Polyolefin resin film and adhesive sheet using the same

Abstract

To provide a polyolefin-based resin film that is applicable to heating treatment in a process of coating an adhesive layer or the like, generates little foreign material or the like, and has excellent expandability.SOLUTION: A polyolefin-based resin film takes, as at least one surface layer, a layer that contains polyethylene-based resin particles and polyolefin-based resin other than the polyethylene-based resin particles and substantially does not contain an organic slipping agent other than the polyethylene-based resin particles. The maximum projection height of the at least one surface layer is equal to or larger than 2 μm and equal to or smaller than 15 μm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyolefin resin film that is suitable for use as a substrate film for adhesive sheets that fix semiconductors and the like when they are cut and separated to obtain chips, and that can also be used as a substrate film for surface protection films that protect the surface condition of plastic products, glass products, ceramic products, and the like that have been given electrical conductivity, decoration, etc. [Background technology]

[0002] Semiconductor manufacturing processes include a dicing process in which semiconductor wafers such as silicon or gallium arsenide or semiconductor wafer chips are cut and separated after a die bonding process in which they are laminated onto plastic, glass, ceramic, etc. In the dicing process, to fix the semiconductor wafer or substrate and prevent misalignment during dicing by a blade or the like and to prevent chips from scattering, a dicing tape is used, which is an adhesive sheet having a resin film base and an adhesive layer on at least one side.

[0003] Dicing tape also needs to be expandable during the expanding process, which widens the spaces between individual chips using a suction jig or other tool to make them easier to pick up. It also needs to be flexible to reduce the load on the tape during the pick-up process, which involves extracting the chips.

[0004] For example, a multilayer film is known in which a resin composition consisting of a vinyl aromatic hydrocarbon or a hydrogenated conjugated diene hydrocarbon copolymer and a polypropylene resin is laminated (for example, Patent Document 1, etc.). However, although such multilayer films generally have satisfactory expandability, they are not necessarily satisfactory in terms of deflection due to the weight of the wafer.

[0005] Also known are substrate films in which a resin layer containing a friction reducer such as silicone oil, silicone resin powder, or tetrafluoroethylene resin powder is provided on a substrate of an ethylene-based resin such as ethylene-ethyl acrylate (EEA) or ethylene vinyl alcohol (EVA) (see, for example, Patent Document 2). While such substrate films generally have satisfactory expandability and flexibility, there are concerns about the contamination of chips by silicone oil and the environmental impact of hydrogen fluoride gas generated by tetrafluoroethylene resin powder during incineration.

[0006] Furthermore, a substrate film has been disclosed in which friction is reduced and expandability is ensured by providing a layer containing silica particles on the side of an ethylene resin film opposite to the side on which a pressure-sensitive adhesive layer or the like is provided (for example, Patent Document 3, etc.). However, silica particles generally have a high specific gravity and tend to aggregate easily, which raises concerns about difficulties in controlling foreign matter such as fisheyes. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-94418 [Patent Document 2] Japanese Patent Application Publication No. 7-221052 [Patent Document 3] Japanese Patent Application Publication No. 11-189755 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide a polyolefin-based resin film that is suitable primarily as a base film for adhesive sheets that fix semiconductors and the like when they are cut and separated to obtain chips, and that can also be used as a base film for surface protection films that protect the conductive, decorated, etc. surfaces of plastic products, glass products, ceramic products, etc., and that can withstand heat treatment in the coating process of adhesive layers, etc., generates little foreign matter, and has excellent expandability. [Means for solving the problem]

[0009] As a result of extensive research to solve the above problems, the inventors discovered that by arranging polyethylene resin particles on at least one surface layer to form specific surface irregularities, it is possible to obtain a polyolefin resin film that has expandability, reduces deflection due to the weight of a wafer or the like, and does not cause defects in the base film during heat treatment in the coating process of an adhesive layer or the like, and thus completed the present invention.

