Multilayer film, and semiconductor manufacturing process film

Abstract

To provide a multilayer film which substitutes a film of a soft polyvinyl chloride-based resin composition, thereby fundamentally solving a problem caused by a plasticizer, and is suitable as a film base material of a semiconductor manufacturing process film, and a semiconductor manufacturing process film using the multilayer film as a film base material.SOLUTION: A multilayer film is formed by directly stacking (α1) a first polypropylene layer, (β) a propylene-based soft polyolefin layer, and (α2) a second polypropylene layer in this order, wherein (α1) the first polypropylene layer and (α2) the second polypropylene layer are composed of (A) polypropylene having high crystallinity and a high melting point, and (β) the propylene-based soft polyolefin layer is composed of amorphous or low crystalline (B) propylene-based soft polyolefin.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a multilayer film and a semiconductor manufacturing process film using the multilayer film as a film substrate.

Background Art

[0002] A large number of semiconductor chips are formed together on a large-diameter silicon wafer, and then the silicon wafer is polished to a desired thickness from the back surface (the surface opposite to the surface (circuit-forming surface) on which the circuit is formed). Subsequently, the individual semiconductor chips are diced (cut and separated) for production. This step of polishing the silicon wafer is often performed after attaching an adhesive film (hereinafter referred to as a "back grind film") to the circuit-forming surface of the silicon wafer for the purpose of protecting the circuit-forming surface of the silicon wafer. This step of dicing the individual semiconductor chips is often performed after attaching an adhesive film (hereinafter referred to as a "dicing film") to the circuit-forming surface and / or the back surface of the silicon wafer for the purpose of protecting the surface of the semiconductor chip and fixing and picking up the cut individual semiconductor chips. In addition, an adhesive film (hereinafter referred to as a "die attach film") is often used to adhesively laminate and mount the semiconductor chip on a substrate. Thus, in the semiconductor manufacturing process, many types of process films are used.

[0003] Conventionally, as the film base material of the semiconductor manufacturing process film, it has many advantages such as a high balance between heat resistance and flexibility; having tensile properties suitable for the expansion process (a process of cutting a silicon wafer, pulling a dicing film, and widening the distance between individual semiconductor chips to facilitate pickup); high transparency; and low cost. Therefore, films of soft polyvinyl chloride-based resin compositions are widely used. On the other hand, since a large amount of plasticizer is blended in the film of the soft polyvinyl chloride-based resin composition, the plasticizer may migrate to the adhesive, making the adhesive properties unstable (decreasing or increasing the adhesive strength); there is also the disadvantage that the plasticizer may contaminate semiconductor chips and the like. Therefore, films of polyolefin-based resins have been proposed as the film base material of the semiconductor manufacturing process film (for example, Patent Documents 1 to 3). However, the films of polyolefin-based resins heretofore have not reached the performance of the films of soft polyvinyl chloride-based resin compositions as the film base material of the semiconductor manufacturing process film. In particular, when trying to impart sufficient flexibility and expandability (tensile properties suitable for the expansion process) to the film of the polyolefin-based resin, there is a disadvantage that the blocking resistance and heat resistance become insufficient.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a multilayer film suitable as a film base material for a semiconductor manufacturing process film that replaces a film of a soft polyvinyl chloride resin composition, thereby fundamentally solving problems caused by plasticizers, and a semiconductor manufacturing process film using the multilayer film as a film base material.

Means for Solving the Problems

[0006] As a result of intensive research, the present inventor has found that the above problems can be achieved by a specific multilayer film.

[0007] That is, aspects of the present invention are as follows. [1]. A multilayer film, wherein (α1) a first polypropylene layer, (β) a propylene-based soft polyolefin layer, and (α2) a second polypropylene layer are directly laminated in this order, The above (α1) first polypropylene layer is composed of (A1) polypropylene satisfying the following characteristics (a1-1) and (a1-2), the above (β) propylene-based soft polyolefin layer is composed of (B) propylene-based soft polyolefin satisfying the following characteristic (b-1), and the above (α2) second polypropylene layer is composed of (A2) polypropylene satisfying the following characteristics (a2-1) and (a2-2): the above multilayer film: (a1-1) The melting enthalpy is 90 J / g or more: (a1-2) The melting point is 145 °C or more: (b-1) The melting enthalpy is 50 J / g or less: (a2-1) The melting enthalpy is 90 J / g or more: (a2-2) The melting point is 145 °C or more. [2]. The multilayer film according to [1], wherein the above (B) propylene-based soft polyolefin satisfies the following characteristics (b-1-2) and (b-2): (b-1-2) The melting enthalpy is 5 to 30 J / g: (b-2) The melting point is 130 °C or more. [3]. The multilayer film according to item [1], wherein the above-mentioned (B) propylene-based soft polyolefin does not show a melting peak derived from a crystalline polyethylene component in the second melting curve measured by a differential scanning calorimeter. [4]. The multilayer film according to item [1], wherein the above-mentioned (A1) polypropylene satisfies the following characteristics (a1-1-2) and (a1-2-2), and the above-mentioned (A2) polypropylene satisfies the following characteristics (a2-1-2) and (a2-2-2): (a1-1-2) The melting enthalpy is 95 J / g or more. (a1-2-2) The melting point is 155°C or more. (a2-1-2) The melting enthalpy is 95 J / g or more. (a2-2-2) The melting point is 155°C or more. [5]. The multilayer film according to item [1], wherein the thickness of the above-mentioned (α1) first polypropylene layer is 1 μm or more, the thickness of the above-mentioned (β) propylene-based soft polyolefin layer is 70% or more of the total thickness of the multilayer film, and the thickness of the above-mentioned (α2) second polypropylene layer is 1 μm or more. [6]. The multilayer film according to item [1], wherein the total thickness of the above-mentioned multilayer film is 50 to 300 μm. [7]. The multilayer film according to any one of items [1] to [6], which is used for the film base material of a semiconductor manufacturing process film. [8]. A semiconductor manufacturing process film including the multilayer film according to any one of items [1] to [6].

Effect of the Invention

[0008] The multilayer film of the present invention fundamentally solves the problems caused by the plasticizer in the film of the soft polyvinyl chloride resin composition by not blending the plasticizer, and has high flexibility and good antiblocking properties. A preferred multilayer film of the present invention further has good expandability and heat resistance, and has a high balance between flexibility, expandability, antiblocking properties, and heat resistance. Therefore, the multilayer film of the present invention can be suitably used as a film substrate for semiconductor manufacturing process films, such as dicing films, backgrind films, and die attach films.

Mode for Carrying Out the Invention

[0009] In this specification, the term "resin" is used as a term that includes a resin mixture containing two or more resins and a resin composition containing components other than the resin.

