Polyester film for semiconductor manufacturing processes

Abstract

A polyester film for semiconductor manufacturing processes, comprising a thermoplastic polyester layer containing a thermoplastic polyester, the thermoplastic polyester layer being a surface layer (A) of the polyester film, the hardness of the surface layer (A) being 450 MPa or less as measured at 23±5°C using a nanoindenter, and the Young's modulus of the polyester film being 2 GPa or more.

Description

[Technical Field]

[0001] The present invention relates to a polyester film for use in semiconductor manufacturing processes and a method for using the same. [Background technology]

[0002] Semiconductor devices are generally manufactured by forming electronic circuits on the surface of a semiconductor wafer such as a silicon wafer, then dicing the semiconductor wafer into semiconductor chips, and packaging the individual semiconductor chips. Blade dicing is commonly used for the dicing process, but stealth dicing, which uses laser light for dicing, is also becoming more common. Furthermore, to thin the chips, the backside of the semiconductor wafer is generally ground to adjust the thickness.

[0003] In recent years, a process called the front-end dicing method has been used to further thin semiconductor chips. The front-end dicing method involves forming grooves of a predetermined depth on the front side of the wafer using a dicing blade, grinding the wafer from the back side, and then dicing the wafer into individual chips. Another front-end dicing method that has been studied in recent years is stealth front-end dicing, which utilizes stealth dicing.

[0004] During backside grinding of semiconductor wafers, a dicing tape made of adhesive tape is generally applied to the front side of the wafer to protect the electronic circuits. Dicing tape base materials are known to be made of a support material such as polyester film with a soft layer such as a polyethylene layer laminated as a surface layer to mitigate the shear force acting on the wafer and individual chips during wafer grinding (see, for example, Patent Document 1).

[0005] In addition to the above, various other films have been known for use in semiconductor manufacturing processes. For example, Patent Document 2 discloses a surface protection film having an anchor coat layer containing a copolymer polyurethane resin on one side of a core film. Patent Documents 3 and 4 disclose, as substrate films for backgrinding tapes, three-layer films in which the front and back layers and the middle layer are each made of a soft polyester and a polyester-based elastomer, and three-layer films in which the front and back layers are made of a polyester-based resin and the middle layer is made of a soft polyester-based resin. Furthermore, Patent Document 5 discloses a carrier tape in which the middle layer is made of a copolymer polyester and both surface layers are made of polybutylene terephthalate or polybutylene naphthalate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-94525 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-216619 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-225675 [Patent Document 4] Patent Publication No. 2021-146675 [Patent Document 5] Japanese Patent Application Publication No. 04-257444 Summary of the Invention [Problem to be solved by the invention]

[0007] Meanwhile, polyester resins are widely used in large quantities and can be recycled not only physically but also chemically by depolymerization, so they have attracted attention as resins with excellent recyclability, and the reuse of PET bottles, which are consumed in large quantities, is progressing. In recent years, from the viewpoint of environmental protection, there has been a growing demand for the reuse of not only PET bottles but also polyesters used in various applications, and for example, there is also a growing demand for the reuse of the substrate of process films such as dicing tape used in semiconductor manufacturing processes.

[0008] However, although conventional polyester films have excellent recyclability, they are difficult to practically use in semiconductor manufacturing processes because they cannot sufficiently relieve stress by themselves or cannot have sufficiently high mechanical strength. For example, the polyester films disclosed in Patent Documents 3 to 5 have difficulty in obtaining excellent stress relaxation properties while also having high mechanical strength. On the other hand, as in Patent Documents 1 and 2, laminating a different resin layer such as a polyethylene layer on a substrate made of PET or the like provides excellent stress relaxation properties, but there is a problem that recycling is difficult. Furthermore, when recycling the core film disclosed in Patent Document 2, it is difficult to use it as a recycled raw material unless the anchor coat layer containing the copolymer polyurethane resin applied to the core film is removed by washing with a cleaning agent or the like.

[0009] Therefore, an object of the present invention is to provide a polyester film for use in semiconductor manufacturing processes that has good recyclability and also has excellent stress relaxation properties, particularly excellent stress relaxation properties and mechanical strength. [Means for solving the problem]

[0010] The present invention provides the following [1] to

[22] . [1] A polyester film having a thermoplastic polyester layer containing a thermoplastic polyester, the thermoplastic polyester layer is a surface layer (A) of the polyester film, the hardness of the surface layer (A) measured at 23±5°C using a nanoindenter is 450 MPa or less, The polyester film for semiconductor manufacturing processes has a Young's modulus of 2 GPa or more. [2] A polyester film for semiconductor manufacturing processes, having a hardness of 450 MPa or less measured on one surface of the film using a nanoindenter at 23±5°C. [3] The polyester film for semiconductor manufacturing processes according to [1] or [2] above, wherein the hardness has a gradient in which the hardness increases from one surface of the film toward the center in the thickness direction of the film. [4] A copolymer polyester comprising a copolymer of a dicarboxylic acid component and a diol component, The ratio (mol %) of the dicarboxylic acid component having 4 to 10 carbon atoms other than terephthalic acid to the dicarboxylic acid components in all the polyesters contained on one surface of the film is defined as (A1), The ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained on one surface is defined as (A4). The ratio (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than terephthalic acid to all dicarboxylic acid components contained in the center portion of the film in the thickness direction is (B1), and If the ratio (mol%) of diol components other than ethylene glycol to all diol components in the polyester contained in the center of the film in the thickness direction is (B4), then: A polyester film for semiconductor manufacturing processes, in which (A1)+(A4) is higher than (B1)+(B4). [5] The polyester film for use in semiconductor manufacturing processes according to any one of the above [1] to [4], which contains a copolymerized polyester (a) that is a copolymer of a dicarboxylic acid component containing terephthalic acid and a diol component containing an aliphatic diol (Y). [6] The polyester film for use in semiconductor manufacturing processes according to the above item [5], wherein the copolymerized polyester (a) comprises a copolymerized polyester (a1) obtained by copolymerizing a dicarboxylic acid component containing terephthalic acid and a dicarboxylic acid component (X2) having 4 to 10 carbon atoms with a diol component containing an aliphatic diol (Y). [7] The polyester film for use in semiconductor manufacturing processes according to the above [5] or [6], wherein the copolymerized polyester (a) comprises a copolymerized polyester (a1-1) obtained by copolymerizing a dicarboxylic acid component containing terephthalic acid (X1) and a dicarboxylic acid component (X2) having 4 to 10 carbon atoms with a diol component containing an aliphatic diol (Y2) having 4 to 8 carbon atoms. [8] The polyester film for use in the semiconductor manufacturing process according to any one of the above items [1] to [7], which is a multilayer film comprising the surface layer (A) and an intermediate layer (B). [9] The surface layer (A) contains a copolymer polyester composed of a copolymer of a dicarboxylic acid component and a diol component, the proportion (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than terephthalic acid in all dicarboxylic acid components contained in the surface layer (A) is defined as (A1), When the ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained in the surface layer (A) is (A4), The polyester film for use in semiconductor manufacturing processes according to any one of the above [1], [3] and [5] to [8], wherein (A1)+(A4) is 5 mol % or more.

[10] The intermediate layer (B) contains a copolymer polyester composed of a copolymer of a dicarboxylic acid component and a diol component, the ratio (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than terephthalic acid to all dicarboxylic acid components in the polyester contained in the intermediate layer (B) is (B1); and When the ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained in the intermediate layer (B) is (B4), The polyester film for use in semiconductor manufacturing processes according to the above [8] or [9], wherein (B1)+(B4) is 30 mol % or less.

[11] The surface layer (A) contains a copolymer polyester composed of a copolymer of a dicarboxylic acid component and a diol component, the intermediate layer (B) contains a copolymer polyester formed from a copolymer of a dicarboxylic acid component and a diol component, the proportion (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than terephthalic acid in all dicarboxylic acid components contained in the surface layer (A) is defined as (A1), the proportion (mol %) of diol components other than ethylene glycol in all diol components in the polyesters contained in the surface layer (A) is (A4), the ratio (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than terephthalic acid to all dicarboxylic acid components in the polyester contained in the intermediate layer (B) is (B1); and When the ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained in the intermediate layer (B) is (B4), The polyester film for use in the semiconductor manufacturing process according to any one of the above [8] to

[10] , wherein (A1)+(A4) is higher than (B1)+(B4) and the difference therebetween is 5 mol % or more.

[12] The polyester film for use in semiconductor manufacturing processes according to any one of the above [1], [3], and [5] to

[11] , wherein the surface layer (A) contains an impact resistance improver.

[13] The polyester film for use in semiconductor manufacturing processes according to the above

[12] , wherein the content of the impact resistance improver in the surface layer (A) is 30% by mass or less.

[14] The polyester film for semiconductor manufacturing processes according to the above

[12] or

[13] , wherein the content of the impact modifier in the polyester film is 15 mass % or less.

[15] The polyester film for use in semiconductor manufacturing processes according to any one of the above [1] to

[14] , which is a stretched film.

[16] The polyester film for use in semiconductor manufacturing processes according to any one of the above [1] to

[15] , which is a coextrusion stretched film.

[17] The polyester film for use in semiconductor manufacturing processes according to any one of the above [1] to

[16] , which is for use as a backgrinding tape or a dicing tape.

[18] A laminated film comprising the polyester film for use in a semiconductor manufacturing process according to any one of [1] to

[17] above, and at least one resin layer provided on one surface or the other surface of the polyester film for use in a semiconductor manufacturing process.

[19] The resin layer includes an antistatic layer, and the surface on which the antistatic layer is provided has a surface resistivity of 1×10 12 The laminated film according to

[18] above, having a resistance to deformation of Ω / □ or less.

[20] The laminated film according to the above

[18] or

[19] , wherein the resin layer includes an adhesive layer.

[21] The laminated film according to any one of the above

[18] to

[20] , which has an easy-adhesion layer on one surface and an antistatic layer on the other surface.

[22] A method of using the polyester film for semiconductor manufacturing process according to any one of the above [1] to

[17] or the laminate film according to any one of the above

[18] to

[21] for back grinding or dicing. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a polyester film for use in semiconductor manufacturing processes, which has good recyclability and also has excellent stress relaxation properties, particularly excellent stress relaxation properties and mechanical strength. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below, and can be implemented by modifying them as desired within the scope of the gist of the present invention.

[0013] <Hardness> In one embodiment, the polyester film for semiconductor manufacturing process of the present invention (hereinafter sometimes simply referred to as "the film") has a hardness of 450 MPa or less as measured on one surface of the film using a nanoindenter at 23±5°C (hereinafter sometimes simply referred to as "hardness").

[0014] The present film is a polyester film having a thermoplastic polyester layer containing a thermoplastic polyester, and the thermoplastic polyester layer is the surface layer (A) of the present film. The surface layer (A) is a layer that constitutes the surface of the present film. As described above, the present film has a hardness of 450 MPa or less on one surface, and therefore the hardness of the surface layer (A) measured with a nanoindenter at 23±5°C is 450 MPa or less.

[0015] This film has excellent recyclability due to the use of polyester film. Furthermore, the hardness of one surface (i.e., the hardness of the surface layer (A)) is 450 MPa or less, resulting in good stress relaxation properties. Therefore, by attaching a protective sheet based on this film to a semiconductor wafer, wafers and chips can be adequately protected during the semiconductor manufacturing process. More specifically, stresses such as shear forces acting on wafers and chips during wafer grinding can be adequately relaxed, effectively preventing cracking of the wafers and chips.

[0016] From the viewpoint of improving stress relaxation properties, the hardness is preferably 350 MPa or less, more preferably 310 MPa or less, even more preferably 250 MPa or less, even more preferably 200 PMa or less, and even more preferably 180 MPa or less. The hardness of the present film is not particularly limited, but is preferably 40 MPa or more, more preferably 60 MPa or more, even more preferably 80 MPa or more, and even more preferably 100 PMa or more. By making the hardness of one side of the present film (i.e., the surface layer (A)) a certain level or higher, the mechanical strength of the present film, such as Young's modulus, is increased, giving the film stiffness and enabling it to properly hold a wafer when attached to the wafer as a protective sheet.

[0017] The hardness of at least one surface of this film is sufficient as long as it is within the above-mentioned range, but it is also preferable that the hardness of both surfaces be within the above-mentioned range. A wafer with a protective sheet attached may be placed on a suction table via the protective sheet during grinding. In this case, the surface opposite to the surface bonded to the wafer contacts the suction table. Therefore, when the hardness of both surfaces is below the predetermined value as described above, stress is alleviated on one surface, while unevenness caused by foreign matter on the suction table is filled on the other surface, allowing for close contact with the suction table. As a result, cracks in wafers and chips due to foreign matter can be further reduced.

[0018] The hardness of the present film can be adjusted by the type of resin used in the present film, the composition and amount of each resin, etc. It can also be adjusted by various manufacturing conditions in the manufacturing method of the present film, such as the heat setting temperature. More specifically, if the heat setting temperature is increased, the crystals contained in the film are more likely to melt during heat setting, which tends to reduce the hardness. The surface hardness of the polyester film (hardness of the surface layer (A)) can be measured by pressing the probe of a nanoindenter into the surface of the polyester film. However, even if a resin layer is present on the surface of the polyester film, the hardness of the surface of the polyester film (surface layer (A)) can be measured by pressing the probe into the surface of the resin layer as long as the thickness of the resin layer is several hundred nanometers or less (for example, 500 nm or less).

[0019] <Young's modulus> The Young's modulus of the present film is preferably 2 GPa or more. A Young's modulus of 2 GPa or more improves mechanical strength, allowing the present film to properly hold wafers or chips and more effectively prevent damage to wafers or chips during semiconductor manufacturing processes. This makes the present film suitable for use in semiconductor manufacturing. A Young's modulus of 3 GPa or more is more preferable, and 3.5 GPa or more is even more preferable. From the viewpoint of ensuring the flexibility of the present film and reducing hardness, the Young's modulus is preferably 20 GPa or less, more preferably 15 GPa or less, even more preferably 10 GPa or less, and even more preferably 5 GPa or less. Details of the method for measuring Young's modulus are as described in the Examples. The Young's modulus can be obtained by measuring the Young's modulus in the longitudinal direction (MD) and transverse direction (TD) of the film and calculating the average value. While one or both surfaces of the polyester film may have a resin layer, such as an easy-adhesion layer or an antistatic layer, the influence of the resin layer in measuring Young's modulus can be substantially ignored as long as the thickness of the resin layer is no more than several hundred nanometers (e.g., no more than 500 nm). Therefore, the Young's modulus of the polyester film can be determined by measuring the Young's modulus of the polyester film having such a resin layer on the surface. The same applies to the various physical properties of the polyester film described below. The Young's modulus can be appropriately controlled by the layer structure of the film, the thickness of each layer, the type and amount of resin used in each layer, the production method, and the like.

