Extended film

Abstract

To provide a stretched film that has excellent handling properties after hot processing and suppresses dipping and / or adhesion failures. 【Solution means】A stretched film containing a polyethylene resin, wherein for at least one of the longitudinal direction and the width direction, the average linear expansion coefficient from 30°C to 85°C when the temperature is raised at 10°C / min is 8.00×10 -4 / °C or less, and the peel force at a peel rate of 50 mm / min measured by a 180° peel test on at least one surface is 4.00 N / 25 mm or less.

Description

Technical Field

[0001] The present invention relates to a stretched film 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 films and industrial material films. In particular, in recent years, polyolefin films have been widely used in the manufacturing processes of electronic components and printed circuit boards, protective materials used for thermosetting resin members such as fiber-reinforced plastics, release materials, etc., taking advantage of their excellent peelability, and their utility value has been increasing.

[0003] When used as a protective film, thermal lamination may be performed to obtain a laminate with other layers. However, curling occurs during thermal lamination, which deteriorates the handleability in subsequent processes and reduces the production efficiency. In Patent Document 1, a polyethylene film formed by an inflation method with reduced fish eyes is proposed as a cover film for a dry film resist, but this film is prone to curling.

[0004] Also, when used as a protective film of a resin layer having adhesiveness, problems such as dipping (stick slip) occurring when peeling the protective film at the operating speed and a horizontal stripe pattern being formed on the adhesive surface, and the protective film floating due to poor adhesion may occur.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a film that has excellent handling properties after heat processing and suppresses dipping and / or adhesion failure.

Means for Solving the Problems

[0007] As a result of intensive research in view of the above problems, the present inventors have found that a stretched film containing a polyethylene resin, in at least one of the longitudinal direction and the width direction, has an average linear expansion coefficient of 30 ° C. to 85 ° C. when the temperature is raised at 10 ° C. / min. is 8.00×10 -4 / °C or less, and the peel force at a peel rate of 50 mm / min measured by a 180° peel test on at least one surface is 4.00 N / 25 mm or less. The present inventors have further studied based on this finding and completed the present invention. That is, the present invention includes the following aspects.

[0008] Item 1. A stretched film containing a polyethylene resin, in at least one of the longitudinal direction and the width direction, the average linear expansion coefficient from 30 ° C. to 85 ° C. when the temperature is raised at 10 ° C. / min is 8.00×10 -4 / °C or less, and the peel force at a peel rate of 50 mm / min measured by a 180° peel test on at least one surface is 4.00 N / 25 mm or less, stretched film.

[0009] Item 2. The average linear expansion coefficient is 1.20×10 -4 / °C or more and 8.00×10 -4 / °C or less, and the peel force is 0.05 N / 25 mm or more and 4.00 N / 25 mm or less, The stretched film according to Item 1.

[0010] Item 3. The stretched film according to Item 1 or 2, wherein the curl curvature at a lamination temperature of 85 ° C. is less than 0.21 / mm.

[0011] Item 4. The stretched film according to any one of Items 1 to 3, having a tensile strength in the longitudinal direction of 30 MPa or more and a tensile strength in the widthwise direction of 50 MPa or more.

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

[0013] Item 6. The stretched film according to any one of Items 1 to 5, having a thickness of 10 μm or more and 50 μm or less.

[0014] Item 7. A protective film, a release film, or a packaging film containing the stretched film according to any one of Items 1 to 6.

[0015] Item 8. A laminate containing the stretched film according to any one of Items 1 to 6 and another layer.

Advantages of the Invention

[0016] According to the present invention, it is possible to provide a film having excellent handling properties after heat processing and suppressing dipping and / or adhesion failure.

Embodiments for Carrying Out the Invention

[0017] In this specification, the expressions “containing” and “comprising” include the concepts of “containing”, “comprising”, “consisting essentially of”, and “consisting only of”.

[0018] In this specification, “~” in a numerical range means “or more” and “or less”. 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.

[0019] In this specification, when the upper limit value and the lower limit value are described separately, a range formed by arbitrarily combining the described upper limit value and lower limit value is also disclosed in this specification.

[0020] In identifying the inventions encompassed by the present disclosure, the respective configurations (properties, structures, functions, 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 combinations of the combinable configurations described herein.