[0010] In this specification, the term "film" is used interchangeably or equivalently with "sheet". In this specification, the terms "film" and "sheet" are used for those that can be industrially wound into a roll. The term "plate" is used for those that cannot be industrially wound into a roll. Also, in this specification, laminating one layer on top of another layer in order includes both directly laminating those layers and laminating them with one or more other layers, such as an anchor coat, intervening between those layers.

[0011] In this specification, the term "above" related to a numerical range is used to mean a certain numerical value or more than a certain numerical value. For example, "above 20%" means 20% or more than 20%. The term "below" related to a numerical range is used to mean a certain numerical value or less than a certain numerical value. For example, "below 20%" means 20% or less than 20%. Also, the symbol "~" related to a numerical range is used to mean a certain numerical value, more than a certain numerical value and less than another certain numerical value, or another certain numerical value. Here, the other certain numerical value is a numerical value larger than the certain numerical value. For example, "10~90%" means 10%, more than 10% and less than 90%, or 90%. Furthermore, the upper limit and the lower limit of the numerical range can be arbitrarily combined, and the embodiments arbitrarily combined should be construed. For example, from the description such as "usually above 10%, preferably above 20%. On the other hand, usually below 40%, preferably below 30%." or "usually 10~40%, preferably 20~30%" related to the numerical range of a certain characteristic, it should be construed that the numerical range of the certain characteristic is 10~40%, 20~30%, 10~30%, or 20~40% in one embodiment.

[0012] Except in examples or unless otherwise specified, all numerical values used in this specification and the claims should be understood to be modified by the term "about". Without attempting to limit the application of the doctrine of equivalents to the claims, each numerical value should be construed in light of the significant figures and by applying ordinary rounding techniques.

[0013] In this specification, for terms specifying shapes and geometric conditions, such as terms like parallel, orthogonal, and perpendicular, in addition to their exact meanings, substantially the same states are also included.

[0014] In this specification, when describing "including a certain substance", in one embodiment, it shall be construed as including a certain substance, consisting of a certain substance, or consisting only of a certain substance. For example, from the description "Composition A includes substance a1 and substance a2", in one embodiment, it shall be construed that Composition A includes substance a1 and substance a2, Composition A consists of substance a1 and substance a2, or Composition A consists only of substance a1 and substance a2.

[0015] 1. Multilayer film: The multilayer film of the present invention has a (α1) first polypropylene layer, a (β) propylene-based soft polyolefin layer, and a (α2) second polypropylene layer directly laminated in this order.

[0016] The above-mentioned (α1) first polypropylene layer and the above-mentioned (α2) second polypropylene layer (hereinafter sometimes simply referred to as "(α) polypropylene layer") are made of (A) polypropylene. The above-mentioned (α) polypropylene layer functions to suppress troubles during the film formation of the multilayer film of the present invention, and functions to impart sufficient blocking resistance, heat resistance, and solvent resistance to the multilayer film of the present invention. The above-mentioned component (A) polypropylene (hereinafter referred to as "(A1) polypropylene") constituting the above-mentioned (α1) first polypropylene layer and the above-mentioned component (A) polypropylene (hereinafter referred to as "(A2) polypropylene") constituting the above-mentioned (α2) second polypropylene layer may be the same polypropylene or different polypropylenes.

[0017] The above-mentioned (β) propylene-based soft polyolefin layer is made of (B) propylene-based soft polyolefin. The above-mentioned (β) propylene-based soft polyolefin layer functions to impart sufficient flexibility and expandability to the multilayer film of the present invention.

[0018] The thickness of the multilayer film of the present invention is not particularly limited and can be appropriately selected in consideration of the specific type of the target semiconductor manufacturing process film and its usage mode. The thickness of the multilayer film of the present invention is usually 30 to 500 μm, preferably 50 to 300 μm, more preferably 60 to 200 μm, still more preferably 70 to 150 μm, and most preferably 80 to 120 μm.

[0019] The thickness of the above-mentioned (α1) first polypropylene layer can be appropriately selected in consideration of the specific type of the target semiconductor manufacturing process film and its usage mode, from the viewpoints of blocking resistance, heat resistance, and solvent resistance. The thickness of the above-mentioned (α1) first polypropylene layer can be usually 1 μm or more, preferably 2 μm or more, and more preferably 3 μm or more from the viewpoints of blocking resistance, heat resistance, and solvent resistance. On the other hand, from the viewpoints of flexibility and expandability, it can be usually 15% or less, preferably 12% or less, more preferably 10% or less, and still more preferably 8% or less of the thickness of the multilayer film of the present invention.

[0020] The thickness of the above-mentioned (α2) second polypropylene layer can be appropriately selected in consideration of the specific type of the target semiconductor manufacturing process film and its usage mode, from the viewpoints of blocking resistance, heat resistance, and solvent resistance. The thickness of the above-mentioned (α2) second polypropylene layer can be usually 1 μm or more, preferably 2 μm or more, and more preferably 3 μm or more from the viewpoints of blocking resistance, heat resistance, and solvent resistance. On the other hand, from the viewpoints of flexibility and expandability, it can be usually 15% or less, preferably 12% or less, more preferably 10% or less, and still more preferably 8% or less of the thickness of the multilayer film of the present invention.

[0021] The thickness of the above-mentioned (β) propylene-based soft polyolefin layer can be appropriately selected from the perspective of flexibility and expandability, taking into account the specific type of the target semiconductor manufacturing process film and its usage mode. From the perspective of flexibility and expandability, the thickness of the above-mentioned (β) propylene-based soft polyolefin layer may be usually 70% or more, preferably 76% or more, more preferably 80% or more, and still more preferably 84% or more of the thickness of the multilayer film of the present invention. On the other hand, from the perspective of blocking resistance, heat resistance, and solvent resistance, it may be usually 98% or less, preferably 96% or less, and more preferably 94% or less of the thickness of the multilayer film of the present invention.

[0022] Hereinafter, each component constituting each layer of the multilayer film of the present invention will be described.

[0023] (A) Polypropylene: The above-mentioned component (A) polypropylene constitutes the above-mentioned (α1) first polypropylene layer and the above-mentioned (α2) second polypropylene layer of the multilayer film of the present invention. The above-mentioned component (A) polypropylene is a resin mainly containing structural units derived from propylene and having high crystallinity. Here, "having high crystallinity" means that the melting enthalpy (the measurement method will be described later) is 90 J / g or more. Here, "mainly containing structural units derived from propylene" means that the content of structural units derived from propylene is large enough to exhibit the above-mentioned high crystallinity, typically 90 to 100 mol%.

