under the trade name "SALD-2000J" manufactured by Shimadzu Corporation. As a result, the average particle diameter was 12.5 μm. Furthermore, by X-ray CT (Xradia520versa (measurement conditions: tube voltage 60 KV, tube current 83 μA, pixel size 0.20 μm / pixel) manufactured by ZEISS), it was found that the solvent in the thermally expanded microspheres was isobutane. The weight of the thermally expandable microspheres includes 13% by weight. Moreover, when measured by the above-mentioned computed tomography (computed tomography), the thickness of the shell of the thermally expandable microsphere was 2.8 μm. [Manufacturing Examples 2 to 11] Heat-expandable microspheres B to K Preparation amount of colloidal silica when preparing an aqueous solution, oil-based additives (acrylonitrile, methacrylonitrile, isomethacrylate, methyl methacrylate) Esters, vinylidene chloride), organic solvents (isobutane, isopentane (boiling point: 27.7 ° C), petroleum ether, isooctane (boiling point: 99 ° C)) intended to be enclosed in the shell, and The initial stirring conditions at the time of polymerization were as described in Table 1, except that heat-expandable microspheres B to K were produced in the same manner as in Production Example 1. The average particle diameter of the thermally expandable microspheres, the amount of the organic solvent contained, and the thickness of the shell were measured in the same manner as in Production Example 1. The results are shown in Table 1. [Table 1] [Example 1] Copolymerization of an acrylic copolymer (ethyl acrylate (EA), methyl methacrylate (MMA), 2-ethylhexyl acrylate (2EHA), and 2-hydroxyethyl acrylate (HEA) Substance, EA structural unit: MMA structural unit: 2EHA structural unit: HEA structural unit = 60: 5: 30: 5 (weight ratio); weight average molecular weight: 350,000; hydroxyl value: 24) 100 parts by weight, adhesion imparting agent (YASUHARA 20 parts by weight of Chemical Company, trade name "YS POLYSTAR S145"), 3 parts by weight of isocyanate-based crosslinker (manufactured by TOSOH company, trade name "Coronate L"), 30 parts by weight of thermally expandable microsphere A, and 210 parts by weight of toluene The components were mixed to prepare a composition for forming an adhesive layer. The weight average molecular weight of the acrylic copolymer was measured by the method described in the above evaluation (1). The above-mentioned composition for forming an adhesive layer was coated on a PET film (thickness: 50 μm) as a substrate and dried to obtain an adhesive tape (adhesive layer (thickness: 30 μm) / substrate). Furthermore, 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 7, Comparative Examples 1 to 4] It was obtained in the same manner as in Example 1 except that the composition of the acrylic copolymer and the composition of the composition for forming an adhesive layer were shown in Table 2. Adhesive tape. The obtained adhesive tape was subjected to the above evaluations (3) to (8). The results are shown in Table 2. In addition, in Table 2, "cross-linking agent TETRAD C" is an epoxy-based cross-linking agent (trade name "TETRAD C") manufactured by MITSUBISHI GAS CHEMICAL Company, and "DPHA" is dipentaerythritol hexaacrylate (Shinakamura Industrial Chemical Co., Ltd. (Manufactured by the company), "IRGACURE 184" is a light initiator (trade name "IRGACURE 184") manufactured by BASF Japan Co., Ltd. [Table 2]

10‧‧‧ Adhesive layer

20‧‧‧ substrate

100‧‧‧ Adhesive tape

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 an adhesive tape according to an embodiment of the present invention is subjected to thermomechanical analysis.

Claims (9)

An adhesive tape includes a substrate and an adhesive layer disposed on at least one side of the substrate. The adhesive layer includes thermally expandable microspheres, and the adhesive tape is heated at a heating rate in a thermomechanical analysis. When heating at ℃ / minute, the deformation starting point is set to point A, and the point where the deformation amount of the adhesive tape becomes the largest after the point A is expanded is set to point C, and the amount of deformation from point A to point C When the point that becomes half of the amount of deformation at point C is set to point B, the time from point A to point B is 45 seconds to 200 seconds. For example, the adhesive tape of claim 1, wherein the time from the point B to the point C is 200 seconds or more. For example, the adhesive tape of item 1, wherein the temperature at the above point B is 50 ° C to 250 ° C. For example, the adhesive tape of claim 1, wherein the thermally expandable microspheres include a shell made of a resin and an organic solvent contained in the shell, and the thickness of the shell is 1 μm to 15 μm. For example, the adhesive tape of claim 1, wherein the thermally expandable microspheres include a shell formed of a resin and an organic solvent contained in the shell, and the glass transition temperature of the resin is 50 ° C to 250 ° C. For example, the adhesive tape of claim 1, wherein the thermally expandable microspheres include a shell made of a resin and an organic solvent contained in the shell, and the resin forming the shell contains a material selected from the group consisting of structural units derived from isoacrylate and Structural units derived from acrylonitrile, structural units derived from acrylonitrile, structural units derived from methyl (meth) acrylate, structural units derived from vinylidene chloride, and structural units derived from (meth) acrylic acid At least one of the group. The adhesive tape according to any one of claims 4 to 6, wherein the boiling point of the organic solvent is -50 ° C to 100 ° C. For example, the adhesive tape of claim 1, wherein the elastic modulus of the above adhesive layer measured by the nanoindentation method is 0.1 MPa to 500 MPa. For example, the adhesive tape of claim 1, wherein the gel fraction of the adhesive constituting the adhesive layer is 30% to 99% by weight.