[0010] That is, the present invention comprises the following: 1. A polyolefin resin film comprising polyethylene resin particles and a polyolefin resin other than the polyethylene resin particles, with at least one surface layer being a layer that is substantially free of organic slip agents other than the polyethylene resin particles, wherein the maximum protrusion height of the at least one surface layer is 2 μm or more and 15 μm or less. 2. The polyolefin resin film described in 1 above, wherein the polyethylene resin forming the polyethylene resin particles has a viscosity average molecular weight of 1.5 million or more and a melting point of 150°C or less according to JIS K 7121:2012 "Method for measuring transition temperature of plastics." 3. A polyolefin resin film as described in the above item 1 or 2, in which the coefficient of static friction between surface layers having a maximum projection height of 2 μm or more and 15 μm or less is 0.9 or less. 4. A polyolefin resin film according to any one of items 1 to 3 above, wherein the polyolefin resin other than the polyethylene resin particles is a homopolymer of an ethylene monomer, a copolymer containing 80% by mass or more of linear low-density polyethylene and one or more α-olefins as comonomers, or a mixture containing these. 5. A polyolefin resin film according to any one of items 1 to 3 above, wherein the polyolefin resin other than the polyethylene resin particles is a polypropylene homopolymer, a copolymer containing 70% by mass or more of propylene and one or more α-olefins as comonomers, or a mixture containing these. 6. The polyolefin resin film according to the fourth or fifth aspect above, wherein the polyolefin resin other than the polyethylene resin particles further contains at least 5% by mass of an ethylene-acrylic acid ester copolymer. 7. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on at least one surface of the polyolefin resin film described in any one of items 1 to 6 above. [Effects of the Invention]

[0011] The polyolefin resin film of the present invention has flexibility that allows it to exhibit appropriate expandability because it uses a polyolefin resin, and since polyethylene resin particles are disposed on at least one surface layer, friction is reduced, making it possible to obtain more uniform expandability. In addition, since it does not contain substantially any organic slip agent other than the polyethylene resin particles, it is easy to control environmental impact and foreign matter. Therefore, the polyolefin resin film of the present invention is mainly suitable as a substrate film for pressure-sensitive adhesive sheets that fix semiconductors and the like when cutting and separating them to obtain chips. In addition, it can withstand heat treatment in the coating process of pressure-sensitive adhesive layers, etc., generates little foreign matter, and has excellent expandability, making it possible to provide a polyolefin resin film that can also be used as a substrate film for surface protection films that protect the surfaces of plastic products, glass products, ceramic products, etc., which have been given electrical conductivity or decoration. DETAILED DESCRIPTION OF THE INVENTION

[0012] The polyolefin resin film of the present invention has, for example, the compounds and structures described below.

[0013] <Surface texture> At least one surface layer of the polyolefin resin film of the present invention contains polyethylene resin particles, and the surface of the surface layer preferably has a maximum protrusion height of 2 μm or more, and preferably 15 μm or less. A maximum protrusion height of 2 μm or more is preferable because it can reduce surface friction. More preferably, the maximum protrusion height of the surface is 3 μm or more. On the other hand, a maximum protrusion height of 15 μm or less is preferable because it can provide a high quality appearance without flickering. More preferably, the maximum protrusion height of the surface is 10 μm or less. The number of protrusions of 15 μm or more is 1 / 0.2 mm. 2 It is preferable that the number of particles is 0.5 or less per mm. 2 More preferably, it is:

[0014] In the polyolefin resin film of the present invention, the static friction coefficient on the surface of at least one surface layer containing polyethylene resin particles is preferably 0.10 or more, more preferably 0.15 or more. Also, it is preferably 0.7 or less, more preferably 0.5 or less. The static friction coefficient is the static friction coefficient between at least one surface layer containing polyethylene resin particles.

[0015] A static friction coefficient of 0.10 or more is preferred because there is no risk of roll sway or winding slippage occurring during the film-forming process or processing step. A static friction coefficient of 0.7 or less is preferred because there is no risk of problems such as wrinkles occurring, and when used as a base film for a pressure-sensitive adhesive sheet that fixes semiconductors and the like when cutting and separating them to obtain chips, uniform expandability is obtained during the expanding step.

