JP5623125B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to an adhesive sheet suitable for precision polishing and grinding.

  In a manufacturing process of a light emitting element (LED), a flat panel display (FPD) or the like, precision polishing or grinding of a substrate made of sapphire glass or the like is usually performed in a state where the substrate is fixed to a pedestal via a temporary fixing member. The temporary fixing member is required to have a high fixing force when the substrate is processed, and when the substrate is removed, the fixing force is required to be reduced so that the substrate can be removed without scratches or dirt. Moreover, in order to stabilize the fixed state of the substrate, it is preferable that the temporary fixing member has a higher elastic modulus. Examples of the temporary fixing member include a foamed adhesive sheet and wax.

The foamed pressure-sensitive adhesive sheet contains a foaming agent in a predetermined pressure-sensitive adhesive, and the adhesive force is reduced by expansion or foaming of the foaming agent by heat treatment (see, for example, Patent Documents 1 and 2).
However, since the foaming adhesive sheet has a low fixing force and a low elastic modulus, there is a problem that the fixing state of the substrate is difficult to stabilize, and therefore the processing accuracy of the substrate is inferior.

On the other hand, the wax is crystallized at a temperature lower than the melting point to develop a fixing force, exhibits a fluidity at a temperature higher than the melting point, and decreases the fixing force.
However, the reduction in fixing force due to wax is not sufficient. Therefore, when removing a board | substrate from wax, it is necessary to shift a board | substrate, As a result, a damage | wound will arise in a board | substrate. Further, the wax tends to remain on the removed substrate, and a separate cleaning process is required.

JP 63-33487 A JP-A-5-43851

  An object of the present invention is to provide a pressure-sensitive adhesive sheet that has a high fixing force and elastic modulus when fixing an adherend, is easy to remove, and hardly causes adhesive residue.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a solution means having the following constitution and have completed the present invention.
(1) containing a side chain crystalline polymer and 10 to 110 parts by weight of a foaming agent with respect to 100 parts by weight of the side chain crystalline polymer, and the side chain crystalline polymer has a melting point of 30 ° C. or more and The foaming agent is at a temperature lower than the foaming temperature, crystallized at a temperature lower than the melting point, exhibits fluidity at a temperature higher than the melting point, has a weight average molecular weight of 10,000 to 700,000, and has a thickness of 10 A pressure-sensitive adhesive sheet having a thickness of ˜70 μm.
(2) The side chain crystalline polymer has 30 to 100 parts by weight of (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, and (meth) acrylate 0 to 0 having an alkyl group having 1 to 6 carbon atoms. The pressure-sensitive adhesive sheet according to (1), which is a polymer obtained by polymerizing 70 parts by weight and 0 to 10 parts by weight of a polar monomer.
(3) The pressure-sensitive adhesive sheet according to (1) or (2), wherein the (meth) acrylate having an alkyl group having 1 to 6 carbon atoms is butyl acrylate.
(4) The pressure-sensitive adhesive according to any one of (1) to (3), wherein a vertical peel strength at 23 ° C. after passing through the temperature not lower than the melting point and lower than the foaming temperature of the foaming agent is 10 to 500 N / cm ^2. Sheet.
(5) The pressure-sensitive adhesive sheet according to any one of (1) to (4), wherein the storage elastic modulus G ′ at 23 ° C. is 4 × 10 ^{6 to} 5 × 10 ⁷ Pa.
(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5), wherein the storage elastic modulus G ′ at 60 ° C. is 1 × 10 ^{3 to} 7 × 10 ⁴ Pa.
(7) The adherend adhered at a temperature equal to or higher than the melting point and lower than the foaming temperature of the foaming agent is fixed at a temperature lower than the melting point, and removed at a temperature equal to or higher than the foaming temperature of the foaming agent. The pressure-sensitive adhesive sheet according to any one of (6).

  The pressure-sensitive adhesive sheet of the present invention can also be used in the form of a tape. That is, the pressure-sensitive adhesive tape according to the present invention is provided with a pressure-sensitive adhesive layer on at least one surface of the base film, and the pressure-sensitive adhesive layer is composed of the pressure-sensitive adhesive sheet according to any one of (1) to (7). Features.

