Polyolefin film

Abstract

To provide a polyolefin film with suppressed dipping and poor adhesion under various operating speeds. 【Solution means】A polyolefin film containing a polyolefin resin, wherein the peel strength measured by a 180° peel test on at least one surface is 1.00 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 300 mm / min, 1.60 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 1000 mm / min, and 2.30 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 2500 mm / min.

Description

Technical Field

[0001] The present invention relates to polyolefin films and the like.

Background Art

[0002] Polyolefin films typified by polyethylene films and polypropylene films are excellent in lightness, thermal stability, and mechanical properties, and are widely used as packaging materials and industrial material films. In particular, in recent years, polyolefin films have been widely used in the manufacturing processes of electronic components and electronic substrates, protective materials used for thermosetting resin members such as fiber-reinforced plastics, release materials, etc., by utilizing their excellent peelability, and their utility value is increasing.

[0003] Especially when used as a protective film for a resin layer having adhesiveness, when peeling the polyolefin film from the adherend, it may not peel cleanly, deform the shape of the adherend, or leave peeling marks on the surface of the adherend. In order to solve such problems, techniques for forming appropriate irregularities on the film surface and techniques for adjusting the resin composition of the surface in contact with the adherend to make the peeling force within a certain range have been disclosed (Patent Document 1, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the course of the research, the present inventor has noticed that when a laminate having a protective film is conveyed at the operating speed of the processing step and the protective film is peeled off at a speed lower than the operating speed, problems such as dipping (slip-stick) occurring and a horizontal stripe pattern being formed on the adhesive surface, and the problem that the protective film floats due to poor adhesion occur. And since the operating speed can vary depending on the content of the processing and other factors, the present inventor has focused on suppressing the above problems even in such an environment.

[0006] An object of the present invention is to provide a polyolefin film in which dipping and poor adhesion at various operating speeds are suppressed.

Means for Solving the Problems

[0007] As a result of intensive research in view of the above problems, the present inventor has found that a polyolefin film containing a polyolefin resin, wherein the peel strength measured by a 180° peel test on at least one surface is 1.00 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 300 mm / min, 1.60 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 1000 mm / min, and 2.30 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 2500 mm / min, can solve the above problems. Based on this finding, the present inventor has further conducted research and as a result, completed the present invention. That is, the present invention includes the following aspects.

[0008] Item 1. A polyolefin film containing a polyolefin resin, wherein the peel strength measured by a 180° peel test on at least one surface is 1.00 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 300 mm / min, 1.60 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 1000 mm / min, and 2.30 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 2500 mm / min, a polyolefin film.

[0009] Item 2. The polyolefin film according to Item 1, wherein the peeling force is 0.30 N / 25 mm or more and 4.00 N / 25 mm or less when the peeling speed is 50 mm / min.

[0010] Item 3. The polyolefin film according to Item 1 or 2, wherein the elastic modulus in the thickness direction at 23°C measured by the nanoindentation method of the surface is 2.00 GPa or less.

[0011] Item 4. The polyolefin film according to any one of Items 1 to 3, wherein the polyolefin resin contains a polyethylene resin.

[0012] Item 5. The polyolefin film according to any one of Items 1 to 4, which is a stretched film.

[0013] Item 6. The polyolefin film according to any one of Items 1 to 5, which is a biaxially stretched film.

[0014] Item 7. The polyolefin film according to any one of Items 1 to 6, wherein the thickness is 10 μm or more and 50 μm or less.

[0015] Item 8. A protective film comprising the polyolefin film according to any one of Items 1 to 7.

[0016] Item 9 . Doe The protective film according to Item 8, which is a protective film for a life film resist.

[0017] Item 10. A laminate comprising the polyolefin film according to any one of Items 1 to 7 and another layer.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a polyolefin film in which dipping and poor adhesion at various operating speeds are suppressed.

Modes for Carrying Out the Invention

[0019] In this specification, with respect to the expressions "containing" and "comprising", the concepts of "containing", "comprising", "consisting essentially of", and "consisting only of" are included.

[0020] In this specification, "~" in a numerical range means "above" and "below". That is, the notation α~β means α or more and β or less, or β or more and α or less, and includes α and β as a range.

[0021] In this specification, when the upper limit value and the lower limit value are separately described, the ranges formed by arbitrarily combining the described upper limit value and lower limit value are also disclosed in this specification.

[0022] In identifying the inventions encompassed by the present disclosure, each configuration (property, structure, function, etc.) described in each embodiment of the present disclosure may be combined in any manner. That is, the present disclosure encompasses all the subject matters consisting of any combination of the combinable configurations described in this specification.

[0023] 1. Polyolefin Film In one aspect, the present invention relates to a polyolefin film containing a polyolefin resin, wherein the peel strength measured by a 180° peel test on at least one surface is 1.00 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 300 mm / min, 1.60 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 1000 mm / min, and 2.30 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 2500 mm / min (in this specification, it may also be referred to as "the polyolefin film of the present invention"). Hereinafter, this will be described.

[0024] The polyolefin film of the present invention is one in which dipping and poor adhesion under various operating speeds are suppressed. In the present invention, paying attention to the peel strength at various operating speeds and adjusting this within a certain range, we have successfully obtained a polyolefin film in which dipping and poor adhesion under various operating speeds are suppressed, leading to the completion of the present invention.