[0024] From the perspective of blocking resistance, heat resistance, and solvent resistance, the melting enthalpy of the above-mentioned component (A) polypropylene is usually 90 J / g or more, preferably 95 J / g or more, and more preferably 100 J / g or more. On the other hand, from the perspective of expandability and flexibility, the melting enthalpy of the above-mentioned component (A) polypropylene may be usually 120 J / g or less, preferably 115 J / g or less, and more preferably 110 J / g or more.

[0025] From the viewpoints of blocking resistance, heat resistance, and solvent resistance, the melting point of the above-mentioned component (A) polypropylene is usually 145°C or higher, preferably 150°C or higher, more preferably 155°C or higher, and still more preferably 160°C or higher. From the viewpoints of blocking resistance, heat resistance, and solvent resistance, a higher melting point of the above-mentioned component (A) polypropylene is preferable. Further, as the above-mentioned component (A) polypropylene, from the viewpoints of blocking resistance, heat resistance, and solvent resistance, it is preferable that no peak with a peak top temperature of less than 145°C, which is a sub-peak, appears in the DSC second melting curve described later.

[0026] In this specification, the melting point and melting enthalpy of the above-mentioned component (A) polypropylene are measured in accordance with JIS K7121-1987, using a differential scanning calorimeter (DSC measuring device), holding at 230°C for 5 minutes, cooling to -50°C at 10°C / min, holding at -50°C for 5 minutes, and heating to 230°C at 10°C / min. The DSC second melting curve (the melting curve measured in the last heating process) is calculated. At this time, the melting point is the peak top temperature of the melting peak appearing in the above-mentioned second melting curve. When two or more melting peaks are observed, the peak top temperature of the melting peak with the maximum peak top height is taken as the melting point. FIG. 1 shows a measurement example of the following component (A-1) propylene homopolymer used in the examples. The lower curve in FIG. 1 is the DSC second melting curve, and the upper curve is the DSC crystallization curve. It should be noted that the melting peak appearing in the DSC second melting curve of crystalline polypropylene usually has a gently long extension of the tail on the low temperature side; and the baseline should be drawn so that the straight line extending the high temperature side baseline of FIG. 1 in the reading method of the 9.DTA or DSC curve of JIS K7121-1987 to the low temperature side coincides with the straight line extending the low temperature side baseline to the high temperature side.

[0027] As the above-mentioned component (A) polypropylene, polypropylene having the above-mentioned characteristics can be appropriately selected and used.

[0028] As the polypropylene of the above-mentioned component (A) that can be used, examples of the polypropylene having the above-mentioned properties include isotactic polypropylene such as a propylene homopolymer and a copolymer (including block copolymer and random copolymer) of propylene and one or more of other small amounts of α-olefins (for example, ethylene, 1-butene, 1-hexene, 1-octene, and 4-methyl-1-pentene, etc.).

[0029] The meso-diad fraction (the proportion of the stereostructure of the constitutional units derived from two consecutive propylenes having an isotactic structure) of the above-mentioned isotactic polypropylene is usually 90 mol% or more, more preferably 95 mol% or more, and typically 97 to 100 mol%.

[0030] When the above-mentioned isotactic polypropylene is a copolymer of the above-mentioned propylene and one or more of other small amounts of α-olefins, the content of the constitutional units derived from the α-olefin depends on the meso-diad fraction and the amount of abnormal insertion, but from the viewpoints of trouble suppression during film formation, blocking resistance, heat resistance, and solvent resistance, it is preferably 4.0 mol% or less, more preferably 3.0 mol% or less, still more preferably 2.0 mol% or less, and even more preferably 1.0 mol% or less.

[0031] Based on JIS K7210-1:2014, the melt mass flow rate of the above-mentioned component (A) polypropylene measured under the conditions of 230 °C and 21.18 N is preferably 0.1 to 50 g / 10 min, more preferably 1 to 40 g / 10 min, and still more preferably 3 to 30 g / 10 min from the viewpoint of film formability.

[0032] As the above-mentioned component (A) polypropylene, a mixture of one or more of these can be used.

[0033] In the above-mentioned component (A) polypropylene, additives commonly used in polypropylene can be included as desired, to the extent that it does not conflict with the object of the present invention. Examples of the above additives include antioxidants, neutralizing agents, slip agents, antiblocking agents, antifogging agents, antioxidants, weather resistance stabilizers, light resistance stabilizers, antistatic agents such as glycerin fatty acid esters, nucleating agents, inorganic colorants, organic colorants, and masterbatches for dry blending of these additives, etc.

[0034] Examples of the above antioxidants include hindered phenol-based antioxidants, phosphite-based antioxidants, and thioether-based antioxidants, etc.

[0035] Examples of the above neutralizing agents include fatty acid metal salts such as calcium stearate, zinc stearate, and magnesium stearate, hydrotalcites, and composite metal hydroxides such as lithium aluminum composite hydroxide, etc.

[0036] Examples of the above slip agents include fatty acid amides such as erucic acid amide, oleic acid amide, stearic acid amide, behenic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, stearyl erucic amide, and oleyl palmitoamide, etc.

[0037] Examples of the above antiblocking agents include inorganic fine particles such as silica, and organic fine particles such as crosslinked acrylic resin, etc.

[0038] As the above additives, one or more of these can be used.

[0039] Since the compounding quantity of the above additive is an optional component, it is not particularly limited as long as it does not conflict with the object of the present invention. In one embodiment, the compounding quantity of the above additive may be 5 parts by mass or less, 4 parts by mass or less, 3 parts by mass or less, 2 parts by mass or less, 1 part by mass or less, 0.5 part by mass or less, 0 to 0.5 part by mass, or about 0.01 to 5 parts by mass with respect to 100 parts by mass of the above component (A) polypropylene.

[0040] In one embodiment, the above component (A) polypropylene may not contain any one or two or more of the above additives.

[0041] In this specification, not containing a certain component means that the component is not intentionally compounded. In the technical field of resin compositions, when intentionally compounded, usually 0.01 part by mass or more is compounded. Therefore, not containing a certain component can also be rephrased as that the content of the component is usually less than 0.01 part by mass, preferably 0.001 part by mass or less, more preferably 0 to 0.0001 part by mass with respect to 100 parts by mass of the above component (A) polypropylene.

[0042] The above component (A1) polypropylene and the above component (A2) polypropylene may be the same or different. The types and compounding quantities of the above additives contained in the above component (A1) polypropylene and the types and compounding quantities of the above additives contained in the above component (A2) polypropylene may be the same or different.

[0043] (B) Propylene-based soft polyolefin: The above-mentioned component (B), the propylene-based soft polyolefin, constitutes the above-mentioned (β) propylene-based soft polyolefin layer of the multilayer film of the present invention. The above-mentioned component (B), the propylene-based soft polyolefin, mainly contains structural units derived from propylene and is a resin having amorphous or low crystallinity. Here, "having amorphous or low crystallinity" means that no melting peak is observed in the DSC second melting curve (the measurement method will be described later), or the melting enthalpy calculated from the melting peak is 50 J / g or less. Here, "mainly containing structural units derived from propylene" means that the content of structural units derived from propylene is 50 to 100 mol%.

