Release film and laminate

Abstract

This release film has a base material constituted from a biaxially oriented polypropylene film that satisfies requirements (1) and (2). Requirement (1): when the temperature is increased from 30°C to 160°C at a temperature increase rate of 10°C / min in thermomechanical analysis, the temperature at which the length of the biaxially oriented polypropylene film becomes 0.9950X0 or less is 129°C or higher. Requirement (2): the storage elastic modulus in the longitudinal direction at 23°C is 2.0 GPa or more, and the storage elastic modulus in the transverse direction at 23°C is 8.0 GPa or more.

Description

Release film and laminate

[0001] The present disclosure relates to a release film having a biaxially oriented polypropylene film as a substrate, and a laminate having the release film.

[0002] Because biaxially oriented polypropylene film has moisture-proof properties, it is used for industrial purposes such as packaging, release films, and adhesive tape. Release films based on biaxially oriented polyester film are also widely used. Compared to biaxially oriented polyester film, biaxially oriented polypropylene film has a lower specific gravity, resulting in lighter film rolls, which reduces the energy required for transportation and is easier to recycle.

[0003] International Publication No. 2020 / 196602 International Publication No. 2021 / 070671 International Publication No. 2020 / 137789

[0004] Patent Documents 1 to 3 disclose biaxially oriented polypropylene films that can be used for packaging applications and have various excellent physical properties. Specifically, the films of Patent Documents 1 and 2 have a low heat shrinkage rate and an excellent Young's modulus, while the film of Patent Document 3 has a low heat shrinkage rate and an excellent stress at 5% elongation. However, since biaxially oriented polypropylene films are inferior in rigidity and heat resistance to biaxially oriented polyester films, when used as release films, there is a problem in that flatness is deteriorated by heat during processing.

[0005] The present disclosure aims to solve the above-mentioned problems, that is, to provide a release film using a biaxially oriented polypropylene film as a base material and having excellent flatness even after heating. The present disclosure also provides a film for thin film manufacturing processes and a laminate having the release film of the present disclosure.

[0006] The release film according to the present disclosure, which has been able to solve the above-mentioned problems, and the film and laminate for the thin film manufacturing process having the release film, are as follows: [1] A release film having a substrate made of a biaxially oriented polypropylene film that satisfies the following requirements (1) and (2): (1) In a thermomechanical analysis, when the temperature is increased from 30°C to 160°C at a heating rate of 10°C / min, the length in the width direction of the biaxially oriented polypropylene film is 0.9950X ０or higher is 129°C. (2) The storage modulus in the longitudinal direction at 23°C is 2.0 GPa or higher, and the storage modulus in the width direction at 23°C is 8.0 GPa or higher. [2] The biaxially oriented polypropylene film has a sum of the storage modulus in the longitudinal direction at 23°C and the storage modulus in the longitudinal direction at 140°C of 3.0 GPa or higher, and a sum of the storage modulus in the width direction at 23°C and the storage modulus in the width direction at 140°C of 8.9 GPa or higher. [3] A release film having a substrate composed of a biaxially oriented polypropylene film that satisfies the following requirements (1) and (2). (1) The storage modulus in the longitudinal direction at 23°C is 2.8 GPa or higher, and the storage modulus in the width direction at 23°C is 8.0 GPa or higher. (2) The heat shrinkage rate in the longitudinal direction at 150°C is 4.5% or less, and the heat shrinkage rate in the width direction at 150°C is 9.0% or less. [4] The release film according to [3], wherein the biaxially oriented polypropylene film has a sum of the storage modulus in the longitudinal direction at 23°C and the storage modulus in the longitudinal direction at 140°C of 3.0 GPa or more, and a sum of the storage modulus in the width direction at 23°C and the storage modulus in the width direction at 140°C of 8.9 GPa or more. [5] A release film having a substrate composed of a biaxially oriented polypropylene film satisfying the following requirements (1), (2), and (3): (1) The sum of the storage modulus in the longitudinal direction at 23°C and the storage modulus in the longitudinal direction at 140°C is 3.0 GPa or more. (2) The sum of the storage modulus in the width direction at 23°C and the storage modulus in the width direction at 140°C is 9.2 GPa or more. (3) In dynamic viscoelasticity measurement, when the minimum value of the loss modulus at 25°C to 75°C is E"(B) and the maximum value of the loss modulus at 100°C to 160°C is E"(C), E"(B) / E"(C) is 0.60 or more. [6] In thermomechanical analysis of the biaxially oriented polypropylene film, when the temperature is increased from 30°C to 160°C at a heating rate of 10°C / min, the length in the width direction of the biaxially oriented polypropylene film is 0.9950X ０The release film according to [5], wherein the temperature at which the storage modulus in the longitudinal direction at 23°C is 129°C or higher, the storage modulus in the longitudinal direction at 23°C is 2.0 GPa or higher, and the storage modulus in the width direction at 23°C is 8.0 GPa or higher. [7] The release film according to any one of [1] to [6], further comprising a release agent layer laminated on at least one surface of the substrate. [8] The release film according to [7], wherein the release agent layer comprises a silicone-based release agent. [9] The release film according to [7], wherein the release agent layer comprises a non-silicone-based release agent.

[10] A film for thin film manufacturing processes, comprising the release film according to any one of [1] to [9].

[11] A pressure-sensitive adhesive layer laminate comprising the release film according to any one of [1] to [9], a pressure-sensitive adhesive layer provided on the release surface of the release film, and a protective film provided on the pressure-sensitive adhesive layer on the surface opposite the release film.

[12] A photosensitive resin laminate having the release film according to any one of [1] to [9], a photosensitive resin layer provided on the release surface of the release film, and a protective film provided on the surface of the photosensitive resin layer opposite the release film.

[13] A transfer laminate having the release film according to any one of [1] to [9], and at least one transfer layer selected from a printing layer, a decorative metal thin film, a thermal transfer ink layer, an optically functional layer, a conductive layer, a circuit, an adhesive layer, a pressure-sensitive adhesive layer, and a rubber sheet layer.

[0007] The release film according to the present disclosure uses a biaxially oriented polypropylene film as a base material and can maintain a high degree of flatness even after heating. Therefore, by using the release film according to the present disclosure, it is possible to provide a release film, a film for a thin film manufacturing process, a pressure-sensitive adhesive layer laminate, a photosensitive resin laminate, and a transfer laminate that exhibit excellent flatness even when used at high temperatures.

[0008] FIG. 1 is a diagram showing the relationship between temperature and the length in the width direction of the film in Example 4, Comparative Example 1, and Comparative Example 8. FIG. 2 is a diagram showing the relationship between temperature and loss modulus in Example 4 and Comparative Example 1. FIG. 3 is a diagram showing the relationship between temperature and storage modulus in Example 4 and Comparative Example 8. FIG. 4 is a schematic diagram of a method for evaluating wrinkles in a release film roll and a laminate roll in the examples.

[0009] The release film according to the present disclosure has a substrate made of a biaxially oriented polypropylene film. The biaxially oriented polypropylene film according to the present disclosure is made of a polypropylene resin composition.

[0010] (1) Polypropylene Resin Composition The polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure may contain only one type of polypropylene polymer, or may be a mixture of two or more different polypropylene polymers (polypropylene resins). The mixture of polypropylene polymers may be, for example, two or more different polypropylene homopolymers, polypropylene copolymers containing two or more different α-olefins other than propylene, or a mixture of one or more polypropylene homopolymers and one or more polypropylene copolymers containing one or more α-olefins other than propylene.

[0011] Various suitable physical properties of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure are described below. When two or more different polypropylene polymers are used, the physical properties other than the melt flow rate are the mass average values ​​of the physical properties of each polypropylene polymer.

[0012] The melting point (hereinafter sometimes referred to as Tm) of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure is preferably 158 to 170°C, more preferably 159 to 169°C, even more preferably 160 to 168°C, particularly preferably 161 to 167°C, and most preferably 162 to 166°C. When the melting point is 158°C or higher, flatness, rigidity, heat resistance at high temperatures, and the like are likely to be obtained. When the melting point is 170°C or lower, it is easy to suppress cost increases in terms of polypropylene production, and the film is less likely to break during film formation.

[0013] The melting point of the polypropylene resin composition is the main peak temperature of the endothermic peak accompanying melting, which is observed when 5 mg of the polypropylene resin composition is packed into an aluminum pan, set in a differential scanning calorimeter (DSC), heated from 30°C to 230°C at a heating rate of 20°C / min in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin composition, then cooled to 30°C at a heating rate of -10°C / min, held at 30°C for 5 minutes, and then heated at a heating rate of 10°C / min.

[0014] The crystallization temperature (hereinafter sometimes referred to as Tc) of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure is preferably 105 to 135°C, more preferably 108 to 133°C, even more preferably 110 to 132°C, even more preferably 112 to 130°C, particularly preferably 114 to 128°C, and most preferably 116 to 127°C. If the crystallization temperature is 105°C or higher, crystallization is likely to proceed during width direction stretching and the subsequent cooling step, making it easier to obtain rigidity and heat resistance at high temperatures. If the crystallization temperature is 135°C or lower, it is less likely to increase costs in terms of polypropylene production and the film is less likely to break during film formation.

[0015] The crystallization temperature of the polypropylene resin composition is the main peak temperature of the exothermic peak observed when 5 mg of the polypropylene resin composition is packed into an aluminum pan, set in a DSC, heated from 30°C to 230°C at a heating rate of 20°C / min in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin composition, and then cooled to 30°C at a cooling rate of -10°C / min.

[0016] The melting point and crystallization temperature of the polypropylene resin composition may be increased to fall within the above range by blending a crystal nucleating agent into the polypropylene resin composition.

[0017] The polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure preferably has a mesopentad fraction ([mmmm]%), an index of stereoregularity, of 97.0 to 99.9%, more preferably 97.5 to 99.7%, and even more preferably 98.0 to 99.5%. If the mesopentad fraction is less than 97.0%, there is a risk that high orientation cannot be achieved during stretching, or that crystallization is inhibited, resulting in deterioration of rigidity and heat resistance. On the other hand, if the mesopentad fraction is 97.0% or more, the crystallinity of the polypropylene resin composition is increased, improving the melting point, crystallinity, and crystalline orientation of the crystals in the film, making it easier to achieve flatness, rigidity, heat resistance at high temperatures, and the like. If the mesopentad fraction is 99.9% or less, it is easier to reduce the cost of polypropylene production and makes the film less susceptible to breakage during film formation. The mesopentad fraction is measured by nuclear magnetic resonance spectroscopy (NMR spectroscopy). In order to adjust the mesopentad fraction of the polypropylene resin composition to fall within the above range, for example, methods such as washing the obtained polypropylene resin powder with a solvent such as n-heptane, or using an appropriate catalyst and / or co-catalyst may be used.

[0018] The melt flow rate (MFR) of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure, when measured in accordance with JIS K 7210 (1995) condition M (230°C, 2.16 kgf), is preferably 4.0 to 30 g / 10 min, more preferably 4.5 to 25 g / 10 min, even more preferably 4.8 to 22 g / 10 min, even more preferably 5.0 to 20 g / 10 min, particularly preferably 6.0 to 20 g / 10 min, and most preferably 7.5 to 15 g / 10 min. When the MFR of the polypropylene resin composition is 4.0 g / 10 min or more, a biaxially oriented polypropylene film with a low heat shrinkage rate is easily obtained. Furthermore, when the MFR of the polypropylene resin composition is 30 g / 10 min or less, the film formability of the film is easily maintained.

[0019] In the GPC cumulative curve of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure, the amount of components having a molecular weight of 100,000 or less in the film is preferably 35% by mass or more, more preferably 38 to 65% by mass, even more preferably 40 to 60% by mass, particularly preferably 41 to 55% by mass, and most preferably 42 to 50% by mass. When the amount of components having a molecular weight of 100,000 or less is 35% by mass or more, heat resistance is unlikely to decrease. When the amount of components having a molecular weight of 100,000 or less is 65% by mass or less, film strength is unlikely to decrease. In this case, if a high-molecular-weight component with a long relaxation time or a long-chain branched component is included, it becomes easier to adjust the amount of components having a molecular weight of 100,000 or less contained in the polypropylene resin composition without significantly changing the overall viscosity, and therefore film formability can be easily improved without significantly affecting physical properties such as planarity, rigidity, and heat resistance.

[0020] The polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure contains polypropylene resin as a main component, but as long as the effects of the release film of the present disclosure are not impaired, the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure may contain additives such as resins other than polypropylene resin, known heat stabilizers, antioxidants, ultraviolet absorbers, nucleating agents, adhesives, anti-fogging agents, flame retardants, inorganic or organic fillers, etc.

[0021] However, it is preferable that these additives be added in small amounts, and in the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure, the content of resins other than polypropylene resin is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less. Also, in the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure, the content of additives other than resin is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less.

[0022] Examples of resins other than polypropylene resin include polyolefin resins other than polypropylene resins, various elastomers, etc. These may be sequentially polymerized using a multi-stage reactor, blended with polypropylene resin using a Henschel mixer, master pellets prepared in advance using a melt kneader may be diluted with polypropylene resin to a predetermined concentration, or the entire amount may be melt kneaded in advance before use.

[0023] (2) Polypropylene Resin The biaxially oriented polypropylene film of the present disclosure is made of a polypropylene resin composition containing a polypropylene resin as a main component. The term "main component" means that the proportion of the polypropylene resin in the polypropylene resin composition is 90% by mass or more, more preferably 93% by mass or more, even more preferably 95% by mass or more, and particularly preferably 97% by mass or more. When the polypropylene resin composition contains two or more different polypropylene resins, the total content of the polypropylene resins in the polypropylene resin composition is preferably within the above range.

[0024] The polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure, may be a polypropylene homopolymer or a polypropylene copolymer containing α-olefins other than propylene. However, it is preferable to use a polypropylene polymer that is substantially free of α-olefins other than propylene. Specifically, a "polypropylene polymer that is substantially free of α-olefins other than propylene" refers to a polypropylene (co)polymer whose constituent units are 99 mol% or more of propylene and 1 mol% or less of α-olefins other than propylene. Even when α-olefins other than propylene are contained, the content of α-olefins other than propylene (the total amount of ethylene and α-olefins having 4 or more carbon atoms) is preferably 1 mol% or less, more preferably 0.5 mol% or less, even more preferably 0.3 mol% or less, particularly preferably 0.1 mol% or less, and most preferably 0 mol%. Crystallinity is likely to be improved within the above range.

[0025] Examples of the α-olefin component having 4 or more carbon atoms include 1-butene, 1-pentene, 3-methyl-1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 5-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, and 1-eicosene.

[0026] The polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure, may be a mixture of two or more different polypropylene polymers, for example, two or more different polypropylene homopolymers, a polypropylene copolymer containing two or more different α-olefins other than propylene, or a mixture of one or more polypropylene homopolymers and one or more polypropylene copolymers containing one or more α-olefins other than propylene. In the case of a mixture of two or more different polypropylene polymers, it is preferable that the total content of the polypropylene polymers in the polypropylene resin composition is within the above range.

[0027] The following describes various suitable physical properties of the polypropylene resin that is the main component of the polypropylene resin composition that constitutes the biaxially oriented polypropylene film of the present disclosure. When two or more different polypropylene resins are used, the physical properties other than the melt flow rate are the mass average values ​​of the physical properties of each polypropylene resin.

[0028] The melting point of the polypropylene resin that is the main component of the polypropylene resin composition that constitutes the biaxially oriented polypropylene film of the present disclosure is preferably 158 to 170°C, more preferably 159 to 169°C, even more preferably 160 to 168°C, particularly preferably 161 to 167°C, and most preferably 162 to 166°C. When the melting point is 158°C or higher, flatness, rigidity, heat resistance at high temperatures, and the like are likely to be obtained. When the melting point is 170°C or lower, it is easy to suppress cost increases in terms of polypropylene production, and the film is less likely to break during film formation.

[0029] The melting point of the polypropylene resin is the main peak temperature of the endothermic peak accompanying melting, which is observed when 5 mg of polypropylene resin is packed into an aluminum pan, set in a differential scanning calorimeter (DSC), heated from 30°C to 230°C at a heating rate of 20°C / min in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin, then cooled to 30°C at a heating rate of -10°C / min, held at 30°C for 5 minutes, and then heated at a heating rate of 10°C / min.

[0030] The crystallization temperature of the polypropylene resin that is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure is preferably 105 to 135°C, more preferably 108 to 133°C, even more preferably 110 to 132°C, even more preferably 112 to 130°C, particularly preferably 114 to 128°C, and most preferably 116 to 127°C. If the crystallization temperature is 105°C or higher, crystallization is likely to proceed during width direction stretching and the subsequent cooling step, making it easier to obtain rigidity and heat resistance at high temperatures. If the crystallization temperature is 135°C or lower, it is less likely to increase costs in terms of polypropylene production and the film is less likely to break during film formation.

