Polyolefin film

Abstract

The present invention addresses the problem of providing a polyolefin film in which zipping and poor adhesion at various operating speeds are suppressed. This problem is solved by a polyolefin film containing a polyolefin resin, wherein the peel force of at least one surface measured by a 180° peel test is 1.00-4.00 N / 25 mm at a peel rate of 300 mm / minute, 1.60-4.00 N / 25 mm at a peel rate of 1000 mm / minute, and 2.30-4.00 N / 25 mm at a peel rate of 2500 mm / minute.

Description

Polyolefin Film

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

[0002] Polyolefin films, such as polyethylene films and polypropylene films, are lightweight, thermally stable, and have excellent mechanical properties, and are widely used as industrial material films, including for packaging. In particular, in recent years, polyolefin films have been widely used as protective materials and release agents for thermosetting resin materials such as fiber-reinforced plastics in the manufacturing process of electronic components and electronic substrates, taking advantage of their excellent releasability, and their utility value has been increasing.

[0003] In particular, when used as a protective film for a resin layer having adhesiveness, the polyolefin film cannot be peeled cleanly from the adherend, which may cause deformation of the adherend or leave peeling marks on the surface of the adherend. To solve these problems, techniques for forming appropriate irregularities on the film surface and techniques for adjusting the resin composition of the surface that comes into contact with the adherend to keep the peel force within a certain range have been disclosed (Patent Documents 1 and 2).

[0004] JP 2023-142503 A JP 2022-100316 A

[0005] In the course of research, the inventors noticed that when a laminate having a protective film is conveyed at the operating speed of a processing process and the protective film is peeled off at the operating speed, problems occur in which zipping (stick-slip) occurs, leaving a striped pattern on the adhesive surface, and the protective film floats due to poor adhesion. The operating speed can change depending on the processing content and other factors, and the inventors focused on suppressing the above problems even under such an environment.

[0006] An object of the present invention is to provide a polyolefin film that is suppressed from zipping and poor adhesion under various operating speeds.

[0007]

[0009] In view of the above problems, the present inventors have conducted extensive research and found that the above problems can be solved by a polyolefin film containing a polyolefin resin, wherein the peel strength of at least one surface measured in a 180° peel test is 1.00 N / 25 mm or more and 4.00 N / 25 mm or less at a peel rate of 300 mm / min, 1.60 N / 25 mm or more and 4.00 N / 25 mm or less at a peel rate of 1000 mm / min, and 2.30 N / 25 mm or more and 4.00 N / 25 mm or less at a peel rate of 2500 mm / min. Based on this finding, the present inventors have conducted further research and have completed the present invention. That is, the present invention encompasses the following aspects.

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

[0009] Item 2. The polyolefin film according to Item 1, wherein the peel force is 0.30 N / 25 mm or more and 4.00 N / 25 mm or less at a peel rate of 50 mm / min.

[0010] Item 3. The polyolefin film according to Item 1 or 2, wherein the elastic modulus of the surface in the thickness direction at 23°C measured by a nanoindentation method 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, having a thickness of 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. The protective film according to Item 8, which is a protective film for a dry film resist.

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

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

[0019] In this specification, the expressions "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0020] In this specification, the term "to" in a numerical range means "greater than or equal to" or "less than or equal to." That is, the expression "α to β" means "greater than or equal to α and less than or equal to β," or "greater than or equal to β and less than or equal to α," and includes both α and β as a range.

[0021] In the present specification, when an upper limit and a lower limit are separately described, any range formed by combining the described upper limit and lower limit is also disclosed in the present specification.

[0022] In specifying the inventions included in the present disclosure, the components (properties, structures, functions, etc.) described in each embodiment of the present disclosure may be combined in any manner. In other words, the present disclosure includes all subject matter consisting of all combinations of the components that can be combined as 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 of at least one surface, measured in a 180° peel test, is from 1.00 N / 25 mm to 4.00 N / 25 mm at a peel rate of 300 mm / min, from 1.60 N / 25 mm to 4.00 N / 25 mm at a peel rate of 1000 mm / min, and from 2.30 N / 25 mm to 4.00 N / 25 mm at a peel rate of 2500 mm / min (sometimes referred to herein as the "polyolefin film of the present invention"). This will be described below.