[0021] 1. Stretch film In one aspect, the present invention relates to a stretched film containing a polyethylene resin, wherein the average linear expansion coefficient from 30°C to 85°C when the temperature is raised at 10°C / min is 8.00×10 -4 / °C or less in at least one of the longitudinal direction and the width direction, and the peel force at a peel rate of 50 mm / min measured by a 180° peel test on at least one surface is 4.00 N / 25 mm or less. (In this specification, it may also be referred to as "the stretched film of the present invention".) The following will explain this.

[0022] The stretched film of the present invention is excellent in handling properties after heat processing and suppresses dipping and / or adhesion failure.

[0023] The present inventor has found that, from the viewpoints of handling properties after heat processing, dipping (especially dipping under high-speed operation), adhesion failure, etc., the average linear expansion coefficient from 30°C to 85°C when the temperature is raised at 10°C / min (hereinafter, may also be simply referred to as "average linear expansion coefficient"), and the peel force at a peel rate of 50 mm / min measured by a 180° peel test (hereinafter, may also be simply referred to as "peel force") are important. By adjusting these within the above ranges, it is possible to improve the handling properties after heat processing and suppress dipping and / or adhesion failure.

[0024] From the viewpoint of handling properties after heat processing (especially from the viewpoint of handling properties after heat processing), the average linear expansion coefficient is preferably 0.80×10 -4 / °C or more and 8.00×10 -4 / °C or less, more preferably 0.90×10 -4 / °C or more and 8.00×10 -4 / °C or lower, more preferably 1.00×10 -4 / °C or higher and 8.00×10 -4 / °C or lower, particularly preferably 1.10×10 -4 / °C or higher and 7.50×10 -4 / °C or lower, even more preferably 1.20×10 -4 / °C or higher and 7.00×10 -4 / °C or lower, even more preferably 1.30×10 -4 / °C or higher and 6.50×10 -4 / °C or lower, even more preferably 1.30×10 -4 / °C or higher and 6.00×10 -4 / °C or lower. In one aspect of the present invention, the average linear expansion coefficient is, for example, 1.50×10 -4 / °C or higher, 2.00×10 -4 / °C or higher, 2.50×10 -4 / °C or higher, 3.00×10 -4 / °C or higher, or 3.50×10 -4 / °C or higher, and also, for example, 5.50×10 -4 / °C or lower, or 5.00×10 -4 / °C or lower.

[0025] The average linear expansion coefficient is a value measured according to the method of (4-1) in the examples described below.

[0026] The peel strength is preferably 0.05 N / 25 mm or more and 4.00 N / 25 mm or less, more preferably 0.05 N / 25 mm or more and 3.50 N / 25 mm or less, still more preferably 0.05 N / 25 mm or more and 3.00 N / 25 mm or less, even more preferably 0.05 N / 25 mm or more and 2.50 N / 25 mm or less, and particularly preferably 0.06 N / 25 mm or more and 2.30 N / 25 mm or less, from the viewpoints of dipping (especially dipping under high-speed operation), poor adhesion, etc. (particularly from the viewpoints of dipping and poor adhesion). In one aspect of the present invention, the peel strength is, for example, 0.10 N / 25 mm or more, 0.20 N / 25 mm or more, 0.30 N / 25 mm or more, 0.40 N / 25 mm or more, 0.50 N / 25 mm or more, or 0.60 N / 25 mm or more, and is also, for example, 2.00 N / 25 mm or less, 1.50 N / 25 mm or less, 1.20 N / 25 mm or less, or 1.00 N / 25 mm or less.

[0027] The peel strength is a value measured according to the method of (4-2) in the examples described below.

[0028] From the viewpoint of the handleability after heat treatment (particularly from the viewpoint of the handleability after heat treatment), the curl curvature of the stretched film of the present invention is preferably less than 0.21 / mm when the lamination temperature is 85°C. The curl curvature is more preferably 0.01 / mm or more and less than 0.21 / mm, still more preferably 0.01 / mm or more and 0.20 / mm or less, even more preferably 0.02 / mm or more and 0.20 / mm or less, particularly preferably 0.03 / mm or more and 0.20 / mm or less, even more particularly preferably 0.05 / mm or more and 0.20 / mm or less, still more particularly preferably 0.07 / mm or more and 0.20 / mm or less, even more particularly preferably 0.07 / mm or more and 0.18 / mm or less, and particularly preferably 0.07 / mm or more and 0.16 / mm or less. In one aspect of the present invention, the curl curvature is, for example, 0.09 / mm or more, 0.11 / mm or more, or 0.12 / mm or more, and is also, for example, 0.15 / mm or less.