[0031] The crystallization temperature of the polypropylene resin is the main peak temperature of the exothermic peak observed when 5 mg of the polypropylene resin is packed into an aluminum pan, set in a DSC, heated from 30°C to 230°C at a heating rate of 20°C / min in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin, and then cooled to 30°C at a cooling rate of -10°C / min.

[0032] The melting point and crystallization temperature can be increased by blending a nucleating agent into the polypropylene resin. When a nucleating agent is blended, it is preferable that the melting point and crystallization temperature of the polypropylene resin blended with the nucleating agent be within the above ranges.

[0033] The polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure, preferably has a mesopentad fraction ([mmmm]%), an index of stereoregularity, of 97.0 to 99.9%, more preferably 97.5 to 99.7%, and even more preferably 98.0 to 99.5%. If it is less than 97.0%, there is a risk that high orientation cannot be achieved during stretching, or that crystallization is inhibited, resulting in deterioration of rigidity and heat resistance. On the other hand, if it is 97.0% or more, the crystallinity of the polypropylene resin is increased, improving the melting point, crystallinity, and crystalline orientation of the crystals in the film, making it easier to achieve flatness, rigidity, heat resistance at high temperatures, and the like. If it is 99.9% or less, it is easier to reduce the cost of polypropylene production and makes it less likely to break during film formation. The mesopentad fraction is measured by nuclear magnetic resonance spectroscopy (NMR spectroscopy). In order to adjust the mesopentad fraction of the polypropylene resin to fall within the above range, for example, methods such as washing the obtained polypropylene resin powder with a solvent such as n-heptane, or using an appropriate catalyst and / or co-catalyst may be used.

[0034] The melt flow rate (MFR) of the polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present disclosure, when measured in accordance with JIS K 7210 (1995) condition M (230°C, 2.16 kgf), is preferably 4.0 to 30 g / 10 min, more preferably 4.5 to 25 g / 10 min, even more preferably 4.8 to 22 g / 10 min, even more preferably 5.0 to 20 g / 10 min, particularly preferably 6.0 to 20 g / 10 min, and most preferably 7.5 to 15 g / 10 min. When the MFR of the polypropylene resin is 4.0 g / 10 min or more, a biaxially oriented polypropylene film with a low heat shrinkage rate is easily obtained. Furthermore, when the MFR of the polypropylene resin is 30 g / 10 min or less, the film formability of the film is easily maintained.

[0035] (3) Film-forming method for biaxially oriented polypropylene film The biaxially oriented polypropylene film of the present disclosure is preferably obtained by preparing an unstretched sheet made of a polypropylene resin composition containing a polypropylene resin as a main component, and biaxially stretching the sheet. Regarding biaxial stretching, it is preferable to stretch the sheet in the longitudinal direction and then in the width direction, but it may also be stretched in the width direction and then in the longitudinal direction. Examples of biaxial stretching methods include inflation simultaneous biaxial stretching, tenter simultaneous biaxial stretching, tenter sequential biaxial stretching, and tube stretching. From the viewpoints of film-forming stability and thickness uniformity, tenter sequential biaxial stretching is preferred.

[0036] The following describes a method for producing a biaxially oriented polypropylene film according to the present disclosure. Hereinafter, a method for producing a single-layer biaxially oriented polypropylene film using a tenter sequential biaxial stretching method will be described, but the method is not limited to the following method.

[0037] First, a polypropylene resin composition is heated and melted in a single-screw or twin-screw extruder, extruded through a T-die into a sheet, and then cooled and solidified by contacting it with a cooling roll to obtain an unstretched sheet. Next, this unstretched sheet is stretched in the longitudinal direction between two pairs of heated stretching rolls by increasing the rotation speed of the rear stretching roll to obtain a uniaxially stretched film. Subsequently, the uniaxially stretched film is heated in a preheating step, stretched in the width direction while gripping the film edges in a tenter-type stretching machine, heat-treated, and finally cooled to obtain a biaxially oriented polypropylene film. If necessary, at least one side of the biaxially oriented polypropylene film can be surface-treated, and then wound up on a winder to obtain a film roll.

[0038] The extrusion step, the longitudinal stretching step, the preheating step, the widthwise stretching step, the heat treatment step, and the cooling step will be described in this order below.

[0039] (3-1) Extrusion step First, a polypropylene resin composition containing a polypropylene resin as a main component is heated and melted in a range of 200 to 300°C in a single-screw or twin-screw extruder, and the sheet-shaped molten polypropylene resin composition is extruded from a T-die, brought into close contact with a metal cooling roll using a contacting device such as an air knife, and cooled and solidified to obtain an unstretched sheet. The obtained unstretched sheet may further be placed in a water tank.

[0040] The temperature of the cooling roll, or the cooling roll and water bath, is preferably 10°C or higher and Tc°C or lower, and when it is desired to increase the transparency of the film, it is preferable to cool and solidify it with a cooling roll at 10 to 50°C. When a propylene homopolymer having a mesopentad fraction of 97.0% or higher is used, the cooling temperature is preferably 40°C or lower from the viewpoint of facilitating the stretching in the next step, and more preferably 30°C or lower from the viewpoint of reducing thickness unevenness. However, when it is desired to increase the degree of crystal orientation after successive biaxial stretching, a cooling temperature of 40°C or higher may be preferable.

[0041] From the viewpoint of cooling efficiency, the thickness of the unstretched sheet is preferably 3500 μm or less, more preferably 3000 μm or less. The thickness of the unstretched sheet may be appropriately adjusted depending on the thickness of the film after sequential biaxial stretching. The thickness of the unstretched sheet can be controlled by the extrusion speed of the polypropylene resin composition, the lip width of the T-die, etc.

[0042] (3-2) Longitudinal Stretching Step The longitudinal stretching temperature is preferably Tm-30 to Tm-7°C, more preferably Tm-27 to Tm-12°C, and even more preferably Tm-25 to Tm-10°C. If the temperature is Tm-30°C or higher, the subsequent widthwise stretching becomes easy and thickness unevenness tends to be reduced. If the temperature is Tm-7°C or lower, the heat shrinkage rate tends to be small, and there is little risk of the film sticking to the stretching rolls, making stretching difficult, or of the film becoming rough on the surface, resulting in a decrease in quality.

[0043] The stretching ratio in the longitudinal direction is preferably 3.5 to 8.0 times, more preferably 3.8 to 7.0 times, and even more preferably 4.2 to 6.0 times. When the stretching ratio is 3.5 times or more, strength is easily increased and thickness unevenness is easily reduced. When the stretching ratio is 8.0 times or less, width direction stretching is easily performed in the width direction stretching step, and productivity is easily improved.

[0044] Although the longitudinal stretching may be performed in two or more stages using three or more pairs of stretching rolls, it is preferable to perform the stretching in one stage using two pairs of stretching rolls. When the stretching is performed in multiple stages, it is preferable that the highest stretching temperature is within the above range.

[0045] (3-3) Preheating Step It is preferable to heat the uniaxially stretched film after longitudinal stretching in the preheating step to sufficiently soften the polypropylene resin composition before the widthwise stretching step. The heating temperature in the preheating step is preferably Tm to Tm + 25°C, more preferably Tm + 2 to Tm + 20°C, and even more preferably Tm + 3 to Tm + 15°C. By setting the heating temperature in the preheating step to the melting point or higher, softening proceeds, making widthwise stretching easier. Furthermore, by setting the heating temperature in the preheating step to Tm + 25°C or lower, orientation proceeds during widthwise stretching, making it easier to develop rigidity. Note that if the preheating step consists of multiple zones, the temperature of the hottest zone among them is taken as the preheating temperature.

[0046] (3-4) Width Direction Stretching Step The width direction stretching temperature is preferably Tm-10°C or higher and the heating temperature in the preheating step or lower. If it is Tm-10°C or higher, the rigidity of the obtained film is likely to be improved. Furthermore, it is more preferably Tm-9 to Tm+10°C, even more preferably Tm-7 to Tm+7°C, and particularly preferably Tm-5 to Tm+5°C. If it is Tm+10°C or lower, stretching unevenness is less likely to occur.

[0047] In the width direction stretching step, it is preferable to add a later stretching step in which the film is stretched at a lower temperature following the width direction stretching step (hereinafter sometimes referred to as the early stretching step) in the above temperature range. By providing the later stretching step, the rigidity of the film can be easily increased.

[0048] The stretching ratio in the width direction is preferably 10 to 20 times, more preferably 11 to 17 times, even more preferably 12 to 15 times, and particularly preferably 12.5 to 15 times. If it is 10 times or more, rigidity is likely to be increased and thickness unevenness is likely to be reduced. Furthermore, if it is 20 times or less, the heat shrinkage rate is likely to be reduced and the film is unlikely to break during stretching. When a later stretching step is added, it is preferable that the total stretching ratio be within the above range.

[0049] (3-5) Heat Treatment Step Heat treatment is performed after the width direction stretching step is completed. Specific means for heat treatment include a method of providing a zone with a higher temperature than the stretching zone after the width direction stretching is completed, a method of increasing the zone temperature in the latter half of stretching and passing the film through a zone of the same temperature after the stretching is completed, etc. Heating means include a method of blowing hot air or a method of heating with an infrared heater, but are not particularly limited as long as the method is capable of increasing the temperature of the film from that at the end of the width direction stretching step.

[0050] The heat treatment step is preferably carried out immediately after the width direction stretching step is completed (i.e., immediately after the width direction stretching reaches the final stretch ratio). The temperature in the heat treatment step is preferably higher than that at the end of the width direction stretching step, and specifically, is preferably the width direction stretching temperature + 1°C or more. The heat treatment step is preferably carried out in two stages: an early heat treatment step and a later heat treatment step, and it is preferable that the early heat treatment step is performed at a temperature higher than that at the end of the width direction stretching step, and then the later heat treatment step is performed at a temperature lower than that in the early heat treatment step. The early heat treatment step and the later heat treatment step will be described below.

[0051] (Preliminary Heat Treatment Step) The heating temperature in the initial heat treatment step is preferably Tm to Tm + 20°C, more preferably Tm + 3 to Tm + 18°C, even more preferably Tm + 4 to Tm + 14°C, and particularly preferably Tm + 5 to Tm + 10°C. Heating in the heat treatment step after the stretching step relaxes the molecular chain orientation formed during stretching, making crystallization more likely to occur in the final heat treatment step. Heating at a temperature lower than Tm°C prevents relaxation, leaving the molecular chains highly tense and potentially inhibiting crystallization. On the other hand, heating at a temperature higher than Tm + 20°C promotes melting, relaxing many of the oriented molecular chains and reducing rigidity. The temperature can be gradually increased from the temperature at the end of width direction stretching to the heating temperature, or it can be increased in stages or in a single step. Raising the temperature in stages or in a single step is preferred because it makes it easier to control the molecular chain orientation in the film.

[0052] In the heat treatment step, the film may or may not be relaxed (relaxed) in the width direction. Specifically, the relaxation rate is preferably 0 to 3%, more preferably 0 to 1%, and even more preferably 0% (no relaxation). Within the above range, the rigidity is less likely to decrease and the film thickness fluctuations tend to be small. If the relaxation rate is higher than 3%, many of the oriented molecular chains are relaxed, so the rigidity tends to decrease. Note that relaxation is not necessary when it is desired to further increase the rigidity. Furthermore, as long as the effects of the release film of the present disclosure are not impaired, the film may be slightly expanded to suppress sagging, etc.

[0053] (Later Heat Treatment Step) The heating temperature in the later heat treatment step is preferably Tm-70 to Tm°C, more preferably Tm-50 to Tm-1°C, even more preferably Tm-40 to Tm-2°C, and particularly preferably Tm-30 to Tm-3°C. When the heat treatment is performed at a temperature higher than Tm°C, crystallization does not proceed and the heat shrinkage rate is less likely to decrease. On the other hand, when the heat treatment is performed at a temperature lower than Tm-70°C, lamellar thickening does not proceed and the melting point of the film is less likely to increase. In other words, heat resistance at high temperatures is impaired.

[0054] In the latter heat treatment step, the film may be relaxed in the width direction in order to adjust the thermal shrinkage rate. When relaxed, the relaxation rate is preferably 1 to 8%, more preferably 2 to 6%, and even more preferably 3 to 5%, but relaxation is not necessary. Within the above range, the rigidity is less likely to decrease and the thickness variation of the film is likely to be small. However, relaxation is not necessary when a higher rigidity is desired.

[0055] During the widthwise stretching process, molecular chains are oriented by stretching, but remain strongly entangled, resulting in an excessively constrained state of the molecular chains. If a heat treatment process is performed in this state, the excessively constrained molecular chains due to entanglement make it difficult to increase the crystallinity, and the lamellae in the crystalline region do not increase in thickness. This leads to the formation of crystalline regions that melt at lower temperatures, resulting in insufficient heat resistance at high temperatures. Therefore, in conventional film-forming processes, in order to eliminate the entanglement of molecular chains after widthwise stretching, the film is relaxed by several percent to several tens of percent during the heat treatment process to promote crystallization. However, relaxation reduces the molecular chain orientation generated during the widthwise stretching process, resulting in a decrease in the rigidity of the film. Therefore, it is difficult to achieve both heat resistance and rigidity in conventional film-forming processes. Furthermore, heat treatment at high temperatures can cause excessive melting, resulting in the whitening of the film.

[0056] To solve this problem, it is preferable to perform a heat treatment immediately after the widthwise stretching step at a temperature higher than that used for the widthwise stretching step, at a relaxation rate of 3% or less, thereby eliminating the constraint of the molecular chains due to excessive entanglement while maintaining the molecular chain orientation. By performing this heat treatment step, the presence of constrained molecular chains due to entanglement of molecular chains is reduced, which increases the degree of crystallinity and makes it easier to increase the thickness of the lamellae in the crystalline portion, thereby enabling the film to exhibit sufficient heat resistance even at high temperatures.

[0057] Furthermore, increasing the amount of low molecular weight polypropylene components in the polypropylene resin composition constituting the biaxially oriented polypropylene film can reduce the entanglement of molecular chains, thereby weakening the heat shrinkage stress in parts other than the lamellae of the crystalline portion and further reducing the heat shrinkage rate, which is preferable.

[0058] (3-6) Cooling Step It is preferable to cool the film immediately after the heat treatment step. The cooling temperature is preferably 10°C or higher and 140°C or lower, more preferably 15°C or higher and 135°C or lower, even more preferably 20°C or higher and 130°C or lower, particularly preferably 20°C or higher and 80°C or lower, and most preferably 20°C or higher and 50°C or lower. By providing a cooling step, the state of molecular orientation within the film can be fixed.

[0059] Although the manufacturing method for the biaxially oriented polypropylene film of the present disclosure when it is a single layer has been described above, the biaxially oriented polypropylene film of the present disclosure may have a layer having another function (hereinafter referred to as a functional layer) laminated on at least one side. The functional layer may be laminated on only one side or on both sides. When the functional layer contains a resin, the resin may be the polypropylene resin constituting the biaxially oriented polypropylene film, or a resin other than the polypropylene resin constituting the biaxially oriented polypropylene film may be used. The number of functional layers laminated on each side may be one, two, or three or more, but from the viewpoint of ease of manufacturing, one or two layers is preferred. The lamination method is not particularly limited, and for example, coextrusion using a feed block method or a multi-manifold method is preferred. In addition, to impart printability, corona treatment may be applied to one or both sides of the film.

[0060] The biaxially oriented polypropylene film of the present disclosure can be wound into a roll to produce a film roll having a width of about 2000 to 12000 mm and a length of about 1000 to 50000 m, making it possible to obtain a long film roll. It can also be slit according to the application to produce a slit roll having a width of about 300 to 2000 mm and a length of about 500 to 5000 m.

[0061] (4) Physical Properties of Biaxially Oriented Polypropylene Film The biaxially oriented polypropylene film according to the present disclosure preferably has the following properties: Here, the "longitudinal direction (MD)" of the biaxially oriented polypropylene film according to the present disclosure refers to the direction corresponding to the flow direction in the film production process, and the "transverse direction (TD)" refers to the direction perpendicular to the flow direction in the film production process, and the same applies hereinafter.

[0062] For polypropylene films whose flow direction in the film manufacturing process is unknown, wide-angle X-rays are incident perpendicularly to the film surface, and the scattering peaks resulting from the (110) plane of the α-type crystals are scanned in the circumferential direction. The direction with the greatest diffraction intensity in the obtained diffraction intensity distribution is designated the "longitudinal direction," and the direction perpendicular to that is designated the "width direction."