[0024] The polyolefin film of the present invention is one in which zipping and poor adhesion are suppressed under various operating speeds. In the present invention, the present inventors focused on the peel force at various operating speeds and adjusted this within a certain range, thereby successfully obtaining a polyolefin film in which zipping and poor adhesion are suppressed under various operating speeds, leading to the completion of the present invention.

[0025] The polyolefin film of the present invention has, on at least one surface, a peel strength measured in a 180° peel test of 1.00 N / 25 mm or more and 4.00 N / 25 mm or less at a peel rate of 300 mm / min, 1.60 N / 25 mm or more and 4.00 N / 25 mm or less at a peel rate of 1000 mm / min, and 2.30 N / 25 mm or more and 4.00 N / 25 mm or less at a peel rate of 2500 mm / min.

[0026] From the viewpoint of suppressing zipping and poor adhesion, the peel force at a peel speed of 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, even more preferably 1.20 N / 25 mm or more and 3.50 N / 25 mm or less, and still more preferably 1.20 N / 25 mm or more and 3.00 N / 25 mm or less.

[0027] From the viewpoint of suppressing zipping and poor adhesion, the peel force at a peel speed of 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, even more preferably 1.80 N / 25 mm or more and 3.70 N / 25 mm or less, still 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.

[0028] From the viewpoint of suppressing zipping and poor adhesion, the peel force at a peel speed of 2500 mm / min 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, even more preferably 2.40 N / 25 mm or more and 3.40 N / 25 mm or less, and still more preferably 2.40 N / 25 mm or more and 3.15 N / 25 mm or less.

[0029] From the viewpoint of suppressing zipping and poor adhesion, the polyolefin film of the present invention preferably has a peel strength of 0.30 N / 25 mm to 4.00 N / 25 mm at a peel speed of 50 mm / min, more preferably 0.33 N / 25 mm to 4.00 N / 25 mm, even more preferably 0.35 N / 25 mm to 3.80 N / 25 mm, still more preferably 0.35 N / 25 mm to 3.00 N / 25 mm, particularly preferably 0.35 N / 25 mm to 2.00 N / 25 mm, and especially preferably 0.35 N / 25 mm to 1.50 N / 25 mm.

[0030] The peel strength is a value measured according to the method of (4-1) in the Examples described later.

[0031] The polyolefin film of the present invention preferably has a thickness direction elastic modulus of 2.00 GPa or less at 23°C measured by nanoindentation on the surface having the peel force, from the viewpoint of suppressing zipping and poor adhesion. The elastic modulus is more preferably 0.40 GPa to 1.95 GPa, even more preferably 0.50 GPa to 1.90 GPa, still more preferably 0.55 GPa to 1.80 GPa, and particularly preferably 0.60 GPa to 1.60 GPa.

[0032] The 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 contains a polyolefin resin as a main component. In this specification, "containing a polyolefin resin as a main component" means that the polyolefin resin is contained in an amount of 50% by mass or more relative to the entire polyolefin film (when the entire polyolefin film is taken as 100% by mass). The content of the polyolefin resin relative to the entire polyolefin film is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and particularly preferably 99% by mass or more. The upper limit of the polyolefin resin content relative to the entire polyolefin film is, for example, 100% by mass or 99.9% by mass.

[0034] Examples of polyolefin resins include a wide range of polyolefin resins used for producing films. For example, polyolefin resins include polymers obtained by polymerizing olefin compounds. Examples of such olefin compounds include olefin compounds having preferably 2 to 20 carbon atoms, more preferably 2 to 10 carbon atoms, and even more preferably 3 to 6 carbon atoms. Specific polyolefin resins include polyethylene resins, polypropylene resins, poly(1-butene) resins, polyisobutene resins, poly(1-pentene) resins, and poly(4-methylpentene-1) resins. Furthermore, polyolefin resins may be copolymers containing two or more structural units derived from different olefin compounds, such as ethylene-propylene copolymers.