[0020] [Thermoplastic polyester layer] As described above, the present film contains a thermoplastic polyester in the thermoplastic polyester layer constituting the surface layer (A). The thermoplastic polyester layer only needs to contain at least a thermoplastic polyester. By containing a thermoplastic polyester in the surface layer (A), the present film can be made excellent in stress relaxation while ensuring recyclability and mechanical strength.

[0021] [Copolymer polyester (a)] The present film contains a copolymer polyester formed from a copolymer of a dicarboxylic acid component and a diol component. By including the copolymer polyester, the present film has low hardness and is likely to have good stress relaxation properties. Specific examples of the copolymer polyester include copolymer polyester (a), which is a copolymer of a dicarboxylic acid component containing terephthalic acid (X1) and a diol component containing an aliphatic diol (Y). However, the copolymer polyester (a) is other than the polyarylate (c) described below. The copolymer polyester (a) contained in the present film preferably has thermoplastic properties.

[0022] (Copolymer polyester (a1)) The copolymer polyester (a) is preferably a copolymer polyester (a1) which is a copolymer of a dicarboxylic acid component containing terephthalic acid (X1) and a dicarboxylic acid component (X2) having 4 to 10 carbon atoms, and a diol component containing an aliphatic diol (Y). Here, the dicarboxylic acid component (X2) having 4 to 10 carbon atoms means a dicarboxylic acid component having 4 to 10 carbon atoms excluding terephthalic acid (X1). The copolymer polyester (a1) is a polycondensate of a dicarboxylic acid component containing terephthalic acid (X1) and a dicarboxylic acid component (X2) having 4 to 10 carbon atoms, and a diol component containing an aliphatic diol (Y). By using a dicarboxylic acid component (X2) having 4 to 10 carbon atoms other than terephthalic acid as the dicarboxylic acid, it becomes easier to reduce the hardness and improve the stress relaxation properties.

[0023] Examples of the dicarboxylic acid component (X2) having 4 to 10 carbon atoms include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and polyfunctional acids. Among these, aromatic dicarboxylic acids and aliphatic dicarboxylic acids are preferred, and aliphatic dicarboxylic acids are particularly preferred from the viewpoint of facilitating lowering hardness. The aliphatic dicarboxylic acid may be used alone as the dicarboxylic acid component (X2) having 4 to 10 carbon atoms, or two or more dicarboxylic acid components having 4 to 10 carbon atoms may be used in combination. Examples of the aliphatic dicarboxylic acid having 4 to 10 carbon atoms include saturated aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Among these, from the viewpoint of ease of reaction during polymerization, adipic acid and sebacic acid are more preferred, and adipic acid is even more preferred. Furthermore, as the aromatic dicarboxylic acid, isophthalic acid is preferred.

[0024] The proportion of the dicarboxylic acid component (X2) having 4 to 10 carbon atoms in the dicarboxylic acid components constituting the copolymer polyester (a1) is not particularly limited, but is, for example, 5 mol% or more and 35 mol% or less, preferably 7 mol% or more and 30 mol% or less, more preferably 9 mol% or more and 25 mol% or less, and even more preferably 11 mol% or more and 20 mol% or less. The proportion of terephthalic acid (X1) in the dicarboxylic acid components constituting the copolymer polyester (a1) is, for example, 65 mol % or more and 95 mol % or less, preferably 75 mol % or more and 92 mol % or less, and more preferably 80 mol % or more and 90 mol % or less.

[0025] In the copolymer polyester (a1), the dicarboxylic acid component may consist of terephthalic acid (X1) and a dicarboxylic acid component (X2) having 4 to 10 carbon atoms, or may contain a dicarboxylic acid component (other dicarboxylic acid component (X3)) other than terephthalic acid (X1) and the dicarboxylic acid component (X2) having 4 to 10 carbon atoms as a copolymerization component, provided that the gist of the present invention is not impaired. Examples of such dicarboxylic acid components include dodecanedioic acid, eicosanoic acid, dimer acid, and derivatives thereof. The proportion of the other dicarboxylic acid component (X3) in the dicarboxylic acid components constituting the copolymer polyester (a1) is, for example, 10 mol % or less, preferably 5 mol % or less, more preferably 3 mol % or less, and most preferably 0 mol %.

[0026] Examples of the aliphatic diol (Y) include chain aliphatic diols such as ethylene glycol, 1,4-butanediol, 1,4-hexanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, pentamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, and 2-ethyl-2-butyl-1,3-propanediol; alicyclic diols such as 1,2-cyclohexanediol, 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethanol, and 2,5-norbornanedimethylol; and aliphatic dimer diols. These may be used alone or in combination. Among the above, from the viewpoint of flexibility, the aliphatic diol is preferably an aliphatic diol having 2 to 8 carbon atoms, more preferably an aliphatic diol having 4 to 8 carbon atoms, and even more preferably an aliphatic diol having 4 to 6 carbon atoms. Furthermore, the aliphatic diol is preferably a chain aliphatic diol. More specifically, the aliphatic diol is preferably at least one selected from ethylene glycol, diethylene glycol, 1,4-butanediol, 1,4-hexanediol, and 1,6-hexanediol.

[0027] The copolymerized polyester (a1) may contain a diol component other than the aliphatic diol (Y). Examples of the diol component other than the aliphatic diol (Y) include aromatic diols such as xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, and bis(4-β-hydroxyethoxyphenyl)sulfonic acid; ethylene oxide adducts or propylene oxide adducts of 2,2-bis(4'-hydroxyphenyl)propane; and aromatic dimer diols.

[0028] The proportion of the aliphatic diol (Y) in the diol components constituting the copolymer polyester (a1) is, for example, 50 mol % or more and 100 mol % or less, preferably 70 mol % or more and 100 mol % or less, more preferably 90 mol % or more and 100 mol % or less. The copolymer polyester (a1) preferably has thermoplasticity.

[0029] (Copolymer polyester (a1-1)) As one embodiment, the copolymer polyester (a1) is preferably a copolymer polyester (hereinafter also referred to as copolymer polyester (a1-1)) containing an aliphatic diol other than ethylene glycol (Y1) as the aliphatic diol component (Y), and among these, a copolymer polyester (a1-1) containing an aliphatic diol (Y2) having 4 to 8 carbon atoms as the aliphatic diol component (Y) is more preferred. The copolymerized polyester (a1-1) more preferably contains at least 1,4-butanediol as the aliphatic diol component (Y). Furthermore, in the copolymerized polyester (a1-1), two or more types of aliphatic diols (Y) are preferably used. When two or more types are used, the aliphatic diol (Y) preferably contains two or more aliphatic diols having 4 to 8 carbon atoms, and more preferably contains both 1,4-butanediol and 1,6-hexanediol. By using two or more types of aliphatic diols (Y), it becomes easier to reduce the hardness. When the aliphatic diol (Y) contains both 1,4-butanediol and 1,6-hexanediol, the mass ratio thereof (1,4-butanediol / 1,6-hexanediol) is preferably 10 / 90 to 70 / 30, more preferably 20 / 80 to 60 / 40, and even more preferably 30 / 70 to 50 / 50. The proportion of the aliphatic diol having 4 to 8 carbon atoms in the diol component constituting the copolymer polyester (a1-1) is, for example, 50 mol% or more and 100 mol% or less, preferably 70 mol% or more and 100 mol% or less, and more preferably 90 mol% or more and 100 mol% or less. In the copolymer polyester (a1-1), it is preferable to use an aliphatic dicarboxylic acid having 4 to 10 carbon atoms as the dicarboxylic acid component (X2) having 4 to 10 carbon atoms, and adipic acid is particularly preferable. The copolymer polyester (a1-1) preferably has thermoplastic properties.

[0030] (Copolymer polyester (a1-2)) In another embodiment, the copolymer polyester (a1) is preferably a copolymer polyester containing ethylene glycol as the aliphatic diol component (Y) (hereinafter, also referred to as copolymer polyester (a1-2)). The diol component in the copolymer polyester (a1-2) may be ethylene glycol alone, or may contain a diol component other than ethylene glycol. Specific examples of the diol component other than ethylene glycol are as described for the copolymer polyester (a1), and preferably an aliphatic diol (Y2) having 4 to 8 carbon atoms. The proportion of ethylene glycol in the diol component constituting the copolymer polyester (a1-2) is, for example, 50 mol % to 100 mol %, preferably 70 mol % to 100 mol %, and more preferably 90 mol % to 100 mol %. In the copolymer polyester (a1-2), it is preferable to use an aromatic dicarboxylic acid as the dicarboxylic acid component (X2) having 4 to 10 carbon atoms, and among these, isophthalic acid is preferred. The copolymer polyester (a1-2) preferably has thermoplastic properties.

[0031] (Copolymer polyester (a2)) Further, the copolymer polyester (a) may also be a copolymer polyester (a2) that is a copolymer of a diol component containing terephthalic acid (X1) and two or more aliphatic diols (Y). Specific examples of the aliphatic diol (Y) are as described above, but among them, an aliphatic diol having 4 to 8 carbon atoms is preferred. It is also preferred to use an aliphatic diol having 4 to 8 carbon atoms in combination with ethylene glycol. On the other hand, the dicarboxylic acid component may be composed of terephthalic acid (X1) alone, but may also contain other dicarboxylic acids. The copolymer polyester (a2) preferably has thermoplastic properties.

[0032] [Homopolyester (b)] The present film may contain a homopolyester (b). By containing the homopolyester (b), the present film is likely to have good mechanical strength (Young's modulus, etc.) and heat resistance. Examples of the homopolyester (b) include a polymer of terephthalic acid (X1) and any one of the diol components of the aliphatic diol (Y). Specific examples of the aliphatic diol (Y) are as described above, but among the above, the aliphatic diol (Y) is preferably any of the aliphatic diols having 2 to 8 carbon atoms. More specifically, the aliphatic diol is preferably any of ethylene glycol, diethylene glycol, 1,4-butanediol, 1,4-hexanediol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol, with ethylene glycol or 1,4-cyclohexanedimethanol being more preferred.

[0033] As the homopolyester, polyethylene terephthalate in which the dicarboxylic acid component is terephthalic acid (X1) and the diol component is ethylene glycol (Y1) is preferred. However, the polyethylene terephthalate referred to as a homopolyester may contain diethylene glycol, which is an unavoidable diol component. Specifically, in the polyethylene terephthalate (homopolyester), the proportion of diethylene glycol in the diol component may be, for example, 5 mol% or less, or may be 3 mol% or less. When polyester is produced (polycondensed) using ethylene glycol as one of the raw materials, part of the ethylene glycol is modified to become diethylene glycol, which is then introduced into the polyester skeleton.

[0034] Further, examples of the polyester (b) include polycyclohexylene dimethylene terephthalate, which is a polymer of terephthalic acid (X1) and 1,4-cyclohexanedimethanol. The homopolyester (b) preferably has thermoplastic properties.

[0035] [Polyarylate (c)] The present film may contain a polyarylate (c) in addition to the copolymer polyester (a) or the copolymer polyester (a) and the homopolyester (b). The use of the copolymer polyester (a) in the present film tends to lower the glass transition temperature (Tg), but the addition of polyarylate (c) makes it possible to obtain a film with a high glass transition temperature. This reduces breakage during stretching and improves handling during processing. It also makes it easier to obtain a film with excellent heat resistance.

[0036] The polyarylate (c) is a polycondensate of a dicarboxylic acid component (c-1) and a dihydric phenol component (c-2). The glass transition temperature of the polyarylate (c) can be adjusted by appropriately selecting the dicarboxylic acid component (c-1) and the dihydric phenol component (c-2), particularly by appropriately selecting the dihydric phenol component.

[0037] The dicarboxylic acid component (c-1) constituting the polyarylate (c) is not particularly limited as long as it is a divalent aromatic carboxylic acid, but among these, a mixture of a terephthalic acid component and an isophthalic acid component is preferred. The mixing ratio (mol %) of the terephthalic acid component and the isophthalic acid component is preferably terephthalic acid / isophthalic acid=99 / 1 to 1 / 99, more preferably 90 / 10 to 10 / 90, still more preferably 80 / 20 to 20 / 80, particularly preferably 70 / 30 to 30 / 70, and especially preferably 60 / 40 to 40 / 60. When the mixing ratio of terephthalic acid and isophthalic acid as the dicarboxylic acid component (c-1) is within the above range, the polyarylate (c) has excellent heat resistance and melt moldability.

[0038] The polyarylate (c) may be prepared by copolymerizing an acid component other than terephthalic acid and isophthalic acid as the dicarboxylic acid component. Specific examples include aromatic dicarboxylic acids such as phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, benzophenonedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3'-diphenyldicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid, and aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. In order not to impair the heat resistance of the polyarylate resin (B), the copolymerization ratio of acid components other than the divalent aromatic carboxylic acid is preferably less than 10 mol%.

[0039] The dihydric phenol component (c-2) constituting the polyarylate (c) is not particularly limited as long as it is a dihydric phenol, but it preferably contains either a bisphenol A component, a bisphenol TMC (1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane) component, or both bisphenol A and bisphenol TMC. In general, the inclusion of bisphenol A component results in polyarylate with excellent melt moldability (fluidity), while the inclusion of bisphenol TMC component results in polyarylate (c) with an improved glass transition temperature and excellent heat resistance. When a balance between melt moldability and heat resistance is desired, both bisphenol A and bisphenol TMC components are used. In this case, the ratio (mol %) of the bisphenol A component to the bisphenol TMC component is preferably bisphenol A / bisphenol TMC=99 / 1 to 1 / 99, more preferably 90 / 10 to 10 / 90, still more preferably 80 / 20 to 20 / 80, particularly preferably 70 / 30 to 30 / 70, and especially preferably 60 / 40 to 40 / 60. By setting the ratio of the bisphenol A component and the bisphenol TMC component within this range, the polyarylate (c) will have an excellent balance between heat resistance and melt moldability.