[0025] For the polyolefin film of the present invention, with respect to at least one surface, the peel strength measured by a 180° peel test is 1.00 N / 25 mm or more and 4.00 N / 25 mm or less when the peel speed is 300 mm / min, 1.60 N / 25 mm or more and 4.00 N / 25 mm or less when the peel speed is 1000 mm / min, and 2.30 N / 25 mm or more and 4.00 N / 25 mm or less when the peel speed is 2500 mm / min.

[0026] The peel strength when the peel speed is 300 mm / min is preferably 1.05 N / 25 mm or more and 3.95 N / 25 mm or less, more preferably 1.10 N / 25 mm or more and 3.90 N / 25 mm or less, still more preferably 1.20 N / 25 mm or more and 3.50 N / 25 mm or less, and even more preferably 1.20 N / 25 mm or more and 3.00 N / 25 mm or less, from the viewpoints of suppressing dipping and poor adhesion.

[0027] The peel strength when the peel speed is 1000 mm / min is preferably 1.65 N / 25 mm or more and 3.95 N / 25 mm or less, more preferably 1.70 N / 25 mm or more and 3.90 N / 25 mm or less, still more preferably 1.80 N / 25 mm or more and 3.70 N / 25 mm or less, even more preferably 1.90 N / 25 mm or more and 3.50 N / 25 mm or less, and particularly preferably 1.95 N / 25 mm or more and 3.35 N / 25 mm or less, from the viewpoints of suppressing dipping and poor adhesion.

[0028] When the peeling speed is 2500 mm / min, the peeling force is preferably 2.35 N / 25 mm or more and 3.90 N / 25 mm or less, more preferably 2.40 N / 25 mm or more and 3.80 N / 25 mm or less, still more preferably 2.40 N / 25 mm or more and 3.40 N / 25 mm or less, and even more preferably 2.40 N / 25 mm or more and 3.15 N / 25 mm or less, from the viewpoints of suppressing dipping and suppressing poor adhesion.

[0029] For the polyolefin film of the present invention, from the viewpoints of suppressing dipping and suppressing poor adhesion, it is preferable that the peeling force is 0.30 N / 25 mm or more and 4.00 N / 25 mm or less when the peeling speed is 50 mm / min. The peeling force is more preferably 0.33 N / 25 mm or more and 4.00 N / 25 mm or less, still more preferably 0.35 N / 25 mm or more and 3.80 N / 25 mm or less, even more preferably 0.35 N / 25 mm or more and 3.00 N / 25 mm or less, particularly preferably 0.35 N / 25 mm or more and 2.00 N / 25 mm or less, and particularly more preferably 0.35 N / 25 mm or more and 1.50 N / 25 mm or less.

[0030] The above peeling force is a value measured according to the method of (4-1) in the examples described later.

[0031] For the polyolefin film of the present invention, regarding the surface having the above peeling force, the elastic modulus in the thickness direction at 23°C measured by the nanoindentation method is preferably 2.00 GPa or less from the viewpoints of suppressing dipping and suppressing poor adhesion. The elastic modulus is more preferably 0.40 GPa or more and 1.95 GPa or less, still more preferably 0.50 GPa or more and 1.90 GPa or less, even more preferably 0.55 GPa or more and 1.80 GPa or less, and particularly preferably 0.60 GPa or more and 1.60 GPa or less.

[0032] The above elastic modulus is a value measured according to the method of (4-2) in the examples described later.

[0033] The polyolefin film of the present invention contains a polyolefin resin. The polyolefin film of the present invention has, as a main componentPolyolefin It contains a resin. In this specification, containing a polyolefin resin as the main component means that, with respect to the entire polyolefin film (when the entire polyolefin film is 100% by mass), it contains 50% by mass or more of the polyolefin resin. With respect to the entire polyolefin film Polyolefin The content of the resin is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and especially preferably 99% by mass or more. The upper limit of the content of the polyolefin resin is, for example, 100% by mass or 99.9% by mass with respect to the entire polyolefin film.

[0034] Examples of the polyolefin resin can broadly include polyolefin resins used for manufacturing films. For example, as the polyolefin resin, polymers obtained by polymerizing olefin compounds can be mentioned. Such olefin compounds preferably include olefin compounds having 2 to 20 carbon atoms, more preferably 2 to 10 carbon atoms, and still more preferably 3 to 6 carbon atoms. Specific polyolefin resins include polyethylene resin, polypropylene resin, poly(1-butene) resin, polyisobutene resin, poly(1-pentene) resin, poly(4-methylpentene-1) resin, and the like. Further, the polyolefin resin may be a copolymer containing two or more structural units derived from different olefin compounds, such as an ethylene-propylene copolymer.

[0035] Among them, in terms of the ease of adjusting the peel strength and the elastic modulus of the polyolefin film of the present invention to the desired range, the polyolefin resin preferably contains at least one selected from the group consisting of polyethylene resin and polypropylene resin, and particularly preferably contains polyethylene resin. Among polyethylene resins, low-density polyethylene or high-density polyethylene is preferred, and linear low-density polyethylene, so-called LLDPE, is more preferred.