[0016] <Polyethylene resin particles> In the present invention, it is preferable that the viscosity average molecular weight of the polyethylene resin particles contained in at least one surface layer is 1,500,000 or more, and that the peak temperature, as measured by JIS K 7121:2012 "Measurement method for transition temperature of plastics," is 130°C or more and 150°C or less, since a high melting point may cause filter clogging during melt extrusion, and a low melting point may cause the particles to flatten during melt extrusion and not function as protrusions.

[0017] In the present invention, if the average particle size of the polyethylene resin particles contained in the surface layer is small, they may not function as protrusions, and if it is large, they may cause foreign matter or filter clogging during melt extrusion, so the average particle size is preferably 2 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more, more preferably 15 μm or less, and even more preferably 10 μm or less.

[0018] In addition, it is preferable that the film does not contain more than 1% by mass of coarse particles of 25 μm or more. More preferably, it does not contain any coarse particles of 25 μm or more. Even if the average particle size is 15 μm or less, if the content of particles of 25 μm or more (hereinafter referred to as coarse particles) is less than 1% by mass, there will be no large protrusions on the film surface due to these coarse particles, and so-called flickering will not occur on the film surface, which is preferable.

[0019] The particle size distribution was determined in accordance with JIS Z 8832:2010 "Method for measuring particle size distribution, electrical detection zone method," and the median diameter at which the occurrence frequency was 50% was taken as the average particle size. The amount of coarse particles was also determined from the particle size distribution.

[0020] The average particle size of particles in a film can also be estimated by measuring it as follows, using data from the method conforming to JIS Z 8832:2010. For example, particles in a cross section of the film are observed using a scanning electron microscope, and the average value of 50 particles is used as the average particle size. The shape of the particles is not particularly limited, and spherical particles and irregular, non-spherical particles can be used. In the measurement method using microscope observation, the particle size of irregular particles can be calculated as the circle-equivalent diameter. The circle-equivalent diameter is calculated by dividing the area of ​​the observed particles by π, calculating the square root, and then multiplying it by two.

[0021] The viscosity average molecular weight of the polyethylene constituting the polyethylene resin particles in the present invention is preferably 1.5 million or more, more preferably 1.6 million or more, and even more preferably 1.7 million or more, and is preferably 2.5 million or less, more preferably 2.2 million or less, and even more preferably 2 million or less.

[0022] Although the reason for this is not clear, it is presumed that if the viscosity average molecular weight is within this range, the difference in molecular weight between the polyethylene resin particles and the other polyolefin resins that make up the base film is very large, so the molecules do not mix, and the shape of the polyethylene resin particles can be maintained even in the film obtained by melting, mixing, and extruding.Furthermore, aggregation due to fusion or adhesion between particles is unlikely to occur, so protrusions commensurate with the particle size can be formed on the film surface, just like inorganic particles.

[0023] Furthermore, when the viscosity-average molecular weight of the polyethylene resin particles is 1,500,000 or more, they are less likely to decompose due to heat or shear during melting or mixing, and changes in particle shape due to fusion and aggregation or partial compatibility with the base resin are less likely to occur. This makes it easier to form appropriate protrusions, maintains the function as an antiblocking agent, and maintains the appearance such as transparency and the mechanical strength of the film, which is preferable.

[0024] On the other hand, even if the viscosity average molecular weight is 2.5 million or less, the particle shape is easily maintained when the film is formed by melting, mixing, and then extruding, and protrusions on the film surface can be effectively formed. Regarding viscosity-average molecular weight, it is possible to apply the value calculated from the intrinsic viscosity and the Mark-Houwink-Sakurada equation in accordance with JIS K7252:2016 "Plastics - Determination of average molecular weight and molecular weight distribution of polymers by size exclusion chromatography."

[0025] In the present invention, the content of polyethylene resin particles in the surface layer varies depending on the average particle size and the thickness of the surface layer, but is preferably approximately 0.5% by mass or more, more preferably 1.0% by mass or more. Also, it is preferably 3.0% by mass or less. When the amount of polyethylene resin particles added is 0.5% by mass or more, it is easy to make the maximum protrusion height of at least one surface layer 2 μm or more, which is preferable. On the other hand, when it is 3.0% by mass or less, there is no risk of lip contamination during extrusion, and there is no risk of poor appearance, which is preferable.