[0040] The polyarylate (c) may be copolymerized with a bisphenol component other than bisphenol A (2,2-bis(4-hydroxyphenyl)propane) and bisphenol TMC (1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane) as the dihydric phenol component (c-2). Specifically, bisphenol AP (1,1-bis(4-hydroxyphenyl)-1-phenylethane), bisphenol AF (2,2-bis(4-hydroxyphenyl)hexafluoropropane), bisphenol B (2,2-bis(4-hydroxyphenyl)butane), bisphenol BP (bis(4-hydroxyphenyl)diphenylmethane), bisphenol C (2,2-bis(3-methyl-4-hydroxyphenyl)propane), bisphenol E (1,1-bis(4-hydroxyphenyl)ethane), bisphenol F (bis(4-hydroxyphenyl)methane ... C (2,2-bis(3-methyl-4-hydroxyphenyl)propane), bisphenol E (1,1-bis(4-hydroxyphenyl)ethane), bisphenol F (bis(4-hydroxyphenyl)methane), bisphenol B (2,2-bis(4-hydroxyphenyl)butane), bisphenol B (2,2-bis(4-hydroxyphenyl)butane), bisphenol B (2,2-bis(4-hydroxyphenyl)butane), bisphenol B (2,2-bis(4-hydroxyphenyl)butane), bisphenol B (2,2-bis(4-hydroxyphenyl)butane), bisphenol B (2,2-bis(4-hydroxyphenyl)butane), bisphenol B (2,2 Examples of suitable bisphenols include phenol G (2,2-bis(4-hydroxy-3-isopropylphenyl)propane), bisphenol M (1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene), bisphenol S (bis(4-hydroxyphenyl)sulfone), bisphenol P (1,4-bis(2-(4-hydroxyphenyl)-2-propyl)benzene), bisphenol PH (5,5'-(1-methylethylidene)-bis[1,1'-(bisphenyl)-2-ol]propane), and bisphenol Z (1,1-bis(4-hydroxyphenyl)cyclohexane). The copolymerization ratio of the above compounds is preferably less than 10 mol% so as not to impair the heat resistance of the polyarylate (c).

[0041] For the polyarylate (c), it is preferable to select a mixture of a terephthalic acid component and an isophthalic acid component as the dicarboxylic acid component (c-1), and either a bisphenol A component, a bisphenol TMC component, or a mixture of bisphenol A and bisphenol TMC as the dihydric phenol component (c-2).

[0042] The polyarylate (c) may be mixed with polycarbonate to improve melt moldability. Since the polyarylate (c) and polycarbonate are compatible with each other, mixing the polyarylate (c) with polycarbonate can lower the glass transition temperature of the polyarylate (c) while maintaining its transparency and mechanical properties, thereby improving melt moldability. When polyarylate (c) and polycarbonate are mixed, the mixing ratio (mass %) of polyarylate (c) / polycarbonate is preferably from 99 / 1 to 50 / 50, more preferably from 98 / 2 to 60 / 40, still more preferably from 97 / 3 to 70 / 30, and particularly preferably from 96 / 5 to 80 / 20. If the mixing ratio of polyarylate (c) to polycarbonate is within this range, the melt moldability of polyarylate (c) can be improved while maintaining the heat resistance of the polyarylate (c). It is preferable to mix polyarylate (c) and polycarbonate by using a pre-mix of these two components as a raw material, but this is not limited to this method. The above structure may also be achieved by selecting polycarbonate as another resin and using it as an independent raw material. In addition, the polycarbonate mixed with the polyarylate (c) is not included in the content of the polyarylate (c).

[0043] (film thickness) The thickness of the present film is not particularly limited, but is, for example, in the range of 20 μm to 250 μm, preferably 30 μm to 220 μm, more preferably 35 μm to 200 μm, even more preferably 40 μm to 180 μm, and even more preferably 45 μm to 120 μm. By setting the film thickness within the above-mentioned range, chips and wafers can be appropriately protected in the semiconductor manufacturing process without increasing the thickness more than necessary. The present film may be a stretched film or a non-stretched film, but is preferably a stretched film. The stretched film may be a uniaxially stretched film, but is preferably a biaxially stretched film. By forming the present film into a stretched film, mechanical strength such as Young's modulus can be easily improved. The stretched film is preferably a coextrusion stretched film formed by coextrusion.

[0044] [Laminated structure] The present film may be a single-layer film having a single layer structure, or a multilayer film having a multilayer structure, but is preferably a multilayer film. In the case of a multilayer film, it is preferable to have an intermediate layer (B) and a surface layer (A) provided on at least one side of the intermediate layer (B), but it is preferable to have the surface layer (A) provided on both sides of the intermediate layer (B). Therefore, the present film may have a two-layer structure of intermediate layer (B) / surface layer (A), but is preferably a three-layer structure of surface layer (A) / intermediate layer (B) / surface layer (A). Furthermore, as long as the surface layer is on the surface of the film, it is not limited to a two-layer or three-layer structure, and may have a layer structure of four or more layers, with two or more intermediate layers (B).

[0045] The present film has a surface layer (A) that reduces the surface hardness while the intermediate layer (B) provides mechanical strength such as a high Young's modulus. Furthermore, by providing the surface layer (A) on both sides of the present film, it is possible to incorporate a layer with low hardness on both sides. Therefore, as described above, stress can be alleviated on one side while unevenness caused by foreign matter, etc., can be filled on the other side, further preventing cracks in wafers and chips.

[0046] In the multilayer film, at least one surface layer (A), preferably both surface layers (A), contains a thermoplastic polyester. The intermediate layer (B) in the multilayer film may also contain a thermoplastic polyester. By including a thermoplastic polyester in the intermediate layer (B), the recyclability of the film can be improved, while the mechanical strength, such as Young's modulus, can be improved.

[0047] The thickness of each surface layer (A) in the multilayer film is preferably 1% to 25% of the overall thickness of the film, more preferably 3% to 20%, and even more preferably 5% to 15%. When the thickness of the surface layer (A) is within this range, the surface layer (A) with its low surface hardness can adequately relieve stress without impairing the mechanical strength of the entire film. From the same viewpoint, the thickness of each surface layer (A) in the multilayer film is, for example, 2 μm to 40 μm, preferably 3 μm to 30 μm, more preferably 3.5 μm to 20 μm, and even more preferably 4 μm to 15 μm.

[0048] The thickness of the intermediate layer (B) in the multilayer film is preferably 60% to 98% of the total thickness of the film, more preferably 70% to 96%, and even more preferably 75% to 92%. When the thickness of the intermediate layer (B) is within this range, the surface layer (A) can adequately perform stress relaxation, while the intermediate layer (B) can impart appropriate mechanical strength to the entire film. From a similar viewpoint, the thickness of the intermediate layer (B) in the multilayer film is, for example, 10 μm or more and 200 μm or less, preferably 20 μm or more and 150 μm or less, more preferably 25 μm or more and 125 μm or less, even more preferably 30 μm or more and 100 μm or less, and even more preferably 40 μm or more and 80 μm or less.

[0049] In the case of a monolayer film, the monolayer film itself constitutes the surface layer (A). That is, in the case of a monolayer film, the present film can be said to be a film consisting of surface layers (A) that constitute both surfaces of the present film.

[0050] In the present invention, the present film preferably contains a copolymer polyester on one surface of the film, and preferably on both surfaces. Accordingly, in a multilayer film, the surface layer (A) preferably contains a copolymer polyester, and when surface layers (A) are provided on both surfaces of the film, both surface layers (A) preferably contain a copolymer polyester. By incorporating a copolymer polyester into the surface of the film, i.e., the surface layer (A), the present film can easily reduce the hardness of one or both surfaces of the film, as described above. Here, the copolymer polyester contained on the surface is preferably the copolymer polyester (a) described above. Similarly, in the case of a monolayer film, the present film (that is, the surface layer (A)) preferably contains a copolymer polyester, more preferably the above-mentioned copolymer polyester (a).

[0051] The content of copolymerized polyester (a) on each surface of the present film is not particularly limited as long as it is adjusted so that the proportions of each component (A1) and (A4) described below fall within the specified ranges, and is, for example, 10% by mass or more and 97% by mass or less, preferably 10% by mass or more and 90% by mass or less, more preferably 15% by mass or more and 85% by mass or less, even more preferably 20% by mass or more and 70% by mass or less, and even more preferably 25% by mass or more and 60% by mass or less. The content of copolymerized polyester (a) on each surface means the content of copolymerized polyester (a) in the surface layer (A) in a multilayer film, and in the case of a monolayer film with no gradient in the blending, it means the content of copolymerized polyester (a) in the entire film (i.e., the surface layer (A)). Furthermore, even in the case of a monolayer film, the blending may gradually change along the thickness direction, as described below, and the content of (a) may change along the thickness direction. In this case, the content of (a) on the surface may be determined by, for example, sampling from a region up to 10% of the total thickness from the film surface and determining the content of component (a) using a known measurement method. The same applies to the contents of components (b), (c), etc. below.

[0052] The present film preferably contains a homopolyester (b) in addition to the copolymer polyester (a) on one surface of the film, and preferably contains a homopolyester (b) in addition to the copolymer polyester (a) on both surfaces. Therefore, in a multilayer film, the surface layer (A) preferably contains the copolymer polyester (a) and the homopolyester (b), and when the surface layer (A) is provided on both surfaces of the film, it is preferable that both surface layers (A) contain the copolymer polyester (a) and the homopolyester (b). By containing the copolymer polyester (a) and the homopolyester (b) on the surface of the film, i.e., in the surface layer (A), the present film is likely to improve mechanical strength such as Young's modulus while reducing the hardness of one or both surfaces of the film. Similarly, in the case of a monolayer film, the present film (that is, the surface layer (A) constituting the monolayer film) preferably contains a homopolyester (b) in addition to the copolymer polyester (a).

[0053] The content of homopolyester (b) on each surface of the present film is not particularly limited as long as it is adjusted so that the proportions (A1) and (A4) of each component described below fall within the specified ranges, but is, for example, 0% by mass to 90% by mass, preferably 5% by mass to 85% by mass, more preferably 8% by mass to 70% by mass, and even more preferably 10% by mass to 65% by mass. Note that 0% by mass means that no homopolyester (b) is contained. The same applies hereinafter.

[0054] The present film may contain a polyarylate (c) in addition to the copolymer polyester (a), or the copolymer polyester (a) and the homopolyester (b), on one surface of the film, or may contain a polyarylate (c) in addition to the copolymer polyester (a), or the copolymer polyester (a) and the homopolyester (b), on both surfaces. Thus, in a multilayer film, the surface layer (A) may contain a copolymer polyester (a) and a polyarylate (c), or a copolymer polyester (a), a homopolyester (b), and a polyarylate (c), and when the surface layer (A) is provided on both surfaces of the film, both surface layers (A) may contain a copolymer polyester (a) and a polyarylate (c), or a copolymer polyester (a), a homopolyester (b), and a polyarylate (c). By incorporating polyarylate (c) into the surface of this film, the glass transition temperature at the surface of the film can be increased even though the film contains copolymer polyester (a). This reduces the difference in glass transition temperature between the film and the intermediate layer (B), reducing the likelihood of defects during processing. Furthermore, the glass transition temperature of the entire film can be increased, which also makes it easier to improve heat resistance. Furthermore, in the case of a monolayer film, the present film (i.e., the surface layer (A) constituting the monolayer film) may contain, in addition to the copolymer polyester (a), a polyarylate (c) in addition to the copolymer polyester (a) and the homopolyester (b).

[0055] The content of polyarylate (c) is not particularly limited as long as it is adjusted so that the proportions (A1) and (A4) of each component described below fall within the specified range, but is preferably 55% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. The content of polyarylate (c) on each surface of the present film may be 0% by mass or more, but when each surface of the present film contains polyarylate (c), in order to properly exert the effect of the addition, it is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more.

[0056] In the present invention, the film may contain at least one of the copolymer polyester (a) and the homopolyester (b) in the central portion in the thickness direction of the film, but preferably contains both of them. Furthermore, the central portion in the thickness direction of the film may further contain a polyarylate (c) in addition to at least one of the copolymer polyester (a) and the homopolyester (b). Therefore, in the multilayer film, the intermediate layer (B) may contain at least one of the copolymer polyester (a) and the homopolyester (b), but it is preferable that it contains at least the copolymer polyester (a), and more preferably that it contains both of them.The intermediate layer (B) may also contain a polyarylate (c). By including homopolyester (b) in the intermediate layer (B), the mechanical strength of the film, such as Young's modulus, can be improved. Furthermore, by including copolymer polyester (a) or polyarylate (c), the composition of the central portion of the film in the thickness direction (i.e., intermediate layer (B)) can be made closer to the composition of the film surface (i.e., surface layer (A)). This facilitates stretching during the manufacturing process, improving productivity. Furthermore, the adhesive strength between the intermediate layer (B) and the surface layer (A) can be improved.

[0057] The content of the copolymerized polyester (a) in the central portion of the film in the thickness direction is preferably smaller than the content of the copolymerized polyester (a) on the surface. In addition, the ratios of the components (B1) and (B4) described below may be adjusted to fall within the specified ranges. The content of copolymerized polyester (a) in the central portion in the thickness direction of the present film is not particularly limited, but is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 30% by mass or less, and even more preferably 20% by mass or less. The content of copolymerized polyester (a) in the central portion in the thickness direction may be 0% by mass or more, but is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. The content of copolymerized polyester (a) in the central portion in the thickness direction means the content of copolymerized polyester (a) in the intermediate layer (A) in a multilayer film. Even in a single-layer film, the blending may gradually change along the thickness direction, as described below, and the content of (a) may also change along the thickness direction. In such cases, it is sufficient that the content of copolymerized polyester (a) in the central portion in the thickness direction is within the above-mentioned range. In the case of films other than multilayer films, the content of component (a) in the central portion can be determined by, for example, sampling an area of ​​10% of the total thickness centered on the center in the thickness direction of the film, and determining the content of component (a) using a known measurement method. The same applies to the contents of components (b), (c), etc. below.

[0058] The content of the homopolyester (b) in the central portion of the film in the thickness direction is preferably higher than the content of the homopolyester (b) on the surface. The proportions of the components (B1) and (B4) described below may be adjusted to fall within the specified ranges. The content of the homopolyester (b) in the central portion in the thickness direction of the film is not particularly limited, but is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more. The content of the homopolyester (b) in the central portion in the thickness direction may be 100% by mass or less, but is preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 95% by mass or less.

[0059] The content of polyarylate (c) in the central part of the film in the thickness direction is preferably smaller than the content of polyarylate (c) on the surface. In addition, the ratios of the components (B1) and (B4) described below may be adjusted to fall within the specified ranges. The content of polyarylate (c) in the central part of the present film in the thickness direction is not particularly limited, but is preferably 40% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and even more preferably 10% by mass or less. The content of polyarylate (c) in the central portion in the thickness direction may be 0% by mass or more, but when the central portion of the present film contains polyarylate (c), the content should be a certain value or more, preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more.

[0060] [Proportion of each component on the surface (surface layer (A))] In the present film, if the proportion (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than terephthalic acid to the dicarboxylic acid components in all the polyesters contained in one surface is (A1), and the proportion (mol %) of diol components other than ethylene glycol to the diol components in all the polyesters contained in one surface is (A4), then (A1) + (A4) is preferably 5 mol % or more, more preferably 8 mol % or more, even more preferably 15 mol % or more, and even more preferably 25 mol % or more. By ensuring that (A1) + (A4) is at least the above-mentioned certain value, it becomes easier to reduce the hardness of one surface and improve stress relaxation properties. The upper limit of (A1)+(A4) is not particularly limited, but from the viewpoint of easily improving the mechanical strength, heat resistance, etc. of the film, it is preferably 150 mol% or less, more preferably 130 mol% or less, even more preferably 120 mol% or less, and even more preferably 110 mol% or less.