[0036] The polyolefin resin preferably contains 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 99% by mass or more of polyethylene resin and / or polypropylene resin (particularly preferably polyethylene resin). It is particularly preferable that the polyolefin resin consists only of polyethylene resin and / or polypropylene resin (particularly preferably polyethylene resin).

[0037] In the polyolefin film of the present invention, it is preferable to contain 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 99% by mass or more of polyethylene resin and / or polypropylene resin (particularly preferably polyethylene resin) with respect to 100% by mass of the resin component. It is particularly preferable that the resin component of the polyolefin film of the present invention consists only of polyethylene resin and / or polypropylene resin (particularly preferably polyethylene resin).

[0038] From the viewpoints of thickness uniformity, mechanical properties, thermo-mechanical properties, etc., the weight average molecular weight (Mw) of the polyolefin resin is preferably 200,000 or more and 400,000 or less.

[0039] The preferable physical property values of the polyolefin resin are as follows: The molecular weight distribution (Mw / Mn) calculated as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polyolefin resin is preferably 3 or more and 13 or less from the viewpoint of obtaining appropriate resin fluidity during biaxial stretching and efficiently obtaining a film without breakage; The number average molecular weight (Mn) of the polyolefin resin is preferably 80,000 or less, and more preferably 10,000 or more and 70,000 or less from the viewpoint of suppressing the elastic modulus after stretching and obtaining a flexible film; The Z average molecular weight (Mz) of the polyolefin resin is, for example, 500,000 or more and 1,800,000 or less; The melt flow rate (MFR) of the polyolefin resin at a load of 2.16 kg is not particularly limited, but is preferably 7 g / 10 min or less, more preferably 0.5 g / 10 min or more and 6 g / 10 min or less, from the viewpoint of reducing the mechanical load in the film forming process. The test temperature for MFR measurement is 190 °C for polyethylene resin and 230 °C for polypropylene resin. For other resins, the temperature shall be in accordance with the above.

[0040] The above average molecular weight and molecular weight distribution of the polyolefin resin are values measured according to the method of (2-1) in the examples described below. Also, the above MFR of the polyolefin resin is a value measured according to the method of (2-2) in the examples described below.

[0041] Preferred physical property values of the polyethylene resin (particularly, preferred physical property values when the polyethylene resin is the main component) are as follows: The molecular weight distribution (Mw / Mn) calculated as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polyethylene resin is preferably 3 or more and 13 or less, more preferably 3.3 or more and 12 or less, from the viewpoint of obtaining appropriate resin fluidity during biaxial stretching and efficiently obtaining a film without breakage; The number average molecular weight (Mn) of the polyethylene resin is preferably 80,000 or less, more preferably 10,000 or more and 70,000 or less, from the viewpoint of suppressing the elastic modulus after stretching and obtaining a flexible film; The Z average molecular weight (Mz) of the polyethylene resin is, for example, 500,000 or more and 1,800,000 or less; The melt flow rate (MFR) of the polyethylene resin at 190 °C and a load of 2.16 kg is not particularly limited, but is preferably 5 g / 10 min or less, more preferably 0.2 g / 10 min or more and 4 g / 10 min or less, from the viewpoint of reducing the mechanical load in the film forming process and from the viewpoint of making the thickness of the polyolefin film of the present invention uniform.

[0042] When using polypropylene resin, especially when using polypropylene resin as the main component, it is preferable to use at least two types of polypropylene resins. For example, when two types of polypropylene resins are designated as polypropylene resin A and polypropylene resin B respectively, polypropylene resin A is preferably a highly crystalline polypropylene raw material from the viewpoints of obtaining thickness uniformity, mechanical properties, thermo-mechanical properties, etc. The other polypropylene resin B is preferably a polypropylene raw material with low crystallinity and a low melting point from the viewpoints of obtaining flexibility and peelability.

[0043] The preferable physical property values of polypropylene resin A (especially the preferable physical property values when polypropylene resin is the main component) are as follows: The weight average molecular weight (Mw) of polypropylene resin A is preferably 200,000 or more and 500,000 or less, more preferably 230,000 or more and 400,000 or less, from the viewpoints of thickness uniformity, mechanical properties, thermo-mechanical properties, etc.; The molecular weight distribution (Mw / Mn) calculated as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of polypropylene resin A is preferably 5 or more and 12 or less, more preferably 5 or more and 10 or less, from the viewpoint of obtaining appropriate resin fluidity during biaxial stretching and efficiently obtaining a film without breakage; The number average molecular weight (Mn) of polypropylene resin A is preferably 80,000 or less, more preferably 10,000 or more and 70,000 or less, from the viewpoint of suppressing the elastic modulus after stretching and obtaining a flexible film; The Z average molecular weight (Mz) of polypropylene resin A is, for example, 500,000 or more and 1,800,000 or less; The melt flow rate (MFR) of polypropylene resin A at 230 °C under a load of 2.16 kg is not particularly limited, but is preferably 7 g / 10 min or less from the viewpoint of reducing the mechanical load in the film-forming process, and more preferably 0.5 g / 10 min or more and 6 g / 10 min or less from the viewpoint of improving the thickness accuracy of the polyolefin film of the present invention.