[0029] The above curl curvature is a value measured according to the method of (4-3) in the examples described below.

[0030] The drawn film of the present invention preferably has a longitudinal tensile strength of 30 MPa or more and a transverse tensile strength of 50 MPa or more from the viewpoints of film breakage, handling properties after heat processing, dipping (especially dipping under high-speed operation), and poor adhesion.

[0031] The longitudinal tensile strength is more preferably 30 MPa or more and 200 MPa, even more preferably 30 MPa or more and 150 MPa, still more preferably 30 MPa or more and 120 MPa, and particularly preferably 30 MPa or more and 100 MPa from the viewpoint of suppressing film breakage. In one aspect of the present invention, the longitudinal tensile strength is, for example, 40 MPa or more, 50 MPa or more, or 60 MPa or more, and is also, for example, 90 MPa or less.

[0032] The transverse tensile strength is more preferably 50 MPa or more and 350 MPa or less, even more preferably 70 MPa or more and 300 MPa or less, and still more preferably 90 MPa or more and 280 MPa or less. In one aspect of the present invention, the transverse tensile strength is, for example, 100 MPa or more, 120 MPa or more, 140 MPa or more, or 160 MPa or more, and is also, for example, 250 MPa or less, 230 MPa or less, or 220 MPa or less.

[0033] The longitudinal / transverse tensile strength is a value measured according to the method of (4-4) in the following examples. By increasing the tensile strength, the impact resistance can be improved.

[0034] The stretched film of the present invention contains a polyethylene resin. The stretched film of the present invention contains a polyethylene resin as a main component. In this specification, containing a polyethylene resin as a main component means that the stretched film of the present invention contains 30% by mass or more of the polyethylene resin with respect to the entire stretched film of the present invention (when the entire stretched film of the present invention is 100% by mass). The content of the polyethylene resin with respect to the entire stretched film of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, particularly more preferably 95% by mass or more, and especially preferably 99% by mass or more. The upper limit of the content of the polyethylene resin is, for example, 100% by mass or 99.9% by mass with respect to the entire stretched film of the present invention.

[0035] The origin of the polyethylene resin is not particularly limited, and it can be, for example, a resin using a petroleum-derived raw material, or it can also be a resin using a plant-derived raw material (so-called biomass plastic).

[0036] Among the polyethylene resins, low-density polyethylene or high-density polyethylene is preferred, and linear low-density polyethylene, so-called LLDPE, is more preferred.

[0037] The weight average molecular weight (Mw) of the polyethylene resin is preferably 200,000 or more and 400,000 or less, and more preferably 210,000 or more and 300,000 or less, from the viewpoints of thickness uniformity, mechanical properties, thermo-mechanical properties, etc.

[0038] 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.

[0039] 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.

[0040] 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 making the thickness of the stretched film of the present invention uniform. Further, the MFR is preferably 0.8 g / 10 min or more, more preferably 1.2 g / 10 min or more, from the viewpoint of handling properties after heat processing.

[0041] The Z average molecular weight (Mz) of the polyethylene resin is, for example, 500,000 or more and 1,800,000 or less.

[0042] The density of the polyethylene resin is, for example, 0.910 g / cm 3 or more and 0.970 g / cm 3 or less, preferably 0.915 g / cm 3 or more and 0.960 g / cm 3 or less, more preferably 0.918 g / cm 3 or more and 0.950 g / cm 3 or less, still more preferably 0.920 g / cm 3 or more and 0.940 g / cm 3 or less, particularly preferably 0.922 g / cm 3 or more and 0.930 g / cm 3 or less.

[0043] The above average molecular weight and molecular weight distribution of the polyethylene resin are values measured according to the method of (2-1) in the examples described later. The above MFR of the polyethylene resin is a value measured according to the method of (2-2) in the examples described later. The density of the polyethylene resin is a value measured according to the method of (2-3) in the examples described later.

