Heat-resistant film

Abstract

[Problem] To provide a heat-resistant film which is suitable for protection of the surface state of a plastic product, a glass product, a ceramic product and the like, said surface having been subjected to electric conduction, decoration or the like, or suitable for fixation of a semiconductor and the like when the semiconductor and the like are cut and separated, thereby obtaining chips. [Solution] A heat-resistant film which is formed of a thermoplastic resin, wherein: the thermoplastic resin is a polyester elastomer that is obtained by bonding a hard segment and a soft segment to each other; the hard segment has a polyester unit that is composed of an aromatic dicarboxylic acid and an aliphatic diol or an alicyclic diol; the soft segment is mainly composed of a specific polycarbonate; the weight ratio of the hard segment contained in the polyester elastomer is more than 50%; and the thermoplastic resin film has an elastic modulus of from 30 MPa to 500 MPa, an elongation at break of from 200% to 700%, and a ratio of the stress F50 at the elongation of 50% to the stress F25 at the elongation of 25%, namely F50 / F25 of 1.05 or more.

Description

[Technical Field]

[0001] The present invention relates to a heat-resistant film suitable for protecting the surface condition of plastic products, glass products, ceramic products, etc., which have been given electrical conductivity or decoration, or for fixing semiconductors, etc., when cutting and separating them to obtain chips. [Background technology]

[0002] Plastic, glass, ceramic, and other products have not only flat surfaces but also curved surfaces and even uneven shapes, so the films used to protect them must be adaptable to a variety of uses. For example, adhesive sheets, which are made by laminating an adhesive onto a film, require conformability, which means uniform conformability within the surface.

[0003] The semiconductor manufacturing process involves a dicing process in which wafers and substrates are cut into chips, an expanding process in which the individual chips are spaced apart to make them easier to pick up using a suction jig, and a pick-up process in which the chips are collected. There are various demands for protective films, adhesive sheets, etc. that can reduce the load during these processes.

[0004] In the dicing process, moderate rigidity is required to fix the wafer or substrate and prevent misalignment during dicing by the blade or other tool, and to prevent chips from flying off, while in the expanding process, extensibility is required to ensure uniform expansion of the chip spacing. Furthermore, with the increasing demands of high performance technologies such as TSV (Through Silicon Via), which stacks multiple semiconductor chips, simplification of processes such as transfer molding, which directly apply encapsulant, and processing of wafers at temperatures of over 150°C, the substrates used for surface protection films and dicing tapes must be heat-resistant.

[0005] In particular, a multilayer film has been disclosed in which a resin composition consisting of, for example, a vinyl aromatic hydrocarbon or a hydrogenated conjugated diene hydrocarbon copolymer and a polypropylene resin is laminated as a surface protection film in semiconductor manufacturing processes or as a substrate for an adhesive sheet used as dicing tape. However, although the expandability is sufficient, there are problems such as distortion caused by the weight of the wafer, and defects such as wrinkles and pressure marks on the substrate caused by heat treatment in the coating process of the adhesive layer, etc., and further by the high-temperature treatment mentioned above (Patent Document 1).

[0006] Polyester resins have a high glass transition temperature and are excellent heat-resistant materials, and taking advantage of this, amorphous polyesters with glass transition temperatures of 0 to 50°C have been disclosed to achieve a certain level of expandability. However, tension is not maintained even after expansion, so deflection is likely to occur, and the modulus of elasticity decreases above the glass transition temperature. Also disclosed is a method of laminating polyester resins with glass transition temperatures of -100 to 0°C and 0 to 100°C. However, because the layer basically contains a low melting point or softening point, problems arise when high-temperature processing is performed, such as defects such as wrinkles and pressure marks, and deflection due to the weight of the wafer (Patent Documents 2 and 3).