[0044] Preferred physical property values of polypropylene resin B (particularly, preferred physical property values when polypropylene resin is the main component) are as follows: The weight average molecular weight (Mw) of polypropylene resin B is preferably 200,000 or less, more preferably 50,000 or more and 150,000 or less, from the viewpoint of imparting flexibility to the film and more easily and preferably exhibiting the effects of the present invention; The molecular weight distribution (Mw / Mn) calculated as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of polypropylene resin B is preferably 1 or more and 4 or less, more preferably 1.4 or more and 2.5 or less, from the viewpoint of achieving both the uniformity of the film thickness and the effects of the present invention; The number average molecular weight (Mn) of polypropylene resin B is preferably 80,000 or less, more preferably 30,000 or more and 70,000 or less, from the viewpoint of suppressing the elastic modulus after stretching and obtaining a flexible film; The Z average molecular weight (Mz) of polypropylene resin B is, for example, 500,000 or more and 1,000,000 or less; The melt flow rate (MFR) of polypropylene resin B at 230 ° C. and a load of 2.16 kg is not particularly limited, but is preferably 100 g / 10 min or less, more preferably 30 g / 10 min or more and 80 g / 10 min or less, from the viewpoint of obtaining appropriate resin fluidity during sheet molding.

[0045] When polypropylene resin A and polypropylene resin B are used, the mass ratio of polypropylene resin A: polypropylene resin B is preferably 50 to 90:20 to 50, more preferably 60 to 85:15 to 40, still more preferably 65 to 85:15 to 35, and even more preferably 68 to 82:18 to 32.

[0046] The polyolefin film of the present invention can contain other components other than the polyolefin resin as long as the effects of the present invention are not inhibited. Examples of other components can widely include additives contained in known resin films, such as antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, plasticizers, lubricants, crosslinking agents, flame retardants, antistatic agents, heat resistance improvers, antiblocking agents, inorganic particles, resin particles, chlorine scavengers, antifogging agents, hydrolysis inhibitors, and the like. These components can be used alone or in combination of a plurality thereof as needed. When the polyolefin film of the present invention contains the above-mentioned other components, the content ratio is 10% by mass or less, preferably 5% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less based on the total mass of the polyolefin film.

[0047] From the viewpoint that the above peeling force is easily obtained, the polyolefin film of the present invention is preferably a stretched film. The polyolefin film of the present invention may be a uniaxially stretched film stretched in one axial direction, or a biaxially stretched film stretched in two axial directions. When the polyolefin film of the present invention is a biaxially stretched film, it is preferably a biaxially stretched film stretched in two axial directions of the MD direction and the TD direction, and is particularly preferably a sequential biaxially stretched film from the viewpoint that uniform thickness can be stably obtained and the mechanical strength of the film can be easily adjusted.

[0048] The polyolefin film of the present invention can have a single-layer structure or a multilayer structure. The polyolefin film of the present invention preferably has a single-layer structure. When the polyolefin film of the present invention has a multilayer structure, each layer contains the above-mentioned polyolefin resin. In this case, the polyolefin resins contained in each layer may be the same as each other, or at least one or all of them may be different.

[0049] The thickness of the polyolefin film of the present invention is not particularly limited and can be set to a desired thickness according to the intended use. From the viewpoint of avoiding film breakage and stably obtaining a uniform thickness, the lower limit of the thickness is preferably 2 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, and even more preferably 15 μm or more. On the other hand, from the viewpoint of suppressing production costs and reducing the mechanical load in the film-forming process, the upper limit of the thickness is preferably 100 μm or less, more preferably 70 μm or less, still more preferably 50 μm, and even more preferably 30 μm or less. In the case where the polyolefin film of the present invention has the above-mentioned multilayer structure, the thickness of the polyolefin film of the present invention means the total value of the thicknesses of each layer.

[0050] 2. Manufacturing Method The method for producing the polyolefin film of the present invention is not particularly limited, and for example, a method similar to that for known films can be widely adopted. Specifically, for example, the polyolefin film of the present invention can be produced by a production method including a step of obtaining a cast sheet containing a polyolefin resin and performing stretching treatment on the cast sheet in the MD direction and the TD direction. Hereinafter, the method, which is an example, will be described in detail.

[0051] The cast sheet serving as the stretching precursor can be obtained using a known method. For example, polyolefin resin pellets, dry-mixed polyolefin resin pellets, or mixed polyolefin resin pellets prepared by previously melt-kneading are supplied to an extruder, heated and melted, and after removing foreign substances and modified polymers through a filter, they are extruded in a sheet shape from a T-die and cooled and solidified with at least one cooling drum to obtain a cast sheet.

[0052] In an extruder, the polyolefin resin is inevitably modified by thermal degradation and oxidative degradation. From the viewpoint of suppressing such polymer modification, the resin temperature during melt extrusion is 170°C or higher and 320°C or lower, preferably 200°C or higher and 300°C or lower. Further, it is possible to suppress degradation by nitrogen substitution in the extruder, screw shape, internal shape of the T-die at the time of casting, addition amount of antioxidant, and the like.

