JP6429227B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to an adhesive sheet.

  With recent reduction in weight and thickness of electronic devices, substrates used in the electronic devices are becoming thinner. The thin substrate has a problem that it is difficult to handle in processing, processing, transport and the like. For example, when a thin substrate is processed alone when forming a pattern on a thin substrate, the thin substrate is likely to be distorted due to poor handling properties, and it is difficult to form a pattern accurately and stably. is there.

  In order to solve the above problems, a thin substrate is attached to a predetermined pedestal via an adhesive, and the thin substrate temporarily fixed to the pedestal is subjected to processing, processing, transportation, and the like. Things have been done.

  For example, a technique is known in which a semiconductor wafer as a thin film substrate and a support wafer as a pedestal are bonded to each other with a double-sided pressure-sensitive adhesive sheet, and the formed laminate is conveyed (for example, Patent Documents 1 to 3). In this technique, in consideration of peeling the semiconductor wafer from the pedestal after processing, a thermal expansion adhesive or an ultraviolet photosensitive adhesive is used as the double-sided adhesive sheet.

  The thermal expansion type adhesive is an adhesive containing microcapsules, and the microcapsules are foamed by heating and the adhesive strength is reduced. However, when a thin substrate (semiconductor wafer) is temporarily fixed using a thermal expansion adhesive, when the thin film substrate is subjected to processing under vacuum conditions (for example, sputtering processing, CVD processing), the microcapsule There is a problem in that gas is released and the adhesive force is unnecessarily lowered or the vacuum chamber is contaminated. Further, there is a problem that the thin substrate cannot be processed at a temperature higher than the heating temperature at the time of peeling (that is, the temperature at which the microcapsule foams). Furthermore, there is a problem that impurities derived from the adhesive remain on the thin substrate during peeling.

  The ultraviolet photosensitive adhesive is an adhesive containing an ultraviolet curable resin and a photopolymerization initiator, and the adhesive strength is reduced by ultraviolet irradiation. In the case of UV-sensitive adhesive, there is a problem that the processing temperature of the thin substrate is restricted due to the thermal decomposability of the photopolymerization initiator, and there is a decrease in adhesive strength due to UV irradiation when high-temperature processing is performed. The problem of becoming insufficient arises.

  In addition, conventional resins such as thermal expansion adhesives and ultraviolet photosensitive adhesives generate gas (for example, thermally decomposable gas) at high temperatures and contaminate adherends, processing / processing apparatuses, and the like. There's a problem.

  Furthermore, conventional pressure-sensitive adhesives are insufficient in durability against acids and polar solvents. For example, in an etching process when forming a pattern on a thin substrate, a cleaning process using a polar solvent, etc. There is a problem that the adhesiveness is unnecessarily lowered depending on the chemical used.

JP 2005-116948 A JP 2010-56562 A JP-A-6-216092

  The present invention has been made to solve the above-described conventional problems, and has an object of having excellent adhesiveness as a temporary fixing adhesive sheet, and excellent in heat resistance, chemical resistance and cleanliness. It is to provide an adhesive sheet.

The pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer contains polytetrafluoroethylene having a crystallinity of 80% or more.
In one embodiment, the elasticity modulus by the nanoindentation method in 25 degreeC of the said adhesion layer is 0.5 Mpa or less.
In one embodiment, the thickness of the adhesion layer is 0.03 mm or more.
In one embodiment, the pressure-sensitive adhesive sheet of the present invention has a weight reduction rate of 1% by weight or less when heated from 25 ° C. to 300 ° C. at a temperature rising rate of 10 ° C./min.

  The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer containing a polytetrafluoroethylene having a crystallinity of 80% or more, thereby having excellent adhesiveness as a pressure-sensitive adhesive sheet for temporary fixing, and having heat resistance and chemical resistance. Excellent in cleanliness and cleanliness.

(A)-(c) is a schematic sectional drawing of the adhesive sheet by one Embodiment of this invention.

A. Whole of the pressure-sensitive adhesive sheet diagram 1 (a) is a schematic sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. An adhesive sheet 100 shown in FIG. 1A includes an adhesive layer 10. The adhesive layer 10 includes polytetrafluoroethylene having a crystallinity of 80% or more as a main component. As shown to Fig.1 (a), the adhesive sheet which consists only of the adhesion layer 10 can function as a double-sided adhesive sheet.