  Moreover, if the adhesive sheet of this invention is used, precision grinding | polishing and grinding can be performed accurately. That is, the precision polishing method according to the present invention is a method of precisely polishing an object to be polished using the adhesive sheet according to any one of (1) to (7), wherein the adhesive sheet is used as an object to be polished. A step of interposing between the base and the temperature of the pressure-sensitive adhesive sheet is set to a temperature not lower than the melting point after the temperature of the pressure-sensitive adhesive sheet is equal to or higher than the melting point and lower than the foaming temperature of the foaming agent. A step of fixing to the pedestal, a step of precisely polishing the fixed object to be polished, and a step of bringing the temperature of the pressure-sensitive adhesive sheet to a temperature equal to or higher than the foaming temperature of the foaming agent and removing the object to be polished precisely from the pressure-sensitive adhesive sheet It is characterized by including these.

  A grinding method according to the present invention is a method for grinding an object to be ground using the adhesive sheet according to any one of (1) to (7), wherein the adhesive sheet is interposed between the object to be ground and a pedestal. And the temperature of the pressure-sensitive adhesive sheet is set to a temperature not lower than the melting point after the temperature of the pressure-sensitive adhesive sheet is higher than the melting point and lower than the foaming temperature of the foaming agent, and the object to be ground is fixed to the base via the pressure-sensitive adhesive sheet. A step of grinding the fixed object to be ground, and a step of setting the temperature of the adhesive sheet to a temperature equal to or higher than the foaming temperature of the foaming agent and removing the ground object to be ground from the adhesive sheet. Features.

The “sheet” in the present invention is not limited to a sheet shape, and is a concept including a sheet shape or a film shape as long as the effects of the present invention are not impaired.
The “foaming temperature” in the present invention means a temperature at which the foaming agent starts to expand or foam.

  According to the present invention, the fixing force and the elastic modulus when fixing the adherend are high, and therefore the fixing state of the adherend is stabilized, so that there is an effect that precision polishing and grinding can be performed with high accuracy. In addition, it is easy to remove and has an effect that adhesive residue hardly occurs.

<Adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention contains a side chain crystalline polymer and a foaming agent. The side-chain crystalline polymer is a polymer that crystallizes at a temperature lower than the melting point and exhibits fluidity by phase transition at a temperature higher than the melting point. That is, the side chain crystalline polymer is a polymer that reversibly causes a crystalline state and a fluid state in response to a temperature change.

  The pressure-sensitive adhesive sheet of the present invention contains a side chain crystalline polymer as a main component, and the foaming agent is 10 to 110 parts by weight, preferably 20 to 80 parts by weight, more preferably 100 parts by weight of the side chain crystalline polymer. It is contained at a ratio of 40 to 60 parts by weight. As a result, the pressure-sensitive adhesive sheet exhibits adhesive strength by the side-chain crystalline polymer exhibiting fluidity at a temperature higher than the melting point and lower than the foaming temperature of the foaming agent, so that the adherend can be adhered. become.

  In addition, the pressure-sensitive adhesive sheet enters the fine irregularities and voids existing on the adherend surface without any gaps. When the pressure-sensitive adhesive sheet in this state is cooled to a temperature lower than the melting point, the side chain crystalline polymer is crystallized to develop an anchor effect, and hence a high fixing force can be obtained. In addition, since the pressure-sensitive adhesive sheet containing the crystallized side chain crystalline polymer exhibits a high elastic modulus, the fixed state of the adherend can be stabilized and the adherend can be processed with high accuracy.

  Further, when the pressure-sensitive adhesive sheet is heated to a temperature equal to or higher than the foaming temperature of the foaming agent, the cohesive force of the pressure-sensitive adhesive sheet decreases due to the fluidity of the side chain crystalline polymer, and the foaming agent expands or foams. The force can be sufficiently reduced, and the adherend can be easily detached from the adhesive sheet. Therefore, the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive that fixes an adherend adhered at a temperature higher than the melting point and lower than the foaming temperature of the foaming agent at a temperature lower than the melting point and is removed at a temperature higher than the foaming temperature of the foaming agent. Can be used as a sheet.

  On the other hand, if the content of the foaming agent is less than 10 parts by weight, it is difficult to obtain a reduction in fixing force due to the foaming agent. So-called adhesive residue remaining on the adherend increases. Further, if the content of the foaming agent is more than 110 parts by weight, the ratio of the side chain crystalline polymer is relatively reduced, so that the fixing force when fixing the adherend is reduced, and the processing accuracy is also lowered accordingly. To do.

  The melting point of the side chain crystalline polymer means a temperature at which a specific portion of the polymer originally aligned in an ordered arrangement becomes disordered by an equilibrium process, and is measured by a differential thermal scanning calorimeter (DSC). It is a value obtained by measurement under measurement conditions of 10 ° C./min.