[0044] From the viewpoints of flexibility and expandability, the melting enthalpy of the above-mentioned component (B), the propylene-based soft polyolefin, is usually 50 J / g or less, preferably 40 J / g or less, more preferably 30 J / g or less, still more preferably 25 J / g or less, and most preferably 20 J / g or less. On the other hand, from the viewpoint of suppressing troubles during film formation, it may be 5 J / g or more.

[0045] From the viewpoint of suppressing troubles during film formation, the above-mentioned component (B), the propylene-based soft polyolefin, may preferably have a melting peak in the above-mentioned DSC second melting curve. In this case, the melting point of the above-mentioned component (B), the propylene-based soft polyolefin, is usually 120°C or higher, preferably 130°C or higher, more preferably 140°C or higher, still more preferably 150°C or higher, and most preferably 155°C or higher. From the viewpoint of suppressing troubles during film formation, a higher melting point of the above-mentioned component (B), the propylene-based soft polyolefin, is preferable. Also, from the viewpoint of the interlayer adhesion strength with the above-mentioned (α) polypropylene layer made of the above-mentioned component (A) polypropylene, it is preferable that the above-mentioned component (B), the propylene-based soft polyolefin, has a melting peak in the above-mentioned DSC second melting curve.

[0046] In this specification, the melting point and melting enthalpy of the above-mentioned component (B) propylene-based soft polyolefin are measured in accordance with JIS K7121-1987, using a differential scanning calorimeter (DSC measuring device), holding at 230°C for 5 minutes, cooling to -50°C at 10°C / min, holding at -50°C for 5 minutes, and heating to 230°C at 10°C / min, and calculated from the DSC second melting curve (the melting curve measured in the last heating process). At this time, the melting point is the peak top temperature of the melting peak appearing in the above-mentioned second melting curve. When two or more melting peaks are observed, the peak top temperature of the melting peak with the maximum peak top height is taken as the melting point. FIG. 2 shows a measurement example of the following component (B-1) propylene-based soft polyolefin used in the examples. The lower curve in FIG. 2 is the DSC second melting curve, and the upper curve is the DSC crystallization curve. Regarding the melting peak appearing in the DSC second melting curve of the soft polyolefin, it should be noted that usually, the trailing edge on the low temperature side gently extends for a long time, often the trailing edge on the high temperature side also gently extends for a long time, and the baseline should be drawn so that the straight line extending the high temperature side baseline in FIG. 1 of the reading method of the DTA or DSC curve in JIS K7121-1987 to the low temperature side coincides with the straight line extending the low temperature side baseline to the high temperature side.

[0047] As the above-mentioned component (B) propylene-based soft polyolefin, those having the above-mentioned characteristics can be appropriately selected and used.

[0048] Examples of the propylene-based soft polyolefin having the above-described properties and usable as the above component (B) propylene-based soft polyolefin include atactic polypropylene and copolymers of propylene and one or more other α-olefins (e.g., ethylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, etc.). When the above (B) propylene-based soft polyolefin is a copolymer of propylene and one or more other α-olefins, the content of the structural unit derived from the α-olefin depends on the meso dyad fraction and the amount of abnormal insertion, but from the viewpoint of imparting the above-described amorphous or low crystallinity, it is usually 5 to 50 mol% (the content of the structural unit derived from propylene is 95 to 50 mol%), preferably 10 to 45 mol% (the content of the structural unit derived from propylene is 90 to 55 mol%), more preferably 15 to 40 mol% (the content of the structural unit derived from propylene is 85 to 60 mol%).

[0049] The melt mass flow rate of the above component (B) propylene-based soft polyolefin measured under the conditions of 230 °C and 21.18 N in accordance with JIS K7210-1:2014 is preferably 0.1 to 50 g / 10 min, more preferably 1 to 40 g / 10 min, and still more preferably 3 to 30 g / 10 min from the viewpoint of film formability.

[0050] From the viewpoint of expandability, in one preferred embodiment, the above component (B) propylene-based soft polyolefin may be one in which no melting peak derived from the crystalline polyethylene component appears in the above DSC second melting curve. The fact that the melting peak is derived from the crystalline polyethylene component can be determined from the degree of supercooling (the difference between the peak top temperature of the melting peak appearing in the DSC second melting curve and the peak top temperature of the crystallization peak appearing in the corresponding DSC crystallization curve), which is about 10 to 20 °C. The degree of supercooling of isotactic polypropylene (crystalline polypropylene) is about 40 to 60 °C.

[0051] Although there is no intention to be restricted by theory, when the crystalline polyethylene component exists in the above-mentioned component (B) propylene-based soft polyolefin in an amount such that a melting peak appears in the DSC second melting curve, the reason for the decrease in expandability is considered as follows. Among crystalline polyolefins, crystalline polyethylene has particularly high crystallinity and is prone to orientation crystallization. And the expansion process can also be regarded as a process of cold stretching the film to promote orientation crystallization. Therefore, when the crystalline polyethylene component exists in the above-mentioned component (B) soft polyolefin in an amount such that a melting peak appears in the DSC second melting curve, orientation crystallization occurs during the expansion process, and inconveniences such as uneven stretching are likely to occur.

[0052] As the above-mentioned component (B) propylene-based soft polyolefin, one or a mixture of two or more of these can be used.

[0053] The above-mentioned component (B) propylene-based soft polyolefin can contain, if desired, additives usually used in polypropylene, to the extent that it does not conflict with the object of the present invention. Specific examples of the additive were described above in the description of the above-mentioned component (A) polypropylene. As the above-mentioned additive, one or two or more of these can be used.

[0054] Since the blending amount of the above-mentioned additive is an optional component, it is not particularly limited as long as it does not conflict with the object of the present invention. The blending amount of the above-mentioned additive may be 5 parts by mass or less, 4 parts by mass or less, 3 parts by mass or less, 2 parts by mass or less, 1 part by mass or less, 0.5 part by mass or less, 0 to 0.5 part by mass, or about 0.01 to 5 parts by mass with respect to 100 parts by mass of the above-mentioned component (B) propylene-based soft polyolefin in one embodiment.

[0055] In one embodiment, the above-mentioned component (B) propylene-based soft polyolefin may not contain any one or two or more of the above-mentioned additives.