[0035] In particular, the polyolefin resin preferably contains at least one selected from the group consisting of polyethylene resins and polypropylene resins, and particularly preferably contains a polyethylene resin, in that the peel strength and modulus of the polyolefin film of the present invention can be easily adjusted to the desired ranges. Among the 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 of polyethylene resin and / or polypropylene resin (particularly preferably polyethylene resin), more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. It is particularly preferable that the polyolefin resin consists solely of polyethylene resin and / or polypropylene resin (particularly preferably polyethylene resin).

[0037] The polyolefin film of the present invention preferably contains 80% by mass or more, more preferably 90% by mass or more, even 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) relative to 100% by mass of the resin component. It is particularly preferred that the resin component of the polyolefin film of the present invention consists solely of polyethylene resin and / or polypropylene resin (particularly preferably polyethylene resin).

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

[0039] Preferred physical property values ​​of the polyolefin resin are as follows: The molecular weight distribution (Mw / Mn) of the polyolefin resin, calculated as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), 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, and 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 test temperature is similar to the above.

[0040] The average molecular weight and molecular weight distribution of the polyolefin resin are values ​​measured according to the method (2-1) of the Examples described later, and the MFR of the polyolefin resin is a value measured according to the method (2-2) of the Examples described later.

[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) of the polyethylene resin, calculated as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 3 or more and 13 or less, and 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, 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 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 from the viewpoint of reducing the mechanical load in the film-forming process, and more preferably 0.2 g / 10 min or more and 4 g / 10 min or less from the viewpoint of achieving a uniform thickness of the polyolefin film of the present invention.

[0042] When using polypropylene resin, particularly when polypropylene resin is used as the main component, it is preferable to use at least two types of polypropylene resin. For example, when the two types of polypropylene resins are polypropylene resin A and polypropylene resin B, polypropylene resin A is preferably a polypropylene raw material with high crystallinity from the viewpoint of obtaining uniformity in thickness, 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 viewpoint of obtaining flexibility and releasability.

[0043] Preferred physical property values ​​of the polypropylene resin A (particularly preferred physical property values ​​when polypropylene resin is the main component) are as follows: The weight average molecular weight (Mw) of the polypropylene resin A is preferably 200,000 or more and 500,000 or less, and 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) of the polypropylene resin A, calculated as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 5 or more and 12 or less, and more preferably 5 or more and 10 or less, from the viewpoints of obtaining appropriate resin fluidity during biaxial stretching and efficiently obtaining a film without breakage; The number average molecular weight (Mn) of the polypropylene resin A is preferably 80,000 or less, and more preferably 10,000 or more and 70,000 or less, from the viewpoints of suppressing the elastic modulus after stretching and obtaining a flexible film; The Z average molecular weight (Mz) of the 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 and 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: From the viewpoint of imparting flexibility to the film and making it easier to exhibit the effects of the present invention, the weight average molecular weight (Mw) of polypropylene resin B is preferably 200,000 or less, and more preferably 50,000 or more and 150,000 or less; From the viewpoint of achieving both uniformity in film thickness and the effects of the present invention, the molecular weight distribution (Mw / Mn) of polypropylene resin B, calculated as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 1 or more and 4 or less, and more preferably 1.4 or more and 2.5 or less; From the viewpoint of suppressing the elastic modulus after stretching and obtaining a flexible film, the number average molecular weight (Mn) of polypropylene resin B is preferably 80,000 or less, and more preferably 30,000 or more and 70,000 or less; 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 under a load of 2.16 kg is not particularly limited, but is preferably 100 g / 10 min or less, and 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 50-90:20-50, more preferably 60-85:15-40, even more preferably 65-85:15-35, and still more preferably 68-82:18-32.