  The lower limit of the melting point is 30 ° C. or higher. Thereby, since the side chain crystalline polymer is crystallized at room temperature (23 ° C.), the pressure-sensitive adhesive sheet is in a state where it does not express adhesive force. Therefore, the adhesive sheet can be easily positioned with respect to the adherend, and workability is improved. The upper limit of the melting point is a temperature lower than the foaming temperature of the foaming agent when the adherend is stuck and fixed without expanding or foaming the foaming agent. A preferable range of the melting point is 30 to 70 ° C, more preferably 40 to 60 ° C. The melting point can be arbitrarily set by changing the composition of the side chain crystalline polymer.

  As the composition of the side chain crystalline polymer, for example, 30 to 100 parts by weight of a (meth) acrylate having a linear alkyl group having 16 or more carbon atoms and (meth) acrylate 0 having an alkyl group having 1 to 6 carbon atoms. Examples include a polymer obtained by polymerizing ˜70 parts by weight and 0-10 parts by weight of a polar monomer.

  Examples of the (meth) acrylate having a linear alkyl group having 16 or more carbon atoms include 16 to 16 carbon atoms such as cetyl (meth) acrylate, stearyl (meth) acrylate, eicosyl (meth) acrylate, and behenyl (meth) acrylate. (Meth) acrylate having 22 linear alkyl groups can be mentioned. Examples of the (meth) acrylate having 1 to 6 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) ) Acrylate, hexyl (meth) acrylate, etc., and examples of the polar monomer include carboxyl group-containing ethylenically unsaturated monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid; Ethyl (meth) acrylate, hydroxy Propyl (meth) acrylate, ethylenically unsaturated monomer having a hydroxyl group such as hydroxymethyl (meth) acrylate and the like, which may be used alone or in combination.

  A preferred composition of the side chain crystalline polymer is, for example, a copolymer obtained by polymerizing 39 to 50 parts by weight of behenyl acrylate, 40 to 60 parts by weight of butyl acrylate, and 1 to 10 parts by weight of hydroxyethyl acrylate. Is mentioned. In particular, it is preferable to employ butyl acrylate as the (meth) acrylate having an alkyl group having 1 to 6 carbon atoms because the fixing force tends to be improved.

  The polymerization method is not particularly limited, and for example, a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method and the like can be employed. For example, when the solution polymerization method is employed, the monomer can be polymerized by mixing the monomer exemplified above in a solvent and stirring at about 40 to 90 ° C. for about 2 to 10 hours.

  The weight average molecular weight of the side chain crystalline polymer is 10,000 to 700,000, preferably 10,000 to 600,000. When the weight average molecular weight is less than 10,000, the adhesive strength of the pressure-sensitive adhesive sheet tends to be strong, the peelability is lowered, and the adhesive residue increases. On the other hand, if the weight average molecular weight is larger than 700,000, the fluidity of the side chain crystalline polymer is lowered, so that the anchor effect is hardly exhibited, and the fixing force and the processing accuracy when processing the adherend are reduced. To do. The weight average molecular weight is a value obtained by measuring a side chain crystalline polymer by gel permeation chromatography (GPC) and converting the obtained measurement value to polystyrene.

  On the other hand, the foaming agent is not particularly limited, and any of ordinary chemical foaming agents and physical foaming agents can be employed. Chemical foaming agents include pyrolytic and reactive organic foaming agents and inorganic foaming agents.

  Examples of the pyrolytic organic foaming agent include various azo compounds (such as azodicarbonamide), nitroso compounds (such as N, N′-dinitrosopentamethylenetetramine), and hydrazine derivatives [4,4′-oxybis (benzene). Sulfonyl hydrazide) and the like], semicarbazide compounds (hydrazodicarbonamide and the like), azide compounds, tetrazole compounds and the like. Examples of the reactive organic foaming agent include isocyanate compounds.

  Examples of the thermal decomposition type inorganic foaming agent include bicarbonate / carbonate (sodium bicarbonate, etc.), nitrite / hydride, etc. Examples of the reaction type inorganic foaming agent include sodium bicarbonate and the like. The combination with an acid, the combination of hydrogen peroxide and yeast, the combination of zinc powder and an acid, etc. are mentioned.

  Examples of the physical foaming agent include organic physical foaming agents such as aliphatic hydrocarbons such as butane, pentane and hexane, chlorohydrocarbons such as dichloroethane and dichloromethane, and fluorochlorohydrocarbons such as chlorofluorocarbons; air, carbonic acid Examples thereof include inorganic physical foaming agents such as gas and nitrogen gas.