[0026] <Structure> The polyolefin resin film of the present invention can have a layer structure such as A: single layer, A / B, A / C, A / B / A, or A / B / C using the following resins, and it is also possible to provide a layer of another polyolefin resin between the layers. Layers A and C: Layers containing polyethylene resin particles Layer B: Layer containing no polyethylene resin particles

[0027] <Thickness> The polyolefin resin film of the present invention preferably has an overall thickness of 60 μm or more, more preferably 80 μm or more, and preferably 180 μm or less from the viewpoint of handling.

[0028] When the total thickness of the polyolefin resin film of the present invention is 60 μm or more, it has a firm feel, and further, when used as a base film for an adhesive sheet to fix semiconductors and the like when cutting and separating them to obtain chips, it is preferable because it has uniform expandability.

[0029] When a layer containing polyethylene resin particles is disposed as at least one surface layer of the polyolefin resin film of the present invention, the thickness of the surface layer is preferably at least half the average particle size of the polyethylene resin particles, and is preferably equal to or smaller than the average particle size of the polyethylene resin particles, more preferably at least 1 μm smaller than the average particle size of the polyethylene resin particles.

[0030] When the thickness of the surface layer containing the polyethylene-based resin particles is at least half the average particle diameter of the polyethylene-based resin particles, lip staining during extrusion is not generated and there is no risk of poor appearance, which is preferable. On the other hand, when the thickness of the surface layer containing the polyethylene-based resin particles is equal to or less than the average particle diameter of the polyethylene-based resin particles, a suitable maximum protrusion height can be obtained on the surface layer, which is preferable.

[0031] <Polyolefin resin> The surface layer located on at least one side of the polyolefin resin film of the present invention preferably contains the polyethylene resin particles as described above, and the polyolefin resin forming the surface layer preferably contains a homopolymer of an ethylene monomer, a copolymer of 80% by mass or more of linear low-density polyethylene and one or more α-olefins as comonomers, an olefin resin with improved compatibility with polar rubber, or a mixture containing at least two of these. Low-density polyethylene produced with a metallocene catalyst is preferred because it minimizes bleed-out of low-molecular-weight substances. In the case of a copolymer, a linear low-density polyethylene of 80% by mass or more is preferred because it is less likely to stick to process rolls and less likely to wrinkle, even when heated for drying during the application process of an adhesive or the like.

[0032] Furthermore, the surface layer located on at least one side of the polyolefin resin film preferably contains the polyethylene resin particles as described above and also contains a polypropylene homopolymer, a copolymer containing 70% by mass or more of propylene and one or more α-olefins as comonomers, or a mixture containing these. When the polyolefin resin used in the polyolefin resin film of the present invention contains 70% by mass or more of propylene, it is preferable because the film is less likely to stick to process rolls and is less likely to wrinkle even when heated for drying in the coating process of an adhesive or the like.

[0033] Examples of the α-olefin in the polyolefin resin used mainly in the surface layer of the polyolefin resin film of the present invention include propylene, 1-butene, 1-hexene, 1-decene, 1-octene, 4-methyl-1-pentene, 1-nonene, and 4-methyl-1-hexene. From the viewpoint of improving break resistance and expandability, butene-1, pentene-1, hexene-1, and 4-methyl-1-pentene are preferred.

[0034] Furthermore, the surface layer located on at least one side of the polyolefin resin film preferably contains, in addition to the polyolefin resins described above, an ethylene-acrylic acid ester copolymer in an amount of at least 5% by mass relative to the polyolefin resin other than the polyethylene resin particles forming the surface layer, from the viewpoint of improving expandability, and preferably 25% by mass or less from the viewpoint of preventing precipitation of low-molecular-weight substances, etc. Furthermore, it is preferable to introduce an acrylic acid ester, exemplified by methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, into the position where the alkyl group of the α-olefin is bonded, instead of the alkyl group.