[0007] Polyester elastomers are known as block copolymers formed by combining hard segments consisting of polyesters composed of aromatic dicarboxylic acids and aliphatic or alicyclic diols with soft segments primarily consisting of alicyclic diols. These have higher heat resistance than polystyrene elastomers, polyolefin elastomers, and polyamide elastomers, and are used in a variety of applications. However, many block copolymers exhibit a yield point at low elongations of 10 to 25%, making uniform elongation difficult above this level. Addressing these issues by increasing the proportion of soft segments results in a decrease in heat resistance, making it impossible to achieve both heat resistance and extensibility. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-094418 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-092273 [Patent Document 3] Japanese Patent Application Publication No. 2017-034618 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a heat-resistant film suitable for protecting the surface condition of plastic products, glass products, ceramic products, etc. that have been subjected to electrical conductivity or decoration, or for fixing wafers and the like when cutting and separating them to obtain chips in the semiconductor manufacturing process. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems and have completed the following invention: [1] A heat-resistant film made of a thermoplastic resin, the thermoplastic resin being a polyester elastomer formed by bonding hard segments and soft segments; The hard segment has a polyester unit constituted of an aromatic dicarboxylic acid and an aliphatic diol or an alicyclic diol, The soft segment is mainly composed of an aliphatic polycarbonate, the weight ratio of the hard segment contained in the polyester-based elastomer exceeds 50%, The film made of the thermoplastic resin is a heat-resistant film having an elastic modulus of 30 to 500 MPa, a breaking elongation of 200 to 700%, and a ratio F50 / F25 of the stress F50 at 50% elongation to the stress F25 at 25% elongation, of 1.05 or more. [2] The heat-resistant film as described above, wherein the hard segment of the polyester elastomer is composed of polybutylene terephthalate units, and the melting point of the polyester elastomer is 195 to 220°C. [3] The heat-resistant film as described above, wherein the hard segment of the polyester elastomer is composed of polybutylene naphthalate units, and the melting point of the polyester elastomer is 210 to 240°C. [4] The heat-resistant film described above, which is used as a protective film. [5] An adhesive sheet having an adhesive on at least one surface of the heat-resistant film. [Effects of the Invention]

[0011] The heat-resistant film of the present invention is formed from a specific polyester elastomer. In particular, since the soft segment of the present invention is contained, a heat-resistant film having excellent heat resistance and high extensibility can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0012] The heat-resistant film of the present invention is suitable for use as a dicing tape for fixing semiconductors and the like when cutting and separating them to obtain chips, and can withstand heat treatment in the coating process of adhesive layers, etc., and has excellent stretchability, making it applicable to surface protection films that protect the conductive, decorated, etc. surfaces of plastic products, glass products, ceramic products, etc. It is also possible to provide an adhesive sheet having an adhesive.

[0013] The heat-resistant film of the present invention has the compounds and structures described below.

[0014] <Polyester elastomer> The polyester-based elastomer used in the heat-resistant film of the present invention is composed of a hard segment made of a polyester composed of an aromatic dicarboxylic acid and an aliphatic diol or an alicyclic diol, and a soft segment made mainly of an aliphatic polycarbonate bonded to the hard segment.

[0015] The aromatic dicarboxylic acid constituting the polyester of the hard segment in the polyester-based elastomer is generally a conventional aromatic dicarboxylic acid. Specifically, the aromatic dicarboxylic acid is preferably terephthalic acid or naphthalenedicarboxylic acid. These compounds may also be included as the main component of the aromatic dicarboxylic acid according to the present invention. Examples of other acid components include aromatic dicarboxylic acids such as diphenyldicarboxylic acid, isophthalic acid, and 5-sodium sulfoisophthalic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and tetrahydrophthalic anhydride, and those obtained by adding aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid, and hydrogenated dimer acid. These aliphatic dicarboxylic acids are used in an amount that does not significantly lower the melting point of the resin, and the amount used is less than 30 mol %, preferably less than 20 mol %, of the total acid components. The aliphatic diol or alicyclic diol constituting the polyester of the hard segment is not particularly limited, but is preferably an alkylene glycol having 2 to 8 carbon atoms. Specific examples include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol, with 1,4-butanediol and 1,4-cyclohexanedimethanol being most preferred. These compounds may also be included as the main component of the diol of the present invention. Therefore, it is desirable that the hard segment polyester is mainly composed of butylene terephthalate units or butylene naphthalate units in terms of physical properties, moldability and cost performance.