[0061] The proportions (A1) and (A4) on one surface described above, and further the proportions (A2), (A3), and (A5) to (A7) described below, refer to the respective proportions in the surface layer (A) in the multilayer structure. Therefore, in the case of a multilayer structure, it is preferable that one surface layer (A) satisfies the requirements for the respective proportions (A1) to (A7) described above or below, and it is more preferable that both surface layers (A) satisfy the requirements for the respective proportions (A1) to (A7) described above or below. Furthermore, when the present film has a single-layer structure and the composition does not gradually change as described below, the specifications for the proportions (A1) to (A7) on one surface described above or below should be the same as the specifications for the proportions (A1) to (A7) in the entire present film (i.e., the surface layer (A) in a single-layer film). Furthermore, as will be described later, the composition of the present film may change gradually, and the values ​​of the above or below-described proportions (A1) to (A7) may change along the thickness direction. In such cases, the proportions of each component on the surface may be determined by, for example, sampling from a region extending from the film surface to 10% of the total thickness and measuring the proportions by a known method.

[0062] In the present film, if the proportion (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than polyarylate (c)-derived and terephthalic acid in the dicarboxylic acid components of all polyesters contained in one surface (i.e., surface layer (A)) is (A2), and the proportion (mol %) of diol components other than polyarylate (c)-derived and ethylene glycol in the diol components of all polyesters contained in one surface (i.e., surface layer (A)) is (A5), then (A2) + (A5) is preferably 5 mol % or more, more preferably 8 mol % or more, even more preferably 15 mol % or more, and even more preferably 25 mol % or more. By ensuring that (A1) + (A4) is equal to or greater than the above-mentioned certain value, it becomes easier to reduce the hardness of one surface and improve stress relaxation properties. (A2)+(A5) is not particularly limited, but from the viewpoint of easily improving the mechanical strength and heat resistance of the film, it is preferably 100 mol% or less, more preferably 90 mol% or less, even more preferably 80 mol% or less, and even more preferably 70 mol% or less.

[0063] The ratio (A1) is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, and even more preferably 15 mol% or more, from the viewpoint of easily reducing the hardness of one surface. Also, the ratio (A1) is preferably 50 mol% or less, more preferably 40 mol% or less, even more preferably 35 mol% or less, and even more preferably 32 mol% or less, from the viewpoint of easily incorporating a certain amount or more of terephthalic acid (X1) on one surface.

[0064] The ratio (A2) is preferably 2 mol% or more. When the ratio (A2) is 2 mol% or more, the hardness of one surface can be easily reduced, and stress relaxation properties can be easily improved. The ratio (A2) is more preferably 3 mol% or more, even more preferably 4 mol% or more, and even more preferably 5 mol% or more. In addition, from the viewpoint of easily incorporating a certain amount or more of terephthalic acid (X1) on one surface, the ratio (A2) is preferably 50 mol % or less, more preferably 40 mol % or less, even more preferably 30 mol % or less, and even more preferably 20 mol % or less.

[0065] In the present film, the proportion (A3) of aliphatic dicarboxylic acid components having 4 to 10 carbon atoms in all dicarboxylic acid components of all polyesters contained in one surface (i.e., surface layer (A)) is preferably 2 mol% or more. When the proportion (A3) is 2 mol% or more, the hardness of one surface can be easily reduced and the stress relaxation properties can be easily improved. The proportion (A3) is more preferably 3 mol% or more, even more preferably 4 mol% or more, and even more preferably 5 mol% or more. Furthermore, from the viewpoint of easily incorporating a certain amount or more of terephthalic acid (X1) on one surface as well, the ratio (A3) is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, and even more preferably 10 mol% or less.

[0066] In the present film, the ratio (A4) may be 0 mol% or more, but is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more. The ratio (A4) is preferably 95 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, and even more preferably 80 mol% or less.

[0067] The ratio (A5) may be 0 mol% or more, preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more, and is preferably 70 mol% or less, more preferably 65 mol% or less, even more preferably 60 mol% or less, and even more preferably 55 mol% or less.

[0068] In the present film, the proportion (A6) of terephthalic acid components in all the polyesters contained in one surface (i.e., the surface layer (A)) of dicarboxylic acid components is preferably 50 mol% or more, more preferably 60 mol% or less, even more preferably 65 mol% or more, and even more preferably 68 mol% or more. Also, the proportion (A6) is preferably 97 mol% or less, more preferably 95 mol% or more, even more preferably 90 mol% or more, and even more preferably 85 mol% or more.

[0069] In the present film, the proportion (A7) of ethylene glycol in the diol components of all polyesters contained in one surface (i.e., the surface layer (A)) is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, and even more preferably 20 mol% or more. The proportion (A7) may be 100 mol% or less, but is more preferably 95 mol% or less, even more preferably 90 mol% or less, and even more preferably 80 mol% or less.

[0070] [Ratio of each component in the center of the thickness direction (intermediate layer (B))] In the present film, if the proportion (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than terephthalic acid to the dicarboxylic acid components of all the polyesters contained in the center portion in the thickness direction is (B1), and the proportion (mol %) of diol components other than ethylene glycol to the diol components of all the polyesters contained in the center portion in the thickness direction is (B4), in one embodiment, the above-mentioned (A1) + (A4) is preferably higher than (B1) + (B4). By making (A1) + (A4) higher than (B1) + (B4), the hardness of the film surface is reduced, while the mechanical strength of the film is maintained at a certain level, making it easier to impart stiffness to the film. The difference between [(A1) + (A4)] and [(B1) + (B4)] is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, and more preferably 30 mol% or more, and is preferably 140 mol% or less, more preferably 120 mol% or less, even more preferably 110 mol% or less, and even more preferably 100 mol% or less. In one embodiment of the present invention, when (A1) + (A4) is higher than (B1) + (B4), the hardness of one surface of the present film is preferably 450 MPa or less, but in the present invention, the hardness does not necessarily have to be 450 MPa or less.

[0071] From the viewpoint of improving the mechanical strength and heat resistance of the film, (B1)+(B4) should be a certain value or less, preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, and even more preferably 10 mol% or less. Although (B1)+(B4) may be 0 mol% or more, from the viewpoint of making the composition closer to that of the surface layer (A) and facilitating stretching, it is better to set the value to a certain value or more, preferably 2 mol% or more, more preferably 4 mol% or more, and even more preferably 6 mol% or more.

[0072] The above-mentioned ratios (B1) and (B4) at the center in the thickness direction, as well as the ratios (B2), (B3), and (B5) to (B7) described below, refer to the respective ratios in the intermediate layer (B) in a multilayer structure. Therefore, in the case of a multilayer structure, it is preferable that the intermediate layer (B) satisfies the requirements for the above-mentioned or later-described ratios (B1) to (B7). Furthermore, even if the film is a single-layer film, the composition may change as described below, and the values ​​of the above or below-described ratios (B1) to (B7) may change along the thickness direction. In this case, the ratio of each component at the center may be determined, for example, by sampling a sample at 10% of the total thickness centered in the thickness direction and determining the content of each component by a known measurement method.

[0073] In the present film, if the proportion (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than polyarylate (c)-derived and terephthalic acid in the dicarboxylic acid components of all polyesters contained in the central portion in the thickness direction (i.e., intermediate layer (B)) is (B2), and the proportion (mol %) of diol components other than polyarylate (c)-derived and ethylene glycol in the diol components of all polyesters contained in the central portion in the thickness direction (i.e., intermediate layer (B)) is (B5), it is preferable that (A2) + (A5) is higher than (B2) + (B5). By making (A2) + (A5) higher than (B2) + (B5), the hardness of the film surface is reduced while maintaining the mechanical strength of the film at a certain level, making it easier to impart stiffness to the film. The difference between [(B2) + (B5)] and [(A2) + (A5)] is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more, and is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 60 mol% or less.

[0074] Furthermore, from the viewpoint of providing the film with a certain level of mechanical strength and stiffness, (B2)+(B5) is preferably a certain level or less, preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less, and even more preferably 10 mol% or less. Furthermore, (B2)+(B5) may be 0 mol% or more, but from the viewpoint of making the composition closer to that of the surface layer (A) and facilitating stretching, it is preferably a certain level or more, preferably 2 mol% or more, more preferably 4 mol% or more, and even more preferably 6 mol% or more.

[0075] In the present film, the proportion (B3) of aliphatic dicarboxylic acid components having 4 to 10 carbon atoms in all dicarboxylic acid components in all polyesters contained in the central portion in the thickness direction (i.e., the intermediate layer (B)) is preferably lower than the above proportion (A3). By making (B3) lower than (A3), the hardness of the film surface can be reduced while the mechanical strength, heat resistance, etc. of the film can be easily improved. The proportion (B3) is more preferably lower than (A3) by 1 to 25 mol%, more preferably by 2 to 15 mol%, and even more preferably by 3 to 10 mol%. The specific value of the ratio (B3) is not particularly limited, but it may be 0 mol% or more, but from the viewpoint of making the composition closer to that of the surface layer (A) and facilitating stretching, it is better to have a certain value or more, and it may be 0.5 mol% or more, or may be 1 mol% or more. Furthermore, the ratio (B3) may be, for example, 8 mol% or less, but is preferably 4 mol% or less, and more preferably 3 mol% or less.

[0076] In the present film, the proportions (B4) and (B5) are not particularly limited as long as they are 0 mol% or more, but may be 2 mol% or more, or 4 mol% or more, from the viewpoint of making the composition closer to that of the surface layer (A). Furthermore, from the viewpoint of improving the mechanical strength and heat resistance of the film, the proportion (B4) is preferably 20 mol% or less, more preferably 15 mol% or less, and even more preferably 10 mol% or less.

[0077] In the present film, the proportion (B6) of terephthalic acid components in all the polyesters contained in the center portion in the thickness direction (i.e., the intermediate layer (B)) is preferably 70 mol% or more, more preferably 80 mol% or less, even more preferably 90 mol% or more, and even more preferably 95 mol% or more, from the viewpoint of improving mechanical strength and heat resistance. Furthermore, the proportion (A6) may be 100 mol% or less, but may also be 99.5 mol% or less, or 99 mol% or less.

[0078] In the present film, the proportion (B7) of ethylene glycol in the diol components of all polyesters contained in the center portion in the thickness direction (i.e., the intermediate layer (B)) is preferably 55 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more. The proportion (B7) may be 100 mol% or less, but is more preferably 99 mol% or less, and even more preferably 96 mol% or less.

[0079] The present film preferably contains polyester as a main component, and the content of polyester in the entire film may be, for example, 65% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more. The polyester content in the surface (i.e., surface layer (A)) may be, for example, 65% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and may be 100% by mass or less, but from the viewpoint of containing other components such as an impact resistance modifier, it is preferably 99.9% by mass or less, more preferably 99% by mass or less, and even more preferably 98% by mass or less. On the other hand, the polyester content in the center in the thickness direction (i.e., the intermediate layer (B)) may be, for example, 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more, and may be 100% by mass or less, but may be less than 100% by mass from the viewpoint of containing other components.

[0080] [Impact modifier] The present film may contain an impact modifier. The present film preferably contains an impact modifier on one surface (i.e., one surface layer (A)). By containing an impact modifier on the surface (surface layer (A)) of the film, the surface hardness of the present film is reduced, which makes it easier to improve the stress relaxation properties. It is also preferable that the present film contains an impact modifier on both surfaces (i.e., on both surfaces of the surface layer (A)). By containing an impact modifier on both surfaces, the stress relaxation properties of one surface are improved, while the other surface is easily adsorbed to an adsorption table, which further facilitates reducing cracks in wafers and chips. In addition, even when the present film is a single-layer film, an impact resistance modifier may be incorporated into the single-layer film (that is, the surface layer (A)).

[0081] Examples of impact modifiers include soft styrene-based resins and elastomers. The elastomer may be a core-shell elastomer. One type of impact modifier may be used alone, or two or more types may be used in combination. Of the above, core-shell elastomers are preferred as impact modifiers. Use of a core-shell elastomer further improves impact resistance and improves reliability over long-term use.

[0082] Examples of the flexible styrene resin include a block copolymer containing a styrene polymer block and a conjugated diene polymer block, and a block copolymer containing a styrene polymer block and an acrylonitrile block. The styrene content in the flexible styrene-based resin is, for example, 5% by mass or more and 80% by mass or less, preferably 10% by mass or more and 50% by mass or less, and more preferably 15% by mass or more and 30% by mass or less. When the styrene content is in the above range, the effect of imparting impact resistance is further improved.

[0083] The conjugated diene polymer block used in the flexible styrene resin may be a homopolymer of butadiene, isoprene, 1,3-pentadiene, or the like, a copolymer thereof, or a copolymer containing a monomer copolymerizable with the conjugated diene monomer in the block. Specific examples of flexible styrene resins include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), silicone-acrylic composite rubber-acrylonitrile-styrene copolymer (SAS), methyl methacrylate-maleic anhydride-styrene copolymer (SMM), acrylonitrile-styrene copolymer (AS), acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene-acrylic rubber copolymer (ASA), and acrylonitrile-ethylene propylene rubber-styrene copolymer (AES). Specific commercial products include the Kraton D series manufactured by Kraton Polymers, the AR-100 series manufactured by Aron Kasei, the Dialac series manufactured by UMG ABS, and the Delpet series manufactured by Asahi Kasei Chemicals. In addition, as the soft styrene-based resin, the "Dynaron" series manufactured by JSR Corporation, the "Tuftec" series manufactured by Asahi Kasei Chemicals Corporation, the "Hybler" series manufactured by Kuraray Co., Ltd., and the like can be used as the styrene-based elastomer described below.

[0084] Block copolymers include pure block, random block, tapered block, etc., and there are no particular restrictions on the copolymerization form. Furthermore, the block units may have multiple repeating units. Specifically, in the case of styrene-butadiene block copolymers, multiple block units may be repeated, such as styrene-butadiene copolymer, styrene-butadiene-styrene block copolymer, and styrene-butadiene-styrene-butadiene block copolymer.

[0085] Hydrogenated styrene-butadiene-styrene block copolymers (SEBS) and hydrogenated styrene-isoprene-styrene block copolymers (SEPS) can also be used, in which some or all of the double bonds in the conjugated diene polymer blocks of SBS and SIS are hydrogenated. Specific examples of such products include the "Tuftec H" series manufactured by Asahi Kasei Chemicals Corporation and the "Kraton G" series manufactured by Kraton Polymers.