[0063] (4-1) Width direction length In thermomechanical analysis, when the temperature is increased from 30°C to 130°C at a temperature increase rate of 10°C / min, the width direction length of the biaxially oriented polypropylene film of the present disclosure at 30°C is X ０ The maximum value of the width direction length during the temperature rise is X １ , the minimum value of the length in the width direction during the temperature rise is X ２ Then, (X １ -X ０ ) / X ０ The percentage of is preferably 0.20% or less, more preferably 0.19% or less, even more preferably 0.18% or less, particularly preferably 0.17% or less, and most preferably 0.16% or less. When it is 0.20% or less, deformation of the film can be suppressed even after the film is heated at high temperatures, such as during coating and drying of a release agent, adhesive, or photosensitive resin, or during heat processing with a roll, so that the flatness of the film is less likely to deteriorate and the processability of the film can be improved. Furthermore, when high-temperature printing ink is transferred during printing, printing pitch deviation is less likely to occur. (X １ -X ０ ) / X ０ The lower limit is not particularly limited, but in view of technical difficulties, it is, for example, 0.01% or more, preferably 0.02% or more.

[0064] (X ２ -X ０ ) / X ０ is preferably -0.50% or more, more preferably -0.45% or more, even more preferably -0.40% or more, particularly preferably -0.35% or more, and most preferably -0.30% or more. When it is -0.50% or more, deformation of the film can be suppressed even after the film is heated at high temperatures, such as during coating and drying of a release agent, adhesive, or photosensitive resin, or during heat processing with a roll, so that the flatness of the film is less likely to deteriorate and the processability of the film can be improved. (X ２ -X ０ ) / X ０ The larger the content, the better. There is no particular upper limit to the content, but in view of technical difficulties, it is, for example, 0.01% or less, and preferably 0.00% or less.

[0065] In a thermomechanical analysis, when the temperature was increased from 30°C to 160°C at a heating rate of 10°C / min, the length in the width direction of the biaxially oriented polypropylene film of the present disclosure was 0.9950X. ０ The temperature at which the shrinkage becomes equal to or less than 0.9950°C (the temperature at 0.5% shrinkage) is preferably 129°C or higher, more preferably 130°C or higher, even more preferably 131°C or higher, particularly preferably 132°C or higher, and most preferably 133°C or higher. ０ The temperature at which the width is 0.9950X or less when the temperature is increased from 30°C to 160°C at a rate of 10°C / min. ０ It refers to the lowest temperature that is below 0.9950X ０ When the temperature at which the temperature becomes equal to or lower than 129°C, deformation of the film can be suppressed even after the film is heated at high temperatures, such as during coating and drying of a release agent, adhesive, or photosensitive resin, or during heat processing with a roll, so that the flatness of the film is less likely to deteriorate and the processability of the film can be improved. ０The temperature at which the thickness becomes equal to or less than 0.9950X is preferably higher, and the upper limit is not particularly limited, but is, for example, 160°C or lower, preferably 156°C or lower. When the temperature is 160°C or lower, practical production is easy and transparency is easily maintained. In addition, even when the temperature is increased from 30°C to 160°C, the length in the width direction never becomes equal to or less than 0.9950X. ０ If it is not below this, the temperature at 0.5% shrinkage is determined to exceed 160°C.

[0066] (4-2) Storage Modulus The storage modulus is determined by dynamic viscoelasticity measurement, specifically, by raising the temperature from -60°C to 160°C at a heating rate of 5°C / min in a nitrogen atmosphere under a measuring load of 10 gf and a frequency of 10 Hz, and measuring the storage modulus at each temperature during the heating. The present inventors have found that while increasing the rigidity and heat resistance alone may not be enough to maintain the flatness of the film after heating, controlling the storage modulus in a predetermined temperature range so that it falls within a predetermined range makes it possible to maintain the flatness of the film even after heating.

[0067] The storage modulus of the biaxially oriented polypropylene film in the present disclosure in the longitudinal direction at 23° C. is preferably 2.0 GPa or more, more preferably 2.8 GPa or more. The storage modulus of the biaxially oriented polypropylene film in the longitudinal direction at 23° C. is preferably 2.0 to 5.0 GPa, more preferably 2.3 to 4.5 GPa, even more preferably 2.5 to 4.3 GPa, even more preferably 2.8 to 4.2 GPa, particularly preferably 2.9 to 4.1 GPa, and most preferably 3.0 to 4.0 GPa.

[0068] The storage modulus in the width direction of the biaxially oriented polypropylene film of the present disclosure at 23°C is preferably 8.0 GPa or more, preferably 8.0 to 15.0 GPa, more preferably 8.2 to 14.0 GPa, even more preferably 8.4 to 13.5 GPa, and particularly preferably 8.6 to 13.0 GPa.

[0069] When the storage modulus at 23°C in the longitudinal and transverse directions is within the above range, the strength of the biaxially oriented polypropylene film is significantly increased, and even if the film is thin, it can maintain its stiffness and strength, which contributes greatly to reducing the volume of the film. In addition, the flatness of the film is less likely to deteriorate and the processability of the film can be improved.

[0070] The storage modulus in the longitudinal direction of the biaxially oriented polypropylene film in the present disclosure at 120° C. is preferably 0.5 to 2.5 GPa, more preferably 0.6 to 2.3 GPa, even more preferably 0.7 to 2.1 GPa, and particularly preferably 0.8 to 2.0 GPa. When the storage modulus in the longitudinal direction at 120° C. is within the above range, strength at high temperatures tends to be high, and printing pitch deviation is less likely to occur when hot printing ink is transferred during printing.

[0071] The storage modulus in the width direction at 120°C of the biaxially oriented polypropylene film of the present disclosure is preferably 2.1 to 8.0 GPa, more preferably 2.2 to 7.8 GPa, even more preferably 2.3 to 7.6 GPa, and particularly preferably 2.4 to 7.4 GPa. When the storage modulus in the width direction at 120°C is within the above range, strength at high temperatures tends to be increased, and printing pitch deviation is less likely to occur when transferring high-temperature printing ink during printing. Furthermore, the flatness of the film is less likely to deteriorate, and the processability of the film can be improved.

[0072] The storage modulus in the longitudinal direction of the biaxially oriented polypropylene film in the present disclosure at 140°C is preferably 0.3 to 1.5 GPa, more preferably 0.35 to 1.45 GPa, even more preferably 0.4 to 1.4 GPa, and particularly preferably 0.45 to 1.35 GPa.

[0073] The storage modulus in the width direction of the biaxially oriented polypropylene film in the present disclosure at 140°C is preferably 1.3 to 5.0 GPa, more preferably 1.35 to 4.6 GPa, even more preferably 1.4 to 4.2 GPa, and particularly preferably 1.45 to 3.8 GPa.

[0074] When the storage modulus at 140°C in the longitudinal and transverse directions is within the above range, the strength at high temperatures tends to be high, and printing pitch deviation is less likely to occur when transferring high-temperature printing ink during printing. In addition, the flatness of the film is less likely to deteriorate and the processability of the film can be improved.

[0075] The storage modulus in the longitudinal direction of the biaxially oriented polypropylene film in the present disclosure at 150°C is preferably 0.1 to 1.0 GPa, more preferably 0.15 to 0.9 GPa, even more preferably 0.2 to 0.8 GPa, and particularly preferably 0.25 to 0.7 GPa.

[0076] The storage modulus in the width direction of the biaxially oriented polypropylene film in the present disclosure at 150°C is preferably 0.85 to 2.5 GPa, more preferably 0.9 to 2.4 GPa, even more preferably 0.95 to 2.3 GPa, and particularly preferably 1.0 to 2.2 GPa.

[0077] When the storage modulus at 150°C in the longitudinal and transverse directions is within the above range, the strength at high temperatures tends to be high, and printing pitch deviation is less likely to occur when transferring high-temperature printing ink during printing. In addition, the flatness of the film is less likely to deteriorate and the processability of the film can be improved.

[0078] The sum of the longitudinal storage modulus at 23°C and the longitudinal storage modulus at 120°C of the biaxially oriented polypropylene film in the present disclosure is preferably 3.0 to 8.0 GPa, more preferably 3.1 to 7.5 GPa, even more preferably 3.2 to 7.0 GPa, and particularly preferably 3.3 to 6.5 GPa.

[0079] The sum of the storage modulus in the width direction at 23°C and the storage modulus in the width direction at 120°C of the biaxially oriented polypropylene film in the present disclosure is preferably 8.9 to 19.0 GPa, more preferably 9.2 to 18.0 GPa, even more preferably 9.8 to 17.0 GPa, and particularly preferably 10.0 to 16.0 GPa.

[0080] The sum of the longitudinal storage modulus at 23°C and the longitudinal storage modulus at 140°C of the biaxially oriented polypropylene film in the present disclosure is preferably 3.0 GPa or more, more preferably 3.0 to 8.0 GPa, even more preferably 3.1 to 7.5 GPa, particularly preferably 3.2 to 7.0 GPa, and most preferably 3.3 to 6.5 GPa.

[0081] The sum of the storage modulus in the width direction at 23°C and the storage modulus in the width direction at 140°C of the biaxially oriented polypropylene film in the present disclosure is preferably 9.2 GPa or more, more preferably 9.2 to 19.0 GPa, even more preferably 9.2 to 18.0 GPa, particularly preferably 9.8 to 17.0 GPa, and most preferably 10.0 to 16.0 GPa.

[0082] When the sum of the longitudinal storage modulus at 23°C and the longitudinal storage modulus at 120°C or 140°C in the longitudinal and transverse directions is within the above range, the strength at high temperatures tends to be high, and printing pitch deviation is less likely to occur when hot printing ink is transferred during printing. In addition, the flatness of the film is less likely to deteriorate and the processability of the film can be improved.

[0083] (4-3) Loss Modulus The loss modulus is determined by dynamic viscoelasticity measurement. Specifically, the temperature is raised from -60°C to 160°C at a heating rate of 5°C / min under a nitrogen atmosphere with a measurement load of 10 gf and a frequency of 10 Hz, and the loss modulus is measured at each temperature during the heating process. Five parameters related to the loss modulus are described below: the maximum value E"(A) of the loss modulus at -25°C to 25°C, the minimum value E"(B) of the loss modulus at 25°C to 75°C, the maximum value E"(C) of the loss modulus at 100°C to 160°C, E"(C) / E"(A), and E"(B) / E"(C). Note that in this specification, even when simply referring to the "loss modulus," it all refers to the loss modulus in the width direction.

[0084] (Maximum value of loss modulus E"(A) at -25°C to 25°C) Takayanagi Motoo, "Temperature Dispersion of Crystalline Polymers", Polymer, Society of Polymer Science, 1961, Vol. 10, No. 3, pp. 289-295, describes that in polypropylene films, relaxation (main dispersion) due to micro-Brownian motion of the main chain occurs at -25°C to 25°C, and also describes that the loss modulus at -25°C to 25°C increases as the degree of orientation by stretching increases. E"(A) is preferably 0.40 GPa or more, more preferably 0.42 GPa or more, even more preferably 0.44 GPa or more, particularly preferably 0.46 GPa or more, and most preferably 0.48 GPa or more. When E"(A) is 0.40 GPa or more, rigidity tends to be high, deformation due to heating can be suppressed, and flatness after heating can be easily ensured. There is no particular upper limit to E"(A), but a realistic value is, for example, 0.70 GPa or less, and preferably 0.60 GPa or less.

[0085] (Minimum value E"(B) of loss modulus at 25°C to 75°C) Takayanagi Motoo, "Temperature Dispersion of Crystalline Polymers", Polymer, Society of Polymer Science, 1961, Vol. 10, No. 3, pp. 289-295, describes that by increasing the crystallinity in the film, which greatly contributes to heat resistance, and reducing the amount of crystals that melt in a relatively low temperature range above the glass transition temperature of the polypropylene resin (hereinafter referred to as the low temperature range), relaxation due to melting is less likely to occur, and as a result, relaxation of the amorphous portion is also suppressed (even when treated at high temperatures, the mobility of the amorphous portion is reduced, resulting in good heat resistance). E"(B) is preferably 0.26 GPa or more, more preferably 0.27 GPa or more, even more preferably 0.28 GPa or more, even more preferably 0.29 GPa or more, and particularly preferably 0.30 GPa or more. If E"(B) is 0.26 GPa or more, the heat shrinkage rate is likely to decrease. Furthermore, since few crystals melt in the low temperature region and melting is suppressed, deformation after heating can be suppressed and flatness can be improved. There are no particular restrictions on the upper limit of E"(B), but a realistic value is, for example, 0.60 GPa or less, and preferably 0.50 GPa or less.

[0086] (Maximum value of loss modulus E"(C) at 100°C to 160°C) Takayanagi Motoo, "Temperature Dispersion of Crystalline Polymers", Polymers, Society of Polymer Science, 1961, Vol. 10, No. 3, pp. 289-295, describes that when the temperature of a stretched polypropylene film is increased and the loss modulus is measured at each temperature, a peak due to crystal dispersion appears at 100°C or higher. This crystal dispersion peak is thought to be due to an increase in frictional viscosity between the planes of the crystalline structure, and increases when the film is stretched at an optimum temperature during film formation. An increase in frictional viscosity indicates strong stress transmission within the crystalline phase, and is thought to correlate with increased rigidity. E"(C) is preferably 0.28 to 0.80 GPa, more preferably 0.29 to 0.75 GPa, even more preferably 0.30 to 0.70 GPa, particularly preferably 0.31 to 0.65 GPa, and most preferably 0.32 to 0.60 GPa. When E"(C) is 0.28 GPa or more, the rigidity is likely to be high, deformation due to heating can be suppressed, and flatness after heating can be easily ensured. In addition, the film is less likely to deform during processing such as printing. In addition, when E"(C) is 0.80 GPa or less, practical production is easy and tearing in the width direction is less likely.

[0087] E"(C) / E"(A) is preferably 0.60 to 1.30, more preferably 0.62 to 1.20, even more preferably 0.64 to 1.10, particularly preferably 0.66 to 1.00, and most preferably 0.68 to 0.90. When E"(C) / E"(A) is 0.60 or more, rigidity tends to be high, deformation due to heating can be suppressed, and flatness after heating can be easily ensured. Furthermore, when E"(C) / E"(A) is 1.30 or less, practical manufacturing becomes easy and tearing in the width direction becomes less likely.

[0088] E"(B) / E"(C) is preferably 0.60 or more, more preferably 0.60 to 1.30, even more preferably 0.61 to 1.25, even more preferably 0.62 to 1.20, particularly preferably 0.63 to 1.15, and most preferably 0.64 to 1.10. When E"(B) / E"(C) is 0.60 or more, there is little crystal melting in the low temperature range, making it difficult for relaxation to occur due to melting, which in turn suppresses relaxation of the amorphous portion. As a result, the mobility of the amorphous portion is low even when treated at high temperatures, and flatness and heat resistance can be improved. When E"(B) / E"(C) is 1.30 or less, rigidity is less likely to decrease, and thickness fluctuation of the film is likely to be small.

[0089] (4-4) Thickness The thickness of the biaxially oriented polypropylene film in the present disclosure is not particularly limited and may be appropriately set depending on the application, but is preferably 2 to 100 μm, more preferably 3 to 80 μm, even more preferably 4 to 60 μm, particularly preferably 8 to 50 μm, and most preferably 10 to 40 μm. A thickness of 2 μm or more makes it easier to obtain rigidity in the film, and as a result, makes it easier to obtain strength in the film. Furthermore, a thickness of 100 μm or less makes it difficult for the cooling rate of the unstretched sheet to decrease during the extrusion process.

[0090] (4-5) Stress at 5% Elongation (F5) The stress at 5% elongation in the longitudinal direction (F5) of the biaxially oriented polypropylene film of the present disclosure at 23°C is preferably 40 to 70 MPa, more preferably 42 to 65 MPa, even more preferably 46 to 62 MPa, and particularly preferably 48 to 60 MPa. At 40 MPa or higher, the film has high rigidity, which can suppress deformation due to heating and makes it easier to ensure flatness after heating. At 70 MPa or lower, practical manufacturing becomes easier and the balance between the longitudinal and transverse directions tends to improve. The stress at 5% elongation in the longitudinal direction can be kept within the above range by adjusting the stretch ratio or relaxation rate, or by adjusting the temperature during film formation.

[0091] The stress at 5% elongation in the width direction (F5) of the biaxially oriented polypropylene film of the present disclosure at 23°C is preferably 150 to 280 MPa, more preferably 152 to 250 MPa, even more preferably 154 to 230 MPa, particularly preferably 156 to 210 MPa, and most preferably 158 to 200 MPa. At 150 MPa or higher, the film has high rigidity, which can suppress deformation due to heating and makes it easier to ensure flatness after heating. At 280 MPa or lower, practical manufacturing is easy and the film is less likely to tear in the width direction. The stress at 5% elongation in the width direction can be kept within the above range by adjusting the stretch ratio and relaxation rate, or by adjusting the temperature during film production.

[0092] (4-6) Heat Shrinkage The heat shrinkage in the longitudinal direction of the biaxially oriented polypropylene film of the present disclosure at 120°C is preferably 2.5% or less, more preferably 2.0% or less, even more preferably 1.7% or less, and particularly preferably 1.5% or less. If it is 2.5% or less, printing pitch deviation is less likely to occur when transferring printing ink. A lower heat shrinkage in the longitudinal direction at 120°C is preferable, and although the lower limit is not particularly limited, it is, for example, 0.1% or more, preferably 0.3% or more, in consideration of technical difficulties. The heat shrinkage in the longitudinal direction at 120°C can be adjusted to fall within the above range by adjusting the stretch ratio, stretching temperature, and heat treatment temperature.