[0016] The aliphatic diol constituting the soft segment in the polyester elastomer used in the heat-resistant film of the present invention is preferably an aliphatic polycarbonate diol having a low melting point (e.g., 70°C or less) and a low glass transition temperature. For example, an aliphatic polycarbonate diol made from 1,6-hexanediol has a low glass transition temperature of about -60°C and a melting point of about 50°C, which is suitable because it provides extensibility at room temperature. Furthermore, an aliphatic polycarbonate diol obtained by copolymerizing the above aliphatic polycarbonate diol with an appropriate amount of, for example, 3-methyl-1,5-pentanediol has a slightly higher glass transition temperature than the original aliphatic polycarbonate diol, but has a lower melting point or is amorphous, making it a good aliphatic polycarbonate diol. Furthermore, for example, an aliphatic polycarbonate diol made of 1,9-nonanediol and 2-methyl-1,8-octanediol has a melting point of about 30°C and a glass transition temperature of about -70°C, which are sufficiently low, and therefore corresponds to a similarly good aliphatic polycarbonate diol. These aliphatic polycarbonate diols may be copolymerized with small amounts of other glycols, dicarboxylic acids, ester compounds, ether compounds, etc., and examples of copolymerization components include glycols such as dimer diol, hydrogenated dimer diol, and modified products thereof, dicarboxylic acids such as dimer acid and hydrogenated dimer acid, polyesters composed of aliphatic, aromatic, or alicyclic dicarboxylic acids and glycols, or oligoesters, polyesters composed of ε-caprolactone, etc., oligoesters, polytetramethylene glycol, polyoxyethylene glycol, etc., or oligoalkylene glycols, and can be used to an extent that does not substantially eliminate the effect of the aliphatic polycarbonate segment. Furthermore, it is composed of aliphatic diol residues mainly having 2 to 12 carbon atoms, such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,9-nonanediol, and 2-methyl-1,8-octanediol, and in particular, aliphatic diols having 5 to 12 carbon atoms are preferred from the viewpoints of heat resistance and extensibility. These components may be used alone, or two or more types may be used in combination as necessary. Furthermore, copolymer components such as polyalkylene glycols such as polyethylene glycol and polyoxytetramethylene glycol, and polyesters such as polycaprolactone and polybutylene adipate may be introduced as soft segments to the extent that the effects of the invention are not lost.

[0017] In the polyester-based elastomer used in the heat-resistant film of the present invention, the mass ratio of hard segments made of a polyester composed of an aromatic dicarboxylic acid and an aliphatic diol or an alicyclic diol to soft segments made of an aliphatic polycarbonate and optional copolymerization components is generally 40:60 to 80:20. Because a high mass ratio of hard segments can result in decreased extensibility, and a high mass ratio of soft segments can result in decreased heat resistance, the hard segment:soft segment ratio is preferably greater than the soft segment weight ratio in the polyester-based elastomer, and the hard segment weight ratio in the polyester-based elastomer exceeds 50%. For example, the hard segment:soft segment ratio is 50.1:49.9 to 70:30, with 55:45 to 75:25 being preferred. In one embodiment, the hard segment:soft segment ratio is 55:45 to 70:30.

[0018] The polyester-based elastomer used in the heat-resistant film of the present invention preferably has hard segments made of a polyester constituted of an aromatic dicarboxylic acid and an aliphatic diol or an alicyclic diol, and soft segments made mainly of an aliphatic polycarbonate, in which the units constituting the hard segments and / or soft segments are directly bonded via ester bonds or carbonate bonds.

[0019] Furthermore, it is more preferable that the hard segment and soft segment in the polyester-based elastomer are bonded with a chain extender such as an isocyanate compound. In this case, it is preferable that the polycarbodiimide compound contains 0.5 to 10 parts by mass, and for example, 0.5 to 6 parts by mass, more preferably 1.0 to 3.0 parts by mass, of a polycarbodiimide compound per 100 parts by mass of a product (hereinafter sometimes referred to as a blocked reaction product) obtained by repeatedly performing transesterification and depolymerization reactions for a certain period of time in a melt of a polyester constituting the hard segment, a polycarbonate constituting the soft segment, and, if necessary, various copolymerization components.

[0020] The polycarbodiimide compound can be obtained, for example, by the decarbonation reaction of a diisocyanate compound. The diisocyanate to be used includes 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane diisocyanate, tetramethylxylylene diisocyanate, 1,3,5-triisopropylphenylene-2,4-diisocyanate, and the like, which can be used alone or in copolymerization of two or more kinds. It is also possible to introduce a branched structure or a functional group other than a carbodiimide group or an isocyanate group by copolymerization. Although the terminal isocyanate can be used as is, it is possible to control the degree of polymerization by further reacting the terminal isocyanate, and it is also possible to block a portion of the terminal isocyanate.