[0046] The polyolefin film of the present invention may contain other components in addition to the polyolefin resin, as long as the effects of the present invention are not impaired. Examples of other components include a wide range of additives commonly found in resin films, such as antioxidants, heat stabilizers, light stabilizers, UV absorbers, plasticizers, lubricants, crosslinking agents, flame retardants, antistatic agents, heat resistance improvers, antiblocking agents, inorganic particles, resin particles, chlorine trapping agents, antifogging agents, and hydrolysis inhibitors. These components can be used alone or in combination as needed. When the polyolefin film of the present invention contains the other components, the content of these components is 10% by weight or less, preferably 5% by weight or less, more preferably 1% by weight or less, and particularly preferably 0.5% by weight or less, based on the total weight of the polyolefin film.

[0047] The polyolefin film of the present invention is preferably a stretched film from the viewpoint of easily obtaining the above-mentioned peel strength. The polyolefin film of the present invention may be a uniaxially stretched film stretched in one direction, or a biaxially stretched film stretched in two 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, i.e., in the MD direction and the TD direction, and is particularly preferably a sequentially biaxially stretched film from the viewpoint of stably obtaining a uniform thickness and easily adjusting the mechanical strength of the film.

[0048] The polyolefin film of the present invention can have a single-layer structure or a multi-layer structure. The polyolefin film of the present invention is preferably a single-layer structure. When the polyolefin film of the present invention has a multi-layer 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 depending on the intended use. From the viewpoint of avoiding film breakage and obtaining a stable uniform thickness, the lower limit of the thickness is preferably 2 μm or more, more preferably 5 μm or more, even 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, even more preferably 50 μm or less, and even more preferably 30 μm or less. When 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 manufacturing method of the polyolefin film of the present invention is not particularly limited, and for example, a method similar to that used for known films can be widely adopted. Specifically, for example, the polyolefin film of the present invention can be manufactured by a manufacturing method including a step of obtaining a cast sheet containing a polyolefin resin and stretching the cast sheet in the MD direction and the TD direction. An example of this method is described in detail below.

[0051] A cast sheet, which is a stretched precursor, can be obtained by a known method. For example, polyolefin resin pellets, dry-mixed polyolefin resin pellets, or mixed polyolefin resin pellets prepared in advance by melt-kneading are fed into an extruder, heated and melted, passed through a filter to remove foreign matter and modified polymers, extruded into a sheet form from a T-die, and cooled and solidified on at least one cooling drum to obtain a cast sheet.

[0052] In the extruder, polyolefin resins are subject to considerable thermal and oxidative degradation. To prevent such polymer degradation, 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. Degradation can also be prevented by nitrogen substitution in the extruder, the screw shape, the internal shape of the T-die during casting, the amount of antioxidant added, and the like.

[0053] The temperature of the cooling drum is preferably 10°C or higher and 90°C or lower, and more preferably 20°C or higher and 80°C or lower. The method for adhering the sheet resin to the casting drum may be any of the air knife method, touch roll method, electrostatic application method, water-cooled casting method, etc., but the air knife method is preferred because it allows easy adjustment when adhering the sheet resin to the cooling drum and is simple to handle. When an air knife is used, 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 the cooling drum temperature and AK air temperature within the above ranges is less likely to crystallize, is subjected to a small mechanical load during stretching, and has moderate flexibility after biaxial stretching. This improves peelability, and as a result, it is believed 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 biaxially stretching the cast sheet in the longitudinal and transverse 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 for heating the cast sheet is not particularly limited, but a preferred method is to alternately heat both sides of the cast sheet using a group of four or more rolls arranged in the machine direction, and then simultaneously heat both the front and back sides of the sheet just before longitudinal stretching. By maintaining the temperature in this range, the cast sheet does not undergo excessive thermal expansion, and can be stretched in the longitudinal direction (described later) while maintaining its flatness.