[0056] In this specification, "not containing a certain component" means that the component is not intentionally compounded. In the technical field of resin compositions, when intentionally compounded, usually 0.01 part by mass or more is compounded. Therefore, "not containing a certain component" can also be rephrased as that the content of the component is usually less than 0.01 part by mass, preferably 0.001 part by mass or less, more preferably 0 to 0.0001 part by mass, based on 100 parts by mass of the above (B) propylene-based soft polyolefin.

[0057] 2. Film forming method: The method for forming the multilayer film of the present invention is not particularly limited, and a known method for forming a multilayer film can be appropriately selected. As a preferred method for forming the multilayer film of the present invention, for example, a film forming apparatus including a plurality of extruders, a co-extrusion T-die, and a winding device having a first chill roll and a mechanism for pressing a molten film against the first chill roll is used. (1) A step of continuously co-extruding a molten multilayer film from the co-extrusion T-die. (2) A step of pressing and holding the molten multilayer film extruded in the above step (1) against the rotating first chill roll by the above pressing mechanism, and (3) A step of feeding the multilayer film held by the first chill roll in the above step (2) from the first chill roll to the next rotating roll. A method including these steps can be mentioned.

[0058] The above extruder is not particularly limited, and a known extruder can be appropriately selected and used. Examples of the above extruder include a single-screw extruder, a co-rotating twin-screw extruder, and a counter-rotating twin-screw extruder.

[0059] In order to suppress the deterioration of the raw material resin, it is preferable to purge the inside of the extruder with nitrogen. It is preferable to dry the raw material resin before using it for film formation. It is also preferable to directly transport and charge these resins dried by a dryer from the dryer to the extruder.

[0060] The above coextrusion T-die is not particularly limited, and known coextrusion T-dies can be appropriately selected and used. Examples of the above coextrusion T-die include those of the multi-manifold type, stack plate type, and feed block type.

[0061] The above first chill roll is not particularly limited, and a rotating roll having a known cooling mechanism can be appropriately selected and used. Examples of the above first chill roll include a mirror or matte metal rotating roll having a mechanism for circulating a cooling medium such as water or oil inside the roll.

[0062] The above pressing mechanism is not particularly limited, and a known pressing mechanism can be appropriately selected and used. Examples of the above pressing mechanism include an air knife, air chamber, vacuum chamber, nip roll, and combinations thereof.

[0063] The set temperature of the outlet (lip) of the above coextrusion T-die in the above step (1) can be appropriately selected from the viewpoints of stably performing the step of continuously coextruding the molten multi-layer film and suppressing the deterioration of the raw material resin. From the viewpoint of stably performing the step of continuously coextruding the molten multi-layer film, the set temperature is usually 200 °C or higher, preferably 220 °C or higher, more preferably 230 °C or higher. On the other hand, from the viewpoint of suppressing the deterioration of the raw material resin, it may be usually 300 °C or lower, preferably 280 °C or lower, more preferably 260 °C or lower.

[0064] The surface temperature of the first chill roll can be appropriately selected from the viewpoints of ensuring that the multilayer film is completely cooled and solidified when the multilayer film is sent from the first chill roll to the next rotating roll in the above step (3), and preventing condensation from occurring on the surface of the first chill roll. From the viewpoint of ensuring that the multilayer film is completely cooled and solidified when the multilayer film is sent from the first chill roll to the next rotating roll in the above step (3), the surface temperature of the first chill roll is usually 80°C or lower, preferably 60°C or lower, more preferably 50°C or lower. On the other hand, from the viewpoint of preventing condensation from occurring on the surface of the first chill roll, although it depends on the temperature and humidity of the film-forming environment, it is usually 15°C or higher, preferably 20°C or higher, more preferably 25°C or higher, and even more preferably 30°C or higher.

[0065] When using a nip roll as the pressing mechanism, it is preferable to use one having a mechanism for controlling the surface temperature of the nip roll. In this case, the surface temperature of the nip roll can be appropriately selected in consideration of the material of the surface of the nip roll from the viewpoints of suppressing and preventing troubles such as the adhesion of the molten multilayer film to the nip roll, and preventing condensation from occurring on the surface of the nip roll. From the viewpoint of suppressing and preventing troubles such as the adhesion of the molten multilayer film to the nip roll, the surface temperature of the nip roll is usually 80°C or lower, preferably 70°C or lower, more preferably 60°C or lower, although it depends on the material of the surface of the nip roll. On the other hand, from the viewpoint of preventing condensation from occurring on the surface of the nip roll, although it depends on the temperature and humidity of the film-forming environment, it is usually 15°C or higher, preferably 20°C or higher, more preferably 25°C or higher, and even more preferably 30°C or higher.

[0066] The above step (3) is a step of sending out the multilayer film pressed against and held by the first chill roll in the above step (2) to the next rotating roll. By pressing and holding the multilayer film in a molten state against the first chill roll, it can be ensured that the multilayer film is completely cooled and solidified when it is sent to the next rotating roll.

[0067] Figure 3 is a conceptual diagram of the film forming apparatus used in the examples. The film forming apparatus includes a coextrusion T-die 1 of a two-component three-layer multi-manifold type, an extruder 2 for both outer layers, an extruder 3 for the intermediate layer, and a winding device having a mechanism for nipping with a first chill roll (mirror-finished metal roll) 5 and a nip roll (matte silicone rubber roll) 6. (1) The raw material resins for both outer layers are continuously coextruded from the coextrusion T-die 1 by the extruder 2, and the raw material resin for the intermediate layer is continuously coextruded by the extruder 3 as a two-component three-layer molten multilayer film 4. (2) The molten multilayer film 4 extruded in the above step (1) is nipped by the nip roll 6 and pressed against and held by the rotating first chill roll 5. (3) The multilayer film 4 held by the first chill roll 5 in the above step (2) is sent out from the first chill roll 5 to the next rotating roll 7, and the multilayer film 8 is formed.

[0068] 3. Film for semiconductor manufacturing process: The semiconductor manufacturing process film of the present invention includes the multilayer film of the present invention. The semiconductor manufacturing process film of the present invention is usually produced by forming an adhesive layer directly or via an anchor coat on one side of the multilayer film of the present invention as a film base material and then slitting it to a desired width.

[0069] Examples of the adhesive for forming the adhesive layer include acrylic adhesives such as poly(alkyl (meth)acrylate) and copolymers of alkyl (meth)acrylate and other monomers copolymerizable with (meth)acrylic acid such as (meth)acrylic acid, natural rubbers, rubber adhesives such as butyl-isoprene rubber, polyurethane adhesives, polyester adhesives, polystyrene adhesives, and silicone adhesives.