[0021] Among these polycarbodiimide compounds, preferred are alicyclic polycarbodiimides whose main raw materials are dicyclohexylmethane diisocyanate, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, etc. Furthermore, from the viewpoint of stability and ease of handling, those having an isocyanate group at the terminal and an isocyanate group content of about 0.5 to 4 mass% are preferred, and an isocyanate group content of about 1 to 3 mass% is more preferred. In particular, polycarbodiimides derived from dicyclohexylmethane diisocyanate or isophorone diisocyanate are preferred, and those with an isocyanate group content of 0.5 to 4 mass % are more preferred, with those with an isocyanate group content of 1 to 3 mass % being even more preferred.The isocyanate group content can be measured using a standard method (a method of dissolving in an amine and performing back titration with hydrochloric acid).

[0022] The number of carbodiimide groups in the carbodiimide compound is preferably 2 to 50 in terms of thermal stability, more preferably 5 to 30. Furthermore, since the compound has such a degree of polymerization, it is solid at around room temperature, and powdering it improves workability and compatibility when mixed with a polyester-based elastomer, which is preferable in that uniform reaction and bleed-out resistance can be expected. The number of carbodiimide groups is the number of carbodiimides in the polycarbodiimide compound, and corresponds to the degree of polymerization in the case of a polycarbodiimide obtained from a diisocyanate compound. Polycarbodiimides are usually mixtures of molecules of various lengths, and the number of carbodiimide groups is expressed as an average value. The number of carbodiimide groups can be measured using a standard method (dissolving in an amine and back-titrating with hydrochloric acid) as described above. By using such a polycarbodiimide compound having an isocyanate group content of 0.5 to 4 mass% and a carbodiimide group number of 2 to 50, it is possible to adjust the MFR in accordance with JIS K 7210 "Determination of melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of plastics-thermoplastics" to 1 to 10 g / 10 min, and to suppress the occurrence of uneven extrusion during melt extrusion such as film formation.

[0023] Furthermore, it contains two or more glycidyl groups per molecule, has a weight average molecular weight of 4,000 to 25,000, and has an epoxy value of 400 to 780 equivalents / 10 6 g of a reactive compound can be applied, and in this case, the reactive compound is preferably contained in an amount of 0.1 to 30 parts by mass, more preferably 0.5 to 5 parts by mass.

[0024] When the reduced viscosity of the composition obtained by this formulation is compared before and after molding, such as film formation, the reduced viscosity after molding is maintained, and the generation of foreign matter such as gel-like matter is suppressed.Furthermore, although the mechanism is unclear, the ratio F50 / F25 of the stress F50 at 50% elongation to the stress F25 at 25% elongation is large, resulting in uniform elongation. Here, the heat-resistant film of the present invention has a ratio F50 / F25 of the stress F50 at 50% elongation to the stress F25 at 25% elongation of 1.05 or more, for example, 2.0 or less. In one embodiment, F50 / F25 may be 1.05 or more and 1.6 or less. By keeping F50 / F25 within this range, abnormalities such as wrinkles and distortions are less likely to occur when stretched in one direction or multiple directions.

[0025] The polyester-based elastomer contained in the heat-resistant film of the present invention, which is formed by bonding hard segments made of polyester composed of an aromatic dicarboxylic acid and an aliphatic diol or an alicyclic diol to soft segments mainly made of aliphatic polycarbonate, may have problems with heat resistance if its melting point is low, while a high melting point may result in reduced extensibility. In one embodiment, the polyester-based elastomer has a melting point of 195°C or higher, and when the hard segments are made of polybutylene terephthalate units, the melting point is preferably 195 to 220°C. Furthermore, when the hard segments are made of polybutylene naphthalate units, the melting point is preferably 210 to 240°C.

[0026] Polyester elastomers can also contain inorganic particles such as silica, talc, zeolite, and aluminum borate, as well as organic particles such as polymethyl methacrylate, melamine-formaldehyde resin, melamine-urea resin, and polyester resin, provided that the intended purpose is not compromised. However, organic slip agents, such as hydrocarbons (e.g., liquid paraffin, paraffin wax, and synthetic polyethylene wax), aliphatic and higher alcohols (e.g., stearic acid and stearyl alcohol), and fatty acid amides (e.g., stearic acid amide, oleic acid amide, and erucic acid amide), can bleed and cause contamination. Therefore, it is important that the extractable amount of these agents, measured by Soxhlet extraction with chloroform in accordance with JIS K 6229 "Determination of rubber-solvent extractables (quantitative)," is 1 wt% or less, and that they are essentially absent. If added, the amount of each organic slip agent should be 0.5 wt% or less, and preferably 0.1 wt% or less.