[0057] The cast sheet is stretched in the longitudinal direction (MD stretching) and immediately thereafter relaxed to obtain an MD-stretched sheet. The stretching ratio in the longitudinal direction (MD ratio) is 3 to 11 times, preferably 3.5 to 9 times. 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 its flatness and suppresses oriented crystallization, thereby reducing the mechanical load during widthwise stretching, as described below. The method for longitudinal stretching and relaxation is not particularly limited, but a method utilizing the difference in peripheral speed between two or more rolls arranged in the machine direction is preferred.

[0059] Next, the stretched sheet is introduced into a tenter and stretched in the width direction (TD stretching). The temperature for stretching in the width direction (TD temperature) is 130° C. to 190° C., preferably 140° C. to 185° C., and more preferably 150° C. to 180° C. The stretching ratio in the width direction (TD ratio) is 4 to 13 times, preferably 5 to 12 times, and more preferably 6 to 11 times.

[0060] By adjusting the stretching ratio within the above range, stretching breakage due to the unstretched portion (remaining stretched portion) can be suppressed, and a polyolefin film of uniform thickness can be efficiently obtained.

[0061] Finally, the biaxially stretched film is relaxed in the width direction, and then the clips are released at the film temperature described below 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%. The film temperature when the clip is subsequently released 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 the stretching stress within the above range, the residual stretching stress in the biaxially stretched film is uniformly relaxed, and the film has a suitable flexibility while maintaining its planarity, which improves the peelability and, as a result, is believed to facilitate the attainment of the desired physical properties of the present invention.

[0064] The film fed from the tenter is wound into a roll by a winder to obtain the polyolefin film of the present invention. Furthermore, the polyolefin film of the present invention can be subjected to a surface treatment depending on the intended use, provided that the properties of the film are not impaired. Examples of surface treatments include corona discharge treatment, plasma treatment, and flame treatment.

[0065] 3. Applications The polyolefin film of the present invention can be used in a variety of applications. Among these, the polyolefin film of the present invention is particularly suitable as a protective film for electronic components. The polyolefin film of the present invention can also be used as a protective film other than those mentioned above.

[0066] 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 embodiment, the dry film resist can be a film obtained by laminating the polyolefin film of the present invention, a resist layer, and a base film (e.g., a film containing polyethylene terephthalate (PET)) in this order.

[0067] The polyolefin film of the present invention can be used for various applications by disposing other layers on one or both sides 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 containing a release agent (such as a silicone coating) on ​​one or both sides thereof as needed.

[0068] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0069] (1) Preparation of Polyolefin Resins The polyolefin resins used in the examples and comparative examples are as follows. PE represents polyethylene resin, and PP represents polypropylene resin. PE1: "TF80" (LLDPE) manufactured by Dow Chemical Company; PE2: "SP3010" (LLDPE) manufactured by Prime Polymer; PE3: "BX202" (LLDPE) manufactured by SABIC; PE4: "LO4904P" (HDPE) manufactured by LG Chemical; PP1: "F135A" manufactured by Prime Polymer; PP2: "HC300BF" manufactured by Borealis; PP3: "S901S" manufactured by Idemitsu Kosan Co., Ltd. The physical properties of these polyolefin resins are shown below. The measurement methods are as follows.

[0070]

[0071] (2) Measurement of physical properties 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-8321 GPC / HT (detector: differential refractometer (RI)) (manufactured by Tosoh Corporation) Column: TSKgel Guard column H ＨＲ (30) HT (7.5mm I.D. x 7.5cm) x 1 + TSKgel GMH ＨＲ-H(20)HT (7.8 mm I.D. x 30 cm) x 3 (Tosoh Corporation) Eluent: 1,2,4-trichlorobenzene (GPC grade, 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 a solvent (1,2,4-trichlorobenzene with 0.1% dibutylhydroxytoluene added) was added and the mixture was dissolved by shaking at 140°C for 1 hour. The mixture was then heated and filtered through a 0.5 μm sintered filter. Visual observation of the sample solution revealed no undissolved matter. Calibration curve: A quintic approximation calibration curve was created using standard polystyrene from Tosoh Corporation. Therefore, the obtained value is the molecular weight in terms of polystyrene. However, the molecular weights of PP1, PP2, and PP3 were converted into the molecular weight of polyolefin using the Q-factor.