[0070] In one preferred embodiment, the above-mentioned adhesive may be curable by heat treatment or active energy ray irradiation to reduce the adhesive strength. By reducing the adhesive strength, when peeling the semiconductor manufacturing process film from the workpiece, there will be no adhesive residue and it can be easily peeled off cleanly. Also, the amount of static electricity generated when peeling the semiconductor manufacturing process film from the workpiece can be suppressed. Examples of the adhesive capable of reducing the above-mentioned adhesive strength include adhesives having two or more reactive functional groups (such as amino group, vinyl group, epoxy group, methacryloxy group, acryloxy group, and isocyanate group, etc.) in one molecule, and adhesive compositions of such adhesives with at least one of isocyanate-based curing agents, photopolymerization initiators, and organic peroxides, etc.

[0071] In one preferred embodiment, the above-mentioned adhesive may be excellent in transparency from the viewpoint of sufficiently ensuring the transparency required for the semiconductor manufacturing process film, for example, the visibility during laser marking. Here, the "adhesive excellent in transparency" means an adhesive having a visible light transmittance of usually 50% or more, preferably 70% or more, more preferably 80% or more, and still more preferably 85% or more. Here, the visible light transmittance can be calculated as the ratio of the integrated area of the transmittance spectrum of the adhesive measured using a spectrophotometer "Solid Spec-3700" (trade name) of Shimadzu Corporation and a quartz cell with an optical path length of 10 mm at wavelengths of 380 to 780 nanometers to the integrated area of the transmittance spectrum assuming that the transmittance in the entire range of wavelengths of 380 to 780 nanometers is 100%.

[0072] In one preferred embodiment, the above-mentioned adhesive may be an adhesive having antistatic properties. The surface resistivity of the adhesive layer formed using the adhesive having antistatic properties is usually 1×10 6 ~1×10 11 Ω / □, preferably 1×10 7 ~1×10 10 Ω / □, more preferably 1×10 8 ~1×109 It may be Ω / □. Examples of the pressure-sensitive adhesive having the antistatic property include the pressure-sensitive adhesives disclosed in, for example, JP-A-2007-191532, JP-A-2008-007702, JP-A-2009-242745, and WO 2015 / 030186.

[0073] As the pressure-sensitive adhesive, one or a mixture of two or more of these can be used.

[0074] The method for forming the pressure-sensitive adhesive layer using the pressure-sensitive adhesive is not particularly limited, and a known web coating method can be appropriately selected and used. From the viewpoint of coating a paint with good productivity by a roll-to-roll method, for example, methods such as rod coating, roll coating, gravure coating, reverse coating, kiss reverse coating, and die coating are preferable.

[0075] The thickness of the pressure-sensitive adhesive layer is not particularly limited, and can be appropriately selected in consideration of the specific type of the target semiconductor manufacturing process film, its usage mode, and the properties of the pressure-sensitive adhesive used. The thickness of the pressure-sensitive adhesive layer may usually be 1 to 30 μm, preferably 5 to 25 μm, more preferably about 10 to 20 μm.

Examples

[0076] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto.

[0077] Measurement method In the following tests (a) to (c), after the samples were conditioned for 16 hours or more in an environment of a temperature of 23 ± 2°C and a humidity of 50 ± 10%, the tests were conducted in the same temperature and humidity environment unless otherwise specified.

[0078] (a) Tensile test: (a-1) Measurement of stress-strain curve in the machine direction: In accordance with JIS K7127:1999, using the tensile testing machine "Autograph AGS-1kNG (trade name)" of Shimadzu Corporation, samples were punched out from a multilayer film into the shape of test piece type 1B (Figure 3 of this JIS standard) of the above standard, with the machine direction being the tensile direction. A tensile test was conducted under the condition of a tensile speed of 200 mm / min to obtain a stress-strain curve in the machine direction.

[0079] (A-2) Measurement of the stress-strain curve in the transverse direction: A tensile test was conducted in the same manner as in the above (A-1) except that samples were punched out from the multilayer film with the transverse direction being the tensile direction, and a stress-strain curve in the transverse direction was obtained.

[0080] (A-3) Calculation of the tensile stress at strain (unit: MPa): In accordance with item 10.1 of JIS K7161-1:2014, from the obtained stress-strain curve in the machine direction, the tensile stress at 5% strain in the machine direction (described as "5% MD" in the table), the tensile stress at 10% strain in the machine direction (described as "10% MD" in the table), the tensile stress at 25% strain in the machine direction (described as "25% MD" in the table), and the tensile stress at 100% strain in the machine direction (described as "100% MD" in the table) were calculated. Similarly, from the obtained stress-strain curve in the transverse direction, the tensile stress at 5% strain in the transverse direction (described as "5% CD" in the table), the tensile stress at 10% strain in the transverse direction (described as "10% CD" in the table), the tensile stress at 25% strain in the transverse direction (described as "25% CD" in the table), and the tensile stress at 100% strain in the transverse direction (described as "100% CD" in the table) were calculated.

[0081] The tensile stress at 5% strain measured by the method of the above test (A) tensile test may preferably be 6.0 MPa or less, more preferably 5.0 MPa or less, and still more preferably 4.0 MPa or less in both the machine direction and the transverse direction from the viewpoint of flexibility.

[0082] The 10% tensile stress measured by the method of the above test (a) tensile test may preferably be 7.0 MPa or less, more preferably 6.0 MPa or less, and still more preferably 5.0 MPa or less in both the machine direction and the transverse direction from the viewpoint of flexibility.

[0083] The 25% tensile stress measured by the method of the above test (a) tensile test may preferably be 8.0 MPa or less, more preferably 7.0 MPa or less, and still more preferably 6.0 MPa or less in both the machine direction and the transverse direction from the viewpoint of flexibility.

[0084] The 100% tensile stress measured by the method of the above test (a) tensile test may preferably be 8.0 MPa or less, more preferably 7.0 MPa or less, and still more preferably 6.0 MPa or less in both the machine direction and the transverse direction from the viewpoint of flexibility.

[0085] The difference between the 25% tensile stress and the 100% tensile stress measured by the method of the above test (a) tensile test (25% tensile stress - 100% tensile stress) may preferably be 0.5 MPa or less, more preferably 0.4 MPa or less, still more preferably -0.5 to 0.3 MPa, and most preferably -0.3 to 0.2 MPa from the viewpoint of suppressing necking of the film in the expand process.

[0086] The ratio of the machine direction tensile stress to the transverse direction tensile stress measured by the method of the above test (a) tensile test may preferably be 0.80 to 1.20, more preferably 0.90 to 1.10 for any of 5%, 10%, 25%, and 100% from the viewpoint of enabling the film to be uniformly stretched in the expand process.