  The pressure-sensitive adhesive sheet of the present invention may further include any appropriate layer in addition to the pressure-sensitive adhesive layer. FIG.1 (b) is a schematic sectional drawing of the adhesive sheet by another embodiment of this invention. The adhesive sheet 200 shown in FIG. 1B further includes a base material layer 20 on one side of the adhesive layer 10. As shown in FIG. 1B, the pressure-sensitive adhesive sheet in which one surface of the pressure-sensitive adhesive layer 10 is covered with the base material layer 20 can function as a single-sided pressure-sensitive adhesive sheet. FIG.1 (c) is a schematic sectional drawing of the adhesive sheet by another embodiment of this invention. An adhesive sheet 300 shown in FIG. 1C includes the adhesive layer 10 on both surfaces of the base material layer 20. The pressure-sensitive adhesive sheet 300 can function as a double-sided pressure-sensitive adhesive sheet.

  The pressure-sensitive adhesive sheet of the present invention can have any suitable shape. For example, it may be a long shape with a length of about 10 m to 3000 m, or may be a shape punched or cut into any appropriate shape. The long pressure-sensitive adhesive sheet can be wound into a roll.

  As an adherend to which the pressure-sensitive adhesive sheet of the present invention can be applied, an adherend formed from any appropriate material can be used as long as it has sufficient smoothness. The surface roughness Rmax of the adherend surface of the adherend is preferably less than 100 μm, more preferably less than 80 μm, and still more preferably 0.01 μm to 50 μm.

  The pressure-sensitive adhesive sheet of the present invention can be suitably used as a pressure-sensitive adhesive sheet for temporarily fixing a member for an electronic device (for example, a substrate). The pressure-sensitive adhesive sheet of the present invention has sufficient adhesiveness to temporarily fix a member used in an electronic device on a predetermined pedestal in a process of processing, processing, transporting, etc. After passing, it is preferable that the adhesive strength is such that the member can be easily peeled off from the pedestal. Examples of the member include a member made of silicon, a member made of sapphire, a member made of silicon carbide, a member made of glass (for example, made of soda lime, made of tempered glass), a member made of resin (for example, made of polyimide, made of polycarbonate, A member made of polytelsulfone), a member made of metal (for example, stainless steel), a member containing glass fiber, and a member made of an organic-inorganic hybrid material (for example, silsesquioxane and a thermoplastic resin such as polycarbonate) Substrate). Examples of the pedestal include a glass pedestal (for example, soda lime, tempered glass), a silicon pedestal, a sapphire pedestal, and a metal (for example, stainless steel) pedestal. Moreover, the adhesive sheet of this invention can also be used in order to stick the said members.

  The pressure-sensitive adhesive sheet of the present invention can exhibit adhesiveness by sticking an adherend (for example, the substrate) on the pressure-sensitive adhesive sheet and further pressure-bonding it with a predetermined pressure. The pressure at the time of pressure bonding is, for example, 0.001 MPa to 100 MPa.

  The adhesive strength of the adhesive sheet of the present invention to the glass plate is preferably 0.03 N / 20 mm or more, more preferably 0.05 N / 20 mm or more, and further preferably 0.08 N / 20 mm to 0.2 N / 20 mm. And particularly preferably 0.08 N / 20 mm to 0.1 N / 20 mm. An adhesive sheet having such an adhesive force in such a range is particularly useful as an adhesive sheet for temporarily fixing a member for an electronic device. In addition, in this specification, the adhesive force with respect to a glass plate sticks the whole surface of the adhesive sheet cut out to predetermined size (20 mm x 150 mm) on a glass plate on the conditions of 2 kg hand roller 10 reciprocation at 25 degreeC. Further, an evaluation sample produced by pressurization under conditions of temperature 25 ° C./pressure 5 atm / hour 10 minutes is subjected to a peel test and measured. The conditions of the peeling test are a measurement environment temperature of 25 ° C., a peeling angle of 60 °, and a peeling speed of 50 mm / min. Moreover, as said glass plate, the glass plate whose surface roughness Rmax is 30 micrometers-40 micrometers is used. As such a glass plate, for example, trade name “MICRO SLIDE GLASS S200423” (65 mm × 165 mm, thickness 1.2 mm) manufactured by Matsunami Glass Co., Ltd. may be used.

  In the present invention, a predetermined adhesive force can be expressed by an adhesive surface formed without surface treatment. That is, in this invention, it is preferable that the said adhesive sheet is equipped with the adhesive layer which is not surface-treated. Here, the “surface treatment” means a surface treatment commonly used for increasing the adhesive force or adhesive force, and examples thereof include plasma treatment and corona treatment.