[0072] 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 analytical software for the measuring device. The molecular weight distribution (Mw / Mn) was obtained using the Mw and Mn values.

[0073] (2-2) Measurement of Melt Flow Rate (MFR) The melt flow rate (MFR) of each resin in the form of raw resin pellets was measured in accordance with JIS K 7210 (1999) using a melt indexer manufactured by Toyo Seiki Co., Ltd. Specifically, a weighed 4 g sample was first inserted into a cylinder heated to the test temperature (190°C for PE, 230°C for PP) and preheated for 3.5 minutes under a load of 2.16 kg. The weight of the sample extruded from the bottom hole over 30 seconds was then measured, and the MFR (g / 10 min) was calculated. The above measurement was repeated three times, and the average value was used as the measured MFR.

[0074] (3) Production of biaxially oriented polyolefin film (Example 1) PE1 was supplied to an extruder and melted at a resin temperature of 260° C. After that, foreign matter, modified polymers, etc. were removed using a filter installed midway through the polymer tube, and the extruded film was then wound around a casting drum whose surface temperature was maintained at 50° C. and solidified to produce a cast sheet.

[0075] To adhere the film to the casting drum, an air knife was used and the temperature of the blown air was set to 25°C.

[0076] The resulting cast sheet was preheated to a temperature of 100° C., stretched 6 times in the longitudinal direction, relaxed 3.5% in the same direction, and immediately returned to room temperature.

[0077] The stretched film was then introduced into a tenter, held at both ends with clips at 110°C, preheated to 165°C, stretched 7.8 times in the width direction, and then relaxed 10% in the same direction. Subsequently, the temperature of the biaxially stretched film was cooled to 60°C, and the tenter clips were released to obtain a biaxially stretched polyethylene film having a thickness of 20 µm.

[0078] The film thickness was measured using a micrometer (JIS-B7502) in accordance with JIS-C2330.

[0079] Example 2 A biaxially oriented polyethylene film was obtained in the same manner as in Example 1, except that the resin supplied to the extruder was PE2.

[0080] Example 3 A biaxially oriented polyethylene film was obtained in the same manner as in Example 1, except that the resin supplied to the extruder was PE3.

[0081] Example 4 A biaxially oriented 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 transverse direction.

[0082] Example 5 A biaxially oriented polyethylene film was obtained in the same manner as in Example 1, except that the resin was melted at a temperature of 240°C, and the surface temperature of the casting drum and the temperature of the air blown out of the air knife were set to 70°C.

[0083] Example 6 A biaxially oriented polyethylene film was obtained in the same manner as in Example 1, except that the film temperature was set to 95°C when the tenter clips were released.

[0084] Example 7 A biaxially oriented polyethylene film was obtained in the same manner as in Example 1, except that the film was relaxed by 10% in the longitudinal direction and by 20% in the transverse direction.

[0085] (Example 8) A biaxially oriented 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 was 50°C when the tenter clips were released.

[0086] (Example 9) A biaxially oriented 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 was 100°C when the tenter clips were released.

[0087] Example 10 A biaxially oriented 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 13 times in the width direction.

[0088] (Example 11) A biaxially oriented polyethylene film was obtained in the same manner as in Example 2, except that the resin was melted at a temperature of 240°C, the surface temperature of the casting drum and the temperature of the air blown out of the air knife were set to 70°C, and the film was stretched 8 times in the longitudinal direction and 11 times in the width direction.

[0089] (Example 12) A biaxially oriented 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 temperature of the air blown out of the air knife was 15°C, the relaxations in the longitudinal and transverse directions were 10% and 20%, respectively, and the film temperature when the tenter clips were released was 95°C.