[0093] The heat shrinkage rate in the width direction of the biaxially oriented polypropylene film of the present disclosure at 120°C is preferably 1.1% or less, more preferably 1.0% or less, even more preferably 0.7% or less, particularly preferably 0.5% or less, and most preferably 0.3% or less. When it is 1.1% or less, deterioration of flatness and wrinkles are unlikely to occur even after the film is heated at high temperatures, such as during coating and drying of a release agent, adhesive, or photosensitive resin, or during heat processing with a roll. The lower limit of the heat shrinkage rate in the width direction at 120°C is not particularly limited, but is, for example, -0.2%. The heat shrinkage rate in the width direction at 120°C can be kept within the above range by adjusting the stretch ratio, stretching temperature, and heat treatment temperature.

[0094] The heat shrinkage rate in the longitudinal direction of the biaxially oriented polypropylene film in the present disclosure at 150°C is preferably 10% or less, more preferably 7.0% or less, even more preferably 6.0% or less, even more preferably 5.0% or less, particularly preferably 4.5% or less, and most preferably 4.0% or less. If it is 10% or less, printing pitch deviation is less likely to occur when transferring printing ink. A lower heat shrinkage rate in the longitudinal direction at 150°C is preferable, and although there is no particular lower limit, it is, for example, 0.1% or more, preferably 0.5% or more, in consideration of technical difficulties. The heat shrinkage rate in the longitudinal direction at 150°C can be kept within the above range by adjusting the stretch ratio, stretching temperature, and heat treatment temperature.

[0095] The heat shrinkage rate in the width direction of the biaxially oriented polypropylene film of the present disclosure at 150°C is preferably 20% or less, more preferably 15% or less, even more preferably 12% or less, even more preferably 10% or less, particularly preferably 9.0% or less, and most preferably 8.5% or less. When the heat shrinkage rate is 20% or less, deformation of the film can be suppressed even after heating at high temperatures, such as during coating and drying of a release agent, adhesive, or photosensitive resin, or during heat processing with a roll. This prevents deterioration of the film's flatness and improves the film's processability. The lower limit of the heat shrinkage rate in the width direction at 150°C is not particularly limited, but is, for example, 0% or more, preferably 1% or more. The heat shrinkage rate in the width direction at 150°C can be kept within the above range by adjusting the stretch ratio, stretching temperature, and heat treatment temperature.

[0096] When the heat shrinkage rate in the longitudinal direction at 150°C is 10% or less and the heat shrinkage rate in the width direction is 20% or less, deformation of the film can be suppressed even after heating at high temperatures, such as during coating and drying of a release agent, adhesive, or photosensitive resin, or during heat processing with a roll. This prevents deterioration of the film's flatness and improves the film's processability. In particular, when the heat shrinkage rate in the longitudinal direction at 150°C is 8.0% or less and the heat shrinkage rate in the width direction at 150°C is 15% or less, the above effects can be more effectively achieved. To reduce the heat shrinkage rate at 150°C, it is effective to set the amount of components with a molecular weight of 100,000 or less to 35% by mass or more when measuring the gel permeation chromatography (GPC) integrated curve of the polypropylene resin composition constituting the film.

[0097] (4-7) Thickness Uniformity The lower limit of the thickness uniformity of the biaxially oriented polypropylene film of the present disclosure is preferably 0% or more, more preferably 0.1% or more, even more preferably 0.5% or more, and particularly preferably 1% or more. The upper limit of the thickness uniformity is preferably 20% or less, more preferably 17% or less, even more preferably 15% or less, particularly preferably 12% or less, and most preferably 10% or less. Within the above range, defects are less likely to occur during post-processing such as coating or printing, making it suitable for use in applications requiring precision.

[0098] The thickness uniformity was measured as follows: A test piece 40 mm in width was cut out from a steady region where the film properties were stable in the length direction of the film, and the film thickness was measured continuously over 20,000 mm using a film feeder (Micron Measurement Instruments, A90172) and a continuous film thickness measuring instrument (Anritsu Corporation, K-313A wide-range high-sensitivity electronic micrometer), and the thickness uniformity was calculated using the following formula: Thickness uniformity (%) = [(maximum thickness - minimum thickness) / average thickness] x 100

[0099] (4-8) Preferred Aspects of Film Properties The release film of the present disclosure has a substrate made of a biaxially oriented polypropylene film, and the biaxially oriented polypropylene film of the release film according to the first embodiment satisfies the following requirements (1) and (2) among the properties of the biaxially oriented polypropylene film described above. (1) In a thermomechanical analysis, when the temperature is increased from 30°C to 160°C at a rate of 10°C / min, the length in the width direction of the biaxially oriented polypropylene film is 0.9950X ０ (2) The storage modulus in the longitudinal direction at 23°C is 2.0 GPa or more, and the storage modulus in the transverse direction at 23°C is 8.0 GPa or more.

[0100] The biaxially oriented polypropylene film of the release film according to the second embodiment satisfies the following requirements (1) and (2) among the properties of the biaxially oriented polypropylene film described above: (1) The storage modulus in the longitudinal direction at 23° C. is 2.8 GPa or more, and the storage modulus in the width direction at 23° C. is 8.0 GPa or more. (2) The heat shrinkage rate in the longitudinal direction at 150° C. is 4.5% or less, and the heat shrinkage rate in the width direction at 150° C. is 9.0% or less.

[0101] The biaxially oriented polypropylene film of the release film according to the third embodiment satisfies the following requirements (1), (2), and (3) among the properties of the biaxially oriented polypropylene film described above. (1) The sum of the longitudinal storage modulus at 23°C and the longitudinal storage modulus at 140°C is 3.0 GPa or more. (2) The sum of the widthwise storage modulus at 23°C and the widthwise storage modulus at 140°C is 9.2 GPa or more. (3) In dynamic viscoelasticity measurement, when the minimum value of the loss modulus from 25°C to 75°C is E''(B) and the maximum value of the loss modulus from 100°C to 160°C is E''(B) / E''(C), the ratio is 0.60 or more.

[0102] The release films of the first to third embodiments described above maintain excellent flatness even after heating. In other words, when the biaxially oriented polypropylene film according to the present disclosure is used, the flatness is not easily lost even after heat drying, making it suitable as a release film for optical applications and other applications requiring high flatness. Furthermore, it is possible to achieve both rigidity and dimensional stability from room temperature to high temperatures, resulting in a release film with excellent flatness. The use of the biaxially oriented polypropylene film according to the present disclosure can provide a release film suitable for thin film manufacturing processes, which does not wrinkle or curl due to heat during release processing and has good flatness. It can also provide various laminates, such as pressure-sensitive adhesive layer laminates, photosensitive resin laminates, and transfer laminates, which do not wrinkle or curl due to heat during post-processing and have good flatness.

[0103] (5) Uses of Release Films The release film according to the present disclosure can be used to protect adhesive surfaces and as a base for the production of resin films and functional sheets. The biaxially oriented polypropylene film according to the present disclosure can suppress deformation of the film even after high-temperature heating, such as during heat processing with a roll, printing, or heat sealing, and is less likely to lose its flatness and can improve the processability of the film. Therefore, even after applying a silicone release agent or a polymer solution to the biaxially oriented polypropylene film according to the present disclosure and drying it by heating, the film is less likely to lose its flatness, making it suitable as a release film for optical applications and other applications requiring high flatness.

[0104] (5-1) Release Film Laminated with a Release Agent Layer The release film according to the present disclosure may be used without any particular release treatment, or may be used by applying a release agent such as a silicone resin to at least one surface of the biaxially oriented polypropylene film. The release agent layer is formed by applying the release agent to the biaxially oriented polypropylene film.

[0105] When obtaining a release film having a release agent applied to its surface, the surface wet tension of the biaxially oriented polypropylene film is preferably 38 mN / m or more. A wet tension of 38 mN / m or more improves the adhesion between the release agent layer and the biaxially oriented polypropylene film. To achieve a wet tension of 38 mN / m or more, it is preferable to perform a physicochemical surface treatment such as corona treatment, flame treatment, or plasma treatment. For example, in corona treatment, it is preferable to use a preheating roll or a treatment roll and discharge in the air. If the wet tension is too high, workability during release processing will be impaired, so it is preferably 44 mN / m or less, more preferably 43 mN / m or less, and even more preferably 42 mN / m or less.

[0106] The release agent to be applied to the biaxially oriented polypropylene film of the present disclosure is not particularly limited, and silicone-based release agents and non-silicone-based release agents (fluororesins, alkyd resins, various waxes, aliphatic olefins, etc.) can be used, and each resin can be used alone or in combination of two or more types.

[0107] (Silicone-based release agents) The silicone-based release agents can be selected from silicone resins commonly used in the relevant field, as described in "Silicone Materials Handbook" (edited by Toray Dow Corning, August 1993) and the like. Generally, heat-curable or ionizing radiation-curable silicone resins (which encompass resins and resin compositions) are used. As heat-curable silicone resins, for example, condensation reaction and addition reaction silicone resins can be used, and as ionizing radiation-curable silicone resins, ultraviolet or electron beam-curable silicone resins can be used. These can be applied to a film substrate and dried or cured to form a release agent layer.

[0108] The curable silicone resin preferably has a degree of polymerization after curing of about 500,000 to 200,000, and more preferably about 1,000 to 100,000.

[0109] Condensation reaction type silicone resins of the curable silicone resins include, for example, silicone resins into which epoxy groups have been introduced. Specific examples of these include the following resins: KS-718, KS-774, KS-775, KS-778, KS-779H, KS-830, KS-835, KS-837, KS-838, KS-839, KS-841, KS-843, KS-847, KS-847H, X-62-2418, X-62-2422, and X-62-2, manufactured by Shin-Etsu Chemical Co., Ltd. 125, X-62-2492, X-62-2494, X-62-5048, X-62-470, X-62-2366, X-62-630, X-92-140, X-92-128, KS-723A / B, KS-705F, KS-708A, KS-883, KS-709, KS-719; TPR-6701, TPR-6702, TPR manufactured by Toshiba Silicone Co., Ltd. -6703, TPR-3704, TPR-6705, TPR-6721, TPR-6722, TPR-6700, XSR-7029, YSR-3022, YR-3286; DK-Q3-202, DK-Q3-203, DK-Q3-204, DK-Q3-205, DK-Q3-210, DK-Q3-240, DK-Q3-3003 manufactured by Dow Corning Corporation; DK-Q3-3057, SFXF-2560; SD-7226, SD-7229, SD-7320, BY-24-900, BY-24-171, BY-24-312, BY-24-374, SRX-375, SYL-OFF23, SRX-244, SEX-290 manufactured by Dow-Toray Industries, Inc.; SILCOLEASE 425 manufactured by ICI Japan, Inc. Furthermore, silicone resins described in JP-A-47-34447 and JP-B-52-40918 can also be used. These curable silicone resins may be used alone or in combination of two or more.

[0110] The addition reaction type silicone resin of the curable silicone resin may be, for example, a silicone resin obtained by reacting a polydimethylsiloxane having vinyl groups introduced at the end or side chain with a hydrogen siloxane using a platinum catalyst to cure the silicone resin. In this case, it is more preferable to use a resin that can be cured within 30 seconds at 120°C, as this allows processing at low temperatures. Examples include low-temperature addition cure types (LTC1006L, LTC1056L, LTC300B, LTC303E, LTC310, LTC314, LTC350G, LTC450A, LTC371G, LTC750A, LTC755, LTC760A, etc.) and thermal UV cure types (LTC851, BY24-510, BY24-561, BY24-562, etc.) manufactured by Dow-Toray Industries, and solvent addition + UV cure types (X62-5040, X62-5065, X62-5072T, KS5508, etc.) and dual cure cure types (X62-2835, X62-2834, X62-1980, etc.) manufactured by Shin-Etsu Chemical Co., Ltd.

[0111] An example of the condensation reaction silicone resin of the curable silicone resin is one in which a three-dimensional crosslinked structure is formed by condensing a polydimethylsiloxane having an OH group at its terminal with a polydimethylsiloxane having an H group at its terminal using an organotin catalyst.

[0112] Examples of the UV-curable or electron beam-curable silicone resins among the above-mentioned curable silicone resins include, for example, the most basic types: resins that crosslink and cure by a radical reaction similar to normal silicone rubber crosslinking, resins that photocure by the introduction of acrylic groups, resin compositions in which an onium salt is decomposed by UV light to generate a strong acid that then cleaves the epoxy ring to crosslink, and resin compositions that crosslink by an addition reaction of a thiol to a vinyl siloxane. Because electron beams have more energy than UV rays, a radical-based crosslinking reaction occurs without the need for an initiator as in the case of UV curing.

[0113] (Non-Silicone-Based Mold Release Agent) Examples of non-silicone-based mold release agents include fluorine-based resins, amino resins, alkyd resins, various waxes, aliphatic olefins, and resins containing long-chain alkyl groups.

[0114] Examples of fluorine-based resins include polymers of olefin compounds containing fluorine atoms and polymers of compounds having a perfluoroalkyl group. Examples of compounds having a perfluoroalkyl group include perfluoroalkyl group-containing (meth)acrylates such as perfluoroalkyl (meth)acrylate, perfluoroalkylmethyl (meth)acrylate, 2-perfluoroalkylethyl (meth)acrylate, 3-perfluoroalkylpropyl (meth)acrylate, 3-perfluoroalkyl-1-methylpropyl (meth)acrylate, and 3-perfluoroalkyl-2-propenyl (meth)acrylate, and polymers thereof, as well as perfluoroalkyl group-containing vinyl ethers such as perfluoroalkylmethyl vinyl ether, 2-perfluoroalkylethyl vinyl ether, 3-perfluoropropyl vinyl ether, 3-perfluoroalkyl-1-methylpropyl vinyl ether, and 3-perfluoroalkyl-2-propenyl vinyl ether. The polymer may be a polymer of a single compound or multiple compounds, and may be further copolymerized with a copolymerizable compound that does not have a perfluoroalkyl group.

[0115] The amino resin refers to a resin obtained by an addition-condensation reaction between an aldehyde and a compound containing an amino group, such as urea, melamine, guanamine, or aniline, and examples thereof include aniline aldehyde resin, urea resin, melamine resin, benzoguanamine resin, and acetoguanamine resin. The amino resin may be modified with a long-chain alkyl group.

[0116] Alkyd resins are resins obtained by the condensation reaction of polyhydric alcohols and polybasic acids, and are condensates of polycarboxylic acids and polyhydric alcohols, to which fatty acids, etc., are added as necessary. Examples of polyhydric alcohols include dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, and neopentyl glycol, trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane, and polyhydric alcohols such as diglycerin, triglycerin, pentaerythritol, pentaerythritol, dipentaerythritol, mannitol, and sorbitol. Examples of polybasic acids include saturated polybasic acids such as phthalic anhydride, terephthalic acid, succinic acid, adipic acid, and sebacic acid; unsaturated polybasic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic anhydride, isophthalic acid, and trimellitic anhydride; and polybasic acids produced by the Diels-Alder reaction such as cyclopentadiene-maleic anhydride adduct, terpene-maleic anhydride adduct, and rosin-maleic anhydride adduct.

[0117] Examples of various waxes include paraffin wax, microcrystalline wax, palm wax, carnauba wax, candelilla wax, rice wax, soy wax, wax, beeswax, and lanolin wax.

[0118] Examples of the aliphatic olefin include polyethylene-based, polypropylene-based, and polymethylpentene-based resins.

[0119] Examples of long-chain alkyl group-containing resins include those obtained by reacting a polymer such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinyl butyral, polyvinyl acetate, polyethyleneimine, polyethyleneamine, reactive group-containing polyester resin, or reactive group-containing poly(meth)acrylic resin, which serves as the main chain, with a compound having a group reactive with the polymer and a long-chain alkyl group, thereby introducing a pendant long-chain alkyl group into the polymer; and copolymers of long-chain alkyl (meth)acrylates and monomers copolymerizable therewith.

[0120] The carbon number of the long-chain alkyl group is preferably 6 to 32, more preferably 8 to 26, and even more preferably 10 to 22. Examples of the group reactive with the polymer include an isocyanate group, a glycidyl group, a carboxyl group, an acid chloride group, and an oxazoline group, with an isocyanate group being particularly preferred. Specific examples include octyl isocyanate, decyl isocyanate, lauryl isocyanate, octadecyl isocyanate, and behenyl isocyanate.

[0121] As release agents containing these long-chain alkyl group-containing resins, for example, Resem (trade name) from Chukyo Yushi Co., Ltd., Piroil (registered trademark) from Lion Specialty Chemicals Co., Ltd., and octadecyl isocyanate-modified polyethyleneimine (trade name: RP-20) from Nippon Shokubai Co., Ltd. are commercially available.