  As other foaming agents, microencapsulated thermally expandable fine particles (so-called microballoon foaming agents) can be employed. The microballoon foaming agent is obtained by encapsulating a heat-expandable substance made of a solid, liquid, or gas inside a polymer shell made of a thermoplastic or thermosetting resin. The microballoon foaming agent expands 40 times or more in volume by heating, and a foam in the form of closed cells is obtained. Therefore, the microballoon foaming agent has a characteristic that the expansion ratio is considerably larger than that of a normal foaming agent.

  The average particle size of the microballoon foaming agent is about 5 to 50 μm. The average particle diameter is a value obtained by measuring with a particle size distribution measuring apparatus. As the microballoon foaming agent, a commercially available product can be used. For example, “551DU40” manufactured by EXPANCEL is suitable.

  The foaming temperature of the foaming agent is not particularly limited, but is usually 180 ° C. or lower, and preferably 90 ° C. or higher in order to suppress foaming during coating drying. . In particular, it is preferable that expansion or foaming is started at 90 ° C. and foaming is substantially complete at 120 ° C.

  The pressure-sensitive adhesive sheet of the present invention containing the above-mentioned side chain crystalline polymer and foaming agent has a thickness of 10 to 70 μm, preferably 10 to 50 μm. When the thickness of the pressure-sensitive adhesive sheet is less than 10 μm, the surface of the pressure-sensitive adhesive sheet is uneven due to the foaming agent, or the anchor effect is hardly exhibited, and the fixing force is reduced. Further, if the thickness of the pressure-sensitive adhesive sheet is larger than 70 μm, the thickness of the pressure-sensitive adhesive sheet varies, so that it is difficult to obtain a uniform fixing force and the like, and the solvent in the coating liquid described later is difficult to volatilize. The amount of solvent remaining on the adhesive sheet increases.

The pressure-sensitive adhesive sheet preferably has a vertical peel strength at 23 ° C. of 10 to 500 N / cm ² after passing through the temperature not lower than the melting point and lower than the foaming temperature of the foaming agent, preferably 30 to 500 N / cm ² . More preferably, it is more preferably 100 to 400 N / cm ² , and even more preferably 150 to 400 N / cm ² . Thereby, since this adhesive tape can show high fixing force at room temperature, a to-be-adhered body can be fixed reliably at room temperature.

On the other hand, if the vertical peel strength is less than 10 N / cm ² , the adherend may not be fixed. If it exceeds 500 N / cm ² , it is difficult to sufficiently reduce the fixing force. May not be removed. The vertical peel strength can be arbitrarily adjusted, for example, by changing the composition of the side chain crystalline polymer, the ratio of the foaming agent, and the like. The vertical peel strength is a value obtained by measurement by a measurement method described in Examples described later.

The pressure-sensitive adhesive sheet usually has a storage elastic modulus G ′ at 23 ° C. of 4 × 10 ^{6 to} 5 × 10 ⁷ Pa. Thereby, the fixed state of the adherend can be stabilized, and the adherend can be processed with high accuracy.

Further, the adhesive sheet is preferably the storage modulus G 'is ^{1 × 10 3 ~7 × 10 4} Pa at 60 ° C., and more preferably ^{1 × 10 3 ~5 × 10 4} Pa. If the storage elastic modulus G ′ at 60 ° C. is too small, the adhesive strength of the pressure-sensitive adhesive sheet tends to increase, so that the peelability is lowered and the adhesive residue may increase. Moreover, when the storage elastic modulus G ′ at 60 ° C. is too large, the fluidity of the side chain crystalline polymer tends to be lowered. Therefore, since the anchor effect is difficult to be exhibited, the fixing force may be reduced. Moreover, there exists a possibility that peelability may also fall with the fluidity | liquidity of a side chain crystalline polymer falling.

  The storage elastic modulus G ′ at each temperature can be arbitrarily adjusted, for example, by changing the composition of the side chain crystalline polymer. The storage elastic modulus G ′ at each temperature is a value obtained by measurement using a measurement method described in Examples described later.

  In addition, it is preferable to provide a release-treated film, that is, a release film, on at least one side of the pressure-sensitive adhesive sheet. Examples of the release film include a film surface made of polyethylene terephthalate or the like and subjected to release treatment with silicon, fluorine, or the like. In order to provide a release film on at least one surface of the pressure-sensitive adhesive sheet, for example, a coating solution obtained by adding a side chain crystalline polymer and a foaming agent to a solvent may be applied on the release film and dried.

  Various additives such as a crosslinking agent, a tackifier, a plasticizer, an anti-aging agent, and an ultraviolet absorber can be added to the coating solution. The application can be generally performed by a knife coater, a roll coater, a calendar coater, a comma coater or the like. Further, depending on the coating thickness and the viscosity of the coating solution, a gravure coater, a rod coater or the like can be used. In addition to the application, the pressure-sensitive adhesive sheet can be formed into a sheet by, for example, extrusion molding or calendering.