[0027] The raw materials used for the polyester elastomer are not particularly limited and may be derived from petroleum or plants, but are preferably derived from plants from an environmental point of view.

[0028] <Sheeting> The heat-resistant film of the present invention is obtained by forming a polyester elastomer, which is formed by bonding a hard segment made of a polyester constituted of an aromatic dicarboxylic acid and an aliphatic diol or an alicyclic diol, and a soft segment made mainly of an aliphatic polycarbonate, into a sheet by melt extrusion or the like.

[0029] In melt extrusion, the material is extruded as a sheet from a T-die through a single-screw or twin-screw extruder. The extruded sheet is then pressed against the surface of a metal roll through which cooling water or oil circulates, using an air knife, air chamber, hard rubber roll, steel belt, metal roll, or the like, to cool and solidify. Alternatively, the sheet can be cooled and solidified by sandwiching both sides of the sheet between steel belts. The above-mentioned sheet can also be obtained as a heterogeneous multilayer sheet by using a feed block or multi-manifold. The above-mentioned sheet can be stretched uniaxially or biaxially as needed. A high total stretching ratio can impair extensibility, while a low total stretching ratio can result in significant thickness variation, so a stretching ratio of 3 to 12 is preferred.

[0030] <Structure of heat-resistant film> The heat-resistant film of the present invention can have a layer structure such as A: single layer, A / B, A / B / A, or A / B / C, using similar polyester-based elastomers, different elastomers, polyester-based resins, or different resins, and it is also possible to provide another resin layer between the layers to prevent problems such as delamination.

[0031] In such a configuration, if the static friction coefficient of at least one surface is low, problems such as slippage during winding of the roll may occur, and if it is high, wrinkles may remain, so the lower limit is preferably 0.10 or more, more preferably 0.15 or more. The upper limit is preferably 0.9 or less, and particularly when applied to dicing tape used in semiconductor processes, uniform expandability may not be obtained during the expanding process, so 0.5 or less is more preferred.

[0032] <Thickness of heat-resistant film> The heat-resistant film of the present invention, depending on the usage, has a low stiffness when the overall thickness is small, and a large thickness can cause problems in handling. In particular, when applied to dicing tape used in semiconductor manufacturing processes, defects occurring during the cutting process can cause breakage and / or prevent uniform expandability, so the overall thickness is preferably 60 μm or more, more preferably 80 μm or more. Furthermore, a thickness of 180 μm or less is preferred from the viewpoint of handling.

[0033] The thermoplastic resin film of the present invention has a modulus of elasticity of preferably 30 to 500 MPa, more preferably 30 to 100 MPa, since a high modulus of elasticity makes it difficult to obtain extensibility, and a low modulus of elasticity makes it difficult to obtain stiffness. The elongation at break may be 200 to 700%, for example, 350 to 700%.

[0034] <Adhesive> In one embodiment, a pressure-sensitive adhesive sheet is provided having a pressure-sensitive adhesive on at least one surface of the heat-resistant film according to the present invention. Examples of pressure-sensitive adhesives that can be used in the pressure-sensitive adhesive sheet of the present invention include (meth)acrylic pressure-sensitive adhesives, silicone pressure-sensitive adhesives, urethane pressure-sensitive adhesives, olefin pressure-sensitive adhesives, and styrene pressure-sensitive adhesives. The pressure-sensitive adhesive can be selected depending on the application, such as a surface protection film that protects the conductive, decorative, or other surface condition of plastic products, glass products, ceramic products, and the like. Furthermore, for dicing tape that fixes wafers and the like when cutting and separating them to obtain chips in semiconductor processes, among these, (meth)acrylic pressure-sensitive adhesives are preferred, as they can easily adjust adhesive strength.

[0035] The thickness of the adhesive layer of the above-mentioned adhesive is not particularly limited, but when applied to dicing tape that fixes wafers and the like when cutting and separating them to obtain chips in the semiconductor process, or to surface protection films that protect the conductive, decorated, etc. surfaces of plastic products, glass products, ceramic products, etc., the thickness is preferably 1 to 50 μm, and more preferably 3 to 30 μm, from the viewpoints of adhesive strength and uniformity of the thickness of the adhesive layer.