[0044] The stretched film of the present invention can contain other resins other than the polyethylene resin as long as the effects of the present invention are not inhibited. Examples of other resins include polyolefin resins other than polyethylene resins. The polyolefin resin can be broadly exemplified by polyolefin resins used for producing films. For example, as the polyolefin resin, a polymer obtained by polymerizing an olefin compound 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 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. The content of other resins in the entire stretched film of the present invention is, for example, less than 70% by mass, preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, even more preferably 20% by mass or less, particularly preferably 10% by mass or less, particularly more preferably 5% by mass or less, and particularly preferably 1% by mass or less. In one aspect, the stretched film of the present invention does not contain other resins.

[0045] The stretched film of the present invention can contain components other than resin as long as the effects of the present invention are not inhibited. Examples of other components can broadly 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 necessary. When the stretched film of the present invention contains the above-mentioned other components, the content ratio thereof 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 stretched film of the present invention.

[0046] The stretched film of the present invention is a stretched film stretched in at least one uniaxial direction of the longitudinal direction (MD direction) and the TD direction (width direction). The stretched film of the present invention may be a biaxially stretched film stretched in the biaxial direction. When the stretched film of the present invention is a biaxially stretched film, it is preferably a biaxially stretched film stretched in the biaxial direction of the longitudinal direction and the width direction. The stretched film of the present invention is particularly preferably a sequentially biaxially stretched film from the viewpoint that uniform thickness can be stably obtained and the mechanical strength of the film can be easily adjusted.

[0047] The stretched film of the present invention can have a single-layer structure or a multilayer structure (for example, 2 to 7 layers, 2 to 5 layers, 2 to 3 layers, or 3 layers). The stretched film of the present invention preferably has a multilayer structure. When the stretched film of the present invention has a multilayer structure, at least one layer (for example, 2 to 6 layers, 2 to 4 layers, or 2 layers, preferably all layers) contains the above-mentioned polyethylene resin (preferably as the main component). When the polyethylene resin is contained in a plurality of layers, the polyethylene resins contained in each layer may be the same as each other, or at least one or all of them may be different.

[0048] The thickness of the stretched 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. When the stretched film of the present invention has the above-described multilayer structure, the thickness of the stretched film of the present invention means the total value of the thicknesses of each layer.

[0049] 2. Manufacturing method The method for producing the stretched film of the present invention is not particularly limited, and for example, a method similar to that for known films can be widely employed. Specifically, for example, a stretched film of the present invention can be produced by a production method including a step of obtaining a cast sheet containing a polyethylene resin and subjecting the cast sheet to stretching treatment in the MD direction and the TD direction. Hereinafter, the method, which is an example, will be described in detail.

[0050] The cast sheet, which is a stretching precursor, can be obtained using known methods. For example, polyethylene resin pellets, dry-mixed polyethylene resin pellets, or mixed polyethylene resin pellets prepared by previously melt-kneading are supplied to an extruder, heated and melted, foreign matters and modified polymers are removed through a filter, and then extruded in a sheet shape from a T-die and cooled and solidified with at least one or more cooling drums to obtain a cast sheet.

[0051] In the extruder, the polyethylene resin is inevitably modified due to 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, degradation can be suppressed by nitrogen substitution in the extruder, screw shape, internal shape of the T-die during casting, addition amount of antioxidant, and the like.

[0052] The temperature of the cooling drum is preferably 20°C or higher and 90°C or lower, and more preferably maintained at 40°C or higher and 80°C or lower. As the method of adhering to the cooling drum, any method such as an air knife method, a touch roll method, an electrostatic printing method, or a water-cooled casting method 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 10°C or higher and 90°C or lower, and more preferably 20°C or higher and 80°C or lower.

[0053] The cast sheet obtained by adjusting within the above ranges of the cooling drum temperature and the AK air temperature has suppressed crystallization and a small mechanical load during stretching. As a result, it is considered that the desired physical properties of the present invention can be easily obtained.

[0054] In one embodiment, the stretched film of the present invention can be obtained by stretching the cast sheet in two axes in the longitudinal and widthwise directions (MD and TD directions).

[0055] First, the cast sheet is heated to 70°C or higher and 130°C or lower, preferably 80°C or higher and 120°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 four or more roll groups 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 as described below while maintaining flatness.

[0056] The cast sheet is stretched in the longitudinal direction (MD stretching), and immediately thereafter, it is relaxed 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 0% or more and 12% or less, more preferably 5% or more and 11% or less, and still more preferably 6% or more and 10% or less.