[0122] Examples of long-chain alkyl (meth)acrylates include hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate, behenyl (meth)acrylate, etc. Examples of monomers copolymerizable with long-chain alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, vinyl acetate, styrene, acrylonitrile, etc. Furthermore, hydroxyl group-containing (meth)acrylic monomers such as 2-hydroxyethyl acrylate, carboxyl group-containing (meth)acrylic monomers such as acrylic acid and methacrylic acid, maleic acid, maleic anhydride, fumaric acid, cyano group-containing monomers, amino group-containing monomers, epoxy group-containing monomers, etc. may also be copolymerized.

[0123] The release agent contained in the release agent layer may be crosslinked. Examples of crosslinking agents include, but are not limited to, isocyanate compounds, glycidyl group-containing compounds, oxazoline group-containing compounds, and amino resins. Alternatively, a double bond may be introduced into a precursor of the resin that will become the release agent layer, and the precursor may be subjected to a crosslinking reaction using ultraviolet light, an electron beam, or the like.

[0124] The release agent used in the release agent layer may be one type or a mixture of two or more types. In order to adjust the release force, it is also possible to mix an additive such as a light release additive or a heavy release additive.

[0125] The release agent layer may contain particles having a particle size of 1 μm or less, but from the viewpoint of preventing pinholes, it is preferable that the release agent layer does not substantially contain particles that form protrusions.

[0126] The release agent layer may contain additives such as an adhesion improver and an antistatic agent. In order to improve adhesion to the biaxially oriented polypropylene film serving as the substrate, it is also preferable to subject the surface of the biaxially oriented polypropylene film to pretreatment such as anchor coating, corona treatment, plasma treatment, or atmospheric pressure plasma treatment before providing the release agent layer.

[0127] The thickness of the release agent layer may be set depending on the intended use and is not particularly limited, but is preferably in the range of 0.005 to 2 μm after curing. A thickness of 0.005 μm or more is preferable because release performance is maintained. Furthermore, a thickness of 2 μm or less is preferable because the curing time is not too long and there is no risk of thickness unevenness due to a decrease in the flatness of the release film.

[0128] The method for forming the release agent layer is not particularly limited. A coating liquid containing a releasable resin dissolved or dispersed therein is applied to one side of a biaxially oriented polypropylene film substrate by coating or the like, and the solvent is removed by drying, followed by heat drying, heat curing, or UV curing. In this case, the drying temperature during solvent drying and heat curing is preferably 100 to 170°C. A drying temperature higher than 170°C may cause heat-induced wrinkles in the film. On the other hand, a low drying temperature may result in insufficient heat curing of the release agent layer, making it difficult to achieve release properties. Biaxially oriented polypropylene films have lower thermal dimensional stability at high temperatures than biaxially oriented polyester films, and thus are prone to heat-induced wrinkles during drying of the coating film. However, the biaxially oriented polypropylene film according to the present disclosure can suppress wrinkles. The heat drying time is typically 10 to 60 seconds.

[0129] As a method for applying the release agent coating liquid, any known application method can be applied, and for example, a conventionally known method such as a roll coating method such as a gravure coating method or a reverse coating method, a bar coating method such as a wire bar, a die coating method, a spray coating method, or an air knife coating method can be used.

[0130] (5-2) Film for thin film manufacturing process The release film according to the present disclosure can be used as a film for thin film manufacturing process. When a biaxially oriented polypropylene film without a release agent layer is used, the release properties can be adjusted to a preferred range by blending a release resin into the film or adjusting the conditions of the corona treatment.

[0131] An example of the use of the release film according to the present disclosure as a film for a thin film manufacturing process is as a process film for producing a thermosetting resin film. A thermosetting resin solution is applied to the release film according to the present disclosure, and after drying in a hot air drying oven, the film is heated to a high temperature to produce a laminated film. The polypropylene film is then peeled off from the laminate to obtain a thermosetting resin film. The release film according to the present disclosure has excellent dimensional stability from room temperature to high temperatures, so that a thermosetting resin film with good wrinkle-free flatness and excellent appearance can be obtained.

[0132] The release film according to the present disclosure can also be used as a process film for producing a highly heat-resistant resin film. For example, a solution of an aromatic polyamide in N-methyl-2-pyrrolidone can be applied to the release film according to the present disclosure, dried in a hot air drying oven, and then heated to a high temperature to produce a laminated film. The polypropylene film can then be peeled off from the laminate to obtain an aromatic polyamide film. The release film according to the present disclosure has excellent dimensional stability from room temperature to high temperatures, making it possible to obtain a highly heat-resistant resin film that is wrinkle-free, has good flatness, and has an excellent appearance.

[0133] The release film according to the present disclosure can also be used as a process film for producing a porous film of a heat-resistant resin. For example, a resin solution prepared by mixing and dissolving a polyamideimide solution, polyvinylpyrrolidone, and a silicone surfactant is applied to the release film according to the present disclosure, and the resin solution is immersed in water to solidify. After drying in a hot air drying oven, a laminated film is produced by heat treatment at high temperature, and the polypropylene film is peeled off from the laminate to obtain a heat-resistant porous film. The release film according to the present disclosure has excellent dimensional stability from room temperature to high temperatures, so a highly heat-resistant porous film with excellent wrinkle-free flatness and excellent appearance can be obtained.

[0134] (5-3) Laminate with Pressure-Sensitive Adhesive Layer The release film according to the present disclosure can be used as a laminate member in which a pressure-sensitive adhesive layer is provided on the surface of the release agent layer (hereinafter referred to as the release surface) and a protective film is provided on the surface of the pressure-sensitive adhesive layer opposite the release film. Pressure-sensitive adhesives that can be used include rubber-based, acrylic-based, urethane-based, and silicone-based pressure-sensitive adhesives, with acrylic pressure-sensitive adhesives being particularly preferred. Acrylic pressure-sensitive adhesives are described below.

[0135] An acrylic pressure-sensitive adhesive is a pressure-sensitive adhesive that uses an acrylic resin as a base polymer. Examples of acrylic monomers used in acrylic resins include (meth)acrylic acid alkyl esters having 1 to 20 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl acrylate. Furthermore, functional groups are preferably introduced using hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; carboxyl group-containing monomers such as (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid; or glycidyl group-containing monomers such as glycidyl (meth)acrylate and methylglycidyl (meth)acrylate. In addition, polyfunctional monomers such as hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate may also be used. Furthermore, oligomers such as polyester polyacrylate and urethane polyacrylate may also be used.

[0136] The acrylic pressure-sensitive adhesive used in the pressure-sensitive adhesive layer is preferably crosslinked. Examples of the crosslinking method include a method of crosslinking an acrylic resin having a functional group introduced therein with a crosslinking agent, and a method of crosslinking with a polyfunctional monomer or oligomer.

[0137] Examples of crosslinking agents include isocyanate compounds, epoxy resins, and melamine resins. A coating liquid containing an acrylic resin and a crosslinking agent can be applied to a film, heated to remove the solvent, and subjected to a crosslinking reaction to form a crosslinked pressure-sensitive adhesive layer. When crosslinking with a polyfunctional monomer or a polyfunctional oligomer, a coating liquid containing a monofunctional monomer added to the polyfunctional monomer or polyfunctional oligomer can be applied to a film, and then irradiated with radiation or heated to form a crosslinked pressure-sensitive adhesive layer. A solvent may be added at this time. In these crosslinking processes, it is preferable to add a catalyst or a polymerization initiator depending on the type of crosslinking.

[0138] After the pressure-sensitive adhesive layer is thus provided on the release film, another release film is laminated on the other side of the pressure-sensitive adhesive layer, and the resulting pressure-sensitive adhesive layer laminate is taken up in a roll.

[0139] Furthermore, by creating a difference in peel strength between the release films on both sides of the adhesive layer, when in use, the light release film is peeled off and the adhesive layer is bonded to component A, and then the heavy release film is peeled off to transfer only the adhesive layer, and then the adhesive layer is bonded to component B, thereby laminating components A and B together.

[0140] (5-4) Laminate having a photosensitive resin layer The release film according to the present disclosure has a photosensitive resin layer provided on the release surface and a protective film on the side of the photosensitive resin layer opposite the release film. It can be used as a member of a photosensitive resin laminate.

[0141] The photosensitive resin layer is a layer containing a photosensitive resin. Photosensitive resins are resins that undergo a curing reaction when exposed to radiation such as ultraviolet light or electron beams. Representative examples include resins and oligomers having a (meth)acryloyl group. Also included are compositions containing an epoxy resin and an onium compound. Examples of resins having an acryloyl group include polyurethane-based, polyester-based, polyamide-based, polycarbonate-based, acrylic-based, and rubber-based resins. Examples of photosensitive oligomers include those with low molecular weights having a number average molecular weight of approximately 1,000 to 10,000. The photosensitive resin may be hydrophobic or hydrophilic, and an appropriate one can be selected depending on the application, the developer (a liquid that removes uncured resin), and the like.

[0142] The photosensitive resin laminate preferably contains a non-photosensitive resin in addition to the photosensitive resin. Examples of the non-photosensitive resin include the resins listed above, and the non-photosensitive resin may be either compatible or incompatible with the photosensitive resin. When the photosensitive resin and the non-photosensitive resin are incompatible, they may form a sea-island structure or an interpenetrating structure. Alternatively, the non-photosensitive resin may have a core-shell dispersed phase in which the non-photosensitive resin is the core and the photosensitive resin is the shell in a continuous phase of the non-photosensitive resin. Furthermore, the photosensitive resin layer may contain various particles, colorants, polymerization inhibitors, reaction initiators, ultraviolet absorbers, antioxidants, etc.

[0143] The photosensitive resin layer has the biaxially oriented polypropylene film described above as a protective film on at least one side, but the opposite side does not necessarily have to be the biaxially oriented polypropylene film described above. The opposite side may be made of a resin film other than the above, such as a biaxially oriented polypropylene film, a polyester film, or a polyamide film; a resin sheet such as acrylic, polyester, polyamide, polycarbonate, polystyrene, polypropylene, rubber, or ABS; a fiber-reinforced resin plate; a metal plate; a glass plate; a ceramic plate; MDF; or a wood board, and the like, and may be appropriately selected depending on the application. The film, sheet, or plate provided on the opposite side may be provided with a release agent, or may be provided with an adhesion-improving layer or an adhesive layer, and may be laminated to the photosensitive resin layer via these. It may also be laminated to the photosensitive resin layer directly without these layers.

[0144] Examples of methods for producing a photosensitive resin laminate include: (1) a method in which a photosensitive resin layer is provided on a film, sheet, plate, etc. on the opposite side by coating or the like, and then the biaxially oriented polypropylene film is laminated on top of this; (2) a method in which a photosensitive resin layer is provided on the biaxially oriented polypropylene film by coating or the like, and then the film, sheet, plate, etc. on the opposite side is laminated on top of this; and (3) a method in which the photosensitive resin layer is extrusion-pressed between the film, sheet, plate, etc. on the opposite side and the biaxially oriented polypropylene film.

[0145]

[0033] In the above methods (2) and (3), either a method of dissolving or dispersing the photosensitive resin composition in a solvent, applying the coating, and then drying, or a method of heating the photosensitive resin composition to soften it and extruding it into a sheet form through a slit die, may be used. In these production methods, even when exposed to high temperatures, such as when the temperature of the resin extruded or dried during drying in the above method (1) reaches several hundred degrees Celsius, or when the temperature of the resin extruded in the above method (3) reaches several hundred degrees Celsius, the biaxially oriented polypropylene film used in the release film of the present disclosure has excellent heat resistance, and therefore is less likely to wrinkle, shrink, or deteriorate in flatness, and the laminate itself is less likely to curl, resulting in a photosensitive resin laminate with excellent appearance.

[0146] A typical application of photosensitive resin laminates is printing plates. Examples of printing plates include letterpress (relief printing) plates and flexographic printing plates. To produce a printing plate, the biaxially oriented polypropylene film used as a protective film for the photosensitive resin laminate is peeled off, and a negative is placed on the peeled surface of the photosensitive resin laminate in an exposure device and adhered to the peeled surface. The negative surface is irradiated with ultraviolet light or other radiation to harden the exposed areas, and the plate is then removed. The unexposed areas are then removed with a developer to produce a printing plate. Instead of using a negative, patterned exposure of the photosensitive resin may be performed using an ultraviolet laser or the like. The developer used for development may be aqueous or organic solvent-based. The plate may be scrubbed with a brush during development. In a broader sense, printing plates also include rubber stamps and seals.

[0147] Printing plates are usually cut into sheets and stored and transported in a stacked manner. The photosensitive resin laminate uses a biaxially oriented polypropylene film with excellent rigidity as a protective film, and even if a small foreign object is caught during storage or transportation or if an impact is applied during handling, the uncured, soft photosensitive resin layer is less likely to be indented and is less likely to get caught during peeling. Even if a catch occurs during peeling, peeling marks are less likely to be left. The photosensitive resin laminate not only provides a printing plate with excellent handleability, but also allows the production of a printing plate that is capable of producing high-definition, high-quality printing with no unevenness.

[0148] Another application of the photosensitive resin laminate is a relief board. A relief board is a plate with concave and convex portions, and can be used for nameplates, Braille boards, nameplates, various decorations, molds, etc. As with printing plates, a relief board is obtained by peeling off the biaxially oriented polypropylene film used as a protective film, exposing it to light, and developing it. Similarly, a high-quality relief board can be obtained, with no dents or peeling marks, and with excellent handleability.

[0149] Another use of photosensitive resin laminates is as a masking material. Masking materials are used to cover areas that are not to be processed during surface treatment processes such as sandblasting and etching. For example, in the case of a sandblasting masking material, the biaxially oriented polypropylene film used as a protective film is peeled off, and the photosensitive resin surface of the photosensitive resin layer laminate is attached to the object to be processed. The transparent resin film on the opposite side is then either peeled off or left on, and exposed to radiation such as ultraviolet light over a negative. Exposure may be performed in a pattern without using a negative, as with a printing plate. The unexposed areas are then removed by development. Sandblasting is then performed on top of this, and the hardened masking material is peeled off, resulting in a sandblasted pattern.

[0150] Another example of a masking material is dry film resist. In dry film resist, a transparent resin film such as a polyester film or a polypropylene film is preferably used on the surface opposite the photosensitive resin layer. In dry film resist, the biaxially oriented polypropylene film used as a protective film for the photosensitive resin laminate is peeled off, and the peeled surface is placed on the object to be etched, such as copper foil, and then bonded by a method such as heat pressing. The transparent resin film on the opposite side is then exposed to radiation such as ultraviolet light, either without being peeled off or after being peeled off and a negative is placed on top. The exposure may be performed in a pattern without using a negative, as with a printing plate. The resin film on the opposite side is then peeled off, and development and etching are performed. Dry resist films are also similarly resistant to indentations and peeling marks, easy to handle, and produce high-quality, high-definition etching patterns.

[0151] (5-5) Transfer Laminate The release film according to the present disclosure can be used as a component of a transfer laminate having at least one transfer layer selected from a printing layer, a decorative metal thin film, a thermal transfer ink layer, an optically functional layer, a conductive layer, a circuit, an adhesive layer, a pressure-sensitive adhesive layer, and a rubber sheet layer provided on the release surface.

[0152] Examples of transfer layers include printed layers such as patterns and letters, decorative metal thin films, thermal transfer ink layers, photosensitive resin layers, retardation layers, polarizing layers, circularly polarized reflective layers, hard coat layers, anti-reflection layers, low-reflection layers, and other optically functional layers, as well as conductive layers, circuits, adhesive layers, pressure-sensitive adhesive layers, and rubber sheet layers. These transfer layers require high temperatures or high precision when provided or transferred. The release film of the present disclosure has excellent heat resistance, exhibiting minimal shrinkage even under conditions exceeding 130°C during coating, drying, and other processes. It can be used at temperatures exceeding 150°C for short periods of time, and also has excellent rigidity. Therefore, the transfer layer and the release film of the present disclosure are an ideal combination. Furthermore, the excellent rigidity of the release film allows for smooth release, which also allows for high-speed transfer and increased productivity.

[0153] The printing layer is transferred to a molded product or the like to impart a design to the surface. The printing layer can be provided by printing on a release film. Examples of printing methods include gravure printing, letterpress printing, offset printing, screen printing, inkjet printing, and pad printing. The printing layer may be provided directly in contact with the release film, or a protective layer may be provided on the release film and printed on top of this. The protective layer serves as a protective layer for the printing layer after transfer. A UV absorber may be added to the protective layer. Examples of materials to be transferred include paper, film, cloth, wood, glass, ceramics, metal, and resin molded bodies, and composites thereof may also be used. The wood, glass, ceramics, metal, and resin molded bodies may be plate-shaped, columnar, or shaped for a specific purpose, such as a container or a part of an article. In transfer printing, a transfer laminate is placed on the transfer target, and the printing is performed using a heated roll or a heated mold. By using the release film of the present disclosure, dimensional change and deterioration of flatness are minimized even when the printing layer is dried at a higher temperature, thereby improving productivity. Furthermore, transfer printing can be performed at higher speeds, making it easier to perform highly accurate transfer printing without misalignment.