[0090] Example 13 A biaxially oriented polyethylene film was obtained in the same manner as in Example 1, except that the resin supplied to the extruder was PE4.

[0091] Example 14 A biaxially oriented polyethylene film was obtained in the same manner as in Example 12, except that the resin supplied to the extruder was PE4.

[0092] (Example 15) The resin to be fed to the extruder was a resin obtained by mixing PP1 and PP3 in a mass ratio of 80:20, the preheating temperature of the cast sheet was 145 ° C, the longitudinal stretching ratio was 5 times, the relaxation in the same direction was 0%, the preheating temperature before widthwise stretching was 175 ° C, and the widthwise stretching ratio was 11 times. Except for this, a biaxially stretched polypropylene film was obtained in the same manner as in Example 1.

[0093] 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 mixture of PP2 and PP3 in a mass ratio of 70:30.

[0094] 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 temperature of 240°C, and the surface temperature of the casting drum and the temperature of the air blown out of the air knife were both set to 70°C.

[0095] (Comparative Example 2) A biaxially stretched polyethylene film was obtained in the same manner as in Example 1, except that the film was relaxed by 13% in the longitudinal direction and 23% in the width direction, and the film temperature was set to 98°C when the tenter clips were released.

[0096] Comparative Example 3 A biaxially oriented polyethylene film was obtained in the same manner as in Example 1, except that the film temperature was 45° C. when the tenter clips were released.

[0097] Comparative Example 4 A biaxially oriented polyethylene film was obtained in the same manner as in Example 11, except that the film temperature was 45° C. when the tenter clips were released.

[0098] (Comparative Example 5) A biaxially stretched polyethylene film was obtained in the same manner as in Example 2, except that the film was relaxed by 13% in the longitudinal direction and 23% in the width direction, and the film temperature was set to 98°C when the tenter clips were released.

[0099] (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 temperature of 245°C, the surface temperature of the casting drum was 65°C, and the temperature of the air blown out of the air knife was 70°C.

[0100] 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 PP1.

[0101] Comparative Example 8 A biaxially stretched polypropylene film was obtained in the same manner as in Example 16, except that the resin supplied to the extruder was a mixture of PP2 and PP3 in a mass ratio of 65:35.

[0102] (4) Measurement of Physical Properties of Polyolefin Films (4-1) Measurement of Peel Force The peel force of the polyolefin films of the Examples and Comparative Examples was measured as follows. (1) A 50 mm wide x 150 mm long adhesive tape (No. 31B tape, acrylic adhesive, manufactured by Nitto Denko Corporation) was applied to the surface of each polyolefin film that was to be bonded to the adherend by rolling a 2 kg roller twice back and forth to obtain a laminate. (2) The obtained laminate was left to stand for 20 hours in an environment of 70°C and 50% humidity, and then cut into a 25 mm wide piece to serve as a measurement sample. (3) The measurement sample was subjected to 180° peeling at constant peel rates (50 mm / min, 300 mm / min, 1000 mm / min, and 2500 mm / min) using a tensile tester (a universal tensile tester "Technograph TGI-1kN" manufactured by Minebea Co., Ltd.), and the peel force was measured. (4) Measurements were made for n=10 for each peel rate, and the average value was used as the measurement result.

[0103] (4-2) Measurement of Elastic Modulus The elastic modulus in the thickness direction at 23°C was measured by nanoindentation for the surfaces of the polyolefin films of the Examples and Comparative Examples that were used to measure the peel force in (4-1). Specifically, the measurement was performed as follows.

[0104] Measurements were performed using a dynamic ultra-microhardness tester "DUH-211S" manufactured by Shimadzu Corporation in accordance with the method specified in ISO 14577 (2002). A drop of "Aron Alpha" (registered trademark) professional impact resistant adhesive manufactured by Toagosei Co., Ltd. was applied to the polyolefin film, and the film was fixed to a dedicated sample fixing stand using instant adhesive. Measurements were performed on the side of both sides of the film that was bonded to the adherend as the measurement surface. A triangular pyramidal diamond indenter (Berkovich indenter) with an inter-edge angle of 115° was used for the measurement. The measurement data was processed using dedicated analysis software, and the indentation elastic modulus EIT (GPa) was calculated with a Poisson's ratio of 0.44. Measurements were performed with n = 10, and the average value was calculated. The measurement conditions were as follows.