[0057] The MD-stretched sheet obtained by adjusting within the above range maintains planarity and suppresses orientation crystallization, so that the mechanical load can be reduced in the later-described stretching in the width direction. Incidentally, the method of stretching and relaxing in the longitudinal direction is not particularly limited, but a method using the peripheral speed difference of two or more roll groups arranged in the flow direction is preferable.

[0058] Next, the above-mentioned stretched sheet is guided to a tenter and stretched in the width direction (TD stretching). The temperature for stretching in the width direction (TD temperature) is preferably 150°C or higher and 190°C or lower, more preferably 155°C or higher and 185°C or lower, still more preferably 160°C or higher and 180°C or lower, and even more preferably 165°C or higher and 180°C or lower. The stretching ratio in the width direction (TD ratio) is 4 times or more and 13 times or less, preferably 5 times or more and 12 times or less, and still more preferably 6 times or more and 11 times or less.

[0059] By adjusting within the above range, stretching breakage due to undrawn residue (leftover) is suppressed, and a stretched film with a uniform thickness can be efficiently obtained.

[0060] Finally, the biaxially stretched film is relaxed in the width direction to obtain the stretched film of the present invention.

[0061] The relaxation rate in the width direction (TD relaxation rate) is 0% or higher and less than 23%, preferably 5% or higher and 20% or lower, and more preferably 8% or higher and 15% or lower.

[0062] By adjusting within the above range, it is considered that the desired physical properties of the present invention can be easily obtained. In particular, by adjusting the stretching temperature (especially the preheating temperature for TD stretching) within the above range, and further relaxing at a relaxation rate of a certain level or more in at least one (preferably both) of after MD stretching and after TD stretching, it is considered that the desired physical properties of the present invention can be easily obtained. More specifically, by stretching, orientation and crystallization occur, and the average linear expansion coefficient can be adjusted. By setting the preheating temperature for TD stretching high, it becomes difficult for minute crystals to grow due to rapid heating, and the crystals grow large, and the linear expansion coefficient can be adjusted. By setting the MD relaxation rate high, the unoriented polymer chains are relaxed by MD relaxation, and it becomes easier to orient and crystallize during subsequent TD stretching. By setting the TD relaxation rate high, the stress in the TD direction weakens, so that stress is more likely to be applied in the MD direction, and strong orientation and crystallization can occur in the MD direction.

[0063] The film sent out from the tenter is wound into a roll by a winder, and the stretched film of the present invention can be obtained. Further, the stretched film of the present invention can be surface-treated within a range that does not impair its properties according to the application. Examples of the surface treatment include corona discharge treatment, plasma treatment, flame treatment, etc.

[0064] 3. Use The stretched film of the present invention can be applied to various uses. Among them, the stretched film of the present invention is particularly suitable as a protective film for electronic members. Further, the stretched film of the present invention can also be used for protective films, release films, and packaging films other than the above.

[0065] The stretched 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 stretched film of the present invention, a resist layer, and a base film (for example, a film containing polyethylene terephthalate (PET)) in this order.

[0066] If necessary, the stretched film of the present invention can be used for various applications by disposing other layers on one or both surfaces. For example, if necessary, a release layer (such as a silicon coating) containing a release agent is disposed on one or both surfaces of the stretched film of the present invention, and it can be used as the above-mentioned protective film, release film, etc. As another example, if necessary, a coating layer (such as a gas barrier layer) is disposed on one or both surfaces of the stretched film of the present invention, and it can be used as a packaging film, etc.

Examples

[0067] Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited by these examples.

[0068] (1) Preparation of resin The 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: "BX202" (LLDPE) manufactured by SABIC ·PE3: "LO4904P" (HDPE) manufactured by LG Chem ·PE4: "LC520" (LDPE) manufactured by Nippon Polyethylene ·PE5: "LF128" (LDPE) manufactured by Nippon Polyethylene ·PP: "F-300SP" manufactured by Prime Polymer The physical property values of these resins are shown below. The measurement methods are as follows. In the table, "-" indicates that the measurement was not performed.

[0069]

Table 1

[0070] (2) Physical property measurement of resin (2-1) Measurement of various average molecular weights and various molecular weight distributions of 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 (7.5mm I.D. × 7.5cm) × 1 piece + TSKgel GMH HR -H (20)HT (7.8mm I.D. × 30cm) × 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 a 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 values are polystyrene-equivalent molecular weights.