[0053] The temperature of the cooling drum is preferably 10°C or higher and 90°C or lower, and more preferably maintained at 20°C or higher and 80°C or lower. As a method of adhering to the casting drum, any method such as an air knife method, a touch roll method, an electrostatic printing method, a water-cooled casting method, etc. may be used, but the air knife method which is easy to adjust when adhering the sheet resin to the cooling drum and can be simply handled is preferred. When using an air knife, the temperature of the blown air (AK air temperature) is preferably 5°C or higher and 90°C or lower, more preferably 10°C or higher and 80°C or lower.

[0054] The cast sheet obtained by adjusting within the above range of the cooling drum temperature and the AK air temperature has suppressed crystallization, a small mechanical load during stretching, and the film after biaxial stretching has appropriate flexibility. Therefore, the peelability is improved, and as a result, it is considered that the desired physical properties of the present invention can be easily obtained.

[0055] The polyolefin film of the present invention can be obtained by stretching the cast sheet biaxially in the longitudinal and widthwise directions (MD and TD directions).

[0056] First, the cast sheet is heated to 70°C or higher and 155°C or lower, preferably 80°C or higher and 150°C or lower. The method of heating the cast sheet is not particularly limited, but a method of alternately heating both sides of the cast sheet using a roll group of 4 or more rolls arranged in the flow direction and simultaneously heating the front and back surfaces of the sheet immediately before stretching in the longitudinal direction is preferred. By setting such a temperature range, the cast sheet does not expand excessively due to heat and can be stretched in the longitudinal direction described below while maintaining flatness.

[0057] The cast sheet is stretched in the longitudinal direction (MD stretching), and immediately relaxed thereafter to obtain an MD-stretched sheet. The stretching ratio in the longitudinal direction (MD ratio) is 3 times or more and 11 times or less, preferably 3.5 times or more and 9 times or less. Also, the relaxation rate (MD relaxation rate) is preferably 12% or less, more preferably 11% or less, and even more preferably 10% or less.

[0058] The MD-stretched sheet obtained by adjusting within the above range maintains flatness and suppresses orientation crystallization, so that the mechanical load can be reduced in the later-described stretching in the transverse direction. Incidentally, the method of longitudinal stretching and relaxation is not particularly limited, but a method using the peripheral speed difference of two or more roll groups arranged in the flow direction is preferred.

[0059] Next, the above-mentioned stretched sheet is guided to a tenter and stretched in the transverse direction (TD stretching). The stretching temperature in the transverse direction (TD temperature) is 130°C or more and 190°C or less, preferably 140°C or more and 185°C or less, and even more preferably 150°C or more and 180°C or less. The stretching ratio in the transverse direction (TD ratio) is 4 times or more and 13 times or less, preferably 5 times or more and 12 times or less, and even more preferably 6 times or more and 11 times or less.

[0060] By adjusting within the above range, stretching breakage due to undrawn residue (remaining) is suppressed, and a polyolefin film with a uniform thickness can be efficiently obtained.

[0061] Finally, the biaxially stretched film is relaxed in the transverse direction, and then the clips are opened at the film temperature described later to obtain the polyolefin film of the present invention.

[0062] The relaxation rate in the transverse direction (TD relaxation rate) is 5% or more and less than 23%, preferably 8% or more and less than 22%, and more preferably 9% or more and less than 21%. Thereafter, the film temperature when the clips are opened is 50°C or more and less than 98°C, preferably 55°C or more and less than 97°C, and more preferably 60°C or more and less than 96°C.

[0063] By adjusting within the above range, the stretching stress remaining in the film after biaxial stretching is uniformly relaxed, and while maintaining flatness, it becomes moderately flexible. Therefore, it is considered that the peelability is improved and, as a result, the desired physical properties of the present invention can be easily obtained.

[0064] The film sent out from the tenter is wound into a roll by a winder, and the polyolefin film of the present invention can be obtained. Further, the polyolefin film of the present invention can be surface-treated within a range that does not impair its characteristics according to the application. Examples of the surface treatment include corona discharge treatment, plasma treatment, flame treatment, etc.

[0065] 3. Use The polyolefin film of the present invention can be applied to various uses. Among them, the polyolefin film of the present invention is particularly suitable as a protective film for electronic members. Further, the polyolefin film of the present invention can also be used for protective films other than the above.

[0066]

[0067] The polyolefin film of the present invention can be used as a protective film for dry film resist. The type of dry film resist is not particularly limited, and for example, it can be widely applied to known dry film resists. Such a protective film is provided to protect the adhesive layer of the dry film resist. In one aspect, the dry film resist can be a film formed by laminating the polyolefin film of the present invention, a resist layer, and a base film (for example, a film containing polyethylene terephthalate (PET)) in this order.

[0068] The polyolefin film of the present invention can be used for various applications by disposing other layers on one or both surfaces thereof as needed. For example, the polyolefin film of the present invention can be used as the above-mentioned protective film, release film, etc. by disposing a release layer (such as a silicon coating) containing a release agent on one or both surfaces thereof as needed.

Examples

[0069] Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited by these examples.