[0105] Measurement mode: Load-unload test Maximum load: 0.5 mN Holding time when maximum load is reached: 5 seconds Loading rate, unloading rate: 0.02 mN / sec.

[0106] (5) Performance Evaluation of Polyolefin Films (5-1) Zipping Evaluation A 50 mm wide x 150 mm long adhesive tape (Nitto Denko Corporation No. 31B tape, acrylic adhesive) was applied to the surface of each of the polyolefin films of the Examples and Comparative Examples, which was to be bonded to the adherend, by rolling it back and forth twice with a 2 kg roller to obtain a laminate. The resulting laminate was left to stand for 20 hours in an environment of 70°C and 50% humidity, and then cut into 25 mm wide pieces to serve as measurement samples. The measurement samples were subjected to 180° peeling at peel rates of 50 mm / min, 300 mm / min, 1000 mm / min, and 2500 mm / min using a tensile tester (Minebea Co., Ltd.'s universal tensile tester "Technograph TGI-1kN") to check for the occurrence of zipping. Measurements were performed with n = 10 for each peel rate, and the number of measurement samples that exhibited zipping was counted. The most frequent number of zippings among the results of each peeling speed was used as the measurement result, and zipping was evaluated according to the following evaluation criteria.

[0107] A++: The number of measured samples in which zipping occurred was 0 out of 10.

[0108] A+: Zipping occurred in 1 out of 10 measured samples.

[0109] A: The number of measurement samples in which zipping occurred was 2 or more and 4 or less out of 10 samples.

[0110] B: The number of measured samples in which zipping occurred was 5 out of 10.

[0111] C: The number of measurement samples in which zipping occurred was 6 or more out of 10 samples.

[0112] (5-2) Evaluation of Poor Adhesion: A 50 mm wide x 150 mm long adhesive tape (Nitto Denko Corporation No. 31B tape, acrylic adhesive) was applied to the surface of each of the polyolefin films of the Examples and Comparative Examples, which was to be bonded to the adherend, by rolling it back and forth twice with a 2 kg roller to obtain a laminate. The resulting laminate was left to stand for 20 hours in an environment of 70°C and 50% humidity, and then cut into 25 mm wide pieces to serve as measurement samples. The measurement samples were subjected to 180° peeling at peel rates of 50 mm / min, 300 mm / min, 1000 mm / min, and 2500 mm / min using a tensile tester (Minebea Co., Ltd.'s "Technograph TGI-1kN" universal tensile tester), and the occurrence of film lifting was confirmed. Measurements were performed with n = 10 for each peel rate, and the number of measurement samples that exhibited lifting was counted. The most frequent number of peelings among the results of each peeling speed was used as the measurement result, and the adhesion failure was evaluated according to the following evaluation criteria.

[0113] A++: The number of measurement samples in which floating occurred was 0 out of 10.

[0114] A+: The number of measurement samples in which floating occurred was 1 out of 10.

[0115] A: The number of measurement samples in which floating occurred was 2 or more and 4 or less out of 10 samples.

[0116] B: The number of measurement samples in which floating occurred was 5 out of 10.

[0117] C: The number of measurement samples in which floating occurred was 6 or more out of 10.

[0118] (6) Results The resin composition, production conditions, physical property measurement results, and performance evaluation results are shown in Tables 2 and 3.

[0119]

[0120]

Claims

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

2. The polyolefin film according to claim 1, wherein the peel force is 0.30 N / 25 mm or more and 4.00 N / 25 mm or less at a peel speed of 50 mm / min.

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

4. The polyolefin film according to claim 1, wherein the polyolefin resin comprises a polyethylene resin.

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 oriented 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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