[0086] A polar functional group can also be added to the flexible styrene-based resin. Specific examples of the polar functional group include an acid anhydride group, a carboxylic acid group, a carboxylic acid ester group, a carboxylic acid chloride group, a carboxylic acid amide group, a carboxylic acid salt group, a sulfonic acid group, a sulfonic acid ester group, a sulfonic acid chloride group, a sulfonic acid amide group, a sulfonic acid salt group, an epoxy group, an amino group, an imide group, and an oxazoline group. Among these, it is preferable to add an acid anhydride group or an epoxy group. As flexible styrene-based resins to which polar functional groups have been added, modified SEBS and SEPS are preferably used. Specific examples include maleic anhydride-modified SEBS, maleic anhydride-modified SEPS, epoxy-modified SEBS, and epoxy-modified SEPS. Specific commercial products include the "Tuftec M" series manufactured by Asahi Kasei Chemicals Corporation, the "Dynalon" series manufactured by JSR Corporation, and the "Epofriend" series manufactured by Daicel Chemical Industries, Ltd.

[0087] The soft styrene-based resin may also be a styrene-based elastomer containing an elastomer component. Specific examples of the above include block copolymers of a styrene component with butadiene, isoprene, 1,3-pentadiene, etc., and modified or hydrogenated products thereof. More specific examples include SBS, SIS, SEBS, and SEPS.

[0088] The elastomer may be other than a styrene-based elastomer, and examples thereof include known elastomers such as polyester-based elastomers, polyolefin-based elastomers, diene-based elastomers, acrylic-based elastomers, polyamide-based elastomers, polyurethane-based elastomers, fluorine-based elastomers, and silicone-based elastomers. The elastomer is generally a thermoplastic elastomer. The elastomer is preferably a polyester-based elastomer or the above-mentioned styrene-based elastomer.

[0089] The polyester elastomer is a thermoplastic polyester that has rubber properties at room temperature, preferably a thermoplastic elastomer primarily composed of a polyester block copolymer, and is preferably a block copolymer having a high-melting-point, highly crystalline aromatic polyester as the hard segment and an amorphous polyester or amorphous polyether as the soft segment. The soft segment content of the polyester elastomer is at least 20 to 95 mol% of the total segments, and in the case of a block copolymer of polybutylene terephthalate and polytetramethylene glycol (PTMG-PBT copolymer), it is 50 to 95 mol%. The soft segment content is preferably 50 to 90 mol%, particularly 60 to 85 mol%. Of these, polyester ether block copolymers, especially PTMG-PBT copolymers, are preferred because they minimize the loss of transmittance.

[0090] A core-shell elastomer is composed of an innermost layer (i.e., a core) and one or more outer layers (i.e., shells) surrounding it. The core-shell elastomer is preferably a core-shell graft copolymer in which a graft-copolymerizable monomer component is graft-copolymerized onto the core as the shell.

[0091] Core-shell graft copolymers usually have a polymer component called a rubber component as the core. In core-shell graft copolymers, the polymer component constituting the core is preferably graft-copolymerized with a monomer component copolymerizable with this polymer component as the shell. The core-shell graft copolymer may be produced by any of the following methods: bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. The copolymerization method may be either single-stage grafting or multi-stage grafting. However, commercially available core-shell elastomers can usually be used as they are. Examples of commercially available core-shell elastomers are given below.

[0092] Specific examples of polymer components forming the core include butadiene-based rubbers such as polybutadiene and styrene-butadiene copolymers, isoprene-based rubbers, acrylic rubbers such as polybutyl acrylate, poly(2-ethylhexyl acrylate), and butyl acrylate-2-ethylhexyl acrylate copolymers, silicone-based rubbers such as polyorganosiloxane rubber, butadiene-acrylic composite rubbers, silicone-acrylic composite rubbers such as IPN (Interpenetrating Polymer Network) composite rubbers made of polyorganosiloxane rubber and polyalkyl acrylate rubber, ethylene-α-olefin-based rubbers such as ethylene-propylene copolymers, ethylene-butene copolymers, and ethylene-octene copolymers, ethylene-acrylic rubbers, and fluororubbers. These may be used alone or in combination. Among these, at least one selected from butadiene-based rubbers, acrylic rubbers, silicone-based rubbers, and silicone-acrylic composite rubbers is preferred in terms of mechanical properties and surface appearance, with at least one selected from butadiene-based rubbers and silicone-acrylic composite rubbers being more preferred.

[0093] Specific examples of the monomer component constituting the shell and capable of graft copolymerization with the core polymer component include aromatic vinyl compounds; vinyl cyanide compounds; (meth)acrylic compounds such as (meth)acrylic ester compounds, (meth)acrylic acid compounds, and epoxy group-containing (meth)acrylic ester compounds such as glycidyl (meth)acrylate; maleimide compounds such as maleimide, N-methylmaleimide, and N-phenylmaleimide; α,β-unsaturated carboxylic acid compounds such as maleic acid, phthalic acid, and itaconic acid, and anhydrides thereof (e.g., maleic anhydride). These monomer components may be used alone or in combination of two or more. Among these, aromatic vinyl compounds, vinyl cyanide compounds, and (meth)acrylic compounds are preferred from the viewpoint of mechanical properties and surface appearance, and aromatic vinyl compounds and (meth)acrylic compounds are more preferred, with (meth)acrylic ester compounds being particularly preferred. Specific examples of aromatic vinyl compounds include styrene, α-methylstyrene, 1-vinylnaphthalene, 4-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, and halogenated styrenes, and among these, styrene and α-methylstyrene are more preferred. Specific examples of the (meth)acrylic acid ester compound include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, and octyl (meth)acrylate. Among these, methyl (meth)acrylate and ethyl (meth)acrylate, which are relatively easily available, are preferred, and methyl (meth)acrylate is more preferred. Note that "(meth)acrylic" collectively refers to "acrylic" and "methacrylic."

[0094] Particularly preferred core-shell elastomers are core-shell graft copolymers, which have a core made of at least one polymer component selected from butadiene rubber, acrylic rubber, silicone rubber, and silicone-acrylic hybrid rubber, and a shell formed by graft copolymerizing a (meth)acrylic compound such as a (meth)acrylic acid ester or an aromatic vinyl compound around the core. The content of the polymer component in the core of the core-shell graft copolymer is preferably 40% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. The total content of the (meth)acrylic compound (especially, the (meth)acrylic acid ester) component and the aromatic vinyl compound component in the shell of the core-shell graft copolymer is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and even more preferably 70% by mass or more. In the shell, either the (meth)acrylic compound or the aromatic vinyl compound may be used alone, or they may be used in combination.

[0095] Preferred examples of core-shell elastomers include methyl methacrylate-butadiene-styrene copolymer (MBS), methyl methacrylate-acrylonitrile-butadiene-styrene copolymer (MABS), methyl methacrylate-butadiene copolymer (MB), methyl methacrylate-acrylic rubber copolymer (MA), methyl methacrylate-acrylic rubber-styrene copolymer (MAS), methyl methacrylate-acrylic-butadiene rubber copolymer, methyl methacrylate-acrylic-butadiene rubber-styrene copolymer, and methyl methacrylate-(acrylic-silicone composite rubber) copolymer.

[0096] Commercially available core-shell type graft copolymers include, for example, "Paraloid EXL2602," "Paraloid EXL2603," "Paraloid EXL2690," "Paraloid EXL2691J," "Paraloid EXL2650J," "Paraloid EXL2655," "Paraloid EXL2311," "Paraloid EXL2313," "Paraloid EXL2315," "Paraloid KM330," "Paraloid KM336P," and "Paraloid EXL2311," manufactured by Dow Chemical Japan. Examples of such polymers include "KCZ201" manufactured by Mitsubishi Chemical Corporation, "Metablen C-223A", "Metablen E-901", "Metablen S-2001", "Metablen W-450A", and "Metablen SRK-200" manufactured by Mitsubishi Chemical Corporation, and "Kane Ace M-210", "Kane Ace M-511", "Kane Ace M-600", "Kane Ace M-400", "Kane Ace M-580", "Kane Ace M-590", "Kane Ace M-711", "Kane Ace MR-01", and "Kane Ace M-300" manufactured by Kaneka Corporation. These impact modifiers such as core-shell type graft copolymers may be used alone or in combination of two or more.

[0097] The content of the impact modifier is preferably 30% by mass or less on each surface of the film (i.e., each surface layer (A)). By setting it to 30% by mass or less, it is possible to achieve effects commensurate with the content and also to prevent a decrease in various physical properties such as the mechanical strength of the film. Furthermore, the content of the impact modifier is preferably 1% by mass or more. By setting the content of the impact modifier to 1% by mass or more, it is possible to reduce the hardness on the surface and easily improve stress relaxation properties, etc. The content of the impact modifier is preferably 2.5% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, and more preferably 20% by mass or less, more preferably 16% by mass or less, and even more preferably 12% by mass or less.

[0098] It is preferable that the impact modifier is not contained in the center of the film in the thickness direction (i.e., the intermediate layer (B)), and even if it is contained, it is contained in a content less than that in the surface of the film (i.e., the surface layer (A)). When the intermediate layer (B) does not contain an impact modifier or contains a small amount of it, the mechanical strength of the present film is easily increased. The content of impact modifier in the intermediate layer (B) should be less than the content of impact modifier in each surface layer (A) based on the mass of each layer, and is preferably less than 4 mass%, more preferably less than 2 mass%, even more preferably 1 mass% or less, even more preferably 0.5 mass% or less, and most preferably 0 mass%.

[0099] The content of the impact modifier in the present film (i.e., the entire film) is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less, and even more preferably 5% by mass or less. The content of the impact modifier in the entire film is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and even more preferably 1.5% by mass or more.

[0100] [particle] The present film may contain particles. By containing particles, the present film can be provided with properties such as easy slippage, thereby improving the handleability of the film. Examples of particles include, but are not limited to, inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide; crosslinked polymers such as crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles; and organic particles such as calcium oxalate and ion exchange resins. Among these, silica and aluminum oxide are preferred, and silica is more preferred.

[0101] Considering both the transparency and ease of handling of the film, the average particle size of the particles is usually in the range of 0.05 μm to 10 μm, preferably 0.1 μm to 6 μm, more preferably 0.3 μm to 5 μm, and even more preferably 0.6 μm to 4.5 μm. The average particle size of the particles is the particle size at an integrated volume fraction of 50% (d50) in the equivalent sphericity distribution measured using a centrifugal sedimentation particle size distribution analyzer.

[0102] The particles may be contained throughout the entire film, but are preferably contained on at least one surface of the film. Therefore, in the above-described multilayer structure, it is sufficient to contain particles in at least one of the surface layers (A). However, when the film has surface layers (A) on both sides, it is more preferable to contain particles in both surface layers (A). The particle content is not particularly limited, but is usually less than 5% by mass, preferably 0.0003% to 3% by mass, more preferably 0.001% to 2.5% by mass, and even more preferably 0.01% to 1% by mass. When particles are not contained or when the particle content is low, the film has excellent transparency. On the other hand, when particles are contained within the above range, the slipperiness can be improved and the handling can be improved. Even when particles are contained, the transparency of the film can be sufficiently ensured as long as the particle content is less than 5% by mass. The particle content should be within the above range at least in a region from the surface of the film to a depth of 1 μm in the thickness direction. When the film has a multilayer structure, the particle content in the surface layer (A) should be within the above range. When the film has a single-layer structure, the particle content relative to the entire film should be within the above range. Furthermore, when the film has a multilayer structure, the particle content relative to the entire film is preferably 0.0001% by mass or more and 2% by mass or less, more preferably 0.0005% by mass or more and 1.5% by mass or less, even more preferably 0.001% by mass or more and 1% by mass or less, and even more preferably 0.005% by mass or more and 0.7% by mass or less.

[0103] [Other ingredients] In addition to the above-mentioned particles, the film may contain conventionally known antioxidants, ultraviolet absorbers, antistatic agents, heat stabilizers, lubricants, colorants such as dyes and pigments, etc., as needed.

[0104] [Hardness other than the surface] The hardness measured at 23±5° C. with a nanoindenter at the center in the thickness direction of the film is preferably higher than the hardness measured at 23±5° C. with a nanoindenter on one surface of the film. Increasing the hardness at the center in this way provides a certain degree of stiffness to the substrate, making it easier to properly hold a wafer when attached to the wafer as a protective sheet. From the same viewpoint, the hardness measured at 23±5°C with a nanoindenter in the central portion is preferably higher than the hardness measured at 23±5°C with a nanoindenter on both surfaces of the film. The hardness at the center in the thickness direction can be measured by cutting the film along the surface direction using known means to expose the center in the thickness direction of the film, cutting the cross section with a diamond knife or the like to create a smooth surface as needed, and measuring the hardness at the center in the thickness direction of the film using a nanoindenter.

[0105] The present film also preferably has a gradient in which the hardness increases from one surface of the film toward the center in the thickness direction of the film, i.e., it is preferable that at least a region with low hardness (first region) and a region with a higher hardness than the first region (second region) are provided in this order from one surface of the film toward the center.

[0106] Furthermore, the hardness gradient preferably increases from one surface toward the center and then decreases again toward the other surface. That is, it is preferable that a low hardness region (first region), a high hardness region (second region), and a low hardness region (first region) are provided in this order from one surface toward the other surface.

[0107] As described above, the present film is preferably a multilayer film, and in the case of a multilayer film, it is preferable that the film has the above-mentioned hardness gradient by having a surface layer (A) and an intermediate layer (B) as described above. Furthermore, even in the case of a monolayer film, the hardness may be adjusted to have a gradient. In the monolayer film, the composition may be adjusted so that it gradually changes from the surface toward the center in the thickness direction. By gradually changing the composition from the surface toward the center in the thickness direction, the hardness at each position in the thickness direction can also be gradually changed. The hardness at each position in the thickness direction can be measured by cutting the film along the surface direction using known means to expose each position in the thickness direction of the film, cutting the cross section with a diamond knife or the like to create a smooth surface, and measuring the hardness at each position in the thickness direction of the film using a nanoindenter.

[0108] To achieve a gradual change in the blending ratio, the film may contain two or more polyesters, and the content of at least one polyester may be adjusted so that it gradually decreases from the surface toward the center, while the content of at least one other polyester may be adjusted so that it gradually increases from the surface toward the center. By gradually changing the blending ratio in this way, the blending ratio between the center and the surface in the thickness direction can be changed without providing an interlayer gap.

[0109] More specifically, if the proportion (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than terephthalic acid in the dicarboxylic acid components of all polyesters contained at each position in the thickness direction is (C1), and the proportion (mol %) of diol components other than ethylene glycol in the diol components of all polyesters contained at each position in the thickness direction is (C4), then (C1) + (C4) should gradually decrease from each surface toward the center. Similarly, if the proportion of the dicarboxylic acid component (X2) having 4 to 10 carbon atoms other than polyarylate (c) and terephthalic acid in the dicarboxylic acid components in all the polyesters contained at each position in the thickness direction is (C2), and the proportion of the diol component (X2) other than polyarylate (c) and ethylene glycol in the diol components in all the polyesters contained at each position in the thickness direction is (C5), then (C2) + (C5) should gradually decrease from each surface toward the center.