[0087] (b) Heat seal start temperature (heat resistance): It was measured with reference to the heat seal strength test in 7.4 of JIS Z1707:2019. Using a heat seal bar calibrated by a surface thermometer, the glossy surfaces (the surfaces on the 5th side of the first chill roll) of two sample pieces taken from the multilayer film were heat sealed under several conditions with a seal area of 15 mm × 10 mm, a seal pressure of 0.20 MPa, a seal time of 1 second, and a seal temperature such that the heat seal start temperature could be interpolated. At this time, the long side of the test piece was made parallel to the machine direction. After the heat-sealed sample was conditioned for 16 hours or more in an environment of temperature 23 ± 2°C and humidity 50 ± 10%, a T-peel test was conducted under the condition of a peel rate of 200 mm / min in the same environment, the peel strength at each seal temperature was measured, and a seal temperature - peel strength curve was created. From the obtained seal temperature - peel strength curve, the temperature at which the peel strength becomes 300 g / 15 mm was defined and calculated as the heat seal start temperature.

[0088] The heat seal start temperature measured by the method of the above test (b) heat seal start temperature (heat resistance) may preferably be 140°C or higher, more preferably 145°C or higher, and still more preferably 150°C or higher from the viewpoint of heat resistance.

[0089] (c) Blocking strength (blocking resistance): The glossy surfaces (the surfaces on the 5th side of the first chill roll) of two sample pieces with a size of 30 cm in the machine direction and 12 cm in the transverse direction taken from the multilayer film were overlapped so that each piece of both samples substantially coincided, set in a jig with a contact area of 10 × 10 cm, and a load of 36 g / cm 2, it was blocked under the conditions of a temperature of 60°C and for 3 hours. A conceptual diagram of the state in which two sample pieces were stacked on the jig is shown in Fig. 4. When the view from above is taken as a plan view, Fig. 4(a) is a right side view and Fig. 4(b) is a bottom view. On the surface of the lower metal plate 11 with a length and width of 15 cm × 15 cm and a thickness of 3 mm, a lower silicone rubber sheet 12 with a length and width of 10 cm × 10 cm and a thickness of 1 mm, a stack of two sample pieces 13, an upper silicone rubber sheet 14 with a length and width of 10 cm × 10 cm and a thickness of 1 mm, and an upper metal plate 15 with a length and width of 15 cm × 15 cm and a thickness of 3 mm are set in this order so that each side is substantially parallel. A weight 16 is placed on the surface of the upper metal plate 15. After blocking, the stack of two sample pieces 13 was taken out from the jig, conditioned for 16 hours or more in an environment of a temperature of 23 ± 2°C and a humidity of 50 ± 10%, and then, in the same environment, a T-peel test was performed under the condition of a peel rate of 20 mm / min, and the peel strength was measured. At this time, a load cell with a rated capacity of 2 Kg was used.

[0090] The blocking strength measured by the method of the above test (h) blocking strength (blocking resistance) may preferably be 0.4 N / 10 cm or less, more preferably 0.3 N / 10 cm or less, and still more preferably 0.25 N / 10 cm or less from the viewpoint of blocking resistance.

[0091] Raw materials used (A) Polypropylene: (A-1) Propylene homopolymer "Novatec MA1B (trade name)" of Nippon Polypropylene Corporation, melt mass flow rate (230°C, 21.18 N) 21 g / 10 min, melting point 162°C, melting enthalpy 104 J / g. (A-2) Propylene homopolymer "Prime Polypro F-704NP (trade name)" of Prime Polymer Co., Ltd., melt mass flow rate (230°C, 21.18 N) 7.0 g / 10 min, melting point 161°C, melting enthalpy 103 J / g. (A-3) Prime Polymer Co., Ltd.'s propylene-ethylene random copolymer "Prime Polypro F-724NPC (trade name)", melt mass flow rate (230 °C, 21.18 N) 7.0 g / 10 min, melting point 147 °C, melting enthalpy 94 J / g, content of structural units derived from ethylene 3.2 mol% (2.1 mass%), content of structural units derived from propylene 96.8 mol% (97.9 mass%).

[0092] (A’) Other polypropylenes: (A’-1) Prime Polymer Co., Ltd.'s propylene-ethylene random copolymer "Prime Polypro F-730NV (trade name)", melt mass flow rate (230 °C, 21.18 N) 6.2 g / 10 min, melting point 139 °C, melting enthalpy 87 J / g, content of structural units derived from ethylene 5.0 mol% (3.4 mass%), content of structural units derived from propylene 95.0 mol% (96.6 mass%).

[0093] (B) Propylene-based soft polyolefin: (B-1) Mitsui Chemicals, Inc.'s propylene-based soft polyolefin "Tafmer PN2070 (trade name)", melt mass flow rate (230 °C, 21.18 N) 6.0 g / 10 min, melting point 136 °C, melting enthalpy 14 J / g, no melting peak derived from crystalline polyethylene component. According to JP-A-2020-111709, propylene-ethylene-1-butene random copolymer, content of structural units derived from ethylene 15 mol% (10 mass%), content of structural units derived from 1-butene 15 mol% (20 mass%), and content of structural units derived from propylene 70 mol% (70 mass%). (B-2) Mitsui Chemicals, Inc.'s propylene-based soft polyolefin "Tafmer PN2060 (trade name)", melt mass flow rate (230 °C, 21.18 N) 7.0 g / 10 min, melting point 161 °C, melting enthalpy 11 J / g, no melting peak derived from the crystalline polyethylene component. According to JP-A-2019-136911, it is a propylene·ethylene·1-butene random copolymer, with a content of structural units derived from ethylene of 9% by mass (13 mol%), a content of structural units derived from 1-butene of 7% by mass (5 mol%), and a content of structural units derived from propylene of 84% by mass (82 mol%). (B-3) Mitsui Chemicals, Inc.'s propylene-based soft polyolefin (propylene·1-butene copolymer) "Tafmer XM-7070S (trade name)", melt mass flow rate (230 °C, 21.18 N) 7.0 g / 10 min, melting point 75 °C, melting enthalpy 31 J / g, no melting peak derived from the crystalline polyethylene component.

[0094] (B’) Other soft polyolefins: (B’-1) Propylene·ethylene copolymer "Wellnex RFX4V (trade name)" of Japan Polypropylene Corporation, melt mass flow rate (230 °C, 21.18 N) 6.0 g / 10 min, melting point 131 °C, melting enthalpy 55 J / g, having a melting peak derived from the crystalline polyethylene component (peak top temperature in the DSC second melting curve is 91 °C, and the corresponding peak top temperature in the DSC crystallization curve is 75 °C). According to JP-A-2017-100357, it is a propylene·ethylene block copolymer, with a content of structural units derived from ethylene of 29 mol% (21% by mass), and a content of structural units derived from propylene of 71 mol% (79% by mass).