[0035] Additionally, the polyolefin resin film of the present invention can contain, to the extent that the intended purpose is not impaired, known inorganic compound particles such as silica, talc, zeolite, and aluminum borate, as well as organic compound particles such as polymethyl methacrylate, melamine formalin resin, melamine urea resin, and polyester resin. However, due to concerns about contamination due to bleeding, organic slip agents, such as hydrocarbon-based agents such as liquid paraffin, paraffin wax, and synthetic polyethylene wax, aliphatic and higher alcohol-based agents such as stearic acid and stearyl alcohol, and fatty acid amide-based agents such as stearic acid amide, oleic acid amide, and erucic acid amide, are preferably substantially free of these agents. In the present invention, "substantially free of organic slip agents" means that the total amount of extractable material, as determined by Soxhlet extraction with chloroform in accordance with JIS K6229:2015 "Determination of rubber-solvent extractables (quantitative)," is 1% by mass or less. For each organic slip agent, 0.5% by mass or less, preferably 0.1% by mass or less, is preferred, and it is preferable that the amount is not detectable.

[0036] The melt flow rate (MFR) of the polyolefin resin used in the present invention, as determined in accordance with JIS K6921:2010 "Plastics - Polypropylene (PP) materials for molding and extrusion - Part 2: Methods for preparing test specimens and determining properties," is preferably 1 to 20 g / 10 min, more preferably 2 to 8 g / 10 min, depending on the width and thickness of the target sheet. An MFR of 1 g / 10 min or more is preferred because it facilitates extrusion. An MFR of 20 g / 10 min or less is preferred because it minimizes fluctuations in the thickness of the sheet.

[0037] The polyolefin resin raw material used in the present invention is not particularly limited and may be derived from petroleum or plants, but is preferably derived from plants from an environmental point of view.

[0038] <Polyolefin resin film production> The polyolefin resin film used in the present invention can be obtained by extrusion molding, calendar molding, or the like.

[0039] For extrusion molding, the resin is extruded into a sheet form from a T-die through a single-screw or twin-screw extruder. The extruded sheet is then pressed against the surface of a metal roll through which cooling water or oil circulates using an air knife, air chamber, hard rubber roll, steel belt, metal roll, or the like, and cooled and solidified. Alternatively, the sheet can be cooled and solidified by sandwiching both sides of the sheet between steel belts. In addition to the extruder used to form the polyolefin resin sheet of the present invention, a heterogeneous multilayer sheet can also be obtained by using an extruder for recycled resins, etc., and a feed block or multi-manifold.

[0040] The polyolefin resin film of the present invention can be stretched uniaxially or biaxially as necessary. If the total stretching ratio is too high, the expandability may be impaired, and if it is too low, thickness fluctuations may become large. Therefore, it is preferable that the stretching ratio be 3 to 12 times in both the longitudinal and transverse directions.

[0041] <Adhesive> When the present invention is applied to an adhesive sheet for fixing semiconductors and the like when cutting and separating them to obtain chips, or to a surface protection film for protecting the surface condition of plastic products, glass products, ceramic products, etc. that have been subjected to electrical conductivity or decoration, it is preferable to provide an adhesive layer on a polyolefin-based resin film.

[0042] Examples of adhesives that constitute the adhesive layer include (meth)acrylic adhesives, silicone adhesives, urethane adhesives, olefin adhesives, and styrene adhesives. Among these, (meth)acrylic adhesives are preferred because they allow for easy adjustment of adhesive strength.

[0043] Examples of the (meth)acrylic polymer contained in the (meth)acrylic pressure-sensitive adhesive include a homopolymer of a (meth)acrylic acid ester compound and a copolymer of a (meth)acrylic acid ester compound and a comonomer. Examples of the (meth)acrylic acid ester compound include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate. These (meth)acrylic acid ester compounds may be used alone or in combination of two or more. Examples of comonomers constituting the (meth)acrylic copolymer include vinyl acetate, (meth)acrylonitrile, (meth)acrylamide, styrene, (meth)acrylic acid, itaconic acid, (meth)acrylamide, methylol (meth)acrylamide, and maleic anhydride. These comonomers may be used alone or in combination of two or more.

[0044] The adhesive agent mentioned above can be a radiation-crosslinked adhesive agent whose adhesive strength is reduced by radiation. The adhesive layer formed by this method has its adhesive strength significantly reduced by crosslinking due to radiation exposure, making it easier to pick up the chip.