[0110] [Physical properties of this film] (glass transition temperature) The glass transition temperature (Tg) of the present film is not particularly limited, but is preferably 30°C or higher. When the present film has a Tg of 30°C or higher, the heat resistance of the present film is good. Tg is more preferably 40°C or higher, even more preferably 50°C or higher, and even more preferably 60°C or higher. Furthermore, from the viewpoint of reducing hardness and improving stress relaxation properties, Tg is preferably set to a certain value or lower, preferably 80°C or lower, more preferably 75°C or lower, even more preferably 73°C or lower, and more preferably 71°C or lower.

[0111] (Tensile elongation at break) The present film preferably has a tensile breaking elongation of 160% or more at 25°C. When the tensile breaking elongation at 25°C is 160% or more, the film tends to have a high elongation percentage at room temperature, which makes it possible to appropriately carry out the stretching process described below. In addition, the flexibility of the present film can be ensured, and the surface hardness can be easily reduced. In order to ensure excellent elongation while maintaining flexibility at room temperature, the tensile elongation at break of the present film at 25°C is more preferably 170% or more, even more preferably 180% or more, and even more preferably 190% or more. The tensile elongation at break is not particularly limited, but is, for example, 500% or less, preferably 400% or less, and more preferably 300% or less, in order to easily impart a certain level of mechanical strength to the present film.

[0112] (tensile breaking stress) The present film preferably has a tensile breaking stress of 50 MPa or more at 25°C. By setting the tensile breaking stress to 50 MPa or more, it becomes easier to impart a certain level of mechanical strength to the present film. From this viewpoint, the tensile breaking stress at 25°C is more preferably 70 MPa or more, even more preferably 80 MPa or more, and even more preferably 100 MPa or more. The tensile breaking stress at 25°C is, for example, 500 MPa or less, preferably 400 MPa or less, more preferably 300 MPa or less, and even more preferably 200 MPa or less, from the viewpoint of easily increasing the tensile breaking elongation described above.

[0113] (tensile stress at 5% or 100% elongation) The present film is not particularly limited, but for example, the tensile stress at 5% elongation is preferably 10 MPa or more and 150 MPa or less, more preferably 20 MPa or more and 100 MPa or less, even more preferably 40 MPa or more and 90 MPa or less, and even more preferably 50 MPa or more and 85 MPa or less. Furthermore, although not particularly limited, the tensile stress of the present film at 100% elongation is preferably 20 MPa or more and 200 MPa or less, more preferably 35 MPa or more and 180 MPa or less, even more preferably 50 MPa or more and 160 MPa or less, and even more preferably 90 MPa or more and 150 MPa or less. The tensile elongation at break, tensile stress at break, and tensile stress at 5% or 100% elongation of the present film may be measured in both MD and TD and averaged. Details of these measurement methods are as described in the Examples.

[0114] <Manufacturing method of this film> As an example of the method for producing the present film, a method for producing a biaxially stretched film will be described below, although the present film is not limited to the method described here. When the present film is a biaxially stretched polyester film, it is preferable to first produce an unstretched sheet, which is then stretched in two directions to obtain a biaxially stretched polyester film.

[0115] The unstretched sheet is preferably obtained by feeding polyester and, optionally, impact modifiers, particles, and other additives into an extruder, mixing them appropriately, extruding the mixture as a molten sheet from a die using the extruder, and then cooling and solidifying it on a cooling roll. In this case, it is preferable to increase the adhesion between the sheet and the cooling roll to improve the flatness of the sheet, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably used. In the extruder, the polyesters are preferably mixed so that they are compatible with each other, specifically, kneaded at a temperature of 260 to 300°C, preferably 265 to 295°C, and more preferably 270 to 290°C.

[0116] Next, the unoriented sheet is stretched in one direction using a roll or tenter type stretching machine, at a stretching temperature of usually 25 to 120°C, preferably 35 to 100°C, and at a stretching ratio of usually 2.5 to 7 times, preferably 2.8 to 6 times. Next, the film is stretched in a direction perpendicular to the first-stage stretching direction, at a stretching temperature of usually 50 to 140° C. and a stretching ratio of usually 3.0 to 7 times, preferably 3.5 to 6 times. In the above stretching, a method of performing unidirectional stretching in two or more stages can also be employed.

[0117] After stretching, the film is subsequently heat-set at a heat-setting temperature of, for example, 130 to 270°C, preferably 165 to 260°C, and more preferably 200 to 240°C, under tension or under relaxation of 30% or less, to obtain the present film as a biaxially oriented film. By subjecting the present film to heat-setting, the flexibility, heat resistance, etc. can be improved. It also makes it easier to adjust the surface hardness described above. The heat-setting is preferably performed at a temperature 5 to 70°C lower than the melting point of the polyester. When the present film is a multi-layer polyester film, the polyester layers constituting each layer may be co-extruded, and then stretched and heat-set as an integrated film as described above. Whether or not the film has been stretched can be confirmed by measuring the orientation direction and degree of orientation of molecular chains in the film, retardation, etc.

[0118] <Laminated film> The present film may be used as a laminate film by laminating another layer on one or both surfaces of the present film. A laminate film according to one embodiment of the present invention has the present film described above and a functional layer provided on one or the other surface of the present film.

[0119] (resin layer) The functional layer is not particularly limited, but may be a resin layer. In the present film, one resin layer may be provided, or two or more resin layers may be provided. Preferred examples of the resin layer include an easy-adhesion layer and an antistatic layer. The easy-adhesion layer is a layer provided to adhere other layers or films to the present film, and is not particularly limited, and may be formed from a binder resin such as a polyurethane resin, a vinyl resin, a polyamide resin, a polyester resin, an acrylic resin, or a polyvinyl acetal resin. The resin in the easy-adhesion layer may be appropriately blended with additives such as various crosslinking agents and particles. The thickness of the easy-adhesion layer is not particularly limited, but is, for example, 0.001 μm to 3 μm, preferably 0.005 μm to 1 μm, more preferably 0.01 μm to 0.5 μm, and even more preferably 0.03 μm to 0.3 μm.

[0120] Furthermore, when an easy-adhesion layer is provided in the laminate film, the easy-adhesion layer is preferably provided on one surface of the present film having a hardness of not more than a certain value as measured with a nanoindenter at 23° C. The surface on the easy-adhesion layer side is often provided with an adhesive layer or the like described below and is attached to an adherend such as a wafer or chip, so by lowering the hardness of the surface on which the easy-adhesion layer is provided as described above, damage to the adherend such as a wafer or chip can be effectively suppressed when the film is attached to the adherend such as a wafer.

[0121] The antistatic layer is a layer containing an antistatic agent. The antistatic agent is not particularly limited, and conventionally known antistatic agents can be used. The antistatic agent is preferably a polymeric antistatic agent. Examples of polymeric antistatic agents include compounds having an ammonium group, polyether compounds, compounds having a sulfonic acid group, betaine compounds, and conductive polymers. Among these, compounds having an ammonium group and compounds having a sulfonic acid group are preferred in terms of antistatic performance, and compounds having an ammonium group are more preferred. Furthermore, among compounds having an ammonium group, compounds having a pyrrolidinium ring are also preferred because of their excellent antistatic properties and heat resistance. Compounds having a pyrrolidinium ring are preferably obtained by cyclopolymerizing a diallylamine derivative using a radical polymerization catalyst. Furthermore, a compound having a carbon-carbon unsaturated bond polymerizable with the diallylamine derivative may be used as a copolymerization component. On the other hand, conductive polymers are preferred because of their excellent antistatic properties. Examples of conductive polymers include polythiophenes, polyanilines, polypyrroles, and polyacetylenes. Among these, polythiophenes, such as poly(3,4-ethylenedioxythiophene) used in combination with polystyrene sulfonic acid, are preferred. The antistatic layer may contain a binder resin in addition to the antistatic agent. The binder resin is as described above. The binder resin may also contain various crosslinking agents, particles, and other additives as appropriate.

[0122] The thickness of the antistatic layer is not particularly limited, but is, for example, from 0.001 μm to 3 μm, preferably from 0.005 μm to 1 μm, more preferably from 0.01 μm to 0.5 μm, and even more preferably from 0.02 μm to 0.2 μm.

[0123] The laminated film on which the antistatic layer is provided has a surface resistivity of 1×10 12By setting the surface resistivity of the laminated film to a certain value or less as described above, charging is prevented, and problems such as damage to circuits formed on a wafer due to electrical effects such as static electricity can be prevented. The surface resistivity is 1×10 11 Ω / □ or less is more preferable, and 1×10 10 The surface resistivity is more preferably 1×10 Ω / □ or less. 4 It may be Ω / □ or more, or 1×10 5 It may be Ω / □ or more.

[0124] A preferred embodiment of the laminated film is one in which an easy-adhesion layer is provided on one surface of the present film and an antistatic layer is provided on the other surface. Furthermore, the present film provided with a functional layer such as an antistatic layer or an easy-adhesion layer is preferably stretched together with the present film in a state in which the antistatic layer or the easy-adhesion layer is laminated on the present film. This allows the functional layer to be easily thinned in thickness through a simple process.

[0125] (Adhesive layer) The laminate film also preferably contains an adhesive layer as the resin layer. The laminate film becomes an adhesive tape when it has an adhesive layer. The laminate film can be attached to a wafer or the like when it is used, making it suitable for use as a protective tape. The adhesive layer is a layer having pressure-sensitive adhesive properties and may be formed from a known adhesive. The adhesive is not particularly limited, and conventionally known materials such as acrylic, silicone, urethane, and polyester can be used. The adhesive layer may also be UV-curable, and may be cured by UV irradiation to reduce its adhesive strength to the adherend. When the adhesive layer is UV-curable, UV irradiation before peeling the adherend, such as a wafer or chip, improves the releasability when peeling the adherend.

[0126] The adhesive layer may be provided on either surface of the present film, but is preferably provided on one surface of the present film on which the hardness measured at 23°C using a nanoindenter is equal to or less than the above-mentioned certain value. Furthermore, when an easy-adhesion layer is provided on the laminated film, the adhesive layer is preferably laminated on the easy-adhesion layer. By laminating the adhesive layer on the easy-adhesion layer, the adhesive layer is held to the present film with high holding power. A laminated film having an adhesive layer is attached to an adherend such as a wafer via the adhesive layer. By lowering the hardness of the surface of the film on the side where the adhesive layer is provided as described above, the film can appropriately relieve stress when attached to a wafer or the like, effectively preventing damage to the wafer or chip.

[0127] <How to use this film> The present film is used in the semiconductor manufacturing process, and is preferably used, for example, as a protective tape that is attached to a wafer to protect the wafer or chips obtained by dividing the wafer. In general, semiconductor manufacturing processes include a back-grinding process in which a predetermined circuit pattern is formed on the surface of a semiconductor wafer, followed by a back-grinding process in which the opposite surface of the semiconductor wafer is polished to adjust the thickness of the wafer, a dicing process in which the semiconductor wafer is separated into individual chips, and a pick-up process in which the separated chips are picked up. The present film is preferably used as a base material for a protective tape to be adhered to the circuit surface of a semiconductor wafer in any of these processes, and is more preferably used for the back-grinding tape used in the back-grinding process. Since the hardness of one surface of this film is low, by attaching it to a wafer via one surface, stresses such as shear forces acting on the wafer or chip during wafer grinding, etc., can be appropriately alleviated, effectively preventing cracking of the wafer or chip.

[0128] The dicing process may be performed by blade dicing, which cuts the wafer with a blade, or by stealth dicing. Stealth dicing is a method in which a modified layer that serves as the starting point for cutting is formed by laser light, and then external stress is applied to the wafer to separate it into individual chips starting from the modified layer. In stealth dicing, external stress may be applied by a so-called expanding process, in which tape attached to the wafer is pulled in the circumferential direction.

[0129] The dicing process is generally performed after a back-grinding process, but it is also preferable to perform it by the so-called dicing-first (DBG) method, in which grooves are formed on the front side of the wafer with a dicing blade, and then the back side of the wafer is ground to reach the grooves, thereby separating the wafer into multiple chips starting from the grooves. Alternatively, the first dicing method may be stealth first dicing (SDBG) using laser irradiation. In stealth first dicing, a modified layer is formed on the wafer by laser irradiation, and then the modified layer is used as a starting point for separating the wafer into individual chips by back grinding.

[0130] As described above, this film is preferably used as a substrate for backgrinding, and more preferably as a substrate for backgrinding tape used in the dicing-first method. In the dicing-first method, chips are singulated and ground simultaneously, making it easy for cracks to occur in the singulated chips during grinding. However, as described above, this film has low hardness on one surface and excellent stress relaxation properties, so even when used in the dicing-first method, it can adequately prevent cracks in wafers and chips.

[0131] <<Explanation of terms>> In the present invention, the term "film" includes the term "sheet", and the term "sheet" includes the term "film". In the present invention, when it is stated that "X to Y" (X and Y are any numbers), unless otherwise specified, it means "X or more and Y or less", and also means "preferably larger than X" or "preferably smaller than Y". Furthermore, when it is stated that the amount is "X or more" (X is any number), it also means that the amount is "preferably greater than X" unless otherwise specified, and when it is stated that the amount is "Y or less" (Y is any number), it also means that the amount is "preferably smaller than Y" unless otherwise specified. [Example]

[0132] Examples and comparative examples will be shown below, but the present invention is not limited by these examples.

[0133] The evaluation and measurement methods are as follows. [Hardness (nano indenter)] The polyester films obtained in each Example, Comparative Example, and Reference Example were cut into 20 mm x 20 mm squares, and the resulting test specimens were attached to glass substrates with wood glue. The hardness of the surface layer (A) of the test specimens attached to the glass substrate was measured at room temperature (23±5°C) using a nanoindenter "Hysitron TI980 (manufactured by BRUKER)." Specifically, an indentation test was performed on the surface layer (A) side of the resulting test specimens using a diamond Berkovich-type (triangular pyramid-shaped) probe, and a displacement-load hysteresis curve was obtained. The indentation test was performed by setting the maximum load so that the contact depth of the probe was approximately 1000±100 nm. The process of the nanoindenter indentation test is as follows. (1) To detect the surface of the test piece, the probe is brought close to the surface of the test piece until a predetermined load (2 μN) is detected. (2) The probe is removed from the sample until the load becomes 0 μN. At this time, if the probe is in contact with the surface of the sample, a negative load is detected. When the probe is completely removed from the sample, a flat section appears in the load-displacement curve. (3) The probe is pushed into and pulled out of the sample. In each of the Examples, Comparative Examples, and Reference Examples, the lift height was 100 nm, the loading time was 5 seconds, the holding time was 2 seconds, and the unloading time was 5 seconds. Note that Lift Height is the probe separation distance at which the load is definitely 0 μN in the above (2). The load may become 0 μN when the separation distance reaches the value of Lift Height, but it is preferable that the load becomes 0 μN before the separation distance reaches the value of Lift Height. The displacement-load hysteresis curve obtained by the above method was numerically processed using the software (Triboscan 10.2.0.2) provided with the device, and the hardness was calculated. The test was performed at 40 locations (10 μm intervals), and the average hardness value obtained was used as the hardness. The area function required for indenter shape correction during numerical analysis was created using the measurement results of fused quartz.