  In the pressure-sensitive adhesive sheet of the present invention, the weight reduction rate when heated from 25 ° C. to 300 ° C. at a temperature rising rate of 10 ° C./min is preferably 1% by weight or less, and preferably 0.3% by weight or less. More preferred. The small weight reduction rate due to the heating means that the gas generated from the pressure-sensitive adhesive sheet at a high temperature (for example, the gas generated by thermally decomposing the pressure-sensitive adhesive layer component) is small. Such a pressure-sensitive adhesive sheet is suitable for use at high temperatures. For example, when the pressure-sensitive adhesive sheet of the present invention is used when temporarily fixing a member such as a substrate and processing at high temperatures, contamination of the apparatus is prevented. can do.

B. Adhesive layer The adhesive layer contains polytetrafluoroethylene (hereinafter also referred to as PTFE). An adhesive layer containing PTFE as a main component is excellent in heat resistance, chemical resistance, and the like. Moreover, the adhesion layer containing PTFE as a main component has little outgas. The pressure-sensitive adhesive sheet of the present invention having such a pressure-sensitive adhesive layer is exposed to high temperatures (for example, 110 ° C. or higher), various chemicals (for example, acidic chemicals such as hydrofluoric acid and oxalic acid, N-methyl-2-pyrrolidone, etc. , Even in an environment in contact with a polar solvent such as dimethyl sulfoxide, the adhesiveness, cleanliness and shape can be maintained.

  The content of the PTFE is preferably 80% by weight or more, more preferably 90% by weight or more, and further preferably 90% by weight to 100% by weight with respect to the total weight of the resin in the adhesive layer. . In one embodiment, the adhesion layer is formed using only PTFE as a resin.

  The degree of crystallinity of the PTFE is 80% or more, preferably 90% or more, more preferably 95% or more. If it is such a range, the adhesive sheet which has sufficient adhesive force can be obtained. The crystal part of PTFE is different from crystals such as polyethylene and polypropylene, but the molecular chain is rigid but the interaction between molecules is small, and the oriented molecular chains are slippery. Therefore, when PTFE is adhered to the adherend as the degree of crystallinity increases, it is estimated that PTFE follows the micro unevenness of the adherend, and as a result, high adhesive force can be obtained. The upper limit of the crystallinity of the PTFE is preferably 100% or less, more preferably 99% or less, and still more preferably 98% or less. It is difficult to obtain completely crystallized PTFE (PTFE having a crystallinity of 100%). Considering productivity, it is preferable to use PTFE having a crystallinity of 99% or less. In the present specification, the degree of crystallinity is determined from the heat of fusion (J / g) when a PTFE sample is heated to 0 ° C. to 400 ° C., measured using a high temperature differential scanning calorimeter. That is, the degree of crystallinity (%) of PTFE is expressed by the following formula: (Measured heat of fusion of PTFE sample (J / g) / heat of fusion of PTFE of 100% crystallinity 92.84 (J / g)) × 100 Desired.

  The adhesive layer may further contain a resin other than PTFE. As the resin other than PTFE, a fluororesin is preferably used. Examples of fluororesins other than PTFE include partially fluorinated resins such as polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF); perfluoroalkoxy fluororesin (PFA), Fluorinated resin copolymers such as fluorinated ethylene / hexafluoropropylene copolymer (FEP), ethylene / tetrafluoroethylene copolymer (ETFE), and ethylene / chlorotrifluoroethylene copolymer (ECTFE); Acrylic resin; fluororubber and the like. The content of the resin other than PTFE is preferably less than 20% by weight and more preferably less than 10% by weight with respect to the total weight of the resin in the adhesive layer.

  In one embodiment, the adhesive layer is formed as a resin sheet containing PTFE (hereinafter also referred to as PTFE sheet). That is, when the pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive layer and a base material layer, the pressure-sensitive adhesive sheet can be formed by sticking a PTFE sheet as a pressure-sensitive adhesive layer on the base material layer. Moreover, when the adhesive sheet of this invention is comprised only from an adhesive layer, the said adhesive sheet is formed as a PTFE sheet. The PTFE sheet has adhesiveness as its own characteristic. For this reason, it is difficult for the adhesive strength to decrease with time, and the adhesive strength is unlikely to decrease even if sticking and peeling are repeated.

  The thickness of the adhesive layer (that is, PTFE sheet) is preferably 0.03 mm or more, more preferably 0.03 mm to 20 mm, still more preferably 0.05 mm to 10 mm, and particularly preferably 0.07 mm. ~ 2mm, most preferably 0.1mm ~ 1mm. If it is such a range, cost can be suppressed and the adhesion layer with high thickness uniformity can be formed.