[0045] Such radiation crosslinkable pressure sensitive adhesives use a pressure sensitive adhesive such as the above (meth)acrylic pressure sensitive adhesive, and a resin containing a crosslinkable compound, a photopolymerization initiator, and the like. Examples of the crosslinkable compound include monomers, oligomers, and polymers that can be crosslinked by radical polymerization. Examples include esters of (meth)acrylic acid and polyhydric alcohols, such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; ester (meth)acrylate oligomers; and isocyanurates or isocyanurate compounds, such as 2-propenyldi-3-butenyl cyanurate, 2-hydroxyethylbis(2-(meth)acryloxyethyl)isocyanurate, and tris(2-methacryloxyethyl)isocyanurate. The content of these crosslinkable compounds varies depending on the compound selected, but from the viewpoint of adjusting the viscosity of the solution during application and adjusting the adhesive strength, it is preferably 5 to 100 parts by mass, and more preferably 10 to 50 parts by mass, per 100 parts by mass of the adhesive.

[0046] The photopolymerization initiator may be any compound that is cleaved by irradiation to generate radicals, and examples thereof include benzoin alkyl ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; aromatic ketones such as benzil, benzoin, benzophenone, and α-hydroxycyclohexyl phenyl ketone; aromatic ketals such as benzil dimethyl ketal; and polyvinyl benzophenone; and thioxanthones such as chlorothioxanthone, dodecylthioxanthone, dimethylthioxanthone, and diethylthioxanthone.

[0047] The thickness of the adhesive layer made of the above adhesive is not particularly limited, but from the viewpoint of adhesive strength and uniformity of the thickness of the adhesive layer, it is preferably 1 to 50 μm, more preferably 3 to 30 μm. [Example]

[0048] The present invention will be described in more detail below with reference to examples. Note that the present invention is not limited to the following examples, and modifications can be made within the scope of the present invention, and all such modifications are included in the technical scope of the present invention.

[0049] The physical properties in the examples were evaluated as follows.

[0050] (1) Film-forming properties (lip stains) After 5 hours of film formation, the state of the die lip and the surface of the film were observed and evaluated according to the following criteria. ◎: No lip stains observed, no abnormalities on the film surface ○: Signs of lip staining are observed, but there is no abnormality on the film surface △: Lip stains can be seen, but there is no abnormality on the film surface ×: Lip staining is evident, and streaks are observed near the staining on the film surface.

[0051] (2) Maximum protrusion height (Rz) Using a contact surface roughness meter (Kosaka Laboratory, Model ET4000A), the surface roughness of a 1mm x 0.2mm measurement surface was measured at three locations on a 3cm x 3cm square film, and the average value was taken as the maximum protrusion height Rz.

[0052] (3) Number of protrusions of 15 μm or more (R15) (pieces / 0.2 mm 2 ) The number of protrusions of 15 μm or more was determined by using a contact surface roughness meter (manufactured by Kosaka Laboratory, model ET4000A) to measure the surface roughness of a 1 mm x 0.2 mm area selected from a 3 cm x 3 cm square film, and the number of protrusions with a height of 15 μm or more was confirmed for three locations, and the average value was taken as the number of protrusions of 15 μm or more, R15.

[0053] (4) Static friction coefficient μs In accordance with JIS P 8147:2010 "Paper and paperboard -- Measurement method for static and dynamic friction coefficients (inclined method)," the static friction coefficient μs was determined as the tangent of the sliding angle between surfaces containing polyethylene resin particles.

[0054] (5) Thickness The value obtained in accordance with JIS K 7130:1999 "Method for measuring thickness of plastic films and sheets (Method A)" ​​was taken as the thickness.