[0095] Example 1 A film-forming apparatus showing a conceptual diagram in Fig. 3, that is, a co-extrusion T-die 1 of a two-component three-layer multi-manifold system, an extruder 2 for both outer layers, an extruder 3 for the intermediate layer, and a take-up device having a mechanism for nipping with a first chill roll (mirror-finished metal roll) 5 and a nip roll (textured silicone rubber roll) 6 is used. The above (A-1) is extruded by the extruder 2 as both outer layers, and the above (B-1) is extruded by the extruder 3 as the intermediate layer. They are continuously co-extruded from the co-extrusion T-die 1 as a two-component three-layer molten multilayer film 4. The extruded molten multilayer film 4 is nipped by the rotating nip roll 6, pressed against and held by the rotating first chill roll 5, and then sent from the first chill roll 5 to the next rotating roll 7 to form a multilayer film 8 with a thickness of 6 μm for each of the both outer layers, a thickness of 88 μm for the intermediate layer, and a total thickness of 100 μm. At this time, the resin temperature at the die outlet was 230°C, the surface temperature of the first chill roll 5 was 25°C, the temperature of the cooling water flowing through the nip roll 6 was 20°C, and the take-up speed was 5 m / min. Annealing treatment was performed at a temperature of 40°C (humidity not controlled) for 24 hours, and after further conditioning at a temperature of 23 ± 2°C and a humidity of 50 ± 10% for 16 hours or more, the above tests (a) to (c) were performed under the same temperature and humidity environment except in the case specifically indicated. The results are shown in Table 1.

[0096] Examples 2 to 9 A multilayer film was formed in the same manner as in Example 1 except that the layer configuration of the multilayer film was changed as shown in Table 1, and the above tests (a) to (c) were performed. The results are shown in Table 1.

[0097]

Table 1

[0098] Fig. 5 shows the stress-strain curve in the machine direction of Example 2, and Fig. 6 shows the stress-strain curve in the transverse direction of Example 2. It was found that the multilayer film of Example 2 had a stress-strain curve that was very similar to that of a film made of a soft polyvinyl chloride resin composition, with the stress remaining almost constant at a strain of about 20 to 120% in both the machine direction and the transverse direction. Therefore, it was considered that the multilayer film of Example 2 had very excellent expandability similar to that of a film made of a soft polyvinyl chloride resin composition.

[0099] Example 10 Using an applicator, a coating material for forming an adhesive layer, which consisted of 333 parts by mass (100 parts by mass in terms of solid content) of the transparent adhesive "Acrybase LKG-1013 (trade name)" of Fujikura Kasei Co., Ltd., 1 part by mass of the isocyanate-based curing agent "CL-201 (trade name)" of Fujikura Kasei Co., Ltd., and 222 parts by mass of ethyl acetate, was applied onto the matte surface (the surface on the nip roll 6 side) of the multilayer film of Example 2 so that the film thickness after drying would be 10 μm, and then dried at a temperature of 85°C to form an adhesive layer, thereby obtaining a semiconductor manufacturing process film.

[0100] The haze of the semiconductor manufacturing process film of Example 10 (measured under the condition of incident light from the glossy surface (the surface on the first chill roll 5 side) of the multilayer film using the turbidity meter "NDH2000 (trade name)" of Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7136:2000) was 6.5%.

[0101] In the multilayer film of the present invention, the problems caused by the plasticizer in the film of the soft polyvinyl chloride resin composition are fundamentally solved by not blending the plasticizer, and it has been found that it has high flexibility and good antiblocking properties. The preferred multilayer film of the present invention further has good expandability and heat resistance, and it has been found that the balance between flexibility, expandability, antiblocking properties, and heat resistance is high. In addition, it has been found that the preferred multilayer film of the present invention has sufficient transparency as a film base material for a semiconductor manufacturing process film. Therefore, it is considered that the multilayer film of the present invention can be suitably used as a film base material for semiconductor manufacturing process films, such as dicing films, backgrinding films, and die attach films.

Brief Description of Drawings

[0102]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Explanation of Signs

[0103] 1: Coextrusion T-die 2: Extruder for both outer layers 3: Extruder for intermediate layer 4: Multilayer film in a molten state 5: First chill roll (mirror-finished metal roll) 6: Nip roll (textured silicone rubber roll) 7: Rotating roll 8: Multilayer film 11: Lower metal plate 12: Lower silicone rubber sheet 13: Two sample pieces stacked together 14: Upper silicone rubber sheet 15: Upper metal plate 16: Weight

Claims

1. A multilayer film comprising: (α1) a first polypropylene layer, (β) a propylene-based soft polyolefin layer, and (α2) a second polypropylene layer, which are directly laminated in this order; said (α1) first polypropylene layer is made of (A1) polypropylene satisfying the following characteristics (a1-1) and (a1-2); said (β) propylene-based soft polyolefin layer is made of (B) propylene-based soft polyolefin satisfying the following characteristic (b-1); said (α2) second polypropylene layer is made of (A2) polypropylene satisfying the following characteristics (a2-1) and (a2-2); said multilayer film: (a1-1) having a melting enthalpy of 90 J / g or more; (a1-2) having a melting point of 145 °C or more; (b-1) having a melting enthalpy of 50 J / g or less; (a2-1) having a melting enthalpy of 90 J / g or more; (a2-2) having a melting point of 145 °C or more.

2. The multilayer film according to claim 1, wherein said (B) propylene-based soft polyolefin satisfies the following characteristics (b-1-2) and (b-2): (b-1-2) having a melting enthalpy of 5 to 30 J / g; (b-2) having a melting point of 130 °C or more.

3. The multilayer film according to claim 1, wherein said (B) propylene-based soft polyolefin shows no melting peak derived from a crystalline polyethylene component in the second melting curve measured by a differential scanning calorimeter.

4. The multilayer film according to claim 1, wherein said (A1) polypropylene satisfies the following characteristics (a1-1-2) and (a1-2-2), and said (A2) polypropylene satisfies the following characteristics (a2-1-2) and (a2-2-2): (a1-1-2) having a melting enthalpy of 95 J / g or more; (a1-2-2) having a melting point of 155 °C or more; (a2-1-2) having a melting enthalpy of 95 J / g or more; (a2-2-2) having a melting point of 155 °C or more.

5. The thickness of said (α1) first polypropylene layer is 1 μm or more; the thickness of said (β) propylene-based soft polyolefin layer is 70% or more of the total thickness of the multilayer film; the thickness of said (α2) second polypropylene layer is 1 μm or more. The multilayer film according to claim 1.

6. The multilayer film according to claim 5, wherein the total thickness of said multilayer film is 50 to 300 μm.

7. The multilayer film according to any one of claims 1 to 6, which is for a film base material of a semiconductor manufacturing process film. **Claim 8** A semiconductor manufacturing process film comprising the multilayer film according to any one of claims 1 to 6.

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