  The elastic modulus of the pressure-sensitive adhesive layer (that is, PTFE sheet) by a nanoindentation method at 25 ° C. is preferably 0.5 MPa or less, more preferably 0.2 MPa or less, and further preferably 0.001 MPa or more and 0.00. It is less than 2 MPa, particularly preferably 0.002 MPa or more and less than 0.15 MPa. If it is such a range, it can have an adhesive force suitable as an adhesive sheet which temporarily fixes the member for electronic devices, and can obtain the adhesive sheet excellent in the balance of fixability and peelability. The elastic modulus by the nano-indentation method means that the load and indentation depth applied to the indenter when the indenter is pushed into the sample are continuously measured during loading and unloading, and the obtained load load minus indentation depth. It refers to the elastic modulus obtained from the height curve. In this specification, the elastic modulus by the nanoindentation method is the elastic modulus when the indentation depth is 1 μm. Details of the measurement conditions of the elastic modulus by the nanoindentation method will be described later.

  The pressure-sensitive adhesive layer (that is, PTFE sheet) preferably has a weight reduction rate of 1% by weight or less when heated from 25 ° C. to 300 ° C. at a heating rate of 10 ° C./min, and is 0.3% by weight or less. It is more preferable that A small weight reduction rate due to the heating means that a gas generated from the adhesive layer at a high temperature (for example, a gas generated by thermally decomposing the adhesive layer component) is small. The pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer is suitable for use at high temperatures. For example, when the substrate is temporarily fixed and processed at high temperatures, contamination of the apparatus can be prevented.

  The PTFE sheet may be porous or nonporous. If the porous PTFE sheet is used, the PTFE sheet is easily deformed when the adherend is attached. Therefore, even if the adherend is pressure-bonded with a low pressure, sufficient adhesive strength can be obtained. On the other hand, when using a non-porous PTFE sheet, it is necessary to perform pressure bonding at a pressure higher than that required for the porous PTFE sheet in order to obtain a predetermined adhesion force. The

When the PTFE sheet is porous, the porosity of the PTFE sheet is preferably 50% to 90%, more preferably 60% to 85%, and further preferably 65% to 80%. When the porosity is less than 50%, the PTFE sheet is hardly deformed when the adherend is attached, and there is a possibility that sufficient adhesive force cannot be obtained. When the porosity exceeds 90%, it may be difficult to control the conditions (for example, the thickness when pressed and pressure-bonded) when attaching the adherend. The porosity (%) can be obtained from the equation {apparent density of 1-PTFE sheet (g / cm 3) / true density of PTFE sheet (g / cm 3)} × 100. When the PTFE sheet is formed only from PTFE, the true density of the PTFE sheet is 2.18 g / cm ³ .

  Any appropriate method can be adopted as a method for producing the PTFE sheet. The PTFE sheet is obtained, for example, by obtaining a paste-like admixture containing PTFE powder and a liquid lubricant, preforming the admixture, further extruding the preform, and heating the extrudate. be able to. Prior to the heating, the extruded product may be rolled. Moreover, the PTFE sheet may be made porous through a predetermined stretching process.

  Examples of the form of the PTFE powder include fine powder, molding powder, and dispersion. Preferably, fine powder is used as the PTFE powder. If a fine powder is used, a PTFE sheet with high moldability and high crystallinity can be obtained. The fine powder means a powder obtained by aggregating, separating and drying PTFE from an aqueous dispersion of PTFE obtained by an emulsion polymerization method. The particle size of the fine powder is, for example, 100 μm to 1000 μm.

  The liquid lubricant is not particularly limited as long as it can wet the surface of PTFE powder (for example, PTFE fine powder) and can be removed by extraction or heating, and any appropriate liquid can be used. As the liquid lubricant, for example, hydrocarbon solvents such as liquid paraffin, naphtha and white oil are used. The amount of the liquid lubricant added is preferably 5 to 50 parts by weight with respect to 100 parts by weight of the PTFE powder. A PTFE sheet having higher adhesive strength can be obtained as the amount of the liquid lubricant added is larger within the range.

  The paste-like mixture may further contain a resin other than the above-mentioned PTFE.

  After obtaining the paste-like mixture, the mixture is preformed. In the preforming, the mixture is pressed and hardened by applying a predetermined pressure. The pressure at the time of preforming is preferably a pressure that does not squeeze out the liquid lubricant. The shape of the preform obtained by the preforming is, for example, a rod shape.