[0070] (1) Preparation of Polyolefin Resin The polyolefin resins used in the examples and comparative examples are as follows. PE represents a polyethylene resin, and PP represents a polypropylene resin. ·PE1: "TF80" (LLDPE) manufactured by Dow Chemical ·PE2: "SP3010" (LLDPE) manufactured by Prime Polymer ·PE3: "BX202" (LLDPE) manufactured by SABIC ·PE4: "LO4904P" (HDPE) manufactured by LG Chem ·PP1: "F135A" manufactured by Prime Polymer ·PP2: "HC300BF" manufactured by Borealis ·PP3: "S901S" manufactured by Idemitsu Kosan The physical property values of these polyolefin resins are shown below. The measurement methods are as follows.

[0071]

Table 1

[0072] (2) Physical Property Measurement of Polyolefin Resin (2-1) Measurement of Various Average Molecular Weights and Various Molecular Weight Distributions of Polyolefin Resin Using SEC (size exclusion chromatography), various average molecular weights and various molecular weight distributions were measured under the following conditions. Apparatus: HLC-8321GPC / HT (Detector: Differential Refractometer (RI)) (manufactured by Tosoh Corporation) Column: TSKgel guardcolumnH HR (30) HT (7.5 mm I.D. × 7.5 cm) × 1 piece + TSKgel GMH HR -H (20) HT (7.8 mm I.D. × 30 cm) × 3 pieces (manufactured by Tosoh Corporation) Eluent: 1,2,4-trichlorobenzene (for GPC, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) + dibutylhydroxytoluene (0.05%) Flow rate: 1.0 mL / min Detection conditions: polarity = (-) Injection volume: 300 μL Column temperature: 140 °C System temperature: 40 °C Sample concentration: 1 mg / mL Pretreatment: The sample was weighed, and the solvent (1,2,4-trichlorobenzene added with 0.1% dibutylhydroxytoluene) was added, and it was shaken and dissolved at 140 °C for 1 hour. Then, it was heated and filtered through a 0.5 μm sintered filter. In addition, no insoluble matter was confirmed in the visual observation of the sample solution. Calibration curve: A calibration curve of a fifth-order approximation curve was created using standard polystyrene manufactured by Tosoh Corporation. Therefore, the obtained value is the polystyrene-equivalent molecular weight. However, the molecular weights of PP1, PP2, and PP3 were converted to the molecular weights of polyolefins using the Q-factor.

[0073] From the obtained calibration curve and SEC chromatogram, the number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) were obtained using the analysis software for the measuring device. Using these values of Mw and Mn, the molecular weight distribution (Mw / Mn) was obtained.

[0074] (2-2) Measurement of Melt Flow Rate (MFR) For each resin, the melt flow rate (MFR) in the form of raw resin pellets was measured in accordance with Condition M of JIS K 7210 using a melt indexer manufactured by Toyo Seiki Seisaku-sho, Ltd. Specifically, first, a weighed 4 g sample was inserted into a cylinder set at the test temperature (190 °C for PE and 230 °C for PP), and preheated under a load of 2.16 kg for 3.5 minutes. Then, the weight of the sample extruded from the bottom hole in 30 seconds was measured to obtain the MFR (g / 10 min). The above measurement was repeated three times, and the average value was taken as the measured value of MFR.

[0075] (3) Production of Biaxially Oriented Polyolefin Film (Example 1) PE1 was supplied to an extruder and melted at a resin temperature of 260 °C. Then, after removing foreign substances, modified polymers, etc. with a filter installed in the middle of the polymer tube, it was extruded using a T-die and wound around a casting drum with a surface temperature maintained at 50 °C to be solidified, thereby producing a cast sheet.

[0076] Also, as a method for adhering to the casting drum, an air knife was used, and the air temperature of the blown air was set at 25 °C.

[0077] The obtained cast sheet was preheated at a temperature of 100 °C, stretched 6 times in the longitudinal direction, then relaxed by 3.5% in the same direction, and immediately returned to room temperature.

[0078] Thereafter, the stretched film was led to a tenter, both ends were gripped with clips at 110 °C and preheated at 165 °C, stretched 7.8 times in the width direction, and then relaxed by 10% in the same direction. Subsequently, after cooling the temperature of the biaxially stretched film to 60 °C, the clips of the tenter were opened to obtain a biaxially stretched polyethylene film with a thickness of 20 μm.

[0079] Note that the film thickness was measured in accordance with JIS-C2330 using a micrometer (JIS-B7502).

[0080] (Example 2) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that the resin supplied to the extruder was changed to PE2.

[0081] (Example 3) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that the resin supplied to the extruder was changed to PE3.

[0082] (Example 4) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that the film was stretched 8 times in the longitudinal direction and 11 times in the width direction.

[0083] (Example 5) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that the resin was melted at a resin temperature of 240°C, and the surface temperature of the casting drum and the air temperature of the blown air from the air knife were set to 70°C.

[0084] (Example 6) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that the film temperature when the clips of the tenter were opened was set to 95°C.

[0085] (Example 7) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that relaxation was applied by 10% in the longitudinal direction and 20% in the width direction.

[0086] (Example 8) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that the film was stretched 8 times in the longitudinal direction and 11 times in the width direction, and the film temperature when the clips of the tenter were opened was set to 50°C.