[0154] Decorative metal thin films are transferred onto molded products, paper, films, etc. to impart design. The transfer may be performed on the entire surface of the target object, or on a portion of the target object. Metals used in decorative metal thin films include gold, silver, copper, aluminum, nickel, and tin. Decorative metal thin films can be formed by laminating metal foil, or by methods such as vapor deposition and sputtering. The decorative metal thin film may be directly attached to the release film, via an adhesive layer if it is a metal foil, or may be formed on a protective layer provided on the release film. The protective layer serves as a protective layer for the decorative metal thin film after transfer. Alternatively, the protective layer may be colored and an uncolored metal thin film, such as aluminum, may be used, resulting in a gold or copper appearance after transfer. A printed layer may also be provided between the decorative metal thin film and the release film. Examples of transfer targets include those similar to the printed layer. By using the release film of the present disclosure, dimensional changes and deterioration of flatness due to temperatures such as vapor deposition are reduced, transfer at higher speeds is possible, and even patterns that impart fine design features can be easily transferred with high precision and without misalignment.

[0155] The thermal transfer ink layer is used to print designs, characters, etc. on a receiver such as paper, film, or cloth using a heating head. The thermal transfer ink layer may be a melt ink layer or a sublimation dye-containing ink layer. By using the release film of the present disclosure, the temperature of the heating head can be increased, making it easier to print at higher speeds.

[0156] The retardation layer is transferred to a polarizing plate or film and becomes an optical compensation layer of an image display device, a λ / 4 layer, a λ / 2 layer, or the like of a circular polarizing plate. A liquid crystal compound is preferably used in the retardation layer, and retardation is generated by the orientation of the liquid crystal compound. The liquid crystal compound may be either a rod-shaped liquid crystal compound or a discotic liquid crystal compound, but preferably has a reactive group such as a double bond and can fix the orientation. The orientation of the liquid crystal compound can be achieved by rubbing the surface of the release film or, if a protective layer as described below is provided, the surface of the protective layer, or by irradiating the liquid crystal compound with polarized light, or by providing an orientation control layer as a lower layer of the retardation layer and rubbing the orientation control layer or by irradiating it with polarized light to impart an orientation control function. This orientation control is also considered part of the retardation layer. The retardation layer may be a multi-layered layer. The retardation layer may be provided in direct contact with the release film, or may be provided on a protective layer provided on the release film.

[0157] The polarizing layer is a layer that converts natural light into linearly polarized light. As one form of the polarizing layer, it is preferable that the liquid crystal compound is oriented in the same manner as the retardation layer. In this case, the polarizing layer contains a dichroic dye, which is oriented along the orientation of the liquid crystal compound and exhibits a polarizing function. It is preferable to use multiple dichroic dyes so that the light is polarized over the entire visible light range. As another form of the polarizing layer, it may be a wire grid type.

[0158] The circularly polarized light reflective layer reflects light in one direction of optical rotation and transmits light rotated in multiple directions. It is preferable to use a cholesteric liquid crystal.

[0159] The retardation layer, polarizing layer, and circularly polarized reflective layer may be laminated in combination. The retardation layer, polarizing layer, and circularly polarized reflective layer may be provided in direct contact with a release film, or may be provided on a protective layer provided on a release film. Examples of objects to which the retardation layer, polarizing layer, and circularly polarized reflective layer are transferred include films, glass plates, and resin plates. The objects to be transferred are preferably transparent, but may also be specularly reflective depending on the application.

[0160] In order to align these liquid crystal compounds, they are often heated to 110 to 140°C. However, by using the release film of the present disclosure, the dimensional change and deterioration of flatness due to heat when orienting or fixing the liquid crystal compounds are reduced, and the liquid crystal can be oriented as designed, and a higher quality and uniform retardation layer, polarizing layer, and circularly polarized light reflective layer can be provided.

[0161] The hard coat layer prevents dents and scratches on the surface of the transfer target. The low-reflection layer is provided on the surface of the transfer target with a layer having a lower refractive index than the transfer target, suppressing surface reflection. The anti-reflection layer is provided on the surface of the transfer target with layers having different refractive indexes, suppressing reflection by interference of reflected light at multiple interfaces. Examples of the transfer target include films, glass plates, resin plates, and resin molded products. The transfer target is preferably transparent, and preferred examples include those provided on the surface of an image display device. It may also be provided on the surface of a colored object to suppress surface reflection and make the color appear more vivid. While curable resins are used for the hard coat layer, low-reflection layer, and anti-reflection layer, the use of the release film of the present disclosure maintains high dimensional stability and flatness even when irradiated with stronger radiation if a radiation-curable resin is used, or even when irradiated with higher temperatures if a thermosetting resin is used, enabling high-speed processing. Curable adhesives are also used during transfer, which similarly facilitates high-speed transfer.

[0162] The conductive layer imparts conductivity to the surface of the transfer target. It is used as an antistatic layer, an electromagnetic wave shielding layer, or an electrode layer for image display cells, such as touch panels and liquid crystal cells of liquid crystal display devices. The conductive layer is preferably a transparent conductive layer, and examples thereof include metal oxide films such as ITO, conductive polymer films such as polyacetylene, polythiophene, and polyaniline, metal nanowire-dispersed polymer films, conductive pastes containing metal particles printed in a mesh pattern, and metal foils etched into a mesh pattern. Examples of transfer targets include films, glass plates, resin plates, and resin molded bodies. Use of the release film of the present disclosure provides high dimensional stability and maintains flatness even when subjected to high temperatures by vapor deposition, sputtering, CVD, and the like, thereby enabling the production of high-quality conductive films.

[0163] The circuit is formed by processing the conductive layer into a circuit shape, and is used to provide a touch sensor function, an antenna, or an electric or electronic circuit to an object. The conductive layer and circuit may be provided in contact with a release film, or may be provided on a protective layer provided on the release film. The circuit may be processed into a circuit after providing the conductive layer as described above, or may be a circuit printed using a conductive polymer or conductive paste. Examples of the transfer object include a film, a glass plate, a ceramic plate, and a resin plate, and the resin plate may be a composite plate containing paper, glass fiber, or the like. By using the release film of the present disclosure, it is possible to form a more precise circuit.

[0164] A suitable adhesive for use in the adhesive layer is a hot melt adhesive. Examples of hot melt adhesives include polyolefin-based, ethylene vinyl acetate-based, rubber-based, polyamide-based, polyester-based, and polyurethane-based adhesives. The adhesive may be a reactive adhesive. A reactive adhesive is one that is not solidified when laminated on the release film, but reacts and hardens after transfer. A reactive adhesive is an adhesive containing a reactive group, and examples of the reactive group include an isocyanate group, a blocked isocyanate group, an oxirane group, an oxetane group, a carbodiimide group, an acryloyl group, an oxazoline group, a silyl group, and a cyanoacrylate group. Examples of adhesives include those with heat curing reactivity, moisture curing reactivity, and radiation curing reactivity, and an appropriate reactive group can be selected for each type of adhesive, such as an isocyanate group, blocked isocyanate group, oxirane group, oxetane group, carbodiimide group, acryloyl group, oxazoline group, etc. for heat curing reactivity, an isocyanate group, silyl group, cyanoacrylate group, etc. for moisture curing reactivity, and an oxirane group, oxetane group, acryloyl group, etc. for radiation curing reactivity. Furthermore, by using a catalyst that exhibits catalytic action when exposed to heat or radiation, a heat curing reactivity or radiation curing reactivity adhesive can also be made.

[0165] The reactive adhesive may be reacted by heat or radiation after the release film of the adhesive layer has been peeled off after transfer and the object to be bonded is placed on the surface, or the adhesive reaction may be initiated by irradiation with radiation before the release film is peeled off or by heat during transfer, and then the release film may be peeled off and the object to be bonded placed on the surface. In the case of a moisture-curing adhesive, the reaction is initiated when the adhesive layer absorbs moisture after the release film on the opposite side of the adhesive layer is peeled off. The hot melt adhesive may have the above reactivity.

[0166] Many of these adhesives require high temperatures when applied to the release film or when transferred, and by using the release film of the present disclosure, processing and transfer can be easily performed at higher temperatures.

[0167] To ensure stronger adhesion of the adhesive, an adhesion-promoting coating may be applied to the adhesive layer or the object to be adhered during transfer. When the transfer layer is affected by oxygen or humidity, such as in the case of a reactive adhesive, a barrier layer may be provided on the release film of the present disclosure. Examples of the barrier layer include a vapor-deposited layer of aluminum, silicon oxide, aluminum oxide, or the like, and a barrier coat layer of an inorganic layered compound or polyvinylidene chloride, or the like.

[0168] The adhesive used in the adhesive layer may be an acrylic or rubber-based adhesive, and a suitable example is an acrylic optical adhesive, or may be a hot-melt adhesive. When providing an adhesive layer on a release film, high temperatures are required during coating, and a crosslinking reaction due to radiation or heat is required after coating. However, by using the release film of the present disclosure, higher temperatures can be achieved, thereby improving productivity.

[0169] When a transfer layer other than an adhesive layer or a pressure-sensitive adhesive layer is transferred to a transfer object, it is attached to the transfer object via an adhesive layer or a pressure-sensitive adhesive layer. The adhesive layer or the pressure-sensitive adhesive layer may be provided on the transfer layer or the transfer object at the time of transfer, or may be provided on the transfer layer in advance. Note that when the transfer layer itself has tackiness or adhesiveness to the transfer object, or when the transfer object itself has tackiness or adhesiveness to the transfer layer, it is not necessarily necessary to provide an adhesive layer or a pressure-sensitive adhesive layer. The same applies when the transfer layer and the transfer object exhibit tackiness or adhesiveness upon heating.

[0170] Examples of rubber sheet layers include natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber, styrene-butadiene rubber, nitrile rubber, and polyisobutylene rubber. Rubber sheet laminates are used, for example, as repair patches for rubber products and as rubber sheets for vulcanization bonding. These rubbers are manufactured by mixing them using a calendaring method and laminating them on a release film to form a sheet, or by extruding them into a sheet form from an extruder and laminating them on a release film. Even at the temperatures used during lamination, these methods are less likely to cause wrinkles and curl, resulting in laminates with excellent flatness. Furthermore, when heated during transfer, high temperatures can be used, and the excellent rigidity allows for smooth peeling.

[0171] As described above, the release film according to the present disclosure is less likely to wrinkle, change in size, or deteriorate in flatness when the transfer layer is provided or processed, and not only does it improve the appearance quality of the transfer laminate, but it can also be used as a transfer film for high-definition transfer applications. Furthermore, even at high temperatures during transfer, it is less likely to wrinkle or change in size, and not only does it improve the appearance quality but also enables highly accurate transfer.

[0172] In order to make the most of its excellent properties, the release film according to the present disclosure is preferably used when the step of providing a transfer layer or the step of processing a transfer laminate includes a step in a high-temperature environment, such as a drying step, a crosslinking reaction step, a phase conversion step, a phase separation step, or a surface planarization step.

[0173] Specifically, the step of providing a transfer layer or the step of treating a transfer laminate preferably includes a step in an environment of 110°C or higher, and the temperature may be 115°C or higher, 120°C or higher, or 125°C or higher, or 160°C or lower, 155°C or lower, or 150°C or lower. The time for the step of reaching the above temperature may be 2 seconds or more, 5 seconds or more, or 10 seconds or more, and may be 60 minutes or less, 45 minutes or less, or 30 minutes or less. However, if the temperature exceeds 155°C, the time for the step of reaching the temperature may be less than 30 seconds, less than 20 seconds, or less than 15 seconds. If the temperature exceeds 150°C, the time for the step of reaching the temperature may be less than 90 seconds, less than 60 seconds, or less than 45 seconds. If the temperature exceeds 140°C, the time for the step of reaching the temperature may be less than 3 minutes, less than 2 minutes, or less than 1 minute. If the temperature exceeds 130°C, the time for the step of reaching the temperature may be less than 5 minutes, less than 4 minutes, or less than 3 minutes.

[0174] When the transfer layer is provided on the release film by melting using a melt extrusion method or the like, the temperature of the molten transfer layer may be 180°C or less, 170°C or less, 160°C or less, 150°C or less, or 145°C or less. However, if the temperature exceeds 150°C, it is preferable to pass the release film through a cooling roll or cooling belt and cool it from the opposite side. The temperature of the molten transfer layer is preferably 120°C or more, and may be 125°C or more or 130°C or more.

[0175] When contacting with a heating body such as a heat roll, the temperature of the heating body may be 120°C or higher, 125°C or higher, or 130°C or higher, and may be 160°C or lower, 155°C or lower, or 150°C or lower. The contact time with the heating body may be 0.5 seconds or more, 1 second or more, 1.5 seconds or more, or 2 seconds or more, and may be 180 seconds or less, 120 seconds or less, 90 seconds or less, or 60 seconds or less. If the temperature of the heating body exceeds 155°C, the contact time with the heating body may be less than 90 seconds, and if the temperature exceeds 150°C, the contact time with the heating body may be less than 60 seconds.

[0176] In the vapor deposition, sputtering, CVD, etc., the release film may be cooled so that the temperature does not exceed 150°C.

[0177] The release film of the present disclosure can also be suitably used when the transfer process is heat transfer and the temperature and time of a heating body such as a heat roll or a heat press mold are similar to the conditions for contact with the heating body described above.

[0178] The transfer laminate is preferably wound into a long roll. When wound into a roll, a masking film (surface protection film) may be attached to protect the transfer layer. Examples of the masking film include polyester films, polypropylene films, and polyethylene films. The masking film may be provided with a release layer and an adhesive layer.

[0179] This application claims the benefit of priority based on Japanese Patent Applications Nos. 2024-097734, 2024-097735, and 2024-097736 filed on June 17, 2024, and Japanese Patent Applications Nos. 2024-228560, 2024-228561, and 2024-228562 filed on December 25, 2024. The entire contents of the specifications of Japanese Patent Applications Nos. 2024-097734, 2024-097735, and 2024-097736 filed on June 17, 2024, and Japanese Patent Applications Nos. 2024-228560, 2024-228561, and 2024-228562 filed on December 25, 2024 are incorporated herein by reference.

[0180] The release film and laminate of the present disclosure will be described in detail below with reference to examples, but the release film and laminate of the present disclosure are not limited to these examples.

[0181] (1) Analysis and Evaluation Methods of Resin Compositions and Films The analysis methods for the polypropylene resin compositions used in the Examples and Comparative Examples are explained in (1-1) to (1-4) below, and the analysis and evaluation methods for the polypropylene films produced in the Examples and Comparative Examples are explained in (1-5) to (1-12) below. In (1-2) to (1-4) below, various physical properties of the polypropylene resin were measured, and for polypropylene resin compositions using two types of polypropylene resins, the mass average of the physical property values ​​of each polypropylene resin was used as the physical property value of the polypropylene resin composition. In (1-1) below, for polypropylene resin compositions using two types of polypropylene resins, the melt flow rate of the two polypropylene resins in a blended state was measured.

[0182] (1-1) Melt Flow Rate The melt flow rate (MFR) was measured in accordance with JIS K 7210 at a temperature of 230° C. and a load of 2.16 kgf.

[0183] (1-2) Mesopentad Fraction The mesopentad fraction ([mmmm]%) was measured by １３ The mesopentad fraction was calculated according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973). １３ C-NMR measurement was performed using an AVANCE 500 manufactured by BRUKER, by dissolving 200 mg of a sample in a 8:2 mixture of o-dichlorobenzene and deuterated benzene at 135°C and at 110°C.

[0184] (1-3) Amount of components with a molecular weight of 100,000 or less: Gel permeation chromatography (GPC) was used to determine the molecular weight in terms of polypropylene using monodisperse polystyrene as the standard. When the baseline was unclear, the baseline was set to the lowest point on the high molecular weight side of the elution peak closest to the elution peak of the standard substance. The GPC measurement conditions were as follows: Apparatus: HLC-8321PC / HT manufactured by Tosoh Corporation Detector: RI Solvent: 1,2,4-trichlorobenzene + dibutylhydroxytoluene (0.05%) Column: TSK gelguard column HHR (30) HT (7.5 mm I.D. × 7.5 cm) × 1 + TSK gel GMHHR-H (20) HT (7.8 mm I.D. × 30 cm) × 3 Flow rate: 1.0 mL / min Injection amount: 0.3 mL Measurement temperature: 140°C The mass proportion of components having a molecular weight of 100,000 or less was determined from the integral curve of the molecular weight obtained by GPC.

[0185] (1-4) Melting point and crystallization temperature Thermal measurements were performed using a differential scanning calorimeter (TA Instruments, Q1000). Approximately 5 mg was cut out from the pellet, packed into an aluminum pan for measurement, and set in a differential scanning calorimeter. Under a nitrogen atmosphere, the resin was melted by heating from 30 ° C. to 230 ° C. at a heating rate of 20 ° C. / min and holding at 230 ° C. for 5 minutes, and then cooled to 30 ° C. at a heating rate of -10 ° C. / min and held at 30 ° C. for 5 minutes. The temperature was then increased to 230 ° C. at a heating rate of 10 ° C. / min. The melting point was the main peak temperature of the endothermic peak associated with melting observed during the second heating. The crystallization temperature was the main peak temperature of the exothermic peak observed when the temperature was lowered from 230 ° C. to 30 ° C.