  The preform is further extruded to obtain an extruded product. The shape of the extrusion-molded body is, for example, a long tape shape. The thickness of the extruded product can be adjusted according to the desired thickness of the PTFE sheet, the presence or absence of a stretching step as a subsequent step, and the like. The thickness of the extruded molded body is, for example, 0.5 mm to 4 mm. In extrusion molding, for example, the preform is preferably extruded while being heated at a temperature of 50 ° C to 80 ° C. By extruding while heating, a PTFE sheet having high adhesive strength can be obtained.

  The extruded product may be rolled according to the desired thickness of the PTFE sheet, the presence or absence of a stretching step as a subsequent step, and the like. Rolling can be performed, for example, by passing an extruded product between a pair of rolls arranged with a predetermined gap. The thickness of the extruded product after rolling is preferably 5% to 80%, more preferably 10% to 60%, relative to the thickness of the extruded product before rolling.

  The extrusion molded body formed as described above is heated. The liquid lubricant is removed by the heating. Examples of the heating method include a method of heating on a roll heated to a predetermined heating temperature, a method of heating in an atmosphere heated to a predetermined heating temperature, and the like. Preferably, after the heating, cooling is performed under any appropriate conditions. In one embodiment, the dry molded object obtained by the said heating and cooling becomes a PTFE sheet. In this embodiment (that is, an embodiment that does not include a stretching step), a nonporous PTFE sheet can be obtained.

  It is preferable that the heating temperature when heating the extrusion-molded body is not higher than the melting point of PTFE. Specifically, the heating temperature is preferably 340 ° C. or less, more preferably 25 ° C. to 280 ° C., further preferably 80 ° C. to 250 ° C., and 100 ° C. to 200 ° C. It is particularly preferred. Within such a range, a PTFE sheet containing PTFE having a high degree of crystallinity, specifically, a PTFE sheet containing PTFE having a degree of crystallinity of 80% or more can be obtained. The extrusion molded body may be heated by raising or lowering the heating temperature stepwise. The heating time can be appropriately set according to the thickness of the extruded molded body, the amount of liquid lubricant in the extruded molded body, and the like. The heating time is, for example, 1 second to 10 minutes.

  In one embodiment, the PTFE sheet can be obtained by stretching the extruded molded body or a dried molded body obtained by heating the extruded molded body. A porous PTFE sheet can be obtained through the stretching step.

  The stretching in the stretching step may be uniaxial stretching or biaxial stretching. Stretching may be performed in one stage or in multiple stages.

  Examples of the stretching method when performing uniaxial stretching include a method of stretching in the longitudinal direction (MD) using a roll stretching machine and a method of stretching in the width direction (TD) using a tenter stretching machine. Can be mentioned. When uniaxial stretching is performed, the stretching ratio is preferably 2 to 15 times, more preferably 5 to 10 times. Within such a range, stretching unevenness or breakage can be prevented, and a PTFE sheet having uniform properties such as thickness can be obtained stably. The stretching temperature is preferably not higher than the melting point of PTFE. Specifically, the stretching temperature is preferably 340 ° C. or lower, more preferably 25 ° C. to 300 ° C., further preferably 150 ° C. to 300 ° C., and 240 ° C. to 300 ° C. Is particularly preferable, and most preferably 270 ° C to 290 ° C. Within such a range, a PTFE sheet containing PTFE having a high degree of crystallinity, specifically, a PTFE sheet containing PTFE having a degree of crystallinity of 80% or more can be obtained.

  Examples of the stretching method in the case of performing biaxial stretching include a method of further TD stretching a uniaxially stretched sheet that has been MD stretched, a method that uses a biaxial stretching machine, and the like. When biaxial stretching is performed, the area stretching ratio (product of MD stretching ratio and TD stretching ratio) is preferably 50 to 900 times, and more preferably 100 to 300 times. Even when biaxial stretching is performed, the stretching temperature is preferably 340 ° C. or lower, more preferably 25 ° C. to 300 ° C., further preferably 150 ° C. to 300 ° C., and 240 ° C. to 300 ° C. It is particularly preferable that the temperature is 270 ° C to 290 ° C.

  After the stretching step, it is preferable to cool the PTFE sheet under any appropriate conditions.