[0087] (Example 9) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that the film was stretched 8 times in the longitudinal direction and 11 times in the width direction, and the film temperature when the clips of the tenter were opened was set to 100°C.

[0088] (Example 10) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that it was stretched 8 times in the longitudinal direction and 13 times in the width direction.

[0089] (Example 11) A biaxially stretched polyethylene film was obtained in the same manner as in Example 2, except that the resin was melted at a resin temperature of 240°C, the surface temperature of the casting drum and the air temperature of the blown air from the air knife were set to 70°C, and it was stretched 8 times in the longitudinal direction and 11 times in the width direction.

[0090] (Example 12) A biaxially stretched polyethylene film was obtained in the same manner as in Example 2, except that the surface temperature of the casting drum was 35°C, the air temperature of the blown air from the air knife was 15°C, the relaxation in the longitudinal and width directions was 10% and 20% respectively, and the film temperature when the clips of the tenter were opened was 95°C.

[0091] (Example 13) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that the resin supplied to the extruder was changed to PE4.

[0092] (Example 14) A biaxially stretched polyethylene film was obtained in the same manner as in Example 12, except that the resin supplied to the extruder was changed to PE4.

[0093] (Example 15) A biaxially stretched polypropylene film was obtained in the same manner as in Example 1, except that the resin supplied to the extruder was a resin obtained by mixing PP1 and PP3 at a mass ratio of 80:20, the preheating temperature of the cast sheet was 145°C, the draw ratio in the longitudinal direction was 5 times, the relaxation in the same direction was 0%, the preheating temperature before stretching in the width direction was 175°C, and the draw ratio in the width direction was 11 times.

[0094] (Example 16) A biaxially stretched polypropylene film was obtained in the same manner as in Example 15, except that the resin supplied to the extruder was a resin obtained by mixing PP2 and PP3 at a mass ratio of 70:30.

[0095] (Comparative Example 1) A biaxially oriented polyethylene film was obtained in the same manner as in Example 4, except that the resin was melted at a resin temperature of 240°C, and the surface temperature of the casting drum and the air temperature of the blown air from the air knife were set to 70°C.

[0096] (Comparative Example 2) A biaxially oriented polyethylene film was obtained in the same manner as in Example 1, except that relaxation was performed at 13% in the longitudinal direction and 23% in the width direction, and the film temperature when the clips of the tenter were released was set to 98°C.

[0097] (Comparative Example 3) A biaxially oriented polyethylene film was obtained in the same manner as in Example 1, except that the film temperature when the clips of the tenter were released was set to 45°C.

[0098] (Comparative Example 4) A biaxially oriented polyethylene film was obtained in the same manner as in Example 11, except that the film temperature when the clips of the tenter were released was set to 45°C.

[0099] (Comparative Example 5) A biaxially oriented polyethylene film was obtained in the same manner as in Example 2, except that relaxation was performed at 13% in the longitudinal direction and 23% in the width direction, and the film temperature when the clips of the tenter were released was set to 98°C.

[0100] (Comparative Example 6) A biaxially oriented polyethylene film was obtained in the same manner as in Example 13, except that the resin was melted at a resin temperature of 245°C, the surface temperature of the casting drum was set to 65°C, and the air temperature of the blown air from the air knife was set to 70°C.

[0101] (Comparative Example 7) A biaxially oriented polypropylene film was obtained in the same manner as in Example 15, except that the resin supplied to the extruder was changed to PP1.

[0102] (Comparative Example 8) A biaxially oriented polypropylene film was obtained in the same manner as in Example 16, except that the resin supplied to the extruder was a resin in which PP2 and PP3 were mixed at a mass ratio of 65:35.

[0103] (4) Physical Property Measurement of Polyolefin Film (4-1) Measurement of Peel Force The peel strength of the polyolefin films of the examples and comparative examples was measured as follows. (1) On the surface of one of the two sides of the polyolefin film that is to be bonded to the adherend, an adhesive tape (Nitto Denko Corporation's No. 31B tape, acrylic adhesive) with a width of 50 mm and a length of 150 mm was affixed by reciprocating a 2 kg roller twice to obtain a laminate. (2) The obtained laminate was allowed to stand in an environment at a temperature of 70°C and a humidity of 50% for 20 hours, and then cut into a width of 25 mm to obtain a measurement sample. (3) Using a tensile testing machine (Minebea Co., Ltd.'s universal tensile testing machine "Technograph TGI-1kN"), the measurement sample was subjected to 180° peeling at a constant peeling rate (50 mm / min, 300 mm / min, 1000 mm / min, and 2500 mm / min), and the peeling force at that time was measured. (4) The measurement was performed with n = 10 for each peeling rate, and the average value was taken as the measurement result.

[0104] (4-2) Measurement of Elastic Modulus The elastic modulus in the thickness direction at 23°C of the surface of the polyolefin films of the examples and comparative examples used for measuring the peel strength in (4-1) was measured by the nanoindentation method. Specifically, the measurement was performed as follows.