[0134] [Glass transition temperature of polyester film] Using a differential scanning calorimeter "DSC8500" (manufactured by PerkinElmer), the glass transition temperature was measured in accordance with JIS K7121:2012 by increasing the temperature from -30°C to 200°C at a rate of 10°C / min, decreasing the temperature to 30°C at a rate of 20°C / min, and then increasing the temperature again to 200°C at a rate of 10°C / min. The glass transition temperature was determined by the midpoint glass transition temperature (Tmg).

[0135] [Surface specific resistivity] (1) 1×10 7 If less than Ω / □ Using a low resistivity meter "Loresta GP MCP-T600" manufactured by Mitsubishi Chemical Corporation, the surface resistivity was measured after the sample was conditioned for 30 minutes in a measurement atmosphere at a temperature of 23°C and a relative humidity of 50%, and the value after 1 minute was taken as the surface resistivity. (2) Cases other than those mentioned above Using a high resistance resistivity meter "Hiresta UX MCP-HT800" and measurement electrode "UR-100" manufactured by Mitsubishi Chemical Analytech Co., Ltd., the sample was conditioned for 30 minutes in a measurement atmosphere of 23°C and 50% RH, and then measurement was performed with an applied voltage of 500 V. The value after 1 minute was taken as the surface resistivity. If the surface resistivity exceeded the upper limit of the measurable range, measurement was not possible.

[0136] [Young's modulus of polyester film] Sample films measuring 20 mm wide and 170 mm long were taken from the polyester films obtained in each Example, Comparative Example, and Reference Example, and Young's modulus was measured using an Autograph AGX-V manufactured by Shimadzu Corporation in a room controlled at a temperature of 23°C and a humidity of 50% RH. Tensile measurements were performed in the machine direction (MD) and the transverse direction (TD) of the sample film under conditions of a chuck distance of 120 mm and a pulling speed of 10 mm / min. The following equation was used to calculate Young's modulus. E=Δσ / Δε (In the above formula, E is Young's modulus (GPa), Δσ is the stress difference (GPa) due to the original average cross-sectional area between two points on the line, and Δε is the strain difference between the same two points / initial length.) Measurements were taken at five points in each of the machine direction (MD) and the transverse direction (TD) of the film, and the average values ​​were calculated to determine the Young's modulus in MD and the Young's modulus in TD. The average values ​​of the Young's modulus in MD and the Young's modulus in TD were used as the Young's modulus of the polyester film.

[0137] [Tensile test] (1) Tensile breaking stress Using a tensile testing machine (Intesco Model 2001, manufactured by Intesco Corporation) in a room adjusted to a temperature of 25°C and a humidity of 50% RH, a 15 mm wide polyester film (sample) was set in the testing machine so that the gap between the chucks was 50 mm, and the film was pulled at a strain rate of 200 mm / min. The tensile breaking stress in both the machine direction (MD) and the cross direction (TD) of the film was calculated using the following formula. Tensile breaking stress (MPa) = F / A In the above formula, F is the load (N) at the time of breakage, and A is the original cross-sectional area of ​​the test piece (mm2 ) Measurements were taken at five points in each of the machine direction (MD) and the transverse direction (TD) of the film, and the average values ​​were calculated to determine the MD tensile stress at break and the TD tensile stress at break. The average values ​​of the MD tensile stress at break and the TD tensile stress at break were determined to be the tensile stress at break of the polyester film.

[0138] (2) Tensile elongation at break The polyester films (samples) obtained in the Examples, Comparative Examples, and Reference Examples were subjected to the same test as for the tensile breaking stress described above, and the tensile breaking elongation in each of the machine direction (MD) and the transverse direction (TD) of the film was calculated using the following formula. Tensile elongation at break (%) = 100 × (L-L0) / L0 In the above formula, L is the gauge length (mm) at break, and L0 is the original gauge length (mm). Measurements were taken at five points in each of the machine direction (MD) and the transverse direction (TD) of the film, and the average values ​​were calculated to determine the MD tensile breaking elongation and TD tensile breaking elongation. The average of the MD tensile breaking elongation and TD tensile breaking elongation was determined to be the tensile breaking elongation of the polyester film.

[0139] (3) Tensile stress at 5% and 100% elongation The polyester films (samples) obtained in the Examples, Comparative Examples, and Reference Examples were subjected to the same test as for the tensile breaking stress described above, and the tensile stress at 5% elongation in each of the machine direction (MD) and the transverse direction (TD) of the film was calculated using the following formula. Tensile stress at 5% elongation (MPa) = F5 / A In the above formula, F5 is the load (N) at 5% elongation, and A is the original cross-sectional area of ​​the test piece (mm 2 ) Measurements were taken at five points in each of the machine direction (MD) and the cross direction (TD) of the film, and the average values ​​for each were calculated to determine the tensile stress at 5% elongation in MD and the tensile stress at 5% elongation in TD. The average value of the tensile stress at 5% elongation in MD and the tensile stress at 5% elongation in TD was determined to be the tensile stress at 5% elongation of the polyester film. The load (N) at 100% elongation was also measured in the same manner, and the tensile stress at 100% elongation was determined in the same manner as the tensile stress at 5% elongation.

[0140] (raw materials) The following raw materials were used in the Examples, Comparative Examples and Reference Examples. Copolymer polyester (1): Thermoplastic polyester A copolymer polyester (1) was prepared, which contained terephthalic acid and adipic acid (having 6 carbon atoms) as dicarboxylic acid components, with the terephthalic acid content being 85 mol % and the adipic acid content being 15 mol %, and which contained 45 mol % of 1,4-butanediol and 55 mol % of 1,6-hexanediol as diol components.

[0141] Copolymer polyester (2): Thermoplastic polyester A copolymer polyester (2) (intrinsic viscosity (IV) of 0.70 dL / g) was prepared, which contained terephthalic acid and isophthalic acid as dicarboxylic acid components, with the terephthalic acid content being 78 mol % and the isophthalic acid content being 22 mol %, and which contained ethylene glycol 98 mol % and diethylene glycol 2 mol % as diol components.

[0142] Copolymer polyester (3): Thermoplastic polyester A copolymer polyester (3) was prepared in which the dicarboxylic acid component was terephthalic acid, ethylene glycol was 68 mol %, and 1,4-cyclohexanedimethanol (CHDM) was 32 mol %.

[0143] Polyarylate U Polymer (registered trademark) U-100 (manufactured by Unitika Ltd., dicarboxylic acid component: terephthalic acid / isophthalic acid = 50 / 50 mol %, bisphenol component: bisphenol A = 100 mol %, Tg = 210°C) was prepared.

[0144] Homopolyester (1): Thermoplastic polyester A particle-containing homopolyester (1) (particle-containing homoPET) was prepared. The polyester had a dicarboxylic acid component of terephthalic acid and diol components of 98 mol % ethylene glycol and 2 mol % diethylene glycol, an intrinsic viscosity (IV) of 0.62 dl / g, and contained 0.55 mass % silica particles with an average particle size of 3 μm.

[0145] Homopolyester (2): Thermoplastic polyester A homopolyester (2) was prepared, which was a polyester having a dicarboxylic acid component of terephthalic acid and a diol component of 98 mol % ethylene glycol and 2 mol % diethylene glycol, and had an intrinsic viscosity (IV) of 0.645 dl / g.

[0146] Homopolyester (3): Thermoplastic polyester A particle-containing homopolyester (3) (particle-containing homoPET) was prepared. The polyester had a dicarboxylic acid component of terephthalic acid and diol components of 98 mol % ethylene glycol and 2 mol % diethylene glycol, an intrinsic viscosity (IV) of 0.590 dl / g, and contained 0.7 mass % silica particles with an average particle size of 3 μm.

[0147] Homopolyester (4): Thermoplastic polyester A homopolyester (4) was prepared, which was a polyester having a dicarboxylic acid component of terephthalic acid and a diol component of 98 mol % ethylene glycol and 2 mol % diethylene glycol, and had an intrinsic viscosity (IV) of 0.7 dl / g.

[0148] Homopolyester (5): Thermoplastic polyester A particle-containing homopolyester (5) (particle-containing homoPET) was prepared. The polyester had a dicarboxylic acid component of terephthalic acid and diol components of 98 mol % ethylene glycol and 2 mol % diethylene glycol, an intrinsic viscosity (IV) of 0.65 dL / g, and contained 0.6 mass % silica particles with an average particle size of 3 μm.

[0149] Homopolyester (6): Thermoplastic polyester A homopolyester (4) was prepared, which was a polyester having a dicarboxylic acid component of terephthalic acid and a diol component of 98 mol % ethylene glycol and 2 mol % diethylene glycol, and had an intrinsic viscosity (IV) of 0.580 dl / g.

[0150] Impact modifier Maleic anhydride-modified hydrogenated styrenic thermoplastic elastomer (SEBS), manufactured by Asahi Kasei Chemicals Corporation, "Tuftec M1943"

[0151] Example 1 As shown in Table 1, as the raw materials for the surface layer (A), 38 parts by mass of copolymer polyester (1), 42 parts by mass of polyarylate, 10 parts by mass of homopolyester (1), and 10 parts by mass of impact resistance modifier were dry blended, and as the raw materials for the intermediate layer (B), 10 parts by mass of copolymer polyester (2) and 90 parts by mass of homopolyester (2) were dry blended. The mixed raw materials for the surface layer (A) and the intermediate layer (B) were each fed into separate twin-screw extruders, kneaded at 285°C, and co-extruded at 285°C. The materials were then cooled and solidified on a cooling roll set at 25°C using an electrostatic adhesion method, yielding an unstretched film with two types and three layers (surface layer (A) / intermediate layer (B) / surface layer (A)). The resulting unstretched film was then stretched 3 times in the machine direction (MD) at 65°C using a roll stretching machine. Thereafter, a coating solution for an easy-adhesion layer (solid content: 9.0% by mass) having the following composition was applied to one side of the polyester film by in-line coating, and the coating solution was applied to one side of the polyester film so that the thickness after drying and stretching would be as shown in Table 1, forming an easy-adhesion layer. The film was then introduced into a tenter stretching machine and stretched to 3.1°C in the transverse direction (TD). Subsequently, the film was subjected to a heat setting treatment at a heat setting temperature of 210°C for 7 seconds, and then a cooling treatment to 140°C under 2.5% relaxation in the transverse direction (TD) to obtain a polyester film with a thickness of 80 μm (each surface layer (A): 8 μm, intermediate layer (B): 64 μm). (Formulation of coating solution for easy adhesion layer) Aqueous dispersion of polyester resin formed from terephthalic acid / isophthalic acid / sodium sulfoisophthalate / ethylene glycol / diethylene glycol / triethylene glycol=61 / 32 / 7 / 44 / 43 / 13 (mol%): 20 parts by mass 65 parts by mass of a water dispersion of a polyester-based urethane resin formed from isophorone diisocyanate units, terephthalic acid units, isophthalic acid units, ethylene glycol units, diethylene glycol units, and dimethylolpropanoic acid units in a ratio of 12:19:18:21:25:5 (mol%) Hexamethoxymethylol melamine: 10 parts by mass Collodil silica with a particle size of 50-80 nm: 5 parts by mass Acetylenic nonionic surfactant with polyethylene oxide in the side chain and HLB of 8.0: 0.3 parts by mass *The above figures are parts by mass based on solid content.

[0152] Example 2 After the coating liquid for the easy-adhesion layer was applied and before the transverse stretching, the other side of the polyester film was further coated with the coating liquid for the antistatic layer (1) (solid content concentration: 3.3 mass%) having the following formulation, and the coating liquid was applied to the other side of the polyester film so that the thickness after drying and stretching would be as shown in Table 1, thereby forming the antistatic layer (1), as in Example 1. (Formulation of coating liquid (1) for antistatic layer) Polymer with a pyrrolidinium ring in the main chain, polymerized with diallyldimethylammonium chloride / dimethylacrylamide / N-methylolacrylamide = 90 / 5 / 5 (mol%). Number average molecular weight: approximately 30,000: 40 parts by mass Water dispersion of acrylic resin formed from ethyl acrylate / methyl methacrylate = 36 / 64 (mol%): 37 parts by mass Amidea MA-S (DIC Corporation), a melamine crosslinking agent: 20 parts by mass Epocross WS-500 (manufactured by Nippon Shokubai Co., Ltd.), an oxazoline group-containing polymer: 3 parts by mass 2-amino-2-methylpropanol hydrochloride: 1 part by mass *The above figures are parts by mass based on solid content.

[0153] Example 3 After the coating liquid for the easy-adhesion layer was applied and before the transverse stretching, the other side of the polyester film was further coated with the coating liquid for the antistatic layer (2) (solid content concentration: 2.8 mass%) having the following formulation, and the coating liquid was applied to the other side of the polyester film so that the thickness after drying and stretching would be as shown in Table 1, thereby forming the antistatic layer (2), as in Example 1. (Formulation of coating liquid (2) for antistatic layer) Conductive agent "Orgacon ICP1010" (manufactured by Agfa-Gevaert), whose main components are polyethylenedioxythiophene and polystyrene sulfonic acid, was neutralized with concentrated ammonia water to a pH of 9. When a polyester polyol containing 282 parts by weight of terephthalic acid, 282 parts by weight of isophthalic acid, 62 parts by weight of ethylene glycol, and 250 parts by weight of neopentyl glycol is designated as (C1a), 876 parts by weight of (C1a), 244 parts by weight of tolylene diisocyanate, 81 parts by weight of ethylene glycol, and 67 parts by weight of dimethylolpropionic acid are neutralized with ammonia and dispersed in water: 49 parts by weight A compound in which an average of four polyethylene oxide molecules are added to a polyglycerin skeleton with an average n=2 in the formula shown below. [ka] Collodil silica with particle size of 50-80 nm: 1 part by mass A nonionic surfactant having a structure having polyethylene oxide in the side chain, in which the average of m+n in the following formula is 10. [ka] *The above figures are parts by mass based on solid content.