  As mentioned above, it is preferable that the PTFE sheet is produced without passing through a thermal history not lower than the melting point (340 ° C.) of PTFE. A PTFE sheet with a high degree of crystallinity can be obtained by manufacturing without passing through a thermal history not lower than the melting point of PTFE. More specifically, PTFE having a high crystallinity can be obtained without lowering the crystallinity of the PTFE powder as a raw material by producing it without passing through a thermal history not lower than the melting point of PTFE.

  The adhesive layer may further contain any appropriate additive. Specific examples of the additive include glass beads, balloons, fillers, pigments and the like. These additives can be added, for example, by mixing with PTFE powder (eg, fine powder) and then molding. The content of the additive is preferably 50% by weight or less, more preferably 40% by weight or less, still more preferably 30% by weight or less, particularly preferably 20% by weight, based on the weight of the adhesive layer. It is as follows. Further, the liquid lubricant may remain in the adhesive layer. The content ratio of the liquid lubricant in the adhesive layer is, for example, 0.01% by weight to 5% by weight with respect to the weight of the adhesive layer.

C. Base Material Layer Any appropriate material can be adopted as the material constituting the base material layer. Examples of the material constituting the base material layer include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene · Resin film formed from polyolefin resin such as vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, ethylene / vinyl alcohol copolymer; formed from polyester resin such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate Resin film formed from polyacrylate; Resin film formed from polystyrene; Resin film formed from polyamide resins such as nylon 6, nylon 6,6, partially aromatic polyamide; From polyvinyl chloride Formed Resin film; Resin film formed from polyvinylidene chloride; Resin film formed from polycarbonate; Foam substrate such as polyurethane foam and polyethylene foam; Paper such as kraft paper, crepe paper and Japanese paper; Cotton cloth, soft cloth, etc. Cloth; Nonwoven fabric such as polyester nonwoven fabric and vinylon nonwoven fabric; Metal foil such as aluminum foil and copper foil.

  The thickness of the base material layer is preferably 15 μm to 50 μm, more preferably 25 μm to 38 μm.

  When the pressure-sensitive adhesive sheet of the present invention includes a base material layer, the pressure-sensitive adhesive sheet can be formed by pressure-bonding the pressure-sensitive adhesive layer and the base material layer. The pressure at the time of pressure bonding is, for example, 0.001 MPa to 15 MPa.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all. In Examples and Comparative Examples, stretching in the longitudinal direction is stretching between rolls having different peripheral speeds, and stretching in the width direction is tenter stretching.

[Example 1]
100 parts by weight of PTFE fine powder (trade name “Polyflon PTFE F-104”, compressive strength (ASTM D695, 1% deformation, 25 ° C.) 5-6 MPa, manufactured by Daikin Industries, Ltd.) and n-dodecane as a liquid lubricant 20 parts by weight was mixed to obtain a paste-like mixture. The obtained mixture was molded by paste extrusion to obtain an extruded molded body (thickness 2 mm). Next, the obtained extruded product was passed through a pair of metal rolls and rolled to a thickness of 0.2 mm. Then, it heated at 150 degreeC for 60 second, the liquid lubricant was dried and removed, and the dry molded object was obtained. Furthermore, the obtained dry molded body was heated at 100 ° C. for 5 minutes and then cooled at room temperature of 25 ° C. to obtain a pressure-sensitive adhesive sheet composed of a PTFE sheet having a thickness of 0.2 mm.

[Example 2]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was heated at 200 ° C. for 5 minutes and then cooled at room temperature of 25 ° C. to obtain a pressure-sensitive adhesive sheet composed of a PTFE sheet having a thickness of 0.2 mm.

[Example 3]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was heated at 320 ° C. for 5 minutes and then cooled at room temperature of 25 ° C. to obtain an adhesive sheet made of a PTFE sheet having a thickness of 0.2 mm.

[Example 4]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was stretched 3 times in the longitudinal direction at a stretching temperature of 25 ° C., and then cooled at room temperature of 25 ° C. to obtain an adhesive sheet made of a PTFE sheet having a thickness of 0.15 mm.

[Example 5]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was stretched 3 times in the longitudinal direction at a stretching temperature of 100 ° C., and then cooled at room temperature of 25 ° C. to obtain an adhesive sheet made of a PTFE sheet having a thickness of 0.16 mm.

[Example 6]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was stretched 3 times in the longitudinal direction at a stretching temperature of 200 ° C. and then cooled at room temperature of 25 ° C. to obtain a pressure-sensitive adhesive sheet made of a PTFE sheet having a thickness of 0.17 mm.

[Example 7]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was stretched 3 times in the longitudinal direction at a stretching temperature of 280 ° C., and then cooled at room temperature of 25 ° C. to obtain a pressure-sensitive adhesive sheet made of a PTFE sheet having a thickness of 0.18 mm.