[0036] [Example]

[0037] The present invention will be described in more detail below with reference to examples. Note that the present invention is not limited to the following examples, and modifications can be made within the scope of the present invention, and all such modifications are included in the technical scope of the present invention.

[0038] The physical properties in the examples were evaluated as follows.

[0039] (1) Number average molecular weight An aliphatic polycarbonate diol sample was dissolved in deuterated chloroform (CDCl3), and the terminal group was calculated by measuring H-NMR, and was determined using the following formula. Number average molecular weight = 1,000,000 / ((end group amount (equivalents / ton)) / 2)

[0040] (2) Reduced viscosity According to JIS K 7367-5:1998 "Plastics - Determining the viscosity of polymer dilute solutions using a capillary viscometer" and phenol / tetrachloroethane = 60 / 40 (mass %) mixed solvent was used, and the viscosity number obtained by measurement using an Ostwald viscometer was taken as the reduced viscosity.

[0041] (3) Tm (melting point) The melting peak temperature in the curve obtained by DSC (differential scanning calorimetry) was used in accordance with JIS K 7121:1987 "Method for measuring transition temperature of plastics."

[0042] (4) Software (segment) volume Using a Fourier transform nuclear magnetic resonance spectrometer (AVANCE-NEO500 manufactured by BRUKER, Germany), the sample was dissolved in a solvent (deuterated chloroform / trifluoroacetic acid = 85 / 15 vol%) at a concentration of 3 to 5 vol%, and then proton NMR measurement was performed at 25°C. The mass ratio of the hard segment to the soft segment was calculated from the signal intensity ratio of the methylene peaks adjacent to various oxygen atoms in the molecular structure.

[0043] (5) Film thickness The thickness was determined in accordance with JIS K 7130:1999 "Method for measuring thickness of plastic films and sheets (Method A)".

[0044] (6) Strength, elongation, elastic modulus, F25, F50 In accordance with JIS K 7127:1999 "Plastics - Testing methods for tensile properties", strength, elongation and modulus of elasticity were determined from tensile strength, tensile breaking elongation and tensile modulus of elasticity, and the specified strains were set to 25% and 50%, with the tensile stresses at these strains being F25 and F50. The index of extensibility is expressed as the ratio of stress at the specified strains, F50 / F25.

[0045] (7) Coatability A solution containing an acrylic copolymer (weight average molecular weight 500,000) obtained by copolymerizing butyl acrylate / acrylic acid = 90 / 10 in a toluene solution by a conventional method was added to 80 parts by weight of commercially available dipentaerythritol hexaacrylate "Karayat DPHA: manufactured by Nippon Kayaku Co., Ltd.", 5 parts by weight of photopolymerization initiator "Omnirad184: manufactured by IGM Resins RV Co., Ltd.", and 5 parts by weight of polyisocyanate compound "Coronate L: manufactured by Tosoh Co., Ltd.". The adhesive solution was applied to a commercially available release film "E7002: manufactured by Toyobo Co., Ltd." to a thickness of about 10 μm, and then laminated with the heat-resistant film (Example) according to the present invention or a general-purpose film (Comparative Example) to obtain an adhesive sheet. The obtained adhesive sheet was evaluated according to the following items. ◎ Single adhesive sheet product with no curl ○ Although curling occurs in sheet adhesive sheets, this can be addressed by adjusting the tension of the sheet. △ Curling occurs in sheet adhesive sheets, making it difficult to adjust the tension of the sheet. × It is difficult to adjust the tension of the sheet material when laminating, resulting in uneven adhesive thickness on the sheet products.

[0046] (8) Extensibility The adhesive sheet was fixed to a 6-inch dicing frame with double-sided tape, and concentric circles of 50 mm and 100 mm diameter were drawn around the center point. The sheet was then expanded with an expander (stage: temperature 30°C, rising speed 50 mm / min, held for 60 seconds) to achieve the specified elongation relative to the inner diameter of the dicing frame, and the following evaluations were made from the elongation measured at 45° intervals relative to the concentric circles. The specified elongation was calculated using the following formula: Elongation (%) = (stage travel distance x 2) / frame inner diameter x 100 ◎: Reached 65% or more of the specified elongation in all directions, with the maximum difference being less than 2% ○: Reaches 65% or more of the specified elongation in all directions, but there is a maximum difference of 2-5% △: 50-65% of the specified elongation in some directions, with a maximum difference of 2-5% ×: Elongation less than 50% of the specified elongation in some directions, or a difference of up to 5% or more