[0186] (1-5) Film Thickness The film thickness was measured using a Millitron 1202D manufactured by Seiko EM Corporation.

[0187] (1-6) Thermomechanical analysis (TMA) measurement (measurement of film width direction length from 30°C to 130°C) A film was cut out so that the width direction of the film was 40 mm and the length direction of the film was 4 mm, and the film was set in a thermomechanical analyzer (TMA-60, manufactured by Shimadzu Corporation) so that the chuck width was 10 mm. The temperature was increased from 30°C to 130°C at a temperature increase rate of 10°C / min with a measurement load of 0.5 gf, and the length X of the sample in the width direction during the temperature increase was continuously measured. The maximum value of the length between the chucks during the temperature increase was taken as X. １ (mm), the minimum value of the length between the chucks during the temperature rise is X ２ (mm), (X １ -10) / 10((X １ -X ０ ) / X ０ ) percentage and (X ２ -10) / 10((X ２ -X ０ ) / X ０ ) and the percentage were calculated.

[0188] (1-7) Thermomechanical analysis (TMA) measurement (temperature measurement at 0.5% shrinkage) A film was cut so that the width direction of the film was 40 mm and the length direction of the film was 4 mm, and the film was set in a thermomechanical analyzer TMA-60 manufactured by Shimadzu Corporation so that the chuck width was 10 mm. The temperature was increased from 30°C to 160°C at a heating rate of 10°C / min with a measurement load of 0.5 gf, and the width direction length of the sample was continuously measured during the temperature increase. From the measurement results, the lowest temperature at which the width direction length of the sample was 9.95 mm or less was determined as the temperature at 0.5% shrinkage.

[0189] (1-8) Storage modulus by dynamic viscoelasticity measurement (DMA) The storage modulus in the longitudinal and transverse directions of the film was measured by the following method. A film was cut so that the measurement direction was 40 mm and the direction perpendicular thereto was 4 mm, and the film was set in a dynamic viscoelasticity measuring device (manufactured by TA Instruments Japan, RSA-G2) so that the chuck width was 10 mm. The temperature was raised from -60 ° C to 160 ° C at a heating rate of 5 ° C / min under a nitrogen atmosphere with a measurement load of 10 gf and a frequency of 10 Hz, and the storage moduli at 23 ° C, 120 ° C, 140 ° C, and 150 ° C were determined. In addition, from the obtained values, the sum of the storage modulus at 23 ° C in the longitudinal direction and the storage modulus at 140 ° C, and the sum of the storage modulus at 23 ° C in the transverse direction and the storage modulus at 140 ° C were calculated, respectively.

[0190] (1-9) Loss Modulus by Dynamic Mechanical Analysis (DMA) A film was cut so that the width direction of the film was 40 mm and the length direction of the film was 4 mm, and the film was set in a dynamic mechanical analysis device (TA Instruments Japan, RSA-G2) so that the chuck width was 10 mm. The film was heated from -60°C to 160°C at a heating rate of 5°C / min under a nitrogen atmosphere with a measurement load of 10 gf and a frequency of 10 Hz, and the loss modulus of the film was measured during the heating in the width direction. A graph was drawn with temperature on the horizontal axis and loss modulus on the vertical axis, and the maximum loss modulus E"(A) from -25°C to 25°C, the minimum loss modulus E"(B) from 25°C to 75°C, and the maximum loss modulus E"(C) at 100°C or higher were calculated. The values ​​of E"(C) / E"(A) and E"(B) / E"(C) were also calculated.

[0191] (1-10) Stress at 5% Elongation (F5) The stress at 5% elongation (F5) during a tensile test in the longitudinal and transverse directions of a film was measured at 23°C in accordance with JIS K 7127. A film was cut so that the measurement direction was 200 mm and the direction perpendicular thereto was 15 mm, and the film was set in a tensile tester (Instron Japan Company Limited, dual column tabletop testing machine Instron 5965) with a chuck width of 100 mm. A tensile test was then carried out at a tensile speed of 200 mm / min. From the obtained strain-stress curve, the stress at 5% elongation was taken as F5.

[0192] (1-11) Heat Shrinkage Rate The heat shrinkage rate of the film in the longitudinal direction and width direction at 120°C was measured in accordance with JIS Z 1712 by the following method. A film was cut so that the measurement direction was 200 mm and the direction perpendicular thereto was 20 mm, and the film was hung in a hot air oven at 120°C and heated for 5 minutes. The length after heating was measured, and the heat shrinkage rate at 120°C was calculated as the ratio of the shrunken length to the original length. The heat shrinkage rate at 150°C was also calculated by the same measurement method as the heat shrinkage rate at 120°C, except that the film was hung in a hot air oven at 150°C.

[0193] (1-12) Evaluation of flatness after heat treatment at 130°C A sample was cut out from the film so that both the width and length directions were 200 mm, and used as an evaluation sample. The sample was hung in a hot air oven at 130°C and heated for 5 minutes. After cooling to room temperature, the film was placed on a black mount, and the film surface was observed at a 45-degree angle under a fluorescent lamp. A: No heat wrinkles or large waviness of 5 mm or more were present. B: No heat wrinkles were observed, but large waviness of 5 mm or more was observed. C: Heat wrinkles were observed.

[0194] (2) Preparation of Polypropylene Film (2-1) Example 1 As the polypropylene resin, 80 parts by mass of propylene homopolymer PP-1 (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Noblen FLX80E4) having an MFR of 7.5 g / 10 min, a mesopentad fraction ([mmmm]%) of 98.9%, a melting point of 162.5 ° C., a crystallization temperature of 116.2 ° C., and a molecular weight of 100,000 or less of 40.5% by mass, and 20 parts by mass of propylene homopolymer PP-2 (manufactured by Sumitomo Chemical Co., Ltd., EL80F5) having an MFR of 11 g / 10 min, a mesopentad fraction ([mmmm]%) of 98.8%, a melting point of 161.5 ° C., a crystallization temperature of 116.5 ° C., and a molecular weight of 100,000 or less of 53.1% by mass were blended and used.

[0195] The extruded sheet was extruded through a T-die at 250°C into a sheet, brought into contact with a 20°C cooling roll, and then placed directly into a 20°C water bath. It was then stretched 4.5 times in the longitudinal direction using two pairs of rolls at 142°C. It was then clamped at both ends with clips and introduced into a hot air oven, preheated to 172°C, and then stretched 12.7 times in the width direction at 162°C. Immediately after stretching in the width direction, it was heat-treated at 170°C while still held by the clips without relaxation, and then heat-treated at 140°C to relax the width direction by 3%. Finally, it was cooled to room temperature (23°C). The thickness of the film thus obtained was 20.0 μm. The resulting film was free of wrinkles and swells and had excellent flatness. In all of the following examples and comparative examples, the resulting films were free of wrinkles and swells and had excellent flatness.

[0196] The film production conditions are shown in Table 1, and the physical properties of the film and the results of the flatness evaluation after heat treatment are shown in Table 2. As shown in Table 2, the film of Example 1 has excellent flatness after heat treatment at 130°C.

[0197] (2-2) Examples 2 to 7 In Examples 2 to 7, the films were produced by the same production method as in Example 1, except that the film production conditions were changed to those shown in Table 1. Table 1 shows the film production conditions, and Table 2 shows the physical properties of the films and the results of the flatness evaluation after heat treatment. As shown in Table 2, all of the films of Examples 2 to 7 had excellent flatness after heat treatment at 130°C.

[0198] (2-3) Comparative Examples 1 to 5 In Comparative Examples 1 to 5, the films were produced by the same production method as in Example 1, except that the film production conditions were changed to those shown in Table 1. Table 1 shows the film production conditions, and Table 2 shows the physical properties of the films and the results of the flatness evaluation after heat treatment. In Comparative Example 1 and Comparative Example 9 described below, the first stage of the heat treatment was performed at 100°C, which means that the first stage of the heat treatment was essentially cooling.

[0199] (2-4) Comparative Example 6 Comparative Example 6 was produced by the same production method as in Example 1, except that only PP-3 (WF836DG3, manufactured by Sumitomo Chemical Co., Ltd.) having an MFR of 7 g / 10 min, a mesopentad fraction ([mmmm]%) of 95.2%, a melting point of 157.8°C, a crystallization temperature of 111.2°C, an ethylene monomer content of 0.4 mol%, and an amount of components having a molecular weight of 100,000 or less of 39.1 mass% was used as the polypropylene resin, and the film production conditions were changed to those shown in Table 1. Table 1 shows the film production conditions, and Table 2 shows the physical properties of the film and the results of the flatness evaluation after heat treatment.

[0200] (2-5) Comparative Example 7 A film was produced by the same production method as in Example 1, except that the production conditions were changed to those shown in Table 1. Immediately after stretching in the width direction, the film was cooled (heat-treated) at 120°C while still held by the clips, and then re-stretched to 1.1 times the width at 177°C. Table 1 shows the film production conditions, and Table 2 shows the physical properties of the film and the results of the flatness evaluation after heat treatment.

[0201] (2-6) Comparative Example 8 The same procedures as in Example 1 were carried out, except that the film was introduced into a hot air oven and preheated to 177°C, then stretched 6.8 times in the width direction at 169°C, and immediately after the width direction stretching, it was heat-treated at 170°C while still held by the clips to relax by 16% in the width direction. Table 1 shows the film production conditions, and Table 2 shows the film properties and the results of flatness evaluation after heat treatment.

[0202] (2-7) Comparative Example 9 The film was introduced into a hot air oven and preheated to 170°C, and then stretched 6.0 times in the width direction at 162°C in the first stage, followed by 1.36 times stretching at 145°C in the second stage, for a total stretching of 8.16 times. Immediately after the width direction stretching, the film was heat-treated at 100°C while held by the clips without relaxation, and then heat-treated at 165°C without relaxation, in the same manner as in Example 1. Table 1 shows the film production conditions, and Table 2 shows the film properties and the results of flatness evaluation after heat treatment.

[0203] The films of Examples 1 to 7 all had excellent flatness after heat treatment at 130°C, whereas the films of Comparative Examples 1 to 9 all had poor flatness after heat treatment at 130°C. In Comparative Example 6, the mesopentad fraction of PP-3 was too low, so the flatness was poor. Note that Figure 1 is a diagram showing the relationship between temperature and the length in the film width direction in Example 4, Comparative Example 1, and Comparative Example 8, and strictly speaking, it is the relationship between temperature and (X-X ０ ) / X ０ Percentage of (X: film length in the width direction at the temperature, X ０ 2 is a graph showing the relationship between temperature and loss modulus in Example 4 and Comparative Example 1, and FIG. 3 is a graph showing the relationship between temperature and storage modulus in Example 4 and Comparative Example 8.

[0204] (3) Practical Evaluation of Films The application of each film obtained in Examples 1 to 7 and Comparative Examples 1 to 9 to various uses was examined. The method for practical evaluation of the films and the method for producing films and laminates for each use are described below.

[0205] (3-1) Evaluation of Peelability From the release film rolls produced from the biaxially oriented polypropylene films described in Examples 1 to 7 and Comparative Examples 1 to 9 and the laminate rolls obtained from the release film rolls, samples were cut to a width of 30 mm and a length of 80 mm so that the width direction was the long side, to prepare samples for measuring peel force. After discharging using a static eliminator (Keyence Corporation, SJ-F020), the samples were peeled using a peel tester (Kyowa Interface Science Co., Ltd., VPA-3) at a peel angle of 30 degrees, a peel temperature of 25 ° C., and a peel speed of 10 m / min. The peel angle in this evaluation method refers to the angle in the direction in which the release film is pulled relative to the evaluation sample axis fixed to the peel tester.

[0206] In the case of a release film roll, the peeling direction was determined by attaching double-sided adhesive tape (Nitto Denko Corporation, No. 535A) to a SUS plate attached to the peel tester, fixing half of the release film on the tape so that the release layer was adhered to the double-sided tape, and then pulling the edge of the release film that was not adhered to the tape to peel it off. Of the obtained measured values, the average peel force over a peel distance of 20 mm to 70 mm was calculated, and this value was taken as the peel force. A total of five measurements were performed, and the average peel force value was used for evaluation. In the case of a laminate roll obtained from a release film roll, half of the laminate film was fixed so that the following various process films, adhesive layer, photosensitive resin layer, hard coat layer, and metal thin film layer provided on the surface of the release layer were adhered to the double-sided tape. The obtained peel force value was evaluated according to the following criteria: ○: 60 mN / mm or less ×: Greater than 60 mN / mm

[0207] (3-2) Evaluation of Wrinkles in Release Film Rolls and Laminate Rolls A laminate was unwound from the release film rolls prepared from the biaxially oriented polypropylene films described in Examples 1 to 7 and Comparative Examples 1 to 9 and the laminate rolls prepared from the release film rolls, and the wrinkles that occurred on the laminate rolls were evaluated by the following method. Specifically, a 120 cm long, 60 cm wide release film was hung vertically in the longitudinal direction in a room at 25°C and 65% humidity, and a load of 10 N / m was applied and left to stand for 30 minutes. A fluorescent lamp was projected onto the film surface from 45° above and 1 m away from the surface on which the number of continuous corrugated wrinkles in the longitudinal direction was counted. The number of wrinkles was visually counted and evaluated from 45° below and 0.5 m away from the surface on which the wrinkles were counted. Each wrinkle that was convex in the longitudinal direction of the film relative to the surface being observed was counted as one wrinkle, and the number of wrinkles in the width direction of the film was counted. ○: The number of wrinkles is 10 or less per meter. ×: The number of wrinkles is 11 or more per meter.

[0208] (3-3) Evaluation of Flatness of Release Film and Laminate From the release film rolls and laminate rolls described in Examples 1 to 7 and Comparative Examples 1 to 9, the release films and laminates were cut into 10 cm x 10 cm sizes, and the release film samples were placed on a glass plate with the release surface facing up, and the height of the part floating above the glass plate was measured. The curl that occurred in the release films and laminates was evaluated by the following method. At this time, the height of the part that floated the most above the glass plate was taken as the measured value. The curling was evaluated according to the following criteria. ○: Curl was 5 mm or less ×: Curl was more than 5 mm

[0209] (3-4) Preparation of Release Film Laminated with Silicone-Based Release Agent Layer The inner surface of the roll-shaped biaxially oriented polypropylene films obtained in Examples 1 to 7 and Comparative Examples 1 to 9 was subjected to a corona treatment under the condition of an applied current value of 0.75 A. A coating liquid was applied to the corona-treated surface in an amount (wet) of 3 g / m with a toluene / methyl ethyl ketone=50 / 50 solution (solid content concentration 1 wt %) of a thermosetting silicone compound (KS-774, manufactured by Shin-Etsu Silicones Co., Ltd.) to which a Pt catalyst (PL-50T, manufactured by Shin-Etsu Silicones Co., Ltd.) was added in an amount of 1 part by mass per 100 parts by mass of the solid content of KS-774. ２ The release agent layer was dried for 20 seconds at a conveying tension of 2000 kPa and a drying temperature of 150°C using an air floating conveying type drying device with a gap between the upper and lower airflow outlets of 38 cm, so that the weight of the release agent layer after drying and hardening was 0.03 g / m ２ After drying, the film was cooled at a rate of 20°C / sec using a cooling roll at 50°C, and then taken up into a roll to obtain a release film roll. The wrinkles and flatness of the release film were evaluated, and the results are shown in Table 3.

[0210] (3-5) Preparation of Release Film Laminated with Non-Silicone-Based Release Agent Layer The inner surface of the roll of each of the biaxially oriented polypropylene films obtained in Examples 1 to 7 and Comparative Examples 1 to 9 was subjected to a corona treatment under the condition of an applied current value of 0.75 A. A coating liquid prepared by diluting a long-chain alkyl pendant compound (Rezem P-677, manufactured by Chukyo Yushi Co., Ltd.) with a water / isopropyl alcohol mixed solvent was applied to the corona-treated surface, and the release layer was dried for 20 seconds at a conveying tension of 2000 kPa and a drying temperature of 150°C using an air floating conveying type drying device with a distance of 38 cm between the lower and upper air flow outlets, so that the weight of the release layer after drying and hardening was 0.03 g / m ２ After drying, the film was cooled at a rate of 20°C / sec using a cooling roll at 50°C, and then taken up into a roll to obtain a release film roll. The wrinkles and flatness of the release film were evaluated, and the results are shown in Table 3.