[Example 8]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was stretched 5 times in the longitudinal direction at a stretching temperature of 280 ° C., and then cooled at room temperature of 25 ° C. to obtain a pressure-sensitive adhesive sheet made of a PTFE sheet having a thickness of 0.13 mm.

[Example 9]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was stretched 10 times in the longitudinal direction at a stretching temperature of 280 ° C., and then cooled at room temperature of 25 ° C. to obtain an adhesive sheet composed of a PTFE sheet having a thickness of 0.07 mm.

[Example 10]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was stretched 15 times in the longitudinal direction at a stretching temperature of 280 ° C., and then cooled at room temperature of 25 ° C. to obtain an adhesive sheet composed of a PTFE sheet having a thickness of 0.04 mm.

[Example 11]
100 parts by weight of PTFE fine powder (trade name “Polyflon PTFE F-104”, compressive strength (ASTM D695, 1% deformation, 25 ° C.) 5-6 MPa, manufactured by Daikin Industries, Ltd.) and n-dodecane as a liquid lubricant 20 parts by weight was mixed to obtain a paste-like mixture. The obtained mixture was molded by paste extrusion to obtain an extruded molded body (thickness 2 mm). Next, the obtained extruded product was passed through a pair of metal rolls and rolled to a thickness of 0.51 mm. Then, it heated at 150 degreeC for 60 second, the liquid lubricant was dried and removed, and the dry molded object was obtained. Further, the obtained dried molded body was stretched twice in the longitudinal direction at a stretching temperature of 280 ° C. and then cooled at room temperature of 25 ° C. to obtain a pressure-sensitive adhesive sheet composed of a PTFE sheet having a thickness of 0.4 mm.

[Example 12]
In the same manner as in Example 11, a dried molded body was obtained. The obtained dried molded body was stretched 5 times in the longitudinal direction at a stretching temperature of 280 ° C., and then cooled at room temperature of 25 ° C. to obtain a pressure-sensitive adhesive sheet composed of a PTFE sheet having a thickness of 0.26 mm.

[Comparative Example 1]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was heated at 360 ° C. for 5 minutes and then cooled at room temperature of 25 ° C. to obtain a pressure-sensitive adhesive sheet made of a PTFE sheet having a thickness of 0.2 mm.

[Comparative Example 2]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was heated at 400 ° C. for 5 minutes and then cooled at room temperature of 25 ° C. to obtain a pressure-sensitive adhesive sheet composed of a PTFE sheet having a thickness of 0.2 mm.

[Comparative Example 3]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded body was stretched 5 times in the longitudinal direction at a stretching temperature of 380 ° C., and then cooled at room temperature of 25 ° C. to obtain a pressure-sensitive adhesive sheet composed of a PTFE sheet having a thickness of 0.12 mm.

[Comparative Example 4]
A dried molded body was obtained in the same manner as in Example 1. The obtained dried molded article was stretched at a stretching temperature of 380 ° C., stretched 4 times in the longitudinal direction and 6 times in the width direction, then cooled at room temperature of 25 ° C., and a pressure-sensitive adhesive sheet comprising a PTFE sheet having a thickness of 0.1 mm Got.

[Comparative Example 5]
A double-sided pressure-sensitive adhesive sheet was prepared by laminating a silicone pressure-sensitive adhesive layer on one side of a heat-peelable double-sided pressure-sensitive adhesive sheet (trade name “Riva Alpha No. 31950E”, 200 ° C. foaming type, manufactured by Nitto Denko Corporation).

[Evaluation]
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were subjected to the following evaluation. The results are shown in Table 1.

(1) Elastic modulus by nanoindentation method The surface elastic modulus of the adhesive sheet was measured using “TriboScope” manufactured by Nanoindenter HYSITRON. A spherical indenter having a diameter of 10 μm was pushed from the surface by 1 μm, held for 60 seconds, and the elastic modulus was analyzed by the following equation from the sample deformation amount-load gradient S when unloaded. The indentation and unloading speed was 100 nm / sec. Here, β is a constant determined by the shape of the indenter, and β = 1 in the case of a spherical indenter was used in this evaluation. A is the contact projected area, and was calculated as A = π (2Dh−h ² ). Here, D is the radius of the spherical indenter (D = 5 μm), and h is the amount of deformation of the sample. The pressure-sensitive adhesive sheet was subjected to this evaluation after being adhered and fixed to a SUS holder using “EZL1-W” manufactured by Pentel.