[0055] (6) Expandability The sample olefin resin film was fixed to a 6-inch dicing frame with double-sided tape, and concentric circles of 50 mm and 100 mm diameter were drawn around the center point. The film was then expanded using an expander (stage: temperature 30°C, rising speed 50 mm / min, held for 60 seconds) to achieve an elongation of 20% of the inner diameter of the dicing frame. The following evaluations were made based on the elongation measured at 45° intervals around the concentric circles. ◎: Elongation of 13% or more in all directions, with the maximum difference being less than 2% ○: Elongation of 13% or more in all directions, but with a maximum difference of 2-5% △: 10-13% elongation in some directions, with a maximum difference of 2-5% ×: Elongation is less than 10% in some directions, or the maximum difference is 5% or more

[0056] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0057] The following raw materials were used in the examples and comparative examples. (Polyolefin resin)

[0058] <Resin 1> Sumitomo Chemical Co., Ltd. Sumikathene E FV405 (metallocene catalyst-based LLDPE, density: 924 kg / m 3 , MFR: 3.8 g / 10 min, melting point: 118° C., linear low-density polyethylene: 90 mass % or more) was used as resin 1.

[0059] <Resin 2> Resin 2 was Rexpearl EEA A4250 (ethylene-ethyl acrylate copolymer, ethyl acrylate content 25% by mass, MFR: 5 g / 10 min, melting point: 92° C.) manufactured by Japan Polyethylene Corporation.

[0060] <Resin 3> A pellet-shaped resin 3 was prepared by adding 15% by mass of Mitsui Chemicals' Mipelon (registered trademark) PM200 (ultra-high molecular weight polyethylene particles, average particle diameter 10 μm, melting point 136°C, viscosity-average molecular weight 1.8 million, proportion of particle diameters exceeding 25 μm 0%) to the above resin 1.

[0061] <Resin 4> Resin 4 in pellet form was prepared by adding 15 mass % of spherical silica (average particle diameter 12 μm, proportion of particle diameters exceeding 25 μm being 2%) to the above-mentioned Resin 1.

[0062] <Examples 1 to 11 and Comparative Examples 1 to 3> Using two extruders, a mixture of pellets was kneaded in advance so as to form a two-layer laminate structure, and melt-extruded from a T-die at a resin temperature of 240°C, and cast onto a cooling roll at a temperature of 40°C to obtain sheets of Examples 1 to 11 and Comparative Examples 1 to 3. The thickness, layer structure, resin blending ratio, and evaluation results for Examples 1 to 11 and Comparative Examples 1 to 3 are shown in Table 1.

[0063] [Table 1]

[0064] From Examples 1 to 11, it can be seen that within the range of the material composition and compounding ratio, the polyolefin resin film containing the polyethylene resin particles of the present invention has no abnormalities in film-forming properties, the surface irregularities are within the specified range, there is no foreign body sensation, and the slip properties are good, so that it has expandability and is particularly suitable for use as a substrate for adhesive sheets that fix semiconductors and the like when cutting and separating them to obtain chips.

[0065] Comparing Examples 1 and 2 with Comparative Examples 1 and 2, it is clear that unless particles made of polyethylene resin are used in polyolefin resin films, problems such as an inability to obtain an appropriate protrusion height will occur and expandability will not be obtained.

[0066] Examples 1, 4, 8, 10, and 2, 7, 9, and 11 show that when the maximum protrusion height on the surface of the layer containing particles made of polyethylene-based resin in the polyolefin-based resin film of the present invention increases, signs are observed that film-forming properties are likely to deteriorate, and it is clear that the problem becomes apparent when particles made of polyethylene-based resin are not used, as in Comparative Example 3.

[0067] <Resin 5> Prime Polymer Evolue SP1071C (metallocene catalyst LLDPE, density: 911 kg / m 3 , MFR: 10 g / 10 min, melting point: 101° C., linear low-density polyethylene: 90 mass % or more) was used as resin 5.

[0068] <Resin 6> A pellet-shaped resin 6 was prepared by adding 15% by mass of Mitsui Chemicals' Mipelon (registered trademark) PM200 (ultra-high molecular weight polyethylene particles, average particle diameter 10 μm, melting point 136°C, viscosity-average molecular weight 1.8 million, proportion of particle diameters exceeding 25 μm 0%) to the above resin 5.

[0069] <Resin 7> Sumitomo Chemical Noblen FW836DG3 (homo-polypropylene, density: 900 kg / m 3 , MFR: 7 g / 10 min, melting point: 158°C) was used as resin 5.