[0047] (9) Heat resistance In accordance with JIS K 7206:1999 "Plastics - Thermoplastics - Determination of Vicat softening temperature (A120 method)", the following evaluations were carried out on 3 mm thick samples obtained by a press from the resins obtained in the following examples and comparative examples. ◎: Vicat softening point is 180℃ or higher △: Vicat softening point is 170-180℃ △: Vicat softening point is 160-170℃ ×: Vicat softening point is 160°C or less

[0048] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0049] <Examples 1 and 2> A mixture of commercially available 1,6-hexanediol-type aliphatic polycarbonate diol (molecular weight 2,000) and diphenyl carbonate was reacted at a temperature of 205°C and a pressure of 130 Pa for 2 hours to obtain a preparation (number average molecular weight 10,000). PBT (polybutylene terephthalate) was then subjected to condensation polymerization at elevated temperature and reduced pressure to obtain a resin having the specified soft segment mass ratio shown in Table 1. The obtained resin (for layer A) and a pellet-shaped MB (masterbatch) containing 15 wt% of commercially available spherical silica (average particle size 12 μm) were prepared using the same resin as the base, and the spherical silica was adjusted to 7,500 ppm using the masterbatch. This resin (for layer B) was then extruded from a T-die through an extruder so that the film thickness of structure A was 10% of the total thickness and further had a structure of structure A / B. After pressing the film against a cooling roll with an air knife, the edges were trimmed in the process to obtain a roll of heat-resistant film of Examples 1 to 2 with a total film thickness of 100 μm, a width of 650 mm, and a winding length of 1,000 m. In the above example, sheeting was carried out for about 4 to 5 hours at a temperature about 10°C higher than the melting point, but no abnormalities in extrusion or discharge pressure were observed. The properties of the resin used and the evaluation results of the heat-resistant film and roll are shown in Table 1.

[0050] <Comparative Examples 1 and 2> In Comparative Examples 1 and 2, films were produced in the same manner as in Example 1, except that resins according to the conditions shown in Table 1 were used. Table 1 also shows the physical properties of the films obtained.

[0051] <Examples 3 and 4> A resin was obtained in the same manner as in Example 1 above, except that PBN (polybutylene naphthalate) was used for a preparation (number average molecular weight 10,000) obtained by reacting a mixture of commercially available 1,6-hexanediol type aliphatic polycarbonate diol (molecular weight 2000) and diphenyl carbonate at a temperature of 205°C and a pressure of 130 Pa for 2 hours. Furthermore, as in Example 1, the film thickness of Structure A was 10% of the total thickness, and further, a film was formed so as to have a structure of Structure A / B, and a roll of heat-resistant film was obtained with a total thickness of 100 μm, a width of 650 mm, and a roll length of 1,000 m. In the above example, sheeting was carried out for about 4 to 5 hours at a temperature about 10°C higher than the melting point, but no abnormalities in extrusion or discharge pressure were observed. The properties of the resin used and the evaluation results of the heat-resistant film and roll are shown in Table 1.

[0052] <Comparative Examples 3 and 4> In Comparative Examples 3 and 4, films were produced in the same manner as in Example 3, except that resins according to the conditions shown in Table 1 were used. Table 1 also shows the physical properties of the films obtained.

[0053] [Table 1]

[0054] The pressure-sensitive adhesive sheet of the present invention is a heat-resistant film that uses a resin in which a polyester elastomer is bonded to a hard segment made of a polyester composed of an aromatic dicarboxylic acid and an aliphatic diol or an alicyclic diol, and a soft segment made mainly of an aliphatic polycarbonate. In the examples, tension can be easily adjusted during the application of the pressure-sensitive adhesive, thereby reducing unevenness in the pressure-sensitive adhesive thickness and curling of the sheet due to the lamination of a release film. In addition, in terms of extensibility, high elongation and uniform elongation can be obtained, and the high heat resistance that is characteristic of polyester elastomers is also maintained.