[0071] 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.

[0072] (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.

[0073] (2-3) Measurement of density For each resin, the density in the form of raw resin pellets was measured in accordance with JIS K7112 using a density gradient tube type specific gravity measuring device Model A manufactured by Shibayama Kagaku Kikai Seisakusho Co., Ltd. Specifically, ethanol / water was used as the gradient liquid, and the measurement was carried out at a temperature of 23 °C after approximately 24 hours had elapsed since the gradient liquid was introduced. The above measurement was repeated three times, and the average value was taken as the measured value of the density.

[0074] (3) Production of stretch film (Example 1) As shown in Table 2 below, a stretched film was produced in which surface layer A and surface layer B were respectively disposed on both sides of a base material layer. First, 100 parts by mass of PE1 (hereinafter referred to as pellet 1) as a resin for forming the base material layer and 100 parts by mass of PE1 (hereinafter referred to as pellet 2) as a resin for forming surface layer A and surface layer B were prepared. Pellet 1 was fed from a hopper into a single-screw type extruder a, and pellet 2 was fed from a hopper into a single-screw type extruder b different from extruder a. The above pellet 1 and the above pellet 2 were each melted at 260° C., and these were laminated into a three-layer structure inside a three-layer multi-manifold die, and then cooled and solidified while pressing with an air knife on a cooling drum. The air temperature of the blown air was 25° C. Thereby, a raw sheet was obtained in which layers of PE2 derived from pellet 2 were directly formed on both sides of the layer of PE-1 derived from pellet 1.

[0075] The obtained cast sheet was preheated at a temperature of 100° C., stretched 6 times in the longitudinal direction (MD direction), then relaxed 0% in the same direction, and immediately returned to room temperature. Thereafter, the stretched film was led to a tenter, both ends were gripped with clips and preheated at 155° C., and then stretched 7.8 times in the width direction (TD direction) in a stretching zone at 125° C., and then relaxed 10% in the same direction to obtain a stretched film having a thickness of 20 μm. The obtained stretched film was a stretched film in which surface layer A, the base material layer, and surface layer B were laminated in this order, and the thickness ratio was 1:2:1 (surface layer A: base material layer: surface layer B). In such a stretched film, surface layer B was a layer that was directly in contact with the cooling drum, and surface layer A was a layer that was not in contact with the cooling drum.

[0076] In addition, the film thickness was measured in accordance with JIS-C2330 using a micrometer (JIS-B7502).

[0077] (Example 2) A stretched film was obtained in the same manner as in Example 1 except that relaxation was performed at 8% in the longitudinal direction and 0% in the width direction.

[0078] (Example 3) An oriented film was obtained in the same manner as in Example 1, except that a 8% relaxation was applied in the longitudinal direction.

[0079] (Example 4) An oriented film was obtained in the same manner as in Example 3, except that the preheating temperature before stretching in the width direction was set to 165°C.

[0080] (Example 5) An oriented film was obtained in the same manner as in Example 3, except that the preheating temperature before stretching in the width direction was set to 175°C.

[0081] (Example 6) An oriented film was obtained in the same manner as in Example 5, except that the resin for forming the base material layer was changed to PE2, and the resins for forming the surface layer A and the surface layer B were changed to PE2.

[0082] (Example 7) An oriented film was obtained in the same manner as in Example 5, except that the resin for forming the base material layer was changed to PE3, and the resins for forming the surface layer A and the surface layer B were changed to PE3.

[0083] (Example 8) An oriented film was obtained in the same manner as in Example 1, except that the resin for forming the base material layer was changed to PP1, and the preheating temperature when stretching in the TD direction was changed to 195°C.

[0084] (Comparative Example 1) PE4 pellets were charged from a hopper into a single-screw type extruder and melted at a resin temperature of 200°C. Then, after removing foreign substances, modified polymers, etc. with a filter installed in the middle of the polymer tube, extrusion was carried out using a ring die and wound through pinch rolls. Next, air was fed into the ring, and the resin was inflated into a balloon shape between the ring die and the pinch rolls. Both ends of the balloon folded through the pinch rolls were cut off, and a polyethylene film with a thickness of 20 μm was obtained by winding each as two films.

[0085] (Comparative Example 2) A polyethylene film was obtained in the same manner as in Comparative Example 1, except that the resin fed into the extruder was changed to PE5.