[0105] Measurement was carried out in accordance with the method specified in ISO 14577 (2002) using the dynamic ultra-micro hardness tester "DUH-211S" manufactured by Shimadzu Corporation. One drop of "Aron Alpha" (registered trademark) impact-resistant for professional use manufactured by Toagosei Co., Ltd. was applied to the polyolefin film, and the film was fixed to a dedicated sample fixing table via an instant adhesive. Among the two sides of the film, the side to be bonded to the adherend was used as the measurement surface for measurement. A triangular pyramid diamond indenter (Berkovich indenter) with an included angle of 115° between the edges was used for the measurement. The measurement data was processed by dedicated analysis software, and the indentation modulus EIT (GPa) was calculated assuming a Poisson's ratio of 0.44. The measurement was performed with n = 10, and the average value was obtained. The measurement conditions were as follows.

[0106] · Measurement mode: Load-unload test · Maximum load: 0.5 mN · Holding time when the maximum load is reached: 5 seconds · Loading rate, unloading rate: 0.02 mN / sec.

[0107] (5) Performance Evaluation of Polyolefin Film (5-1) Dipping Evaluation On the surface of the side to be bonded to the adherend among the two sides of the polyolefin films of the examples and comparative examples, an adhesive tape (Nitto Denko Corporation No. 31B tape, acrylic adhesive) with a width of 50 mm × a length of 150 mm was attached by reciprocating a 2 kg roller twice to obtain a laminate. The obtained laminate was left standing in an environment of 70°C and 50% humidity for 20 hours, then cut into a width of 25 mm, and this was used as a measurement sample. Using a tensile testing machine (Universal tensile testing machine "Technograph TGI-1kN" manufactured by Minebea Co., Ltd.), 180° peeling was performed at respective peeling speeds of 50 mm / min, 300 mm / min, 1000 mm / min, and 2500 mm / min, and the occurrence of dipping was confirmed. The measurement was performed with n = 10 for each peeling speed, and the number of measurement samples in which dipping occurred was counted. The largest occurrence number among the results of each peeling speed was adopted as the measurement result, and dipping evaluation was performed according to the following evaluation criteria.

[0108] A++: The number of measurement samples with lifting is 0 / 10.

[0109] A+: The number of measurement samples with lifting is 1 / 10.

[0110] A: The number of measurement samples with lifting is 2 or more and 4 or less / 10.

[0111] B: The number of measurement samples with lifting is 5 / 10.

[0112] C: The number of measurement samples with lifting is 6 or more / 10.

[0113] (5-2) Adhesion Failure Evaluation Among both sides of the polyolefin films of the examples and comparative examples, an adhesive tape (Nitto Denko Corporation No. 31B tape, acrylic adhesive) with a width of 50 mm and a length of 150 mm was attached to the surface on the side to be bonded to the adherend by reciprocating a 2 kg roller twice to obtain a laminate. The obtained laminate was allowed to stand in an environment of 70°C and 50% humidity for 20 hours, and then cut into a width of 25 mm, which was used as a measurement sample. Using a tensile testing machine (Universal Tensile Testing Machine "Technograph TGI-1kN" manufactured by Minebea Co., Ltd.), 180° peeling was performed at respective peeling speeds of 50 mm / min, 300 mm / min, 1000 mm / min, and 2500 mm / min to confirm the occurrence of film lifting. The measurement was performed with n = 10 for each peeling speed, and the number of measurement samples with lifting was counted. The largest number of occurrences among the results of each peeling speed was adopted as the measurement result, and the adhesion failure evaluation was performed according to the following evaluation criteria.

[0114] A++: The number of measurement samples with lifting is 0 / 10.

[0115] A+: The number of measurement samples with lifting is 1 / 10.

[0116] A: The number of measurement samples with lifting is 2 or more and 4 or less / 10.

[0117] B: The number of measurement samples with floating is 5 / 10.

[0118] C: The number of measurement samples with floating is 6 or more / 10.

[0119] (6) Results The resin composition, manufacturing conditions, physical property measurement results, and performance evaluation results are shown in Table 2 and Table 3.

[0120] [Table 2]

[0121] [Table 3]

Claims

1. A polyolefin film containing a polyolefin resin, wherein the content of the polyethylene resin with respect to 100% by mass of the polyolefin film is 80% by mass or more, and the peel strength measured by a 180° peel test on at least one surface is 1.00 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 300 mm / min, 1.60 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 1000 mm / min, and 2.30 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 2500 mm / min, a polyolefin film.

2. The polyolefin film according to claim 1, wherein the peel strength is 0.30 N / 25 mm or more and 4.00 N / 25 mm or less when the peel rate is 50 mm / min.

3. The polyolefin film according to claim 1, wherein the elastic modulus in the thickness direction at 23°C measured by nanoindentation of the surface is 2.00 GPa or less.

4. The polyolefin film according to claim 1, wherein the content of the polyethylene resin with respect to 100% by mass of the polyolefin film is 90% by mass or more.

5. The polyolefin film according to claim 1, which is a stretched film.

6. The polyolefin film according to claim 1, which is a biaxially stretched film.

7. The polyolefin film according to claim 1, having a thickness of 10 μm or more and 50 μm or less.

8. A protective film comprising the polyolefin film according to any one of claims 1 to 7.

9. The protective film according to claim 8, which is a protective film for a dry film resist.

10. A laminate comprising the polyolefin film according to any one of claims 1 to 7 and another layer.

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