<Adhesive tape>
Next, the adhesive tape concerning this invention is demonstrated. The pressure-sensitive adhesive tape according to the present invention comprises a pressure-sensitive adhesive layer on at least one surface of a base film, and the pressure-sensitive adhesive layer is composed of the pressure-sensitive adhesive sheet of the present invention described above. Therefore, the pressure-sensitive adhesive tape of the present invention has the same effects as the pressure-sensitive adhesive sheet described above, and also has the effect that the rigidity is higher than that of the pressure-sensitive adhesive sheet and the handleability is excellent because the base film is included.

  Examples of the base film include synthetic resins such as polyethylene, polyethylene terephthalate, polypropylene, polyester, polyamide, polyimide, polycarbonate, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene polypropylene copolymer, and polyvinyl chloride. A film is mentioned.

  The said base film may consist of a single layer body or a multilayer body, and thickness is about 25-250 micrometers normally. The surface of the base film can be subjected to surface treatment such as corona discharge treatment, plasma treatment, blast treatment, chemical etching treatment, and primer treatment in order to improve the adhesion to the pressure-sensitive adhesive layer.

  In order to provide the pressure-sensitive adhesive layer on one side of the base film, a coating solution obtained by adding the aforementioned side chain crystalline polymer and foaming agent to a solvent may be applied to one side of the base film and dried. The thickness of the pressure-sensitive adhesive layer is 10 to 70 μm, preferably 10 to 50 μm, similar to the above-described pressure-sensitive adhesive sheet.

  Meanwhile, the pressure-sensitive adhesive tape may be used in the form of a double-sided pressure-sensitive adhesive tape by providing a pressure-sensitive adhesive layer on the other surface of the base film. The pressure-sensitive adhesive layer on the other surface is not particularly limited, and may be a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive sheet of the present invention, for example, similarly to the pressure-sensitive adhesive layer on one side. In this case, the pressure-sensitive adhesive layer on one side and the pressure-sensitive adhesive layer on the other side may be the same or different in composition and thickness. Other configurations are the same as those of the above-described pressure-sensitive adhesive sheet.

<Precision polishing method and grinding method>
Next, the precision polishing method and the grinding method according to the present invention will be described. The precision polishing method according to the present invention is a method for precisely polishing an object to be polished using the above-described pressure-sensitive adhesive sheet of the present invention, and includes the following steps (i) to (iv).
(I) A step of interposing the adhesive sheet between an object to be polished and a pedestal.
(Ii) A step of setting the temperature of the pressure-sensitive adhesive sheet to a temperature not lower than the melting point after the temperature of the pressure-sensitive adhesive sheet is higher than the melting point and lower than the foaming temperature of the foaming agent, and fixing the object to be polished to the base via the pressure-sensitive adhesive sheet.
(Iii) A step of precisely polishing the fixed object to be polished.
(Iv) The process of making the temperature of the said adhesive sheet the temperature more than the foaming temperature of a foaming agent, and removing the said to-be-polished material which carried out precision grinding | polishing from an adhesive sheet.

Moreover, the grinding method concerning this invention is a method of grinding a to-be-ground material using the above-mentioned adhesive sheet of this invention, and is equipped with the following processes (I)-(IV).
(I) A step of interposing the adhesive sheet between an object to be ground and a pedestal.
(II) A step of setting the temperature of the pressure-sensitive adhesive sheet to a temperature not lower than the melting point after the temperature of the pressure-sensitive adhesive sheet is higher than the melting point and lower than the foaming temperature of the foaming agent, and fixing the object to be ground to the pedestal via the pressure-sensitive adhesive sheet.
(III) A step of grinding the fixed object to be ground.
(IV) The temperature of the said adhesive sheet is made into the temperature more than the foaming temperature of a foaming agent, and the process removes the ground said to-be-ground material from an adhesive sheet.

  In the precision polishing method and the grinding method according to the present invention, since the above-mentioned pressure-sensitive adhesive sheet is used, if the steps (i) and (I) are performed at room temperature, the pressure-sensitive adhesive sheet exhibits adhesive force for the reasons described above. Therefore, the adhesive sheet can be easily positioned with respect to the object to be polished and the object to be ground.

  In the steps (ii) and (II), the object to be polished and the object to be ground can be stably fixed to the pedestal for the reasons described above. Therefore, in the process (iii), micrometer-scale precision polishing can be performed with high accuracy. In the step (III), the workpiece can be ground into a desired shape.