[0086] (Comparative Example 3) A stretched film was obtained in the same manner as in Example 1, except that 0% relaxation was applied in the width direction.

[0087] (Comparative Example 4) A stretched film was obtained in the same manner as in Example 3, except that the preheating temperature before stretching in the width direction was set to 145°C.

[0088] (Comparative Example 5) A stretched film was obtained in the same manner as in Example 5, except that the resin fed into the extruder was changed to PP, the preheating temperature during stretching in the MD direction was set to 130°C, and the stretching zone temperature during stretching in the TD direction was set to 160°C.

[0089] (4) Physical property measurement of film (4-1) Measurement of average linear expansion coefficient Regarding the longitudinal direction of the films of the examples and comparative examples, in accordance with JIS K7197, using a thermomechanical analyzer (manufactured by Seiko Instruments Inc., TMA / SS6000), the average linear expansion coefficient (1 / °C) was measured as follows. The film was cut out with a longitudinal length of 30 mm and a width of 4 mm, and the sample was set in the thermomechanical analyzer with a chuck distance of 15 mm. While applying a load of 0.2 N / mm in the tensile direction, the temperature was raised from 25°C to 105°C (as the ambient temperature) at a heating rate of 10°C / min and held for 7 minutes. At this time, the average linear expansion coefficient (1 / °C) was measured in the temperature range of 30°C to 85°C (as the sample temperature) of the sample.

[0090] (4-2) Measurement of peel force Of both sides of the films of the examples and comparative examples, an adhesive tape with a width of 25 mm and a length of 150 mm (Nitto Denko Corporation's No. 31B tape, total thickness 53 μm, acrylic adhesive) 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 cooled to room temperature, which was used as a measurement sample. The measurement sample was subjected to 180° peeling at a speed of 50 mm / min using a tensile tester (Minelco Co., Ltd.'s universal tensile tester "Technograph TGI-1kN"), and the peeling force at that time was measured. The measurement was performed with n = 10 for each peeling speed, and the average value was taken as the measurement result.

[0091] (4-3) Measurement of curl curvature Of both sides of the films of the examples and comparative examples, an adhesive tape with a width of 25 mm and a length of 150 mm (Nitto Denko Corporation's No. 31B tape, total thickness 53 μm, acrylic adhesive) 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 placed on a 0.1 mm thick SUS plate with the 31B tape side on the top. It was covered with a 38 μm thick PET film from above and passed through a laminator (LM-A3 manufactured by Aurora Japan Co., Ltd.). The heating temperature confirmed with a thermolabel was 85°C. After passing through the laminator, the laminate was removed from the paper and the SUS plate and cut into a size of 25 mm in width and 70 mm in length. Then, the above laminate was allowed to stand on graph paper with the long side surface facing down, and the curl diameter of the laminate was measured. The curl curvature was calculated as the reciprocal of the curl radius (2 / curl diameter). The measurement was performed with n = 3, and the average value was taken as the measurement result.

[0092] (4-4) Measurement of tensile strength The tensile strength in the longitudinal and transverse directions of the films of the examples and comparative examples was measured using a tensilon universal material testing machine RTG-1210 (trade name) of A&D Company, Limited. Specifically, the film was cut into a size of 15×150 mm with the longitudinal and transverse directions as the long sides, and the tensile strength was measured under the conditions of a chuck distance of 100 mm and a tensile speed of 200 mm / min, and the strength (unit: Mpa) at the breaking point was determined.

[0093] (4-5) Measurement of impact resistance For the films of the examples and comparative examples, the impact strength was measured using a film impact tester manufactured by Yasuda Seiki Co., Ltd. based on ASTM-D3420. For this measurement, a 15 Kgf·cm weight was used, and a metal ball with a radius of 6.35 mm was used as the impact ball. The impact strength measurement was performed 3 times per sample, and the average value was taken as the impact strength.