[0211] (3-6) Preparation of Film for Thermosetting Resin Film Manufacturing Process The following phenoxy resin solution was applied to the release layer surface of a release film roll having a silicone-based release layer obtained using the biaxially oriented polypropylene film rolls of Examples 1 to 7 and Comparative Examples 1 to 9, so that the thickness of the resin film after drying would be 5 μm. The film was dried in a hot air drying oven at 100°C for 30 seconds and then heated at 140°C for 100 seconds to prepare a laminate roll. The release film was then peeled from the laminate roll to obtain a thermosetting resin film. The peelability, wrinkles, and flatness of the obtained laminate were evaluated, and the results are shown in Table 3. (Phenoxy resin solution) Polyvinyl butyral (S-LEC (registered trademark) B BL-10, manufactured by Sekisui Chemical Co., Ltd.) 9.9 parts by mass Epoxy resin A: bisphenol A type epoxy resin (EPICLON (registered trademark) EXA-4850-1000, manufactured by DIC Corporation) 37.9 parts by mass Epoxy resin B: dicyclopentadiene type epoxy resin (EPICLON (registered trademark) HP-7200, manufactured by DIC Corporation) 24.7 parts by mass Heat curing agent: novolac type phenolic resin (SHOWOL (registered trademark) BRG-556, manufactured by Showa Denko K.K.) 18.3 parts by mass Curing accelerator: 2-phenyl-4,5-dihydroxymethylimidazole (Curesol (registered trademark) 2PHZ, manufactured by Shikoku Chemicals Corporation) 0.2 parts by mass Filler: spherical silica (manufactured by Admatechs Co., Ltd., Admanano (registered trademark) YA050C-MKK) 9.0 parts by mass Surface conditioner: silicone surfactant (manufactured by BYK Japan KK, BYK-370) 0.4 parts by mass Solvent: methyl ethyl ketone 100 parts by mass

[0212] (3-7) Preparation of Film for Aromatic Polyamide Film Manufacturing Process Referring to Example 1 of JP 2015-168194 A, an N-methyl-2-pyrrolidone solution (solids concentration 10.5% by mass) of aromatic polyamide obtained from 2-chloro-p-phenylenediamine and 4,4'-diaminodiphenyl ether (85 mol% / 15 mol%) as aromatic diamine components and 2-chloroterephthalic acid dichloride as acid component was prepared. The resulting aromatic polyamide solution was applied to the corona-treated biaxially oriented polypropylene films (without release agent coating) obtained in Examples 1 to 7 and Comparative Examples 1 to 9, heated at 150°C for 60 seconds to evaporate the solvent, and then the substrate film was peeled off. The resulting aromatic polyamide film was introduced into a water bath and subjected to extraction treatment. The film was then secured with clips and heat-treated in an oven at 250°C to obtain a 5 μm-thick aromatic polyamide film. The resulting laminate roll was evaluated for peelability, wrinkles, and flatness, and the results are shown in Table 3.

[0213] (3-8) Preparation of Film for Polymer Electrolyte Film Manufacturing Process

[0046] Referring to JP 2008-181856 A, an N-methyl-2-pyrrolidone solution (solids concentration 20% by mass) of an ionic group-containing resin obtained by reacting 3,3'-disulfo-4,4'-dichlorodiphenyl sulfone disodium salt, 2,6-dichlorobenzonitrile, 4,4'-biphenol, and potassium carbonate in N-methyl-2-pyrrolidone was applied to the release agent layer surface of a release film roll obtained by laminating a non-silicone release agent layer on the corona-treated surface of the biaxially oriented polypropylene of Examples 1 to 7 and Comparative Examples 1 to 9 above, and then dried at 130 °C for 10 minutes. The film was then immersed in a 20% by mass aqueous sulfuric acid solution at 30 °C for 10 minutes, then immersed in 30 °C pure water for 40 minutes, and further dried at 40 °C to obtain a laminate roll. The release film was then peeled off to obtain a polymer electrolyte membrane with a thickness of 18 μm. The resulting laminate roll was evaluated for peelability, wrinkles, and flatness. The results are shown in Table 3.

[0214] (3-9) Preparation of Film for Porous Membrane Manufacturing Process A resin solution was prepared by mixing and dissolving 100 parts by weight of polyamideimide solution (manufactured by Toyobo MC Co., Ltd., Viromax (registered trademark) HR11NN), 30 parts by weight of polyvinylpyrrolidone (molecular weight 55,000), and a silicone-based surfactant. This resin solution was applied to the release agent surface of a release film roll prepared in Examples 1 to 7 and Comparative Examples 1 to 9 above, which had a silicone-based release agent layer on the corona-treated surface of the biaxially oriented polypropylene. The film was then held in an atmosphere of 25°C and 95% RH for 3 minutes, immersed in water to solidify, and then dried in an oven with an inlet at 80°C and an outlet at 120°C to obtain a laminate roll. The release film was then peeled off, and a porous film with a thickness of 25 μm was obtained. The releasability, wrinkles, and flatness of the obtained laminate roll were evaluated, and the results are shown in Table 3.

[0215] (3-10) Preparation of Pressure-Sensitive Adhesive Layer Laminate With reference to WO 2012 / 029471, an acrylic pressure-sensitive adhesive was obtained by the following method. To an ethyl acetate solution (solids concentration 30%) of an acrylic polymer obtained by reacting 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate, 0.15 parts of trimethylolpropane xylylene diisocyanate and 0.2 parts of an acetoacetyl group-containing silane coupling agent per 100 parts of solids were added, and the mixture was diluted with ethyl acetate to obtain a pressure-sensitive adhesive solution with a solids concentration of 12%. The acrylic pressure-sensitive adhesive solution was applied to the release surface of a release film roll obtained by laminating a non-silicone release agent layer onto the corona-treated surface of the biaxially oriented polypropylene of Examples 1 to 7 and Comparative Examples 1 to 9 above, and dried at 130°C for 5 minutes to provide a pressure-sensitive adhesive layer with a thickness of 20 μm. Subsequently, the release surface of the release film laminated with the silicone release agent layer described above was bonded to the pressure-sensitive adhesive layer surface and wound up to obtain a laminate roll. The unwound optical pressure-sensitive adhesive transfer laminate was cut to the size of a commercially available polarizing plate, and after peeling off the protective film of the pressure-sensitive adhesive transfer laminate, the adhesive layer surface was bonded to a polarizing plate. The release film surface was then peeled off, and the laminate was bonded to a glass plate simulating a liquid crystal cell. The peelability, wrinkles, and flatness of the obtained laminate roll were evaluated, and the results are shown in Table 3.

[0216] (3-11) Preparation of Photosensitive Resin Laminate for Flexographic Printing Plates An aqueous solution of polyvinyl alcohol (PVA) was applied to the corona-treated surface of the biaxially oriented polypropylene film obtained in Examples 1 to 7 and Comparative Examples 1 to 9, and the biaxially oriented polypropylene film with a PVA coating layer was prepared by drying at 130°C. The photosensitive resin was removed from a flexographic printing plate (Cosmolite (registered trademark) NS284F, manufactured by Toyobo MC Co., Ltd.), and the base film (PET) of the original printing plate, the removed photosensitive resin, and the biaxially oriented polypropylene film with the PVA coating layer were stacked so that the PVA coating layer surface faced the photosensitive resin surface. The resulting mixture was pressed in a hot press heated to 125°C and cut to A4 size to obtain a photosensitive resin laminate for a flexographic printing plate. The thickness of the photosensitive resin layer was adjusted to 0.95 mm using aluminum spacers.

[0217] The photosensitive resin laminate had excellent peelability and flatness, and no wrinkles or warping were observed. Ten photosensitive resin laminates were produced and stored in a stack for one week. The bottom laminate was then removed, and the biaxially oriented polypropylene film was peeled off. A full-color halftone dot negative was then overlaid, exposed, and developed to create a flexographic printing plate. The biaxially oriented polypropylene film exhibited appropriate rigidity during peeling, allowing for smooth peeling without leaving any peel marks. Furthermore, when the resulting plate was used for printing, there were no dents due to dust or other factors trapped during storage, and high-quality prints were obtained.

[0218] (3-12) Preparation of Laminate for Printing Layer Transfer A urethane acrylate hard coating agent (HX-RSC, manufactured by Kyoeisha Chemical Co., Ltd.) was applied as a protective layer to one side of the corona-treated biaxially oriented polypropylene film (without release agent coating) obtained in Examples 1 to 7 and Comparative Examples 1 to 9, and after drying at 100°C, a protective layer of 5 μm in thickness was formed by irradiating with ultraviolet light. Further, full-color printing was performed on the protective layer using an ink containing butyl acetate as a solvent, and then a toluene / MEK solution of Nichigo Polyester (registered trademark) SP-154 was applied as an adhesive layer, dried, and then wound into a roll to obtain a laminate for transfer printing.

[0219] Printing and adhesive drying were performed in an oven at 130°C, but there was no printing misalignment, and the resulting laminate was wrinkle-free and had excellent peelability and flatness. The resulting laminate for transfer printing was unwound from a roll and passed through a silicone transfer roll heated to 150°C so that the film surface served as the transfer roll, and the adhesive layer surface was pressed against a polycarbonate molded body to transfer the protective layer / printing layer / adhesive layer. The contact time with the transfer roll was 3 seconds. During transfer, the film and protective layer peeled smoothly, there was only slight film shrinkage, and transfer printing was possible without transfer defects or misalignment.

[0220] (3-13) Preparation of a Laminate for Metal Thin Film Layer Transfer One side of the corona-treated biaxially oriented polypropylene film (without release agent coating) obtained in Examples 1 to 7 and Comparative Examples 1 to 9 was coated with a transparent yellow-colored acrylic resin solution and dried at 130°C for 30 seconds to form a 5 μm-thick colored protective layer. Aluminum was then vacuum-deposited onto the colored layer. The coated film was wrinkle-free and had good flatness after deposition. The above adhesive layer was then deposited on the aluminum-deposited layer to obtain a roll-shaped laminate for metal thin film layer transfer. The resulting laminate was wrinkle-free and had excellent releasability and flatness. The resulting metal thin film layer laminate was unwound, and the adhesive layer surface was placed on a printed cardboard. A mold heated to 150°C was pressed against the film surface for 3 seconds to hot-stamp the metal thin film layer onto the printed cardboard. A gold leaf-like pattern was formed in the desired position on the cardboard.

[0221] (3-14) Preparation of Laminate for Dry Film Resist Transfer

[0049] The following photosensitive resin solution, obtained with reference to the examples in JP-A 2006-114735, was applied to the release surface of a release film obtained by laminating a non-silicone release agent layer on the corona-treated surface of the biaxially oriented polypropylene film roll of Examples 1 to 7 and Comparative Examples 1 to 9 above, and the solvent was removed to provide a 30 μm thick photosensitive resin layer. A release film roll provided with a silicone release layer as a protective film was laminated to the surface of the photosensitive resin layer opposite the substrate, to obtain a photosensitive resin laminate roll. The obtained photosensitive resin laminate roll was free of warping and had excellent releasability and flatness. (Photosensitive resin solution) Methyl ethyl ketone solution (solid content concentration 34%) of a copolymer consisting of 65% by mass of methyl methacrylate, 25% by mass of methacrylic acid, and 10% by mass of butyl acrylate: 65 g Triethoxymethylolpropane acrylate: 10 g Dimethacrylate of propylene glycol ethylene glycol copolymer: 17 g p-nonylphenoxyheptaethoxydipropoxy acrylate: 5 g 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer: 3 g 4,4'-bis(diethylamino)benzophenone: 0.14 g Diamond green: 0.04 g Leuco crystal violet: 0.5 g Polypropylene glycol: 10 g p-toluenesulfonamide: 5 g Methyl ethyl ketone: 15 g

[0222] The protective film was then peeled off from the resulting photosensitive resin laminate roll, and the photosensitive resin layer surface was pressed against the copper foil surface of the copper-clad film on the optical device. A negative was then placed on the side of the release film opposite the photosensitive resin layer, and the pressure was reduced to allow for close contact. After exposure from the negative side, the release film was peeled off, and the uncured portions were removed with an aqueous sodium carbonate solution. A resist layer was formed on the copper foil, with the photosensitive resin cured according to the negative pattern.

[0223] As described above, the films of the Examples could be used in a variety of applications. On the other hand, the films of the Comparative Examples were prone to wrinkling and deterioration of flatness due to heat in the drying process, etc., which limited their applications, as can be seen from the evaluations of the releasability, wrinkles, and flatness of release films coated with silicone-based release agents and non-silicone-based release agents, as well as various laminates using these.

[0224]

[0225]

[0226]

[0227] The release film of the present disclosure is resistant to wrinkling when the release agent dries at high temperatures, and the film exhibits little curling after coating and excellent flatness, making it suitable for use as a release film for high-temperature applications. Furthermore, it is resistant to dents caused by the entrapment or contact of foreign matter, and peeling is excellent, leaving few peel marks. Therefore, it can be suitably used as a release film member for thin film manufacturing processes, laminates in which a pressure-sensitive adhesive layer is further provided on the release surface of a release film, photosensitive resin laminates in which a photosensitive resin layer is further provided on the release surface of a release film, and transfer laminates in which a transfer layer such as a printing layer, a decorative metal thin film, a thermal transfer ink layer, a photosensitive resin layer, an optically functional layer, a conductive layer, a circuit, an adhesive layer, a pressure-sensitive adhesive layer, or a rubber sheet layer is further provided on the release surface of a release film.

Claims

1. A release film having a substrate made of a biaxially oriented polypropylene film that satisfies the following requirements (1) and (2): (1) In a thermomechanical analysis, when the temperature is increased from 30°C to 160°C at a rate of 10°C / min, the length in the width direction of the biaxially oriented polypropylene film is 0.9950X ０ (2) The storage modulus in the longitudinal direction at 23°C is 2.0 GPa or more, and the storage modulus in the transverse direction at 23°C is 8.0 GPa or more.

2. The release film according to claim 1, wherein the biaxially oriented polypropylene film has a sum of the longitudinal storage modulus at 23°C and the longitudinal storage modulus at 140°C of 3.0 GPa or more, and a sum of the widthwise storage modulus at 23°C and the widthwise storage modulus at 140°C of 8.9 GPa or more.

3. A release film having a substrate made of a biaxially oriented polypropylene film that satisfies the following requirements (1) and (2): (1) The storage modulus in the longitudinal direction at 23°C is 2.8 GPa or more, and the storage modulus in the transverse direction at 23°C is 8.0 GPa or more. (2) The heat shrinkage in the longitudinal direction at 150°C is 4.5% or less, and the heat shrinkage in the transverse direction at 150°C is 9.0% or less.

4. The release film according to claim 3, wherein the biaxially oriented polypropylene film has a sum of the longitudinal storage modulus at 23°C and the longitudinal storage modulus at 140°C of 3.0 GPa or more, and a sum of the widthwise storage modulus at 23°C and the widthwise storage modulus at 140°C of 8.9 GPa or more.

5. A release film having a substrate made of a biaxially oriented polypropylene film that satisfies the following requirements (1), (2), and (3): (1) The sum of the longitudinal storage modulus at 23°C and the longitudinal storage modulus at 140°C is 3.0 GPa or more. (2) The sum of the widthwise storage modulus at 23°C and the widthwise storage modulus at 140°C is 9.2 GPa or more. (3) In dynamic viscoelasticity measurement, when E"(B) is the minimum value of the loss modulus from 25°C to 75°C and E"(C) is the maximum value of the loss modulus from 100°C to 160°C, E"(B) / E"(C) is 0.60 or more.

6. In a thermomechanical analysis, when the biaxially oriented polypropylene film is heated from 30°C to 160°C at a heating rate of 10°C / min, the length of the biaxially oriented polypropylene film in the width direction is 0.9950X ０ 6. The release film according to claim 5, wherein the temperature at which the storage modulus is less than or equal to 129°C is 129°C or higher, the storage modulus in the longitudinal direction at 23°C is 2.0 GPa or higher, and the storage modulus in the width direction at 23°C is 8.0 GPa or higher.

7. The release film according to any one of claims 1 to 6, further comprising a release agent layer laminated on at least one surface of the substrate.

8. The release film according to claim 7, wherein the release agent layer comprises a silicone-based release agent.

9. The release film according to claim 7, wherein the release agent layer is made of a non-silicone release agent.

10. A film for thin film manufacturing processes, comprising the release film according to any one of claims 1 to 6.

11. A pressure-sensitive adhesive layer laminate comprising: a release film according to any one of claims 1 to 6; a pressure-sensitive adhesive layer provided on the release surface of said release film; and a protective film provided on the surface of said pressure-sensitive adhesive layer opposite to said release film.

12. A photosensitive resin laminate comprising: a release film according to any one of claims 1 to 6; a photosensitive resin layer provided on the release surface of said release film; and a protective film provided on the surface of said photosensitive resin layer opposite said release film.

13. A transfer laminate comprising the release film according to any one of claims 1 to 6 and at least one transfer layer selected from a printing layer, a decorative metal thin film, a thermal transfer ink layer, an optically functional layer, a conductive layer, a circuit, an adhesive layer, a pressure-sensitive adhesive layer, and a rubber sheet layer.

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