[0070] <Resin 8> A pellet-shaped resin 6 was prepared by adding 15% by mass of Mitsui Chemicals' Mipelon (registered trademark) PM200 (ultra-high molecular weight polyethylene particles, average particle diameter 10 μm, melting point 136°C, viscosity-average molecular weight 1.8 million, proportion of particle diameters exceeding 25 μm 0%) to the above resin 7.

[0071] <Examples 12 to 15> Using two extruders, the pellet mixture was kneaded in advance to form a two-layer laminate structure, and melt-extruded from a T-die at a resin temperature of 240°C, and cast onto a cooling roll at a temperature of 40°C to obtain a sheet in the same manner as in Examples 1 to 11 and Comparative Examples 1 to 3. The thickness, layer structure, resin blending ratio, and evaluation results for Examples 12 to 15 are shown in Table 2.

[0072] [Table 2]

[0073] The films of Examples 12 to 15, like the films of Examples 1 and 2, have a surface layer containing polyolefin-based resin and polyethylene-based resin particles, and therefore have good film-forming properties, appropriately controlled surface irregularities, and good slip properties, resulting in expandability. They are particularly suitable as base films for pressure-sensitive adhesive sheets that fix semiconductors and the like when cutting and separating them to obtain chips.

[0074] For Examples 1 to 15 and Comparative Examples 1 to 3, approximately 2 g of sample was collected, cut, and then subjected to Soxhlet extraction with chloroform (extraction for 4 hours). It was confirmed that the extract was 0.6 mass% or less, and solid-state NMR spectrum analysis confirmed that no organic slip agent was detected. [Industrial Applicability]

[0075] The polyolefin resin film of the present invention has flexibility to obtain appropriate expandability because it uses a polyolefin resin in at least one surface layer. Furthermore, since polyethylene resin particles are contained in at least one surface layer, friction is reduced and more uniform expandability can be obtained. Therefore, it is suitable for use as a substrate film for adhesive sheets that fix semiconductors and the like when cutting and separating them to obtain chips, and it can also be used as a substrate film for surface protection films that protect the surface condition of conductive, decorated, etc. on plastic products, glass products, ceramic products, etc. The industrial applicability of the present invention is extremely high.

Claims

1. A polyolefin-based resin film comprising polyethylene-based resin particles and a polyolefin-based resin other than the polyethylene-based resin particles, and having at least one surface layer that is substantially free of organic slip agents other than the polyethylene-based resin particles, The maximum protrusion height of the at least one surface layer is 2 μm or more and 15 μm or less, and The thickness of the surface layer is 6 μm or more, The polyethylene resin particles have an average particle size of 2 μm or more and 15 μm or less, and the content of particles having a size of 25 μm or more in the polyethylene resin particles is less than 1% by mass, the static friction coefficient of the surface of the surface layer containing the polyethylene-based resin particles is 0.10 or more and 0.5 or less; The at least one surface layer comprises the following resin: As the polyolefin resin other than the polyethylene resin particles, low density polyethylene and ethylene-acrylic acid ester copolymers, A polyolefin resin film used in the semiconductor manufacturing process.

2. 2. The polyolefin resin film for use in a semiconductor manufacturing process according to claim 1, wherein the polyethylene resin forming the polyethylene resin particles has a viscosity average molecular weight of 1,500,000 or more and a melting point of 150°C or less according to JIS K 7121:2012 "Method for measuring transition temperature of plastics."

3. 3. The polyolefin resin film for use in a semiconductor manufacturing process according to claim 1, wherein the coefficient of static friction between surface layers having a maximum protrusion height of 2 μm or more and 15 μm or less is 0.9 or less.

4. In at least one surface layer of the polyolefin resin film, the number of protrusions of 15 μm or more is 1 / 0.2 mm ２ 2. The polyolefin resin film for use in a semiconductor manufacturing process according to claim 1, wherein:

5. A pressure-sensitive adhesive sheet for use in a semiconductor manufacturing process, comprising a pressure-sensitive adhesive layer on at least one surface of the polyolefin resin film for use in a semiconductor manufacturing process according to any one of claims 1 to 4.

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