[0055] <Examples 5 to 12> A mixture of commercially available 1,6-hexanediol type aliphatic polycarbonate diol (molecular weight 2000) and diphenyl carbonate described in Examples 1 to 4 was reacted at a temperature of 205°C and a pressure of 130 Pa for 2 hours to obtain a preparation (number average molecular weight 10,000). PBT (polybutylene terephthalate) or PBN (polybutylene naphthalate) was then subjected to condensation polymerization at elevated temperature and reduced pressure to obtain a resin with a predetermined soft segment mass ratio. The resulting resin (resin for Layer A) and a pellet-shaped MB (masterbatch) containing 15 wt% of commercially available spherical silica (average particle size 12 μm) were prepared using the same resin as the resin for Layer B. The masterbatch was used to prepare a resin containing 7,500 ppm of spherical silica. A heat-resistant film was produced using this resin in the same manner as in Example 1, except that a predetermined amount of a carbodiimide compound (Carbodilite LA-1) was added as a side feed during the extrusion of the resin for Layer A and the resin for Layer B. Specifically, the film was extruded through a T-die through an extruder so that the film thickness of Structure A was 10% of the total thickness and further had a structure of Structure A / B. The film was pressed against a cooling roll with an air knife, and then the edges were trimmed in the process to obtain a roll of the heat-resistant film of Examples 5 to 12 having a total thickness of 100 μm, a width of 650 mm, and a winding length of 1,000 m.

[0056] Table 2 shows the properties of the resins in Examples 5 to 12 and the evaluation results of the sheets and rolls of the resins.

[0057] [Table 2]

[0058] The pressure-sensitive adhesive sheet of the present invention is a heat-resistant film that uses a resin in which a polyester elastomer is bonded to a hard segment made of a polyester composed of an aromatic dicarboxylic acid and an aliphatic diol or an alicyclic diol, and a soft segment made mainly of an aliphatic polycarbonate. Although the mechanism by which this occurs is unknown, the addition of a polycarbodiimide compound improves extensibility and increases the reduced viscosity corresponding to the molecular weight, thereby reducing the chance of whitening on the cooling roll when obtaining a heat-resistant film and making it easier to control the temperature of the cooling roll.

[0059] For Examples 1 to 12 and Comparative Examples 1 to 4, approximately 2 g of sample was collected, cut, and then subjected to Soxhlet extraction with chloroform (extraction for 4 hours), and it was confirmed that the extractables were 0.6 wt % or less. [Industrial Applicability]

[0060] The pressure-sensitive adhesive sheet of the present invention is a heat-resistant film of a polyester elastomer, and has its characteristic high heat resistance. Furthermore, by applying a predetermined soft segment to the polyester elastomer in an appropriate amount, the pressure-sensitive adhesive sheet is stable in processing steps such as coating, and can achieve uniform elongation even at high elongation. Therefore, the pressure-sensitive adhesive sheet is suitable as a surface protection film for protecting the conductive, decorated, etc. surfaces of plastic products, glass products, ceramic products, etc., and is particularly suitable as a surface protection film or dicing tape in semiconductor processes.

Claims

1. A heat-resistant film made of a thermoplastic resin, the thermoplastic resin being a polyester-based elastomer having a structure in which a blocking reaction product obtained from a polyester constituting a hard segment and a polycarbonate constituting a soft segment is bonded via a polycarbodiimide compound; The polyester constituting the hard segment has a polyester unit constituted by an aromatic dicarboxylic acid and an aliphatic diol, the polycarbonate constituting the soft segment is mainly composed of an aliphatic polycarbonate, the weight ratio of the hard segment contained in the polyester-based elastomer exceeds 50%, The heat-resistant film made of the thermoplastic resin has an elastic modulus of 30 to 500 MPa, a breaking elongation of 200 to 700%, and a ratio F50 / F25 of the stress F50 at 50% elongation to the stress F25 at 25% elongation of 1.18 or more.

2. 2. The heat-resistant film according to claim 1, wherein the hard segment of the polyester elastomer comprises a polybutylene terephthalate unit, and the polyester elastomer has a melting point of 195 to 220°C.

3. 2. The heat-resistant film according to claim 1, wherein the hard segment of the polyester elastomer comprises a polybutylene naphthalate unit, and the melting point of the polyester elastomer is 210 to 240°C.

4. The heat-resistant film according to any one of claims 1 to 3, which is used for a protective film.

5. A pressure-sensitive adhesive sheet comprising the heat-resistant film according to any one of claims 1 to 3 and a pressure-sensitive adhesive on at least one surface thereof.

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