(2) Crystallinity Using a high-temperature differential scanning calorimeter “Q2000” (TA Instruments Co., Ltd.), the heat of fusion [J / g] was measured when the temperature was raised from 0 ° C. to 400 ° C. The heating rate was 20 ° C./min. The degree of crystallinity of PTFE constituting the pressure-sensitive adhesive sheet was calculated from an equation of (measured heat of fusion / 92.84) × 100 (%), assuming that the heat of fusion at the time of complete crystallization of PTFE was 92.84 [J / g].

(3) Thermal decomposition evaluation (weight change under high temperature)
Using a differential thermal analyzer “TG / DTA220” (manufactured by SII Nano Technology Inc.), the thermal decomposition rate at 300 ° C. (thermal decomposition rate when the temperature is raised from 25 ° C. to 300 ° C.) of the adhesive sheet is measured. did. The measurement conditions were a heating rate of 10 ° C./min, an air atmosphere, and a flow rate of 200 ml / min. The thermal decomposition rate is obtained by the following formula: (sample weight at start of temperature rise-sample weight at end of temperature rise) / sample weight at start of temperature rise × 100. In Table 1, when the thermal decomposition rate was less than 1% by weight, it was evaluated as ◯, and when it was 1% by weight or more, it was marked as x.

(4) Adhesive strength (peeling strength)
The pressure-sensitive adhesive sheet cut out to 20 mm × 150 mm is made of glass (manufactured by Matsunami Glass Co., Ltd., trade name “MICRO SLIDE GLASS S200034”, size 65 mm × 165 mm, thickness 1.2 mm) on the entire surface of 10 kg with a 2 kg hand roller. After pasting, pressure treatment was performed in an autoclave manufactured by Kurihara Seisakusho. The autoclave treatment conditions were a temperature of 25 ° C., a pressure of 5 atm, and a time of 10 minutes. Next, a peeling test was performed with a Yamamoto variable angle peel tester manufactured by Asahi Seiko Co., Ltd. The peeling angle was 60 degrees and the peeling speed was 50 mm / min.

(5) Fixing The adhesive sheet cut out to 40 mm × 100 mm is 2 kg hand roller on the entire surface of the first glass (made by Matsunami Glass, trade name “MICRO SLIDE GLASS S200423”, size 65 mm × 165 mm, thickness 1.2 mm). Was pasted under conditions of 10 reciprocations. Furthermore, 2 kg hand roller of the second glass (manufactured by Matsunami Glass Co., Ltd., trade name “MICRO SLIDE GLASS S1214”, size 25 mm × 75 mm, thickness 1.2 mm) on the surface of the adhesive sheet opposite to the first glass Was pasted under conditions of 10 reciprocations. The laminated body thus obtained was allowed to stand at 25 ° C. with an inclination of 45 ° C. so that the second glass was on the lower side. In Table 1, the case where the second glass did not fall even after the passage of one day was marked as ◯, and the case where the second glass fell due to its own weight within one day was marked as x.

  As apparent from the examples, the pressure-sensitive adhesive sheet of the present invention, that is, the pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing PTFE having a crystallinity of 80% or more has sufficient adhesive force and low thermal decomposability. Show. On the other hand, the pressure-sensitive adhesive sheet formed from PTFE having a low crystallinity does not exhibit adhesive strength (Comparative Examples 1 to 4). Moreover, the conventional heat peeling type double-sided adhesive sheet has high thermal decomposability (Comparative Example 5).

  The pressure-sensitive adhesive sheet of the present invention can be suitably used, for example, as a pressure-sensitive adhesive sheet that temporarily fixes a member used in an electronic device when processing or processing the member.

10 Adhesive layer 20 Base material layer 100 Adhesive sheet

Claims (3)

With an adhesive layer,
The adhesive layer contains polytetrafluoroethylene having a crystallinity of 80% or more,
The adhesive layer has a thickness of 0.1 mm to 1 mm,
The adhesive force to the glass plate is 0.03 N / 20 mm to 0.2 N / 20 mm.
Adhesive sheet.   The pressure-sensitive adhesive sheet according to claim 1, wherein an elastic modulus of the pressure-sensitive adhesive layer by a nanoindentation method at 25 ° C is 0.5 MPa or less. The pressure-sensitive adhesive sheet according to claim 1 or 2 , wherein a weight reduction rate when heated from 25 ° C to 300 ° C at a temperature rising rate of 10 ° C / min is 1% by weight or less.