  In the steps (iv) and (IV), the fixing force can be sufficiently reduced for the reason described above, so that the object to be polished and the object to be ground can be easily removed. In addition, as a to-be-polished object and a to-be-ground object, a desired thing can be employ | adopted, Although it does not specifically limit, A sapphire glass etc. are suitable.

  EXAMPLES Hereinafter, although a synthesis example and an Example are given and this invention is demonstrated in detail, this invention is not limited only to the following synthesis examples and Examples. In the following description, “part” means part by weight.

(Synthesis Example 1)
45 parts of behenyl acrylate (manufactured by NOF Corporation), 50 parts of butyl acrylate (manufactured by Nippon Shokubai Co., Ltd.), 5 parts of hydroxyethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.), and 0.5 part of perbutyl ND (manufactured by NOF Corporation) In a proportion of parts, the mixture was added to 230 parts of a mixed solvent of ethyl acetate: n-heptane = 7: 3 (weight ratio) and mixed, and the mixture was stirred at 60 ° C. for 5 hours to polymerize these monomers. The resulting copolymer had a melting point of 45 ° C. and a weight average molecular weight of 550,000.

(Synthesis Example 2)
Further, the monomer was polymerized in the same manner as in Synthesis Example 1 except that 3 parts of dodecyl mercaptan (manufactured by NOF Corporation) was added. The resulting copolymer had a melting point of 45 ° C. and a weight average molecular weight of 15,000.

(Synthesis Example 3)
35 parts of behenyl acrylate (manufactured by NOF Corporation), 10 parts of stearyl acrylate, 50 parts of methyl acrylate (manufactured by Nippon Shokubai Co., Ltd.), 5 parts of acrylic acid, and 0.5 part of perbutyl ND (manufactured by NOF Corporation) In this ratio, the mixture was added to 230 parts of a mixed solvent of ethyl acetate: n-heptane = 7: 3 (weight ratio) and mixed, and the mixture was stirred at 60 ° C. for 5 hours to polymerize these monomers. The resulting copolymer had a melting point of 45 ° C. and a weight average molecular weight of 550,000.

(Comparative Synthesis Example 1)
The monomer was polymerized in the same manner as in Synthesis Example 1 except that the ratio of the mixed solvent was changed to 130 parts instead of 230 parts. The resulting copolymer had a melting point of 45 ° C. and a weight average molecular weight of 800,000.

(Comparative Synthesis Example 2)
45 parts of behenyl acrylate (manufactured by NOF Corporation), 50 parts of butyl acrylate (manufactured by Nippon Shokubai Co., Ltd.), 5 parts of hydroxyethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.), 6 parts of dodecyl mercaptan (manufactured by NOF Corporation), dodecyl 6 parts of mercaptan (manufactured by NOF Corporation) and 1 part of perhexyl PV (manufactured by NOF Corporation) were added to 100 parts of toluene, mixed, and stirred at 80 ° C. for 5 hours. Polymerized. The resulting copolymer had a melting point of 45 ° C. and a weight average molecular weight of 7,900.

  Each of the copolymers of Synthesis Examples 1 to 3 and Comparative Synthesis Examples 1 and 2 is a side chain crystalline polymer. Each of these copolymers is shown in Table 1. In addition, the said weight average molecular weight is a value which measured the copolymer by GPC and converted the obtained measured value into polystyrene. The said melting | fusing point is the value measured on 10 degree-C / min measurement conditions using DSC.

[Examples 1 to 3 and Comparative Examples 1 to 5]
<Production of adhesive sheet>
First, each copolymer solution obtained in Synthesis Examples 1 to 3 and Comparative Synthesis Examples 1 and 2 was adjusted so that the solid content was 30% using ethyl acetate to obtain each copolymer solution. Subsequently, a foaming agent was added to each copolymer solution at a ratio shown in Table 2. As the foaming agent, “551DU40” manufactured by EXPANCEL, which is a microencapsulated thermally expandable fine particle having a foaming start temperature (foaming temperature) of 93 to 98 ° C. and an average particle diameter of 10 to 16 μm, was used. Moreover, in Table 2, the addition amount of a foaming agent shows the value with respect to 100 weight part of copolymers (side chain crystalline polymer) in conversion of solid content.

  Next, the copolymer solution containing a foaming agent was applied to one side of a 100 μm-thick polyethylene terephthalate film (release film) that had been subjected to a release treatment with silicon, and dried at an ambient temperature of 80 ° C. 2 were obtained (Examples 1 to 3 and Comparative Examples 1 to 5 in Table 2).