[0094] (5) Performance evaluation of film (5-1) Evaluation of handleability Of both sides of the films of the examples and comparative examples, an adhesive tape with a width of 150 mm × a length of 250 mm (No. 31B tape manufactured by Nitto Denko Corporation, total thickness 53 μm, acrylic adhesive) was attached to the surface on the side to be bonded to the adherend by reciprocating a 2 kg roller 2 times to obtain a laminate. The obtained laminate was placed on a 0.1 mm thick SUS plate with the 31B tape side as the upper surface. It was covered with a 38 μm thick PET film from above and passed through a laminator. The heating temperature confirmed with a thermolabel was 85°C. After the obtained sample was left standing at room temperature for 24 hours, the stretched film was peeled off again. The obtained 31B tape was bonded to a 50 μm thick PET film using a tabletop laminator, and the presence or absence of defects was confirmed. The evaluation was performed with n = 10, the number of measured samples with appearance defects such as folds, wrinkles, and irregularities was calculated, and the handling property evaluation was performed according to the following evaluation criteria.

[0095] ◎: The number of measured samples with defects is 0.

[0096] 〇: The number of measured samples with defects is 1 to 5.

[0097] ×: The number of measurement samples with defects is 6 to 10 pieces.

[0098] (5-2) Evaluation of dipping Among both sides of the films of the examples and comparative examples, on the surface on the side to be bonded to the adherend, an adhesive tape with a width of 25 mm × a length of 150 mm (No. 31B tape manufactured by Nitto Denko Corporation, total thickness 53 μm, acrylic-based adhesive) was attached by reciprocating a 2 kg roller twice to obtain a laminate. The obtained laminate was allowed to stand in an environment of a temperature of 70°C and a humidity of 50% for 20 hours, and then cooled to room temperature, which was used as a measurement sample. Using an adhesion / film peeling analyzer ("VPA" manufactured by Kyowa Interface Science Co., Ltd.), the 180° peeling was performed at a speed of 1250 mm / min, and the occurrence of dipping was confirmed. The measurement was performed with n = 10, the number of measurement samples with dipping was calculated, and the dipping evaluation was performed according to the following evaluation criteria.

[0099] ◎: The number of measurement samples with dipping is 0 piece.

[0100] 〇: The number of measurement samples with dipping is 1 to 5 pieces.

[0101] ×: The number of measurement samples with dipping is 6 to 10 pieces.

[0102] (5-3) Evaluation of poor adhesion Among both sides of the films of the examples and comparative examples, on the surface on the side to be bonded to the adherend, an adhesive tape with a width of 25 mm × a length of 150 mm (No. 31B tape manufactured by Nitto Denko Corporation, acrylic-based adhesive) was attached by reciprocating a 2 kg roller twice to obtain a laminate. The obtained laminate was allowed to stand in an environment of a temperature of 70°C and a humidity of 50% for 20 hours. This was allowed to stand at room temperature for 24 hours, and the occurrence of film lifting (natural peeling) from the adhesive tape was confirmed. The measurement was performed with n = 10, the number of measurement samples with lifting was calculated, and the adhesion failure evaluation was performed according to the following evaluation criteria.

[0103] ◎: The number of measurement samples with lifting is 0 piece.

[0104] 〇: The number of measurement samples with floating is 1 to 5 pieces.

[0105] ×: The number of measurement samples with floating is 6 to 10 pieces.

[0106] (6) Results The resin composition, manufacturing conditions, physical property measurement results, and performance evaluation results are shown in Table 2.

[0107]

Table 2

Claims

1. A stretched film containing a polyethylene resin, The average linear expansion coefficient from 30° C. to 85° C. when the temperature is increased at a rate of 10° C. / min in at least one of the longitudinal and transverse directions is 8.00×10 －４ / °C or less, and The peel strength of at least one surface at a peel speed of 50 mm / min measured in a 180° peel test is 4.00 N / 25 mm or less; Stretched film.

2. The average linear expansion coefficient is 1.20×10 －４ / ℃ or more 8.00 x 10 －４ / °C or less, and The peel strength is 0.05 N / 25 mm or more and 4.00 N / 25 mm or less. The stretched film according to claim 1 .

3. 2. The stretched film according to claim 1, which has a curl curvature of less than 0.21 / mm when laminating at a temperature of 85°C.

4. 2. The stretched film according to claim 1, having a tensile strength in the longitudinal direction of 30 MPa or more and a tensile strength in the transverse direction of 50 MPa or more.

5. 10. The stretched film of claim 1 which is a biaxially stretched film.

6. 2. The stretched film according to claim 1, having a thickness of 10 μm or more and 50 μm or less.

7. A protective film, a release film, or a packaging film comprising the stretched film according to any one of claims 1 to 6.

8. A laminate comprising the stretched film according to any one of claims 1 to 6 and other layers.

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