[0154] Example 4 As shown in Table 1, the raw materials for the surface layer (A) were a dry blend of 27 parts by mass of copolymer polyester (1), 10 parts by mass of homopolyester (1), 53 parts by mass of homopolyester (2), and 10 parts by mass of impact resistance modifier, and the same procedure as in Example 1 was repeated except that the kneading temperature and extrusion temperature were changed to 280°C, the heat setting temperature was changed to 230°C, and the thickness was changed to 77 μm (each surface layer (A): 7.7 μm, intermediate layer (B): 61.6 μm).

[0155] Example 5 The same procedure as in Example 4 was carried out, except that after the coating liquid for the easy-adhesion layer and before the transverse stretching, the above-mentioned coating liquid for the antistatic layer (1) (solid content concentration: 3.3 mass%) was further coated on the other side of the polyester film, and the coating liquid was coated on the other side of the polyester film so as to have a thickness shown in Table 1 after drying and stretching, thereby forming the antistatic layer (1).

[0156] Example 6 The same procedure as in Example 4 was carried out, except that after the coating liquid for the easy-adhesion layer and before the transverse stretching, the coating liquid for the antistatic layer (2) (solid content concentration: 2.8 mass%) having the above-mentioned composition was further coated on the other side of the polyester film, and the coating liquid was coated on the other side of the polyester film so as to have a thickness shown in Table 1 after drying and stretching, thereby forming the antistatic layer (2).

[0157] Example 7 The same procedure as in Example 4 was carried out, except that the heat fixation temperature was changed to 240°C and the thickness was 73 µm (each surface layer (A): 7.3 µm, intermediate layer (B): 58.4 µm).

[0158] Example 8 In Example 8, a monolayer polyester film was produced. As shown in Table 2, 85 parts by mass of copolymer polyester (2), 10 parts by mass of homopolyester (4), and 5 parts by mass of homopolyester (5) were dry blended as raw materials. The mixed raw materials were fed into a twin-screw extruder, kneaded at 280°C, extruded at 280°C, and cooled and solidified on a cooling roll set at 16°C using an electrostatic adhesion method, to obtain an unstretched monolayer film. The unstretched film was then stretched 3.4 times in the machine direction (MD) at 81°C using a roll stretching machine. The above-described adhesive layer coating solution (solid content: 9.0% by mass) was then applied to one side of the polyester film by in-line coating, and the coating solution was applied to one side of the polyester film so that the thickness after drying and stretching would be as shown in Table 2, forming an adhesive layer. The film was then introduced into a tenter stretching machine and stretched 3.9 times in the transverse direction (TD) at 80°C. Subsequently, the film was heat-set for 10 seconds at a heat setting temperature of 187°C, and cooled to 125°C under 8% relaxation in the transverse direction (TD) to obtain a polyester film with a thickness of 50 μm.

[0159] Example 9 As shown in Table 2, the same procedure as in Example 8 was repeated except that a dry blend of 40 parts by mass of copolymer polyester (2), 5 parts by mass of homopolyester (5), and 55 parts by mass of copolymer polyester (3) was used as raw materials, and the heat setting temperature was changed to 169°C.

[0160] (Comparative Example 1) As shown in Table 2, the raw material for the surface layer (A) was a dry blend of 70 parts by mass of homopolyester (2) and 30 parts by mass of homopolyester (3), and the raw material for the intermediate layer (B) was a dry blend of 45 parts by mass of homopolyester (2) and 55 parts by mass of homopolyester (6). The mixed raw materials for the surface layer (A) and the intermediate layer (B) were each fed into separate twin-screw extruders, kneaded at 290°C, and co-extruded at 290°C. The materials were then cooled and solidified on a cooling roll set at 20°C using an electrostatic adhesion method, yielding an unstretched film with two types and three layers (surface layer (A) / intermediate layer (B) / surface layer (A)). The unstretched film was then stretched 3.4 times in the machine direction (MD) at 90°C using a roll stretching machine. It was then introduced into a tenter stretching machine and stretched 4.3 times in the transverse direction (TD) at 145°C. The film was subsequently heat-set at a heat setting temperature of 210°C for 10 seconds, and cooled to 135°C under 8% relaxation in the transverse direction (TD) to obtain a polyester film with a thickness of 50µm (surface layer (A): 4.2µm, middle layer (B): 41.6µm).

[0161] (Reference example 1) As shown in Table 2, the raw material for the surface layer (A) was a dry blend of 50 parts by mass of copolymer polyester (1), 10 parts by mass of homopolyester (1), and 40 parts by mass of homopolyester (2), and the raw material for the intermediate layer (B) was a dry blend of 50 parts by mass of copolymer polyester (1), 10 parts by mass of homopolyester (1), and 40 parts by mass of homopolyester (2). The mixed raw materials for the surface layer (A) and the intermediate layer (B) were each fed into separate twin-screw extruders, kneaded at 285°C, and co-extruded at 285°C. The materials were then cooled and solidified on a cooling roll set at 25°C using an electrostatic adhesion method, yielding an unstretched film with two types and three layers (surface layer (A) / intermediate layer (B) / surface layer (A)). The unstretched film was then stretched 3 times in the machine direction (MD) at 40°C using a roll stretching machine. It was then introduced into a tenter stretching machine and stretched 4.3 times in the transverse direction (TD) at 100°C. The film was then heat-set at 235°C for 7 seconds and cooled to 140°C under 3.4% relaxation in the transverse direction (TD) to obtain a polyester film with a thickness of 50µm (surface layer (A): 8.3µm, middle layer (B): 33.4µm).

[0162] [Table 1] [Table 2]

[0163] In each of the above examples, by using a specific copolymerized polyester and adjusting the type and amount of the dicarboxylic acid component and diol component, the hardness measured on one surface using a nanoindenter at 23°C was 450 MPa or less. Therefore, it can be seen that the stress relaxation properties are excellent, and when used in semiconductor manufacturing, it can reduce chip and wafer damage. Furthermore, since polyester was the main component, it can be seen that the recyclability is also good. Furthermore, since the hardness measured using a nanoindenter at 23°C was low while the Young's modulus was high, it can be seen that the mechanical strength is also good and it is suitable for semiconductor manufacturing. Furthermore, since Examples 1 to 7 were multilayer films, by adjusting the dicarboxylic acid component and diol component in the surface layer (A) and the dicarboxylic acid component and diol component in the intermediate layer (B) to a specific blend such that (A1) + (A4) was higher than (B1) + (B4), it was possible to lower the hardness measured at 23°C with a nanoindenter while increasing Young's modulus, etc. Therefore, it can be seen that the films have excellent stress relaxation properties while maintaining good mechanical strength, making them more suitable for semiconductor manufacturing. In contrast, in Comparative Example 1, the hardness measured at 23°C using a nanoindenter was higher than 450 MPa, and the stress relaxation properties were insufficient. In addition, in Reference Example 1, although the stress relaxation properties were excellent, the Young's modulus could not be increased, and the mechanical strength was not sufficient.

Claims

1. A polyester film having a thermoplastic polyester layer comprising a thermoplastic polyester, the thermoplastic polyester layer is a surface layer (A) of the polyester film, the hardness of the surface layer (A) measured by a nanoindenter at 23±5°C is 450 MPa or less, The polyester film for semiconductor manufacturing processes has a Young's modulus of 2 GPa or more.

2. The hardness of one surface of the film measured by a nanoindenter at 23±5°C is 450 MPa or less, A polyester film for semiconductor manufacturing processes, having a gradient in hardness that increases from one surface of the film toward the center in the thickness direction of the film.

3. 2. The polyester film for semiconductor manufacturing processes according to claim 1, wherein the hardness has a gradient in which the hardness increases from one surface of the film toward the center in the thickness direction of the film.

4. It contains a copolymer polyester composed of a copolymer of a dicarboxylic acid component and a diol component, the proportion (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than terephthalic acid in all dicarboxylic acid components contained in the polyesters on one surface of the film is (A1), The ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained on the one surface is defined as (A4). The ratio (mol %) of dicarboxylic acid components having 4 to 10 carbon atoms other than terephthalic acid to all dicarboxylic acid components contained in the center portion of the film in the thickness direction is (B1), and When the ratio (mol %) of diol components other than ethylene glycol to all diol components in the polyesters contained in the center portion of the film in the thickness direction is (B4), A polyester film for use in semiconductor manufacturing processes, wherein (A1) + (A4) is higher than (B1) + (B4).

5. The hardness of one surface of the film measured by a nanoindenter at 23±5°C is 450 MPa or less, A polyester film for use in semiconductor manufacturing processes, comprising a copolymer polyester (a) which is a copolymer of a dicarboxylic acid component including terephthalic acid and a diol component including an aliphatic diol (Y).

6. The polyester film for semiconductor manufacturing process according to any one of claims 1 to 4, comprising a copolymerized polyester (a) which is a copolymer of a dicarboxylic acid component containing terephthalic acid and a diol component containing an aliphatic diol (Y).

7. 6. The polyester film for semiconductor manufacturing processes according to claim 5, wherein the copolymer polyester (a) comprises a copolymer polyester (a1) obtained by copolymerizing a dicarboxylic acid component containing terephthalic acid (X1) and a dicarboxylic acid component (X2) having 4 to 10 carbon atoms with a diol component containing an aliphatic diol (Y).

8. 6. The polyester film for semiconductor manufacturing processes according to claim 5, wherein the copolymer polyester (a) comprises a copolymer polyester (a1-1) obtained by copolymerizing a dicarboxylic acid component containing terephthalic acid (X1) and a dicarboxylic acid component (X2) having 4 to 10 carbon atoms with a diol component containing an aliphatic diol (Y2) having 4 to 8 carbon atoms.

9. A polyester film for use in semiconductor manufacturing processes described in any one of claims 1 to 5, which is a multilayer film having a surface layer (A) and an intermediate layer (B).

10. the surface layer (A) contains a copolymer polyester formed from a copolymer of a dicarboxylic acid component and a diol component, the proportion (mol %) of the dicarboxylic acid component having 4 to 10 carbon atoms other than terephthalic acid in all the dicarboxylic acid components contained in the surface layer (A) is defined as (A1), When the ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained in the surface layer (A) is (A4), 2. The polyester film for semiconductor manufacturing processes according to claim 1, wherein (A1) + (A4) is 5 mol % or more.

11. A multilayer film having a surface layer (A) and an intermediate layer (B), the hardness of which is 450 MPa or less as measured at 23±5°C by a nanoindenter on one surface of the film, the intermediate layer (B) contains a copolymer polyester formed from a copolymer of a dicarboxylic acid component and a diol component, the ratio (mol %) of the dicarboxylic acid component having 4 to 10 carbon atoms other than terephthalic acid to the dicarboxylic acid components in all the polyesters contained in the intermediate layer (B) is (B1); and When the ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained in the intermediate layer (B) is (B4), A polyester film for use in semiconductor manufacturing processes, wherein (B1) + (B4) is 30 mol % or less.

12. the intermediate layer (B) contains a copolymer polyester formed from a copolymer of a dicarboxylic acid component and a diol component, the ratio (mol %) of the dicarboxylic acid component having 4 to 10 carbon atoms other than terephthalic acid to the dicarboxylic acid components in all the polyesters contained in the intermediate layer (B) is (B1); and When the ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained in the intermediate layer (B) is (B4), The polyester film for semiconductor manufacturing processes according to claim 9, wherein (B1) + (B4) is 30 mol % or less.

13. A multilayer film having a hardness of 450 MPa or less as measured at 23±5°C by a nanoindenter on one surface of the film, the multilayer film comprising a surface layer (A) and an intermediate layer (B), the surface layer (A) contains a copolymer polyester formed from a copolymer of a dicarboxylic acid component and a diol component, the intermediate layer (B) contains a copolymer polyester formed from a copolymer of a dicarboxylic acid component and a diol component, the proportion (mol %) of the dicarboxylic acid component having 4 to 10 carbon atoms other than terephthalic acid in all the dicarboxylic acid components contained in the surface layer (A) is defined as (A1), The ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained in the surface layer (A) is (A4), the ratio (mol %) of the dicarboxylic acid component having 4 to 10 carbon atoms other than terephthalic acid to the dicarboxylic acid components in all the polyesters contained in the intermediate layer (B) is (B1); and When the ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained in the intermediate layer (B) is (B4), A polyester film for use in semiconductor manufacturing processes, wherein (A1) + (A4) is higher than (B1) + (B4) and the difference therebetween is 5 mol % or more.

14. the surface layer (A) contains a copolymer polyester formed from a copolymer of a dicarboxylic acid component and a diol component, the intermediate layer (B) contains a copolymer polyester formed from a copolymer of a dicarboxylic acid component and a diol component, the proportion (mol %) of the dicarboxylic acid component having 4 to 10 carbon atoms other than terephthalic acid in all the dicarboxylic acid components contained in the surface layer (A) is defined as (A1), The ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained in the surface layer (A) is (A4), the ratio (mol %) of the dicarboxylic acid component having 4 to 10 carbon atoms other than terephthalic acid to the dicarboxylic acid components in all the polyesters contained in the intermediate layer (B) is (B1); and When the ratio (mol %) of the diol components other than ethylene glycol to the diol components in all the polyesters contained in the intermediate layer (B) is (B4), 10. The polyester film for semiconductor manufacturing processes according to claim 9, wherein (A1) + (A4) is higher than (B1) + (B4) and the difference therebetween is 5 mol % or more.

15. 2. The polyester film for semiconductor manufacturing processes according to claim 1, wherein the surface layer (A) contains an impact modifier.

16. 16. The polyester film for semiconductor manufacturing processes according to claim 15, wherein the content of the impact modifier in the surface layer (A) is 30% by mass or less.

17. 16. The polyester film for semiconductor manufacturing processes according to claim 15, wherein the content of the impact modifier in the polyester film is 15% by mass or less.

18. The polyester film for semiconductor manufacturing processes according to any one of claims 1 to 5, which is a stretched film.

19. The polyester film for semiconductor manufacturing processes according to any one of claims 1 to 5, which is a coextruded stretched film.

20. The polyester film for semiconductor manufacturing processes according to any one of claims 1 to 5, which is used for a backgrinding tape or a dicing tape.

21. A laminated film comprising the polyester film for use in a semiconductor manufacturing process according to claim 1 and at least one resin layer provided on one surface or the other surface of the polyester film for use in a semiconductor manufacturing process.

22. The resin layer includes an antistatic layer, and the surface on which the antistatic layer is provided has a surface resistivity of 1×10 １２ The laminated film according to claim 21, having a modulus of elasticity of Ω / □ or less.

23. The laminate film according to claim 21 , wherein the resin layer comprises an adhesive layer.

24. The laminate film according to claim 22, which has an easy-adhesion layer on one surface and the antistatic layer on the other surface.

25. A method for using the polyester film for semiconductor manufacturing processes according to any one of claims 1 to 5 or the laminate film according to any one of claims 21 to 24 for back grinding or dicing.