<Evaluation>
About each adhesive sheet obtained above, storage elastic modulus G ', vertical peel strength, peelability, adhesive residue, and grinding | polishing precision were evaluated. Each evaluation method is shown below, and the results are also shown in Table 2.

(Storage modulus G ')
Using a dynamic viscoelasticity measuring device “DMS 6100” manufactured by Seiko Instruments Inc., a pressure sensitive adhesive sheet at 23 ° C. and 60 ° C. in a temperature rising process of 10 Hz, 5 ° C./min, 0 ° C. to 100 ° C. The storage elastic modulus G ′ of was measured.

(Vertical peel strength)
The vertical peel strength at 23 ° C. after passing through a temperature higher than the melting point and lower than the foaming temperature of the foaming agent was measured. Specifically, first, at an atmospheric temperature of 23 ° C., the pressure-sensitive adhesive sheet peeled from the release film was placed on a stainless steel (SUS) plate serving as a base plate. Subsequently, after raising the ambient temperature to 60 ° C., the pressure-sensitive adhesive sheet surface was pressure-bonded for 10 seconds with a pressure of ² kg / cm ² with a stainless steel probe having a length of 10 mm × width of 10 mm × thickness of 10 mm. Next, the pressure was released, and the probe was left on the pressure-sensitive adhesive sheet surface for 20 minutes, and then the ambient temperature was lowered from 60 ° C. to 23 ° C. and left for 20 minutes. And the intensity | strength at the time of peeling a probe to the orthogonal | vertical direction from the adhesive sheet surface at the speed | rate of 300 mm / min was measured.

(Peelability)
First, at an atmospheric temperature of 23 ° C., the pressure-sensitive adhesive sheet peeled from the release film was placed on a stainless steel plate serving as a base plate. Next, after raising the ambient temperature to 60 ° C., the pressure-sensitive adhesive sheet surface was pressure-bonded for 10 seconds with a pressure of ² kg / cm ^{2 using} a circular glass plate having a diameter of 100 mm and a thickness of 500 μm. Subsequently, the pressure was released, and the glass plate was left on the pressure-sensitive adhesive sheet surface for 20 minutes, and then the ambient temperature was lowered from 60 ° C. to 23 ° C. and left for 20 minutes.

And the atmospheric temperature was raised from 23 degreeC to 120 degreeC, and it visually observed whether the glass plate peeled from the adhesive sheet surface only by the dead weight of the glass plate in the said atmospheric temperature. The 120 ° C. is a temperature equal to or higher than the melting point of the side chain crystalline polymer, and is a temperature at which the foaming agent is substantially completely foamed. In addition, the following criteria were used.
○: The glass plate was peeled from the surface of the adhesive sheet only by its own weight within 1 minute after the temperature was raised to 120 ° C.
X: Even if it exceeded 5 minutes after 120 degreeC temperature rising, the glass plate did not peel from the adhesive sheet surface only by the dead weight of the glass plate.

(Adhesive residue)
In the evaluation of the peelability, the surface of the peeled glass plate was observed with an electron microscope (magnification: 100 times), and the presence or absence of adhesive residue was confirmed. In addition, about the thing of peelability evaluation x, it evaluated by peeling a glass plate from the adhesive sheet surface by hand. In addition, the following criteria were used.
○: There is no adhesive residue.
X: There is adhesive residue.

(Polishing accuracy)
First, at an atmospheric temperature of 23 ° C., the pressure-sensitive adhesive sheet peeled from the release film was placed on a ceramic plate serving as a base plate. Next, after raising the ambient temperature to 60 ° C., the pressure-sensitive adhesive sheet surface was pressure-bonded for 10 seconds with a circular sapphire glass plate having a diameter of 100 mm × thickness of 500 μm and a pressure of ² kg / cm ² . Next, the pressure was released, and the sapphire glass plate was left on the pressure-sensitive adhesive sheet surface for 20 minutes, and then the ambient temperature was lowered from 60 ° C. to 23 ° C. and left for 20 minutes.

Thereafter, the sapphire glass plate was polished with a wafer sequence gauge. After polishing until the thickness of the sapphire glass plate became 500 μm to 250 μm, the ambient temperature was raised from 23 ° C. to 120 ° C., and the sapphire glass plate was peeled off from the pressure-sensitive adhesive sheet surface. And the thickness of the peeled sapphire glass plate was measured using a wafer sequence gauge at five points, and the variation was measured. The following criteria were used.
○: Thickness variation is within 3 μm.
X: Thickness variation is larger than 3 μm.

  As can be seen from Tables 1 and 2, Examples 1 to 3 have high vertical peel strength, and hence excellent fixing force when fixing the adherend. Further, the storage elastic modulus G ′ at 23 ° C. was high, and the result was excellent in polishing accuracy. Further, it can be seen that good results are also shown in the evaluation of peelability and adhesive residue. The reason why the vertical peel strength evaluation result of Example 3 is slightly inferior to that of Examples 1 and 2 is presumed to be that the storage elastic modulus G ′ at 60 ° C. is higher than that of Examples 1 and 2. The

  On the other hand, Comparative Example 1 in which the content of the foaming agent is less than a specific ratio showed results inferior to the evaluation of peelability and adhesive residue. Further, Comparative Example 2 in which the content of the foaming agent is larger than a specific ratio, Comparative Example 3 in which the thickness is thinner than the specific thickness, and Comparative Example in which the weight average molecular weight of the side chain crystalline polymer is larger than the specific value No. 4 showed a low vertical peel strength and inferior polishing accuracy. Comparative Example 5 in which the weight average molecular weight of the side chain crystalline polymer is smaller than a specific value showed results inferior to evaluation of peelability and adhesive residue.

Claims (9)

Containing a side chain crystalline polymer, and 10 to 110 parts by weight of a foaming agent with respect to 100 parts by weight of the side chain crystalline polymer,
The side chain crystalline polymer is
The melting point is 30 ° C. or higher and lower than the foaming temperature of the foaming agent,
While crystallizing at a temperature below the melting point and exhibiting fluidity at a temperature above the melting point,
The weight average molecular weight is 10,000 to 700,000,
A thickness of 10 to 70 μm, and an adherend adhered at a temperature equal to or higher than the melting point and lower than the foaming temperature of the foaming agent is fixed at a temperature lower than the melting point, and at a temperature equal to or higher than the foaming temperature of the foaming agent. A pressure-sensitive adhesive sheet that is removed. The side chain crystalline polymer is
30 to 100 parts by weight of (meth) acrylate having a linear alkyl group having 16 or more carbon atoms,
0 to 70 parts by weight of (meth) acrylate having an alkyl group having 1 to 6 carbon atoms;
0-10 parts by weight of polar monomer,
The pressure-sensitive adhesive sheet according to claim 1, which is a polymer obtained by polymerizing a polymer. The pressure-sensitive adhesive sheet according to claim 2, wherein the (meth) acrylate having an alkyl group having 1 to 6 carbon atoms is butyl acrylate. The pressure-sensitive adhesive sheet according to claim 1 vertical peeling strength is 10~500N / cm ² at 23 ° C. after undergoing a temperature below the foaming temperature of the melting point or more and the blowing agent. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the storage elastic modulus G 'at 23 ° C is 4 x 10 ^{6 to} 5 x 10 ⁷ Pa. The pressure-sensitive adhesive sheet according to claim 1, wherein the storage elastic modulus G ′ at 60 ° C. is 1 × 10 ^{3 to} 7 × 10 ⁴ Pa.   A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer on at least one surface of a base film, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive sheet according to claim 1. A method for precisely polishing an object to be polished using the pressure-sensitive adhesive sheet according to claim 1,
Interposing the adhesive sheet between an object to be polished and a pedestal;
The temperature of the pressure-sensitive adhesive sheet is set to a temperature lower than the melting point after the temperature of the pressure-sensitive adhesive sheet is equal to or higher than the melting point and lower than the foaming temperature of the foaming agent, and the object to be polished is fixed to a pedestal via the pressure-sensitive adhesive sheet;
Precision polishing the fixed object to be polished;
The temperature of the pressure-sensitive adhesive sheet is set to a temperature equal to or higher than the foaming temperature of the foaming agent, and the precision-polished object to be polished is removed from the pressure-sensitive adhesive sheet;
A precision polishing method comprising: A method for grinding an object to be ground using the pressure-sensitive adhesive sheet according to claim 1,
Interposing the pressure-sensitive adhesive sheet between an object to be ground and a pedestal;
The temperature of the pressure-sensitive adhesive sheet is set to a temperature not lower than the melting point after the temperature of the pressure-sensitive adhesive sheet is higher than the melting point and lower than the foaming temperature of the foaming agent, and fixing the object to be ground to the base via the pressure-sensitive adhesive sheet;
Grinding the fixed object to be ground;
The temperature of the pressure-sensitive adhesive sheet is set to a temperature equal to or higher than the foaming temperature of the foaming agent, and the ground object to be ground is removed from the pressure-sensitive adhesive sheet;
A grinding method comprising: